Lifestyle Modification On Expression Of Toll-like Receptor4and Insulin Resistance In High-fat-induced Obese Rats

ObjectiveTo investigate the life modification effects on Toll-like receptor4(TLR4)expression and insulin resistance (IR) of aerobic exercise and dietary adjustment tohigh-fat-induced (DIO) SD rats as well as some mechanisms.MethodsIn this study, the DIO and obesity-resistant (DIO-R) SD male rats were used asexperimental subjects.79normal adult male SD rats were randomly divided intonormal diet control group (NC group, n=16) and high-fat diet group (HF group, n=63), the HF group were fed high-fat diet (caloric40%fat,40%carbohydrate,20%protein, the energy about458Kcal/100g) for8weeks, combined with the bodyweight(BW), fasting plasma glucose (FBG), total cholesterol (TC), triglyceride (TG),low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol(HDL-C) and free fatty acid (FFA) to evaluate the rat model of DIO and DIO-R. Afterpre-screened the treadmill exercise capacity model rats and normal rats wererandomly divided into eight groups: normal diet control group (C group), normal dietexercise group (E group), high-fat diet obesity control group (OHC group),high-fat-diet obesity exercise group(OHE group), normal diet obesity controlgroup(ONC group), normal diet obesity exercise group(ONE group)，high-fat dietobesity-resistant control group(ORC group) and high-fat diet obesity-resistantexercise group (ORE group). After1week treadmill running adaptation (10m/min, agradient of0°), all the exercise intervention groups were exerted moderate-intensityaerobic treadmill running(15m/min, a gradient of5°) equivalent to the maximaloxygen uptake (64.0±4.5)%for9weeks(30min/day,5days/week). After10weeksintervention, the rats weight，epididymal fat and perirenal fat wet weight, blood lipids(TC, TG, HDL-C, LDL-C and FFA), FBG, fasting insulin (FINS), insulin resistanceindex (HOMA-IR), insulin sensitivity index (ISI) were tested; adopting real-timequantitative PCR to observe TLR4mRNA and NF-kBmRNA expression in rat liverand skeletal muscle and using western blotting to determinate TNF-α proteinexpression to observe the role of lifestyle modification on liver and skeletal muscleinflammation state; by means of the electron microscope to distinguish theultrastructure of liver and skeletal muscle cells in the experimental rats.Results1SD male adult rats induced by8weeks high-fat diet, the success rate of DIO ratswas53.97%(34/63). Body weight growth of the normal rats was convergence and hadno significant difference (P>0.05) with the DIO-R rats being under the quarter ofhigh-fat diet rats (16/63).2Compared E, OHE and ONE group with C group respectively, no obvious difference was found in wet weight and index of the perirenal fat or epididymal fat(P>0.05).3TC and LDL-C of DIO rats and DIO-R rats were high than NC group (P<0.05), TGof DIO rats was significantly higher than NC group (P<0.01) and of the DIO-R ratswas obviously lower than DIO group (P<0.01); FBG of the DIO rats and DIO-R ratswere significantly increased (P<0.01and P<0.05); FFA had no significant differenceamong NC, DIO and DIO-R groups (P>0.05).4After10weeks lifestyle modification, in all lipid indices only the TG and LDL-C ofOHC group was significantly increased compared with C group (P<0.05); LDL-C ofONC group and ONE group was lower than OHC group (P<0.05and P<0.01); theORC group and ORE group showed no significant difference (P>0.05).5After10weeks lifestyle modification, compared with C group, FBG, FINS andHOMA-IR of OHC group and FBG of ONE group were significantly increased(P<0.01), FBG of ONC group was raised (P<0.05); compared with OHC group, FINSand HOME-IR of OHE, ONC and ONE group were significantly lower (P<0.01),FBG of OHE group was decreased (P<0.05).6After10weeks lifestyle modification, compared with C group, in all groups onlythe relative expression level of liver TLR4of OHC group was significantly increased(P<0.05), in each group the mean number of large to small: OHC group>ONCgroup>ONE group>ORC group>OHE group>ORE group>C group>E group; therewas no significant difference in the relative expression level of skeletal muscle TLR4in each group, the mean number of large to small: OHC Group> OHE group>ONCgroup>C group>ONE group>ORC group>E Group>ORE group.7After10weeks lifestyle modification, compared with C group, NF-kBmRNAexpression level of liver had no significant difference in every group (P>0.05); that ofskeletal muscle, ONC group was lower than C group (P<0.05), ONE group, ORCgroup and ORE group was significantly lower than C group (P<0.01), group of ONC,ONE, ORC and ORE was apparently lower than OHC group (P <0.01).8After10weeks lifestyle modification, the mean TNF-a protein expression level putin order according to the decreasing order, in liver: OHC group>ONC group>ONEgroup>ORC group>OHE group>ORE group>C group>E group; in skeletal muscle:OHC group>OHE group>C group>ONC group>ORC group>ONE group>Egroup>ORE group.9Expression level of NF-kBmRNA in skeletal muscle showed a moderate positivecorrelation with HOMA-IR (R=0.435), that of TLR4mRNA and NF-kBmRNA inliver and of TLR4mRNA in skeletal muscle had weak correlation withHOMA-IR(R=0.195, R=0.089and R=0.127).10Electron microscopy showed that the Golgi complex and the number ofmitochondria in liver cells of obesity rats is a relatively less, part of the mitochondrialmargins were irregular and poor continuity; liver and skeletal muscle mitochondrialnumber and volume of exercise groups increased, glycogen particles are relativelylarge; arrangement of bright bands with dark bands in skeletal muscle fibers ofexercise group was relatively compact, the rules slightly worse. The main conclusions1High-fat diet feeding for8weeks may induce normal adult SD rats show obesityand obesity resistance phenomenon simultaneously, individual susceptibility toobesity have the difference, the DIO rat weight gain is similar with the normal rats.2DIO rats and DIO-R rats both are able to cause dyslipidemia, the degree of DIO-Rrats was lighter than DIO rats.3Body in obesity or obesity resistance state, regardless of continuing the high-fat dietor changing into the ordinary diet, aerobic exercise modification is an effective way tocontrol fat and loss weight, only recovering to normal diet structure can noteffectively reduce weight.4Aerobic exercise and dietary adjustments make better the obesity, hyperinsulinemiaand IR, the NF-kB expression may be moderate positive correlation with IR.5TLR4is high expression in high-fat diet obesity rats, long-term regular exercise anddiet lifestyle modification to a certain extent to ameliorate IR of the obesity may berelevant to delaying high expression of TLR4.6Aerobic exercise may increase the number and volume of skeletal muscle,accelerate arrangement intensity of skeletal muscle and grow the intracelluar glycogencontent, all above may be related to changes in glucose and lipid metabolism.