HMB Attenuates ARDS Associated ICU-AW By Modulating The Akt Mediated Signaling

Objective:ICU-acquired weakness(ICU-AW)is a common complication of critical diseases,which affects neuromuscular function and not only prolonging mechanical ventilation time and hospital stay,but also the severity of ICU-AW is related to the increase of mortality,and even the surviving patients’ prognosis quality of life is seriously reduced.Therefore,in-depth research on the molecular mechanism of ICU-AW and the search for effective interventions to prevent and treat ICU-AW are the focus of attention.β-hydroxy-β-methylbutyrate(HMB)has proven efficacy in enhancing skeletal muscle mass and strength,and supplementation of HMB can reduce skeletal muscle atrophy in the elderly and in patients with cancer-related cachexia.HMB is clinically effective in enhancing muscle mass and strength.However,the mechanism of HMB on ICU-AW skeletal muscle atrophy is rarely reported.Therefore,the purpose of this study was to test the hypothesis that HMB administration can prevent the development of skeletal muscle atrophy and loss of function in a mouse ICU-AW model of ARDS induced by sepsis,and to further explore the mechanism of HMB on ICU-AW.Methods:Sixty SPF grade male C57BL/6 mice were randomly divided into control group,sham operation group,model group,treatment group,Akt inhibitor group(ARQ-092 group)and solvent group(Vehicle group),with 10 mice in each group.The model group,the treatment group,the ARQ-092 group and the Vehicle group were given 3mg/kg intratracheal injection of lipopolysaccharide(LPS)to prepare the ICU-AW model associated with ARDS.The sham operation group was given the same amount of sterile water,and the control group was not given modeling operation.On the second day of modeling,the treatment group,ARQ-092 group and Vehicle group were given 340 mg/(kg·d)dose of HMB by intragastric administration,and the other three groups were given equal volume of normal saline for continuous intragastric administration for 2 weeks.In addition,starting from the second day of modeling,ARQ-092 group and Vehicle group were given oral intragastric administration of ARQ-092(ARQ-092 group)or equivalent volume of Vehicle(Vehicle group)10 hours after HMB intragastric administration every day for 12 days.Draw the survival curve of mice;The daily weight of the mice was continuously weighed and recorded.Muscle grasp and muscle reduction index(SI)were measured.The lung and gastrocnemius tissues of mice were stained with HE to observe the pathological changes.qRT-PCR was used to detect the mRNA expressions of Akt,FoxO3 a,Atrogin1 and MuRF1 as well as mTOR and P70S6 K in mouse gastrocnemius.Western Blot was used to verify PCR results,so the expression of Akt signaling pathway related proteins in mouse gastrocnemius was further detected.Results:The pathological sections of the lung tissues of mice in each group at 48 hours after modeling showed that there was no injury in the lung tissues of the control group and the sham operation group,while the model group and the treatment group showed obvious pathological manifestations of ARDS.HMB increased survival,body weight,grasping power and SI of forelimb skeletal muscle,and reduced the severity of muscle fiber injury and preserved muscle bundle integrity in an ARDS related muscular atrophy mouse model.Moreover,HMB decreased the expression levels of TNF-α,IL-1β and IL-6 in SERUM of ICU-AW mice.In addition,HMB increased the mRNA expressions of Akt,FoxO3 a and mTOR,increased the phosphorylation levels of Akt,FoxO3 a,mTOR and P70S6 K,and decreased the mRNA and protein expressions of Atrogin1 and MuRF1.However,Akt inhibitor ARQ-092 can reverse the protective effect of HMB,reduce the expression of Akt-Foxo3A/ mTOR signaling pathway at mRNA level and protein phosphorylation level,and increase the expression of Atrogin1 and MuRF1 at mRNA and protein level.Conclusion:HMB can reduce protein degradation,promote synthesis and reduce muscle atrophy by regulating Akt-FoxO3A-Mur F1/ Atrogin1 and MTOR-P70S6 K signaling pathways,which plays a protective role in ICU-AW and may have important value for ICU-AW prevention and treatment.