Effects Of Selenium-enriched Probiotics On Murine Lipid Metabolism Abnormality, Pathological Lesions And Potential Male Infertility Induced By Feeding A High Fat Diet

Back groundHyperlipidemia poses a major problem to many societies and it represents a high risk factor for frequent diseases. Hyperlipidemia has also been associated with poor semen quality that may lead to male infertility.Selenium (Se) possesses many unique and novel nutritional, biochemical, and molecular biology properties that continue to make it an exciting target for nutrition research. Dietary Se acting through selenoproteins is involved in lipid metabolism and fertility.Probiotic is used as adjuncts in food to provide a wide variety of health benefits. Probiotic has attracted attention as potential cholesterol lowering additives.Se-enriched probiotics (Se-P) is a new product developed by utilizing several strains of probiotics that can efficiently transform and enrich organic Se from inorganic source in our laboratory. As a new organic source of Se, this Se-P product was granted a patent in China in the year of2006(number ZL200510040990.2).Aim of studyThe experiment was conducted to investigate the effects of Se-P, inorganic Se (ISe) and probiotic on mice lipid metabolism abnormality, pathological lesions and male infertility induced by feeding a high fat diet and to explore their mechanism.MethodA total of150ICR male mice,4weeks of age and at average body weight of20g were allotted to5groups in a randomized complete block design, namely4high fat diets groups and one negative control group (A). Mice in Group A were fed a basal diet and served as negative control. Mice in group B were fed a high fat diet (HFD) and constituted the positive control, while three groups of mice were fed the HFD supplemented with the probiotics (group C), ISe [(Se concentration was0.3μg/g diet)(group D)] or the Se-P (group E). The probiotics compromise a mixture of two probiotic strains, Candida utilis (Cu.M02), and Streptococcus thermophilus (St.S07). The number of viable cells was approximately109CFU/g. The HFD was composed of83.7%basal diet plus15%lard,1%cholesterol and0.3%cholic acid. Mice were weekly weighed and health conditions were observed on daily basis. Mice were fed daily for75days after which time they were ether anaesthetized, and blood was collected. Serum was separated for determination of total cholesterol (TC), triglycerides (TG), low density lipoprotein (LDL), high density lipoprotein (HDL), Se,3,5,3’Triiodothyronine (T3)&Thyroxine (T4) and testosterone levels. Plasma samples were taken from7mice/per group for determination of post heparin plasma lipoprotein lipase (Php LPL).All mice were killed at the end of the experiment. Post-mortem examination was carried out immediately to identify gross lesions. Heart, liver, pancreas, spleen and kidneys were removed and testis dissected out and weighed. Suitable samples from these tissues were taken for histopathological examination. Unfixed specimens of liver were taken instantly for determination of liver LPL and fatty acid Synthase (FAS) mRNA expressions by quantitative real-time PCR.Epididymis was dissected in20ml normal saline (0.9%NaCl) for semen evaluation. Sperm index (motility, count and abnormalities) and penis length were measured.ResultsAll mice groups showed no apparent abnormal clinical signs and no significance difference in body weight gain was observed between all groups.The biochemical results showed that in mice fed the HFD there were significant elevation of serum TC, TG, LDL and T4, and decrease of HDL, T3, Php LPL levels as compared to mice fed the basal diet. Addition of probiotics, ISe or Se-p to the HFD significantly decreased the serum TC, TG, LDL and T4, and significantly alleviated Php LPL as compared to mice in group B. Serum T3level was improved by feeding the ISe and Se-p diets, while the probiotic had no effect. Serum HDL was increased only by Se-p supplement diet. Mice fed ISe or Se-p diets showed a significant increase in serum Se level, while mice in group B&C showed a significant decrease in serum Se level as compared to the mice fed the basal diet.Real-time PCR results showed that feeding the HFD to mice induced significant increase of liver LPL and FAS mRNA levels as compared to mice fed the basal diet. Feeding probiotic,(ISe or Se-p) diets to mice significantly (p<0.05;p＜0.01) down-regulated the liver LPL mRNA level respectively, while the liver FAS mRNA level was decreased (p＜0.01) by feeding both of ISe and Se-p as compared to group B. The probiotic had no effect on regulating the liver FAS mRNA.The HFD caused reduced semen quality, a decline in serum testosterone and atrophy and degeneration of seminiferous tubules with loss of spermatogenesis. No significant effects on penis length or relative testis weight were observed. Addition of probiotics, ISe or Se-p to the high fat diet significantly alleviated the adverse effects of hyperlipidemia by increasing testosterone level, improving sperm index and reducing testicular tissue injury. Se-p and ISe had greater effects than probiotics. It was concluded that hyperlipidemia had significant adverse effects on male fertility, which could be ameliorated to varying degrees by feeding probiotics, ISe and Se-p.The post mortem examination displayed that all mice fed the HFD had large, round, pale and fragile liver. Se-p and ISe diets reduced the lesion more than probiotics and the Se-p had the greater effect.A variety of histopathological lesions were seen in mice fed the HFD but the main histopathological changes were liver fatty degeneration; degeneration and necrosis of cardiac muscle, liver and kidney, atrophy of islet of langerhans in pancreas and hyperplasia of splenic white pulp. Se-p markedly reduced these pathological lesions more than the probiotic or ISe; while the probiotic had no effect in improving the spleen lesion and it possessed the least effect in protecting tissue damage than ISe or Se-p.Conclusion1. A high fat diet can cause significant lipid metabolism abnormality, pathological lesions and potential male infertility in mice.2. The probiotics, ISe and Se-p have hypolipidemic effect, improve male fertility and protect tissues from fatty deposition and damage induced by high fat diet. Se-p diet has the greater effect than ISe diet though both of them were more effective than the probiotics diet.3. The mechanism of Se-p in lipid metabolism is through decrease synthesis and increase catabolism of the lipid.