ABSTRACT
BACKGROUND: We have recently demonstrated that palmitoleic acid (16:1n7) increases lipolysis, glucose uptake and glucose utilization for energy production in white adipose cells. In the present study, we tested the hypothesis that palmitoleic acid modulates bioenergetic activity in white adipocytes. METHODS: For this, 3 T3-L1 pre-adipocytes were differentiated into mature adipocytes in the presence (or absence) of palmitic (16:0) or palmitoleic (16:1n7) acid at 100 or 200 µM. The following parameters were evaluated: lipolysis, lipogenesis, fatty acid (FA) oxidation, ATP content, oxygen consumption, mitochondrial mass, citrate synthase activity and protein content of mitochondrial oxidative phosphorylation (OXPHOS) complexes. RESULTS: Treatment with 16:1n7 during 9 days raised basal and isoproterenol-stimulated lipolysis, FA incorporation into triacylglycerol (TAG), FA oxidation, oxygen consumption, protein expression of subunits representing OXPHOS complex II, III, and V and intracellular ATP content. These effects were not observed in adipocytes treated with 16:0. CONCLUSIONS: Palmitoleic acid, by concerted action on lipolysis, FA esterification, mitochondrial FA oxidation, oxygen consumption and ATP content, does enhance white adipocyte energy expenditure and may act as local hormone.
Subject(s)
Adenosine Triphosphate/metabolism , Adipocytes, White/drug effects , Adipocytes, White/metabolism , Fatty Acids, Monounsaturated/pharmacology , Fatty Acids/metabolism , Oxygen Consumption/drug effects , 3T3-L1 Cells , Adipocytes/drug effects , Adipocytes/metabolism , Animals , Lipid Metabolism/drug effects , Lipogenesis/drug effects , Lipolysis/drug effects , Mice , Oxidation-Reduction/drug effects , Triglycerides/metabolismABSTRACT
Excessive caloric intake leading to obesity is associated with insulin resistance and dysfunction of islet ß cells. High-fat feeding decreases desnutrin (also called ATGL/PNPLA2) levels in islets. Here we show that desnutrin ablation via RIP-Cre (ßKO) or RIP-CreER results in hyperglycemia with impaired glucose-stimulated insulin secretion (GSIS). Due to decreased lipolysis, islets have higher TAG content but lower free FA levels. ßKO islets exhibit impaired mitochondrial respiration and lower production of ATP required for GSIS, along with decreased expression of PPARδ target genes involved in mitochondrial oxidation. Furthermore, synthetic PPARδ, but not PPARα, agonist restores GSIS and expression of mitochondrial oxidative genes in ßKO mice, revealing that desnutrin-catalyzed lipolysis generates PPARδ ligands. Finally, adenoviral expression of desnutrin in ßKO islets restores all defects of ßKO islet phenotype and function, including GSIS and mitochondrial defects, demonstrating the critical role of the desnutrin-PPARδ-mitochondrial oxidation axis in regulating islet ß cell GSIS.
