Our meta analysis of a homogeneous set of studies is the first to provide valuable LLNs for fiber CSA according to fiber type and gender .
Skeletal muscle atrophy is a major systemic impairment in chronic diseases .
Yet its determinants have been hard to identify because a clear research definition has not been agreed upon .
The reduction in muscle fiber cross-sectional area ( CSA ) is a widely acknowledged marker of muscle atrophy , but no reference values for the muscle fiber CSA at the age of the onset of chronic disease have ever been published .
Muscle atrophy and preferential loss of myosin in prolonged critically ill patients*
Objective : Muscle weakness contributes to prolonged rehabilitation and adverse outcome of critically ill patients . Distinction between a neurogenic and /or myogenic underlying problem is difficult using routine diagnostic tools . Preferential loss of myosin has been suggested to point to a myogenic component . We evaluated markers of muscle atrophy and denervation , and the myosin/actin ratio in limb and abdominal wall skeletal muscle of prolonged critically ill patients and matched controls in relation to insulin therapy and known risk factors for intensive care unit-acquired weakness . Design : Secondary analysis of two large , prospect i ve , single-center r and omized clinical studies . Setting : University hospital surgical and medical intensive care unit . Patients : Critically ill patients and matched controls . Interventions : Intensive care unit patients had been r and omized to blood glucose control to 80–110 mg/dL with insulin infusion or conventional glucose management , where insulin was only administered when glucose levels rose above 215 mg/dL. Measurements and Main Results : As compared with controls , rectus abdominis and vastus lateralis muscle of critically ill patients showed smaller myofiber size , decreased mRNA levels for myofibrillar proteins , increased proteolytic enzyme activities , and a lower myosin/actin ratio , virtually irrespective of insulin therapy . Increased forkhead box O1 action may have played a role . Most alterations were more severe in patients treated with corticosteroids . Duration of corticosteroid treatment , independent of duration of intensive care unit stay or other risk factors , was a dominant risk factor for a low myosin/actin ratio . The immature acetylcholine receptor subunit & ggr ; messenger RNA expression was elevated in vastus lateralis , independent of the myosin/actin ratio . Conclusions : Both limb and abdominal wall skeletal muscles of prolonged critically ill patients showed downregulation of protein synthesis at the gene expression level as well as increased proteolysis . This affected myosin to a greater extent than actin , result ing in a decreased myosin/actin ratio . Muscle atrophy was not ameliorated by intensive insulin therapy , but possibly aggravated by corticosteroids
Our meta analysis of a homogeneous set of studies is the first to provide valuable LLNs for fiber CSA according to fiber type and gender .
Skeletal muscle atrophy is a major systemic impairment in chronic diseases .
Yet its determinants have been hard to identify because a clear research definition has not been agreed upon .
The reduction in muscle fiber cross-sectional area ( CSA ) is a widely acknowledged marker of muscle atrophy , but no reference values for the muscle fiber CSA at the age of the onset of chronic disease have ever been published .