Hyperinsulinaemia is not a major coronary risk factor in elderly men. The study of men born in 1913

The Epidemiological Boehringer Ingelheim Employee Study (Part 3): Association of Elevated Fasting Insulin Levels but Not HOMA-IR With Increased Intima Media Thickness and Arteriosclerosis in Middle-Aged Persons

Background: Recently published genetic studies have indicated a causal link between elevated insulin levels and cardiovascular disease (CVD) risk. We, therefore, hypothesized that increased fasting insulin levels are also associated with precursors of CVD such as endothelial lesions. Methods: Middle-aged (≥40 years, n = 1,639) employees were followed up for the occurrence of increased intima media thickness (IMT ≥ 1 mm) or plaques in abdominal or cervical arteries (arteriosclerosis). Multivariable logistic regression analyses determined the incidence of increased IMT or arteriosclerosis. Adjusted relative risk (ARR) for increased IMT and arteriosclerosis was calculated by using Mantel-Haenszel analysis. Results: Increased IMT was diagnosed in 238 participants (15 %) and 328 (20 %) developed arteriosclerosis after 5 years of follow-up. Logistic regression analysis identified fasting insulin, BMI and smoking as risk factors for both cardiovascular endpoints (all p < 0.05), whereas age and diastolic blood pressure were risk factors for increased IMT only, and male sex was associated with incident arteriosclerosis only (all p < 0.01). Additional adjustment for BMI change during follow-up did not modify these associations (including fasting insulin), but adjustment for fasting insulin change during follow-up removed BMI as risk factor for both cardiovascular endpoints. Fasting insulin change during follow-up but not BMI change associated with increased IMT and arteriosclerosis (both p < 0.001). ARR analysis indicated that high fasting insulin and BMI added to age and sex as risk factors. Homeostatic model assessment of insulin resistance (HOMA-IR) did not associate with either cardiovascular endpoint in any model and smoking did not increase the risk conferred by high fasting insulin levels. Conclusions: Higher fasting insulin levels and increases in fasting insulin over time are associated with atherogenic progression and supersede BMI as well as HOMA-IR as risk factors.

Insulin resistance is a cardiovascular risk factor in humans

Diabetes is a common metabolic disorder associated to elevated cardiovascular morbidity and mortality that is not explained by hyperglycemia or traditional cardiovascular risk factors such as smoking or hypercholesterolemia. Intensive glycemic control with insulin that achieves near-normal glycemia does not reduce significantly macrovascular complications compared with conventional glycemic control. Cardiovascular disease continues to develop in patients with diabetes despite adequate glycemic control. In contrast, intensive control with metformin (leading to insulin resistance improvement) reduces diabetes complications, including cardiovascular events, suggesting that enhancement of insulin sensitivity rather than plasma glucose level has a major role improving diabetes outcomes. Accordingly, insulin resistance estimated by glucose tolerance tests is better predictor of future cardiovascular events than fasting glucose level in nondiabetic individuals. Insulin resistance precedes for decades the clinical onset of type 2 diabetes and deteriorates metabolic control of type 1 diabetes. Numerous investigations including cross-sectional and prospective studies, meta-analyses, and systematic reviews provide compelling evidence that insulin resistance by itself is a cardiovascular risk factor in a variety of population groups, including the general population and patients with diabetes. Several estimations of insulin resistance have been consistently associated with elevated rate of cardiovascular events independently of other cardiovascular risk factors and diabetes status. The clinical expression of insulin resistance (the metabolic syndrome or any of its components including obesity, hyperinsulinemia, hypertension, and dyslipemia) has been related to cardiovascular disease as well. An estimation conducted by the Archimedes model confirms that insulin resistance is the most important single cause of coronary artery disease.

Insulin enhances dendritic cell maturation and scavenger receptor-mediated uptake of oxidised low-density lipoprotein

OBJECTIVES

The prevalence of atherosclerotic cardiovascular disease is increased in patients with type 2 diabetes. The role of hyperinsulinaemia as an independent participant in the atherogenic process is controversial. Therefore, we examined whether insulin regulates the expression of scavenger receptors responsible for oxidised low-density lipoprotein (oxLDL) uptake in dendritic cells (DCs). In addition, we investigated the impact of insulin on DC maturation with regard to changes in phenotype and cytokine secretion.

METHODS

Immature DCs were cultured with different concentrations of insulin (1nmol/L, 10nmol/L, 50nmol/L, and 100nmol/L) in the absence or presence of LY294002 or PD98059 for 24h. The expression of the scavenger receptors SR-A and CD36 was determined by real-time PCR and Western blot analysis. Furthermore, DCs were incubated with 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI)-labelled oxLDL. The DiI-oxLDL-incorporated fraction was investigated by flow cytometry. Finally, flow cytometry was used to investigate immunophenotypic protein expression (CD83, CD86, and CD11a). Supernatant cytokine measurements were used as indicators of immune function.

RESULTS

The incubation of DCs with insulin enhanced SR-A and CD36 gene and protein expression in a dose-dependent manner. This effect was partially abolished by PD98059, which is an extracellular signal-regulated kinase (ERK) inhibitor. However, LY294002 did not inhibit the effect of insulin on scavenger receptor expression. A high concentration of insulin increased the oxLDL-uptake capacity of DCs. Inhibition of the scavenger receptors SR-A and CD36 significantly reduced oxLDL uptake. Furthermore, a high concentration of insulin induced DC maturation. The pro-atherosclerotic chemokines IL-6 and IL-12 were induced by a high concentration of insulin, whereas the release of anti-atherosclerotic IL-10 was reduced.

CONCLUSION

This study suggests that hyperinsulinaemia can promote DC activation and up-regulate the expression of the scavenger receptors SR-A and CD36, which can increase the oxLDL-uptake capacity of DCs. The results of the present study indicate that one of the mechanisms by which insulin promotes atherogenesis is mediated by its effects on DCs.

[The association of hyperinsulinemia with cardiovascular risk and cancer poses new challenges in the treatment of the insulin resistance type 2 diabetes patient]

Hyperinsulinemia has been associated with cardiovascular risk, both independently and by facilitating the development of other cardiovascular risk factors. It has also been associated by different routes with increased cancer risk. Thus, this makes it a priority to identify and treat the hyperinsulinemic patient early in order to delay or prevent cardiovascular risk and the development of type 2 diabetes mellitus (T2DM) and certain types of cancer. A new strategy is needed for the treatment of hyperglycemia in these patients, whose primary objective would be to achieve weight loss, reduce insulin resistance and thereby hyperinsulinemia. That is, prescribing insulin secretors and insulin should be used with caution in these patients.

Validation of insulin sensitivity surrogate indices and prediction of clinical outcomes in individuals with and without impaired renal function

As chronic kidney disease (CKD) progresses with abnormalities in glucose and insulin metabolism, commonly used insulin sensitivity indices (ISIs) may not be applicable in individuals with CKD. Here we sought to validate surrogate ISIs against the glucose disposal rate by the gold-standard hyperinsulinemic euglycemic glucose clamp (HEGC) technique in 1074 elderly men of similar age (70 years) of whom 495 had and 579 did not have CKD (estimated glomerular filtration rate (eGFR) under 60 ml/min per 1.73 m(2) (median eGFR of 46 ml/min per 1.73 m(2))). All ISIs provided satisfactory (weighted κ over 0.6) estimates of the glucose disposal rate in patients with CKD. ISIs derived from oral glucose tolerance tests (OGTTs) agreed better with HEGC than those from fasting samples (higher predictive accuracy). Regardless of CKD strata, all ISIs allowed satisfactory clinical discrimination between the presence and absence of insulin resistance (glucose disposal rate under 4 mg/kg/min). We also assessed the ability of both HEGC and ISIs to predict all-cause and cardiovascular mortality during a 10-year follow-up. Neither HEGC nor ISIs independently predicted mortality. Adjustment for renal function did not materially change these associations. Thus, ISIs can be applied in individuals with moderately impaired renal function for diagnostic purposes. For research matters, OGTT-derived ISIs may be preferred. Our data do not support the hypothesis of kidney function mediating insulin sensitivity (IS)-associated outcomes nor a role for IS as a predictor of mortality.

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

BACKGROUND

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

OBJECTIVE

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

DESIGN

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

RESULTS

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

CONCLUSIONS

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

Insulin and cardiovascular disease: biomarker or association?

In the 1980s prospective studies using whole populations suggested a relationship between insulin and cardiovascular disease, and these studies proposed that both metabolic and haemodynamic factors were associated with cardiovascular events. The initial analysis of the Paris Prospective Study (Diabetologia 19: 205-210), published in 1980, showed a positive correlation between insulin and cardiovascular events in healthy middle-aged policemen after a 5 year follow-up. In the Bedford Survey (Diabetologia 22: 79-84), also performed in the 1980s, a higher cardiovascular risk was demonstrated in diabetic patients and in those with borderline diabetes; however, in contrast to the Paris Prospective Study, insulin was negatively correlated to cardiovascular endpoints in the Bedford Survey. The initial enthusiasm for insulin as a cardiovascular risk marker was dampened when the 15 year follow-up data of the Paris Prospective Study (Diabetologia 34: 356-361) showed that the correlation between insulin and cardiovascular risk subsided with increased duration of follow-up. Despite the fact that hyperinsulinaemia was always strongly associated with other classical cardiovascular risk factors, univariate analyses usually failed to show a strong correlation between insulin and cardiovascular risk. The San Antonio Heart Study (Diabetologia 34: 416-422) performed in a bi-ethnic population that included a large proportion of Mexican-American participants again emphasised that insulin resistance may be the underlying factor associated with a cluster of metabolic and haemodynamic abnormalities. However, recently performed meta-analyses that included larger studies have not been able to confirm a critical role for insulin levels in cardiovascular risk. Indeed, it has been suggested that proinsulin or other factors may be better markers than insulin per se.

Insulin promotes macrophage foam cell formation: potential implications in diabetes-related atherosclerosis

The prevalence of atherosclerotic cardiovascular disease is higher in patients with type 2 diabetes, a disorder characterized by hyperinsulinemia and insulin resistance. The role of hyperinsulinemia as an independent participant in the atherogenic process has been controversial. In the current study, we tested the effect of insulin and the insulin sensitizer, adiponectin, on human macrophage foam cell formation. We found that both insulin and adiponectin increased the expression of the type 2 scavenger receptor CD36 by approximately twofold and decreased the expression of the ATP-binding cassette transporter ABCA1 by >80%. In both cases regulation was post-transcriptional. As a consequence of these changes, we found that oxidized LDL (oxLDL) uptake was increased by 80% and cholesterol efflux to apolipoprotein A1 (apoA1) was decreased by ∼25%. This led to two- to threefold more cholesterol accumulation over a 16-h period. As reported previously in studies of murine systems, scavenger receptor-A (SR-A) expression on human macrophages was downregulated by insulin and adiponectin. Insulin and adiponectin did not affect oxLDL-induced secretion of monocyte attractant protein-1 (MCP-1) and interleukin-6 (IL-6). These studies suggest that hyperinsulinemia could promote macrophage foam cell formation and thus may contribute to atherosclerosis in patients with type 2 diabetes.

Effect of pre-diabetes on future risk of stroke: meta-analysis

OBJECTIVES

To assess the association between pre-diabetes and risk of stroke, and to evaluate whether this relation varies by diagnostic criteria for pre-diabetes.

DESIGN

Systematic review and meta-analysis of prospective studies.

DATA SOURCES

A search of Medline, Embase, and the Cochrane Library (1947 to 16 July 2011) was supplemented by manual searches of bibliographies of key retrieved articles and relevant reviews.

SELECTION CRITERIA

Prospective cohort studies that reported multivariate adjusted relative risks and corresponding 95% confidence intervals for stroke with respect to baseline pre-diabetes were included.

DATA EXTRACTION

Two independent reviewers extracted data on pre-diabetes status at baseline, risk estimates of stroke, study quality, and methods used to assess pre-diabetes and stroke. Relative risks were pooled using random effects models when appropriate. Associations were tested in subgroups representing different characteristics of participants and studies. Publication bias was evaluated with funnel plots.

RESULTS

The search yielded 15 prospective cohort studies including 760,925 participants. In 8 studies analysing pre-diabetes defined as fasting glucose 100-125 mg/dL (5.6-6.9 mmol/L), the random effects summary estimate did not show an increased risk of stroke after adjustment for established cardiovascular risk factors (1.08, 95% confidence interval 0.94 to 1.23; P = 0.26). In 5 studies analysing pre-diabetes defined as fasting glucose 110-125 mg/dL (6.1-6.9 mmol/L), the random effects summary estimate showed an increased risk of stroke after adjustment for established cardiovascular risk factors (1.21, 1.02 to 1.44; P = 0.03). In 8 studies with information about impaired glucose tolerance or combined impaired glucose tolerance and impaired fasting glucose, the random effects summary estimate showed an increased risk of stroke after adjustment for established cardiovascular risk factors (1.26, 1.10 to 1.43; P < 0.001). When studies that might have enrolled patients with undiagnosed diabetes were excluded, only impaired glucose tolerance or a combination of impaired fasting glucose and impaired glucose tolerance independently raised the future risk of stroke (1.20, 1.07 to 1.35; P = 0.002).

CONCLUSION

Pre-diabetes, defined as impaired glucose tolerance or a combination of impaired fasting glucose and impaired glucose tolerance, may be associated with a higher future risk of stroke, but the relative risks are modest and may reflect underlying confounding.

Evaluation of insulin resistance in normoglycemic patients with coronary artery disease

BACKGROUND

Insulin resistance is clearly associated with coronary artery disease (CAD) in diabetics. Insulin resistance may also be present in normoglycemic individuals, and some of these patients can be diagnosed as having metabolic syndrome (MS) according to various definitions. However, the relationship between hyperinsulinemia and CAD is obscure in normoglycemic individuals, especially in patients who do not meet the criteria for MS.

HYPOTHESIS

This study evaluated insulin resistance in normoglycemic patients with CAD, and investigated the association of insulin resistance with inflammation and lipid levels.

METHODS

Fifty-six CAD patients, and 57 age- and sex-matched controls with normal coronary arteries confirmed by conventional coronary arteries angiography were included in the study. Participants were considered for the diagnosis of MS according to criteria of the National Cholesterol Education Program (NCEPATP III) and the International Diabetes Federation (IDF). Fasting plasma glucose, insulin, lipids, and c-reactive protein (CRP) levels were studied. The homeostasis model assessment insulin resistance index (HOMA IR) was calculated.

RESULTS

The ratio of subjects with MS was similar in the 2 groups. Insulin, CRP, low-density lipoprotein (LDL) cholesterol, and HOMA IR were higher in the study group than in the controls. The HOMA IR, LDL cholesterol, and serum CRP levels were determined as predictors of CAD.

CONCLUSION

Our data revealed that insulin resistance and subclinical inflammation are present in normoglycemic patients with CAD. As the proportion of patients with MS was similar in the 2 groups, we suggest that HOMA IR values may provide more sensitive information than MS definitions about the association between insulin resistance and CAD in normoglycemic patients.

Relationship of glycemic control, exogenous insulin, and C-peptide levels to ischemic heart disease mortality over a 16-year period in people with older-onset diabetes: the Wisconsin Epidemiologic Study of Diabetic Retinopathy (WESDR)

OBJECTIVE

The purpose of this study was to examine the relationship of glycemic control and exogenous and endogenous insulin levels with all-cause and cause-specific mortality (ischemic heart disease and stroke) in an older-onset diabetic population.

RESEARCH DESIGN AND METHODS

The Wisconsin Epidemiologic Study of Diabetic Retinopathy (WESDR) is an ongoing, prospective, population-based cohort study of individuals with diabetes first examined in 1980-1982. A stratified sample of all individuals with diabetes diagnosed at 30 years of age or older was labeled "older-onset" (n = 1,370). Those participating in the 1984-1986 examination phase (n = 1,007) were included in the analysis. Endogenous insulin was determined by measurements of plasma C-peptide (in nanomoles per liter), and exogenous insulin was calculated in units per kilogram per day. Glycemic control was determined by levels of glycosylated hemoglobin (HbA(1)).

RESULTS

After 16 years of follow-up, 824 individuals died (all-cause mortality); 358 deaths involved ischemic heart disease and 137 involved stroke. C-peptide and HbA(1) were significantly associated with all-cause and ischemic heart disease mortality in our study. The hazard ratio (95% CI) values for all-cause mortality were 1.12 (1.07-1.17) per 1% increase in HbA(1), 1.20 (0.85-1.69) per 1 unit x kg(-1) x day(-1) increase in exogenous insulin, and 1.15 (1.04-1.29) per 1 nmol/l increase in C-peptide and for ischemic heart disease mortality were 1.14 (1.06-1.22), 1.50 (0.92-2.46), and 1.19 (1.02-1.39) for HbA(1), exogenous insulin, and C-peptide, respectively, after adjusting for relevant confounders. C-peptide was associated with stroke mortality only among men (1.65 [1.07-2.53]).

CONCLUSIONS

Our results show that individuals with higher endogenous insulin levels are at higher risk of all-cause, ischemic heart disease, and stroke mortality.

Age and follow-up time affect the prognostic value of the ECG and conventional cardiovascular risk factors for stroke in adult men

OBJECTIVES

To explore whether the predictive power of mid-life ECG abnormalities and conventional cardiovascular risk factors for future stroke change over a 30-year follow-up period, and whether a repeated examination improves their predictive power.

DESIGN AND SETTING

Longitudinal population-based study.

PARTICIPANTS

2,322 men aged 50 years, with a follow-up period of 30 years. 1,221 subjects were re-examined at age 70 years

MAIN OUTCOME MEASURE

Risk for fatal and non-fatal stroke during three decades of follow-up. Investigations included resting ECG and traditional cardiovascular risk factors.

RESULTS

When measured at age 50 years, ST segment depression and T wave abnormalities, together with ECG-left ventricular hypertrophy, were of importance only during the first 20 years, but regained importance when re-measured at age 70 years. Blood pressure was a significant predictor for stroke over all three decades of follow-up. In elderly people only, there is evidence that apolipoprotein A1 may protect from future stroke.

CONCLUSION

Mid-life values for blood pressure and ECG abnormalities retain their predictive value over long follow-up periods even though they improved in predictive power when re-measured in elderly people. Despite lower prevalence, ECG abnormalities had greater impact at age 50 years than at age 70 years. By contrast, apolipoprotein A1 was protective for future stroke only at age 70 years.

Serum leptin and its relation to anthropometric measures of obesity in pre-diabetic Saudis

Background

Little information is available on leptin concentrations in individuals with IGT. This study aims to determine and correlate leptin levels to anthropometric measures of obesity in pre-diabetic, (IFG and IGT), type 2 diabetic and normoglycaemic Saudis.

Methods

308 adult Saudis (healthy controls n = 80; pre-diabetes n = 86; Type 2 diabetes n = 142) participated. Anthropometric parameters were measured and fasting blood samples taken. Serum insulin was analysed, using a solid phase enzyme amplified sensitivity immunoassay and also leptin concentrations, using radio-immunoassay. The remaining blood parameters were determined using standard laboratory procedures.

Results

Leptin levels of diabetic and pre-diabetic men were higher than in normoglycaemic men (12.4 [3.2–72] vs 3.9 [0.8–20.0] ng/mL, (median [interquartile range], p = 0.0001). In females, leptin levels were significantly higher in pre-diabetic subjects (14.09 [2.8–44.4] ng/mL) than in normoglycaemic subjects (10.2 [0.25–34.8] ng/mL) (p = 0.046). After adjustment for BMI and gender, hip circumference was associated with log leptin (p = 0.006 with R2 = 0.086) among all subjects.

Conclusion

Leptin is associated with measures of adiposity, hip circumference in particular, in the non-diabetic state among Saudi subjects. The higher leptin level among diabetics and pre-diabetics is not related to differences in anthropometric measures of obesity.

The metabolic syndrome: time for a critical appraisal: joint statement from the American Diabetes Association and the European Association for the Study of Diabetes

The term "metabolic syndrome" refers to a clustering of specific cardiovascular disease (CVD) risk factors whose underlying pathophysiology is thought to be related to insulin resistance. Since the term is widely used in research and clinical practice, we undertook an extensive review of the literature in relation to the syndrome's definition, underlying pathogenesis, and association with CVD and to the goals and impact of treatment. While there is no question that certain CVD risk factors are prone to cluster, we found that the metabolic syndrome has been imprecisely defined, there is a lack of certainty regarding its pathogenesis, and there is considerable doubt regarding its value as a CVD risk marker. Our analysis indicates that too much critically important information is missing to warrant its designation as a "syndrome." Until much needed research is completed, clinicians should evaluate and treat all CVD risk factors without regard to whether a patient meets the criteria for diagnosis of the "metabolic syndrome."

The metabolic syndrome: time for a critical appraisal. Joint statement from the American Diabetes Association and the European Association for the Study of Diabetes

BACKGROUND

The term 'metabolic syndrome' refers to a clustering of specific cardiovascular disease (CVD) risk factors whose underlying pathophysiology is thought to be related to insulin resistance.

METHODS

Since the term is widely used in research and clinical practice, we undertook an extensive review of the literature in relation to the syndrome's definition, underlying pathogenesis, association with cardiovascular disease and to the goals and impact of treatment.

DISCUSSION

While there is no question that certain CVD risk factors are prone to cluster, we found that the metabolic syndrome has been imprecisely defined, there is a lack of certainty regarding its pathogenesis, and there is considerable doubt regarding its value as a CVD risk marker. Our analysis indicates that too much critically important information is missing to warrant its designation as a 'syndrome'.

CONCLUSION

Until much-needed research is completed, clinicians should evaluate and treat all CVD risk factors without regard to whether a patient meets the criteria for diagnosis of the 'metabolic syndrome'.

Fasting intact proinsulin is a highly specific predictor of insulin resistance in type 2 diabetes

OBJECTIVE

In later stages of type 2 diabetes, proinsulin and proinsulin-like molecules are secreted in increasing amounts with insulin. A recently introduced chemiluminescence assay is able to detect the uncleaved "intact" proinsulin and differentiate it from proinsulin-like molecules. This investigation explored the predictive value of intact proinsulin as an insulin resistance marker.

RESEARCH DESIGN AND METHODS

In total, 48 patients with type 2 diabetes (20 women and 28 men, aged 60 +/- 9 years [means +/- SD], diabetes duration 5.1 +/- 3.8 years, BMI 31.2 +/- 4.8 kg/m2, and HbA1c 6.9 +/- 1.2%) were studied by means of an intravenous glucose tolerance test and determination of fasting values of intact proinsulin, insulin, resistin, adiponectin, and glucose. Insulin resistance was determined by means of minimal model analysis (MMA) (as the gold standard) and homeostatis model assessment (HOMA).

RESULTS

There was a significant correlation between intact proinsulin values and insulin resistance (MMA P<0.05 and HOMA P<0.01). Elevation of intact proinsulin values above the reference range (>10 pmol/l) showed a very high specificity (MMA 100% and HOMA 92.9%) and a moderate sensitivity (MMA 48.6% and HOMA 47.1%) as marker for insulin resistance. Adiponectin values were slightly lower in the insulin resistant group, but no correlation to insulin resistance could be detected for resistin in the cross-sectional design.

CONCLUSIONS

Elevated intact proinsulin seems to indicate an advanced stage of beta-cell exhaustion and is a highly specific marker for insulin resistance. It might be used as arbitrary marker for the therapeutic decision between secretagogue, sensitizer, or insulin therapy in type 2 diabetes.

HOMA-estimated insulin resistance is an independent predictor of cardiovascular disease in type 2 diabetic subjects: prospective data from the Verona Diabetes Complications Study

OBJECTIVE

To evaluate whether homeostasis model assessment-estimated insulin resistance (HOMA-IR) is an independent predictor of cardiovascular disease (CVD) in type 2 diabetes.

RESEARCH DESIGN AND METHODS

Conventional CVD risk factors (sex, age, smoking, plasma lipids, blood pressure, and metabolic control) and insulin resistance (estimated by HOMA) were evaluated at baseline in 1,326 patients with type 2 diabetes examined within the Verona Diabetes Complications Study. At baseline and after a mean follow-up of 4.5 years, CVD was assessed by medical history, physical examination, electrocardiography, and echo-Doppler of carotid and lower limb arteries. Death certificates and medical records of subjects who died during the follow-up were carefully scrutinized to identify cardiovascular deaths. In statistical analyses, CVD was an aggregate end point including both fatal and nonfatal coronary, cerebrovascular, and peripheral vascular disease as well as ischemic electrocardiographic abnormalities and vascular lesions identified by echo-Doppler.

RESULTS

At baseline, 441 subjects were coded positive for CVD (prevalent cases). Incident cases numbered 126. Multiple logistic regression analyses showed that, along with sex, age, smoking, HDL/total cholesterol ratio, and hypertension, HOMA-IR was an independent predictor of both prevalent and incident CVD. A 1-unit increase in (log)HOMA-IR value was associated with an odds ratio for prevalent CVD at baseline of 1.31 (95% CI 1.10-1.56, P = 0.002) and for incident CVD during follow-up of 1.56 (95% CI 1.14-2.12, P < 0.001).

CONCLUSIONS

HOMA-IR is an independent predictor of CVD in type 2 diabetes. The improvement of insulin resistance might have beneficial effects not only on glucose control but also on CVD in patients with type 2 diabetes.

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

BACKGROUND

The role of a cluster of risk factors characteristic for the insulin resistance syndrome as a predictor for coronary heart disease (CHD) has not been studied previously.

METHODS AND RESULTS

Clustering of cardiovascular risk factors was analyzed by factor analysis to investigate whether these clusters (factors) predict CHD events (CHD death or nonfatal myocardial infarction) in a nondiabetic population of 1069 subjects 65 to 74 years old from eastern Finland followed up for 7 years. There were 151 CHD events (92 for men, 59 for women) during the follow-up period. In men, factor 1 (the insulin resistance factor, which reflected primarily body mass index, waist-to-hip ratio, triglycerides, fasting plasma glucose, and insulin) (hazards ratio [HR] with 95% CI, 1.33, CI 1.08, 1.65, P=0.008), factor 2 (alcohol consumption, high HDL cholesterol, low triglycerides) (HR 0.78, CI 0.63, 0.96, P=0.020), factor 3 (age, systolic blood pressure, urinary albumin/creatinine ratio, left ventricular hypertrophy) (HR 1.52, CI 1.26, 1.83, P<0.001), and factor 4 (high total cholesterol and triglycerides) (HR 1.42, CI 1. 15, 1.77, P=0.002) predicted CHD events in multivariate Cox regression analysis. In women, the insulin resistance factor did not predict CHD events (HR 1.06, CI 0.82, 1.36), but factor 2 (previous stroke, low HDL cholesterol and high triglycerides) (HR 1.34, CI 1. 06, 1.69, P=0.014) and factor 3 (age, systolic blood pressure, urinary albumin/creatinine ratio, left ventricular hypertrophy) (HR 1.44, CI 1.15, 1.82, P=0.002) predicted CHD events.

CONCLUSIONS

Our study supports the notion that the insulin resistance syndrome is a risk factor for CHD in elderly men.

Western-type diets induce insulin resistance and hyperinsulinemia in LDL receptor-deficient mice but do not increase aortic atherosclerosis compared with normoinsulinemic mice in which similar plasma cholesterol levels are achieved by a fructose-rich diet

The role of insulin resistance (IR) in atherogenesis is poorly understood, in part because of a lack of appropriate animal models. We assumed that fructose-fed LDL receptor-deficient (LDLR-/-) mice might be a model of IR and atherosclerosis because (1) fructose feeding induces hyperinsulinemia and IR in rats; (2) a preliminary experiment showed that fructose feeding markedly increases plasma cholesterol levels in LDLR-/- mice; and (3) hypercholesterolemic LDLR-/- mice develop extensive atherosclerosis. To test whether IR could be induced in LDLR-/- mice, 3 groups of male mice were fed a fructose-rich diet (60% of total calories; n=16), a fat-enriched (Western) diet intended to yield the same plasma cholesterol levels (n=18), or regular chow (n=7) for approximately 5.5 months. The average cholesterol levels of both hypercholesterolemic groups were similar (849+/-268 versus 964+/-234 mg/dL) and much higher than in the chow-fed group (249+/-21 mg/dL). Final body weights in the Western diet group were higher (39+/-6.2 g) than in the fructose- (27.8+/-2.7 g) or chow-fed (26.7+/-3.8 g) groups. Contrary to expectation, IR was induced in mice fed the Western diet, but not in fructose-fed mice. The Western diet group had higher average glucose levels (187+/-16 versus 159+/-12 mg/dL) and 4.5-fold higher plasma insulin levels. Surprisingly, the non-insulin-resistant, fructose-fed mice had significantly more atherosclerosis than the insulin-resistant mice fed Western diet (11.8+/-2.9% versus 7.8+/-2. 5% of aortic surface; P<0.01). These results suggest that (1) fructose-enriched diets do not induce IR in LDLR-/- mice; (2) the Western diets commonly used in LDLR-/- mice may not only induce atherosclerosis, but also IR, potentially complicating the interpretation of results; and (3) IR and hyperinsulinemia do not enhance atherosclerosis in LDLR-/- mice, at least under conditions of very high plasma cholesterol levels. The fact that various levels of hypercholesterolemia can be induced in LDLR-/- mice by fat-enriched diets and that such diets induce IR and hyperinsulinemia suggest that LDLR-/- mice may be used as models to elucidate the effect of IR on atherosclerosis, eg, by feeding them Western diets with or without insulin-sensitizing agents.

Insulin potentiates platelet-derived growth factor action in vascular smooth muscle cells

Correlative studies have indicated that hyperinsulinemia is present in many individuals with atherosclerosis. Insulin resistance has also been linked to cardiovascular disease. It has proved to be difficult to decipher whether hyperinsulinemia or insulin resistance plays the most important role in the pathogenesis of atherosclerosis and coronary artery disease. In this study, we demonstrate that insulin increases the amount of farnesylated p21Ras in vascular smooth muscle cells (VSMC), thereby augmenting the pool of cellular Ras available for activation by platelet-derived growth factor (PDGF). In VSMC incubated with insulin for 24 h, PDGF's influence on GTP-loading of Ras was significantly increased. Furthermore, in cells preincubated with insulin, PDGF increased thymidine incorporation by 96% as compared with a 44% increase in control cells (a 2-fold increment). Similarly, preincubation of VSMC with insulin increased the ability of PDGF to stimulate gene expression of vascular endothelial growth factor 5- to 8-fold. The potentiating influence of insulin on PDGF action was abrogated in the presence of a farnesyltransferase inhibitor. Thus, the detrimental influence of hyperinsulinemia on the arterial wall may be related to the ability of insulin to augment farnesyltransferase activity and provide greater amounts of farnesylated p21Ras for stimulation by various growth promoting agents.

Hyperinsulinemia predicts coronary heart disease risk in healthy middle-aged men: the 22-year follow-up results of the Helsinki Policemen Study

BACKGROUND

The Helsinki Policemen Study is one of the first prospective epidemiological studies demonstrating an association of hyperinsulinemia to the risk of coronary heart disease (CHD). The aim of the present study was to investigate the predictive value of hyperinsulinemia with regard to CHD risk during a 22-year follow-up of the Helsinki Policemen Study population.

METHODS AND RESULTS

The study was based on a cohort of 970 men who were 34 to 64 years of age and free of CHD, other cardiovascular disease, and diabetes. Risk factor measurements at baseline examination included an oral glucose tolerance test (OGTT) with blood glucose and plasma insulin measurements at 0, 1, and 2 hours. Area under the plasma insulin response curve (AUC insulin) during OGTT was used as a composite variable reflecting plasma insulin levels. During the 22-year follow-up, 164 men had a major CHD event (CHD death or nonfatal myocardial infarction). Age-adjusted hazard ratios for a major CHD event comparing men in the highest AUC insulin quintile with those in the combined 4 lower quintiles during 5-, 10-, 15-, and 22-year follow-up periods were 3.29 (95% CI, 1.56 to 6.91), 2.72 (95% CI, 1.67 to 4.42), 2.14 (95% CI, 1.43 to 3.21), and 1.61 (95% CI, 1.14 to 2.27), respectively. Further adjustment for other risk factors attenuated these hazard ratios to 2.36 (95% CI, 1.00 to 5.57), 2.29 (95% CI, 1.31 to 4.02), 1.76 (95% CI, 1.09 to 2.82), and 1.32 (95% CI, 0.89 to 1.97), respectively.

CONCLUSIONS

Hyperinsulinemia predicted CHD risk in Helsinki policemen over the 22-year follow-up, and to a large extent independently of other CHD risk factors, but its predictive value diminished with lengthening follow-up time.

Proinsulin and insulin concentrations in relation to carotid wall thickness: Insulin Resistance Atherosclerosis Study

BACKGROUND AND PURPOSE

Insulin resistance and hyperinsulinemia have been associated with atherosclerosis. Recent attention has focused on the possible role of proinsulin because most radioimmunoassays for insulin cross-react with proinsulin. Therefore, it is not known which of the two, insulin per se or proinsulin, is more strongly related to atherosclerosis.

METHODS

We examined the relation between fasting proinsulin, fasting split proinsulin, fasting and 2-hour insulin (after oral glucose load), and intima-media wall thickness (IMT) in the common carotid artery (CCA) and internal carotid artery (ICA) in 985 nondiabetic subjects from the Insulin Resistance Atherosclerosis Study, a multiethnic study of insulin resistance and atherosclerosis.

RESULTS

In the overall population, a weak but significant relation between proinsulin and CCA IMT was observed (r=0.07, P=0.029). However, the relation between proinsulin and IMT was stronger in Hispanics and non-Hispanic whites than in African Americans. In non-Hispanic whites and Hispanics, significant correlations between CCA and proinsulin (r=0.087) and between ICA and proinsulin (r=0.101), split proinsulin (r = 0.092), and fasting insulin (r = 0.087) were observed. The significant correlations became more attenuated (and nonsignificant) after adjustment for cardiovascular risk factors, especially plasminogen activator inhibitor-1 (PAI-1).

CONCLUSIONS

The association between proinsulin and IMT, while weak, appears to be stronger than the association between insulin and IMT. Adjustment for PAI-1 markedly attenuated the association between proinsulin and IMT, suggesting a possible mediating role for PAI-1 in this association. It is possible that proinsulin may represent a marker of atherosclerosis rather than a causal factor for atherosclerosis. Studies of the insulin resistance syndrome and atherosclerosis that use insulin as a surrogate for insulin resistance should consider the use of specific insulin assays as well as determination of proinsulin concentrations.

Insulin resistance in hypertension is associated with body fat rather than blood pressure

The insulin resistance syndrome has been characterized by hypertension, upper body obesity, insulin resistance, hyperinsulinemia, glucose intolerance, and hypertriglyceridemia. Previous studies are inconsistent regarding the relationship between blood pressure and insulin resistance. We therefore compared the metabolic profile in 60 hypertensive subjects (mean+/-SD arterial pressure, 116+/-7 mm Hg) and 60 normotensive subjects (mean arterial pressure, 88+/-5 mm Hg) matched for age, gender, and body mass index. Hypertensives had significantly higher waist-to-hip ratio than normotensives (P=0.002). The groups did not differ in fasting plasma glucose (0.2 mmol/L, P=0.09), insulin (6 pmol/L, P=0.14), insulin sensitivity index (-0.01 micromol x kg(-1) x min(-1) x pmol/L(-1), P=0.7), and suppression of nonesterified fatty acids during a hyperglycemic clamp (1%, P=0.40). There were significant differences in fasting levels of C-peptide (50 pmol/L, P=0.004) and proinsulin (2 pmol/L, P=0.01), 2-hour postload levels of glucose (0.8 mmol/L, P=0.01) and insulin (84 pmol/L, P=0.01) after oral glucose challenge, and hepatic glucose production during the clamp (2.87 micromol x kg(-1) x min(-1), P=0.02). These differences were not significant when controlling for waist-to-hip ratio. Body mass index and waist-to-hip ratio were similarly associated with the insulin sensitivity index in the hypertensive (r=-0.59, P=0.0001 and r=-0.32, P=0.05) and normotensive (r=-0.58, P=0.0001 and r=-0.39, P=0.05) groups. Hypertension per se is not associated with insulin resistance. However, even small increments in both body mass index and waist-to-hip ratio, as often seen in hypertension, may lead to impairment in insulin sensitivity, probably mediated through altered lipid metabolism.

Vasculopathy and insulin resistance in the JCR:LA-cp rat

The JCR:LA-cp rat is one of a number of strains incorporating the autosomal recessive cp gene that induces obesity. This strain is unique in the development of not only a profound insulin resistance, but an accompanying cardiovascular disease that correlates strongly with hyperinsulinemia. The hyperinsulinemia develops rapidly after 4 weeks of age, with an age at half-maximum of 5.5 weeks. This reflects postprandial plasma insulin levels that peak at 1000 mU/l in a standardized meal tolerance test. Defective acetylcholine-mediated vascular relaxation develops with a 1-week lag over the developing hyperinsulinemia. The frequency of staining for the vascular adhesion molecules, VCAM-1 and ICAM, does not show either age or genotype variation, although plasma levels do show an age variation. Treatment of the rats with the alpha-glucosidase inhibitor, miglitol (Bay m1099), obviates the exaggerated postprandial glucose and, especially, the insulin responses of the cp/cp rat. This causes an improvement in insulin sensitivity, prevention of the impaired vascular relaxation, and reduction in plasma levels of advanced glycated end-products. Arterial wall morphology, as visualized by both scanning and transmission electron microscopy, shows abnormal endothelium, adherent macrophages, and activated migrating smooth muscle cells in the intima. Oil-Red-O staining reveals lipid deposits in the intimal spaces, as confirmed by the presence of foam cells. The lesions resemble fatty streaks or modest atherosclerosis in man, rather than the extensive cholesterol-laden lesions seen in familial hypercholesterolemia or cholesterol-fed rabbit models. The lean rats of the strain show similar, but less marked, intimal abnormalities. The vasculopathy in this animal model appears to be precipitated by the developing hyperinsulinemia, but also requires an underlying abnormality of vascular smooth muscle and possibly also of the endothelium.

Insulin and risk of cardiovascular disease: a meta-analysis

BACKGROUND

Our purposes were to estimate the strength of the longitudinal relationship between hyperinsulinemia and cardiovascular diseases (CVD) from the available literature and to identify study characteristics that modify this relationship.

METHODS AND RESULTS

Articles were identified by means of a MEDLINE and Embase search and citation tracking. Eligible studies were prospective population-based cohort studies and nested case-control studies on the relationship between, on the one hand, fasting or nonfasting insulin levels and, on the other hand, myocardial infarction, death from coronary heart disease, and/or ECG abnormalities. Data were extracted pertaining to insulin measurements, type of outcome studied, adjustment for confounding, sex, mean age of the study population, follow-up period, insulin assay, and ethnic background (white or nonwhite). Associations of insulin and CVD were reexpressed in a uniform manner, an estimate of relative risk (RR) and 95% CI, to be used in meta-regression analyses. Twelve of 17 potentially eligible articles provided sufficient information. Overall, a weak positive association was found. The meta-analysis resulted in an estimated summary RR (95% CI) of 1.18 (1.08 to 1.29) for differences in insulin level, equivalent to the difference between the 75th and the 25th percentiles of the general population in The Netherlands. Ethnic background and type of insulin assay modified the relationship between insulin and CVD with borderline significance.

CONCLUSIONS

Hyperinsulinemia is a weak risk indicator for the occurrence of CVD. The relationship between hyperinsulinemia and CVD was modified by ethnic background and by the type of insulin assay involved.

Is metabolic syndrome a discrete entity in the general population? Evidence from the Caerphilly and Speedwell population studies

OBJECTIVE

To examine the clinical and epidemiological utility of the concepts of metabolic syndrome and insulin resistance syndrome in two prospective cohort studies of white men.

METHODS

Men aged 45-63 years were screened for evidence of ischaemic heart disease (IHD) between 1979 and 1982 and followed up at regular intervals thereafter. Non-fatal coronary events were validated from hospital records and fatal coronary events from death certificates.

RESULTS

Analysis of serum insulin concentrations in non-diabetic individuals measured at entry to the study showed no independent contribution to the prediction of subsequent IHD at 10 year follow up. Blood glucose concentrations, however, showed a small independent contribution in the combined cohort in the upper fifth of the distribution. Three different models of metabolic syndrome among non-diabetic individuals were defined based on tertiles, medians, and clusters. The predictive value of each model was assessed using logistic regression before and after adjustment for conventional and metabolic risk factors. After adjustment the odds were non-significant and close to unity.

CONCLUSIONS

This study did not detect any complex relation among the five variables defining metabolic syndrome; the excess risk seems to be no greater than can be explained by individual effects of the defining variables in a multiple logistic model.

Hyperinsulinemia and cardiovascular disease in elderly men: the Honolulu Heart Program

Hyperinsulinemia has been associated with cardiovascular disease (CVD), but whether this relation is independent of other CVD risk factors is uncertain. Most studies have focused on coronary heart disease (CHD), but few have included peripheral vascular disease (PVD) and stroke. Moreover, evidence in elderly and minority populations is limited. Between 1991 and 1993, 3562 elderly (71 to 93 years) Japanese-American men from the Honolulu Heart Program were examined and had fasting insulin levels measured. Hyperinsulinemia, defined as a fasting insulin > or =95th percentile among nonobese men with normal glucose tolerance and no diabetic history or medication use, was observed in 22% of the population. Subjects with hyperinsulinemia had a more adverse CVD risk factor profile and had higher age-adjusted prevalences of CHD, angina, PVD, thromboembolic stroke, and hemorrhagic stroke compared with those without hyperinsulinemia. Age-adjusted fasting insulin levels but not 2-hour levels were also significantly elevated (P<.01) in those with prevalent CVD compared with those without. In logistic regression analyses, adjustment for multiple CVD risk factors attenuated the relations of hyperinsulinemia with CHD, angina, and PVD to nonsignificant levels, whereas those involving thromboembolic and hemorrhagic stroke were strengthened and remained significant (odds ratios=2.27 and 7.53, 95% confidence intervals=1.25 to 4.13 and 1.65 to 34.25, respectively). When multivariate analyses were restricted to nondiabetic subjects, associations were slightly weaker and in general nonsignificant. Nondiabetic men with thromboembolic stroke were twice as likely to have hyperinsulinemia as those who were stroke-free, although this association was of borderline significance (odds ratio= 1.99, 95% confidence interval=0.95 to 4.17, P=.069). In subjects with elevated total cholesterol levels, somewhat stronger associations were observed for PVD and stroke but not for CHD. Although further prospective studies are indicated, particularly for PVD and stroke, these cross-sectional results are consistent with an indirect role for insulin in CVD, wherein hyperinsulinemia or an underlying insulin-resistant state may adversely affect other CVD risk factors or serve as a marker for an atherogenic or thrombogenic state.

Elevated fasting plasma insulin in a general aged population: an innocent companion of cardiovascular diseases

OBJECTIVE

Although high insulin levels have been linked to cardiovascular disease, the role of insulin as an independent risk factor has been questioned. Our objective was to examine the association of fasting plasma insulin with cardiovascular disease as well as to investigate the prognostic value of insulin with respect to survival.

DESIGN

A 5-year follow-up of random samples from four birth cohorts age 65 (n = 660), 75 (n = 194), 80 (n = 179), and 85 (n = 162) years at baseline.

SETTING

Two urban communities in southern Finland.

MEASUREMENTS

Clinical and laboratory investigation at base line with collection of date and cause of death information during follow-up.

RESULTS

Subjects with cardiovascular disease generally had higher levels of fasting plasma insulin than did subjects without cardiovascular disease (13.9 mU/L vs 11.2 mU/L, P < .001). Heart failure and hypertension were associated with significant 30 to 80% elevations of insulin levels in all but the oldest group. In the 65-year-old group, all vascular diseases were associated with significantly elevated insulin. The associations were generally not explained by body mass index or by use of diuretics or beta-blockers. During the follow-up insulin was generally not associated with an impaired survival. On the contrary, in subjects with manifest cardiovascular disease, high insulin was associated with a rather favorable 5-year survival prognosis. Exclusion of subjects who died during the first 500 days of follow-up did not change these associations.

CONCLUSION

Albeit fasting plasma insulin appeared to be secondarily associated with cardiovascular disease in this general aged population, it was related to a fair or favorable survival prognosis.

Carotid artery intima-media thickness in elderly patients with NIDDM and in nondiabetic subjects

BACKGROUND AND PURPOSE

The risk of atherosclerotic vascular disease is increased both in subjects with non-insulin-dependent diabetes mellitus (NIDDM) and in those with impaired glucose tolerance compared with nondiabetic subjects. Although classic cardiovascular risk factors are operative in subjects with NIDDM, other factors closely related to insulin resistance syndrome such as diabetic dyslipidemia and hyperglycemia itself may contribute to an excessive cardiovascular disease risk in subjects with NIDDM. The purpose of this study was to investigate the carotid intimal-medial thicknesses (IMTs) and their determinants in elderly patients with NIDDM and in control subjects.

METHODS

We investigated the common carotid and carotid bifurcation IMTs and their determinants in groups of elderly patients (n = 84, age 67.2 +/- 0.6 years) with NIDDM and in 119 control subjects (21 with impaired and 98 with normal glucose tolerance; ages 67.5 +/- 1.0 and 65.1 +/- 0.6 years, respectively).

RESULTS

Common carotid and carotid bifurcation IMTs were greater in the NIDDM group than in control subjects (P < .05 to .01). In NIDDM patients, the mean carotid IMT correlated with postglucose 1-hour plasma insulin (r = .305, P = .01, adjusted for age and sex), serum LDL triglyceride (r = .237, P < .05), and apolipoprotein B concentrations (r = .263, P < .05). Fasting plasma immunoreactive insulin, proinsulin, or specific insulin levels were not significantly associated with carotid IMT. Both diabetic status (P < .05) and the presence of clinical macrovascular disease (P < .01) contributed independently to carotid IMT.

CONCLUSIONS

Carotid IMT was greater in NIDDM patients than in control subjects. The main determinants of IMT in NIDDM patients were related to both postglucose insulin levels and abnormal lipoprotein profiles characteristic of NIDDM and insulin resistance syndrome. Treatment of these factors is likely to reduce the atherosclerotic burden in NIDDM.

Distribution and correlates of insulin in elderly men. The Honolulu Heart Program

The role of insulin in cardiovascular disease is uncertain, and studies in elderly or minority populations are infrequent. Fasting and 2-hour insulin concentrations and their cross-sectional associations with cardiovascular risk factors were examined in 3562 elderly (aged 71 to 93 years) Japanese American men from the Honolulu Heart Program who were reexamined between 1991 and 1993. Insulin distributions were skewed (mean and median: 16.8 and 12 microU/mL for fasting; 117.2 and 93 microU/mL for 2-hour); fasting but not 2-hour insulin levels declined significantly with age (P < .0001 and P = .54, respectively). Factors most strongly correlated with insulin included measures of obesity, fat distribution, and levels of triglyceride, glucose (r = .38 to r = .50 fasting, r = .21 to r = .27 2-hour), and HDL cholesterol (r = -.41 and r = -.22, respectively). Other correlates included fibrinogen, hematocrit, heart rate, blood pressure, cigarettes per day (all positive), alcohol, physical activity, and forced vital capacity (negative). Associations were also evident across risk factor quintiles. Insulin levels were significantly elevated in men with hypertension and diabetes. In multiple linear regression analyses, log10 fasting insulin was positively and independently associated with body mass index, triglycerides, glucose, fibrinogen, hematocrit, heart rate, diabetes, and hypertension and negatively associated with HDL cholesterol, physical activity, and forced vital capacity. In general, results were similar for log10 2-hour insulin and when subjects who fasted < 12 hours or had diabetes were excluded. Substitution of medication use and blood pressure for hypertension indicated independent associations of medication use but not blood pressure with insulin.(ABSTRACT TRUNCATED AT 250 WORDS)

Hyperinsulinemic microalbuminuria. A new risk indicator for coronary heart disease

BACKGROUND

Both hyperinsulinemia and microalbuminuria have been shown to increase coronary heart disease (CHD) risk, but the interaction among hyperinsulinemia, microalbuminuria, and the risk for CHD has not been investigated in previous studies.

METHODS AND RESULTS

The risk of CHD in relation to hyperinsulinemia and microalbuminuria was examined in a cohort of 1069 elderly nondiabetic subjects from Kuopio, east Finland, during 3.5 years of follow-up. The overall incidence of CHD death was 2.8%, and 6.9% of study subjects died of CHD or had a nonfatal myocardial infarction (later referred to as all CHD events). In the highest fasting-insulin quintile (fasting insulin > or = 114.0 pmol/L), there was a slightly but insignificantly higher incidence rate of both CHD mortality and all CHD events compared with lower quintiles. The incidence rates of CHD mortality and all CHD events were significantly higher in the highest urinary albumin/creatinine ratio (ACR) quintile (ACR > or = 3.22 mg/mmol) compared with lower quintiles (P < .05 and P < .01, respectively). Hyperinsulinemic microalbuminuria (simultaneous presence of fasting insulin > or = 114.0 pmol/L and ACR > or = 3.22 mg/mmol) markedly increased the risk of CHD mortality (12.5%, P < .001) and all CHD events (18.8%, P < .001) compared with normoinsulinemic subjects without microalbuminuria (2.2% and 5.8%, respectively). In univariate logistic regression analyses, hyperinsulinemic microalbuminuria was a strong predictor of both CHD death (odds ratio [OR], 5.93; P < .001) and all CHD events (OR, 3.39; P = .002). Multivariate logistic regression analyses were also performed, including sex, current smoking, waist-hip ratio, systolic blood pressure, and HDL cholesterol, with insulin, ACR, or both as independent variables. Even after adjustment for these variables, hyperinsulinemic microalbuminuria remained a strong predictor of CHD death (OR, 7.91; P < .001) and all CHD events (OR, 2.95; P = .014). The group with hyperinsulinemic microalbuminuria was characterized by the most adversely affected risk factor pattern (high triglycerides > or = 2.3 mmol/L, low HDL cholesterol < or = 0.9 mmol/L in men and < or = 1.20 mmol/L in women, and hypertension).

CONCLUSIONS

Simultaneous occurrence of hyperinsulinemia and microalbuminuria identifies a group of subjects with a highly increased risk for CHD in elderly nondiabetic subjects.

Absence of clinically overt atherosclerotic vascular disease and adverse changes in cardiovascular risk factors in 70 patients with insulinoma

Hyperinsulinemia has been assumed to contribute to the pathogenesis of atherosclerosis. To assess the reliability of such claim we planned a retrospective study on a cohort of patients with pancreatic insulin producing neoplasm. A correlation was sought between fasting insulin plasma levels and the metabolic profile emerging from those parameters known to be cardiovascular risk factors, i.e. plasma triglycerides and cholesterol, insulin resistance, hypertension. Special attention was paid to the duration of disease, because the time exposure to hyperinsulinemia could play an important role in developing cardiovascular disease. Seventy patients, 41 females and 29 males, aged 44.9 +/- 1.96 yr (range 15-80), with surgically proved insulinoma were included in the study. Chronic exposure to hyperinsulinemia was documented through the measurement of insulin plasma levels either in the fasting state or post-prandially, resulting in 44.7 +/- 3.28 and 149.9 +/- 12.22 microU/ml, respectively. Fasting glycemia in average was 45.3 +/- 1.34 mg/dl. Plasma triglycerides and cholesterol concentrations were 136.3 +/- 7.93 and 195.8 +/- 5.18 mg/dl, respectively, their distribution overlapping that anticipated for the general population. No correlation arose between the degree of hyperinsulinemia and the lipidic profile. Preoperative blood pressure was 136.9 +/- 2.87 mmHg, systolic and 81.9 +/- 1.32 mmHg, diastolic. Hypertension was present in 5 (7.1%) out of 70 patients and persisted after tumor removal. A condition of insulin resistance (M = 4.06 +/- 0.4 mg/kg min vs 7.41 +/- 0.21) was documented through the euglycemic hyperinsulinemic clamp technique in 20 patients and showed a positive and significant correlation with fasting insulinemia.(ABSTRACT TRUNCATED AT 250 WORDS)