| Obesity which is a high risk factor for chronic disease has became a global epidemic disease,such as hypertension,diabetes,cardiovascular disease and metabolic diseases.Obesity could cause left ventricular hypertrophy,ventricular hypertrophy and cardiac dyfunction.It is an independent risk factor for myocardial ischemia,heart failure and sudden cardiac death.Improper diet and exercise can lead to the accumulation of fat in the body and then lead to obesity.Exercise and improved diet can reverse or delay ventricular remodeling and correct impairment of heart function.However,the mechanism of obesity that leads to left ventricular remodeling and impaired function,as well as diet and exercise reversal and improvement,still lacks strong animal experimental evidence.The purpose of this study was to establish dietary and exercise intervention models in obese and obese rats,using conventional echocardiography and speckle tracking techniques to detect left ventricular subclinical myocardial remodeling and impairment of function,in combination with rat serology and myocardial histopatology,which can provide an experimental basis for the mechanism of left ventricular dysfunction in early obese patients.And it was alsodiscussed whether diet and exercise intervention could be used as a non-drug therapy for obesity related risk factors of cardiovascular disease.Objective1.To investigate whether the left ventricular systolic function was changed in early simple obesity rats.2.To investigate the effects of diet and exercise intervention on left ventricular remodeling and left ventricular systolic function in obese rats.MethodsTotal of 48 Sprague-Dawley rats(adult male,3 months old,specefic pathogen free,average weight were 285 ~ 305g)were randomly divided into the normal diet(NF,n=6)group and the high-fat diet(HFD,n=42)group.After 12 weeks of feeding,the obese rats models were established.The obese rats were selected with the weight of 20% of the body weight more than the normal diet group as the obesity standard,28 rats were successfully modeled.6 of them were randomly selected and compared with the normal diet group,and the general data of the rats were recorded and the blood glucose and blood lipid were detected in the rats.By routine and special staining,the degree of mast cell infiltration,the amount of collagen fibrils and the positive expression of LC3 protein were observed under microscope.Routine echocardiographic images were collected,and the left ventricular routine parameters of two-dimensional echocardiography were recorded at EchPAC workstation offline.Two-dimensional strain analysis software was used to analyze the radial,circumferential and longitudinal strain and strain rates of each segment of left ventricular systolic phase in each group.The final data was taken for the average of 3measurements.The two groups were compared with independent sample t test,and the difference of P<0.05 was statistically significant.20 of the heaviest weight rats in the remaining obese rats were randomly divided into four groups: restore normal diet sedentary group(HFD/NF-S,n=5),restore normal diet exercise group(HFD/NF-Ex,n=5),continuous high-fat diet sedentary group(HFD-S,n=5),and continuous high-fat diet exercise group(HFD-Ex,n=5).Exercise groups followed the following exercise plan: first day: running speed 5m/min,time 30min;second day:running speed 7m/min,time 30min;third day: running speed 10m/min,time 30min;fourth day: run speed 15m/min,time 45min;fifth day: run speed 20m/min,time 60 min.After 1week of adaptive training,aerobic exercise was forced for 8 weeks according to the speed and time of 20m/min,60 min,5d/w and 1 time/day.The general data of the rats were recorded and the blood glucose and blood lipid were detected in the rats.By routine and special staining,the degree of mast cell infiltration,the amount of collagen fibrils and the positive expression of LC3 protein were observed under microscope.The ultrastructural changes of myocardium were observed under electron microscope.Routine echocardiographic images were collected,and the left ventricular routine parameters of two-dimensional echocardiography were recorded at EchPAC workstation offline.Two-dimensional strain analysis software was used to analyze the radial,circumferential and longitudinal strain and strain rates of each segment of left ventricular systolic phase in each group.Data selected the average of 3 measurements.Comparison between the 4 groups by single factor analysis of variance,and the difference of P<0.05 was statistically significant.Results1.Group HFD obese rats model of body weight,abdominal circumference,abdominal fat content,blood glucose and TG were significantly higher than that of group NF(P<0.05).2.Group HFD rats conventional echocardiography parameters compared with group NF rats had no obvious changes(all P >0.05);but the left ventricular radial strain rate of anterior septum and anterior wall,the radial strain of anterior wall decreased(all P < 0.05),posterior septal basal segment,middle segment and apical segment and basal segment of lateral wall longitudinal strain rate decreased(all P < 0.05),posterior septum and the lateral wall of the basal segment,middle segment and apical segment longitudinal strain were decreased significantly,middle segment and apical segment longitudinal strain were decreased significantly(all P < 0.05).3.Compared with group NF,myocardial cells in group HFD were arranged in disorder,fat vacuoles were formed,myocardial collagen fiber deposition increased significantly(P<0.05),mast cell infiltration increased significantly(P<0.05),and the expression levelof LC3 was significantly decreased(P<0.05).4.After 8 weeks of diet and exercise intervention,compared with group HFD-S,group HFD/NF-Ex rats weight,abdominal fat content,abdominal circumference,heart mass,blood glucose,TG and LDL decreased,HDL increased(all P<0.01);group HFD/NF-S and group HFD-Ex compared with group HFD-S,rats body weight,abdominal fat content,waist circumference,group HFD/NF-Ex rats each index also changed(all P<0.05);compared with group HFD/NF-S,group HFD-Ex rats body weight,abdominal fat,abdominal circumference and blood glucose increased(all P<0.05),no significant changes in blood lipid(all P >0.05).5.After 8 weeks of diet and exercise intervention,compared to the other three groups,group HFD/NF-Ex rats myocardial collagen deposition,myocardial mast cell infiltration were significantly decreased(all P<0.01),myocardial HE staining and ultrastructural changes of electron microscope were obviously improved;myocardial collagen deposition in HFD-Ex rats,cardiac mast cells infiltration and the expression level of LC3 increased significantly compared with group HFD/NF-S(all P<0.01),partial myocardial ultrastructre disorder.Compared with the 3 groups of intervention group,myocardial collagen deposition in HFD-S rats,cardiac mast cells infiltration and the expression level of LC3 protein increased significantly(all P<0.01),myocardial cell necrosis,sarcomere breakage,lysis of myofilament,mitochondrial disorder,partial autophagy.6.After 8 weeks of diet and exercise intervention,group HFD-S rats left ventricular anterior and posterior diameter than group HFD/NF-Ex and group HFD-Ex increased(P<0.05).The long diameter of the left ventricle in group HFD-S obese rats were greater than group HFD/NF-S(P<0.05).There were no significant changes in the parameters of the conventional echocardiography in the remaining 4 groups of left ventricular structures(P>0.05).Compared with the 3 intervention groups,group HFD-S obese rats LVEF and LVFS were significantly decreased(P<0.05),group HFD/NF-Ex compared with group HFD/NF-S and group HFD-Ex rats LVEF and LVFS increased(P<0.05);and group HFD/NF-S compared with group HFD-Ex,the changes of LVEF and FS in rats were not significant(P>0.05).7.After 8 weeks of diet and exercise intervention,compared with the intervention groups,the radial,circumferential and longitudinal strain and strain rate of the left ventricular systolic phase in group HFD-S were decreased(all P <0.05).Compared with group HFD/NF-Ex,the radial,circumferential and longitudinal strain and strain rates of the left ventricular systolic phase in the two single intervention groups obese rats were reduced(all P<0.05).Compared with group HFD/NF-S,rats radial,circumferential and longitudinal strain and strain rates of the left ventricular systolic segments in group HFD-Ex were changed not very obviously(P>0.05).Conclusion1.The parameters of conventional echocardiography in early obesity rats did not change significantly,but their left ventricular systolic function were damaged to varying degrees.STI was an effective assessment tool.2.Diet and exercise intervention effectively delaied or improved left ventricular remodeling and systolic dysfunction in obese rats,and the two combination intervention were better than single diet or exercise intervention.3.Diet and exercise intervention can be used as a non-drug therapy for clinical obesity intervention,and STI can be used as an effective evaluation method. |
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