Targeted disruption of hormone-sensitive lipase results in male sterility and adipocyte hypertrophy, but not in obesity
18 Jan 2000-Proceedings of the National Academy of Sciences of the United States of America (National Academy of Sciences)-Vol. 97, Iss: 2, pp 787-792
TL;DR: It is shown that HSL is required for spermatogenesis but is not the only enzyme that mediates the hydrolysis of triacylglycerol stored in adipocytes, and that adipocytes were significantly enlarged and the size differences between cell and tissue suggests the heterogeneity of adipocytes.
Abstract: Hormone-sensitive lipase (HSL) is known to mediate the hydrolysis not only of triacylglycerol stored in adipose tissue but also of cholesterol esters in the adrenals, ovaries, testes, and macrophages. To elucidate its precise role in the development of obesity and steroidogenesis, we generated HSL knockout mice by homologous recombination in embryonic stem cells. Mice homozygous for the mutant HSL allele (HSL−/−) were superficially normal except that the males were sterile because of oligospermia. HSL−/− mice did not have hypogonadism or adrenal insufficiency. Instead, the testes completely lacked neutral cholesterol ester hydrolase (NCEH) activities and contained increased amounts of cholesterol ester. Many epithelial cells in the seminiferous tubules were vacuolated. NCEH activities were completely absent from both brown adipose tissue (BAT) and white adipose tissue (WAT) in HSL−/− mice. Consistently, adipocytes were significantly enlarged in the BAT (5-fold) and, to a lesser extent in the WAT (2-fold), supporting the concept that the hydrolysis of triacylglycerol was, at least in part, impaired in HSL−/− mice. The BAT mass was increased by 1.65-fold, but the WAT mass remained unchanged. Discrepancy of the size differences between cell and tissue suggests the heterogeneity of adipocytes. Despite these morphological changes, HSL−/− mice were neither obese nor cold sensitive. Furthermore, WAT from HSL−/− mice retained 40% of triacylglycerol lipase activities compared with the wild-type WAT. In conclusion, HSL is required for spermatogenesis but is not the only enzyme that mediates the hydrolysis of triacylglycerol stored in adipocytes.
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TL;DR: The development of brown adipose tissue with its characteristic protein, uncoupling protein-1 (UCP1), was probably determinative for the evolutionary success of mammals, as its thermogenesis enhances neonatal survival and allows for active life even in cold surroundings.
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TL;DR: The results indicate that ATGL is rate limiting in the catabolism of cellular fat depots and plays an important role in energy homeostasis.
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References
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TL;DR: In this paper, the authors described a simplified version of the method and reported the results of a study of its application to different tissues, including the efficiency of the washing procedure in terms of the removal from tissue lipides of some non-lipide substances of special biochemical interest.
59,550 citations
4,041 citations
01 Feb 1964
TL;DR: This article marks the beginning of Rodbell's interest in cell receptors and related his discovery that fat cells could be isolated from other cells by treating them with preparations of collagenase, and also found that insulin could stimulate glucose uptake.
Abstract: This article marks the beginning of Rodbell's interest in cell receptors. In it, he related his discovery that fat cells
could be isolated from other cells by treating them with preparations of collagenase, and also found that insulin could stimulate
glucose uptake. This had far-reaching implications for the treatment of various diseases, as it was the first demonstration
that insulin acted on individual cells.
3,787 citations
TL;DR: It is concluded that the LDL receptor is responsible in part for the low levels of VLDL, IDL, and LDL in wild-type mice and that adenovirus-encoded LDL receptors can acutely reverse the hypercholesterolemic effects of LDL receptor deficiency.
Abstract: We employed homologous recombination in embryonic stem cells to produce mice lacking functional LDL receptor genes. Homozygous male and female mice lacking LDL receptors (LDLR-/- mice) were viable and fertile. Total plasma cholesterol levels were twofold higher than those of wild-type litter-mates, owing to a seven- to ninefold increase in intermediate density lipoproteins (IDL) and LDL without a significant change in HDL. Plasma triglyceride levels were normal. The half-lives for intravenously administered 125I-VLDL and 125I-LDL were prolonged by 30-fold and 2.5-fold, respectively, but the clearance of 125I-HDL was normal in the LDLR-/- mice. Unlike wild-type mice, LDLR-/- mice responded to moderate amounts of dietary cholesterol (0.2% cholesterol/10% coconut oil) with a major increase in the cholesterol content of IDL and LDL particles. The elevated IDL/LDL level of LDLR-/- mice was reduced to normal 4 d after the intravenous injection of a recombinant replication-defective adenovirus encoding the human LDL receptor driven by the cytomegalovirus promoter. The virus restored expression of LDL receptor protein in the liver and increased the clearance of 125I-VLDL. We conclude that the LDL receptor is responsible in part for the low levels of VLDL, IDL, and LDL in wild-type mice and that adenovirus-encoded LDL receptors can acutely reverse the hypercholesterolemic effects of LDL receptor deficiency.
1,604 citations
TL;DR: In this article, the role of UCP in the regulation of body mass was determined by targeted inactivation of the gene encoding it, and it was found that UCP-deficient mice consume less oxygen after treatment with a β3-adrenergic-receptor agonist and are sensitive to cold, indicating that their thermo-regulation is defective.
Abstract: The mitochondrial uncoupling protein (UCP) in the mitochondrial inner membrane of mammalian brown adipose tissue generates heat by uncoupling oxidative phosphorylation1. This process protects against cold2 and regulates energy balance3. Manipulation of thermogenesis could be an effective strategy against obesity4–9. Here we determine the role of UCP in the regulation of body mass by targeted inactivation of the gene encoding it. We find that UCP-deficient mice consume less oxygen after treatment with a β3-adrenergic-receptor agonist and that they are sensitive to cold, indicating that their thermo-regulation is defective. However, this deficiency caused neither hyperphagia nor obesity in mice fed on either a standard or a high-fat diet. We propose that the loss of UCP may be compensated by UCP2, a newly discovered homologue of UCP; this gene is ubiquitously expressed and is induced in the brown fat of UCP-deficient mice.
1,309 citations