Sugar kelp (Saccharina latissima) inhibits hepatic inflammation and fibrosis in a mouse model of diet-induced nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH), closely associated with obesity, is a health concern worldwide. We investigated whether the consumption of U.S.-grown sugar kelp (Saccharina latissima), an edible brown alga, can prevent obesity-associated metabolic disturbances and NASH in a mouse model of diet-induced NASH. Male C57BL/6J mice were fed a low-fat diet, a high-fat/high-sucrose/high-cholesterol diet (HF), or a HF diet containing sugar kelp (HF-Kelp) for 14 weeks. HF-Kelp group showed lower body weight with increased O2 consumption, CO2 production, physical activity, and energy expenditure compared with the HF. In the liver, there were significant decreases in weight, triglycerides, total cholesterol, and steatosis with HF-Kelp. The HF-Kelp group decreased hepatic expression of a macrophage marker adhesion G protein-coupled receptor E1 (Adgre1) and an M1 macrophage marker integrin alpha x (Itgax). HF-Kelp group also exhibited decreased liver fibrosis, as evidenced by less expression of fibrogenic genes and collagen accumulation than those of HF group. In epididymal white adipose tissue (eWAT), HF-Kelp group exhibited decreases in eWAT weight and adipocyte size compared with those of the HF. HF-Kelp group showed decreased expression of collagen type VI alpha 1 chain, Adgre1, Itgax, and tumor necrosis factor α in eWAT. We demonstrated, for the first time, that the consumption of U.S-grown sugar kelp prevented the development of obesity and its associated metabolic disturbances, steatosis, inflammation, and fibrosis in the liver and eWAT of a diet-induced NASH mouse model.