Extended lifespan and reduced adiposity in mice lacking the FAT10 gene

Abstract

The HLA-F adjacent transcript 10 (FAT10) is a member of the ubiquitin-like gene family that alters protein function/stability through covalent ligation. Although FAT10 is induced by inflammatory mediators and implicated in immunity, the physiological functions of FAT10 are poorly defined. We report the discovery that FAT10 regulates lifespan through pleiotropic actions on metabolism and inflammation. Median and overall lifespan are increased 20% in FAT10ko mice, coincident with elevated metabolic rate, preferential use of fat as fuel, and dramatically reduced adiposity. This phenotype is associated with metabolic reprogramming of skeletal muscle (i.e., increased AMP kinase activity, β-oxidation and -uncoupling, and decreased triglyceride content). Moreover, knockout mice have reduced circulating glucose and insulin levels and enhanced insulin sensitivity in metabolic tissues, consistent with elevated IL-10 in skeletal muscle and serum. These observations suggest novel roles of FAT10 in immune metabolic regulation that impact aging and chronic disease.

Keywords: longevity; mammals; obesity.

Fig. 1.

FAT10 KO mice live longer than littermate controls. (Right) Males and (Left) females are shown separately. The number of animals in each group is shown near the upper right corner of each graph. Arrows in the graphs represent the population of KO mice that exceeded the total lifespan of the WT littermate controls. The actual number and percentile of this population are shown to the right of the arrow inside the graphs’ areas. Kaplan–Meier analysis was performed on these data. The probability of survival is normalized to the final size of each group.

Fig. 2.

Adipose mass and adipocyte size are reduced in FAT10ko mice. (A) Body weight, (B) lean mass, (C) body fat, and (D) percent body fat of 12-wk-old WT and KO mice. (E) Representative H&E-stained sections of eWAT. (F) Adipocyte size distributions determined from eWAT histomorphometry and image analysis; (Inset) adiponectin (Adpn) and leptin gene expression in eWAT. *P < 0.05 (n = 6 per group).

Fig. 3.

The repatterning of energy metabolism in KO mice is shown by nighttime and daytime values for (A) energy intake, (B) energy expenditure, (C) locomotor activity, (D) energy balance, and (E) respiratory quotient in WT and KO mice. Data are presented as means ± SEMs. *P < 0.05 (n = 8 per group).

Fig. 4.

Molecular signatures promoting fatty acid oxidation are up-regulated in skeletal muscle of FAT10ko mice. (A) Expression of genes promoting fatty acid oxidation in quadriceps of WT and KO mice. (B) Total ACACA and phosphorylated ACACA (p∼ACACA) in quadriceps of WT and KO mice. Ubiquitin-E1 (E1) levels were used as a nonaffected reference. Representative blots are shown in Left. Densitometry data from multiple blots are summarized in Right. (C) Triglyceride turnover increase in adipocytes of KO mice is shown by increased in vitro basal and PKA-stimulated lipolysis (glycerol release) in KO adipocytes. (D) Western blots of eWAT lysates showing elevated levels of phosphorylated perilipin (p∼Plin) protein in KO mice with densitometry. (E) Western blots of eWAT lysates showing enhanced levels of p∼ACACA vs. total ACACA in KO mice with densitometry. (F) Up-regulation of genes promoting β-oxidation in epididymal AT of KO mice. Data are presented as means ± SEM. *P < 0.05 (n = 6 per group).

Fig. 5.

Increased efficiency of glucose–insulin regulation in FAT10ko mice. (A) I.p. ITTs (Left) and areas under curves (AUCs; Right; n = 8 per group). (B) I.p. GTTs (Left) and AUCs (Right) for WT and KO mice (n = 8 per group).

Fig. 6.

Altered profiles of inflammatory gene expression in FAT10ko mice are consistent with enhanced glucose–insulin homeostasis and delayed aging. (A) Attenuated proinflammatory gene expression in muscle of KO mice. (B) IL-10 protein in quadriceps (Left) and plasma (Right). Data are presented as means ± SEMs. *P < 0.05 (n = 6 per group).

Fig. 7.

FAT10 and TNF-α gene expressions are up-regulated in perigonadal adipose tissue of old WT mice, which is shown by RNA extracted from perigonadal adipose tissue of 2- (black bars) and 22-mo-old (striped bars) C57BL/6N males. RNA samples were assayed by QPCR to evaluate the expression levels of TNF-α and FAT10 using β-actin as a reference gene. t Test P values shown in graphs were obtained by EXCEL.