Abstract:Objective To observe the effect of modified Dahuang Huanglian Xiexintang on mitochondrial autophagy and browning of visceral adipose tissue in obese type 2 diabetes mellitus （T2DM） model ZDF rats.Method Forty ZDF rats were induced with a high-fat diet to establish an obese T2DM model. The rats were randomly divided into five groups： Model group， metformin group （0.18 g·kg-1）， and high， medium， and low dose groups of modified Dahuang Huanglian Xiexintang （2.16， 1.08， 0.54 g·kg-1）， with eight rats in each group. Additionally， eight ZDF （fa/+） rats were assigned to the normal group. All groups received an intragastric volume of 10 mL·kg-1， with the model and normal groups receiving the same volume of purified water once daily for 12 weeks. Fasting blood glucose （FBG） was regularly measured. After 12 weeks of intervention， the body weight， epididymal fat weight， and serum levels of glucose （GLU）， glycated serum protein （GSP）， triglyceride （TG）， total cholesterol （TC）， high-density lipoprotein cholesterol （HDL-C）， and low-density lipoprotein cholesterol （LDL-C） were measured. Hematoxylin-eosin （HE） staining was used to observe pathological changes in epididymal fat tissue. Transmission electron microscopy （TEM） was employed to observe mitochondrial autophagy in adipocytes. Real-time PCR was used to detect the mRNA expression of hypoxia-inducible factor-1α （HIF-1α）， Bcl-2/adenovirus E1B 19 kDa interacting protein 3 （BNIP3）， microtubule-associated protein 1 light chain 3B （LC3B）， p62/SQSTM1， uncoupling protein 1 （UCP1）， iodothyronine deiodinase 2 （Dio2）， and PR domain containing 16 （Prdm16） in epididymal fat. Western blot was used to detect the protein expression of HIF-1α， BNIP3， LC3B， p62， and UCP1 in epididymal fat.Result Compared with the normal group， the model group showed pathological changes in epididymal fat， with adipocyte mitochondrial condensation and numerous autophagosomes indicating mitochondrial autophagy. The model group also exhibited significantly increased body weight， epididymal fat weight， FBG， GLU， GSP， TC， TG， and LDL-C levels （P<0.01）， significantly decreased HDL-C levels （P<0.01）， significantly elevated mRNA and protein expression of HIF-1α， BNIP3， and LC3B （P<0.01）， significantly reduced mRNA and protein expression of p62 and UCP1 （P<0.01）， and significantly reduced mRNA expression of Dio2 and Prdm16 （P<0.01）. Compared with the model group， all intervention groups showed varying degrees of improvement in epididymal fat pathology. The metformin group and high-dose modified Dahuang Huanglian Xiexintang group displayed intact mitochondrial morphology， clear cristae， uniform matrix， and few autophagosomes and autophagosomes in the adipocyte cytoplasm. The metformin group and high- and medium-dose groups of modified Dahuang Huanglian Xiexintang showed significantly reduced body weight and epididymal fat weight （P<0.01）. The epididymal fat index was reduced in all intervention groups （P<0.05）， and FBG was lowered in all intervention groups （P<0.01）.Serum GSP， GLU， TG， and LDL-C levels were reduced in the metformin group and the high- and medium-dose groups of modified Dahuang Huanglian Xiexintang （P<0.05， P<0.01）. The serum TC level was significantly reduced in the metformin group and high-dose group of modified Dahuang Huanglian Xiexintang （P<0.01）， and HDL-C levels were significantly increased in all intervention groups （P<0.05， P<0.01）. The mRNA and protein expression of HIF-1α， BNIP3， and LC3B were significantly reduced， and UCP1 protein expression was significantly increased in the metformin group and high- and medium-dose groups of modified Dahuang Huanglian Xiexintang （P<0.05， P<0.01）. The mRNA and protein expression of p62， Dio2， and Prdm16 were significantly increased in the metformin group and high-dose group of modified Dahuang Huanglian Xiexintang （P<0.05， P<0.01）.Conclusion Modified Dahuang Huanglian Xiexintang may inhibit mitochondrial autophagy and promote the browning of visceral adipose tissue through the HIF-1α/BNIP3/LC3B pathway， thereby improving glucose and lipid metabolism in obese T2DM rats.
