1498-P: A Feedback Loop between miRNA Processing Complex and miR-3975 in Western Diet–Induced Brown Adipose Tissue Dysfunction

Brown adipose tissue (BAT) is considered as promising therapeutic targets for obesity and metabolic disorder through modulation of energy homeostasis. microRNAs (miRNAs) are established as essential modulators of biological processes in many tissues, including the differentiation and function of BAT. Here we demonstrated that high-fat/high fructose associated dysfunction of BAT coincides with impaired miRNA-processing pathway in a feedback loop with miR-3975 activation. Eight-week-old male C57BL/6 mice were fed a low-fat diet (10% fat and 17% sucrose; LFD) and high fat-high fructose (45% fat, 17% sucrose, and 17% fructose; HFHFD) for 4, 12, and 20 weeks (n=6-9 per group). We evaluated expression levels of apoptosis markers, thermogenesis markers, miRNA biogenesis regulators, and miRNAs in BAT. Mice fed an HFHFD showed a gradually significance increased body weight and brown adipose tissue weight when compared to the mice fed with LFD. BAT of HFHFD fed mice has a pale appearance versus feeding period matched LFD fed mice. The protein expression of thermogenesis markers, UCP1 (P <0.05), and PGC1α (P <0.05) were shown to decrease after 12 weeks of HFHFD diet feeding. The apoptosis marker, the Bax/Bcl-2 ratio, was upregulated at 12 weeks (P < 0.01). Mice fed HFHFD for 12 and 20 weeks showed a significant decrease in Dicer (P < 0.01 for 12 and 20 weeks) and TRBP2 (P < 0.01 for 12 weeks and P < 0.0001 for 20 weeks). miR-3975, which is predicted miRNA to regulate both Dicer and TRBP2 by IPA was activated at 12 weeks (P < 0.01), while inactivated at 20 weeks (P < 0.001). Our results suggest that miR-3975 acts as a component of a negative feedback loop that blocks miRNA biogenesis machinery through the inhibition of Dicer and TRBP2 expression. Therefore, long-term HFHFD may disturb miRNA processing and contribute to brown adipose tissue dysfunction and apoptosis by modulation of miRNA expression. We are currently investigating the novel feedback loop in brown adipocyte primary cells. Disclosure M. Park: None. S. Meruvu: None. J. Zhang: None. M. Choudhury: None.