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Query: UMLS:C0028754 (obesity)
 124,988 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The existence of a DNA polymorphism at the hormone-sensitive lipase locus could be of great interest for genetic analysis of obesity and related disorders since hormone-sensitive lipase is the rate-limiting enzyme of adipose tissue lipolysis and therefore plays a key role in energy metabolism. The polymorphic dinucleotide repeat D19S120 was identified within a human genomic clone selected with a rat hormone-sensitive lipase cDNA. This marker was subsequently localized to the short arm of chromosome 19 (p13.3) whereas human hormone-sensitive lipase (LIPE) had been mapped to the long arm of chromosome 19 (q13.1-->13.2). A duplication of the hormone-sensitive lipase gene or the presence of a pseudogene could explain the discrepancy. Cosmids from the two regions were analyzed in Southern blot experiments. A human adipose tissue hormone-sensitive lipase full-length cDNA probe hybridized only to cosmids from the 19q13.1-->13.2 region whereas the D19S120 amplicon probe hybridized only to cosmids from the p13.3 region. These data show that the occurrence of gene duplication or the presence of a pseudogene on the short arm of chromosome 19 is very unlikely and that D19S120 is unrelated to the hormone-sensitive lipase gene.
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PMID:The hormone-sensitive lipase (LIPE) gene located on chromosome 19q13.1-->13.2 is not duplicated on 19p13.3. 748 32

An elevation of lipoprotein lipase (LPL) activity in adipose tissue is considered a possible cause of obesity. However, transgenic mice that overexpress the human LPL gene showed no increase in fat deposition as compared with controls. In the present study, we investigated effects of LPL on fat accumulation. Respiratory quotients and uptake of [3H] triolein by tissues (white and brown adipose tissue, and skeletal muscles) did not differ significantly for transgenic and non-transgenic mice. The mRNA levels of hormone-sensitive lipase (HSL) and HSL activity in adipose tissue during feeding were higher in LPL transgenic mice than in controls. Results suggest that the overexpression of LPL does not induce obesity by enhancing the hydrolysis of triglycerides in adipose tissue.
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PMID:Overexpression of human lipoprotein lipase increases hormone-sensitive lipase activity in adipose tissue of mice. 759 4

The lipolysis in adipose tissue is controlled by the hormone-sensitive lipase activity which is dependent on the intracellular cAMP level. In human adipose tissue, cAMP level is increased by catecholamines (through beta-adrenoceptor stimulation) or decreased by insulin, catecholamine (through alpha 2-adrenoceptor stimulation), neuropeptide Y, prostaglandins and adenosine. The mobilization of lipids from adipose tissue is an adaptative mechanism in response to starvation or hypocaloric diet, which involves reduction of the antilipolytic effect of insulin and the increase of catecholamine sensitivity. The regulatory pathways of lipolysis and their adaptation to caloric reduction are not defective in obesity state. Pharmacological approaches proposed for the activation of lipolysis are limited; they mainly consist either to stimulate the fat cell beta-adrenoceptors (beta-sympathomimetic drugs) or to indirectly activate the sympathetic nervous system (ephedrine and its derivatives, methylxanthines, alpha 2-antagonists). However, the side effects elicited by these drugs frequently limit their clinical use.
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PMID:[Lipid mobilization, physiopathological and pharmacological aspects]. 775 46

A primary culture of undigested fat tissue fragments was used to obtain fat cells in vitro. On day 2 of culture, immature fat cells, which are fibroblast-like fat cells containing fine lipid droplets, appeared, surrounding the fat tissue fragments, and began to proliferate extensively. Afterwards, these fibroblast-like fat cells grew to become multilocular fat cells containing larger intracytoplasmic lipid droplets, and differentiated further into unilocular fat cells containing a single large intracytoplasmic lipid droplet. Treatment with dibutyryl-cAMP, which is a second messenger of the lipolytic factor, caused the cultured fat cells to retract, and the intracytoplasmic lipid droplets of those fat cells became finely granulated and decreased along with an increase of hormone-sensitive lipase activities. Conversely, administration of insulin caused the lipid droplets in the fat cells to increase and become larger along with an increase of alpha-glycerophosphate dehydrogenase activities. These findings indicate the occurrence of lipolysis and lipogenesis of fat cells in vitro. Immuno-cytochemistry revealed that vimentin surrounded intracytoplasmic lipid droplets, and became distinct with an increase of lipid droplets through lipogenesis in the fat cells. Vimentin seems to be correlated to the behavior of lipid droplets in the fat cells. Fat cells in this study showed the appropriate cellular structures and functions in response to stimulation of lipolysis and lipogenesis under culture conditions. It is expected that in vitro culture of fat cells will facilitate cell biological elucidation of obesity in the future.
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PMID:Cellular structure and function of rat fat cells in the primary culture. 779 65

Obesity is a risk factor of atherosclerosis. The TG content of a fat cell is determined by the balance of lipogenesis from plasma FFA and glucose and lipolysis by hormone-sensitive lipase (HSL). Plasma FFA is produced by TG lipolysis by lipoprotein lipase (LPL). Insulin stimulates LPL activity and inhibits HSL activity. Therefore, hyperinsulinemia stimulates TG accumulation in fat cells. Insulin also stimulates fat cell proliferation. Hyperinsulinemia is a major factor for obesity. Portal FFA stimulates VLDL synthesis and gluconeogenesis and inhibits insulin degradation in the liver. Therefore, visceral obesity is important as a risk factor of atherosclerosis. However the increase of total adipose tissue mass is more important for blood pressure and cardiac performance.
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PMID:[Atherosclerotic and hemodynamic effects of obesity]. 841 92

In this study we investigated whether fat cell lipolysis could be involved in the aetiology of obesity by comparing non-obese subjects with (Hob) or without (Hnorm) a family trait for overweight. A family history of obesity was present when at least one of the first-degree relatives had body mass index of 27 kg/m2 or more. Twenty-seven healthy, drug-free non-obese adult subjects were investigated; 13 were Hob and the remaining 14 were Hnorm. Eleven Hob had at least one obese parent. Isolated fat cells from abdominal subcutaneous adipose tissue were incubated in vitro. Glycerol release (lipolysis index), mRNA levels and enzymatic activity of hormone-sensitive lipase and radioligand binding to beta 1- and beta 2-adrenoceptors were determined. The lipolytic effects of noradrenaline (major endogenous lipolytic agent), isoprenaline (a non-selective beta-adrenoceptor agonist), forskolin (a direct activator of adenylyl cyclase) and dibutyryl cyclic AMP (activating protein kinase and thereby hormone-sensitive lipase) were reduced by about 50% (p from 0.001 to 0.01). The maximum activity of hormone-sensitive lipase was reduced 50% in Hob (p < 0.05) and correlated with the lipolytic responsiveness of fat cells in the whole population (r = 0.71). However, there was no difference between the groups in steady-state mRNA levels for the enzyme. Beta 1-->, beta 2- and alpha 2-adrenoceptor sensitivity as well as beta 1- and beta 2-adrenoceptor numbers were normal in Hob. Fasting plasma insulin was 49.1 and 32.6 pmol/l, respectively in Hob and Hnorm (p = 0.01). There was, however, no significant correlation between lipolysis in vitro and plasma insulin. Thus, lipolytic catecholamine resistance in fat cells, at least partly due to impaired function of hormone-sensitive lipase, is an adipocyte abnormality associated with a family tendency to obesity.
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PMID:Adipocyte lipolysis in normal weight subjects with obesity among first-degree relatives. 885 14

We evaluated the effect of diet-induced weight loss on whole body and cellular lipid metabolism in persons with severe upper body obesity in two study protocols. In protocol 1, palmitate and glycerol rates of appearance (Ra) in plasma were determined during basal conditions in seven subjects [initial body mass index (BMI) = 41.3 +/- 2.2 kg/m2] before and after 20.4 +/- 3.0 kg weight loss. Total glycerol and palmitate Ra decreased from 231.0 +/- 19.4 and 166.2 +/- 16.6 mumol/min, respectively, before weight loss to 162.7 +/- 9.5 and 105.0 +/- 9.7 mumol/min, respectively, after weight loss (P < 0.01). However, glycerol and palmitate Ra expressed per kilogram fat mass were similar both before and after weight loss. In protocol 2, subcutaneous abdominal adipose tissue was obtained before and after 14.4 +/- 2.1 kg weight loss in five subjects (initial BMI = 41.6 +/- 2.6 kg/m2). Weight loss caused a 38 +/- 8% decrease in adipocyte hormone-sensitive lipase concentration (P < 0.05) but was not associated with any consistent changes in the concentrations of GTP-dependent regulatory proteins, Gi1 alpha, Gi2 alpha, and G3 alpha. We conclude that diet-induced weight loss ameliorates the increase in basal lipolytic rates in persons with severe upper body obesity. These alterations are associated with changes in cellular hormone-sensitive lipase but not GTP-dependent regulatory protein concentrations.
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PMID:Effect of weight loss on whole body and cellular lipid metabolism in severely obese humans. 896 59

The adipocyte is a metabolically active cell that functions to store energy for times of energy deprivation or enhanced need. Obesity is characterized by increased lipid accumulation and turnover compared with the nonobese state. Both triglyceride synthesis and lipolysis are regulated metabolic processes in the adipocyte. Current research on the metabolic activities of the human adipocyte focus on plasma triglyceride hydrolysis and uptake of fatty acids by LPL, esterification of these fatty acids, and the subsequent triglyceride breakdown by hormone-sensitive lipase in response to stimulation of adrenergic receptors. These topics are discussed in relationship to the development of obesity.
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PMID:Fat cells. 897 49

The metabolic response of adipose tissue to stimuli leading to lipid mobilization is important in determining the direction of metabolism and the degree to which adipose tissue can store lipids and release fatty acids in times of need. The lipolytic machinery is controlled by the activity of hormone-sensitive lipase, which in turn is controlled by the cellular levels of cAMP. The production of cAMP is abnormal in the adipose tissue of some animal models of obesity. In the ob/ob mouse, the defective cAMP production has been associated with deficient levels of some of the isoforms of the guanine nucleotide transducing G-proteins and also with the low expression and functionality of the beta 3-adrenergic receptor (beta 3-AR). The recent discovery of the ob gene product leptin calls into question the role of the ob gene in the regulation of the cAMP cascade in adipose tissue. The importance of the beta 3-AR and leptin in regulating human adipose tissue metabolism remains to be clarified.
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PMID:Of mice and women: the beta 3-adrenergic receptor leptin and obesity. 901 68

High levels of adipose tissue-derived tumor necrosis factor-alpha (AT-TNF) mRNA and protein have previously been associated with genetic models of obesity and insulin resistance. Because there are endogenous TNF inhibitors it is unknown if AT-TNF activity is also increased. We hypothesized that AT-TNF activity would increase in older animals because of an accumulation of fat mass. We chose to study 2 different-aged male Fischer 344 rats, 3-month-old (young) and 14-month-old (mature) because fat mass should be quite different but insulin action on glucose metabolism similar. Indeed, mature rats had over 1.5-fold more fat mass, but whole body insulin resistance, as estimated by fasting plasma insulin, was similar to young rats. Mature rats had twice as much AT-TNF activity as the young in both the epididymal (EPI) and retroperitoneal (Retro) fat pads (p < .0005). AT-TNF correlated with fasting plasma insulin in Retro only (r = .48, p = .04). AT-TNF activity strongly correlated with cell size in both EPI and Retro (r = .79 and .81, respectively, p < .0001). Because cytokines can be regulated at several levels, AT-TNF activity, protein, and mRNA were measured. AT-TNF protein levels were higher in young rats, suggesting that these animals may secrete an inhibitor that reduces AT-TNF activity. There were no significant differences in AT-TNF mRNA between groups. Since TNF has been shown to affect several key genes in tissue culture, mRNA for lipoprotein lipase, hormone-sensitive lipase, and Glut4 were measured. No differences were found between groups. In summary, AT-TNF activity increased in mature animals in relation to adipose cell size.
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PMID:Adipose tissue-derived tumor necrosis factor-alpha activity is elevated in older rats. 922 23


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