| Hypoxic training can effectively reduce the body weight and fat, affect serumlipid levels, regulate the body lipid metabolism. MiRNAs are small single strandno-coding RNAs, which regulate gene expression at the post-transcriptional level, inmost cases, by sequence-specific hybridization to complementary target sites in the3’UTR of mRNA to inhibit mRNA translation or cause mRNA degradation. Previousresearches have demonstrated that some miRNAs play important roles in regulatinglipid metabolism. However, it is unclear if hypoxic exercise training alters miRNAexpression and lipid metabolism. In this study, our aim was to study the effects ofhypoxic exercise training on miRNA expression and the role of different expressionmiRNA in lipid metabolism by studying the expression characteristics of miRNA,genes and proteins related to lipid metabolism in the liver of high fat diet rats, and theexpression characteristics of miRNA, genes and proteins related to lipid metabolismin the liver of high fat diet rats under hypoxic training, to explore the molecularmechanisms of miRNA regulation of hepatic lipid metabolism in hypoxic exercisetraining.Materials and methods:This study was divided into two parts, the first part,100male SD rats of21-day-old were divided into two groups, common group (n=10) fed with standard ratchow, high fat diet group (n=90) received a high-fat diet. After12weeks, the ratswhich body weight were greater than the average body weight of common group werechosen from high fat diet group for further experiment. After12h fasting, the normalgroup rats and10rats chosen randomly from high fat diet group were utilized to drawmaterial. Body weight, fat mass and body length were measured. Blood samples werecollected and the right lobe of liver was removed. The miRNAs differentiallyexpressed in rats liver were screened using miRNA microarray. The mRNA andprotein expression levels of peroxisome proliferator activated receptor (PPAR),fatty acid synthetase (FAS), carnitine palmitoyl transferase1A (CPT1A), fatty acidtranslocase (FAT/CD36), Apolipoprotein AI (ApoAI) in rat liver were verified bySYBR Green real-time polymerase chain reaction (real-time PCR) and enzyme-linkedimmunosorbent assay (ELISA) technique. The aim was to study the expressioncharacteristics of miRNA, genes and proteins related to lipid metabolism in the liverof high fat diet rats. The second part, forty high fat diet SD rats chosen from the highfat diet group after2weeks adaptive training were divided into a normoxic sedentarygroup (n=10), a normoxic training group (n=10), a hypoxic sedentary group (n=10,oxygen content:13.6%, simulated altitude of3500m) and a hypoxic exercise traininggroup (n=10, oxygen content:13.6%, simulated altitude of3500m). The four groupsrats were fed high fat diet continuely for4weeks. The expression levels of threemiRNA related to lipid metabolism were verified using SYBR Green real-time PCR.Other testing index and methods were consistent with the first part of the study. Theaim was to study the expression characteristics of miRNA, genes and proteins relatedto lipid metabolism in the liver of high fat diet rats under normoxic training, hypoxic sedentary and hypoxic exercise training, to explore the molecular mechanisms ofmiRNA regulation of hepatic lipid metabolism in hypoxic exercise training.Results:1. The Lee’s index, body fat, fat/weight ratio, serum TC, HDL-C and LDL-Clevels of high fat diet rats were all higher significantly than those of normal rats(P<0.05).2. The expression of miRNA in liver: the expression of10miRNA in liver weresignificantly different detected by miRNA microarray between the two groups(P<0.05). The expression levels of miR-203a-3p and miR-6215in high fat diet ratsliver were significantly lower than normal rats, and the expression levels of let-7f-5p,let-7a-5p, let-7c-5p, miR-352, let-7b-5p, miR-25-3p, miR-483-5p and miR-221-3p inhigh fat diet rats liver were significantly higher than normal rats.3. The expression levels of genes and protein: the expression of FAS and ApoAImRNA in high fat diet rats liver were significant lower than those in normal rats liver(P<0.05, P<0.01). The expression of PPAR and FAT/CD36mRNA in hig fat diet ratsliver were higher than those in normal rats liver, the mRNA level of CPT1A and theprotein levels of PPAR, FAS, CPT1A, FAT/CD36and ApoAI were lower than thosein normal rats liver, while the results had no significant difference between the twogroups (P>0.05).4. Compared with normoxic sedentary group, the body weight, body fat, fat/weight ratio and serum FFA concentration of normoxic training group were allsignificantly lower (P<0.05); the body weight, Lee’s index, TC and HDL-Cconcentration of hypoxic sedentary group were significantly lower, TG and FFAlevels were significantly higher (P<0.05); the body weight, Lee’s index, body fat, fat/weight ratio, serum TC and HDL-C concentration of hypoxic exercise training groupwere all significantly lower (P<0.05).5. The expression of miRNA in liver:The results of miRNA microarray, the expression of miR-193-3p of normoxictraining group was significantly lower than normoxic sedentary group (P<0.05).Compared with hypoxic sedentary group,5miRNA were significantly different inhypoxic training group (P<0.05), the expression of miR-378b and miR-21-5p weresignificantly lower, the expression of miR-133b-5p, miR-146b-5p and miR-6215weresignificantly higher. The expression of miR-92a-2-5p, miR-378a-3p and miR-1224were significantly lower in hypoxic training group than those in normoxic traininggroup (P<0.05). Compared with normoxic sedentary group,5miRNA weresignificantly different in hypoxic training group (P<0.05), the expression of miR-378bwas significantly lower, the expression of miR-100-5p, miR-142-3p, miR-142-5p andmiR-494-3p were significantly higher.The results of SYBR Green real-time PCR showed that the expression ofmiR-378b in hypoxic training group was significantly lower than that in normoxicsedentary group (P<0.05). The expression of miR-378b and miR-21-5p in hypoxictraining group was significantly lower than that in normoxic training group (P<0.05).The expression of miR-378b and miR-21-5p in hypoxic training group wassignificantly lower than that in hypoxic sedentary group (P<0.05). 6. The expression levels of genes and protein: the mRNA expression ofFAT/CD36in hypoxic sedentary group was significantly lower than that of normoxictraining group (P<0.05). The mRNA expression of ApoAI in normoxic training groupwas significantly higher than normoxic sedentary group (P<0.05). The proteinexpression of CPT1A in hypoxic training group was significantly lower thannormoxic sedentary group (P<0.05).The expression of PPAR mRNA in training groups was higher respective thansedentary groups, while the hypoxic groups was lower respective than normoxicgroups (P>0.05). The expression of FAS and CPT1A mRNA in training groups werelower respective than sedentary, while the hypoxic groups were higher respective thannormoxic group (P>0.05). The mRNA expression of ApoAI in hypoxic sedentarygroup and hypoxic training group were higher than normoxic sedentary group(P>0.05). The protein expression of PPAR in normoxic training group, hypoxicsedentary group and hypoxic training group were lower than normoxic sedentarygroup (P>0.05). The protein expression of FAS in training groups and hypoxic groupswas higher respectively than sedentary groups and normoxic groups (P>0.05). Theprotein expression of CPT1A in training groups and hypoxic groups was lowerrespectively than sedentary groups and normoxic groups (P>0.05). The proteinexpression of FAT/CD36in training groups and hypoxic sedentary group was lowerrespectively than sedentary groups and normoxic sedentary group (P>0.05). Theprotein expression of ApoAI in normoxic training group was lower than normoxicsedentary group (P>0.05). The protein expression of ApoAI in hypoxic sedentarygroup and hypoxic training group were higher than normoxic sedentary group(P>0.05).Conclusion:1. High fat diet can significantly increase the body fat and serum lipid levels inthe SD rats. Overexpressed of let-7miRNA family may play an important role inglycometabolism and increase ectopic fat accumulation in high fat diet rats liver. Fattyacid synthesis in liver and reverse cholesterol transport may be decreased in the highfat diet rats by reducing the expression of FAS and ApoAI mRNA.2. Normoxic training can lower body weight, body fat and serum FFAconcentration in high fat diet rats. Normoxic training significantly reduced theexpression level of miR-193-3p in high fat diet rats liver, and possibly throughupregulation the expression of its target gene FASN, increased fatty acid synthesis inthe liver. Normoxic training increased reverse cholesterol transport by elevatingApoAI mRNA expression in high fat diet rats liver.3. Hypoxic training was more effective in decreasing body weight, body fat,serum TC and HDL-C level of high fat diet rats. Hypoxic training could reduce theexpression of miR-378b to elevate the ablity of resistion high fat diet in the rats, lowerthe protein expression of CPT1A to decrease the ablity of mitochondrial oxidation. |
PDF Full Text Request