Altered muscle transcriptome as molecular basis of long-term muscle weakness in survivors from critical illness.

Purpose: Critically ill patients requiring intensive care unit (ICU) admission suffer from muscle weakness that persists for years, compromising quality-of-life. The pathophysiology of this long-term weakness remains unclear. We hypothesized that former ICU-patients show a long-term abnormal RNA-expression profile, which may contribute to lower long-term strength and for which modifiable risk factors can be identified.

Methods: This pre-planned secondary analysis of the EPaNIC-trial compared muscle transcriptomes of 115 former ICU-patients 5 years after critical illness and 30 matched controls with RNA-sequencing, followed by pathway over-representation and differential co-expression analyses of the differentially expressed RNAs. We used multivariable linear regression analyses to identify which of the abnormal RNA-expressions associated with the long-term muscle strength of the patients and to identify potential risk factors for the abnormal RNA-expressions.

Results: In former patients, 234 down-regulated and 116 up-regulated RNAs were identified after adjustment for age, sex, and BMI. Pathway over-representation and further molecular and histological analyses indicated impaired mitochondrial energy metabolism, disturbed lipid metabolism, and increased collagen formation/fibrosis in former patients. Abnormal muscle RNA-expression in former patients correlated with lower long-term muscle strength. Several treatments given in-ICU and at 5-year follow-up associated with abnormal RNA-expression, most notably in-ICU early parenteral nutrition (early PN) and glucocorticoid use.

Conclusion: Abnormal RNA-expression profiles 5 years after critical illness suggest disrupted mitochondrial function, disturbed lipid metabolism, and fibrosis, associated with lower long-term muscle strength and partly attributable to possibly avoidable risk factors. These findings open perspectives for prevention and possibly treatment of long-term muscle weakness after critical illness.

Trial registration number and date: ClinicalTrials.gov-NCT00512122, July 31, 2007.