LACY, Eva L*; WILSON, Mark E; Emory University: Social Rank Affects Feeding Patterns and Metabolic Hormones in Female Monkeys

Chronic social stress can disrupt reproductive physiology and may involve significant changes in energy balance. Details of the behavioral and endocrine features of energy balance in socially stressed animals are lacking, however. To address the energetic consequences of social stress we examined feeding patterns, daily patterns of metabolic hormones and baseline insulin sensitivity in female rhesus macaques in social groups with well established dominance ranks. We collected blood and observed feeding in groups fed ad libitum and after an 18 h overnight fast. We collected blood 30 min before AM feeding, at mid-day, and mid-afternoon, and observed groups immediately following morning feeding. Feeding onset was advanced and feeding durations were longer in the first 15-30 min of observations after a fast, regardless of social rank. The increased duration persisted in dominant (DOM) females after 30 min. Subordinate (SUB) females visited the food bin more frequently than DOM females during 0-15 min of observations. This difference disappeared with fasting because only DOM females increased visit frequency. Circulating cortisol profiles were similar and fasting reduced cortisol levels at all time points, regardless of social rank. Fasting had a rank-dependent effect on triiodothyronine (T3) levels; AM T3 was lower in fasted SUB females, but remained elevated until noon in DOM females. Insulin secretion in response to glucose was similar across ranks, but SUB females had significantly lower glucose than DOM females. These differences in feeding patterns and metabolic hormone secretion may reflect baseline differences energy balance associated with social stress and may represent long term metabolic strategies that the reflect the patterns food access subordinate females.