Differences In Hepatic Mitochondrial Energy Metabolism And Intervention Of Sodium Butyrate Between Two Obesity Phenotype Rats Induced By HFD

Obesity is a metabolic disease in which energy intake is greater than energy expenditure and is accompanied by oxidative stress.Mitochondria are the main sites for cellular energy metabolism and free radical production,and they are also the target organelles for free radical attack.Mitochondrial dysfunction is closely related to the occurrence and development of metabolic diseases such as obesity,nonalcoholic fatty liver,and high blood lipids.The differences in mitochondrial redox homeostasis and energy metabolism between obesity prone(OP)and obesity resistance(OR)are unclear.Butyrate is a natural product produced by the fermentation of the intestinal flora and is combined with sodium to form sodium butyrate(NaB).Studies have confirmed that NaB can increase mitochondrial antioxidant enzyme activity,improve mitochondrial function and affect the body’s energy metabolism,but the specific mechanism is not yet clear.This study intends to establish different obese phenotype rats through high fat diet(HFD),compare and analyze the periodic changes of hepatic mitochondrial redox homeostasis and energy metabolism.Different doses of NaB intervention were used for further clarification of the regulatory mechanism and dose effect of NaB on redox homeostasis and energy metabolism in OP and OR rats.After 8 weeks of high-fat diet,SD rats were divided into the OP group and the OR group according to the top 30%and the bottom 30%of body weight,and continued to be fed with HFD until the 20th week.At the 8th,14th,and 20th week,they were sacrificed for sampling,and the indexes such as body weight gain,organ index,and metabolic activity were analyzed;blood lipid levels and redox-related indexes were measured;and the activity of hepatic mitochondrial antioxidant enzymes(GSH-Px and Mn-SOD)were measured.Mitochondrial energy metabolism related indicators(acetyl CoA,NADH/NAD~+ratio,ATP and mitochondrial membrane potential)were measured.The results showed that for OP rats,8-week HFD resulted in decreased mitochondrial antioxidant enzyme activity and increased production of ROS,which promoted oxidative stress,accompanied by abnormal mitochondrial oxidative phosphorylation,reduced membrane potential and decreased ATP production.With the extension of the feeding cycle,the body energy consumption of OP rats was further reduced,resulting in elevated blood lipids and increased body weight.In contrast,OR rats had higher mitochondrial antioxidant enzyme activity and normal redox homeostasis throughout the whole period,which was beneficial to energy utilization and ATP production.In OR rats,the increase in energy expenditure reduced the dyslipidemia and weight gain induced by HFD.Therefore,the difference in mitochondrial redox homeostasis between the OP and OR rats at the initial stage of HFD is an important reason for their phenotypic differences.After establishing OP and OR rat models at week 8,4%,5%,and 6%NaB were added to the HFD for 12 weeks.NaB can regulate the GSK-3β/Nrf2 antioxidant pathway,inhibit the expression of GSK-3βmRNA and protein,increase the expression of Nrf2 mRNA and protein,up-regulate the expression of downstream antioxidant genes NQO1 and HO-1 mRNA,and increase the hepatic mitochondrial antioxidant enzyme(GSH-Px,Mn-SOD)activity,increased T-AOC and GSH/GSSG ratio,reduced ROS levels and MDA content,enhanced the body’s antioxidant capacity.At the same time,Na B showed a protective effect on mitochondrial function.NaB increased significantly the mitochondrial DNA copy number,TFAM mRNA expression and protein levels,promoted the expression of PGC-1α,and then activated the expression of PPARαand PPARγand downstream lipolysis-related genes.NaB enhanced hepatic mitochondrial energy metabolism,promoted fatty acidβoxidation,effectively reduced body weight gain in obese rats,and improved the body’s metabolic indicators,blood lipid levels,blood hormone levels and other apparent indicators.In addition,there was a dose-dependent effect of NaB intervention on rats in the OP group and the OR group,ie,the 6%NaB in the OP group and 4%NaB in the OR group had the most significant intervention effect.