MiR-503-5p alleviates peripheral neuropathy-induced neuropathic pain in T2DM mice by regulating SEPT9 to inhibit astrocyte activation.

Diabetic peripheral neuropathy (DPN) is a common complication of type 2 diabetes mellitus (T2DM) that causes peripheral and autonomic nervous system dysfunction. Dysregulation of miRNAs plays a crucial role in DPN development. However, the role of miR-503-5p in DPN remains unknown. Herein, T2DM mice (db/db) were used as a DPN model in vivo, and astrocytes isolated from db/db mice were induced with high glucose levels as a DPN model in vitro. MiR-503-5p expression was analyzed using qRT-PCR. GFAP, MCP-1, and SEPT9 protein levels were analyzed using western blotting and immunofluorescence. Luciferase assays were performed to investigate the interaction between miR-503-5p and SEPT9. We found that miR-503-5p expression decreased in the spinal cord of DPN model mice and astrocytes treated with high glucose (HG). The db/db mice displayed higher body weight and blood glucose, lower mechanical withdrawal threshold and thermal withdrawal latency, and higher GFAP and MCP-1 protein levels than db/m mice. However, tail vein injection of agomiR-503-5p remarkably reversed these parameters, whereas antigomiR-503-5p enhanced them. HG markedly facilitated GFAP and MCP-1 protein expression in astrocytes, whereas miR-503-5p mimic or inhibitor transfection markedly blocked or elevated GFAP and MCP-1 protein expression, respectively, in astrocytes with HG. SEPT9 was a target of miR-503-5p. In addition, SEPT9 protein levels were found to be elevated in db/db mice and astrocytes treated with HG. Treatment with agomiR-503-5p and miR-503-5p mimic was able to reduce SEPT9 protein levels, whereas treatment with antigomiR-503-5p and miR-503-5p inhibitor led to inhibition of the protein. Furthermore, SEPT9 overexpression suppressed the depressing effect of miR-503-5p overexpression in astrocytes subjected to HG doses. In conclusion, miR-503-5p was found to alleviate peripheral neuropathy-induced neuropathic pain in T2DM mice by regulating SEPT9 expression.

Therapy of empagliflozin plus metformin on T2DM mice shows no higher amelioration for glucose and lipid metabolism than empagliflozin monotherapy.

AIMS: This study was designed to compare the effects of empagliflozin monotherapy and its combination with metformin on glucose and lipid modulations in T2DM mice. MAIN METHODS: Nine-week-old male C57BLKS/J db/db mice (n = 32) were used as T2DM model, and their age-matched C57BLKS/J db/m mice (n = 8) were used as normal control. A total of 32 db/db mice were randomly divided into four groups (n = 8/group): the DMT1 group, treated with metformin (250 mg/kg/day); the DMT2 group, treated with metformin (250 mg/kg/day) plus empagliflozin (10 mg/kg/day); the DMT3 group, treated with empagliflozin (10 mg/kg/day); the T2DM control group (DM), received 0.5% Natrosol. The db/m mice received same administration as DM group. KEY FINDINGS: After four-week treatments, compared with T2DM control (DM), the empagliflozin or its combination with metformin dramatically increased the levels of plasma HDL-C (139.6% and 154.9%, respectively), with significant decrease in plasma TC (22.9% and 13.7%, respectively) and plasma TG (26% and 19.7%, respectively) and in hepatic TG (30.3% and 28.6%, respectively). The protein expressions of SREBP1c (75.3% and 54.0%, respectively) and APOC-III (51.2% and 50.2%, respectively) were reduced, while CPT1A (304.0% and 221.4%, respectively) and ApoA1 levels (90.0% and 85.3%, respectively) were enhanced. Although both interventions improve above-mentioned lipid homeostasis, there were no statistic differences between two groups (p > 0.05). SIGNIFICANCE: Our study demonstrated that current dose of combination therapy may have no higher amelioration than empagliflozin monotherapy for glucose and lipid metabolism in male T2DM mice when it followed a treatment shorter than that expected during clinical treatment.

Physicochemical properties and antidiabetic effects of a polysaccharide from corn silk in high-fat diet and streptozotocin-induced diabetic mice.

This study aimed to investigate the physicochemical properties and antidiabetic effects of a polysaccharide obtained from corn silk (PCS2). PCS2 was isolated and the physicochemical properties were characterized. The hypoglycemic effects were determined using the high-fat diet and streptozocin induced type 2 diabetic mellitus (T2DM) insulin resistance mice. The results showed that PCS2 was a heteropolysaccharide with the average molecular weight of 45.5kDa. PCS2 was composed of d-galactose, d-mannose, d-(+)-glucose, d-(+)-xylose, l-arabinose and l-rhamnose. PCS2 treatment significantly reduced the body weight loss, decreased blood glucose and serum insulin levels, and improved glucose intolerance (P<0.05). The levels of serum lipid profile were regulated and the levels of glycated serum protein, non-esterified fatty acid were decreased significantly (P<0.01). The activities of superoxide dismutase, glutathione peroxidase and catalase were notably improved (P<0.05). PCS2 also exerted cytoprotective action from histopathological observation. These results suggested that PCS2 could be a good candidate of functional food or medicine for T2DM treatment.