The metabolic syndrome

Perceived discrimination has been studied with regard to its impact on several types of health effects. This meta-analysis provides a comprehensive account of the relationships between multiple forms of perceived discrimination and both mental and physical health outcomes. In addition, this meta-analysis examines potential mechanisms by which perceiving discrimination may affect health, including through psychological and physiological stress responses and health behaviors. Analysis of 134 samples suggests that when weighting each study's contribution by sample size, perceived discrimination has a significant negative effect on both mental and physical health. Perceived discrimination also produces significantly heightened stress responses and is related to participation in unhealthy and nonparticipation in healthy behaviors. These findings suggest potential pathways linking perceived discrimination to negative health outcomes.

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Perceived discrimination and health: a meta-analytic review.

This preliminary study compared the associations between objective and subjective socioeconomic status (SES) with psychological and physical variables among 157 healthy White women, 59 of whom subsequently participated in a laboratory stress study. Compared with objective indicators, subjective social status was more consistently and strongly related to psychological functioning and health-related factors (self-rated health, heart rate, sleep latency, body fat distribution, and cortisol habituation to repeated stress). Most associations remained significant even after controlling for objective social status and negative affectivity. Results suggest that, in this sample with a moderately restricted range on SES and health, psychological perceptions of social status may be contributing to the SES-health gradient.

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Relationship of subjective and objective social status with psychological and physiological functioning: preliminary data in healthy white women.

Obesity is globally prevalent and highly heritable, but its underlying genetic factors remain largely elusive. To identify genetic loci for obesity susceptibility, we examined associations between body mass index and similar to 2.8 million SNPs in up to 123,865 individuals with targeted follow up of 42 SNPs in up to 125,931 additional individuals. We confirmed 14 known obesity susceptibility loci and identified 18 new loci associated with body mass index (P < 5 x 10(-8)), one of which includes a copy number variant near GPRC5B. Some loci (at MC4R, POMC, SH2B1 and BDNF) map near key hypothalamic regulators of energy balance, and one of these loci is near GIPR, an incretin receptor. Furthermore, genes in other newly associated loci may provide new insights into human body weight regulation.

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Association analyses of 249,796 individuals reveal 18 new loci associated with body mass index

Naturally occurring variations in maternal care alter the expression of genes that regulate behavioral and endocrine responses to stress, as well as hippocampal synaptic development. These effects form the basis for the development of stable, individual differences in stress reactivity and certain forms of cognition. Maternal care also influences the maternal behavior of female offspring, an effect that appears to be related to oxytocin receptor gene expression, and which forms the basis for the intergenerational transmission of individual differences in stress reactivity. Patterns of maternal care that increase stress reactivity in offspring are enhanced by stressors imposed on the mother. These findings provide evidence for the importance of parental care as a mediator of the effects of environmental adversity on neural development.

Maternal care, gene expression, and the transmission of individual differences in stress reactivity across generations.

Abdominal obesity has been suggested to be associated with perturbations of the regulation of the hypothalamic-pituitary-adrenal (HPA) axis. In a population of 51-yr-old men (n = 284) salivary cortisol concentrations were determined on repeated (n = 7) occasions over a random working day, and perceived stress was reported in parallel. Cortisol values were then related to reported stress (stress-related cortisol). A standardized lunch was used as a physiological challenge. A low dose (0.5 mg) dexamethasone suppression test was also performed as well as determinations of testosterone and insulin-like growth factor I (IGF-I). Body mass index [weight (kilograms)/height (meters)2]; waist/hip circumference ratio (WHR); sagittal trunk recumbent diameter (D); fasting insulin; blood glucose; triglycerides; and total, low density (LDL), and high density (HDL) lipoprotein cholesterol were also determined. Cortisol concentrations were highest in the morning, and lunch was followed by a peak (P = 0.044). Two types of diurnal cortisol curves were identified, one characterized by a high variability with high morning values, and another with low variability and low morning values. Both correlated strongly with suppression of salivary cortisol by dexamethasone (P < 0.001). Stress-related cortisol secretion was associated with D (P = 0.051), low IGF-I (P = 0.006), and diastolic blood pressure (P = 0.078). When the type of diurnal cortisol curve was taken into consideration by statistical weighting, stress-related cortisol secretion in subjects with high variability showed associations with testosterone (P < 0.001), D, total and LDL cholesterol, diastolic blood pressure (P < 0.001), fasting insulin (P = 0.039), and glucose (P = 0.030) as well as, negatively, triglycerides (P < 0.001). When weighted for a low variability of diurnal cortisol secretion, stress-related cortisol secretion showed strong negative relationships with IGF-I, testosterone, and HDL. Furthermore, strong, consistent relationships (all P < 0.001) were found with obesity factors (body mass index, WHR, and D), and with metabolic (insulin, glucose, triglycerides, and total and LDL cholesterol) as well as hemodynamic variables (systolic and diastolic blood pressure and heart rate). These results clearly show interactions between diurnal cortisol secretion related to perceived stress and anthropometric, endocrine, metabolic, and hemodynamic variables. This seems to occur with apparently normal regulation of the HPA axis (high morning peaks and variability as well as dexamethasone suppression of cortisol), where other endocrine variables are not affected. With a low diurnal cortisol variation and blunted dexamethasone suppression, indicating abnormal regulation of the HPA axis, perceived stress-dependent cortisol values were strongly related to perturbations of other endocrine axes as well as abdominal obesity with metabolic and hemodynamic abnormalities. Perturbations of the regulations of the HPA axis such as those described in combination with low dexamethasone suppressibility are known to follow long term overactivation of the axis by factors such as environmental stress.

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Stress-related cortisol secretion in men: relationships with abdominal obesity and endocrine, metabolic and hemodynamic abnormalities

Obesity and cortisol

. Rosmond R, Bjorntorp P (University of Goteborg, Sahlgrenska University Hospital, Goteborg, Sweden). The hypothalamic–pituitary–adrenal axis activity as a predictor of cardiovascular disease, type 2 diabetes and stroke. J Intern Med 2000; 247: 188–197.



Objectives. The hypothalamic–pituitary–adrenal (HPA) axis, the mediator of cortisol, plays a central role in the homeostatic processes. In this study, we addressed the potential impact of HPA axis activity on established anthropometric, metabolic and haemodynamic risk factors for cardiovascular disease (CVD), type 2 diabetes mellitus and stroke.



Design. A cross-sectional study.



Subjects. A subgroup of 284 men from a population sample of 1040 at the age of 51 years.



Main outcome measures. Anthropometric measurements included body mass index (BMI, kg m–2), waist/hip circumference ratio (WHR) and abdominal sagittal diameter (D). Overnight fasting values of blood glucose, serum insulin, triglycerides, total, low (LDL) and high density (HDL) lipoprotein cholesterol, as well as resting heart rate and blood pressure, were also determined. By using repeated diurnal salivary cortisol measurements during everyday conditions, methods were developed to characterize the status of the HPA axis, and set in relation to the anthropometric, metabolic and haemodynamic measurements.



Results. In bivariate analyses, risk factors intercorrelated in clusters of anthropometric (BMI, WHR, D), metabolic (insulin, glucose and their ratio, triglycerides, cholesterol [total and LDL], HDL cholesterol [negative]) and haemodynamic (systolic and diastolic blood pressure and heart rate) measurements. This was also the case in the two-dimensional scaling analysis, where, however, HDL separated out. A normal HPA axis status, characterized by high variability and morning cortisol values, as well as a clear response to a standardized lunch and dexamethasone suppression test, was then introduced by a statistical weighting procedure. This did not essentially change the results of either the bivariate correlation matrix or the two-dimensional scaling analysis. A similar introduction of a pathological HPA axis, characterized by low variability and morning cortisol values, a poor lunch-induced cortisol response and a blunted dexamethasone suppression of cortisol, changed the results markedly. Now strong and consistent correlations were found not only within but also between different clusters of risk factors, which also congregated into one distinct cluster, again except for HDL cholesterol.



Conclusions. These results disclose the prospect of an overriding function of a pathological HPA axis on other, established risk factors for CVD, type 2 diabetes and stroke. Its close association to HPA axis dysfunction may explain the previously reported powerful risk indication of abdominal obesity for the diseases mentioned. The HPA axis abnormality has been reported to be a characteristic consequence of frequently repeated or chronic environmental stress challenges.

https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2796.2000.00603.x

The hypothalamic-pituitary-adrenal axis activity as a predictor of cardiovascular disease, type 2 diabetes and stroke.

https://psych415.class.uic.edu/Readings/Rosmond,%20Stress%20&%20Met%20Syndrome,%20Psyneurend,%202005.pdf

Role of stress in the pathogenesis of the metabolic syndrome.

Summary
Aims Type 2 diabetes mellitus (DM) develops when insulin resistance overcomes the capacity of compensatory insulin secretion. Insulin resistance may be induced via psychoneuroendocrine pathways, a possibility which has received little previous attention.

Methods We have used salivary cortisol measurements to monitor the activity of the hypothalamic–pituitary–adrenal (HPA) axis, the major controller of hormones involved in the regulation of peripheral insulin sensitivity under everyday conditions. The influence of external challenges, as well as the sensitivity of feedback regulation, were followed in randomly selected middle-aged population samples.

Results In health there is a rhythmicity of cortisol secretion, with a high plasticity and efficient feedback control. In contrast, a group of subjects were identified with a flat, rigid day curve and poor feedback control, who showed consistent abnormalities in stress-related cortisol secretion, including inhibited secretions of sex steroids and growth hormone; insulin resistance; abdominal obesity; elevated leptin levels; hyperglycaemia; dyslipidaemia and hypertension with elevated heart rate. The endocrine abnormalities are probably responsible for the anthropometric and metabolic abnormalities. The circulatory perturbations seem to be induced by a parallel activation of the central sympathetic nervous system suggesting an ‘hypothalamic arousal syndrome’, gradually developing into an independent risk for disease. An associated cluster of environmental factors, including psychosocial and socio-economic stress, traits of depression and anxiety, alcohol consumption and smoking, all factors known to activate hypothalamic centres, has been identified. A polymorphism of the glucocorticoid receptor gene, with 13.7% homozygotes in the male Swedish population, parallels receptor dysfunction, and may be responsible for the associated insulin resistance, central obesity and hypertension.

Conclusions This is the first detailed examination of psychoneuroendocrinological processes in the natural environment on a population basis in relation to somatic health. The results suggest that an hypothalamic arousal syndrome, with parallel activation of the HPA axis and the central sympathetic nervous system, is responsible for development of endocrine abnormalities, insulin resistance, central obesity, dyslipidaemia and hypertension, leading to frank disease, including Type 2 DM. We suggest that this syndrome is probably based on environmental pressures in genetically susceptible individuals.

Diabet. Med. 16, 373–383 (1999)

Roland Rosmond

Papers

Stress-related cortisol secretion in men: relationships with abdominal obesity and endocrine, metabolic and hemodynamic abnormalities

Obesity and cortisol

The hypothalamic-pituitary-adrenal axis activity as a predictor of cardiovascular disease, type 2 diabetes and stroke.

Role of stress in the pathogenesis of the metabolic syndrome.

Hypothalamic arousal, insulin resistance and Type 2 diabetes mellitus.