G Protein‐Coupled Receptor 17 (Gpr17) Enhances Leptin and Insulin Sensitivity in Lean and Obese Mouse Models

Figures

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  FIGURE 1. Improved energy expenditure in Gpr17 germline knockout (KO) mice under NCD. (A) The mRNA levels of Gpr17 in the hypothalamus (WT = 13, KO = 7). An unpaired two‐tailed Student's t‐test was performed. (B) Body weight of adult WT and whole‐body Gpr17 KO mice (WT = 6, KO = 7). (C, D) The mRNA levels of Pomc and Agrp in the hypothalamus (WT = 17–20, KO = 9). An unpaired two‐tailed Student's t‐test was performed. (E–I) Representative mouse energy expenditure (EE), oxygen consumption (VO2), activity, respiratory exchange ratio (RER), and food intake (FI) during ad libitum feeding (WT = 6, KO = 7). Two‐way ANOVA was performed. (J, K) Representative mouse energy expenditure and oxygen consumption recordings during night fasting (WT = 6, KO = 7). An unpaired two‐tailed Student's t‐test was performed. (L) Body weight of adult WT and whole‐body Gpr17 KO mice after 1 week of HFD (WT = 6, KO = 7). (M) The activity of WT and whole‐body Gpr17 KO mice during short‐term HFD (WT = 6, KO = 7). Two‐way ANOVA was performed. *p < 0.05, **p < 0.01, ****p < 0.0001. Data were displayed as means ± SEM. [Color figure can be viewed at wileyonlinelibrary.com]

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  FIGURE 2. Leptin‐deficient (ob/ob) Gpr17 knockout (KO) mice are more sensitive to leptin‐mediated feeding suppression. (A, B) Growth curves of male (n = 11 for each group) and female (WT ob/ob = 12–19, KO ob/ob = 6) WT and KO ob/ob mice from 1 to 3 weeks. Two‐way ANOVA was performed. (C) Growth curves of adult male mice from 16 to 18 weeks (WT ob/ob = 6–7, KO ob/ob = 8–10). (D, E) Agrp and Pomc mRNA levels in the hypothalamus (WT ob/ob = 7, KO ob/ob = 8). An unpaired two‐tailed Student's t‐test was performed. (F–J) Individual changes of activity, energy expenditure (EE), oxygen consumption (VO2), respiratory exchange ratio (RER), and food intake (FI) in WT and KO ob/ob mice after 3 days of leptin treatment (WT ob/ob = 5, KO ob/ob = 7). Two‐way ANOVA was performed. (K) Individual changes in food intake after the first day of leptin treatment (WT ob/ob = 5, KO ob/ob = 7). Two‐way ANOVA was performed. (L–M) Cumulative food intake for 3 days before and after leptin treatment (WT ob/ob = 5, KO ob/ob = 7). Two‐way ANOVA was performed.*p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001. Data were displayed as means ± SEM. [Color figure can be viewed at wileyonlinelibrary.com]

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  FIGURE 3. Gpr17 regulates leptin signaling. (A) The time course of detectable pStat3 after leptin treatment in N2A cells (n = 4 per each group). (B) Representative Western blotting and quantitative analysis of pStat3 and Stat3 in N2A cells with or without Gpr17 overexpression (n = 6–7 per each group). A two‐tailed unpaired t‐test was performed. (C) The hepatic mRNA levels of leptin signaling inhibitors in ob/ob Gpr17 knockout (KO) mice (WT ob/ob = 7, KO ob/ob = 8). Two‐way ANOVA was performed. **p < 0.01, ****p < 0.0001. Data were displayed as means ± SEM. [Color figure can be viewed at wileyonlinelibrary.com]

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  FIGURE 4. Gpr17 knockout (KO) ob/ob mice show increased hypothalamic leptin sensitivity. (A) Representative images with pStat3 in fasted mice with 1‐h leptin treatment. (B) Quantitative analysis of pStat3‐positive cell number in DMH (n = 6 for each group), VMH (n = 6 for each group), and ARC (WT ob/ob = 5, KO ob/ob = 4). A two‐tailed unpaired t‐test was performed. (E, F) Representative images and quantitative analysis of cFos‐positive cell number in PVN (n = 6 for each group). (G, H) Representative images and quantitative analysis of cFos‐positive cell number in ARC (WT ob/ob = 4, KO ob/ob = 3). DMH, dorsal hypothalamic nucleus; VMH, ventromedial hypothalamic nucleus; ARC, hypothalamic arcuate nucleus; PVN, hypothalamic paraventricular nucleus. [Color figure can be viewed at wileyonlinelibrary.com]

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  FIGURE 5. Gpr17 knockout (KO) sensitizes insulin signaling. (A) Serum insulin levels of WT and KO ob/ob mice (n = 7 for each group). (B) The weight of epididymal white adipose tissue in WT and KO ob/ob mice (n = 7 for each group). (C) Normalized serum nonesterified fatty acid (NEFA) levels in WT and KO ob/ob mice (n = 7 for each group). (D) The time course of detectable pAkt after insulin treatment in N2A cells (n = 4 for each group). (E) Representative Western blotting and quantitative analysis of pAkt and Akt in N2A cells with or without Gpr17 overexpression (n = 7 for each group). (F–I) Glycogen synthesis, glycolysis, glucose uptake, and glucose infusion rate of whole‐body Gpr17 KO mice in hyperinsulinemic‐euglycemic clamp (WT = 7, KO = 5–6) An unpaired two‐tailed Student's t‐test was performed. *p < 0.05, ***p < 0.001. Data were displayed as means ± SEM. [Color figure can be viewed at wileyonlinelibrary.com]