This review addresses the molecular mechanisms of corticotropin-releasing factor (CRF) regulation in the hypothalamus under stress and stress resilience. CRF in the hypothalamus plays a central role in regulating the stress response. CRF stimulates adrenocorticotropic hormone (ACTH) release from the anterior pituitary. ACTH stimulates glucocorticoid secretion from the adrenal glands. Glucocorticoids are essential for stress coping, stress resilience, and homeostasis. The activated hypothalamic-pituitary-adrenal axis is suppressed by the negative feedback from glucocorticoids. Glucocorticoid-dependent repression of cAMP-stimulated Crf promoter activity is mediated by both the negative glucocorticoid response element and the serum response element. Conversely, the inducible cAMP-early repressor can suppress the stress response via inhibition of the cAMP-dependent Crf gene, as can the suppressor of cytokine signaling-3 in the hypothalamus. CRF receptor type 1 is mainly involved in a stress response, depression, anorexia, and seizure, while CRF receptor type 2 mediates “stress coping” mechanisms such as anxiolysis in the brain. Differential effects of FK506-binding immunophilins, FKBP4 and FKBP5, contribute to the efficiency of glucocorticoids under stress resilience. Together, a variety of factors contribute to stress resilience. All these factors would have the differential roles under stress resilience.

Glucocorticoids (GCs) are well known to induce insulin resistance. However, the effect of GCs on insulin secretion has not been well characterized under physiological conditions in human. We here evaluated the effect of GCs on insulin secretion/ß-cell function precisely in a physiological condition. A population-based study of 1,071 Japanese individuals enrolled in the 2014 Iwaki study (390 men, 681 women; aged 54.1 ± 15.1 years), those excluded individuals taking medication for diabetes or steroid treatment, were enrolled in the present study. Association between serum cortisol levels and insulin resistance/secretion assessed by homeostasis model assessment using fasting blood glucose and insulin levels (HOMA-R and HOMA-ß, respectively) were examined. Univariate linear regression analyses showed correlation of serum cortisol levels with HOMA-ß (ß = -0.134, p <0.001) but not with HOMA-R (ß = 0.042, p = 0.172). Adjustments for age, gender, and the multiple clinical characteristics correlated with HOMA indices showed similar results (HOMA-ß: ß = -0.062, p = 0.025; HOMA-R: ß = -0.023, p = 0.394). The correlation between serum cortisol levels and HOMA-ß remained significant after adjustment for HOMA- R (ß = -0.057, p = 0.034). When subjects were tertiled based on serum cortisol levels, the highest tertile was at greater risk of decreased insulin secretion (defined as lower one third of HOMA-ß (≤70)) than the lowest tertile, after adjustment for multiple factors including HOMA- R (odds ratio 1.26, 95% confidence interval 1.03–1.54). In conclusion, higher serum cortisol levels are significantly associated with decreased insulin secretion in the physiological cortisol range in a Japanese population.

It is suggested that activation of receptor for advanced glycation end products (RAGE) induces proinflammatory response in diabetic nerve tissues. Macrophage infiltration is invoked in the pathogenesis of diabetic polyneuropathy (DPN), while the association between macrophage and RAGE activation and the downstream effects of macrophages remain to be fully clarified in DPN. This study explored the role of RAGE in the pathogenesis of DPN through the modified macrophages. Infiltrating proinflammatory macrophages impaired insulin sensitivity, atrophied the neurons in dorsal root ganglion, and slowed retrograde axonal transport (RAT) in the sciatic nerve of type 1 diabetic mice. RAGE-null mice showed an increase in the population of antiinflammatory macrophages, accompanied by intact insulin sensitivity, normalized ganglion cells, and RAT. BM transplantation from RAGE-null mice to diabetic mice protected the peripheral nerve deficits, suggesting that RAGE is a major determinant for the polarity of macrophages in DPN. In vitro coculture analyses revealed proinflammatory macrophage–elicited insulin resistance in the primary neuronal cells isolated from dorsal root ganglia. Applying time-lapse recording disclosed a direct impact of proinflammatory macrophage and insulin resistance on the RAT deficits in primary neuronal cultures. These results provide a potentially novel insight into the development of RAGE-related DPN.

Prolactin (PRL) has roles in various physiological functions. Although experimental studies showed that PRL has both beneficial and adverse effects on type 2 diabetes mellitus, clinical findings in subjects with hyperprolactinemia indicate adverse effects on glucose metabolism. However, effects of PRL within the physiological range in human are controversial. A population-based study of 370 Japanese men enrolled in the 2014 Iwaki study (aged 52.0 ± 14.8 years). In this cross-sectional study, associations between serum PRL levels and homeostatic model assessment (HOMA) indices representing glucose metabolism in a physiological setting were examined using multivariable regression analysis. Although univariate linear regression analyses showed significant associations between serum PRL levels and HOMA indices, adjustment with multiple factors made the association with HOMA-ß (insulin secretion) insignificant, while those with HOMA-R (insulin resistance) remained significant (ß = 0.084, p = 0.035). Non-linear regression analyses showed a regression curve with a peak at serum PRL level, 12.4 ng/mL and a positive association of serum PRL level with HOMA-R below the peak (ß = 0.119, p = 0.004). Higher serum PRL levels within the physiological range seem to be associated with insulin resistance in men.

Type 2 diabetes mellitus (T2DM) is associated with a high prevalence of depression, which is influenced by personality traits and coping style. However, these psychological factors have not been well studied in individuals with T2DM. The association between coping behaviors and the reported levels of depressive symptoms was examined in individuals with T2DM. The subjects were 435 T2DM patients (mean age 63.1 ± 12.6 years). Depressive status, personality traits and coping behaviors were assessed using the Center for Epidemiologic Studies Depression Scale (CES-D) and the Brief Scale for Coping Profile (BSCP). Lifestyle factors and glycated hemoglobin A1c (HbA1c) levels in the patients were also included in the analyses. Among the 435 subjects with T2DM, 130 (29.9%) exhibited possible depression, and 68 (15.6%) displayed probable depression. After adjustment for confounders, logistic and multiple regression analyses revealed that certain coping profile scores, such as Changing one’s point of view, Emotional expression involving others and Avoidance and suppression, were consistently and significantly associated with the presence and severity of depression. No relationship was found between depression and HbA1c. These findings indicate that Maladaptive emotion-focused coping strategies, such as Emotional expression involving others and Avoidance and suppression, are protective factors and that Adaptive emotion-focused coping, such as Changing one’s point of view, is a risk factor for depression in T2DM patients. Psychological intervention focusing on the coping profile may reduce depressive symptoms. Additional studies are needed to examine the relationships between psychological factors and depressive symptoms using a longitudinal study design.

Aims/Objectives: Glycemic control varies according to stress level and the efficacy of control measures, affecting the outcomes of diabetes. Although detailed coping styles have not been well studied in patients with type 2 diabetes mellitus, problem‐focused coping strategies are believed to be related to better control of blood glucose. Associations between coping profiles/dimensions and blood glucose control were examined in individuals with type 2 diabetes.Materials and Methods: The participants included 503 Japanese patients (mean age 63.9 ± 12.6 years) with type 2 diabetes. The average glycated hemoglobin A1c (HbA1c) levels were calculated from HbA1c levels measured more than four times within the 12 months before the assessment. Coping profiles were assessed using the Brief Scale for Coping Profile. Lifestyle factors were also included in the analyses.Results: Factors other than age were not associated with HbA1c levels in patients who used insulin. Conversely, habitual alcohol consumption, single status, the adaptive emotion‐focused coping dimension, and changing mood and changing one’s point of view profiles were associated with HbA1c levels.Conclusions: These findings suggest that adaptive emotion‐focused coping supports glycemic control in type 2 diabetes patients who do not use insulin. Additional studies using a longitudinal design are required to further examine the relationships between psychological factors and glycemic control.