Mechanism of Flavonoids from Mulberry Leaves on Insulin Resistance and Inflammatory Response in Diabetic Mice / 中国实验方剂学杂志

ABSTRACT

ObjectiveTo observe the glucose-lowering， insulin resistance-improving， and anti-inflammatory effects of flavonoids from mulberry leaves （FML） and explore their underlying mechanism. MethodMale db/db mice aged 6-7 weeks were randomly divided into a model group， a high-dose FML group （1.00 g·kg·d-1）， and a low-dose FML group （0.50 g·kg-1·d-1）. C57BL mice of the same age were assigned to the normal group. After six weeks of intervention， fasting blood glucose （FBG）， serum fasting insulin levels （Fins）， interleukin-6 （IL-6）， tumor necrosis factor-α （TNF-α）， free fatty acid （FFA）， blood creatinine （SCr）， blood urea nitrogen （BUN）， and aspartate aminotransferase （AST） levels were measured， and the homeostasis model assessment of insulin resistance （HOMA-IR） was calculated. Superoxide dismutase （SOD）， glutathione peroxidase （GSH-Px）， and catalase activities in the liver were measured. Morphological changes in the liver were assessed by hematoxylin-eosin （HE） staining. The protein expression of cyclooxygenase-2 （COX-2）， inducible nitric oxide synthase （iNOS）， and nuclear factor-κB （NF-κB） in the liver was detected by Western blot. ResultCompared with the model group， the high-dose and low-dose FML groups showed significant reductions in FBG， Fins， HOMA-IR， IL-6， TNF-α， and FFA levels （P<0.05， P<0.01）， and increased levels of SOD， GSH-Px， and catalase in the liver （P<0.05， P<0.01）. HE staining of the liver in the FML groups showed improved arrangement of hepatocytes， reduced inflammatory cell infiltration， and alleviated cellular steatosis compared with the model group. The protein expression of COX-2， iNOS， and NF-κB in the liver significantly decreased in the FML groups as compared with that in the model group （P<0.05， P<0.01）. ConclusionFML have glucose-lowering and insulin resistance-improving effect， which may be attributed to their regulation of the NF-κB pathway in the liver of diabetic mice， leading to the suppression of the release of COX-2， iNOS， and inflammatory cytokines， thereby improving the inflammatory state.