Insulin resistance syndrome predicts coronary heart disease events in elderly nondiabetic men

Association of food insecurity with successful aging among older Indians: study based on LASI

PURPOSE

Whether food insecurity (FI), a social determinant of health, is linked with successful aging (SA) in the older generation remains uncertain. This study explored the association of FI with SA among older Indians.

METHODS

Data were collected from the Longitudinal Ageing Study in India (LASI) wave 1 (2017-2018). Older adults (≥ 60 years) who completed both the FI and the SA surveys were selected. FI was indicated by the lack of access to enough food in the past year. SA was determined by five components: (1) low probability of diseases; (2) low probability of disability; (3) high cognitive functionality; (4) low probability of depression; and (5) active social engagement. The association of FI and SA was assessed using multivariable logistic regression adjusted for potential covariates. Subgroup analyses were performed to evaluate interactions with age, sex, alcohol use, smoking, and place of residence.

RESULTS

27,579 participants met the eligibility criteria. Overall prevalence was 7.13% for FI and 19.41% for SA. Following full adjustment, FI was inversely associated with SA (OR 0.56; 95% CI 0.49-0.65) and with each of SA's five components. No significant interactions of FI and SA were observed in subgroup analyses stratified by age, sex, alcohol use, smoking, or place of residence.

CONCLUSIONS

FI was inversely associated with SA among older Indians. These findings need to be validated by future studies which should also explore potential underlying mechanisms, and whether interventions decreasing FI might increase SA.

Hyperinsulinemia and plasma glucose level independently associated with all-cause and cardiovascular mortality in Chinese people without diabetes-A post-hoc analysis of the 30-year follow-up of Da Qing diabetes and IGT study

AIMS

We aimed to characterize the effect of insulin resistance and plasma glucose on all-cause and cardiovascular disease (CVD) death.

METHODS

A total of 462 individuals without diabetes in the original Da Qing Diabetes and IGT Study were enrolled in the present analysis, and further divided into G1 (low insulin low glucose), G2 (high insulin low glucose), G3 (low insulin high glucose) and G4 (high insulin high glucose) groups according to medians of glucose and insulin level at baseline. The all-cause and CVD death were assessed from 1986 to 2016.

RESULTS

During the 30-year follow-up, compared with G1, G2, G3, and G4 groups were all at increased death risk after adjusting covariates. G2 and G3 were associated with similar risks in both all-cause (G2: HR 1.65, 95%CI 1.02-2.67; G3: HR 1.76, 95%CI 1.11-2.81) and CVD death (G2: HR 2.03, 95%CI 1.01-4.05; G3: HR 1.85, 95%CI 0.93-3.68). The highest risk was observed in G4 (all-cause death: HR 2.32, 95%CI 1.45-3.69; CVD death: HR 2.68, 95%CI 1.35-5.29).

CONCLUSIONS

In this post-hoc study, participants with either high glucose or high insulin were related to increased risk of mortality, implying that strategies targeting eliminating both hyperglycemia and hyperinsulinemia may favor the long-term outcomes.

Insulin Resistance and Vitamin D Deficiency: A Link Beyond the Appearances

Vitamin D is a steroid hormone that plays a key role in the regulation of body homeostasis, including cardiovascular function. Although the chronic deficiency of vitamin D is associated with cardiovascular risk factors, as well as with an adverse prognosis, randomized controlled trials have failed in demonstrating that dietary vitamin D supplementation could ameliorate the prognosis of patients with cardiovascular diseases, and suggested that vitamin D deficiency is the expression of the effects of other determinants of cardiovascular risk. Thus, the supplementation of vitamin D is not sufficient to improve the cardiovascular risk profile and prognosis. Insulin resistance is a complex phenomenon that plays a key role in the pathogenesis of conventional cardiovascular risk factors. Interestingly, defects of vitamin D and insulin resistance have a superimposable epidemiological distribution. According to the common view, Insulin resistance is considered the direct or indirect consequence of vitamin D deficiency. However, it is also reasonable to speculate that the deficit or the impaired action of vitamin D, in some circumstances, could be the result of the same pathogenic mechanisms responsible of insulin resistance development. In this case, vitamin D deficiency could be considered an epiphenomenon of insulin resistance. Insulin resistance is a reversible condition, being possibly ameliorated by physical activity and hypocaloric diets. Notably, both physical exercise and energy-restricted dietary regimens are associated with an increase of vitamin D levels. These findings indicate that improving insulin resistance condition is a necessary step to ameliorate vitamin D supplementation-based strategies in cardiovascular prevention.

Modulation of insulin resistance by renin angiotensin system inhibitors: implications for cardiovascular prevention

Insulin resistance (IR) and the related hyperinsulinamia play a key role in the genesis and progression of the continuum of cardiovascular (CV) disease. Thus, it is reasonable to pursue in primary and secondary CV prevention, the pharmacological strategies that are capable to interfere with the development of IR. The renin-angiotensin-aldosterone system (RAAS) plays an important role in the pathogenesis of IR. In particular, angiotensin II (Ang II) through the generation of reactive oxygen species, induces a low grade of inflammation, which impairs the insulin signal transduction. The angiotensin converting enzyme (ACE) inhibitors are effective not only as blood pressure-lowering agents, but also as modulators of metabolic abnormalities. Indeed, experimental evidence indicates that in animal models of IR, ACE inhibitors are capable to ameliorate the insulin sensitivity. The Ang II receptor blockers (ARBs) modulate the peroxisome proliferator-activated receptor (PPAR)-γ activity. PPARâ€"γ is a transcription factor that controls the gene expression of several key enzymes of glucose metabolism. A further mechanism that accounts for the favorable metabolic properties of ARBs is the capability to modulate the hypothalamicâ€"pituitary-adrenal (HPA) axis. The available clinical evidence is consistent with the concept that both ACE inhibitors and ARBs are able to interfere with the development of IR and its consequences like type 2 diabetes. In addition, pharmacological inhibition of the RAAS has favourable effects on dyslipidaemias, metabolic syndrome and obesity. Therefore, the pharmacological antagonism of the RAAS, nowadays, represents the first choice in the prevention of cardio-metabolic diseases.

Novel biomarkers associated with incident heart failure in 10 106 Finnish men

AIMS

There are only a few studies on novel biomarkers for incident heart failure (HF). We investigated the association of multiple circulating biomarkers with incident HF in a large prospective population-based study.

METHODS AND RESULTS

Conventional risk factors and inflammatory biomarkers were measured, and systemic metabolic measures determined by a high-throughput serum nuclear magnetic resonance platform in a population-based Metabolic Syndrome in Men study including 10 106 Finnish men without HF at baseline. During an 8.8 year follow-up, 172 (1.7%) participants developed HF. Adiponectin, high-sensitivity C-reactive protein (hs-CRP), glycoprotein acetyls, alanine, phenylalanine, glycerol, and pyruvate were associated with incident HF in unadjusted Cox regression analyses, in addition to age, systolic blood pressure, body mass index (BMI), waist circumference, fasting plasma glucose and insulin, haemoglobin A1c (HbA1c), and urinary albumin excretion rate (UAER). After adjustment for age, BMI, diabetes, and statin medication, only adiponectin [hazard ratio (HR) 1.18 (1.10-1.26, P = 4.1E-08)], pyruvate [HR 1.38 (1.28-1.50, P = 8.2E-05)], and UAER [HR 1.15 (1.11-1.18, P = 7.8E-06)] remained statistically significant. In principal component analysis of biomarkers associated with HF in univariate Cox regression analysis, we identified six components, explaining 61.7% of total variance. Four principal components, one with significant loadings on waist, BMI, fasting plasma insulin, interleukin 1 receptor antagonist, and hs-CRP; another on pyruvate, glycoprotein acetyls, alanine, glycerol and HbA1c; third on age and glomerular filtration rate; and fourth on systolic blood pressure, UAER, and adiponectin, significantly associated with incident HF.

CONCLUSIONS

Several novel metabolic and inflammatory biomarkers were associated with incident HF, suggesting early activation of respective pathways in the pathogenesis of HF.

The 7-Year Change in the Prevalence of Insulin Resistance, Inflammatory Biomarkers, and Their Determinants in an Urban South African Population

BACKGROUND

Insulin resistance (IR) and subclinical inflammation are involved in pathological pathways leading to the development of biological cardiovascular risk factors and subsequent cardiovascular events. Therefore, monitoring these processes can provide advanced information on the trajectory of cardiovascular risk profile of a population and inform prevention and control strategies. We investigated changes in IR and subclinical inflammation in a population from Cape Town, South Africa, between 2008/09 and 2014/16.

METHODS

In a total of 2503 (n = 797, 2008/09) and (n = 1706, 2014/16) participants, IR was calculated using five indices, i.e., insulin fasting, HOMA-IR, QUICKI, McAuley, and Matsuda while subclinical inflammation was measured using usCRP and gamma GT. Linear and logistic regression analyses and interaction tests were conducted.

RESULTS

The mean age of participants was 53.2 (2008/09) and 48.2 (2014/16), respectively. In females, IR prevalence significantly decreased between 2008/09 and 2014/2016 by all indices (p ≤ 0.021), while subclinical inflammation prevalence increased from 54.7% (2008/09) to 57.1% (2014/16) based on usCRP and 29.6% to 33.4% based on gamma GT. In a multivariate analysis adjusted for the year of study, age, and gender, prominent factors associated with increased IR or subclinical inflammation were obesity levels measured using waist circumference, glycated haemoglobin, and fasting insulin levels.

CONCLUSIONS

Over the 7-year period, subclinical inflammation increased and this was associated with IR and the metabolic syndrome components, both of which are strong predictors of CVDs. The decrease in IR over the year period reflects in part the much younger age in the second survey.

Subclinical hypothyroidism, lipid metabolism and cardiovascular disease

Subclinical hypothyroidism is defined by elevated serum thyrotropin in presence of normal free thyroid hormones. Lipid metabolism is influenced by thyroid hormone and many reports showed that lipids status worsen along with TSH level. Subclinical hypothyroidism has been also linked to other cardiovascular risk factors such as alteration in blood pressure and increased atherosclerosis. Further evidences suggested that mild dysfunction of thyroid gland is associated with metabolic syndrome and heart failure. Thyrotropin level seems the best predictor of cardiovascular disease, in particular when its levels are above 10mU/L. However, despite these observations, there is no clear evidence that levothyroxine therapy in subjects with milder form of subclinical hypothyroidism could improve lipid status and the other cardiovascular risk factors. In this review, we address the effect of thyroid hormone and cardiovascular risk, with a focus on lipid metabolism.

An intervention to reduce sitting and increase light-intensity physical activity at work: Design and rationale of the 'Stand & Move at Work' group randomized trial

BACKGROUND

American workers spend 70-80% of their time at work being sedentary. Traditional approaches to increase moderate-vigorous physical activity (MVPA) may be perceived to be harmful to productivity. Approaches that target reductions in sedentary behavior and/or increases in standing or light-intensity physical activity [LPA] may not interfere with productivity and may be more feasible to achieve through small changes accumulated throughout the workday METHODS/DESIGN: This group randomized trial (i.e., cluster randomized trial) will test the relative efficacy of two sedentary behavior focused interventions in 24 worksites across two states (N=720 workers). The MOVE+ intervention is a multilevel individual, social, environmental, and organizational intervention targeting increases in light-intensity physical activity in the workplace. The STAND+ intervention is the MOVE+ intervention with the addition of the installation and use of sit-stand workstations to reduce sedentary behavior and enhance light-intensity physical activity opportunities. Our primary outcome will be objectively-measured changes in sedentary behavior and light-intensity physical activity over 12months, with additional process measures at 3months and longer-term sustainability outcomes at 24months. Our secondary outcomes will be a clustered cardiometabolic risk score (comprised of fasting glucose, insulin, triglycerides, HDL-cholesterol, and blood pressure), workplace productivity, and job satisfaction DISCUSSION: This study will determine the efficacy of a multi-level workplace intervention (including the use of a sit-stand workstation) to reduce sedentary behavior and increase LPA and concomitant impact on cardiometabolic health, workplace productivity, and satisfaction.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02566317 (date of registration: 10/1/2015).

Chronic administration of ethanol leaf extract of Moringa oleifera Lam. (Moringaceae) may compromise glycaemic efficacy of Sitagliptin with no significant effect in retinopathy in a diabetic rat model

ETHNOPHARMACOLOGICAL RELEVANCE

Moringa oleifera Lam. (Moringaceae) has gained awareness for its antidiabetic effect, and is used as alternative therapy or concurrently with orthodox medicines such as sitagliptin in diabetes mellitus. This is without ascertaining the possibility of drug-herb interactions, which could either lead to enhanced antidiabetic efficacy, increased toxicity, or compromised glycaemic control with negative consequence in diabetic retinopathy.

AIM OF THE STUDY

To investigate the effect, of sitagliptin (50mg/kg), Moringa oleifera (300mg/kg) leaf extract, and a combination of both on glycaemic control parameters, lenticular opacity and changes in retinal microvasculature in alloxan (150mg/kg i.p) induced diabetic rat model.

MATERIALS AND METHOD

Seven groups of eight rats per group were used, with groups I, II and VII as normal (NC), diabetic (DC) and post-prandial controls (PPC). Groups III to VI were diabetic rats on sitagliptin (III), M. oleifera (IV), sitagliptin and M. oleifera (SM) (V), for 42 days with 2 weeks delayed treatment in a post-prandial hyperglycaemic group (PPSM) (VI). Glycaemic control parameters, insulin levels, body weights, and effects of retinal microvasculature on lenticular opacity/morphology were investigated.

RESULTS

A significant decrease in fasting blood glucose (FBG) levels was displayed in SM group from day 14(60%) (p<0.01) to day 28 (38%) (p<0.01) of treatment, compared to day 1. Thereafter, a steady increase of up to 57% on day 42 compared to day 28 was observed. A significant decrease in random blood glucose (RBG) levels, were demonstrated on day 42 (24%) (p<0.001), compared to day 1. No significant difference was seen in mean serum levels of insulin across groups. No significant changes in body weights. Evidence of mild lenticular opacity was observed, with no significant effect in pathologic lesions in the retina.

CONCLUSION

The chronic co-administration of sitagliptin and M. oleifera showed a progressive decrease in anti-hyperglycaemic effect of sitagliptin, and although it delayed the onset of lenticular opacity (i.e. cataract-like changes) it did not prevent the progression nor ameliorated pathologic lesions in the retina.

Insulin resistance and cardiovascular disease

Insulin resistance is characterised by a decreased rate of insulin-mediated glucose uptake and is associated with adverse changes in cardiovascular risk factors, such as high triglyceride levels, low levels of high-density lipoprotein cholesterol, raised blood pressure, obesity and increased levels of plasminogen activator inhibitor 1. The term `insulin resistance syndrome' (IRS) is used to describe the complex of factors associated with insulin resistance that is found in patients both with and without type 2 diabetes. Although the presence of insulin resistance syndrome is generally considered to be a risk factor for cardiovascular disease, there is a lack of definitive evidence for a causal link. Recently, however, a statistical method known as factor analysis has been applied to the cluster of cardiovascular risk factors associated with IRS. This has been able to show that the `insulin resistance factor' (high plasma insulin and glucose levels, body mass index, waist-to-hip ratio and triglyceride levels) predicted coronary heart disease events in elderly non-diabetic men as well as in patients with type 2 diabetes. Therefore, treatment of insulin resistance whether by pharmacological (eg. thiazolidinediones) or nonpharmacological means has the potential to offer both improvements in glycaemic control and in cardiovascular events.

Electrophysiological basis of metabolic-syndrome-induced cardiac dysfunction

Myocardial contractility is controlled by intracellular Ca2+ cycling with the contribution of sarcoplasmic reticulum (SR). In this study, we aimed to investigate the role of altered SR function in defective regulation of intracellular Ca2+ levels in rats with metabolic syndrome (MetS) induced by a 16-week high-sucrose drinking-water diet. Electric-field stimulated transient intracellular Ca2+ changes in MetS cardiomyocytes exhibited significantly reduced amplitude (∼30%) and prolonged time courses (2-fold), as well as depressed SR Ca2+ loading (∼55%) with increased basal Ca2+ level. Consistent with these data, altered ryanodine receptor (RyR2) function and SERCA2a activity were found in MetS cardiomyocytes through Ca2+ spark measurements and caffeine application assay in a state in which sodium calcium exchanger was inhibited. Furthermore, tetracaine application assay results and hyperphosphorylated level of RyR2 also support the “leaky RyR2” hypothesis. Moreover, altered phosphorylation levels of phospholamban (PLN) support the depressed SERCA2a-activity thesis and these alterations in the phosphorylation of Ca2+-handling proteins are correlated with altered protein kinase and phosphatase activity in MetS cardiomyocytes. In conclusion, MetS-rat heart exhibits altered Ca2+ signaling largely due to altered SR function via changes in RyR2 and SERCA2a activity. These results point to RyR2 and SERCA2a as potential pharmacological targets for restoring intracellular Ca2+ homeostasis and, thereby, combatting dysfunction in MetS-rat heart.

Insulin resistance, haemostatic factors and cardiovascular risk

Increased insulin resistance, which is present in the majority of type 2 diabetics patients, is associated with other metabolic and pro-coagulant cardiovascular risk factors and may account for the accelerated atherosclerosis and increased thrombotic potential observed in these patients. In individuals with normoglycaemia or impaired glucose tolerance (IGT), hyperinsulinaemia (a marker of insulin resistance) is associated with a similar clustering of risk factors and is predictive of cardiovascular events. The origins of insulin resistance are not well understood but data from families, twins and extended pedigrees suggest significant genetic and environmental contributions. The clustering of atherogenic traits begins in childhood, carries through to adult life and may result from the multiple effects of individual genes (pleiotropy) and environmental influences. Important environmental determinants of insulin resistance may occur before birth and, in conjunction with subsequent diet and exercise habits which result in obesity, lead to increased insulin resistance and cardiovascular risk. Therefore, primary prevention should centre around lifestyle changes which increase insulin sensitivity, maintain normoglycaemia and ameliorate atherothrombotic risk factor clustering.

Propofol (Diprivan®) and Intralipid® exacerbate insulin resistance in type-2 diabetic hearts by impairing GLUT4 trafficking

BACKGROUND

The IV anesthetic, propofol, when administered as fat emulsion-based formulation (Diprivan) promotes insulin resistance, but the direct effects of propofol and its solvent, Intralipid, on cardiac insulin resistance are unknown.

METHODS

Hearts of healthy and type-2 diabetic rats (generated by fructose feeding) were aerobically perfused for 60 minutes with 10 μM propofol in the formulation of Diprivan or an equivalent concentration of its solvent Intralipid (25 μM) ± insulin (100 mU•L). Glucose uptake, glycolysis, and glycogen metabolism were measured using [H]glucose. Activation of Akt, GSK3β, AMPK, ERK1/2, p38MAPK, S6K1, JNK, protein kinase Cθ (PKCθ), and protein kinase CCβII (PKCβII) was determined using immunoblotting. GLUT4 trafficking and phosphorylations of insulin receptor substrate-1 (IRS-1) at Ser307(h312), Ser1100(h1101), and Tyr608(hTyr612) were measured. Mass spectrometry was used to determine acylcarnitines, phospholipids, and sphingolipids.

RESULTS

Diprivan and Intralipid reduced insulin-induced glucose uptake and redirected glucose to glycogen stores in diabetic hearts. Reduced glucose uptake was accompanied by lower GLUT4 trafficking to the sarcolemma. Diprivan and Intralipid inactivated GSK3β but activated AMPK and ERK1/2 in diabetic hearts. Only Diprivan increased phosphorylation of Akt(Ser473/Thr308) and translocated PKCθ and PKCβII to the sarcolemma in healthy hearts, whereas it activated S6K1 and p38MAPK and translocated PKCβII in diabetic hearts. Furthermore, only Diprivan phosphorylated IRS-1 at Ser1100(h1101) in healthy and diabetic hearts. JNK expression, phosphorylation of Ser307(h312) of IRS-1, and PKCθ expression and translocation were increased, whereas GLUT4 expression was reduced in insulin-treated diabetic hearts. Phosphatidylglycerol, phosphatidylethanolamine, and C18-sphingolipids accumulated in Diprivan-perfused and Intralipid-perfused diabetic hearts.

CONCLUSIONS

Propofol and Intralipid promote insulin resistance predominantly in type-2 diabetic hearts.

Is metabolic syndrome predictive of prevalence, extent, and risk of coronary artery disease beyond its components? Results from the multinational coronary CT angiography evaluation for clinical outcome: an international multicenter registry (CONFIRM)

Although metabolic syndrome is associated with increased risk of cardiovascular disease and events, its added prognostic value beyond its components remains unknown. This study compared the prevalence, severity of coronary artery disease (CAD), and prognosis of patients with metabolic syndrome to those with individual metabolic syndrome components. The study cohort consisted of 27125 consecutive individuals who underwent ≥64-detector row coronary CT angiography (CCTA) at 12 centers from 2003 to 2009. Metabolic syndrome was defined as per NCEP/ATP III criteria. Metabolic syndrome patients (n=690) were matched 1:1:1 to those with 1 component (n=690) and 2 components (n=690) of metabolic syndrome for age, sex, smoking status, and family history of premature CAD using propensity scoring. Major adverse cardiac events (MACE) were defined by a composite of myocardial infarction (MI), acute coronary syndrome, mortality and late target vessel revascularization. Patients with 1 component of metabolic syndrome manifested lower rates of obstructive 1-, 2-, and 3-vessel/left main disease compared to metabolic syndrome patients (9.4% vs 13.8%, 2.6% vs 4.5%, and 1.0% vs 2.3%, respectively; p<0.05), while those with 2 components did not (10.5% vs 13.8%, 2.8% vs 4.5% and 1.3% vs 2.3%, respectively; p>0.05). At 2.5 years, metabolic syndrome patients experienced a higher rate of MACE compared to patients with 1 component (4.4% vs 1.6%; p=0.002), while no difference observed compared to individuals with 2 components (4.4% vs 3.2% p=0.25) of metabolic syndrome. In conclusion, Metabolic syndrome patients have significantly greater prevalence, severity, and prognosis of CAD compared to patients with 1 but not 2 components of metabolic syndrome.

Association of IL-6 polymorphism -174G/C and metabolic syndrome in hypertensive patients

Introduction. Visceral obesity, the central core of metabolic syndrome (MetS), is conceived as the pathogenic basis of an increased cardiovascular burden and is related with changes in cytokines. We investigated whether IL-6-174G/C gene polymorphism is associated with MetS prevalence in hypertensive patients. Method. A population of hypertensive patients was included and stratified by the presence of MetS according to IDF criteria and evaluated by Framingham risk score. The IL-6-174G/C genotyping was performed by polymerase chain reaction and the prevalence of MetS was compared between “C” carrier and “non-C” carrier groups. Results. From an original sample of 664 patients, 612 (34.2% men, age 57.3 ± 10.1, 30.4% diabetics) were included. MetS was diagnosed in 51.3% of total population and “C” carriers demonstrated high prevalence of MetS (P < 0.05) and each of its components. On binary logistic regression, it was observed that the IL-6 polymorphism was independently associated with occurrence of MetS, even after adjusting for covariates (OR 1.13–2.37, 95% CI, P < 0.05). Conclusion. The C allele at the -174 locus of IL-6 gene is independently associated with the occurrence of metabolic syndrome, emphasizing the importance of inflammatory genetic background in the pathogenesis of visceral obesity and related cardiovascular burden.

Gender differences in the association between metabolic syndrome and periodontal disease: the Hisayama Study

Aims: Periodontal disease and metabolic syndrome (MS) are more prevalent in males than in females. However, whether there is a gender difference in the association between these health conditions has not yet been investigated. This study examined the gender difference in this association, considering the definition of periodontal disease.

Materials and Methods: We recruited 1040 males and 1330 females, aged ≥40 years, with at least ten teeth from subjects of the 2007 Hisayama health examination. We performed a logistic regression analysis with various definitions of periodontal disease the dependent variable and MS as the independent variable. Following the analysis, the data were reanalysed with the structural equations model.

Results: The logistic regression analysis suggested a stronger association between periodontal disease and MS in females than that in males when periodontal disease was more severely defined. When we constructed the structural equations model in each gender, the model showed a good fit to the data of females, suggesting the association between periodontal disease and MS in females, but not in males.

Conclusions: Gender differences seem to exist in the association between periodontal disease and MS; MS might show a stronger association with periodontal disease in females than in males.

Furuta M, Shimazaki Y, Takeshita T, Shibata Y, Akifusa S, Eshima N, Kiyohara Y, Ninomiya T, Hirakawa Y, Mukai N, Nagata M, Yamashita Y. Gender differences in the association between metabolic syndrome and periodontal disease: the Hisayama Study. J Clin Periodontol 2013; 40: 743–752. doi: 10.1111/jcpe.12119.

Cardiac aging and insulin resistance: could insulin/insulin-like growth factor (IGF) signaling be used as a therapeutic target?

Intrinsic cardiac aging is an independent risk factor for cardiovascular disease and is associated with structural and functional changes that impede cardiac responses to stress and to cardio-protective mechanisms. Although systemic insulin resistance and the associated risk factors exacerbate cardiac aging, cardiac-specific insulin resistance without confounding systemic alterations, could prevent cardiac aging. Thus, strategies aimed to reduce insulin/insulin-like growth factor (IGF) signaling in the heart prevent cardiac aging in lower organisms and in mammals but the mechanisms underlying this protection are not fully understood. In this review, we describe the impact of aging on the cardiovascular system and discuss the mounting evidence that reduced insulin/IGF signaling in the heart could alleviate age-associated alterations and preserve cardiac performance.

The factor structure of the metabolic syndrome in obese individuals with binge eating disorder

OBJECTIVE

Metabolic syndrome (MetS) is strongly linked with cardiovascular disease and type-II diabetes, but there has been debate over which metabolic measures constitute MetS. Obese individuals with binge eating disorder (BED) are one of the high risk populations for developing MetS due to their excess weight and maladaptive eating patterns, yet, the clustering patterns of metabolic measures have not been examined in this patient group.

METHODS

347 adults (71.8% women) were recruited for treatment studies for obese individuals with BED. We used the VARCLUS procedure in the Statistical Analysis System (SAS) to investigate the clustering pattern of metabolic risk measures.

RESULTS

The analysis yielded four factors: obesity (body-mass-index [BMI] and waist circumference), lipids (HDL and triglycerides), blood pressure (systolic and diastolic blood pressure), and glucose regulation (fasting serum glucose and Hb1Ac). The four factors accounted for 84% of the total variances, and variances explained by each factor were not substantially different. There was no inter-correlation between the four factors. Subgroup analyses by sex and by race (Caucasian vs. African American) yielded the same four-factor structure.

CONCLUSION

The factor structure of MetS in obese individuals with BED is not different from those found in normative population studies. This factor structure may be applicable to the diverse population.

Treatment with omega-3 fatty acid ethyl-ester alters fatty acid composition of lipoproteins in overweight or obese adults with insulin resistance

INTRODUCTION

The effects of dietary fatty acid supplementation on lipoprotein fatty acid composition have rarely been described.

PATIENTS AND METHODS

Sixty-one overweight and obese adults with dyslipidemia and insulin resistance were randomized to placebo, 2g/day extended-release nicotinic acid (ERN), 4g/day prescription omega-3 fatty acid ethyl ester (P-OM3), or combination therapy for 16 weeks. Lipoprotein fatty acid composition was analyzed by gas chromatography pre- and post-treatment.

RESULTS

Treatment with P-OM3 or combination, but not ERN, increased proportions of eicosapentaenoic acid, docosahexaenoic acid, and docosapentaenoic acid, and reduced those for arachidonic acid in all lipoprotein fractions, with greatest impact in the high-density lipoprotein fraction. P-OM3-induced changes in eicosapentaenoic acid within low-density lipoproteins and very low-density lipoproteins were associated with beneficial effects on mean arterial pressure and pulse pressure.

CONCLUSIONS

P-OM3 supplementation, with or without ERN, was associated with differentially altered lipoprotein fatty acid composition and improved blood pressure parameters.

Disruptions in ovarian function are related to depression and cardiometabolic risk during premenopause

OBJECTIVE

The aim of this study was to evaluate the extent to which mild disruptions in ovarian function, indexed by changes in menstrual cycle length, may relate to cardiometabolic and psychological health in premenopausal women.

METHODS

Among 804 healthy, regularly cycling women (aged 25-45 y; mean [SD] age, 35.5 [5.5] y), patterns of any change (shortening, lengthening, or increased variability) versus no change in menstrual cycle length were examined in relation to a composite of cardiometabolic risk and individual risk factors (high-density lipoprotein, triglycerides, waist circumference, glucose, and hypertensive status), as well as in relation to depression indicators (Center for Epidemiological Studies Depression Scale score ≥16 [yes/no], lifetime depression diagnosis [yes/no], and lifetime antidepressant medication use [yes/no]). Models were also explored to test whether changes in menstrual cycle length mediated relations between depression history and cardiometabolic risk.

RESULTS

In covariate-adjusted models compared with no change, any change in menstrual cycle length was associated with higher cardiometabolic risk composite scores and lower high-density lipoprotein (P < 0.05). In addition, compared with no change, any change in menstrual cycle length was associated with a Center for Epidemiological Studies Depression Scale score of 16 or higher, having received a depression diagnosis, and having used antidepressant medications (P < 0.05). In exploratory analyses, any change in menstrual cycle length partially mediated the relation between depression history and cardiometabolic risk (b = 0.152, P = 0.040), which attenuated (b = 0.129, P = 0.083) when any change in menstrual cycle length was covaried.

CONCLUSIONS

Findings suggest that disruptions in ovarian function, marked by subtle changes in menstrual cycle length, may relate to aspects of cardiometabolic and psychological health among healthy, premenopausal women.

Identification of cardiovascular risk components in urban Chinese with metabolic syndrome and application to coronary heart disease prediction: a longitudinal study

Background

Metabolic syndrome (MetS) is proposed as a predictor for cardiovascular disease (CVD). It involves the mechanisms of insulin resistance, obesity, inflammation process of atherosclerosis, and their complex relationship in the metabolic network. Therefore, more cardiovascular risk-related biomarkers within this network should be considered as components of MetS in order to improve the prediction of CVD.

Methods

Factor analysis was performed in 5311 (4574 males and 737 females) Han Chinese subjects with MetS to extract CVD-related factors with specific clinical significance from 16 biomarkers tested in routine health check-up. Logistic regression model, based on an extreme case-control design with 445 coronary heart disease (CHD) patients and 890 controls, was performed to evaluate the extracted factors used to identify CHD. Then, Cox model, based on a cohort design with 1923 subjects followed up for 5 years, was conducted to validate their predictive effects. Finally, a synthetic predictor (SP) was created by weighting each factor with their risks for CHD to develop a risk matrix to predicting CHD.

Results

Eight factors were obtained from both males and females with a similar pattern. The AUC to classify CHD under the extreme case-control suggested that SP might serve as a useful tool in identifying CHD with 0.994 (95%CI 0.984-0.998) for males and 0.998 (95%CI 0.982-1.000) for females respectively. In the cohort study, the AUC to predict CHD was 0.871 (95%CI 0.851-0.889) for males and 0.899 (95%CI 0.873-0.921) for females, highlighting that SP was a powerful predictor for CHD. The SP-based 5-year CHD risk matrix provided as convenient tool for CHD risk appraisal.

Conclusions

Eight factors were extracted from sixteen biomarkers in subjects with MetS and the SP adds to new insights into studies of prediction of CHD risk using data from routine health check-up.

Fasting insulin concentrations and incidence of hypertension, stroke, and coronary heart disease: a meta-analysis of prospective cohort studies

BACKGROUND

Insulin resistance is a precursor of numerous chronic diseases, including cardiovascular disease (CVD). The fasting insulin concentration is considered a reasonable surrogate of insulin resistance, especially among nondiabetic individuals.

OBJECTIVE

We aimed to quantitatively summarize the literature on the association of fasting insulin concentrations with risk of hypertension, stroke, and coronary heart disease (CHD) by conducting a meta-analysis of prospective cohort studies.

DESIGN

Eligible studies were identified by searching PubMed and EMBASE through January 2013. Additional information was retrieved through Google Scholar or a hand review of the reference lists from relevant articles. Prospective cohort studies that reported RRs and corresponding 95% CIs for the association of interest were identified. Data were extracted independently by 2 investigators, and the weighted RRs and 95% CIs for the associations were obtained by using a random-effects model.

RESULTS

Of the 22 identified studies, 10 reported results on hypertension (36,617 individuals and 4491 cases), 7 on stroke (27,887 individuals and 1550 cases), and 9 on CHD (22,379 individuals and 1986 cases). Comparison of the highest with the lowest quantile of fasting insulin concentrations showed a pooled RR (95% CI) of 1.63 (1.35, 1.97) for hypertension, 1.18 (0.87, 1.60) for stroke, and 1.50 (1.28, 1.77) for CHD. Each 50-pmol/L increment in fasting insulin was associated with a 25% increase in risk of hypertension [RR: 1.25 (1.14, 1.36)] and a 16% increase in risk of CHD [RR: 1.16 (1.10, 1.22)] but was not associated with risk of stroke [RR: 0.999 (0.99, 1.01)].

CONCLUSIONS

A higher fasting insulin concentration or hyperinsulinemia was significantly associated with an increased risk of hypertension and CHD but not stroke. This meta-analysis suggests that early fasting insulin ascertainment in the general population may help clinicians identify those who are potentially at high risk of CVD.

Metabolically healthy obesity: epidemiology, mechanisms, and clinical implications

Obesity has become a worldwide epidemic that poses substantial health problems for both individuals and society. However, a proportion of obese individuals might not be at an increased risk for metabolic complications of obesity and, therefore, their phenotype can be referred to as metabolically healthy obesity. This novel concept of metabolically healthy obesity might become increasingly important to stratify individuals in the clinical treatment of obesity. However, no universally accepted criteria exist to define metabolically healthy obesity. Furthermore, many questions have been raised regarding the biological basis of this phenotype, the transitory nature of metabolically healthy obesity over time, and predictors of this phenotype. We describe the observational studies that gave rise to the idea of metabolically healthy obesity and the key parameters that can help to distinguish it from the general form of obesity. We also discuss potential biological mechanisms underlying metabolically healthy obesity and its public health and clinical implications.

The role of resistance and aerobic exercise training on insulin sensitivity measures in STZ-induced Type 1 diabetic rodents

Individuals with Type 1 Diabetes Mellitus (T1DM) can develop insulin resistance. Regular exercise may improve insulin resistance partially through increased expression of skeletal muscle GLUT4 content.

OBJECTIVE

To examine if different exercise training modalities can alter glucose tolerance through changes in skeletal muscle GLUT4 content in T1DM rats.

METHODS

Fifty rats were divided into 5 groups; control, diabetic control, diabetic resistance exercised, and diabetic high and low intensity treadmill exercised. Diabetes was induced using multiple low dose Streptozotocin (20 mg/kg/day) injections and blood glucose concentrations were maintained moderately hyperglycemic through subcutaneous insulin pellets. Resistance trained rats climbed a ladder with incremental loads, while treadmill trained rats ran on a treadmill at 27 or 15 m/min, respectively, all for 6 weeks.

RESULTS

At weeks 3 and 6, area under the curve measurements following an intravenous glucose tolerance test (AUC-IVGTT) in all diabetic groups were higher than control rats (p<0.05). At 6 weeks, all exercise groups had significantly lower AUC-IVGTT values than diabetic control animals (p<0.05). Treadmill trained rats had the lowest insulin dose requirement of the T1DM rats and the greatest reduction in insulin dosage was evident in high intensity treadmill exercise. Concomitant with improvements in glucose handling improvements, tissue-specific elevations in GLUT4 content were demonstrated in both red and white portions of vastus lateralis and gastrocnemius muscles, suggesting that glucose handling capacity was altered in the skeletal muscle of exercised T1DM rats.

CONCLUSIONS

These results suggest that, while all exercise modalities can improve glucose tolerance, each mode leads to differential improvements in insulin requirements and protein content alterations.

Clusters of AMI risk factors and their association with left ventricular hypertrophy: a population-based study within the Skaraborg Project, Sweden

OBJECTIVES

Risk factors for acute myocardial infarction (AMI) are known to cluster and to be differently distributed in men and women. The aim of this study was to sex-specifically explore clusters of acknowledged AMI risk factors by factor analysis, and to study whether such clusters are associated with left ventricular hypertrophy (LVH), used as a subclinical measure of CHD.

METHODS

In 2001-2005, 2328 subjects (30-74 years) were randomly selected from two municipalities in Sweden (participation-rate 76%) and were assessed with regard to cardiovascular risk factors; 852 participants also had an echocardiographic examination performed.

RESULTS

Factor analysis identified three identical factors in men and women. WHR, HOMA-ir, systolic blood pressure, and ApoB/ApoA1 loaded significantly on the principal "metabolic factor", leisure-time physical activity and self-rated health loaded significantly on the "vitality factor", and smoking and alcohol consumption loaded significantly on the "addiction factor". The metabolic factor was associated with LVH in both men (P<0.001) and women (P<0.001), whereas the addiction factor was associated with LVH solely in men (P=0.002).

CONCLUSIONS

The consistent pattern in the clustering of acknowledged AMI risk factors suggests common underlying mechanisms in both men and women. However, whereas the metabolic factor was paramount in both men and women in the association with LVH, the addiction factor had an impact solely in men. As LVH often precedes AMI, a deeper understanding of risk factors for LVH, including consideration of the supposed sex differences, can be useful in order to explore prevention strategies for AMI.

Sphingosine kinase 1 is regulated by peroxisome proliferator-activated receptor α in response to free fatty acids and is essential for skeletal muscle interleukin-6 production and signaling in diet-induced obesity

We previously demonstrated that sphingosine kinase 1 (Sphk1) expression and activity are up-regulated by exogenous palmitate (PAL) in a skeletal muscle model system and in diet-induced obesity in mice; however, potential functions and in vivo relevance of this have not been addressed. Here, we aimed to determine the mechanism by which PAL regulates SphK1 in muscle, and to determine potential roles for its product, sphingosine-1-phosphate (S1P), in muscle biology in the context of obesity. Cloning and analysis of the mouse Sphk1 promoter revealed a peroxisome proliferator-activated receptor (PPAR) α cis-element that mediated activation of a reporter under control of the Sphk1 promoter; direct interaction of PPARα was demonstrated by chromatin immunoprecipitation. PAL treatment induced the proinflammatory cytokine interleukin (IL)-6 in a manner dependent on SphK1, and this was attenuated by inhibition of the sphingosine-1-phosphate receptor 3 (S1PR3). Diet-induced obesity in mice demonstrated that IL-6 expression in muscle, but not adipose tissue, increased in obesity, but this was attenuated in Sphk1(-/-) mice. Moreover, plasma IL-6 levels were significantly decreased in obese Sphk1(-/-) mice relative to obese wild type mice, and muscle, but not adipose tissue IL-6 signaling was activated. These data indicate that PPARα regulates Sphk1 expression in the context of fatty acid oversupply and links PAL to muscle IL-6 production. Moreover, this function of SphK1 in diet-induced obesity suggests a potential role for SphK1 in obesity-associated pathological outcomes.

Insulin resistance is associated with significant clinical atherosclerosis in nondiabetic patients with acute myocardial infarction

OBJECTIVE

The prevalence of insulin resistance (IR) is increasing worldwide because of increasing age, obesity, and physical inactivity. Emerging evidence supports a direct proatherogenic effect of IR on the coronary vasculature, but the relation between IR and angiographic atherosclerosis in a real-world clinical setting is uncertain. In this work, we assessed whether IR is independently associated with clinically significant angiographic atherosclerosis in nondiabetic individuals.

APPROACH AND RESULTS

We examined the association between IR and the extent of coronary atherosclerosis determined by angiography in 1073 nondiabetic patients surviving acute myocardial infarction. Patients were divided into quartiles on the basis of the homeostasis model assessment grading of IR, and associations between IR and multivessel coronary artery disease, defined as ≥ 2 arteries with ≥ 70% stenosis (or ≥ 50% left main stenosis), were analyzed in bivariate and multivariable modeling. Overall, the cohort had a median age of 56 years; 28.9% women and 21.8% nonwhite. The crude prevalence of multivessel coronary artery disease was 37.8%, 42.3%, 47.2%, and 48.0% for homeostasis model assessment grading of IR quartiles 1, 2, 3, and 4, respectively (P(trend) = 0.009). In multivariable modeling, compared with quartile 1, both quartile 3 (relative risk [95% confidence interval], 1.31 [1.07-1.60]) and quartile 4 (1.29 [1.03-1.60]) were independently associated with multivessel coronary artery disease. Covariates in the model included patient demographic and clinical characteristics and metabolic factors (low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol, triglyceride, glycosylated hemoglobin, and high-sensitivity C-reactive protein).

CONCLUSIONS

We demonstrate an independent association between IR and multivessel coronary artery disease in nondiabetic postmyocardial infarction patients. Our findings strengthen the experimental evidence for a direct atherogenic effect of IR independent of glucose control and other components of the metabolic syndrome.

Obesity and Cardiac Function - The Role of Caloric Excess and its Reversal

Obesity is recognized as an independent and increasingly prevalent risk factor for cardiovascular morbidity and mortality. This stems in part from the contribution of obesity towards insulin resistance and diabetes, which associate with premature atherosclerosis, enhanced thrombogenicity and activation of systemic inflammatory programs with resultant cardiovascular dysfunction. This review will focus on the more direct mechanisms underpinning obesity-associated cardiac pathophysiology including the metabolic consequences of lipid accumulation in the myocardium and the consequences of direct systemic effects of lipid toxicity. Furthermore, there is growing recognition that metabolic intermediates, which may be perturbed with caloric excess, may play an important role in intracellular signal transduction and on the post-translational control of metabolic functioning within the heart. As strategies to reverse obesity appear to have ameliorative cardiac effects, surgical and therapeutic approaches to facilitate weight reduction this will also be discussed.

Body adiposity index and other indexes of body composition in the SAPHIR study: association with cardiovascular risk factors

OBJECTIVE

The accuracy of anthropometric surrogate markers such as the body adiposity index (BAI) and other common indexes like the body mass index (BMI), waist-to-hip ratio (WHR) and waist-to-height ratio (WHtR) to predict metabolic sequelae is essential for its use in clinical practice.

DESIGN AND METHODS

Thus, we evaluated the strength of BAI and other indexes to relate with anthropometric parameters, adipocytokines, blood lipids, parameters of glucose-homeostasis and blood pressure in 1,770 patients from the Salzburg Atherosclerosis Prevention Program in Subjects at High Individual Risk (SAPHIR) study in a crosssectional design. Measurements were BAI, BMI, WHR, WHtR, abdominal subcutaneous and visceral adipose tissue (aSAT and VAT), total body adipose tissue mass, body weight, waist- and hip circumference (WC and HC), leptin, adiponectin, high-density lipoprotein-cholesterol (HDL-C), low-density lipoprotein-cholesterol (LDL-C), triglycerides (TG), fasting plasma glucose, fasting plasma insulin, the homeostasis model assessment of insulin resistance (HOMAIR), systolic and diastolic blood pressure.

RESULTS AND CONCLUSIONS

BAI was significantly associated with leptin and HC. We conclude that BAI was the best calculator for leptin. BAI was inferior to BMI to predict anthropometric parameters other than HC, adiponectin, blood lipids, parameters of glucose homeostasis, and blood pressure in this cross-sectional study.

Relationship of PGC-1α Gene Polymorphism With Insulin Resistance Syndrome in Korean Children

This study aimed to investigate the associations between peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) gene Gly482Ser polymorphism (rs8192678) and parameters of insulin resistance in a sample of Korean children. A total of 286 children aged 10 to 12 years old were recruited from local elementary schools. Measured variables included body fat, blood pressures, blood lipids, glucose, insulin, homeostasis model assessment of insulin resistance (HOMA-IR), and accelerometer-based physical activity (PA). Significant differences in percentage body fat ( P = .016), insulin ( P = .013), and HOMA-IR ( P = .007) were found according to Gly482Ser genotype, with no significant genotype differences in the other measured variables. The genotype-specific differences in insulin ( P = .136) and HOMA-IR ( P = .067) were significantly attenuated when adjusted for age, sex, Tanner stage, body fat, and PA. The findings of the study suggest that the genetic effects of the PGC-1α genotypes on parameters of insulin resistance might be modulated by lifestyle factors, including PA and body fatness.

Apelin ameliorates TNF-α-induced reduction of glycogen synthesis in the hepatocytes through G protein-coupled receptor APJ

Apelin, a novel adipokine, is the specific endogenous ligand of G protein-coupled receptor APJ. Consistent with its putative role as an adipokine, apelin has been linked to states of insulin resistance. However, the function of apelin in hepatic insulin resistance, a vital part of insulin resistance, and its underlying mechanisms still remains unclear. Here we define the impacts of apelin on TNF-α-induced reduction of glycogen synthesis in the hepatocytes. Our studies indicate that apelin reversed TNF-α-induced reduction of glycogen synthesis in HepG2 cells, mouse primary hepatocytes and liver tissues of C57BL/6J mice by improving JNK-IRS1-AKT-GSK pathway. Moreover, Western blot revealed that APJ, but not apelin, expressed in the hepatocytes and liver tissues of mice. We found that F13A, a competitive antagonist for G protein-coupled receptor APJ, suppressed the effects of apelin on TNF-α-induced reduction of glycogen synthesis in the hepatocytes, suggesting APJ is involved in the function of apelin. In conclusion, we show novel evidence suggesting that apelin ameliorates TNF-α-induced reduction of glycogen synthesis in the hepatocytes through G protein-coupled receptor APJ. Apelin appears as a beneficial adipokine with anti-insulin resistance properties, and thus as a promising therapeutic target in metabolic disorders.

The glycaemic and C-peptide responses of foods rich in dietary fibre from oat, buckwheat and lingonberry

Dietary fibre has a beneficial effect on metabolic syndrome, e.g. by influencing the absorption of glucose. The source and structure of fibre affect the glucose response. In this study, the glycaemic and insulinaemic response to oat bread, oat bread with lingonberry fibre, oat-buckwheat bread and buckwheat porridge were tested in a small-scale clinical study (KHSHP E514/09). Nine healthy volunteers consumed test foods after overnight fasting. Serum glucose and C-peptide levels were determined by colorimetric and ELISA methods, respectively, from samples taken at seven time points during 120 min. The mean glycaemic and C-peptide indexes (C-pepIs) were 32 and 100 for oat bread, 47 and 119 for oat-lingonberry fibre bread, 58 and 105 for oat-buckwheat bread and 71 and 77 for buckwheat porridge. Similar to rye, buckwheat porridge having a relatively high glycaemic index (GI) tended to have a low C-pepI. Buckwheat and lingonberry fibres provide new alternatives for low GI foods.

Association of adiponectin with dietary factors and cardiovascular risk factors in type 2 diabetes mellitus patients

BACKGROUND AND AIM

Adiponectin, is an adipose tissue-specific adipokine, that circulates in human plasma at high levels, although lower levels are noted with insulin resistance and atherosclerosis. We investigated the relationship of adiponectin concentrations with dietary factors and some of the cardiovascular risk factors in patients with T2DM.

METHODS AND RESULTS

Totally 107 patients with T2DM were recruited from the out patients clinic of Shariati Hospital, Tehran, Iran. Patients were evaluated for laboratory and anthropometric measurements including serum adiponectin, fasting insulin, FPG, OGTT, HbA1c, HOMA-IR, hsCRP, weight, height, BMI and WHR. Nutrients intakes were obtained via 24-h recall from each patient in three successive days. Nutrients and data analysis were done using FPII and SPSS version 13 softwares. The mean of log10-transformed serum adiponectin concentration was 0.79±0.27μg/ml. The univariate linear regression analysis could not show any significant relation between the log of serum adiponectin and dietary factors. In multivariate linear regression after multiple adjustment, the log of serum adiponectin was independently associated with WHR (P=0.02, t=-2.33), HDL-C (P=0.050, t=2.03) and markedly but not significantly with age of patients (P=0.058, t=1.92).

CONCLUSIONS

Our findings showed that WHR, one of the important cardiovascular risk factors, can modulate independently adiponectin levels of T2DM patients in inverse manner. Also, the age of patients and HDL-C levels have marked positive effect on circulating levels of this adipocytokine. Thus, adiponectin might be a useful biomarker to prevent developing CVD in type 2 diabetes.

Factor structure underlying components of allostatic load

Allostatic load is a commonly used metric of health risk based on the hypothesis that recurrent exposure to environmental demands (e.g., stress) engenders a progressive dysregulation of multiple physiological systems. Prominent indicators of response to environmental challenges, such as stress-related hormones, sympatho-vagal balance, or inflammatory cytokines, comprise primary allostatic mediators. Secondary mediators reflect ensuing biological alterations that accumulate over time and confer risk for clinical disease but overlap substantially with a second metric of health risk, the metabolic syndrome. Whether allostatic load mediators covary and thus warrant treatment as a unitary construct remains to be established and, in particular, the relation of allostatic load parameters to the metabolic syndrome requires elucidation. Here, we employ confirmatory factor analysis to test: 1) whether a single common factor underlies variation in physiological systems associated with allostatic load; and 2) whether allostatic load parameters continue to load on a single common factor if a second factor representing the metabolic syndrome is also modeled. Participants were 645 adults from Allegheny County, PA (30–54 years old, 82% non-Hispanic white, 52% female) who were free of confounding medications. Model fitting supported a single, second-order factor underlying variance in the allostatic load components available in this study (metabolic, inflammatory and vagal measures). Further, this common factor reflecting covariation among allostatic load components persisted when a latent factor representing metabolic syndrome facets was conjointly modeled. Overall, this study provides novel evidence that the modeled allostatic load components do share common variance as hypothesized. Moreover, the common variance suggests the existence of statistical coherence above and beyond that attributable to the metabolic syndrome.

Filter paper blood spot enzyme linked immunoassay for insulin and application in the evaluation of determinants of child insulin resistance

Background

In large-scale epidemiology, bloodspot sampling by fingerstick onto filter paper has many advantages, including ease and low costs of collection, processing and transport. We describe the development of an enzyme-linked immunoassay (ELISA) for quantifying insulin from dried blood spots and demonstrate its application in a large trial.

Methods

We adapted an existing commercial kit (Mercodia Human Insulin ELISA, 10-1113-01) to quantify insulin from two 3-mm diameter discs (≈6 µL of blood) punched from whole blood standards and from trial samples. Paediatricians collected dried blood spots in a follow-up of 13,879 fasted children aged 11.5 years (interquartile range 11.3–11.8 years) from 31 trial sites across Belarus. We quantified bloodspot insulin levels and examined their distribution by demography and anthropometry.

Results

Mean intra-assay (n = 157) coefficients of variation were 15% and 6% for ‘low’ (6.7 mU/L) and ‘high’ (23.1 mU/L) values, respectively; the respective inter-assay values (n = 33) were 23% and 11%. The intraclass correlation coefficient between 50 paired whole bloodspot versus serum samples, collected simultaneously, was 0.90 (95% confidence interval 0.85 to 0.95). Bloodspot insulin was stable for at least 31 months at −80°C, for one week at +30°C and following four freeze-thaw cycles. Paediatricians collected a median of 8 blood spots from 13,487 (97%) children. The geometric mean insulin (log standard deviation) concentrations amongst 12,812 children were 3.0 mU/L (1.1) in boys and 4.0 mU/L (1.0) in girls and were positively associated with pubertal stage, measures of central and peripheral adiposity, height and fasting glucose.

Conclusions

Our simple and convenient bloodspot assay is suitable for the measurement of insulin in very small volumes of blood collected on filter paper cards and can be applied to large-scale epidemiology studies of the early-life determinants of circulating insulin.

Ambulatory blood pressure and the metabolic syndrome in normotensive and untreated hypertensive men

BACKGROUND

Components of the metabolic syndrome are typically intercorrelated in epidemiologic studies and, when combined, predict type 2 diabetes and cardiovascular diseases. However, it remains unclear whether a single construct underlies the various components and which of the components are most closely associated with the underlying syndrome. Here, we use our confirmatory factor analytic model of the metabolic syndrome to examine the extent to which measures of ambulatory blood pressure, reflecting blood pressure variability throughout the day and night, may strengthen the association between blood pressure and the other components of the syndrome.

METHODS

Participants were a community sample of 358 men (248 with hypertension), ages 40-70, not receiving antihypertensive medications. Confirmatory factor analysis was employed to examine model fit and the strength of association between clinic and ambulatory blood pressure and the metabolic syndrome.

RESULTS

The blood pressure factor loaded significantly on the underlying metabolic syndrome but the strength of association was not as great (loading = 0.34, p < 0.01) as those observed for the obesity, insulin resistance and lipid factors. The factor loadings for the ambulatory measures (awake loading = 0.19; sleep loading = 0.16, p values < 0.01) were significant but smaller in magnitude than the loadings for clinic blood pressure.

CONCLUSIONS

Both clinic and ambulatory measures of blood pressure are significantly associated with the underlying metabolic syndrome using confirmatory factor analytic methods. However, the strength of association appears greater for the clinic measures relative to the ambulatory measures in this study.

Evidence for Genetic Factors Underlying the Insulin Resistance Syndrome in American Indians

Previous analyses of American Indians of the Strong Heart Study have demonstrated that various insulin-resistance variables cluster, although knowledge about the genetic determination of these clusters is unknown. In an effort to explore the influences on the aggregation of insulin-resistance phenotypes, we used principal component factor analysis to examine the clustering of these phenotypes in participants of the Strong Heart Family Study and evaluated the genetic and environmental contributions of such factors. Nine traits were chosen for principal component factor analysis: BMI, diastolic blood pressure, fasting glucose, high-density lipoprotein-cholesterol, natural log-transformed insulin, natural log-transformed triglycerides, percentage of body fat, systolic blood pressure, and waist-to-hip ratio. Analyses revealed three clusters: glucose/insulin/obesity, blood pressure, and dyslipidemia factors. Using a variance component approach and accounting for the effects of age, sex, center, and medication, we detected significant heritabilities (h2) for the three factors: h2 = 0.67, h2 = 0.33, and h2 = 0.61, respectively. In multivariate analysis, no significant genetic correlations among factors were found. These results suggest that heredity explains a substantial proportion of the variability of the factors that underlie the insulin resistance syndrome in American Indians and that these factors are genetically independent.

Clinical usefulness of the metabolic syndrome for the risk of coronary heart disease does not exceed the sum of its individual components in older men and women. The Three-City (3C) Study

Objectives

To investigate the respective associations and clinical usefulness of the metabolic syndrome (MetS) and its individual components to predict the risk of first coronary heart disease (CHD) events in elderly.

Design

The Three-City is a French prospective multisite community-based cohort.

Setting

Three large French cities: Bordeaux, Dijon and Montpellier.

Participants

7612 subjects aged 65 and over who were free of CHD at baseline.

Main outcome measures

The MetS was defined by the 2005 National Cholesterol Education Program Adult Treatment Panel III criteria.

Results

During a median follow-up of 5.2 years, 275 first CHD events were adjudicated. The MetS was associated with increased risks of total (adjusted HR: 1.78; 95% CI 1.39 to 2.28), fatal (HR: 2.40; 95% CI 1.41 to 4.09) and non-fatal (HR: 1.64; 95% CI 1.24 to 2.17) CHD events. The association with total CHD was significant in women (HR: 2.56; 95% CI 1.75 to 3.75) but not in men (HR: 1.39; 95% CI 0.99 to 1.94; p for interaction=0.012). When in the same multivariable model, hyperglycemia and abdominal adiposity in women, hyperglycemia, lower HDL cholesterol and abdominal adiposity (inverse association) in men were the components significantly associated with CHD. The components of the MetS but not the MetS itself improved risk prediction beyond traditional risk factors (NRI= 9.35%, p<0;001).

Conclusion

The MetS is a risk marker for CHD in community-dwelling elderly subjects but may not be useful for CHD risk prediction purposes compared to its individual components.

A systematic review of body fat distribution and mortality in older people

We conducted a systematic review investigating body fat distribution in older adults and its association with morbidity and mortality. Our search yielded 2702 citations. Following three levels of screening, 25 studies were selected to evaluate the association between body fat distribution and comorbidity, and 17 studies were used in the mortality analysis. Most of the selected studies in our analyses used anthropometric measures, e.g., body mass index (BMI), waist circumference, and waist-hip ratio; relatively few studies used direct measures, such as body fat/lean mass, and percentage body fat. Studies reported inconsistent findings regarding the strongest predictor(s) of morbidity and mortality. However, the majority of studies suggested that BMI per se was not the most appropriate predictor of morbidity and mortality in the elderly because of its inability to discern or detect age-related body fat redistribution. In addition, studies using BMI found that the optimal BMI range for the lowest mortality in the elderly was overweight (25 kg/m(2)≤BMI<30 kg/m(2)) or mildly obese (30 kg/m(2)≤BMI<35 kg/m(2)). Our findings suggest that the current clinical guidelines, recommending that overweight and obesity are major risk factors for increased morbidity and mortality are not applicable to this population. Therefore, the central message of this review is to advise the government to establish new guidelines specifically for this population, using a combination of body fat distribution measurements, and to certify that these guidelines will not be applied to inappropriate populations.

Leisure time and occupational physical activity in relation to obesity and insulin resistance: a population-based study from the Skaraborg Project in Sweden

The objective was to study obesity and insulin resistance in relation to leisure time physical activity (LTPA) and occupational physical activity (OPA) in a Swedish population, with particular focus on sex differences. Using a cross-sectional design, waist circumference, body mass index (BMI), glucose/insulin metabolism, blood pressure, heart rate, self-reported education, smoking, alcohol consumption, LTPA, and OPA were assessed in 1745 men and women (30-74 years) randomly chosen from 2 municipalities in southwestern Sweden. In both men and women, LTPA was inversely associated with BMI, waist circumference, and the homeostasis model assessment of insulin resistance (HOMA-IR), respectively. These associations remained statistically significant after adjustments for age, OPA, education, alcohol consumption, smoking, and study area, and also for BMI in the analyses concerning waist circumference and HOMA-IR. A statistically significant interaction term (P = .030), adjusted for multiple confounders, revealed a stronger association between LTPA and HOMA-IR in women compared with men. Occupational physical activity was positively associated with BMI (P < .001), waist circumference (P < .001), and HOMA-IR (P = .001), however, only in women. These associations remained when adjusting for multiple confounders. The sex differences were confirmed by statistically significant interaction terms between sex and OPA in association with BMI, waist circumference, and HOMA-IR, respectively. The observed sex differences regarding the strength of the association between LTPA and insulin resistance, and the positive association between OPA and obesity and insulin resistance found solely in women, warrant further investigation. Although exploration of the metabolic effects of OPA appears to be needed, thorough measurement of potential confounders is also vital to understand contextual effects.

Metabolic Syndrome Derived from Principal Component Analysis and Incident Cardiovascular Events: The Multi Ethnic Study of Atherosclerosis (MESA) and Health, Aging, and Body Composition (Health ABC)

Background. The NCEP metabolic syndrome (MetS) is a combination of dichotomized interrelated risk factors from predominantly Caucasian populations. We propose a continuous MetS score based on principal component analysis (PCA) of the same risk factors in a multiethnic cohort and compare prediction of incident CVD events with NCEP MetS definition. Additionally, we replicated these analyses in the Health, Aging, and Body composition (Health ABC) study cohort. Methods and Results. We performed PCA of the MetS elements (waist circumference, HDL, TG, fasting blood glucose, SBP, and DBP) in 2610 Caucasian Americans, 801 Chinese Americans, 1875 African Americans, and 1494 Hispanic Americans in the multiethnic study of atherosclerosis (MESA) cohort. We selected the first principal component as a continuous MetS score (MetS-PC). Cox proportional hazards models were used to examine the association between MetS-PC and 5.5 years of CVD events (n = 377) adjusting for age, gender, race, smoking and LDL-C, overall and by ethnicity. To facilitate comparison of MetS-PC with the binary NCEP definition, a MetS-PC cut point was chosen to yield the same 37% prevalence of MetS as the NCEP definition (37%) in the MESA cohort. Hazard ratio (HR) for CVD events were estimated using the NCEP and Mets-PC-derived binary definitions. In Cox proportional models, the HR (95% CI) for CVD events for 1-SD (standard deviation) of MetS-PC was 1.71 (1.54–1.90) (P < 0.0001) overall after adjusting for potential confounders, and for each ethnicity, HRs were: Caucasian, 1.64 (1.39–1.94), Chinese, 1.39 (1.06–1.83), African, 1.67 (1.37–2.02), and Hispanic, 2.10 (1.66-2.65). Finally, when binary definitions were compared, HR for CVD events was 2.34 (1.91–2.87) for MetS-PC versus 1.79 (1.46–2.20) for NCEP MetS. In the Health ABC cohort, in a fully adjusted model, MetS-PC per 1-SD (Health ABC) remained associated with CVD events (HR = 1.21, 95%CI 1.12–1.32) overall, and for each ethnicity, Caucasian (HR = 1.24, 95%CI 1.12–1.39) and African Americans (HR = 1.16, 95%CI 1.01–1.32). Finally, when using a binary definition of MetS-PC (cut point 0.505) designed to match the NCEP definition in terms of prevalence in the Health ABC cohort (35%), the fully adjusted HR for CVD events was 1.39, 95%CI 1.17–1.64 compared with 1.46, 95%CI 1.23–1.72 using the NCEP definition. Conclusion. MetS-PC is a continuous measure of metabolic syndrome and was a better predictor of CVD events overall and in individual ethnicities. Additionally, a binary MetS-PC definition was better than the NCEP MetS definition in predicting incident CVD events in the MESA cohort, but this superiority was not evident in the Health ABC cohort.

Effects of continuous positive airway pressure on glycemic control and insulin resistance in patients with obstructive sleep apnea: a meta-analysis

BACKGROUND

Previous studies addressing the question of whether continuous positive airway pressure (CPAP) could improve the insulin resistance and glucose control in patients with obstructive sleep apnea (OSA) have led to conflicting results. Therefore, we conducted the meta-analysis to evaluate the effects of CPAP on glycemic control and insulin resistance in OSA patients.

METHODS

We searched PubMed, HighWire Press, Ovid Medline (R), Cochrane library, and EMBASE before December 2011 on original English language studies. The meta-analysis was conducted using Review Manager Version 5.

RESULTS

The summary estimate for mean difference of homeostasis model assessment insulin resistance (HOMA) from 12 non-diabetic studies was -0.55 (95 % CI, -0.91 to -0.20; P = 0.002). When compared with fasting blood glucose at baseline, 3 to 24 weeks of CPAP treatment did not improve glycemic control in non-diabetic subjects (-0.12; 95 % CI, -0.3 to 0.06; P = 0.20), as well as in diabetic subjects (-0.71; 95 % CI, -2.24 to 0.83; P = 0.37). There were no intervention-related changes in body mass index.

CONCLUSIONS

Our analysis showed that CPAP significantly improved insulin resistance in non-diabetic patients with moderate to severe OSA, while no significant change in body mass index was detected. Compared with fasting blood glucose at baseline, there was no change in glycemic control with CPAP. Further large-scale, randomized, and controlled studies are needed to evaluate the longer treatment and its possible effects on weight loss and glycemic homeostasis.

Stress in obesity and associated metabolic and cardiovascular disorders

Obesity has significant implications for healthcare, since it is a major risk factor for both type 2 diabetes and the metabolic syndrome. This syndrome is a common and complex disorder combining obesity, dyslipidemia, hypertension, and insulin resistance. It is associated with high atherosclerotic cardiovascular risk, which can only partially be explained by its components. Therefore, to explain how obesity contributes to the development of metabolic and cardiovascular disorders, more and better insight is required into the effects of personal and environmental stress on disease processes. In this paper, we show that obesity is a chronic inflammatory disease, which has many molecular mechanisms in common with atherosclerosis. Furthermore, we focus on the role of oxidative stress associated with obesity in the development of the metabolic syndrome. We discuss how several stress conditions are related to inflammation and oxidative stress in association with obesity and its complications. We also emphasize the relation between stress conditions and the deregulation of epigenetic control mechanisms by means of microRNAs and show how this impairment further contributes to the development of obesity, closing the vicious circle. Finally, we discuss the limitations of current anti-inflammation and antioxidant therapy to treat obesity.

Insulin resistance and atrial fibrillation (from the Framingham Heart Study)

Diabetes mellitus and obesity are increasing in prevalence and are associated with an elevated risk of atrial fibrillation (AF). Given the aging of the United States population, AF is projected to concomitantly increase in prevalence in the upcoming decades. Both diabetes and obesity are associated with insulin resistance. Whether insulin resistance is an intermediate step for the development of AF is uncertain. We hypothesized that insulin resistance is associated with an increased risk of incident AF. We examined the association of insulin resistance with incident AF using multivariate Cox proportional hazards regression analysis adjusting for the established AF risk factors (i.e., age, gender, systolic blood pressure, hypertension treatment, PR interval, significant heart murmur, heart failure, and body mass index). Of the 3,023 eligible participants (55% women; mean age 59 years) representing 4,583 person-examinations (Framingham Offspring fifth and seventh examination cycles), 279 participants developed AF (9.3%) within ≤10 years of follow-up. With multivariate modeling, insulin resistance was not significantly associated with incident AF (hazard ratio comparing top quartile to other 3 quartiles of homeostatic model assessment index 1.18, 95% confidence interval 0.84 to 1.65, p = 0.34). In a community-based cohort with ≤10 years of follow-up, no significant association was observed between insulin resistance and incident AF.

A systematic evaluation of the insulin resistance syndrome as an independent risk factor for cardiovascular disease mortality and derivation of a clinical index

Insulin resistance-related risk factor clustering (the insulin resistance syndrome or IRS) may be a cardiovascular disease (CVD) risk factor, but a convincing demonstration of this requires a rigorously derived reference measure and a systematic evaluation of measures and indices that derive from that measure. Using established IRS characteristics, factor analysis in 832 white men, generally healthy at baseline, generated a priori an IRS reference measure. An IRS diagnostic was chosen by evaluating CVD mortality risk in percentiles of the reference measure. An IRS clinical index was derived by (1) identification of readily measured, independent predictors of the IRS reference measure by multiple linear regression; (2) assignment to each predictor of a cut point optimal for discrimination of participants diagnosed with IRS; and (3) selection of a combination of the dichotomized predictors that further optimized IRS discrimination. The reference IRS diagnostic was defined by the top 16.7% of the IRS reference measure and predicted CVD mortality in Cox proportional hazards modeling (hazard ratio, 2.7; 95% confidence interval, 1.5-5.2; P = .002). An optimized IRS index was defined by triglycerides of at least 1.6 mmol/L and uric acid of at least 400 μmol/L plus any one of fasting plasma glucose of at least 5.4 mmol/L, diastolic blood pressure of at least 90 mm Hg, or body mass index of at least 27.0 kg/m(2) and predicted CVD mortality (hazard ratio, 2.14 [1.08-4.24]; P = .02). Prediction was independent of hypertension, hypercholesterolemia, and smoking. Conventionally derived glucoregulatory insulin resistance and metabolic syndrome were not predictive. The IRS is an independent risk factor for CVD mortality; and an effective, clinically usable index can be derived from readily measured variables.