Androgen And Estrogen: Experiment And Clinical Study On Lipid Metabolism In Male Rats And Middle Old-aged Men

BackgroundData suggest that atherosclerosis (AS) is more common in men than in women and men has higher risk than women in getting coronary heart disease. It has been shown that old-age male has lower androgen level , especially the lower biologically active androgen level.It is noticed that endogenous sex hormones testosterone, estradiol and dihydrotestosterone influence cardiovascular disease risk factors. So there is viewpoint that androgen level has close relation with the start and development of risk factors of atherosclerosis,low androgen level is an independent risk factor of atherosclerosis.Hyperlipemia has close relation with AS .Many studies show that androgen affects the process of AS by causing lipid metabolism disorder.Objective:1. To establish a castrated hyperlipidemia rat model with high-fat diet.2. To evaluate the effects of dihydrotestosterone and estradiol on lipid metabolism in high fat and cholesterol-fed male rats and its possible mechanisms.3. To observe the effect of totally and partly inhibited endogenous androgen and estradiol on serum lipids in high-fat diet male rats.4. To investigate the relationship between endogenous sex hormone and serum lipids in middle old-aged men.Methods and Materials:1. 12 male orchidectomized Sprague-dawley (SD) rats were randomly divided into two groups for nomal diet group(n=6)and high fatty diet group (n=6) Which were fed with different diet for 10 weeks. Total cholesterol, triglyceride, high density lipoprotein and low density lipoprotein concentrations in serum were measured using an enzymatic technique.The slices of liver were stained by HE. The Stastical analysis was done by Student's unpaired t-test.2. 24 orchidectomized male Sprague-dawley rats were randomly divided into four groups.Control group rats underwent medical maize oil (placebo), low dose and high dose dihydrotestosterone group rats were treated with dihydrotestosterone transdermal injected (0.6 mg·kg·day, 6.0 mg·kg·d); Estradiol group rats were treated with estradiol hypodermic injected (0.2 mg·kg·day) until the end of the experiment. Animals were fed with high-fat diet. Animals were sacrificed after blood samples were collected and centrifugated. Weights were recorded. The liver tissue was treated with liquid nitrogen and 10% formalin solution.Serum was used for measuring total cholesterol, triglyceride, high density lipoprotein and low density lipoprotein concentrations using an enzymatic technique. The dihydrotestosterone concentration in serum was measured using an enzyme-linked immunospecific assay. The level of testosterone and estradiol in serum were measured using a radioimmunoassay. The mRNA expression of Cholesterol 7alpha -hydroxylase and hepatic lipase in liver tissue were determined using a reverse transcription PCR technique.Liver slices was stained with HE and SudanⅢmethods. The changes of Liver were compared with pathology. All data were expressed as means±SD. Stastical analysis was done by analysis of variance followed by one way analysis of variance and multiple comparisons. A probability value less than 0.05 was considered statistically significant.3. Nine old weeks'male SD rats were randomly divided into three groups for Antiandrogen group, antientrogen group and control group, each group contained 6 rats. Antiandrogen group rats were treated with flutamide administrated (1 mg·kg·day), antientrogen group rats were underwented with tamoxifen (2 mg·kg·day) for 14 weeks;Control group were intragastricly administrated with Sodium Chloride. Weights were recorded .Animals were sacrificed after blood samples were collected and centrifugated. Total cholesterol, triglyceride, high density lipoprotein and low density lipoprotein concentrations in serum were measured using an enzymatic technique. Stastical analysis was done by analysis of variance followed by one way analysis of variance and multiple comparisons. A probability value less than 0.05 was considered statistically significant.4. Sixty men with ultrasound proven arteriosclerosis and without arteriosclerosis were recruited and entered the study. 32 men with arteriosclerosis were divided into arteriosclerosis group, and 28 men without arteriosclerosis were treated control group. Blood samples were collected and centrifugated. The testosterone and estradiol concentrations in serum were measured using a radioimmunoassay.Total cholesterol, triglyceride, high density lipoprotein and low density lipoprotein concentrations in serum were determined using an enzymic technique. The mean different between arteriosclerosis group and control group was compared. The correlation between free testosterone and serum lipids was analyzed. Both of serum lipids and sex hormone were analyzed by Student t-test. The relation between serum lipids and sex hormone were analyzed by Pearson correlation analysis.Results1. The levels of total cholesterol, triglyceride and low density lipoprotein in serum were significantly increasing in high fat-diet group compare with normal diet group(P<0.05); The level of high density lipoprotein in serum has no change. The intracytoplasm of liver cell showed fat vacuole in high-fat diet group.2. Total cholesterol , low density lipoprotein cholesterol and low density lipoprotein cholesterol concentrations in serum of two groups with dihydrotestosterone were decreased compared with control group(P<0.05), The levels of total cholesterol , low density lipoprotein cholesterol and low density lipoprotein cholesterol in serum of estradiol group were increased compared with control group(P<0.05).Yet The levels of triglyceride in serum was caused increases in dihydrotestosterone and estradiol group compared with control group. The extent of descending total cholesterol correlated with the the level of dihydrotestosterone in serum. Cholesterol 7alpha-hydroxylase and hepatic lipase mRNA expression of the low dose dihydrotestosterone group were significantly increased compared with the control group. Cholesterol 7alpha-hydroxylase and hepatic lipase mRNA expression of the estradiol group were suppressed than control group(P<0.05). The severe hepatic steatosis was showed in control group. however much less lesion were observed in low dose dihydrotestosterone and high dose dihydrotestosterone groups.3 .Total cholesterol and low dose lipoprotein were caused decreases in antiestrogen group compare with Control group, but serum triglycerides and high density lipoprotein cholesterol were increased(P<0.05). The levels of serum total cholesterol and low dose lipoprotein were caused increases in antiandrogen group compare with control group (P<0.05),however The level of high density lipoprotein cholesterol in serum had no statistic significance in antiandrogen group compare with control group(P>0.05).4. Middle old-aged men with arteriosclerosis had significantly lower levels of free testosterone compared with controls(P<0.05),No obvious deference in level of serum estradiol was found between two groups. serum testosterone were negatively correlated with total cholesterol and low density lipoprotein cholesterol,serum estradiol positively correlated with low density lipoprotein cholesterol (P<0.05).Estradiol and testosterone were uncorrelated with triglycerides.the level of total cholesterol, low density lipoprotein cholesterol and triglycerides of male atherosclerosis is greater than control group (P<0.05).Conclusions:1. The results suggested that exogenous dihydrotestosterone could decrease serum total cholesterol, high density lipoprotein cholesterol and low dose lipoprotein cholesterol. The mRNA expressions of cholesterol 7alpha -hydroxylase and hepatic lipase were up-regulated by dihydrotestosterone. The results of exogenous were opposite compared with dihydrotestosterone.2. It was concluded the down-regulation and up-regulation of cholesterol 7alpha-hydroxylase and hepatic lipase were possible mechanisms involved in the effect of exogenous dihydrotestosterone and estradiol on serum total cholesterol; high density lipoprotein cholesterol and low dose lipoprotein cholesterol. The mechanism of exogenous dihydrotestosterone on serum triglycerides may be that it can strengthen liver fat catabolism.3. The results suggested that Inhibiton of endogenous androgen can increase the level of serum, but inhibition of endogenous estrogen decreases serum total cholesterol and serum low dose lipoprotein cholesterol while increase the level of high density lipoprotein cholesterol in male rat. Together with the effects on risk factors of arteriosclerosis, the data strongly support clinical treatment of men with arteriosclerosis.4. The results suggest that estradiol and testosterone were correlated with hyperlipemia and arteriosclerosis in middle old-aged men. Low testosterone concentration in serum is an independent predictor of atherosclerosis.