Heterogeneous glycaemic and insulinaemic responses to oral glucose in non-diabetic men: interactions between duration of obesity, body fat distribution and family history of diabetes mellitus

Abdominal adiposity distribution in diabetic/prediabetic and nondiabetic populations: a meta-analysis

Excess fat in the abdomen can be classified generally as visceral and subcutaneous adiposity. Evidence suggests that visceral adiposity has greater implications for diabetes than other fat depots. The purpose of this study is to explore the disparities in the distribution of abdominal adiposity in diabetic/prediabetic and nondiabetic populations and to identify moderators that influence the pattern of central obesity via a meta-analysis technique. The Hedges' g was used as a measure of effect size and 95% confidence interval was computed. A total of 41 relevant studies with 101 effect sizes were retrieved. Pooled effect sizes for visceral and subcutaneous adiposity were 0.69 and 0.42, respectively. Diabetic/prediabetic populations exhibited greater visceral and subcutaneous adiposity compared to nondiabetic populations (Z = 10.35, P < 0.05). Significant moderator effects of gender (Z = -2.90) and assessment method of abdominal adiposity (Z = -2.17) were found for visceral fat (P < 0.05), but not for subcutaneous fat. Type of health condition influenced both visceral (Z = -5.10) and subcutaneous (Z = -7.09) abdominal adiposity volumes (P < 0.05). Abdominal adiposity distributions were significantly altered in the diabetic/prediabetic population compared to the nondiabetic population. Gender, assessment method of abdominal adiposity, and type of health conditions (diabetic/prediabetics) were identified as crucial moderators that influence the degree of abdominal adiposity.

Dietary intervention causes redistribution of zinc in obese adolescents

Obese people tend to have low zinc circulation levels; this is not always related to zinc intake but can reflect the distribution of zinc in relation to the proportion of body fat and factors related to the inflammatory processes that cause obesity. The purpose of this study was to assess zinc distribution in 15 obese adolescent girls before and after a nutritional orientation program. Participants ranged from 14 to 18 years old (postpubescent) and had a body fat percent (BF%) of >35 %. Zinc nutritional status and other zinc-dependent parameters, such as superoxide dismutase (SOD) and insulin levels, were assessed by biochemical analysis of plasma and erythrocytes, salivary sediment, and urine. Samples were collected before and after 4 months of dietary intervention. Dual energy X-ray absorptiometry (DXA) was used to verify BF% both at the beginning and at the end of the study. Food consumption was assessed in ten individual food questionnaires throughout the study; food groups were separated on the questionnaires in the same way as suggested by some authors to develop the Healthy Eating Index (HEI) but with the addition of zinc. After 4 months of nutritional orientation, 78 % of the participants showed a decrease in BF%. Intraerythrocytic zinc increased over the study period, while salivary sediment zinc, SOD, insulin, and Zn urinary24 h/creatinine all decreased (p < 0.05). There was no difference in zinc intake throughout the study but participants did increase their consumption of fruits, dairy, and meats during the study (p < 0.05). There were inverse and statistically significant correlations between the increased levels of intraerythrocytic zinc and decreased levels of SOD. There was also a statistically significant correlation between BF% and Zn urinary 24h/creatinine, and SOD. All these parameters were diminished at the end of the study. The dietary intervention for obese adolescent girls is effective with decrease of BF that led to the redistribution of zinc in the body as shown by the changes in erythrocytes, plasma, salivary, urine zinc, as well as the complementary parameters of insulin and SOD. These changes were not affected by zinc intake.

Racial differences in the interaction between family history and risk factors associated with diabetes in the National Health and Nutritional Examination Survey, 1999-2004

PURPOSE

We sought to determine whether the association between family history, a surrogate for genetic predisposition, and diabetes was modified by any known diabetes risk factors and if these relationships were constant across different ethnic groups.

METHODS

We examined 10,899 adults from the National Health and Nutrition Examination Survey (1999 -2004) to identify interactions between family history and clinical, demographic, and lifestyle variables for the outcome of diabetes using logistic regression analysis in racial/ethnic subgroups.

RESULTS

There was significant heterogeneity by race/ethnicity in the interaction between covariates and family history in relation to diabetes. In black (P = 0.0001) and Hispanic (P = 0.013), but not white (P = 0.75) subgroups, high-familial risk was a strong risk factor for diabetes among lean individuals but less so among overweight or obese subjects.Among blacks, high-familial risk conferred a 20-fold increased odds of diabetes among lean subjects and only a sixfold increased odds among obese individuals.

CONCLUSIONS

These findings suggest possible race/ethnic-specific differences in gene by environment interaction and identify body mass index as an important effect modifier of familial risk in diabetes in non-white populations. These findings may help guide future genetic studies and improve the utility of family history as a public health screening tool.

Unique effect of visceral fat on insulin sensitivity in obese Hispanic children with a family history of type 2 diabetes

OBJECTIVE

This study aimed to establish whether total fat or central fat was related to measures of insulin in obese Hispanic children with a family history of type 2 diabetes.

RESEARCH DESIGN AND METHODS

Subjects were 32 children aged 8-13 years. Visceral fat and subcutaneous abdominal fat were determined by magnetic resonance imaging at the umbilicus and total body fat was determined by dual-energy X-ray absorptiometry. Insulin sensitivity (S(i)) and acute insulin response (AIR) were determined by frequently sampled intravenous tolerance test with minimal modeling.

RESULTS

Mean fasting glucose and insulin, S(i), and AIR (+/- SD) were 5.3 +/- 0.3 mmol/l, 206 +/- 105 pmol/l, 11.8 +/- 5.7 [x 10(-4) min(-1)/(pmol/l)], and 17,175 +/- 9,695 (pmol/l x 10 min), respectively. In multivariate regression analysis, total fat mass was independently and positively related to fasting insulin (P < 0.01) and negatively related to S(i) (P < 0.05) but was not related to AIR. Visceral fat was independently and positively related to fasting insulin (P < 0.05) and AIR (P < 0.01) and negatively related to S(i) (P < 0.001).

CONCLUSIONS

-These findings support the hypothesis that specific accumulation of visceral fat in addition to overall adiposity in Hispanic children increases the risk of type 2 diabetes.

Duration of obesity and risk of non-insulin-dependent diabetes mellitus

Although obesity is one of the major risk factors for diabetes mellitus, the association of the duration of obesity with glucose intolerance or insulin dysregulation has not yet been clarified. Thirteen articles were picked up from the MEDLINE database by using the four key-word phrases, "duration of obesity," "duration of overweight," "prolonged obesity," and "prolonged overweight." Although the definition of overweight was similar among the children-based studies (> = 20% or 2 SD over ideal weight), the cutoff point for adults ranged from 25.0 to 30.0 kg/m2 of body mass index. With regard to the definition of the duration of obesity, the articles were roughly divided into two groups, with some researchers bearing the definition on the number of years from the onset of overweight and some calculating using the person-years method. The prevalence or incidence of non-insulin-dependent diabetes mellitus (NIDDM) or impaired glucose tolerance (IGT) are probably associated with the duration of obesity. The effect of prolonged obesity on insulin dysregulation is still unclear.

The genetic basis of type 2 diabetes mellitus: impaired insulin secretion versus impaired insulin sensitivity

Despite the fact that it is the prevalent view that insulin resistance is the main genetic factor predisposing to development of type 2 diabetes, review of several lines of evidence in the literature indicates a lack of overwhelming support for this concept. In fact, the literature better supports the case of impaired insulin secretion being the initial and main genetic factor predisposing to type 2 diabetes, especially 1) the studies in people at high risk to subsequently develop type 2 diabetes (discordant monozygotic twins and women with previous gestational diabetes), 2) the studies demonstrating compete alleviation of insulin resistance with weight loss, and 3) the studies finding that people with type 2 diabetes or IGT can have impaired insulin secretion and no insulin resistance compared with well matched NGT subjects. The fact that insulin resistance may be largely an acquired problem in no way lessens its importance in the pathogenesis of type 2 diabetes. Life style changes (exercise, weight reduction) and pharmacological agents (e.g., biguanides and thiazolidendiones) that reduce insulin resistance or increase insulin sensitivity clearly have major beneficial effects (122, 144-146, 153-155).

Decreased glucose tolerance, not decreased insulin sensitivity, is a maturational abnormality in the male offspring of a parent with early coronary artery disease

We investigated whether the male offspring of a parent with early coronary artery disease (before the age of 60; n = 61) exhibit decreased insulin sensitivity compared with controls matched for age and body mass index (BMI) (n = 39). The insulin sensitivity index (S[I]) was determined by the minimal modeling method of Bergman from a frequently sampled intravenous glucose tolerance test with intravenous tolbutamide. Offspring and controls had a similar S[I], insulin-independent glucose utilization (S[G]), first-phase insulin response (AIR[G]), and area under the glucose curve. When subjects were separated into two age groups, younger subjects aged 15 to 30 years and older subjects aged 31 to 45 years, important differences were seen. S[G] was significantly increased in younger offspring compared with controls (22.8 +/- 2.3 v 16.8 +/- 2.3 x 10(-3) x min(-1), P < .05). Older offspring had a significantly increased area under the glucose curve compared with controls (18,250 +/- 322 v 17,225 +/- 347 mg/dL x min(-1), P < .05). Older offspring also had decreased S[I] compared with younger offspring (5.0 +/- 0.4 v 6.6 +/- 0.9 x 10(-4) x min(-1) x micro U/mL, P < .05), but this difference was eliminated after adjusting for BMI and waist to hip ratio (5.5 +/- 0.4 v5.8 +/- 0.9 x 10(-3) x min(-1), nonsignificant). This study does not support the concept that insulin resistance is an early atherogenic risk factor in offspring at risk for coronary disease because of their family history. However, it does point to the importance of maturational changes in glucose homeostasis in these offspring.

Simple anthropometric indices associated with ischemic heart disease

In a case-control study of 217 hospitalized incident cases of ischemic heart disease and 261 controls we compared various anthropometric indices for the strength of their associations to the outcome event. The ratio of supine sagittal abdominal diameter to midthigh girth ("abdominal diameter index"; ADI) was the simple index that best discriminated cases from controls for both men (standardized difference, 0.65; p < 0.0001) and women (standardized difference, 0.95; p < 0.0001). The waist-to-thigh ratio of girths (WTR) (standardized difference, 0.57 and 0.90; p < 0.0001) was nearly as strong as the ADI and stronger than the traditional waist-to-hip ratio (standardized difference, 0.34 and 0.68; p < 0.005). After adjustments for age and race, the men's odds ratio for ischemic heart disease (tertile 3 vs. tertile 1) was 5.5 (95% CI, 2.9-10) using ADI and 5.1 (2.6-10) using the WTR. The women's odds ratio was 6.3 (1.9-20) using ADI and 8.7 (2.3-33) using the WTR. Further adjustments for body mass index and cardiovascular risk factors did not substantially change these risk estimates. Similar odds ratios were estimated by analyses restricted to 169 neighborhood-matched case-control pairs. In contrast, increased midthigh girth and subcutaneous fat mass (sum of three skinfolds) were associated with a protective effect against ischemic heart disease. Anthropometry using the ADI or WTR could offer a low-cost, noninvasive method for the clinical or epidemiologic evaluation of ischemic heart disease risk.

Dyslipidaemia and obesity

Obesity is frequently associated with a dyslipidaemic state. Several metabolic and epidemiological studies published in the 1980s have, however, emphasized the importance of considering the regional distribution of body fat in the assessment of the health hazards of obesity. The development of imaging techniques such as computed tomography has also allowed it to be established that the fat located in the abdominal cavity, i.e. the visceral adipose tissue, was the critical correlate of the metabolic complications found in abdominal obesity which include insulin resistance and hyperinsulinaemia, glucose intolerance, hypertriglyceridaemia, hypoalphalipoproteinaemia and increased concentrations of dense LDL particles. Furthermore, since several genes are involved in the regulation of plasma lipoprotein-lipid levels and they have been reported to show polymorphism, visceral obesity should be considered as a permissive factor that exacerbates an individual's susceptibility to dyslipidaemia and premature coronary heart disease rather than a primary regulator of the dyslipidaemic state observed in visceral obese patients. Finally, as insulin resistance and the level of visceral adipose tissue are two main correlates of the dyslipidaemic state which characterizes abdominal obesity, treatment should be aimed at reducing visceral fat and improving insulin sensitivity. Prospective studies are clearly warranted to evaluate the potential benefits of such interventions on the incidence of coronary heart disease.

Study of the rate of early glucose disappearance following insulin injection: insulin sensitivity index

The euglycaemic hyperinsulinaemic glucose clamp is usually considered as the reference technique to evaluate insulin sensitivity. As it is an expensive and time-consuming tool, we therefore tried to validate a simple insulin tolerance test (ITT) (IV bolus of 0.1 IU/kg of regular insulin, with glucose sampling at -5, 0, 3, 5, 7, 10 and 15 min) and to demonstrate its usefulness. Insulin sensitivity was measured by DG/G0 ratio (G0 = initial glycaemia, DG is the variation between G0 and the glycaemia obtained at 15 min by the calculation of the regression plot). We confirmed the existence of a correlation between the glucose uptake (mg/kg per min) evaluated by glucose clamp and the DG/G0 index (r = 0.9, P < 0.01). There was no stimulation of hormonal counter regulation during the test. The ITT was significantly correlated both with fasting insulin (r = -0.43, P < 0.01), and post-glucose load insulin concentration (r = -0.67, P < 0.01); each measurement expressing insulin sensitivity. Four groups of patients with different insulin sensitivity: controls, NIDDM, gynoid and android obese subjects, were clearly separated by ITT. We showed that fasting glycaemia and DG/G0 were correlated (y = 2.63/x - 0.093; r = 0.82, P < 0.01). These results suggest that ITT could be an easy, quick and low cost method to evaluate insulin resistance in clinical practice and epidemiological studies.