Beneficial Effects of Poplar Buds on Hyperglycemia, Dyslipidemia, Oxidative Stress, and Inflammation in Streptozotocin-Induced Type-2 Diabetes

Abstract

The effects of propolis on blood glucose regulation and the alleviation of various complications caused by diabetes have been widely studied. The main source of propolis in the northern temperate zone is poplar buds. However, there is limited research on the antidiabetic activity of poplar buds. In order to evaluate the effect of poplar buds on type-2 diabetes, crude extract and 50% fraction of poplar buds were used to feed streptozotocin-induced type-2 diabetic mice. The results showed that 50% fraction could increase insulin sensitivity and reduce insulin resistance, as well as decrease the levels of fasting blood glucose, glycated hemoglobin, and glycosylated serum proteins in diabetic mice. Compared with the model control group, the 50% fraction-treated group showed significant decreases of malondialdehyde (MDA) and increases of superoxide dismutase (SOD) in serum and liver homogenate. Moreover, 50% fraction could significantly decrease total cholesterol (TC), alleviate abnormal lipid metabolism, and enhance antioxidant capacity in the serum. For inflammatory factors, feeding of 50% fraction could also reduce the levels of interleukin 6 (IL-6), tumor necrosis factor α (TNF-α), monocyte chemotactic protein 1 (MCP-1), and cyclooxygenase-2 (COX-2) in liver homogenate. Taken together, our results suggest that crude extract and 50% fraction of poplar buds, particularly the latter, can decrease blood glucose levels and insulin resistance, and 50% fraction can significantly relieve dyslipidemia, oxidative stress, and inflammation caused by type-2 diabetes.

Recent Advances Regarding the Phytochemical and Therapeutic Uses of Populus nigra L. Buds

“…It is well known that diabetes can cause different types of inflammation. In this study was also shown that this extract could reduce inflammatory factors, such as IL-6, TNF-α, MCP-1 and COX-2 in liver homogenate [65].…”

Effects of Propolis Extract and Propolis-Derived Compounds on Obesity and Diabetes: Knowledge from Cellular and Animal Models

“…On the other hand, glycated albumin can be used to assess blood glucose level for a shorter period since its half-life is less than three weeks [197]. For animal models, Hb1Ac is often used to assess diabetic states [129,130,131,154,157].…”

“…Thus, the antioxidation abilities of tissues can be tested to elucidate intrinsic anti-diabetes properties. For this purpose, amounts of antioxidant enzymes such as GPx, CAT, superoxide dismutase (SOD), glutathione S-transferase (GST), and antioxidant glutathione (GSH) have often been measured [131,132,133,134,135,136,137,138,139,140,155,157,162,202]. Alternatively, oxidation of polyunsaturated fatty acids is also measured to evaluate oxidative stress in diabetic animals.…”

“…ROS degrade polyunsaturated fatty acids, resulting in the formation of malondialdehyde (MDA) [203]. Hence, accumulation of MDA is a useful index of oxidative stress [131,133,135,136,137,138,139,155,157]. To quantify tissue MDA content, a simple colormetric 2-thiobarbituric acid reactive substances (TBARS) assay is usually performed [203].…”

“…Poplar is one of the major ingredients of Chinese propolis. Application of 50% poplar bud extracts (50 or 100 mg/kg for 4 weeks) resulted in decreased serum levels of FBG, glycated hemoglobin, glycated serum protein, total cholesterol, and LDL-C in HFD/STZ-treated Kunming mice, whereas it did not influence serum triglyceride level [157]. Regarding chemical compounds, APC, coumaric acid, and kaempferide (1 μM for 15 min) enhanced phosphorylation of AMPK and PI3K and translocation of GLUT4 to the plasma membrane of L6 cells [236].…”