Genetic architecture and biology of youth-onset type 2 diabetes

The prevalence of youth-onset type 2 diabetes (T2D) and childhood obesity has been rising steadily1, producing a growing public health concern1 that disproportionately affects minority groups2. The genetic basis of youth-onset T2D and its relationship to other forms of diabetes are unclear3. Here we report a detailed genetic characterization of youth-onset T2D by analysing exome sequences and common variant associations for 3,005 individuals with youth-onset T2D and 9,777 adult control participants matched for ancestry, including both males and females. We identify monogenic diabetes variants in 2.4% of individuals and three exome-wide significant (P < 2.6 × 10-6) gene-level associations (HNF1A, MC4R, ATXN2L). Furthermore, we report rare variant association enrichments within 25 gene sets related to obesity, monogenic diabetes and β-cell function. Many youth-onset T2D associations are shared with adult-onset T2D, but genetic risk factors of all frequencies-and rare variants in particular-are enriched within youth-onset T2D cases (5.0-fold increase in the rare variant and 3.4-fold increase in common variant genetic liability relative to adult-onset cases). The clinical presentation of participants with youth-onset T2D is influenced in part by the frequency of genetic risk factors within each individual. These findings portray youth-onset T2D as a heterogeneous disease situated on a spectrum between monogenic diabetes and adult-onset T2D.

Beta cell function and insulin sensitivity in obese youth with maturity onset diabetes of youth mutations vs type 2 diabetes in TODAY: Longitudinal observations and glycemic failure

OBJECTIVE

In treatment options for type 2 diabetes in adolescents and youth (TODAY), 4.5% of obese youth clinically diagnosed with type 2 diabetes (T2D) had genetic variants consistent with maturity onset diabetes of youth (MODY) diagnosis. The course of IS and β-cell function in obese youth with MODY remains unknown. In this secondary analysis, we examined IS and β-cell function in MODY vs. non-MODY obese youth at randomization and over time.

METHODS

Genetic data in TODAY included 426 non-MODY (T2D) and 22 MODY youth (7 glucokinase MODY mutation positive [GCK-MODY], 12 hepatocyte nuclear factor MODY mutation positive [HNF-MODY], 2 Insulin gene mutation [insulin (INS)-MODY], and 1 Kruppel-like factor 11 [KLF11-MODY]). Oral glucose tolerance test (OGTT)-derived IS, C-peptide index, and β-cell function relative to IS oral disposition index (oDI) was measured at randomization, and over 24 months in addition to total and high-molecular-weight adiponectin (HMWA).

RESULTS

At randomization, IS, total adiponectin, and HMWA were significantly higher in the two MODY groups than in non-MODY. β-cell function measured by C-peptide oDI was 3-fold higher in GCK-MODY than in HNF-MODY and 1.5-fold higher than non-MODY (P for both <.05). Glycemic failure rate was 75.0% in HNF-MODY, 46.9% in non-MODY, and zero in GCK-MODY youth. While the changes in IS and oDI were not different among the three groups in the first 6 months, IS improved from 6 to 24 months in HNF-MODY vs GCK-MODY youth.

CONCLUSIONS

In TODAY, β-cell function at randomization was worse in obese HNF-MODY youth compared with GCK-MODY youth, while insulin sensitivity was worse in non-MODY compared with the other two MODY groups. Over time, IS showed the greatest improvement in HNF-MODY youth. This raises the possibility that TODAY therapeutic modalities of insulin sensitization in these obese HNF-MODY youth may have played a beneficial role.

The association between dispositional mindfulness and glycemic control in type 1 diabetes during early adulthood: Differences by age and adverse childhood experiences

BACKGROUND

The study objective was to determine whether higher levels of dispositional mindfulness were associated with lower HbA_1c levels among young adults with type 1 diabetes (T1D) and whether this association differed by age or exposure to adverse childhood experiences (ACEs).

METHODS

An online cross-sectional survey, called T1 Flourish, was completed in 2017 by 423 of 743 (56.9%) young adults (19-31 years) with T1D receiving outpatient care at a diabetes specialty clinic in New York City. HbA_1c levels were abstracted from medical records. Respondents were categorized by age, high and low dispositional mindfulness (median split on Cognitive and Affective Mindfulness Scale-Revised), and exposure to any of 10 ACEs.

RESULTS

Respondents had a mean (SD) HbA_1c of 64 (18) mmol/mol [8.0 (1.7)%]; 59.3% were female and 69.4% were non-Hispanic white. The covariate-adjusted association between dispositional mindfulness and HbA_1c differed by age group and ACEs. Among 27- to 31-year-olds, those with high mindfulness had HbA_1c levels that were 8 mmol/mol [0.7%] lower (95% confidence interval, 2-13 mmol/mol [0.2-1.2%]) than those with low mindfulness, and this association tended to be stronger in those with ≥1 ACEs. Weaker, non-significant associations in the same direction occurred in 23- to 26-year-olds. Among 19- to 22-year-olds, those with high mindfulness and no ACEs tended to have higher HbA_1c levels.

CONCLUSIONS

In young adults with T1D, higher mindfulness was significantly associated with lower HbA_1c only among 27- to 31-year-olds. In early adulthood, the impact of mindfulness-based interventions on glycemic control may vary by age and childhood trauma history.

Monogenic diabetes in overweight and obese youth diagnosed with type 2 diabetes: the TODAY clinical trial

PurposeMonogenic diabetes accounts for 1-2% of diabetes cases. It is often undiagnosed, which may lead to inappropriate treatment. This study was performed to estimate the prevalence of monogenic diabetes in a cohort of overweight/obese adolescents diagnosed with type 2 diabetes (T2D).MethodsSequencing using a custom monogenic diabetes gene panel was performed on a racially/ethnically diverse cohort of 488 overweight/obese adolescents with T2D in the Treatment Options for Type 2 Diabetes in Adolescents and Youth (TODAY) clinical trial. Associations between having a monogenic diabetes variant and clinical characteristics and time to treatment failure were analyzed.ResultsMore than 4% (22/488) had genetic variants causing monogenic diabetes (seven GCK, seven HNF4A, five HNF1A, two INS, and one KLF11). Patients with monogenic diabetes had a statistically, but not clinically, significant lower body mass index (BMI) z-score, lower fasting insulin, and higher fasting glucose. Most (6/7) patients with HNF4A variants rapidly failed TODAY treatment across study arms (hazard ratio = 5.03, P = 0.0002), while none with GCK variants failed treatment.ConclusionThe finding of 4.5% of patients with monogenic diabetes in an overweight/obese cohort of children and adolescents with T2D suggests that monogenic diabetes diagnosis should be considered in children and adolescents without diabetes-associated autoantibodies and maintained C-peptide, regardless of BMI, as it may direct appropriate clinical management.

Identifying monogenic diabetes in a pediatric cohort with presumed type 1 diabetes

OBJECTIVE

Monogenic diabetes (MD) is rare and can often be confused with type 1 diabetes (T1D) in a pediatric cohort. We sought to determine clinical criteria that could optimally identify candidates for genetic testing of two common forms of MD that alter therapy: glucokinase (GCK) and hepatocyte nuclear factor 1 alpha (HNF1α).

RESEARCH DESIGN AND METHODS

We performed a retrospective chart review of 939 patients with a presumed diagnosis of T1D, 6 months-20 yr of age, and identified four clinical criteria that were unusual for T1D and could warrant further evaluation for MD: (i) negative pancreatic autoantibodies, (ii) evidence of prolonged endogenous insulin production, or (iii) strong family history of diabetes in multiple generations. One hundred and twenty-one patients were identified as having one or more of these high-risk clinical criteria and were offered screening for mutations in GCK and HNF1α; 58 consented for genetic testing.

RESULTS

Of 58 patients with presumed T1D who underwent genetic testing, four were found to have GCK and one had HNF1α. No patients with only one high-risk feature were found to have MD. Of 10 patients who had two or more high risk criteria, five had MD (50%).

CONCLUSION

A high frequency of MD from mutations in GCK/HNF1α may be identified among pediatric diabetic patients originally considered to have T1D by performing genetic testing on those patients with multiple clinical risk factors for MD.