Pumpkin Polysaccharide Extracted by Subcritical Water: Physicochemical Characterization and Anti-Diabetic Effects in T2DM Rats

SCOPE

This study aims to optimize the extraction of pumpkin polysaccharide by subcritical water, investigates the physicochemical properties and biological activities of pumpkin polysaccharide.

METHODS AND RESULTS

Subcritical water is used to extract pumpkin polysaccharide. The structure and composition of pumpkin polysaccharide are analyzed by infrared spectroscopy, gel filtration chromatography, and high-performance liquid chromatography. The hypoglycemic and hypolipidemic potential of pumpkin polysaccharide aere determined by the physicochemical indexes, pathological, and immunohistochemical analysis in T2DM rats induced by STZ + high-fat diet. The optimal conditions for subcritical water are 1:15, 150°C, and 10 min. Pumpkin polysaccharide has α-configurations and are mainly composed of seven different monosaccharides, and it exhibits good free-radical scavenging ability and inhibition of α-amylase, α-glucosidase, and pancreatic lipase activities. Pumpkin polysaccharide treatment in T2DM rats significantly decreases the concentrations of blood glucose, insulin, TC, TG, LDL-C, and MDA; increases the levels of HDL-C; and enhances the antioxidant enzymes activities (SOD and CAT). Histopathology and immunohistochemical analyses reveal that pumpkin polysaccharide has protective effects on kidney and pancreatic organs in T2DM rats.

CONCLUSION

Pumpkin polysaccharide extracted by SWE shows great potential as functional food ingredients and candidates for T2DM treatment.

Polysaccharide from Hemerocallis citrina Borani by subcritical water: Bioactivity, purification, characterization, and anti-diabetic effects in T2DM rats

Hemerocallis citrina Borani (daylily) has various health benefits. However, the structural characterization and hypoglycemic effects of its polysaccharide remain unclear. Here, we first report for the first time, the effects of subcritical water extraction temperature on bioactivity of Hemerocallis citrina Borani polysaccharide (HCBP). HCBP extracted at 160 °C had better scavenging ability of free-radical and pancreatic lipase inhibition. This study aimed to investigate the structural characterization and anti-diabetic effects of aforementioned HCBP. HCBP was separated into three fractions using a DEAE-Sepharose Fast Flow. HCBP-1 was the major component with lower molecular weight, HCBP-2 was the least abundant component, HCBP-3 was the component with higher uronic acid and molecular weight. HCBP treatment significantly decreased the concentrations of fasting blood glucose, insulin, total cholesterol, triglyceride, and low density lipoprotein, as well as improved glucose intolerance and insulin resistance in type 2 diabetes mellitus (T2DM) rats. HCBP also protected the kidneys and pancreatic organs by histopathology and immunohistochemical analyses in T2DM rats. In addition, HCBP significantly increased the antioxidant enzymes activities and decreased the level of malonaldehyde to alleviated the oxidative stress injury. The results indicate HCBP extracted by subcritical water is promising functional food ingredients and could be used in T2DM treatment.

Gymnemic Acid Alleviates Type 2 Diabetes Mellitus and Suppresses Endoplasmic Reticulum Stress in Vivo and in Vitro

Gymnemic acid (GA) is an herbal ingredient that can improve glucose metabolism in patients with diabetes mellitus. In this study, we evaluated the ameliorative effects of GA on insulin resistance (IR) and identified the mechanisms in type 2 diabetes mellitus (T2DM) rats and IR HepG2 cells. GA effectively enhanced glucose uptake in IR HepG2 cells from 11.9 ± 1.09 to 14.7 ± 1.38 mmol/L and lowered fasting blood glucose (blood glucose levels in groups treated with GA at 40 and 80 mg/kg/day were reduced by 15.2% and 26.7%, respectively) and oral glucose tolerance. Both in vivo and in vitro, GA downregulated the expression of endoplasmic reticulum (ER) stress indicator proteins such as ORP150, p-c-Jun, p-PERK, and p-eIF2α. In addition, the improvement of ER stress regulated the insulin signal transduction proteins, reducing p-IRS-1(ser) levels and increasing p-IRS-1(tyr) in GA-treated T2DM rats and IR HepG2 cells. In summary, the mechanism underlying the hypoglycemic effects of GA may be associated with alleviation of ER stress and facilitation of insulin signal transduction in T2DM rats and IR HepG2 cells.

Antioxidant and anti-diabetic effects of Auricularia auricular polysaccharides and their degradation by artificial gastrointestinal digestion - Bioactivity of Auricularia auricular polysaccharides and their hydrolysates

BACKGROUND

Auricularia auricular polysaccharides (AAPs) derived from the dried fruit body of A. auricular are valuable compounds with many bioactivities. This research aimed to investigate the antioxidant and anti- diabetic activities of these polysaccharides and their artificial gastrointestinal fluid hydrolysates (AAPHs).

METHODS

Artificially simulated gastrointestinal fluid was used to obtain polysaccharide-de- rived fragments, and a rat model of type 2 diabetes mellitus (T2DM) using a high-fat diet and low-dose streptozotocin (STZ) was established to assess their antioxidant and anti-diabetic effects.

RESULTS

It was found that AAPs and AAPHs were both heteropolysaccharides and were comprised of arab- inose, xylose, mannose, 2-deoxy-glucose, glucose and glucosamine, but at different mole ratios. AAPHs was purified by Sephadex G-100 chromatography to produce three fractions, namely, AAPHs1, AAPHs2, and AAPHs3. The molecular weights of these three fractions were 320, 169, and 62 kDa respectively. Both AAPs and AAPHs exhibited the evident ability to enhance the activities of antioxidant enzymes and the level of GSH, while increasing the content of liver glycogen and plasma C-peptide compared with the diabetic model group (p < 0.05). Furthermore, AAPHs could cause a marked improvement in glucose-stimulated GLP-1 secretion from 0 min to 30 min (p < 0.05).

CONCLUSIONS

The possible mechanism was that AAPHs could partly restore the STZ-induced impairment of GLP-1 secretion, and inhibit the oxidative stress pathway, and thereby alleviate the progression of diabetes. This data demonstrated that the molecular mole ratio and molecular weight had a definite effect on antioxi- dant and anti-diabetic activities.