End-stage chronic liver disease (ESCLD) is associated with aberrations of systemic metabolism like sarcopenia and low respiratory quotient (RQ) linked to gluconeogenesis and fatty acid oxidation. We wanted to investigate correlations between genes expressed in the liver with genes expressed in muscle and adipose tissue in the context of childhood ESCLD aiming to discover genes or related molecular pathways that could inform future studies of how liver disease influences muscle and adipose tissue metabolism.

Liver tissue, muscle from the abdominis rectus and subcutaneous adipose tissue was collected at the time of liver transplant and samples were processed for gene expression by microarray analysis. Patients also had indirect calorimetry¹ (RQ and resting energy expenditure per kilogram weight REE/Wt), basic anthropometry and standard labs including biochemistry recorded prior to liver transplant. Network analysis identified gene clusters in the liver, muscle, and adipose tissue and subsequently correlations were sought amongst gene clusters and clinical data.

13 patients had samples collected (6M:7F). Age range 7 months to 17 years. Median RQ 0.79 (mean 0.78), REE/Wt 53.7 Kcal/kg (mean 55.5), weight z-score -0.7 (mean -0.5), height z-score -1 (mean -0.7) and BMI z-score -0.3 (mean -0.3).

Liver gene cluster-1 which included genes related to liver fibrosis (e.g., ANXA5, DSG2, TES, BCL2L11, EPS8, HEG1, KIF3A, ITGB1, SUCO, ADGRL4, VCAN) correlated strongly with liver fibrosis biopsy index r=0.87** (both metavir and modified Ishak) and had a strong negative correlation with respiratory quotient (RQ) r= -0.77*, albumin r=-0.75* and urea r=-0.94**. It also had a strong significant negative correlation with muscle gene clusters-32 (r=-0.69*) and 35 (r=-0.78*). These included genes linked to inflammation, metabolism and proliferation of skeletal muscle like RelA (subunit of NfkB that sensitizes the cell to glycolytic enzymes and increases proliferation), IRF4 (metabolism of branch-chain amino acids and energy expenditure), FOXM1 (cell proliferation), TCF19 (regulates response to inflammation and DNA damage response), FHL2 (role in autophagy and myopathies), USF2 (role in mitophagy), FOXD3 (muscle development), FOXA2 (glucose sensing and fat metabolism), PREB (expression of glucokinase), RUVBL1 (ATP hydrolysis). These 2 muscle gene clusters also correlated independently with liver fibrosis index r=-0.84** and -0.85** respectively.

Liver gene cluster-1 had a strong negative correlation with muscle gene cluster-5 which had genes very well known for their association with muscle atrophy like TRIM-63 and FBX032, but muscle-5 didn’t have any correlation with measures of indirect calorimetry.

Liver gene cluster-1 had a strong positive association with multiple genes regulated by RelA in adipose tissue gene cluster-1 (r=0.82*) and a strong negative correlation with multiple genes regulated by RXRA (when up-regulated increases import of fatty acids) and ZBTB16 (determines substrate utilisation in brown adipocytes and an increase in adiposity) in adipose tissue clusters-18 (r=-0.69*) and 35 (r=-0.7*) respectively.

Respiratory quotient had a negative relationship with liver tissue fibrosis and markers of liver function like urea and albumin. Genes related to fibrosis in the liver had a strong negative correlation with genes related to muscle metabolism and proliferation.

Reference

1. Glass C, Hipskind P, Tsien C, Malin SK, Kasumov T, Shah SN, Kirwan JP, Dasarathy S. Sarcopenia and a physiologically low respiratory quotient in patients with cirrhosis: a prospective controlled study. J Appl Physiol (1985) 2013 Mar 1;114(5):559–65. doi: 10.1152/japplphysiol.01042.2012. Epub 2013 Jan 3. PMID: 23288550; PMCID: PMC3615594.