[Show abstract][Hide abstract] ABSTRACT: Recombinant human growth hormone (rhGH) has been in use for 30 years, and over that time its safety and efficacy in children and adults has been subject to considerable scrutiny. In 2001, a statement from the GH Research Society (GRS) concluded that 'for approved indications, GH is safe'; however, the statement highlighted a number of areas for on-going surveillance of long-term safety including; cancer risk, impact on glucose homeostasis and use of high dose pharmacological rhGH treatment. Over the intervening years, there have been a number of publications addressing the safety of rhGH with regard to mortality, cancer and cardiovascular risk and the need for longterm surveillance of the increasing number of adults who were treated with rhGH in childhood. Against this backdrop of interest in safety, the European Society of Paediatric Endocrinology (ESPE), the GRS and the Pediatric Endocrine Society (PES) convened a meeting to reappraise the safety of rhGH. The ouput of the meeting is a concise position statement.
Full-text · Article · Nov 2015 · European Journal of Endocrinology
[Show abstract][Hide abstract] ABSTRACT: Low insulin-like growth factor-1 (IGF-1) signaling is associated with improved longevity, but is paradoxically linked with several age-related diseases in humans. Insulin-like growth factor-1 has proven to be particularly beneficial to the brain, where it confers protection against features of neuronal and cognitive decline. While aging is characterized by central insulin resistance in the face of hyperinsulinemia, the somatotropic axis markedly declines in older humans. Thus, we hypothesized that increasing IGF-1 in the brain may prove to be a novel therapeutic alternative to overcome central insulin resistance and restore whole-body insulin action in aging. Utilizing hyperinsulinemic-euglycemic clamps, we show that old insulin-resistant rats with age-related declines in IGF-1 level demonstrate markedly improved whole-body insulin action, when treated with central IGF-1, as compared to central vehicle or insulin (P < 0.05). Furthermore, central IGF-1, but not insulin, suppressed hepatic glucose production and increased glucose disposal rates in aging rats (P < 0.05). Taken together, IGF-1 action in the brain and periphery provides a 'balance' between its beneficial and detrimental actions. Therefore, we propose that strategies aimed at 'tipping the balance' of IGF-1 action centrally are the optimal approach to achieve healthy aging and longevity in humans.
[Show abstract][Hide abstract] ABSTRACT: Humanin is a peptide that is cytoprotective against stresses in many cell types. We investigated whether a potent humanin analogue HNG would protect against chemotherapy-induced damage to normal cells without interfering with the chemotherapy-induced suppression of cancer cells. Young adult male mice were inoculated intravenously with murine melanoma cells. After 1-week, cancer-bearing mice were randomized to receive either: no treatment; daily intraperitoneal injection of HNG; a single intraperitoneal injection of cyclophosphamide (CP); or CP+HNG and killed at the end of 3-weeks. HNG rescued the CP-induced suppression of leucocytes and protected germ cell from CP-induced apoptosis. Lung metastases were suppressed by HNG or CP alone, and further suppressed by CP+HNG treatment. Plasma IGF-1 levels were suppressed by HNG with or without CP treatment. To investigate whether HNG maintains its protective effects on spermatogonial stem cells (SSCs), sperm output and peripheral leucocytes after repeated doses of CP, normal adult male mice received: no treatment; daily subcutaneously injection of HNG; six IP injections of CP at 5-day intervals; and the same regimens of CP+HNG and killed at the end of 4-weeks of treatment. Cauda epididymal sperm counts were elevated by HNG and suppressed by CP. HNG rescued the CP-induced suppression of SSCs, sperm count and peripheral leucocytes. We conclude that HNG: 1) protects CP-induced loss of male germ cells and leucocytes; 2) enhances CP-induced suppression of cancer metastases; and 3) acts as a caloric-restriction mimetic by suppressing IGF-1 levels. Our findings suggest that humanin analogues may be promising adjuvants to chemotherapy.
[Show abstract][Hide abstract] ABSTRACT: Prolonged fasting (PF) promotes stress resistance, but its effects on longevity are poorly understood. We show that alternating PF and nutrient-rich medium extended yeast lifespan independently of established pro-longevity genes. In mice, 4 days of a diet that mimics fasting (FMD), developed to minimize the burden of PF, decreased the size of multiple organs/systems, an effect followed upon re-feeding by an elevated number of progenitor and stem cells and regeneration. Bi-monthly FMD cycles started at middle age extended longevity, lowered visceral fat, reduced cancer incidence and skin lesions, rejuvenated the immune system, and retarded bone mineral density loss. In old mice, FMD cycles promoted hippocampal neurogenesis, lowered IGF-1 levels and PKA activity, elevated NeuroD1, and improved cognitive performance. In a pilot clinical trial, three FMD cycles decreased risk factors/biomarkers for aging, diabetes, cardiovascular disease, and cancer without major adverse effects, providing support for the use of FMDs to promote healthspan.
[Show abstract][Hide abstract] ABSTRACT: Human (HN) prevents stress-induced apoptosis in many cells/tissues. In this study we showed that HN ameliorated chemotherapy [cyclophosphamide (CP) and Doxorubicin (DOX)]-induced male germ cell apoptosis both ex vivo in seminiferous tubule cultures and in vivo in the testis. HN acts by several putative mechanisms via binding to: an IL-12 like trimeric membrane receptor; BAX; or insulin-like growth factor binding protein-3 (IGFBP-3, a proapoptotic factor). To understand the mechanisms of HN on male germ cell apoptosis, we studied five HN analogues including: HNG (HN-S14G, a potent agonist), HNG-F6A (no binding to IGFBP-3), HN-S7A (no self-dimerization), HN-C8P (no binding to BAX), and HN-L12A (a HN antagonist) on CP-induced male germ cell apoptosis in mice. CP-induced germ cell apoptosis was inhibited by HN, HNG, HNG-F6A, HN-S7A, and HN-C8P (less effective); but not by HN-L12A. HN-L12A, but not HN-S7A or HN-C8P, blocked the protective effect of HN against CP-induced male germ cell apoptosis. HN, HN-S7A, and HN-C8P restored CP-suppressed STAT3 phosphorylation. These results suggest that HN: (1) decreases DOX (ex vivo) and CP (in vivo) induced male germ cell apoptosis; (2) action is mediated by the membrane receptor/STAT3 with minor contribution by BAX-binding pathway; (3) self-dimerization or binding to IGFBP-3 may not be involved in HN's effect in testis. HN is an important molecule in the regulation of germ cell homeostasis after injury and agonistic analogues may be developed for treating male infertility or protection against chemotherapy side effects.
[Show abstract][Hide abstract] ABSTRACT: Diabetes mellitus (DM) is associated with a loss of renal and vascular protection in women compared with men, but the responsible mechanisms are unclear. Recent experimental work implicated humanin (HN) as a novel cytoprotective hormone in DM. Our goal was to measure sex-related differences in HN levels in uncomplicated type 1 DM patients (T1D) and healthy controls (HC), as well as the interaction between HN, circulating neurohormones, and vascular function. Plasma HN, cGMP and aldosterone, blood pressure (BP), glomerular filtration rate, and effective renal plasma flow (inulin and para-aminohippurate) were measured in HC (11 men, 10 women) and T1D (23 men and 18 women) during clamped euglycemia (4-6 mmol·L(-1)). Plasma HN levels were generally lower in HC men by comparison with the women, but the differences were not statistically significant. In contrast, levels in the T1D men were higher compared with the T1D women (p = 0.026) and HC men (p < 0.0001). In the HC men, but not the women, HN correlated negatively with BP, but not with renal function, cGMP, or aldosterone. In the T1D men, HN negatively correlated with plasma cGMP. In the T1D women, HN did not correlate with neurohormones or vascular function. Future work should determine the role of HN in the pathogenesis of sex-related vascular function differences in DM.
No preview · Article · Dec 2014 · Canadian Journal of Physiology and Pharmacology
[Show abstract][Hide abstract] ABSTRACT: Aging is influenced by endocrine pathways including the growth hormone/insulin-like growth factor-1 (GH/IGF) axis. Mitochondrial function has also been linked to the aging process, but the relevant mitochondrial signals mediating the effects of mitochondria are poorly understood. Humanin is a novel signaling peptide that acts as a potent regulator of cellular stress responses and protects from a variety of in vitro and in vivo toxic and metabolic insults. The circulating levels of humanin decline with age in mice and humans. Here, we demonstrate a negative correlation between the activity of the GH-IGF axis and the levels of humanin, as well as a positive correlation between humanin and lifespan in mouse models with altered GH/IGF-I axis. Long-lived, GH-deficient Ames mice displayed elevated humanin levels, while short-lived GH-transgenic mice have reduced humanin levels. Furthermore, treatment with GH or IGF-I reduced circulating humanin levels in both mice and human subjects. Our results indicate that GH and IGF are potent regulators of humanin levels and that humanin levels correlate with lifespan in mice. This suggests that humanin represents a circulating mitochondrial signal that participates in modulating the aging process, adding a coordinated mitochondrial element to the endocrine regulation of aging.
[Show abstract][Hide abstract] ABSTRACT: Attenuated growth hormone and insulin-like growth factor-1 (GH/IGF-1) signaling is associated with extended lifespan in several animal models. However, the effect of diminished GH/IGF-1 activity on survival in humans has not been confirmed. We tested the hypothesis that IGF-1 levels in nonagenarians (n = 184), measured at study enrollment, predict the duration of their incremental survival. In the Kaplan-Meier analysis, females with IGF-1 levels below the median (≤ 96 ng mL(-1) ) had significantly longer survival compared with females with levels above the median, P < 0.01. However, this survival advantage was not observed in males (P = 0.83). On the other hand, in both males and females with a history of cancer, lower IGF-1 levels predicted longer survival (P < 0.01). IGF-1 level remained a significant predictor of survival duration in linear regression models after multivariable adjustment in females (P = 0.01) and individuals with a history of cancer (P < 0.01). We show for the first time that low IGF-1 levels predict life expectancy in exceptionally long-lived individuals.
[Show abstract][Hide abstract] ABSTRACT: Mice and humans with growth hormone receptor/IGF-1 deficiencies display major reductions in age-related diseases. Because protein restriction reduces GHR-IGF-1 activity, we examined links between protein intake and mortality. Respondents aged 50-65 reporting high protein intake had a 75% increase in overall mortality and a 4-fold increase in cancer death risk during the following 18 years. These associations were either abolished or attenuated if the proteins were plant derived. Conversely, high protein intake was associated with reduced cancer and overall mortality in respondents over 65, but a 5-fold increase in diabetes mortality across all ages. Mouse studies confirmed the effect of high protein intake and GHR-IGF-1 signaling on the incidence and progression of breast and melanoma tumors, but also the detrimental effects of a low protein diet in the very old. These results suggest that low protein intake during middle age followed by moderate to high protein consumption in old adults may optimize healthspan and longevity.
[Show abstract][Hide abstract] ABSTRACT: Ganitumab is a fully human monoclonal antibody to the human type I insulin-like growth factor receptor (IGF1R). Binding assays showed that ganitumab recognized murine (m)IGF1R with sub-nanomolar affinity (KD=0.22nM) and inhibited the interaction of murine IGF1R with IGF-1 and IGF-2. Ganitumab inhibited IGF-1-induced activation of IGF1R in murine lungs and CT-26 murine colon carcinoma cells and tumors. Adding ganitumab to 5-fluorouracil resulted in enhanced inhibition of tumor growth in the CT-26 model. Pharmacological intervention with ganitumab in naïve nude mice resulted in a number of physiological changes previously described in animals with targeted deletions of IGF-1 and IGF1R, including inhibition of weight gain, reduced glucose tolerance, and significant increase in serum levels of mGH, mIGF-1, and mIGFBP-3. FACS analysis identified GR1/CD11b-positive cells as the highest IGF1R-expressing cells in murine peripheral blood. Administration of ganitumab led to a dose-dependent, reversible decrease in the number of peripheral neutrophils with no effect on erythrocytes or platelets. These findings indicate that acute IGF-availability for its receptor plays a critical role in physiological growth, glucose metabolism, and neutrophil physiology and support the presence of a pituitary IGF1R-driven negative-feedback loop that tightly regulates serum IGF-1 levels through growth hormone signaling.
Full-text · Article · Feb 2014 · Journal of Endocrinology
[Show abstract][Hide abstract] ABSTRACT: Titrating the dosage of growth hormone (GH) to serum levels of insulin-like growth factor-I (IGF-I) is a feasible treatment strategy in children with GH deficiency (GHD) and idiopathic short stature (ISS). The objective was to assess the dose-sparing effect and theoretical safety of IGF-I based GH therapy.
This was a post-hoc analysis of previously described 2-year, multicenter, open-label, randomised, outpatient, controlled clinical trial in 172 prepubertal short children (age 7.5±2.4 years; height standard deviation score [HSDS] -2.64±0.61) classified by baseline peak GH levels as GHD (<7 ng/mL) or ISS (≥7 ng/mL).
Conventional weight-based dosing of GH (0.04 mg/kg/day) (n=34) or GH dosing titrated to an IGF-I target of 0 SDS (IGF0T; n=70) or IGF-I target of +2 SDS (IGF2T; n=68).
Change in HSDS per GH mg/kg/day dose (∆HSDS/GH-dose ratio) and proportion of IGF-I levels above +2 SDS at end of 2 years.
GH dosing titrated to an IGF-I target of 0 SDS was the most dose-sparing treatment regimen for GHD or ISS children (mean±SE ∆HSDS/GH-dose ratios 48.1±4.4 and 32.5±2.8, respectively) compared with conventional dosing (30.3±6.6 and 21.3±3.5, respectively; P=0.02, P=0.005) and IGF2T (32.7±4.8 and 16.3±2.8, respectively; P=0.02, P<0.0001). IGF0T also resulted in fewest IGF-I excursions above +2 SDS (6.8% vs 30.0% for conventional dosing; P<0.01).
IGF-I-based GH dosing, targeted to age- and gender-adjusted means, may offer a more dose sparing and potentially safer mode of therapy than traditional weight-based dosing. This article is protected by copyright. All rights reserved.
Full-text · Article · Jan 2014 · Clinical Endocrinology
[Show abstract][Hide abstract] ABSTRACT: We previously reported that a 4-6 week low-fat fish oil (LFFO) diet did not affect serum IGF-1 levels (primary outcome) but resulted in lower omega-6 to omega-3 fatty acid ratios in prostate tissue and lower prostate cancer proliferation (Ki67) as compared to a Western diet (WD). In this post-hoc analysis, the effect of the LFFO intervention on serum pro-inflammatory eicosanoids, LTB4 and 15(S)-HETE, and the cell cycle progression (CCP) score were investigated. Serum fatty acids and eicosanoids were measured by gas chromatography and ELISA. CCP score was determined by RT-PCR. Associations between serum eicosanoids, Ki67, and CCP score were evaluated using partial correlation analyses. BLT1 (LTB4 receptor) expression was determined in prostate cancer cell lines and prostatectomy specimens. Serum omega-6 fatty acids and 15(S)-HETE levels were significantly reduced, and serum omega-3 levels were increased in the LFFO group relative to the WD group, whereas there was no change in LTB4 levels. The CCP score was significantly lower in the LFFO compared to the WD group. The 15(S)-HETE change correlated with tissue Ki67 (R=0.48; p<0.01) but not with CCP score. The LTB4 change correlated with the CCP score (r=0.4; p=0.02) but not with Ki67. The LTB4 receptor BLT1 was detected in prostate cancer cell lines and human prostate cancer specimens. In conclusion, a LFFO diet resulted in decreased 15(S)-HETE levels and lower CCP score relative to a WD. Further studies are warranted to determine whether the LFFO diet anti-proliferative effects are mediated through the LTB4/BLT1 and 15(S)-HETE pathways.
Full-text · Article · Oct 2013 · Cancer Prevention Research
[Show abstract][Hide abstract] ABSTRACT: Humanin (HN) is a novel 24-amino acid mitochondrial-derived peptide that has demonstrated diverse cytoprotective effects, including an emerging role in diabetes. The purpose of this study was to examine the pharmacokinetics of humanin analogues, which show great potential as therapeutic agents (HNG and the nonIGFBP-3 binding, HNGF6A). 11-week-old male IGFBP-3(-/-) and wild type (WT) mice were divided into three groups: WT mice treated with HNG, WT mice treated with HNGF6A, and IGFBP-3(-/-)mice treated with HNG. Plasma was obtained from mice following intraperitonial (IP) injection with HN analogues, and HN levels were measured with ELISA. WT mice treated with HNGF6A and IGFBP-3(-/-)mice treated with HNG displayed a longer half-life of HN compared with WT mice treated with HNG. Following HNG injection, both IGF-1 and IGFBP-3 levels decreased over time. Adult male Sprague Dawley rats were also IP injected with HNG, and HN levels were measured in various tissues (plasma, liver, heart, and brain) by ELISA. The half-life of HN was found to be longer in rats compared with mice. In rats, HN levels were found to be highest in plasma, present in liver, and undetectable in brain or heart. The current study provides evidence of HN and IGFBP-3 association in the circulation, and suggests that native HN may modulate the distribution of IGF-1 and IGFBP-3. The results also demonstrate varying kinetic profiles of HN analogues and interspecies variation in rodents. Sustainable levels of circulating HN measured in plasma underline the potential value of HN analogues as a new therapeutic intervention in the treatment of diabetes.
[Show abstract][Hide abstract] ABSTRACT: Calorie restriction (CR) inhibits prostate cancer progression, partially through modulation of the IGF axis. IGF-1 receptor (IGF-1R) blockade reduces prostate cancer xenograft growth. We hypothesized that combining calorie restriction with IGF-1R blockade would have an additive effect on prostate cancer growth. Severe combined immunodeficient mice were subcutaneously injected with 22Rv1 cells and randomized to: (1) Ad libitum feeding/intraperitoneal saline (Ad-lib); (2) Ad-lib/20 mg/kg twice weekly, intraperitoneal ganitumab [anti-IGF-1R antibody (Ad-lib/Ab)]; (3) 40% calorie restriction/intraperitoneal saline (CR); (4) CR/ intraperitoneal ganitumab, (CR/Ab). CR and ganitumab treatment were initiated one week after tumor injection. Euthanasia occurred 19 days post treatment. Results showed that CR alone decreased final tumor weight, plasma insulin and IGF-1 levels, and increased apoptosis. Ganitumab therapy alone reduced tumor growth but had no effect on final tumor weight. The combination therapy (CR/Ab) further decreased final tumor weight and proliferation, increased apoptosis in comparison to the Ad-lib group, and lowered plasma insulin levels relative to the Ad-lib and Ad-lib/Ab groups. Tumor AKT activation directly correlated with plasma IGF-1 levels. In conclusion, whereas ganitumab therapy modestly affected 22Rv1 tumor growth, combining IGF-1R blockade with calorie restriction resulted in a significant decrease in final tumor weight and improved metabolic profile.
Full-text · Article · Jul 2013 · International Journal of Molecular Sciences
[Show abstract][Hide abstract] ABSTRACT: Background/aims:
Limited data exist on long-term dose response to recombinant human growth hormone (rhGH) in prepubertal GH-deficient (GHD) children. The effect of low, intermediate, and high-dose rhGH (25, 50, and 100 μg/kg/day, respectively) on growth and puberty in children with GHD was investigated for 48 months.
A prospective, dose-response study in 111 patients (aged 3-16 years) evaluated growth velocity (cm/year), height standard deviation score (HSDS), corrected HSDS, bone age/chronologic age ratio, body mass index SDS, and the percentage starting puberty.
Dose-related increases were observed in growth velocity (p < 0.001), HSDS (p < 0.001), and corrected HSDS (p < 0.001) from baseline to 48 months. Increases in the bone age/chronologic age ratio (p = 0.043) and body mass index SDS (p = 0.018) occurred up to 36 months at intermediate and high doses versus low-dose rhGH; increases at 48 months were not significant. No significant differences in growth were found between intermediate and high doses of rhGH. Percentages of rhGH-treated patients starting puberty at each dose were equivalent (p = 0.607).
rhGH, 50 and 100 μg/kg/day, induced greater growth than 25 μg/kg/day without altering the proportion of children starting puberty. The maximum approved dose for pubertal patients (100 μg/kg/day) is not required or recommended for prepubertal children with GHD.
Full-text · Article · Jun 2013 · Hormone Research in Paediatrics