Fig. 6

Cathepsin L knockout promoted fat loss and central serotonin synthesis in HFD-fed mice. a Real-time PCR analysis of cathepsin L expression in metabolic and neuronal tissues in LFD- and HFD-fed mice. EAT, epididymal adipose tissue; SAT, subcutaneous adipose tissue; BAT, brown adipose tissue. b–i Male 6-week-old Ctsl^+/+ and Ctsl^−/− mice were fed with HFD for 12 weeks. b Body weight was recorded every week. c White adipose tissue weights were measured at 18 weeks old. d Hematoxylin-eosin staining in the epididymal fat and subcutaneous fat, scale bars 100 μm in length (× 200). e, f At 18 weeks old, the mouse metabolic parameters were measured during a 12-h light and 12-h dark cycle and the average for each group in the light or dark cycle. e Oxygen consumption (VO₂) and f carbon dioxide production (VCO₂). g Real-time PCR analysis of genes involved in lipolysis and β-oxidation in WAT. h The contents of serotonin in mice brain. i Real-time PCR analysis of the expression of Tph-2 in mouse brain. β-Actin was used as the reference gene in real-time PCR analysis. The data in a–c and e–i are presented as mean ± SEM, n = 10 per group. *p < 0.05; **p < 0.01; ***p < 0.001. n.s. not significant in a nonparametric Mann-Whitney test