Journal
DIABETES
Volume 62, Issue 7, Pages 2347-2358Publisher
AMER DIABETES ASSOC
DOI: 10.2337/db12-1229
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Funding
- National Institutes of Health [HL-079584, HL-074399, HL-080499, HL-089920, HL-096032, HL-110488, HL-105157]
- Warren Chair in Diabetes Research of the University of Oklahoma Health Science Center
- American Heart Association Scientist Development Grant [11SDG5560036]
- National Established Investigator Award from the American Heart Association
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White adipose tissue (WAT) is not only a lipogenic and fat storage tissue but also an important endocrine organ that regulates energy homeostasis, lipid metabolism, appetite, fertility, and immune and stress responses. Liver kinase B1 (LKB1), a tumor suppressor, is a key regulator in energy metabolism. However, the role of LKB1 in adipogenesis is unknown. The current study aimed to determine the contributions of LKB1 to adipogenesis in vivo. Using the Fabp4-Cre/loxP system, we generated adipose tissue-specific LKB1 knockout (LKB1(ad-/-)) mice. LKB1(ad-/-) mice exhibited a reduced amount of WAT, postnatal growth retardation, and early death before weaning. Further, LEB1 deletion markedly reduced the levels of insulin receptor substrate 1 (IRS1), peroxisome proliferator-activated receptor gamma, CCAAT/enhancer-binding protein alpha, and phosphorylated AMP-activated protein kinase (AMPK). Consistent with these results, overexpression of constitutively active AMPK partially ablated IRS1 degradation in LKB1-deficient cells. LKB1 deletion increased the levels of F-box/WD repeat-containing protein (Fbw) 8, the IRS1 ubiquitination E3 ligase. Silencing of Fbw8 increased IRS1 levels. Finally, promoter analysis and DNA chromatin immunoprecipitation analysis identified three sterol regulatory element (SRE) sites in the Fbw8 promoter, where SRE-binding protein 1c binds and induces the expression of Fbw8. Taken together, these data indicate that LKB1 controls IRS1-dependent adipogenesis via AMPK in WAT.
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