| Part I Establishment of intestinal I/R injury rat model and correlation analysis of skeletal muscle hypercatabolism with gastrointestinal hormones and central neuropeptidesObjective: I/R injury is a common pathophysiological process in critically ill patients,and the intestinal tract is the most vulnerable organ.Hypercatabolism is one of the prominent features of the acute phase of critically ill patients,but the role of intestinal I/R injury in hypercatabolism has not been studied.Previous studies have shown that high catabolism after stress is regulated by hypothalamic arcuate nucleotide.Therefore,we speculate that skeletal muscle hypercatabolism caused by intestinal I/R injury is associated with changes in intestinal endocrine hormones and changes in hypothalamic neuropeptides.Methods: Adult male Spragu-Dawley rats were randomly divided into intestinal I/R group and control group.Intestinal I/R group was laparotomy with superior mesenteric artery occlusion for 30 minutes.The control group performed the same procedure without occlusion of the superior mesenteric artery.The food intake and body weight of rats 24 h after operation,Day1,Day3,Day5 and Day7 were recorded.And the rats were sacrificed according to the above time points,and the extensor digitorum longus,hypothalamus and blood were collected for correlation detection.The detection indicators included: the weight of extensor digitorum longus and atrophy gene mRNA expression(Mur F-1,MAFBx),hypothalamic arcuate nuclear neuropeptide mRNA expression(POMC,CART,AgRP,NPY),and serum gastrointestinal hormone levels(Ghrelin,CCK,GLP-1,PYY).Results: Regardless of whether I/R intervention was performed,the body weight of both groups decreased significantly and the expression of skeletal muscle atrophy increased.The mRNA expression of hypothalamic anorexia peptide(POMC,CART)increased and the expression of ingestion peptide(AgRP,NPY)mRNA decreased in both groups.Serum ghrelin was significantly decreased in both groups,and CCK,GLP-1 and PYY levels were significantly increased.The changes in the left and right indicators will be more obvious in Day1 and Day3,when in Day5 and Day7 they gradually recovered.Compared with the rats without intestinal I/R intervention,the body weight,the weight of extensor digitorum longus,the weight of extensor digitorum longus and body radio decreased more significantly in intestinal I/R intervention group.Intestinal I/R intervention in rats showed that the mRNA expression of muscle atrophy gene was increased,the expression of anorexia peptide mRNA was increased,and the expression of ingestion peptide mRNA was decreased.The level of serum ghrelin in rats with intestinal I/R intervention was more obvious,moreover,the increase of CCK,GLP-1 and PYY was more obvious.Correlation analysis revealed that the expression of hypothalamic neuropeptide POMC mRNA was significantly positively correlated with the expression of skeletal muscle atrophy index mRNA,while the expression of AgRP mRNA was significantly negatively correlated with the expression of skeletal muscle atrophy index.Blood CCK level was positively correlated with skeletal muscle atrophy gene mRNA expression.Serum CCK level was significantly positively correlated with the expression of POMC mRNA,and was significantly negatively correlated with the expression of AgRP mRNA.Conclusion: Intestinal I/R injury can lead to hypercatabolism of skeletal muscle.This change may be related to the change of blood CCK level caused by intestinal I/R injury and affect the expression of AgRP in hypothalamus.Part? The effect of CCK on central AgRP neuropeptides in the acute skeletal muscle depletion induced by intestinal I/R injury in ratsOBJECTIVE: To determine whether CCK affects the expression of AgRP neuropeptides in the arcuate nucleus of the hypothalamus,thereby affecting the high catabolism of skeletal muscle caused by intestinal I/R.METHODS: Two weeks before model establishment,rats were injected with a POMC interference sequence virous in the third ventricle.Five days before modeling,all rats were placed tube in the third ventricle.The experiment is divided into two parts.In the first part,rats were randomly divided into four groups: Intestinal I/R rat central injection of AgRP analogue group(AgRP/EG),intestinal I/R rat central injection saline group(Vehicle/EG),simple laparotomy group injected with AgRP analogue group(AgRP/CG)and simple laparotomy group injected with saline(Vehicle/CG).After the model was established,AgRP analogue was injected into the third ventricle at 12 h and 36 h,and the control group was given normal saline.The material was taken 48 hours after modeling,and the changes in food intake and body weight were recorded.The long extensor digitorum,hypothalamic tissue and blood were taken for measurement.The measurement index was the same as before.In the second part,the rats were randomly divided into four groups: the intestinal I/R rat central injection CCK blocker group(CCK-/EG),and the intestinal I/R rat central injection saline group(Nacl/ EG),simple laparotomy group with injection of CCK blocker(CCK-/CG)and laparotomy group with injection of saline(Nacl/ CG).After modeling,the CCK blocker group was decomposed and injected with CCK receptor analogs(L-364,718,1?g;LY-288,513,1?g)at 12 h,24h,and 36 h.The material was taken 48 hours after modeling,and the changes in food intake and body weight were recorded.The long extensor digitorum,hypothalamic tissue and blood were taken for measurement.The measurement index was the same as before.RESULTS: The expression of POMC neuropeptides and CART neuropeptides in the hypothalamus of rats was significantly decreased after central injection of POMC virus.In the subsequent experiments,intestinal I/R injury had no significant effect on the expression of POMC neuron-related peptide mRNA.Compared with the central injection of normal saline,the levels of blood gastrointestinal hormones and hypothalamic neuropeptides were not significantly changed after central injection of AgRP analogues,but the intake,body weight were significantly increased in the central injection of AgRP analogues.The increase suggests that although there is no effect on the synthesis of AgRP,central injection of AgRP analogues can play a metabolic regulatory role.In addition,central injection of AgRP analogues can significantly improve skeletal muscle atrophy caused by intestinal I/R injury.Whether it was simple laparotomy or intestinal I/R injury intervention,the expression of AgRP decreased in rats,but the level of AgRP was higher in the central injection of CCK receptor blockers than in saline-injected rats.In addition,central injection of CCK receptor blockers did not reveal an effect on gastrointestinal hormone expression.Conclusion: Intestinal I/R injury can regulate the high catabolism of skeletal muscle through the action of CCK on hypothalamic AgRP neurons.Part III: Effect of early enteral nutrition support on acute skeletal muscle depletion in rats induced by intestinal I/R injuryOBJECTIVE: Former two parts found that CCK affects the high catabolism of acute skeletal muscle caused by intestinal I/R injury in rats by hypothalamic AgRP.Early enteral nutrition is one of the important treatments for critically ill patients and has been shown to be beneficial in reducing epithelial cell damage caused by intestinal I/R.Therefore,we speculate early enteral nutrition can attenuate skeletal muscle catabolism through CCK-AgRP connection.METHODS: SD rats were randomly divided into four groups: intestinal I/R intervention for early enteral nutrition(EN/EG),intestinal I/R intervention for early parenteral nutrition(PN/EG),simple laparotomy with early enteral nutrition group(EN/CG),and simple laparotomy with early parenteral nutrition group(PN/CG).Four groups of rats were given a right internal jugular vein catheter and a gastrostomy tube,and fixed feeding in a single cage.Rats were fasted after modeling,and began to initiate nutrition 24 hours later,giving a calorie of 40Kcal/kg.day,using a micro pump 24 h uninterrupted infusion.After three days of nutritional support,the body weight was measured and taken,and the long extensor digitorum,hypothalamic tissue,and blood were measured.The measurement index was the same as before.RESULTS: Due to the low calorie feeding,the rats showed a decrease in body weight,a decrease in the weight of the extensor digitorum and a decrease in the ratio of the toe length to the body weight.The effects of different nutritional support methods vary according to the severity of the trauma.In the simple laparotomy group,continuous PN increased blood CCK levels,decreased AgRP expression,increased skeletal muscle atrophy gene expression,and weight,the ration of length extensor digitorum to weight,and the weight of length extensor digitorum were lower than EN.In rats with intestinal I/R intervention,continuous PN reduced blood CCK levels,increased hypothalamic AgRP expression,decreased skeletal muscle gene expression.Body weight and the weight of length extensor digitorum were higher than the EN group.Conclusion: Compared with early parenteral nutrition,early enteral nutrition increased acute skeletal muscle consumption in rats with intestinal I/R intervention.However,in rats with simple laparotomy,early enteral nutrition significantly decreased acute skeletal muscle consumption.Therefore,the application of early enteral nutrition is determined by the degree of damage to the intestines. |
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