Effects of vitamin D3 on endoplasmic reticulum stress in adipose tissue and insulin resistance induced by high fat diet in mice

Abstract

Objective To study the effect of vitamin D3 on adipose tissue endoplasmic reticulum stress and insulin resistance induced by high fat diet in mice. Methods Eighty male C57BL/6 mice were divided into control group(n=20)and experimental group(n=60), fed with common food and high fat diet, respectively. After the establishment of the obesity model, the experimental mice were divided into control group, low-dose(50 IU/kg)vitamin D3 group(VitD-L), and high-dose(250 IU/kg)vitamin D3 group(VitD-H). After the mice were fed for 1 week, Western blot was used to detect the expressions of immunoglobulin heavy chain-binding protein(Bip), phosphorylated inositol-requiring enzyme 1(p-IRE1), phosphorylated protein kinase R(PKR)-like endoplasmic reticulum kinase(p-PERK), and NF-κB protein in adipose tissue. Serum levels of TNF-α, IL-6, serum 25-hydroxyvitamin D, fasting plasma glucose, HbA1C, triacylglyceride, and fasting insulin were measured and the insulin resistance index was calculated. Results Vitamin D3 down-regulated the expressions of endoplasmic reticulum stress key genes including Bip, p-IRE1, and p-PERK; and decreased the protein expression of NF-κB and the serum levels of TNF-α and IL-6(P<0.05). Vitamin D3 also significantly reduced the levels of fasting blood glucose, HbA1C, triacylglyceride, and fasting insulin in obese mice(P<0.05), while alleviated the insluin resistance in obese mice. Conclusion Vitamin D3 may significantly improve inflammatory response and insulin resistance via inhibiting endoplasmic reticulum stress in adipose tissue of obese mice. (Chin J Endocrinol Metab, 2017, 33: 861-864) Key words: Obesity; Vitamin D3; Endoplasmic reticulum stress; Insulin resistance