Elevated circulating fatty acid concentration is a hallmark of insulin resistance and is at least in part attributed to the action of adipose tissue-derived tumor necrosis factor-␣ (TNF-␣) on lipolysis. Cell death-inducing DFFA (DNA fragmentation factor-␣)-like effector A (CIDEA) belongs to a family of proapoptotic proteins that has five known members in humans and mice. The action of CIDEA is unknown, but CIDEA-null mice are resistant to obesity and diabetes. We investigated CIDEA in adipose tissue of obese and lean humans and mice. The mRNA was expressed in white human fat cells and in brown mouse adipocytes. The adipose mRNA expression of CIDEA in mice was not influenced by obesity. However, CIDEA expression was decreased twofold in obese humans and normalized after weight reduction. Low adipose CIDEA expression was associated with several features of the metabolic syndrome. Human adipocyte depletion of CIDEA by RNA interference stimulated lipolysis and increased TNF-␣ secretion by a posttranscriptional effect. Conversely, TNF-␣ treatment decreased adipocyte CIDEA expression via the mitogen-activated protein kinase c-Jun NH 2 -terminal kinase. We propose an important and human-specific role for CIDEA in lipolysis regulation and metabolic complications of obesity, which is at least in part mediated by cross-talk between CIDEA and TNF-␣. Diabetes 54:1726 -1734, 2005

Obesity is associated with the increased expression of several chemokine genes in adipose tissue. However, only MCP1 is secreted into the extracellular space, where it primarily acts as a local factor, because little or no spillover into the circulation occurs. MCP1 influences the function of adipocytes, is a recruitment factor for macrophages, and may be a crucial link among chemokines between adipose tissue inflammation and insulin resistance.

Impaired oxidative phosphorylation is suggested as a factor behind insulin resistance of skeletal muscle in type 2 diabetes. The role of oxidative phosphorylation in adipose tissue was elucidated from results of Affymetrix gene profiling in subcutaneous and visceral adipose tissue of eight nonobese healthy, eight obese healthy, and eight obese type 2 diabetic women. Downregulation of several genes in the electron transport chain was the most prominent finding in visceral fat of type 2 diabetic women independent of obesity, but the gene pattern was distinct from that previously reported in skeletal muscle in type 2 diabetes. A similar but much weaker effect was observed in subcutaneous fat. Tumor necrosis factor-␣ (TNF-␣) is a major factor behind inflammation and insulin resistance in adipose tissue. TNF-␣ treatment decreased mRNA expression of electron transport chain genes and also inhibited fatty acid oxidation when differentiated human preadipocytes were treated with the cytokine for 48 h. Thus, type 2 diabetes is associated with a tissue-and region-specific downregulation of oxidative phosphorylation genes that is independent of obesity and at least in part mediated by TNF-␣, suggesting that impaired oxidative phosphorylation of visceral adipose tissue has pathogenic importance for development of type 2 diabetes. Diabetes 55:1792-1799, 2006

Macronutrients have a secondary role in changes in adipocyte gene expression after energy-restricted diets. The most striking alteration after energy restriction is a coordinated reduction in the expression of genes regulating the production of polyunsaturated fatty acids.

Tumor necrosis factor-a (TNF-a) promotes lipolysis in mammal adipocytes via the mitogen-activated protein kinase (MAPK) family, resulting in reduced expression/ function of perilipin (PLIN). The role of another pivotal intracellular messenger activated by TNF-a, nuclear factorkB (NF-kB), has not been recognized. We explored the role of NF-kB in TNF-a-induced lipolysis of human fat cells. Primary cultures of human adipocytes were incubated in the presence of a cell-permeable peptide that inhibits NF-kB signaling (WP). Incubation with WP, but not with a biologically inactive peptide (MP), abolished the nuclear translocation of NF-kB and effectively abrogated TNF-a-induced lipolysis in a concentration-dependent manner. Western blot analysis demonstrated that although TNF-a per se reduced mainly PLIN protein expression, TNF-a in the presence of WP resulted in a pronounced combined reduction of both hormone-sensitive lipase (HSL) and PLIN protein.The expression of a set of other lipolytic or adipocyte-specific proteins was not affected. The regulation was presumably at the transcriptional level, because mRNA expression for HSL and PLIN was markedly reduced with TNF-a in the presence of NF-kB inhibition. This was confirmed in gene reporter assays using human PLIN and HSL promoter constructs. We conclude that in the presence of NF-kB inhibition, TNF-a-mediated lipolysis is reduced, which suggests that NF-kB is essential for retained human fat cell lipolysis.-Laurencikiene, J., V. van Harmelen, E. Arvidsson Nordström, A. Dicker, L. Blomqvist, E. Näslund, D. Langin, P. Arner, and M. Rydén. NF-kB is important for TNF-a-induced lipolysis in human adipocytes. J. Lipid Res.

Objective: To determine whether oestrogen receptor (ER)a messenger RNA (mRNA) levels or single nucleotide polymorphisms (SNPs) are associated with obesity in Swedish women. Design: ERa mRNA expression levels were measured by real-time qPCR in subcutaneous adipose tissue from non-obese (N ¼ 16, BMI o30) and obese (N ¼ 17, BMI X30) women. In addition, ERa mRNA expression levels were determined in isolated adipocytes. ERa promoter usage was characterized by 5 0 RACE and by real-time qPCR in subcutaneous adipose tissue from the same non-obese and obese women. Two ERa SNPs were scored in 509 non-obese and 489 obese females. Results: ERa mRNA expression levels were lower in obese compared to non-obese women in both subcutaneous adipose tissue and in adipocytes. We show that two ERa promoters are differentially utilized in obese and non-obese individuals. We did not find any significant association between obesity and the ERa SNPs or haplotypes assayed. Conclusion: The reduced ERa mRNA levels observed in adipose tissue from obese compared to non-obese women support a role for oestrogen signaling via ERa, in control of body weight. Mechanistic studies of the role of ERa in adipocytes and how its expression is regulated in relation to fat mass should be performed. The latter studies should focus on the two promoters that are used differently in obese and non-obese individuals.

Acyl-CoA thioesterase (ACOT) activities are found in prokaryotes and in several compartments of eukaryotes where they hydrolyze a wide range of acyl-CoA substrates and thereby regulate intracellular acyl-CoA/CoA/fatty acid levels. ACOT9 is a mitochondrial ACOT with homologous genes found from bacteria to humans and in this study we have carried out an in-depth kinetic characterization of ACOT9 to determine its possible physiological function. ACOT9 showed unusual kinetic properties with activity peaks for short-, medium-, and saturated long-chain acyl-CoAs with highest V max with propionyl-CoA and (iso) butyryl-CoA while K cat/K m was highest with saturated long-chain acyl-CoAs. Further characterization of the short-chain acyl-CoA activity revealed that ACOT9 also hydrolyzes a number of short-chain acyl-CoAs and short-chain methyl-branched CoA esters that suggest a role for ACOT9 in regulation also of amino acid metabolism. In spite of markedly different K ms, ACOT9 can hydrolyze both short- and long-chain acyl-CoAs simultaneously, indicating that ACOT9 may provide a novel regulatory link between fatty acid and amino acid metabolism in mitochondria. Based on similar acyl-CoA chain-length specificities of recombinant ACOT9 and ACOT activity in mouse brown adipose tissue and kidney mitochondria, we conclude that ACOT9 is the major mitochondrial ACOT hydrolyzing saturated C2-C20-CoA in these tissues. Finally, ACOT9 activity is strongly regulated by NADH and CoA, suggesting that mitochondrial metabolic state regulates the function of ACOT9.

Loss of fat mass in cancer cachexia is linked to increased adipocyte lipolysis; however, the fate of the excess fatty acids (FA) generated by lipolysis is not known. We investigated if the adipocyte-specific gene cell death-inducing DNA fragmentation factor-A-like effector A (CIDEA) could be involved.