Sea cucumber derived sulfated sterols significantly ameliorated insulin resistance and decreased lipid accumulation compared to plant sterols. Interestingly, our recent study found that intervention with sea cucumber sulfated sterols could significantly increase blood glucose levels of healthy mice in the presence of glucose, while cholesterol sulfate, as one of sulfated sterols, did not have the same effect. However, the exact mechanism of sulfated sterols on glucose metabolism is still unknown. In the present study, we investigated the potential mechanism by which sulfated sterols influenced blood glucose homeostasis in healthy mice. Results showed that intervention with sea cucumber sulfated sterols did not affect the levels of hormones related to glucose metabolism, while led to a significant decrease in the synthesis of liver glycogen and muscle glycogen. Besides, the expression of proteins associated with the promotion of gluconeogenesis dramatically increased in the mice intervened with sea cucumber sulfated sterols. These findings suggested that sea cucumber sulfated sterols might change blood glucose metabolism in healthy mice by reducing glycogenesis and promoting gluconeogenesis.

It has been reported that sea cucumber intestine hydrolysates (SCIH) could promote glutamine metabolism in mice, while there is a close connection between glutamine metabolism and insulin sensitivity. However, the effect of SCIH on insulin resistance is still unclear. The results showed that SCIH hydrolyzed by flavor protease had significant activity using the insulin-induced HepG2 cell model. Animal experiments exhibited that SCIH supplementation significantly improved the high-fat and high-sucrose diet-induced impaired glucose tolerance, reduced fasting serum glucose and glycosylated serum protein. Besides, SCIH ameliorated islet vacuolization and decreased the pancreas TNF-α and IL-6 by 32.1% and 36.2%, respectively. Immunofluorescence staining results showed that SCIH promoted insulin secretion. Interestingly, SCIH significantly increased the liver glutamine levels and upregulated the expression of glutaminase1 (GLS1) and glutamate dehydrogenase 1 (GLUD1). Furthermore, SCIH increased liver acetyl-CoA levels to enhance histone acetylation and activate the gene transcription and translation on glucose metabolism-related IRS/PI3K/AKT signaling pathway, thereby attenuating insulin resistance. The present findings proposed the potential value for developing functional foods in SCIH utilization.

Alpha-linolenic acid (ALA) is capable of synthesizing EPA and DHA in vivo, but the conversion rate is hard to meet the body's need for rapid DHA supplementation. Studies have shown that fucoxanthin can increase DHA content in the liver of mice, but the mechanism is not clear. Moreover, the effect of fucoxanthin and its metabolite fucoxanthinol on the chain lengthening reaction of n-6 polyunsaturated fatty acids (PUFAs) is little studied. In this study, the effects of fucoxanthin and fucoxanthinol on the chain elongation of n-3 and n-6 series PUFAs were investigated in mice. Results showed that fucoxanthin and fucoxanthinol significantly increased the conversion of n-3 series ALA to DHA and n-6 series LA to AA in the serum, liver, small intestine, and heart of mice. In addition, fucoxanthin accelerated the rate of DHA supplementation by ALA in the brain. Further mechanistic studies revealed that the role of fucoxanthin in promoting PUFAs conversion was not regulated at transcriptional level, but by increasing the activity of fatty acid desaturase 2 (FADS2), a key enzyme of chain elongation reaction of n-3 and n-6 PUFAs. This study fundamentally provided theoretical bases for a new strategy of dietary supplementation of n-3 and n-6 PUFAs.

Trimethylamine N-oxide (TMAO) is a risk factor of various chronic diseases, which was produced by metabolism from precursors to trimethylamine (TMA) in gut and the oxidation from TMA in liver. The TMA generation was influenced by diet, mainly due to the rich TMAO precursors in diet. However, it was still unclear that the effects of different proportion and source of macronutrients in different dietary pattern on the production process of TMAO. Here, the generation of TMA from precursors and TMAO from TMA was determined after single oral choline chloride and intraperitoneal injection TMA, respectively, in mice fed with carbohydrates, proteins and fats in different proportion and sources. The results suggested that the generation of TMAO was increased by low non-meat protein and high fat via enhancing the production of TMAO from TMA, and decreased by plant protein and refined sugar via reducing TMA production from precursors in gut and TMAO transformation from TMA in liver. The high fat and high sugar diets accelerating the development of atherosclerosis did not increase the production of TMAO, the risk factor for atherosclerosis, which indicated that the dietary compositions rather than the elevated TMAO level might be a more key risk factor for atherosclerosis.

Sea cucumber saponins have attracted more attention in recent years due to biological activities. It is a popular practice to soak sea cucumber in Baijiu at home and being applied to industrial manufacturing in China. However, knowledge of the effect of alcohol on the absorption and metabolism of sea cucumber saponins is limited. The effects of alcohol on digestion, absorption and metabolism of sea cucumber saponins in BALB/c mice were investigated after gavage and tail intravenous injection. The results showed that the content of saponins in serum and liver was significantly higher under the influence of alcohol than that in the control group after oral administration. Alcohol promoted the absorption of sea cucumber saponins prototype as well as inhibited the process of saponins being transformed into deglycositic metabolites in the small intestine. Moreover, sea cucumber saponins remained in circulation for a long time and alcohol slowed down the clearance of sea cucumber saponins under the influence of alcohol after intravenous injection. This confirmed the feasibility of marinating sea cucumber in Baijiu to improve the efficacy of saponins and provides an important theoretical basis for the utilization of sea cucumber and the development of sea cucumber liquor.

Antarctic krill (Euphausia superba) oil has been gaining increasing attention due to its nutritional and functional potentials. Krill oil usually contains a high concentration (about 50%) of phospholipids (AKOP) rich in DHA and EPA accompanied with 30%–40% triacylglycerols. Phospholipids can be made into liposomes without emulsifiers due to its amphiphilic characteristics. However, the absorption kinetics of AKOP liposome in vivo is not clear, which restrict the molecular mechanism analysis related to its distinct bioactivities. The lipid analysis in serum, small intestinal content and wall was carried out after oral administration of AKOP liposome to illustrate its absorption kinetics in blood and the digestive tract of healthy mice by single gavage. The major type of the obtained AKOP was phosphatidylcholine, and the total contents of the DHA and EPA were 29.31%. AKOP liposome was almost completely digested in the small intestine in 1 h and the hydrolysis products could be quickly absorbed by intestinal enterocytes. The DHA in serum peaked at 2 h after administration of AKOP liposome. AKOP liposome could be quickly digested and absorbed in vivo. The obtained results might provide a scientific basis for the molecular mechanism analysis related to distinct bioactivities of Antarctic krill oil phospholipid.