OBJECTIVE-Recent observations indicate that the delivery of nitric oxide by endothelial nitric oxide synthase (eNOS) is not only critical for metabolic homeostasis, but could also be important for mitochondrial biogenesis, a key organelle for free fatty acid (FFA) oxidation and energy production. Because mice deficient for the gene of eNOS (eNOS Ϫ/Ϫ ) have increased triglycerides and FFA levels, in addition to hypertension and insulin resistance, we hypothesized that these knockout mice may have decreased energy expenditure and defective ␤-oxidation.RESEARCH DESIGN AND METHODS-Several markers of mitochondrial activity were assessed in C57BL/6J wild-type or eNOS Ϫ/Ϫ mice including the energy expenditure and oxygen consumption by indirect calorimetry, in vitro ␤-oxidation in isolated mitochondria from skeletal muscle, and expression of genes involved in fatty acid oxidation. RESULTS-eNOSϪ/Ϫ mice had markedly lower energy expenditure (Ϫ10%, P Ͻ 0.05) and oxygen consumption (Ϫ15%, P Ͻ 0.05) than control mice. This was associated with a roughly 30% decrease of the mitochondria content (P Ͻ 0.05) and, most importantly, with mitochondrial dysfunction, as evidenced by a markedly lower ␤-oxidation of subsarcolemmal mitochondria in skeletal muscle (Ϫ30%, P Ͻ 0.05). Finally, impaired mitochondrial ␤-oxidation was associated with a significant increase of the intramyocellular lipid content (30%, P Ͻ 0.05) in gastrocnemius muscle. CONCLUSIONS-These data indicate that elevated FFA and triglyceride in eNOSϪ/Ϫ mice result in defective mitochondrial ␤-oxidation in muscle cells. Diabetes

OBJECTIVEIncrease in adipose cAMP-responsive element\x{2013}binding protein (CREB) activity promotes adipocyte dysfunction and systemic insulin resistance in obese mice. This is achieved by increasing the expression of activating transcription factor 3 (ATF3). In this study, we investigated whether impaired expression of the inducible cAMP early repressor (ICER), a transcriptional antagonist of CREB, is responsible for the increased CREB activity in adipocytes of obese mice and humans.RESEARCH DESIGN AND METHODSTotal RNA and nuclear proteins were prepared from visceral adipose tissue (VAT) of human nonobese or obese subjects and white adipose tissue (WAT) of C57Bl6-Rj mice that were fed with normal or high-fat diet for 16 weeks. The expression of genes was monitored by real-time PCR, Western blotting, and electromobility shift assays. RNA interference was used to silence the expression of Icer.RESULTSThe expression of Icer/ICER was reduced in VAT and WAT of obese humans and mice, respectively. Diminution of Icer/ICER was restricted to adipocytes and was accompanied by a rise of Atf3/ATF3 and diminution of Adipoq/ADIPOQ and Glut4/GLUT4. Silencing the expression of Icer in 3T3-L1 adipocytes mimicked the results observed in human and mice cells and hampered glucose uptake, thus confirming the requirement of Icer for appropriate adipocyte function.CONCLUSIONSImpaired expression of ICER contributes to elevation in CREB target genes and, therefore, to the development of insulin resistance in obesity.