Study The Effect Of Hypothalamic PLC-γ/Ca²⁺/GnRH Pathway On Mouse Testosterone Decline In Diet Induced Obesity

Objective:An obese animal model（C57BL/6J male mice are fed with high-fat diet）is established to investigate the effect of hypothalamic PLCγ/Ca²⁺/GnRH pathway on testosterone decline by detecting the levels of serum estrogen and androgen,Ca²⁺concentration and the levels of PLCγ,IP3-R,CAMKII,CREB,GnRH protein expression and PLCγ,IP3-R,CAMKII,CREB mRNA in the hypothalamus.Methods:In this experiment,forty-eight C57BL/6J male mice（4-5 weeks）were randomly divided into two groups:12 in control group with basal diet,36 in the experimental group with high fat diet.In 19 weeks,the mice were divided into diet-induced obese（DIO）group and diet-induced obese resistant（DIO-R）group according to body weight gain of the mice（n=12/group）.Levels of hypothalamus Ca²⁺concentration were rapidly measured.Perirenal and periepididymal adipose tissue were weighted.Levels of serum estrogen and testosterone were determined by ELISA.Levels of GnRH,IP3-R,PLCγ,CAMKⅡ,CREB protein expression were determined by immunohistochemical method and Westernblot method.Levels of IP3-R,PLCγ,CAMKⅡ,CREB mRNA were determined by RT-PCR.Results:1 Body weight in the control,DIO and DIO-R groupsThere was no significant different among the three group in 1 week.From 2week,compared to the control group,there was significant higher body in DIO group（P<0.05）.The body weight in DIO group is significant higher than in the control group in 19 weeks（P<0.05）.2 Food intake and drinking water consumption in the control,DIO and DIO-R groupsCompared to the control group,there was significant higher food intake consumption in DIO group（P<0.05）.However,there was significant lower drinking water consumption in DIO group（P<0.05）.3 Body fat and the percentage of body fat in the control,DIO and DIO-R groupsIn week 4,8,12,16,compared to the control group,mean body fat and the percentage of body fat were significant higher in DIO and DIO-R groups（P<0.05）.And in week 4,8,12,16,compared to the DIO-R group,mean body fat and the percentage of body fat were significant higher in DIO group（P<0.05）.4 Lean body mass and the percentage of lean body mass in the control,DIO and DIO-R groupsIn 4 weeks,the lean body mass and the percentage of lean body mass were significant higher in DIO and DIO-R groups than in the control group（P<0.05）.In week 8,12,compared to the control and DIO-R groups,there was significant higher lean body mass in DIO group（P<0.05）.However,there was significant lower the percentage of lean body mass in DIO group（P<0.05）.In week 16,there was no significant different of lean body mass in the three groups.Compared to the control and DIO-R groups,there was significant lower percentage of lean body mass in DIO group（P<0.05）.5 Fat weight in the control,DIO and DIO-R groupsCompared to the control group,perirenal and epididymis fat weight,perirenal and the epididymis fat coefficient were significant higher in DIO and DIO-R group（P<0.05）.Compared to the DIO group,perirenal and epididymis fat weight,perirenal and the epididymis fat coefficient were significant lower in DIO-R group（P<0.05）.6 Levels of serum estradiol and testosterone in the control,DIO and DIO-R groupsThe level of serum estradiol was significantly higher in the DIO and DIO-R groups than in the control group（P<0.05）.The level of serum testosterone was significantly lower in the DIO group than in the control group（P<0.05）.7 The level of GnRH protein expression in the control,DIO and DIO-R groupsThe level of GnRH protein expression in hypothalamus was significantly lower in the DIO and DIO-R groups than in the control group（P<0.05）.There was no significant difference between DIO group and DIO-R group（P>0.05）.8 Ca²⁺concentration of the hypothalamus in the control,DIO and DIO-R groupsThe level of hypothalamus Ca²⁺concentration was significantly higher in the DIO and DIO-R groups than in the control group（P<0.05）.There was no significant difference between DIO group and DIO-R group（P>0.05）.9 IP3-R,P-IP3-R,PLCγand P-PLCγprotein expression in the control,DIO and DIO-R groupsCompared to the control group,levels of IP3-R,P-IP3-R,PLCγand P-PLCγprotein expression in hypothalamus were significantly higher in the DIO and DIO-R groups（P<0.05）.There was no significant difference between DIO group and DIO-R group（P>0.05）.10 P-CAMKⅡand P-CREB protein expression in the control,DIO and DIO-RgroupsCompared to the control group,levels of P-CAMKⅡand P-CREB protein expression in hypothalamus were significantly higher in the DIO and DIO-R groups（P<0.05）.There was no significant difference between DIO group and DIO-R group（P>0.05）.11 IP3-R,PLCγ,CAMKⅡand CREB mRNA in the control,DIO and DIO-R groupsCompared to the control group,levels of IP3-R,PLCγ,CAMKⅡand CREB mRNA in hypothalamus were significantly higher in DIO and DIO-R groups（P<0.05）.There was no significant difference between DIO group and DIO-R group（P>0.05）.Conclusion:Diet induced obesity caused decreased testosterone.A high level of IP3-R,P-IP3-R,PLCγ,P-PLCγprotein expression and Ca²⁺concentration which may contribute to decrease GnRH expression in the hypothalamus may provide some evidence to clarify the mechanism of decreased testosterone caused by diet induced obesity.