Common genetic basis between type 1 and type 2 diabetes mellitus indicated by interview-based assessment of family history

β-Cell failure in diabetes: Common susceptibility and mechanisms shared between type 1 and type 2 diabetes

Diabetes mellitus is etiologically classified into type 1, type 2 and other types of diabetes. Despite distinct etiologies and pathogenesis of these subtypes, many studies have suggested the presence of shared susceptibilities and underlying mechanisms in β-cell failure among different types of diabetes. Understanding these susceptibilities and mechanisms can help in the development of therapeutic strategies regardless of the diabetes subtype. In this review, we discuss recent evidence indicating the shared genetic susceptibilities and common molecular mechanisms between type 1, type 2 and other types of diabetes, and highlight the future prospects as well.

Heritability, parental transmission and environment correlation of pediatric-onset type 2 diabetes mellitus and metabolic syndrome-related traits

AIM

To estimate the heritability, parental transmission and environmental contributions to the phenotypic variation in type 2 diabetes mellitus and metabolic syndrome-related traits in families of Mexican children and adolescents.

METHODS

We performed a cross-sectional study of 184 tri-generational pedigrees with a total of 1160 individuals (99 families with a type 2 diabetes mellitus proband before age 19). The family history of type 2 diabetes mellitus in three generations was obtained by interview. Demographic, anthropometric, biochemical and lifestyle information was corroborated in parents and offspring. We obtained correlations for metabolic traits between relative pairs, and variance component methods were used to determine the heritability and environmental components.

RESULTS

The heritability of early-onset of type 2 diabetes mellitus was 0.50 (p<1.0e-7). The heritability was greater than 0.5 for hypertension, hypoalphalipoproteinemia, hypercholesterolemia, body mass index, waist circumference, blood pressure, 2-h insulin, and cholesterol (p<0.001). In contrast, we observed a high environmental correlation (>0.50) for blood pressure, HbA1c and HDL-cholesterol after multivariate adjustment (p<0.05). Several traits, such as type 2 diabetes mellitus and insulin resistance, were significantly correlated only through the mother and others, such as hypertriglyceridemia, were significantly correlated only through the father.

CONCLUSION

This study demonstrates that type 2 diabetes mellitus and metabolic syndrome-related traits are highly heritable among Mexican children and adolescents. Furthermore, several cardiometabolic factors have strong heritability and/or high environmental contributions that highlight the complex architecture of these alterations.

Synthesis and biological evaluation of 2'-oxo-2,3-dihydro-3'H- spiro[chromene-4,5'-[1,3]oxazolidin]-3'yl]acetic acid derivatives as aldose reductase inhibitors

Aldose reductase (ARL2) is the first enzyme in the polyol pathway which catalyzes the NADPH-dependent reduction of glucose to sorbitol. Its involvement on diabetic complications makes this enzyme a challenge therapeutic target widely investigated to limit and/or prevent them. On this basis, a limited series of 4-spiro-oxazolidinone-benzopyran derivatives (1-7) were synthesized to evaluate them as potential ARL2 inhibitors. The activity was determined spectrophotometrically by monitoring the oxidation of NADPH catalyzed by ALR2. Within the series of compounds, the 4-methoxy derivative 1b showed to be the most active compound, exhibiting inhibitory levels in the submicromolar range. In addition, the activity against the aldehyde reductase isoform (ARL1) was also evaluated. Unlike sorbinil (reference drug) that lack of selectivity towards the two enzyme all the tested compounds resulted to be devoid of ARL1 inhibitory activity (IC(50) > 10 µM), thus proving to be selective.

Parental diabetes status reveals association of mitochondrial DNA haplogroup J1 with type 2 diabetes

Background

Although mitochondrial dysfunction is consistently manifested in patients with Type 2 Diabetes mellitus (T2DM), the association of mitochondrial DNA (mtDNA) sequence variants with T2DM varies among populations. These differences might stem from differing environmental influences among populations. However, other potentially important considerations emanate from the very nature of mitochondrial genetics, namely the notable high degree of partitioning in the distribution of human mtDNA variants among populations, as well as the interaction of mtDNA and nuclear DNA-encoded factors working in concert to govern mitochondrial function. We hypothesized that association of mtDNA genetic variants with T2DM could be revealed while controlling for the effect of additional inherited factors, reflected in family history information.

Methods

To test this hypothesis we set out to investigate whether mtDNA genetic variants will be differentially associated with T2DM depending on the diabetes status of the parents. To this end, association of mtDNA genetic backgrounds (haplogroups) with T2DM was assessed in 1055 Jewish patients with and without T2DM parents ('DP' and 'HP', respectively).

Results

Haplogroup J1 was found to be 2.4 fold under-represented in the 'HP' patients (p = 0.0035). These results are consistent with a previous observation made in Finnish T2DM patients. Moreover, assessing the haplogroup distribution in 'DP' versus 'HP' patients having diabetic siblings revealed that haplogroup J1 was virtually absent in the 'HP' group.

Conclusion

These results imply the involvement of inherited factors, which modulate the susceptibility of haplogroup J1 to T2DM.

Family history of diabetes, autoimmunity, and risk factors for cardiovascular disease among children with diabetes in the SEARCH for Diabetes in Youth Study

BACKGROUND

While type 1 diabetes and type 2 diabetes (T2D) are considered etiologically distinct, mixed features of autoimmunity and insulin resistance are increasingly common. We explored a familial contribution to this admixture by evaluating diabetes family history (FH) and its relationship to diabetes type, ethnicity, age at diagnosis, and cardiovascular risk factors in SEARCH for Diabetes in Youth Study participants.

METHODS

Diabetes FH was assessed by questionnaire, with FH categories defined by relative's(s') age at diagnosis as follows: <25 (early FH), >/=25 (later FH), and both <25 and >/=25 (mixed FH). Diabetes type was classified based on a biochemical algorithm using diabetes autoantibodies and fasting C-peptide (FCP).

RESULTS

A positive FH was common in all diabetes types, particularly T2D (83%). Minorities were more likely to have a positive FH than non-Hispanic Whites [odds ratio (OR) 1.96, 95% confidence interval (CI) 1.69-2.27]. The likelihood of having an early FH decreased with age at diagnosis (OR 0.95, 95% CI 0.93-0.98), and the likelihood of having a later/mixed or any positive FH increased with age (OR 1.03, 95% CI 1.01-1.04; OR 1.03, 95% CI 1.02-1.05, respectively). Higher FCP concentrations and less desirable values for almost all cardiovascular risk factors were associated with a later/mixed FH. The association between a later/mixed FH and FCP, body mass index, waist circumference, triglycerides, and high-density lipoprotein remained significant in a subgroup of autoimmune participants.

CONCLUSIONS

Later FH confers cardiovascular risk factors in diabetic youth, including those youth with islet cell autoimmunity. This characterization of diabetes FH may provide a better understanding of familial contributors to diabetes.

Permeability characteristics of novel aldose reductase inhibitors using rat jejunum in vitro

The aim of this study was to estimate in vivo permeability and bioavailability of epalrestat and newly synthesized compounds with possible therapeutic activity as aldose enzyme inhibitors (ARIs). For this purpose permeability in vitro using rat jejunum mounted in side-by-side diffusion cells was determined. Tested substances were found to be low and moderately permeable and some of them were also substrates for efflux transporters. It was shown, that the higher efflux for some derivatives was due to MRP-2, but not Pgp involvement. Tested ARIs do not share the same efflux transporter with epalrestat, the only ARI currently on the market in Japan. The most permeable compound, a 2,6-difluoro-4-pyrrol-1ylphenol derivative, is not a substrate for efflux transporters and would therefore be the most promising lead compound for further investigation of potent ARIs.