The As and Ds of stress: metabolic, morphological and behavioral consequences

Unlike responses to acute stressful events that are protective and adaptive in nature, chronic stress elicits neurochemical, neuroanatomical and cellular changes that may have deleterious consequences upon higher brain functioning. For example, while exposure to acute stress facilitates memory formation and consolidation, chronic stress or chronic exposure to stress levels of glucocorticoids impairs cognitive performance. Chronic stress or glucocorticoid exposure, as well as impairments in hypothalamic-pituitary-adrenal (HPA) axis function are proposed to participate in the etiology and progression of neurological disorders such as depressive illness, anxiety disorders and post-traumatic stress disorder (PTSD). HPA axis dysfunction, impaired stress responses and elevated basal levels of glucocorticoids are also hallmark features of experimental models of type 1 and type 2 diabetes, as well as diabetic subjects in poor glycemic control. Such results suggest that stress and glucocorticoids contribute to the neurological complications observed in diabetes patients. Interestingly, many of the hyperglycemia mediated changes in the brain are similar to those observed in depressive illness patients and in experimental models of chronic stress. Such results suggest that common mechanisms may be involved in the development of the neurological complications associated with Anxiety, Depressive illness and Diabetes: the As and Ds of stress. The aim of the current review will be to discuss the mechanisms through which limbic structures such as the hippocampus and amygdala respond and adapt to the deleterious consequences of chronic stress and hyperglycemia.