Downregulation of adipose LPL by PAR2 contributes to the development of hypertriglyceridemia
Yiheng Huang, Liujun Chen, Lisha Li, Yadan Qi, Haibin Tong, Hong Wu, Jinjie Xu, Lin Leng, Sukhinder Cheema, Guang Sun, Zhengyuan Xia, John McGuire, Brian Rodrigues, Lawrence H. Young, Richard Bucala, Dake Qi
Yiheng Huang, Liujun Chen, Lisha Li, Yadan Qi, Haibin Tong, Hong Wu, Jinjie Xu, Lin Leng, Sukhinder Cheema, Guang Sun, Zhengyuan Xia, John McGuire, Brian Rodrigues, Lawrence H. Young, Richard Bucala, Dake Qi
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Research Article Metabolism

Downregulation of adipose LPL by PAR2 contributes to the development of hypertriglyceridemia

Abstract

Lipoprotein lipase (LPL) hydrolyzes circulating triglycerides (TGs), releasing fatty acids (FA) and promoting lipid storage in white adipose tissue (WAT). However, the mechanisms regulating adipose LPL and its relationship with the development of hypertriglyceridemia are largely unknown. WAT from obese humans exhibited high PAR2 expression, which was inversely correlated with the LPL gene. Decreased LPL expression was also inversely correlated with elevated plasma TG levels, suggesting that adipose PAR2 might regulate hypertriglyceridemia by downregulating LPL. In mice, aging and high palmitic acid diet (PD) increased PAR2 expression in WAT, which was associated with a high level of macrophage migration inhibitory factor (MIF). MIF downregulated LPL expression and activity in adipocytes by binding with CXCR2/4 receptors and inhibiting Akt phosphorylation. In a MIF overexpression model, high-circulating MIF levels suppressed adipose LPL, and this suppression was associated with increased plasma TGs but not FA. Following PD feeding, adipose LPL expression and activity were significantly reduced, and this reduction was reversed in Par2–/– mice. Recombinant MIF infusion restored high plasma MIF levels in Par2–/– mice, and the levels decreased LPL and attenuated adipocyte lipid storage, leading to hypertriglyceridemia. These data collectively suggest that downregulation of adipose LPL by PAR2/MIF may contribute to the development of hypertriglyceridemia.

Authors

Yiheng Huang, Liujun Chen, Lisha Li, Yadan Qi, Haibin Tong, Hong Wu, Jinjie Xu, Lin Leng, Sukhinder Cheema, Guang Sun, Zhengyuan Xia, John McGuire, Brian Rodrigues, Lawrence H. Young, Richard Bucala, Dake Qi

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Figure 3

PAR2 gene expression increases adipose MIF release and circulating MIF levels, thereby downregulating LPL expression and activation in WAT.

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PAR2 gene expression increases adipose MIF release and circulating MIF l...
(A–D) Adipose tissues were collected from C57BL/6 WT mice at 4–25 weeks of age with normal chow feeding. F2rl1 gene was measured by qPCR (A). Plasma MIF levels were evaluated in 4- and 25-week WT or Par2–/– mice by ELISA (B) and LPL protein expression and activity were measured in C and D. (E–G) WT and Par2–/– mice at 20 weeks were fed with normal chow (NC) or high palmitic acid diet (PD) feeding for 8 weeks. Plasma MIF levels were quantified subsequently in E. LPL expression (F) and F2rl1 gene (G) were quantified in WT mice with high palmitic acid diet feeding following MIF neutralization with anti-MIF antibody (20 mg/kg, i.p. twice a week). n = 3–9 each animal group. All data are analyzed by Student’s t test or 1-way ANOVA and presented as mean ± SD. *P ≤ 0.05 increase vs. 4 weeks in A, vs. other groups in B and E, or vs. IgG in F; #P ≤ 0.05 reduction vs. other groups in C and D.