The Study On The Mechanism Of Dexmedetomidine Regulating Endotoxemia-induced Hypercatabolism Through Hypothalamic IKKβ/NF-κB-POMC Pathway

Part Ⅰ Clinical Study-The efficacy of dexmedetomidine administration on hypercatabolism in postoperative patientsObjective:To evaluate the efficacy and safety of dexmedetomidine use in patients after abdominal operations,especially to ensure whether dexmedetomidine has the property of attenuating hypercatabolism and lay the foundation for further research.Methods:A prospective randomized controlled trial of 145 patients undergoing abdominal operations was conducted in the Surgical Intensive Care Unit(SICU)of Jinling Hospital between October 8th and December 31st 2015.Thirty-two patients were excluded and 113 were included and divided randomly into the experimental group(59 patients)receiving dexmedetomidine for 72 hours after abdominal operations,and the control group(54 patients)receiving the same amount of saline.All patients received the same postoperative analgesic routine.Postoperative rest energy expenditure(REE),muscle wasting(urine 3-Methylhistidine,3-MH),Prince Henry Pain Scale(PHPS),inflammatory response,recovery of gastrointestinal function and adverse events were analyzed at 24h,48h and 72h.Results:Compared with control group,postoperative REE and muscle wasting,assessed by urine 3-MH,were significantly lower in the experimental group at 48h and 72h.Pain level,assessed by PHPS,in the experimental group were significantly lower than in the control group at 24h,48h and 72h.Time to defecation was 0.60 days shorter in the experimental group than the control group(2.51 vs 3.11,p=0.01).There were no significant difference between inflammatory responses in the two groups(p>0.05).Both groups had similar blood pressure,heart rate,prevalence of bradycardia,and hypotension requiring interventions.Conclusions:Appropriate administration of dexmedetomidine after abdominal operations is safe and could attenuate hypercatabolism.It could also enhance gastrointestinal function recovery and improve pain control when monitored carefully.The capacity of dexmedetomidine to attenuate inflammatory responses requires further investigation.Part Ⅱ Animal Study1.The efficacy of dexmedetomidine on hypercatabolism and its relationship with hypothalamic inflammation and neuropeptides in endotoxemic ratsObjective:Dexmedetomidine is generally used for sedaton in critically ill,it could shorten duration of mechanical ventilation,ICU stay and lower metabolism.However,the exact mechanism of these positive effects remains unkown.Here we investigated the hypothesis that dexmedetomidine could ameliorate muscle wasting in endotoxemic rats and whether it was related to hypothalamic neuropeptides alteration and inflammation.Methods:Thirty-two adult male Sprague-Dawley rats were randomly divided into four groups,LPS+Saline group,LPS+Dex group,control group and pair feed(PF)group.The first two groups were all intraperitoneally injected with 10mg/kg lipopolysaccharide(LPS)followed by 4μg/kg dexmedetomidine or saline administration via the jugular vein catheter.Control group were intraperitoneally injected with saline(10mg/kg).PF group were fed with the same amount of food as LPS groups.Twenty-four hours later,hypothalamus tissues and skeletal muscle were obtained.Muscle wasting was measured by 3-methylhistidine(3-MH)and tyrosine release as well as the mRNA expression of two E3 ubiquitin ligases,muscle atrophy F-box(MAFbx)and muscle ring finger 1(MuRF-1).Hypothalamic inflammatory markers,IL-1β and TNF-α,and neuropeptides,proopiomelanocortin(POMC),cocaine and amphetamine-related transcript(CART),agouti-related protein(AgRP)and neuropeptides Y(NPY),expression were also detected in all four groups.Results:LPS administration led to significant increase in hypothalamic inflammation together with muscle wasting.Increased hypothalamic neuropeptides,POMC and CART and decreased AgRP were also observed,while NPY expression did not differ.Compared with control,dexmedetomidine administration ameliorated muscle wasting,hypothalamic inflammation and attenuated the alteration of neuropeptides,POMC,CART and AgRP in endotoxemic rats,while NPY expression did not differ.Conclusions:Dexmedetomidine could alleviate muscle wasting in endotoxemic rats,which was related to the alteration of hypothalamic neuropeptides and reduced hypothalamic inflammation2.The effect of inhibition of IKKβ-NF/κB activation on dexmedetomidine alleviating hypercatabolism,hypothalamic inflammation and neuropeptides in endotoxemic ratsObjective:Dexmedetomidine could attenuate hypercatabolism in endotoxemic rats,however,little was known about the possible mechanism.Here we tested the hypothesis that central inflammatory IKKβ/NF-κB pathway and neuropeptides were involved in the process.Methods:Thirty-two adult male Sprague-Dawley rats were cannulated in the third ventricle one week before the experiment.After intraperitoneal 10mg/kg lipopolysaccharide(LPS)injection,all rats were randomly divided into four groups,PS1145+Saline group,PS1145+Dex group,Control+Saline group and Control+Dex group.The first two groups received central infusion of NF-κB inhibitor(PS 1145)through third ventricle cannulation,followed by 4μg/kg dexmedetomidine or saline administration via the jugular vein catheter.The last two groups central infusion of saline through third ventricle cannulation,followed by 4μg/kg dexmedetomidine or saline administration via the jugular vein catheter.Twenty four hours later,the hypothalamus and skeletal muscle were harvested for the measurement of central neuropeptides and inflammation,and muscle wasting.Results:Inhibition of central IKKβ/NF-κB pathway activation could reduce muscle wasting as well as attenuate hypothalamic neuropeptides alteration.Furthermore,in the endotoxemic rats treated with dexmedetomidine,inhibition of IKKβ/NF-κB pathway activation could attenuate muscle wasing significantly while the alteration of neuropeptides did not differ from those with normal IKKβ/NF-κB pathway activity.In those with inhibited IKKβ/NF-κB pathway activation,dexmedetomidine could reduce muscle wasting while did not affect alteration of neuropeptides.Conclusions:Activation of hypothalamic IKKβ/NF-κB pathway was related with muscle wasting induced by endotoxemia.Inhibition of hypothalamic IKKβ/NF-κB pathway could improve dexmedetomidine’s ability of attenuating muscle wasting while reduce its effect on neuropeptides alterations.Thus,dexmedetomidine might affect muscle wasting by acting on IKKP/NF-κB pathway.3.The effect of interference of POMC expression on dexmedetomidine alleviating hypercatabolism,hypothalamic inflammation and neuropeptides in endotoxemic ratsObjective:To ensure the relationship between central IKKβ/NF-κB pathway and neuropeptides and their exact roles in the process of dexmedetomidine attenuating muscle wasting.Methods:Thirty-two adult male Sprague-Dawley rats received intraperitoneal lipopolysaccharide(LPS)injection(10mg/kg)and were randomly divided into four groups,POMC+Saline group,POMC+Dex group,Vehicle+Saline group and Vehicle+Dex group.In the first two groups,the ARC of hypothalamus were injected with lentiviral vector containing shRNA against neuropeptide proopiomelanocortin(POMC),followed by 4μg/kg dexmedetomidine or saline administration via the jugular vein catheter.The last two groups were injected with lentiviral vector containing vehicle shRNA through ARC of hypothalamus,followed by 4μg/kg dexmedetomidine or saline administration via the jugular vein catheter.Two weeks later,the hypothalamus and skeletal muscle were collected for the same measurements as above.Results:Knockdown of the expression of anorexigenic neuropeptide POMC could alleviate endotoxemic muscle wasting,whereas hypothalamic inflammation or NF-κB pathway was barely affected.Furthermore,in the endotoxemic rats treated with dexmedetomidine,muscle wasting in those with lower expression of neuropeptide POMC did not differ from those with normal POMC expression,and hypothalamic inflammatory mediators and Ikkβ/NF-KB pathway activation were both reduced.In those with lower POMC expression,dexmedetomidine could reduce muscle wasting and attenuate neuropeptides alterations.Conclusions:Neuropeptide POMC expression was pivotal in the process of dexmedetomidne attenuating muscle wasting.In endotoxemic rats,the action target of dexmedetomidine might be IKKβNF-κB pathway,rather than neuropeptide POMC.Neuropeptide POMC expression may have mediated the contribution of hypothalamic inflammation to peripheral muscle wasting.Thus,dexmedetomidine might affect muscle wasting through the IKKβ/NF-κB-POMC pathway.