AgRP neurons control compulsive exercise and survival in an activity-based anorexia model

Hypothalamic agouti-related peptide (AgRP) and neuropeptide Y-expressing neurons have a critical role in driving food intake, but also in modulating complex, non-feeding behaviours1. We interrogated whether AgRP neurons are relevant to the emergence of anorexia nervosa symptomatology in a mouse model. Here we show, using in vivo fibre photometry, a rapid inhibition of AgRP neuronal activity following voluntary cessation of running. All AgRP neuron-ablated, food-restricted mice die within 72 h of compulsive running, while daily activation of AgRP neurons using a chemogenetic tool increases voluntary running with no lethality of food-restricted animals. Animals with impaired AgRP neuronal circuits are unable to properly mobilize fuels during food-restriction-associated exercise; however, when provided with elevated fat content through diet, their death is completely prevented. Elevated fat content in the diet also prevents the long-term behavioural impact of food-restricted fit mice with elevated exercise volume. These observations elucidate a previously unsuspected organizational role of AgRP neurons, via the mediation of the periphery, in the regulation of compulsive exercise and its related lethality with possible implications for psychiatric conditions, such as anorexia nervosa.

Is problematic exercise really problematic? A dimensional approach

OBJECTIVE

Though moderate exercise has numerous health benefits, some individuals may become excessively preoccupied with exercise, endorsing features akin to "addiction." The aim of this study was to evaluate the relationships between problematic exercise (viewed dimensionally), quality of life, and psychological measures.

METHODS

Young adults were recruited from an established population-based cohort in the United Kingdom and completed an online survey. The factor structure of the Exercise Addiction Inventory (EAI) was characterized. Relationships between dimensional EAI factor scores and other variables (impulsivity, compulsivity, emotional dysregulation) were elicited.

RESULTS

Six hundred and forty-two individuals took part in the study (mean age 23.4 years, 64.7% female). The EAI yielded two factors - a "general factor" and a "relationship conflict factor." Both EAI factor scores were associated with disordered eating, impulsivity (UPPS), and compulsivity (CHI-T). Only the relationship conflict factor score was significantly associated with impaired quality of life (all domains) and with maladaptive personality traits (emotional dysregulation and obsessive-compulsive personality disorder traits). Few participants met conventional threshold for full exercise addiction (1.1%).

CONCLUSION

Higher problematic exercise scores, in a sample largely free from exercise addiction, were associated with impulsive and compulsive personality features, emotional dysregulation, and disordered eating. Further research is needed to examine whether these results generalize to other populations (such as gym attendees) and are evident using more rigorous in-person clinical assessment rather than online assessment. Longitudinal research is needed to examine both positive and negative impacts of exercise, since moderate exercise may, in fact, be useful for those with impulsive/compulsive tendencies, by dampening negative emotional states or substituting for other more damaging types of repetitive habit.