The combined T3/TRH test in depressed patients and healthy controls

Polymorphisms in the serotonin reuptake transporter gene modify the consequences of social status on metabolic health in female rhesus monkeys

Individuals vary substantially in their vulnerability to physical and psychosocial stressors. The causes of such variation in susceptibility to stress are poorly understood, but are thought to relate in part to genetic factors. The present study evaluated the extent to which polymorphisms in the gene encoding the serotonin reuptake transporter (5HTTLPR or SERT) modulated physiologic responses to the imposition of psychosocial stress (social reorganization and subordinate social status) in female rhesus monkeys. Forty females, drawn from the middle ranking genealogies of several large social groups, were reorganized into eight groups containing 5 monkeys each; four groups were comprised entirely of animals homogeneous for the long promoter variant in the SERT gene (l/l), while the other four groups had monkeys with at least one allele of the short promoter variant (l/s or s/s). Females were sequentially introduced into these new groups in random order and dominance ranks were established within several days. During the ensuing 6 weeks, dominant monkeys exhibited elevated rates of aggression while subordinates displayed high rates of submission. Notably, females with the s-variant SERT genotype, collapsed across social status positions, exhibited the highest overall rates of both aggression and submission. Although neither social status nor SERT genotype influenced morning cortisol concentrations, glucocorticoid negative feedback was reduced significantly in subordinate compared to dominant females irrespective of genotype. All animals lost weight and abdominal fat across the experiment. However, decreases were greatest in subordinates, regardless of genotype, and least in dominant females with the l/l genotype. Serum concentrations of insulin, glucose, and ghrelin decreased significantly during the group formation process, effects that were independent of genotype or social status. In contrast, social status and genotype interacted to influence changes in serum concentrations of leptin and triiodothyronine (T3), as dominant, l/l females had the highest levels while subordinate s-variant females had the lowest levels. The order in which a female was introduced to her group generally predicted her eventual social rank. However, rank was additionally predicted by pre-experimental T3 and abdominal fat values, but only in the l/l animals. While these findings must be replicated with a larger sample size, the data suggest that the s-variant SERT genotype confers increased vulnerability to the adverse effects of psychosocial stress associated with subordinate status while the l/l genotype benefits the most from the absence of stress conferred by dominant social status. These findings suggest that genetic factors modify the responses of monkeys to social subordination and perhaps other psychosocial stressors.

Icariin from Epimedium brevicornum attenuates chronic mild stress-induced behavioral and neuroendocrinological alterations in male Wistar rats

Chronic mild stress (CMS) is suggested to produce abnormalities in the hypothalamic-pituitary-adrenal (HPA) axis and hypothalamus-pituitary-thyroid (HPT) axis. Therefore, compound that attenuates the neuroendocrinological alterations may have potential as antidepressant. The behavioral and neuroendocrinological effects of icariin, a major constituent of flavonoids isolated from Epimedium brevicornum, were investigated in the CMS model of depression in male Wistar rats. CMS procedure caused an anhedonic state in rats resulted in increased corticotropin-releasing factor (CRF) concentrations in dissected brain regions and serum, decreased total triiodothyronine (tT3) in serum with no significant changes in serum adrenocorticotrophic hormone (ACTH) and thyroxine (tT4). Administration of icariin reversed CMS-induced sucrose intake reduction and CRF elevation. These results suggested that icariin possessed potent antidepressant-like activities which were at least in part mediated by improving the abnormalities in the HPA axis functions. However, we did not find a clear correlation between the HPT axis and icariin treatment in the CMS-treated rats.

The influence of 4-week treatment with sertraline on the combined T3/TRH test in depressed patients

In the present study, the influence of a 4-week treatment with sertraline on the regulation of hypothalamic-pituitary-thyroid (HPT) axis activity in depression was investigated, in particular the impact of sertraline on the thyroid receptor (TR)-mediated negative feedback control as measured by the combined T3/TRH test. In 20 drug-free patients (8 men, 12 women) suffering from a major depressive episode according to DSM-IV criteria the single TRH-stimulation test (administration of 200 microg TRH at 09:00h) was carried out followed by a combined T3/TRH test (pre-treatment with 40 microg 3,5,3'-triiodothyronine [T3] the night before; administration of 200 microg TRH at 09:00h the next day). After 4 weeks of treatment with sertraline at a standard dosage of 50 mg/day, both the single TRH test and the combined T3/TRH test were repeated in the depressed patients. Using repeated-measures ANOVA for statistical analysis, antidepressant therapy with sertraline did not have any significant impact on the TRH-induced TSH and prolactin stimulation (deltaTSH, deltaPRL) during the single TRH test nor during the combined T3/TRH test, neither in responders (n = 10) nor in non-responders (n = 10). Moreover, the percentage suppression of TRH-induced TSH stimulation (deltaTSH) after pre-treatment with 40 microg T3 was comparable before (-61.07%) and after the 4-week treatment with sertraline (-58.92%). Apparently, the therapeutic efficacy of antidepressants such as sertraline is not related to the regulation of HPT axis activity in depressed patients.