Metabolic Flux Analysis of Mitochondrial Uncoupling in 3T3-L1 Adipocytes

BACKGROUND:Increasing energy expenditure at the cellular level offers an attractive option to limit adiposity and improve whole body energy balance. In vivo and in vitro observations have correlated mitochondrial uncoupling protein-1 (UCP1) expression with reduced white adipose tissue triglyceride (TG) content. The metabolic basis for this correlation remains unclear. METHODOLOGY/PRINCIPAL FINDINGS:This study tested the hypothesis that mitochondrial uncoupling requires the cell to compensate for the decreased oxidation phosphorylation efficiency by up-regulating lactate production, thus redirecting carbon flux away from TG synthesis. Metabolic flux analysis was used to characterize the effects of non-lethal, long-term mitochondrial uncoupling (up to 18 days) on the pathways of intermediary metabolism in differentiating 3T3-L1 adipocytes. Uncoupling was induced by forced expression of UCP1 and chemical (FCCP) treatment. Chemical uncoupling significantly decreased TG content by ca. 35%. A reduction in the ATP level suggested diminished oxidative phosphorylation efficiency in the uncoupled adipocytes. Flux analysis estimated significant up-regulation of glycolysis and down-regulation of fatty acid synthesis, with chemical uncoupling exerting quantitatively larger effects. CONCLUSIONS/SIGNIFICANCE:The results of this study support our hypothesis regarding uncoupling-induced redirection of carbon flux into glycolysis and lactate production, and suggest mitochondrial proton translocation as a potential target for controlling adipocyte lipid metabolism

The effects of orlistat on weight and on serum lipids in obese patients with hypercholesterolemia: a randomized, double-blind, placebo-controlled, multicentre study.

OBJECTIVE: Assessment of the effects of orlistat 120 mg three times daily vs placebo on weight loss and serum lipids in obese hypercholesterolemic patients. DESIGN: A 24 week multicentre, double-blind, randomized, placebo-controlled trial. After a 2-week single-blind run-in period (placebo+diet (-600 kcal/day; or =5% (64 vs 39%) or > or =10% (23 vs 13%) at week 24. Treatment with orlistat was associated with significantly greater changes in total cholesterol (-11.9% vs -4.0%; P or =1 event in 64 vs 38% of patients). CONCLUSION: Orlistat as an adjunct to dietary intervention promotes weight loss and reduces LDL-C beyond the effect of weight loss in overweight or obese patients with concomitant hypercholesterolemia