The AT1 receptor blocker telmisartan (TEL) prevents diet-induced obesity. Hypothalamic lipid metabolism is functionally important for energy homeostasis, as a surplus of lipids induces an inflammatory response in the hypothalamus, thus promoting the development of central leptin resistance. However, it is unclear as to whether TEL treatment affects the lipid status in the hypothalamus. C57BL/6N mice were fed with chow (CONchow) or high-fat diet (CONHFD). HFD-fed mice were gavaged with TEL (8 mg/kg/day, 12 weeks, TELHFD). Mice were phenotyped regarding weight gain, energy homeostasis, and glucose control. Hypothalamic lipid droplets were analyzed by fluorescence microscopy. Lipidomics were assessed by performing liquid chromatography-mass spectrometry in plasma and hypothalami. Adipokines were investigated using immunosorbent assays. Glial fibrillary acidic protein (GFAP) was determined by Western blotting and immunohistochemical imaging. We found that body weight, energy homeostasis, and glucose control of TEL-treated mice remained normal while CONHFD became obese. Hypothalamic ceramide and triglyceride levels as well as alkyne oleate distribution were normalized in TELHFD. The lipid droplet signal in the tanycyte layer was higher in CONHFD than in CONchow and returned to normal under TELHFD conditions. High hypothalamic levels of GFAP protein indicate astrogliosis of CONHFD mice while normalized GFAP, TNFα, and IL1α levels of TELHFD mice suggest that TEL prevents hypothalamic inflammation. In conclusion, TEL has anti-obese efficacy and prevented lipid accumulation and lipotoxicity, which is accompanied by an anti-inflammatory effect in the murine hypothalamus. Our findings support the notion that a brain-related mechanism is involved in TEL-induced weight loss.
Fig. s1: Workflow of the 1st part of the study: C57/B6 N mice were fed with HFD or standard chow diet and treated with vehicle or telmisartan (TEL, 8 mg/kg/d) for 13 weeks. Mice were functionally phenotyped by indirect calorimetry (at w6), insulin tolerance test (ITT at w7), and leptin resistance test (LRT at w8) and quantified for fat mass by MRI (at w10). For hypothalamic lipid analyses, lipid droplets and lipid distribution were quantified by fluorescence microscopy and lipid composition and metabolism were analyzed by LC-MS and thin-layer chromatography (TLC), respectively. The plasma lipid composition was also investigated. Inflammation analyses were performed by determining hypothalamic GFAP levels via immunohistochemistry and Western blotting and by quantifying cytokines using immunosorbent assays. Adipokines were also determined in plasma.
Fig. s2: Workflow of the 2nd part of the study: C57/B6 N mice were fed with HFD or standard chow diet and treated with vehicle or telmisartan (TEL, 8 mg/kg/d) for 6 weeks. After the treatment period, mice were sacrificed and hypothalamic gene expression was determined
Fig. s3: Body weight of mice before or after chow or HFD feeding plus vehicle treatment and HFD feeding plus TEL treatment (8 mg/kg/d), which were used for the microarray gene analyses; * p<0.05 vs. CONchow; † p<0.05 vs. CONHFD following ANOVA and Bonferroni's multiple comparison test.
Fig. s4: Plasma lipid concentration in mice upon chow (n=13) or HFD feeding plus vehicle treatment (n=11) and HFD feeding plus TEL treatment (8 mg/kg/d, n=12) as analyzed by LC-MS; * p<0.05 vs. CONchow; † p<0.05 vs. CONHFD following ANOVA and Bonferroni's multiple comparison test
Fig. s5: Hypothalamic lipid concentration in mice upon chow (n=5) or HFD feeding plus vehicle treatment (n=5) and HFD feeding plus TEL treatment (8 mg/kg/d, n=5) as analyzed by LC/MS measurement. Following 2-way ANOVA a difference in kind of lipids was observed (F=447, p<0.0001) while no difference was observed between the groups (F=0.82,. p=0.417).
Fig. s6: Hypothalamic concentrations of free fatty acid by LC/MS measurement followed by 2-way ANOVA and Bonferroni's multiple comparison test (lipid: F= 197.8, p<0.0001; treatment: F=0.3, p=0.778; interaction: F=0.3, p=0.999). * p<0.05 vs. CONchow; † p<0.05 vs. CONHFD. The group size is 5 in each group.
Fig. s7: Gene expression of the RAS signaling in the hypothalamus of CONNFD, CONHFD, and TELHFD-treated mice. *, p < 0.05, n=20 each group
Fig. s8: Graphical abstract. When mice were fed with HFD compared to chow diet, lipid droplets (LD) in tanycytes became increased and hypothalamic levels of the neutral lipids, triglycerides, and ceramides were higher in CONHFD than in CONchow. This may induce inflammation in the arcuate nucleus (ARC) as GFAP and TNF were increased. Thus, leptin transport across the blood-brain barrier (BBB) is diminished, which further results in reduction of energy expenditure and increase of energy intake (left and middle panels). Due to chronic telmisartan treatment, size and composition of LDs are normalized and development of brain inflammation and leptin resistance is prevented (right panel).