Relationship Of Serum Leptin, Reproductive Performance And Certain Blood Biochemical Indexes In Rabbits

Leptin is a research hotspot in recent years. However, researches in relationship of leptin, animal reproductive performance and blood biochemical indices is few. In this paper, relationship of leptin, animal reproductive performance and blood biochemical indices is studied respectively from correlations of body weight, serum leptin, blood lipid, fatty liver, liver function, reproductive performance and renal function. The results are as following:i) According to body mass number,20rabbits at the age of40days were randomly divided into two groups:(a)high-lipid group (n=10), which was maintained on high-lipid diet for12weeks (formulation of high-lipid diet:83%normal feed+2%cholesterol and7%egg yolk powder+8%lard), and (b) control group (n=10), which was fed with normal diet for12weeks. Liver tissue pathological changes were observed and blood lipids parameters, serum leptin level were analysed at0,6, and12weeks in both groups. Compared with the control group, rabbits fed with high-lipid diets showed higher levels of serum total cholesterol, low-density lipoprotein cholesterol, and leptin (P<0.01). The serum leptin levels of high-lipid groups are8.15ng/ml and8.36ng/ml improved60.4%and61.6%higher than the control group at sixth weeks and twelfth weeks. High density lipoprotein cholesterol (HDL-C) and triglyceride (TG) was not significant difference between two groups. After raising for12weeks, hepatocytes of the high-lipid group rabbits developed diffuse fatty degeneration, inflammatory cell infiltration, necrosis and fibrosis were observed in the portal area and lobules. Abnormal liver was not observed in the control group. In conclusion, high-lipid diet induce hypercholesterolemia and elevated serum leptin levels in rabbits. This study indicate that hypercholesterolemia itself might induce increased serum leptin levels,ii) According to body mass number,30rabbits at the age of40days were randomly divided into three groups:control group (n=10) was fed with normal diet, excessive feeding group (n=10) was fed with diet increased by30%on the basis of control group, restricted feeding group (n=10) was fed with diet reduced by30%on the basis of control group. The body weight of each group showed significant differences (P<0.05) after12weeks of feeding. At the same time, serum leptin (Leptin) level, total protein (TP) and hepatic function index analyses were performed including alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bile acid (TBA), total bilirubin (T-BIL). Leptin mRNA relative expression in adipose cells of culture medium were detected at the end of the12week. The weight of excessive feeding group and restricted feeding group had significant difference (P<0.05) compared with the control group after12weeks; Serum leptin levels of restricted feeding group and excessive feeding group were17.64ng/ml and13.43ng/ml which were significantly higher than those in control group (9.96ng/ml); Serum leptin levels of restricted feeding group even higher than the excessive feeding groups (P<0.05). The leptin levels of excessive feeding group and restricted feeding group in fat cell culture medium were19.36ng/ml and22.17ng/ml which were higher than the control group (13.73ng/ml), and difference of the leptin levels between excessive feeding group and restricted feeding group was significant (P<0.05). Expression of leptin mRNA in fatty of excessive feeding group and restricted feeding group were0.63mmol/L and0.85mmol/L which were significantly higher than that of the control group (0.42mmol/L), and difference of the leptin levels between excessive feeding group and restricted feeding group was significant (P<0.05). Level of leptin in adipose cell culture medium and leptin mRNA relative expression in adipose cell were associated with the changes of serum leptin. Serum ALT, AST, TBA and T-BIL of restricted feeding group were higher than those in control group and excessive feeding group (P<0.05), and excessive feeding group showed no significant change compared with the control group. Serum TP of restricted feeding group was lower than that of control group and feeding groups (P<0.05), and excessive feeding group showed no significant change compared with the control group. Animals suffered from malnutrition and weight loss can lead to impaired liver function and hyperleptinemia because of restricted feeding. At the same time, leptin level in adipose tissue and its mRNA expression are also increased correspondingly. Therefore, long-term restriction not only leads to elevating leptin and regulating fat mobilization but also the occurrence of fatty liver and injury of liver tissue. When animal was in energy positive balance, the larger the body weight of rabbits is,-the higher the leptin level is.iii) According to body mass number,30rabbits at the age of40days were randomly divided into three groups:normal control group (n=10), excessive feeding group (n=10) and restricted feeding group (n=10), the design for3groups were same as previous test. Serum leptin levels, reproductive performance-and body weight were recorded at the period of puberty, pregnancy and childbirth. With significant difference between the body weight in3groups, the weight bigger, the sooner the initial estrus appears. Serum leptin level of excessive feeding group was28.23ng/ml which was increase by69%and37%higher than that of control group (8.76ng/ml, P<0.01) and restricted feeding group (17.65ng/ml, P<0.05). Sexual hormone FSH (follicle stimulating hormone) and LH (luteinizing hormone) levels of excessive feeding group were significantly higher than control group and restricted feeding group in the period of initial estrus (P<0.01), and different between restricted feeding group and control group was not significant. FSH and LH level of each group had no significant difference during pregnancy and tate delivery. Conception rate of excessive feeding group was the highest (100%), followed by control group (90%) and restricted feeding group (50%). Birth weight of excessive feeding group and restricted feeding group were significantly higher and lower than that of control group (P<0.05) during late delivery, and litter size have no significant difference among groups. Puberty was related with nutritional status and serum leptin levels. Nutrition was supplied more sufficient, body weight was greater, leptin level is higher, the early oestrus became sooner. Serum leptin levels showed the same trend with FSH and LH in puberty which indicated the predisposing factors of animal estrus. Leptin, FSH and LH had the same variation in the period of puberty, pregnancy and childbirth. When the animal’energy and protein is balant, the greater of the weight, the higher of serum leptin level which can improve animal reproductive performance in a certain extent. Conversely, animal can lead to weight loss and serum leptin level in virtual high which results in reduction of animal reproductive performance.iv) According to body mass number,30rabbits at the age of40days were randomly divided into three groups:normal control group (n=10), excessive feeding group (n=10), restricted feeding group (n=10). The design for3groups were same as previous test. The body weight of each group showed significant differences (P<0.05) after12weeks of feeding. At the same time, serum leptin (Leptin) level and renal function index analyses were performed including blood urea nitrogen (BUN), uric acid (UA), serum creatinine (SCr) and total protein (TP). Serum leptin levels of restricted feeding group and excessive feeding group were17.64ng/ml and13.43ng/ml which were significantly higher than those in control group (9.96ng/ml); and the restricted feeding group even showed higher serum leptin levels than those of the excessive feeding groups (P<0.05). The restricted feeding group also showed higher levels of serum UA, SCr, BUN and lower levels of serum TP than those of the control group and the excessive feeding groups (P<0.05), and the excessive feeding groups showed no significant change compared with the control group. On one hand, animals suffered from malnutrition and weight loss can lead to impaired renal function and hyperleptinemia because of restricted feeding, on the other hand, impaired renal function and high levels of serum leptin intensify the malnutrition, which led to a further decline in body weight. Thus, impairment of renal function and the increasing level of leptin have a feedback mechanism and negative correlation between the weight.