Association of prenatal exposure to gestational diabetes with offspring body composition and regional body fat distribution

The aim of this cohort study was to compare body composition and regional body fat distribution between children exposed (GDM+) or unexposed (GDM-) in utero to gestational diabetes mellitus (GDM) and to investigate the association with the glycaemic and the insulin profile. Data from 56 GDM+ and 30 GDM- were analysed. Height, weight and waist circumference were measured. Total and regional body composition was measured by dual-energy X-ray absorptiometry. Insulin, glucose and HbA_1c were obtained from a fasting plasma sample, and the HOMA-IR index was calculated. anova was performed to compare adiposity measures between GDM+ and GDM-. Associations between the glycaemic and insulin profile and adiposity measures were studied using partial Pearson correlations. Mean age was 6.6 ± 2.3 years. Waist circumference, fat mass percentage, android fat mass, android fat mass percentage and android-to-gynoid fat mass ratio were higher among GDM+, and lean mass percentage was lower (P < 0.05). Among GDM+ children, body mass index (BMI) z score, waist circumference, fat mass percentage, android fat mass percentage and android-to-gynoid fat mass ratio were all positively correlated with HbA_1C (r = 0.32-0.43, P < 0.05). Prenatal exposure to GDM is associated with increased total and abdominal adiposity. This increased adiposity observed among GDM+ children is associated with an altered glycaemic profile. This study is registered in the Clinical Trials.gov registry (NCT01340924).

An explained variance-based genetic risk score associated with gestational diabetes antecedent and with progression to pre-diabetes and type 2 diabetes: a cohort study

OBJECTIVE

To determine whether an explained-variance genetic risk score (GRS), with 36 single nucleotide polymorphisms (SNPs) previously associated with type 2 diabetes (T2D), is also associated with gestational diabetes mellitus (GDM), and with the progression to pre-diabetes and T2D among women with prior GDM.

DESIGN

A cohort study.

SETTING

Clinical investigation unit of Laval University, Quebec, Canada.

POPULATION

A cohort of 214 women with prior GDM and 82 controls recruited between 2009 and 2012.

METHODS

Associations between the GRS and GDM.

MAIN OUTCOMES MEASURES

GDM and prevalence of pre-diabetes and T2D.

RESULTS

Women with prior GDM had a higher GRS compared with controls (38.6 ± 3.9, 95% CI 38.1-39.1, versus 37.4 ± 3.2, 95% CI 36.7-38.1; P < 0.0001). In women with prior GDM, the explained-variance GRS was higher for pre-diabetic women compared with women who remained normoglucotolerant at testing (1.21 ± 0.18, 95% CI 1.18-1.23, versus 1.17 ± 0.15, 95% CI 1.13-1.20; P < 0.0001). Similarly, women with T2D had a higher explained-variance GRS compared with women with prior GDM who remained normoglucotolerant (1.20 ± 0.18, 95% CI 1.14-1.25, versus 1.17 ± 0.17, 95% CI 1.13-1.20; P < 0.0001). The predictive effects of the explained-variance GRS, age, and body mass index (BMI), or the additive effects of the three variables, were tested for pre-diabetes and T2D. We observed an area under the curve of 0.6269 (95% CI 0.5638-0.6901) for age and BMI, and adding the explained-variance GRS into the model increased the area to 0.6672 (95% CI 0.6064-0.7281) for the prediction of pre-diabetes.

CONCLUSIONS

An explained-variance GRS is associated with both GDM and progression to pre-diabetes and T2D in women with prior GDM.

The Barriers to Physical Activity in Type 1 Diabetes (BAPAD-1) scale: predictive validity and reliability

AIM

Perceived barriers are one determinant of physical activity. Depending on the study population, these barriers can vary. The aim of this study was to assess the reliability and predictive validity of the 'Barriers to Physical Activity in Type 1 Diabetes' (BAPAD-1) scale, developed by Dubé et al.

METHODS

A total of 77 adults (48% women; age: 43.5±10.4; body mass index: 25.2±4.3kg/m(2); HbA(1c): 7.6±1.3%) with type 1 diabetes completed the questionnaire and an evaluation of their physical activity using an accelerometer (8.4±1.2 days) and cardiorespiratory fitness assessment (VO(2)(peak)). To evaluate the temporal stability of the questionnaire, a subgroup of 17 participants answered the BAPAD-1 scale on both visits required by the protocol (10±4 days).

RESULTS

The BAPAD-1 scale showed good internal validity with an inter-items correlation coefficient (Cronbach's correlation) of 0.85. The intraclass correlation coefficient for the two times the scales were completed was 0.80. The BAPAD-1 score was negatively correlated with both physical activity energy expenditure (r=-0.25; P=0.03) and VO(2)(peak) adjusted for gender and age (r=-0.27; P=0.02).

CONCLUSION

The BAPAD-1 scale is a reliable and valid tool for assessing salient barriers to physical activity. In future, this scale could be used to describe the factors accounting for physical activity, and for planning interventions aimed at promoting physical activity among adults with type 1 diabetes.

Effect of sitagliptin therapy on postprandial lipoprotein levels in patients with type 2 diabetes

AIM

Recent studies indicate that type 2 diabetes is associated with an increased secretion of both hepatic and intestinal lipoproteins, leading to the accumulation of atherogenic triglyceride (TG)-rich lipoproteins. Sitagliptin is a selective inhibitor of dipeptidyl peptidase-4 that has been shown to reduce fasting and postprandial glucose levels in patients with type 2 diabetes presumably through incretin hormone-mediated improvements in islet function. The objective of the present study is to examine the effects of treatment with sitagliptin on postprandial lipid and incretin hormone levels as well as glucose homeostasis in patients with type 2 diabetes.

METHODS

Thirty-six subjects with type 2 diabetes (30 men/6 postmenopausal women with a mean age of 58.1 ± 6.4 years and a body mass index of 30.7 ± 4.9 kg/m(2) ) were recruited in this double-blind cross-over study using sitagliptin 100 mg/day or placebo for a 6-week period each, with a 4-week washout period between the two phases. At the end of each phase of treatment, patients underwent an oral lipid tolerance test providing 35 g of fat per m(2) of body surface area and blood samples were taken over an 8-h period.

RESULTS

Sitagliptin therapy significantly decreased the postprandial area under the curves (AUCs) for plasma apolipoprotein (apo)B (-5.1%, p = 0.002), apoB-48 (-7.8%, p = 0.03), TG (-9.4%, p = 0.006), very low-density lipoprotein (VLDL)-cholesterol (-9.3%, p = 0.001), free fatty acids (FFAs) (-7.6%, p = 0.005) and glucose (-9.7%, p < 0.0001). Furthermore, the postprandial AUCs for plasma intact glucagon-like peptide-1 (+67.8%, p < 0.0001) and glucose-dependent insulinotropic polypeptide (+67.3%, p < 0.0001) were significantly increased following treatment with sitagliptin, whereas the AUC for plasma glucagon was reduced by -9.7% (p = 0.001) with no significant changes in the AUCs for plasma insulin and C-peptide. Sitagliptin therapy also improved homeostasis model assessment (HOMA) index for insulin resistance (-14.6%, p = 0.01) and β-cell function (+32.3%, p = 0.007).

CONCLUSIONS

Treatment with sitagliptin for 6 weeks reduced postprandial plasma levels of TG-rich lipoproteins of both intestinal and hepatic origin, most likely by increasing incretin hormone levels, reducing circulating plasma FFA concentrations and improving insulin sensitivity and β-cell function.

Relationship of mid-thigh adiposity to the metabolic syndrome in postmenopausal women

BACKGROUND

In postmenopausal women, a population at risk for the metabolic syndrome, the relative contribution of central fat versus peripheral muscle fat to the metabolic risk profile is unknown. This study explored the relationship between muscle fat infiltration derived from computed tomography (CT) scans and metabolic syndrome.

METHODS

Mid-thigh CT scans measured the surface of muscle with low attenuation (LAMS) [0-34 Hounsfield units (HU)], which represented the specific component of fat-rich muscle. Insulin sensitivity was evaluated by an euglycemic-hyperinsulinemic clamp. National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) criteria were used to determine the presence of the metabolic syndrome.

RESULTS

A total of 103 postmenopausal women were studied. Metabolic syndrome was found in 43 women with significantly higher levels of abdominal adiposity, higher LAMS (27 +/- 8 vs. 23 +/- 7 cm(2)), and lower insulin sensitivity compared to those without the metabolic syndrome. Women with higher levels of LAMS presented higher metabolic risk features such as higher blood pressure, abdominal adiposity, inflammatory markers, and blood lipid levels. LAMS and visceral adipose tissue correlated significantly with the presence of metabolic syndrome, but these relationships were lost when LAMS was adjusted for visceral adipose tissue but not when visceral adipose tissue was adjusted for LAMS.

CONCLUSIONS

These results suggest that postmenopausal women who present with metabolic syndrome had increased fat-rich mid-thigh muscle. Moreover, women with more fat-rich muscle had many features of the metabolic syndrome. These relations were weakened when visceral adipose tissue was taken into account suggesting that LAMS may play a relatively smaller role, compared to VAT, in the contribution to the metabolic syndrome.

Improvements in glucose homeostasis in response to regular exercise are influenced by the PPARG Pro12Ala variant: results from the HERITAGE Family Study

AIMS/HYPOTHESIS

Exercise training improves glucose homeostasis, but large inter-individual differences are reported, suggesting a role of genetic factors. We investigated whether variants either confirmed or newly identified as diabetes susceptibility variants through genome-wide association studies (GWAS) modulate changes in phenotypes derived from an IVGTT in response to an endurance training programme.

METHODS

We analysed eight polymorphisms in seven type 2 diabetes genes (CDKAL1 rs7756992; CDKN2A and CDKN2B rs10811661 and rs564398; HHEX rs7923837; IGF2BP2 rs4402960; KCNJ11 rs5215; PPARG rs1801282; and TCF7L2 rs7903146) in a maximum of 481 sedentary, non-diabetic white individuals, who participated in a 20-week endurance training programme. Associations were tested between the variants and changes in IVGTT-derived phenotypes.

RESULTS

The only evidence of association with training response was found with PPARG rs1801282 (Pro12Ala). We observed that Ala carriers experienced greater increase in overall glucose tolerance (Deltaglucose disappearance index Ala/Ala 0.22 +/- 0.22, Pro/Ala 0.14 +/- 0.06, Pro/Pro 0.004 +/- 0.03; p = 0.0008), glucose effectiveness (Ala/Ala 0.28 +/- 0.41, Pro/Ala 0.44 +/- 0.14, Pro/Pro 0.09 +/- 0.06; p = 0.004), acute insulin response to glucose (Ala/Ala 64.21 +/- 37.73, Pro/Ala -11.92 +/- 40.30, Pro/Pro -46.30 +/- 14.70; p = 0.03) and disposition index (Ala/Ala 551.8 +/- 448.5, Pro/Ala 534.6 +/- 218.3, Pro/Pro -7.44 +/- 88.18; p = 0.003).

CONCLUSIONS/INTERPRETATION

Compared with Pro/Pro individuals, PPARG Ala carriers experienced greater improvements in glucose and insulin metabolism in response to regular endurance training. However, we did not find evidence of association between type 2 diabetes susceptibility variants recently identified through GWAS and glucose homeostasis response to exercise. Our results extend those of previous studies showing that Ala carriers appear to be more responsive to beneficial health effects of lifestyle interventions.

Using restrictive messages to limit high-fat foods or nonrestrictive messages to increase fruit and vegetable intake: what works better for postmenopausal women?

BACKGROUND/OBJECTIVES

To compare the effects of two dietary approaches on changes in dietary intakes and body weight: (1) an approach emphasizing nonrestrictive messages directed toward the inclusion of fruits and vegetables (HIFV) and (2) another approach using restrictive messages to limit high-fat foods (LOFAT).

SUBJECTS/METHODS

A total of 68 overweight-obese postmenopausal women were randomly assigned to one of the two dietary approaches. The 6-month dietary intervention included three group sessions and ten individual sessions with a dietitian. Dietary food intake and anthropometric variables were measured at baseline, at 3 months and at 6 months.

RESULTS

Energy density decreased in both groups after the intervention compared with baseline (HIFV, -0.3+/-0.2 kcal/g; LOFAT, -0.3+/-0.3 kcal/g; P<0.0001). Although body weight decreased significantly in both groups after the intervention compared with baseline (HIFV, -1.6+/-2.9 kg; LOFAT, -3.5+/-2.9 kg; P<0.0001), women in the LOFAT group lost significantly more body weight than women in the HIFV group (P=0.01). In the HIFV group, the decrease in energy density was found to be an independent predictor of body weight loss.

CONCLUSIONS

The LOFAT approach induces more weight loss than does the HIFV approach in our sample of overweight-obese postmenopausal women.

Evidence for interaction between PPARG Pro12Ala and PPARGC1A Gly482Ser polymorphisms in determining type 2 diabetes intermediate phenotypes in overweight subjects

BACKGROUND

The peroxisome proliferator-activated receptor-gamma ( PPARG) Pro12Ala and the PPARG co-activator-1alpha ( PPARGC1A) Gly482Ser polymorphisms (SNPs) have been associated with type 2 diabetes mellitus (T2DM) risk. We hypothesized that independent and interactive effects of the PPARG Pro12Ala and PPARGC1A Gly482Ser polymorphisms influence T2DM intermediate phenotypes.

MATERIAL AND METHODS

PPARG Pro12Ala and PPARGC1A Gly482Ser SNPs were studied in 680 non diabetic subjects who underwent a 75 g oral glucose tolerant test (OGTT). Glucose and insulin plasma levels in the fasting state and derived from the OGTT were included in the present study.

RESULTS

We found significant independent effects of the PPARG and PPARGC1A variants on fasting insulin levels (p=0.02 for both), HOMA-IR (p=0.03 and p=0.02, respectively), insulin area under the curve (AUC) (p=0.007 and p=0.006, respectively) and 2-h glucose levels (p=0.02 for PPARGC1A). Furthermore, significant gene-gene interactions were found for fasting insulin, HOMA-IR and insulin AUC (p=0.03 for all). Carriers of the PPARGC1A Gly allele who were also PPARG Ala-carriers had higher fasting insulin levels (p=0.02), HOMA-IR (p=0.01) and insulin AUC (p=0.01) compared to the Ser/Ser-Ala+genotype combination, whereas no differences between the PPARGC1A genotypes among the PPARG Pro/Pro carriers were observed.

CONCLUSION

Together, these results showed that PPARG Pro12Ala and PPARGC1A Gly482Ser variants are associated, alone and in interaction, with insulin and glucose homeostasis and suggest that gene-gene interactions should be taken into account in candidate gene studies of T2DM to identify subjects with markedly different risks of developing the disease.

Associations between glucose tolerance, insulin sensitivity and insulin secretion phenotypes and polymorphisms in adiponectin and adiponectin receptor genes in the Quebec Family Study

AIMS

Studies suggest that adiponectin (APM1) and its receptors 1 and 2 (AdipoR1 and AdipoR2) play an important role in the development of insulin resistance (IR). Our objective was to examine associations between APM1 (+45T>G, +276G>T and -3971A>G), AdipoR1 (-100G>T and -3882T>C) and AdipoR2 (-35361A>G and -1352G>A) genes single-nucleotide polymorphisms (SNPs) and adiponectin plasma levels, indicators of glucose tolerance, insulin sensitivity (IS) and insulin secretion.

METHODS

Six hundred and twenty-two non-diabetic subjects from the Quebec Family Study (QFS) underwent a 75-g oral glucose tolerance test (OGTT), with measurement of fasting adiponectin, glucose, insulin and C-peptide levels. Indices of glucose tolerance, IS and insulin secretion were derived from fasting and OGTT measurements.

RESULTS

Significant evidence of association was found between indices of IS and APM1 and AdipoR1 SNPs. The APM1 -3971G/G homozygotes exhibited a reduced area under the curve of insulin during the OGTT (P = 0.007) and higher Cederholm index (P = 0.01) compared to the A/A homozygotes. The APM1+45T>G variant was also associated with fasting (P = 0.002) and 2-h (P = 0.007) glucose values as well as with higher Cederholm index (P = 0.04) and disposition index (P = 0.02). Finally, the AdipoR1-3882T>C SNP was associated with fasting glucose (P = 0.03), the homeostasis model assessment for insulin resistance (P = 0.04) and an index of insulin secretion (P30/G30, P = 0.02). No evidence of association was found with plasma adiponectin levels.

CONCLUSIONS

These results provide evidence for an influence of common SNPs in the APM1 and AdipoR1 genes on different phenotypes of glucose and insulin metabolism associated with increased risk of type 2 diabetes.

Substrate source utilization during moderate intensity exercise with glucose ingestion in Type 1 diabetic patients

Substrate oxidation and the respective contributions of exogenous glucose, glucose released from the liver, and muscle glycogen oxidation were measured by indirect respiratory calorimetry combined with tracer technique in eight control subjects and eight diabetic patients (5 men and 3 women in both groups) of similar age, height, body mass, and maximal oxygen uptake, over a 60-min exercise period on cycle ergometer at 50.8% (SD 4.0) maximal oxygen uptake [131.0 W (SD 38.2)]. The subjects and patients ingested a breakfast (containing ∼80 g of carbohydrates) 3 h before and 30 g of glucose (labeled with 13C) 15 min before the beginning of exercise. The diabetic patients also received their usual insulin dose [Humalog = 9.1 U (SD 0.9); Humulin N = 13.9 U (SD 4.4)] immediately before the breakfast. Over the last 30 min of exercise, the oxidation of carbohydrate [1.32 g/min (SD 0.48) and 1.42 g/min (SD 0.63)] and fat [0.33 g/min (SD 0.10) and 0.30 g/min (SD 0.10)] and their contribution to the energy yield were not significantly different in the control subjects and diabetic patients. Exogenous glucose oxidation was also not significantly different in the control subjects and diabetic patients [6.3 g/30 min (SD 1.3) and 5.2 g/30 min (SD 1.6), respectively]. In contrast, the oxidation of plasma glucose and oxidation of glucose released from the liver were significantly lower in the diabetic patients than in control subjects [14.5 g/30 min (SD 4.3) and 9.3 g/30 min (SD 2.8) vs. 27.9 g/30 min (SD 13.3) and 21.6 g/30 min (SD 12.8), respectively], whereas that of muscle glycogen was significantly higher [28.1 g/30 min (SD 15.5) vs. 11.6 g/30 min (SD 8.1)]. These data indicate that, compared with control subjects, in diabetic patients fed glucose before exercise, substrate oxidation and exogenous glucose oxidation overall are similar but plasma glucose oxidation is lower; this is associated with a compensatory higher utilization of muscle glycogen.

Disinhibition, as assessed by the Three-Factor Eating Questionnaire, is inversely related to psychological well-being in postmenopausal women

Psychological correlates of obesity remain under controversy. As eating behaviors and dieting history have been previously related to obesity status, these dietary variables may contribute to identify overweight and obese individuals who are at higher risk of having an impaired psychological well-being.

OBJECTIVE

The main purpose of this cross-sectional study was to verify the hypothesis of a relationship between weight status and psychological well-being, and to examine whether cognitive dietary restraint, disinhibition, susceptibility to hunger and dieting history could be related to psychological well-being.

DESIGN AND SUBJECTS

In a sample of 101 postmenopausal women, we performed anthropometric measurements (weight, height and body mass index (BMI)), and measured psychological well-being (PER Questionnaire). The Three-Factor Eating Questionnaire (TFEQ) and a questionnaire about dieting history (dieters: had already been on a diet; non-dieters: had never been on a diet) were also administrated.

RESULTS

A trend for a significant relationship was observed between BMI and psychological well-being (r=-0.17; P=0.08). Significant negative relationships were observed for disinhibition, susceptibility to hunger and all their subscales with psychological well-being (-0.28</=r</=-0.48), whereas no significant differences in psychological well-being were observed between dieters and non-dieters. Finally, women displaying a higher score for habitual susceptibility to disinhibition (which is the subscale of TFEQ that was the most closely related to psychological well-being) had a lower level of psychological well-being, regardless of their weight status.

CONCLUSION

These results show that, as well as being related to weight status, TFEQ-factors are also related to psychological well-being. More specifically, individuals who display higher levels of disinhibition may be at higher risk of having an impaired psychological well-being.

Is early and late post-meal exercise so different in type 1 diabetic lispro users?

To compare blood glucose (BG) responses during a 60 min moderate intensity exercise session performed in early or late postprandial periods. Nine generally well-controlled (HbA(1c): 7.3+/-0.1%) type 1 diabetic patients performed, at least one week apart, two exercise sessions, 60 (early exercise) and 180 min (late exercise) after a standardized breakfast. All subjects were using Humulin N (N) and Humalog (Lispro, LI) insulin. During exercise, the overall decrease in BG was 4.8+/-0.6 mmol/l and 3.6+/-0.8 mmol/l in early and late exercise, respectively (P=0.051). To prevent hypoglycemia, a dextrose infusion was initiated when BG reached 5 mmol/l. The quantity of dextrose infused was 6.2+/-3.0 g and 10.5+/-3.2g in early and late exercise, respectively (NS). The time free of dextrose infusion during exercise was 41.2+/-7.8 min and 31.7+/-7.5 min in early and late exercise, respectively (NS). In N-LI users, overall drop in BG during exercise tends to be greater in the early postprandial period. However, early and late exercise present similar quantity of dextrose infused and time free of dextrose infusion. Consequently, the similar risk of exercise-induced hypoglycemia suggests similar precautions in either exercise times.

Muscle adiposity and body fat distribution in type 1 and type 2 diabetes: varying relationships according to diabetes type

OBJECTIVE

To compare the relationships between markers of total and regional adiposity with muscle fat infiltration in type 1 diabetic and type 2 diabetic subjects and their respective nondiabetic controls, and to document these relationships in type 1 diabetic subjects.

DESIGN

Cross-sectional study.

SUBJECTS

In total, 86 healthy, with type 1 diabetes, type 2 diabetes or control subjects. Each diabetic group was matched for age, sex and body mass index with its respective nondiabetic control group.

MEASUREMENTS

Measures of body composition (hydrodensitometry), fat distribution (waist circumference, abdominal and mid-thigh computed tomography scans) and blood lipid profiles were assessed.

RESULTS

Low attenuation mid-thigh muscle surface correlated similarly with markers of adiposity and body composition in all groups, regardless of diabetes status, except for visceral adipose tissue and waist circumference. Indeed, relationships between visceral adiposity and muscle adiposity were significantly stronger in type 2 vs type 1 diabetic subjects (P<0.05 for comparison of slopes). In addition, in well-controlled type 1 diabetic subjects (mean HbA(1c) of 6.8%), daily insulin requirements tended to correlate with low attenuation mid-thigh muscle surface, a specific component of fat-rich muscle (r=0.36, P=0.08), but not with glycemic control (HbA(1c)).

CONCLUSION

This study suggests that the relationship of central adiposity and muscle adiposity is modulated by diabetes status and is stronger in the insulin resistant diabetes type (type 2 diabetes). In well-controlled nonobese type 1 diabetic subjects, the relationship between muscle fat accumulation and insulin sensitivity was also maintained.

Physical activity barriers in diabetes: development and validation of a new scale

To develop and validate a questionnaire measuring perceived Barriers to Physical Activity in Diabetes (type 1) or BAPAD1. Initially, an open-ended questionnaire was filled by 36 patients. The modal accessible beliefs obtained on this pilot study were analysed and a scale composed of 12 items (BAPAD1) was developed and validated. Seventy-four type 1 diabetic patients filled the BAPAD1 scale. Cronbach alpha coefficient was 0.85 and the correlation between the test-retest scores was 0.84, both indicating adequate reliability of the barriers scale. Each item of BAPAD1 scale displayed very good item characteristic curve except for item 12, which was withdrawn. The test reliability curve indicated that the BAPAD1 scale is informative (value>or=0.82) at all levels of perceived barriers toward physical activity. Moreover, among diabetic-related items, the risk of hypoglycemia showed a particularly good item characteristic curve. In summary, the BAPAD1 scale presents excellent psychometric proprieties and among diabetic-related items, the risk of hypoglycemia should be considered as a significant target to overcome in order to increase physical activity. This new validated tool should be useful in identifying the most salient barriers toward the practice of physical activity and thus, permit more focused intervention in order to overcome those barriers.

Genome-wide linkage scans for prediabetes phenotypes in response to 20 weeks of endurance exercise training in non-diabetic whites and blacks: the HERITAGE Family Study

AIMS/HYPOTHESIS

Impaired insulin secretion, insulin action, insulin-independent glucose effectiveness, glucose tolerance and the associated abnormalities in insulin and glucose metabolism phenotypes are precursors of type 2 diabetes. Genome-wide multipoint variance component linkage scans were carried out using 654 markers to identify quantitative trait loci for insulin sensitivity, acute insulin response to glucose, disposition index and glucose effectiveness training responses in whites and blacks in the HERITAGE Family Study.

METHODS

These phenotypes were obtained from an IVGTT with the minimal model. The distributions of insulin sensitivity, acute insulin response to glucose and disposition index training responses (post-training minus baseline) were approximately normalised using a square-root transformation. All phenotypes were adjusted for the effects of age, BMI and their respective baseline values within sex and generation by race prior to linkage scans.

RESULTS

In blacks, a promising linkage with a maximum lod score of 3.1 on 19q (54-62 Mb) for glucose effectiveness training response was found. Six interesting linkages with lod scores of at least 1.0 were found for disposition index training response in whites. They included 1p (30 Mb), 3q (152 Mb), 6p (23-42 Mb), 7q (95-96 Mb), 10p (15 Mb) and 12q (119-126 Mb).

CONCLUSIONS/INTERPRETATION

Quantitative trait loci for 20 weeks of endurance exercise training responses in insulin action and glucose metabolism phenotypes were found on chromosome 19q as well as 6p and 7q, with nominal (6p, 7q) but consistent (6p) linkages across the races.

High normal 2-hour plasma glucose is associated with insulin sensitivity and secretion that may predispose to type 2 diabetes

AIMS/HYPOTHESIS

The aim of this study was to evaluate differences in insulin sensitivity, insulin secretion and risk factors for cardiovascular disease between subjects with a 2-h plasma glucose (2hPG) level within the normal range (NPG) and subjects with IGT, following a 75-g OGTT. We also aimed to determine the respective contributions made by 2hPG and fasting plasma glucose to the metabolic risk profile.

METHODS

We compared cardiovascular risk factors and insulin sensitivity and insulin secretion by using several indices calculated using measurements obtained during an OGTT. Subjects (n=643, age 18-71 years) were participants in the Quebec Family Study and were categorised according to 2hPG as having low NPG (2hPG <5.6 mmol/l, the group median for normal values), high NPG (2hPG 5.6-7.7 mmol/l) or IGT (2hPG 7.8-11.0 mmol/l). Subjects with type 2 diabetes were excluded from all analyses.

RESULTS

Beta cell function and insulin sensitivity progressively decreased with increasing 2hPG. Compared with subjects with low NPG, subjects with high NPG were more insulin-resistant (p<0.05) and had reduced insulin secretion (adjusted for insulin resistance) (p<0.001). They also had higher plasma triglyceride concentrations (p<0.01) and cholesterol:HDL cholesterol ratios (p<0.05). These differences remained even after adjustment for age, sex, BMI and waist circumference. Multivariate analyses showed that 2hPG was closely associated with risk factors for diabetes and with cardiovascular variables, including triglycerides (p<0.0001) and apolipoprotein B (p<0.01).

CONCLUSIONS/INTERPRETATION

These results show that deteriorations in glucose-insulin metabolism, which may predispose individuals to type 2 diabetes and cardiovascular disease, are already present in subjects with 2hPG concentrations within the high normal range. Independently of obesity, 2hPG was found to explain, in part, the variance observed in cardiovascular and diabetes risk factors. In addition, elevated 2hPG was associated with metabolic alterations that appear to be the most detrimental to metabolic health. Thus, 2hPG values within the high normal range may be an important marker for the identification of people at risk of complications related to type 2 diabetes.

Human resistin gene polymorphism is associated with visceral obesity and fasting and oral glucose stimulated C-peptide in the Québec Family Study

Obesity and insulin resistance are common features of Type 2 Diabetes. A new protein called resistin has been shown to be secreted by adipocytes in mice and to influence insulin sensitivity. The goal of the present study was to investigate the associations between one polymorphism (g-420C>G) of the human resistin gene and phenotypes related to adiposity and glucose metabolism. We genotyped 725 (including 42 diabetics) adult subjects participating in the Quebec Family Study (QFS) by a minisequencing method. Forty-two were diabetic subjects. Phenotypes measured were: body mass index (BMI) and waist circumference (WC), % body fat (PFAT) and fat mass (FM) assessed by under water weighing, abdominal total, subcutaneous and visceral fat assessed by computed tomography and fasting plasma glucose, insulin and C-peptide and their responses to an oral glucose tolerance test (OGTT). Comparisons between genotypes were performed in non-diabetic men (no.=280) and women (no.=403) separately by analyses of covariance (ANCOVA). Among men, g-420 G homozygotes had less visceral fat (p < 0.05), lower levels of acute insulin responses to an OGTT and lower levels of C-peptide in a fasting state and in responses to an OGTT than carriers of the C allele (p < 0.01). These associations were independent of age and adiposity but were not observed in women. These results suggest that in men, the human resistin gene is associated with reduced amount of visceral obesity and lower insulin secretory responses to a glucose load.

Impaired fasting glucose vs. glucose intolerance in pre-menopausal women: distinct metabolic entities and cardiovascular disease risk?

BACKGROUND

Impaired glucose tolerance (IGT) is associated with an increased cardiovascular disease risk. Less is known about cardiovascular disease risk among subjects with impaired fasting glucose (IFG) or with combined IFG and IGT.

AIMS

To compare body composition, body fat distribution, plasma glucose-insulin homeostasis and plasma lipid-lipoprotein profile between pre-menopausal women having either a normal glucose tolerance (NGT), isolated IFG, isolated IGT or combined IFG and IGT.

METHODS

Three hundred and thirty-four women with NGT, 11 women with IFG, 35 women with IGT and 10 women with both IFG and IGT were studied.

RESULTS

Women with IFG were characterized by a higher visceral adipose tissue (AT) accumulation than women with NGT (P < 0.05). Also, they were characterized by a higher subcutaneous AT area and by higher body fat mass than NGT and IGT women (P < 0.05). However, their lipid-lipoprotein profile was comparable with that of NGT women, except for reduced HDL-cholesterol concentrations (P < 0.05). After adjustment for visceral AT, women with IFG had lower total cholesterol, LDL-cholesterol and apolipoprotein B (apoB) levels than the three other groups. They also had lower HDL(2)-cholesterol than NGT women and lower total cholesterol/HDL-cholesterol ratio than IGT women. Women with IGT showed higher triglyceride and apoB concentrations and a higher total cholesterol/HDL-cholesterol ratio than women with NGT (P < 0.05). Overall, women with combined IFG and IGT showed body fatness characteristics and alterations in their metabolic risk profile which were essentially similar to women with isolated IGT.

CONCLUSIONS

These results indicate that there are significant differences in anthropometric and metabolic variables between pre-menopausal women with IFG vs. IGT and that the association between body fatness-body fat distribution indices and the metabolic profile may differ between IFG and IGT women.

Familial resemblance for glucose and insulin metabolism indices derived from an intravenous glucose tolerance test in Blacks and Whites of the HERITAGE Family Study

Type 2 diabetes mellitus (T2DM), characterized by hyperglycemia, is a complex disease primarily caused by impairment in insulin sensitivity (SI) and insulin secretion. While a strong genetic component for T2DM is well established, there are few reports on racial differences in the magnitude of the genetic effects of T2DM and indices of glucose and insulin metabolism. We report here on the familial resemblance for traits related to glucose metabolism at pre-exercise training levels in 492 members from 99 sedentary White families and 259 members from 108 Black families participating in the multicenter HERITAGE Family Study. All these traits were obtained from the frequently sampled intravenous glucose tolerance test (IVGTT). They include glucose disappearance index (Kg), an overall index for glucose tolerance, acute insulin response to glucose (AIR(Glucose)) which is an index for insulin secretion, and those derived from the minimal model including SI and the disposition index (DI). DI, derived as the product of SI and AIR(Glucose), is a measure of the activity of the B-cells adjusted for insulin resistance. After adjustment for age, sex, and body mass index, the maximal heritability estimates in Blacks (Whites) are 48+/-14% (25+/-8%) for Kg, 44+/-14% (46+/-8%) for AIR(Glucose), 38+/-12% (44+/-8%) for SI and 32+/-14% (24+/-8%) for DI. Interestingly, Blacks have higher heritability for overall glucose tolerance than Whites but there is no race difference in heritability estimates for insulin sensitivity or insulin secretion.

Decreased fasting and oral glucose stimulated C-peptide in nondiabetic subjects with sequence variants in the sulfonylurea receptor 1 gene

The high-affinity sulfonylurea receptor 1 (SUR1) plays an important role in regulating insulin secretion. In the Québec Family Study, we genotyped 731 individuals (685 nondiabetic [ND] subjects) for the SUR1 gene IVS15-3c-->t and exon 18 Thr759(ACC-->ACT) polymorphisms using polymerase chain reaction-restriction fragment-length polymorphism analysis. Phenotypes measured were fasting plasma glucose (GLU), fasting plasma insulin (INS), and fasting C-peptide (CPEP), as well as oral glucose tolerance test (OGTT) responses; they were adjusted for age, sex, waist circumference, and the sum of six skinfold thicknesses. In ND subjects, exon 18 Thr759(ACC-->ACT) T allele carriers (T+) had lower CPEP (P = 0.022, -12.8%) and acute C-peptide responses (area above basal in first 30 min [CP30]) (P = 0.051, -12.4%) than noncarriers (T-). Also, in those with the cT/tC haplotype (from both IVS15-3c-->t and exon 18 Thr759[ACC-->ACT] polymorphisms), CPEP (P = 0.005, -21.2%), CP30 (P = 0.034, -19.2%), and total C-peptide responses (P = 0.016, -20.2%) were lower than that in cT- subjects. In overweight individuals (BMI >25 kg/m2), differences between carriers and noncarriers of the T or cT alleles were greater for GLU (P = 0.023-0.034), CPEP (P = 0.021-0.015), acute OGTT insulin response (P = 0.014-0.019), and CP30 (P = 0.034-0.019). These results suggest that the T and cT allele variants are associated with lower insulin secretion parameters, particularly in female and overweight subjects, adding evidence to the role of SUR1 sequence variants in decreased insulin secretion.

Interactions among the glucocorticoid receptor, lipoprotein lipase, and adrenergic receptor genes and plasma insulin and lipid levels in the Quebec Family Study

The aim of the study was to investigate the possible interactions among the glucocorticoid receptor (GRL), lipoprotein lipase (LPL), and adrenergic receptor (ADR) genes on plasma insulin and lipid levels. The study was cross-sectional and based on 742 individuals from phase 2 of the Quebec Family Study (QFS) cohort. Gene markers were identified by Southern blot analysis or polymerase chain reaction (PCR). Plasma glucose and insulin in the fasted state and during an oral glucose tolerance test (OGTT) were determined and insulin and glucose areas were computed. Triglyceride (TG) and cholesterol concentrations in plasma and lipoprotein fractions were determined enzymatically. The results show that GRL and LPL variants had independent effects on plasma high-density lipoprotein cholesterol (HDL-C) and two beta2-ADR variants were related to total cholesterol concentrations. The alpha2-ADR gene Dral polymorphism was the only variant that had an independent effect on the plasma insulin area. Gene-gene interaction effects were found between GRL and alpha2-ADR genes for low-density lipoprotein cholesterol ([LDL-C] P = .013) and between GRL and LPL genes for HDL-C (P = .045). Higher-order interaction effects involving GRL, LPL, and ADR markers were observed for the plasma insulin area (P = .001 to .025) but not the glucose area. After correction for multiple tests, the findings remained essentially unchanged for the insulin area but became nonsignificant for the lipid phenotypes. In conclusion, multiple interactions among GRL, LPL, and ADR gene markers contribute to insulin metabolism and perhaps to lipid levels, while no significant effect is found for each gene separately. The LPL locus appears to determine the pattern of interactions with ADR and GRL loci. These results suggest that gene-gene interaction effects could play a role in the etiology of risk factors for common chronic diseases.

The human obesity gene map: the 2000 update

This report constitutes the seventh update of the human obesity gene map incorporating published results up to the end of October 2000. Evidence from the rodent and human obesity cases caused by single-gene mutations, Mendelian disorders exhibiting obesity as a clinical feature, quantitative trait loci uncovered in human genome-wide scans and in cross-breeding experiments in various animal models, and association and linkage studies with candidate genes and other markers are reviewed. Forty-seven human cases of obesity caused by single-gene mutations in six different genes have been reported in the literature to date. Twenty-four Mendelian disorders exhibiting obesity as one of their clinical manifestations have now been mapped. The number of different quantitative trait loci reported from animal models currently reaches 115. Attempts to relate DNA sequence variation in specific genes to obesity phenotypes continue to grow, with 130 studies reporting positive associations with 48 candidate genes. Finally, 59 loci have been linked to obesity indicators in genomic scans and other linkage study designs. The obesity gene map reveals that putative loci affecting obesity-related phenotypes can be found on all chromosomes except chromosome Y. A total of 54 new loci have been added to the map in the past 12 months and the number of genes, markers, and chromosomal regions that have been associated or linked with human obesity phenotypes is now above 250. Likewise, the number of negative studies, which are only partially reviewed here, is also on the rise.

Interactions among the alpha2-, beta2-, and beta3-adrenergic receptor genes and obesity-related phenotypes in the Quebec Family Study

The gene-gene interactions between markers in the alpha2-, beta2-, and beta3-adrenergic receptor (ADR) genes and obesity-related phenotypes were studied in the Quebec Family Study (QFS) cohort. The prevalence of the Arg allele of the Arg16Gly polymorphism in the beta2-ADR gene was higher (49%) in males with a body mass index (BMI) of 35 kg/m2 or higher versus those with a BMI less than 35 kg/m2 (33%; P = .010). The beta2-ADR gene Arg16Gly and Gln27Glu polymorphisms were associated with plasma total and low-density lipoprotein (LDL) cholesterol concentrations. In addition, the homozygotes for the 6.3-kb allele of DraI polymorphism in the alpha2-ADR gene had the lowest mean abdominal subcutaneous fat area (P = .012) and total fat area (P = .003), as well as insulin area, under the curve during an oral glucose tolerance test ([OGTT] P = .004). Several ADR gene-gene interaction effects on abdominal fat distribution and plasma lipids were detected. First, significant interactions between alpha2- and beta3-ADR genes were observed on total (P = .015) and subcutaneous (P = .004) abdominal fat. Second, interaction effects between alpha2- and beta2-ADR gene variants influenced total, high-density lipoprotein (HDL), and LDL cholesterol concentrations. Finally, there were interactions between markers within the beta2-ADR gene affecting plasma triglyceride concentrations and subcutaneous abdominal fat. From these results, we conclude that polymorphisms in the ADR genes contribute to body fat and plasma lipid variability in men. Gene-gene interactions among the ADR genes contribute to the phenotypic variability in abdominal obesity and plasma lipid and lipoprotein, but not in visceral fat levels.

The human obesity gene map: the 1999 update

This report constitutes the sixth update of the human obesity gene map incorporating published results up to the end of October 1999. Evidence from the rodent and human obesity cases caused by single gene mutations, Mendelian disorders exhibiting obesity as a clinical feature, quantitative trait loci (QTL) uncovered in human genome-wide scans and in crossbreeding experiments with mouse, rat, pig and chicken models, association and linkage studies with candidate genes and other markers is reviewed. Twenty-five human cases of obesity can now be explained by variation in five genes. Twenty Mendelian disorders exhibiting obesity as one of their clinical manifestations have now been mapped. The number of different QTLs reported from animal models reaches now 98. Attempts to relate DNA sequence variation in specific genes to obesity phenotypes continue to grow, with 89 reports of positive associations pertaining to 40 candidate genes. Finally, 44 loci have linked to obesity indicators in genomic scans and other linkage study designs. The obesity gene map depicted in Figure 1 reveals that putative loci affecting obesity-related phenotypes can be found on all autosomes, with chromosomes 14 and 21 showing each one locus only. The number of genes, markers, and chromosomal regions that have been associated or linked with human obesity phenotypes continues to increase and is now well above 200.