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Berardinelli-seip congenital lipodystrophy 2/seipin is a cell-autonomous regulator of lipolysis essential for adipocyte differentiation.

ABSTRACT: Mutations in BSCL2 underlie human congenital generalized lipodystrophy. We inactivated Bscl2 in mice to examine the mechanisms whereby absence of Bscl2 leads to adipose tissue loss and metabolic disorders. Bscl2(-/-) mice develop severe lipodystrophy of white adipose tissue (WAT), dyslipidemia, insulin resistance, and hepatic steatosis. In vitro differentiation of both Bscl2(-/-) murine embryonic fibroblasts (MEFs) and stromal vascular cells (SVCs) reveals normal early-phase adipocyte differentiation but a striking failure in terminal differentiation due to unbridled cyclic AMP (cAMP)-dependent protein kinase A (PKA)-activated lipolysis, which leads to loss of lipid droplets and silencing of the expression of adipose tissue-specific transcription factors. Importantly, such defects in differentiation can be largely rescued by inhibitors of lipolysis but not by a gamma peroxisome proliferator-activated receptor (PPAR?) agonist. The residual epididymal WAT (EWAT) in Bscl2(-/-) mice displays enhanced lipolysis. It also assumes a "brown-like" phenotype with marked upregulation of UCP1 and other brown adipose tissue-specific markers. Together with decreased Pref1 but increased C/EBP? levels, these changes highlight a possible increase in cAMP signaling that impairs terminal adipocyte differentiation in the EWAT of Bscl2(-/-) mice. Our study underscores the fundamental role of regulated cAMP/PKA-mediated lipolysis in adipose differentiation and identifies Bscl2 as a novel cell-autonomous determinant of activated lipolysis essential for terminal adipocyte differentiation.

SUBMITTER: Chen W

PROVIDER: S-EPMC3295006 | biostudies-literature | 2012 Mar

REPOSITORIES: biostudies-literature

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Berardinelli-seip congenital lipodystrophy 2/seipin is a cell-autonomous regulator of lipolysis essential for adipocyte differentiation.

Chen Weiqin W Chang Benny B Saha Pradip P Hartig Sean M SM Li Lan L Reddy Vasumathi Theegala VT Yang Yisheng Y Yechoor Vijay V Mancini Michael A MA Chan Lawrence L

Molecular and cellular biology 20120123 6

Mutations in BSCL2 underlie human congenital generalized lipodystrophy. We inactivated Bscl2 in mice to examine the mechanisms whereby absence of Bscl2 leads to adipose tissue loss and metabolic disorders. Bscl2(-/-) mice develop severe lipodystrophy of white adipose tissue (WAT), dyslipidemia, insulin resistance, and hepatic steatosis. In vitro differentiation of both Bscl2(-/-) murine embryonic fibroblasts (MEFs) and stromal vascular cells (SVCs) reveals normal early-phase adipocyte differenti ...[more]

PMID: 22269949

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Project description:ObjectiveUnderstanding the mechanisms that control brown adipose tissue (BAT) mass and functionality is crucial for our understanding of how the disruption of energy homeostasis leads to obesity. Bernerdinali Seip Congenital Lipodystrophy (BSCL) type 2 (BSCL2, a.k.a. SEIPIN), a lipodystrophy-associated protein, has been shown to not be required for brown adipogenesis, but it has been shown to be essential for perinatal BAT development. However, its role in mature BAT maintenance and thermogenic programing remains poorly understood.MethodsWe subjected Bscl2f/f and Bscl2UCP1-BKO (BKO) mice with a brown adipose-specific loss of BSCL2 through UCP1 promoter-driven Cre to environmental, pharmacological and diet interventions to challenge BAT functionality and reprogramming. We carried out physiological, molecular and transcriptomic analyses of BAT.ResultsThe deletion of BSCL2 in mature brown adipocytes increased sympathetic nervous system-independent cAMP/protein kinase A (PKA) signaling in BAT. Such activation reduced BAT triglyceride content and mass and was sufficient to reduce plasma triglyceride, but not enough to combat thermoneutral and high fat diet-induced obesity. Surprisingly, BKO mice displayed an impaired response to acute and chronic cold challenges despite cAMP/PKA activation. When subjected to chronic cold exposure or the administration of a β3-adrenergic agonist, CL 316,243, BKO mice failed to induce BAT recruitment and underwent dramatic brown adipocyte loss. Transcriptomic analysis revealed pathological BAT remodeling with inflammation and fibrosis, which was further exacerbated by a chronic thermogenic challenge in BKO mice. Mechanistically, we found abnormal mitochondrial shapes and function in BAT of BKO mice housed at 21 °C; as well as mitochondrial DNA depletion and necroptotic-mediated brown adipocyte death after chronic thermogenic insult.ConclusionBSCL2-mediated lipid catabolism within BAT is crucial for mature brown adipocyte function and survival both during times of activation and quiescence. BSCL2 is an important regulator of mature brown adipocyte mitochondrial metabolism, necroptosis and thus adaptive thermogenesis.

Project description:Berardinelli-Seip congenital lipodystrophy (BSCLD) (OMIM#269700) is a rare autosomal recessive disorder characterized by marked paucity of adipose tissue, a muscular habitus, insulin resistance, hypertriglyceridemia and hepatic steatosis. It is an anabolic syndrome due to the deficiency of leptin, a lipid modulator, leading to the inappropriate mobilization of fat. Four types of BSCLD have been described based on the site of genetic mutation. Type 2 accounts for an earlier onset, more severe complications and intellectual disability. This is due to the lower leptin levels and the loss of functional seipin in type 2 BSCLD. We report the evolving phenotype of type 2 BSCLD in a boy clinically diagnosed at age 5 months and confirmed by molecular genetic study which revealed a pathogenic mutation in the BSCL2 gene: c.782dupG, p.lle262Hisfs*12homozygous. He is the firstborn of non-consanguineous parents with no significant family history. He has a muscular habitus with a distinct facies, hypertrichosis, absence of subcutaneous fat and hepatomegaly. Investigations revealed hypertriglyceridemia and insulin resistance. A conventional approach to management with dietary fat restriction successfully controlled his biochemical parameters, thus preventing catastrophic complications such as systemic arterial hypertension, heart failure and pancreatitis. Genetic counseling was conferred and prenatal testing recommended for future pregnancies. On follow-up, he had a muscular habitus with hepatomegaly and global developmental delay. Despite early correction of his biochemical parameters, an abdominal ultrasound revealed early onset fatty liver disease and an echocardiogram showed a thickened interventricular septum suggestive of early hypertrophic obstructive cardiomyopathy (HOCM). A fasting serum leptin done was low at 0.8 ng/mL (normal range, 2.0-5.6 ng/mL) confirming leptin deficiency. A leptin analog is now available as an adjunct to mollify the metabolic complications of BSCLD. However, it is yet to be available in developing nations and whether it is able to assuage progressive hepatic cholestasis and HOCM remains a field to venture. This report highlights the importance of early recognition and confirmation by molecular diagnosis to direct appropriate surveillance of complications. This also enables early genetic counseling and prenatal testing for future pregnancies. We describe the evolving phenotype, pertinent investigations and the conventional approach to the management of BSCLD.

Dataset Information

Berardinelli-seip congenital lipodystrophy 2/seipin is a cell-autonomous regulator of lipolysis essential for adipocyte differentiation.

Publications

Berardinelli-seip congenital lipodystrophy 2/seipin is a cell-autonomous regulator of lipolysis essential for adipocyte differentiation.

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