Myeloid PGC1β attenuates high-fat-diet induced inflammation via mitochondrial fission/mtDNA/Nlrp3 pathway

Peroxisome proliferator-activated receptor gamma coactivators 1β (PGC1β) is essential in mitochondrial oxidative phosphorylation and alternative macrophages activation. To determine the contribution of PGC1β in obesity induced inflammation, Ppargc1b (PGC1β coding gene) myeloid conditional knockout mice (cKO) were fed with high fat diet (HFD) to examine the following effects. We found that HFD-fed cKO mice gained more fat with increased serum triglyceride (TG), low density lipoprotein (LDL), adiponectin, and leptin. Adipogenesis was stimulated while lipolysis was retarded in HFD-fed cKO mice adipose. Gluconeogenesis, lipogenesis, and fatty acid uptake were provoked while lipolysis was inhibited in HFD-fed cKO liver. Serum alanine transaminase (ALT) level, indicating fatty liver, also increased. Inflammatory cytokine including tumor necrosis factor-α (TNF-α), IL-1β, and IL-6 was elevated in cKO mice, accompanied with glucose intolerant and insulin resistance. Energy expenditure was decreased in HFD-fed cKO mice. Further evidence showed that cKO macrophages were prone to repolarize into M1 inflammatory type in vitro. In addition to mitochondrial biogenesis and oxidative respiration, PGC1β also modulated mitochondrial fission and cytosolic mitochondrial DNA (mtDNA) release, contributing to NLR family pyrin domain containing 3 (Nlrp3) inflammasome priming and activation. Treatment of mitochondrial fission inhibitor abolished the increased mRNA levels of Nlrp3 and IL-1β induced by PGC1β depletion. Nlrp3 knockdown restored the induced IL-1β mRNA expression by PGC1β deficiency. Myeloid PGC1β regulated adipocyte adipogenesis and lipolysis. PGC1β loss-of-function and mtDNA abundance correlated with obesity and diabetes. These observations uncovered the protective role of PGC1β against obesity induced systemic inflammation. Enhancing myeloid PGC1β function may be a potential strategy for the intervention of obesity and related diseases.