Hypoglycemic activity and potential mechanism of a polysaccharide from the loach in streptozotocin-induced diabetic mice.

The present study was designed to investigate the hypoglycemic activity and the potential mechanisms of Misgurnus anguillicaudatus polysaccharide (MAP) in streptozotocin-induced diabetic mice. MAP oral administration significantly decreased the blood levels of glucose, TC, TG, LDL-C, and increased the blood levels of HDL-C and insulin in diabetic mice, concurrent with increases in body weights and pancreatic insulin contents. Moreover, MAP reversed the increased mRNA expressions of PEPCK and the reduced glycogen contents in the liver of diabetic mice. Concurrently, MAP exhibited potent anti-inflammatory and anti-oxidative activities, as evidenced by the decreased blood levels of TNF-α, IL-6, monocyte chemoattractant protein-1, MDA, and also the elevated SOD and GPx activities in the serum of diabetic mice. Furthermore, MAP also significantly improved the blood markers of the impaired liver function and renal function in diabetic mice. Altogether, these results suggest that MAP may be a potential therapeutic option for type 1 diabetes.

Zhou J ，Yan J ，Bai Z ，Li K ，Huang K ... -  《-》

Rehmannia glutinosa (Gaertn.) DC. polysaccharide ameliorates hyperglycemia, hyperlipemia and vascular inflammation in streptozotocin-induced diabetic mice.

Rehmannia glutinosa (Gaertn.) DC. (RG) has been widely used as traditional Chinese herbal medicine for treatment of diabetes and its complications. The polysaccharide fraction of RG has been proposed to possess hypoglycemic effect by intraperitoneal administration, however, the mechanisms responsible for the hypoglycemic effect of RG polysaccharide (RGP) remain poorly understood. Here we studied the anti-hyperglycemic and anti-hyperlipidemic effect of oral administration of a purified RGP and its underlying mechanisms in streptozotocin (STZ)-induced diabetic mice. The preliminary structure of RGP was determined by GC and FT-IR. Mice were injected with STZ to induce type 1 diabetes. RGP at doses of 20, 40 and 80 mg/kg/day was orally administered to mice for 4 weeks, and metformin was used as positive control. After 4 weeks, the blood biochemical parameters, the pancreatic insulin contents, in vitro insulin secretion, the hepatic glycogen contents and mRNA expression of phosphoenolpyruvate carboxyl kinase (PEPCK) were assayed. RGP was composed of rhamnose, arabinose, mannose, glucose and galactose in the molar ratio of 1.00:1.26:0.73:16.45:30.40 with the average molecular weight of 63.5 kDa. RGP administration significantly decreased the blood levels of glucose, total cholesterol, triglycerides, low density lipoprotein-cholesterol, and increased the blood levels of high density lipoprotein-cholesterol and insulin in diabetic mice, concurrent with increases in body weights and pancreatic insulin contents. The in vitro study revealed that RGP significantly enhanced both basal and glucose-stimulated insulin secretions, as well as islet insulin contents in the pancreatic islets of diabetic mice. Moreover, RGP reversed the increased mRNA expression of PEPCK and the reduced glycogen contents in the liver of diabetic mice. Furthermore, RGP exhibited potent anti-inflammatory and anti-oxidative activities, as evidenced by the decreased blood levels of TNF-α, IL-6, monocyte chemoattractant protein-1, MDA, and also the elevated blood levels of SOD and GPx activities in diabetic mice. Taken together, RGP can effectively ameliorate hyperglycemia, hyperlipemia, vascular inflammation and oxidative stress in STZ-induced diabetic mice, and thus may be a potential therapeutic option for type 1 diabetes.

Zhou J ，Xu G ，Yan J ，Li K ，Bai Z ，Cheng W ，Huang K ... -  《-》

Antihyperglycemic activity of Anoectochilus roxburghii polysaccharose in diabetic mice induced by high-fat diet and streptozotocin.

Anoectochilus roxburghii is a traditional Chinese herb used for treatment of diabetes and some other diseases. Anoectochilus roxburghii polysaccharose (ARP) is the main constituent of Anoectochilus roxburghii. The present study aimed to investigate the antidiabetic effects of ARP in diabetic mice induced by high-fat diet and streptozotocin. Two doses of ARP (100 or 300 mg/kg) were administered once daily for 25 days to diabetic mice. To evaluate the antidiabetic effects of ARP, the fasting glucose levels, aspartate aminotransferase (AST), alanine transaminase (ALT) and superoxide dismutase (SOD) activities, malondialdehyde (MDA) content, triglyceride (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C) and liver glycogen were examined. Furthermore, histological examinations were carried out on the separated pancreas and liver of mice. Compared with untreated diabetic mice, ARP (100 or 300 mg/kg) caused a significant decrease in blood glucose levels, activities of AST and ALT, and MDA contents, and a significant increase in liver glycogen contents, SOD activities, thymus index and spleen index. Simultaneously, the alteration in lipid metabolism was partially attenuated as evidenced by decreased serum TC, TG and LDL-C concentrations in diabetic mice. In addition, histological examinations showed that administration of ARP (100 or 300 mg/kg) significantly attenuated the pathologic lesions in pancreas and liver of diabetic mice, and improved pancreas and liver function. The antidiabetic activity of ARP may be attributed to the improvement of glucose and lipid metabolism, increase of immune protection and reduction of oxidative stress.

Zhang JG ，Liu Q ，Liu ZL ，Li L ，Yi LT ... -  《-》

Antidiabetic effects of Morus alba fruit polysaccharides on high-fat diet- and streptozotocin-induced type 2 diabetes in rats.

Type 2 diabetes mellitus (T2DM) is becoming a serious threat to human health. The fruit of Morus alba L. is widely used as a traditional Chinese medicine for the treatment of DM, dizziness, tinnitus, insomnia, and premature graying, as well as to protect the liver and kidneys. Several studies have demonstrated that the aqueous extracts of the roots bark, leaves, and ramuli of mulberry, which are known to contain polyphenols and polysaccharides, have antihyperglycemic and antihyperlipidemic activities. The aim of the present study was to further investigate the active polysaccharides from M. alba fruit by evaluating the antidiabetic activities of different fractions on T2DM rats and elucidate the mechanism underlying these activities. Diabetic rats were treated with two fractions of M. alba fruit polysaccharides (MFP50 and MFP90). The disease models were induced by a high-fat diet and low dose injection of streptozotocin and were compared to normal rats and metformin-treated diabetic rats. After seven weeks, the fasting blood glucose (FBG), oral glucose tolerance test (OGTT), fasting serum insulin (FINS) levels, homeostasis model of assessment-insulin resistance (HOMA-IR), glycated serum protein (GSP), and serum alanine transaminase (ALT) levels, as well as serum lipid profiles and histopathological changes in the pancreas were measured. Next, the expressions of the insulin signaling pathway were measured by western blot analysis to elucidate the potential mechanism underlying these antidiabetic activities. After seven weeks of treatment, a significant reduction in the FBG levels, OGTT-area under the curve (OGTT-AUC), FINS, HOMA-IR, ALT, and triglyceride (TG) values of the MFP50 group was observed. On the other hand, in the MFP90 group, the FBG, OGTT-AUC, FINS, HOMA-IR, GSP, and TG levels were significantly reduced. The level of high-density lipoprotein cholesterol (HDL-c) and the proportion of HDL-c to total cholesterol (TC) significantly increased in the MFP50 group. Moreover, MFP50 and MFP90 induced repair of damaged pancreatic tissues of the diabetic rats. The hypoglycemic effect of MFP50 was more stable than MFP90, whereas the hypolipidemic effect of MFP90 was slightly better than MFP50. Moreover, the expression levels of InsR, IRS-2, Akt and GLUT4 in the MFP90 group significantly increased relative to that of the T2DM group. MFP50 and MFP90 have markedly antihyperglycemic and antihyperlipidemic effects and can clearly relieve diabetes symptoms in the T2DM rat model. The M. alba fruit polysaccharides may potentially be utilized as an effective treatment for T2DM. Further research into the structures of active M. alba fruit polysaccharides and their mechanisms in promoting antidiabetic effects are underway.

Jiao Y ，Wang X ，Jiang X ，Kong F ，Wang S ，Yan C ... -  《-》

Anti-Diabetic and Anti-Nephritic Activities of Grifola frondosa Mycelium Polysaccharides in Diet-Streptozotocin-Induced Diabetic Rats Via Modulation on Oxidative Stress.

Kou L ，Du M ，Liu P ，Zhang B ，Zhang Y ，Yang P ，Shang M ，Wang X ... -  《-》