Psychosocial influences on female 'protection' among cynomolgus macaques

We evaluated atherosclerosis (coronary artery, aortic and carotid bifurcation), plasma lipids, and blood pressure in 15 male and 23 female cynomolgus macaques (Macaca fascicularis). In addition, female social behavior and ovarian function were monitored. The females lived in stable (unmanipulated) or unstable (periodically altered composition) social groups while males lived in stable groupings. All animals were fed for 30 months an atherogenic diet which resulted in moderate hyperlipoproteinemia (median total plasma cholesterol congruent to 275 mg/dl). Socially dominant females had less extensive and severe coronary artery atherosclerosis than males or socially subordinate females; atherosclerosis extent and severity were similar in these latter two groups. Importantly, dominant females also had regular ovarian function and relatively small adrenal glands while subordinate females had impaired ovarian function (increased frequency of anovulatory cycles and luteal phase deficiencies) and relatively large adrenal glands. The dominant and subordinate females did not differ in plasma lipids. These results suggest that female 'protection' from coronary artery atherosclerosis may be influenced as much by behavioral and hormonal characteristics as by plasma lipids. Among other findings, males had more extensive atherosclerotic lesions at the carotid bifurcations than females. In addition, males had lower high density lipoprotein cholesterol concentrations and higher blood pressures than females. The gender difference in extent of atherosclerosis at the carotid bifurcation was unrelated to social factors or plasma lipids; it may have been due, in part, to the higher blood pressures of the males.