Role of reduced suppression of glucose production and diminished early insulin release in impaired glucose tolerance

Association of early-onset coronary heart disease in South Asian men with glucose intolerance and hyperinsulinemia

BACKGROUND

Rates of coronary heart disease are higher in South Asians (Indians, Pakistanis, and Bangladeshis) settled overseas than in other ethnic groups. We tested the hypothesis that this excess risk results from metabolic disturbances associated with insulin resistance.

METHODS AND RESULTS

There were 1,421 South Asian men and 1,515 European men aged 40-69 years in London examined in the Southall Study. Prevalence of ischemic ECG abnormalities was higher in South Asians than in Europeans (17% versus 12%, p < 0.001), with an excess of major Q waves (Minnesota codes 1-1 or 1-2) in younger South Asian men (p = 0.01 for the age-ethnicity interaction). Major Q waves were strongly associated with glucose intolerance and hyperinsulinemia in younger South Asians; these factors accounted statistically for 73% of major Q waves in those aged 40-54 years. Age-standardized prevalence of a positive history of coronary heart disease was similar in South Asians and Europeans (8.5% versus 8.2%, NS), and positive history without Q waves was not associated with glucose intolerance or hyperinsulinemia in South Asians. Smoking rates and average plasma cholesterol were lower in South Asians than in Europeans; in a logistic model controlling for smoking and cholesterol, the odds ratio for major Q waves in South Asians compared with Europeans was 2.4 (95% CI, 1.5-3.8). Adjusting for glucose intolerance and hyperinsulinemia reduced this ratio to 1.5 (95% CI, 0.9-2.5).

CONCLUSIONS

These results are consistent with the hypothesis that insulin resistance underlies the high coronary risk in South Asian people and strengthen the evidence for a fundamental role of this metabolic pattern in the etiology of coronary heart disease.

Nutrition Support of the Diabetic Patient

Diabetes, as the component of the past medical history of individuals requiring nutrition support, poses specific problems to the clinician managing the patient. Besides an exaggerated glucose response to nutritional intervention, diabetics may have conditions or treatments that increase the morbidity and mortality associated with nutrition support therapy. As such, nutritional intervention should only be considered in patients for whom therapy is appropriately indicated. Then, the caloric dose, rate, and route of enteral and parenteral nutrition needs to be determined precisely. Glucose homeostasis along with etiologies and clinical manifestations of hyper- and hypoglycemia are to be clearly understood before initiating any nutritional support therapy in the diabetic. Without such, confusion may arise in determining the etiology of glucose problems occurring in patients from all the possible variables that influence the final serum glucose concentration in the patient. A cautious approach to initiating nutrition support is recommended, starting with low flow rates (10 to 20 mL/h for enteral nutrition and 40 mL/h for parenteral nutrition) and gradual incremental increases (in the 10- to 20-mL/h/d range) based on careful observation of blood glucose concentrations. A goal for tolerance should be established for each patient at the beginning of therapy, specifically, acceptable peak and trough glucose concentrations. This provides an extremely good template for adjusting the route (subcutaneous or intravenous) or type (intermittent vs continuous infusion) of insulin therapy. When the nutrient dose is stabilized at the optimal rate and insulin requires no further adjustment, transition of the patient to more appropriate, chronic therapy such as long-acting insulin or oral hypoglycemics is desired. The management of the diabetic patient on nutrition support is a challenge for even the most experienced individual. The potential for complications is abundant. A cautious, conservative approach is recommended with particular attention to minimizing the sources of both glucose and insulin administration.

Insulin sensitivity and secretion in healthy elderly human subjects with 'abnormal' glucose tolerance

Glucose tolerance deteriorates dramatically with advancing age. It is not known whether the underlying pathophysiology is different in older subjects. We employed a two step hyperinsulinaemic euglycaemic glucose clamp with [6(14)C] glucose infusion to compare peripheral and hepatic insulin sensitivity in eight elderly (EAGT) with eight young (YAGT) subjects with abnormal (matched) glucose tolerance and nine elderly subjects with normal glucose tolerance (ENGT). There was no difference in basal HGO (EAGT 14.5 +/- 0.9, YAGT 15.3 +/- 1.1 mumol kg-1 min-1). Glucose turnover was similar in both groups at step 1 (EAGT 13.2 +/- 0.8, YAGT 13.4 +/- 0.8 mumol kg-1 min-1) and step 2 (EAGT 25.1 +/- 3.1, YAGT 27.2 +/- 2.7 mumol kg-1 min-1). HGO was lower in the EAGT subjects at step 1 (2.3 +/- 0.4 vs. 4.3 +/- 0.6 mumol kg-1 min-1 P = 0.01). Incremental serum insulin response to oral glucose was comparable (EAGT 66.8 +/- 11.6 YAGT 57.8 +/- 12.2 mU l-1.h). Compared to the ENGT group the EAGT group was insulin resistant with a lower MCR of glucose at step 1 (2.03 +/- 0.28 vs. 3.23 +/- 0.44 ml kg-1 min-1 P = 0.04) and at step 2 (6.18 +/- 0.83 vs. 9.64 +/- 0.38 ml kg-1 min-1 P = 0.004) and had a lower early insulin response (AUC 0-30 min 5.9 +/- 1.1 vs. 9.8 +/- 1.4 mU l-1.h P = 0.04).(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship of glucose intolerance and hyperinsulinaemia to body fat pattern in south Asians and Europeans

Type 2 (non-insulin-dependent) diabetes mellitus and insulin resistance are associated with centrally-distributed obesity. These disturbances are especially prevalent in people of South Asian (Indian, Pakistani and Bangladeshi) descent. We examined the relationship of glucose intolerance to body fat pattern in a population survey of 2936 men and 537 women of South Asian and European origin living in London, UK. In both groups glucose intolerance (defined as diabetes or impaired glucose tolerance) was more strongly associated with waist-hip girth ratio than with skinfolds or body mass index. The associations between body mass index and glucose intolerance were fully accounted for by waist-hip ratio. In European men with normal glucose tolerance fasting insulin levels were more strongly correlated with body mass index than with waist-hip ratio. Physical activity scores were lower in South Asians than in Europeans but no statistically significant associations between glucose intolerance and low physical activity were detectable. Leisure-time physical activity scores were inversely correlated with 2 h insulin levels in both groups. In contrast with other studies these results suggest that a specific effect of intra-abdominal fat deposition underlies the association between glucose intolerance and obesity. The association between hyperinsulinaemia and obesity is less specific for centrally-distributed fat. When measured appropriately waist-hip ratio is the most valid anthropometric index for identifying individuals whose obesity predisposes them to glucose intolerance.