Biology subjects

Breen, L.

Publications and source records attributed to Breen, L..

4 recordsLinked to original sources

bioRxiv2025

Increased Quadriceps Intermuscular Adipose Tissue in Chronic Liver Disease is Associated with an Altered Muscle Transcriptome compared with Healthy Age Matched Controls.

Muscle fat infiltration (i.e., myosteatosis) is an important index of muscle health and pathology in disease states, such as chronic liver disease (CLD). However, it is unknown whether myosteatosis differs due to anatomical location. Further, the mechanistic implications of divergent intermuscular adipose tissue (IMAT) deposition remains unknown in patients with CLD. 33 patients with CLD (55.0{+/-}10.5years) and 17 healthy controls (HC) (49.6{+/-}15.4years) were recruited. Quadriceps IMAT was estimated between 20-80% of muscle length and psoas IMAT at L3 via MRI. Body composition, muscle strength and habitual activity were assessed. Fasted vastus lateralis muscle biopsies were collected and subjected to RNA sequencing analysis. https://ClinicalTrials.gov identifier: NCT04734496. IMAT was greater in CLD compared with HC in both quadriceps and psoas (P<0.0001). Quadriceps IMAT positively correlated with BMI (r=0.62), body fat (r=0.65), age (r=0.36) and negatively correlated with maximal knee extensor strength (r=-0.45) and habitual physical activity (r=-0.50) in CLD and HC. 169 differentially expressed genes (DEGs) were identified in low IMAT CLD vs HC, and 178 DEGs were identified in high IMAT CLD vs HC. CLD patients with high and low IMAT exhibited defined expression profiles, with only 39 DEGs (representing 12.7%) in common. Pathway analysis of DEGs revealed enrichment of atrophic and pro-inflammatory pathways in the high IMAT group. IMAT is greater in patients with CLD compared to HC, irrespective of anatomical location and is associated with reductions in muscle function and may be exacerbated by physical inactivity. IMAT appears to alter the muscle transcriptome in COLD, potentially exacerbating muscle loss.

physiology↗

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↗

bioRxiv2020

Protein-carbohydrate ingestion alters Vps34 cellular localization independent of changes in kinase activity in human skeletal muscle

The mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) regulates cell size and growth in response to nutrients, however, the mechanisms by which nutrient levels are sensed by mTORC1 in human skeletal muscle are yet to be fully elucidated. The Class III PI3Kinase Vps34 has recently been proposed as a sensor essential for mTORC1 activation following nutrient stimulation. We therefore investigated the effects of increasing nutrient availability through protein-carbohydrate (PRO-CHO) feeding on Vps34 kinase activity and cellular localization in human skeletal muscle. Eight young, healthy males (age - 21 {+/-} 0.5yrs, mean {+/-} SEM) ingested a PRO-CHO beverage containing 20/44/1g PRO/CHO/FAT respectively, with skeletal muscle biopsies obtained at baseline and 1h and 3h post-feeding. PRO-CHO feeding did not alter Vps34 kinase activity, but did stimulate Vps34 translocation toward the cell periphery (PRE (mean{+/-}SEM) - 0.273{+/-}0.021, 1h - 0.347{+/-}0.022, Pearsons Coefficient (r)) where it co-localized with mTOR (PRE - 0.312{+/-}0.018, 1h - 0.348{+/-}0.024, Pearsons Coefficient (r))). These alterations occurred in parallel to an increase in S6K1 kinase activity - 941{+/-}164% of PRE at 1h post-feeding). Subsequent in vitro experiments in C2C12 and human primary myotubes displayed no effect of the Vps34-specific inhibitor SAR405 on mTORC1 signalling responses to elevated nutrient availability. Therefore, in summary, PRO-CHO ingestion does not increase Vps34 activity in human skeletal muscle, whilst pharmacological inhibition of Vps34 does not prevent nutrient stimulation of mTORC1 in vitro. However, PRO-CHO ingestion promotes Vps34 translocation to the cell periphery, enabling Vps34 to associate with mTOR. Therefore, our data suggests that interaction between Vps34 and mTOR, rather than changes in Vps34 activity per se may be involved in PRO-CHO activation of mTORC1 in human skeletal muscle.

physiology↗

bioRxiv2018

KH-type splicing regulatory protein controls colorectal cancer cell growth and modulates the tumor microenvironment

KH-type splicing regulatory protein (KHSRP) is a multifunctional nucleic acid binding protein implicated in key aspects of cancer cell biology: inflammation and cell-fate determination. However, the role KHSRP plays in colorectal cancer (CRC) tumorigenesis remains largely unknown. Using a combination of in silico analysis of large datasets, ex vivo analysis of protein expression in patients, and mechanistic studies using in vitro models of CRC, we investigated the oncogenic role of KHSRP. We demonstrated KHSRP expression in the epithelial and stromal compartments of both primary and metastatic tumors. Elevated expression was found in tumor versus matched normal tissue, and we validated these findings in larger independent cohorts in silico. KHSRP expression was a prognostic indicator of worse overall survival (HR=3.74, 95% CI = 1.43-22.97, p=0.0138). Mechanistic data in CRC cell line models supported a role of KHSRP in driving epithelial cell proliferation in both a primary and metastatic setting, through control of the G1/S transition. Additionally, KHSRP promoted a pro-angiogenic extracellular environment by regulating the secretion of oncogenic proteins involved in diverse cellular processes such as migration and response to cellular stress. Our study provides novel mechanistic insight into the tumor-promoting effects of KHSRP in CRC.

cancer biology↗