Sex differences in the association between proinsulin and intact insulin with coronary heart disease in nondiabetic older adults: the Rancho Bernardo Study

Association of sulphonylurea treatment with all-cause and cardiovascular mortality: a systematic review and meta-analysis of observational studies

We conducted a meta-analysis of cohort and case-control studies to evaluate all-cause and cardiovascular (CV) mortality of patients with type 2 diabetes mellitus (T2DM) who received sulphonylurea (SU) treatment, when compared to any other diabetes treatment. Only studies reporting raw data on mortality during SU treatment were included. Data were combined using random-effects (RE) models. Unadjusted odds ratios (ORs) are presented. Of 4991 publication titles and abstracts reviewed, 20 studies (n = 551,912 patients) were included. For cohort studies (n = 276,050), patients receiving SU monotherapy or combination treatment had significantly higher all-cause and CV mortality risks compared to any non-SU treatment [all-cause, 13 studies: OR = 1.92, 95% confidence interval (CI) = 1.48-2.49; CV, 5 studies: OR = 2.72, 95% CI = 1.95-3.79]. Validity was limited by the high treatment group heterogeneity (I (2) > 90%) and study-inherent biases/design differences. In conclusion, patients receiving SU treatment had increased all-cause and CV mortality risks. However, the meta-analysis was limited by the high heterogeneity of non-randomized studies.

Risk factors for type 2 diabetes mellitus preceded by β-cell dysfunction, insulin resistance, or both in older adults: the Cardiovascular Health Study

Insulin resistance (IR) and pancreatic β-cell dysfunction lead to type 2 diabetes mellitus (DM). We tested whether risk factors would differ for DM that was preceded predominantly by IR, β-cell dysfunction, or both among 4,384 older adults (mean age, 72.7 (standard deviation, 5.6) years) in the Cardiovascular Health Study, which was conducted in North Carolina, California, Maryland, and Pennsylvania (1989-2007). When evaluating established risk factors, we found older age, greater adiposity, higher systolic blood pressure, a lower high-density lipoprotein cholesterol level, a higher triglyceride level, and a lower alcohol intake to be independently associated with greater IR but, conversely, with better β-cell function (P < 0.001). The prospective associations between some risk factors and incident DM varied significantly depending on whether DM was preceded predominantly by IR, β-cell dysfunction, or both. For example, obesity and lower high-density lipoprotein cholesterol levels were positively associated with DM preceded predominantly by IR (hazard ratio (HR) = 5.02, 95% confidence interval (CI): 2.81, 9.00; and HR = 1.97, 95% CI: 1.32, 2.93, respectively), with a significant association with and an insignificant trend toward a lower risk of DM preceded predominantly by β-cell dysfunction (HR = 0.33, 95% CI: 0.14, 0.80; and HR = 0.78, 95% CI: 0.43, 1.39, respectively). In conclusion, among older adults, DM risk factors were differentially associated with DM preceded predominantly by IR or β-cell dysfunction. Biologic and clinical implications of putative subtypes of DM require further investigation.

The Rancho Bernardo Study: 40 years studying why women have less heart disease than men and how diabetes modifies women's usual cardiac protection

Forty years ago, few cohort studies of cardiovascular disease (CVD) included women and fewer still included diabetes or glycemia as a risk factor. I describe here the Rancho Bernardo Study (RBS), a single-site, >40-year cohort study of sex differences in heart disease and how diabetes modifies women's natural cardioprotection. More than 6000 participants were followed for morbidity and mortality, with nearly 3000 survivors (and death certificates for >85% of decedents). In RBS more than half of diabetes was undiagnosed without an oral glucose tolerance test (OGTT); more women than men had isolated post-challenge hyperglycemia (IPH) as their only glucose evidence of diabetes; men had more diabetes than women, with higher fasting but lower post-challenge glucose levels than women; women with diabetes had more classical CVD risk factors than men; excess risk-factor clustering partially explained how diabetes eradicates female cardioprotection. Post-challenge glucose was a stronger CVD risk factor than fasting glucose. Endogenous insulin was not an independent CVD risk factor in women or men. Men with higher testosterone levels developed less diabetes and had fewer metabolic syndrome components. In men higher total testosterone levels predicted a reduced risk of all-cause and CVD but not cancer mortality. In women both extremes of bioavailable testosterone predicted fatal coronary heart disease but not all-cause mortality. Summary point estimates from large systematic reviews of individual data have replicated most RBS findings. Ongoing research can further clarify how diabetes modifies women's cardioprotection from mid-life to old age.

Association of proinsulin and hepatic steatosis in a random, population-based sample

OBJECTIVE

Proinsulin may represent a predictive marker for assessing insulin resistance and reduced β-cell function. The objective of this study was to investigate the association between hepatic steatosis, proinsulin and other parameters in a random, population-based sample.

DESIGN

Cross-sectional study, conducted in south-western Germany.

METHODS

Upper abdominal ultrasound examinations were performed in 343 subjects (147 females, 196 males; average age 40.0±11.5 years). Proinsulin, the proinsulin-to-insulin ratio and other laboratory parameters were determined, and the BMI, waist-to-hip ratio (WHR) and other anthropometric data were documented.

RESULTS

HEPATIC STEATOSIS WAS OBSERVED IN 80 SUBJECTS (23.3%: 29.6%, males; 15.0%, females). Multivariate analysis showed an association with hepatic steatosis for male gender (P=0.0212), advancing age (P=0.0241), elevated BMI (P<0.0001), elevated WHR (P=0.0024), alanine aminotransferase (P=0.0046), proinsulin (P=0.0403) and proinsulin-to-insulin ratio (P=0.0116).

CONCLUSIONS

There is an association between elevated proinsulin concentrations and hepatic steatosis.

In type 2 diabetes patients, insulin glargine is associated with lower postprandial release of intact proinsulin compared with sulfonylurea treatment

OBJECTIVE

Our objective was to investigate how postprandial processing of intact proinsulin is influenced by different pharmacological strategies in type 2 diabetes mellitus (T2DM).

MATERIALS/METHODS

This exploratory, nonrandomized, cross-sectional study recruited T2DM patients and healthy subjects. Upon recruitment, eligible T2DM patients had been treated for ≥6 months with insulin glargine (GLA) plus metformin (MET), sulfonylureas (SU) plus MET, or dipeptidyl-peptidase-4 inhibitors (DPP-4-I) plus MET. Blood samples were drawn from study participants after an 8 h fast and at regular intervals for up to 5 h after consumption of a standardized meal. Study endpoints included postprandial intact proinsulin and insulin levels and the insulin/proinsulin ratio.

RESULTS

As expected, postprandial secretion of proinsulin was greater in all T2DM treatment groups than in healthy subjects (p < .01 for all comparisons). Postprandial release of proinsulin was significantly greater in T2DM patients treated with SU plus MET than in those treated with GLA plus MET (p = .003). Treatment with DPP-4-I plus MET was associated with reduced proinsulin secretion versus SU plus MET and an increased insulin/proinsulin ratio versus the other T2DM groups.

CONCLUSIONS

Treatment of T2DM with GLA plus MET or DPP-4-I plus MET was associated with a more physiological postprandial secretion pattern of the β cell compared with those treated with SU plus MET.

Cardiovascular benefits of GLP-1-based herapies in patients with diabetes mellitus type 2: effects on endothelial and vascular dysfunction beyond glycemic control

Type 2 diabetes mellitus (T2DM) is a progressive multisystemic disease accompanied by vascular dysfunction and a tremendous increase in cardiovascular mortality. Numerous adipose-tissue-derived factors and beta cell dysfunction contribute to the increased cardiovascular risk in patients with T2DM. Nowadays, numerous pharmacological interventions are available to lower blood glucose levels in patients with type 2 diabetes. Beside more or less comparable glucose lowering efficacy, some of them have shown limited or probably even unfavorable effects on the cardiovascular system and overall mortality. Recently, incretin-based therapies (GLP-1 receptor agonists and DPP-IV inhibitors) have been introduced in the treatment of T2DM. Beside the effects of GLP-1 on insulin secretion, glucagon secretion, and gastrointestinal motility, recent studies suggested a couple of direct cardiovascular effects of GLP-1-based therapies. The goal of this paper is to provide an overview about the current knowledge of direct GLP-1 effects on endothelial and vascular function and potential consequences on the cardiovascular outcome in patients with T2DM treated with GLP-1 receptor agonists or DPP-IV inhibitors.

The association of intensity and overall level of physical activity energy expenditure with a marker of insulin resistance

AIMS/HYPOTHESIS

Physical activity is important in preventing insulin resistance, but it is unclear which dimension of activity confers this benefit. We examined the association of overall level and intensity of physical activity with fasting insulin level, a marker of insulin resistance.

METHODS

This was a cross-sectional analysis of the Medical Research Council Ely population-based cohort study (2000--2002). Physical activity energy expenditure (PAEE) in kJ kg(-1) min(-1) was measured by heart rate monitoring with individual calibration over a period of 4 days. The percentage of time spent above 1.5, 1.75 and 2 times resting heart rate (RHR) represented all light-to-vigorous, moderate-to-vigorous and vigorous activity, respectively.

RESULTS

Data from a total of 643 non-diabetic individuals (319 men, 324 women) aged 50 to 75 years were analysed. In multivariate linear regression analyses, adjusting for age, sex and body fat percentage, PAEE was significantly associated with fasting insulin (pmol/l) (beta = -0.875, p = 0.006). Time (% of total) spent above 1.75 x RHR and also time spent above 2 x RHR were both significantly associated with fasting insulin (beta = -0.0109, p = 0.007 and beta = -0.0365, p = 0.001 respectively), after adjusting for PAEE, age, sex and body fat percentage. Time spent above 1.5 x RHR was not significantly associated with fasting insulin in a similar model (beta = -0.0026, p = 0.137).

CONCLUSIONS/INTERPRETATION

The association between PAEE and fasting insulin level, a marker of insulin resistance, may be attributable to the time spent in moderate-to-vigorous and vigorous activity, but not to time spent in light-intensity physical activity.

Association between proinsulin, insulin, proinsulin/insulin ratio, and insulin resistance status with the metabolic syndrome

The Metabolic Syndrome (MS) constitutes an independent risk factor of cardiovascular disease. There is evidence that proinsulin blood levels and the proinsulin/insulin ratio are associated to the MS. The purpose of this study was to compare proinsulin and insulin, insulin resistance index, and the proinsulin/insulin ratio as predictors of MS. This is a cross-sectional study involving 440 men and 556 women with a mean age of 24 years. Diagnosis of MS was made according to the National Cholesterol Education Program Adult Treatment Panel III. Blood levels of insulin and proinsulin were measured, and the insulin resistance status was estimated using the homeostatic model assessment (HOMA-IR). The prevalence of MS was 10.1%. HOMA-IR was the best MS risk factor for both women and men (OR = 2.04; 95% CI: 1.68-2.48 and 1.09; 95% CI: 1.05-1.13, respectively). HOMA-IR presented the best positive predictive value for MS: 22% and 36% for men and women, respectively, and was the best MS indicator. The proinsulin/insulin ratio did not show significant association with MS. HOMA-IR, proinsulin, and insulin presented good negative predictive values for both genders that could be used to identify an at-risk population.

Proinsulin:insulin and insulin:glucose ratios as predictors of carotid plaque growth: a population-based 7 year follow-up of the Tromsø Study

AIMS/HYPOTHESIS

Proinsulin is increased in persons at cardiovascular risk. Increased secretion of proinsulin relative to insulin has been suggested as a sign of defective conversion of proinsulin to insulin and C-peptide and is associated with beta cell dysfunction. It has also been suggested that proinsulin has more of a pro-atherogenic effect than insulin, the levels of which are also increased in the insulin resistance state. In this prospective population-based study, we examined whether the proinsulin:insulin ratio (PIR) or insulin:glucose ratio (IGR, an insulin resistance surrogate) predicted carotid plaque size in nondiabetic participants.

MATERIALS AND METHODS

The study included 1,859 men and 1,998 women aged 25-82 years from the Tromsø Study, who were examined with B-mode high resolution ultrasound at baseline in 1994-1995 and at follow-up in 2001-2002. All images were computer processed to yield mm(2) measures of plaque. Proinsulin and insulin were measured at baseline. All analyses were stratified for sex.

RESULTS

After adjusting for age, baseline plaque area, BMI, cholesterol, HDL-cholesterol, HbA(1c), IGR, albumin:creatinine ratio, fibrinogen, BP and lifestyle factors (tobacco smoking, alcohol consumption, physical activity), PIR was significantly associated with plaque size at follow-up in women but not men. For each SD in the PIR in women, the mean plaque area increased by 0.97 mm(2) (95% CI 0.44-1.50). IGR was not associated with carotid plaque size.

CONCLUSIONS/INTERPRETATION

The PIR is associated with progressive carotid artery plaque size in women.

Effect of simvastatin and/or pioglitazone on insulin resistance, insulin secretion, adiponectin, and proinsulin levels in nondiabetic patients at cardiovascular risk--the PIOSTAT Study

We investigated the effect of pioglitazone in comparison with and in combination with simvastatin on insulin resistance, plasma adiponectin, postprandial plasma glucose, insulin, and intact proinsulin levels in a nondiabetic population at cardiovascular risk. One hundred twenty-five nondiabetic patients at cardiovascular risk were randomized to pioglitazone (PIO), pioglitazone and simvastatin (PIO/SIM), or simvastatin (SIM) treatments. Blood samples were taken for the measurement of adiponectin and lipid levels. In addition, an oral glucose load with the measurements of glucose, insulin, and intact proinsulin levels was performed. Adiponectin levels increased from 14.0+/-8.2 to 27.6+/-14.5 microg/mL (P<.0001) during PIO treatment and from 11.7+/-10.0 to 26.7+/-15.7 microg/mL (P<.0001) during PIO/SIM treatment. A decrease in adiponectin levels from 15.5+/-12.7 to 11.6+/-7.0 microg/mL (P<.05) was observed during SIM treatment. Although fasting intact proinsulin levels remained unchanged, the increase in postprandial intact proinsulin levels could be reduced from 29.5+/-21.4 to 22.1+/-17.5 pmol/L (P<.01) during PIO treatment and from 24.3+/-27.4 to 21.1+/-16.5 mmol/L (P<.05) during PIO/SIM treatment. Lipid parameters improved during SIM treatment but not during PIO treatment. Combined treatment with PIO/SIM was superior in improving overall cardiovascular risk profile than every single drug.

Association between the ankle-brachial index and carotid intimal medial thickness in the Rancho Bernardo Study

Previous cross-sectional studies have demonstrated significant associations between the ankle-brachial index (ABI) and carotid intimal medial thickness (IMT). In a longitudinal study, 637 participants who had ABI measurements from 1992 to 1994 were tested for carotid IMT an average of 4.8 years later. Mean age was 72.5 years; 60% were women. More than half (51%) were hypertensive, whereas 28% had dyslipidemia, 56% were past or current smokers, and 6% had diabetes. The mean +/- SD ABI and IMT were 1.06 +/- 0.13 and 1.28 +/- 0.44 mm, respectively. Mean age- and gender-adjusted IMTs for the ABI groups of <or=0.90, 0.91 to 0.99, and 1.00 to 1.09 were significantly greater than those from 1.10 to 1.26 (1.53, 1.49, 1.28, and 1.18 mm, respectively, p <0.05 for all). In logistic regression analyses, each of these ABI groups was significantly associated with increased odds for an IMT in the highest decile compared with an ABI of 1.10 to 1.26 (odds ratios 3.2, 4.3, and 2.3, respectively, p <0.05 for all). In conclusion, an ABI of 1.10 to 1.26 was associated with the lowest levels of cardiovascular disease risk factors and carotid atherosclerosis, suggesting that a new cut point for ABI risk stratification should be considered.

Association of serum proinsulin with hormone replacement therapy in nondiabetic older women: the Rancho Bernardo Study

OBJECTIVE

One putative benefit of hormone replacement therapy (HRT) is a reduced risk of diabetes or reduced fasting glucose level. We report here the association of HRT with proinsulin, insulin, and fasting and postchallenge glucose levels in older adults.

RESEARCH DESIGN AND METHODS

Current HRT use was validated and cross-sectionally compared with diabetes-related variables in 785 women without diabetes by history or glucose tolerance test.

RESULTS

Median age was 72 years (range 50-97); median value of fasting plasma glucose, postchallenge plasma glucose, and proinsulin was 5.08 mmol/l, 6.93 mmol/l, and 9.3 pmol/l, respectively. In age-adjusted comparisons, current HRT use was associated with significantly lower fasting plasma glucose and higher postchallenge plasma glucose compared with never/previous HRT use, as well as with lower LDL and higher HDL cholesterol and higher triglycerides. Fasting and postchallenge intact insulin did not differ by HRT group, but proinsulin was significantly lower in current HRT users than in previous and never HRT users. The significant association between proinsulin and HRT status persisted after adjustment for age, waist-to-hip ratio, pulse pressure, LDL-to-HDL cholesterol ratio, triglycerides, fasting and postchallenge glucose, and intact insulin.

CONCLUSIONS

Reduced fasting and increased 2-h glucose replicate findings in a randomized clinical trial. The proinsulin effect has not been previously reported. Decreased fasting glucose and proinsulin levels in current HRT use suggest a potential antidiabetes effect of HRT. Increased postchallenge glucose in HRT, however, suggests insulin resistance and would be expected to increase the risk of heart disease.

Relationship between true fasting plasma insulin level and angiographic characteristics of coronary atherosclerosis

BACKGROUND

Reports about the relationships between specific insulin concentration and coronary heart disease risk are controversial.

HYPOTHESIS

The objective of this study was to examine the association between insulin level and the severity of coronary atherosclerosis.

METHODS

The study population consisted of 507 consecutive patients (376 men and 131 women) who underwent coronary angiography for suspected or known coronary atherosclerosis. The patients' habits of smoking and drinking were investigated, and anthropometric measurements including body mass index, systolic and diastolic blood pressures, as well as plasma measurements including lipids and blood glucose were taken. The true insulin level was measured using a highly sensitive two-site sandwich ELISA. The severity of coronary atherosclerosis was defined by the Gensini score system. The statistical methods including Kruskal-Wallis test, chi-square analysis, Spearman correlation analysis, and multivariate stepwise linear regression analysis were employed to explore the relationship between specific insulin level and coronary atherosclerosis.

RESULTS

When the Gensini score was examined as a categorical variable classified by tertile values, subjects with a high Gensini score had significantly higher values of fasting plasma specific insulin level (p = 0.022). The Spearman correlation analysis suggest that the Gensini score correlated significantly with true insulin (mIU/l) (r = 0.095, p = 0.033). However, the results from the multivariate stepwise linear regression analysis show that the association between specific insulin level and severity of coronary atherosclerosis lost its significance.

CONCLUSIONS

The level of plasma fasting specific insulin was associated significantly with the severity of coronary atherosclerosis, as measured by Gensini score, but hyperinsulinemia showed no association with the severity of coronary atherosclerosis in multivariate analyses.

Impact of rosiglitazone on beta-cell function, insulin resistance, and adiponectin concentrations: results from a double-blind oral combination study with glimepiride

Addition of rosiglitazone to sulfonylurea has been shown to improve glycemic control in patients with type 2 diabetes previously treated with sulfonylurea monotherapy alone. This investigation was performed to assess the specific impact of rosiglitazone on insulin resistance, beta-cell function, cardiovascular risk markers, and adiponectin secretion in this treatment concept. One hundred two patients from a double-blind, 3-arm comparator trial (group 0, glimepiride + placebo, n = 30; group 4, glimepiride + 4 mg rosiglitazone, n = 31; group 8, glimepiride + 8 mg rosiglitazone, n = 41; 48 women, 54 men; age [mean +/- SD], 62.8 +/- 9.1 years; body mass index, 28.7 +/- 4.5 kg/m2; diabetes duration, 6.4 +/- 4.8 years; HbA1c, 8.1% +/- 1.5%) were analyzed after 0 and 16 weeks of treatment. Observation parameters were HbA1c, glucose, homeostasis model assessment for insulin resistance score, insulin, intact proinsulin, and adiponectin. Insulin resistance was defined by elevated intact proinsulin values or homeostasis model assessment for insulin resistance score of more than 2. All parameters were comparable in the 3 groups at baseline. Substantial and significant dose-dependent improvements were observed after addition of rosiglitazone for fasting glucose (group 0, -9 +/- 48 mg/dL; group 4, -38 +/- 47 mg/dL; group 8, -46 +/- 53 mg/dL), HbA1c (-0.1% +/- 0.7%, -1.1% +/- 1.2%, -1.3% +/- 1.2%), insulin (1.4 +/- 6.2, -1.2 +/- 5.3, -3.7 +/- 9.9 microU/mL), intact proinsulin (1.6 +/- 7.1, -2.0 +/- 4.6, -3.1 +/- 6.1 pmol/L), and high-sensitivity C-reactive protein (0.2 +/- 2.6, -1.7 +/- 3.5, -2.1 +/- 3.5 mg/L). After adjustment for changes in body weight, significant increases in adiponectin were detected with rosiglitazone, whereas glimepiride alone did not induce a comparable effect (-0.5 +/- 5.8, 8.8 +/- 22.9, 14.3 +/- 19.9 mg/L). The number of insulin-resistant patients decreased in both rosiglitazone treatment groups, whereas no change was seen with glimepiride alone. Next to the reported effects on glucose control, rosiglitazone provided an additional beneficial effect on insulin resistance, beta-cell function, and cardiovascular risk markers. In conclusion, our short-term investigation of rosiglitazone action provides further experimental support for the rationale of combining rosiglitazone with sulfonylurea drugs in patients with type 2 diabetes.

Fasting insulin concentrations and coronary heart disease incidence in France and Northern Ireland: the PRIME Study

BACKGROUND

Reports about the relationships between insulin concentrations and CHD risk are controversial. The objective of this survey was to study the association between insulin levels and CHD risk in middle-aged male participants of the PRIME Study after 5 years of follow-up.

METHODS

Our study adopted a nested case-control design including 294 cases of CHD and 536 controls randomly selected among healthy participants from the PRIME cohort. Data were obtained by questionnaires (medical history, lifestyle), standardised clinical measurements (blood pressure, anthropometric measurements), and a blood sample was obtained for biological measurements. Odds-Ratios for associations of four ordered classes of insulin concentration with CHD risk after adjustment for confounding factors were estimated using conditional logistic regression.

RESULTS

In Belfast, a significant trend (p<0.03) was observed between insulin classes and CHD risk in bivariate analyses, but this association lost its significance after multiple adjustments. In the French centres, a high risk of CHD (OR=3.24 [1.80-5.85], p<0.0001) was observed only for the second class of insulin concentration (6.5 to 9.9 mIU/l), compared with the reference class (<6.5 mIU/l). After multiple adjustments, this association remained highly significant (OR=2.92 [1.44-5.92], p<0.005).

CONCLUSIONS

In Belfast (high-risk population), a significant trend was observed between insulin concentration classes and CHD risk but hyperinsulinaemia lost its association with CHD risk in multivariate analyses. In the French centres (lower risk population), slightly increased insulin concentrations were associated with a high risk of CHD, independently of cardiovascular risk factors and other features of the metabolic syndrome, but very high insulin concentrations were not.

Insulin sensitivity, proinsulin and insulin as predictors of coronary heart disease. A population-based 10-year, follow-up study in 70-year old men using the euglycaemic insulin clamp

AIMS/HYPOTHESIS

The association between CHD and insulin sensitivity (Si) measured by the euglycaemic insulin clamp has not been examined previously. Earlier studies found a relationship between CHD and elevated plasma insulin, an analysis that may have been confounded by co-determination of proinsulin, which has evolved as a stronger predictor of CHD. The aim was to determine the longitudinal relationships between Si, intact proinsulin, 32-33 split proinsulin, specific insulin and subsequent CHD.

METHODS

This was a population-based cohort study of 815 men in Uppsala, Sweden, aged 70 years at baseline with a follow-up of up to 10 years. Baseline insulin sensitivity was determined by euglycaemic insulin clamp. Fasting proinsulin, 32-33 split proinsulin and specific insulin concentrations were analysed using specific two-site immunometric assays. CHD was taken as diagnosed, if stated (in the event of death) on the Cause of Death Registry, or for subjects hospitalised for the first time with CHD, if CHD was recorded in the Hospital-Discharge Registry. The associations were analysed using Cox's proportional hazards, presented as hazard ratios (HRs) with their 95% CIs for a one-SD increase in the predictor.

RESULTS

In multivariate analysis, Si (HR:0.80, CI:0.65-0.97) adjusted for serum cholesterol, systolic blood pressure, fasting plasma glucose, BMI and smoking predicted CHD. Intact proinsulin (HR:1.18, CI:1.01-1.38), adjusted as the model above, predicted CHD, whereas 32-33 split proinsulin (HR:1.13, CI:0.95-1.35) or specific insulin (HR:1.07, CI:0.89-1.30) did not.

CONCLUSIONS/INTERPRETATION

Insulin resistance measured by the euglycaemic insulin clamp predicts subsequent CHD in elderly men. Proinsulin provides a better prediction of CHD than insulin.

Proinsulin concentration is an independent predictor of all-cause and cardiovascular mortality: an 11-year follow-up of the Hoorn Study

OBJECTIVE

High proinsulin concentration may be a better predictor for cardiovascular disease (CVD) mortality than insulin concentration. Previous observations may have been confounded by glucose tolerance status or lack of precision because of high intraindividual variability. We investigated the longitudinal relation of means of duplicate measurements of insulin and proinsulin with all-cause and CVD mortality in a population-based cohort taking glucose tolerance status into account.

RESEARCH DESIGN AND METHODS

Fasting and post-75-g glucose-load (2-h) glucose, insulin, and proinsulin values were determined in duplicate on separate days in 277 participants with normal glucose metabolism, 208 participants with impaired glucose metabolism, and 119 newly detected patients with type 2 diabetes of the Hoorn Study. Insulin resistance and beta-cell function were estimated by homeostasis model assessment (HOMA-IR and HOMA-B, respectively), and the fasting proinsulin-to-insulin ratio was calculated. Subjects were followed with respect to mortality until January 2003.

RESULTS

Fasting proinsulin levels were significantly associated with all-cause and CVD mortality. The hazard ratios (HRs) per increase in interquartile range adjusted for age and sex were 1.21 (95% CI 1.04-1.42) for all-cause mortality and 1.33 (1.06-1.66) for CVD mortality. Adjustment for glucose tolerance status and HOMA-IR did not substantially change the associations.

CONCLUSIONS

Fasting proinsulin was associated with all-cause and CVD mortality, independent of glucose tolerance status and insulin resistance and largely independent of other CVD risk factors. Proinsulin might play a role in the relationship between insulin resistance and CVD.

Significant association of insulin and proinsulin with clustering of cardiovascular risk factors

AIM: To investigate the association between true insulin and proinsulin and clustering of cardiovascular risk factors.

METHODS: Based on the random stratified sampling principles, 1196 Chinese people (533 males and 663 females, aged 35-59 years with an average age of 46.69 years) were recruited. Biotin-avidin based double monoclonal antibody ELISA method was used to detect the true insulin and proinsulin, and a risk factor score was set to evaluate individuals according to the number of risk factors.

RESULTS: The median (quartile range) of true insulin and proinsulin was 4.91 mIu/L (3.01-7.09 mIu/L) and 3.49 pmol/L (2.14-5.68 pmol/L) respectively, and the true insulin level of female subjects was significantly higher than that of male subjects (P = 0.000), but the level of proinsulin displayed no significant difference between males and females (P = 0.566). The results of covariate ANOVA after age and sex were controlled showed that subjects with any of the risk factors had a significantly higher true insulin level (P = 0.002 for hypercholesterolemia, P = 0.021 for high low-density lipoprotein cholesterol, P = 0.003 for low high-density lipoprotein cholesterol, and P = 0.000 for other risk factors) and proinsulin level (P = 0.001 for low high-density lipoprotein cholesterol, and P = 0.000 for other risk factors) than those with no risk factors. Furthermore, subjects with higher risk factor scores had a higher true insulin and proinsulin level than those with lower risk factor scores (P = 0.000). The multiple linear regression models showed that true insulin and proinsulin were significantly related to cardiovascular risk factor scores respectively (P = 0.000).

CONCLUSION: True insulin and proinsulin are significantly associated with the clustering of cardiovascular risk factors.

The plasminogen activator inhibitor-1 -675 4G/5G genotype influences the risk of myocardial infarction associated with elevated plasma proinsulin and insulin concentrations in men from Europe: the HIFMECH study

Although the potential role of plasminogen activator inhibitor-1 (PAI-1) in the development of coronary artery disease is strongly supported by its biological characteristics, results of clinical studies remain controversial.

OBJECTIVES

To investigate whether plasma PAI-1 concentrations and the -675 4G/5G polymorphism located in the PAI-1 gene could constitute risk markers for myocardial infarction (MI).

PATIENTS AND METHODS

We used a European case-control study, the HIFMECH study, comparing 598 men with MI and 653 age-matched controls.

RESULTS

Insulin resistance explained a major part of the variation in PAI-1 (24%) whereas inflammation had only a minor contribution (0.01%). For both cases and controls plasma PAI-1 concentrations were significantly higher in the North than the South, and in both regions were higher in individuals with MI compared with control subjects [overall odds ratio (OR) for a 1 SD increase=1.54, 95% confidence interval (CI) 1.34, 1.77]. This difference was observed in all the centers studied. Overall, the difference between cases and control subjects remained significant after controlling for inflammation variables (OR=1.30, 95% CI 1.08, 1.57), but lost significance after controlling for insulin resistance variables (OR=1.17, 95% CI 0.98, 1.40). The 4G allele was associated with significantly higher PAI-1 levels in cases but not controls and, taken independently, did not modify the risk of MI (P=0.9). However, a significant interaction was observed with both insulin or proinsulin and the risk of MI (P=0.05 and 0.02, respectively), but not with triglycerides or body mass index (BMI). The insulin or proinsulin effect on risk was observed only in the carriers of the 4G/4G genotype. This interaction appeared not to be mediated by plasma PAI-1 antigen concentrations (P=0.01 and 0.02 after adjustment for PAI-1 plasma levels). The interaction with proinsulin but not insulin remained statistically significant after further adjustment for other factors associated with insulin resistance (triglycerides and BMI) and C-reactive protein (P=0.01).

CONCLUSION

This study suggests that PAI-1 has a role in risk of MI in the presence of underlying insulin resistance. A significant interaction between insulin or proinsulin and the -675 4G/5G polymorphism was observed in risk for MI. The mechanisms for these interactions remain to be determined.