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Seipin deficiency is responsible for type 2 congenital generalized lipodystrophy with severe loss of adipose tissue and can lead to hepatic steatosis, insulin resistance (IR), and dyslipidemia in humans. Adipose tissue secretes many adipokines that are central to the regulation of metabolism. In this study, we investigated whether transplantation of normal adipose tissue could ameliorate severe hepatic steatosis, IR, and dyslipidemia in lipoatrophic seipin knockout (SKO) mice. Normal adipose tissue from wild-type mice was transplanted into 6-wk-old SKO mice. At 4 mo after adipose tissue transplantation (AT), the transplanted fat survived with detectable blood vessels, and the reduced levels of plasma leptin, a major adipokine, were dramatically increased. Severe hepatic steatosis, IR, and dyslipidemia in SKO mice were ameliorated after AT. In addition, abnormal hepatic lipogenesis and β-oxidation gene expression in SKO mice were improved after AT. Our results suggest that AT may be an effective treatment to improve lipodystrophy-associated metabolic disorders. [ABSTRACT FROM AUTHOR]

Brown adipose tissue (BAT) plays a key role in thermogenesis to protect the body from cold and obesity. White adipose tissue (WAT) stores excess energy in the form of triglycerides. To better understand the genetic effect on regulation of WAT and BAT, we investigated the fat fraction (FF) in two types of adipose tissues in ob/ob, human BSCL2/seipin gene knockout (SKO), Fsp27 gene knockout (Fsp27-/-), and wild-type (WT) mice in vivo using chemical shift selective imaging and 1H-MR spectroscopy. We reported that the visceral fat volume in WAT was significantly larger in ob/ob mice, but visceral fat volumes were lower in SKO and Fsp27-/- mice compared with WT mice. BAT FF was significantly higher in ob/ob mice than the WT group and similar to that of WAT. In contrast, WAT FFs in SKO and Fsp27-/- mice were lower and similar to that of BAT. The adipocyte size of WAT in ob/ob mice and the BAT adipocyte size in ob/ob, SKO, and Fsp27 mice were significantly larger compared with WT mice. However, the WAT adipocyte size was significantly smaller in SKO mice than in WT mice. Positive correlations were observed between the adipocyte size and FFs of WAT and BAT. These results suggested that smaller adipocyte size correlates with lower FFs of WAT and BAT. In addition, the differences in FFs in WAT and BAT measured by MR methods in different mouse models were related to the different regulation effects of ob, seipin, or Fsp27 gene on developing WAT and BAT. [ABSTRACT FROM AUTHOR]

Berardinelli-Seip congenital lipodystrophy type 2 (BSCL2) is a recessive disorder characterized by an almost complete loss of adipose tissue, insulin resistance, and fatty liver. BSCL2 is caused by lossof- function mutations in the BSCL2/seipin gene, which encodes seipin. The essential role for seipin in adipogenesis has recently been established both in vitro and in vivo. However, seipin is highly upregulated at later stages of adipocyte development, and its role in mature adipocytes remains to be elucidated. We therefore generated transgenic mice overexpressing a short isoform of human BSCL2 gene (encoding 398 amino acids) using the adipocyte-specific aP2 promoter. The transgenic mice produced ∼150% more seipin than littermate controls in white adipose tissue. Surprisingly, the increased expression of seipin markedly reduced the mass of white adipose tissue and the size of adipocytes and lipid droplets. This may be due in part to elevated lipolysis rates in the transgenic mice. Moreover, there was a nearly 50% increase in the triacylglycerol content of transgenic liver. These results suggest that seipin promotes the differentiation of preadipocytes but may inhibit lipid storage in mature adipocytes. [ABSTRACT FROM AUTHOR]