Hypotriglyceridemic effects of brown seaweed consumption via regulation of bile acid excretion and hepatic lipogenesis in high fat diet-induced obese mice

Abstract

BACKGROUND/OBJECTIVES: The present study aimed to further investigate the potential health beneficial effects of long-term seaweed supplementation on lipid metabolism and hepatic functions in DIO mice. MATERIALS/METHODS: Four brown seaweeds (Undaria pinnatifida [UP], Laminaria japonica [LJ], Sargassum fulvellum [SF], or Hizikia fusiforme [HF]) were added to a high fat diet (HFD) at a 5% ratio and supplemented to C57BL/6N mice for 16 weeks. Triglycerides (TGs) and total cholesterol (TC) in the liver, feces, and plasma were measured. Fecal bile acid (BA) levels in feces were monitored. Hepatic insulin signaling-and lipogenesis-related proteins were evaluated by Western blot analysis. RESULTS: Fasting blood glucose levels were significantly reduced in the LJ, SF, and HF groups compared to the HFD group by the end of 16-week feeding period. Plasma TG levels and hepatic lipid accumulation were significantly reduced in all 4 seaweed supplemented groups, whereas plasma TC levels were only suppressed in the UP and HF groups compared to the HFD group. Fecal BA levels were significantly elevated by UP, LJ, and SF supplementation compared to HFD feeding only. Lastly, regarding hepatic insulin signaling-related proteins, phosphorylation of 5′-AMP-activated protein kinase was significantly up-regulated by all 4 types of seaweed, whereas phosphorylation of protein kinase B was up-regulated only in the SF and HF groups. Lipogenesis-related proteins in the liver were effectively down-regulated by HF supplementation in DIO mice. CONCLUSIONS: Brown seaweed consumption showed hypotriglyceridemic effects in the prolonged DIO mouse model. Specifically, combinatory regulation of BA excretion and lipogenesis-related proteins in the liver by seaweed supplementation contributed to the reduction of plasma and hepatic TG levels, which inhibited hyperglycemia in DIO mice. Thus, the discrepant and species-specific functions of brown seaweeds provide novel insights for the selection of future targets for therapeutic agents.

The Effect of Laminaria japonica on Metabolic Syndrome: A Systematic Review of Its Efficacy and Mechanism of Action

“…Han et al reported that LJP exerted a hypotriglyceridemic effect on HFD-fed mice by phosphorylating 5 AMP-activated protein kinase [ 31 ]. LJP was supplemented with 5% of the diet during the 16-week experiment.…”

“…In addition to fucoidan and iodine, alginates, polyphenols, and polysaccharides as bioactive nutritional compounds extracted from LJP have been evaluated as solutions for the treatment and prevention of Met-related diseases [ 81 ]. In this review, alginates, polyphenols and polysaccharides have been reported to possess anti-diabetic [ 3 , 10 , 19 , 24 , 33 ], anti-obesity [ 29 , 30 , 31 , 32 , 38 ], antioxidant [ 15 , 34 , 37 ], anti-inflammatory [ 37 , 38 ], and hypolipidemic [ 15 , 33 , 34 , 37 ] effect.…”

Bioactivities of the Popular Edible Brown Seaweed Sargassum fusiforme: A Review

“…Recently, there are reports about the mechanism of S. fusiforme inhibiting symptoms of diabetes. ,− In Wei’s research, five polysaccharides extracted from S. fusiforme , and their influences on fasting hypoglycemia and intestinal flora imbalance caused by high-fat diet (HFD) were investigated . The studies showed that C57BL/6J male mice fed HFD for 4 weeks had severe hypoglycemia.…”