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The inhibition of malignant cell growth by ketone bodies
Abstract
The effect of ketone bodies on the growth, in culture, of transformed lymphoblasts (Raji cells) was investigated. Cell growth was inhibited and this effect was reversible, non-toxic, and proportional to the concentration of D-beta-hydroxybutyrate up to 20mM. The total glucose utilisation and the total lactate production were reduced in proportion to the inhibition of cell proliferation. D-beta-hydroxybutyrate was not metabolised by the cells. Other glycolytic inhibitors and chemical analogues of D-beta-hydroxybutyrate either did not inhibit or proved to be too toxic for cell growth. D-beta-hydroxybutyrate also inhibited the growth of rabbit kidney (RK13), HeLa, mouse melanoma (B16), fibroblast and trypsin-dispersed human thyroid and beef testis cells. Moreover, in vivo dietary-induced ketosis reduced the number of B16 melanoma deposits in the lungs of C57BL/6 mice by two-thirds. The significance of these results in the clinical management of cancer cachexia is discussed.
... In contrast, it was shown that a ketogenic diet significantly reduces tumor growth in mice [37,38]. Further, an antiproliferative effect of 3-OHB was already shown for different cancer cells, such as glioblastoma and tumor stem cells [37], melanoma, cervical carcinoma, or neuroblastoma [39][40][41]. Several studies also described a significant delay of tumor growth in mice and humans in a systemic ketosis [16,18,37,38,40,[42][43][44][45][46][47][48][49]. ...
... In our in vitro experiments, the MDA-MB 231 cell line showed no increased proliferation in the presence of 3-OHB. Moreover, no notable inhibition of proliferation by 3-OHB could be seen in our short-term (5 days) and long-term (at least 14 days) experiments, as described for other cell lines [39][40][41]. In this context, it should be noted that the growth inhibitory effects for 3-OHB previously reported were predominantly seen with very high and non-physiological concentrations of 3-OHB (5-40 mM), an observation we have seen in our cell lines as well (not shown). ...
... In this context, it should be noted that the growth inhibitory effects for 3-OHB previously reported were predominantly seen with very high and non-physiological concentrations of 3-OHB (5-40 mM), an observation we have seen in our cell lines as well (not shown). In detail, the first description of an antiproliferative effect of 3-OHB on different cancer cell lines was published by Magee et al. in 1979. The authors tested concentrations of 3-OHB between 10 and 40 mM [39]. ...
Background:
Ketogenic diets (KDs) or short-term fasting are popular trends amongst supportive approaches for cancer patients. Beta-hydroxybutyrate (3-OHB) is the main physiological ketone body, whose concentration can reach plasma levels of 2-6 mM during KDs or fasting. The impact of 3-OHB on the biology of tumor cells described so far is contradictory. Therefore, we investigated the effect of a physiological concentration of 3 mM 3-OHB on metabolism, proliferation, and viability of breast cancer (BC) cells in vitro.
Methods:
Seven different human BC cell lines (BT20, BT474, HBL100, MCF-7, MDA-MB 231, MDA-MB 468, and T47D) were cultured in medium with 5 mM glucose in the presence of 3 mM 3-OHB at mild hypoxia (5% oxygen) or normoxia (21% oxygen). Metabolic profiling was performed by quantification of the turnover of glucose, lactate, and 3-OHB and by Seahorse metabolic flux analysis. Expression of key enzymes of ketolysis as well as the main monocarboxylic acid transporter MCT2 and the glucose-transporter GLUT1 was analyzed by RT-qPCR and Western blotting. The effect of 3-OHB on short- and long-term cell proliferation as well as chemo- and radiosensitivity were also analyzed.
Results:
3-OHB significantly changed the oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) in BT20 cells resulting in a more oxidative energetic phenotype. MCF-7 and MDA-MB 468 cells had increased ECAR only in response to 3-OHB, while the other three cell types remained uninfluenced. All cells expressed MCT2 and GLUT1, thus being able to uptake the metabolites. The consumption of 3-OHB was not strongly linked to mRNA overexpression of key enzymes of ketolysis and did not correlate with lactate production and glucose consumption. Neither 3-OHB nor acetoacetate did interfere with proliferation. Further, 3-OHB incubation did not modify the response of the tested BC cell lines to chemotherapy or radiation.
Conclusions:
We found that a physiological level of 3-OHB can change the energetic profile of some BC cell lines. However, 3-OHB failed to influence different biologic processes in these cells, e.g., cell proliferation and the response to common breast cancer chemotherapy and radiotherapy. Thus, we have no evidence that 3-OHB generally influences the biology of breast cancer cells in vitro.
... However, it is becoming increasingly clear that ketosis, unlike most cancer therapies that target a single vulnerability in the cancer cell, induces widespread metabolic, genetic, and immune changes [62][63][64]. Although glucose deprivation was the original intent of KD as a potential cancer treatment [65], further investigation has suggested multiple other mechanisms by which ketosis may elicit anti-cancer effects [58,[66][67][68][69][70]. Many of these are now thought to be mechanistically attributable to the ketone bodies themselves, which in addition to serving as energy substrates also have important signaling properties [71]. ...
... Many of these are now thought to be mechanistically attributable to the ketone bodies themselves, which in addition to serving as energy substrates also have important signaling properties [71]. Indeed, ketones appear to demonstrate intrinsic anti-cancer properties in some cancer subtypes as they have been shown to inhibit cancer in vitro and in vivo [58,67,72,73]. ...
... Perhaps the earliest report of direct anti-cancer effects of ketones, by Magee et al. in 1979, demonstrated that βHB exerted a dose-dependent inhibition of proliferation in lymphoma, cervical cancer, and melanoma cells and a significant reduction of metastatic spread in a murine melanoma model [67]. Similarly, AcAc was shown to produce a dose-dependent inhibition in ATP production and proliferation in four colon and three breast cancer cell lines, while eliciting no similar effect on three control fibroblast cell lines [66]. ...
Gliomas are a highly heterogeneous tumor, refractory to treatment and the most frequently diagnosed primary brain tumor. Although the current WHO grading system (2016) demonstrates promise towards identifying novel treatment modalities and better prediction of prognosis over time, to date, existing targeted and mono therapy approaches have failed to elicit a robust impact on disease progression and patient survival. It is possible that tumor heterogeneity as well as specifically targeted agents fail because redundant molecular pathways in the tumor make it refractory to such approaches. Additionally, the underlying metabolic pathology, which is significantly altered during neoplastic transformation and tumor progression, is unaccounted for. With several molecular and metabolic pathways implicated in the carcinogenesis of CNS tumors, including glioma, we postulate that a systemic, broad spectrum approach to produce robust targeting of relevant and multiple molecular and metabolic regulation of growth and survival pathways, critical to the modulation of hallmarks of carcinogenesis, without clinically limiting toxicity, may provide a more sustained impact on clinical outcomes compared to the modalities of treatment evaluated to date. The objective of this review is to examine the emerging hallmark of reprogramming energy metabolism of the tumor cells and the tumor microenvironment during carcinogenesis, and to provide a rationale for exploiting this hallmark and its biological capabilities as a target for secondary chemoprevention and treatment of glioma. This review will primarily focus on interventions to induce ketosis to target the glycolytic phenotype of many cancers, with specific application to secondary chemoprevention of low grade glioma- to halt the progression of lower grade tumors to more aggressive subtypes, as evidenced by reduction in validated intermediate endpoints of disease progression including clinical symptoms.
... 249 Many studies investigating the effect of the KD on tumor metastasis indicate a metastasis-inhibiting effect of the KD. [250][251][252] An early study reported that KBs could inhibit the growth rate of malignant lymphoblasts (Raji cells) and diet-induced ketosis could reduce the number of B16 melanoma deposits in mouse lung. 251 Combined treatment with the KD and hyperbaric oxygen significantly reduced the tumor-growth rate and diminished metastatic spread, while increasing survival, in the VM-M3 mouse model of metastatic cancer, possibly through induction of ROS production in tumor cells. ...
... [250][251][252] An early study reported that KBs could inhibit the growth rate of malignant lymphoblasts (Raji cells) and diet-induced ketosis could reduce the number of B16 melanoma deposits in mouse lung. 251 Combined treatment with the KD and hyperbaric oxygen significantly reduced the tumor-growth rate and diminished metastatic spread, while increasing survival, in the VM-M3 mouse model of metastatic cancer, possibly through induction of ROS production in tumor cells. 250 Apart from preclinical studies, clinical trials have demonstrated the beneficial effects of the KD on antitumor therapy. ...
The ketogenic diet (KD) is a high-fat, adequate-protein, and very-low-carbohydrate diet regimen that mimics the metabolism of the fasting state to induce the production of ketone bodies. The KD has long been established as a remarkably successful dietary approach for the treatment of intractable epilepsy and has increasingly garnered research attention rapidly in the past decade, subject to emerging evidence of the promising therapeutic potential of the KD for various diseases, besides epilepsy, from obesity to malignancies. In this review, we summarize the experimental and/or clinical evidence of the efficacy and safety of the KD in different diseases, and discuss the possible mechanisms of action based on recent advances in understanding the influence of the KD at the cellular and molecular levels. We emphasize that the KD may function through multiple mechanisms, which remain to be further elucidated. The challenges and future directions for the clinical implementation of the KD in the treatment of a spectrum of diseases have been discussed. We suggest that, with encouraging evidence of therapeutic effects and increasing insights into the mechanisms of action, randomized controlled trials should be conducted to elucidate a foundation for the clinical use of the KD.
... 119 In another study, a lower number of lung metastases was observed when mice of this strain bearing the B16 melanoma were fed a zero-CHO, zero-protein (100E% from polyunsaturated fatty acids) diet. 140 In contrast, growth of the CT-2A Astrocytoma in these mice was not influenced by an unrestricted KD containing 17E% protein, 141 but significantly reduced on a calorically restricted KD containing only 8E% protein, along with significant reductions in blood glucose and IGF-1. 142 These findings might be correlated to the metabolic abnormalities that these mice develop on KDs that are not concurrently low in protein as discussed above. ...
... In the studies that proofed tumor growth inhibition by a KD fed ad libitum, there was a significant increase in KB levels, but not necessarily decreases in blood glucose levels or body weight. 74,140,[143][144][145][146][147][148] In some models, also non-ketogenic low-CHO diets (10-15E% CHO) led to significant tumor growth retardation that was correlated to low blood glucose and insulin levels. 149,150 Clinical data. ...
As more and more links between cancer and metabolism are discovered, new approaches to treat cancer using these mechanisms are considered. Dietary restriction of either calories or macronutrients has shown great potential in animal studies to both reduce the incidence and growth of cancer, and to act synergistically with other treatment strategies. These studies have also shown that dietary restriction simultaneously targets many of the molecular pathways that are targeted individually by anticancer drugs. The insulin/insulin-like growth factor-1 (IGF-1) system has thereby emerged as a key regulator of cancer growth pathways. Although lowering of insulin levels with diet or drugs such as metformin and diazoxide seems generally beneficial, some practitioners also utilize strategic elevations of insulin levels in combination with chemotherapeutic drugs. This indicates a broad spectrum of possibilities for modulating the insulin/IGF-1 system in cancer treatment. With a specific focus on dietary restriction, insulin administration and the insulin-lowering drug diazoxide, such modifications of the insulin/IGF-1 system are the topic of this review. Although preclinical data are promising, we point out that insulin regulation and the metabolic response to a certain diet often differ between mice and humans. Thus, the need for collecting more human data has to be emphasized.
... The anti-tumor potential of KD was demonstrated in some in vitro studies. These studies revealed that tumor cell lines (glioma, breast, and colon) are not able to employ ketones as their dietary energy source when starved of glucose thus resulting in decreased glycolysis and tumor proliferation [32][33][34]. Moreover, a multitude of mouse studies supported the anti-tumor effects of KD in various types of cancers, including brain [35], prostate [36][37][38][39][40], breast [41], lung [42], gastric [43], and colon [44] cancers and its efficacy to inhibit tumor progression and prolong survival in mice with metastatic cancer [45]. ...
Some diets, such as high lipid and high glucose diets, are known to increase the risk of colorectal cancer. On the other hand, little is known about diets that prevent colonic carcinogenesis. The ketogenic diet, which is characterized by high fat and very low carbohydrate content, is one such diet. The ketogenic diet decreases the amount of available glucose for tumors and shifts to the production of ketone bodies as an alternative energy source for healthy cells. Cancer cells are unable to use the ketone bodies for energy thus depriving them of the energy needed for progression and survival. Many studies reported the beneficial effects of the ketogenic diet in several types of cancers. Recently, the ketone body β-hydroxybutyrate has been found to possess anti-tumor potential in colorectal cancer. Despite its beneficial effects, the ketogenic diet also has some drawbacks, some of which are related to gastrointestinal disorders and weight loss. Thus, studies are being directed at this time towards finding alternatives to following a strict ketogenic diet and supplementing patients with the ketone bodies responsible for its beneficial effects in the hope of overcoming some potential setbacks. This article discusses the mechanism by which a ketogenic diet influences growth and proliferation of tumor cells, it sheds the light on the most recent trials regarding its use as an adjunctive measure to chemotherapy in patients with metastatic colorectal cancer, and it explains the limitations of its usage in metastatic patients and the promising role of exogenous ketone supplementation in this setting.
... Due to the difficulty in adapting to KD and fasting, the use of ketone supplements such as ketone salts, 1,3-butanediol, and ketone esters is currently being evaluated as a way to reach ketosis without dietary restriction [30,35,156,157]. KBs have been shown to exert growth inhibitory and cytotoxic effect in various cancer cell lines including lymphoma, cervical cancer, melanoma, glioblastoma, neuroblastoma, and pancreatic cancer cells [35,[42][43][44]. ...
The ketone bodies (KBs) β-hydroxybutyrate and acetoacetate are important alternative energy sources for glucose during nutrient deprivation. KBs synthesized by hepatic ketogenesis are catabolized to acetyl-CoA through ketolysis in extrahepatic tissues, followed by the tricarboxylic acid cycle and electron transport chain for ATP production. Ketogenesis and ketolysis are regulated by the key rate-limiting enzymes, 3-hydroxy-3-methylglutaryl-CoA synthase 2 and succinyl-CoA:3-oxoacid-CoA transferase, respectively. KBs participate in various cellular processes as signaling molecules. KBs bind to G protein-coupled receptors. The most abundant KB, β-hydroxybutyrate, regulates gene expression and other cellular functions by inducing post-translational modifications. KBs protect tissues by regulating inflammation and oxidative stress. Recently, interest in KBs has been increasing due to their potential for treatment of various diseases such as neurological and cardiovascular diseases and cancer. Cancer cells reprogram their metabolism to maintain rapid cell growth and proliferation. Dysregulation of KB metabolism also plays a role in tumorigenesis in various types of cancer. Targeting metabolic changes through dietary interventions, including fasting and ketogenic diets, has shown beneficial effects in cancer therapy. Here, we review current knowledge of the molecular mechanisms involved in the regulation of KB metabolism and cellular signaling functions, and the therapeutic potential of KBs and ketogenic diets in cancer.
... n = 9-13 in CTRL groups and n = 14-24 in KD groups. Alpha-AAA: alpha-aminoadipic acid, BABA: beta-aminobutyric acid, Cit: Citrulline, HArg, homoarginine, ↑: increased, ↓: decreased injected with B16 melanoma cells via the tail vein and subsequently fed either sucrose or pure vegetable oil, in which mice provided vegetable oil displayed a ~ 66% reduction in lung metastases [32]. ...
Background
Growing evidence supports the use of low-carbohydrate/high-fat ketogenic diets as an adjunctive cancer therapy. However, it is unclear which genetic, metabolic, or immunological factors contribute to the beneficial effect of ketogenic diets. Therefore, we investigated the effect of ketogenic diets on the progression and metabolism of genetically and metabolically heterogeneous melanoma xenografts, as well as on the development of melanoma metastases in mice with a functional immune system.
Methods
Mice bearing BRAF mutant, NRAS mutant, and wild-type melanoma xenografts as well as mice bearing highly metastatic melanoma allografts were fed with a control diet or ketogenic diets, differing in their triglyceride composition, to evaluate the effect of ketogenic diets on tumor growth and metastasis. We performed an in-depth targeted metabolomics analysis in plasma and xenografts to elucidate potential antitumor mechanisms in vivo.
Results
We show that ketogenic diets effectively reduced tumor growth in immunocompromised mice bearing genetically and metabolically heterogeneous human melanoma xenografts. Furthermore, the ketogenic diets exerted a metastasis-reducing effect in the immunocompetent syngeneic melanoma mouse model. Targeted analysis of plasma and tumor metabolomes revealed that ketogenic diets induced distinct changes in amino acid metabolism. Interestingly, ketogenic diets reduced the levels of alpha-amino adipic acid, a biomarker of cancer, in circulation to levels observed in tumor-free mice. Additionally, alpha-amino adipic acid was reduced in xenografts by ketogenic diets. Moreover, the ketogenic diets increased sphingomyelin levels in plasma and the hydroxylation of sphingomyelins and acylcarnitines in tumors.
Conclusions
Ketogenic diets induced antitumor effects toward melanoma regardless of the tumors´ genetic background, its metabolic signature, and the host immune status. Moreover, ketogenic diets simultaneously affected multiple metabolic pathways to create an unfavorable environment for melanoma cell proliferation, supporting their potential as a complementary nutritional approach to melanoma therapy.
... Although the combined use of radiation, chemotherapy, and surgery is a good strategy of care in different cancers [258], no effective standard therapy is available for highly aggressive cancer types with poor prognosis-for example, triple negative breast cancer [263]. Therefore, there is an urgent need to develop new approaches or strategies that enhance therapeutic efficacy in these types of cancer. ...
Although cancer is still one of the most significant global challenges facing public health, the world still lacks complementary approaches that would significantly enhance the efficacy of standard anticancer therapies. One of the essential strategies during cancer treatment is following a healthy diet program. The ketogenic diet (KD) has recently emerged as a metabolic therapy in cancer treatment, targeting cancer cell metabolism rather than a conventional dietary approach. The ketogenic diet (KD), a high-fat and very-low-carbohydrate with adequate amounts of protein, has shown antitumor effects by reducing energy supplies to cells. This low energy supply inhibits tumor growth, explaining the ketogenic diet’s therapeutic mechanisms in cancer treatment. This review highlights the crucial mechanisms that explain the ketogenic diet’s potential antitumor effects, which probably produces an unfavorable metabolic environment for cancer cells and can be used as a promising adjuvant in cancer therapy. Studies discussed in this review provide a solid background for researchers and physicians to design new combination therapies based on KD and conventional therapies.
... This therapeutic strategy reduced simultaneously the availability of glucose and glutamine to the glycolytic and glutaminolysis pathways in the tumor cells. Moreover, ketone bodies enhance the metabolic efficiency of normal host cells, but are growth inhibitory or even toxic to many tumor cells (Clarke et al., 2012;Veech, 2004;Cahill and Veech, 2003;Bartmann et al., 2018;Skinner et al., 2009;Fine et al., 2009;Poff et al., 2017;Magee et al., 1979;Hagihara et al., 2020;Ji et al., 2020). Abnormalities in cardiolipin and other phospholipids in the inner mitochondrial membranes would prevent tumor cells from using ketone bodies for ATP synthesis (El Kebbaj et al., 1986;Kiebish et al., 2008Kiebish et al., , 2009). ...
ATP is required for mammalian cells to remain viable and to perform genetically programmed functions. Maintenance of the ΔG′ATP hydrolysis of −56 kJ/mole is the endpoint of both genetic and metabolic processes required for life. Various anomalies in mitochondrial structure and function prevent maximal ATP synthesis through OxPhos in cancer cells. Little ATP synthesis would occur through glycolysis in cancer cells that express the dimeric form of pyruvate kinase M2. Mitochondrial substrate level phosphorylation (mSLP) in the glutamine-driven glutaminolysis pathway, substantiated by the succinate-CoA ligase reaction in the TCA cycle, can partially compensate for reduced ATP synthesis through both OxPhos and glycolysis. A protracted insufficiency of OxPhos coupled with elevated glycolysis and an auxiliary, fully operational mSLP, would cause a cell to enter its default state of unbridled proliferation with consequent dedifferentiation and apoptotic resistance, i.e., cancer. The simultaneous restriction of glucose and glutamine offers a therapeutic strategy for managing cancer.
... Beneficial impacts of ketogenic diets (KD) in ovarian cancer have recently reported and a randomized controlled trial revealed that KD may improve physical function, increase energy in patients with ovarian cancer. Many studies suggest ketogenic diets and ketones as a complementary and beneficial treatment to cope with tumor growth and metastasis in a variety of cancers [8][9][10]. The heterogeneity of metabolic preferences in tumor cells, mainly cancer stem cells(CSCs), and the impact of metabolic reprogramming on the behavior of cancer cells such as migration and metastasis have not been studied yet. ...
Background:
Alteration of metabolic pathways in cancer cells can intensely modulate their migration as an important step in invasion and metastasis. Ketogenic diet showed some contradictory results in cancer patients. In this study the impact of metabolic reprogramming of A2780CP as a model of ovarian cancer stem-like cells on cell migration by two in vitro methods: wound healing and soft agar colony-forming assays.
Materials and methods:
short term and long term metabolic reprogramming were done by restriction of glucose to 250mg/L with or without enrichment with beta-hydroxybutyrate (5 milimolar) for 48 hours and 30 days, respectively. Wound healing assay was done and the wound ratio was calculated for 24 and 48 hours. Soft agar colony formation assay was also done in treated and control cells. For method comparison, ten biological replicates were analyzed in triplicate.
Results:
Migration of A2780CP ovarian cancer stem-like cells were significantly alleviated by long term glucose restriction but no significant changes were observed in short term study. Beta-hydroxybutyrate enrichment did not produce significant impacts on glucose restriction in short or long term studies.
Conclusion:
The results of colony formation in soft agar and wound or scratch healing assay were in good correlation and convergence which could be used interchangeably in the investigation of metabolic reprogramming in cancer cells.
... KD and CR target the same molecular pathways including PI3K, PKB, mTORC, and AMPK. Several preclinical models have reported that ketosis is associated with tumor growth inhibition either by direct action or as an indicator of the effect of maximal insulin inhibition [61][62][63][64]. KD has been shown to delay human gastric cancer cell growth in nude mice [65] and in a xenograft model of prostate cancer [66]. ...
It is widely acknowledged that cancer cell energy metabolism relies mainly on anaerobic glycolysis; this phenomenon is described as the Warburg effect. However, whether the Warburg effect is caused by genetic dysregulation in cancer or is the cause of cancer remains unknown. The exact reasons and physiology of this abnormal metabolism are unclear; therefore, many researchers have attempted to reduce malignant cell growth in tumors in preclinical and clinical studies. Anticancer strategies based on the Warburg effect have involved the use of drug compounds and dietary changes. We recently reviewed applications of the Warburg effect to understand the benefits of this unusual cancer-related metabolism. In the current article, we summarize diet strategies for cancer treatment based on the Warburg effect.
... There are a variety of seemingly conflicting results reported in experiments which explore the effect of BHB on cancer cells in vitro and on experimental tumors in mice in vivo. In some cases, an anti-proliferative effect of BHB was shown for multiple cancer cells, such as glioblastoma and tumor stem cells (26), melanoma, cervical carcinoma, or neuroblastoma (27)(28)(29). While in other cases, BHB was identified as the factor inducing enhanced proliferation (30). ...
Background/aim:
The ketogenic diet has recently gained interest as potential adjuvant therapy for cancer. Many researchers have endeavored to support this claim in vitro. One common model utilizes treatment with exogenous acetoacetate in lithium salt form (LiAcAc). We aimed to determine whether the effects of treatment with LiAcAc on cell viability, as reported in the literature, accurately reflect the influence of acetoacetate.
Materials and methods:
Breast cancer and normal cell lines were treated with acetoacetate, in lithium and sodium salt forms, and cell viability was assessed.
Results:
The effect of LiAcAc on cells was mediated by Li ions. Our results showed that the cytotoxic effects of LiAcAc treatment were significantly similar to those caused by LiCl, and also treatment with NaAcAc did not cause any significant cytotoxic effect.
Conclusion:
Treatment of cells with LiAcAc is not a convincing in vitro model for studying ketogenic diet. These findings are highly important for interpreting previously published results, and for designing new experiments to study the ketogenic diet in vitro.
... After several days of fasting or a ketogenic diet, the human body enters a state of physiological ketosis characterized by low blood glucose levels, emptied liver glycogen stores, and hepatic production of ketones, which serve as a major energy source for brain and muscle. Ketones cannot be effectively utilized by cancer cells and may inhibit their growth (15,16). Moreover, both interventions can decrease glucose, glutamine, and growth factor availability, depriving cancer cells of their major fuels and creating an unfavorable physiological environment for unchecked growth and proliferation. ...
Thymomas consist of neoplastic thymic cells intermixed with variable numbers of non-neoplastic lymphocytes. Metastatic thymomas are typically managed with non-curative chemotherapy to control tumor-related symptoms; no prolonged survival is expected. Metabolic-based approaches, such as fasting and ketogenic diets, target cancer cell metabolism by creating an increased reliance on ketones while decreasing glucose, glutamine, and growth factor availability, theoretically depriving cancer cells of their metabolic fuels while creating an unfavorable environment for cancer growth, which may be beneficial in metastatic thymoma. We report the case of a 37-year-old woman with myasthenia gravis, diagnosed with an inoperable type AB, stage IVA thymoma, who pursued a metabolic intervention consisting of periodic fasting (7-day, fluid-only fasts every 1–2 months), combined with a modified ketogenic diet on feeding days, for 2 years. months), combined with a modified ketogenic diet on feeding days, for 2 years. Fasting-related adverse effects included cold intolerance, fatigue, and generalized muscle aches, all of which resolved during the second year. She experienced two myasthenia relapses, each associated with profoundly reduced oral intake, marked weight loss, and tumor regression—the first relapse was followed by a 32% decrease in tumor volume over four months, the second relapse by a dramatic 96% decrease in tumor volume over four months. The second relapse also required prednisone to control the myasthenia symptoms. We hypothesize that two years of fasting and ketogenic diet therapy metabolically weakened the neoplastic thymic cell component of the thymoma, “setting the stage” for immune activation and extreme energy restriction to destroy the majority of cancer cells during both relapses, while prednisone–induced apoptosis eradicated the remaining lymphocytic component of the thymoma during the second relapse. This case is unique in that a metabolic-based fasting and ketogenic diet intervention was used as the primary management strategy for a metastatic cancer in the absence of surgery, chemotherapy, or radiotherapy, culminating in a near-complete regression. Nearly three years after being diagnosed with inoperable metastatic cancer, our patient shows no signs of disease and leads a full and active life.
... Antitumor effects of the ketone bodies AcAc and BHB have been demonstrated in several cancer cell lines in vitro [59,92]. However, whether the antitumor properties of KDs are exclusively attributable to the antiproliferative effects of ketone bodies and low blood glucose levels seems rather unlikely. ...
Background:
Cancer is one of the greatest public health challenges worldwide, and we still lack complementary approaches to significantly enhance the efficacy of standard anticancer therapies. The ketogenic diet, a high-fat, low-carbohydrate diet with adequate amounts of protein, appears to sensitize most cancers to standard treatment by exploiting the reprogramed metabolism of cancer cells, making the diet a promising candidate as an adjuvant cancer therapy.
Scope of review:
To critically evaluate available preclinical and clinical evidence regarding the ketogenic diet in the context of cancer therapy. Furthermore, we highlight important mechanisms that could explain the potential antitumor effects of the ketogenic diet.
Major conclusions:
The ketogenic diet probably creates an unfavorable metabolic environment for cancer cells and thus can be regarded as a promising adjuvant as a patient-specific multifactorial therapy. The majority of preclinical and several clinical studies argue for the use of the ketogenic diet in combination with standard therapies based on its potential to enhance the antitumor effects of classic chemo- and radiotherapy, its overall good safety and tolerability and increase in quality of life. However, to further elucidate the mechanisms of the ketogenic diet as a therapy and evaluate its application in clinical practice, more molecular studies as well as uniformly controlled clinical trials are needed.
... Thus, we used 0, 5, 10, and 20 μM βHB in the study. These ketone body concentrations have also been applied in many other published articles [16,[41][42][43]. Our data demonstrated that ketone body supplementation reduces the increased proliferation and migration of HMGCS2 knockdown cells ( Figure 6; Figure 7). ...
Hepatocellular carcinoma (HCC) is the most common primary malignant tumor worldwide; however, the traditional therapeutic approaches and survival rates are still limited. To improve current therapies, it is necessary to investigate the molecular mechanisms underlying liver cancer and to identify potential therapeutic targets. The aims of this study were to verify the mechanisms and therapeutic potential of the ketogenesis rate-limiting enzyme 3-Hydroxymethylglutaryl-CoA synthase 2 (HMGCS2) in HCC. Immunohistochemical staining of human liver disease tissue arrays showed that HMGCS2 is abundantly expressed in normal liver tissues but is downregulated in cirrhosis and HCC tissues. In HCC patients, lower HMGCS2 expression was correlated with higher pathological grades and clinical stages. In our investigation of the molecular mechanisms of HMGCS2 in HCC, we showed that knockdown of HMGCS2 decreased ketone production, which promoted cell proliferation, cell migration, and xenograft tumorigenesis by enhancing c-Myc/cyclinD1 and EMT signaling and by suppressing the caspase-dependent apoptosis pathway. Ketone body treatment reduced the proliferation- and migration-promoting effects of HMGCS2 knockdown in cells. In contrast, HMGCS2 overexpression increased the intracellular ketone level and inhibited cell proliferation, cell migration, and xenograft tumorigenesis. Finally, ketogenic diet administration significantly inhibited liver cancer cell growth in mice. Our studies highlight the potential therapeutic strategy of targeting HMGCS2-mediated ketogenesis in liver cancer.
... Fasting regimens also prevent tumors in most rodent cancer models; however, the results are more variable in comparison with calorie restriction [105]. These findings might be explained by variability across studies with regards to the specific fasting regimen used, as well as the macronutrient ratio employed in the refeeding periods; both may strongly influence the degree of tumor prevention, which in many cases exceeds the tumor-preventive effects of calorie restriction [108][109][110][111]. Compared to calorie restriction, fasting results in the production of large amounts of ketones, which cannot be effectively utilized by cancer cells and may inhibit their growth [112][113][114]. Fasting also intermittently reduces glucose, glutamine, and growth factor availability to a greater extent than calorie restriction, which theoretically deprives cancer cells of their major fuels and disrupts their ability to proliferate. ...
Fasting is deeply entrenched in evolution, yet its potential applications to today’s most common, disabling neurological diseases remain relatively unexplored. Fasting induces an altered metabolic state that optimizes neuron bioenergetics, plasticity, and resilience in a way that may counteract a broad array of neurological disorders. In both animals and humans, fasting prevents and treats the metabolic syndrome, a major risk factor for many neurological diseases. In animals, fasting probably prevents the formation of tumors, possibly treats established tumors, and improves tumor responses to chemotherapy. In human cancers, including cancers that involve the brain, fasting ameliorates chemotherapy-related adverse effects and may protect normal cells from chemotherapy. Fasting improves cognition, stalls age-related cognitive decline, usually slows neurodegeneration, reduces brain damage and enhances functional recovery after stroke, and mitigates the pathological and clinical features of epilepsy and multiple sclerosis in animal models. Primarily due to a lack of research, the evidence supporting fasting as a treatment in human neurological disorders, including neurodegeneration, stroke, epilepsy, and multiple sclerosis, is indirect or non-existent. Given the strength of the animal evidence, many exciting discoveries may lie ahead, awaiting future investigations into the viability of fasting as a therapy in neurological disease.
... Due to impaired mitochondrial function, cancer cells are depending on substrate-level phosphorylation, and during ketone body metabolism, mSLP is bypassed. Ketone bodies may elicit their anticancer effects, most likely by glycolytic enzyme inhibition [198]. Numerous research studies documented that in vitro cancer cells were deficient in metabolizing of ketone bodies [199,200]. ...
A clear understanding of the origins of cancer is the basis of successful strategies for effective cancer prevention and management. The origin of cancer at the molecular and cellular levels is not well understood. Is the primary cause of the origin of cancer the genomic instability or impaired energy metabolism? An attempt was made to present cancer etiology originating from life’s major evolutionary transition. The first evolutionary transition went from simple to complex cells when eukaryotic cells with glycolytic energy production merged with the oxidative mitochondrion (The Endosymbiosis Theory first proposed by Lynn Margulis in the 1960s). The second transition went from single-celled to multicellular organisms once the cells obtained mitochondria, which enabled them to obtain a higher amount of energy. Evidence will be presented that these two transitions, as well as the decline of NAD+ and ATP levels, are the root of cancer diseases. Restoring redox homeostasis and reactivation of mitochondrial oxidative metabolism are important factors in cancer prevention.
... In these three papers, genetically altered culture systems were used; however, there is no evidence that this occurs naturally in cancer cells in vitro or in tumors in vivo. On the other hand, previous evidence strongly suggests that cancer cells cannot effectively use ketones for fuel [83][84][85][86], instead, they may have anti-tumoral effects [86][87][88][89][90][91][92]. ...
Background: Previous evidence suggests that metabolically supported chemotherapy (MSCT), ketogenic diet, hyperthermia and hyperbaric oxygen therapy (HBOT) could all target vulnerabilities of cancer cells. This study aimed to evaluate the efficacy and the tolerability of this combination therapy in the treatment of stage IV non-small cell lung cancer (NSCLC).
Methods: Forty-four NSCLC patients with distant metastasis that received MSCT (administration of chemotherapy regimen following induced hypoglycemia) plus ketogenic diet, hyperthermia and HBOT combination were included in this retrospective study. Survival and treatment response rates as well as toxicities were evaluated.
Results: Overall response rate (ORR, complete response plus partial response) was 61.4%; whereas, 15.9% and 22.7% of patients had stable disease (SD) and progressive disease (PD), respectively. Mean overall survival (OS) and progression-free survival (PFS) was 42.9 months (95% CI: 34.0–51.8) and 41.0 months (95% CI: 31.1–50.9), respectively. A higher Eastern Cooperative Oncology Group (ECOG) performance status (ECOG ≥2) was associated with worse OS and PFS. Patients received chemotherapy cycles with acceptable toxicity and adverse events. No problems were encountered due to fasting, hypoglycemia, ketogenic diet, hyperthermia or hyperbaric oxygen therapy.
Conclusions: Findings of this study suggest that MSCT combined with other modalities targeting multiple pathways and cellular vulnerabilities may bring about remarkable improvements in survival outcomes and treatment response rates in metastatic NSCLC, without additional safety concerns. Large comparative studies are warranted to draw robust conclusions.
... However, in some malignancies such as brain and gastric cancers, tumor cells cannot effectively use ketone bodies for energy. Extracellular ketone bodies have strong anti-proliferative and pro-apoptotic effects in several cancers, including pancreatic and gastric cancer, as well as EBV-positive lymphoblasts [29][30][31] . In addition, ketone bodies affect intracellular oxidative stress 32 , which is crucial for the survival and function of tumor cells 33 . ...
Altered metabolism is considered as a hallmark of cancer. Here we investigated expression of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) 2 lyase (HMGCL), an essential enzyme in ketogenesis, which produces ketone bodies by the breakdown of fatty acids to supply energy, in nasopharyngeal carcinoma (NPC). The expression of HMGCL was silenced in NPC tissue. Downregulation of HMGCL in NPC was associated with low intracellular β-hydroxybutyrate (β-HB) production, thereby reducing reactive oxygen species (ROS) generation. Ectopic expression of HMGCL restored β-HB level, associated with suppressed proliferation and colony formation of NPC cells in vitro and decreased tumorigenicity in vivo. HMGCL suppressed the migration and invasion of NPC cells in vitro via mesenchymal-epithelial transition. Furthermore, extracellular β-HB supply suppressed the proliferation and migration of NPC cells. Both intra- and extracellular β-HB exerting a suppressive role in NPC depends on ROS generation. Ketogenesis may be impaired in NPC cells due to lack of HMGCL expression, suggesting that it may be a promising target in NPC therapy.
... Ketone bodies and fats are nonfermentable fuels [177]. Tumor cells have difficulty using ketone bodies and fats for fuel when glucose is reduced [57,[178][179][180]. Although some tumor cells might appear to oxidize ketone bodies by the presence of ketolytic enzymes [181], it is not clear if ketone bodies and fats can provide sufficient energy for cell viability in the absence of glucose and glutamine. ...
... A high level of ketone bodies in the blood is termed ketosis. These ketone bodies may play an additional role in cancer treatment, having a cytostatic effect on cells in vitro through blockage of glucose uptake [72] and providing an energy source for normal cells that cannot be utilized by cancer cells [73]. ...
Modern medicine has developed many ways of treating cancer but, unfortunately, we are still a long ways from being able to successfully treat every patient. Some cancer patients may feel that their oncologists are not aware of other options while others may prefer a treatment that has not been approved for use in patients. The prevalence of complementary and alternative medicine in cancer treatment is surprisingly large and information regarding these treatments, whether true or false, is spread easily over the internet. In this review I hope to touch on a few of the most “popular” cancer treatments that can be found on the internet. By no means does this review cover even a small portion of those that can be found, and it is not meant to be a comprehensive review on any one of them. It should be viewed as a scientific snapshot of the current laboratory and clinical data that are available for these methods and to serve as a contrast to the hype, insufficient data, and incorrect information that can be found on any number of websites.
... Ketone bodies and fats are nonfermentable fuels [177]. Tumor cells have difficulty using ketone bodies and fats for fuel when glucose is reduced [57,[178][179][180]. Although some tumor cells might appear to oxidize ketone bodies by the presence of ketolytic enzymes [181], it is not clear if ketone bodies and fats can provide sufficient energy for cell viability in the absence of glucose and glutamine. ...
BackgroundA shift from respiration to fermentation is a common metabolic hallmark of cancer cells. As a result, glucose and glutamine become the prime fuels for driving the dysregulated growth of tumors. The simultaneous occurrence of “Press-Pulse” disturbances was considered the mechanism responsible for reduction of organic populations during prior evolutionary epochs. Press disturbances produce chronic stress, while pulse disturbances produce acute stress on populations. It was only when both disturbances coincide that population reduction occurred. Methods
This general concept can be applied to the management of cancer by creating chronic metabolic stresses on tumor cell energy metabolism (press disturbance) that are coupled to a series of acute metabolic stressors that restrict glucose and glutamine availability while also stimulating cancer-specific oxidative stress (pulse disturbances). The elevation of non-fermentable ketone bodies protect normal cells from energy stress while further enhancing energy stress in tumor cells that lack the metabolic flexibility to use ketones as an efficient energy source. Mitochondrial abnormalities and genetic mutations make tumor cells vulnerable metabolic stress. ResultsThe press-pulse therapeutic strategy for cancer management is illustrated with calorie restricted ketogenic diets (KD-R) used together with drugs and procedures that create both chronic and intermittent acute stress on tumor cell energy metabolism, while protecting and enhancing the energy metabolism of normal cells. Conclusions
Optimization of dosing, timing, and scheduling of the press-pulse therapeutic strategy will facilitate the eradication of tumor cells with minimal patient toxicity. This therapeutic strategy can be used as a framework for the design of clinical trials for the non-toxic management of most cancers.
... KD was suggested to have anti-tumoral and anti-angiogenic effects which hampered the growth and vascularity of malignant tumors in animal models, and significantly reduced tumor growth and prolonged survival [15,18,19]. Yet, clinical studies of KD in patients with malignant brain tumors are very limited, reporting only small samples or case studies [7][8][9][10][11][12]20]. ...
Normal brain cells depend on glucose metabolism, yet they have the flexibility to switch to the usage of ketone bodies during caloric restriction. In contrast, tumor cells lack genomic and metabolic flexibility and are largely dependent on glucose. Ketogenic-diet (KD) was suggested as a therapeutic option for malignant brain cancer. This study aimed to detect metabolic brain changes in patients with malignant brain gliomas on KD using proton magnetic-resonance-spectroscopy ((1)H-MRS). Fifty MR scans were performed longitudinally in nine patients: four patients with recurrent glioblastoma (GB) treated with KD in addition to bevacizumab; one patient with gliomatosis-cerebri treated with KD only; and four patients with recurrent GB who did not receive KD. MR scans included conventional imaging and (1)H-MRS acquired from normal appearing-white-matter (NAWM) and lesion. High adherence to KD was obtained only in two patients, based on high urine ketones; in these two patients ketone bodies, Acetone and Acetoacetate were detected in four MR spectra-three within the NAWM and one in the lesion area -4 and 25 months following initiation of the diet. No ketone-bodies were detected in the control group. In one patient with gliomatosis-cerebri, who adhered to the diet for 3 years and showed stable disease, an increase in glutamin + glutamate and reduction in N-Acetyl-Aspartate and myo-inositol were detected during KD. (1)H-MRS was able to detect ketone-bodies in patients with brain tumors who adhered to KD. Yet it remains unclear whether accumulation of ketone bodies is due to increased brain uptake or decreased utilization of ketone bodies within the brain.
... The ketogenic diet and its calorie restricted variant that augments fasting responses, have been proposed to support anti-glioma therapy [190,191]. Indeed, bHB and acetoacetate exerted cytotoxic and growth inhibitory action on various cancer cells including lymphoma, melanoma, neuroblastoma, kidney and thyroid cancer cells [192,193]. Relatively mild adverse effects associated with ketogenic diet make it an ideal option for an adjunct anti-cancer regimen or even sometimes the main line of treatment. This approach turned out to be successful in treating malignant gliomas in experimental animals [194][195][196][197][198], and more importantly, for brain tumor patients [199][200][201]. ...
Ketogenesis and ketolysis are central metabolic processes activated during the response to fasting. Ketogenesis is regulated in multiple stages, and a nuclear receptor peroxisome proliferator activated receptor α (PPARα) is one of the key transcription factors taking part in this regulation. PPARα is an important element in the metabolic network, where it participates in signaling driven by the main nutrient sensors, such as AMP-activated protein kinase (AMPK), PPARγ coactivator 1α (PGC-1α), and mammalian (mechanistic) target of rapamycin (mTOR) and induces hormonal mediators, such as fibroblast growth factor 21 (FGF21). This work describes the regulation of ketogenesis and ketolysis in normal and malignant cells and briefly summarizes the positive effects of ketone bodies in various neuropathologic conditions.
... We note that there was an inexplicable (though not statistically significant) increase in acetone levels in the W group, which might also act as a source of enhanced ketogenesis [51]. While healthy cells, such as skeletal muscle cells, readily adapt to use ketones as an efficient energy substrate, some cancers cells do not exhibit this metabolic flexibility [52][53][54]. For instance, some neoplastic cells lack certain key mitochondrial enzymes and have thus a decreased ability to metabolise ketone bodies for energy production [53,[55][56][57]. ...
Background
Cachexia is one of the most important causes of cancer-related death. Supplementation with branched-chain amino acids, particularly leucine, has been used to minimise loss of muscle tissue, although few studies have examined the effect of this type of nutritional supplementation on the metabolism of the tumour-bearing host. Therefore, the present study evaluated whether a leucine-rich diet affects metabolomic derangements in serum and tumour tissues in tumour-bearing Walker-256 rats (providing an experimental model of cachexia).
Methods
After 21 days feeding Wistar female rats a leucine-rich diet, distributed in L-leucine and LW-leucine Walker-256 tumour-bearing groups, we examined the metabolomic profile of serum and tumour tissue samples and compared them with samples from tumour-bearing rats fed a normal protein diet (C – control; W – tumour-bearing groups). We utilised ¹H-NMR as a means to study the serum and tumour metabolomic profile, tumour proliferation and tumour protein synthesis pathway.
Results
Among the 58 serum metabolites examined, we found that 12 were altered in the tumour-bearing group, reflecting an increase in activity of some metabolic pathways related to energy production, which diverted many nutrients toward tumour growth. Despite displaying increased tumour cell activity (i.e., higher Ki-67 and mTOR expression), there were no differences in tumour mass associated with changes in 23 metabolites (resulting from valine, leucine and isoleucine synthesis and degradation, and from the synthesis and degradation of ketone bodies) in the leucine-tumour group. This result suggests that the majority of nutrients were used for host maintenance.
Conclusion
A leucine rich-diet, largely used to prevent skeletal muscle loss, did not affect Walker 256 tumour growth and led to metabolomic alterations that may partially explain the positive effects of leucine for the whole tumour-bearing host.
... For instance, a reciprocal association between blood glucose and KB levels has been shown in both mice [136] and human cancer patients [135]. The significance of high KBs lies in their ability to retard tumor growth [137][138][139][140]. For example, KBs inhibit glycolysis in both normal and cancer cells, but while normal tissues easily switch to KBs and fatty acids for fuel when glucose is limited, cancer cells in general cannot compensate for energy loss when glycolysis is impaired [21,22]. ...
The confluence of basic cell biochemistry, epidemiological and anthropologic evidence points to high dietary carbohydrate and the associated disruption of the glucose-insulin axis as causes of the current increase in metabolic disorders, metabolic syndrome, hypertension and cardiovascular disease. This hyperinsulinemic state likely contributes, as well, to an increased mutagenic microenvironment, with increased risk for cancer. This critical review discusses these risks in their historical and evolutionary context. The evidence supports the benefits of lowering the glycemic load of the diet as a preventive measure against the development of cancer.
... Cancer cells that are not able to metabolize bHB and acetoacetate frequently suffer from ketone body-induced toxicity, which has already been reported in neuroblastoma (30). Moreover, ketone bodies exert strong anti-proliferative and pro-apoptotic effects in melanoma, pancreatic, gastric, colon, and cervical cancer cells, as well as in transformed lymphoblasts (32)(33)(34)(35). These observations provide a rationale for proposing a dietary restricted KD as a supportive Ketogenesis in Melanoma and Glioblastoma Frontiers in Endocrinology | www.frontiersin.org ...
Ketone bodies (beta-hydroxybutyrate, bHB, acetoacetate) are mainly produced in the liver during prolonged fasting or starvation. bHB is a very efficient energy substrate for sustaining ATP production in peripheral tissues; importantly its consumption is preferred over glucose. However, the majority of malignant cells, particularly cancer cells of neuroectodermal origin such as glioblastoma, are not able to use ketone bodies as a source of energy. Here, we report a novel observation that fenofibrate, a synthetic peroxisome proliferator-activated receptor alpha (PPARa) agonist, induces bHB production in melanoma and glioblastoma cells, as well as in neurospheres composed of nontransformed cells. Unexpectedly, this effect is not dependent on PPARa activity or its expression level. The fenofibrate-induced ketogenesis is accompanied by growth arrest and down-regulation of transketolase, but the NADP/NADPH and GSH/GSSG ratios remain unaffected. Our results reveal a new, intriguing aspect of cancer cell biology and highlight the benefits of fenofibrate as a supplement to both canonical and dietary (ketogenic) therapeutic approaches against glioblastoma.
Background: Despite recent advances that have been made in cancer treatment, we still lack complementary approaches to significantly improve the effectiveness of current anti-cancer therapies. The high-fat, low-carbohydrate ketogenic diet can cause metabolic changes in the tumor microenvironment, thus targeting cancer metabolism, making it an attractive candidate for adjuvant cancer therapy. This review is an attempt to explore the origin and trace the historical use of the ketogenic diet as a metabolic therapy in medical oncology. Methods: A detailed literature review was conducted through specialized databases. Only those articles pertinent to the specific needs of the review were included. Relevant references in those articles were also followed. Results: There is a sound biological rationale for the anti-tumor force of the ketogenic diet primarily manifested through its anti-Warburg effect. It is no less true that Otto Warburg's experiments have based the ketogenic diet in cancer research on solid footing. However, precisely tracing the initial, original anti-tumor use of the keto-genic diet in medical oncology literature has indeed proved to be a hard needle to thread. The currently available data are considered promising in the pre-clinical rodent models. Yet, the number of rigorous human trials is small and suffers from methodological limitations. Conclusions: Further research, both pre-clinical and clinical, is needed to accurately define the anti-tumor effect of the ketogenic diet and to overcome the current methodological limitations that hinder us from deriving a sound judgment about the use of the ketogenic diet in clinical practice.
Ketogenic diets have been used to treat epilepsy for nearly a century. Alongside enduring clinical success with a ketogenic diet, metabolism’s critical role in health and in diseases in the central nervous system and throughout the body is increasingly appreciated. Furthermore, metabolism-based strategies have been proven equal or even superior to pharmacological treatments in specific cases and for specific diseases. Rather than causing unwanted off-target pharmacological side effects, addressing metabolic dysfunction can improve overall health simultaneously. Enduring interest in the ketogenic diet’s proven efficacy in stopping seizures and emerging efficacy in other disorders has fueled renewed efforts to determine key mechanisms and diverse applications of metabolic therapies. In parallel, multiple strategies are being developed to mobilize similar metabolic benefits without reliance on such a strict diet. Research interest in metabolic therapies has spread into laboratories and clinics of every discipline, and could yield entirely new classes of drugs and treatment regimens. This work is the first comprehensive scientific resource on the ketogenic diet, covering the latest research into the mechanisms, established and emerging applications, metabolic alternatives, and implications for health and disease. Experts in clinical and basic research share their research into mechanisms spanning from ion channels to epigenetics, their insights based on decades of experience with the ketogenic diet in epilepsy, and their evidence for emerging applications ranging from autism to Alzheimer’s disease to brain cancer.
Ketogenic diets have been used to treat epilepsy for nearly a century. Alongside enduring clinical success with a ketogenic diet, metabolism’s critical role in health and in diseases in the central nervous system and throughout the body is increasingly appreciated. Furthermore, metabolism-based strategies have been proven equal or even superior to pharmacological treatments in specific cases and for specific diseases. Rather than causing unwanted off-target pharmacological side effects, addressing metabolic dysfunction can improve overall health simultaneously. Enduring interest in the ketogenic diet’s proven efficacy in stopping seizures and emerging efficacy in other disorders has fueled renewed efforts to determine key mechanisms and diverse applications of metabolic therapies. In parallel, multiple strategies are being developed to mobilize similar metabolic benefits without reliance on such a strict diet. Research interest in metabolic therapies has spread into laboratories and clinics of every discipline, and could yield entirely new classes of drugs and treatment regimens. This work is the first comprehensive scientific resource on the ketogenic diet, covering the latest research into the mechanisms, established and emerging applications, metabolic alternatives, and implications for health and disease. Experts in clinical and basic research share their research into mechanisms spanning from ion channels to epigenetics, their insights based on decades of experience with the ketogenic diet in epilepsy, and their evidence for emerging applications ranging from autism to Alzheimer’s disease to brain cancer.
Ketogenic diets have been used to treat epilepsy for nearly a century. Alongside enduring clinical success with a ketogenic diet, metabolism’s critical role in health and in diseases in the central nervous system and throughout the body is increasingly appreciated. Furthermore, metabolism-based strategies have been proven equal or even superior to pharmacological treatments in specific cases and for specific diseases. Rather than causing unwanted off-target pharmacological side effects, addressing metabolic dysfunction can improve overall health simultaneously. Enduring interest in the ketogenic diet’s proven efficacy in stopping seizures and emerging efficacy in other disorders has fueled renewed efforts to determine key mechanisms and diverse applications of metabolic therapies. In parallel, multiple strategies are being developed to mobilize similar metabolic benefits without reliance on such a strict diet. Research interest in metabolic therapies has spread into laboratories and clinics of every discipline, and could yield entirely new classes of drugs and treatment regimens. This work is the first comprehensive scientific resource on the ketogenic diet, covering the latest research into the mechanisms, established and emerging applications, metabolic alternatives, and implications for health and disease. Experts in clinical and basic research share their research into mechanisms spanning from ion channels to epigenetics, their insights based on decades of experience with the ketogenic diet in epilepsy, and their evidence for emerging applications ranging from autism to Alzheimer’s disease to brain cancer.
The ketogenic diet (KD) is a high-fat, adequate-protein and very low-carb diet regimen that simulates/mimics the metabolism of the fasting state to stimulate the production of ketone bodies. KD has long stood out as a highly successful dietary approach for the treatment of epilepsy. According to the latest data, the therapeutic effect of KD seems promising for many diseases such as cancer, diabetes, obesity as well as epilepsy. Given the widespread practice of this diet, even among individuals who do not need to lose weight, there is some concern about the potential long-term consequences of widespread adoption of this diet by large sections of the population. In this review, prominent concepts related to KD and the KD are expressed, and experimental and/or clinical data on the efficacy and safety of KD in different diseases are summarized. The possible mechanisms of the understood effects of KD at the cellular and molecular level were discussed, emphasizing that there may be multiple mechanisms that need further clarification. Scientific data on the therapeutic effects and mechanisms of action of KD are insufficient, and more studies are required in order to expand the clinical application of KD.
Mounting evidence indicates that cancer is primarily a mitochondrial metabolic disease rather than a genetic disease. Abnormalities in cancer cell mitochondria impair oxidative phosphorylation, thus causing a gradual shift in cellular energy production from respiration to fermentation. Glucose and glutamine are the two major fermentable fuels for cancer cells. Glucose drives tumor growth through glycolysis in the cytoplasm, while glutamine drives tumor growth through glutaminolysis in the mitochondria. Restriction of fermentable fuels is therefore an effective therapeutic strategy for cancer management. Ketogenic metabolic therapy (KMT) lowers blood glucose while elevating blood ketone bodies, a “super fuel” for normal cells, but a nonfermentable fuel for cancer cells. The efficacy of KMT for cancer management can be enhanced when used together with glutamine-targeting drugs and procedures that further inhibit fermentation. Hence, KMT represents an alternative, nontoxic strategy for managing and preventing a broad range of cancers and could also be important in reducing healthcare costs in the emerging era of global budgeting.
The physiologic state of ketosis is characterized by decreased blood glucose, suppression of insulin, and an increase in the blood ketones β-hydroxybutyrate (βHB) and acetoacetate (AcAc), which serve as alternative sources of ATP in the brain. Ketones are elevated by fasting, caloric restriction, exercise, or the ketogenic diet (KD), and until recently these were the only known methods of inducing and sustaining ketosis in a nonpathologic setting. Many studies have revealed therapeutic effects of the KD, and data suggest that the benefits are mediated largely by ketone body metabolism and signaling. However, the KD often causes reduced patient compliance, which can make the KD a suboptimal long-term treatment. This has led researchers to develop exogenous ketone supplements—compounds that release or are metabolized into βHB and/or AcAc. The supplements rapidly elevate blood ketones in a dose-dependent manner, making them a practical method for inducing therapeutic ketosis. Ketone supplementation could potentially be used as stand-alone therapy in certain conditions, or possibly as a way to further augment the efficacy of the KD in the conditions in which it is being used or investigated, and it could increase compliance by allowing patients to maintain a less restrictive diet. Ketone supplements may also serve as an effective preventative medicine due to their potential to protect and enhance mitochondrial function. Preliminary evidence suggests there are several conditions for which ketone supplementation may be beneficial, including epilepsy, Alzheimer’s disease, glucose transporter type 1 deficiency syndrome, cancer, atrophy-related diseases, and metabolic syndrome.
Malignant brain tumors are devastating despite aggressive treatments, including surgical resection, chemotherapy, and radiation therapy. The average life expectancy of patients with newly diagnosed glioblastoma is approximately 18 months, and increased survival requires the design of new therapeutic modalities, especially those that enhance currently available treatments. One novel therapeutic arena is the metabolic dysregulation that results in an increased need for glucose in tumor cells. This phenomenon suggests that a reduction in tumor growth could be achieved by decreasing glucose availability, which can be accomplished through pharmacologic means or through the use of a high-fat, low-carbohydrate ketogenic diet (KD). Preclinical work has shown that the KD does indeed reduce tumor growth in vivo, and it reduces angiogenesis, inflammation, peritumoral edema, migration, and invasion. Furthermore, the KD can enhance the activity of radiation and chemotherapy in a mouse model of glioma, thus increasing survival. Additional studies in vitro have indicated that increasing ketones in the absence of glucose reduction can also inhibit cell growth and potentiate the effects of radiation. The pluripotent effects exhibited by ketogenic therapy may be due, in part, to epigenetic changes. The main ketone, β-hydroxybutyrate, is a class 1 histone deacetylase inhibitor, and we have shown that the expression of a number of microRNAs is altered in tumors of mice fed a KD compared to standard diet. Thus, the emerging data provide strong support for the use of a KD in the treatment of malignant gliomas.
Chronic disease states of aging should be viewed through the prism of metabolism and biophysical processes at all levels of physiological organization present in the human body. This book connects these insights to what causes them to go awry in the context of unhealthy human behaviors and aging, aiming to buttress scientific creativity. It also provides links between the art and science of medicine that strengthens problem-solving in patient care. New and important discoveries in the area of metabolic health and metabolic diseases are discussed in exquisite detail. Key Features: Broad and up-to-date overview of the field of metabolic aspects of health and chronic disease development, especially connecting the spectrum of topics that range from molecular clocks to stress response to nuclear hormone receptors and the role of microbiota in human health Provides a deeper basic science and interdisciplinary understanding of biological systems that broaden the perspectives and therapeutic problem solving by elaborating on the usefulness of the Physiological Fitness Landscape Describes the importance of insulin resistance in metabolic disease, especially diabetes but also includes links to cancer and Alzheimer's disease Examines the process of aging from the perspective of metabolic decline illustrating it with the Physiological Fitness Landscape This book, the second volume in a two-volume set, primarily targets an audience of clinical and science students, biomedical researchers and physicians who would benefit from understanding each other's language.
Background
Aberrant metabolism is recognized as a hallmark of cancer, a pillar necessary for proliferation. Regarding bioenergetics (ATP-generation), most cancers display a preference towards aerobic glycolysis (“Warburg effect”) and glutaminolysis (mitochondrial substrate level-phosphorylation), but also other metabolites such as lactate, pyruvate, and fat-derived sources. These secondary metabolites can assist in proliferation but cannot fully cover ATP demands.
Scope of Review
The concept of a static metabolic profile is challenged by instances of heterogeneity and flexibility to meet fuel/anaplerotic demands. Although metabolic therapies are a promising tool to improve therapeutic outcomes, either via pharmacological targets or press-pulse interventions, metabolic plasticity is rarely considered. Lack of bioenergetic analysis in vitro and patient-derived models is hindering translational potential. Here, we review the bioenergetics of cancer and propose a simple analysis of major metabolic pathways, encompassing both affordable and advanced techniques. A comprehensive compendium of Seahorse XF bioenergetic measurements is presented for the first time.
Major conclusions
Standardization of principal readouts might help researchers collect a complete metabolic picture of cancer using the most appropriate methods depending on the sample of interest.
Brustkrebs ist die häufigste maligne Erkrankung der Frau. Die Therapie setzt sich in der Regel individuell aus den Bausteinen der chirurgischen Tumorexzision, der Bestrahlung und der systemischen Therapie zusammen. Daneben gewinnt die ketogene Diät als supportiver Therapieansatz immer mehr an Aufmerksamkeit und Forschungsinteresse. Diese Ernährungsform imitiert durch starke Restriktion der Kohlenhydratzufuhr den Fastenstoffwechsel, da Blutzucker- und konsekutiv auch Insulinspitzen im Blut vermieden werden. Eine tragende Rolle kommt dabei der Bildung von Ketonkörpern, allen voran Betahydroxybutyrat, zu, die sowohl in den Tumorstoffwechsel als auch in immunologische Prozesse eingreifen können. In dieser Arbeit wurde ausgewählten Brustkrebszellen 3 mM Betahydroxybutyrat zugesetzt und ihr Wachstumsverhalten, ihre Chemo- und Radiosensitivität im Vergleich zu Kontrollzellen erfasst. Die Kontrollzellen wurden identisch behandelt, jedoch wurde Ihnen kein Betahydroxybutyrat zugefügt. Es zeigte sich dabei kein statistisch signifikanter Unterschied zwischen den beiden Zellgruppen.
Introduction:
Complementary and alternative medicine (CAM) are highly utilized amongst those diagnosed with glioma. Further research is warranted, however, as it remains important to clearly delineate CAM practices that are unproven, disproven, or promising for future research and implementation.
Methods:
A systematic review was conducted to identify all articles that investigated the effect of any CAM therapy on survival of patients with newly diagnosed or recurrent glioma.
Results:
Eighteen papers and 4 abstracts pertaining to the effects of: ketogenic diet (4), antioxidants (3), hyperbaric oxygen (4), cannabinoids (CBD) (2), carbogen and nicotinamide (3), mistletoe extract (2), hypocupremia and penicillamine (1), and overall CAM use (3) on overall (OS) and progression-free survival (PFS) in patients with low- and high-grade glioma were identified (Levels of Evidence I-IV). Ketogenic diets, hyperbaric oxygen therapy and cannabinoids appear to be safe and well tolerated by patients; preliminary studies demonstrate tumor response and increased PFS and OS when combined with standard of care therapies. Antioxidant usage exhibit mixed results perhaps associated with glioma grade with greater effect on low-grade gliomas; vitamin D intake was associated with prolonged survival. Conversely, carbogen breathing and hypocupremia were found to have no effect on glioma patient survival, with associated significant toxicity. Most modalities under the CAM umbrella have not been appropriately studied and require further investigation.
Conclusion:
Despite widespread use, Level I or II evidence for CAM for the treatment of glioma is lacking, representing future research directions in order to optimally counsel and treat glioma patients.
Cancer cells (CCs) predominantly use aerobic glycolysis (Warburg effect) for their metabolism. This important characteristic of CCs represents a potential metabolic pathway to be targeted in the context of tumor treatment. Being this mechanism related to nutrient oxidation, dietary manipulation has been hypothesized as an important strategy during tumor treatment. Ketogenic diet (KD) is a dietary pattern characterized by high fat intake, moderate-to-low protein consumption, and very-low-carbohydrate intake (<50 g), which in cancer setting may target CCs metabolism, potentially influencing both tumor treatment and prognosis. Several mechanisms, far beyond the originally proposed inhibition of glucose/insulin signaling, can underpin the effectiveness of KD in cancer management, ranging from oxidative stress, mitochondrial metabolism, and inflammation. The role of a qualified Nutritionist is essential to reduce and manage the short and long-term complications of this dietary therapy, which must be personalized to the individual patient for the planning of tailored KD protocol in cancer patients. In the present review, we summarize the proposed antitumor mechanisms of KD, the application of KD in cancer patients with obesity and cachexia, and the preclinical and clinical evidence on KD therapy in cancer.
The beneficial impacts of the ketogenic diet and metabolic reprograming were recently reported for ovarian cancer patients. In this study, the effects of glucose restriction with or without beta-hydroxybutyrate (bHB) enrichment were studied in drug-resistant CD133high A2780CP and CD133low SK-OV-3 ovarian cancer cells to scrutinize the impact of experimental ketosis on ATP production, epithelial to mesenchymal transition (EMT), and related signaling pathways including Wnt, Hippo, and Hedgehog. Cells were adapted and maintained for a month with restricted levels of glucose (250 mg/l) with or without the therapeutic concentration of bHB (5 mM). Quantitative PCR, Western blot analysis, flow cytometry, chemiluminescence, and wound healing assay were used in this study. Glucose restriction and bHB enrichment reduced the stemness marker and diminished In Vitro migration in both cell lines. Glucose restriction significantly reduced ATP levels in both cells, but bHB enrichment was partially compensated for the ATP levels solely in SK-OV-3 cells. Glucose restriction mainly inhibited the Wnt pathway in the CD133high A2780CP cells, but the Hedgehog pathway was the main target in CD133low SK-OV-3 cells. In Conclusion, Prior targeted evaluations of key genes' expression would help to predict the distinctive impacts of metabolic fuels and to optimize the efficacy of ketogenic diets.
This review aims to answer to two basic questions: a) Which substrates does a tumour utilize and is there a regimen that might potentially favour the host over the tumour? and b) Does nutritional intervention disproportionally affect tumour growth? Literature to date focuses on humans; although some references to molecular mechanisms regulating cancer cells metabolism derive from studies on experimental tumours and cell biology. Literature shows that some tumours, especially those of the brain and head/neck and lung, are glucose-dependent, and patients with these tumours could benefit from a normocaloric ketogenic diet provided these tumours exhibit high fluorodeoxyglucose (¹⁸F-FDG) captation. A high fat-protein, low carbohydrate diet appears to better fulfil the nutritional requirements of the cancer patient. Current evidence shows no improvement in tumoral response after restricting patients' caloric intake; whereas malnutrition is acknowledged as an important negative predictive and prognostic factor in all cancer patients.
Background
Ketogenic metabolic therapy (KMT) using ketogenic diets (KD) is emerging as viable alternative or complementary strategy for managing cancer; however, few clinical trials have been reported. The present study aimed to evaluate the effects of a KD in patients with locally advanced and metastatic breast cancer receiving chemotherapy.
Methods
A total of 80 patients undergoing treatment with chemotherapy were randomly assigned to KD or control group for 12 weeks. Concurrent with the admission, midway point, and at 12 weeks, fasting blood samples were collected for evaluation of insulin, IGF-1, CEA, CA15-3, ESR, CRP, IL-10, and TNF-α. Sonography for patients with locally advanced disease and CT or MRI scans for patients with metastatic disease were done on admission and at 12 weeks. At the completion of the chemotherapy, patients with locally advanced disease underwent surgery and stage was recalculated. Also patients with metastases were evaluated for response rate.
Results
TNF- α decreased significantly after 12 weeks of treatment (MD: 0.64 [CI 95%: -3.7, 5] P<0.001), while IL-10 increased (MD: 0.95 [CI 95%: -1,3] P < 0.001) in the intervention compared to the control group. Patients in the KD group had lower adjusted serum insulin compared to the control group (MD:-1.1 [CI 95%: -3,1] p < 0.002). KD lead to a reduction in tumor size in the KD compared to the control (27 vs 6 mm, P=0.01). Stage decreased significantly in patients with locally advanced disease in the KD group after 12 weeks (P < 0.01). No significant differences in response rate were observed in patients with metastatic disease.
Conclusions
KMT in breast cancer patients might exert beneficial effects through decreasing TNF- α and insulin and increasing IL-10. KD may result in a better response through reductions in tumor size and downstaging in patients with locally advanced disease; however, more studies are needed to elucidate the potential beneficial effects of KD in patients with metastases.
Trial registration
This trial has been registered on Iranian Registry of Clinical Trials (IRCT) under the identification code: IRCT20171105037259N2. https://www.irct.ir/trial/30755.
The way cancer cells utilize nutrients to support their growth and proliferation is determined by cancer cell-intrinsic and cancer cell-extrinsic factors, including interactions with the environment. These interactions can define therapeutic vulnerabilities and impact the effectiveness of cancer therapy. Diet-mediated changes in whole-body metabolism and systemic nutrient availability can affect the environment that cancer cells are exposed to within tumours, and a better understanding of how diet modulates nutrient availability and utilization by cancer cells is needed. How diet impacts cancer outcomes is also of great interest to patients, yet clear evidence for how diet interacts with therapy and impacts tumour growth is lacking. Here we propose an experimental framework to probe the connections between diet and cancer metabolism. We examine how dietary factors may affect tumour growth by altering the access to and utilization of nutrients by cancer cells. Our growing understanding of how certain cancer types respond to various diets, how diet impacts cancer cell metabolism to mediate these responses and whether dietary interventions may constitute new therapeutic opportunities will begin to provide guidance on how best to use diet and nutrition to manage cancer in patients.
Background:
Hepatocellular carcinoma (HCC) ranks as the sixth most prevalent cancer and the third leading cause of tumor-related death, so it is urgently needed to discover efficient markers and targets for therapy. β-1,3-N-acetylgalactosaminyltransferase II (B3GALNT2) belongs to the β-1,3-glycosyltransferases (b3GT) family and has been reported to regulate development of both normal and tumor tissues. However, studies on the functions of B3GALNT2 in cancer are quite limited. Here we investigated the potential role of B3GALNT2 in HCC progression.
Methods:
Western blot, qPCR, and immunohistochemistry assays were performed to quantify the relative expression of B3GALNT2 in HCC. The functions of B3GALNT2 in tumor progression were evaluated in HCC cell lines and nude mice. Metabolomics analysis was applied to detect alternatively expressed small molecules. Enzyme activity assays were employed to determine the tautomerase activity of macrophage inhibitory factor (MIF).
Results:
For expression analysis, higher levels of B3GALNT2 were observed in tumor tissues compared with adjacent normal tissues, and upregulation of B3GALNT2 correlated with increased tumor size and worse overall survival. Changing levels of B3GALNT2 did not influence cell viability in vitro but promoted tumor growth via enhancing macrophage recruitment in vivo. Furthermore, acetoacetate was identified as a key molecule in B3GALNT2-mediated macrophage recruitment. Mechanistically, B3GALNT2 downregulated expression of enzymes involved in acetoacetate-related metabolism, and reduction of acetoacetate revived MIF activity, thus promoting macrophage recruitment.
Conclusions:
This study evaluated B3GALNT2 as a tumor marker in HCC and revealed functions of B3GALNT2 in metabolic transformation and microenvironmental remodeling in HCC. Mechanistically, B3GALNT2 reduced expression of some metabolic enzymes and thus downregulated levels of secreted acetoacetate. This relieved the activity of MIF and enhanced macrophage recruitment to promote tumor growth.
Software Much scientific research makes use of commonly available 'office' software. While numerous more fully-featured open-source alternatives exist, the integration of diverse tools and platforms which their use often entails can be challenging. The mp package for Emacs aims to bring together a number of these elements with the goal of simplifying the process of converting an .R file, as used for data analysis, to a nicely formatted .pdf which includes the complete description of the methods and interpretation. We discuss the rationale for development of the package and illustrate its applications and options with a series of experiments from our laboratory. Experimental work We demonstrate the inhibitory effects of the ketone body \emph(beta)-hydroxybutyrate (BHB) on the growth and motility of a cancer cell line. BHB is produced endogenously; levels may be increased in certain medial conditions e.g. diabetic ketoacidosis. They may also be raised voluntarily e.g. by adopting the ketogenic diet. BHB is known to inhibit the growth of other neoplastic cell lines. However the finding that it can do so in a cell line selected for their propensity to metastasize to the brain is novel. Given the challenges in treating patients with melanoma metastatic to brain, this work strengthens the rationale for investigating the ketogenic diet as a potential adjunct to treatment in such cases.
Research of the last two decades showed that chronic low-grade inflammation, elevated blood glucose and insulin levels may play role in the onset of a number of non-communicable diseases such as type 2 diabetes and some forms of cancer. Regular exercise and fasting can ameliorate high blood glucose and insulin levels as well as increase the concentration of plasma ketone bodies. These, in consequence, may lead to reduction of inflammation. Exercise or severe restriction of caloric intake is not always advisable for patients, in particular those suffering from cancer. The ketogenic diet (KD), characterized by high fat, moderate protein and very low carbohydrate composition can evoke a physiological state similar to that triggered by exercise or fasting. These attributes of KD prompted its possible use in treatment of a number of metabolic diseases, including several types of malignancies. Although results from clinical studies employing KD in the treatment of cancer are still limited, the results obtained from animal models are encouraging and show that KD presents a viable option as an adjunct therapy for cancer.
Altered metabolism was first identified in cancer cells by Otto Warburg, who identified a higher reliance on anaerobic glycolysis rather than cellular respiration even in the presence of sufficient oxygen levels, a phenomenon called the Warburg Effect. Deregulated metabolism is now considered a driving hallmark of cancer and an attractive therapeutic target. While a great deal of work is being done to find genetic therapeutic targets that can be used for personalized medicine, current targeted approaches are typically ineffective because tumors are heterogeneous and contain multiple genetic subpopulations. This often precludes a particular targeted molecule from being found on all cells. In contrast to many genetic alterations, dysregulation of metabolism resulting in the need for high amounts of glucose is found in virtually all cancer cells. Targeting metabolism by reducing blood glucose may be a way to inhibit tumor growth since this, to a large extent, should circumvent the inherent problems associated with tumor heterogeneity. Methods that also provide an energy source for normal tissues such as ketones should reduce side effects associated with an overall reduction in blood glucose. The high-fat, low carbohydrate, and protein ketogenic diet (KD) results in reduced blood glucose and increased blood ketones, as does caloric restriction and fasting. In preclinical mouse models of malignant brain tumors, animals fed a KD had increased survival, particularly when used in combination with radiation or chemotherapy. Metabolic modulation through the use of a KD, caloric restriction, or fasting has been found to change the expression of a number of genes and pathways thought to inhibit tumor growth. Metabolic therapy has also recently been explored in other cancer types. In this chapter, we will examine the mechanisms underlying the KD which suggests its potential as an adjuvant therapy for cancer treatment.
Despite considerable progress in the clinical management of diabetic pregnancy, the incidence of congenital malformations is approximately three times greater in infants of diabetic mothers than in the offspring of nondiabetic women (1–6). Congenital malformations observed in the infants of diabetic mothers more often tend to be multiple, more severe, and lethal than those seen in infants of nondiabetic mothers (3,5,6). The incidence of congenital malformations has not changed over the last few decades, whereas that of almost all other complications has decreased (4). The relative importance of malformations has therefore increased, and they are presently the most common cause of perinatal death among infants of diabetic mothers (5).
Enzymes of ketogenesis were measured in homogenates of liver, kidney, brain, intestine, heart, muscle, and three transplantable hepatomas of the rat. Cholesterol synthesis from acetate-2-¹⁴C was studied in slices from these tissues. The results show that high levels of β-hydroxy-β-methylglutaryl coenzyme A synthase are unique to liver and the well differentiated hepatomas, and thus provide a biochemical basis for liver's role as the primary ketogenic organ. The ability to synthesize cholesterol from acetate was similar in liver, intestine, and immature brain, all of which contained adequate β-hydroxy-β-methylglutaryl-CoA synthase to support the observed rates of cholesterogenesis. The failure of the undifferentiated hepatoma 3924A to synthesize acetoacetate or cholesterol from acetate was consistent with its lack of β-hydroxy-β-methylglutaryl-CoA synthase.
The living cell is characterized by both its potential for change and its tendency towards a stable state. The interaction between the DNA information system and the metabolic steady state is described. A model based on this interaction leads to the conclusion that change can only be initiated from the environment but that the direction of any change is determined by the cell.
Sodium butyrate produces reversible changes in morphology, growth rate, and enzyme activities of several mammalian cell types in culture. Some of these changes are similar to those produced by agents which increase the intracellular level of adenosine 3',5'-cyclic monophosphate (cAMP) or by analogs of cAMP. Sodium butyrate increases the intracellular level of cAMP by about two fold in neuroblastoma cells; therefore, some of the effects of sodium butyrate on these cells may in part be mediated by cAMP. Sodium butyrate appears to have properties of a good chemotherapeutic agent for neuroblastoma tumors because the treatment of neuroblastoma cells in culture causes cell death and "differentiation"; however, it is either innocuous or produces reversible morphological and biochemical alterations in other cell types.
Fatty acid oxidation, reconstituted substrate shuttles, and the activity of the citric acid cycle were studied in mitochondria isolated from Becker transplantable hepatocellular carcinoma H-252 AND Host livers, and the results were compared with those obtained with Morris hepatomas 7288CTC and 5123C. Whereas the activities of the malate-aspartate and the alpha-glycerophosphate shuttles were only slightly lower than those of host livers, the activity of the fatty acid shuttle was much lower in H-252 mitochondria. Oxygen uptake and CO2 production associated with the oxidation of fatty acids was much lower in tumors H-252 and 7288CTC, compared with host livers, whereas tumor 5123C mitochondria show a high capacity to oxidize fatty acids. Ketogenesis and beta-hydroxybutyrate dehydrogenase activity were also lower in tumor H-252 mitochondria. However, neither oxygen uptake associated with the oxidation of other respiratory substrates nor CO2 production from succinate or malate was strikingly elevated in these tumors. These factors suggest that the respiratory phosphorylation chain and activity of the citric acid cycle are fully functional in tumors H-252 and 7288CTC. The defects responsbile for the lower rates of fatty acid oxidation in these tumors probably involves the beta-oxidation pathway, as well as the activation of fatty acids. The impairment of fatty acid oxidation may explain the lower activity of the reconstituted fatty acid shuttle for transporting reducing equivalents into H-252 mitochondria. The different properties with regard to fatty acid oxidation in Morris hepatoma 5123C, compared with those in Becker H-252- AND Morris hepatoma 7288CTC, may reflect the different extent of differentiation in these tumors, the former being a slow-growing, well-differentiated tumor, whereas the latter represent tumors that are less differentiated and of more rapid growth rate.
1. The role of enhanced aerobic glycolysis in the transformation of rat thymocytes by concanavalin A has been investigated. Concanavalin A addition doubled [U-(14)C]glucose uptake by rat thymocytes over 3h and caused an equivalent increased incorporation into protein, lipids and RNA. A disproportionately large percentage of the extra glucose taken up was converted into lactate, but concanavalin A also caused a specific increase in pyruvate oxidation, leading to an increase in the percentage contribution of glucose to the respiratory fuel. 2. Acetoacetate metabolism, which was not affected by concanavalin A, strongly suppressed pyruvate oxidation in the presence of [U-(14)C]glucose, but did not prevent the concanavalin A-induced stimulation of this process. Glucose uptake was not affected by acetoacetate in the presence or absence of concanavalin A, but in each case acetoacetate increased the percentage of glucose uptake accounted for by lactate production. 3. [(3)H]Thymidine incorporation into DNA in concanavalin A-treated thymocyte cultures was sensitive to the glucose concentration in the medium in a biphasic manner. Very low concentrations of glucose (25mum) stimulated DNA synthesis half-maximally, but maximum [(3)H]thymidine incorporation was observed only when the glucose concentration was raised to 1mm. Lactate addition did not alter the sensitivity of [(3)H]-thymidine uptake to glucose, but inosine blocked the effect of added glucose and strongly inhibited DNA synthesis. 4. It is suggested that the major function of enhanced aerobic glycolysis in transforming lymphocytes is to maintain higher steady-state amounts of glycolytic intermediates to act as precursors for macromolecule synthesis.
The binding of insulin to a specific receptor on IM-9-cultured human lymphocytes was studied in vitro under conditions simulating diabetic ketoacidosis. Compared with control incubations at pH 7.4, binding was reduced by 19 per cent at pH 7.1 and by 48 per cent at pH 6.8. Addition of beta-hydroxybutyrate, at concentrations similar to those seen clinically, "restored" insulin binding toward normal. We suggest that, by counteracting the effects of acidosis, ketoacids themselves maintain normal insulin-receptor binding in diabetic ketoacidosis. These data also illustrate that small molecules, present in vivo, can significantly alter the interactions between a hormone and its receptor in vitro.
Methods are described for simultaneous continuous in vivo monitoring of blood glucose, lactate, alanine and 3-hydroxybutyrate. The methods use dialysis, immobilized enzymes and measure generated reduced pyridine nucleotides fluorimetrically. The methods are accurate, sensitive, stable, and are suitable for use in emergency situations or in clinical investigation.
Previous studies have indicated that marked alterations in the proliferative activity of the murine intestinal epithelium can be induced through noninjurious fasting and refeeding. The response to refeeding is especially pronounced in the colon, where proliferative activity exceeds twice the control levels within 12 to 16 hr. In the present study, the role of specific dietary components in the control of the colonic refeeding response and in normal colonic cell renewal was investigated. The results indicate that the colonic refeeding response is dependent upon the presence of sugar, amino acids and minerals, in the form of salts, in the refed diet. In the nonfasting animal, normal colonic cell renewal also requires dietary minerals. The absence of minerals in a maintenance diet results in a marked hypoproliferative state which can be reversed by reintroducing the mineral component of the diet. That the depressed proliferative rate observed with a salt-free diet is not the result of a caloric depletion is evidenced by the maintenance of body weight throughout the experimental period. These findings suggest a potential role for specific dietary components in the control of the colonic cell proliferation, maintenance of the steady state cell renewal system, and represent a tool by which the proliferative activity of the gut may be manipulated.
Male rats were starved for a period of 96 hours. Measurements of crypt cell population showed a small reduction during starvation. The growth fraction remained constant, but the total number of proliferating cells per crypt fell as a consequence of the reduction in crypt population. Both labelling and mitotic indices fell throughout the starvation period. The cell cycle time (Tc), measured by a stathmokinetic technique using vincristine, was increased from 10-4 hours in control rats to 14-7 hours after 96 hours' starvation. Upon refeeding, the proliferative indices were observed to rise. After a small initial fluctuation, the growth fraction remained constant. The crypt population remained substantially unchanged. Sixteen hours after refeeding, the cell cycle time was reduced to 6-5 hours. The hypoproliferative response to starvation is mediated solely by an increase in cell cycle time, and the response to refeeding is interpreted in terms of a reduction in Tc. Changes in the size of the proliferating population are considered not to play an important role in either response, although it is not possible to exclude entirely the presence of resting cells in the proliferative compartment itself.
SUMMARY The interaction of normal, tumor-bearing, nonspecifically sensitized, and immunized syngeneic lymphocytes and the B16 melanoma was tested in vivo by experimental pulmo nary métastases. Various numbers of lymphocytes were mixed and incu bated with the tumor cells for 90 min on a rotating platform, and then the mixtures were injected i.v. into C57BL/6 mice. Normal, tumor-bearing, and nonspecifically sensitized lym phocytes mixed with tumor cells significantly increased the incidence of experimental metastasis. On the other hand, a high number (5000:1) of immunized syngeneic lympho cytes mixed with the B16 melanoma cells brought about a dramatic decrease in the incidence of subsequent pulmonary métastases. Following the in vitro incubation of tumor cells with syngeneic lymphocytes, clumping of tumor cells was observed. The relative importance of this clumping phenom enon to the outcome of experimental metastasis is dis cussed. Mice that were either immunized against the B16 mela noma or thymectomized and X-irradiated demonstrated a significant decrease in incidence of experimental pulmonary metastasis following i.v. injection of tumor cells as com pared to normal, thymectomized. or X-irradiated mice. The decrease in pulmonary métastases in thymectomized X- irradiated mice was completely reversible with i.v. injection of 1 x IO7syngeneic tumor-bearing lymphocytes adminis tered 24 hr prior to tumor cell injection. On the other hand, administration of 1 x 10"syngeneic tumor-bearing lympho cytes brought about a significant decrease in the incidence of pulmonary métastases in all experimental groups. These results further support the hypothesis and work of Prehn and our earlier reports, that the immune response may have a dual role in its relationship to the development, progres sion, and perhaps the spread of cancer.
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