1.
Leptin-Mediated Changes in the Human Metabolome.
Lawler, K, Huang-Doran, I, Sonoyama, T, Collet, TH, Keogh, JM, Henning, E, O'Rahilly, S, Bottolo, L, Farooqi, IS
The Journal of clinical endocrinology and metabolism. 2020;(8):2541-52
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Abstract
CONTEXT While severe obesity due to congenital leptin deficiency is rare, studies in patients before and after treatment with leptin can provide unique insights into the role that leptin plays in metabolic and endocrine function. OBJECTIVE The aim of this study was to characterize changes in peripheral metabolism in people with congenital leptin deficiency undergoing leptin replacement therapy, and to investigate the extent to which these changes are explained by reduced caloric intake. DESIGN Ultrahigh performance liquid chromatography-tandem mass spectroscopy (UPLC-MS/MS) was used to measure 661 metabolites in 6 severely obese people with congenital leptin deficiency before, and within 1 month after, treatment with recombinant leptin. Data were analyzed using unsupervised and hypothesis-driven computational approaches and compared with data from a study of acute caloric restriction in healthy volunteers. RESULTS Leptin replacement was associated with class-wide increased levels of fatty acids and acylcarnitines and decreased phospholipids, consistent with enhanced lipolysis and fatty acid oxidation. Primary and secondary bile acids increased after leptin treatment. Comparable changes were observed after acute caloric restriction. Branched-chain amino acids and steroid metabolites decreased after leptin, but not after acute caloric restriction. Individuals with severe obesity due to leptin deficiency and other genetic obesity syndromes shared a metabolomic signature associated with increased BMI. CONCLUSION Leptin replacement was associated with changes in lipolysis and substrate utilization that were consistent with negative energy balance. However, leptin's effects on branched-chain amino acids and steroid metabolites were independent of reduced caloric intake and require further exploration.
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Hydrogen Sulfide in the Adipose Tissue-Physiology, Pathology and a Target for Pharmacotherapy.
Bełtowski, J, Jamroz-Wiśniewska, A
Molecules (Basel, Switzerland). 2016;(1)
Abstract
Hydrogen sulfide (H₂S) is synthesized in the adipose tissue mainly by cystathionine γ-lyase (CSE). Several studies have demonstrated that H₂S is involved in adipogenesis, that is the differentiation of preadipocytes to adipocytes, most likely by inhibiting phosphodiesterases and increasing cyclic AMP concentration. The effect of H₂S on adipose tissue insulin sensitivity and glucose uptake is controversial. Some studies suggest that H₂S inhibits insulin-induced glucose uptake and that excess of H₂S contributes to adipose tissue insulin resistance in metabolic syndrome. In contrast, other studies have demonstrated that H₂S stimulates glucose uptake and its deficiency contributes to insulin resistance. Similarly, the effect of H₂S on adipose tissue lipolysis is controversial. H₂S produced by perivascular adipose tissue decreases vascular tone by activating ATP-sensitive and/or voltage-gated potassium channels in smooth muscle cells. Experimental obesity induced by high calorie diet has a time dependent effect on H₂S in perivascular adipose tissue; short and long-term obesity increase and decrease H₂S production, respectively. Hyperglycemia has been consistently demonstrated to suppress CSE-H₂S pathway in various adipose tissue depots. Finally, H₂S deficiency may contribute to adipose tissue inflammation associated with obesity/metabolic syndrome.
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Is visceral fat involved in the pathogenesis of the metabolic syndrome? Human model.
Jensen, MD
Obesity (Silver Spring, Md.). 2006;:20S-24S
Abstract
OBJECTIVE To review the evidence for and against the role of visceral adipose tissue as a major contributor to the metabolic complications of obesity through abnormal regulation of lipolysis. RESEARCH METHODS AND PROCEDURES Data from investigators in the field who have studied visceral adiposity and metabolic health and/or regional and systemic free fatty acid (FFA) release were considered. RESULTS Although visceral fat mass was positively correlated with adverse health consequences and excess FFA availability, visceral fat was not the source of excess systemic FFA availability. Upper body non-visceral fat contributes the majority of FFAs in lean, obese, diabetic, and non-diabetic humans. Increasing amounts of visceral fat probably result in greater hepatic FFA delivery. DISCUSSION Systemic, as opposed to hepatic, insulin resistance is unlikely to be caused by high rates of visceral adipose tissue lipolysis.