Epistasis Between HLA-DRB1*16:02:01 and SLC16A11 T-C-G-T-T Reduces Odds for Type 2 Diabetes in Southwest American Indians

We sought to identify genetic/immunologic contributors of type 2 diabetes (T2D) in an indigenous American community by genotyping all study participants for both high-resolution HLA-DRB1 alleles and SLC16A11 to test their risk and/or protection for T2D. These genes were selected based on independent reports that HLA-DRB1*16:02:01 is protective for T2D and that SLC16A11 associates with T2D in individuals with BMI <35 kg/m2. Here, we test the interaction of the two loci with a more complete data set and perform a BMI sensitivity test. We defined the risk protection haplotype of SLC16A11, T-C-G-T-T, as allele 2 of a diallelic genetic model with three genotypes, SLC16A11*11, *12, and *22, where allele 1 is the wild type. Both earlier findings were confirmed. Together in the same logistic model with BMI ≥35 kg/m2, DRB1*16:02:01 remains protective (odds ratio [OR] 0.73), while SLC16A11 switches from risk to protection (OR 0.57 [*22] and 0.78 [*12]); an added interaction term was statistically significant (OR 0.49 [*12]). Bootstrapped (b = 10,000) statistical power of interaction, 0.4801, yielded a mean OR of 0.43. Sensitivity analysis demonstrated that the interaction is significant in the BMI range of 30-41 kg/m2. To investigate the epistasis, we used the primary function of the HLA-DRB1 molecule, peptide binding and presentation, to search the entire array of 15-mer peptides for both the wild-type and ancient human SLC16A11 molecules for a pattern of strong binding that was associated with risk and protection for T2D. Applying computer binding algorithms suggested that the core peptide at SLC16A11 D127G, FSAFASGLL, might be key for moderating risk for T2D with potential implications for type 1 diabetes.

ARTICLE HIGHLIGHTS

The association of insulin responses and insulin sensitivity with cognition in adults with pre-diabetes: The Diabetes Prevention Program Outcomes Study

OBJECTIVE

Dysglycemia is a significant risk factor for cognitive impairment. However, which pathophysiologic determinant(s) of dysglycemia, impaired insulin sensitivity (ISens) or the islet β-cell's response (IResp), contribute to poorer cognitive function, independent of dysglycemia is not established. Among 1052 adults with pre-diabetes from the Diabetes Prevention Program Outcomes Study (DPPOS), we investigated the relationship between IResp, ISens and cognitive function.

RESEARCH DESIGN AND METHODS

IResp was estimated by the insulinogenic index (IGI; pmol/mmol) and ISens as 1/fasting insulin from repeated annual oral glucose tolerance tests. The mean IResp and mean ISens were calculated over approximately 12 years of follow-up. Verbal learning (Spanish-English Verbal Learning Test [SEVLT]) and executive function (Digital Symbol Substitution Test [DSST]) were assessed at the end of the follow-up period. Linear regression models were run for each cognitive outcome and were adjusted for dysglycemia and other factors.

RESULTS

Higher IResp was associated with poorer performance on the DSST (-0.69 points per 100 unit increase in IGI, 95 % CI: -1.37, -0.01). ISens was not associated with DSST, nor were IResp or ISens associated with performance on the SEVLT.

CONCLUSIONS

These results suggest that a greater β-cell response in people at high risk for type 2 diabetes is associated with poorer executive function, independent of dysglycemia and ISens.

Increased genetic risk for β-cell failure is associated with β-cell function decline in people with prediabetes

Partitioned polygenic scores (pPS) have been developed to capture pathophysiologic processes underlying type 2 diabetes (T2D). We investigated the influence of T2D pPS on diabetes-related traits and T2D incidence in the Diabetes Prevention Program. We generated five T2D pPS (β-cell, proinsulin, liver/lipid, obesity, lipodystrophy) in 2,647 participants randomized to intensive lifestyle, metformin or placebo arms. Associations were tested using general linear models and Cox regression adjusted for age, sex, and principal components. Sensitivity analyses included adjustment for BMI. Higher β-cell pPS was associated with lower insulinogenic index and corrected insulin response at one year follow-up adjusted for baseline measures (effect per pPS standard deviation (SD) -0.04, P=9.6 x 10-7; -8.45 uU/mg, P=5.6 x 10-6, respectively) and with increased diabetes incidence adjusted for BMI at nominal significance (HR 1.10 per SD, P=0.035). The liver/lipid pPS was associated with reduced one-year baseline-adjusted triglyceride levels (effect per SD -4.37, P=0.001). There was no significant interaction between T2D pPS and randomized groups. The remaining pPS were associated with baseline measures only. We conclude that despite interventions for diabetes prevention, participants with a high genetic burden of the β-cell cluster pPS had worsening in measures of β-cell function.

Prevalence of Distal Symmetrical Polyneuropathy by Diabetes Prevention Program Treatment Group, Diabetes Status, Duration of Diabetes, and Cumulative Glycemic Exposure

OBJECTIVE

To assess associations between distal symmetric polyneuropathy (DSPN) and Diabetes Prevention Program (DPP) treatment groups, diabetes status or duration, and cumulative glycemic exposure approximately 21 years after DPP randomization.

RESEARCH DESIGN AND METHODS

In the DPP, 3,234 adults ≥25 years old at high risk for diabetes were randomized to an intensive lifestyle (ILS), metformin, or placebo intervention to prevent diabetes. After the DPP ended, 2,779 joined the Diabetes Prevention Program Outcomes Study (DPPOS). Open-label metformin was continued, placebo was discontinued, ILS was provided in the form of semiannual group-based classes, and all participants were offered quarterly lifestyle classes. Symptoms and signs of DSPN were assessed in 1,792 participants at DPPOS year 17. Multivariable logistic regression models were used to evaluate DSPN associations with treatment group, diabetes status/duration, and cumulative glycemic exposure.

RESULTS

At 21 years after DPP randomization, 66% of subjects had diabetes. DSPN prevalence did not differ by initial DPP treatment assignment (ILS 21.5%, metformin 21.5%, and placebo 21.9%). There was a significant interaction between treatment assignment to ILS and age (P < 0.05) on DSPN. At DPPOS year 17, the odds ratio for DSPN in comparison with ILS with placebo was 17.4% (95% CI 3.0, 29.3) lower with increasing 5-year age intervals. DSPN prevalence was slightly lower for those at risk for diabetes (19.6%) versus those with diabetes (22.7%) and was associated with longer diabetes duration and time-weighted HbA1c (P values <0.001).

CONCLUSIONS

The likelihood of DSPN was similar across DPP treatment groups but higher for those with diabetes, longer diabetes duration, and higher cumulative glycemic exposure. ILS may have long-term benefits on DSPN for older adults.

Effects of the ABCC8 R1420H loss-of-function variant on beta-cell function, diabetes incidence, and retinopathy

INTRODUCTION

The ABCC8 gene regulates insulin secretion and plays a critical role in glucose homeostasis. The effects of an ABCC8 R1420H loss-of-function variant on beta-cell function, incidence of type 2 diabetes, and age-at-onset, prevalence, and progression of diabetes complications were assessed in a longitudinal study in American Indians.

RESEARCH DESIGN AND METHODS

We analyzed beta-cell function through the relationship between insulin secretion and insulin sensitivity in members of this population without diabetes aged ≥5 years using standard major axis regression. We used hierarchical logistic regression models to study cross-sectional associations with diabetes complications including increased albuminuria (albumin-to-creatinine ratio (ACR) ≥30 mg/g), severe albuminuria (ACR ≥300 mg/g), reduced estimated glomerular filtration rate (eGFR <60 mL/min/1.73 m2), and retinopathy. This study included 7675 individuals (254 variant carriers) previously genotyped for the R1420H with available phenotypic data and with a median follow-up time of 13.5 years (IQR 4.5-26.8).

RESULTS

Variant carriers had worse beta-cell function than non-carriers (p=0.0004; on average estimated secretion was 22% lower, in carriers), in children and adults, with no difference in insulin sensitivity (p=0.50). At any body mass index and age before 35 years, carriers had higher type 2 diabetes incidence. This variant did not associate with prevalence of increased albuminuria (OR 0.87, 95% CI 0.66 to 1.16), severe albuminuria (OR 0.96, 95% CI 0.55 to 1.68), or reduced eGFR (OR 0.44, 95% CI 0.18 to 1.06). By contrast, the variant significantly associated with higher retinopathy prevalence (OR 1.74, 95% CI 1.19 to 2.53) and this association was only partially mediated (<11%) by glycemia, duration of diabetes, risk factors of retinopathy, or insulin use. Retinopathy prevalence in carriers was higher regardless of diabetes presence.

CONCLUSIONS

The ABCC8 R1420H variant is associated with increased risks of diabetes and of retinopathy, which may be partially explained by higher glycemia levels and worse beta-cell function.

Preventing diabetes in Latino families: A protocol for a randomized control trial

BACKGROUND

Latino families are disproportionately affected by type 2 diabetes (T2D) and lifestyle intervention is the first-line approach for preventing T2D. The purpose of this study is to test the efficacy of a culturally-grounded lifestyle intervention that prioritizes health promotion and diabetes prevention for Latino families. The intervention is guided by a novel Family Diabetes Prevention Model, leveraging the family processes of engagement, empowerment, resilience, and cohesion to orient the family system towards health.

METHOD

Latino families (N = 132) will be recruited and assessed for glucose tolerance as measured by an Oral Glucose Tolerance Test (OGTT) and General and Weight-Specific Quality of Life (QoL) at baseline, four months, and 12 months. All members of the household age 10 and over will be invited to participate. Families will be randomized to the intervention group or a control group (2:1). The 16-week intervention includes weekly nutrition and wellness classes delivered by bilingual, bicultural Registered Dietitians and community health educators at a local YMCA along with two days/week of supervised physical activity classes and a third day of unsupervised physical activity. Control families will meet with a physician and a Registered Dietitian to discuss the results of their metabolic testing and recommend lifestyle changes. We will test the efficacy of a family-focused diabetes prevention intervention for improving glucose tolerance and increasing QoL and test for mediators and moderators of long-term changes.

CONCLUSION

This study will provide much needed data on the efficacy of a family-focused Diabetes Prevention Program among high-risk Latino families.

New-Onset Diabetes After COVID-19

There is evidence suggesting that infection with SARS-CoV-2 can lead to several long-term sequelae including diabetes. This mini-review examines the rapidly evolving and conflicting literature on new-onset diabetes after COVID-19, which we term NODAC. We searched PubMed, MEDLINE, and medRxiv from inception until December 1, 2022, using Medical Subject Headings (MeSH) terms and free text words including "COVID-19," "SARS-CoV-2," "diabetes," "hyperglycemia," "insulin resistance," and "pancreatic β-cell." We also supplemented searches by examining reference lists from retrieved articles. Current evidence suggests that COVID-19 increases the risk of developing diabetes, but the attributable risk is uncertain because of limitations of study designs and the evolving nature of the pandemic, including new variants, widespread population exposure to the virus, diagnostic options for COVID-19, and vaccination status. The etiology of diabetes after COVID-19 is likely multifactorial and includes factors associated with host characteristics (eg, age), social determinants of health (eg, deprivation index), and pandemic-related effects both at the personal (eg, psychosocial stress) and the societal-community level (eg, containment measures). COVID-19 may have direct and indirect effects on pancreatic β-cell function and insulin sensitivity related to the acute infection and its treatment (eg, glucocorticoids); autoimmunity; persistent viral residency in multiple organs including adipose tissue; endothelial dysfunction; and hyperinflammatory state. While our understanding of NODAC continues to evolve, consideration should be given for diabetes to be classified as a post-COVID syndrome, in addition to traditional classifications of diabetes (eg, type 1 or type 2), so that the pathophysiology, natural history, and optimal management can be studied.

Effects of metformin and intensive lifestyle interventions on the incidence of kidney disease in adults in the DPP/DPPOS

AIMS

We analyzed the incidence of kidney disease in the Diabetes Prevention Program Outcomes Study (DPPOS) by originally randomized treatment group assignment: Intensive Lifestyle (ILS), Metformin (MET) or Placebo (PLB).

METHODS

The current analyses used a time-to-event approach in which the primary outcome was kidney disease, ascertained as urine albumin-to-creatinine ratio (ACR) ≥ 3.39 mg/mmol (30 mg/g) or eGFR <45 mL/min/1.73m2, with confirmation required at the next visit, or adjudicated end-stage kidney disease (ESKD).

RESULTS

At a median of 21 years following randomization in DPP, diabetes development was reduced in both the ILS (HR 0.73 [95%CI = 0.62, 0.85]) and MET groups (HR 0.85 [0.73, 0.99]) compared to the PLB group. Although risk for developing the primary kidney disease outcome was higher among those with incident diabetes compared to those without (HR 1.81 [1.43, 2.30]), it did not differ by intervention groups (ILS vs. PLB 1.02 (0.81, 1.29); MET vs. PLB 1.08 (0.86, 1.35). There was a non-significant metformin by age interaction (p = 0.057), with metformin being beneficial for kidney disease in the younger but potentially harmful in the older participants.

CONCLUSIONS

Development of kidney disease was increased in participants who developed diabetes but did not differ by original treatment group assignment.

CLINICAL TRIAL REGISTRATIONS

Diabetes Prevention Program (DPP) Clinical trial reg. no. NCT00004992 DPP Outcomes Study (DPPOS) Clinical trial reg. no. NCT0038727.

Adolescent Growth Spurt and Type 2 Diabetes Risk in Southwestern American Indians

Early puberty onset is associated with higher risk of diabetes, but most studies have not accounted for childhood factors that may confound the association. Using data from a study conducted in an Indigenous community in Arizona (1965-2007), we examined associations of timing and velocity of the adolescent growth spurt with type 2 diabetes, and whether these associations are mediated by childhood body mass index and insulinemia. Adolescent growth parameters were derived from the Preece-Baines growth model, a parametric growth curve fitted to longitudinal height data, for 861 participants with height measurements spanning the whole period of growth. In males, older age at take-off, age at peak velocity, and age at maturation were associated with decreased prevalence of diabetes (odds ratio (OR) = 0.43 per year, 95% confidence interval (CI): 0.27, 0.69; OR = 0.50, 95% CI: 0.35, 0.72; OR = 0.58, 95% CI: 0.41, 0.83, respectively), while higher velocity at take-off was associated with increased risk (OR = 3.47 per cm/year, 95% CI: 1.87, 6.42) adjusting for age, birth year, and maternal diabetes. Similar results were observed with incident diabetes. Our findings suggest that an early and accelerated adolescent growth spurt is a risk factor for diabetes, at least in males. These associations are only partially explained by measures of adiposity and insulinemia.

Identification of Genetic Variation Influencing Metformin Response in a Multiancestry Genome-Wide Association Study in the Diabetes Prevention Program (DPP)

Genome-wide significant loci for metformin response in type 2 diabetes reported elsewhere have not been replicated in the Diabetes Prevention Program (DPP). To assess pharmacogenetic interactions in prediabetes, we conducted a genome-wide association study (GWAS) in the DPP. Cox proportional hazards models tested associations with diabetes incidence in the metformin (MET; n = 876) and placebo (PBO; n = 887) arms. Multiple linear regression assessed association with 1-year change in metformin-related quantitative traits, adjusted for baseline trait, age, sex, and 10 ancestry principal components. We tested for gene-by-treatment interaction. No significant associations emerged for diabetes incidence. We identified four genome-wide significant variants after correcting for correlated traits (P < 9 × 10-9). In the MET arm, rs144322333 near ENOSF1 (minor allele frequency [MAF]AFR = 0.07; MAFEUR = 0.002) was associated with an increase in percentage of glycated hemoglobin (per minor allele, β = 0.39 [95% CI 0.28, 0.50]; P = 2.8 × 10-12). rs145591055 near OMSR (MAF = 0.10 in American Indians) was associated with weight loss (kilograms) (per G allele, β = -7.55 [95% CI -9.88, -5.22]; P = 3.2 × 10-10) in the MET arm. Neither variant was significant in PBO; gene-by-treatment interaction was significant for both variants [P(G×T) < 1.0 × 10-4]. Replication in individuals with diabetes did not yield significant findings. A GWAS for metformin response in prediabetes revealed novel ethnic-specific associations that require further investigation but may have implications for tailored therapy.

Indices of hepatic steatosis and fibrosis in prediabetes and association with diabetes development in the vitamin D and type 2 diabetes study

AIMS

Non-alcoholic fatty liver disease (NAFLD) is a common comorbidity that leads to poor outcomes in people at high risk for development of type 2 diabetes (T2D). Vitamin D is a possible mediator. In the vitamin D and type 2 diabetes study (D2d), we investigated the relationship of baseline indices of NAFLD with incident T2D and whether the effect of vitamin D on diabetes was modified by NAFLD.

METHODS

Cross-sectional associations of indices of NAFLD with glycemia and vitamin D status were assessed in 3972 individuals screened for the D2d study. In those with prediabetes randomized to vitamin D or placebo (n = 2423), we examined longitudinal associations of NAFLD indices with incident T2D. We used validated non-invasive scores to assess steatosis [(hepatic steatosis index (HSI); NAFLD-liver fat score (NAFLD-LFS)] and advanced fibrosis [fibrosis-4 (FIB-4) index; AST to Platelet Ratio Index (APRI)].

RESULTS

Eighty-five percent of screened participants had likely steatosis by HSI and 71 % by NAFLD-LFS; 3 % were likely to have advanced fibrosis by FIB-4 and 1.2 % by APRI. FIB-4 indicated that 20.4 % of individuals require further follow up to assess liver health. Steatosis and fibrosis scores were higher among participants with worse glycemia. The NAFLD-LFS and APRI predicted development of diabetes (hazard ratios [95%CI] 1.35 [1.07, 1.70]; P = 0.012) and 2.36 (1.23, 4.54; P = 0.010), respectively). The effect of vitamin D on diabetes risk was not modified by baseline NAFLD indices. Individuals with likely steatosis had a smaller increase in serum 25-hydroxyvitamin D level in response to vitamin D than those without steatosis.

CONCLUSIONS

The predicted high prevalence of steatosis, the need for further fibrosis workup, and the relationship between liver health and incident T2D suggest that routine screening with clinically accessible scores may be an important strategy to reduce disease burden.

The utility of a type 2 diabetes polygenic score in addition to clinical variables for prediction of type 2 diabetes incidence in birth, youth and adult cohorts in an Indigenous study population

AIMS/HYPOTHESIS

There is limited information on how polygenic scores (PSs), based on variants from genome-wide association studies (GWASs) of type 2 diabetes, add to clinical variables in predicting type 2 diabetes incidence, particularly in non-European-ancestry populations.

METHODS

For participants in a longitudinal study in an Indigenous population from the Southwestern USA with high type 2 diabetes prevalence, we analysed ten constructions of PS using publicly available GWAS summary statistics. Type 2 diabetes incidence was examined in three cohorts of individuals without diabetes at baseline. The adult cohort, 2333 participants followed from age ≥20 years, had 640 type 2 diabetes cases. The youth cohort included 2229 participants followed from age 5-19 years (228 cases). The birth cohort included 2894 participants followed from birth (438 cases). We assessed contributions of PSs and clinical variables in predicting type 2 diabetes incidence.

RESULTS

Of the ten PS constructions, a PS using 293 genome-wide significant variants from a large type 2 diabetes GWAS meta-analysis in European-ancestry populations performed best. In the adult cohort, the AUC of the receiver operating characteristic curve for clinical variables for prediction of incident type 2 diabetes was 0.728; with the PS, 0.735. The PS's HR was 1.27 per SD (p=1.6 × 10-8; 95% CI 1.17, 1.38). In youth, corresponding AUCs were 0.805 and 0.812, with HR 1.49 (p=4.3 × 10-8; 95% CI 1.29, 1.72). In the birth cohort, AUCs were 0.614 and 0.685, with HR 1.48 (p=2.8 × 10-16; 95% CI 1.35, 1.63). To further assess the potential impact of including PS for assessing individual risk, net reclassification improvement (NRI) was calculated: NRI for the PS was 0.270, 0.268 and 0.362 for adult, youth and birth cohorts, respectively. For comparison, NRI for HbA1c was 0.267 and 0.173 for adult and youth cohorts, respectively. In decision curve analyses across all cohorts, the net benefit of including the PS in addition to clinical variables was most pronounced at moderately stringent threshold probability values for instituting a preventive intervention.

CONCLUSIONS/INTERPRETATION

This study demonstrates that a European-derived PS contributes significantly to prediction of type 2 diabetes incidence in addition to information provided by clinical variables in this Indigenous study population. Discriminatory power of the PS was similar to that of other commonly measured clinical variables (e.g. HbA1c). Including type 2 diabetes PS in addition to clinical variables may be clinically beneficial for identifying individuals at higher risk for the disease, especially at younger ages.

Association of Metformin With the Development of Age-Related Macular Degeneration

Importance

Age-related macular degeneration (AMD) is a leading cause of blindness with no treatment available for early stages. Retrospective studies have shown an association between metformin and reduced risk of AMD.

Objective

To investigate the association between metformin use and age-related macular degeneration (AMD).

Design, Setting, and Participants

The Diabetes Prevention Program Outcomes Study is a cross-sectional follow-up phase of a large multicenter randomized clinical trial, Diabetes Prevention Program (1996-2001), to investigate the association of treatment with metformin or an intensive lifestyle modification vs placebo with preventing the onset of type 2 diabetes in a population at high risk for developing diabetes. Participants with retinal imaging at a follow-up visit 16 years posttrial (2017-2019) were included. Analysis took place between October 2019 and May 2022.

Interventions

Participants were randomly distributed between 3 interventional arms: lifestyle, metformin, and placebo.

Main Outcomes and Measures

Prevalence of AMD in the treatment arms.

Results

Of 1592 participants, 514 (32.3%) were in the lifestyle arm, 549 (34.5%) were in the metformin arm, and 529 (33.2%) were in the placebo arm. All 3 arms were balanced for baseline characteristics including age (mean [SD] age at randomization, 49 [9] years), sex (1128 [71%] male), race and ethnicity (784 [49%] White), smoking habits, body mass index, and education level. AMD was identified in 479 participants (30.1%); 229 (14.4%) had early AMD, 218 (13.7%) had intermediate AMD, and 32 (2.0%) had advanced AMD. There was no significant difference in the presence of AMD between the 3 groups: 152 (29.6%) in the lifestyle arm, 165 (30.2%) in the metformin arm, and 162 (30.7%) in the placebo arm. There was also no difference in the distribution of early, intermediate, and advanced AMD between the intervention groups. Mean duration of metformin use was similar for those with and without AMD (mean [SD], 8.0 [9.3] vs 8.5 [9.3] years; P = .69). In the multivariate models, history of smoking was associated with increased risks of AMD (odds ratio, 1.30; 95% CI, 1.05-1.61; P = .02).

Conclusions and Relevance

These data suggest neither metformin nor lifestyle changes initiated for diabetes prevention were associated with the risk of any AMD, with similar results for AMD severity. Duration of metformin use was also not associated with AMD. This analysis does not address the association of metformin with incidence or progression of AMD.

Weight Loss, Lifestyle Intervention, and Metformin Affect Longitudinal Relationship of Insulin Secretion and Sensitivity

CONTEXT

Insulin secretion and sensitivity regulate glycemia, with inadequately compensated deficiencies leading to diabetes.

OBJECTIVE

We investigated effects of weight loss, an intensive lifestyle intervention (ILS), and metformin on the relationship between insulin secretion and sensitivity using repository data from 2931 participants in the Diabetes Prevention Program clinical trial in adults at high risk of developing type 2 diabetes.

METHODS

Insulin secretion and sensitivity were estimated from insulin and glucose concentrations in fasting and 30-minute postload serum samples at baseline and 1, 2, and 3 years after randomization, during the active intervention phase. The nonlinear relationship of secretion and sensitivity was evaluated by standardized major axis regression to account for variability in both variables. Insulin secretory demand and compensatory insulin secretion were characterized by distances along and away from the regression line, respectively.

RESULTS

ILS and metformin decreased secretory demand while increasing compensatory insulin secretion, with greater effects of ILS. Improvements were directly related to weight loss; decreased weight significantly reduced secretory demand (b=-0.144 SD; 95% CI (-0.162, -0.125)/5 kg loss) and increased compensatory insulin secretion (b = 0.287 SD, 95% CI (0.261, 0.314)/5 kg loss). In time-dependent hazard models, increasing compensatory insulin secretion (hazard ratio [HR] = 0.166 per baseline SD, 95% CI 0.133, 0.206) and weight loss (HR = 0.710 per 5 kg loss, 95% CI 0.613, 0.819) predicted lower diabetes risk.

CONCLUSION

Diabetes risk reduction was directly related to the amount of weight loss, an effect mediated by lowered insulin secretory demand (due to increased insulin sensitivity) coupled with improved compensatory insulin secretion.

Risk Factors for the Development of Retinopathy in Prediabetes and Type 2 Diabetes: The Diabetes Prevention Program Experience

OBJECTIVE

To determine glycemic and nonglycemic risk factors that contribute to the presence of diabetic retinopathy (DR) before and after the onset of type 2 diabetes (T2D).

RESEARCH DESIGN AND METHODS

During the Diabetes Prevention Program (DPP) and DPP Outcome Study (DPPOS), we performed fundus photography over time in adults at high risk for developing T2D, including after they developed diabetes. Fundus photographs were graded using the Early Treatment Diabetic Retinopathy Study (ETDRS) grading system, with DR defined as typical lesions of DR (microaneurysms, exudates, hemorrhage, or worse) in either eye.

RESULTS

By DPPOS year 16 (∼20 years after random assignment into DPP), 24% of 1,614 participants who had developed T2D and 14% of 885 who remained without diabetes had DR. In univariate analyses, using results from across the entire duration of follow-up, American Indian race was associated with less frequent DR compared with non-Hispanic White (NHW) race, and higher HbA1c, fasting and 2-h plasma glucose levels during an oral glucose tolerance test, weight, and history of hypertension, dyslipidemia, and smoking, but not treatment group assignment, were associated with more frequent DR. On multivariate analysis, American Indian race was associated with less DR compared with NHW (odds ratio [OR] 0.36, 95% CI 0.20-0.66), and average HbA1c was associated with more DR (OR 1.92, 95% CI 1.46-1.74 per SD [0.7%] increase in HbA1c).

CONCLUSIONS

DR may occur in adults with prediabetes and early in the course of T2D. HbA1c was an important risk factor for the development of DR across the entire glycemic range from prediabetes to T2D.

Functional characterization of a novel p.Ser76Thr variant in IGFBP4 that associates with body mass index in American Indians

Insulin-like growth factor binding protein 4 (IGFBP4) is involved in adipogenesis, and IGFBP4 null mice have decreased body fat through decreased PPAR-γ expression. In the current study, we assessed whether variation in the IGFBP4 coding region influences body mass index (BMI) in American Indians who are disproportionately affected by obesity. Whole exome sequence data from a population-based sample of 6779 American Indians with longitudinal measures of BMI were used to identify variation in IGFBP4 that associated with BMI. A novel variant that predicts a p.Ser76Thr in IGFBP4 (Thr-allele frequency = 0.02) was identified which associated with the maximum BMI measured during adulthood (BMI 39.8 kg/m2 for Thr-allele homozygotes combined with heterozygotes vs. 36.2 kg/m2 for Ser-allele homozygotes, β = 6.7% per Thr-allele, p = 8.0 × 10-5, adjusted for age, sex, birth-year and the first five genetic principal components) and the maximum age- and sex-adjusted BMI z-score measured during childhood/adolescence (z-score 0.70 SD for Thr-allele heterozygotes vs. 0.32 SD for Ser-allele homozygotes, β = 0.37 SD per Thr-allele, p = 8.8 × 10-6). In vitro functional studies showed that IGFBP4 with the Thr-allele (BMI-increasing) had a 55% decrease (p = 0.0007) in FOXO-induced transcriptional activity, reflecting increased activation of the PI3K/AKT pathway mediated through increased IGF signaling. Over-expression and knock-down of IGFBP4 in OP9 cells during differentiation showed that IGFBP4 upregulates adipogenesis through PPARγ, CEBPα, AGPAT2 and SREBP1 expression. We propose that this American Indian specific variant in IGFBP4 affects obesity via an increase of IGF signaling.

Effects of a Diabetes Prevention Program on Type 2 Diabetes Risk Factors and Quality of Life Among Latino Youths With Prediabetes: A Randomized Clinical Trial

IMPORTANCE

Latino youths are disproportionately impacted by prediabetes and type 2 diabetes (T2D). Lifestyle intervention is the first-line approach for preventing or delaying T2D among adults with prediabetes.

OBJECTIVE

To assess the efficacy of a diabetes prevention program among Latino youths aged 12 to 16 years with prediabetes.

DESIGN, SETTING, AND PARTICIPANTS

This 2-group parallel randomized clinical trial with 2:1 randomization assessed a lifestyle intervention against usual care among Latino youths with prediabetes and obesity with 6- and 12-month follow-up. The study was conducted at YMCA facilities in Phoenix, Arizona from May 2016 to March 2020.

INTERVENTION

Participants were randomized to lifestyle intervention (INT) or usual care control (UCC). The 6-month INT included 1 d/wk of nutrition and health education and 3 d/wk of physical activity. UCC included 2 visits with a pediatric endocrinologist and a bilingual, bicultural registered dietitian to discuss diabetes risks and healthy lifestyle changes.

MAIN OUTCOMES AND MEASURES

Insulin sensitivity, glucose tolerance, and weight-specific quality of life (YQOL-W) at 6- and 12-month follow-up.

RESULTS

A total of 117 Latino youths (mean [SD] age, 14 [1] years; 47 [40.1%] girls) were included in the analysis. Overall, 79 were randomized to INT and 38 to UCC. At 6 months, the INT led to significant decreases in mean (SE) 2-hour glucose (baseline: 144 [3] mg/dL; 6 months: 132 [3] mg/dL; P = .002) and increases in mean (SE) insulin sensitivity (baseline: 1.9 [0.2]; 6 months: 2.6 [0.3]; P = .001) and YQOL-W (baseline: 75 [2]; 6 months: 80 [2]; P = .006), but these changes were not significantly different from UCC (2-hour glucose: mean difference, -7.2 mg/dL; 95% CI, -19.7 to 5.3 mg/dL; P for interaction = .26; insulin sensitivity: mean difference, 0.1; 95% CI, -0.7 to 0.9; P for interaction = .79; YQOL-W: mean difference, 6.3; 95% CI, -1.1 to 13.7; P for interaction = .10, respectively). Both INT (mean [SE], -15 mg/dL [4.9]; P = .002) and UCC (mean [SE], -15 mg/dL [5.4]; P = .005) had significant 12-month reductions in 2-hour glucose that did not differ significantly from each other (mean difference, -0.3; 95% CI, -14.5 to 14.1 mg/dL; P for interaction = .97). At 12 months, changes in mean (SE) insulin sensitivity in INT (baseline: 1.9 [0.2]; 12 months: 2.3 [0.2]; P = .06) and UCC (baseline: 1.9 [0.3]; 12 months: 2.0 [0.2]; P = .70) were not significantly different (mean difference, 0.3; 95% CI, -0.4 to 1.0; P for interaction = .37). At 12 months, YQOL-W was significantly increased in INT (basline: 75 [2]; 12 months: 82 [2]; P < .001) vs UCC (mean difference, 8.5; 95% CI, 0.8 to 16.2; P for interaction = .03).

CONCLUSIONS AND RELEVANCE

In this randomized clinical trial, both INT and UCC led to similar changes in T2D risk factors among Latino youths with diabetes; however, YQOL-W was improved in INT compared with UCC. Diabetes prevention interventions that are effective in adults also appeared to be effective in high risk youths.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02615353.

Quantitative trait loci, G×E and G×G for glycemic traits: response to metformin and placebo in the Diabetes Prevention Program (DPP)

The complex genetic architecture of type-2-diabetes (T2D) includes gene-by-environment (G×E) and gene-by-gene (G×G) interactions. To identify G×E and G×G, we screened markers for patterns indicative of interactions (relationship loci [rQTL] and variance heterogeneity loci [vQTL]). rQTL exist when the correlation between multiple traits varies by genotype and vQTL occur when the variance of a trait differs by genotype (potentially flagging G×G and G×E). In the metformin and placebo arms of the DPP (n = 1762) we screened 280,965 exomic and intergenic SNPs, for rQTL and vQTL patterns in association with year one changes from baseline in glycemia and related traits (insulinogenic index [IGI], insulin sensitivity index [ISI], fasting glucose and fasting insulin). Significant (p < 1.8 × 10^-7) rQTL and vQTL generated a priori hypotheses of individual G×E tests for a SNP × metformin treatment interaction and secondarily for G×G screens. Several rQTL and vQTL identified led to 6 nominally significant (p < 0.05) metformin treatment × SNP interactions (4 for IGI, one insulin, and one glucose) and 12G×G interactions (all IGI) that exceeded experiment-wide significance (p < 4.1 × 10^-9). Some loci are directly associated with incident diabetes, and others are rQTL and modify a trait's relationship with diabetes (2 diabetes/glucose, 2 diabetes/insulin, 1 diabetes/IGI). rs3197999, an ISI/insulin rQTL, is a possible gene damaging missense mutation in MST1, is associated with ulcerative colitis, sclerosing cholangitis, Crohn's disease, BMI and coronary artery disease. This study demonstrates evidence for context-dependent effects (G×G & G×E) and the complexity of these T2D-related traits.

Cardiorespiratory Fitness, BMI, Mortality, and Cardiovascular Disease in Adults with Overweight/Obesity and Type 2 Diabetes

INTRODUCTION

We estimated the effects of cardiorespiratory fitness (CRF) and body mass index (BMI) at baseline on mortality and cardiovascular disease events in people with type 2 diabetes who participated in the Look AHEAD randomized clinical trial.

METHODS

Look AHEAD compared effects of an intensive lifestyle intervention with diabetes support and education on cardiovascular disease events in 5145 adults age 45-76 yr with overweight/obesity and type 2 diabetes. In 4773 participants, we performed a secondary analysis of the association of baseline CRF during maximal treadmill test (expressed as metabolic equivalents (METs)) on mortality and cardiovascular disease events during a mean follow-up of 9.2 yr.

RESULTS

The mean (SD) CRF was 7.2 (2.0) METs. Adjusted for age, sex, race/ethnicity, BMI, intervention group, and β-blocker use, all-cause mortality rate was 30% lower per SD greater METs (hazard ratio (HR) = 0.70 (95% confidence interval, 0.60 to 0.81); rate difference (RD), -2.71 deaths/1000 person-years (95% confidence interval, -3.79 to -1.63)). Similarly, an SD greater METs predicted lower cardiovascular disease mortality (HR, 0.45; RD, -1.65 cases/1000 person-years) and a composite cardiovascular outcome (HR, 0.72; RD, -6.38). Effects of METs were homogeneous on the HR scale for most baseline variables and outcomes but heterogeneous for many on the RD scale, with greater RD in subgroups at greater risk of the outcomes. For example, all-cause mortality was lower by 7.6 deaths/1000 person-years per SD greater METs in those with a history of cardiovascular disease at baseline but lower by only 1.6 in those without such history. BMI adjusted for CRF had little or no effect on these outcomes.

CONCLUSIONS

Greater CRF is associated with reduced risks of mortality and cardiovascular disease events.

Effects of Long-term Metformin and Lifestyle Interventions on Cardiovascular Events in the Diabetes Prevention Program and Its Outcome Study

BACKGROUND

Lifestyle intervention and metformin have been shown to prevent diabetes; however, their efficacy in preventing cardiovascular disease associated with the development of diabetes is unclear. We examined whether these interventions reduced the incidence of major cardiovascular events over a 21-year median follow-up of participants in the DPP trial (Diabetes Prevention Program) and DPPOS (Diabetes Prevention Program Outcomes Study).

METHODS

During DPP, 3234 participants with impaired glucose tolerance were randomly assigned to metformin 850 mg twice daily, intensive lifestyle or placebo, and followed for 3 years. During the next 18-year average follow-up in DPPOS, all participants were offered a less intensive group lifestyle intervention, and unmasked metformin was continued in the metformin group. The primary outcome was the first occurrence of nonfatal myocardial infarction, stroke, or cardiovascular death adjudicated by standard criteria. An extended cardiovascular outcome included the primary outcome or hospitalization for heart failure or unstable angina, coronary or peripheral revascularization, coronary heart disease diagnosed by angiography, or silent myocardial infarction by ECG. ECGs and cardiovascular risk factors were measured annually.

RESULTS

Neither metformin nor lifestyle intervention reduced the primary outcome: metformin versus placebo hazard ratio 1.03 (95% CI, 0.78-1.37; P = 0.81) and lifestyle versus placebo hazard ratio 1.14 (95% CI, 0.87-1.50; P = 0.34). Risk factor adjustment did not change these results. No effect of either intervention was seen on the extended cardiovascular outcome.

CONCLUSIONS

Neither metformin nor lifestyle reduced major cardiovascular events in DPPOS over 21 years despite long-term prevention of diabetes. Provision of group lifestyle intervention to all, extensive out-of-study use of statin and antihypertensive agents, and reduction in the use of study metformin together with out-of-study metformin use over time may have diluted the effects of the interventions.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifiers: DPP (NCT00004992) and DPPOS (NCT00038727).

Weight Change During the Postintervention Follow-up of Look AHEAD

OBJECTIVE

Patients with type 2 diabetes are encouraged to lose weight, but excessive weight loss in older adults may be a marker of poor health and subsequent mortality. We examined weight change during the postintervention period of Look AHEAD, a randomized trial comparing intensive lifestyle intervention (ILI) with diabetes support and education (DSE) (control) in overweight/obese individuals with type 2 diabetes and sought to identify predictors of excessive postintervention weight loss and its association with mortality.

RESEARCH DESIGN AND METHODS

These secondary analyses compared postintervention weight change (year 8 to final visit; median 16 years) in ILI and DSE in 3,999 Look AHEAD participants. Using empirically derived trajectory categories, we compared four subgroups: weight gainers (n = 307), weight stable (n = 1,561), steady losers (n = 1,731), and steep losers (n = 380), on postintervention mortality, demographic variables, and health status at randomization and year 8.

RESULTS

Postintervention weight change averaged -3.7 ± 9.5%, with greater weight loss in the DSE than the ILI group. The steep weight loss trajectory subgroup lost on average 17.7 ± 6.6%; 30% of steep losers died during postintervention follow-up versus 10-18% in other trajectories (P < 0001). The following variables distinguished steep losers from weight stable: baseline, older, longer diabetes duration, higher BMI, and greater multimorbidity; intervention, randomization to control group and less weight loss in years 1-8; and year 8, higher prevalence of frailty, multimorbidity, and depressive symptoms and lower use of weight control strategies.

CONCLUSIONS

Steep weight loss postintervention was associated with increased risk of mortality. Older individuals with longer duration of diabetes and multimorbidity should be monitored for excessive unintentional weight loss.

Genetic Predictors of Change in Waist Circumference and Waist-to-Hip Ratio With Lifestyle Intervention: The Trans-NIH Consortium for Genetics of Weight Loss Response to Lifestyle Intervention

Genome-wide association studies have identified single nucleotide polymorphisms (SNPs) associated with waist circumference (WC) and waist-to-hip ratio (WHR) adjusted for BMI (WCadjBMI and WHRadjBMI), but it remains unclear whether these SNPs relate to change in WCadjBMI or WHRadjBMI with lifestyle intervention for weight loss. We hypothesized that polygenic scores (PS) comprised of 59 SNPs previously associated with central adiposity would predict less of a reduction in WCadjBMI or WHRadjBMI at 8-10 weeks in two lifestyle intervention trials, NUGENOB and DiOGenes, and at 1 year in five lifestyle intervention trials, Look AHEAD, Diabetes Prevention Program, Diabetes Prevention Study, DIETFITS, and PREDIMED-Plus. One-SD higher PS related to a smaller 1-year change in WCadjBMI in the lifestyle intervention arms at year 1 and thus predicted poorer response (β = 0.007; SE = 0.003; P = 0.03) among White participants overall and in White men (β = 0.01; SE = 0.004; P = 0.01). At average weight loss, this amounted to 0.20-0.28 cm per SD. No significant findings emerged in White women or African American men for the 8-10-week outcomes or for WHRadjBMI. Findings were heterogeneous in African American women. These results indicate that polygenic risk estimated from these 59 SNPs relates to change in WCadjBMI with lifestyle intervention, but the effects are small and not of sufficient magnitude to be clinically significant.

A missense variant Arg611Cys in LIPE which encodes hormone sensitive lipase decreases lipolysis and increases risk of type 2 diabetes in American Indians

AIMS

Hormone sensitive lipase (HSL), encoded by the LIPE gene, is involved in lipolysis. Based on prior animal and human studies, LIPE was analysed as a candidate gene for the development of type 2 diabetes (T2D) in a community-based sample of American Indians.

MATERIALS AND METHODS

Whole-exome sequence data from 6782 participants with longitudinal clinical measures were used to identify variation in LIPE.

RESULTS

Amongst the 16 missense variants identified, an Arg611Cys variant (rs34052647; Cys-allele frequency = 0.087) significantly associated with T2D (OR [95% CI] = 1.38 [1.17-1.64], p = 0.0002, adjusted for age, sex, birth year, and the first five genetic principal components) and an earlier onset age of T2D (HR = 1.22 [1.09-1.36], p = 0.0005). This variant was further analysed for quantitative traits related to T2D. Amongst non-diabetic American Indians, those with the T2D risk Cys-allele had increased insulin levels during an oral glucose tolerance test (0.07 SD per Cys-allele, p = 0.04) and a mixed meal test (0.08 log₁₀ µU/ml per Cys-allele, p = 0.003), and had increased lipid oxidation rates post-absorptively and during insulin infusion (0.07 mg [kg estimated metabolic body size {EMBS}]^-1  min^-1 per Cys-allele for both, p = 0.01 and 0.009, respectively), compared to individuals with the non-risk Arg-allele. In vitro functional studies showed that cells expressing the Cys-allele had a 17.2% decrease in lipolysis under isoproterenol stimulation (p = 0.03) and a 21.3% decrease in lipase enzyme activity measured by using p-nitrophenyl butyrate as a substrate (p = 0.04) compared to the Arg-allele.

CONCLUSION

The Arg611Cys variant causes a modest impairment in lipolysis, thereby affecting glucose homoeostasis and risk of T2D.

Increased Adiposity and Low Height-for-Age in Early Childhood Are Associated With Later Metabolic Risks in American Indian Children and Adolescents

BACKGROUND

Growth abnormalities in childhood have been related to later cardiometabolic risks, but little is known about these associations in populations at high risk of type 2 diabetes.

OBJECTIVES

We examined the associations of patterns of growth, including weight and height at ages 1-59 months, with cardiometabolic risk factors at ages 5-16 years.

METHODS

We linked anthropometric data collected at ages 1-59 months to cardiometabolic data obtained from a longitudinal study in a southwestern American Indian population at high risk of diabetes. Analyses included 701 children with ≥1 follow-up examination at ages 5-16 years. We derived age- and sex-specific weight-for-height z-scores (WHZ) and height-for-age z-scores (HAZ) at ages 1-59 months. We selected the highest observed WHZ and the lowest observed HAZ at ages 1-59 months and analyzed associations of z-scores and categories of WHZ and HAZ with cardiometabolic outcomes at ages 5-16 years. We used linear mixed-effects models to account for repeated measures.

RESULTS

Overweight/obesity (WHZ >2) at ages 1-59 months was significantly associated with increased BMI, fasting and 2-hour postload plasma glucose, fasting and 2-hour insulin, triglycerides, systolic blood pressure, diastolic blood pressure, and decreased HDL cholesterol at ages 5-16 years relative to normal weight (WHZ ≤1). For example, at ages 5-9 years, 2-hour glucose was 10.4 mg/dL higher (95% CI: 5.6-15.3 mg/dL) and fasting insulin was 4.29 μU/mL higher (95% CI: 2.96-5.71 μU/mL) in those with overweight/obesity in early childhood. Associations were attenuated and no longer significant when adjusted for concurrent BMI. A low height-for-age (HAZ < -2) at ages 1-59 months was associated with 5.37 mg/dL lower HDL (95% CI: 2.57-8.17 mg/dL) and 27.5 μU/mL higher 2-hour insulin (95% CI: 3.41-57.6 μU/mL) at ages 10-16 years relative to an HAZ ≥0.

CONCLUSIONS

In this American Indian population, findings suggest a strong contribution of overweight/obesity in early childhood to cardiometabolic risks in later childhood and adolescence, mediated through persistent overweight/obesity into later ages. Findings also suggest potential adverse effects of low height-for-age, which require confirmation.

Racial/ethnic and socioeconomic disparities in the use of newer diabetes medications in the Look AHEAD study

Background

Among patients with type 2 diabetes, minority racial/ethnic groups have a higher burden of cardiovascular disease, chronic kidney disease, and hypoglycaemia. These groups may especially benefit from newer diabetes medication classes, but high cost may limit access. We examined the association of race/ethnicity with the initiation of newer diabetes medications (GLP-1 receptor agonists, DPP-4 inhibitors, SGLT-2 inhibitors).

Methods

We conducted a secondary analysis of the Look AHEAD (Action for Health in Diabetes) trial including participants with at least one study visit after April 28, 2005. Cox proportional hazards models were used to estimate the association between race/ethnicity and socioeconomic factors with time to initiation of any newer diabetes medication from April 2005 to February 2020. Models were adjusted for demographic and clinical characteristics.

Findings

Among 4,892 participants, 63.6%, 15.7%, 12.6%, 5.2%, and 2.9% were White, Black, Hispanic, American Indian or Alaskan Native (AI/AN), or other race/ethnicity, respectively. During a median follow-up of 8.3 years, 2,180 (45.2%) participants were initiated on newer diabetes medications. Race/ethnicity was associated with newer diabetes medication initiation (p=.019). Specifically, initiation was lower among Black (HR 0.81, 95% CI 0.70 -0.94) and AI/AN participants (HR 0.51, 95% CI 0.26-0.99). Yearly family income was inversely associated with initiation of newer diabetes medications (HR 0.78, 95% CI 0.62-0.98) comparing the lowest and highest income groups. Findings were mostly driven by GLP-1 receptor agonists.

Interpretation

These findings provide evidence of racial/ethnic disparities in the initiation of newer diabetes medications, independent of socioeconomic factors, which may contribute to worse health outcomes.

Comparison of ETDRS 7-Field to 4-Widefield Digital Imaging in the Evaluation of Diabetic Retinopathy Severity

Purpose

To compare Early Treatment Diabetic Retinopathy Study (ETDRS) severity levels between two digital fundus imaging protocols for research studies of diabetic retinopathy: the gold standard 7-field (7F) imaging and the more recent 4-widefield (4W) imaging.

Methods

Two hundred twenty-two participants enrolled in the Diabetes Prevention Program Outcomes Study underwent concurrent 7F and 4W imaging. The ETDRS levels from 220 paired gradable images were determined by masked graders. Each image was graded by two independent graders with adjudication by a senior grader, if necessary. Percent agreement between graders and between imaging protocols was evaluated with kappa statistics and weighted kappa statistics.

Results

Of 220 gradable eyes, diabetic retinopathy was seen in 11.8%; this was mild in 10.4% and more than mild in 1.4% using 7F imaging. The ETDRS levels showed exact agreement of 95% between 7F and 4W imaging (weighted kappa 0.86). Intergrader agreement for each modality had exact agreement of 89% (weighted kappa of 0.73) for 7F and 91% (weighted kappa 0.77) for 4W.

Conclusions

There is substantial agreement in the ETDRS severity level between the 7F and 4W digital imaging protocols, demonstrating that the two imaging protocols are interchangeable. Both 4W and 7F digital imaging protocols can be used for assessing ETDRS levels, even in populations with minimal diabetic retinopathy.

Translational Relevance

The 4W protocol requires fewer images than the 7F, is more comfortable for the patients, is easier for photographic capture, and provides diabetic retinopathy data that is equivalent to the 7F imaging protocol.

Adiposity, related biomarkers, and type 2 diabetes after gestational diabetes: The Diabetes Prevention Program

OBJECTIVE

This study investigated associations of adiposity and adiposity-related biomarkers with incident type 2 diabetes (T2D) among parous women.

METHODS

Among women in the Diabetes Prevention Program (DPP) who reported a previous live birth, circulating biomarkers (leptin, adiponectin, sex hormone-binding globulin, and alanine aminotransferase; n = 1,711) were measured at enrollment (average: 12 years post partum). Visceral (VAT) and subcutaneous adipose tissue areas at the L2-L3 region and the L3-L4 region were quantified by computed tomography (n = 477). Overall and stratified (by history of gestational diabetes mellitus [GDM]) adjusted Cox proportional hazards models were fit.

RESULTS

Alanine aminotransferase, L2-L3 VAT, and L3-L4 VAT were positively associated (hazard ratio [HR] for 1-SD increases: 1.073, p = 0.024; 1.251, p = 0.009; 1.272, p = 0.004, respectively), and adiponectin concentration was inversely associated with T2D (HR 0.762, p < 0.001). Whereas leptin concentration was not associated with T2D overall, in GDM-stratified models, a 1-SD higher leptin was positively associated with risk of T2D in women without GDM (HR: 1.126, p = 0.016) and inversely in women with a history of GDM (HR: 0.776, p = 0.013, interaction p = 0.002).

CONCLUSIONS

Among parous women, alanine aminotransferase and VAT are positively associated with incident T2D, whereas adiponectin is inversely associated. Leptin is associated with higher risk of T2D in women with a history of GDM but a lower risk in women without a history of GDM.

Effect of Metformin and Lifestyle Interventions on Mortality in the Diabetes Prevention Program and Diabetes Prevention Program Outcomes Study

OBJECTIVE

To determine whether metformin or lifestyle modification can lower rates of all-cause and cause-specific mortality in the Diabetes Prevention Program and Diabetes Prevention Program Outcomes Study.

RESEARCH DESIGN AND METHODS

From 1996 to 1999, 3,234 adults at high risk for type 2 diabetes were randomized to an intensive lifestyle intervention, masked metformin, or placebo. Placebo and lifestyle interventions stopped in 2001, and a modified lifestyle program was offered to everyone, but unmasked study metformin continued in those originally randomized. Causes of deaths through 31 December 2018 were adjudicated by blinded reviews. All-cause and cause-specific mortality hazard ratios (HRs) were estimated from Cox proportional hazards regression models and Fine-Gray models, respectively.

RESULTS

Over a median of 21 years (interquartile range 20-21), 453 participants died. Cancer was the leading cause of death (n = 170), followed by cardiovascular disease (n = 131). Compared with placebo, metformin did not influence mortality from all causes (HR 0.99 [95% CI 0.79, 1.25]), cancer (HR 1.04 [95% CI 0.72, 1.52]), or cardiovascular disease (HR 1.08 [95% CI 0.70, 1.66]). Similarly, lifestyle modification did not impact all-cause (HR 1.02 [95% CI 0.81, 1.28]), cancer (HR 1.07 [95% CI 0.74, 1.55]), or cardiovascular disease (HR 1.18 [95% CI 0.77, 1.81]) mortality. Analyses adjusted for diabetes status and duration, BMI, cumulative glycemic exposure, and cardiovascular risks yielded results similar to those for all-cause mortality.

CONCLUSIONS

Cancer was the leading cause of mortality among adults at high risk for type 2 diabetes. Although metformin and lifestyle modification prevented diabetes, neither strategy reduced all-cause, cancer, or cardiovascular mortality rates.

Epidemiology of Type 2 Diabetes in Indigenous Communities in the United States

PURPOSE OF REVIEW

The present review focuses on the epidemiology of type 2 diabetes (T2D) in Indigenous communities in the continental United States (U.S.)-including disease prevention and management-and discusses special considerations in conducting research with Indigenous communities.

RECENT FINDINGS

Previous studies have reported the disparately high prevalence of diabetes, especially T2D, among Indigenous peoples in the U.S. The high prevalence and incidence of early-onset T2D in Indigenous youth relative to that of all youth in the U.S. population pose challenges to the prevention of complications of diabetes. Behavioral, dietary, lifestyle, and genetic factors associated with T2D in Indigenous communities are often investigated. More limited is the discussion of the historical and ongoing consequences of colonization and displacement that impact the aforementioned risk factors. Future research is necessary to assess community-specific needs with respect to diabetes prevention and management across the diversity of Indigenous communities in the U.S.

Relationship Between Insulin Secretion and Insulin Sensitivity and its Role in Development of Type 2 Diabetes Mellitus: Beyond the Disposition Index

We assessed whether the relationship between insulin secretion and sensitivity predicted development of type 2 diabetes in American Indians participating in a longitudinal epidemiologic study. At baseline, when all subjects did not have diabetes, 1566 participants underwent oral tests and 420 had intravenous measures of glucose regulation with estimates of insulin secretion and sensitivity. Standardized major axis regression was used to study the relationship of secretion and sensitivity. Distances away from and along the regression line estimated compensatory insulin secretion and secretory demand, respectively. This relationship differed according to glucose tolerance and BMI categories. The distance away from the line is similar to the disposition index (DI) defined as the product of estimated secretion and sensitivity, but the regression line may differ from a line with constant DI (i.e., it is not necessarily hyperbolic). Subjects with the same DI but different levels of insulin secretion and sensitivity had different incidence rates of diabetes; lower sensitivity with higher secretory demand was associated with greater diabetes risk. Insulin secretion and insulin sensitivity, analyzed together, predict diabetes better than DI alone. Physiologically, this may reflect long-term risk associated with increased allostatic load resulting from the stimulation of insulin hypersecretion by increased glycemia.

Changes in mood and health-related quality of life in Look AHEAD 6 years after termination of the lifestyle intervention

OBJECTIVE

The Action for Health in Diabetes (Look AHEAD) study previously reported that intensive lifestyle intervention (ILI) reduced incident depressive symptoms and improved health-related quality of life (HRQOL) over nearly 10 years of intervention compared with a control group (the diabetes support and education group [DSE]) in participants with type 2 diabetes and overweight or obesity. The present study compared incident depressive symptoms and changes in HRQOL in these groups for an additional 6 years following termination of the ILI in September 2012.

METHODS

A total of 1,945 ILI participants and 1,900 DSE participants completed at least one of four planned postintervention assessments at which weight, mood (via the Patient Health Questionnaire-9), antidepressant medication use, and HRQOL (via the Medical Outcomes Scale, Short Form-36) were measured.

RESULTS

ILI participants and DSE participants lost 3.1 (0.3) and 3.8 (0.3) kg [represented as mean (SE); p = 0.10], respectively, during the 6-year postintervention follow-up. No significant differences were observed between groups during this time in incident mild or greater symptoms of depression, antidepressant medication use, or in changes on the physical component summary or mental component summary scores of the Short Form-36. In both groups, mental component summary scores were higher than physical component summary scores.

CONCLUSIONS

Prior participation in the ILI, compared with the DSE group, did not appear to improve subsequent mood or HRQOL during 6 years of postintervention follow-up.

Pima Indian Contributions to Our Understanding of Diabetic Kidney Disease

Prospective studies in informative populations are crucial to increasing our knowledge of disease. In this perspective, we describe a half century of studies in an American Indian population that transformed our understanding of kidney disease in type 2 diabetes, now recognized as the leading cause of kidney failure worldwide. Serial examinations conducted for many years that included the collection of data and samples across multiple domains captured an unprecedented volume of clinical, physiologic, morphometric, genomic, and transcriptomic data. This work permitted us to extensively characterize the course and determinants of diabetic kidney disease, its pathophysiologic underpinnings, and important secular trends of urgent concern to populations worldwide, including the emergence of youth-onset type 2 diabetes and its effect on development of diabetic kidney disease in midlife. By combining these data using the tools of integrative biology, we are developing new mechanistic insights into the development and progression of diabetic kidney disease in type 2 diabetes. These insights have already contributed to the identification and successful therapeutic targeting of a novel pathway in DKD. We anticipate that this work will continue to expand our understanding of this complex disease and influence its management in the coming years.

Effect of Vitamin D Supplementation on Kidney Function in Adults with Prediabetes: A Secondary Analysis of a Randomized Trial

BACKGROUND AND OBJECTIVES

Low serum 25-hydroxyvitamin D (25[OH]D) concentration has been associated with higher levels of proteinuria and lower levels of eGFR in observational studies. In the Vitamin D and Type 2 Diabetes (D2d) study, we investigated the effect of vitamin D supplementation on kidney outcomes in a population with prediabetes.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Overweight/obese adults with high risk for type 2 diabetes (defined by meeting two of three glycemic criteria for prediabetes) were randomized to vitamin D₃ 4000 IU per day versus placebo. Median duration of treatment was 2.9 years (interquartile range 2.0-3.5 years). Kidney outcomes included (1) worsening in Kidney Disease: Improving Global Outcomes (KDIGO ) risk score (low, moderate, high, very high) on two consecutive follow-up visits after the baseline visit and (2) mean changes in eGFR and urine albumin-to-creatinine ratio (UACR).

RESULTS

Among 2166 participants (mean age 60 years, body mass index 32 kg/m², serum 25(OH)D 28 ng/ml, eGFR 87 ml/min per 1.73 m², UACR 11 mg/g, 79% with hypertension), 10% had moderate, high, or very high KDIGO risk score. Over a median follow-up of 2.9 years, there were 28 cases of KDIGO worsening in the vitamin D group and 30 in the placebo group (hazard ratio, 0.89; 95% confidence interval [95% CI], 0.52 to 1.52]). Mean difference in eGFR from baseline was -1.0 ml/min per 1.73 m² (95% CI, -1.3 to -0.7) in the vitamin D group and -0.1 ml/min per 1.73 m² (95% CI, -0.4 to 0.2) in the placebo group; between-group difference was -1.0 ml/min per 1.73 m² (95% CI, -1.4 to -0.6). Mean difference in UACR was 2.7 mg/g (95% CI, 1.2 to 4.3) in the vitamin D group and 2.0 (95% CI, 0.5 to 3.6) in the placebo group; between-group difference was 0.7 mg/g (95% CI, -1.5 to 2.9).

CONCLUSIONS

Among persons with prediabetes, who were not preselected on the basis of serum 25(OH)D concentration, vitamin D supplementation did not affect progression of KDIGO risk scores and did not have a meaningful effect on change in UACR or eGFR.

The Moderating Effects of Genetic Variations on Changes in Physical Activity Level and Cardiorespiratory Fitness in Response to a Life-Style Intervention: A Randomized Controlled Trial

OBJECTIVE

Prior studies identified single nucleotide polymorphisms (SNPs) associated with physical activity (PA) level in a natural environment and intervention study: rs978656-DNAPTP6, rs10887741-PAPSS2, rs7279064-C18orf2, and rs6265-BDNF. Using the four SNPs' polygenic score (PGS), we examined whether PGS moderates a life-style intervention's effect on changes in PA level and cardiorespiratory fitness (CRF).

METHODS

This is a secondary analysis of Look AHEAD, a multicenter randomized controlled trial designed to test the health benefits of a life-style intervention among 2675 participants with overweight/obesity and type 2 diabetes (ages, 45-76 years). Using linear mixed-effects models, level of PA (Paffenbarger PA questionnaire) and treadmill-assessed CRF were each regressed on four SNPs' PGS, study time (baseline, year 1, and year 4), intervention arm, and interactions between the three. Models adjusted for age, sex, body mass index, ancestry principal components (population stratification), and study sites, with Bonferroni corrections for multiple testing (α < .005). Effect modification by age was examined.

RESULTS

PGS was not predictive of change in CRF or PA level in response to intervention. In analyses without PGS by intervention by time, the relationships between PGS and PA phenotypes were modified by age (p interaction = .048 for CRF and .058 for PA), such that a 1-unit increase in PGS was associated with 24 kcal · wk-1 more in moderate-intensity PA and 0.004 MET higher CRF only among older groups (age >55 years for CRF, >60 years for PA level).

CONCLUSIONS

The effects of the intervention on PA and CRF were not moderated by the four SNPs. Future studies with extended SNP list should confirm the findings on effect modification by age.

Next generation sequencing for HLA loci in full heritage Pima Indians of Arizona, Part II: HLA-A, -B, and -C with selected non-classical loci at 4-field resolution from whole genome sequences

While the samples and data from the Pima Indians of the Gila River Indian Community have been included in many international HLA workshops and conferences and have been the focus of numerous population reports and the source of novel alleles at the classical HLA loci, they have not been studied for the non-classical loci. In order to expand our HLA-disease association studies, we typed over 300 whole genome sequences from full Pima heritage members, controlled for first degree relationship, and employed recently developed computer algorithms to resolve HLA alleles. Both classical-HLA-A, -B, and -C- and non-classical- HLA-E, -F, -G, -J, -L, -W, -Y, -DPA2, -DPB2, -DMA, -DMB, -DOA, -DRB2, -DRB9, TAP1- loci were typed at the 4-field level of resolution. We present allele and selected haplotype frequencies, test the genotype distributions for population structure, discuss the issues that are created for tests of Hardy-Weinberg equilibrium over the four sample spaces of high resolution HLA typing, and address the implications for the evolution of non-classical pseudogenes that are no longer expressed in a phenotype subject to natural selection.

Exome Sequencing of 21 Bardet-Biedl Syndrome (BBS) Genes to Identify Obesity Variants in 6,851 American Indians

OBJECTIVE

In an ongoing effort to identify the genetic variation that contributes to obesity in American Indians, known Bardet-Biedl syndrome (BBS) genes were analyzed for an effect on BMI and leptin signaling.

METHODS

Potentially deleterious variants (Combined Annotation Dependent Depletion score > 20) in BBS genes were identified in whole-exome sequence data from 6,851 American Indians informative for BMI. Common variants (detected in ≥ 10 individuals) were analyzed for association with BMI; rare variants (detected in < 10 individuals) were analyzed for mean BMI of carriers. Functional assessment of variants' effect on signal transducer and activator of transcription 3 (STAT3) activity was performed in vitro.

RESULTS

One common variant, rs59252892 (Thr549Ile) in BBS9, was associated with BMI (P = 0.0008, β = 25% increase per risk allele). Among rare variants for which carriers had severe obesity (mean BMI > 40 kg/m² ), four were in BBS9. In vitro analysis of BBS9 found the Ile allele at Thr549Ile had a 20% increase in STAT3 activity compared with the Thr allele (P = 0.01). Western blot analysis showed the Ile allele had a 15% increase in STAT3 phosphorylation (P = 0.006). Comparable functional results were observed with Ser545Gly and Val209Leu but not Leu665Phe and Lys810Glu.

CONCLUSIONS

Potentially functional variants in BBS genes in American Indians are reported. However, functional evidence supporting a causal role for BBS9 in obesity is inconclusive.

Accuracy of 1-Hour Plasma Glucose During the Oral Glucose Tolerance Test in Diagnosis of Type 2 Diabetes in Adults: A Meta-analysis

OBJECTIVE

One-hour plasma glucose (1-h PG) during the oral glucose tolerance test (OGTT) is an accurate predictor of type 2 diabetes. We performed a meta-analysis to determine the optimum cutoff of 1-h PG for detection of type 2 diabetes using 2-h PG as the gold standard.

RESEARCH DESIGN AND METHODS

We included 15 studies with 35,551 participants from multiple ethnic groups (53.8% Caucasian) and 2,705 newly detected cases of diabetes based on 2-h PG during OGTT. We excluded cases identified only by elevated fasting plasma glucose and/or HbA_1c. We determined the optimal 1-h PG threshold and its accuracy at this cutoff for detection of diabetes (2-h PG ≥11.1 mmol/L) using a mixed linear effects regression model with different weights to sensitivity/specificity (2/3, 1/2, and 1/3).

RESULTS

Three cutoffs of 1-h PG, at 10.6 mmol/L, 11.6 mmol/L, and 12.5 mmol/L, had sensitivities of 0.95, 0.92, and 0.87 and specificities of 0.86, 0.91, and 0.94 at weights 2/3, 1/2, and 1/3, respectively. The cutoff of 11.6 mmol/L (95% CI 10.6, 12.6) had a sensitivity of 0.92 (0.87, 0.95), specificity of 0.91 (0.88, 0.93), area under the curve 0.939 (95% confidence region for sensitivity at a given specificity: 0.904, 0.946), and a positive predictive value of 45%.

CONCLUSIONS

The 1-h PG of ≥11.6 mmol/L during OGTT has a good sensitivity and specificity for detecting type 2 diabetes. Prescreening with a diabetes-specific risk calculator to identify high-risk individuals is suggested to decrease the proportion of false-positive cases. Studies including other ethnic groups and assessing complication risk are warranted.

Interaction of diabetes genetic risk and successful lifestyle modification in the Diabetes Prevention Programme

AIM

To test whether diabetes genetic risk modifies the association of successful lifestyle changes with incident diabetes.

MATERIALS AND METHODS

We studied 823 individuals randomized to the intensive lifestyle intervention (ILS) arm of the Diabetes Prevention Programme who were diabetes-free 1 year after enrolment. We tested additive and multiplicative interactions of a 67-variant diabetes genetic risk score (GRS) with achievement of three ILS goals at 1 year (≥7% weight loss, ≥150 min/wk of moderate leisure-time physical activity, and/or a goal for self-reported total fat intake) on the primary outcome of incident diabetes over 3 years of follow-up.

RESULTS

A lower GRS and achieving each or all three ILS goals were each associated with lower incidence of diabetes (all P < 0.05). Additive interactions were significant between the GRS and achievement of the weight loss goal (P < 0.001), physical activity goal (P = 0.02), and all three ILS goals (P < 0.001) for diabetes risk. Achievement of all three ILS goals was associated with 1.8 (95% CI 0.3, 3.4), 3.1 (95% CI 1.5, 4.7), and 3.9 (95% CI 1.6, 6.2) fewer diabetes cases/100-person-years in the first, second and third GRS tertiles (P < 0.001 for trend). Multiplicative interactions between the GRS and ILS goal achievement were significant for the diet goal (P < 0.001), but not for weight loss (P = 0.18) or physical activity (P = 0.62) goals.

CONCLUSIONS

Genetic risk may identify high-risk subgroups for whom successful lifestyle modification is associated with greater absolute reduction in the risk of incident diabetes.

Per- and polyfluoroalkyl substance plasma concentrations and metabolomic markers of type 2 diabetes in the Diabetes Prevention Program trial

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are widely used chemicals, some of which have been linked to type 2 diabetes. We tested whether PFAS concentrations were cross-sectionally associated with metabolites previously shown to predict incident type 2 diabetes using the Diabetes Prevention Program (DPP), a trial of individuals at high risk of type 2 diabetes.

METHODS

We evaluated 691 participants enrolled in the DPP with baseline measures of 10 PFAS (including total perfluorooctanesulfonic acid (PFOS), total perfluorooctanoic acid (PFOA), and Sb-PFOA [branched isomers of PFOA]) and 77 metabolites. We used log2-transformed PFAS concentrations as exposures and standardized metabolite concentrations as outcomes in linear regression models adjusted for age, sex, race/ethnicity, use of anti-hyperlipidemic or triglyceride-lowering medication, income, years of education, marital status, smoking, and family history of diabetes, with Benjamini-Hochberg linear step-up false discovery rate correction.

RESULTS

Sb-PFOA was associated with the largest number of tested metabolites (29 of 77). Each doubling in Sb-PFOA was associated with higher leucine (β = 0.07 [95%CI: 0.02, 0.11] SD) and lower glycine (-0.08 [95%CI: 0.03, -0.13] SD). Each doubling of either total PFOA or n-PFOA was associated with -0.13 [95%CI: 0.04, -0.22] SD lower glycine. PFOA and Sb-PFOA were positively associated with multiple triacylglycerols and diacylglycerols, and total PFOS, total PFOA, and Sb-PFOA were positively associated with phosphatidylethanolamines.

CONCLUSIONS

PFAS concentrations are associated with metabolites linked to type 2 diabetes (particularly amino acid, glycerolipid and glycerophospholipid pathways). Further prospective research is needed to test whether these metabolites mediate associations of PFAS and type 2 diabetes.

Attenuated early pregnancy weight gain by prenatal lifestyle interventions does not prevent gestational diabetes in the LIFE-Moms consortium

AIMS

To examine the effect of lifestyle (diet and physical activity) interventions on the prevalence of GDM, considering the method of GDM ascertainment and its association with early pregnancy characteristics and maternal and neonatal outcomes in the LIFE-Moms consortium.

METHODS

LIFE-Moms evaluated the effects of lifestyle interventions to optimize gestational weight gain in 1148 pregnant women with BMI ≥ 25 kg/m2 and without known diabetes at enrollment, compared with standard care. GDM was assessed between 24 and 31-weeks gestation by a 2-hour, 75-gram OGTT or by local clinical practice standards.

RESULTS

Lifestyle interventions initiated prior to 16 weeks reduced early excess GWG compared with standard care (0.35 ± 0.24 vs 0.43 ± 0.26 kg per week, p=<0.0001) but did not affect GDM diagnosis (11.1% vs 11.6%, p = 0.91). Using the 75-gram, 2-hour OGTT, 13. 0% of standard care and 11.0% of the intervention group had GDM by the IADPSG criteria (p = 0.45). The 'type of diagnostic test' did not change the result (p = 0.86). Women who developed GDM were significantly heavier, more likely to have obesity, and more likely to have dysglycemia at baseline.

CONCLUSION

Moderate-to-high intensity lifestyle interventions grounded in behavior change theory initiated between 9 and 16-weeks gestation did not affect the prevalence of GDM despite reducing early GWG. CLINICALTRIALS.GOV: NCT01545934, NCT01616147, NCT01771133, NCT01631747, NCT01768793, NCT01610752, NCT01812694.

The Impact of Physical Activity on the Prevention of Type 2 Diabetes: Evidence and Lessons Learned From the Diabetes Prevention Program, a Long-Standing Clinical Trial Incorporating Subjective and Objective Activity Measures

OBJECTIVE

Across the Diabetes Prevention Program (DPP) follow-up, cumulative diabetes incidence remained lower in the lifestyle compared with the placebo and metformin randomized groups and could not be explained by weight. Collection of self-reported physical activity (PA) (yearly) with cross-sectional objective PA (in follow-up) allowed for examination of PA and its long-term impact on diabetes prevention.

RESEARCH DESIGN AND METHODS

Yearly self-reported PA and diabetes assessment and oral glucose tolerance test results (fasting glucose semiannually) were collected for 3,232 participants with one accelerometry assessment 11-13 years after randomization (n = 1,793). Mixed models determined PA differences across treatment groups. The association between PA and diabetes incidence was examined using Cox proportional hazards models.

RESULTS

There was a 6% decrease (Cox proportional hazard ratio 0.94 [95% CI 0.92, 0.96]; P < 0.001) in diabetes incidence per 6 MET-h/week increase in time-dependent PA for the entire cohort over an average of 12 years (controlled for age, sex, baseline PA, and weight). The effect of PA was greater (12% decrease) among participants less active at baseline (<7.5 MET-h/week) (n = 1,338) (0.88 [0.83, 0.93]; P < 0.0001), with stronger findings for lifestyle participants. Lifestyle had higher cumulative PA compared with metformin or placebo (P < 0.0001) and higher accelerometry total minutes per day measured during follow-up (P = 0.001 and 0.047). All associations remained significant with the addition of weight in the models.

CONCLUSIONS

PA was inversely related to incident diabetes in the entire cohort across the study, with cross-sectional accelerometry results supporting these findings. This highlights the importance of PA within lifestyle intervention efforts designed to prevent diabetes and urges health care providers to consider both PA and weight when counseling high-risk patients.

Within-Trial Cost-Effectiveness of a Structured Lifestyle Intervention in Adults With Overweight/Obesity and Type 2 Diabetes: Results From the Action for Health in Diabetes (Look AHEAD) Study

OBJECTIVE

To assess the cost-effectiveness (CE) of an intensive lifestyle intervention (ILI) compared with standard diabetes support and education (DSE) in adults with overweight/obesity and type 2 diabetes, as implemented in the Action for Health in Diabetes study.

RESEARCH DESIGN AND METHODS

Data were from 4,827 participants during their first 9 years of study participation from 2001 to 2012. Information on Health Utilities Index Mark 2 (HUI-2) and HUI-3, Short-Form 6D (SF-6D), and Feeling Thermometer (FT), cost of delivering the interventions, and health expenditures was collected during the study. CE was measured by incremental CE ratios (ICERs) in costs per quality-adjusted life year (QALY). Future costs and QALYs were discounted at 3% annually. Costs were in 2012 U.S. dollars.

RESULTS

Over the 9 years studied, the mean cumulative intervention costs and mean cumulative health care expenditures were $11,275 and $64,453 per person for ILI and $887 and $68,174 for DSE. Thus, ILI cost $6,666 more per person than DSE. Additional QALYs gained by ILI were not statistically significant measured by the HUIs and were 0.07 and 0.15, respectively, measured by SF-6D and FT. The ICERs ranged from no health benefit with a higher cost based on HUIs to $96,458/QALY and $43,169/QALY, respectively, based on SF-6D and FT.

CONCLUSIONS

Whether ILI was cost-effective over the 9-year period is unclear because different health utility measures led to different conclusions.

Assessment of the potential role of natural selection in type 2 diabetes and related traits across human continental ancestry groups: comparison of phenotypic with genotypic divergence

AIMS/HYPOTHESIS

Prevalence of type 2 diabetes differs among human ancestry groups, and many hypotheses invoke differential natural selection to account for these differences. We sought to assess the potential role of differential natural selection across major continental ancestry groups for diabetes and related traits, by comparison of genetic and phenotypic differences.

METHODS

This was a cross-sectional comparison among 734 individuals from an urban sample (none of whom was more closely related to another than third-degree relatives), including 83 African Americans, 523 American Indians and 128 European Americans. Participants were not recruited based on diabetes status or other traits. BMI was calculated, and diabetes was diagnosed by a 75 g oral glucose tolerance test. In those with normal glucose tolerance (n = 434), fasting insulin and 30 min post-load insulin, adjusted for 30 min glucose, were taken as measures of insulin resistance and secretion, respectively. Whole exome sequencing was performed, resulting in 97,388 common (minor allele frequency ≥ 5%) variants; the coancestry coefficient (F_ST) was calculated across all markers as a measure of genetic divergence among ancestry groups. The phenotypic divergence index (P_ST) was also calculated from the phenotypic differences and heritability (which was estimated from genetic relatedness calculated empirically across all markers in 761 American Indian participants prior to the exclusion of close relatives). Under evolutionary neutrality, the expectation is P_ST = F_ST, while for traits under differential selection P_ST is expected to be significantly greater than F_ST. A bootstrap procedure was used to test the hypothesis P_ST = F_ST. RESULTS: With adjustment for age and sex, prevalence of type 2 diabetes was 34.0% in American Indians, 12.4% in African Americans and 10.4% in European Americans (p = 2.9 × 10^-10 for difference among groups). Mean BMI was 36.3, 33.4 and 33.0 kg/m², respectively (p = 1.9 × 10^-7). Mean fasting insulin was 63.8, 48.4 and 45.2 pmol/l (p = 9.2 × 10^-5), while mean 30 min insulin was 559.8, 553.5 and 358.8 pmol/l, respectively (p = 5.7 × 10^-8). F_ST across all markers was 0.130, while P_ST for liability to diabetes, adjusted for age and sex, was 0.149 (p = 0.35 for difference with F_ST). P_ST was 0.094 for BMI (p = 0.54), 0.095 for fasting insulin (p = 0.54) and 0.216 (p = 0.18) for 30 min insulin. For type 2 diabetes and BMI, the maximum divergence between populations was observed between American Indians and European Americans (P_ST-MAX = 0.22, p = 0.37, and P_ST-MAX = 0.14, p = 0.61), which suggests that a relatively modest 22% or 14% of the genetic variance, respectively, can potentially be explained by differential selection (assuming the absence of neutral drift).

CONCLUSIONS/INTERPRETATION

These analyses suggest that while type 2 diabetes and related traits differ significantly among continental ancestry groups, the differences are consistent with neutral expectations based on heritability and genetic distances. While these analyses do not exclude a modest role for natural selection, they do not support the hypothesis that differential natural selection is necessary to explain the phenotypic differences among these ancestry groups. Graphical abstract.

Intratrial Exposure to Vitamin D and New-Onset Diabetes Among Adults With Prediabetes: A Secondary Analysis From the Vitamin D and Type 2 Diabetes (D2d) Study

OBJECTIVE

Postrandomization biases may influence the estimate of efficacy of supplemental vitamin D in diabetes prevention trials. In the Vitamin D and Type 2 Diabetes (D2d) study, repeated measures of serum 25-hydroxyvitamin D [25(OH)D] level provided an opportunity to test whether intratrial vitamin D exposure affected diabetes risk and whether the effect was modified by trial assignment (vitamin D vs. placebo).

RESEARCH DESIGN AND METHODS

The D2d study compared the effect of daily supplementation with 100 μg (4,000 units) of vitamin D₃ versus placebo on new-onset diabetes in adults with prediabetes. Intratrial vitamin D exposure was calculated as the cumulative rolling mean of annual serum 25(OH)D measurements. Hazard ratios for diabetes among participants who had intratrial 25(OH)D levels of <50, 75-99, 100-124, and ≥125 nmol/L were compared with those with levels of 50-74 nmol/L (the range considered adequate by the National Academy of Medicine) in the entire cohort and by trial assignment.

RESULTS

There was an interaction of trial assignment with intratrial 25(OH)D level in predicting diabetes risk (interaction P = 0.018). The hazard ratio for diabetes for an increase of 25 nmol/L in intratrial 25(OH)D level was 0.75 (95% CI 0.68-0.82) among those assigned to vitamin D and 0.90 (0.80-1.02) among those assigned to placebo. The hazard ratios for diabetes among participants treated with vitamin D who maintained intratrial 25(OH)D levels of 100-124 and ≥125 nmol/L were 0.48 (0.29-0.80) and 0.29 (0.17-0.50), respectively, compared with those who maintained a level of 50-74 nmol/L.

CONCLUSIONS

Daily vitamin D supplementation to maintain a serum 25(OH)D level ≥100 nmol/L is a promising approach to reducing the risk of diabetes in adults with prediabetes.

Exome Sequencing Identifies A Nonsense Variant in DAO Associated With Reduced Energy Expenditure in American Indians

BACKGROUND

Obesity and energy expenditure (EE) are heritable and genetic variants influencing EE may contribute to the development of obesity. We sought to identify genetic variants that affect EE in American Indians, an ethnic group with high prevalence of obesity.

METHODS

Whole-exome sequencing was performed in 373 healthy Pima Indians informative for 24-hour EE during energy balance. Genetic association analyses of all high-quality exonic variants (≥5 carriers) was performed, and those predicted to be damaging were prioritized.

RESULTS

Rs752074397 introduces a premature stop codon (Cys264Ter) in DAO and demonstrated the strongest association for 24-hour EE, where the Ter allele associated with substantially lower 24-hour EE (mean lower by 268 kcal/d) and sleeping EE (by 135 kcal/d). The Ter allele has a frequency = 0.5% in Pima Indians, whereas is extremely rare in most other ethnic groups (frequency < 0.01%). In vitro functional analysis showed reduced protein levels for the truncated form of DAO consistent with increased protein degradation. DAO encodes D-amino acid oxidase, which is involved in dopamine synthesis which might explain its role in modulating EE.

CONCLUSION

Our results indicate that a nonsense mutation in DAO may influence EE in American Indians. Identification of variants that influence energy metabolism may lead to new pathways to treat human obesity.

CLINICAL TRIAL REGISTRATION NUMBER

NCT00340132.

Waist Circumference Change During Intensive Lifestyle Intervention and Cardiovascular Morbidity and Mortality in the Look AHEAD Trial

OBJECTIVE

The Action for Health in Diabetes (Look AHEAD) trial was a randomized trial comparing effects of intensive lifestyle intervention (ILI) and diabetes support and education (DSE) on cardiovascular disease (CVD) among individuals with overweight/obesity and type 2 diabetes. A secondary analysis was conducted to evaluate the association between change in weight and waist circumference (WC) and CVD outcomes.

METHODS

Participants (N = 5,490) were classified into four categories based on change in weight and WC between baseline and year 1 (both increased, both decreased, etc.). Separate Cox proportional hazards regression models were fit for ILI and DSE (using group that reduced weight/WC as reference), and time to first occurrence of primary and secondary CVD outcomes from year 1 through a median of almost 10 years were compared. Second, time to first event among all four ILI groups relative to DSE was evaluated.

RESULTS

Within DSE, CVD outcomes did not differ. ILI participants with increased WC had increased risk of primary outcomes, regardless of weight loss (hazard ratio: 1.55 [95% CI: 1.11-2.17]) or weight gain (hazard ratio: 1.76 [95% CI: 1.07-2.89]), and had increased risk of secondary outcomes (overall P < 0.01) relative to ILI participants who reduced both weight and WC and relative to DSE participants.

CONCLUSIONS

In this secondary analysis, increased WC during the first year of ILI, independent of weight change, was associated with higher risk for subsequent cardiovascular outcomes.

Impact of an 8-Year Intensive Lifestyle Intervention on an Index of Multimorbidity

BACKGROUND/OBJECTIVES

Type 2 diabetes mellitus and obesity are sometimes described as conditions that accelerate aging. Multidomain lifestyle interventions have shown promise to slow the accumulation of age-related diseases, a hallmark of aging. However, they have not been assessed among at-risk individuals with these two conditions. We examined the relative impact of 8 years of a multidomain lifestyle intervention on an index of multimorbidity.

DESIGN

Randomized controlled clinical trial comparing an intensive lifestyle intervention (ILI) that targeted weight loss through caloric restriction and increased physical activity with a control condition of diabetes support and education (DSE).

SETTING

Sixteen U.S. academic centers.

PARTICIPANTS

A total of 5,145 volunteers, aged 45 to 76, with established type 2 diabetes mellitus and overweight or obesity who met eligibility criteria for a randomized controlled clinical trial.

MEASUREMENTS

A multimorbidity index that included nine age-related chronic diseases and death was tracked over 8 years of intervention delivery.

RESULTS

Among individuals assigned to DSE, the multimorbidity index scores increased by an average of .98 (95% confidence interval [CI] = .94-1.02) over 8 years, compared with .89 (95% CI = .85-.93) among those in the multidomain ILI, which was a 9% difference (P = .003). Relative intervention effects were similar among individuals grouped by baseline body mass index, age, and sex, and they were greater for those with lower levels of multimorbidity index scores at baseline.

CONCLUSIONS

Increases in multimorbidity over time among adults with overweight or obesity and type 2 diabetes mellitus may be slowed by multidomain ILI. J Am Geriatr Soc 68:2249-2256, 2020.

Weight tracking in childhood and adolescence and type 2 diabetes risk

AIMS/HYPOTHESIS

The aim of this work was to examine the associations of average weight and weight velocity in three growth periods from birth through adolescence with type 2 diabetes incidence.

METHODS

Child participants were selected from a 43 year longitudinal study of American Indians to represent three growth periods: pre-adolescence (birth to ~8 years); early adolescence (~8 to ~13 years); and late adolescence (~13 to ~18 years). Age-, sex- and height-standardised weight z score mean and weight z score velocity (change/year) were computed for each period. Participants were followed for up to 25 years from the end of each growth period until they developed diabetes. Associations of weight z score mean or weight z score velocity with diabetes incidence were determined with sex-, birth date- and maternal diabetes-adjusted Poisson regression models.

RESULTS

Among 2100 participants representing the pre-adolescence growth period, 1558 representing the early adolescence period and 1418 representing the late adolescence period, there were 290, 315 and 380 incident diabetes cases, respectively. During the first 10 years of follow-up, the diabetes incidence rate ratio (95% CI) was 1.72 (1.40, 2.11)/SD of log₁₀ weight z score mean in pre-adolescence, 2.09 (1.68, 2.60)/SD of log₁₀ weight z score mean in early adolescence and 1.85 (1.58, 2.17)/SD of log₁₀ weight z score mean in late adolescence. The diabetes incidence rate ratio (95% CI) was 1.79 (1.49, 2.17)/SD of log₁₀ weight z score velocity in pre-adolescence, 1.13 (0.91, 1.41)/SD of log₁₀ weight z score velocity in early adolescence and 1.29 (1.09, 1.51)/SD of log₁₀ weight z score velocity in late adolescence. There were strong correlations in the weight z score means and weak correlations in the weight z score velocities between successive periods.

CONCLUSIONS/INTERPRETATION

Higher weight and accelerated weight gain in all growth periods associate with increased type 2 diabetes risk. Importantly, higher weight and greater weight velocity during pre-adolescence jointly associate with the highest type 2 diabetes risk. Graphical abstract.