An environment-friendly approach to isolate and purify glucan from spent cells of recombinant Pichia pastoris and the bioactivity characterization of the purified glucan.

While the methylotrophic yeast Pichia pastoris enables the industrial-scale biosynthesis of many recombinant products, large amount of nutrient-rich biomass emerged along this process. Polysaccharides, especially glucans that are abundant in the cell wall of P. pastoris, are yet to be better utilized owing to their various biological activities. However, the isolation and purification of cell wall glucan from P. pastoris has not been reported. In this study, we established an environment-friendly approach, including induced autolysis, hot-water treatment, ultrasonication, isopropanol extraction, and protease treatment, to isolate and purify glucan from the cell wall of P. pastoris. We achieved a purity of 85.3% and a yield of 11.7% for the purified glucan. Proteins, nucleic acids, lipids, and ash were efficiently removed during the purification. The activities of the purified glucan were investigated in mice fed with a high-fat diet. The purified glucan decreased the level of total cholesterol and triglycerides by 30.3 and 29.7%, respectively. This result suggested that the cell wall glucan of P. pastoris could be developed to a therapeutic agent for dyslipidemia. Our study proposed an environment-friendly and effective method to isolate and purify the glucan from P. pastoris, providing solid foundation for the high-value utilization of this yeast.

Synergistic effects of acarbose and an Oroxylum indicum seed extract in streptozotocin and high-fat-diet induced prediabetic mice.

Prediabetes is defined as blood glucose levels above normal but below diabetes thresholds, and up to 70% of individuals with prediabetes will eventually develop diabetes if left untreated. Acarbose, the first FDA approved anti-prediabetes agent, has some disadvantages, such as reducing the risk of diabetes by only 36%, side effects and limited effects on complications. The aim of this study is to develop a new agent to treat prediabetes and to investigate the anti-prediabetes effects and mechanisms of acarbose and an Oroxylum indicum seed extract (OISE) in prediabetic mice. The combined drugs can reduce the dose of acarbose by 80% and reduce the risk of diabetes by 75%, which is one fold higher than acarbose monotherapy. The combined drugs showed synergistic anti-prediabetes effects and could be effective in preventing the complications of prediabetes. The combined drugs could improve glucose tolerance, improve lipid metabolism and reduce oxidative stress and tissue damage. For the mechanisms, the combined drugs can reduce synergistically postprandial hyperglycaemia by inhibiting α-glucosidase. Furthermore, baicalein in OISE was demonstrated to be a major component in reducing oxidative stress and chrysin was the primary compound that activated PPARγ.

Combination of flavonoids from Oroxylum indicum seed extracts and acarbose improves the inhibition of postprandial blood glucose: In vivo and in vitro study.

The combined effect of Oroxylum indicum seed extracts (OISE) or major flavonoids from OISE and acarbose on reducing postprandial blood glucose (PBG) levels was investigated in vitro and in vivo. In vitro, the IC50 values of OISE and baicalein against α-glucosidase were 43.4±0.731µgmL-1 and 25.9±0.412µgmL-1 respectively. A combination of acarbose with OISE or baicalein synergistically inhibited rat intestinal α-glucosidase. The combination index (CI) values for acarbose with OISE ranged from 0.33 to 0.75, suggesting a synergistic but not additive effect. OISE was determined to be a non-competitive inhibitor of maltose-hydrolyzing activity. In vivo, OISE were administered to normoglycemic and diabetic mice, either alone or in combination with acarbose. At doses between 50 and 200mgkg-1, OISE enhanced the efficacy of acarbose by up to 5-fold. These results demonstrated that OISE enhances the efficacy of acarbose in vivo, and that the combination of OISE and acarbose displayed a synergistic effect in vitro. Therefore, OISE can be used to design dietary supplements to treat diabetes.