| Aims：The present study was to evaluate the effects of different exercise protocols on metaboliccharacteristics and regulatories involved in fatty acid metabolism, and to identify theefficiency of different exercises on prevention of obesity in rats concurrently fed withhigh-fat diet. Furthermore based on the molecular biology, the mechanism in regulation offatty acid metabolism was discussed and explained.Materials and methods：Forty-five male Sprague-Dawley rats were randomly divided into five groups: control diet/sedentary group (CS), high-fat diet/sedentary group (HS), high-fat diet/endurance exercise(HE), high-fat diet/interval exercise (HI), high-fat diet/concurrent exercise (HC). Thehigh-fat diet contained45%fat, while control diet consisted of10%fat. Exercise wasperformed on a motor-driven rodent treadmill. Rats were subject to running exercise5days/wk for10weeks according to exercise protocols, respectively. All protocols kept theidentical amount of total running distance. Body weight of all rats and their food intake wereweighed during treatment. After10weeks, all rats were killed. Blood samples were collectedvia abdominal aorta. Serum lipid including TG, TC, HDL-C, and LDL-C, and serum GLUwas determined by an automated analyzer. Fasting insulin was measured with rat-specificELISA kits. Fatty tissues in the mesenteric, retroperitoneal and epididymal areas, and liverwere dissected and weighed. Gastrocnemius muscle samples were immediately isolated andstored. Pieces from the retroperitoneal were sectioned for standard hematoxylin-eosinstaining, and then the size of adipocytes was observed. Sections of liver were used todetermine lipid deposit for H&E staining and standard Oil Red O staining. Relativeexpression of Rev-erbα and SCD1in liver was determined by real-time PCR. Relativeexpressions of several regulatories including Rev-erbα, FAT/CD36, SCD1, and CPT1inskeletal muscle were analyzed by real-time PCR and western blotting.Results：1. Phenotypic characteristics related to high-fat induced obesity in ratsHS was fed significantly less food than control diet during10weeks, while total caloricintake did not differ significantly in rats fed with both diets. Body weight, fat weight, andLee’s index in HS was higher than CS, respectively. HS exhibited higher level of serum lipidand GLU compared with CS, whereas insulin sensitivity as assessed by QUICKI significantlydecreased in HS rats. After10weeks, the size of adipocytes in HS was significantly largerthan CS.2. Effects of different exercise protocols on phenotypic characteristics related to high-fatinduced obesity Exercise resulted in a smaller body weight, Lee’s index, and fat weight in rats fed withhigh-fat diet. The corresponding weight in HE and HC rats was slightly lower than HS, butnot significantly, while HI weighted less significantly than HS. Between all groups fed withhigh-fat diet, exercised group reduced TG, GLU, and increased insulin sensitivity, althoughHI presented statistical significance. All exercised groups dwindled in adipocyte size,meanwhile size in HI was smaller than HE, and HC.Visceral fat weight was positively correlated with TG (r＝0.726，P＜0.01). QUICKI wasinversely correlated with visceral fat weight (r＝－0.685，P＜0.01), as well as GLU (r＝－0.919，P＜0.01).3. Content of lipid droplets and expression of Rev-erbα and SCD1in liverH&E stained sections showed a normal liver structure in CS, while there was extensivehepatocyte vacuoles in HS. Oil Red O staining of liver sections confirmed no significant lipidaccumulation in CS, but a massive accumulation of fatty components in the livers of HS.Exercise interventions efficiently ameliorated lipids droplets in hepatocytes, especially withheavy-intensity interval exercise. Significantly less oil was accumulated in the exercisedgroups, especially in HI.When compared with CS, HS induced down regulation of Rev-erbα mRNAand up-regulationof SCD1. In high-fat groups, all exercised groups trended to increase the expression ofRev-erbα, and moreover, HI elevated Rev-erbα sharply, which was higher significantly thanHE and HC. SCD1mRNA was decreased in all exercised rats, and HI amplified the change.4. Expression of Rev-erbα, FAT/CD36, SCD1, and CPT1in skeletal muscleData indicated that high-fat diet stimulated slightly the decrease of Rev-erbα mRNA andprotein, and however there was no significant difference between HS and CS. The expressionof FAT/CD36and SCD1in HS was obviously higher than CS. HS had no changes in theexpression of CPT1compared to CS. When intervented by exercises, the expression ofRev-erbα trended to increase, but only HI elevated Rev-erbα statistically. FAT/CD36wasincreased in all exercised rats, and its expression in HI was higher than in HE and HC. It issurprising that exercise did not affect SCD1level when fed with high-fat diet. Elevation inCPT1mRNA was observed in all exercised groups, however fold changes in HE and HCcompared with HS was no statistically difference, while HI up-regulated CPT1mRNAsignificantly.Conclusions：1. Lifestyle of high-fat diet and stationary led to obesity, which was was scientific referenceto researches about exercise intervention.2. Different exercise regiments could improve metabolic characteristics of rats fed withhigh-fat diet. Heavy-intensity interval exercise sought to reverse the adverse effects of high-fat diet, which is the alternative to prevention of obesity and related chronic diseases.3. Heavy-intensity exercise was especially beneficial to metabolism adaptation in liver, whichis an optimum selection to prevent hepatic steatosis. Exercise induced the increase ofRev-erbα and the subsequent inhibition of SCD1, which was favorable to less lipid droplets.4. Effects of different exercise protocols with concurrent high-fat diet were different on fattyacid transportation, resynthesis, and oxidation. High-intensity exercise induced the expressionof Rev-erbα, and the subsequent accommodation in expression of FAT/CD36, SCD1, andCPT1, which could be a major mechanism of fatty acid metabolism in skeletal muscles.5. Expression of Rev-erbα was closely related to lipid metabolism in muscle and liver, whichmay be the target regulatory in lipid homeostasis and metabolism balance.6. Above all, heavy-intensity interval exercise was time-efficient for improving the lipidmetabolism and preventing obesity and related chronic diseases. |
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