PTIP Deficiency in B Lymphocytes Reduces Subcutaneous Fat Deposition in Mice

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Yaqin Xu^1,a, Doudou Zhu^2,b, Qin Yang^2,c, Dan Su^2,d*, and Yong Q. Chen^2,3,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

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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.

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KEY WORDS: PTIP, B lymphocytes, subcutaneous fat deposition, adipose homeostasis

DOI: 10.1134/S0006297921050060

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