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Comprehensive Physiology Dec 2017Triglyceride molecules represent the major form of storage and transport of fatty acids within cells and in the plasma. The liver is the central organ for fatty acid... (Review)
Review
Triglyceride molecules represent the major form of storage and transport of fatty acids within cells and in the plasma. The liver is the central organ for fatty acid metabolism. Fatty acids accrue in liver by hepatocellular uptake from the plasma and by de novo biosynthesis. Fatty acids are eliminated by oxidation within the cell or by secretion into the plasma within triglyceride-rich very low-density lipoproteins. Notwithstanding high fluxes through these pathways, under normal circumstances the liver stores only small amounts of fatty acids as triglycerides. In the setting of overnutrition and obesity, hepatic fatty acid metabolism is altered, commonly leading to the accumulation of triglycerides within hepatocytes, and to a clinical condition known as nonalcoholic fatty liver disease (NAFLD). In this review, we describe the current understanding of fatty acid and triglyceride metabolism in the liver and its regulation in health and disease, identifying potential directions for future research. Advances in understanding the molecular mechanisms underlying the hepatic fat accumulation are critical to the development of targeted therapies for NAFLD. © 2018 American Physiological Society. Compr Physiol 8:1-22, 2018.
Topics: Biological Transport; Fatty Acids; Humans; Lipid Metabolism; Lipogenesis; Lipolysis; Liver; Non-alcoholic Fatty Liver Disease; Triglycerides
PubMed: 29357123
DOI: 10.1002/cphy.c170012 -
The American Journal of Cardiology Jul 2016Epidemiologic and clinical studies suggest that elevated triglyceride levels are a biomarker of cardiovascular (CV) risk. Consistent with these findings, recent genetic... (Review)
Review
Epidemiologic and clinical studies suggest that elevated triglyceride levels are a biomarker of cardiovascular (CV) risk. Consistent with these findings, recent genetic evidence from mutational analyses, genome-wide association studies, and Mendelian randomization studies provide robust evidence that triglycerides and triglyceride-rich lipoproteins are in the causal pathway for atherosclerotic CV disease, indicating that they may play a pathogenic role, much like low-density lipoprotein cholesterol (LDL-C). Although statins are the cornerstone of dyslipidemia management, high triglyceride levels may persist in some patients despite statin therapy. Several triglyceride-lowering agents are available, including fibrates, niacin, and omega-3 fatty acids, of which prescription omega-3 fatty acids have the best tolerability and safety profile. In clinical studies, omega-3 fatty acids have been shown to reduce triglyceride levels, but products containing both eicosapentaenoic acid and docosahexaenoic acid may increase LDL-C levels. Icosapent ethyl, a high-purity eicosapentaenoic acid-only product, does not raise LDL-C levels and also reduces triglyceride, non-high-density lipoprotein cholesterol, and triglyceride-rich lipoprotein levels. In conclusion, omega-3 fatty acids are currently being evaluated in large CV outcome studies in statin-treated patients; these studies should help to elucidate the causative role of triglycerides in atherosclerotic CV disease.
Topics: Cardiovascular Diseases; Genome-Wide Association Study; Humans; Lipoproteins; Mendelian Randomization Analysis; Triglycerides
PubMed: 27184174
DOI: 10.1016/j.amjcard.2016.04.004 -
Respiratory Medicine Jan 2010Chylothorax is a rare condition that results from thoracic duct damage with chyle leakage from the lymphatic system into the pleural space, usually on the right side. It... (Review)
Review
Chylothorax is a rare condition that results from thoracic duct damage with chyle leakage from the lymphatic system into the pleural space, usually on the right side. It has multiple aetiologies and is usually discovered after it manifests itself as a pleural effusion. Diagnosis involves cholesterol and triglyceride measurement in the pleural fluid. Complications include malnutrition, immunosuppression and respiratory distress. Treatment may be either conservative or aggressive depending on the clinical scenario. In this review, we discuss the aetiology, diagnosis and treatment of chylothorax. English language publications in MEDLINE and references from relevant articles from January 1, 1980 to February 28, 2008 were reviewed. Keywords searched were chylothorax, aetiology, diagnosis and treatment.
Topics: Biomarkers; Chylothorax; Diagnosis, Differential; Humans; Prognosis; Triglycerides
PubMed: 19766473
DOI: 10.1016/j.rmed.2009.08.010 -
Biochimica Et Biophysica Acta.... Mar 2023Fasting and starvation were common occurrences during human evolution and accordingly have been an important environmental factor shaping human energy metabolism. Humans... (Review)
Review
Fasting and starvation were common occurrences during human evolution and accordingly have been an important environmental factor shaping human energy metabolism. Humans can tolerate fasting reasonably well through adaptative and well-orchestrated time-dependent changes in energy metabolism. Key features of the adaptive response to fasting are the breakdown of liver glycogen and muscle protein to produce glucose for the brain, as well as the gradual depletion of the fat stores, resulting in the release of glycerol and fatty acids into the bloodstream and the production of ketone bodies in the liver. In this paper, an overview is presented of our current understanding of the effects of fasting on adipose tissue metabolism. Fasting leads to reduced uptake of circulating triacylglycerols by adipocytes through inhibition of the activity of the rate-limiting enzyme lipoprotein lipase. In addition, fasting stimulates the degradation of stored triacylglycerols by activating the key enzyme adipose triglyceride lipase. The mechanisms underlying these events are discussed, with a special interest in insights gained from studies on humans. Furthermore, an overview is presented of the effects of fasting on other metabolic pathways in the adipose tissue, including fatty acid synthesis, glucose uptake, glyceroneogenesis, autophagy, and the endocrine function of adipose tissue.
Topics: Humans; Adipose Tissue; Fasting; Adipocytes; Lipolysis; Triglycerides
PubMed: 36521736
DOI: 10.1016/j.bbalip.2022.159262 -
Proceedings of the National Academy of... Mar 2022In response to inflammatory activation by pathogens, macrophages accumulate triglycerides in intracellular lipid droplets. The mechanisms underlying triglyceride...
In response to inflammatory activation by pathogens, macrophages accumulate triglycerides in intracellular lipid droplets. The mechanisms underlying triglyceride accumulation and its exact role in the inflammatory response of macrophages are not fully understood. Here, we aim to further elucidate the mechanism and function of triglyceride accumulation in the inflammatory response of activated macrophages. Lipopolysaccharide (LPS)-mediated activation markedly increased triglyceride accumulation in macrophages. This increase could be attributed to up-regulation of the hypoxia-inducible lipid droplet–associated (HILPDA) protein, which down-regulated adipose triglyceride lipase (ATGL) protein levels, in turn leading to decreased ATGL-mediated triglyceride hydrolysis. The reduction in ATGL-mediated lipolysis attenuated the inflammatory response in macrophages after ex vivo and in vitro activation, and was accompanied by decreased production of prostaglandin-E2 (PGE2) and interleukin-6 (IL-6). Overall, we provide evidence that LPS-mediated activation of macrophages suppresses lipolysis via induction of HILPDA, thereby reducing the availability of proinflammatory lipid precursors and suppressing the production of PGE2 and IL-6.
Topics: Humans; Inflammation; Lipid Droplets; Lipid Metabolism; Lipids; Macrophages; Neoplasm Proteins; Triglycerides
PubMed: 35302892
DOI: 10.1073/pnas.2114739119 -
The Journal of Cell Biology Oct 2019Lipid droplet (LD) catabolism in hepatocytes is mediated by a combination of lipolysis and a selective autophagic mechanism called lipophagy, but the relative...
Lipid droplet (LD) catabolism in hepatocytes is mediated by a combination of lipolysis and a selective autophagic mechanism called lipophagy, but the relative contributions of these seemingly distinct pathways remain unclear. We find that inhibition of lipolysis, lipophagy, or both resulted in similar overall LD content but dramatic differences in LD morphology. Inhibition of the lipolysis enzyme adipose triglyceride lipase (ATGL) resulted in large cytoplasmic LDs, whereas lysosomal inhibition caused the accumulation of numerous small LDs within the cytoplasm and degradative acidic vesicles. Combined inhibition of ATGL and LAL resulted in large LDs, suggesting that lipolysis targets these LDs upstream of lipophagy. Consistent with this, ATGL was enriched in larger-sized LDs, whereas lipophagic vesicles were restricted to small LDs as revealed by immunofluorescence, electron microscopy, and Western blot of size-separated LDs. These findings provide new evidence indicating a synergistic relationship whereby lipolysis targets larger-sized LDs to produce both size-reduced and nascently synthesized small LDs that are amenable for lipophagic internalization.
Topics: Animals; Female; Hepatocytes; Lipid Droplets; Lipolysis; Rats; Rats, Sprague-Dawley; Triglycerides
PubMed: 31391210
DOI: 10.1083/jcb.201803153 -
Lipids in Health and Disease Aug 2021Pancreaticobiliary reflux (PBR) causes chronic inflammation of the gallbladder mucosa and changes in the bile components, which are known to promote gallstone formation....
BACKGROUND
Pancreaticobiliary reflux (PBR) causes chronic inflammation of the gallbladder mucosa and changes in the bile components, which are known to promote gallstone formation. This study aimed to investigate the bile biochemistry changes in gallstone patients with PBR and provide new clues for research on the involvement of PBR in gallstone formation.
METHODS
Patients undergoing surgery for gallstones between December 2020 and May 2021 were eligible for inclusion. The bile biochemistry (including amylase, lipase, triglyceride, cholesterol, free fatty acids [FFAs], alanine aminotransferase [ALT], aspartate aminotransferase [AST], alkaline phosphatase [ALP], and γ-glutamyl transferase [γ-GT]) of the included gallstone patients was analysed to determine correlations with PBR.
RESULTS
In this study, 144 gallstone patients who underwent surgery were enrolled. Overall, 15.97 % of the patients had an increased bile amylase level, which was associated with older age and significantly higher bile levels of ALP, lipase, triglyceride, and FFAs. Positive correlations were observed between amylase and lipase, triglyceride, FFAs levels in the gallbladder bile. However, the bile levels of triglyceride, FFAs, and lipase were positively correlated with each other only in the PBR group and showed no significant correlation in the control (N) group. In addition, elevated bile FFAs levels were found to be an independent risk factor for gallbladder wall thickening.
CONCLUSIONS
In conclusion, PBR-induced increase in FFAs and triglyceride in the gallbladder bile is a cause of gallstone formation, and an increase in bile ALP suggests the presence of cholestasis in PBR.
Topics: Adult; Aged; Bile; Bile Reflux; Fatty Acids, Nonesterified; Female; Gallbladder; Gallstones; Humans; Male; Middle Aged; Mortality; Prospective Studies; Triglycerides
PubMed: 34465364
DOI: 10.1186/s12944-021-01527-4 -
Journal of Lipid Research Aug 2020The risk for metabolic disease, including metabolic syndrome, insulin resistance, and diabetes, increases with age. Altered plasma TG metabolism and changes in fatty... (Review)
Review
The risk for metabolic disease, including metabolic syndrome, insulin resistance, and diabetes, increases with age. Altered plasma TG metabolism and changes in fatty acid partitioning are also major contributors to metabolic disease. Plasma TG metabolism itself is altered by age in humans and rodents. As discussed in this review, the age-induced changes in human TG metabolism include increased plasma TG levels, reduced postprandial plasma TG clearance rates, reduced postheparin LPL activity, decreased adipose tissue lipolysis, and elevated ectopic fat deposition, all of which could potentially contribute to age-associated metabolic diseases. Similar observations have been made in aged rats. We highlight the limitations of currently available data and propose that mechanistic studies are needed to understand the extent to which age-induced alterations in TG metabolism contribute to metabolic disease. Such mechanistic insights could aid in therapeutic strategies for preventing or managing metabolic disease in older individuals.
Topics: Adipose Tissue; Aging; Animals; Humans; Triglycerides
PubMed: 32586846
DOI: 10.1194/jlr.R120000922 -
Neuroscience Letters Jan 2019Clinical and animal studies suggested that a medium-chain triglyceride (MCT)-based ketogenic diet provides an alternative energy substrate to the brain and has...
Clinical and animal studies suggested that a medium-chain triglyceride (MCT)-based ketogenic diet provides an alternative energy substrate to the brain and has neuroprotective effects, but the clinical evidence is still scarce. Here we examined the effect of an MCT-based ketogenic formula on cognitive function in patients with Alzheimer's disease (AD). The subjects were 20 Japanese patients with mild-to-moderate AD (11 males, nine females, mean age 73.4 ± 6.0 years) who, on separate days, underwent neurocognitive tests 120 min after consuming 50 g of a ketogenic formula (Ketonformula) containing 20 g of MCTs or an isocaloric placebo formula without MCTs. The patients then took 50 g of the ketogenic formula daily for up to 12 weeks, and underwent neurocognitive tests monthly. In the first trial, although the patients' plasma levels of ketone bodies were successfully increased 120 min after the single intake of the ketogenic formula, there was no significant difference in any cognitive test results between the administrations of the ketogenic and placebo formulae. In the subsequent chronic intake trial of the ketogenic formula, 16 of the 20 patients completed the 12-week regimen. At 8 weeks after the trial's start, the patients showed significant improvement in their immediate and delayed logical memory tests compared to their baseline scores, and at 12 weeks they showed significant improvements in the digit-symbol coding test and immediate logical memory test compared to the baseline. The chronic consumption of the ketogenic formula was therefore suggested to have positive effects on verbal memory and processing speed in patients with AD.
Topics: Aged; Alzheimer Disease; Cognition; Diet, Ketogenic; Double-Blind Method; Female; Humans; Ketone Bodies; Male; Neuropsychological Tests; Triglycerides
PubMed: 30367958
DOI: 10.1016/j.neulet.2018.10.048 -
Trends in Endocrinology and Metabolism:... Jul 2016GPIHBP1, a GPI-anchored protein in capillary endothelial cells, is crucial for the lipolytic processing of triglyceride-rich lipoproteins (TRLs). GPIHBP1 shuttles... (Review)
Review
GPIHBP1, a GPI-anchored protein in capillary endothelial cells, is crucial for the lipolytic processing of triglyceride-rich lipoproteins (TRLs). GPIHBP1 shuttles lipoprotein lipase (LPL) to its site of action in the capillary lumen and is essential for the margination of TRLs along capillaries - such that lipolytic processing can proceed. GPIHBP1 also reduces the unfolding of the LPL catalytic domain, thereby stabilizing LPL catalytic activity. Many different GPIHBP1 mutations have been identified in patients with severe hypertriglyceridemia (chylomicronemia), the majority of which interfere with folding of the protein and abolish its capacity to bind and transport LPL. The discovery of GPIHBP1 has substantially revised our understanding of intravascular triglyceride metabolism but has also raised many new questions for future research.
Topics: Animals; Humans; Hypertriglyceridemia; Lipoprotein Lipase; Receptors, Lipoprotein; Triglycerides
PubMed: 27185325
DOI: 10.1016/j.tem.2016.04.013