AbstractBackgroundPatients with acute alcohol‐associated hepatitis (AH) have immune dysfunction. Mitochondrial function is critical for immune cell responses and regulates senescence. Clinical translational studies using complementary bioinformatics‐experimental validation of mitochondrial responses were performed in peripheral blood mononuclear cells (PBMC) from patients with AH, healthy controls (HC), and heavy drinkers without evidence of liver disease (HD).MethodsFeature extraction for differentially expressed genes (DEG) in mitochondrial components and telomere regulatory pathways from single‐cell RNAseq (scRNAseq) and integrated ‘pseudobulk’ transcriptomics from PBMC from AH and HC (n= 4 each) were performed. After optimising isolation and processing protocols for functional studies in PBMC, mitochondrial oxidative responses to substrates, uncoupler, and inhibitors were quantified in independent discovery (AHn= 12; HDn= 6; HCn= 12) and validation cohorts (AHn= 10; HCn= 7). Intermediary metabolites (gas‐chromatography/mass‐spectrometry) and telomere length (real‐time PCR) were quantified in subsets of subjects (PBMC/plasma AHn= 69/59; HDn= 8/8; HCn= 14/27 for metabolites; HCn= 13; HDn= 8; AHn= 72 for telomere length).ResultsMitochondrial, intermediary metabolite, and senescence‐regulatory genes were differentially expressed in PBMC from AH and HC in a cell type–specific manner at baseline and with lipopolysaccharide (LPS). Fresh PBMC isolated using the cell preparation tube generated optimum mitochondrial responses. Intact cell and maximal respiration were lower (p≤ .05) in AH than HC/HD in the discovery and validation cohorts. In permeabilised PBMC, maximum respiration, complex I and II function were lower in AH than HC. Most tricarboxylic acid (TCA) cycle intermediates in plasma were higher while those in PBMC were lower in patients with AH than those from HC. Lower telomere length, a measure of cellular senescence, was associated with higher mortality in AH.ConclusionPatients with AH have lower mitochondrial oxidative function, higher plasma TCA cycle intermediates, with telomere shortening in nonsurvivors.