Effect Of Stress On Plasma Ghrelin,Orexin And Galanin Levels In Fasted Rats And Its Potential Mechanism

Objective:Acute and chronic stress can significantly affect appetite and energy homeostasis.Limiting energy intake can lead to elevated levels of cortisol and adrenaline in the body.The purpose of this study is to investigate the effect of stress on weight and plasma ghrelin,orexin and galanin levels in different diet rats and its potential mechanisms.Methods:Male Wistar rats(200~350g)were selected.Constant temperature in animal room(25±1℃),humidity is 50±5%,diurnal cycle is 12 h:12 h.All animals follow the methods of conservation and use of laboratory in Q ingdao University.Before the experiment,rats were fasted for 48 h,and then eat at 8:00Am per day,free water drinking.84 rats were randomly divided into three groups(n=28),and the rats in the first group were given the normal amount of food required(20 g/each/day).The average daily intake of 10 normal rats in 10 days was calculated as the daily food intake of rats.The second group of rats were given 50% of the daily required food intake;the third group of rats received 25% of their daily food intake,lasting 10 days.The changes of body weight in rats under different feeding conditions were measured.The rats were injected with cortisol(4 μg/kg)and epinephrine(4 μg/kg)and a mixture of both by the carotid artery catheter.Blood samples were taken before injection and after injection 30 min,60min and 120 min.The levels of ghrelin,orexin and galanin in plasma were determined by radioimmunoassay.The levels of AC TH,epinephrine and cortisol in plasma were determined by enzyme linked immunosorbent assay(ELISA).Blood glucose level was measured by blood glucose meter.Results:Compared with 100% diet group or before diet group,the body weight of 50% diet and 25% diet rats decreased significantly(P<0.05).Compared with before diet group,the levels of plasma adrenocorticotropic hormone(ACTH),epinephrine and cortisol were significantly increased in 100% diet group and 50% diet group,and there was a significant dose-dependent relationship(P<0.05~0.01).In the 25% diet group,the levels of plasma AC TH,epinephrine and cortisol increased,but the difference was not statistically significant(P>0.05).Compared with before diet,the levels of plasma ghrelin,orexin and galanin in 100%,50% and 25% diet rats were significantly decreased(P<0.05).Compared with the 100% diet group,25% and 50% diet rats plasma ghrelin,orexin and galanin levels increased significantly(P<0.05~0.01).Compared with phosphate buffer control group,before injected group or 100% and 50% diet group,the level of plasma ghrelin in 25% diet rats increased significantly by injection of cortisol into the carotid artery(P<0.05);Compared with phosphate buffer control group or before injected group,50% and 100% diet rats plasma ghrelin concentration decreased significantlyby injection of adrenaline or combined injection of cortisol and adrenaline into the carotid artery(P<0.05).Compared with phosphate buffer control group or before injected group,50% diet rats plasma orexin level was significantly decreased by injection of epinephrine into the carotid artery(P<0.05);andcompared with the phosphate buffer control group or before injection,the injection of combined cortisol and epinephrine into carotid artery decreased the plasma orexin level in 100% diet group(P<0.05).Compared with phosphate buffer control group or before injection,the level of galanin in 50% diet rats significantly decreased by injection of cortisol into the carotid artery(P<0.05);Compared with phosphate buffer control group or before injection,100% and 50% diet rats plasma levels of galanin significantly decreased by combined injection of epinephrine and cortisol(P<0.05).Compared with phosphate buffer group or before injection,carotid artery injection of cortisol,epinephrine or combined injection of adrenaline and cortisol,100% and 50% diet rats plasma glucose levels increased significantly(P<0.05-0.01).Conclusions:Stress can reduce the regulation of neurotransmitter on feeding,and high intensity fasting can disturb the regulation system of energy balance in normal body.Epinephrine is a key hormone in this effect,and cortisol may have synergistic effects.Epinephrine inhibited the secretion of ghrelin,orexin and galanin in fasted rats,and these maybe caused body weight loss.