| ObjectiveObesity and related metabolic diseases caused by energy metabolism disorders are trending worldwide,and safe and effective methods of weight control and fat loss are still the focus of research.Recent studies have found that intermittent hypoxic training can improve the glucose and lipid metabolism disorders in obesity and related metabolic diseases,but the concentration and form of hypoxic exposure are still inconsistent.It has been found that the AMPK/PGC-1αsignaling pathway plays a central regulatory role in cellular energy metabolism,which not only regulates skeletal muscle glucose and lipid metabolism and mitochondrial generation,but also promotes the occurrence of adipose tissue browning.Hypoxia training is an activation method of AMPK/PGC-1α signaling pathway,and it has been reported that mi R-455 and mi R-761 are involved in the regulation of AMPK/PGC-1α signaling pathway through post-transcriptional regulation of genes.Based on this,this study prepared a high-fat diet obese rat model and a hypoxic training model to analyze and compare the effects of different concentrations of hypoxic training on weight control and fat reduction in obese individuals,and to explore its effect on AMPK/PGC-1α signaling pathway in obese rats and the browning of subcutaneous adipose tissue in rats.This provides new evidence for the application of hypoxic training to weight control and fat loss practice,and enriches the molecular mechanism of hypoxic training in regulating energy metabolism disorders in the body.MethodsThe nutritionally obese rat model was prepared by feeding with high-fat feed.After 8 weeks of feeding,80 nutritionally obese rats that met the obesity standard were randomly divided into8 groups.They were the quiet control group(group A,n= 10),16.3% oxygen concentration exposure group(group B,n=10),13.3% oxygen concentration exposure group(group C,n=10),11.3% oxygen concentration exposure group(group D,n=10)and the corresponding endurance training group: endurance training control group(group AE,n=10),16.3% oxygen concentration training group(group BE,n=10),13.3% oxygen concentration training group(group CE,n=10)and 11.3% oxygen concentration training group concentration training group(group DE,n=10).The three hypoxic exposure groups were subjected to intermittent hypoxia exposure corresponding to the oxygen concentration for 12/12 h every day.The rats in the AE group were subjected to moderate-intensity endurance training in a normoxic environment(slope of 0°,treadmill speed of 20 m/min,for 40 min,5 d/w),and rats in three hypoxic training groups underwent moderate-intensity endurance training in a normal pressure environment with an oxygen concentration of 16.3%,13.3%,and 11.3%.After 8 weeks of experimental intervention,the rats were sacrificed and the materials were collected.(1)The effects of hypoxia exposure or/and endurance on body composition in obese rats were detected by measuring the body weight,Lee’s index,visceral fat percentage,and skeletal muscle percentage of the rats;four items of blood glucose concentration and serum lipids were measured.The levels of serum Insulin,Adiponectin and Leptin were detected by Elisa method,and the HOMA-IR of the rats was calculated to analyze the improvement effect of hypoxia exposure or/and endurance training on glucose and lipid dysfunction in obese rats.(2)The soleus muscle of the rat was taken,and the morphology of the skeletal muscle was observed after HE staining.The inguinal adipose tissue of rats was collected,and Western blot was used to detect the relative expressions of PAMPK/AMPK,PGC-1α,LKB1,Sirt1 and other proteins in inguinal adipose tissue of rats.The effect of hypoxic training on AMPK/PGC-1α signal and related protein expression in skeletal muscle and adipose tissue of obese rats was analyzed.(3)The morphology of subcutaneous adipocytes was observed by HE staining;the expressions of FNDC5 and Metrnl in rat skeletal muscle and adipose tissue were detected by Western blot;the concentrations of Irisin and Metrnl in rat serum were detected,and RT-q PCR was used to detect the rat Relative gene expression levels of mi R-455 and mi R-761 in serum.The effect of hypoxic training on white fat browning in obese rats was analyzed.Results(1)During the intervention period,the body weight of the rats in the quiet group continued to increase,and the body weight of the three hypoxic exposure groups increased rapidly in the first 4 weeks,and then slowed down from the 5th week.The body weight of the rats in the endurance training group continued to decrease in the first 4 weeks and increased from the 5th week,but was significantly lower than that of the rats in the quiet control group(P<0.05).The body weight of the rats in the three hypoxic training groups decreased continuously from the beginning,and from the 6th week,the body weight of the rats in the 13.3% hypoxia training group and the 11.3% hypoxia training group was significantly lower than that in the endurance training group(P<0.05).After 8 weeks of intervention,the body weight and visceral fat percentage of the rats in the 13.3% hypoxia exposure group and the 3 hypoxia training groups were significantly lower than those in the quiet control group(P<0.05).The body weight and visceral fat percentage of the rats in the 13.3% and 11.3% hypoxic training groups were significantly lower than those in the endurance training group(P<0.05).The percentage of skeletal muscle in the three hypoxic training groups was significantly higher than that in the quiet control group(P<0.05),and the percentage of skeletal muscle in the group CE was the highest.11.3% hypoxic exposure and hypoxic training could significantly reduce serum Leptin,TG,TC,LDL-C and increase HDL-C in obese rats.Different concentrations of hypoxic exposure or/and endurance training can reduce HOMA-IR levels in obese rats,and 13.3% and 11.3% hypoxic training improved IR in obese rats better than endurance training alone.The serum Adiponectin concentration of the rats in the AE group was the highest,and there was a significant difference compared with the other 7 groups(P<0.05).In the three groups of hypoxic training,with the decrease of hypoxia exposure concentration,the concentration of serum Adiponectin in rats decreased,and the difference was significant(P<0.05).(2)After 8 weeks of intervention,the ratio of P-AMPK/AMPK in skeletal muscle of rats in group C,group D,group CE and group DE was higher than that in group A,indicating that hypoxia exposure and hypoxia training at 13.3% and 11.3% oxygen concentration can significantly improve Phosphorylation of AMPK in obese rat skeletal muscle.The protein expression level of PGC-1α in skeletal muscle of rats in group C,AE and three hypoxic training groups was significantly higher than that in group A(P<0.05),among which,the expression level of group DE was the highest.The relative expression of LKB1 protein in skeletal muscle of rats in group C,D,AE,BE and DE was significantly higher than that in group A(P<0.05),and the level in group DE was the highest among the three groups.The relative expression of Sirt1 protein in skeletal muscle of rats in group A was significantly lower than the other 7 groups,and the difference was significant(P<0.05).The relative expression of Sirt1 protein in skeletal muscle of rats in group D and CE was higher than that in group AE.And the difference was significant(P<0.05).The expressions of MCAD and CPT1 in skeletal muscle of rats in seven groups of hypoxia exposure or/and endurance training were significantly higher than those in group A(P<0.05).After 8 weeks of intervention,the gene transcription level of AMPK in adipose tissue of rats in 7 groups of hypoxia exposure or/and endurance training was significantly higher than that in group A(P<0.05);in group D,group AE,group BE,group CE and group DE the ratio of P-AMPK/AMPK in rat adipose tissue was higher than that in group A,and the difference was significant(P<0.05).The adipose tissue PGC-1α gene transcription level of the three hypoxic training groups was higher than that of the group A(P<0.05).Except for group B,the protein expression level of PGC-1α in adipose tissue of other six groups was higher than that of group A,and the difference was significant(P<0.05).The protein expression level of PGC-1α in the adipose tissue of rats in group DE was the highest,and there was a significant difference compared with group AE(P<0.05).The relative expression of LKB1 protein in adipose tissue of rats in 7 groups of hypoxia exposure or/and endurance training was significantly higher than that in group A(P<0.05).The protein expression level of Sirt1 in the adipose tissue of rats in the group AE and the three hypoxic training groups was significantly higher than that in the group A,and the protein expression level of Sirt1 in the adipose tissue of the rats in group DE was the highest,and the difference was significant compared with the other seven groups(P <0.05).(3)8 weeks of hypoxic exposure or/and endurance exercise can change the shape of fat cells and reduce the fat area.The lower the oxygen concentration is,the more obvious the intervention effect is.Among them,the hypoxic training with 11.3% oxygen concentration is more effective than endurance training alone.The effect is obvious.Hypoxic exposure had little effect on serum Irisin in obese rats,but the serum Irisin concentrations in the endurance training group and the three hypoxic training groups were significantly higher than those in group A.It can be seen that both endurance training and hypoxia training can improve the Serum Irisin concentration in nutritionally obese rats.The concentration of serum Irisin in rats was significantly negatively correlated with body weight,Lee’s index and visceral fat specific gravity,while significantly positively correlated with skeletal muscle specific gravity and FNDC5 protein expression level in skeletal muscle(P<0.05).The serum Metrnl concentration of rats in hypoxia exposure or/and endurance training group was higher than that in group A,and the difference was significant(P<0.05).Among them,16.3% of rats in intermittent hypoxia training group had the highest serum Metrnl concentration.The concentration of Metrnl in rat serum was significantly negatively correlated with body weight,fat specific gravity,Lee’s index and HOMA-IR,but significantly positively correlated with skeletal muscle specific gravity(P<0.05).The relative expression of FNDC5 protein in soleus muscle of rats in 11.3% hypoxia exposure group,endurance training group and three hypoxia training groups was higher than that in group A(P<0.05).The protein expression of Metrnl in skeletal muscle of rats in seven groups of hypoxia exposure or/and endurance training was significantly higher than that in group A(P<0.05).Hypoxia exposure alone had no significant effect on the expression of FNDC5 in subcutaneous adipose tissue of rats(P>0.05);while the relative expression of FNDC5 in subcutaneous adipose tissue of the endurance training group and the three hypoxic training groups increased,and there was a significant difference with group A(P<0.05).The 13.3% hypoxia exposure group,the 11.3%hypoxia exposure group,the endurance training group and the three hypoxia training groups could increase the relative expression of Metrnl protein in subcutaneous adipose tissue of obese rats,and there were significant differences compared with group A(P <0.05).The protein expression of HIF-1α in the subcutaneous fat of rats after 3 concentrations of hypoxia exposure or/and endurance training was lower than that in the obese group A(P<0.05),while the relative protein expression of VEGFA in the inguinal fat of rats was significantly higher than that in group A(P<0.05),indicating that long-term hypoxia exposure or/and endurance training improved the hypoxic state of inguinal fat in rats.The relative expression of UCP1 protein in subcutaneous adipose tissue of rats in 11.3% hypoxia exposure group,endurance training group and three hypoxia training groups was significantly higher than that in group A(P<0.05).Compared with group AE,group BE and group CE,the difference was significant(P<0.05).The expression level of serum mi R-455 in group A was significantly lower than that in group AE(P<0.05).The relative expression of serum mi R-455 in group AE was significantly higher than that in the three hypoxic training groups,and the difference was significant(P<0.05).The relative expression of serum mi R-761 in group CE was significantly lower than that in group A,and the difference was statistically significant(P<0.05).The expression level of serum mi R-761 in group B was the highest,and the difference was significant compared with the rats in the four training groups(P<0.05).Conclusion(1)Hypoxic exposure can inhibit the growth rate of rat body weight,and endurance training and hypoxic training reduce the body weight of obese rats.8 weeks of hypoxic training can play a significant role in weight control and fat reduction,and the lower the oxygen concentration is,the more obvious the effect is.(2)Hypoxic exposure and hypoxic training in simulated medium and high altitude oxygen concentrations activated the AMPK/PGC-1α signaling pathway in skeletal muscle of obese rats,and LKB1 and Sirt1 were involved in the regulation of skeletal muscle metabolic homeostasis.Hypoxic training simulating high-altitude oxygen concentration can promote AMPK/PGC-1αsignaling pathway and the protein expression of LKB1 and Sirt1 in subcutaneous adipose tissue of rats.(3)Both endurance training and hypoxic training can improve the hypoxic state of subcutaneous adipose tissue in obese rats,promote the expression of Metrnl and Irisin in skeletal muscle and adipose tissue,increase the concentrations of serum Irisin and Metrnl,and promote the occurrence of white fat browning in obese rats.Simulated high-altitude oxygen concentration training has more obvious effects on the browning of subcutaneous fat in rats.Hypoxic training at an appropriate concentration decreased the relative expression levels of mi R-455 and mi R-761 in rat serum. |
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