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Medium-chain fatty acids: Evidence for incorporation into chylomicron triqlycerides in humans

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The purpose of this study was to evaluate the fatty acid composition of chylomicron triglycerides isolated from subjects fed liquid-formula diets containing 40% of total energy as medium- (C8:0 and C10:0) or long-chain (C16-C18) triglycerides (MCT, LCT) for 6 d. Medium-chain fatty acids (MCFA) comprised 8% of total chylomicron triglyceride fatty acids after the first MCT meal. After 6 d of continued MCT feeding, chylomicron triglyceride MCFA content increased to 13%. When subjects were fed the LCT (soybean oil) diet, C16:0, C18:1, and C18:2 comprised nearly 90% of the chylomicron triglyceride fatty acids. The mass of triglyceride transported in chylomicrons isolated from subjects fed the MCT diet was approximately 20% of that found when subjects consumed the LCT diet. We conclude that although total triglyceride production during MCT ingestion is low, the chylomicron triglycerides that are synthesized contain significant amounts of MCFA.
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... 53 In contrast, 95% of MCFAs are taken straight into the portal vein. 54 However, existing studies, such as those by Mensink et al, have demonstrated that lauric acid increases total cholesterol, especially HDL cholesterol, and CVD risk. 55 In addition, coconut oil has been thought to promote weight loss based on its high natural medium-chain triglyceride (MCT) (C8, C10) content. ...
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Introduction: Due to the composition and biological properties of coconut oil, there is still considerable debate regarding potential benefits for the management of obesity, including the specific impact on body weight (BW) reduction. This systematic review and meta-analysis of clinical trials aims to assess the impact of coconut oil on BW reduction in comparison to other oils and fats. Evidence acquisition: The databases, PubMed®, Web of Science®, EMBASE®, and SciVerse Scopus® were systematically searched. A combination of medical subject headings and words linked to coconut oil and obesity parameters were utilized. Any clinical trials comparing coconut oil to any other form of oil or fat, with more than one month feeding period among adults were considered. Evidence synthesis: From the 540 potentially relevant papers, 9 were included. The period of coconut oil intake varied from four to twelve weeks, apart from one long-term trial wherecoconut oil was consumed for two years.When compared to other oils and fats, coconut oil substantially decreased BW (n=546), body mass index (BMI) (n=551), and percentage of fat mass (FM%) (n=491) by 0.75 kg (p=0.04), 0.28 kg/m2 (p=0.03), and 0.35% (p=0.008), respectively. Coconut oil consumption did not result in any significant alteration in waist circumference (WC)(n=385) (-0.61 cm; p=0.30), waist-to-hip ratio (WHR) (n=330) (-0.01; p=0.39) and FM (n=86) (-0.25 kg; p=0.29). Conclusions: Results indicate a small statistically significant reduction in BW, BMI, and FM% in the coconut oil group. In contrast, consumption of coconut oil had no statistically significant effect on WC, WHR, or FM.
... SFAs with carbon chain lengths of 6:0-10:0 are preferentially absorbed into the portal vein and rapidly metabolized (3), whereas those with a carbon chain length ≥12:0 are incorporated into chylomicrons and enter the circulation prior to metabolizing. These differences in metabolic properties can influence both energy production efficiency and cholesterol synthesis (4)(5)(6). ...
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Background Dietary saturated fat raises total cholesterol and LDL cholesterol levels. It is unclear whether these effects differ by the fatty acid chain lengths of saturated fats; particularly, it is unclear whether medium-chain fatty acids increase lipid levels. Objectives We conducted a systematic review to determine the effects of medium-chain triglyceride (MCT) oil, consisting almost exclusively of medium-chain fatty acids (6:0–10:0), on blood lipids. Methods We searched Medline and Embase through March 2020 for randomized trials with a minimum 2-week intervention period that compared MCT oil with another fat or oil. Outcomes were total cholesterol, LDL cholesterol, HDL cholesterol, and triglyceride levels. Included studies were restricted to adults above 18 years of age. Studies conducted in populations receiving enteral or parenteral nutrition were excluded. Data were pooled using a random-effects meta-analysis. Results Seven articles were included in the meta-analysis; LDL cholesterol and HDL cholesterol were reported in 6 studies. MCT oil intake did not affect total cholesterol (0.04 mmol/L; 95% CI, −0.11 to 0.20; I2 = 33.6%), LDL cholesterol (0.02 mmol/L; 95% CI, −0.13 to 0.17; I2 = 28.7%), or HDL cholesterol (−0.01 mmol/L; 95% CI, −0.10 to 0.09; I2 = 74.1%) levels, but did increase triglycerides (0.14 mmol/L; 95% CI, 0.01–0.27; I2 = 42.8%). Subgroup analyses showed that the effects of MCT oil on total cholesterol and LDL cholesterol differed based on the fatty acid profile of the control oil (Pinteraction = 0.003 and 0.008, respectively), with MCT oil increasing total cholesterol and LDL cholesterol when compared to a comparator consisting predominantly of unsaturated fatty acids, and with some evidence for reductions when compared to longer-chain SFAs. Conclusions MCT oil does not affect total cholesterol, LDL cholesterol, or HDL cholesterol levels, but does cause a small increase in triglycerides.
... 491,492 Lauric acid is preferably transported via the lymphatic system by chylomicrons. 38,493 For this reason, for the management of familial hyperchylomicronemia, when LPL is absent, the use of medium-chain TGs composed mostly of caproic, caprylic, and capric acids is indicated. 491 ...
... For example, it has been reported that when subjects consume a diet containing different fats, MCFAs tend to be channeled towards the portal vein. However, when the diet is mainly MCFA, some of these may also be incorporated into chylomicrons, suggesting the body adjusts based on the fat content of the diet [40]. This may explain some of the conflicting results that are reported in the literature [33]. ...
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The diet heart hypothesis has driven nutrition recommendations and policy for decades. Recent studies have questioned the hypothesis and sparked great controversy over the assumed connection between saturated fat intake and heart disease. Recent evidence suggests that dietary patterns should be the focus of dietary recommendations, not any one food or nutrient. Furthermore, to classify foods as simply saturated fat, polyunsaturated or monounsaturated fats is to ignore the many other potential nutrients and health benefits. Coconut is classified as a saturated fat and therefore listed as a food to limit to reduce heart disease risk. However, different saturated fats, medium-chain or long-chain, act differently metabolically and thus have different health effects. The medium-chain fatty acids predominate in coconut are absorbed differently and have been associated with several health benefits, including improvements in cognitive function and a more favorable lipid profile compared to longer chain fatty acids. Coconuts provide a healthful source of saturated fats and should not be considered the same as foods with longer chain saturated fats. Future recommendations should take this research into consideration. It is the purpose of this review to discuss the research regarding the connection between saturated fat intake, specifically coconut consumption, and health, while focusing on dietary patterns and lifestyle behaviors.
... Furthermore, no significant amount of MCFAs is transported through chylomicrons. After an overnight fast, the levels of esterified capric acid in total chylomicron TGs was 0%, which increased to 6.3% 3-4 h after an MCT-rich meal (Swift et al., 1990). After 6 days of receiving 93% of fat calories as MCTs, 32% of which was esterified capric acid, it still constituted just 9.4% of the total chylomicron TG pool, highlighting that, while MCFAs can be incorporated into chylomicrons, it will rarely occur in typical Western diets, which receive only 5-10% of calories from MCFAs. ...
Article
GPR84 is an inflammation-induced receptor highly expressed on immune cells, yet its endogenous ligand is still unknown. This makes any interpretation of its physiological activity in vivo difficult. However, experiments with potent synthetic agonists have highlighted what the receptor can do, namely, enhance proinflammatory signaling and macrophage effector functions such as phagocytosis. Developing drugs to block these effects has attracted interest from the scientific community with the aim of decreasing disease activity in inflammatory disorders or enhancing inflammation resolution. In this review, we critically reassess the widely held belief that the major role of GPR84 is that of being a medium-chain fatty acid (MCFA) receptor. While MCFAs have been shown to activate GPR84, it remains to be demonstrated that they are present in relevant tissues at appropriate concentrations. In contrast to four other "full-time" free fatty acid receptor subtypes, GPR84 is not expressed by enteroendocrine cells and has limited expression in the gastrointestinal tract. Across multiple tissues and cell types, the highest expression levels of GPR84 are observed hours after exposure to an inflammatory stimulus. These factors obscure the relationship between ligand and receptor in the human body and do not support the exclusive physiological pairing of MCFAs with GPR84. To maximize the chances of developing efficacious drugs for inflammatory diseases, we must advance our understanding of GPR84 and what it does in vivo.
... Another RCT in healthy individuals reported that dietary saturated fats of varying chain length had differential effects on lowering postprandial TG with results showing MCSFA to be significantly more effective than LCSFA [22]. It is well-established that the key mechanism by which MCSFA lowers postprandial lipaemia is that they are directly transported via the portal circulation with little incorporation into chylomicrons [30,31]. Preclinical studies have suggested that MCSFA decrease the expression of apolipoprotein B-48 which is used to transport dietary lipids from the intestine to the circulatory system [32]. ...
Article
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Nutrition support has played a major role in the treatment of chylothorax, both to prevent malnutrition and to minimize chyle production and flow. This report evaluates chyle composition in a patient with chylothorax who was placed on a low-fat diet, medium-chain triglyceride diet, and total parenteral nutrition in sequence. Both triglyceride content and volume of chyle declined, but drainage persisted, ultimately requiring thoracic duct ligation. The chyle triglyceride while on total parenteral nutrition, which presumably originates from both the intestine and plasma, contained more long-chain unsaturated fatty acids than the circulating serum triglyceride. Of particular interest was the detection of an appreciable amount of medium-chain fatty acids in the chyle triglyceride, constituting 20% of the triglyceride fatty acids when an enteral formulation with medium-chain triglyceride as a sole fat source was administered. The finding of almost threefold more decanoic acid (C10:0) than octanoic acid (C8:0), despite the presence of considerably more octanoic acid in the original diet, suggests that trioctanoin may be a preferable medium-chain triglyceride substrate for the nonsurgical treatment of chylothorax.
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A review of the literature on the medical and nutritional use of medium-chain triglycerides (MCTs) since 1970 is presented with additional discussions on the various modifications and applications of the MCTs in the synthesis of certain structured lipids. The metabolism of MCTs in the liver and extrahepatic tissues is discussed along with further documentation of the use of MCTs in malabsorption and hyperlipidemia cases. Recent applications of MCTs and modified MCTs in hyperalimentation, deficiency in the carnitine system, epilepsy, obesity, and other special areas of application are cited. The use of medium-chain monodiglycerides for dissolving cholesterol gallstones is presented. The contraindications for the use of MCTs in ketosis, acidosis, and cirrhosis are also discussed. Suggestions for use of MCTs in a variety of medical and nutritional applications are presented.