Fig. 6: CTHRC1 requires GPR180 to ameliorate metabolic disturbances in obesity.

Effect of AAV-mediated CTHRC1 overexpression on a body weight (p = 0.0174 week 10, p = 0.0191 week 11 and p = 0.0133 week 12), b fasting blood glucose (p = 0.03070 and c circulating FFA in 20-weeks-old male C57Bl/6 N mice challenged with HFD (n = 5). HSL phosphorylation (at Serine 660) in d iBAT and e iWAT of mice with increased circulating CTHRC1 (n = 5). Gene expression of selected brown adipocyte markers in f iWAT (p = 0.0280 for Ucp1, p = 0.0377 for Cidea and p = 0.0320 for Pgc1α) and g iBAT (p = 0.0111 for Cidea and p = 0.0191 for Cpt1β) of animals overexpressing CTHRC1 (n = 5). h UCP1 protein in iBAT following CTHRC1 treatment in male mice exposed to HFD. Effect of CTHRC1 overexpression on i energy expenditure (AUC p = 0.0014) and j respiratory exchange ratio (effect of CTHRC1 overexpression p = 0.0005) in C57Bl/6 N mice challenged with HFD AAV was injected prior to acclimatization in metabolic cages and measurement (n = 7). k Intraperitoneal glucose tolerance test in wild-type and GPR180 knockout mice fed with HFD and overexpressing stuffer or CTHRC1 (n = 8–9; p = 0.0160 for Gpr180^−/− vs WT at 30 min, p = 0.0011 for Gpr180^−/− vs WT at 60 min, p = 0.0020 for Gpr180^−/− vs WT at 90 min, p = 0.0366 for WT stuffer vs WT CTHRC1 at 90 min, p = 0.0041 for Gpr180^−/− vs WT at 120 min, p = 0.0160 for WT stuffer vs WT CTHRC1 at 120 min). Data are presented as mean ± SEM. Statistical significance was calculated using two-sided Student´s t-test (b–j) or two-way ANOVA with repeated measurements followed by Sidak post-hoc test (a, j, k). Area under the curve was calculated to compare energy expenditure in CTHRC1 overexpressing mice (i). Statistical differences are indicated as *p < 0.05; (k) * WT CTHRC1 vs WT stuffer, # WT stuffer vs GPR180^−/− stuffer, ^#p < 0.05, ^##p < 0.01 and ^###p < 0.001. AAV adeno-associated virus, AUC area under the curve, CIDEA Cell death inducing DFFA like effector a, CPT1β Carnitine palmitoyltransferase 1β, CTHRC1 Collagen triple helix repeat containing 1, DIO2 Iodothyronine deiodinase 2, ELOVL3 Fatty acid elongase 3, GPR180 G protein-coupled receptor 180, HFD high-fat diet, HSL Hormone sensitive lipase, HSP90 Heat shock protein 90, iBAT interscapular brown adipose tissue, iWAT inguinal white adipose tissue, NEFA non-esterified fatty acids, PGC1A PPARγ coactivator 1α, RER respiratory exchange ratio, UCP1 Uncoupling protein 1, WT wild-type.