Long-term High-fat Diet Aggravated Cardiac Lipid Accumulation And Myocardial Lipotoxic Injury In Aging Mice

Part Ⅰ Long-term high-fat diet promoted age-related cardiac lipid accumulation and myocardial lipotoxic injuryBackground: Myocardial lipotoxic injury is the result of excessive accumulation and oxidation of toxic lipids in the heart,and eventually lead to the decline of cardiac function.Aging and obesity are significant risk factors for the development of myocardial lipotoxic injury.The purpose of this part is to observe whether long-term high-fat diet would promote age-related cardiac lipid accumulation and myocardial lipotoxic injury.Methods: Mice of different ages were selected and fed a normal diet for a period of time,and then given a normal diet and a high-fat diet for 8 months,respectively.The mice at the end of feeding were young(4 months),middle-aged(12 months),pre-senile(18 months),and aged(22 months).The mice were divided into 8 groups:normal diet 4 months group(ND 4mo group),normal diet 12 months group(ND12mo group),normal diet 18 months group(ND 18 mo group),normal diet 22 months group(ND 22 mo group),high-fat diet 4 months group(HFD 4mo group),high-fat diet 12 months group(HFD 12 mo group),high-fat diet 18 months group(HFD 18 mo group)and high-fat diet 22 months group(HFD 22 mo group).8 months later,the cardiac function of the eight groups of mice were measured by echocardiograph.Serum was collected from obital venous blood to test the level of serum triglyceride(TG)and total cholesterol(TC).Before the mice were sacrificed,the weight of the mice was measured for the last time.After the mice were sacrificed,the hearts were collected and the hearts of the mice were weighed.The content of TG in myocardial tissue was measured by GPO-PAP method.The degree of myocardial fat infiltration was evaluated by oil red O staining.Masson staining was used to test myocardial interstitial fibrosis in mice and HE staining was used to observe changes in myocardial tissue structure.RT-PCR was used to detect Collagen I,Collagen III,and TGF-β,and to evaluate the degree of myocardial fibrosis at the genetic level.Results: Compared with the normal diet group,the mice showed weight gain at 12 months,18 months,and 22 months from the high-fat diet group;in the high-fat diet group,the weight increased significantly with age.Heart weight of 22-month-old mice in the high-fat diet group was significantly higher than in the other groups.In12-month-old mice,TG levels in the high-fat diet group were higher than in the normal diet group.The serum TG level of 22-month-old mice in the high-fat diet group was significantly higher than that in the control group.TC levels in the high-fat diet group were significantly higher than those in the age-matched normal diet group,and the increase in serum TC levels was greatest in 22-month-old mice.Masson staining showed that in the normal diet group,the myocardial stroma of 22-month-old mice showed significant collagen deposition.In addition,compared with young mice,12-month-old mice in the high-fat diet group showed mild fibrosis,and 22-month-old mice showed the most pronounced fibrosis.RT-PCR showed that the expressions of collagen I,collagen III and TGF-β were consistent with Masson staining.HE staining showed that the gaps in myocardial tissue increased,and myocardial cells were arranged disorderly with increasing age,especially in the high-fat diet group.Echocardiography showed that in the normal diet group,the EF and FS of 22-monthold mice decreased slightly,while in the high fat diet group,the EF and FS decreased with age,but the degree of decrease slowed down in 22-month-old mice;Compared with the 18-month-old mice in the normal diet group,the heart function of the high-fat diet mice also decreased.LVID was significantly increased in 22-month-old mice in the high-fat diet group.Compared to young mice,22-month-old high-fat diet mice showed a significant reduction in LVPW.Conclusion: Long-term high-fat diet promoted age-related cardiac lipid accumulation and myocardial lipotoxic injury,exacerbated age-related cardiac morphological changes and decreased cardiac function.Part Ⅱ Molecular mechanism of long-term high-fat diet promoted age-related cardiac lipid accumulationBackground: The heart accumulates a large amount of lipids and forms a large number of toxic lipid intermediates with non-oxidative pathways,which destroys the structure and function of the heart.The purpose of this part is to study the changes of potential molecular mechanism of age-related cardiac lipid accumulation promoted by long-term high-fat diet.Methods: Mice of different ages were selected and fed a normal diet for a period of time,and then given a normal diet and a high-fat diet for 8 months,respectively.The mice at the end of feeding were young(4 months),middle-aged(12 months),pre-senile(18 months),and aged(22 months).The mice were divided into 8 groups:normal diet 4 months group(ND 4mo group),normal diet 12 months group(ND12mo group),normal diet 18 months group(ND 18 mo group),normal diet 22 months group(ND 22 mo group),high-fat diet 4 months group(HFD 4mo group),high-fat diet 12 months group(HFD 12 mo group),high-fat diet 18 months group(HFD 18 mo group)and high-fat diet 22 months group(HFD 22 mo group).After the mice were euthanized,the hearts were collected and stored in liquid nitrogen.RT-PCR was used to detect CD36,FATP1,PPARα,PGC-1α,and CPT-1β.Western Blot detected CD36,FATP1,PPARα,PGC-1α,and CPT-1β.Results: Compared with young mice,the expression of CD36 and FATP1 protein and m RNA in the myocardium of 22-month-old mice increased in the normal diet group;the expression of CD36 and FATP1 protein and m RNA began to increase from the myocardium of 12-month-old mice in the high-fat environment,and the most significant increase was aged mice.The m RNA and protein expressions of PPAR α,PGC-1 α and CPT-1 β were decreased in 22-month-old mice from normal diet group,while the m RNA and protein expressions of PPAR α,PGC-1 α,CPT-1 β were significantly decreased in 22-month-old from high fat diet group.Conclusion: The mechanism of long-term high-fat diet promoted age-related myocardial lipotoxic injury and decreased cardiac function may be associated with increased fatty acid uptake and reduced fatty acid oxidation capacity involved in CD36 / FATP1 / PPARα / PGC-1α / CPT-1β.