Plasma apolipoproteins and memory function in alcohol use disorder: findings in male C57BL/6J mice and men suggest a role for APOAI

Abstract

Background: Memory impairment is frequent among alcohol use disorder (AUD) patients, and we lack specific biomarkers to detect it. Certain apolipoproteins were linked to cognition, and carrying the APOE4 gene is a vulnerability factor to memory impairment in AUD patients. We explored memory deficits in alcohol-dependent male mice and humans versus controls, and their relationship to Apolipoprotein AI (APOAI), apolipoprotein B (APOB), and apolipoprotein E (APOE) plasma levels. Methods: Male C57BL/6J mice underwent voluntary alcohol drinking (two-bottle choice, 2BC) and chronic intermittent ethanol vapor exposure (CIE) as a model of alcohol dependence; memory was assessed by the Object Location Test (OLT) and Novel Object Recognition Test (NORT). Additionally, male AUD-diagnosed patients were recruited in Spain during an alcohol dishabituation program and assessed by the Wechsler Memory Scale-IV (WMS-IV). Plasma APOAI, APOB, and APOE levels were checked in mice and humans by ELISA kits and Luminex immunoassay technology. APOAI immunolabeling was quantified in mouse brain in early withdrawal and following alcohol consumption. Results: CIE-2BC mice (n = 8) escalated alcohol consumption compared to Air-2BC controls (n = 11) and showed deficits in spatial memory (OLT) and recognition memory (NORT) while AUD patients (n = 12) showed deficits in verbal and visual memory (WMS-IV) versus controls (n = 16). Higher plasma levels of APOAI were detected in CIE-2BC mice and AUD patients, with no differences in APOB and APOE in animals and humans. Significant negative correlations were found between levels of APOAI, APOB, and APOE and memory function tests/scales in the entire sample, with APOAI showing consistent results in both animals and humans. APOAI immunoreactivity was detected in the mice subfornical organ, but the signal did not differ between experimental groups. Conclusions: Both CIE-2BC mice and AUD patients exhibited elevated plasma levels of APOAI during early abstinence. APOAI correlated with poorer memory performance in both species, suggesting a potential role for this apolipoprotein in the context of alcohol-induced cognitive impairment.