Disparities in Hemoglobin A1c Testing During the Transition to Adulthood and Association With Diabetes Outcomes in Youth-Onset Type 1 and Type 2 Diabetes: The SEARCH for Diabetes in Youth Study.

OBJECTIVE: To identify correlates of hemoglobin A1c (HbA1c) testing frequency and associations with HbA1c levels and microvascular complications in youth-onset diabetes. RESEARCH DESIGN AND METHODS: The SEARCH for Diabetes in Youth study collected data from individuals diagnosed with diabetes before age 20 at 8 years (n=1,885 type 1, n=230 type 2) and 13 years (n=649 type 1, n = 84 type 2) diabetes duration. We identified correlates of reporting ≥3 HbA1c tests/year using logistic regression. We examined associations of HbA1c testing with HbA1c levels and microvascular complications (retinopathy, neuropathy, or nephropathy) using sequentially adjusted linear and logistic regression. RESULTS: For type 1 diabetes, odds of reporting ≥3 HbA1c tests/year at 8 and 13 years diabetes duration decreased with older age at diagnosis (odds ratio [OR] 0.91 [95% CI 0.88-0.95]), longer duration of diabetes (OR 0.90 [0.82-0.99]), not having a personal doctor (OR 0.44 [0.30-0.65]), and lapses in health insurance (OR 0.51 [0.27-0.96]). HbA1c testing ≥3 times/year over time was associated with lower HbA1c levels (OR -0.36% [-0.65 to -0.06]) and lower odds of microvascular complications (OR 0.64 [0.43-0.97]) at 13 years duration, but associations were attenuated after adjustment for HbA1c testing correlates (OR -0.17 [-0.46 to 0.13] and 0.70 [0.46-1.07], respectively). For type 2 diabetes, not seeing an endocrinologist decreased the odds of reporting ≥3 HbA1c tests/year over time (OR 0.19 [0.06-0.63]), but HbA1c testing frequency was not associated with HbA1c levels or microvascular complications. CONCLUSIONS: We observed disparities in HbA1c testing frequency predominately by health care-related factors, which were associated with diabetes outcomes in type 1 diabetes.

Cognitive Function in Adolescents and Young Adults With Youth-Onset Type 1 Versus Type 2 Diabetes: The SEARCH for Diabetes in Youth Study.

OBJECTIVE: Poor cognition has been observed in children and adolescents with youth-onset type 1 (T1D) and type 2 diabetes (T2D) compared with control subjects without diabetes. Differences in cognition between youth-onset T1D and T2D, however, are not known. Thus, using data from SEARCH for Diabetes in Youth, a multicenter, observational cohort study, we tested the association between diabetes type and cognitive function in adolescents and young adults with T1D (n = 1,095) or T2D (n = 285). RESEARCH DESIGN AND METHODS: Cognition was assessed via the National Institutes of Health Toolbox Cognition Battery, and age-corrected composite Fluid Cognition scores were used as the primary outcome. Confounder-adjusted linear regression models were run. Model 1 included diabetes type and clinical site. Model 2 additionally included sex, race/ethnicity, waist-to-height ratio, diabetes duration, depressive symptoms, glycemic control, any hypoglycemic episode in the past year, parental education, and household income. Model 3 additionally included the Picture Vocabulary score, a measure of receptive language and crystallized cognition. RESULTS: Having T2D was significantly associated with lower fluid cognitive scores before adjustment for confounders (model 1; P < 0.001). This association was attenuated to nonsignificance with the addition of a priori confounders (model 2; P = 0.06) and Picture Vocabulary scores (model 3; P = 0.49). Receptive language, waist-to-height ratio, and depressive symptoms remained significant in the final model (P < 0.01 for all, respectively). CONCLUSIONS: These data suggest that while youth with T2D have worse fluid cognition than youth with T1D, these differences are accounted for by differences in crystallized cognition (receptive language), central adiposity, and mental health. These potentially modifiable factors are also independently associated with fluid cognitive health, regardless of diabetes type. Future studies of cognitive health in people with youth-onset diabetes should focus on investigating these significant factors.

Dietary Patterns Over Time and Microalbuminuria in Youth and Young Adults With Type 1 Diabetes: The SEARCH Nutrition Ancillary Study.

OBJECTIVE: We assessed the association between diet quality and microalbuminuria in youth-onset type 1 diabetes using three indices: a modified Mediterranean diet score for children and adolescents (mKIDMED), the Dietary Approaches to Stop Hypertension (DASH), and the Healthy Eating Index-2010 (HEI). RESEARCH DESIGN AND METHODS: Youth and young adults from the SEARCH (SEARCH for Diabetes in Youth) Nutrition Ancillary Study (SNAS) diagnosed with type 1 diabetes in 2002-2008, who had repeated dietary assessments at baseline and follow-up visits and urine albumin-to-creatinine ratio (UACR) measured at the outcome visit (2012-2015) (n = 461), were selected for study. Regression models estimated the association between each longitudinally assessed diet score and UACR and microalbuminuria (UACR ≥30 µg/mg). RESULTS: The cohort was 43% female, and at follow-up, mean age was 20 years, disease duration was 108 months, and 7% had microalbuminuria. Adherence to a higher-quality diet was low for the mKIDMED (mean 3.7 of a possible range of -3 to 12) and the DASH (mean 42 of 80) and better, for the HEI (mean 56.3 of 100). A borderline inverse association was observed between the HEI score and microalbuminuria after adjustment for caloric and protein intake and demographic and disease factors (odds ratio [OR]HEI 0.83, P = 0.07), which lost significance with further adjustment for HbA1c and systolic blood pressure (ORHEI 0.86, P = 0.19). Results were similar for continuous UACR. No significant associations were observed for diet quality characterized by the mKIDMED or DASH indices. CONCLUSIONS: Greater adherence to the HEI may be beneficial for kidney health in youth and young adults with type 1 diabetes. Low adherence to the mKIDMED and DASH diets may explain the lack of association with microalbuminuria.

Variation in PPARG is associated with longitudinal change in insulin resistance in Mexican Americans at risk for type 2 diabetes.

CONTEXT: Peroxisome proliferator-activated receptor gamma (PPARG) is a susceptibility locus for type 2 diabetes mellitus (T2DM). Although cross-sectional associations have been reported, primarily for Pro12Ala, few longitudinal studies in nondiabetic populations have been conducted. OBJECTIVE: This study aimed to examine whether and to what extent variation in PPARG is associated with longitudinal changes in anthropometric and metabolic traits in Mexican Americans at risk for T2DM. SETTING AND DESIGN: Subjects were participants of BetaGene, a family-based study of obesity, insulin resistance, and ß-cell function, who completed a baseline and follow-up study visit (n = 378; mean followup, 4.6 ± 1.5 y). Phenotypes included body fat assessed by dual-energy x-ray absorptiometry; insulin sensitivity (SI), acute insulin response, and ß-cell function (disposition index; DI) were estimated from iv glucose tolerance tests with Minimal Model analysis. Eighteen tag single nucleotide polymorphisms (SNPs) capturing variation in a 156-kb region surrounding PPARG were tested for association with changes in longitudinal traits. P-values were Bonferroni-corrected for multiple testing. RESULTS: Six SNPs (rs2972164, rs11128598, rs17793951, rs1151996, rs1175541, rs3856806) were significantly associated with rate of change in SI after adjustment for age, sex, and body fat percentage, but not with changes in adiposity. rs17793951 also had a significant effect on change in DI over time. Association between rs1175541 and change in SI varied by changes in adiposity such that only carriers of the minor allele who reduced body fat over followup improved SI. rs1306470 (captured Pro12Ala, r(2) = 0.9) was not associated with rates of change in any traits and its effects were not modified by changes in adiposity. CONCLUSIONS: Variation in PPARG, but not Pro12Ala, contributes to declining SI and concomitant deterioration in ß-cell function in Mexican Americans at risk for T2DM.

The SEARCH for Diabetes in Youth study: rationale, findings, and future directions.

The SEARCH for Diabetes in Youth (SEARCH) study was initiated in 2000, with funding from the Centers for Disease Control and Prevention and support from the National Institute of Diabetes and Digestive and Kidney Diseases, to address major knowledge gaps in the understanding of childhood diabetes. SEARCH is being conducted at five sites across the U.S. and represents the largest, most diverse study of diabetes among U.S. youth. An active registry of youth diagnosed with diabetes at age <20 years allows the assessment of prevalence (in 2001 and 2009), annual incidence (since 2002), and trends by age, race/ethnicity, sex, and diabetes type. Prevalence increased significantly from 2001 to 2009 for both type 1 and type 2 diabetes in most age, sex, and race/ethnic groups. SEARCH has also established a longitudinal cohort to assess the natural history and risk factors for acute and chronic diabetes-related complications as well as the quality of care and quality of life of persons with diabetes from diagnosis into young adulthood. Many youth with diabetes, particularly those from low-resourced racial/ethnic minority populations, are not meeting recommended guidelines for diabetes care. Markers of micro- and macrovascular complications are evident in youth with either diabetes type, highlighting the seriousness of diabetes in this contemporary cohort. This review summarizes the study methods, describes key registry and cohort findings and their clinical and public health implications, and discusses future directions.

Genetic variation in MTNR1B is associated with gestational diabetes mellitus and contributes only to the absolute level of beta cell compensation in Mexican Americans.

AIMS/HYPOTHESIS: MTNR1B is a type 2 diabetes susceptibility locus associated with cross-sectional measures of insulin secretion. We hypothesised that variation in MTNR1B contributes to the absolute level of a diabetes-related trait, temporal rate of change in that trait, or both. METHODS: We tested rs10830963 for association with cross-sectional diabetes-related traits in up to 1,383 individuals or with rate of change in the same phenotypes over a 3-5 year follow-up in up to 374 individuals from the family-based BetaGene study of Mexican Americans. RESULTS: rs10830963 was associated cross-sectionally with fasting glucose (p = 0.0069), acute insulin response (AIR; p = 0.0013), disposition index (p = 0.00078), glucose effectiveness (p = 0.018) and gestational diabetes mellitus (OR 1.48; p = 0.012), but not with OGTT 30 min Δinsulin (the difference between the 30 min and fasting plasma insulin concentration) or 30 min insulin-based disposition index. rs10830963 was also associated with rate of change in fasting glucose (p = 0.043), OGTT 30 min Δinsulin (p = 0.01) and AIR (p = 0.037). There was no evidence for an association with the rate of change in beta cell compensation for insulin resistance. CONCLUSIONS/INTERPRETATION: We conclude that variation in MTNR1B contributes to the absolute level of insulin secretion but not to differences in the temporal rate of change in insulin secretion. The observed association with the rate of change in insulin secretion reflects the natural physiological response to changes in underlying insulin sensitivity and is not a direct effect of the variant.

Longitudinal associations between sex, diabetes self-care, and health-related quality of life among youth with type 1 or type 2 diabetes mellitus.

OBJECTIVE: To examine the longitudinal associations between sex, diabetes self-care, and the health-related quality of life (HRQL) of children and adolescents with type 1 or type 2 diabetes. STUDY DESIGN: The sample included 910 participants with type 1 and 241 participants with type 2, ages 10-22 years at baseline, from the SEARCH for Diabetes in Youth Study, a longitudinal observational study. The primary outcome measure was the Pediatric Quality of Life Inventory. Repeated measures, mixed-model regression analysis was conducted with the use of data from baseline and at least one follow-up assessment, spanning approximately 4 years. RESULTS: HRQL was greater among those with type 1 versus type 2 diabetes. Among participants with type 1, greater (better) Pediatric Quality of Life Inventory total scores over time were related to greater parent education (P = .0007), lower glycated hemoglobin values (P < .0001), and greater physical activity during the past 7 days (P = .0001). There was a significant interaction between sex and age (P < .0001); girls' HRQL remained stable or decreased over time, whereas males' HRQL increased. For participants with type 2 diabetes, there was no significant interaction by age and sex, but lower total HRQL was related to being female (P = .011) and greater body mass index z-scores (P = .014). CONCLUSIONS: HRQL in this cohort varied by diabetes type. The interaction between sex and age for type 1 participants, coupled with poorer HRQL among female than male participants with type 2 diabetes, suggests the impacts of diabetes on HRQL differ by sex and should be considered in clinical management. Encouraging physical activity and weight control continue to be important in improving HRQL.

High-fat diet is associated with obesity-mediated insulin resistance and ß-cell dysfunction in Mexican Americans.

Consumption of energy-dense, nutrient-poor foods has contributed to the rising incidence of obesity and may underlie insulin resistance and ß-cell dysfunction. Macronutrient intake patterns were examined in relation to anthropometric and metabolic traits in participants of BetaGene, a family-based study of obesity, insulin resistance, and ß-cell dysfunction in Mexican Americans. Dietary intake, body composition, insulin sensitivity (SI), and ß-cell function [Disposition Index (DI)] were assessed by food-frequency questionnaires, dual-energy X-ray absorptiometry, and intravenous glucose-tolerance tests, respectively. Patterns of macronutrient intake were identified by using a K-means model based on the proportion of total energy intake per day attributable to carbohydrate, fat, and protein and were tested for association with anthropometric and metabolic traits. Among 1150 subjects aged 18-65 y (73% female), tertiles of fat intake were associated with greater adiposity and lower SI, after adjustment for age, sex, and daily energy intake. Moreover, 3 distinct dietary patterns were identified: "high fat" (35% fat, 44% carbohydrate, 21% protein; n = 238), "moderate fat" (28% fat, 54% carbohydrate, 18% protein; n = 520), and "low fat" (20% fat, 65% carbohydrate, 15% protein; n = 392). Compared with the low-fat group, the high-fat group had higher age- and sex-adjusted mean body mass index, body fat percentage, and trunk fat and lower SI and DI. Further adjustment for daily energy intake by matching individuals across dietary pattern groups yielded similar results. None of the observed associations were altered after adjustment for physical activity; however, associations with SI and DI were attenuated after adjustment for adiposity. These findings suggest that high-fat diets may contribute to increased adiposity and concomitant insulin resistance and ß-cell dysfunction in Mexican Americans.

Self-reported physical activity is associated with ß-cell function in Mexican American adults.

OBJECTIVE: To examine the association between self-reported physical activity (PA) and diabetes-related quantitative traits. RESEARCH DESIGN AND METHODS: The observational cohort was 1,152 Mexican American adults with dual-energy X-ray absorptiometry, oral and intravenous glucose tolerance tests, and self-reported dietary and PA questionnaires. PA was categorized into three mutually exclusive groups according to the U.S. Department of Health and Human Services PA guidelines for Americans: low (vigorous <75 min/week and moderate <150 min/week), moderate (vigorous ≥75 min/week or moderate ≥150 min/week), and high (vigorous ≥75 min/week and moderate ≥150 min/week). Trends in PA groups were tested for association with metabolic traits in a cross-sectional analysis. RESULTS: The participants' mean age was 35 years (range, 18-66 years), mean BMI was 29.6 kg/m(2), and 73% were female. Among them, 501 (43%), 448 (39%), and 203 (18%) were classified as having low, moderate, and high PA, respectively. After adjustment for age, a higher PA was significantly associated with lower 2-h glucose, fasting insulin, and 2-h insulin and greater ß-cell function (P = 0.001, 0.0003, 0.0001, and 0.004, respectively). The association did not differ significantly by sex. Results were similar after further adjustment for age, sex, BMI, or percent body fat. CONCLUSIONS: An increasing level of PA is associated with a better glucose and insulin profile and enhanced ß-cell function that is not explained by differences in BMI or percent body fat. Our results suggest that PA can be beneficial to ß-cell function and glucose regulation independent of obesity.

Demographic and clinical correlates of diabetes-related quality of life among youth with type 1 diabetes.

OBJECTIVES: To evaluate the reliability and cluster structure of the Pediatric Quality of Life Inventory Type 1 Diabetes Module 3.0 (PedsQL-T1DM) and associated subscales and to explore the associations between PedsQL-T1DM total score and demographic and clinical characteristics and clinical indicators among a large racially/ethnically diverse cohort of youth with type 1 diabetes. STUDY DESIGN: Principal components analysis was conducted on responses from the PedsQL-T1DM child self-report forms completed by SEARCH for Diabetes in Youth study participants aged ≥ 5 years. Multivariate linear regression models were fit to examine the associations among PedsQL-T1DM total score, demographic and clinical characteristics, and clinical indicators. RESULTS: The sample comprised 2602 youth with a mean age of 13.6 ± 4.1 years and a mean T1DM duration of 62.1 ± 47.0 months. Principal components analysis did not support the 5 existing PedsQL-T1DM subscales. In multivariate analyses, the PedsQL-T1DM total score was negatively and significantly associated with younger age (5-7 years), female sex, receiving insulin by injection (vs pump), having parents without a college degree, Medicaid/Medicare insurance, and having a comorbid medical condition. Youth with poor glycemic control based on their age-specific hemoglobin A1c target values and those with depressive symptoms had significantly lower PedsQL-T1DM scores than their counterparts with good control and no or limited depressive symptoms. CONCLUSION: This study has identified sociodemographic and clinical characteristics of youth with T1DM more likely to experience poor diabetes-specific quality of life. The association of lower PedsQL-T1DM scores with depressive symptoms and poor glycemic control is especially concerning and may be the focus of future interventions and studies.

Prevalence of tobacco use and association between cardiometabolic risk factors and cigarette smoking in youth with type 1 or type 2 diabetes mellitus.

OBJECTIVES: To examine prevalence of tobacco use and coexistence of cardiometabolic risk factors according to smoking status in youth with diabetes mellitus. STUDY DESIGN: Youth aged 10 to 22 years who participated in the SEARCH for Diabetes in Youth study (n = 3466) were surveyed about their tobacco use and examined for cardiometabolic risk factors: waist circumference, systolic and diastolic blood pressure, physical activity, and lipid profile. RESULTS: The prevalence of tobacco use in youth aged 10 to 14 years, 15 to 19 years, and ≥20 years with type 1 diabetes mellitus was 2.7%, 17.1%, and 34.0%, respectively, and the prevalence in youth with type 2 diabetes mellitus was 5.5%, 16.4%, and 40.3%, respectively. Smoking was more likely in youth with annual family incomes <$50 000, regardless of diabetes mellitus type. Cigarette smoking was associated with higher odds of high triglyceride levels and physical inactivity in youth with type 1 diabetes mellitus. Less than 50% of youth aged 10 to 14 years (52.2% of participants) reported having ever been counseled by their healthcare provider to not smoke or to stop smoking. CONCLUSIONS: Tobacco use is prevalent in youth with diabetes mellitus. Aggressive tobacco prevention and cessation programs should be a high priority to prevent or delay the development of cardiovascular disease.

Evidence for sex-specific associations between variation in acid phosphatase locus 1 (ACP1) and insulin sensitivity in Mexican-Americans.

CONTEXT: Acid phosphatase locus 1 (ACP1) is a low molecular weight tyrosine phosphatase that has been shown to be an important regulator of insulin receptor signaling. OBJECTIVE: We tested whether variation in ACP1 is associated with type 2 diabetes-related traits in 1035 individuals in 339 Mexican-American families of probands with or without a previous diagnosis of gestational diabetes mellitus (GDM). DESIGN: Study participants were phenotyped by oral glucose tolerance test (for glucose and insulin level) and iv glucose tolerance test (for insulin sensitivity and acute insulin response) and had dual-energy x-ray absorptiometry scans to assess body composition. Six tag single nucleotide polymorphisms (SNPs) were identified from among 15 SNPs genotyped across the ACP1 region. SNPs were tested for association with phenotypes using a likelihood ratio test under a variance components framework. RESULTS: After Bonferroni correction, none of the SNPs were associated with type 2 diabetes mellitus-related phenotypes. However, we observed a significant sex-specific effect of rs3828329. Among males, rs3828329 was significantly associated with fasting insulin (Bonferroni P = 0.007) and insulin sensitivity (Bonferroni P = 0.019) and marginally associated with 2-h insulin (Bonferroni P = 0.058) and percentage body fat (Bonferroni P = 0.09). CONCLUSIONS: There were no significant associations in females. We conclude that variation in ACP1 is associated with fasting insulin and insulin sensitivity in a sex-specific manner.

The association between adiponectin/leptin ratio and diabetes type: the SEARCH for Diabetes in Youth Study.

We tested the association of adiponectin/leptin ratio with diabetes type after adjusting for multiple factors in 1156 youths with newly diagnosed diabetes in the SEARCH study. Although adiponectin/leptin ratio is associated with diabetes type in youth, it is due to differences in adiponectin, but not leptin levels.

Variation in IGF2BP2 interacts with adiposity to alter insulin sensitivity in Mexican Americans.

Genome-wide association studies showed variation in insulin-like growth factor-2 binding protein 2 (IGF2BP2) to be associated with type 2 diabetes mellitus (T2DM). We examined a 20-kb region of IGF2BP2 for association with T2DM-related quantitative traits in Mexican American families of a proband with gestational diabetes mellitus (GDM) from the BetaGene study. We genotyped 14 single-nucleotide polymorphisms (SNPs) in 717 individuals from 146 families phenotyped by oral glucose tolerance test (OGTT), intravenous glucose tolerance tests (IVGTTs) with minimal model analysis, and dual-energy X-ray absorptiometry scan for percent body fat. Three SNPs and one SNP combination that captured the majority of the variation in the region were tested for association with T2DM-related quantitative traits using a variance components framework. After correction for multiple testing, rs11705701 showed association with percent body fat (P(ACT) = 0.041) with body fat decreasing approximately 1.5-2% per copy of the A allele. We next tested whether the interaction between rs11705701 and body fat was associated with T2DM-relative quantitative traits. rs11705701 was significantly associated with insulin sensitivity (Bonferroni P = 0.028) and marginally associated with OGTT 2-h insulin (Bonferroni P = 0.066) and disposition index (DI) (Bonferroni P = 0.072). We conclude that rs11705701 in IGF2BP2 is associated with body fat and this effect on body fat influences insulin resistance which may contribute to T2DM risk.

Evidence of interaction between PPARG2 and HNF4A contributing to variation in insulin sensitivity in Mexican Americans.

OBJECTIVE: We hypothesized that interaction between PPARG2 Pro12Ala and variants in the promoter region of HNF4A are associated with type 2 diabetes-related quantitative traits in Mexican-American families of a proband with previous gestational diabetes. RESEARCH DESIGN AND METHODS: The BetaGene project genotyped PPARG2 Pro12Ala and nine HNF4A single nucleotide polymorphisms (SNPs) in 473 individuals in 89 families. Members of the proband generation had fasting glucose <126 mg/dl and were phenotyped by oral and intravenous glucose tolerance tests. RESULTS: Neither PPARG2 Pro12Ala nor any of the nine HNF4A SNPs were independently associated with type 2 diabetes-related quantitative traits. However, the interaction between PPARG2 Pro12Ala and HNF4A rs2144908 was significantly associated with both insulin sensitivity (S(I)) (Bonferroni P = 0.0006) and 2-h insulin (Bonferroni P = 0.039). Subjects with at least one PPARG2 Ala allele and homozygous for the HNF4A rs2144908 A allele had 40% higher S(I) compared with individuals with at least one G allele. S(I) did not vary by rs2144908 genotype among PPARG2 Pro/Pro. The interaction result for S(I) was replicated by the Insulin Resistance Atherosclerosis Family Study (P = 0.018) in their San Antonio sample (n = 484) where subjects with at least one PPARG2 Ala allele and homozygous for the HNF4A rs2144908 A allele had a 29% higher S(I) compared with individuals with at least one G allele. However, the interaction was not replicated in their San Luis Valley sample (n = 496; P = 0.401). CONCLUSIONS: Together, these results suggest that variation in PPARG2 and HNF4A may interact to regulate insulin sensitivity in Mexican Americans at risk for type 2 diabetes.

Transcription factor 7-like 2 (TCF7L2) is associated with gestational diabetes mellitus and interacts with adiposity to alter insulin secretion in Mexican Americans.

OBJECTIVE: Variation in transcription factor 7-like 2 (TCF7L2) gene has been shown to be associated with type 2 diabetes and diabetes-related quantitative traits. We examined variation in a 0.1-Mb region surrounding marker DG10S478 for association with diabetes-related quantitative traits in 132 Mexican-American families of a proband with previous gestational diabetes mellitus (GDM). RESEARCH DESIGN AND METHODS: Study participants were phenotyped by an oral glucose tolerance test (OGTT) and an intravenous glucose tolerance test and by a dual-energy X-ray absorptiometry scan for percentage of body fat. Of the 42 tag single nucleotide polymorphisms (SNPs) genotyped, 15 were identified. RESULTS: On univariate analysis, none of the SNPs showed association with diabetes-related quantitative traits. However, rs12255372 showed association with 30' Deltainsulin (OGTT 30' min fasting insulin) in an interaction with percentage of body fat (Bonferroni-corrected P = 0.027). The effect of adiposity to increase 30' Deltainsulin was greater in subjects with the T allele. This interaction was not associated with acute insulin response to intravenous glucose. rs12255372 also showed an association with beta-cell compensation for insulin resistance based on 30' Deltainsulin in an interaction with percentage of body fat (Bonferroni-corrected P = 0.014). rs12255372 was also associated with GDM (odds ratio [OR] 2.49 [95% CI 1.17-5.31]; P = 0.018) in our case-control sample. CONCLUSIONS: We conclude that variation in TCF7L2 is associated with GDM and interacts with adiposity to alter insulin secretion in Mexican Americans. Our observations partly explain the increased ORs observed in previous associated studies when analyses were restricted to lean subjects and the variability in quantitative trait association results.