Hazeldine, J. | bioRxiv Science

bioRxiv2025

Systemic drivers and molecular mechanisms of sarcopenia in aetiology-specific end-stage liver disease

IntroductionPatients with end-stage liver disease (ESLD) often present with sarcopenia, defined as loss of skeletal muscle mass and quality, which is associated with reduced quality of life and increased mortality. However, the molecular mechanisms driving sarcopenia in ESLD are not fully understood and there are currently no therapeutic interventions. This study aimed to identify potential circulating factors contributing to sarcopenia progression in ESLD by assessing their role in driving transcriptomic alterations in skeletal muscle. MethodsQuadriceps muscle tissue, plasma and serum were obtained from ESLD patients (n=24) and age/sex-matched healthy controls (HC; n=18) (clinical trial ID: NCT04734496, ethical approval 18/WM/0167). Total RNA from snap-frozen vastus lateralis muscle biopsies underwent RNA sequencing (Illumina). Serum concentrations of 60 cytokines were profiled by Luminex and ELISA, with comparisons made both between ESLD and HC, and across ESLD aetiologies (alcohol-related, NAFLD, viral hepatitis, other). In vitro, primary human myotubes (from non-ESLD aged donors, NRES #16/SS/0172) were treated with 10% ESLD or HC plasma (24 h, n=6 per group) followed by RNA sequencing (BGI Genomics). Differentially expressed genes (p<0.05, fold-change >1.5) were identified via Qlucore and DESeq2, and pathway analysis performed using Ingenuity (Qiagen). The impact of physiological concentrations of candidate cytokines (IL-1, GDF-15, HGF) on myotube thickness, differentiation and mitochondrial function was assessed by immunofluorescence microscopy, RT-qPCR and metabolic flux assays. ResultsIn ESLD muscle, 387 and 225 genes were significantly up- and downregulated compared to HC respectively, with cellular senescence identified as a top dysregulated function. Upstream regulator analysis predicted activation of hepatocyte growth factor (HGF) and interleukin-1 signalling. Subgroup analysis revealed distinct transcriptomic profiles based on disease aetiology. Serum profiling identified 15 cytokines significantly elevated (p<0.05) and 5 reduced (p<0.05) in ESLD, including increased HGF and reduced interleukin-1 receptor antagonist. Stratified analysis also revealed aetiology specific cytokine profiles, with only GDF-15 significantly (P<0.0001) elevated in all groups. 24h ESLD plasma treatment induced 423 differentially expressed genes in human myotubes, which were again associated with significant activation of senescence pathways, with IL-1 identified as a key upstream driver. In vitro, IL-1, GDF-15, and HGF significantly reduced myotube thickness, nuclear fusion index and perturbed metabolism (Increased glycolysis, impaired oxidative phosphorylation). ConclusionsCollectively, these findings suggest that sarcopenia in ESLD is driven by aetiology-specific mechanisms, highlighting the potential for targeted therapies to improve muscle mass and function.

molecular biology↗

bioRxiv2024

Physical activity modifies the metabolic profile of CD4+ and CD8+ T cell subtypes at rest and upon activation in older adults

Aging reduces the functional competence of T cells. T cell metabolism regulates their function, with mitochondrial defects in mice resulting in aged phenotypes, including accelerated senescence. Physical activity (PA) maintains T cell function in older adults, although the mechanisms underlying this effect are poorly understood. This study examined the effects of aging on the metabolic profile of T cell subsets and investigated whether PA could improve metabolic function in T cells from older donors. We recruited nine young adults (23 {+/-} 3y) and 19 healthy older adults who had high PA (HPA, N=9, 75.5 {+/-} 4.7y) or low PA levels (LPA, N=10, 76.4 {+/-} 2.1y), based on their moderate-to-vigorous PA scores. We investigated the metabolic profiles of CD4+ and CD8+ T cells at rest and post-activation (PMA and ionomycin), via SCENITH flow cytometry. Compared to young adults, older adults had higher mitochondrial dependence (MD) in unstimulated CD4+ and CD8+ naive, effector memory (EM) and central memory (CM); and higher protein synthesis in CD4+ EM, CD4+ naive, CD8+ EM, suggesting higher energetic demand in T cells with aging. Upon activation there was a lower reduction in MD of CD4+ EMRA and CD8+ EMRA; and a greater increase in IL-6 and TNF expression in CD8+ cells of older than young adults, indicative of impaired metabolic flexibility with aging. PA effects were more prominent in unstimulated CD8+ cells, where HPA had lower glucose dependence (GD) for overall CD8+, CD8+EM and a trend to higher MD in CD8+ CM than LPA. Upon activation, HPA had a lower increase in CD4+ TNF expression and trended to have a higher reduction in MD of overall CD4+ and a higher reduction in GD of CD4+ EMRA, than LPA. This suggests a lower metabolic demand in CD4+ T cells of HPA. We concluded that PA could modify T cell metabolic profile at rest, and following activation, in older adults, which may explain the better T cell function in physically active older individuals.

immunology↗