Social isolation increases impulsive choice with minor changes on metabolic function in middle-aged rats

Area of Science:

• Neuroscience
• Behavioral Biology
• Endocrinology

Background:

• The impact of social isolation (SI) during middle age on behavior and metabolism is not well understood.
• Middle age is a critical period for physiological changes, making it important to study the effects of environmental factors like SI.

Purpose of the Study:

• To test the hypothesis that social isolation in middle-aged rats increases impulsive choice (IC) behavior, anxiety-like behavior, and metabolic dysfunction.
• To investigate sex-specific differences in response to social isolation and metabolic challenges.

Main Methods:

• Middle-aged male and female rats (11 months old) were housed individually (social isolation) or in groups for two months.
• Impulsive choice behavior was assessed using a delay-discounting task.
• Anxiety-like behavior was measured via a novelty-suppressed feeding task, and metabolic function was evaluated using oral glucose tolerance and insulin tolerance tests after high-fat diet exposure.

Main Results:

• Socially isolated rats exhibited significantly more impulsive choice behavior compared to group-housed rats, irrespective of sex.
• No significant effects of social isolation were observed on anxiety-like behavior, glucose tolerance, or insulin sensitivity.
• Male rats displayed higher plasma insulin concentrations and a greater insulin resistance index than female rats.

Conclusions:

• Social isolation during middle age is sufficient to induce impulsive choice behavior in rats.
• The study highlights significant sex-specific differences in metabolic profiles, with males being more susceptible to insulin resistance.
• Further research is needed to elucidate the mechanisms underlying the effects of social isolation across different life stages.