Role of growth hormone in hepatic and intestinal triglyceride-rich lipoprotein metabolism.

BACKGROUND: Elevated plasma concentrations of hepatic- and intestinally-derived triglyceride-rich lipoproteins (TRL) are implicated in the pathogenesis of atherosclerotic cardiovascular disease and all-cause mortality. Excess of TRL is the driving cause of atherogenic dyslipidemia commonly occurring in insulin-resistant individuals such as patients with obesity, type 2 diabetes and metabolic syndrome. Interestingly, growth hormone (GH)-deficient individuals display similar atherogenic dyslipidemia, suggesting an important role of GH and GH deficiency in the regulation of TRL metabolism. OBJECTIVE: We aimed to examine the direct and/or indirect role of GH on TRL metabolism. METHODS: We investigated the effect on fasting and postprandial hepatic-TRL and intestinal-TRL metabolism of short-term (one month) withdrawal of GH in 10 GH-deficient adults. RESULTS: After GH withdrawal, we found a reduction in fasting plasma TRL concentration (significant decrease in TRL-TG, TRL-cholesterol, TRL-apoB-100, TRL-apoC-III and TRL-apoC-II) but not in postprandial TRL response. This reduction was due to fewer fasting TRL particles without a change in TG per particle and was not accompanied by a change in postprandial TRL-apoB-48 response. Individual reductions in TRL correlated strongly with increases in insulin sensitivity and decreases in TRL-apoC-III. CONCLUSION: In this relatively short term 'loss of function' human experimental model, we have shown an unanticipated reduction of hepatic-TRL particles despite increase in total body fat mass and reduction in lean mass. These findings contrast with the atherogenic dyslipidemia previously described in chronic GH deficient states, providing a new perspective for the role of GH in lipoprotein metabolism.

Impact of bariatric surgery on apolipoprotein C-III levels and lipoprotein distribution in obese human subjects.

BACKGROUND: Elevated apolipoprotein C-III (apoC-III) has been postulated to contribute to the atherogenic dyslipidemia seen in obesity and insulin-resistant states, mainly by impairing plasma triglyceride-rich lipoprotein (TRL) metabolism. Bariatric surgery is associated with improvements of several obesity-associated metabolic abnormalities, including a reduction in plasma triglycerides (TGs) and an increase in plasma high-density lipoprotein cholesterol (HDL-C). OBJECTIVES: We investigated the specific effect of bariatric surgery on apoC-III concentrations in plasma, non-HDL, and HDL fractions in relation to lipid profile parameters evolution. METHODS: A total of 132 obese subjects undergoing bariatric surgery, gastric bypass (n = 61) or sleeve gastrectomy (n = 71), were studied 1 month before surgery and 6 and 12 months after surgery. RESULTS: Plasma apoC-III, non-HDL-apoC-III, and HDL-apoC-III concentrations were markedly reduced after surgery and strongly associated with reduction in plasma TG. This decrease was accompanied by a redistribution of apoC-III from TRL to HDL fractions. In multivariate analysis, plasma apoC-III was the strongest predictor of TG reduction after surgery, and the increase of HDL-C was positively associated with plasma adiponectin and negatively with body mass index. CONCLUSION: Marked reduction of apoC-III and changes in its distribution between TRL and HDL consistent with a better lipid profile are achieved in obese patients after bariatric surgery. These apoC-III beneficial modifications may have implications in dyslipidemia improvement and contribute to cardiovascular risk reduction after surgery.