Depot-specific differences in fat mass expansion in WT and ob/ob mice
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Xinxia Wang1,*, Caihua Yu1,*, Jie Feng1, Jin Chen1, Qin Jiang1, Shihuan Kuang2 and Yizhen Wang1
1College of Animal Sciences, Zhejiang University, Key Laboratory of Animal Nutrition & Feed Sciences, Ministry of Agriculture, Zhejiang Provincial Laboratory of Feed and Animal Nutrition, Hangzhou, Zhejiang 310058, P. R. China
2Department of Animal Sciences and Center for Cancer Research, Purdue University, West Lafayette, IN 47907, USA
*These authors have contributed equally to this work
Yizhen Wang, email: [email protected]
Keywords: adipogenesis, subcutaneous adipose tissue, viseral adipose tissue, fatty acid uptake, β-oxidation
Received: November 11, 2016 Accepted: February 13, 2017 Published: May 16, 2017
The study was designed to investigate the cellular mechanisms underlying the differential fat expansion in different fat depots in wild type (WT) and ob/ob (OB) mice. At 6 weeks old, no differences in fat mass were found between SAT and VAT in WT mice, while O-SAT showed significantly higher weight than that of O-VAT. The average adipocyte size of SAT (~ 4133.47 μm2) was smaller than that of VAT (~ 7438.91 μm2) in OB mice. O-SAT preadipocytes gained higher triglyceride contents and higher levels of PPARγ and C/EBPα than did O-VAT preadipocytes upon in vitro differentiation. W-SAT and W-VAT displayed no significant differences in fatty acid uptake, while 1.36 fold significantly higher fatty acid uptake was found in O-SAT compared to O-VAT. Approximately 52% of the radioactivity recovered in cellular lipids was found in TAG in O-SAT, which was significantly higher than the other three adipocyte types. Significantly more radiolabelled oleic acid was β-oxidized to CO2 in adipocytes from O-VAT than that from O-SAT. ATP production was significantly lower in W-SAT compared with W-VAT, whereas no significantly ATP level was observed between O-SAT and O-VAT. Expression of UCP-1 in SAT from either WT or OB mice was significantly higher than the counterpart of VAT, which demonstrated higher uncoupled respiration and lower oxidative phosphorylation in SAT. Together, a combined increase in adipogenesis and FA uptake, and decreases in β-oxidation and ATP production, contributed to greater expansion of SAT compared to VAT in obese mice.
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