Early abnormalities in coronary heart disease risk factors in relatives of subjects with non-insulin-dependent diabetes

Association between a family history of diabetes and carotid artery atherosclerosis in Korean adults

OBJECTIVES

Diabetes is a well-known risk factor for atherosclerosis, but the association between a family history of diabetes and atherosclerosis remains unknown. In this study, we assessed the association between a family history of diabetes and increased carotid intima-media thickness (IMT), a marker of subclinical atherosclerosis, in a middle-aged Korean population.

METHODS

This cross-sectional study included 3,974 community-dwelling adults (1,404 male and 2,570 female) aged 30-64 years from the Cardiovascular and Metabolic Diseases Etiology Research Center cohort. The presence of a family history of diabetes was assessed through face-to-face interviews using a standardized questionnaire. Carotid IMT was assessed using B-mode ultrasonography, and increased IMT was defined as a value in the top quartile of the IMT values of all participants. Multivariate logistic regression was used to evaluate independent associations between a family history of diabetes and increased IMT.

RESULTS

A family history of diabetes was significantly associated with increased carotid IMT (odds ratio, 1.23; 95% confidence interval, 1.03 to 1.48) after adjusting for sex; age; body mass index; systolic blood pressure; total cholesterol, triglyceride, and hemoglobin A1c levels; smoking; alcohol consumption; exercise; use of antidiabetic, antihypertensive, and antilipidemic drugs; and a family history of hypertension. The positive association remained significant after excluding participants with diabetes (odds ratio, 1.21; 95% confidence interval, 1.00 to 1.47).

CONCLUSIONS

A family history of diabetes was positively associated with increased carotid IMT, even in participants without diabetes. Therefore, information on a family history of diabetes may help identify individuals at high risk of atherosclerotic cardiovascular disease.

Comparison of the effects of sibling and parental history of type 2 diabetes on metabolic syndrome

The aim of this study was to investigate the associations between sibling history, parental history and simultaneous sibling and parental history of diabetes, and the presence of the metabolic syndrome (MetS) and its components. Our study comprised 5000 participants from Taiwan Biobank until April, 2014. The participants were stratified into four groups according to sibling and/or parental family history (FH) of DM. MetS was defined as having 3 of the following 5 abnormalities based on the standard of the NCEP ATP III and modified criteria for Asians. The prevalence of MetS and its traits was estimated and compared among the four familial risk strata. Multivariate logistic regression analysis showed participants with sibling FH of DM [vs. no FH of DM; odds ratio (OR) 1.815; 95% confidence interval (CI) 1.293 to 2.548; p = 0.001], participants with parental FH of DM (vs. no FH of DM; OR 1.771; 95% CI 1.468 to 2.135; p < 0.001), and participants with simultaneous sibling and parental FH of DM (vs. no FH of DM; OR 2.961; 95% CI 2.108 to 4.161; p < 0.001) were significantly associated with MetS. A synergistic effect of sibling FH of DM and parental FH of DM on the association of MetS was also observed. In a nationally representative sample of Taiwan adults, a simultaneous sibling and parental history of diabetes shows a significant, independent association with MetS and its components, except for abdominal obesity. The association highlights the importance of obtaining stratified FH information in clinical practice and may help to identify individuals who should be targeted for screening and early prevention of MetS.

Are there genetic paths common to obesity, cardiovascular disease outcomes, and cardiovascular risk factors?

Clustering of obesity, coronary artery disease, and cardiovascular disease risk factors is observed in epidemiological studies and clinical settings. Twin and family studies have provided some supporting evidence for the clustering hypothesis. Loci nearest a lead single nucleotide polymorphism (SNP) showing genome-wide significant associations with coronary artery disease, body mass index, C-reactive protein, blood pressure, lipids, and type 2 diabetes mellitus were selected for pathway and network analyses. Eighty-seven autosomal regions (181 SNPs), mapping to 56 genes, were found to be pleiotropic. Most pleiotropic regions contained genes associated with coronary artery disease and plasma lipids, whereas some exhibited coaggregation between obesity and cardiovascular disease risk factors. We observed enrichment for liver X receptor (LXR)/retinoid X receptor (RXR) and farnesoid X receptor/RXR nuclear receptor signaling among pleiotropic genes and for signatures of coronary artery disease and hepatic steatosis. In the search for functionally interacting networks, we found that 43 pleiotropic genes were interacting in a network with an additional 24 linker genes. ENCODE (Encyclopedia of DNA Elements) data were queried for distribution of pleiotropic SNPs among regulatory elements and coding sequence variations. Of the 181 SNPs, 136 were annotated to ≥ 1 regulatory feature. An enrichment analysis found over-representation of enhancers and DNAse hypersensitive regions when compared against all SNPs of the 1000 Genomes pilot project. In summary, there are genomic regions exerting pleiotropic effects on cardiovascular disease risk factors, although only a few included obesity. Further studies are needed to resolve the clustering in terms of DNA variants, genes, pathways, and actionable targets.

Evaluating the impact of type 2 diabetes mellitus on cardiovascular risk in persons with metabolic syndrome using the UKPDS risk engine

BACKGROUND

The aim of this study is to evaluate the impact of coexistence of metabolic syndrome (MS) and type 2 diabetes mellitus (T2DM) on the estimated cardiovascular risk as calculated using the United Kingdom Prospective Diabetic Study risk engine (UKPDS-RE) and also to determine the impact of the coexistence of MS and T2DM on the 10-year risk of developing coronary heart disease and stroke.

METHODOLOGY

This is a cross-sectional study in which convenience sampling technique was used to recruit 124 consecutive persons with T2DM and 96 controls using a questionnaire administered technique. The World Health Organization (WHO) criterion was used to define MS and the UKPDS-RE was used to identify persons with increased risk for stroke and those with increased risk for coronary heart disease. The data obtained were analyzed using SPSS version 16. Statistical comparisons were made with chi-square for comparison of proportions. A P-value of less than 0.05 was taken as statistically significant.

RESULTS

Fifteen subjects were identified as having an increased 10-year risk for stroke and ten as having an increased risk for a coronary event. The odds of a T2DM subject with MS having an increased risk for stroke compared with a T2DM subject without MS was 0.9579≈1 while the odds of a T2DM subject with MS developing an increased risk for a coronary event compared with a T2DM subject without MS was =3.451≈3.

CONCLUSION

MS was more common in subjects with T2DM compared with controls (irrespective of the diagnostic criteria used) and MS appears to increase the risk of a coronary event in subjects with T2DM by threefold. Also from this study, MS did not appear to cause an additional increase in the risk of stroke in subjects with T2DM.

Effect of Family History of Type 2 Diabetes on White Blood Cell Count in Adult Women

OBJECTIVE

To evaluate the effect of a first-degree family history of type 2 diabetes on white blood cell (WBC) count, a risk factor for atherosclerotic vascular disease, in glucose-tolerant adult women.

RESEARCH METHODS AND PROCEDURES

WBC count was measured in 174 normal weight, overweight, and obese female offspring of type 2 diabetic patients (FH(+)) and 174 age- and BMI-matched female controls with no family history of type 2 diabetes (FH(-)). Other measurements included fat mass (FM), measured by body impedance analysis; central fat accumulation, evaluated by waist circumference; insulin resistance, estimated by homeostatic model assessment for insulin resistance (HOMA(IR)); systolic and diastolic blood pressure; and fasting concentrations of glucose, insulin, and lipids.

RESULTS

WBC count, waist circumference, systolic blood pressure, and fasting levels of glucose, insulin, and triglycerides were significantly higher in FH(+) than in FH(-) subjects. In FH(+) individuals, WBC count was positively associated with BMI, FM, waist circumference, HOMA(IR), and triglyceride and insulin concentrations, and negatively correlated with age and high-density lipoprotein-cholesterol. In FH(-) subjects, WBC count was directly associated with BMI, FM, waist circumference, and triglyceride and insulin concentrations, and inversely correlated with age and high-density lipoprotein-cholesterol. After multivariate analyses, WBC count maintained a significant association with age, systolic blood pressure, and HOMA(IR) in FH(+) subjects and with age, BMI, FM, and triglycerides in FH(-) individuals.

DISCUSSION

This study indicates that WBC count is increased in adult women with genetic predisposition to type 2 diabetes, and its main correlates are insulin resistance in FH(+) and adiposity in FH(-) individuals.

A family history of type 2 diabetes is associated with glucose intolerance and obesity-related traits with evidence of excess maternal transmission for obesity-related traits in a South East Asian population

AIM

To evaluate family history (FH) of type 2 diabetes (T2DM) as a risk factor for impaired fasting glucose (IFG), impaired glucose tolerance (IGT), T2DM and related metabolic traits in South East Asia and to compare the effects of a paternal versus maternal history.

METHODS

We studied 4717 men and women (68% Chinese, 18% Malays and 14% Asian Indians) living in Singapore. FH was considered positive if at least one first degree relative had T2DM. Obesity, fasting lipids, glucose and insulin levels were measured for all subjects. Insulin resistance (IR) was estimated by homeostasis model assessment (HOMA). An oral glucose tolerance test was carried for all subjects except those on diabetes medication.

RESULTS

A positive FH was associated with increased risk of IFG/IGT (OR=1.67, 95% CI=1.42-1.97) and T2DM (OR=2.95, 95% CI=2.36-3.70) as well as higher levels of obesity, HOMA-IR, fasting triglyceride (TG), and lower levels of high density lipoprotein (HDL) cholesterol and HOMA-beta. A maternal history of T2DM appeared to have a greater impact on obesity-related traits than a paternal history of T2DM. Compared to individuals with no FH of T2DM, a maternal history was associated with (i) greater body mass index (BMI) (24.15kg/m(2) vs. 23.42kg/m(2), p=0.016) and waist-to-hip ratio (WHR) (0.874 vs. 0.865, p=0.037) in men; and (ii) greater WHR (0.788 vs. 0.779, p=0.004), fasting triglyceride (1.23mmol/L vs. 1.09mmol/L, p<0.001), HOMA-IR (2.02 vs. 1.75, p<0.001), fasting plasma glucose (5.25mmol/L vs. 5.18mmol/L, p=0.005) and 2-h plasma glucose (6.01mmol/L vs. 5.78mmol/L, p=0.001) and lower HDL-C (1.41mmol/L vs. 1.47mmol/L, p=0.031) in women.

CONCLUSION

T2DM appears to be heritable in South East Asians with excess maternal transmission of obesity, IR and dyslipidemia.

Effect of parental hypertension and/or parental diabetes on hypertension in Taiwanese diabetic patients

BACKGROUND

Both type 2 diabetes mellitus (T2DM) and hypertension aggregate in families. It is a common thought that diabetic patients with parental diabetes and/or parental hypertension are more likely to develop hypertension. This study evaluated the separate and joint effects of parental hypertension and parental diabetes on the prevalence of hypertension in patients with T2DM.

MATERIALS AND METHODS

A total of 89 956 patients from a national cohort were interviewed by telephone. Information about age, sex, onset age of diabetes, body height, body weight, systolic (SBP) and diastolic blood pressure (DBP), smoking, hypertension, and paternal and maternal history of diabetes and hypertension were obtained. Hypertension was defined in two ways: (1) a positive history; or (2) a positive history or a reported SBP > or = 140 mmHg and/or DBP > or = 90 mmHg in patients without a hypertension history.

RESULTS

While analysed separately in logistic models, both parental diabetes and parental hypertension were positively associated with hypertension. However, when both were analysed together, only parental hypertension was positively associated with hypertension, with paternal and maternal hypertension exerting a similar effect of an approximately 2.5-fold higher risk. While considering the effect of parental hypertension, both paternal and maternal diabetes was significantly associated with a lower risk of hypertension with odds ratios of approximately 0.8. Parental hypertension was also significantly associated with increased SBP and DBP; and parental diabetes with lower values in multiple linear regression.

CONCLUSIONS

Parental hypertension is strongly associated with hypertension. However, parental diabetes may be protective if the effect of parental hypertension is considered.

Is family history a useful tool for detecting children at risk for diabetes and cardiovascular diseases? A public health perspective

Several studies indicate that the risk for type 2 diabetes or cardiovascular disease is detectable in childhood, although these disorders may not emerge until adulthood. In addition, type 2 diabetes and cardiovascular disease seem to share risk factors, including obesity and dyslipidemia, and might even share etiology, which has important implications for screening and prevention strategies for both diseases. Primary prevention, in particular, has gained importance because the results of major randomized, controlled trials strongly suggest that, at least in high-risk adult groups, type 2 diabetes can be prevented or delayed. Furthermore, some intervention studies indicate that the risk factors for diabetes and cardiovascular disease can be reduced in children. A simple way to detect risk for either diabetes or cardiovascular disease is to examine the family history. Numerous studies have shown that adults who have 1 or more first- or second-degree relatives affected with diabetes or cardiovascular disease are at high risk of having or developing these diseases. Currently, there are no overall screening strategies recommended for either diabetes or cardiovascular disease among children and adolescents. The evidence is strong, however, that youth with a positive family history already show signs of increased risk for these conditions. Family history can be part of the approach to screening for children at risk of diabetes and cardiovascular disease and should be part of prevention campaigns aimed at reducing the burden of these diseases and their risk factors in children.

Genetics of the metabolic syndrome

The concept of a metabolic syndrome (MetS), a cluster of pre-clinical metabolic alterations commonly associated with obesity, is the object of much debate. Genetic studies have the potential to contribute to some of the key questions, including the true nature of the cluster of pre-clinical features and whether it is associated with human genetic variation. This review summarizes the evidence for the presence of familial aggregation for the individual components of MetS and their heritability levels. It also provides an overview of the studies that have dealt with candidate genes for MetS. Potential leads from genome-wide linkage scans are also discussed. The assumption is made that obesity, ectopic fat deposition and abnormal adipose tissue metabolism are responsible for alterations in lipid metabolism, which in turn generates the commonly observed pre-clinical shifts in glucose tolerance, lipids and lipoprotein profile, blood pressure, inflammatory markers, endothelial function, and a prothrombotic state. Progress in the understanding of the genetic basis of MetS should occur as soon as a consensus is reached on the true nature of MetS, its components and diagnostic criteria.

Carotid artery intima-media thickness is associated with insulin-mediated glucose disposal in nondiabetic normotensive offspring of type 2 diabetic patients

The aim of this study was to investigate whether insulin resistance is independently associated with early manifestations of atherosclerosis. To this end, 176 normotensive offspring of type 2 diabetic patients were subjected to euglycemic hyperinsulinemic clamp to assess insulin sensitivity. Early atherosclerosis was studied by ultrasonography of the common carotid artery. Of the total 176 subjects, 145 were glucose tolerant, 18 had impaired fasting glucose, and 13 had impaired glucose tolerance. Univariate correlations showed that age, body mass index, waist, blood pressure, 2-h postchallenge glucose, fasting insulin, triglycerides, interleukin-6, fibrinogen, and white blood cell count were significantly correlated with carotid intima-media thickness (IMT), whereas HDL cholesterol and glucose disposal showed a negative correlation. A stepwise multivariate regression analysis including sex, age, waist circumference, smoking status, systolic blood pressure, diastolic blood pressure, triglyceride, HDL cholesterol, 2-h postchallenge glucose, plasma IL-6, fibrinogen, white blood cell count, insulin-stimulated glucose disposal, and fasting insulin showed that the four variables that remained significantly associated with carotid IMT were waist circumference, insulin-stimulated glucose disposal, white blood cell count, and diastolic blood pressure, accounting for 33.7% of its variation. These findings support the concept that insulin sensitivity, rather than plasma insulin levels, is associated with early atherosclerosis in nondiabetic normotensive offspring of type 2 diabetic patients.

Effect of family history of type 2 diabetes on the intima-media thickness of the common carotid artery in normal-weight, overweight, and obese glucose-tolerant young adults

OBJECTIVE

To evaluate the effect of a first-degree family history of type 2 diabetes on the intima-media thickness of the common carotid artery (IMT-CCA), a surrogate marker of coronary atherosclerosis, in glucose-tolerant young adults.

RESEARCH DESIGN AND METHODS

IMT-CCA was measured by high-resolution B-mode ultrasound imaging in 401 individuals aged 18-45 years with normal glucose tolerance (NGT). A total of 213 subjects had no family history of type 2 diabetes until the third generation (FH(-)), and 188 subjects had a family history of type 2 diabetes (FH(+)), defined as having one or both parents with type 2 diabetes. Other measurements included: central fat accumulation, evaluated by waist circumference; insulin resistance, estimated by homeostasis model assessment for insulin resistance (HOMA(IR)); systolic and diastolic blood pressure; fasting and postload concentrations of glucose; fasting insulin levels; and lipid profile.

RESULTS

IMT-CCA and both 1- and 2-h postchallenge glucose concentrations were significantly higher in FH(+) than in FH(-) subjects. IMT-CCA was positively correlated with age, BMI, waist circumference, triglycerides, systolic and diastolic blood pressure levels, basal glucose concentrations, 1- and 2-h postchallenge glucose concentrations, and HOMA(IR). IMT-CCA was inversely associated with HDL cholesterol. After multivariate analysis, IMT-CCA maintained a significant association with family history of type 2 diabetes, BMI, waist circumference, HDL cholesterol, diastolic blood pressure, and fasting glucose.

CONCLUSIONS

This study indicates that a genetic predisposition to type 2 diabetes, probably in association with slightly elevated glucose levels, may accelerate the development of atherosclerosis and increase the risk for coronary heart disease in glucose-tolerant individuals.

Longitudinal changes in risk variables of insulin resistance syndrome from childhood to young adulthood in offspring of parents with type 2 diabetes: the Bogalusa Heart Study

The occurrence of metabolic abnormalities related to insulin resistance syndrome in nondiabetic offspring of type 2 diabetic parents is known. However, information is lacking on the timing and the course of development of the components of this syndrome from childhood to adulthood in the offspring of parents with diabetes. This aspect was examined in a community-based cohort with (n = 303) and without (n = 1,136) a parental history of type 2 diabetes followed longitudinally since childhood (ages 4 to 17 years; mean follow-up period, 15 years) by repeated surveys. Offspring with parental diabetes versus those without such history had significantly excess generalized and truncal adiposity as measured by body mass index (BMI) and subscapular skinfold beginning in childhood, higher levels of fasting insulin and glucose and homeostasis model assessment index of insulin resistance (HOMA-IR) from adolescence, and higher levels of low-density lipoprotein (LDL) cholesterol and triglycerides and lower levels of high-density lipoprotein (HDL) cholesterol in adulthood. Many of these risk variables changed adversely at an increased rate in offspring of diabetic parents. In a multivariate analysis, parental diabetes was an independent predictor of longitudinal changes in adiposity, glucose, insulin, HOM-IR, systolic and diastolic blood pressure, and LDL cholesterol in the offspring, regardless of race and gender. As young adults, the offspring of diabetic parents had a higher prevalence of generalized (BMI > 30, 36% v 16%, P =.0001) and visceral (waist > 100 cm, 15% v 6%, P =.0001) obesity, hyperinsulinemia indicative of insulin resistance (insulin > 18 microU/mL, 15% v 8%, P =.0001), hyperglycemia (>or=110 mg/dL, 2% v 0.5%, P =.02), high LDL cholesterol (>or=160 mg/dL, 11% v 7%, P =.02), low HDL cholesterol (<40 mg/dL for males and <50 mg/dL for females, 40% v 31%, P =.004), high triglycerides (>or=150 mg/dL, 23% v 15%, P =.0001), and hypertension (>140/90 mm Hg, 11% v 6%, P =.004). Thus, the offspring of diabetic parents displayed excess body fatness beginning in childhood and accelerated progression of adverse risk profile characteristics of insulin resistance syndrome from childhood to young adulthood. These observations have important implications for early prevention and intervention.

A family history of Type 2 diabetes is associated with increased plasma levels of C-reactive protein in non-smoking healthy adult women

AIMS

The aim of our study was to test whether a family history of Type 2 diabetes (FH) in women is associated with plasma C-reactive protein (CRP).

METHODS

CRP plasma levels were measured in 162 women, aged 18-60 years; 95 had a positive family history of Type 2 diabetes in a parent or grandparent (FH+), and 67 gave no family history of this disease (FH-). Other measurements included: central fat accumulation, as evaluated by waist circumference; insulin resistance, as calculated by homeostatic model assessment (HOMAIR); systolic and diastolic blood pressure; and fasting concentrations of glucose, insulin, and lipids.

RESULTS

CRP plasma levels were significantly higher in FH+ than in FH- subjects. Moreover, CRP was independently associated with age, body mass index, waist circumference, HOMAIR, and FH.

CONCLUSIONS

Our study, performed in a selected population of women free from well-known risk factors for atherothrombosis, demonstrates that subjects with a family history of Type 2 diabetes have higher CRP plasma levels than age- and BMI-matched controls with no family history. Our results show that a family history of Type 2 diabetes is an independent contributor of CRP concentrations, in addition to age, total fatness, central fat accumulation, and insulin resistance.

New amino acid substitutions in the IRS-2 gene in Finnish and Chinese subjects with late-onset type 2 diabetes

We investigated the significance of the variants of the IRS-2 gene in patients with type 2 diabetes. The entire coding part of the IRS-2 gene was screened by single-strand conformation polymorphism analysis in 40 Chinese and 40 Finnish patients with late-onset type 2 diabetes. The association of the variants of the IRS-2 gene with type 2 diabetes was studied in 85 Finnish diabetic patients and 82 Finnish control subjects and in 100 Chinese diabetic patients and 85 Chinese control subjects. The four variants predicting structural changes in the insulin receptor substrate (IRS)-2 protein included an insertion of AAC (Asn) in the Asn repeat sequence centered around codons 29-36 (allele frequencies of 0 vs. 0.6% and 1.5 vs. 0%), the Ala157Thr substitution (0 vs. 0% and 0.5 vs. 0%), the Leu647Val substitution (0.6 vs. 0% and 0 vs. 0%), and the Gly1057Asp polymorphism (31 vs. 31% and 35 vs. 30%) (P = NS for all comparisons). Furthermore, six silent variants were observed (CGC147CGG, CCC155CCG, GCC156GCT, AGT723AGC, TGT816TGC, and CCC829CCT). The Gly1057Asp polymorphism was not associated with insulin resistance or impaired insulin secretion in Finnish subjects with normal glucose tolerance (n = 295) or impaired glucose tolerance (n = 38). These data indicate that structural variants of the IRS-2 gene were uncommon in Finnish and Chinese patients with type 2 diabetes. Thus, the variants in the coding part of the IRS-2 gene are unlikely to have a major role in the development of type 2 diabetes in Finnish or Chinese subjects.

Cardiovascular disease in type 2 diabetes: challenge for treatment and prevention

Type 2 diabetes increases the risk of cardiovascular disease (CVD) two- to fourfold compared with the risk in non-diabetic subjects. Although type 2 diabetes is associated with a clustering of risk factors (small, dense low-density lipoprotein [LDL] particles, low high-density lipoprotein [HDL] cholesterol, high triglycerides, elevated blood pressure, obesity, central obesity, hyperinsulinaemia, hyperglycaemia, etc.), the cause for an excess risk of CVD remains unknown. Recent drug treatment trials have indicated that the lowering of total and LDL cholesterol and blood pressure is similarly beneficial in diabetic and non-diabetic subjects. The treatment of hyperglycaemia reduces micro- and macrovascular complications in type 2 diabetic patients. Beta-blocking agents, angiotensin-converting enzyme inhibitors, aspirin, and thrombolytic therapy are also effective in the treatment of CVD amongst diabetic patients.

Increased high-density lipoprotein-3 binding to leukocytes following weight loss and improved glycemic control in type 2 diabetic patients

This study evaluates the effect on high-density lipoprotein (HDL) binding activity in cultured granulocytes before and after metabolic control of non-insulin-dependent diabetes mellitus ([NIDDM] type 2 diabetes) patients. In 20 type 2 diabetic patients, diabetic control was accomplished by administration of oral antidiabetic agents and dietary restrictions. Adequate metabolic control was reflected by a decrease in the fasting glucose, glycosylated hemoglobin (HbA1c), mean insulin, and body mass index (BMI). After control of the diabetes, the mean HDL3 cholesterol was increased from 0.918 +/- 0.05 to 1.008 +/- 0.05 mmol/L (P < .05) and apolipoprotein AI (apo AI) was increased from 103 +/- 5.8 to 115 +/- 5.1 mg/dL (P < .01). The HDL3 maximum specific binding was higher after versus before diabetic control, 77 +/- 6 versus 122 +/- 8 ng/mg cell protein (P < .01). This increase was related to an increase in maximum binding ([Bmax] from 4.97 x 10(-10) to 8.3 x 10(-10) mol/L, P < .001), and no significant changes were observed in the Kd (from 1.47 x 10(-7) v 2.04 x 10(-7) mol/L). These results suggest that the metabolic control of type 2 diabetes increases HDL3 binding activity.

Peripheral tissue glucose uptake is not reduced after an oral glucose load in Southern Italian subjects at risk of developing non-insulin-dependent diabetes mellitus

Studies searching for the inherited defects that cause non-insulin-dependent diabetes mellitus (NIDDM) have been performed mostly in Northern European subjects using the hyperinsulinemic clamp technique. The conclusion drawn from most of these studies is that peripheral insulin resistance is likely a primary inherited defect. Our aim was to examine early defects in glucose metabolism using a more physiological technique in a different ethnic group. For this, a double-label oral glucose tolerance test (OGTT) was performed in young diabetes-prone Southern Italian subjects who had both parents with NIDDM (relatives) and in subjects with no family history of NIDDM (matched for age, weight, and ethnicity). Fasting plasma glucose and insulin in the relatives were normal; however, they had impaired glucose tolerance during the OGTT. This was due to reduced hepatic glucose uptake (17.9+/-2.8 v. 28.1+/-2.3 g, P<.02). No defects were found in the metabolic clearance rate (MCR) of glucose or endogenous glucose production. During an intravenous glucose tolerance test (IVGTT), insulin sensitivity was again found to be normal (3.04+/-0.65 in relatives v. 2.33+/-0.38 min(-1) per micromol x L(-1) x min in controls), with a marked reduction in first-phase insulin secretion in the relatives (110+/-12 v. 211+/-18 pmol x L(-1) x min per mmol x L(-1), P<.001). A strong correlation was found between hepatic glucose uptake and insulin secretion (r = .81, P<.001), which may suggest that the same abnormality operates in both the liver and pancreas. Therefore, the metabolic defect that causes hyperglycemia in diabetes-prone subjects is not always a reduced peripheral insulin sensitivity. The genetic basis of NIDDM may differ between different ethnic groups.

Lipoprotein composition and serum apolipoproteins in normoglycaemic first-degree relatives of non-insulin dependent diabetic patients

Cardiovascular disease is the leading cause of death in non-insulin dependent diabetes mellitus and first degree relatives of such patients are at increased risk of developing diabetes and cardiovascular disease. The aim of the present study was to determine whether lipid abnormalities occur in normoglycaemic relatives of non-insulin dependent diabetic patients. Cholesterol, triglycerides, apolipoprotein A-I and apolipoprotein B concentrations were measured in serum; the lipoprotein fractions very low density, intermediate density, low density and high density lipoprotein were prepared by sequential flotation ultracentrifugation and their composition investigated. The groups were matched for age, sex and blood glucose concentrations although the relatives (n = 126) were more insulin resistant as determined using the homeostasis model assessment method [1.9 (0.8-9.0) vs 1.6 (0.4-4.9) mmol/mU per l (mean [95% confidence intervals]); p < 0.001] and had greater body mass indices [26.6 (4.1) vs 24.8 (3.9) (mean [S.D.]); p = 0.001] than control subjects (n = 126). Relatives had higher serum apolipoprotein B concentrations than control subjects [0.9 (0.3) vs 0.8 (0.3) g/l, p = 0.02) and lower serum apolipoprotein A-I concentrations (1.4 (0.3) vs 1.5 (0.3), p = 0.02). In multivariate linear regression analysis of all subjects log insulin resistance (p = 0.0001), age (p = 0.002) and waist:hip ratio (p = 0.01) were independent predicators of apolipoprotein B concentrations while waist:hip ratio (p < 0.001) and smoking status (p = 0.002) were independent predictors of apolipoprotein A-I concentrations. Lipoprotein composition (measured in a subgroup of 76 control subjects and 88 relatives), serum cholesterol and serum triglyceride concentrations did not differ between the groups. We conclude that atherogenic apolipoprotein abnormalities occur in normoglycaemic relatives of non-insulin dependent diabetic patients.

Epidemiology of risk factors for cardiovascular disease in diabetes and impaired glucose tolerance

Diabetes mellitus is a strong risk factor for all manifestations of atherosclerotic vascular disease, coronary heart disease (CHD), cerebrovascular disease and peripheral vascular disease. Diabetes can be classified into two main subtypes, insulin-dependent diabetes mellitus and non-insulin-dependent diabetes mellitus (NIDDM). This review focuses only on NIDDM. Also, in impaired glucose tolerance (IGT), a precursor stage of diabetes, the risk of macrovascular disease is substantially increased. NIDDM and IGT are known to be associated with several adverse cardiovascular risk factors, including hypertension, obesity, central obesity, hyperinsulinemia and serum lipid and lipoprotein abnormalities, characterized mainly by elevated serum total triglycerides and low high-density lipoprotein cholesterol. Practically no information is available on the role of different cardiovascular risk factors to predict macrovascular complications in subjects with IGT. The role of different cardiovascular risk factors with respect to the risk of CHD, stroke and peripheral vascular disease will be discussed.

New variants in the glycogen synthase gene (Gln71His, Met416Val) in patients with NIDDM from eastern Finland

Impaired glycogen synthesis after insulin stimulation accounts for most of the insulin resistance in patients with non-insulin-dependent diabetes mellitus (NIDDM). The glycogen synthase gene (GYS1), which encodes the rate-limiting enzyme for glycogen synthesis, is a promising candidate gene for NIDDM. Therefore, we screened all 16 exons of this gene by single-strand conformation polymorphism analysis in 40 patients with NIDDM (age 67 +/- 2 years, body mass index 28.2 +/- 0.6 kg/m2) from Taipalsaari, eastern Finland. The Gly464Ser variant (exon 11) and a silent polymorphism TTC342TTT (exon 7) have been reported previously. In addition, we found a new variant Gln71His (exon 2) and a new amino acid polymorphism Met416Val (exon 10). An additional sample of 65 patients with NIDDM and 82 normoglycaemic men (age 54 +/- 1 years, body mass index 26.3 +/- 1.4 kg/m2) were screened. The allele frequency of the TTC342TTT silent substitution was 0.29 in both NIDDM and normoglycaemic subjects. The Gln71His and Gly464Ser variants were found in 1 (1%) and 3 (3%) subjects, respectively, of the 105 NIDDM patients and in none of the 82 normoglycaemic men. The Met416Val polymorphism was found in 16 (15%) of the 105 NIDDM patients and in 14 (17%) of the 82 control subjects (all heterozygous). The Met416Val polymorphism was not associated with insulin resistance in two groups of normoglycaemic subjects. In conclusion, the new Gln71His and Met416Val substitutions and other variants of the glycogen synthase gene are unlikely to make a major contribution to insulin resistance and NIDDM in diabetic patients from eastern Finland.

Family history of coronary heart disease is a stronger predictor of coronary heart disease morbidity and mortality than family history of non-insulin dependent diabetes mellitus

The aim of this study was to compare the effect of family history of non-insulin dependent diabetes mellitus (NIDDM) and coronary heart disease (CHD) as risk factors for CHD morbidity and mortality. Altogether, 394 siblings of NIDDM probands and non-diabetic probands, with and without CHD, were followed for 8 years with respect to CHD events in a prospective population-based study. The baseline study was conducted from 1983 to 1985. Age- and sex-adjusted cumulative occurrence of CHD events was higher in the siblings of the probands with CHD and with NIDDM (13.1%; P = 0.037) and in the siblings of the probands with CHD and without NIDDM (15.4%; P = 0.054), compared with the siblings of the probands without NIDDM and without CHD (4.8%). The incidence of fatal CHD events tended to be higher in a group with a family history of NIDDM and CHD, but the trend was not statistically significant. In univariate logistic regression analyses, a family history of CHD was positively associated with cumulative occurrence of CHD events (odds ratio 2.53, P = 0.009), whereas a family history of NIDDM had no significant association (odds ratio 1.39, P = 0.312). After adjustment for age, sex, family history of NIDDM and major cardiovascular risk factors, the association between family history of CHD and cumulative occurrence of CHD events remained significant (odds ratio 2.25, P = 0.048). In conclusion, the present study indicates that a family history of CHD is a stronger predictor of future CHD events than a family history of NIDDM.

Postprandial cholesteryl ester transfer and high density lipoprotein composition in normotriglyceridemic non-insulin-dependent diabetic patients

Altered postprandial HDL metabolism is a possible cause of defective reverse cholesterol transport and increased cardiovascular risk in diabetic patients with a normal fasting lipoprotein profile. Ten normolipidemic, normoponderal non-insulin dependent diabetes mellitus (NIDDM) patients and seven controls received a 980 kcal meal containing 78 g lipids with 100 000 IU vitamin A. Chylomicron clearance was not different, but area under the curve (AUC) for retinyl palmitate in chylimicron-free serum (remnant clearance) was greater in patients (P < 0.02). LCAT activity increased postprandially to the same extent in both groups. In control subjects, cholesteryl ester transfer protein (CETP) activity (CETA) also increased by 20% (P < 0.01 at 6 h) in parallel with a 20% decrease in HDL2-CE (r = -0.55, P = 0.009). In NIDDM patients, on the contrary, CETA which was 35% higher in the fasting state (P < 0.005), decreased postprandially yet HDL2-CE remained unchanged. Postprandial HDL3 of controls were enriched with phospholipid (PL) (30.3 +/- 2.6% at 6 h) with respect to fasting (25.6 +/- 2.5%, P < 0.01) and to NIDDM-HDL3 (25.8 +/- 1.7% at 6 h, P < 0.01). These results show that variation in plasma CETA has little impact on HDL2-CE in NIDDH subjects. They support the concept that, in controls, the combined enrichment of HDL3 with PL, increased LCAT and CETA create the conditions for stimulation of cell cholesterol efflux and CE transfer to apo B lipoproteins. In NIDDM, because of the lesser HDL3 enrichment with PL and of the inverse trend of CETA, these conditions fail to occur, depriving the patients of a potentially efficient mechanism of unesterified cholesterol (UC) clearance, despite their strictly normal preprandial profile.

Metabolic defects in persistent impaired glucose tolerance are related to the family history of non-insulin-dependent diabetes mellitus

Recent studies have suggested that the family history of non-insulin-dependent diabetes mellitus (NIDDM) influences glucose metabolism in subjects with normal glucose tolerance (NGT). However, it is not known whether the family history of NIDDM influences glucose metabolism in impaired glucose tolerance (IGT). We studied in a well-characterized group the impact of family history of NIDDM (diabetes mellitus [DM]-positive) in subjects with IGT on glucose disposal rate (GDR) measured by the euglycemic hyperinsulinemic clamp technique combined with indirect calorimetry. We recruited subjects from our previous population-based studies, and verified their glucose tolerance status twice during the follow-up period of 1 year. Subjects with NGT (n = 10) and IGT (n = 18) were comparable with respect to age, sex distribution, body mass index, smoking habits, and hypertension. As a group, IGT subjects showed lower GDR than the NGT group (28.6 +/- 12.1 v 38.9 +/- 13.6 mumol/kg/min, P < .05). IGT DM-positive subjects showed a 40% lower GDR than the NGT group (P < .05) and a 29% lower GDR than IGT DM-negative subjects (P = NS). IGT DM-positive subjects had lower glucose oxidation (P = NS, P < .01), glucose nonoxidation (P = NS, P = .01), and suppression of lipid oxidation (P = NS, P < .05) during the hyperinsulinemic euglycemic clamp as compared with IGT DM-negative and NGT groups, respectively. In conclusion, in subjects with persistent IGT, the family history of NIDDM is associated with the reduced total whole-body, oxidative, and nonoxidative GDR.

Changes of lipolytic enzymes cluster with insulin resistance syndrome. Botnia Study Group

The activities of hepatic and lipoprotein lipase and the levels of lipo- and apoproteins were compared in two groups of normoglycaemic men representing the highest (n = 18) and lowest (n = 15) fasting insulin quintiles of first degree male relatives of non-insulin-dependent diabetic patients. The high insulin group representing insulin-resistant individuals had significantly lower post-heparin plasma lipoprotein lipase activity than the low insulin group (14.2 +/- 4.0 vs 20 +/- 5.8 mumol NEFA.ml-1.h-1, p < 0.001); hepatic lipase activity did not differ between the two groups (24.2 +/- 11 vs 18.0 +/- 5.3 mumol NEFA.ml-1.h-1, NS). The lipoprotein lipase/hepatic lipase ratio in the high insulin group was decreased by 66% as compared to the low insulin group (0.75 +/- 0.57 vs 1.25 +/- 0.65, p < 0.01). In the high insulin group both total and VLDL triglycerides were higher than in the low insulin group (1.61 +/- 0.57 vs 0.86 +/- 0.26 mmol/l, p < 0.001 and 1.00 +/- 0.47 vs 0.36 +/- 0.16 mmol/l, p < 0.001, respectively) whereas HDL cholesterol and HDL2 cholesterol were lower (1.20 +/- 0.30 vs 1.43 +/- 0.22 mmol/l, p < 0.05 and 0.49 +/- 0.21 vs 0.71 +/- 0.17 mmol/l, p < 0.05, respectively). Total cholesterol, LDL cholesterol or HDL3 cholesterol did not differ between the two groups. The mean particle size of LDL was smaller in the high insulin group than in the low insulin group (258 +/- 7 vs 265 +/- 6 A, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin receptor substrate-1 variants in non-insulin-dependent diabetes

Insulin receptor substrate-1 (IRS-1) plays an important role in insulin-stimulated signaling mechanisms. Therefore, we investigated the frequency and clinical significance of variants in the coding region of this gene in patients with non-insulin-dependent diabetes (NIDDM). Initial screening included a population-based sample of 40 Finnish patients with typical NIDDM. Applying single strand conformation polymorphism analysis the following amino acid substitutions were found among the 40 NIDDM patients: Gly818-Arg, Ser892Gly, and Gly971Arg. The first two variants have not been previously reported. Additional samples of 72 patients with NIDDM and 104 healthy control subjects with completely normal oral glucose tolerance test and a negative family history of diabetes were screened. The most common polymorphism was the Gly971Arg substitution which was found in 11 (9.8%) of 112 NIDDM patients and in 9 (8.7%) of 104 control subjects. The Gly818Arg substitution was found in 2 (1.8%) of NIDDM patients and in 2 (1.9%) of control subjects, and the Ser892Gly substitution was found in 3 (2.7%) NIDDM patients and in 1 (1.0%) control subject. The Gly971Arg substitution was not associated with an impairment in insulin secretion capacity (estimated by insulin responses in an oral glucose tolerance test or by the hyperglycemic clamp) or insulin action (estimated by the euglycemic clamp). Of the three amino acid substitutions observed Ser892Gly is the most interesting one since it abolishes one of the potential serine phosphorylation sites (SPGE) which is located immediately NH2-terminal to the only SH2 binding site of growth factor receptor-bound protein (GRB2), and thus could potentially influence some aspects of signal transduction and metabolic response to insulin.

Dyslipidaemias, insulin resistance and atherosclerosis

Recent studies have demonstrated that insulin resistance, a proportionate decrease in insulin action at all insulin concentrations, is associated with clustering of many cardiovascular risk factors, particularly hyperlipidaemias. Already epidemiological studies have indicated that high insulin levels are related to low high-density lipoprotein (HDL) cholesterol and high total and very-low-density lipoprotein (VLDL) triglyceride levels. Recent studies based on the direct quantification of insulin resistance by the euglycaemic clamp method have verified these findings. In contrast, insulin resistance seems not to be associated with high low-density lipoprotein (LDL) cholesterol. Abnormalities in HDL and VLDL levels may contribute to accelerated atherosclerosis, but there is evidence that insulin resistance is also directly associated with asymptomatic atherosclerosis. Thus, prevention of atherosclerosis should not be targeted only to the lowering of LDL cholesterol, but also to the reduction of the degree of insulin resistance either with diet, weight reduction, regular exercise or drug therapy.