Excess maternal transmission and familial aggregation of Type 2 diabetes in Sri Lanka

Parental Transmission Plays the Major Role in High Aggregation of Type 2 Diabetes in Iranian Families: Tehran Lipid and Glucose Study

BACKGROUND

This study is the first to evaluate familial aggregation, heritability and inheritance mode of type 2 diabetes (T2D) in Tehran Lipid Glucose Study (TLGS) participants as a representative sample of the Iranian population.

METHODS

From the ongoing family-based TLGS cohort, 13,741 individuals at least 20 years of age (mean ± standard deviation, 39.71±16.56) were assessed. After correcting family structures using genomic information from the Tehran Cardiometabolic Genetic Study, 2,594 constituent pedigrees were constructed. Familial aggregation was assessed based on genealogic index testing, familial intraclass correlation and positive family history. Family-based heritability was checked with 2 linear mixed models, including 2 different random components: the kinship matrix and the genomic relationship matrix. The mode of inheritance of T2D was investigated by complex segregation analysis (CSA).

RESULTS

Familial aggregation of T2D was significant (p<0.05), and family-based heritability showed a high degree of genetic variation in T2D between individuals at 65% (standard error, 0.034). Within first-degree relatives (parent/offspring and siblings), the likelihood of a parental affect was higher than in siblings (odds ratio, 4.11 vs 1.65). Family history of T2D among first-degree relatives was more noteworthy than for second-degree relatives (odds ratio, 3.84 vs 0.59). CSA revealed that the polygenic model is best to illustrate the mode of inheritance of T2D for TLGS participants.

CONCLUSIONS

Our findings demonstrate that the heritability of T2D with polygenic mode in the Iranian population is higher than the global average. We also found that T2D is transmitted equally into siblings, with parental affect the leading risk factor. These data suggest that policymakers should change individual-level to family-level prevention.

Heritability and Genetics of Type 2 Diabetes Mellitus in Sub-Saharan Africa: A Systematic Review and Meta-Analysis

OBJECTIVES

Sub-Saharan Africa (SSA) is observing an accelerating prevalence rate of type 2 diabetes mellitus (T2DM) influenced by gene-environment interaction of modifiable and nonmodifiable factors. We conducted a systematic review and meta-analysis on the heritability and genetic risk of T2DM in SSA.

METHODS

We reviewed all published articles on T2DM in SSA between January 2000 and December 2019 and available in PubMed, Scopus, and Web of Science. Studies that reported on the genetics and/or heritability of T2DM or indicators of glycaemia were included. Data extracted included the study design, records of family history, pattern and characteristics of inheritance, genetic determinants, and effects estimates.

RESULTS

The pattern and characteristics of T2DM heritability in SSA are preference for maternal aggregation, higher among first degree compared to second-degree relatives; early age-onset (<50 years), and inherited abnormalities of beta-cell function/mass. The overall prevalence of T2DM was 28.2% for the population with a positive family history (PFH) and 11.2% for the population with negative family history (NFH). The pooled odds ratio of the impact of PFH on T2DM was 3.29 (95% CI: 2.40-4.52). Overall, 28 polymorphisms in 17 genes have been investigated in relation with T2DM in SSA. Almost all studies used the candidate gene approach with most (45.8%) of genetic studies published between 2011 and 2015. Polymorphisms in ABCC8, Haptoglobin, KCNJ11, ACDC, ENPP1, TNF-α, and TCF7L2 were found to be associated with T2DM, with overlapping effect on specific cardiometabolic traits. Genome-wide studies identified ancestry-specific signals (AGMO-rs73284431, VT11A-rs17746147, and ZRANB3) and TCF7L2-rs7903146 as the only transferable genetic risk variants to SSA population. TCF7L2-rs7903146 polymorphism was investigated in multiple studies with consistent effects and low-moderate statistical heterogeneity. Effect sizes were modestly strong [odds ratio = 6.17 (95% CI: 2.03-18.81), codominant model; 2.27 (95% CI: 1.50-3.44), additive model; 1.75 (95% CI: 1.18-2.59), recessive model]. Current evidence on the heritability and genetic markers of T2DM in SSA populations is limited and largely insufficient to reliably inform the genetic architecture of T2DM across SSA regions.

Maternal vs paternal diabetes: The parental history is different in younger onset versus older onset type 2 diabetes

BACKGROUND

A number of previous studies exploring family history of type 2 diabetes have reported a predominance of maternal diabetes. These studies have not explicitly compared parental history of diabetes across the spectrum of disease onset from youth to later adulthood.

METHODS

Family history data from 11,467 patients with type 2 diabetes were extracted from the RPA Diabetes Centre database. Parental histories of diabetes were compared across a range of age of diagnosis strata (15-<30, 30-<40, 40-<50, 50-<60 and 60-<70 years). For the young-onset group (diagnosed between 15 and 30 years of age), associations between parental history of diabetes and the presence of cardio-metabolic risk factors and diabetic complications were also explored.

RESULTS

For the total cohort and within each age of diagnosis strata, more individuals reported maternal history than paternal history of diabetes. The young-onset group demonstrated the highest prevalence of any parental history of diabetes (60.7%), the highest combined maternal and paternal history (15.8%) and the smallest differential between maternal (25.1%) and paternal (19.7%) history of diabetes. Within the young-onset group, no significant association between parental history and cardio-metabolic risk factors or diabetic complications were identified after a median of 15.0 years of diabetes exposure.

CONCLUSION

Overall, our results demonstrate a consistent maternal excess of diabetes which could be consistent with an underlying epigenetic effect. However, the differential between maternal and paternal history is significantly lower in the young-onset group. Earlier emergence of type 2 diabetes may therefore reflect a different interaction and impact of genetic and environmental factors.

Effect of Family History of Diabetes on Hemoglobin A1c Levels among Individuals with and without Diabetes: The Dong-gu Study

PURPOSE

We investigated associations between family history of diabetes (FHD) and hemoglobin A1c (HbA1c) level, among people with and without diabetes.

MATERIALS AND METHODS

In total, 7031 people without diabetes and 1918 people with diabetes who participated in the Dong-gu Study were included. Data on FHD in first-degree relatives (father, mother, and siblings) were obtained. Elevated HbA1c levels in people without diabetes and high HbA1c levels in people with diabetes were defined as the highest quintiles of HbA1c ≥5.9% and ≥7.9%, respectively.

RESULTS

In people without diabetes, the odds of elevated HbA1c levels [odds ratio (OR) 1.34, 95% confidence interval (CI) 1.13-1.59] were significantly greater in people with any FHD than in those without. Specifically, the odds of elevated HbA1c levels in people without diabetes with an FHD involving siblings were greater than in those without an FHD involving siblings. Additionally, in people with diabetes, the odds of high HbA1c levels (OR 1.33, 95% CI 1.02-1.72) were greater in people with any FHD than in those without such history. Moreover, people with diabetes with maternal FHD had increased odds of high HbA1c levels.

CONCLUSION

FHD was associated not only with high HbA1c levels in people with diabetes, but also with elevated HbA1c levels in people without diabetes.

Maternal history of diabetes is associated with increased cardiometabolic risk in Chinese

OBJECTIVE

Positive family history is associated with increased type 2 diabetes (T2D) risk, and reflects both genetic and environmental risks. Several studies have suggested an excess maternal transmission of T2D, although the underlying mechanism is unknown. We aimed to examine the association between maternal diabetes and cardiometabolic risk in the offspring.

METHODS

Parental history of diabetes and clinical data including anthropometric traits, fasting plasma glucose and insulin (FPG, FPI), blood pressure and lipid profile were collected from 2581 unrelated Chinese offspring (2026 adolescents from a population-based school survey and 555 adults from a community-based health screening programme). A subset of subjects (n=834) underwent oral glucose tolerance test to measure the glucose and insulin concentrations at 0, 15, 30, 60 and 120 min for evaluation of the areas under the curve (AUC) of glucose and insulin at 0-120 min, homoeostasis model assessment of insulin resistance (HOMA-IR) and bell-cell function, insulinogenic index, insulin sensitivity index (ISI) and oral disposition index (DI).

RESULTS

A positive parental history of diabetes was associated with increased risk of obesity (odd ratios (OR) (95% confidence interval (CI))=1.48 (1.10-2.00)), central obesity (OR (95% CI)=1.67 (1.21-2.32)), higher FPI, HOMA-IR, 2-h insulin, AUC of glucose at 0-120 min, triglycerides, reduced ISI and DI. Compared with individuals without parental diabetes, offspring with diabetic mother had significantly increased risk of obesity (OR (95% CI)=1.59 (1.07-2.35)), central obesity (OR (95% CI)=1.88 (1.23-2.88)), higher glucose levels and BP, were more insulin resistant but also had impaired first-phase insulin response and worse lipid profile. However, paternal history of diabetes had no effect on any of the studied traits, except higher body mass index, waist circumference in females and FPG.

CONCLUSIONS

Our findings suggested that maternal history of diabetes conferred increased risk of cardiometabolic abnormalities, and was associated with both insulin resistance and impaired first-phase insulin secretion. Further investigation into the mechanism of transgenerational diabetes is warranted.

Familial Clustering of Type 2 Diabetes among Omanis

OBJECTIVE

The aim of this study was to screen Omani individuals for the familial aggregation of type 2 diabetes mellitus.

METHODS

A random cohort of 1182 Omani individuals visiting the Family Medicine Clinic at Sultan Qaboos University Hospital (SQUH), Muscat, Oman, for regular medical checkup, aged ≥40 years, were sampled. Patients were categorized into three groups: (1) individuals who claim not to have diabetes and had no family history of diabetes; (2) individuals who claim not to have diabetes but had family history of diabetes; (3) individuals with diabetes. Only 16% of these Omani individuals had no diabetes and no family history of diabetes. Another separate random cohort of 234 Omani type 2 diabetes mellitus patients, from the Diabetes Clinic at SQUH, were interviewed and questioned about their family history of type 2 diabetes mellitus.

RESULTS

Ninety five percent of the patients had a family history of diabetes. Eighty percent had first degree relatives with diabetes and 46% had second degree relatives with diabetes. At least one parent with diabetes was reported among 55% of these diabetics, while maternal diabetes (55%) was found to be higher than paternal diabetes (47%). However, only 15% had both parents with diabetes. Furthermore, almost half of the 234 diabetics were having at least one of the following relatives with diabetes: brother, sister, aunt or an uncle.

CONCLUSION

The findings of this study confirm familial aggregation of diabetes among the Omani population. Compared to other populations, familial aggregation of type 2 diabetes mellitus among Omanis is relatively very high, and is perhaps due to the very high degree of consanguinity among Omanis. Since almost everyone seems to have a genetic predisposition to diabetes, the dramatic lifestyle changes over the past 25 years, could tip the population into an epidemic of type 2 diabetes mellitus.

Developmental origins of type 2 diabetes in aboriginal youth in Canada: it is more than diet and exercise

Type 2 diabetes mellitus (T2DM) is classically viewed as a disease of adults caused by poor nutrition, physical inactivity, and obesity. However, with increasing awareness of the heterogeneity of T2DM, new risk factors are being identified that add complexity. Some of these new risk factors have been identified in Canadian people with Aboriginal Oji-Cree heritage, a group that demonstrates one of the highest rates of T2DM in the world. This high prevalence may be due to the rapid change, over the past 50 years, away from their traditional way of life on the land. Another environmental change is the increased rate of pregnancies complicated by obesity, gestational diabetes, or T2DM, resulting in more children being exposed to an abnormal intrauterine environment. Furthermore, the Oji-Cree of central Canada possesses the unique HNF-1α G319S polymorphism associated with reduced insulin secretion. We propose that intrauterine exposure to maternal obesity and T2DM, associated with the HNF-1α G319S polymorphism, results in fetal programming that accelerates the progression of early-onset T2DM. This paper describes the evolution of T2DM in children with a focus on the Oji-Cree people over the past 25 years and the unique prenatal and postnatal gene-environment interaction causing early-onset T2DM.

Lack of association between the angiotensin-converting enzyme gene (I/D) polymorphism and diabetic nephropathy in Tunisian type 2 diabetic patients

Objective. The aim of the present study was to investigate whether the angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphism is associated with diabetic nephropathy and type 2 diabetes in the Tunisian population.

Design. A case-control study was conducted among 141 unrelated type 2 diabetic patients with (90 patients) or without nephropathy (51 patients) and 103 non-diabetic controls with normal fasting blood glucose. Genotyping was performed using a nested polymerase chain reaction amplification in order to identify correctly heterozygous individuals.

Results. The distribution of DD, ID and II genotypes did not significantly differ between type 2 diabetic patients with or without nephropathy (DD: 44%; ID: 46%; II: 10% vs. DD: 41%; ID: 47 %; II: 12%, respectively).There was also no significant statistical difference between the genotype distribution and allele frequencies of the (I/D) polymorphism in all type 2 diabetic subjects compared to non-diabetic controls with normal fasting blood glucose (DD: 43%; ID: 46%; II: 11% vs. DD: 37%; ID: 48% ;II: 15%, respectively).

Conclusions. In the present preliminary study, the (I/D) polymorphis within the ACE gene is likely not associated with diabetic nephropathy nor with type 2 diabetes in the Tunisian studied population.

Familial history of type 2 diabetes in patients from Southern Brazil and its influence on the clinical characteristics of this disease

OBJECTIVE

To investigate the presence of maternal and paternal history of type 2 diabetes mellitus (DM) in relatives of 644 type 2 diabetic patients from Southern Brazil, and also to evaluate its influence on the clinical characteristics of this disease.

PATIENTS AND METHODS

Familial history of type 2 DM was investigated by a questionnaire. The maternal and paternal history was investigated over two generations. Complete data sets on familial history were obtained from 396 patients.

RESULTS

In general, 76.6% of the patients reported at least one first-degree affected relative. Besides, 31.6% of the patients reported a maternal history of type 2 DM and 12.6% reported a paternal history. Patients with maternal and/or paternal history presented a lower age at type 2 DM diagnosis when compared to patients without familial history. In addition, patients with only paternal history presented a higher frequency of hypertension than patients with no familial history.

CONCLUSIONS

This study suggests that there is a significant maternal effect in the transmission of type 2 DM in Southern Brazil, and that most of the clinical characteristics of this disease do not differ between patients with or without familial history of type 2 DM.

Familial aggregation and excess maternal transmission of type 2 diabetes in Tunisia

AIM

To evaluate the degree of familial aggregation of type 2 diabetes mellitus in Tunisia and to investigate transmission patterns of the disease and their relationships with patients' clinical profiles.

METHODS

Family history of diabetes and clinical data were collected for 132 unrelated type 2 diabetic Tunisian patients. Diabetes status was recorded for first degree relatives (parents, siblings) and second degree relatives (aunts and uncles from both maternal and paternal sides). Information about family history of diabetes was gathered for a total of 1767 individuals.

RESULTS

Familial aggregation of type 2 diabetes was prominent and more important among first degree relatives than among second degree relatives (p = 0.01). Among studied subjects, 70% reported at least one relative with diabetes and 34% had at least one parent with diabetes. Diabetes was more frequent among mothers than fathers of probands (p = 0.03). This maternal effect extends to second degree relatives as diabetes was more common among maternal than paternal aunts and uncles (p = 0.01). There is no significant difference in clinical and metabolic profiles between patients according to transmission patterns of the disease.

CONCLUSION

These results suggest familial aggregation and excess maternal transmission of type 2 diabetes in the Tunisian studied population.

Epidemiology of childhood type 2 diabetes in the developing world

Type 2 diabetes in the young is an increasing problem with potentially serious outcomes. Our understanding of the worldwide burden of this condition is incomplete, with many studies adopting different methodologies to assess the condition and reporting on specific communities or ethnic groups. Most of the data come from developed nations, with few studies from developing nations. The purpose of this review is to bring together the available data on type 2 diabetes in the young from the developing world, in order to highlight deficiencies in the knowledge of the condition and also to promote strategies to deal with it. Noted also are some of the factors associated with the condition, such as family history, genetic influences, intrauterine environment as well as the importance of birth weight, insulin resistance, obesity, and development of complications. These are of relevance in both developed and developing nations.