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Lipid overload in obesity and type 2 diabetes is associated with adipocyte dysfunction, inflammation, macrophage infiltration, and decreased fatty acid oxidation (FAO). Here, we report that the expression of carnitine palmitoyltransferase 1A (CPT1A), the rate-limiting enzyme in mitochondrial FAO, is higher in human adipose tissue macrophages than in adipocytes and that it is differentially expressed in visceral vs. subcutaneous adipose tissue in both an obese and a type 2 diabetes cohort. These observations led us to further investigate the potential role of CPT1A in adipocytes and macrophages. We expressed CPT1AM, a permanently active mutant form of CPT1A, in 3T3-L1 CAR 1 adipocytes and RAW 264.7 macrophages through adenoviral infection. Enhanced FAO in palmitate-incubated adipocytes and macrophages reduced triglyceride content and inflammation, improved insulin sensitivity in adipocytes, and reduced endoplasmic reticulum stress and ROS damage in macrophages. We conclude that increasing FAO in adipocytes and macrophages improves palmitate-induced derangements. This indicates that enhancing FAO in metabolically relevant cells such as adipocytes and macrophages may be a promising strategy for the treatment of chronic inflammatory pathologies such as obesity and type 2 diabetes.

10.1016/j.bbadis.2014.05.025

Palmitate-induced inflammation is involved in the development of insulin resistance in skeletal muscle cells. Here we evaluated the effect of the saturated fatty acid palmitate and the monounsaturated fatty acid oleate on Toll-like receptors (TLR)-2 and -4 and cyclooxygenase 2 (COX-2) expression and examined whether the inhibition of this enzyme modulates fatty acid-induced inflammation. Skeletal muscle cells exposed to palmitate showed enhanced TLR-2 and COX-2mRNA levels, whereas oleate did not modify their expression. Palmitate-induced expression of these genes was dependent on nuclear factor (NF)-kappa B activation, because expression was reduced in the presence of the NF-kappa B inhibitor parthenolide. Co-incubation of palmitate-exposed cells with oleate also prevented the increase in the expression of TLR-2 and COX-2, through a mechanism that may involve activation of peroxisome proliferator-activated receptor-alpha (PPAR alpha) by this monounsaturated fatty acid. COX-2 inhibition by NS-398 enhanced IL-6 and TNF-alpha expression and IL-6 protein secretion induced by palmitate. NF-kappa B binding activity and TNF-alpha mRNA levels were enhanced in palmitate-exposed cells in the absence or in the presence of NS-398, whereas coincubation of palmitate-exposed cells with NS-398 and prostaglandin E-2 (PGE(2)) prevented these changes. In contrast, 12-lypoxygenase and cytochrome P450 hydroxylase pathways were not involved in these changes. Similarly, COX-2 inhibition impaired insulin-stimulated Akt phosphorylation and 2-deoxy-D-[C-14] glucose uptake in palmitate-exposed skeletal muscle cells, and this effect was abolished in the presence of PGE(2). These findings indicate that COX-2 activity, through the production of PGE(2), attenuates the fatty acid-induced inflammatory process and insulin resistance. (Endocrinology 151: 537-548, 2010)