Neuroendocrine perturbations as a cause of insulin resistance

[Energy metabolism of the immune system : Consequences in chronic inflammation]

BACKGROUND

Energy is the currency of life. The systemic and intracellular energy metabolism plays an essential role for the energy supply of the resting and activated immune system and this also applies to chronic inflammatory diseases.

OBJECTIVE

This presentation examines both components of the systemic and cellular energy metabolism in health and chronic inflammation.

MATERIAL AND METHODS

A literature search was conducted using PubMed, Embase and the Cochrane Library. The information is presented in the form of a narrative review.

RESULTS

A chronically activated immune system acquires large amounts of energy-rich substrates that are lost for other functions of the body. In particular, the immune system and the brain are in competition. The consequences of this competition are many known diseases, such as fatigue, anxiety, depression, anorexia, sleep problems, sarcopenia, osteoporosis, insulin resistance, hypertension and others. The permanent change in the brain causes long-term alterations that stimulate disease sequelae even after disease remission. In the intracellular energy supply, chronic inflammation typically involves a conversion to glycolysis (to lactate, which has its own regulatory functions) and the pentose phosphate pathway in disorders of mitochondrial function. The chronic changes in immune cells of patients with rheumatoid arthritis (RA) lead to a disruption of the citric acid cycle (Krebs cycle). The hypoxic situation in the inflamed tissue stimulates many alterations. A differentiation is made between effector functions and regulatory functions of immune cells.

CONCLUSION

Based on the energy changes mentioned, novel treatment suggestions can be made in addition to those already known in energy metabolism.

Morning Serum Cortisol Is Uniquely Associated with Cardiometabolic Risk Independent of Body Composition in Latino Adolescents

Background: Alterations in morning serum cortisol (MSC) have been associated with higher cardiometabolic risk. This finding has been documented primarily in populations with overweight or obesity; however, it has not been clearly established if obesity plays a requisite role in this relationship. This study seeks to extend earlier findings by examining whether body composition measures alter the relationship between MSC with glucose and insulin markers, blood pressure, and lipid parameters in Latino youth in middle adolescence. Methods: This cross-sectional study included 196 healthy adolescents (130F/66M; mean age: 16.4 ± 0.6 years; 95% Latino; mean body mass index, BMI: 24.3 ± 5.7) from Los Angeles, California. Morning cortisol, glucose, insulin, glycated hemoglobin, and lipids (triglycerides and high-density lipoprotein cholesterol) were assessed from a fasting blood sample. Sitting systolic and diastolic blood pressure was averaged from duplicate measures. Body composition measures included BMI and waist circumference, which were used as proxies for total body and abdominal adiposity, respectively. Triplicate measurements of weight and height were averaged for calculation of BMI; age- and sex-specific BMI z-score was used to classify into normal BMI or overweight/obese BMI status. Waist circumference was measured in duplicate and the average was used to classify participants into two strata: normal/healthy waist circumference (<90th percentile for age, sex, and ethnicity) and high waist circumference (≥90th percentile). Results: The primary findings were that higher MSC was associated with higher fasting glucose and systolic blood pressure after adjusting for age, sex, and BMI z-score (and/or waist circumference). BMI status or waist circumference status did not alter these relationships. Main Conclusion: Our results suggest that the relationships between hypothalamic-pituitary-adrenal axis function and certain cardiometabolic risk factors may be independent of adiposity. Future research is warranted to discover the contributors and underlying mechanisms of these relationships in adolescent populations. ClinicalTrials.gov identifier: NCT02088294.

MicroRNA-25 Protects Smooth Muscle Cells against Corticosterone-Induced Apoptosis

Background and Aims

Vascular smooth muscle cells (VSMCs) are central components of atherosclerotic plaque. Loss of VSMCs through apoptotic cell death can cause fibrous cap thinning, necrotic core formation, and calcification that may destabilize plaque. Elevated glucocorticoid levels caused by psychological stress promote VSMC apoptosis and can exacerbate atherosclerosis in mice and humans. Changes in the levels of antiapoptosis microRNA-25 (miR-25) have been linked with heart disease, inflammation, VSMC phenotype, oxidative stress, and apoptosis. Here, we investigated the pathways and mechanisms of glucocorticoid-induced apoptosis of mouse VSMCs and the protective role of miR-25.

Methods

Primary mouse VSMCs were cultured +/- corticosterone for 48 h. Apoptosis, ROS, apoptotic protein activities, miR-25, MOAP1, a miR-25 target, and p70S6 kinase were quantified at intervals. The roles of miR-25 were assessed by treating cells with lenti-pre-miR-25 and anti-miR-25.

Results

VSMC apoptosis, caspase-3 activity, and Bax were increased by corticosterone, and cell death was paralleled by marked loss of miR-25. Protection was conferred by pre-miR-25 and exacerbated by anti-miR-25. Pre-miR-25 conferred reduced expression of the proapoptotic protein MOAP1, and the protective effects of pre-miR-25 were abrogated by overexpressing MOAP1. The antiapoptotic effects of miR-25 were paralleled by inhibition of the p70S6K pathway, a convergence target for the survival signaling pathways, and protection by pre-miR-25 was abrogated by the p70S6k inhibitor rapamycin.

Conclusions

MicroRNA-25 blocks corticosterone-induced VSMC apoptosis by targeting MOAP1 and the p70S6k pathway. Therapeutic manipulation of miR-25 may reduce atherosclerosis and unstable plaque formation associated with chronic stress.

Type 2 diabetes and atherosclerotic cardiovascular disease: do they share common antecedents?

It has been suggested that the association between type 2 diabetes and atherosclerotic cardiovascular disease might result from a shared antecedent — the `common soil' hypothesis. The antecedent could provide a fundamental link between type 2 diabetes and atherosclerosis via the metabolic (or insulin resistance) syndrome. The relative contributions of genes, fetal nutrition and environmental factors to this syndrome remain unclear. Although most patients with type 2 diabetes have insulin resistance, it is uncertain whether the insulin resistance-hyperinsulinaemia complex directly promotes atherogenesis, and whether type 2 diabetes and atheroma are connected via a common mediator such as central obesity, vascular endothelial dysfunction, or disordered lipid metabolism. Insulin sensitivity and cardiovascular risk may be influenced by adipocytokines (e.g. leptin and adiponectin), by excess fatty acids liberated from visceral fat, and inflammatory processes. Disturbances of the neuro-endocrine system, possibly mediated via visceral obesity, are also under investigation. Other putative links between type 2 diabetes and atheroma include polymorphisms in the genes for tumour necrosis factor-α,insulin-like growth factor-1 promoter, and lamin A/C. Trials with certain cardioprotective agents including inhibitors of the renin-angiotensin-aldosterone system and statins can improve cardiovascular outcomes and protect against the development of type 2 diabetes, lending support to the common soil hypothesis.

Global and Targeted Metabolomics Evidence of the Protective Effect of Chinese Patent Medicine Jinkui Shenqi Pill on Adrenal Insufficiency after Acute Glucocorticoid Withdrawal in Rats

Glucocorticoids are commonly used in anti-inflammatory and immunomodulatory therapies, but glucocorticoid withdrawal can result in life-threatening risk of adrenal insufficiency. Chinese patented pharmaceutical product Jinkui Shenqi pill (JKSQ) has potent efficacy on clinical adrenal insufficiency resulting from glucocorticoid withdrawal. However, the underlying molecular mechanism remains unclear. We used an animal model to study JKSQ-induced metabolic changes under adrenal insufficiency and healthy conditions. Sprague-Dawley rats were treated with hydrocortisone for 7 days with or without 15 days of JKSQ pretreatment. Sera were collected after 72 h hydrocortisone withdrawal and used for global and free fatty acids (FFAs)-targeted metabolomics analyses using gas chromatography/time-of-flight mass spectrometry and ultraperformance liquid chromatography/quadruple time-of-flight mass spectrometry. Rats without hydrocortisone treatment were used as controls. JKSQ pretreatment normalized the significant changes of 13 serum metabolites in hydrocortisone-withdrawal rats, involving carbohydrates, lipids, and amino acids. The most prominent effect of JKSQ was on the changes of FFAs and some [product FFA]/[precursor FFA] ratios, which represent estimated desaturase and elongase activities. The opposite metabolic responses of JKSQ in adrenal insufficiency rats and normal rats highlighted the "Bian Zheng Lun Zhi" (treatment based on ZHENG differentiation) guideline of TCM and suggested that altered fatty acid metabolism was associated with adrenal insufficiency after glucocorticoid withdrawal and the protective effects of JKSQ.

Early-life experiences and the development of adult diseases with a focus on mental illness: The Human Birth Theory

In mammals, early adverse experiences, including mother-pup interactions, shape the response of an individual to chronic stress or to stress-related diseases during adult life. This has led to the elaboration of the theory of the developmental origins of health and disease, in particular adult diseases such as cardiovascular and metabolic disorders. In addition, in humans, as stated by Massimo Fagioli's Human Birth Theory, birth is healthy and equal for all individuals, so that mental illness develop exclusively in the postnatal period because of the quality of the relationship in the first year of life. Thus, this review focuses on the importance of programming during the early developmental period on the manifestation of adult diseases in both animal models and humans. Considering the obvious differences between animals and humans we cannot systematically move from animal models to humans. Consequently, in the first part of this review, we will discuss how animal models can be used to dissect the influence of adverse events occurring during the prenatal and postnatal periods on the developmental trajectories of the offspring, and in the second part, we will discuss the role of postnatal critical periods on the development of mental diseases in humans. Epigenetic mechanisms that cause reversible modifications in gene expression, driving the development of a pathological phenotype in response to a negative early postnatal environment, may lie at the core of this programming, thereby providing potential new therapeutic targets. The concept of the Human Birth Theory leads to a comprehension of the mental illness as a pathology of the human relationship immediately after birth and during the first year of life.

Altered DNA methylation of glucose transporter 1 and glucose transporter 4 in patients with major depressive disorder

Alterations in brain glucose metabolism and in peripheral glucose metabolism have frequently been observed in major depressive disorder (MDD). The insulin independent glucose transporter 1 (GLUT1) plays a key role in brain metabolism while the insulin-dependent GLUT4 is the major glucose transporter for skeletal and cardiac muscle. We therefore examined methylation of GLUT1 and GLUT4 in fifty-two depressed inpatients and compared data to eighteen healthy comparison subjects. DNA methylation of the core promoter regions of GLUT1 and GLUT4 was assessed by bisulfite sequencing. Further factors determined were fasting glucose, cortisol, insulin, interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). We found significantly increased methylation of the GLUT1 in depressed inpatients compared to healthy comparison subjects (CG). Further findings comprise increased concentrations of fasting cortisol, glucose, insulin, and increased IL-6 and TNF-α. After six weeks of inpatient treatment, significantly lower GLUT1 methylation was observed in remitted patients compared to non-remitters. GLUT4 methylation was not different between depressed patients and CG, and did not differ between remitted and non-remitted patients. Although preliminary we conclude from our results that the acute phase of major depressive disorder is associated with increased GLUT1 methylation and mild insulin resistance. The successful treatment of depression is associated with normalization of GLUT1 methylation in remitters, indicating that this condition may be reversible. Failure of normalization of GLUT1 methylation in non-remitters may point to a possible role of impeded brain glucose metabolism in the maintenance of MDD.

Examining the mediating roles of binge eating and emotional eating in the relationships between stress and metabolic abnormalities

To test whether binge eating and emotional eating mediate the relationships between self-reported stress, morning cortisol and the homeostatic model of insulin resistance and waist circumference. We also explored the moderators of gender and age. Data were from 249 adults (mean BMI = 26.9 ± 5.1 kg/m(2); mean age = 28.3 ± 8.3 years; 54.2% male; 69.5% white) recruited from the community who were enrolled in a cross-sectional study. Participants completed a comprehensive assessment panel of psychological and physiological assessments including a morning blood draw for plasma cortisol. We found negative relationships between stress and morning cortisol (r = -0.15 to -0.21; p < 0.05), and cortisol and the homeostatic model of insulin resistance and waist circumference (r = -0.16, -0.25, respectively; p < 0.05). There was not statistical support for binge eating or emotional eating as mediators and no support for moderated mediation for either gender or age; however, gender moderated several paths in the model. These include the paths between perceived stress and emotional eating (B = 0.009, p < 0.001), perceived stress and binge eating (B = 0.01, p = 0.003), and binge eating and increased HOMA-IR (B = 0.149, p = 0.018), which were higher among females. Among women, perceived stress may be an important target to decrease binge and emotional eating. It remains to be determined what physiological and psychological mechanisms underlie the relationships between stress and metabolic abnormalities.

Improved glycemic control due to sitagliptin is not related to cortisol or the surrogate marker IGFBP-1 for hepatic insulin sensitivity

IMPORTANCE

Elevated cortisol levels and dysregulated insulin-like growth factor binding protein-1 (IGFBP-1; a marker of hepatic insulin sensitivity) are both related to insulin resistance and glucose abnormalities. It is unknown whether improvement in these parameters is related to improved glucose metabolism during treatment with sitagliptin.

OBJECTIVE

To determine whether improved insulin sensitivity and beta-cell function during treatment with sitagliptin is related to lower cortisol levels and/or improved regulation of IGFBP-1 in patients with recent acute coronary syndrome (ACS) and newly discovered glucose abnormalities.

DESIGN

Samples were taken from The BEta-cell function in Glucose abnormalities and Acute Myocardial Infarction (BEGAMI) trial, a double-blinded, placebo-controlled randomized clinical trial on the efficacy and safety of sitagliptin for patients with ACS and newly discovered glucose abnormalities.

SETTING

Cardiology departments (cardiac ICU and outpatient clinic) in two hospitals in Stockholm, Sweden.

PARTICIPANTS

Subjects hospitalized (or recently hospitalized) for ACS, in whom an oral glucose tolerance test revealed previously unknown glucose abnormalities.

INTERVENTIONS

Subjects were randomized to sitagliptin 100mg once daily (n=34) or placebo (n=37) for twelve weeks. Oral glucose tolerance test (OGTT) and randomization occurred after stabilization median 7 days after ACS.

MAIN OUTCOMES AND MEASURES

Fasting serum cortisol and IGFBP-1 were analyzed before OGTT, around 8a.m., and after at 10a.m. The latter time point was chosen as the spread in cortisol levels around is small then, allowing improved chances to detect differences between groups.

RESULTS

Glucose tolerance and insulin sensitivity improved in both groups, while HbA1c and indices of β-cell function improved only in the sitagliptin group as reported previously. Both groups displayed decreased cortisol levels around 10a.m. (from 338±21 to 278±14 nmol/L, p=0.038, in the sitagliptin group; from 343±17 to 302±15 nmol/L, p=0.017, in the placebo group), and improved correlation between fasting log-IGFBP-1 and insulin.

CONCLUSIONS AND RELEVANCE

These findings suggest that a stress-related elevation in cortisol may have negative impact on glucose tolerance in patients with recent ACS. However, improved glycemic control with sitagliptin does not appear to be related to changes in cortisol levels or hepatic insulin sensitivity as assessed by IGFBP-1.

Gender difference in adrenal sensitivity to ACTH is abolished in type 2 diabetes

OBJECTIVE

Dysfunction of the hypothalamus-pituitary-adrenal (HPA) axis has been implicated in type 2 diabetes (T2D). The aim of this study was to investigate the impact of T2D and gender on the HPA axis.

METHODS

Synthetic ACTH (1 μg) was administered to 21 subjects with T2D (age 62 (54-70) years, 11 men/ten women, HbA1c 49±2 mmol/mol, treated with diet or oral antidiabetic drugs) and 38 controls (age 58 (41-67) years, 20 men/18 women). Fasting basal B-glucose, serum cortisol, insulin, IGF1 and IGFBP1 concentrations were measured, and sampling for all but IGF1 was repeated 30, 60, and 90 min after ACTH injection. Patients took 0.25 mg dexamethasone at 2200-2300 h and returned the next morning for the measurement of serum cortisol concentration.

DESIGN

Cross-sectional study.

RESULTS

Patients with T2D had similar fasting serum cortisol, IGF1 and IGFBP1 concentrations; however, serum cortisol concentration after administration of dexamethasone did not differ between the groups. Healthy women exhibited higher peak cortisol levels compared with healthy men (675±26 vs 582±21 nmol/l, P=0.014), while the peak levels were equally high in men and women with T2D, resulting in a higher peak level in men with T2D compared with healthy men (691±42 vs 582±21 nmol/l, P=0.024). Serum cortisol concentration after administration of dexamethasone did not differ between the groups, nor did IGF1 and IGFBP1.

NOVELTY OF THE FINDINGS

Some studies have previously indicated disturbed regulation of the hypothalamus-pituitary-adrenal (HPA) axis in subjects with type 2 diabetes (T2D); however, much remains unknown in this area. To the best of our knowledge, this is the first study to show that the gender difference in the adrenal response to ACTH (with greater reactivity in women) is abolished in T2D. While the clinical implications cannot be determined by this paper, it is known that gender differences exist in the pathogenesis and complications of T2D. Thus, our findings suggest that further research into gender differences in the HPA axis is warranted.

CONCLUSIONS

Gender differences in adrenal response to ACTH were abolished in T2D. Men with T2D had a higher peak cortisol compared with controls. Further studies are needed to elucidate the clinical implications.

Chronic intermittent psychological stress promotes macrophage reverse cholesterol transport by impairing bile acid absorption in mice

Psychological stress is a risk factor for atherosclerosis, yet the pathophysiological mechanisms involved remain elusive. The transfer of cholesterol from macrophage foam cells to liver and feces (the macrophage-specific reverse cholesterol transport, m-RCT) is an important antiatherogenic pathway. Because exposure of mice to physical restraint, a model of psychological stress, increases serum levels of corticosterone, and as bile acid homeostasis is disrupted in glucocorticoid-treated animals, we investigated if chronic intermittent restraint stress would modify m-RCT by altering the enterohepatic circulation of bile acids. C57Bl/6J mice exposed to intermittent stress for 5 days exhibited increased transit through the large intestine and enhanced fecal bile acid excretion. Of the transcription factors and transporters that regulate bile acid homeostasis, the mRNA expression levels of the hepatic farnesoid X receptor (FXR), the bile salt export pump (BSEP), and the intestinal fibroblast growth factor 15 (FGF15) were reduced, whereas those of the ileal apical sodium-dependent bile acid transporter (ASBT), responsible for active bile acid absorption, remained unchanged. Neither did the hepatic expression of cholesterol 7α-hydroxylase (CYP7A1), the key enzyme regulating bile acid synthesis, change in the stressed mice. Evaluation of the functionality of the m-RCT pathway revealed increased fecal excretion of bile acids that had been synthesized from macrophage-derived cholesterol. Overall, our study reveals that chronic intermittent stress in mice accelerates m-RCT specifically by increasing fecal excretion of bile acids. This novel mechanism of m-RCT induction could have antiatherogenic potential under conditions of chronic stress.

High prevalence of type 2 diabetes and pre-diabetes in adult Zoroastrians in Yazd, Iran: a cross-sectional study

Background:

The prevalence of type 2 diabetes mellitus (T2DM) varies among ethnic groups. We aimed to estimate the prevalence of diagnosed and undiagnosed diabetes mellitus, impaired fasting glucose (IFG), and impaired glucose tolerance (IGT) for the first time in an ethnic population, specifically Zoroastrian citizens in Yazd, Iran whose ages were 30 or older.

Methods:

In a cross-sectional study, participants aged≥30 years were selected using systematic random sampling. An inventory, including socio-demographic data, was completed. Weight, height, body mass index (BMI), and blood pressure (BP) were measured using standard methods. Also, blood levels of glucose, triglycerides (TG), total cholesterol (TC), high density lipoprotein (HDL), low density lipoprotein (LDL), urea, creatinine (Cr), and uric acid were measured. The latest criteria established by the American Diabetes Association (ADA) were used to diagnose DM.

Results:

The mean age of the participants (n=403) was 56.9±12.8 years. The total prevalence of diabetes, including previously diagnosed and undiagnosed diabetes, IFG, and IGT was 26.1%, 18.6%, 7.5%, 34.7% and 25.8%, respectively. Participants with diabetes had higher fasting blood sugar (FBS) (P<0.001), oral glucose tolerance test (OGTT) (P<0.001), urea (P=0.019), BMI (P=0.001), systolic blood pressures (P<0.001), TG (P=0.007) and lower HDL (P=0.034) than patients with IFG, IGT, and normoglycemic subjects.

Conclusions:

The current study showed a high prevalence of T2DM in the Zoroastrian population of Yazd, Iran. One-third of the total cases with diabetes were undiagnosed.

Insulin resistance, selfish brain, and selfish immune system: an evolutionarily positively selected program used in chronic inflammatory diseases

Insulin resistance (IR) is a general phenomenon of many physiological states, disease states, and diseases. IR has been described in diabetes mellitus, obesity, infection, sepsis, trauma, painful states such as postoperative pain and migraine, schizophrenia, major depression, chronic mental stress, and others. In arthritis, abnormalities of glucose homeostasis were described in 1920; and in 1950 combined glucose and insulin tests unmistakably demonstrated IR. The phenomenon is now described in rheumatoid arthritis, systemic lupus erythematosus, ankylosing spondylitis, polymyalgia rheumatica, and others. In chronic inflammatory diseases, cytokine-neutralizing strategies normalize insulin sensitivity. This paper delineates that IR is either based on inflammatory factors (activation of the immune/ repair system) or on the brain (mental activation via stress axes). Due to the selfishness of the immune system and the selfishness of the brain, both can induce IR independent of each other. Consequently, the immune system can block the brain (for example, by sickness behavior) and the brain can block the immune system (for example, stress-induced immune system alterations). Based on considerations of evolutionary medicine, it is discussed that obesity per se is not a disease. Obesity-related IR depends on provoking factors from either the immune system or the brain. Chronic inflammation and/or stress axis activation are thus needed for obesity-related IR. Due to redundant pathways in stimulating IR, a simple one factor-neutralizing strategy might help in chronic inflammatory diseases (inflammation is the key), but not in obesity-related IR. The new considerations towards IR are interrelated to the published theories of IR (thrifty genotype, thrifty phenotype, and others).

The appraisal of chronic stress and the development of the metabolic syndrome: a systematic review of prospective cohort studies

Chronic psychosocial stress has been proposed as a risk factor for the development of the metabolic syndrome (MES). This review gives a systematic overview of prospective cohort studies investigating chronic psychosocial stress as a risk factor for incident MES and the individual elements of MES. Thirty-nine studies were included. An association between chronic psychosocial stress and the development of MES was generally supported. Regarding the four elements of MES: i) weight gain: the prospective studies supported etiological roles for relationship stress, perceived stress, and distress, while the studies on work-related stress (WS) showed conflicting results; ii) dyslipidemi: too few studies on psychosocial stress as a risk factor for dyslipidemia were available to draw a conclusion; however, a trend toward a positive association was present; iii) type 2 diabetes mellitus (DM2): prospective studies supported perceived stress and distress as risk factors for the development of DM2 among men, but not among women, while WS was generally not supported as a risk factor among neither men nor women; iv) hypertension: marital stress and perceived stress might have an influence on blood pressure (BP), while no association was found regarding distress. Evaluating WS the results were equivocal and indicated that different types of WS affected the BP differently between men and women. In conclusion, a longitudinal association between chronic psychosocial stress and the development of MES seems present. However, the number of studies with sufficient quality is limited and the design of the studies is substantially heterogeneous.

Sex differences in type 2 diabetes: focus on disease course and outcomes

BACKGROUND

Women with type 2 diabetes (T2D) are less likely to reach the goals for hemoglobin A1c compared with men, and have higher all-cause mortality. The risk of cardiovascular disease is elevated among both men and women with T2D, however, the risk has declined among men over recent years while it remains stationary in women. Reasons for these sex differences remain unclear, and guidelines for diabetes treatment do not differentiate between sexes. Possible causes for varying outcome include differences in physiology, treatment response, and psychological factors. This review briefly outlines sex differences in hormonal pathophysiology, and thereafter summarizes the literature to date on sex differences in disease course and outcome.

METHODS

Systematic searches were performed on PubMed using "sex", "gender", and various glucose-lowering therapies as keywords. Earlier reviews are summarized and results from individual studies are reported. Reference lists from studies were used to augment the search.

RESULTS

There is an increased risk of missing the diagnosis of T2D when screening women with only fasting plasma glucose instead of with an oral glucose tolerance test. The impact of various risk factors for complications may differ by sex. Efficacy and side effects of some glucose-lowering drugs differ between men and women. Men with T2D appear to suffer more microvascular complications, while women have higher morbidity and mortality in cardiovascular disease and also fare worse psychologically.

CONCLUSION

Few studies to date have focused on sex differences in T2D. Several questions demand further study, such as whether risk factors and treatment guidelines should be sex-specific. There is a need for clinical trials designed specifically to evaluate sex differences in efficacy and outcome of the available treatments.

Nonhuman primates and other animal models in diabetes research

Animal models are important for determining the pathogenesis of and potential treatments for obesity and diabetes. Nonhuman primates (NHPs) are particularly useful for studying these disorders. As in humans, type 2 diabetes mellitus is the most common form of diabetes in NHPs and occurs more often in older obese animals, with a metabolic progression from insulin resistance (IR) and impaired glucose tolerance to overt diabetes. Histopathologic changes in pancreatic islets are also similar to those seen in humans with diabetes. Initially, there is islet hyperplasia with abundant insulin production to compensate for IR, followed by insufficient insulin production with replacement of islets with islet-associated amyloid. Diabetic NHPs also have adverse changes in plasma lipid and lipoprotein concentrations, biomarkers of obesity, inflammation, and oxidative stress, and protein glycation that contribute to the numerous complications of the disease. Furthermore, sex hormones, pregnancy, and environmental factors (e.g., diet and stress) affect IR and can also contribute to diabetes progression in NHPs. Additionally, due to their similar clinical and pathologic characteristics, NHPs have been used in many pharmacological studies to assess new therapeutic agents. For these reasons, NHPs are particularly valuable animal models of obesity and diabetes for studying disease pathogenesis, risk factors, comorbidities, and therapeutic interventions.

Does caring for a spouse with dementia promote cognitive decline? A hypothesis and proposed mechanisms

OBJECTIVE

To discuss why spouse caregivers (CGs) of people with dementia may be at higher risk for cognitive problems and decline than demographically similar people not caring for a spouse with dementia (noncaregivers; NCGs).

DESIGN

Literature review.

SETTING

Community.

PARTICIPANTS

Older adults caring for a family member (primarily spouses) with dementia.

MEASUREMENTS

Cognitive, psychosocial, physiological, and behavioral.

RESULTS

This article reports a review of the literature examining relationships between CG status and cognitive problems in the context of a theoretical model of chronic stress. The model suggests that spouse CGs may be at higher risk of cognitive impairment or dementia than NCG spouses in response to several mediators, including psychosocial (e.g., depression, loneliness, social isolation, sleep problems), behavioral (e.g., exercise, diet), and physiological (e.g., metabolic syndrome and inflammation) variables.

CONCLUSION

This research has important implications because it considers modifiable risk factors for dementia that, if unchecked, may compromise the lives of CGs and their ability to function. It is hoped that an understanding of such stress-mediator-cognitive processes will help clinicians, researchers, policy-makers, and stakeholders mitigate what may be characterized as an "ironic tragedy"-dementia in both members of the caregiving dyad-if left unchecked.

Association of cortisol and the metabolic syndrome in Korean men and women

Obesity and the metabolic syndrome are closely related and have become increasingly prevalent in Korea. The cardiovascular disease (CVD) risk factors comprising the metabolic syndrome have previously been associated with increased hypothalamic-pituitary-adrenal axis (HPAA) activity, but the associations have not been extensively examined in non-Caucasian populations. The aim of the present study was to investigate the relationships between cortisol, adiposity and the metabolic syndrome in a Korean population. A total of 1,881 adults participated in the study between January 2001 and February 2008. Sociodemographic data were assessed by questionnaires. Body composition, clinic blood pressures as well as metabolic variables including glucose, insulin, and lipid profile were assessed and analyzed in relation to cortisol levels. Mean age of the participants was 58.7 ± 10.8 yr. Higher levels of cortisol was associated with elevated blood pressure, fasting glucose and total cholesterol in men, and between cortisol and systolic blood pressure, fasting glucose and total cholesterol in women. There was an increased risk for the metabolic syndrome associated with higher cortisol levels in both men (P < 0.001) and women (P = 0.040) adjusting for age and body mass index. Higher cortisol levels are associated with several CVD risk factors and the metabolic syndrome, independent of overall of adiposity level, in Korean men and women.

Effects of hyperlipidaemia on glucocorticoid metabolism: results of a randomized controlled trial in healthy young women

OBJECTIVE

It is well established that the hypothalamic-pituitary-adrenal (HPA) axis is altered in obese individuals. Hyperlipidaemia with elevated levels of free fatty acids (FFAs) is also frequently seen in obesity and in the metabolic syndrome. We hypothesized, therefore, that hyperlipidaemia may alter the activity of the HPA axis.

PATIENTS AND METHODS

The effects of hyperlipidaemia, including increased circulating FFAs, on ACTH secretion and cortisol metabolism were analysed in 13 healthy young women during the early follicular phase of two subsequent cycles. We administered a 20% lipid/heparin (LHI) or a saline/heparin infusion (SHI) using a crossover design in random order for 330 min. A detailed characterization of glucocorticoid metabolism was performed by measurement of plasma ACTH, cortisol and urinary excretion rates of adrenal glucocorticoids and the glucocorticoid metabolites.

RESULTS

We observed that LHI-induced hyperlipidaemia elevated serum cortisol levels compared to SHI. No changes in plasma ACTH levels, daily urinary excretion rates of adrenal glucocorticoids, glucocorticoid precursors/metabolites and the calculated activities of the 5α-reductase, 3β-hydroxysteroid dehydrogenase (HSD), 11-, 17-, 21-hydroxylase and 11β-HSD 1 or 2 were found.

CONCLUSION

Our randomized controlled trial suggests that the adrenal sensitivity to ACTH may be enhanced by LHI-induced hyperlipidaemia in normal-weight healthy young women. This effect might contribute to the disturbances of the HPA axis described in women with abdominal obesity and impaired lipid metabolism.

Independent and combined associations of abdominal obesity and seated resting heart rate with type 2 diabetes among older Chinese: the Guangzhou Biobank Cohort Study

BACKGROUND

Central obesity and poor physical fitness predict the development of type 2 diabetes and cardiovascular mortality among Caucasian populations. We studied the independent and combined effect of abdominal obesity and seated resting heart rate used as an indicator of physical fitness, on the presence of type 2 diabetes among 30 519 older residents of Guangzhou, Southern China.

METHODS

Participants were stratified into four groups, based on the Asian criteria for abdominal obesity (≥90/≥ 80 cm in men/women) and the 75% cut-off point for seated resting heart rate (≥83 beats per min). The association with type 2 diabetes was assessed using multivariable logistic regression.

RESULTS

A total of 3777 (12.7%) volunteers were diagnosed with type 2 diabetes, which was independently associated with seated resting heart rate and, in particular, increasing levels of abdominal obesity (p < 0.001). An odds ratio of 3.93 (95% confidence interval = 3.48-4.43) was identified for type 2 diabetes in participants who were obese with a seated resting heart rate ≥ 83 beats per min after adjusting for potential confounders.

CONCLUSIONS

Higher seated resting heart rate, a marker of poor physical fitness, independently doubles the risk of type 2 diabetes. The strength of this association is further increased when abdominal obesity is considered.

Role of glucocorticoids and the glucocorticoid receptor in metabolism: insights from genetic manipulations

Since the discovery of the beneficial effects of adrenocortical extracts for treating adrenal insufficiency more than 80 years ago, glucocorticoids and their cognate, intracellular receptor, the glucocorticoid receptor have been characterized as critical checkpoints in the delicate hormonal control of energy homeostasis in mammals. Whereas physiological levels of glucocorticoids are required for proper metabolic control, aberrant glucocorticoid action has been linked to a variety of pandemic metabolic diseases, such as type II diabetes and obesity. Based on its importance for human health, studies of the molecular mechanisms of within the glucocorticoid signaling axis have become a major focus in biomedical research. In particular, the understanding of tissue-specific functions of the glucocorticoid receptor pathway has been proven to be of substantial value for the development of novel therapies in the treatment of chronic metabolic disorders. Therefore, this review focuses on the consequences of endogenous and experimental modulation of glucocorticoid receptor expression for metabolic homeostasis and dysregulation, particularly emphasizing tissue-specific contributions of the glucocorticoid pathway to the control of energy metabolism.

The physical activity, stress and metabolic syndrome triangle: a guide to unfamiliar territory for the obesity researcher

Research aimed at deciphering the aetiology of obesity and the metabolic syndrome remains focused on two behavioural factors, namely diet and physical activity, even though epidemiologic research suggests that these two cornerstones of treatment and prevention account for only a small-to-moderate portion of the variance in these phenotypes. In recent years, this observation has prompted the intensified investigation of the pathogenic potential of factors that extend beyond the traditional concept of energy imbalance and examine the putative causes of this imbalance. Psychosocial stress has emerged as one such factor, raising the need for researchers to be informed about this expansive and complex literature. The purpose of this review is twofold (i) To introduce obesity researchers to fundamental concepts and historically important theoretical developments in the stress field and (ii) To outline the dyadic and triadic interactions between stress, physical activity and the metabolic syndrome. Although the expansion of the research focus to multiple, diverse and interacting putative causal agents will certainly increase the complexity of the research enterprise, this step seems essential for the comprehension and effective response to the continuing rise in the prevalence of obesity and the metabolic syndrome.

Impact of psychological stress on the associations between apolipoprotein E variants and metabolic traits: findings in an American sample of caregivers and controls

OBJECTIVE

To examine the association between apolipoprotein E (APOE) gene variants and waist circumference, fasting plasma glucose, serum insulin, serum high-density lipoprotein cholesterol, and serum triglycerides, all metabolic traits known as cardiovascular disease (CVD) endophenotypes, in a population of stressed individuals and controls. Abdominal obesity, insulin resistance, elevated serum lipid concentration, and APOE polymorphisms have been associated with CVD risk. Current evidence supports the hypothesis that gene-environment interactions modulate serum lipid concentrations.

METHODS

The association between rs769450, rs405509, rs439401, and metabolic traits were analyzed in a U.S. sample of 126 white caregivers of a relative with Alzheimer';s disease or other major dementia and 122 white controls. The associations were analyzed, using multivariate analysis of variance adjusted for age, sex, and medications.

RESULTS

Significant multivariate interactions were found, using both additive (p = .009) and dominant (p = .047) models between rs439401 (C/T) and caregiver stress in relation to a profile of metabolic variables. Univariate analyses found the TT genotype to be associated with more adverse levels of waist circumference (interaction, p = .026), triglycerides (interaction, p = .001) and high-density lipoprotein cholesterol (interaction, p = .001) among caregivers but with a more favorable profile of these endophenotypes among controls. There were no significant associations or interactions involving the other two single nucleotide polymorphisms.

CONCLUSION

The APOE rs439401 TT genotype is associated with an adverse metabolic profile among chronically stressed individuals compared with individuals not similarly stressed in whom a more favorable profile is expressed. Confirmation of these results in further research would indicate that the TT genotype can be used to identify persons at high risk for CVD when subjected to chronic stress.

Neurohormonal and inflammatory hyper-responsiveness to acute mental stress in depression

Depression is associated with dysregulated hypothalamic-pituitary-adrenal (HPA) axis function, overactivity of the sympathoadrenal system, and increased levels of inflammation markers. It is not known whether these biological processes are disproportionately elevated in response to acute negative emotional arousal by mental stress (MS). The present study investigates responses of neurohormones and inflammatory markers to MS in 14 clinically depressed (age: 42+/-10 years; 50% female) and 14 non-depressed control (age: 39+/-6 years; 50% female) participants. Heightened acute MS reactivity was documented in depressed participants (adrenocorticotropic hormone, rho=0.001; norepinephrine, rho=0.042; epinephrine, rho=0.039), and a delayed increase in cortisol was observed (rho=0.002). Inflammation markers increased more strongly in depressed versus non-depressed participants (IL-6, rho=0.027; tumor necrosis factor-alpha, rho=0.050; and recovery C-reactive protein, rho=0.003). It is concluded that depressed individuals display hyper-reactivity of neuroimmunological markers in response to acute negative emotions. This hyper-reactivity may serve a pathologic role in the elevated morbidity and mortality risk associated with depression.

Factors that may impede the weight loss response to exercise-based interventions

The results of exercise programmes designed to reduce body fat are disappointing. However, the reporting of weight loss as mean values disguises those individuals who do lose significant amounts of fat. Why some participants produce significant exercise-induced fat loss whereas others lose little or increase fat stores is likely to be an outcome of a range of behavioural (e.g. sleep deprivation, caloric intake), inherited (e.g. muscle fibre type, gender) and physiological (e.g. hyperinsulinaemia, hypothyroidism) factors. The following review highlights possible factors involved in weight loss and discusses how individual differences may determine the extent of weight loss after an exercise intervention. Finally, implications for the treatment and prevention of obesity are discussed.

Clinical review: The pathogenetic role of cortisol in the metabolic syndrome: a hypothesis

CONTEXT

The metabolic syndrome (MetS) is a cluster of metabolic abnormalities that increase the risk for type 2 diabetes mellitus and vascular disease. The common characteristics of MetS and hypercortisolemic conditions such as Cushing's syndrome (CS) suggest that the pathogenesis of MetS and central obesity might involve prolonged and excessive exposure to glucocorticoids. The present review summarizes the evidence on the potential role of cortisol in the pathogenesis of MetS and discusses new therapeutic approaches for these patients.

EVIDENCE ACQUISITION

Using PubMed, we searched for publications during the last 20 yr regarding the possible pathogenetic role of cortisol in the development of MetS.

EVIDENCE SYNTHESIS

Emerging data suggest that patients with MetS show hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis, which leads to a state of "functional hypercortisolism." The cause for this activation of the HPA axis remains uncertain but may be partly associated with chronic stress and/or low birth weight, which are both associated with increased circulating cortisol levels and greater responsiveness of the HPA axis. Increased exposure to cortisol contributes to increased fat accumulation in visceral depots. However, cortisol metabolism is not only centrally regulated. The action of 11beta-hydroxysteroid dehydrogenase-1 at the tissue level also modulates cortisol metabolism. Increased 11beta-hydroxysteroid dehydrogenase-1 activity in adipose tissue and liver might contribute to the development of several features of the MetS.

CONCLUSIONS

MetS shares many characteristics of CS, and cortisol might play a role in the development of MetS at both a central and a peripheral level.

[Surgical excision of subclinical cortisol secreting incidentalomas: Impact on blood pressure, BMI and glucose metabolism]

OBJECTIVES

To compare clinical, vascular and metabolic parameters before and after surgery in patients with subclinical cortisol secreting incidentalomas.

PATIENTS AND METHODS

Eight patients were investigated before and 12 months after removal of the mass on hemodynamic (blood pressure by MAPA procedure), anthropometric (body weight, body mass index), and metabolic parameters (glucose level, HbA(1c)).

RESULTS

In the whole group, 75% of patients displayed decrease in blood pressure (cessation of at least one hypotensive medication) and 33% of them were definitely cured of hypertension. Seventy-one percent of patients lost body weight and 37.5% lost more than 5%. In the whole group of patients, glucose level decreased by 1.1% and medical treatment was discontinuated in two of three diabetic patients.

CONCLUSION

Subclinical cortisol secreting adrenal incidentalomas are associated with cardiovascular risk factors that may be corrected after removal of the mass. Therefore, surgery may be an appropriate choice in patients with subclinical Cushing's syndrome to improve hypertension, body weight and impaired glucose level. Controlled studies comparing surgical treatment to a medical follow-up including optimal cardiovascular risk factors treatment are needed to define the usefulness of surgery in hypertensive patients with subclinical cortisol secreting incidentalomas.

The psychoneuroimmunology of depression

Chronic stress, by initiating changes in the hypothalamic-pituitary-adrenal (HPA) axis and the immune system, acts as a trigger for anxiety and depression. There is experimental and clinical evidence that the rise in the concentration of pro-inflammatory cytokines and glucocorticoids, which occurs in a chronically stressful situation and also in depression, contribute to the behavioural changes associated with depression. A defect in serotonergic function is associated with these hormonal and immune changes. Neurodegenerative changes in the hippocampus, prefrontal cortex and amygdalae are the frequent outcome of the changes in the HPA axis and the immune system. Such changes may provide evidence for the link between chronic depression and dementia in later life.

Low high-density lipoprotein-cholesterol is the most prevalent metabolic abnormality for Australian Aboriginal men and women even when lean

BACKGROUND

The aim of this study was to investigate the relationship of the prevalence and risk of the metabolic syndrome to body mass index (BMI) in Australian Aboriginal people.

DESIGN

It was a cross-sectional, secondary analysis of data obtained from population-based screenings in Aboriginal communities in central and northern Australia (913 participants recruited between 1993 and 1997).

RESULTS

Forty-one percent of men and 48% of women conformed to the National Cholesterol Education Program definition for the metabolic syndrome (chi2=3.72, P=0.054). The prevalence of low high-density lipoprotein-cholesterol was high in all BMI categories (89 and 95% in men and women, respectively). The prevalence of all other metabolic abnormalities increased linearly with BMI.

CONCLUSION

The metabolic syndrome is highly prevalent in Aboriginal communities and is strongly associated with BMI. Low high-density lipoprotein-cholesterol was the predominant component of the metabolic syndrome across sex groups and BMI strata.

Association between the metabolic syndrome and serum cortisol in overweight Latino youth

OBJECTIVE

The purpose of this report is to investigate the associations between metabolic syndrome (MS) and levels of morning serum cortisol in a cohort of overweight Latino youth.

DESIGN

Subjects were 205 overweight, Latino youth (age 8-13 yr, body mass index percentile > 85, family history positive for type 2 diabetes). Measures included body composition by dual-energy x-ray absorptiometry, intraabdominal adipose tissue (IAAT) by magnetic resonance imaging, insulin sensitivity by frequently sampled iv glucose tolerance test/minimal model, fasting lipids, and serum cortisol.

RESULTS

Children with MS had higher body mass index percentile, total body fat mass, and IAAT and lower insulin sensitivity than those without MS. Children with MS had higher morning serum cortisol levels, whether unadjusted (10.1 +/- 3.7 vs. 9.0 +/- 2.8 microg/dl, P < 0.05) or after adjusting for age, gender, total body fat and lean tissue mass, and insulin sensitivity (10.4 +/- 0.4 vs. 8.9 +/- 0.3 microg/dl, P < 0.01). Increasing number of features of MS was associated with higher cortisol levels, after adjusting for covariates (P = 0.001). Among individual features of MS, systolic blood pressure had the strongest relationship with adjusted cortisol level (r = 0.34; P < 0.001), followed by diastolic blood pressure and fasting plasma glucose (both r = 0.23; P < 0.01). IAAT was associated with cortisol (r = 0.16; P < 0.05), whereas high-density lipoprotein, triglycerides, and waist circumference were not.

CONCLUSIONS

In overweight, Latino youth, MS is associated with higher morning serum cortisol levels, independent of body fat and insulin sensitivity. More studies are needed to investigate the role of relative hypercortisolism and chronic stress in obesity-related metabolic disorders in children.

Are the available experimental models of type 2 diabetes appropriate for a gender perspective?

Several experimental models have so far been developed to improve our knowledge of the pathogenetic mechanisms of type 2 diabetes mellitus (T2D), to determine the possible pharmacological targets of this disease and to better evaluate diabetes-associated complications, e.g. the cardiovascular disease. In particular, the study of T2D gained the attention of several groups working with different animal species: rodents, cats or pigs, as well as other non-human primate species. Each of these species provided useful and different clues. However, T2D has to be considered as a gender-associated disease: sex differences play in fact a key role in the onset as well as in the progression of the disease and a higher mortality for cardiovascular diseases is detected in diabetic women with respect to men. The results obtained from all the available animal models appear to only partially address this issue so that the search for more precise information in this respect appears to be mandatory. In this review we summarize these concepts and literature in the field and propose a reappraisal of the various animal models for a study of T2D that would take into consideration a gender perspective.

Glucocorticoids, metabolism and metabolic diseases

Since the discovery of the beneficial effects of adrenocortical extracts for treating adrenal insufficiency more than 80 years ago, glucocorticoids (GC) and their cognate, intracellular receptor, the glucocorticoid receptor (GR) have been characterized as critical components of the delicate hormonal control system that determines energy homeostasis in mammals. Whereas physiological levels of GCs are required for proper metabolic control, excessive GC action has been tied to a variety of pandemic metabolic diseases, such as type II diabetes and obesity. Highlighted by its importance for human health, the investigation of molecular mechanisms of GC/GR action has become a major focus in biomedical research. In particular, the understanding of tissue-specific functions of the GC-GR pathway has been proven to be of substantial value for the identification of novel therapeutic options in the treatment of severe metabolic disorders. Therefore, this review focuses on the role of the GC-GR axis for metabolic homeostasis and dysregulation, emphasizing tissue-specific functions of GCs in the control of energy metabolism.

New insights into the pathophysiology of gestational diabetes mellitus: possible role of human leukocyte antigen-G

Diabetes can develop in up to 10% of pregnant women who have not previously had the condition. This condition which usually begins in the second half of the pregnancy is called gestational diabetes mellitus (GDM). In most cases, all diabetic symptoms disappear following delivery. However, women with GDM have an increased risk of developing type 2 diabetes mellitus (DM) later in life, especially if they were overweight before the pregnancy. The cause of GDM is unknown. Although hormones present in the pregnancy, especially human placental lactogen, are thought to be responsible for the development of this condition, many questions remain to be answered. It is still not known why GDM develops in a subgroup of pregnant women. It may be possible that events leading to the development of GDM are triggered by an antigenic load which is the fetus itself. Human leukocyte antigen-G (HLA-G) expression that functions to protect the fetus from immune attack by down-regulating cytotoxic T cell responses to fetal trophoblast antigens is postulated to protect the islet cells of the pancreatic tissue also. HLA-G and nuclear factor-kappaB (NF-kappaB) interaction is suggested to be central in the events leading to GDM development. An analogy between the development of DM in some transplant patients and GDM development in a proportion of pregnancies is postulated, so that an antigenic load triggers the diabetogenic process. Further support of this hypothesis with new studies may lead to the possibility that recombinant HLA-G can be used for the prevention of diabetes in high risk patients.

Psychological underpinnings of metabolic syndrome

Metabolic syndrome (MS) is more common among socio-economically disadvantaged individuals and is associated with certain risky lifestyle practices. MS also appears to be triggered by adverse social circumstances and chronic stress. The present paper reviews accumulating evidence to imply that individuals who have certain personality and behaviour traits are particularly predisposed to develop MS, and brings together theories that relate to possible psychological mechanisms underlying MS. It considers how such factors might interact causally to encourage the development of MS. As part of the EU-funded LIPGENE Integrated Project, multi-level modelling will be undertaken to explore potential pathways to MS, taking into consideration the interplay between a range of psycho-social, demographic, cultural and lifestyle factors thought to contribute to the development of MS. Data will be gathered for this purpose from a representative sample of >50-year-olds living in Britain (n 1000) and Portugal (n 500). It is anticipated that this information will assist in the development and targetting of future intervention to prevent and treat MS in the normal population.

Stress, the endoplasmic reticulum, and insulin resistance

Stress, such as nutrient deprivation, viral infections, inflammation, heat shock, or lipid accumulation, imposes a serious threat to the body. These stimuli, acting both on the central control stations of the stress system and its final effectors, catecholamines and glucocorticoids, and on the peripheral target tissues, can modulate insulin action in the body. Metabolic complications, such as diabetes, visceral obesity, and atherosclerosis have emerged as major health threats in the modern societies. Indeed, obesity and atherosclerosis are regarded as states of chronic low-grade inflammation, while inflammatory mediators and lipid accumulation can evoke a chronic stress at the cellular level, principally affecting the endoplasmic reticulum (ER). It has recently been shown that ER responds to metabolic stressors through a well coordinated molecular response that involves the transcriptional activation of multiple genes, the attenuation of protein synthesis and degradation of the ER-localized misfolded proteins, and the onset of apoptosis. This article examines the emerging role of stress on ER and its possible link with obesity, insulin resistance, and type 2 diabetes.

Insulin resistance, endocrine function and adipokines in type 2 diabetes patients at different glycaemic levels: potential impact for glucotoxicity in vivo

OBJECTIVE

To evaluate the interplay between hyperglycaemia, insulin resistance, hormones and adipokines in patients with type 2 diabetes mellitus (T2DM).

DESIGN AND METHODS

Ten patients with T2DM with good glycaemic control (G), 10 with poor control (P) and 10 nondiabetic control subjects (C) were matched for sex (M/F 6/4), age and body mass index. A hyperinsulinaemic, euglycaemic clamp was performed and cytokines and endocrine functions, including cortisol axis activity were assessed.

RESULTS

Patients with diabetes were more insulin resistant than group C, and group P exhibited the highest degree of insulin resistance (P = 0.01, P vs C). Tumour necrosis factor (TNF)-alpha levels were elevated in patients with diabetes (P = 0.05) and group P had the highest levels of fasting serum cortisol (P = 0.05), nonesterified fatty acids (NEFA; P = 0.06) and C-reactive protein (CRP; P = 0.01). Adiponectin levels were lower in the P group. In partial correlation analyses, significant associations were found: glycaemic level (HbA1c) with insulin resistance, TNF-alpha, CRP and basal and ACTH-stimulated cortisol levels, insulin resistance with plasma NEFA, TNF-alpha and stimulated cortisol levels.

CONCLUSION

Poor glycaemic control in patients with T2DM was associated with insulin resistance and with elevated TNF-alpha, CRP and basal as well as stimulated cortisol levels. Inflammatory mediators, e.g. TNF-alpha, may contribute to insulin resistance in hyperglycaemic patients with T2DM and this might be a partial explanation for glucotoxicity.

The adrenocorticotropin stimulation test: contribution of a physiologically based model developed in horse for its interpretation in different pathophysiological situations encountered in man

The present study aimed to characterize the adrenal response to ACTH. A model was developed that coupled the nonlinear disposition of cortisol with a physiologically based model for cortisol secretion by the adrenals. It was assumed that the response to ACTH resulted from two mechanisms: a stimulation of the cortisol secretion rate and control of the duration of the secretion. Seven dose levels of ACTH were tested in horses, a species similar to man as regards adrenal function. The main result was that the secretion rate of the adrenal gland can be modelized by a zero order process that is maximal for a relatively low dose of ACTH (0.1 microg/kg). Beyond this dose, the increasing adrenal gland response is only due to the prolongation of the time of its secretion. The consequences of these different features were explored by simulation to reproduce classical pathophysiological situations encountered in man. Our model was able to reproduce and simply explain many adrenal gland responses that are dimmed by the different nonlinearities of the system.

No effect of free fatty acids on adrenocorticotropin and cortisol secretion in healthy young men

Free fatty acids (FFAs) affect anterior pituitary function. However, the effect of FFAs on corticotropin (ACTH) and cortisol in humans is controversial. Thus, we assessed the effect of a pronounced increase in circulating FFA levels induced by infusion of lipid/heparin on ACTH and cortisol secretion in young men. Eight healthy male volunteers who underwent a 10-hour overnight fast were investigated. A 20% lipid/heparin or saline/heparin infusion was given at a rate of 1.5 mL/min for 6 hours. A euglycemic hyperinsulinemic clamp was performed in 6 subjects 4 hours after the start of infusion. To assess steroid metabolism, we measured ACTH, cortisol, FFAs, and urinary steroids. Lipid infusion increased FFAs (6.06 +/- 0.52 vs 0.70 +/- 0.23 mmol/L; P < .005) and induced insulin resistance (glucose infusion rate, 4.08 +/- 2.15 vs 6.02 +/- 2.60 mg/kg per minute; P < .005). Serum cortisol and plasma ACTH decreased independent of lipid/heparin or saline/heparin infusion. In addition, we found no effect of hyperinsulinemia on ACTH and cortisol levels. There were no differences in urinary free cortisol, urinary free cortisone, 5beta-tetrahydrocortisol, 5alpha-tetrahydrocortisol, and tetrahydrocortisone. In conclusion, FFAs had no effect on basal ACTH and cortisol secretion in normal-weight young men. In addition, no alterations in urinary glucocorticoid metabolites were detected, suggesting unchanged cortisol metabolism during lipid infusion.

Individual differences in glucose homeostasis: do our early life interactions with bacteria matter?

Exposure to endotoxin during the neonatal period in the rat has been shown to alter the development of the hypothalamic-pituitary-adrenal axis, inducing hyper-responsivity and increased glucocorticoid production in later-life. Glucocorticoids are known to have major metabolic effects, therefore, early life endotoxin exposure may have potentially serious consequences for metabolic homeostasis in the exposed animal. The aims of this study were therefore to assess the effect of neonatal bacterial endotoxin exposure on subsequent glucose homeostasis, insulin action and corticosterone production from puberty through to senescence. Male Fischer-344 rat pups were treated with bacterial endotoxin (0.05 mg/kg Salmonella enteritidis i.p.) or vehicle (sterile pyrogen free saline) on days 3 and 5 postnatally. Insulin and glucose levels were assessed before and during and intraperitoneal glucose tolerance test (IPGTT) together with body mass on postnatal days 40, 80, and 400. In addition, circulating levels of corticosterone were measured at 0, 30, and 90 min following a 30-min restraint challenge at these ages. Neonatal endotoxin challenge did not alter fasting plasma glucose or insulin, but impaired glucose tolerance at puberty (p<.05), improved glucose tolerance in adulthood (p<.05) and had no effect at senescence. During the IPGTT insulin was reduced at all ages (p<.05) following neonatal endotoxin challenge, but insulin sensitivity was unaltered, except for an increase in adulthood (p<.05), which is consistent with the observed improvement in glucose tolerance at this age. Neonatal endotoxin challenge reduced body mass during puberty and senescence (p<.05) but did not alter basal or stressed plasma corticosterone levels at any of the three developmental time points examined. These findings suggest that variations in an individual's early life bacterial environment may contribute to differences in glucose homeostasis, insulin action and disease susceptibility later in life.

Associations between liver histology and cortisol secretion in subjects with nonalcoholic fatty liver disease

OBJECTIVES

To assess associations between the activity of hypothalamo-pituitary-adrenal (HPA) axis and liver histology in patients with nonalcoholic fatty liver disease (NAFLD).

DESIGN AND PATIENTS

In a cross-sectional study, we enrolled 50 consecutive, overweight, NAFLD patients and 40 control subjects who were comparable for age, sex and body mass index (BMI).

MEASUREMENTS

NAFLD (by liver biopsy), HPA axis activity (by 24-hour urinary free cortisol [UFC] excretion and serum cortisol levels after 1 mg dexamethasone), insulin resistance (by homeostasis model assessment: HOMA-IR), and metabolic syndrome (MetS) features.

RESULTS

NAFLD patients had markedly higher (P < 0.001) 24-h UFC (149 +/- 24 vs. 90 +/- 16 nmol/day) and postdex suppression cortisol concentrations (32 +/- 10 vs. 16 +/- 7 nmol/l) than controls. The MetS and its individual components were more frequent among NAFLD patients. The marked differences in urinary/serum cortisol concentrations that were observed between the groups were little affected by adjustment for age, sex, BMI, waist circumference, systolic blood pressure, triglycerides, homeostasis model assessment for insulin resistance score and presence of diabetes. Importantly, 24-h UFC and postdex cortisol concentrations strongly correlated to hepatic necroinflammatory grade (P < 0.01) and fibrosis stage (P < 0.001) among NAFLD patients. By logistic regression analysis, 24-h UFC (odds ratio (OR) 1.80, 95%CI 1.3-2.8) or postdex cortisol concentrations (OR 1.95, 95%CI 1.4-3.1) independently predicted the severity of hepatic fibrosis, but not necroinflammation, after adjustment for potential confounders.

CONCLUSIONS

These results suggest that NAFLD patients have a subtle, chronic overactivity in the HPA axis (that is closely associated with the severity of liver histopathology) leading to subclinical hypercortisolism that might be implicated in the development of NAFLD.

Type 2 Diabetes--An Introduction to the Development and Use of Animal Models

Although the epidemiology of type 2 diabetes (T2D) has been well described, there is much about the disease that remains unclear. For example, lifestyle factors-including increased body weight with visceral fat deposition and insufficient physical activity-are thought to be primary contributors to the adverse changes in the metabolism of muscle and fat cells that comprise the first stage of the disease. However, the precise mechanisms underlying these initial alterations are incompletely understood. Other, less obvious questions relate to the presence of sex differences in the development and health consequences of T2D, the etiological role of the central nervous system ("stress"), and the potential evolutionary origins of T2D susceptibility. Some of these issues can be resolved by further study of human populations. However, many questions can be answered only through the kinds of controlled prospective studies that are conducted with appropriate animal models. The use of such models can be an invaluable part of an overall strategy designed to elucidate the mechanisms underlying the development of T2D, understand the natural history of the disease, identify targets for therapy, and evaluate interventions. Current evidence indicates that no single animal model replicates the development of human T2D in all of its details. Nonetheless, the existing models (e.g., naturally occurring and genetically modified rodents, cats, pigs, and nonhuman primates) offer researchers a rich array of opportunities to investigate the myriad complexities of T2D. The individual contributions comprising this issue of ILAR Journal review the research that has been conducted on many of these animals.

HPA and immune axes in stress: involvement of the serotonergic system

Chronic stress, by initiating changes in the hypothalamic-pituitary-adrenal axis and the immune system, acts as a trigger for anxiety and depression. There is experimental and clinical evidence that the rise in the concentration of pro-inflammatory cytokines and glucocorticoids, which occurs in a chronically stressful situation and also in depression, contributes to the behavioural changes associated with depression. A defect in serotonergic function is associated with these hormonal and immune changes. Neurodegenerative changes in the hippocampus, prefrontal cortex and amygdalae are the frequent outcomes of the changes in the hypothalamic-pituitary-adrenal axis and the immune system. Such changes may provide evidence for the link between chronic depression and dementia in later life.

Effects of Tai Chi and resistance training on cardiovascular risk factors in elderly Chinese subjects: a 12-month longitudinal, randomized, controlled intervention study

BACKGROUND

Tai Chi is rapidly gaining in popularity, worldwide. This study was performed to assess its impact on cardiovascular risk factors in comparison with resistance training exercises in elderly Chinese subjects.

METHODS

A total of 207 healthy elderly participants (65-74 years, 113/207 (55%) men) were randomly assigned to one of three intervention groups: (1) Tai Chi, three times/week for 1 h/session (n = 64); (2) resistance training exercise, three times/week for 1 h/session (n = 65); (3) usual level of physical activity control group (n = 78). Anthropometric measures, dual X-ray densitometry body composition, blood pressure, lipids, glycaemic and insulin sensitivity indices were measured at baseline and 12 months. Repeated-measures analysis of variance (anova) was used to assess the between-group changes using a last-observation-carried-forward intention-to-treat approach.

RESULTS

A total of 180 (87.0%) subjects completed the study. No significant changes were identified in the Tai Chi group compared to the resistance training or control group. Of the primary outcomes, only the improvement in the insulin sensitivity index differed, being significantly greater in the resistance training than in the control group [mean difference 0.018 (95% confidence interval ( CI) 0.000-0.037) mmol glucose/min, P = 0.02), and tending to be greater than in the Tai Chi group (mean difference 0.019 (95% CI 0.000-0.038) mmol glucose/min, P < 0.06).

CONCLUSION

Tai Chi had no significant effect on any measure compared to the controls, whereas resistance training improved the insulin sensitivity index in this 12-month study.

Relationship of non-alcoholic hepatic steatosis to cortisol secretion in diet-controlled Type 2 diabetic patients

AIMS

To examine the association of non-alcoholic hepatic steatosis (HS) with the activity of the hypothalamo-pituitary-adrenal (HPA) axis in Type 2 diabetic individuals.

METHODS

The activity of the HPA axis, as measured by 24-h urinary free cortisol (UFC) excretion and serum cortisol levels after 1.0 mg dexamethasone, was measured in 40 diet-controlled, predominantly overweight, Type 2 diabetic patients with non-alcoholic HS and in 40 diabetic patients without HS who were comparable for age, sex and body mass index (BMI).

RESULTS

Subjects with non-alcoholic HS had significantly higher 24-h UFC excretion (191 +/- 4 vs. 102 +/- 3 nmol/24 h; P < 0.001) and post-dexamethasone cortisol concentrations (29.1 +/- 2 vs. 14.4 +/- 1 nmol/l; P < 0.001) than those without HS. Patients with HS had significantly higher values for HOMA insulin resistance score, plasma triglycerides and liver enzymes. Age, sex, BMI, waist-hip ratio (WHR), diabetes duration, HbA1c, LDL-cholesterol and blood pressure values were not different between the groups. The differences in urinary and serum cortisol concentrations between the groups remained significant after adjustment for age, sex, BMI, WHR, HOMA insulin resistance score, plasma triglycerides, HbA1c and liver enzymes. In multiple logistic regression analyses, 24-h UFC or serum cortisol concentrations (P < 0.05 and P = 0.02, respectively), along with age and HOMA insulin resistance, predicted the presence of HS, independently of potential confounders.

CONCLUSIONS

These results demonstrate that non-alcoholic HS is closely associated with a subtle, chronic overactivity of the HPA axis in diet-controlled Type 2 diabetic individuals.

Cortisol, Testosterone, and Coronary Heart Disease

Background— There is a popular belief that chronic stress causes heart disease through psychoneuroendocrine mechanisms. We have examined whether an elevated circulating cortisol-to-testosterone ratio increases the risk of ischemic heart disease.

Methods and Results— We undertook a prospective cohort study of 2512 men aged 45 to 59 years between 1979 and 1983 from Caerphilly, South Wales, with a mean follow-up of 16.5 years. Subjects underwent a clinical examination, and morning fasting blood samples were taken for analysis of cortisol levels, testosterone levels, and other cardiovascular risk factors. The ratio of cortisol to testosterone showed weak associations with potential confounding factors but strong positive associations with components of the insulin resistance syndrome ( P <0.001). A positive linear trend was seen across quintiles of cortisol:testosterone ratio for incident ischemic heart disease (age-adjusted OR per z score change in ratio 1.22, 95% CI 1.07 to 1.38, P =0.003). This was markedly attenuated after adjustment for components of the insulin resistance syndrome (age-adjusted OR per z score change in ratio 1.10, 95% CI 0.96 to 1.25, P =0.18). There was no association between the cortisol:testosterone ratio and other causes of death (age-adjusted hazard ratio 0.99, 95% CI 0.88 to 1.11, P =0.81).

Conclusions— This is the first population-based prospective study that has found a specific association between cortisol:testosterone ratio and incident ischemic heart disease, apparently mediated through the insulin resistance syndrome. Whether this reflects the effects of chronic stress, behavioral factors, or genetic influences remains to be determined.

Biological underpinnings of health alterations in women with PTSD: a sex disparity

Women develop posttraumatic stress disorder (PTSD) at twice the rate of men, even though fewer women than men experience traumatic events over their lifetimes. Current studies of individuals with PTSD provide evidence of alterations in the neuroendocrine system that involve levels and activity of cortisol and DHEA and changes in immune function that predispose these individuals toward an innate (Th1) immune response. Yet few studies have addressed the possible role of these biologic alterations in women's increased vulnerability to developing PTSD. In addition, current studies are limited in their ability to link biologic alterations to the observed fourfold increase in medical conditions in women with PTSD as compared to women without PTSD. And finally, few studies have addressed the biologic impact of co-occurring major depressive disorder (MDD) in individuals with PTSD. This critical review provides an update on neuroendocrine and immune perturbations associated with PTSD with and without co-occurring MDD to suggest links to health and possible mechanisms underlying the observed sex disparity in the development of PTSD.

Molecular endocrinology and physiology of the aging central nervous system

Aging is associated with a progressive decline in physical and cognitive functions. The impact of age-dependent endocrine changes regulated by the central nervous system on the dynamics of neuronal behavior, neurodegeneration, cognition, biological rhythms, sexual behavior, and metabolism are reviewed. We also briefly review how functional deficits associated with increases in glucocorticoids and cytokines and declining production of sex steroids, GH, and IGF are likely exacerbated by age-dependent molecular misreading and alterations in components of signal transduction pathways and transcription factors.

Natural killer cell activity and sensitivity to positive and negative modulation in uncomplicated obese subjects: relationships to leptin and diet composition

BACKGROUND

Natural killer (NK) cells are a key component of innate immunity; their activity is modulated by cytokines and hormones and is influenced by diet. In obesity, a higher risk of cancer and infections has been demonstrated. Studies on NK cell activity have yielded inconsistent results; NK cell sensitivity to modulators has not been assessed before.

OBJECTIVE

In this case-control study, we assessed both spontaneous NK cell activity and responsiveness to positive (interleukin (IL)-2) and negative (cortisol) modulators in uncomplicated obesity; we searched for correlations between NK cell activity and anthropometric, dietary and metabolic variables.

METHODS

In all, 21 obese (six males/15 females) and 21 age- and sex-matched healthy nonobese subjects underwent clinical examination and dietary and laboratory analyses. Spontaneous and modulated NK activities of peripheral blood mononuclear cells were measured by enzyme-release cytotoxicity assay.

RESULTS

Spontaneous NK cell activity was not different in obese subjects vs controls. IL-2 stimulated and cortisol inhibited NK cell activity in both populations. Cortisol-dependent inhibition was lower in the obese than in the control group (-24.4+/-2.9 vs -38.6+/-3.3%, P=0.002), but decreased sensitivity was restricted to women (P=0.0007). In obese subjects, cortisol-dependent inhibition negatively correlated with serum leptin levels (r=-0.54, P=0.02) and, in women, with body mass index (r=-0.63, P=0.01); IL-2-dependent stimulation positively correlated with dietary carbohydrates (r=0.61, P=0.005) and serum LDL levels (r=0.55, P=0.009) and negatively correlated with dietary lipids (r=-0.71, P=0.0006).

CONCLUSION

Spontaneous and IL-2-inducible NK cell activity is normal in uncomplicated obesity. Sensitivity to IL-2 correlates with fat and carbohydrate intake. Sensitivity to glucocorticoids negatively correlates with serum leptin levels and is significantly diminished in obese women, in whom it correlates with body mass index.