Effects of salmon cartilage proteoglycan on obesity in mice fed with a high‐fat diet

This study investigated the effects of salmon nasal cartilage proteoglycan (PG), which shows anti‐inflammatory properties, on obesity induced by high‐fat diet (HFD) in a mouse model. Mice were fed either a HFD or normal diet (ND), with or without PG, for 8–12 weeks. After 12 weeks, the body weight of mice fed with PG‐free HFD was 54.08 ± 4.67 g, whereas that of mice fed with HFD containing PG was 41.83 ± 4.97 g. The results suggest that the increase in body weight was attenuated in mice fed with HFD containing PG. This effect was not observed in mice fed with ND. The PG administration suppressed the elevation of serum lipids (the level of serum lipids ranged between 54% and 69% compared to 100% in mice fed with PG‐free HFD) and the upregulated mRNA expression of sterol regulatory element‐binding protein‐1c (SREBP‐1c), which is a transcription factor that acts as a master regulator of lipogenic gene expression in the liver (the expression level was 77.5% compared to 100% in mice fed with PG‐free HFD). High leptin levels in mice fed with PG‐free HFD were observed during fasting (average at 14,376 ng/ml), and they did not increase after refeeding (average of 14,263 ng/ml), whereas serum leptin levels in mice fed with HFD containing PG were low during fasting (average of 6481 ng/ml) and increased after refeeding (average 13,382 ng/ml). These results suggest that PG feeding has an anti‐obesity effect and that the regulation of SREBP‐1c and leptin secretion play a role in this effect.