Concerted Action of Leptin in Regulation of Fatty Acid Oxidation in Skeletal Muscle and Liver

ArticleinExperimental and Clinical Endocrinology & Diabetes 115(4):244-51 · May 2007with16 Reads
DOI: 10.1055/s-2007-956166 · Source: PubMed
Abstract
Central action of leptin on food intake and energy expenditure is integrated with leptin's peripheral action modulating the fatty acid and glucose metabolism and preventing the accumulation of lipids in nonadipose tissues. However, exact mechanism(s) of the leptin's action in the peripheral tissues has not yet been fully elucidated. Therefore, we investigated the effect of a single intravenous injection of leptin on palmitoyl-CoA and palmitoyl-carnitine oxidation rate in liver and skeletal muscle followed by measurements of the carnitine-palmitoyl transferase 1 (CPT1) activity and activities of ss-oxidation enzymes in mitochondria (acyl-CoA dehydrogenase) and in peroxisomes (acyl-CoA oxidase) of rats. Animals were euthanized and tissues and serum harvested 15 min, 1 hour, 3 hours and 6 hours after leptin administration. Intravenous leptin injection increased mitochondrial palmitoyl-CoA oxidation rate in both liver (95%; P<0.025) and skeletal muscle (2.7-fold; P<0.05). This was paralleled by lowering hepatic (-156%; P<0.001) and skeletal muscle (-191%; P<0.001) triglyceride content. Leptin-induced elevation of palmitoyl-CoA oxidation rate in liver was paralleled by increased CPT1 activity (52%; P<0.05) and ss-oxidation capacity (52%; P<0.05). Lack of the leptin's effect on the CPT1-activity in muscle (20%; p=0.09) suggests the existence of an alternative pathway for increasing the palmitoyl-CoA-oxidation rate bypassing the CPT1 regulatory step. Interestingly, leptin stimulated the overall ss-oxidation capacity in muscle by 69% (P=0.027). This may indicate to an involvement of mitochondrial acyl-CoA dehydrogenases as well as of peroxisomal fat catabolism. Taken together, we showed that leptin acutely increases palmitoyl-CoA oxidation rate in liver and in skeletal muscle, which was associated with tissue specific effect on the CPT1 activity as well as on the downstream enzymes of fatty acid oxidation pathways in rat mitochondria and peroxisomes. Tangible evidence for the leptin-induced increase of fatty acid catabolism was provided by a lowered skeletal muscle and hepatic lipid deposition.
    • "No significant correlations were observed between adiponectin and total or low-density lipoprotein (LDL) cholesterol levels [27]. Similarly, leptin has been shown to increase hepatic fatty acid oxidation and plasma triglyceride as well as reduce triglyceride secretion into plasma [55,56]. However, this study found minimal correlations between leptin and lipid profiles. "
    [Show abstract] [Hide abstract] ABSTRACT: Dysregulation of adipose hormones in obesity has been associated with the hastened development of metabolic syndrome and associated chronic disease sequalae including cardiovascular disease and type 2 diabetes mellitus. This study aims to identify common biochemical and anthropometric markers that impact adipose hormones, including adiponectin and leptin. Based on previous literature, it was hypothesized that these would be adversely impacted by liver function parameters and adiponectin levels would be positively correlated with phospholipid omega-3 fatty acids. Forty non-diabetic adult subjects (body mass index (BMI) ≥ 25.0kg/m2) were recruited. Fasting plasma samples were taken to assess adipokine levels, glucose metabolism, electrolytes, liver enzymes, and blood lipids. Basic anthropometric measurements were also recorded. Adiponectin levels were positively correlated with HDL cholesterol and negatively correlated with anthropometric measures, insulin, liver enzymes, triglycerides, and VLDL cholesterol but not BMI. Conversely, plasma leptin levels were positively correlated with anthropometric measures, C-reactive protein, HDL cholesterol, and plasma phospholipid proportions of omega-3 alpha linoleic acid, but inversely correlated with creatinine levels. These results support other data regarding correlations between adiponectin and relative adipose distribution. Correlations with specific liver enzymes may indicate that adiponectin levels are tied to fatty acid deposition in the liver; however, liver/kidney damage though further mechanistic clarification is required. Leptin levels were associated with measures of adiposity but not liver enzymes. Each of these variables, along with blood lipids, may serve as potential future therapeutic targets for the prevention and management of obesity and related co-morbidities.
    Full-text · Article · May 2014
    • "Leptin has also been shown to increase hepatic fatty acid oxidation by the activation of critical cellular energy sensor, AMP kinase [28,45]. Our studies showed that even though fasting leptin concentrations in patients with NASH were significantly higher than that in controls, there was no change in plasma leptin in response to infusion of intralipid in either group. "
    [Show abstract] [Hide abstract] ABSTRACT: Data from studies in patients with nonalcoholic steatohepatitis (NASH) suggest an increased hepatic fatty acid oxidation. We have previously shown higher fasting plasma bile acid concentrations in patients with NASH. In-vivo and in-vitro studies suggest that bile acids by binding to peroxisome proliferator-activated receptor α activate fibroblast growth factor 21 (FGF21) and increase hepatic fatty acid oxidation. Plasma bile acid levels were quantified in healthy controls (n=38) and patients with biopsy-proven NASH (n=36). Plasma concentration of fatty acids, β-hydroxybutyrate, insulin, glucose, leptin, alanine aminotransferase, FGF21, and 8-hydroxydeoxyguanosine, a measure of oxidative stress, were measured in 16 healthy controls and 10 patients with NASH in the fasted state and in response to 3 h of infusion of intralipid. In a subgroup of these patients (n=6 each), plasma ceramide subspecies were quantified. Fasting plasma bile acids, FGF21, and leptin concentrations were significantly higher in patients with NASH. In response to intralipid infusion there was an increase in plasma β-hydroxybutyrate and free fatty acid levels in both controls and NASH; however, the ratio of β-hydroxybutyrate/free fatty acid was higher in NASH (P=0.02). Plasma FGF21 concentration increased in response to intralipid in patients with NASH only (P<0.01). Plasma leptin, insulin, glucose, and alanine transferase concentrations did not change in either group after infusion of intralipid. Increase in total ceramides in response to intralipid was greater in NASH. Elevated bile acids and FGF21 may be responsible for the higher hepatic fatty acid oxidation in NASH.
    Full-text · Article · Mar 2011
    • "Similar to adiponectin, leptin has been shown to regulate several aspects of lipid metabolism, such as increasing hepatic fatty acid oxidation and plasma TG clearance, as well as reducing TG secretion into plasma [45,46]. However, unlike adiponectin, the plasma level of which is consistently increased by fish oil, the effect of fish oil in modulating plasma leptin levels is unclear. "
    [Show abstract] [Hide abstract] ABSTRACT: Fish oil improves several features of metabolic syndrome (MetS), such as dyslipidemia, insulin resistance and hepatic steatosis. Fish oil may mediate some of its beneficial effects by modulating the storage and/or secretory functions of adipose tissue (AT). The storage of triglycerides in AT is regulated by the availability of free fatty acids and the degree of lipolysis in AT. Fish oil has been shown to reduce lipolysis in several studies, indicating improved triglyceride storage. Importantly, AT secretes a variety of adipokines and fish oil feeding is associated with remarkable changes in the plasma levels of two key adipokines, adiponectin and leptin. Much attention has been focused on the contribution of adiponectin in fish oil-mediated improvements in MetS. However, emerging evidence also indicates a role of leptin in modulating the components of the MetS upon fish oil feeding. In addition to improving the storage and secretory functions of AT, fish oil, and the n-3 fatty acids found in fish oil, has been shown to reduce inflammation in AT. These effects may be in part a result of activation of peroxisome proliferator-activated receptor γ or inhibition of Toll-like receptor 4. Thus, there is compelling evidence that fish oil mediates its beneficial effects on MetS by improving AT storage and secretory functions and by reducing inflammation.
    Full-text · Article · Feb 2011
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