Biochemical genetic variants in mice selectively bred for sensitivity or resistance to ethanol-induced sedation

Common Factors Underlying Diverse Responses in Alcohol Use Disorder

Objective

Interindividual variation in responses to alcohol is substantial, posing challenges for medical management and for understanding the biological underpinnings of alcohol use disorders (AUD). It is important to understand whether diverse alcohol responses such as sedation, which is predictive of risk and partly heritable, occur concurrently or independently from responses such as blackouts and withdrawal. We hypothesized that latent factors accounting for sources of variance in diverse alcohol response phenotypes could be identified in a large, deeply phenotyped sample of patients with AUD.

Methods

We factor analyzed 17 alcohol response related items from the Alcohol Dependence Scale (ADS) in 938 individuals diagnosed with AUD via structured clinical interviews. Demographic, genetic, and clinical characteristics were tested as predictors of the latent factors by multiple indicators, multiple causes analysis.

Results

The final factor solution included three alcohol response factors: Physical Symptoms, Perceptual Disturbances, and Neurobiological Effects. Both gender and genetic ancestry were identified as variables influencing alcohol response. Major depressive disorder positively predicted physical symptoms and aggression negatively predicted physical symptoms. Barratt's Impulsivity Scale total score predicted the Physical and Perceptual domains. Family history, average drinks per drinking day, and negative urgency (an impulsivity measure) predicted all three domains.

Conclusions

Diverse items from the ADS concurrently load onto three correlated alcohol response factors rather than loading independently. Genetic ancestry and clinical characteristics predicted the severity of items that define the alcohol response factors even after accounting for degree of alcohol consumption. Co‐occurring phenotypes point towards an underlying shared physiology of diverse alcohol responses.

Three common factors relevant for diverse alcohol responses are identified: Physical Symptoms, Perceptual Disturbances, and Neurobiological Effects

Alcohol response items from the Alcohol Dependence Scale concurrently load onto these three factors rather than loading independently

The three factors are correlated; patients presenting to clinical settings with a problem such as blackout are likely to experience several other problems either acutely or in the future

Resources for Systems Genetics

A key characteristic of systems genetics is its reliance on populations that vary to a greater or lesser degree in genetic complexity-from highly admixed populations such as the Collaborative Cross and Diversity Outcross to relatively simple crosses such as sets of consomic strains and reduced complexity crosses. This protocol is intended to help investigators make more informed decisions about choices of resources given different types of questions. We consider factors such as costs, availability, and ease of breeding for common scenarios. In general, we recommend using complementary resources and minimizing depth of resampling of any given genome or strain.

Isolate housing alters ethanol sensitivity in long-sleep and short-sleep mice

Beginning at 45 days of age, male long-sleep (LS) and short-sleep (SS) mice were placed into individual cages for 21-22 days. Control animals were group-housed for the same amount of time. At 65-66 days of age, animals were given anesthetic doses of ethanol, IP. Measures taken were sleep time, body temperature at 30 and 60 minutes postinjection and blood ethanol content (BEC) at regain of righting response. Compared to the same measures in group-housed animals, sleep times and hypothermia were attenuated in isolate-housed LS and SS mice. Isolate housing resulted in a 15% increase, compared to levels observed in group-housed animals, in BEC at regain of righting in LS; there was no significant difference in BEC in SS mice. The results indicated an isolation-related decrease in sensitivity to the anesthetic effects of ethanol in LS; the effect of isolation in SS may be an increased clearance rate of ethanol.