Association of fasting insulin with blood pressure and lipids in young adults. The CARDIA study

Association of daily steps on lipid and glycaemic profiles in children: The mediator role of cardiorespiratory fitness

AIM

To analyse, in schoolchildren, the relationship between daily steps with metabolic parameters; and to examine whether this association is mediated by cardiorespiratory-fitness (CRF).

METHODS

A cross-sectional analysis of baseline data from a feasibility trial was performed in children from two primary schools in Cuenca, Spain. Daily steps were measured using the Xiaomi MI Band 3. Lipid and glycaemic profiles were analysed from blood samples. CRF was assessed using the 20-m shuttle run test. ANCOVA models were used to test the mean differences by daily steps quartiles. Mediation analyses were conducted to examine whether CRF mediates the association between daily steps and lipid and glycaemic parameters.

RESULTS

A total of 159 schoolchildren (aged 9-12 years, 53% female) were included in the analysis. Schoolchildren in the highest daily steps quartiles (>10 000 steps) showed significantly lower triglycerides and insulin levels (p = 0.004 and 0.002, respectively). This association did not remain after controlling for CRF. In mediation analyses, a significant indirect effect was observed through CRF in the relationship between daily steps with triglycerides and insulin.

CONCLUSION

Children who daily accumulate more than 10 000 steps have better lipid and metabolic profile, and CRF mediated their relationship in schoolchildren.

Clinical correlates of plasma insulin levels over the life course and association with incident type 2 diabetes: the Framingham Heart Study

INTRODUCTION

Insulin is a glucose-lowering hormone that affects carbohydrate, lipid, and protein metabolism. Limited data exist on the correlates of insulin levels over the life course in healthy community-dwelling individuals.

RESEARCH DESIGN AND METHODS

Using multilevel modeling of multiple serial observations over 21 years, we assessed the longitudinal correlates of fasting insulin and the cross-sectional correlates of fasting and 2-hour (2h, post 75 g glucose challenge) plasma insulin concentrations in 2140 relatively healthy Framingham Heart Study participants without diabetes (61% women; mean age, 42 years). We used multivariable-adjusted Cox regression to relate glycemic markers (fasting and 2h-insulin, fasting glucose, 2h-glucose, and hemoglobin A_1C) to the risk of type 2 diabetes during follow-up.

RESULTS

Over the life course, fasting insulin concentrations were inversely associated with age, male sex, and physical activity, whereas waist circumference, the total/high-density lipoprotein (HDL) cholesterol ratio, and blood triglycerides were positively associated with insulin levels (p<0.005 for all). Male sex (inversely related) and the total/HDL cholesterol ratio (positively related) emerged as the most important cross-sectional correlates of 2h-insulin (p<0.005 for all). All markers were associated with higher risk of type 2 diabetes (352 cases, median follow-up 18 years, p<0.001 for all).

CONCLUSIONS

We observed common and distinct correlates of fasting and 2h-insulin levels. Our findings highlight a potential role of insulin in lipid and lipoprotein metabolism. Furthermore, fasting and 2h-insulin are critical markers of future diabetes risk. Further studies are needed to confirm our findings.

A sex-related mediating effect of uric acid in the association between body composition and blood pressure in children and adolescents

The increase in blood pressure (BP) during somatic growth might have direct determinants but also mediating factors. We investigated whether uric acid (UA) and other metabolic factors would mediate the association between body composition components and BP. A cross-sectional study was conducted in 928 children and adolescents (aged 6-18 years), in which body composition and blood biochemistry were evaluated. Structural equation modeling was performed to test the direct and indirect pathways between systolic blood pressure (SBP) and body composition parameters. Muscle mass (MM) showed a strong direct effect on BP, regardless of sex. In girls, a mediating pathway through UA was not significant, but the association between fat mass (FM) and MM with SBP was mediated by the cluster of metabolic factors. In boys, both MM and FM were associated with SBP through a mediating pathway via UA, but not via the cluster of metabolic factors. The association between body composition and BP in children and adolescents has a complex design and also has a sex-specific mediating component. The increase in the UA levels may affect BP levels early in boys. Also, metabolic changes elicited by FM contribute to the increase in BP at an early age in girls. Novelty: MM showed a strong direct effect on BP, regardless of sex. In girls, the association between FM and MM with SBP was mediated by the cluster of metabolic factors. In boys, both MM and FM were associated with SBP through a mediating pathway via UA.

Plasma C-Peptide and Risk of Developing Type 2 Diabetes in the General Population

C-peptide measurement may represent a better index of pancreatic β-cell function compared to insulin. While insulin is mainly cleared by liver, C-peptide is mainly metabolized by kidneys. The aim of our study was to evaluate the association between baseline plasma C-peptide level and the development of type 2 diabetes independent of glucose and insulin levels and to examine potential effect-modification by variables related to kidney function. We included 5176 subjects of the Prevention of Renal and Vascular End-Stage Disease study without type 2 diabetes at baseline. C-peptide was measured in plasma with an electrochemiluminescent immunoassay. Cox proportional hazards regression was used to evaluate the association between C-peptide level and type 2 diabetes development. Median C-peptide was 722 (566-935) pmol/L. During a median follow-up of 7.2 (6.0-7.7) years, 289 individuals developed type 2 diabetes. In multivariable-adjusted Cox regression models, we observed a significant positive association of C-peptide with the risk of type 2 diabetes independent of glucose and insulin levels (hazard ratio (HR): 2.35; 95% confidence interval (CI): 1.49-3.70). Moreover, we found significant effect modification by hypertension and albuminuria (p < 0.001 and p = 0.001 for interaction, respectively), with a stronger association in normotensive and normo-albuminuric subjects and absence of an association in subjects with hypertension or albuminuria. In this population-based cohort, elevated C-peptide levels are associated with an increased risk of type 2 diabetes independent of glucose, insulin levels, and clinical risk factors. Elevated C-peptide level was not independently associated with an increased risk of type 2 diabetes in individuals with hypertension or albuminuria.

Hormonal Treatment and Cardiovascular Risk Profile in Transgender Adolescents

BACKGROUND AND OBJECTIVES

The effects of endocrinological treatment on cardiovascular risk profile in transgender adolescents are unknown. In this retrospective cohort study, we aim to investigate these effects and assess obesity and dyslipidemia prevalence in transgender adolescents at 22 years compared with peers.

METHODS

Changes in BMI, systolic blood pressure (SBP), diastolic blood pressure (DBP), glucose, homeostatic model assessment for insulin resistance (HOMA-IR), and lipid values during treatment, along with the prevalence of obesity and dyslipidemia at 22 years, were recorded in 71 transwomen and 121 transmen who started gonadotropin-releasing hormone agonists in their adolescence (15 years), with a subsequent addition of sex hormones (17 years).

RESULTS

In transwomen, changes in BMI (+3.0; 95% confidence interval [CI] 1.6 to 4.4), SBP (-2 mm Hg; 95% CI -7 to 3), DBP (+10 mm Hg; 95% CI 7 to 14), glucose (0.0 mmol/L; 95% CI -0.2 to 0.2), HOMA-IR (+0.6; 95% CI -0.6 to 1.9), and lipid values were similar or more favorable compared with peers. The same was true for transmen regarding changes in BMI (+2.3; 95% CI 1.7 to 2.9), SBP (+7 mm Hg; 95% CI 3 to 10), DBP (+7 mm Hg; 95% CI 5 to 10), glucose (+0.1 mmol/L; 95% CI -0.1 to 0.3), HOMA-IR (-0.2; 95% CI -0.8 to 0.3), and lipid values. At age 22, obesity prevalence was 9.9% in transwomen, 6.6% in transmen, 2.2% in ciswomen, and 3.0% in cismen.

CONCLUSIONS

Generally, endocrinological treatment in transgender adolescents is safe regarding cardiovascular risk. Because obesity is more prevalent in transgender adolescents compared with peers, body weight management should be important during the medical trajectory.

The Utility and Cross-Validation of a Composite Physical Activity Score in Relation to Cardiovascular Health Indicators: Coronary Artery Risk Development in Young Adults

BACKGROUND

Single-method assessment of physical activity (PA) has limitations. The utility and cross-validation of a composite PA score that includes reported and accelerometer-derived PA data has not been evaluated.

METHODS

Participants attending the Year 20 exam were randomly assigned to the derivation (two-thirds) or validation (one-third) data set. Principal components analysis was used to create a composite score reflecting Year 20 combined reported and accelerometer PA data. Generalized linear regression models were constructed to estimate the variability explained (R²) by each PA assessment strategy (self-report only, accelerometer only, composite score, or self-report plus accelerometer) with cardiovascular health indicators. This process was repeated in the validation set to determine cross-validation.

RESULTS

At Year 20, 3549 participants (45.2 [3.6] y, 56.7% female, and 53.5% black) attended the clinic exam and 2540 agreed to wear the accelerometer. Higher R² values were obtained when combined assessment strategies were used; however, the approach yielding the highest R² value varied by cardiovascular health outcome. Findings from the cross-validation also supported internal study validity.

CONCLUSIONS

Findings support continued refinement of methodological approaches to combine data from multiple sources to create a more robust estimate that reflects the complexities of PA behavior.

Genetic variation in 9p21 is associated with fasting insulin in women but not men

Background

Single nucleotide polymorphisms (SNPs) in the 9p21 region have been associated with cardiovascular disease (CVD), but previous studies have focussed on older populations. The objective of this study was to determine the association between 9p21 genotypes and biomarkers of CVD risk in young adults from different ethnocultural groups.

Methods

Subjects were 1,626 participants aged 20–29 years from the Toronto Nutrigenomics and Health Study. Fasting blood was collected to measure glucose, insulin, c-reactive protein and serum lipids, as well as to isolate DNA for genotyping subjects for five SNPs in 9p21. Analyses were conducted for the entire population and separately for women (n = 1,109), men (n = 517), Caucasians (n = 771), East Asians (n = 561) South Asians (n = 175) and Others (n = 119). ANOVA and ANCOVA were used to examine if 9p21 genotypes were associated with biomarkers of CVD risk.

Results

In the entire group, the risk alleles of rs10757278 and rs2383206 were associated with higher mean insulin (p = 0.01). Risk alleles for rs4977574, rs10757278, rs2383206, rs1333049 and rs10757274 were associated with higher serum insulin in women (p = 0.008, p = 0.008, p = 0.0003, p = 0.002, and p = 0.001, respectively), but not in men (p = 0.41, p = 0.13, p = 0.31, p = 0.34, and 0.35, respectively). The association between 9p21 and insulin remained significant among women not taking hormonal contraceptives (HC), but was not significant among women taking HCs.

Conclusion

Our findings suggest that 9p21 genotypes may play a role in the development of insulin resistance in early adulthood among women, but not men, and the effects appear to be attenuated by HC use.

Deficiency of PRKD2 triggers hyperinsulinemia and metabolic disorders

Hyperinsulinemia is the earliest symptom of insulin resistance (IR), but a causal relationship between the two remains to be established. Here we show that a protein kinase D2 (PRKD2) nonsense mutation (K410X) in two rhesus monkeys with extreme hyperinsulinemia along with IR and metabolic defects by using extreme phenotype sampling and deep sequencing analyses. This mutation reduces PRKD2 at both the mRNA and the protein levels. Taking advantage of a PRKD2-KO mouse model, we demonstrate that PRKD2 deletion triggers hyperinsulinemia which precedes to IR and metabolic disorders in the PRKD2 ablation mice. PRKD2 deficiency promotes β-cell insulin secretion by increasing the expression and activity of L-type Ca²⁺ channels and subsequently augmenting high glucose- and membrane depolarization-induced Ca²⁺ influx. Altogether, these results indicate that down-regulation of PRKD2 is involved in the pathogenesis of hyperinsulinemia which, in turn, results in IR and metabolic disorders.

Hyperinsulinemia can precede the development of insulin resistance. Here the authors identify a PKD2 mutation that leads to hyperinsulinemia and insulin resistance in Rhesus monkey and show that PKD2 deficiency promotes beta cell insulin secretion by activating L-type Ca2+ channels.

Clinical importance of non-participation in a maximal graded exercise test on risk of non-fatal and fatal cardiovascular events and all-cause mortality: CARDIA study

While poor performance during a maximal graded exercise test (GXT) predicts cardiovascular events and premature mortality, the potential clinical importance of non-participation in a GXT, either for medical or non-medical reasons, is currently unknown. Data are from 4086 and 3547 Coronary Artery Risk Development in Young Adults (CARDIA) participants who attended the Year 7 (ages 25-37years) and/or 20 exams (ages 38-50years), respectively, which included a GXT. Cox proportional hazard models were used to examine the effect of GXT disposition (at Year 7 and 20, separately) on risk of non-fatal and fatal cardiovascular events and all-cause mortality obtained through 28years of follow-up. A GXT was not conducted or completed according to protocol in 12.9% and 19.1% of participants attending the Year 7 and 20 exams, respectively. After adjustment, participants who missed the Year 20 GXT for medical reasons had a higher risk of cardiovascular events [HR: 4.06 (95% CI: 1.43, 11.5)] and all-cause mortality [HR: 3.07 (95% CI: 1.11, 12.3)] compared to GXT completers; participants who missed at Year 20 for non-medical reasons also had higher risk of all-cause mortality [HR: 2.53 (95% CI: 1.61, 3.99)]. Findings suggest that non-participation in a GXT, regardless of medical or non-medical reason, to be an important predictor of excess risk of adverse health outcomes and premature mortality. Additional patient follow-up, including identification of potential targets for intervention (e.g., weight management and smoking cessation programs), should be conducted at the point of a missed GXT.

Homeostasis model assessment of insulin resistance in a general adult population in Korea: additive association of sarcopenia and obesity with insulin resistance

BACKGROUND

Insulin resistance (IR) is a major factor associated with type 2 diabetes. Using homeostasis model assessment of insulin resistance (HOMA-IR), we aimed to elucidate the factors associated with IR risk, especially the cumulative effect of obesity and sarcopenia on IR.

METHODS

A total of 8,707 adults from the fourth and fifth Korean National Health and Examination Surveys were studied. Laboratory, anthropometric and lifestyle factors were analysed to reveal their association with HOMA-IR and IR risk. Subjects were divided into four groups according to the presence of obesity and sarcopenia to identify their effect on IR risk.

RESULTS

We found that high triglycerides and alanine aminotransferase, low high-density lipoprotein cholesterol, obesity and sarcopenia were independent risk factors for IR in both sexes. Obese men with sarcopenia had a significantly higher risk of IR than men who were obese or sarcopenic (but not both). The additive effect of sarcopenia with obesity on IR risk was not observed in women. Cut-offs of HOMA-IR for determining IR were calculated as 75 percentile value of young healthy subpopulation, 2·19 in men and 2·18 in women. These cut-offs could distinguish individuals with impaired fasting glucose from normal ones, with a sensitivity of 65·4% (men) and 73·3% (women), and a specificity of 68·8% (men) and 69·4% (women).

CONCLUSION

These data showed that obese men with sarcopenia exhibited a significantly higher IR risk than obese, nonsarcopenic men. In women, body composition did not affect IR if they were already obese.

Hypertension in young adults

Hypertension remains a major societal problem affecting 76 million, or approximately one third, of US adults. While more prevalent in the older population, an increasing incidence in the younger population, including athletes, is being observed. Active individuals, like the young and athletes, are viewed as free of diseases such as hypertension. However, the increased prevalence of traditional risk factors in the young, including obesity, diabetes mellitus, and renal disease, increase the risk of developing hypertension in younger adults. Psychosocial factors may also be contributing factors to the increasing incidence of hypertension in the younger population. Increased left ventricular wall thickness and mass are increasingly found in young adults on routine echocardiograms and predict future cardiovascular events. This increasing incidence of hypertension in the young calls for early surveillance and prompt treatment to prevent future cardiac events. In this review we present the current epidemiological data, potential mechanisms, clinical implications, and treatment of hypertension in young patients and athletes.

Higher glucose, insulin and insulin resistance (HOMA-IR) in childhood predict adverse cardiovascular risk in early adulthood: the Pune Children's Study

AIMS/HYPOTHESIS

The Pune Children's Study aimed to test whether glucose and insulin measurements in childhood predict cardiovascular risk factors in young adulthood.

METHODS

We followed up 357 participants (75% follow-up) at 21 years of age who had undergone detailed measurements at 8 years of age (glucose, insulin, HOMA-IR and other indices). Oral glucose tolerance, anthropometry, plasma lipids, BP, carotid intima-media thickness (IMT) and arterial pulse wave velocity (PWV) were measured at 21 years.

RESULTS

Higher fasting glucose, insulin and HOMA-IR at 8 years predicted higher glucose, insulin, HOMA-IR, BP, lipids and IMT at 21 years. A 1 SD change in 8 year variables was associated with a 0.10-0.27 SD change at 21 years independently of obesity/adiposity at 8 years of age. A greater rise in glucose-insulin variables between 8 and 21 years was associated with higher cardiovascular risk factors, including PWV. Participants whose HOMA-IR measurement remained in the highest quartile (n = 31) had a more adverse cardiovascular risk profile compared with those whose HOMA-IR measurement remained in the lowest quartile (n = 28).

CONCLUSIONS/INTERPRETATION

Prepubertal glucose-insulin metabolism is associated with adult cardiovascular risk and markers of atherosclerosis. Our results support interventions to improve glucose-insulin metabolism in childhood to reduce cardiovascular risk in later life.

Accumulation of metabolic cardiovascular risk factors in black and white young adults over 20 years

BACKGROUND

Cross-sectional clustering of metabolic risk factors for cardiovascular disease in middle-aged adults is well described, but less is known regarding the order in which risk factors develop through young adulthood and their relation to subclinical atherosclerosis.

METHOD AND RESULTS

A total of 3178 black and white women and men in the Coronary Artery Risk Development in Young Adults study were assessed to identify the order in which cardiovascular disease risk factors including diabetes, hypertension, dyslipidemia (low high-density lipoprotein cholesterol or high triglyceride levels), hypercholesterolemia (high total or low-density lipoprotein cholesterol), and obesity develop. Observed patterns of risk factor development were compared with those expected if risk factors accumulated randomly, given their overall distribution in the population. Over the 20 years of follow-up, 80% of participants developed at least 1 risk factor. The first factor to occur was dyslipidemia in 39% of participants, obesity in 20%, hypercholesterolemia in 11%, hypertension in 7%, and diabetes in 1%. Dyslipidemia was the only risk factor both to occur first and to be followed by additional risk factors more often than expected (P<0.001 for both). Order of risk factor accrual did not affect subclinical atherosclerosis at year 20. Results were similar by sex, race, and smoking status.

CONCLUSIONS

Multiple patterns of cardiovascular risk factor development were observed from young adulthood to middle age. Dyslipidemia, a potentially modifiable condition, often preceded the development of other risk factors and may be a useful target for intervention and monitoring.

The incidental relationship between serum ferritin levels and hypertension

BACKGROUND AND OBJECTIVE

Although several studies have shown an association between ferritin level and hypertension, only a few studies have investigated the longitudinal relationship between them. Thus, we evaluated the incidental risk for hypertension according to baseline ferritin level.

PATIENTS AND METHODS

A total of 7104 healthy Korean men matched by a propensity score, who had participated in a medical health check-up program in 2005, were followed up from 2005 to 2010. They were divided into four groups according to baseline serum ferritin level (first quartile-fourth quartile). The incidence of hypertension was compared among the four groups, and the Cox-proportional hazard model was used to assess whether the development of hypertension was associated with higher baseline serum ferritin level.

RESULTS

A total of 1252 (17.6%) cases had newly developed hypertension during the 26,339.5 person-years of follow-up between 2006 and 2010. The adjusted hazard ratios (HRs) (95% confidence intervals, CIs) for incident hypertension were 1.00 (reference), 1.09 (0.91-1.30), 1.21 (1.01-1.45) and 1.28 (1.07-1.52), respectively (P for trend=0.003) through the quartiles of serum ferritin levels, respectively, after adjusting for multiple confounders. For the log-transformed serum ferritin levels as a continuous variable, adjusted HRs and 95% CIs for HTN were 1.15 (1.02-1.29).

CONCLUSIONS

Elevated serum ferritin level was independently associated with the incidental risk for hypertension in Korean men. This finding suggests the value of elevated ferritin level as an early predictor of hypertension.

Effects of atorvastatin 10 mg/d on insulin resistance: A 12-week, open-label study in hyperlipidemic patients

BACKGROUND

In addition to their cholesterol-lowering effects, hydroxymethylglutaryl coenzyme A reductase inhibitors ("statins") might have pleiotropic, nonlipid effects. Insulin resistance syndrome is known to increase the risk for cardiovascular disease. However, the effects of statins on insulin resistance are a subject of controversy.

OBJECTIVE

We aimed to investigate the effects of atorvastatin on insulin resistance in hyperlipidemic patients.

METHODS

This 12-week, prospective, nonrandomized, open-label study was conducted at the outpatient cardiology clinic, Ege University Medical School, Bornova-Izmir, Turkey. Hyperlipidemic patients aged ≥18 years with insulin resistance and no other components of the metabolic syndrome were included in the study. Atorvastatin 10 mg QD (after the evening meal) was administered by mouth (tablet) over a 12-week period. At baseline and after 12 weeks of treatment, insulin sensitivity was assessed using homeostasis model assessment (HOMA) index methodology. Serum lipid parameters and fasting levels of plasma glucose and insulin (FPG and FPI, respectively) were measured at the same 2 time points. The tolerability of atorvastatin was assessed using laboratory analysis and physical examination, including vital sign measurements.

RESULTS

Fifteen white patients (9 women, 6 men; mean [SD] age, 52 [8] years) participated in the study. No significant changes in HOMA index were found (mean [SD], 3.1 [1.5] vs 3.2 [1.9]). The lipid profile was improved significantly at 12 weeks compared with baseline (mean [SD] low-density lipoprotein cholesterol, 173.2 [21.3] vs 110.8 [43.6] mg/dL; total cholesterol, 270.9 [21.5] vs 201.2 [46.7] mg/dL; and triglycerides, 269.5 [46.3] vs 205.5 [49.3] mg/dL; all, P < 0.001). No significant change in mean (SD) plasma high-density lipoprotein cholesterol level (45.5 [6.6] vs 43.7 [8.1] mg/dL) was found. In addition, no significant changes in FPG (85.3 [12.71 vs 84.8 [10.4] mg/dL), or FPI (13.5 [9.7] vs 13.9 [10.1] μU/mL) were found. None of the patients required withdrawal of medication due to an adverse event.

CONCLUSION

In this pilot study in hyperlipidemic patients with insulin resistance, 12 weeks of treatment with atorvastatin 10 mg QD was effective in controlling hyperlipidemia but did not reduce the severity of insulin resistance.

Impact of hyperinsulinemia on the development of hypertension in normotensive, nondiabetic adults: a 4-year follow-up study

BACKGROUND AND AIMS

This study aimed to investigate the association between baseline fasting insulin levels, changes in fasting insulin levels, and future development of hypertension in normotensive, non-diabetic, healthy adults.

METHODS

We analyzed data from 11,123 adults, aged 20-65years, who had no history of hypertension or diabetes mellitus at a 2004 medical examination in a health promotion program and had attended a repeat examination in 2008. Subjects were divided into four groups according to baseline quartiles of fasting insulin and dichotomized fasting insulin levels at baseline and after 4years: low-low, low-high, high-low, high-high. We also assessed whether the association differed between the younger (20-40years) and older subjects (41-65years).

RESULTS

In four years, 1142 subjects (10.3%) developed hypertension. The odds ratio (OR) for the development for hypertension increased as the quartiles of baseline fasting insulin levels and changes in fasting insulin levels increased from the first to the fourth quartile (OR 1.15, 1.35, and 1.95 vs. 1.07, 1.22, and 1.41, respectively), after adjusting for multiple factors. The OR for hypertension was 2.0-fold higher in the high-high group and 1.34-fold higher in the low-high group than in the low-low group. In comparing the results by age group, we found that these relationships were more prominent in younger subjects.

CONCLUSION

High baseline and continuously increasing fasting insulin levels appeared to be independent determinants for the future development of hypertension during this 4-year follow-up study in normotensive, non-diabetic, healthy adults.

Insulin resistance and the development of cardiovascular disease in a Japanese community: the Hisayama study

AIMS

Although several surrogate measures of insulin resistance have been proposed, their associations with cardiovascular disease (CVD) have not been evaluated sufficiently.

METHODS

A total of 2,356 community-dwelling Japanese individuals aged 40 to 79 years who underwent a 75 g oral glucose tolerance test were followed up for 14 years. The status of insulin resistance was estimated by using the Matsuda index or homeostasis model assessment of insulin resistance (HOMA-IR).

RESULTS

During follow-up, 260 subjects developed CVD. The age- and sex-adjusted hazard ratios of CVD significantly decreased with an increasing Matsuda index and rose with increasing HOMA-IR levels (both p for trend <0.05). After adjustment for age, sex, serum total cholesterol, electrocardiogram abnormalities, proteinuria, smoking habits, alcohol intake, and regular exercise, the risk of CVD was significantly lower in the third to fifth quintiles of the Matsuda index and higher in the fifth quintile of HOMA-IR values compared with the first quintile of the corresponding index (Matsuda index Q3: hazard ratio (HR)= 0.59 [95% confidence interval 0.40-0.87]; Q4: HR= 0.66 [0.45-0.97]; and Q5: HR= 0.67 [0.47-0.97]; HOMA-IR Q5: HR= 1.55 [1.05-2.29]); however, these associations were attenuated after further adjustment for the metabolic syndrome status. In regard to CVD subtypes, the risks for stroke and coronary heart disease significantly decreased with an increasing Matsuda index, while elevated HOMA-IR levels were a significant risk factor for stroke, but not for coronary heart disease.

CONCLUSION

Our findings suggest that insulin resistance significantly increases the risk of incident CVD through metabolic syndrome in Japanese.

Hyperinsulinemia and homeostasis model assessment of insulin resistance as predictors of hypertension: a 5-year follow-up study of Korean sample

BACKGROUND

The relationships between insulin level and indexes of insulin resistance (IR) to predict incident hypertension have been explored only in cross-sectional or prospective studies with small numbers of patients. We investigated whether plasma insulin concentration and the homeostasis model assessment of insulin resistance (HOMA(IR)) are associated with the onset of hypertension in a population of apparently healthy and relatively lean Korean adults.

METHODS

We selected 10,894 of 15,638 subjects who were normotensive at baseline during general health status evaluations in 2003 and 2008. The baseline and follow-up examinations included analyses of fasting glucose, insulin level, and lipid profile. Alcohol consumption, smoking status, exercise habits, and education level were also evaluated using a standard questionnaire.

RESULTS

Of the 10,894 subjects, hypertension developed in 881 (8.1%) during the ensuing 5 years. Incident hypertension was more common among older subjects than it was in younger subjects and was associated with a high baseline body mass index (BMI). In multivariable logistic models, elevated serum insulin, and HOMA(IR) were associated with an increased risk of incident hypertension in both sexes. In a multivariable analysis using quartiles of insulin and HOMA(IR), the odds ratio (OR) for incident hypertension was the highest in the highest quartile of insulin and HOMA(IR). The highest quartile of insulin and HOMA(IR) was associated with a 1.5-1.7 times increased risk of incident hypertension.

CONCLUSIONS

This 5-year follow-up study provides evidence that both a high circulating insulin level and HOMA(IR) are significant risk factors for the development of hypertension in a relatively lean and healthy population.

Basal C-peptide Level as a Surrogate Marker of Subclinical Atherosclerosis in Type 2 Diabetic Patients

BACKGROUND

Recent studies have revealed that C-peptide induces smooth muscle cell proliferation and causes human atherosclerotic lesions in diabetic patients. The present study was designed to examine whether the basal C-peptide levels correlate with cardiovascular risk in type 2 diabetes mellitus (T2DM) patients.

METHODS

Data was obtained from 467 patients with T2DM from two institutions who were followed for four years. The medical findings of all patients were reviewed, and patients with creatinine >1.4 mg/dL, any inflammation or infection, hepatitis, or type 1 DM were excluded. The relationships between basal C-peptide and other clinical values were statistically analyzed.

RESULTS

A simple correlation was found between basal C-peptide and components of metabolic syndrome (MS). Statistically basal C-peptide levels were significantly higher than the three different MS criteria used in the present study, the Adult Treatment Panel III (ATP III) of the National Cholesterol Education Program's (NCEP's), World Health Organization (WHO), and the International Diabetes Federation (IDF) criteria (NCEP-ATP III, P=0.001; IDF, P<0.001; WHO, P=0.029). The multiple regression analysis between intima-media thickness (IMT) and clinical values showed that basal C-peptide significantly correlated with IMT (P=0.043), while the analysis between the 10-year coronary heart disease risk by the United Kingdom Prospective Diabetes Study risk engine and clinical values showed that basal C-peptide did not correlate with IMT (P=0.226).

CONCLUSION

Basal C-peptide is related to cardiovascular predictors (IMT) of T2DM, suggesting that basal C-peptide does provide a further indication of cardiovascular disease.

Biomarkers of the metabolic syndrome and breast cancer prognosis

In spite of its public health importance, our understanding of the mechanisms of breast carcinogenesis and progress is still evolving. The metabolic syndrome (MS) is a constellation of biochemical abnormalities including visceral adiposity, hyperglycemia, hyperinsulinemia, dyslipidemia and high blood pressure. The components of the MS have all been related to late-stage disease and even to a poor prognosis of breast cancer through multiple interacting mechanisms. In this review, we aim to present a summary of recent advances in the understanding of the contribution of the MS to breast cancer with the emphasis on the role of biomarkers of the MS in the prognosis of breast cancer.

Racial and ethnic disparities in assisted reproductive technology outcomes in the United States

OBJECTIVE

To evaluate ethnic differences in assisted reproductive technology (ART) outcomes in the United States.

DESIGN

Historical cohort study.

SETTING

Clinic-based data.

PATIENT(S)

A total of 139,027 ART cycles from the Society for Assisted Reproductive Technology Clinic Outcome Reporting System online database for 2004-2006, limited to white, Asian, black, and Hispanic women.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Logistic regression was used to model the odds of pregnancy and live birth; among singletons and twins, the odds of preterm birth and fetal growth restriction. Results are presented as adjusted odds ratios, with white women as the reference group.

RESULT(S)

The odds of pregnancy were reduced for Asians (0.86), and the odds of live birth were reduced for all groups: Asian (0.90), black (0.62), and Hispanic (0.87) women. Among singletons, moderate and severe growth restriction were increased for all infants in all three minority groups (Asians [1.78, 2.05]; blacks [1.81, 2.17]; Hispanics [1.36, 1.64]), and preterm birth was increased among black (1.79) and Hispanic women (1.22). Among twins, the odds for moderate growth restriction were increased for infants of Asian (1.30) and black women (1.97), and severe growth restriction was increased among black women (3.21). The odds of preterm birth were increased for blacks (1.64) and decreased for Asians (0.70).

CONCLUSION(S)

There are significant disparities in ART outcomes according to ethnicity.

Community-based study on summer-winter difference in insulin resistance in Kin-Chen, Kinmen, Taiwan

BACKGROUND

The aim of this community-based study was to explore the summer-winter difference in insulin resistance in Kin-Chen, Kinmen.

METHODS

A total of 2,412 residents aged 40 and over was enrolled in a mass survey in Kin-Chen, Kinmen, by the Yang-Ming Crusade, a volunteer organization of well-trained medical students from National Yang-Ming University. All participants were investigated in winter (first phase, January and February, before Chinese New Year) and summer (secondary phase, July and August) in 2002. Structured questionnaires, demographic and physical data, lifestyle, and blood chemistry parameters were collected.

RESULTS

Higher levels of fasting insulin, HOMA-insulin resistance and triglycerides, but lower levels of high-density lipoprotein cholesterol were found in summer than in winter. The prevalence of metabolic syndrome was higher in summer than in winter, with differences of 7.7% in both genders (p = 0.0092 in men, p = 0.0037 in women). Body mass index (BMI), age and physical activity were significantly correlated with metabolic syndrome. After controlling for BMI and other risk profiles, summer was independently and positively associated with fasting insulin and insulin resistance regardless of metabolic syndrome.

CONCLUSION

Fasting insulin, insulin resistance and prevalence of metabolic syndrome were higher in summer than in winter. BMI and season were 2 major determinants of the variation in fasting insulin. The contextual impacts of seasonal variation in shaping metabolic syndrome or insulin resistance in populations need to be reemphasized.

Independent role of blood pressure on cardiovascular risk factors in nondiabetic, obese African-American women with family history of type 2 diabetes: Implications for metabolic syndrome components

African-American women (AAW) suffer disproportionately from hypertension and its consequences. We investigated the significance of systolic and diastolic blood pressure (SBP/DBP) as components of metabolic syndrome (MetS) in nondiabetic, overweight/obese AAW. We studied 258 AAW (mean age, 42.4 +/- 8.4 years and body mass index (BMI), 33.4 +/- 8.0 kg/m(2)) in a cross-sectional manner. We estimated the prevalence of MetS and its components using Adult Treatment Panel (ATP III) criteria, insulin sensitivity (Si), insulin resistance (HOMA-IR), and cardiovascular disease risk factors according to the tertiles of blood pressure (BP). Mean age and BMI did not differ with increases in BP tertiles. At screening, 35.7% of our subjects were hypertensive. MetS was found in 32.2% of our AAW. Prevalence of MetS increased as the tertiles of BP increased (SBP = first [10.5%], second [15.1%], third [58.1%], and DBP = first [9.3%], second [23.3%], third [54.7%]). We found that the components of Adult Treatment Panel (ATP) did not track with the corresponding BP tertiles. However, the prevalence of individuals meeting ATP III criteria for BP was highest in the third tertile of both SBP and DBP. Consequently, the prevalence of MetS was highest in the third vs. first and second tertiles. Using linear regression analysis, SBP and DBP did not correlate with the conventional cardiovascular risk factors, HOMA-IR, or Si. In overweight/obese AAW, we found the components of MetS do not track with BP. In the absence of elevated BP, the prevalence of MetS appears to be very low in overweight and obese AAW. Conversely, elevated BP or hypertension was associated with remarkably higher rates of MetS in our AAW. Therefore BP criteria constitute an important and independent determinant of ATP III definition of MetS in AAW.

Vascular disease in paediatric type 2 diabetes: the state of the art

Type 2 diabetes is an emerging problem in the paediatric population. Paediatricians and paediatric endocrinologists are struggling with how to best assess, predict and treat cardiovascular risk factors in these patients. There is a notable lack of consensus in how to proceed, even among experts in the field. There are very limited data from quality trials in established paediatric type 2 diabetes. We address the available information regarding traditional and non-traditional indices of cardiovascular risk, including examination findings, biochemical markers and non-invasive imaging modalities. We discuss the utility and pitfalls of applying knowledge gained in adult medicine to the paediatric population. Potential treatment strategies are reviewed, including the currently available pharmaceutical options, with the acknowledgement that there are few drugs formally approved in the paediatric population.

Prevalence of metabolic syndrome in young men in Japan

AIM

The prevalence of metabolic syndrome, as defined by the Third Report of the National Cholesterol Education Program Expert Panel on Detection, Evaluation and Treatment of High Blood Cholesterol in Adults (ATPIII) modified for age (>or=3 of the following abnormalities): waist circumference of at least 80 cm; serum glucose level of at least 110 mg/dL; triglyceride level of at least 110 mg/dL; high density lipoprotein (HDL) cholesterol level of 40 mg/dL or less; and blood pressure (BP) of at least 130/75 mmHg, was estimated in male high school students who attended an annual school health examination.

METHODS

The subjects were divided into three body mass index (BMI) categories (obese: >or=25; mildly obese: 23-24.9: and normal weight: <23 kg/m2). Of the 1446 students (mean age 15 years), 96 (6.6%) were obese and 158 (10.9%) were mildly obese.

RESULTS

The overall prevalence of metabolic syndrome was 1.4%, being present in; 15.6% of obese subjects. Overall, elevated systolic BP was most common (19.9%). In obese subjects, 51% had an elevated systolic BP.

CONCLUSION

Our study suggests that metabolic syndrome is present in more than 1% of male adolescents and 15% of obese male adolescents in Japan.

Phosphocalcic Metabolism after Biliopancreatic Diversion

BACKGROUND

Malabsorptive techniques to treat morbid obesity have been followed by alterations in phosphocalcic metabolism. Knowledge of the preoperative situation is important to assess the influence of these techniques on phosphocalcic metabolism and to consider treatments for these alterations.

METHODS

61 consecutive morbidly obese patients (50 women, 11 men, age 19 to 63 years) having had biliopancreatic diversion (BPD) were studied in a prospective manner. Preoperative and postoperative levels of calcium, phosphorus, 25-hydroxyvitamin D, tartrate resistant acid phosphate, plasma parathormone (PTH), tubular absorption of phosphate, and urinary calcium and pyridinolines were analyzed, as well as the potential risk factors for their alterations. Follow-up of all patients was a minimum of 4 years.

RESULTS

Before BPD, 42.3% of patients presented an increase in PTH and 54% a decrease in the 25-OH vitamin D, but the values of calcium and plasma phosphorus maintained at normal level. 81.8% of the patients with an increase in the PTH maintained high levels after BPD, while 60% of those with a normal preoperative PTH also presented hyperparathyroidism 4 years after the intervention. A correlation between the levels of plasma PTH and body mass index was not found.

CONCLUSION

Morbid obesity is accompanied by a high percentage of hyperparathyroidism. BPD produces malabsorption of vitamin D during the first years, favoring the persistence or appearance of hyperparathyroidism. It is important to recognize and treat the secondary hyperparathyroidism. The postoperative period could necessitate more energetic interventions to get more efficient control of the phosphocalcic metabolism.

Physical activity in young adults and incident hypertension over 15 years of follow-up: the CARDIA study

OBJECTIVE

We sought to examine the relation between physical activity and incident hypertension in young adults over 15 years of follow-up in the Coronary Artery Risk Development in Young Adults study.

METHODS

A total of 3993 Black and White men and women aged 18 to 30 years were examined at baseline, and 2, 5, 7, 10, and 15 years later. Blood pressure and physical activity were measured at each exam. Hypertension was defined as systolic 140 mm Hg or higher, diastolic 90 mm Hg or higher, or antihypertensive medication use. Average physical activity and incident hypertension over 15 years of follow-up were analyzed.

RESULTS

There were 634 cases of incident hypertension over 15 years of follow-up. Those who were more versus less physically active experienced a reduced risk (hazard rate ratio = 0.83; 95% confidence interval = 0.73, 0.93) for incident hypertension, after adjustment for race, sex, age, education, and family history of high blood pressure.

CONCLUSIONS

Physical activity merits attention in the prevention of incident hypertension among young adults, particularly as they move into middle age.

The metabolic syndrome: prevalence, CHD risk, and treatment

An increased risk of coronary heart disease (CHD) morbidity and mortality is associated with the metabolic syndrome, a condition characterized by the concomitant presence of several abnormalities, including abdominal obesity, dyslipidemia, hypertension, insulin resistance (with or without glucose intolerance or diabetes), microalbuminuria, prothrombotic, and proinflammatory states. Estimates of the prevalence of the metabolic syndrome indicate that this condition is now common and likely to increase dramatically over the coming decades, in parallel with greater rates of obesity and Type 2 diabetes. Risk factors for the metabolic syndrome are already present in obese children and adolescents. Thus, identifying and treating all affected individuals promptly and optimally are critical to ensure that this potentially challenging healthcare burden is minimized. Here, we review the prevalence of the metabolic syndrome, dyslipidemias, and CHD risk. Although changes in lifestyle are fundamental to reducing many of the CHD risk factors associated with the metabolic syndrome, pharmacologic interventions also play an important role. Retrospective subanalyses of the effects of statins on coronary event rates and lipid levels in patients with the metabolic syndrome included in clinical trials indicate that these agents are beneficial in correcting the extensive lipid abnormalities that are frequently present in these individuals. However, the optimal management of metabolic syndrome dyslipidemia will depend on the outcomes of future prospective clinical trials. This review examines the underlying causes and prevalence of the metabolic syndrome and its impact on CHD morbidity and mortality and discusses the role of statins in optimizing its management.

Childhood obesity and the metabolic syndrome

The current epidemic of obesity reflects environmental changes that have an impact on a genetically susceptible population. The scope of obesity and its associated comorbidities warrants its position among the most crucial global public health problems faced today. Society has gained better appreciation for the significance of this problem yet still has much to learn regarding how best to address the obesity crisis. Although strategies for treating individuals who have weight problems successfully continue to evolve, the most profound impacts ultimately will arise from societal changes dictating that all individuals strive to adopt a healthy lifestyle.

Prevention of Type 2 Diabetes by Diet and Lifestyle Modification

Diabetes mellitus is an epidemic of our time. This disease affects nearly 150 million adults worldwide and nearly 11 million in the United States in 2000. Because of the prevalence of obesity and diabetes and associated vascular complications, preventing even a small proportion of cases would save thousands of lives and billions of dollars in healthcare costs and lost productivity. Researchers have made great strides in identifying many lifestyle and dietary factors associated with diabetes, but solidifying the scientific basis for prevention and control of this disease as well as implementation at a national level remains a difficult challenge. The literature on the influence of diet and lifestyle in the development of diabetes is reviewed here, with emphasis on epidemiologic data. We outline a systematic approach to primary and secondary prevention of this disease by evaluating and prioritizing risk factors for which intervention is effective and developing a framework for application of intervention strategies. Effective interventions must target not only the affected individuals but also families, workplaces, schools and communities. Prevention of this devastating disease calls for the identification of culture-sensitive measures that can be applied to the population in general and some high-risk minority groups in particular.

Hypertension in black patients: Special issues and considerations

The excess risk for hypertension in black Americans continues to be a major health concern. Although there is considerable information regarding these disease trends, many of the major underpinnings of the etiology of hypertension remain unclear. The excess mortality in blacks due to heart disease, renal failure, and stroke is clearly directly related to the excess burden of hypertension. Amid the recent findings about the pathophysiology of hypertension, some clear differences in the effects of overweight, salt sensitivity, and vascular biology emerge along ethnic lines. These differences may shed some light on the development of more effective treatment strategies. Based on our current knowledge, aggressive management of hypertension in blacks is critical. This review highlights what is known about various factors affecting hypertension and its treatment in black Americans.

Hypertension in black patients: special issues and considerations

The excess risk of hypertension in black Americans continues to be a major health concern. Although there is considerable information regarding these disease trends, much of the major underpinnings of the etiology of hypertension remain unclear. The excess mortality in blacks due to heart disease, renal failure, and stroke are clearly directly related to the excess burden of hypertension. Amid the recent findings about the pathophysiology of hypertension, some clear differences in the effects of overweight, salt sensitivity, and vascular biology emerge along ethnic lines. These differences may shed some light on the development of more effective treatment strategies. Based on our current knowledge, aggressive management of hypertension in blacks is critical. This review highlights what is known about various factors affecting hypertension and its treatment in black Americans.

The metabolic syndrome in Chinese, Malays and Asian Indians. Factor analysis of data from the 1998 Singapore National Health Survey

We used factor analysis to define and compare the manner in which the various features of the metabolic syndrome are linked or clustered in Chinese, Malays and Asian Indians. One thousand nine hundred and fifty seven men (1324 Chinese, 391 Malays and 261 Asian Indians) and 2308 women (1622 Chinese, 391 Malays and 296 Asian Indians) were examined. Anthropometry, blood pressure, serum glucose, lipid concentrations, and serum insulin were measured for all subjects. These data were then subjected to factor analysis which reduced the variables examined to three factors in all ethnic groups and both genders. The first (dyslipidemia) factor was positively loaded for obesity, insulin resistance (IR), fasting triglyceride and negatively loaded for HDL-cholesterol. The second (hyperglycemia) factor was positively loaded for IR and blood glucose. The third (hypertension) factor was positively loaded for obesity and blood pressure. IR was positively loaded in the hypertension factor in Malay women but not in others. Rather than a single entity causally associated with insulin resistance (IR), our findings support a concept in which the metabolic syndrome represents several distinct entities (dyslipidemia, hypertension and hyperglycemia). It appears that Malay females may be more prone to develop hypertension in association with IR.

Do triglycerides explain the U-shaped relation between alcohol and diabetes risk? Results from a cross-sectional survey of alcohol and plasma glucose

The association between alcohol and blood glucose levels, and whether it is modified by other variables, was examined in a cross-sectional survey of 5518 staff aged 40-65 years at worksites in Auckland and Tokoroa, New Zealand. Diabetes was determined by oral glucose-tolerance tests using 1999 WHO criteria. Usual alcohol intake in the previous 3 months, measured by food frequency questionnaire, was related positively with fasting triglycerides and high-density-lipoprotein (HDL)-cholesterol, and unrelated with fasting glucose, but had an approximate U-shaped relationship with 2-h glucose, which varied from an adjusted mean (S.E.) of 5.62 (0.08) mmol/l in non-drinkers, down to 5.34 (0.08) mmol/l in light alcohol drinkers (alcohol <5 g per day), and back up to 5.52 (0.09) mmol/l in heavy drinkers (> or =20 g per day). Adjusting further for triglycerides increased the mean difference in 2-h glucose for all drinking categories compared with non-drinkers, particularly for heavy drinkers (> or =20 g per day), from -0.22 (S.E. = 0.10) to -0.37 (0.10) mmol/l. The confounding effect of triglycerides suggests alcohol may affect the diabetes risk by a mechanism related to the triglyceride metabolism, which in heavy drinkers may counteract the protective effect of improved insulin sensitivity, resulting in the U-shaped relationship between alcohol and diabetes described in previous studies.

Insulin Resistance and Hypertension

The association between insulin resistance and insulinemia and hypertension is controversial. We examined the relation between insulin resistance and hypertension in 564 non-Hispanic whites (NHW), 505 Hispanics (H), and 413 African Americans (AA) who participated in the Insulin Resistance Atherosclerosis Study (IRAS). Insulin sensitivity was measured with a frequently sampled intravenous glucose tolerance test with minimal model analysis. The prevalence of hypertension was 32.5%, 49.4%, and 32.3% in NHW, AA, and H, respectively ( P <0.001). When subjects without diabetes in all ethnic groups were combined, age, male sex, race (AA), body mass index (BMI), and insulin resistance, but not fasting insulin, were significantly associated with hypertension. When each ethnic group was analyzed separately, insulin resistance was significantly associated with hypertension in NHW and H, but not AA. After excluding subjects taking antihypertensive medications, male sex, BMI, fasting glucose, and insulin resistance, but not fasting insulin, were significant determinants of blood pressure. When the 3 ethnic groups were analyzed separately, insulin resistance was significantly associated with blood pressure in H, but not NHW, or AA. Neither insulin resistance nor fasting insulin was significantly associated with hypertension or blood pressure in subjects with diabetes of the 3 ethnic groups after adjusting for age, sex, BMI, and waist. In conclusion, insulin resistance, but not insulinemia, was related to hypertension and blood pressure in subjects without diabetes, but ethnic differences in these relations appear to exist. Neither insulin resistance nor insulinemia was related to hypertension or blood pressure in patients with type 2 diabetes in the 3 ethnic groups.

Prevalence of hyperinsulinemia and clinical correlates in overweight children referred for lifestyle intervention

Although not well documented in the literature, there is growing evidence that overweight children may develop hyperinsulinemia. Children (n=171) with a body mass index greater than the 85th percentile for age using the Centers for Disease Control and Prevention growth charts for children were recruited through primary care physician offices for a lifestyle change intervention. Laboratory measurements were obtained. About 30% of these children were identified as hyperinsulinemic, using an insulin-to-glucose ratio of > or =33% or a serum insulin > or =25 microU/mL. When compared with non-hyperinsulinemic children, there were significant differences in cardiovascular risk factors. Dietetics professionals providing medical nutrition therapy to overweight children need to be aware of dietary and physical activity recommendations for individuals with marked hyperinsulinemia.

Pathogenesis of Hypertension in African Americans

Hypertension is a compelling disease process that disproportionately affects African Americans. It is the single largest risk factor for cardiovascular disease in African Americans. The end organ manifestations of hypertension are striking and include higher rates of stroke, significantly increased renal disease including end-stage renal disease requiring dialysis, higher risk of left ventricular hypertrophy, and an associated higher risk of heart failure. The cause of these more aggressive end organ phenomena is likely multifactorial and includes a mix of genetic and environmental influences. Intriguing polymorphisms of the epithelial sodium channel are consistent with patterns of hypertension seen in African Americans. Obesity, especially in African-American women, may be closely related to hypertension as a result of sympathetic nervous system stimulation.

Interactive relation of insulin and gender to cardiovascular reactivity in healthy young adults

High levels of insulin may promote hypertension pathogenesis, in part, via enhanced sympathetic nervous system (SNS) activity. This study examined potential interactive relations of fasting insulin levels, gender, and race to cardiovascular reactivity-a correlate of SNS activation. Hemodynamic responses to 4 laboratory challenges were determined by impedance cardiography in 64 healthy young adults (ages 18-26; 48% male; 50% White, 50% African American). Also examined were lipoprotein lipids, central and total adiposity, self-reported dietary factors, and physical activity. High-insulin (>10.2 mU/ml) men showed greater total peripheral resistance and longer pre-ejection period responses than low-insulin ( pound 10.2 mU/ml) men. High-insulin women displayed greater cardiac index responses than high-insulin men. High insulin levels were related to greater percentage body fat, dietary carbohydrate and fat intake, lower high-density lipoprotein (HDL) cholesterol (in men), higher total cholesterol (in women), and a trend toward higher triglycerides. Cardiovascular reactivity findings were unchanged after statistical adjustment for total and HDL cholesterol, triglycerides, percentage body fat, dietary carbohydrates, and fat. The Gender x Insulin (continuous scores) interaction accounted for 7% and 9% of the variance in cardiac index and total peripheral resistance responses, respectively. These results indicate that high insulin levels are associated with greater vascular reactivity in young men and cardiac reactivity in young women. Enhanced cardiovascular reactivity may constitute a biobehavioral dimension of the metabolic syndrome.

Moderate alcohol consumption, estrogen replacement therapy, and physical activity are associated with increased insulin sensitivity: is abdominal adiposity the mediator?

OBJECTIVE

To investigate 1). associations between environmental factors (alcohol consumption, hormone replacement therapy [HRT], and physical activity) and insulin resistance and secretion, independent of genetic influences; 2). the contribution of abdominal adiposity to these relationships; and 3). whether gene-environment interactions mediate these associations.

RESEARCH DESIGN AND METHODS

Reported effects of lifestyle factors on insulin resistance and secretion are inconsistent, possibly due to difficulty in dissecting environmental from genetic influences and to confounding by adiposity. We examined these relationships in 798 nondiabetic female twins. Insulin resistance and secretion were estimated by modified homeostasis model assessment (HOMA-R' and HOMA-beta', respectively). Percent total body fat and percent central abdominal fat (CAF) were measured by dual-energy X-ray absorptiometry.

RESULTS

All categories of alcohol consumption were associated with lower insulin levels and HOMA-beta' than abstinence. Only moderate alcohol consumers (11-20 units/week) had lower HOMA-R' than abstainers (-0.16 +/- 0.09 vs. 0.14 +/- 0.13 SD, P = 0.048). This difference was attenuated after controlling for percent CAF (P = 0.57), which was lower in moderate drinkers. Controlling for genetic and smoking effects in cotwin case-control analysis, monozygotic pairs discordant for alcohol consumption had greater within-pair differences in HOMA-R' than concordant pairs (P = 0.02). Postmenopausal women using estrogen-only HRT had lower HOMA-R' than non-HRT users (-0.33 +/- 0.16 vs. 0.17 +/- 0.08 SD, P = 0.003), even after controlling for percent CAF. Lower fasting glucose levels and insulin resistance and secretion indexes in physically active subjects were partly explained by lower abdominal adiposity.

CONCLUSIONS

Moderate alcohol consumption, estrogen replacement, and physical activity are associated with increased insulin sensitivity in female twins. The favorable effects of moderate alcohol consumption and physical activity on insulin sensitivity are partly mediated by lower abdominal adiposity.

Is glycosylated hemoglobin A1c a surrogate for metabolic syndrome in nondiabetic, first-degree relatives of African-American patients with type 2 diabetes?

Glycosylated hemoglobin (Hb)A1c provides a practical assessment of long-term glycemic control in patients with diabetes. However, whether HbA1c has any clinical significance in metabolic syndrome (MS) in nondiabetic subjects remains debatable. Therefore, we examined the impact of different levels of HbA1c on insulin sensitivity (Si), non-insulin-dependent glucose disposal, and blood pressure (BP), as well as lipids and lipoproteins in nondiabetic, first-degree relatives of African-American patients with type 2 diabetes. The study consisted of 219 nondiabetic, first-degree relatives (offspring and siblings) of African-American patients with type 2 diabetes. To examine the metabolic impact of HbA1c in our population, HbA1c was divided into tertiles (normal range, 3.3-6.4%). The mean HbA1c was 4.7% (range, 3.3-4.8%, n = 74) for tertile 1, 5.4% (range, 4.9-5.6%, n = 73) for tertile 2, and 5.8% (range, 5.7-6.4%, n = 72) for tertile 3. Si and glucose effectiveness (Sg) were determined by the Bergman's minimal model method. Homeostasis model assessment (HOMA)-insulin resistance and HOMA-beta-cell function were also estimated. BP, body compositional variables, and body fat distribution, as well as fasting serum lipid and lipoprotein concentrations, were determined in each subject. The mean age, body weight, body mass index, waist and hip circumference, and systolic and diastolic BPs were significantly (P < 0.02-0.001) greater in the subjects in tertile 3 than those in tertiles 1 and 2. The mean fasting serum glucose was significantly (P < 0.01) higher in tertile 3 (95.5 +/- 3.2 mg/dl) than in tertile 2 (83.0 +/- 2.7 mg/dl) and tertile 1 (78.8 +/- 1.5 mg/dl). Mean fasting serum insulin and c-peptide levels tended to be higher in tertile 3 subjects than in those in tertiles 1 and 2, but the mean differences did not reach statistical significance. The mean Si was significantly (P < 0.001) lower in the subjects in tertile 3 [1.66 +/- 0.2019 x 10(-4).min(-1)( micro U/ml)(-1)], when compared with those in tertile 1 [2.27 +/- 0.20 19 x 10(-4).min(-1)( micro U/ml)(-1)] and tertile 2 [2.61 +/- 0.19 x 10(-4).min(-1)( micro U/ml)(-1)]. The mean Sg was significantly (P < 0.02) lower in tertile 3 (1.95 +/- 0.12 x 10(-2).min(-1)), when compared with those of tertile 1 (2.27 +/- 0.10 x 10(-2).min(-1)) and tertile 2 (2.29 +/- 0.11 x 10(-2).min(-1)). In addition, the (HOMA)-insulin resistance was significantly (P < 0.01) higher in tertile 3 (3.62 +/- 0.26) than in tertile 1 (2.6 +/- 0.21) and tertile 2 (2.55 +/- 0.31) HbA1c. In contrast, HOMA-beta-cell function, was not different among tertiles 1, 2, and 3. Mean fasting serum triglycerides, cholesterol, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol levels also were not significantly different in subjects in tertile 3, when compared with those in tertiles 1 and 2. In summary, the present study demonstrates that the upper tertile HbA1c level (tertile 3) reflects some components of MS in the nondiabetic, obese, first-degree relatives of African-Americans who are genetically predisposed to type 2 diabetes. The metabolic abnormalities in the upper tertile 3 subjects included a reduced insulin action (Si) and reduced Sg, as well as elevated systolic and diastolic BPs, but not beta-cell secretion and lipids and lipoproteins. We conclude that the upper tertile of HbA1c should be considered as a major surrogate of MS in high-risk African-Americans who are genetically predisposed to type 2 diabetes.

Relationship between birthweight and blood lipid concentrations in later life: evidence from the existing literature

BACKGROUND

It has been suggested that there is a link between fetal growth and chronic diseases later in life. Several studies have shown a negative association between birthweight and cardiovascular diseases, as well as cardiovascular disease risk factors, such as blood pressure and type 2 diabetes. Far fewer studies have focused on the association between size at birth and blood lipid concentrations. We have conducted a qualitative assessment of the direction and consistency of the relationship between size at birth and blood lipid concentrations to see whether the suggested relationship between intrauterine growth and cardiovascular diseases is mediated by lipid metabolism.

METHODS

A literature search covering the period January 1966 to January 2003 was performed using Medline, Embase, and Web of Science. All papers written in English and reporting the relationship between size at birth and lipid levels in humans were assessed. Bibliographies were searched for further publications.

RESULTS

From an initial screen of 1198 references, 39 papers were included involving 28 578 individuals. There was no consistent relationship between size at birth and blood lipid levels; the one exception being triglyceride concentration, which showed statistically significant negative or U-shaped, but not positive, relationships with birthweight.

CONCLUSION

This review does not strongly support a link between birthweight and blood lipid levels in later life. However, the research in this area is limited and in order to make any definitive conclusions, longitudinal studies with sufficient power, data, and prospective follow-up are needed.

Insulin sensitivity and cardiovascular risk factors in hypertensive and normotensive native Ghanaians

AIMS/HYPOTHESIS

The objective of this study was to examine the relationships among insulin and insulin sensitivity and risk factors for cardiovascular diseases in native Ghanaians with and without hypertension.

METHODS

We measured the anthropometric parameters, systolic and diastolic blood pressure, fasting serum triglycerides, cholesterol and high-density lipoprotein cholesterol and fasting and stimulated glucose, insulin and C-peptide of 200 Ghanaian subjects, who were between 25 to 74 years of age, and residing in the Accra Metropolitan area. Serum glucose, C-peptide and insulin concentrations were measured at baseline (fasting) and also 2 h after 75 gm oral glucose drink. Homeostasis model assessment was used to measure insulin resistance. Hypertension was defined as a blood pressure higher than 140/90 mmHg.

RESULTS

There were 53 subjects with hypertension (HBP) and 147 subjects with normal blood pressure (NBP). The mean BMI, waist circumference and waist-to-hip circumference ratio for HBP and NBP subjects were 27.4+/-0.8, 24.8+/-0.4 kg/m(2); 89.8+/-11.7, 81.1+/-0.9 cm; and 0.87+/-0.08, 0.82+/-0.08 respectively, (p<0.05). The fasting and 2-h plasma glucose concentrations in HBP and NBP subjects were 5.5+/-0.2, 7.2+/-0.3 mmol/l and 5.2+/-01, 6.8+/-0.2 mmol/l respectively (p>0.05). The corresponding fasting and 2-h insulin concentrations were 10.0+/-0.7, 8.0+/-0.4 uU/ml and 47.3+/-3.7, 37.3+/-2.5 uU/ml respectively (p<0.05). The insulin resistance index (HOMA-IR) in the HBP and the NBP groups were 2.49+/-0.2 and 1.95+/-0.13 (p<0.05). The two groups had similar fasting and stimulated C-peptide, lipids and HDL concentrations. Correlations were found between blood pressure and the concentrations of lipids, HDL, fasting and stimulated insulin and C-peptide, and between fasting insulin and HOMA-IR with lipids and HDL concentrations. On multiple regression analysis, fasting insulin and HOMA-IR did not influence blood pressure variations significantly.

CONCLUSIONS/INTERPRETATION

We found clustering of hyperinsulinaemia, insulin resistance and truncal obesity in hypertensive Ghanaian subjects but dissociation between insulin resistance, hypertension and atherogenic lipid and lipoprotein profile.

Insulin resistance in African Americans

Hypertension and diabetes mellitus are the leading contributors to end-stage renal disease. African Americans suffer higher rates of renal failure as well as other vascular morbidities associated with hypertension and diabetes. Insulin resistance is strongly associated with hypertension. Insulin resistance is a component of diabetes and also precedes the clinical expression of type 2 diabetes. The relationship of blood pressure with insulin resistance, or impaired insulin action, occurs in African Americans and can be detected at young ages prior to the clinical expression of hypertension or diabetes. Through its relationship with hypertension, diabetes, and hyperlipidemia, insulin resistance is associated with endothelial dysfunction. The interface of insulin resistance with endothelial dysfunction may begin to explain the role of insulin resistance in vascular and renal pathology. The injury process, subsequent to both hypertension and diabetes, appears to be mediated by alterations tissue regulatory factors, and include vasoactive peptides such as angiotensin II, endothelin, and growth factors. Understanding the determinants that up-regulate the aberrant pathways and the early phases of these processes will be necessary to formulate strategies to effectively achieve renal protection and reduce the rates of renal failure in African Americans.

Risk factor profile for atherosclerosis among young adults in Israel--results of a large-scale survey from the young adult periodic examinations in Israel (YAPEIS) database

Assessing the prevalence of relevant risk factors among young adults is a critical step in the process of preventing atherosclerotic cardiovascular diseases (ASCVD) later in life. The Israel Defense Force Periodic Health Examination Center performs a routine check-up for subjects aged 25-45 years. Medical history, physical examination notes, laboratory results and ECG tracings are recorded, computerized and processed to form the Young Adults Periodic Examinations in Israel (YAPEIS) database. Data representing 31,640 subjects (27,769 males and 3871 females) examined between the years 1991-1999 were analyzed. The prevalence of documented risk factors for ASCVD were evaluated. The results of all parameters were graded categorically as low, moderate or high and the Framingham risk score was calculated. Fifty-one percent of the study participants were found to be overweight (body mass index > or = 25 kg/m2), 8.5% had high systolic blood pressure and 14.6% had high diastolic blood pressure. The prevalence of hypercholesterolemia and hyperglycemia was found to be 44.7 and 9.7%, respectively. Thirty-two percent of the subjects smoked cigarettes, and 76.7% reported not performing any routine physical activity. Furthermore, 31.8% had a Framingham score indicating a greater than 5% risk for developing a coronary event within the next 10 years. As expected, the prevalence of these risk factors increased with age and were found to be less frequent among females. Thus we conclude that many young Israeli adults hold significant risk factors for future ASCVD. Many of these risk factors are modifiable, and risk behavior is often amenable to alteration. Awareness to the high prevalence of risk factors among young adults should spark vigorous health-promotion programs as well as screening, education, and interventional measures aimed at altering the expected outcome of future ASCVD.

Dyslipidemia of the metabolic syndrome

The three major components of dyslipidemia associated with the metabolic syndrome are increased fasting and postprandial triglyceride-rich lipoproteins (TRLs), decreased high-density lipoprotein (HDL), and increased small, dense low-density lipoprotein (LDL) particles. Insulin resistance and compensatory hyperinsulinemia lead to overproduction of very low-density lipoprotein particles. A relative deficiency of lipoprotein lipase, an insulin-sensitive enzyme, is partly responsible for the decreased clearance of fasting and postprandial TRLs, and the decreased production of HDL particles. The resulting increased concentration of cholesteryl ester-rich fasting and postprandial TRLs is the central lipoprotein abnormality of the metabolic syndrome. The increase of small, dense LDL particles, and decrease of large, buoyant HDL particles are consequential events. All these lipoprotein defects contribute largely to the increased cardiovascular disease risk in individuals with insulin resistance. Peroxisome proliferator-activated receptor (PPAR)a, PPARg, and PPARd agonists seem to improve dyslipidemia of the metabolic syndrome by regulating the expression of important genes involved in the deranged lipoprotein metabolism associated with insulin resistance.

Neighborhood characteristics and components of the insulin resistance syndrome in young adults: the coronary artery risk development in young adults (CARDIA) study

OBJECTIVE

To examine associations of neighborhood characteristics with six components of the insulin resistance syndrome (IRS) in young adults.

RESEARCH DESIGN AND METHODS

Cross-sectional data from the Coronary Artery Risk Development in Young Adults (CARDIA) Study were used to examine associations of neighborhood characteristics with the IRS in 3,093 nondiabetic adults aged 28-40 years. Measures of BMI, fasting HDL cholesterol, triglycerides, insulin, glucose, and systolic blood pressure were combined into an IRS score. U.S. Census-derived neighborhood characteristics were summarized into a neighborhood socioeconomic score, with an increasing score signifying increasing socioeconomic advantage.

RESULTS

Among white men and women, the IRS score was inversely related to neighborhood socioeconomic score. Neighborhood characteristics remained associated with the IRS score after controlling for personal income and education (adjusted mean differences for 95th vs. 5th percentile of neighborhood score: -0.24 standard deviation units [SE = 0.12] in men and -0.56 standard deviation units [SE = 0.10] in women). Among black participants, neighborhood score was inversely associated with IRS score in persons of high income and education (mean differences 95th vs. 5th percentile -0.54 [SE 0.26] in men and -0.52 [SE 0.26] in women) but positively associated or not associated with IRS score in persons of low income and education (mean differences 0.60 [SE 0.21] in men and 0.00 [SE 0.16] in women).

CONCLUSIONS

The IRS score is associated with neighborhood characteristics as early as young adulthood. Features of residential environments may be related to the development of insulin resistance.