Decreased glucose tolerance and plasma adiponectin:resistin ratio in a mouse model of post-traumatic stress disorder

Sexual dimorphism modulates metabolic and cognitive alterations under HFD nutrition and chronic stress exposure in mice. Correlation between spatial memory impairment and BDNF mRNA expression in hippocampus and spleen

AIMS

The accumulated evidence suggests that lifestyle - specifically dietary habits and stress exposure - plays a detrimental role in health. The purpose of the present study was to analyze the interplay of stress, diet, and sex in metabolic and cognitive alterations.

MAIN METHODS

For this purpose, one-month-old C57Bl/6J mice were fed with a standard diet or high-fat diet (HFD). After eight weeks, one subgroup of mice from each respective diet was exposed to 20 weeks of chronic mild stress (CMS), whilst the others were left undisturbed.

KEY FINDINGS

After 28 weeks of HFD feeding, mice from both sexes were overweight, with an increase in caloric intake and abdominal and subcutaneous fat pads. Stress exposure induced a decrease in body weight, related to a decrease in caloric efficiency in both males and females. Results indicate that males are more susceptible than the females in modulating metabolic and cognitive functions under HFD and CMS. Although both sexes demonstrated HFD-induced weight gain, fat accumulation, insulin resistance, high cholesterol, only males exposed to CMS but not females have (i) impaired glucose tolerance with higher glucose level; (ii) significant prolonged latency in Barnes test, suggesting cognitive impairment; (iii) increased IFN-gamma expression in hippocampus, suggesting greater neuroinflammatory response; (iv) poorer cognitive performance related to a decrease in hippocampal and spleen BDNF mRNA expression.

SIGNIFICANCE

The main finding in this study is the presence of a sexual dimorphism in modulating metabolic and cognitive functions under HFD and CMS, showing males are more susceptible than females. In addition, poorer cognitive performance was related to a decrease in hippocampal BDNF mRNA expression. Interestingly, these changes were observed in the spleen as well.

The metabolic stress response: Adaptation to acute-, repeated- and chronic challenges in mice

There is a strong relationship between stress and metabolism. Because acute traumatic- and chronic stress events are often accompanied with metabolic pathophysiology, it is important to understand the details of the metabolic stress response. In this study we directly compared metabolic effects of acute stress with chronic repeated- and chronic unpredictable stress in mouse models. All types of adversities increased energy expenditure, chronic stress exposure decreased body weight gain, locomotor activity and differentially affected fuel utilization. During chronic exposure to variable stressors, carbohydrates were the predominant fuels, whereas fatty acids were catabolized in acutely and repeatedly restrained animals. Chronic exposure to variable stressors in unpredictable manner provoked anxiety. Our data highlight differences in metabolic responses to acute- repeated- and chronic stressors, which might affect coping behavior and underlie stress-induced metabolic and psychopathologies.

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All forms of stress exposure increase energy expenditure and resting metabolic rate

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Increased energy expenditure is fueled in challenge-specific manner

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Acute restraint increases, chronic stress decreases locomotor activity

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Chronic variable stress, but not repeated restraint provokes anxiety/depression

Social isolation alters hypothalamic pituitary adrenal axis activity after chronic variable stress in male C57BL/6 mice

The chronic variable stress (CVS) paradigm is frequently used to model the changes in hypothalamic pituitary adrenal (HPA) axis function characteristic of many stress-related diseases. However, male C57BL/6 mice are typically resistant to CVS's effects, making it difficult to determine how chronic stress exposure may alter acute HPA function and regulation in these mice. As social support in rodents can profoundly influence physiological and behavioral processes, including the HPA axis, we sought to characterize the effects of CVS exposure on basal and acute stress-induced HPA axis function in pair- and single-housed adult male mice. Despite all subjects exhibiting decreased body weight gain after six weeks of CVS, the corticosterone response to a novel, acute restraint stressor was enhanced by CVS exclusively in single-housed males. CVS also significantly increased arginine vasopressin (AVP) mRNA in the hypothalamic paraventricular nucleus (PVN) in single-housed males only. Moreover, in single-, but not pair-housed mice, CVS attenuated decreases in circulating OT found following acute restraint. Only the effect of CVS to elevate PVN corticotropin releasing hormone (CRH) mRNA levels after an acute stressor was restricted to pair-housed mice. Collectively, our findings suggest that social isolation reveals effects of CVS on the HPA axis in male C57BL/6 mice.

Systemic TNF-α blockade attenuates anxiety and depressive-like behaviors in db/db mice through downregulation of inflammatory signaling in peripheral immune cells

Research studies have indicated that the comorbidity burden of mood disorders and obesity is reasonably high. Insulin signaling has been shown to modulate multiple physiological functions in the brain, indicating its association with neuropsychiatric diseases, including mood disorders. Leptin is a hormone responsible for regulating body weight and insulin homeostasis. Previous studies on db/db mice (a mouse model that carries a spontaneous genetic mutation in leptin receptor Lepr^db) have shown that they exhibit inflammation as well as neurobehavioral traits associated with mood. Therefore, targeting inflammatory pathways such as TNF-α may be an effective strategy in the treatment of obesity-linked mood disorders. The objective of this study was to investigate the effect of long-term administration of etanercept (a TNF-α blocker) on anxiety and depressive-like behaviors in db/db mice. This was performed using light/dark box, forced swim, and open field tests with lean littermate wild type (WT) mice serving as a control group. Using flow cytometry in peripheral blood, we further examined the molecular effects of etanercept on NF-κB p65, TNF-α, IL-17A, and TLR-4 expressing CD4+, CD8+, and CD14+ cells in the peripheral blood. Our data show that peripheral administration of etanercept decreased these cells in db/db mice. Furthermore, our results indicated that peripheral administration of etanercept reduced anxiety and depressive-like behaviors. Therefore, targeting TNF-α signaling might be an effective strategy for modulating obesity-associated depression and anxiety.

Morus alba L. Diminishes visceral adiposity, insulin resistance, behavioral alterations via regulation of gene expression of leptin, resistin and adiponectin in rats fed a high-cholesterol diet

Ethanolic extract of leaves of Morus alba L. (M. alba), known as white mulberry, was orally administered (100 mg/kg b.wt) for 8 weeks to female Wistar rats that were fed a high-cholesterol diet (HCD), to investigate the potential of M. alba leaves in attenuation of obesity, dyslipidemia, insulin resistance, and deficits in mood, cognitive as well as motor activity that are linked to the adipokines secretions of visceral adipose tissue. Results showed that M. alba diminished body weight gain, hypercholesterolemia, hypertriglyceridemia, atherogenic (AI) & coronary artery indices (CRI), and ameliorated glucose level and insulin resistance index in rats on HCD, compared with untreated HCD rats. Moreover, M. alba administration significantly decreased serum leptin and resistin contents as well as their mRNA expression in visceral adipose tissue, but significantly increased serum adiponectin level, and its mRNA expression in visceral adipose tissue in rats fed on HCD, compared to those in untreated HCD group. Regarding behavioral alterations, M. alba attenuated motor deficit, declined memory, depression and anxiety-like behavior, as well in rats on HCD, compared to that noticed in untreated HCD rats. The current data showed that serum leptin and resistin showed a positive correlation with and body weight gain, triglycerides (TG), AI as well as CRI, but showed a negative correlation with exploration, declined memory, depression- and anxiety-like behavior. Conversely, serum adiponectin showed a negative correlation with and body weight gain, TG, AI as well as CRI, but showed a positive correlation with locomotor activity, exploration, declined memory, and depression- and anxiety-like behavior. In conclusion, M. alba leaves supplementation could attenuate adiposity, insulin resistance behavioral deficits via down-regulation of regulation of gene expression of leptin, resistin, but up-regulation of adiponectin gene expression in the visceral adipose tissue of rats fed a high-cholesterol diet.

Interplays of estrogen receptor alpha gene rs2234693 with post-traumatic stress disorder influence serum glucose and lipids profiles in Chinese adolescents

Both post-traumatic stress disorder (PTSD) and estrogen receptor alpha (ESR1) gene rs2234693 were reported to influence serum glucose and lipids profiles. However, their interactions on serum glucose and lipids profiles have not been reported. A total of 708 Chinese Han high school students were recruited at 6th months after the 2008 Wenchuan Earthquake. Serum concentrations of fasting blood glucose (FBG), fasting blood insulin (FBI), total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) were detected. Body mass index (BMI) and homeostatic model assessment of insulin resistance (HOMA-IR) were calculated. PTSD was assessed by the PTSD Checklist Civilian Version (PCL-C). Variants of ESR1 rs2234693 was analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analyses and verified by DNA sequencing. The male subjects with PTSD had a trend of higher FBG (p = 0.077) and significantly higher FBI and HOMA-IR than male controls. The PTSD subjects had significantly higher levels of FBG, FBI, HOMA-IR and HDL-C than the controls only in the male C allele carriers irrespective of adjustment for age and BMI. In the male controls group, the C allele carriers had significantly lower HDL-C than the TT homozygotes regardless of adjustment for age and BMI. In female PTSD group, the C allele carriers had significantly higher TC/HDL-C and LDL-C/HDL-C than the TT homozygotes after adjustment for age and BMI. These results suggest the interplays of ESR1 rs2234693 with PTSD influence serum glucose and lipids profiles with a gender dependent manner.

FGF21 regulates insulin sensitivity following long-term chronic stress

Objective

Post-traumatic stress disorder (PTSD) increases type 2 diabetes risk, yet the underlying mechanisms are unclear. We investigated how early-life exposure to chronic stress affects long-term insulin sensitivity.

Methods

C57Bl/6J mice were exposed to chronic variable stress for 15 days (Cvs) and then recovered for three months without stress (Cvs3m).

Results

Cvs mice showed markedly increased plasma corticosterone and hepatic insulin resistance. Cvs3m mice exhibited improved whole-body insulin sensitivity along with enhanced adipose glucose uptake and skeletal muscle mitochondrial function and fatty acid oxidation. Plasma FGF21 levels were substantially increased and associated with expression of genes involved in fatty acid oxidation and formation of brown-like adipocytes. In humans, serum FGF21 levels were associated with stress coping long time after the exposure.

Conclusions

Early-life exposure to chronic stress leads to long term improvements in insulin sensitivity, oxidative metabolism and adipose tissue remodeling. FGF21 contributes to a physiological memory mechanism to maintain metabolic homeostasis.

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Early-life exposure of mice to stress (CVS) causes acute insulin resistance but improves long-term insulin sensitivity.

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3 months after stress, mice had enhanced adipose glucose uptake and higher skeletal muscle mitochondrial function.

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Plasma FGF21 and gene expression for formation of brown-like adipocytes were substantially increased long after stress.

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In humans, serum FGF21 levels were associated with the ability to cope with stress long time after the exposure.

Decreased plasma adiponectin among male firefighters with symptoms of post-traumatic stress disorder

BACKGROUND

Recent studies have reported that adiponectin-mediated neuromolecular pathways are involved in fear extinction, implying that adiponectin may be an important biological marker for posttraumatic stress disorder (PTSD). However, no study has investigated the association between adiponectin and patients with PTSD.

METHODS

We examined plasma adiponectin levels, high-sensitivity C-reactive protein (hs-CRP), and psychopathological factors using the Korean version of the Impact Event Scale-Revised (IES-R-K) and the Center for Epidemiologic Studies Depression Scale in 507 male firefighters. The PTSD symptom group was defined as those with a score of 25 or higher on the IES-R-K. Multiple logistic regression analysis was conducted to examine the covariates for the PTSD symptom group.

RESULTS

Out of 507 male firefighters, 139 (27.4%) had a score of 25 or more on the IES-R-K. The PTSD symptom group had lower plasma adiponectin levels than the controls. There was an inverse correlation between plasma adiponectin levels and PTSD severity. There was no correlation between adiponectin levels and depression. The adiponectin level was associated with the presence of PTSD symptom (odds ratio = 0.955, 95% CI = 0.920-0.991).

LIMITATIONS

A cross-sectional design and using self-rated instruments.

CONCLUSIONS

To the best of our knowledge, the results showed that decreased adiponectin-mediated activity is associated with PTSD. Future studies are necessary to identify the causative role of adiponectin for PTSD as well as any possible covariates.

Phosphodiesterase-1b (Pde1b) knockout mice are resistant to forced swim and tail suspension induced immobility and show upregulation of Pde10a

RATIONALE

Major depressive disorder is a leading cause of suicide and disability. Despite this, current antidepressants provide insufficient efficacy in more than 60% of patients. Most current antidepressants are presynaptic reuptake inhibitors; postsynaptic signal regulation has not received as much attention as potential treatment targets.

OBJECTIVES

We examined the effects of disruption of the postsynaptic cyclic nucleotide hydrolyzing enzyme, phosphodiesterase (PDE) 1b, on depressive-like behavior and the effects on PDE1B protein in wild-type (WT) mice following stress.

METHODS

Littermate knockout (KO) and WT mice were tested in locomotor activity, tail suspension (TST), and forced swim tests (FST). FST was also used to compare the effects of two antidepressants, fluoxetine and bupropion, in KO versus WT mice. Messenger RNA (mRNA) expression changes were also determined. WT mice underwent acute or chronic stress and markers of stress and PDE1B expression were examined.

RESULTS

Pde1b KO mice exhibited decreased TST and FST immobility. When treated with antidepressants, both WT and KO mice showed decreased FST immobility and the effect was additive in KO mice. Mice lacking Pde1b had increased striatal Pde10a mRNA expression. In WT mice, acute and chronic stress upregulated PDE1B expression while PDE10A expression was downregulated after chronic but not acute stress.

CONCLUSIONS

PDE1B is a potential therapeutic target for depression treatment because of the antidepressant-like phenotype seen in Pde1b KO mice.

Resistin's, obesity and insulin resistance: the continuing disconnect between rodents and humans

PURPOSE

This review aimed to discuss the conflicting findings from resistin research in rodents and humans as well as recent advances in our understanding of resistin's role in obesity and insulin resistance.

METHODS

A comprehensive review and synthesis of resistin's role in obesity and insulin resistance as well as conflicting findings from resistin research in rodents and humans.

RESULTS

In rodents, resistin is increased in high-fat/high-carbohydrate-fed, obese states characterized by impaired glucose uptake and insulin sensitivity. Resistin plays a causative role in the development of insulin resistance in rodents via 5' AMP-activated protein kinase (AMPK)-dependent and AMPK-independent suppressor of cytokine signaling-3 (SOCS-3) signaling. In contrast to rodents, human resistin is primarily secreted by peripheral-blood mononuclear cells (PBMCs) as opposed to white adipocytes. Circulating resistin levels have been positively associated with central/visceral obesity (but not BMI) as well as insulin resistance, while other studies show no such association. Human resistin has a role in pro-inflammatory processes that have been conclusively associated with obesity and insulin resistance. PBMCs, as well as vascular cells, have been identified as the primary targets of resistin's pro-inflammatory activity via nuclear factor-κB (NF-κB, p50/p65) and other signaling pathways.

CONCLUSION

Mounting evidence reveals a continuing disconnect between resistin's role in rodents and humans due to significant differences between these two species with respect to resistin's gene and protein structure, differential gene regulation, tissue-specific distribution, and insulin resistance induction as well as a paucity of evidence regarding the resistin receptor and downstream signaling mechanisms of action.

Stress- and PTSD-associated obesity and metabolic dysfunction: a growing problem requiring further research and novel treatments

Posttraumatic stress disorder (PTSD) is a growing public health concern. More recently, evidence has indicated that PTSD leads to obesity and associated metabolic dysfunction. Possible mechanisms of this link are through dysfunction of the hypothalamic-pituitary-adrenal axis and related moderation of appetite hormones and neural activity, leading to changes in consumptive behaviors. Although research has been examining associations between PTSD and obesity, diabetes, cardiovascular disease, and metabolic syndrome, future research should delineate potential mechanisms for these associations and develop targeted treatments to reduce these metabolic outcomes.

Hyperinsulinemic response to oral glucose challenge in individuals with posttraumatic stress disorder

BACKGROUND

Posttraumatic stress disorder (PTSD) is associated with a 2-4 fold increased risk of developing Type 2 diabetes mellitus. However, detailed assessments of glucose metabolism and insulin secretion in a study designed to minimize confounders are lacking. Furthermore, few studies examine potential mechanisms involved. We analyzed data from a case-control study of medically healthy, medication-free adults to determine whether individuals with PTSD had abnormal glucose or insulin response to oral glucose tolerance test (OGTT) compared to controls. Secondarily, we assessed potential mediators such as sleep, cortisol and adiponectin.

METHODS

Data was analyzed from 92 age and gender-matched subjects (44 PTSD, 48 controls). Chronic PTSD was diagnosed using the Structured Clinical Interview for DSM-IV and Clinician Administered PTSD Scale. Subjects underwent 75-g OGTT, actigraphy and sleep diary (to quantify sleep duration), polysomnography (to assess slow wave sleep [SWS] and delta power), and overnight blood sampling (for cortisol and adiponectin).

RESULTS

At baseline, individuals with PTSD had mildly increased insulin levels (by 19%, compared to controls, p=0.048) that was mediated primarily by weight. In response to OGTT, the PTSD group had higher levels of insulin at 120 min (by 44%, p=0.03) and insulin AUC (by 43%, p=0.015) compared to controls, after adjusting for confounders. Glucose levels were similar in the two groups. Although self-reported sleep duration, SWS, and delta power differed between PTSD subjects and controls, they did not mediate the effects of PTSD status on insulin response.

CONCLUSION

In this case-control study, individuals with PTSD had a hyperinsulinemic response to oral glucose challenge compared to controls, suggestive of insulin resistance.

Unique genetic loci identified for emotional behavior in control and chronic stress conditions

An individual's genetic background affects their emotional behavior and response to stress. Although studies have been conducted to identify genetic predictors for emotional behavior or stress response, it remains unknown how prior stress history alters the interaction between an individual's genome and their emotional behavior. Therefore, the purpose of this study is to identify chromosomal regions that affect emotional behavior and are sensitive to stress exposure. We utilized the BXD behavioral genetics mouse model to identify chromosomal regions that predict fear learning and emotional behavior following exposure to a control or chronic stress environment. 62 BXD recombinant inbred strains and C57BL/6 and DBA/2 parental strains underwent behavioral testing including a classical fear conditioning paradigm and the elevated plus maze. Distinct quantitative trait loci (QTLs) were identified for emotional learning, anxiety and locomotion in control and chronic stress populations. Candidate genes, including those with already known functions in learning and stress were found to reside within the identified QTLs. Our data suggest that chronic stress history reveals novel genetic predictors of emotional behavior.

Impaired glucose tolerance in rats fed low-carbohydrate, high-fat diets

Moderate low-carbohydrate/high-fat (LC-HF) diets are widely used to induce weight loss in overweight subjects, whereas extreme ketogenic LC-HF diets are used to treat neurological disorders like pediatric epilepsy. Usage of LC-HF diets for improvement of glucose metabolism is highly controversial; some studies suggest that LC-HF diets ameliorate glucose tolerance, whereas other investigations could not identify positive effects of these diets or reported impaired insulin sensitivity. Here, we investigate the effects of LC-HF diets on glucose and insulin metabolism in a well-characterized animal model. Male rats were fed isoenergetic or hypocaloric amounts of standard control diet, a high-protein "Atkins-style" LC-HF diet, or a low-protein, ketogenic, LC-HF diet. Both LC-HF diets induced lower fasting glucose and insulin levels associated with lower pancreatic β-cell volumes. However, dynamic challenge tests (oral and intraperitoneal glucose tolerance tests, insulin-tolerance tests, and hyperinsulinemic euglycemic clamps) revealed that LC-HF pair-fed rats exhibited impaired glucose tolerance and impaired hepatic and peripheral tissue insulin sensitivity, the latter potentially being mediated by elevated intramyocellular lipids. Adjusting visceral fat mass in LC-HF groups to that of controls by reducing the intake of LC-HF diets to 80% of the pair-fed groups did not prevent glucose intolerance. Taken together, these data show that lack of dietary carbohydrates leads to glucose intolerance and insulin resistance in rats despite causing a reduction in fasting glucose and insulin concentrations. Our results argue against a beneficial effect of LC-HF diets on glucose and insulin metabolism, at least under physiological conditions. Therefore, use of LC-HF diets for weight loss or other therapeutic purposes should be balanced against potentially harmful metabolic side effects.

Rosiglitazone treatment reversed depression- but not psychosis-like behavior of db/db diabetic mice

The objective of the present study was to examine the effect of long-term management of insulin resistance and hyperglycemia on neurobehavioral deficits in db/db mice. In this study, 5-week-old db/db and lean control mice were fed with rosiglitazone (20 mg/kg/day) mixed or standard chow for a duration of 5 weeks. Mice were monitored weekly for blood glucose concentration. Five weeks after the onset of treatment, they were subjected to the forced swim test (FST), pre-pulse inhibition (PPI), open field test (OFT) and fear-potentiated startle (FPS) test to examine for depression, psychosis-like behavior, locomotor activity and emotional learning, respectively. Rosiglitazone normalized hyperglycemia and improved glucose tolerance. Rosiglitazone significantly reduced immobility time in the FST in db/db mice, suggesting an antidepressant-like effect. However, rosiglitazone failed to reverse disruption of PPI in db/db mice, indicating its ineffectiveness against psychosis-like behavior. In the OFT, rosiglitazone did not affect the activity of db/db mice, suggesting its antidepressant-like effect was independent of changes in locomotor activity. In the FPS test, db/db mice showed impaired emotional learning and rosiglitazone failed to correct it. In conclusion, long-term blood glucose management in type-2 diabetics may help to limit the co-occurrence of depression but not the psychotic symptoms and ability to cope with stress.

Novel adiponectin-resistin (AR) and insulin resistance (IRAR) indexes are useful integrated diagnostic biomarkers for insulin resistance, type 2 diabetes and metabolic syndrome: a case control study

Background

Adiponectin and resistin are adipokines which modulate insulin action, energy, glucose and lipid homeostasis. Meta-analyses showed that hypoadiponectinemia and hyperresistinemia are strongly associated with increased risk of insulin resistance, type 2 diabetes (T2DM), metabolic syndrome (MS) and cardiovascular disease. The aim of this study was to propose a novel adiponectin-resistin (AR) index by taking into account both adiponectin and resistin levels to povide a better indicator of the metabolic homeostasis and metabolic disorders. In addition, a novel insulin resistance (IR_AR) index was proposed by integration of the AR index into an existing insulin resistance index to provide an improved diagnostic biomarker of insulin sensitivity.

Methods

In this case control study, anthropometric clinical and metabolic parameters including fasting serum total adiponectin and resistin levels were determined in 809 Malaysian men (208 controls, 174 MS without T2DM, 171 T2DM without MS, 256 T2DM with MS) whose ages ranged between 40-70 years old. Significant differences in continuous variables among subject groups were confirmed by ANCOVA or MANCOVA test using 1,000 stratified bootstrap samples with bias corrected and accelerated (BCa) 95% CI. Spearman's rho rank correlation test was used to test the correlation between two variables.

Results

The AR index was formulated as 1+log₁₀(R₀)-log₁₀(A₀). The AR index was more strongly associated with increased risk of T2DM and MS than hypoadiponectinemia and hyperresistinemia alone. The AR index was more strongly correlated with the insulin resistance indexes and key metabolic endpoints of T2DM and MS than adiponectin and resistin levels alone. The AR index was also correlated with a higher number of MS components than adiponectin and resistin levels alone. The IR_AR index was formulated as log₁₀(I₀G₀)+log₁₀(I₀G₀)log₁₀(R₀/A₀). The normal reference range of the IR_AR index for insulin sensitive individuals was between 3.265 and 3.538. The minimum cut-off values of the IR_AR index for insulin resistance assessment were between 3.538 and 3.955.

Conclusions

The novel AR and IR_AR indexes are cost-effective, precise, reproducible and reliable integrated diagnostic biomarkers of insulin sensitivity for screening subjects with increased risk of future development of T2DM and MS.