Tumor necrosis factor-alpha induces apoptosis in rat brown adipocytes

Accumulating evidence demonstrates that adipose tissue is a major site of tumor necrosis factor-alpha (TNF-alpha) gene expression, which is markedly high in obese animals and may contribute to obesity-linked insulin resistance. We now report that recombinant murine TNF-alpha triggers the apoptotic degeneration of brown adipocytes differentiated in culture. Moreover, noradrenaline, which has been described as having trophic effects on brown fat and accelerating the differentiation of brown adipocytes, is capable of dose-dependently preventing the TNF-alpha-induced apoptosis of brown fat cells. Since obesity is characterized by greatly increased TNF-alpha production and reduced catecholaminergic activity, apoptosis was studied in the brown fat of genetically obese animals. In situ DNA fragmentation analysis revealed a larger number of apoptotic cells in the brown fat of obese (fa/fa) than in that of lean (+/+) Zucker rats. The exposure of obese rats to low temperatures for 7 days, which increases the sympathetic activity of brown adipose tissue, significantly reduces the number of apoptotic brown adipocytes. We hypothesize that TNF-alpha may play a significant role in the control of brown fat homeostasis

Multiple symmetric lipomatosis may be the consequence of defective noradrenergic modulation of proliferation and differentiation of brown fat cells.

Multiple symmetric lipomatosis (MSL) is an inherited disorder in which enlarging and unencapsulated lipomas symmetrically develop in the subcutaneous tissue of the neck, shoulders, mammary, and truncal regions. In some cases, it is associated with mitochondrial DNA abnormalities. The pathogenesis of MSL is completely unknown, although the fat deposits may be due to a neoplastic-like proliferation of functionally defective brown adipocytes. It has recently been demonstrated that the beta(3)-adrenergic receptor is the functionally relevant adrenergic receptor subtype in brown adipocytes and that its stimulation by noradrenaline (NA) modulates the expression of genes, such as uncoupling protein (UCP)-1 and inducible nitric oxide synthase (iNOS), involved in fat cell proliferation and differentiation. Furthermore, Trp64Arg mutation of the beta(3)-adrenoceptor has been implicated in lower NA activity in adipose tissues. The aim of this study was to investigate the molecular and functional characteristics of MSL adipocytes and to analyse the effects of nitric oxide (NO) on the proliferation/differentiation of MSL adipocytes in culture, and the relevance of putative noradrenergic deficit in the development of lipomas in MSL patients. Cultured MSL adipocytes were able to synthesize UCP-1 (the selective marker of brown adipocytes), but unlike that of normally functioning brown fat cells, the expression of the UCP-1 gene was not significantly induced by NA. NA is also defective in inducing iNOS gene expression, thus leading to reduced NO production and a consequent reduction in the anti-proliferative, adipogenic (mitochondrial biogenesis) effects of NA on MSL cells. Furthermore, the transcriptional peroxisome proliferator-activated receptor gamma co-activator-1 (PGC-1), which plays a key role in the sympathetic-stimulated mitochondrial biogenesis of brown adipocytes, is expressed but not induced by NA in MSL cells, as it is in brown adipocytes. The study did not find any association between beta(3)-adrenoceptor gene polymorphism and noradrenergic signalling defects in MSL subjects with or without mitochondrial DNA mutations

D2 dopamine receptor (DRD2) gene Taq1A polymorphism and the eating-related psychological traits in eating disorders (anorexia nervosa and bulimia) and obesity

OBJECTIVE: Food is considered a reinforcing agent, like a variety of substances such as alcohol and other drugs of abuse that produce pleasure. Psychopathological traits related to food intake are demonstrated in eating disorders as in obesity with different genetic aspects for these diseases. Recently, the prevalence of TaqA1 allele has been associated to alcohol, drug abuse and carbohydrate preference. For this reason, the aim of this study was to evaluate if the presence of A1 allele, in eating disorders and obesity, is associated with some particular psycho-pathological characteristics. METHODS: We studied the presence of TaqA1 in Italian subjects affected by obesity (n=71), anorexia (n=28), bulimia (n=20) and in control group (n=54). The Eating Disorders Inventory (EDI test) was used to evaluate the psychological profiles. Patients without alcohol and drugs abuse were selected (>125 ml/day). RESULTS: The A1+ allele, both in A1/A1 and A1/A2 genotypes, was not differently distributed among disease groups; on the contrary two EDI subscales (Drive for thinness and Ineffectiveness) resulted associated with A1+ allele without effect of the eating disease or obesity. CONCLUSION: These results confirm that the presence of A1+ allele is not simply related to body weight but the A1+ allele might be a marker of a genetic psychological condition in people with high risk to develop pathological eating behaviour