Relationship between angiographically assessed coronary artery disease, plasma insulin levels and lipids in Asians and Caucasians

Atherosclerotic Cardiovascular Disease in South Asians in the United States: Epidemiology, Risk Factors, and Treatments: A Scientific Statement From the American Heart Association

South Asians (from Bangladesh, Bhutan, India, the Maldives, Nepal, Pakistan, and Sri Lanka) make up one quarter of the world's population and are one of the fastest-growing ethnic groups in the United States. Although native South Asians share genetic and cultural risk factors with South Asians abroad, South Asians in the United States can differ in socioeconomic status, education, healthcare behaviors, attitudes, and health insurance, which can affect their risk and the treatment and outcomes of atherosclerotic cardiovascular disease (ASCVD). South Asians have higher proportional mortality rates from ASCVD compared with other Asian groups and non-Hispanic whites, in contrast to the finding that Asian Americans (Asian Indian, Chinese, Filipino, Japanese, Korean, and Vietnamese) aggregated as a group are at lower risk of ASCVD, largely because of the lower risk observed in East Asian populations. Literature relevant to South Asian populations regarding demographics and risk factors, health behaviors, and interventions, including physical activity, diet, medications, and community strategies, is summarized. The evidence to date is that the biology of ASCVD is complex but is no different in South Asians than in any other racial/ethnic group. A majority of the risk in South Asians can be explained by the increased prevalence of known risk factors, especially those related to insulin resistance, and no unique risk factors in this population have been found. This scientific statement focuses on how ASCVD risk factors affect the South Asian population in order to make recommendations for clinical strategies to reduce disease and for directions for future research to reduce ASCVD in this population.

Insulin, insulin propeptides and intima-media thickness in the carotid artery in 58-year-old clinically healthy men. The Atherosclerosis and Insulin Resistance study (AIR)

AIMS

To examine the relationship between specific (intact) insulin, insulin propeptides and subclinical atherosclerosis.

METHODS

A cross-sectional study based on a stratified sampling of randomly selected, clinically healthy 58-year-old men (n = 391). Ultrasound examinations of the carotid arteries were performed with measurement of intima-media thickness (IMT) in the common carotid artery and in the carotid artery bulb. Fasting, cross-reacting plasma insulin (RIA), specific (intact) insulin, proinsulin, 32,33 split proinsulin and C-peptide were measured.

RESULTS

Plasma concentrations of cross-reacting plasma insulin, specific insulin, proinsulin, 32,33 split proinsulin and C-peptide were univariately associated with common carotid artery IMT. Established risk factors such as blood pressure, smoking, apoB, triglycerides, body mass index (BMI), and waist--hip ratio were also related to IMT. After adjustment for smoking, apoB, blood pressure and triglycerides, cross-reacting plasma insulin, proinsulin and C-peptide but not specific insulin and split 32,33 proinsulin remained associated with carotid artery IMT. No associations remained after adjustment for BMI.

CONCLUSIONS

Fasting plasma proinsulin, C-peptide, and insulin by cross-reacting RIA was associated with common carotid artery IMT independent of several conventional risk factors for atherosclerosis. The multicollinearity between the insulin peptides and propeptides makes it difficult to clarify the exact role of each peptide.

Intact insulin, insulin propeptides, and intima-media thickness in the femoral artery in 58-year-old clinical healthy men--the Atherosclerosis and Insulin Resistance Study

The aim of this study was to examine the association between intact insulin, insulin propeptides, and femoral artery intima-media thickness. The design was a cross-sectional study and the study group (n = 391) consisted of randomly recruited clinically healthy 58-year-old Swedish men. The intima-media thickness of the common femoral artery was measured with ultrasound. Fasting plasma insulin; intact insulin; proinsulin; 32,33 split-proinsulin; and C-peptide concentrations were assessed. The results showed that the common femoral artery intima-media thickness correlated significantly and univariately with waist-hip ratio, systolic blood pressure, serum total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, ApoB, low-density lipoprotein peak particle size, and cigarette years. Furthermore, of intact insulin and insulin propeptides, only intact insulin and C-peptide were univariately associated with common femoral artery intima-media thickness (r= 0.14, p < 0.01; r= 0.18, p < 0.01; respectively). In a multiple regression analysis, common femoral artery intima-media thickness was independently associated with systolic blood pressure (beta-coefficient = 0.004, p = 0.002), ApoB (beta-coefficient = 0.338, p < 0.001 ) and cigarette years (beta-coefficient = 0.0004, p < 0.001), (R2= 25%, p<O0.00). In conclusion, smoking, systolic blood pressure, and ApoB but not insulin or insulin propeptides were independently associated with femoral atherosclerosis.

Lower insulin sensitivity as an independent risk factor for carotid wall thickening in normotensive, non-diabetic, non-smoking normal weight and obese premenopausal women

OBJECTIVE

Increased thickness of the intima-media complex of the common carotid artery (IMT-CCA) is an early marker of atherosclerosis. The aim of the present study was to investigate the relationship between insulin resistance and IMT-CCA in premenopausal women.

SUBJECTS

86 young women, aged 18-31 y, were recruited for the study: 28 were normal weight (BMI<25 kg/m2), 23 were overweight (BMI 25-30 kg/m2) and 35 were obese (BMI>30 kg/m2).

MEASUREMENTS

The IMT-CCA was measured by high resolution 'B-mode' ultrasonography; insulin sensitivity was determined by insulin tolerance test (ITT) and quantitated by calculation of KITT. Fasting plasma glucose and lipids (triglycerides, total and HDL-cholesterol) were also measured by enzymatic methods. Central fat accumulation was evaluated by measuring waist circumference (WC).

RESULTS

IMT-CCA showed an inverse association with KITT (P<0.05). When the IMT-CCA was considered as the dependent variable in a forward stepwise multiple regression analysis, it maintained an independent association with KITT (P<0.05), after adjusting data for age, BMI, WC, mean blood pressure levels and plasma glucose and lipids.

CONCLUSION

These results suggest that IMT-CCA is significantly associated with insulin resistance, independent of other well-known CVD risk factors. Since the IMT-CCA is an earlier asymptomatic sign of atherosclerosis, this study indicates that insulin resistance per se may accelerate atherogenesis.

Insulin, intact and split proinsulin, and coronary artery disease in young men

BACKGROUND

Glucose intolerance and hyperinsulinemia are common disturbances in nondiabetic men with premature coronary artery disease (CAD). To investigate the relation between insulin-like molecules and severity of coronary atherosclerosis, 62 consecutive nondiabetic men presenting with a first myocardial infarction before the age of 45 were studied along with 41 healthy, age-matched, male, population-based control subjects.

METHODS AND RESULTS

Specific two-site immunoradiometric assays were used to distinguish intact proinsulin, (des 31,32) proinsulin, and "true" insulin in fasting plasma and during an oral glucose tolerance test (OGTT). Global coronary atherosclerosis and number and severity of distinct stenoses were determined in the patients in 15 proximal coronary arterial segments by use of separate semiquantitative classification systems. The patients had a two- to threefold increase in insulin and insulin propeptide concentrations in the fasting state as well as during the OGTT. Severity of coronary atherosclerosis correlated significantly (P < .05 to P < .01) with basal proinsulin (r = .40) and the proinsulin area under the curve (AUC) (r = .34), basal insulin (r = .31), basal C peptide (r = .30), and the glucose AUC (r = .30). In multiple stepwise regression analysis including insulin-like molecules, major plasma lipoproteins, and lipoprotein subfractions, basal proinsulin (increase in R2 = .09) and dense LDL triglycerides (increase in R2 = .10) predicted 19% of the variation of the global coronary atherosclerosis score after adjustment for age, body mass index, fasting insulin concentration, and VLDL triglycerides.

CONCLUSIONS

This study shows that young, nondiabetic, male survivors of myocardial infarction are truly hyperinsulinemic during an OGTT and suggests a close association between proinsulin and coronary atherosclerosis.

Like father like son? Sons of patients of European or Indian origin with coronary artery disease reflect their parents' risk factor patterns

OBJECTIVE

To investigate the extent to which risk factor patterns associated with coronary artery disease (CAD) in patients of Indian origin and in those of North European origin undergoing coronary angiography for suspected angina were reflected in their apparently healthy sons aged 15-30 years.

DESIGN

Prospective study in which risk markers were measured in patients of Indian origin and in matched European patients undergoing angiography and in their sons.

SETTING

Patients attending a regional cardiac centre and their families.

PATIENTS

102 consecutive male patients of Indian origin undergoing diagnostic coronary angiography for suspected angina and 89 of their sons aged between 15 and 30 years; 102 age matched male European patients and 82 sons.

MAIN OUTCOME MEASURES

Father son correlations for risk markers predicting the severity of parental CAD; differences in mean levels of these markers between young males of Indian origin and those of North European origin.

RESULTS

Lp(a) lipoprotein, total cholesterol, and serum insulin were independent predictors of the severity of CAD in patients of Indian origin and in those of North European origin. In both groups, there was strong correlation between paternal and filial serum insulin (r = 0.41 Indian origin, r = 0.49 North European, P < 0.001), Lp(a) lipoprotein (r = 0.44 Indian origin, r = 0.48 North European, P < 0.001), and total cholesterol (r = 0.39 Indian origin, r = 0.45 North European, P < 0.001) concentrations, and the risk factor profiles of the sons were predictive of CAD severity in their fathers. Sons of patients of Indian origin had significantly higher serum insulin (Indian origin 14.3 mU/l v North European 8.4 mU/l, P = 0.002) and Lp(a) lipoprotein (Indian origin 19.1 mmol/l v North European 10.5 mmol/l, P = 0.001) concentrations than sons of patients of North European origin.

CONCLUSIONS

Apparently healthy young men aged 15-30 years from either ethnic community already reflect risk marker patterns associated with coronary artery disease in their parents, both for genetically determined factors such as Lp(a) lipoprotein and environmentally influenced factors such as insulin and cholesterol. Health promotion measures aimed at reducing the prevalence of CAD should include the adolescent and young adult populations, particularly those with a family history of CAD, or who are from ethnic communities in which this diagnosis is prevalent.