Age-related dysfunctions of the neuroendocrine axes in nonhuman primates with depression-like and anxious behavior

With age, the incidence of stress-related pathologies, in the etiopathogenesis of which endocrine dysfunctions play an important role, increases. This review presents data on the study of age-related features in functioning of the key adaptive neuroendocrine axes (hypothalamic-pituitary-adrenal, HPA axis and hypothalamic-pituitary-thyroid, HPT axis) in individuals that differ in adaptive behavior with an emphasis on experimental studies in nonhuman primates. Studies have shown pronounced age-related differences in the functioning of HPA axis in the animals with depression-like and anxiety behavior (DAB): impairment negative feedback regulation with an increase of corticotropin and cortisol level in the afternoon - night time, a higher response to acute stress exposure, and sensitization of the hypothalamic-pituitary axis. A decrease secretion of thyroxine and its response to thyrotropin-releasing hormone (TRH) or thyrotropin administration with increased sensitivity of the adenohypophysis to TRH were identified in old DAB animals. In addition, older overweight DAB monkeys exhibited increased insulin resistance and reduced insulin and triglycerides secretion. Thus, age-related changes of HPA and HPT axes in DAB monkeys are associated with more pronounced endocrine dysfunctions as compared with young individuals, leading to hormonal imbalance that may contribute to the development of severe age-related pathology.