NT-PGC-1α deficiency attenuates high-fat diet-induced obesity by modulating food intake, fecal fat excretion and intestinal fat absorption

Abstract

Transcriptional coactivator PGC-1α and its splice variant NT-PGC-1α regulate metabolic adaptation by modulating many gene programs. Selective ablation of PGC-1α attenuates diet-induced obesity through enhancing fatty acid oxidation and thermogenesis by upregulation of NT-PGC-1α in brown adipose tissue (BAT). Recently, we have shown that selective ablation of NT-PGC-1α reduces fatty acid oxidation in BAT. Thus, the objective of this study was to test our hypothesis that NT-PGC-1α^-/- mice would be more prone to diet-induced obesity. Male and female NT-PGC-1α^+/+ (WT) and NT-PGC-1α^-/- mice were fed a regular chow or 60% high-fat (HF) diet for 16 weeks. Contrary to our expectations, both male and female NT-PGC-1α^-/- mice fed HFD were protected from diet-induced obesity, with more pronounced effects in females. This lean phenotype was primarily driven by reduced dietary fat intake. Intriguingly, HFD-fed female, but not male, NT-PGC-1α^-/- mice further exhibited decreased feed efficiency, which was closely associated with increased fecal fat excretion and decreased uptake of fatty acids by the intestinal enterocytes and adipocytes with a concomitant decrease in fatty acid transporter gene expression. Collectively, our results highlight the role for NT-PGC-1α in regulating whole body lipid homeostasis under HFD conditions.

Figure 1

Analysis of the effects of NT-PGC-1α ablation on diet-induced obesity. (A,B) Measurements of body weight and fat mass of male WT and NT-PGC-1α^−/− mice during chow (n = 11 per group) or HFD (n = 12 per group) feeding. Two-way ANOVA was used to determine the differences between the genotypes. BW: F (1, 24) = 9.726, P = 0.0048; FM: F (1, 22) = 5.939, P = 0.0234 in HFD-fed group. BW: F (1, 22) = 3.485, P = 0.0753; FM: F (1, 20) = 5.843, P = 0.0253 in chow-fed group. (C) Body composition of male WT and NT-PGC-1α^−/− mice after 16 weeks of either chow- or HFD-feeding. Data are presented as the mean ± SEM. *P < 0.05 determined by Student’s t test. (D,E) Body weight and fat mass of female WT and NT-PGC-1α^−/− mice during chow (n = 11 per group) or HFD (n = 12 per group) feeding. Two-way ANOVA was used to determine the differences between the genotypes. BW: F (1, 24) = 20.50, P = 0.0001; FM: F (1, 22) = 21.34, P = 0.0001 in HFD-fed group. BW: F (1, 22) = 0.7853, P = 0.3851; FM: F (1, 20) = 2.426, P = 0.1350 in chow-fed group. (F) Body composition of female WT and NT-PGC-1α^−/− mice after 16 weeks of either chow- or HFD-feeding. Data are presented as the mean ± SEM. **P < 0.01, ***P < 0.001 determined by Student’s t test.

Figure 2

Whole body glucose homeostasis in NT-PGC-1α^−/− mice fed HFD. (A,B) Blood glucose and insulin levels in HFD-fed male and female WT and NT-PGC-1α^−/− mice in the fed and fasted states (n = 9 per group). Data are presented as the mean ± SEM. *P < 0.05, **P < 0.001 determined by Student’s t test. (C,D) Glucose tolerance test in male and female WT and NT-PGC-1α^−/− mice fed HFD for 9 weeks (n = 11–12 per group) in the overnight-fasted state. Two-way ANOVA was used to determine the differences between the genotypes. Males: F (1, 105) = 6.009, P = 0.0159; females: F (1, 110) = 11.15, P = 0.0011. (E,F) Insulin tolerance test in male and female WT and NT-PGC-1α^−/− mice fed HFD for 10 weeks in the 5 h-fasted state (n = 11–12 per group).

Figure 3

Caloric intake and energy metabolism in NT-PGC-1α^−/− mice fed HFD. (A–C) Energy expenditure, food intake, and average locomotor activity of male WT and NT-PGC-1α^−/− mice fed HFD (n = 11–12 per group). (D–F) Energy expenditure, food intake, and average locomotor activity of female WT and NT-PGC-1α^−/− mice fed HFD (n = 11–12 per group). Two-way ANOVA was used to determine the differences in food intake between the genotypes. Males: F (1, 4642) = 23.33, ^#P < 0.0001; females: F (1, 4326) = 834.7, ^#P < 0.0001. (G) Cumulative food intake of male and female WT and NT-PGC-1α^−/− mice during HFD feeding (n = 12 per group). Food intake was monitored once a week for 16 weeks and was expressed as g/mouse. (H) Cumulative weight (g) gained over 16 weeks divided by the cumulative food intake (g/mouse) over the same period on HFD (n = 12 per group). (I) Triglyceride content in feces from male and female WT and NT-PGC-1α^−/− mice fed HFD (n = 10 per group). All data are presented as the mean ± SEM. *P < 0.05, ***P < 0.001 determined by Student’s t test.

Figure 4

NT-PGC-1α ablation reduces HFD-induced adipocyte hypertrophy and inflammation. (A) Weights of tissues collected from female WT and NT-PGC-1α^−/− mice fed HFD for 16 weeks (n = 12 per group). (B) Triglyceride content of livers from female WT and NT-PGC-1α^−/− mice fed HFD (n = 10 per group). (C) Representative images of H&E-stained sections of adipose tissues and livers from female WT and NT-PGC-1α^−/− mice fed HFD. Images were viewed through the NDP.view 2 software (https://www.hamamatsu.com/us/en/product/type/U12388-01/index.html). Magnification ×16.1 (BAT), ×5 (iWAT, gWAT), and ×10 (liver). (D, E) Quantitative real time PCR analysis of genes involved in inflammation in inguinal and gonadal adipose tissue from WT and FL-PGC-1α^−/− female mice fed HFD (n = 10–12 per group). All data are presented as the mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001 determined by Student’s t test.

Figure 5

Decreased fatty acid uptake in adipose tissue from HFD-fed female NT-PGC-1α^−/− mice. (A, B) Quantitative real time PCR analysis in inguinal and gonadal adipose tissue from female WT and NT-PGC-1α^−/− mice fed HFD for 16 weeks (n = 12 per group). (C) Upregulation of fatty acid uptake genes by NT-PGC-1 in 3T3-L1 adipocytes (n = 6 per group). (D, E) Uptake of [¹⁴C]-palmitate in inguinal and gonadal adipose tissue from female WT and NT-PGC-1α^−/− mice fed HFD for 8 weeks (n = 6 per group). (F, G) Expression of fatty acid uptake genes in muscle and liver from female WT and NT-PGC-1α^−/− mice fed HFD for 16 weeks (n = 12 per group). All data are presented as the mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, ^#P < 0.0001 determined by Student’s t test.

Figure 6

Reduced intestinal lipid absorption in NT-PGC-1α^−/− female mice fed HFD. (A) Uptake of [¹⁴C]-palmitic acids in jejunal enterocytes isolated from female WT and NT-PGC-1α^−/− mice fed HFD (n = 5 per group). Data are presented as the mean ± SEM. **P < 0.01 determined by Student’s t test. (B) Quantitative real time PCR analysis of genes involved in intestinal fat absorption and secretion in the jejunum of female WT and NT-PGC-1α^−/− mice fed HFD (n = 6–7 per group). Data are presented as the mean ± SEM. *P < 0.05 determined by Student’s t test. (C) Oral fat tolerance test. Female WT and NT-PGC-1α^−/− mice fed HFD for 8 weeks were fasted overnight and administered by gavage of olive oil. Blood samples were collected at indicated times and analyzed for serum TG concentrations (n = 7 per group). Two-way ANOVA was used to determine the differences in serum TG levels between the genotypes. F (1, 60) = 7.941, **P = 0.0065.