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PTIP Deficiency in B Lymphocytes Reduces Subcutaneous Fat Deposition in Mice

Yaqin Xu1,a, Doudou Zhu2,b, Qin Yang2,c, Dan Su2,d*, and Yong Q. Chen2,3,e*

1School of Food Science and Technology, Jiangnan University, 214122 Wuxi, China

2Wuxi School of Medicine, Jiangnan University, 214122 Wuxi, China

3Wuxi Translational Medicine Research Center and Jiangsu Translational Medicine Research Institute Wuxi Branch, Jiangnan University, 214122 Wuxi, China

* To whom correspondence should be addressed.

Received February 6, 2021; Revised March 26, 2021; Accepted April 8, 2021
Recent studies have predominantly focused on the role of B cells in metabolic diseases, yet the function of B cells in adipose homeostasis remains unclear. Pax transactivation domain-interacting protein (PTIP), a licensing factor for humoral immunity, is necessary for B cell development and activation. Here, using mice that lack PTIP in B cells (PTIP−/− mice), we explored the role of B cells in adipose homeostasis under physiological conditions. Fat deposition in 8-week-old mice was measured by micro-CT, and PTIP−/− mice presented a marked decrease in the deposition of subcutaneous adipose tissue (SAT). Untargeted lipidomics revealed that the triglyceride composition in SAT was altered in PTIP−/− mice. In addition, there was no difference in the number of adipocyte progenitor cells in the SAT of wild-type (WT) and PTIP−/− mice as measured by flow cytometry. To study the effects of steady-state IgM and IgG antibody levels on fat deposition, PTIP−/− mice were injected intraperitoneally with serum from WT mice once every 3-4 days for 4 weeks. The iSAT mass of the recipient mice showed no significant increase in comparison to the controls after 4 weeks of injections. Our findings reveal that PTIP plays an essential role in regulating subcutaneous adipocyte size, triglyceride composition, and fat deposition under physiological conditions by controlling B cells. The decreased subcutaneous fat deposition in PTIP−/− mice does not appear to be related to the number of adipocyte progenitor cells. The steady-state levels of IgM and IgG antibodies in vivo are not associated with the subcutaneous fat deposition.
KEY WORDS: PTIP, B lymphocytes, subcutaneous fat deposition, adipose homeostasis

DOI: 10.1134/S0006297921050060