Maternal transmission of diabetes

The genomic mosaic of mitochondrial dysfunction: Decoding nuclear and mitochondrial epigenetic contributions to maternally inherited diabetes and deafness pathogenesis

Aims

Maternally inherited diabetes and deafness (MIDD) is a complex disorder characterized by multiorgan clinical manifestations, including diabetes, hearing loss, and ophthalmic complications. This pilot study aimed to elucidate the intricate interplay between nuclear and mitochondrial genetics, epigenetic modifications, and their potential implications in the pathogenesis of MIDD.

Main methods

A comprehensive genomic approach was employed to analyze a Sicilian family affected by clinically characterized MIDD, negative to the only known causative m.3243 A > G variant, integrating whole-exome sequencing and whole-genome bisulfite sequencing of both nuclear and mitochondrial analyses.

Key findings

Rare and deleterious variants were identified across multiple nuclear genes involved in retinal homeostasis, mitochondrial function, and epigenetic regulation, while complementary mitochondrial DNA analysis revealed a rich tapestry of genetic diversity across genes encoding components of the electron transport chain and ATP synthesis machinery. Epigenetic analyses uncovered significant differentially methylated regions across the genome and within the mitochondrial genome, suggesting a nuanced landscape of epigenetic modulation.

Significance

The integration of genetic and epigenetic data highlighted the potential crosstalk between nuclear and mitochondrial regulation, with specific mtDNA variants influencing methylation patterns and potentially impacting the expression and regulation of mitochondrial genes. This pilot study provides valuable insights into the complex molecular mechanisms underlying MIDD, emphasizing the interplay between nucleus and mitochondrion, tracing the way for future research into targeted therapeutic interventions and personalized approaches for disease management.

Conplastic strains for identification of retrograde effects of mitochondrial dna variation on cardiometabolic traits in the spontaneously hypertensive rat

Mitochondrial retrograde signaling is a pathway of communication from mitochondria to the nucleus. Recently, natural mitochondrial genome (mtDNA) polymorphisms (haplogroups) received increasing attention in the pathophysiology of human common diseases. However, retrograde effects of mtDNA variants on such traits are difficult to study in humans. The conplastic strains represent key animal models to elucidate regulatory roles of mtDNA haplogroups on defined nuclear genome background. To analyze the relationship between mtDNA variants and cardiometabolic traits, we derived a set of rat conplastic strains (SHR-mtBN, SHR-mtF344 and SHR-mtLEW), harboring all major mtDNA haplotypes present in common inbred strains on the nuclear background of the spontaneously hypertensive rat (SHR). The BN, F344 and LEW mtDNA differ from the SHR in multiple amino acid substitutions in protein coding genes and also in variants of tRNA and rRNA genes. Different mtDNA haplotypes were found to predispose to various sets of cardiometabolic phenotypes which provided evidence for significant retrograde effects of mtDNA in the SHR. In the future, these animals could be used to decipher individual biochemical components involved in the retrograde signaling.

Maternal Roux-en-Y gastric bypass surgery reduces lipid deposition and increases UCP1 expression in the brown adipose tissue of male offspring

Maternal obesity induced by cafeteria diet (CAF) predisposes offspring to obesity and metabolic diseases, events that could be avoided by maternal bariatric surgery (BS). Herein we evaluated whether maternal BS is able to modulate brown adipose tissue (BAT) morphology and function in adult male rats born from obese female rats submitted to Roux-en-Y gastric bypass (RYGB). For this, adult male rat offspring were obtained from female rats that consumed standard diet (CTL), or CAF diet, and were submitted to simulated operation or RYGB. Analysis of offspring showed that, at 120 days of life, the maternal CAF diet induced adiposity and decreased the expression of mitochondrial Complex I (CI) and Complex III (CIII) in the BAT, resulting in higher accumulation of lipids than in BAT from offspring of CTL dams. Moreover, maternal RYGB increased UCP1 expression and prevented excessive deposition of lipids in the BAT of adult male offspring rats. However, maternal RYGB failed to reverse the effects of maternal diet on CI and CIII expression. Thus, maternal CAF promotes higher lipid deposition in the BAT of offspring, contributing to elevated adiposity. Maternal RYGB prevented obesity in offspring, probably by increasing the expression of UCP1.

Mother or Father: Who Is in the Front Line? Mechanisms Underlying the Non-Genomic Transmission of Obesity/Diabetes via the Maternal or the Paternal Line

Extensive epidemiological and experimental evidence have shown that exposure to an adverse intrauterine environment as observed in offspring of pregnancies complicated by obesity or diabetes, can program susceptibility to metabolic, endocrine and cardiovascular disorders later in life. Although most studies have concentrated on the maternal environment, it is also becoming evident that paternal exposure to obesity or diabetes can result in the later development of metabolic disorders in the offspring. Such programmed effects might not be limited to the first directly exposed generation, but could be transmitted to subsequent generations. This suggests the existence of mechanisms by which metabolic changes in parental phenotype are transmissible to offspring. The mechanisms which underpin the transmission of the programmed effects across generations are still unclear. However, epigenetic regulation of transcription has emerged as a strong candidate for mediating the heritability of metabolic diseases. Here, we review the most relevant evidence from human and animal studies showing transmission of programming effects of obesity or diabetes across generations, and the current mechanisms underlying either maternal or paternal influences on the metabolic status of offspring.

Familial History of Diabetes is Associated with Poor Glycaemic Control in Type 2 Diabetics: A Cross-sectional Study

To investigate the association of familial history (FH) of diabetes with the glycaemic control status of patients with type 2 diabetes (T2D), a cross-sectional study using stratified cluster sampling was conducted with 20,340 diabetic patients in Jiangsu, China. In total, 21.3% of the subjects reported a FH of diabetes. Patients with a FH of diabetes showed a higher risk of poor glycaemic control (59.7%) than those without a diabetic FH (49.8%), with an odds ratio (OR) of 1.366 (P < 0.001). Glycaemic control status did not significantly differ between the T2D patients with parental FH and those with sibling FH. Compared with patients with paternal FH, patients with maternal FH had a higher risk of poor glycaemic control (OR = 1.611, P = 0.013). Stratified analyses showed that a FH of diabetes was significantly associated with poor glycaemic control among T2D patients with a low education level (P < 0.05). In the <60 years old, overweight, and low level of physical activity groups, patients with a maternal history of diabetes showed a higher risk of poor glycaemic control than those without a FH (P < 0.05). In conclusion, FH of diabetes, especially a maternal history, had an independently adverse effect on the glycaemic control of T2D patients.

Association between parental history of diabetes and the incidence of type 2 diabetes mellitus differs according to the sex of the parent and offspring's body weight: A finding from a Japanese worksite-based cohort study

OBJECTIVE

To investigate differences in the association of parental history of diabetes with the risk of type 2 diabetes mellitus (T2DM) in the offspring according to the sex of the parent and the offspring's body weight.

METHODS

A prospective cohort study of 4446 middle-aged non-diabetic Japanese men and women were followed in Aichi Prefecture, central Japan, from 2002 to 2011. Subjects were categorized by their self-reported parental history of diabetes ("no parental history," "father only," "mother only," and "both"). The association of parental history of diabetes and incidence in the offspring was examined according to overweight status adjusted for age, sex, birth weight, smoking, alcohol consumption, physical activity, total energy intake, body mass index, and number of metabolic syndrome components.

RESULTS

During follow-up (median 8.9 years), 277 subjects developed T2DM. Parental history of diabetes was positively associated with T2DM incidence. However, stratified analysis by overweight status revealed that only maternal history was associated with increased T2DM incidence in non-overweight subjects (hazard ratio=2.35, 95% confidence interval: 1.41-3.91). While in overweight subjects, paternal history was significantly associated with higher T2DM incidence (hazard ratio=1.98, 95% confidence interval: 1.19-3.28).

CONCLUSIONS

Our results suggest that parental history of diabetes mellitus is associated with the incidence of T2DM in offspring differently according to the sex of the affected parent and the offspring's body weight.

A first-degree relative with diabetes mellitus is an important risk factor for rural Thai villagers to develop type 2 diabetes mellitus

The screening of 609 villagers in rural areas of northeastern Thailand resulted in the detection of 110 (18.1%) new cases of type 2 diabetes (T2DM). The diagnoses were made on the basis of a glycated hemoglobin (HbA1c) value ≤ 6.5%. Among all those screened, 243 (40%) reported having a father or mother with T2DM. Among the new cases, 66 (60%) reported a first-degree relative, predominantly their mothers, who had the disease. Together with age and the body mass index, a mother or father with DM was strong risk factor for the development of T2DM (adjusted odds ratio = 2.9, 95% confidence interval = 1.84-4.57) when compared with the absence of a first-degree relative with DM. It is concluded that family history of a first-degree relative is an important additional information that might improve the validity of the screening procedure.

Paternal or maternal history of cardiovascular disease and the risk of cardiovascular disease in offspring. A systematic review and meta-analysis

BACKGROUND

Parental history of cardiovascular disease (CVD) is an established risk factor for the development of CVD in offspring. Several studies have suggested that a maternal transmission of CVD is more important for the development of CVD than paternal transmission.

METHODS

A systematic search and meta-analysis were conducted, using the Medline and Embase databases. Included were cohort, case-control and cross-sectional studies (n=26) focusing on the relation between paternal and maternal histories of cardiovascular disease and offspring CVD (myocardial infarction, stroke or cardiovascular mortality). The pooled estimates were calculated using a random-effects model.

RESULTS

The pooled OR of CVD in offspring having a positive paternal history of CVD compared to not having a positive parental history was 1.91 (95% CI 1.56-2.34; I(2)53%), the RR1.54 (95% CI 1.33-1.77; I(2)96%). The OR of a maternal history was 2.16 (95% CI 1.71-2.74; I(2)50%), RR1.59 (95% CI 1.38-1.84; I(2)90%). Regarding different age limits, a maternal history <50 years (3.15, 95% CI 2.18-4.55) and paternal history <55 years (2.82, 95% CI 2.25-3.54) were associated with the highest cardiovascular risk. Additional analyses for sons demonstrated an estimate for a positive paternal history of 1.55 (95% CI 1.39-1.71; I(2)74%) and 1.56 (95% CI 1.46-1.67; I(2)16%) for maternal history. For daughters, the estimate for paternal history was 1.48 (95% CI 1.26-1.74; I(2)73%) and 1.79 (95% CI 1.50-2.13; I(2)68%) for maternal history .

CONCLUSIONS

The conferred risk of CVD in offspring was not substantially different between positive paternal and maternal histories of CVD, the highest risk was observed for maternal history <50years. Since a positive parental history of CVD involves an increased cardiovascular risk, parental history inquiry is useful in clinical practice. No distinction has to be made whether the affected parent is the mother or the father.

Maternal diabetes, programming of beta-cell disorders and intergenerational risk of type 2 diabetes

A substantial body of evidence suggests that an abnormal intra-uterine milieu elicited by maternal metabolic disturbances as diverse as malnutrition, placental insufficiency, diabetes and obesity may be able to programme susceptibility of the foetus to later develop chronic degenerative diseases such as obesity, hypertension, cardiovascular diseases and type 2 diabetes (T2D). As insulin-producing cells have been placed centre stage in the development of T2D, this review examines developmental programming of the beta-cell mass (BCM) in various rodent models of maternal protein restriction, calorie restriction, overnutrition and diabetes. The main message is that whatever the initial maternal insult (F0 generation) and whether alone or in combination, it gives rise to the same programmed BCM outcome in the daughter generation (F1). The altered BCM phenotype in F1 females prohibits normal BCM adaptation during pregnancy and, thus, diabetes (gestational diabetes) ensues. This gestational diabetes is then passed from one generation (F1) to the next (F2, F3 and so on). This review highlights a number of studies that have identified epigenetic mechanisms that may contribute to altered BCM development and beta-cell failure, as observed in diabetes. In addition to their role in instilling the programmed defect, these non-genomic mechanisms may also be involved in its intergenerational transmission.

Familial early onset of type-2 diabetes mellitus and its complications

Background:

Globally, the prevalence of chronic, non-communicable diseases is increasing at an alarming rate. Furthermore, approximately 197 million people worldwide have impaired glucose tolerance. Consequently, diabetes is rapidly emerging as a global health problem that threatens to assume a pandemic level by 2030. In Indian population, genetic predisposition to trigger diabetes at an early age as compared to western counterpart has been focused very much.

Aim:

To gain further insight into the positive correlation between the diabetes and family history was the objective of this study.

Materials and Methods:

Patients attending the Diabetes Centre, K.L.E.S Dr. Prabhakar. Kore Hospital and Medical Research Centre; J. N. Medical College; KLE University Belgaum, Karnataka- India, were recruited, diagnosed and analyzed as per WHO criteria.

Results:

The prevalence of diabetes was higher among patients with diabetic mother (25.6%) compared to patients with diabetic father (21.2%) and there was early onset of type -2 diabetes among patients having both parents with diabetic when compared to other patients.

Conclusion:

Based on the present observation, it would be appropriate to emphasize again that a strong family history for diabetes, would signal at an early age, the onset of diabetes perhaps with its complications.

Mitochondrial DNA sequence variation in Finnish patients with matrilineal diabetes mellitus

BACKGROUND

The genetic background of type 2 diabetes is complex involving contribution by both nuclear and mitochondrial genes. There is an excess of maternal inheritance in patients with type 2 diabetes and, furthermore, diabetes is a common symptom in patients with mutations in mitochondrial DNA (mtDNA). Polymorphisms in mtDNA have been reported to act as risk factors in several complex diseases.

FINDINGS

We examined the nucleotide variation in complete mtDNA sequences of 64 Finnish patients with matrilineal diabetes. We used conformation sensitive gel electrophoresis and sequencing to detect sequence variation. We analysed the pathogenic potential of nonsynonymous variants detected in the sequences and examined the role of the m.16189 T>C variant. Controls consisted of non-diabetic subjects ascertained in the same population. The frequency of mtDNA haplogroup V was 3-fold higher in patients with diabetes. Patients harboured many nonsynonymous mtDNA substitutions that were predicted to be possibly or probably damaging. Furthermore, a novel m.13762 T>G in MTND5 leading to p.Ser476Ala and several rare mtDNA variants were found. Haplogroup H1b harbouring m.16189 T > C and m.3010 G > A was found to be more frequent in patients with diabetes than in controls.

CONCLUSIONS

Mildly deleterious nonsynonymous mtDNA variants and rare population-specific haplotypes constitute genetic risk factors for maternally inherited diabetes.

Mitochondrial diabetes in children: seek and you will find it

Maternally Inherited Diabetes and Deafness (MIDD) is a rare form of diabetes due to defects in mitochondrial DNA (mtDNA). 3243 A>G is the mutation most frequently associated with this condition, but other mtDNA variants have been linked with a diabetic phenotype suggestive of MIDD. From 1989 to 2009, we clinically diagnosed mitochondrial diabetes in 11 diabetic children. Diagnosis was based on the presence of one or more of the following criteria: 1) maculopathy; 2) hearing impairment; 3) maternal heritability of diabetes/impaired fasting glucose and/or hearing impairment and/or maculopathy in three consecutive generations (or in two generations if 2 or 3 members of a family were affected). We sequenced the mtDNA in the 11 probands, in their mothers and in 80 controls. We identified 33 diabetes-suspected mutations, 1/33 was 3243A>G. Most patients (91%) and their mothers had mutations in complex I and/or IV of the respiratory chain. We measured the activity of these two enzymes and found that they were less active in mutated patients and their mothers than in the healthy control pool. The prevalence of hearing loss (36% vs 75–98%) and macular dystrophy (54% vs 86%) was lower in our mitochondrial diabetic adolescents than reported in adults. Moreover, we found a hitherto unknown association between mitochondrial diabetes and celiac disease. In conclusion, mitochondrial diabetes should be considered a complex syndrome with several phenotypic variants. Moreover, deafness is not an essential component of the disease in children. The whole mtDNA should be screened because the 3243A>G variant is not as frequent in children as in adults. In fact, 91% of our patients were mutated in the complex I and/or IV genes. The enzymatic assay may be a useful tool with which to confirm the pathogenic significance of detected variants.

Nonsynonymous variants in mt-Nd2, mt-Nd4, and mt-Nd5 are linked to effects on oxidative phosphorylation and insulin sensitivity in rat conplastic strains

Common inbred strains of the laboratory rat can be divided into four different mitochondrial DNA haplotype groups represented by the SHR, BN, LEW, and F344 strains. In the current study, we investigated the metabolic and hemodynamic effects of the SHR vs. LEW mitochondrial genomes by comparing the SHR to a new SHR conplastic strain, SHR-mt(LEW); these strains are genetically identical except for their mitochondrial genomes. Complete mitochondrial DNA (mtDNA) sequence analysis comparing the SHR and LEW strains revealed gene variants encoding amino acid substitutions limited to a single mitochondrial enzyme complex, NADH dehydrogenase (complex I), affecting subunits 2, 4, and 5. Two of the variants in the mt-Nd4 subunit gene are located close to variants known to be associated with exercise intolerance and diabetes mellitus in humans. No variants were found in tRNA or rRNA genes. These variants in mt-Nd2, mt-Nd4, and mt-Nd5 in the SHR-mt(LEW) conplastic strain were linked to reductions in oxidative and nonoxidative glucose metabolism in skeletal muscle. In addition, SHR-mt(LEW) conplastic rats showed increased serum nonesterified fatty acid levels and resistance to insulin stimulated incorporation of glucose into adipose tissue lipids. These results provide evidence that inherited variation in mitochondrial genes encoding respiratory chain complex I subunits, in the absence of variation in the nuclear genome and other confounding factors, can influence glucose and lipid metabolism when expressed on the nuclear genetic background of the SHR strain.

Early-life origins of type 2 diabetes: fetal programming of the beta-cell mass

A substantial body of evidence suggests that an abnormal intrauterine milieu elicited by maternal metabolic disturbances as diverse as undernutrition, placental insufficiency, diabetes or obesity, may program susceptibility in the fetus to later develop chronic degenerative diseases, such as obesity, hypertension, cardiovascular diseases and diabetes. This paper examines the developmental programming of glucose intolerance/diabetes by disturbed intrauterine metabolic condition experimentally obtained in various rodent models of maternal protein restriction, caloric restriction, overnutrition or diabetes, with a focus on the alteration of the developing beta-cell mass. In most of the cases, whatever the type of initial maternal metabolic stress, the beta-cell adaptive growth which normally occurs during gestation, does not take place in the pregnant offspring and this results in the development of gestational diabetes. Therefore gestational diabetes turns to be the ultimate insult targeting the offspring beta-cell mass and propagates diabetes risk to the next generation again. The aetiology and the transmission of spontaneous diabetes as encountered in the GK/Par rat model of type 2 diabetes, are discussed in such a perspective. This review also discusses the non-genomic mechanisms involved in the installation of the programmed effect as well as in its intergenerational transmission.

The influence of parental history of diabetes and offspring birthweight on offspring glucose metabolism in adulthood

BACKGROUND

Links are well established between both family history of diabetes and reduced birthweight and increased risk of diabetes in adulthood.

OBJECTIVES

1) To investigate the influence of parental history of type 2 diabetes (T2DM) on offspring birthweight and adult offspring glucose tolerance status in non-diabetic offspring of patients with T2DM and 2) to study the associations of birthweight with measures of pancreatic beta-cell function and insulin sensitivity.

DESIGN

Family cohort study.

POPULATION

Offspring of patients with verified T2DM diagnosed after age 40 years with a spouse without known diabetes.

METHODS

Oral glucose tolerance tests and frequently sampled intravenous glucose tolerance tests (FSIGT) in non-diabetic offspring. Birthweight and length obtained from birth records.

RESULTS

Among 122 offspring with maternal history of T2DM, 14.8% had diabetes compared to 8.0% in 137 offspring with paternal history of diabetes, p=0.09. Offspring with maternal history of T2DM had a mean birthweight 196 g higher than offspring with paternal T2DM (3,651 ± 640 g (mean ± SD) vs. 3,456 ± 472g (p=0.01)). Non-diabetic offspring with birthweights in the lowest tertile had significantly higher plasma glucose levels after an oral glucose tolerance test (OGTT) [Area under the curve(glucOGTT) , mean (95%CI), 1 795 (1 725-1 866) vs. 1 683 (1 613-1 753) mmol/L/min, p=0.02], and lower insulin sensitivity index calculated from a frequently sampled intravenous glucose tolerance test - Si 9.60 [10(-5) (min*pmol/L)(-1) ] (8.23-10.97) vs. 11.79 (10.41-13.18), p=0.02 - in adulthood compared to offspring with birthweights in the upper tertile.

CONCLUSIONS

Offspring with a family history of maternal T2DM have higher birthweights than those with paternal T2DM. Low birthweight associates with elevated plasma glucose levels after an oral glucose load and decreased insulin sensitivity in adulthood.

The epigenetics of autoimmunity

The etiology of autoimmune diseases remains largely unknown. Concordance rates in monozygotic twins are lower than 50% while genome-wide association studies propose numerous significant associations representing only a minority of patients. These lines of evidence strongly support other complementary mechanisms involved in the regulation of genes expression ultimately causing overt autoimmunity. Alterations in the post-translational modification of histones and DNA methylation are the two major epigenetic mechanisms that may potentially cause a breakdown of immune tolerance and the perpetuation of autoimmune diseases. In recent years, several studies both in clinical settings and experimental models proposed that the epigenome may hold the key to a better understanding of autoimmunity initiation and perpetuation. More specifically, data support the impact of epigenetic changes in systemic lupus erythematosus, rheumatoid arthritis, multiple sclerosis and other autoimmune diseases, in some cases based on mechanistical observations. We herein discuss what we currently know and what we expect will come in the next future. Ultimately, epigenetic treatments already being used in oncology may soon prove beneficial also in autoimmune diseases.

Maternal family history of diabetes is associated with a reduced risk of cardiovascular disease in women with type 2 diabetes: the Fremantle Diabetes Study

OBJECTIVE

To investigate whether parental family history of diabetes influences cardiovascular outcomes in type 2 diabetes.

RESEARCH DESIGN AND METHODS

We studied 1,294 type 2 diabetic patients (mean age 64.1 years, 51.2% female) recruited to a community-based cohort study from 1993 to 1996 and followed until mid-2006. A data linkage system assessed all-cause and cardiac mortality, incident myocardial infarction, and stroke. Cox proportional hazards modeling was used to determine the influence of maternal or paternal family history on these outcomes.

RESULTS

A maternal family history of diabetes was reported by 20.4% of the cohort, 8.3% reported paternal family history, and 2.0% reported both parents affected. Maternal and paternal family history was associated with earlier age of diabetes onset, and maternal family history was associated with worse glycemic control. For all patients, maternal family history was significantly associated with reduced risk of all-cause mortality and cardiac mortality. When analyzed by sex, maternal family history had no effect on male patients, whereas female patients with diabetic mothers had significantly reduced hazard ratios for death from all causes (0.63 [95% CI 0.41-0.96]; P = 0.033), for death from cardiac causes (0.32 [0.14-0.72]; P = 0.006), and for first myocardial infarction (0.45 [0.26-0.76]; P = 0.003). Paternal family history status was not associated with these outcomes.

CONCLUSIONS

A maternal family history of diabetes confers relative protection against cardiovascular disease in female patients but not in male patients with type 2 diabetes. Paternal family history is associated with risks equivalent to those without a family history of diabetes. Some of the clinical heterogeneity of type 2 diabetes is related to maternal transmission effects with differential impact on male and female patients.

An overview of genetics of paediatric rheumatic diseases

The evidence so far suggests that the paediatric inflammatory diseases encountered in rheumatology practice may be largely genetic in origin, where common single nucleotide polymorphisms (SNPs) in multiple genes contribute to risk, with real but variable environmental components. As far as genetic susceptibility to common paediatric rheumatic diseases is concerned, only juvenile idiopathic arthritis (JIA) has been investigated in any substantial way so far. This article discusses susceptibility for different types of JIA, the different methods used and their advantages and disadvantages. The genetic code is also modifiable by epigenetic mechanisms and examples of these in immunity and rheumatoid arthritis are given to indicate another area of research in the elucidation of the genetics of paediatric rheumatic diseases.

Family-based mitochondrial association study of traits related to type 2 diabetes and the metabolic syndrome in adolescents

AIMS/HYPOTHESIS

There has been much focus on the potential role of mitochondria in the aetiology of type 2 diabetes and the metabolic syndrome, and many case-control mitochondrial association studies have been undertaken for these conditions. We tested for a potential association between common mitochondrial variants and a number of quantitative traits related to type 2 diabetes in a large sample of >2,000 healthy Australian adolescent twins and their siblings, many of whom were measured on more than one occasion.

METHODS

To the best of our knowledge, this is the first mitochondrial association study of quantitative traits undertaken using family data. The maternal inheritance pattern of mitochondria means established association methodologies are unsuitable for analysis of mitochondrial data in families. We present a methodology, implemented in the freely available program Sib-Pair for performing such an analysis.

RESULTS

Despite our study having the power to detect variants with modest effects on these phenotypes, only one significant association was found after correction for multiple testing in any of four age groups. This was for mt14365 with triacylglycerol levels (unadjusted p = 0.0006). This association was not replicated in other age groups.

CONCLUSIONS/INTERPRETATION

We find little evidence in our sample to suggest that common European mitochondrial variants contribute to variation in quantitative phenotypes related to diabetes. Only one variant showed a significant association in our sample, and this association will need to be replicated in a larger cohort. Such replication studies or future meta-analyses may reveal more subtle effects that could not be detected here because of limitations of sample size.

Prevalence of 15 mitochondrial DNA mutations among type 2 diabetic patients with or without clinical characteristics of maternally inherited diabetes and deafness

The aim of the present study is to investigate the prevalence of ten described mitochondrial DNA (mtDNA) mutations in patients with type 2 diabetes, and search for new mutations in four mtDNA genes in a subgroup of patients with characteristics of maternally inherited diabetes and deafness (MIDD). These mutations were investigated in 407 type 2 diabetic patients without characteristics of mitochondrial diabetes ('classical' type 2 diabetes group) and in 38 type 2 diabetic patients with characteristics suggestive of MIDD. Through sequencing of four mtDNA genes in MIDD patients, we selected five others potentially pathogenic mutations that were also screened in the remaining patients. Overall, the frequency of the fifteen analyzed mutations was 36.84% in the MIDD group and 2.45% in the 'classical' type 2 diabetes group (p < 0.001). In conclusion, our study reinforces the importance of mtDNA mutations in the pathogenesis of MIDD.

The effect of paternal and maternal history of diabetes mellitus on the development of gestational diabetes mellitus

BACKGROUND

There is an ongoing debate whether maternal diabetes is a more important risk factor for gestational diabetes (GDM) development than paternal diabetes.

AIM

To describe the risk of GDM associated with paternal and maternal diabetes, and to further characterise GDM women with maternal diabetes.

SUBJECTS AND METHODS

Case-control study within a population-based GDM screening program in an urban area of Hungary in 2002-2003. All GDM women (no.=133) and an age-matched control group (no.=135) with a mean age of 31 years was evaluated. Blood pressure, anthropometric data, and blood glucose values from a 75 g Oral Glucose Tolerance Test (OGTT) were recorded at 24-28 weeks of gestation. Family history data were by self-report.

RESULTS

Known paternal diabetes was not related to GDM risk [odds ratio (OR) 0.83, 95% confidence interval (CI) 0.35-2.00]. Known maternal diabetes (OR 2.90, 95% CI 0.99-8.49) and diabetes in the maternal line (OR 2.83, 95% CI 1.16-6.89) were both related to GDM after adjustment for body mass index (BMI). GDM women with known maternal diabetes had a higher BMI, 31.6 [9.1] kg/m2 median [interquartile range], than GDM women with or without diabetes in the maternal line, 26.1 [4.9] and 26.3 [6.1] kg/m2, respectively, while figures for fasting glucose during OGTT were 5.2 [0.7] vs 4.4 [1.1] vs 4.9 [0.8] mmol/l respectively (all p<0.05).

CONCLUSIONS

Maternal history of diabetes and history of diabetes in the maternal line seems to be a stronger predictor of GDM than paternal history.

The genetics and epigenetics of autoimmune diseases

Self tolerance loss is fundamental to autoimmunity. While understanding of immune regulation is expanding rapidly, the mechanisms causing loss of tolerance in most autoimmune diseases remain elusive. Autoimmunity is believed to develop when genetically predisposed individuals encounter environmental agents that trigger the disease. Recent advances in the genetic and environmental contributions to autoimmunity suggest that interactions between genetic elements and epigenetic changes caused by environmental agents may be responsible for inducing autoimmune disease. Genetic loci predisposing to autoimmunity are being identified through multi-center consortiums, and the number of validated genes is growing rapidly. Recent reports also indicate that the environment can contribute to autoimmunity by modifying gene expression through epigenetic mechanisms. This article will review current understanding of the genetics and epigenetics of lupus, rheumatoid arthritis, multiple sclerosis and type 1 diabetes, using systemic lupus erythematosus as the primary example. Other autoimmune diseases may have a similar foundation.

Offspring of diabetic pregnancy: long-term outcomes

Diabetes in pregnancy has been shown to induce long-term effects in offspring. While considerable attention is focused on the increased incidence of type 2 diabetes mellitus (T2DM) in adult offspring from diabetic mothers, cardiovascular alterations, including hypertension, are also part of lifelong consequences of in-utero exposure to increased glucose concentrations. This review examines the epidemiologic and mechanistic issues involved in the developmental programming of long-term consequences in offspring of diabetic mothers, with a particular emphasis on the renal and vascular mechanisms of hypertension. The factors of increased incidence of T2DM and of obesity in adults born after exposure to diabetes during pregnancy are also discussed, as evidence is accumulating that a vicious circle involving lifelong consequences of diabetes in pregnancy in offspring contributes to the current worldwide epidemic of T2DM.

Clinical and genetic features of childhood-onset Type 2 diabetes in Japan

We aimed to define the detailed clinical features of Japanese childhood-onset Type 2 diabetes mellitus (T2DM) patients who were followed-up, and to determine whether discernable characteristics were dissimilar or not from those of adult- and childhood-onset T2DM in other countries. Subjects were 22 patients (10 males and 12 females) under treatment without HNF-1alpha or mitochondrial gene mutations, and who were apparently diagnosed as diabetic when less than 15 years of age. Body mass indexes at onset in boys and girls were 25.8 +/- 6.3 and 24.7 +/- 3.6, respectively, with mean ages 13.3 +/- 1.7 and 12.8 +/- 2.0 years, respectively. Most patients had a short diabetic duration that required insulin treatment. One or both parents of 18 of the 22 T2DM subjects were diabetic and 7 subjects had a history of diabetes in their family across three generations. We demonstrated that a relatively large number of Japanese childhood-onset T2DM cases have a strong genetic factor, and are not necessarily related to excessive obesity. Furthermore, most required insulin therapy in the initial stages because of insufficient pancreatic beta-cell reserves. This suggests that malfunction of pancreatic beta-cells triggers hyperglycemia resulting in the requirement for insulin in Japanese some childhood-onset T2DM patients.

Direct linkage of mitochondrial genome variation to risk factors for type 2 diabetes in conplastic strains

Recently, the relationship of mitochondrial DNA (mtDNA) variants to metabolic risk factors for diabetes and other common diseases has begun to attract increasing attention. However, progress in this area has been limited because (1) the phenotypic effects of variation in the mitochondrial genome are difficult to isolate owing to confounding variation in the nuclear genome, imprinting phenomena, and environmental factors; and (2) few animal models have been available for directly investigating the effects of mtDNA variants on complex metabolic phenotypes in vivo. Substitution of different mitochondrial genomes on the same nuclear genetic background in conplastic strains provides a way to unambiguously isolate effects of the mitochondrial genome on complex traits. Here we show that conplastic strains of rats with identical nuclear genomes but divergent mitochondrial genomes that encode amino acid differences in proteins of oxidative phosphorylation exhibit differences in major metabolic risk factors for type 2 diabetes. These results (1) provide the first direct evidence linking naturally occurring variation in the mitochondrial genome, independent of variation in the nuclear genome and other confounding factors, to inherited variation in known risk factors for type 2 diabetes; and (2) establish that spontaneous variation in the mitochondrial genome per se can promote systemic metabolic disturbances relevant to the pathogenesis of common diseases.

Association studies on human mitochondrial DNA: methodological aspects and results in the most common age-related diseases

Mitochondrial DNA (mtDNA) follows direct maternal inheritance and, as such, can be used in phylogenetic studies to determine a human lineage tree. The presence of common polymorphisms allows a classification of mtDNA in haplogroups and sub-haplogroups, according to the branch they belong to. Thanks to the rapidly growing number of mtDNA sequences available, this classification is being corrected and redefined to be more accurate. In parallel with this process, several studies are trying to identify an association between common mtDNA polymorphisms and common complex traits, as hypothesized by the common disease-common variant theory. Here we review the associations already reported with the main age-related complex diseases and we identify the critical points (sample size, size of the recruiting area, careful matching between cases and controls regarding geographical origin and ethnicity, data quality checking) to be taken in account in planning such studies. On the whole, this research area is opening a new perspective as an important component of "mitochondrial medicine", capable of identifying new molecular targets for the diagnosis, prevention and treatment of common complex diseases.

Consequences of fetal exposure to maternal diabetes in offspring

CONTEXT

Type 2 diabetes is the result of both genetic and environmental factors. Fetal exposure to maternal diabetes is associated with a higher risk of abnormal glucose homeostasis in offspring beyond that attributable to genetic factors, and therefore, may participate in the excess of maternal transmission of type 2 diabetes.

EVIDENCE ACQUISITION

A MEDLINE search covered the period from 1960-2005.

EVIDENCE SYNTHESIS

Human studies performed in children and adolescents suggest that offspring who had been exposed to maternal diabetes during fetal life exhibit higher prevalence of impaired glucose tolerance and markers of insulin resistance. Recent studies that directly measured insulin sensitivity and insulin secretion have shown an insulin secretory defect even in the absence of impaired glucose tolerance in adult offspring. In animal models, exposure to a hyperglycemic intrauterine environment also led to the impairment of glucose tolerance in the adult offspring. These metabolic abnormalities were transmitted to the next generations, suggesting that in utero exposure to maternal diabetes has an epigenetic impact. At the cellular level, some findings suggest an impaired pancreatic beta-cell mass and function. Several mechanisms such as defects in pancreatic angiogenesis and innervation, or modification of parental imprinting, may be implicated, acting either independently or in combination.

CONCLUSION

Thus, fetal exposure to maternal diabetes may contribute to the worldwide diabetes epidemic. Public health interventions targeting high-risk populations should focus on long-term follow-up of subjects who have been exposed in utero to a diabetic environment and on a better glycemic control during pregnancy.

The European-specific mitochondrial cluster J/T could confer an increased risk of insulin-resistance and type 2 diabetes: an analysis of the m.4216T > C and m.4917A > G variants

The aims of this study were to investigate the contributions of the mitochondrial DNA m.4216T > C and m.4917A > G variants, and also of the European-specific mitochondrial cluster J/T, to the development of type 2 diabetes mellitus in Caucasian-Brazilian patients from Southern Brazil. We analyzed 347 type 2 diabetes patients and 350 control subjects. Variant frequencies in patients and control subjects were compared using chi2 tests or odds ratio. We also compared clinical and laboratory characteristics among patients with and without the variants. We found that the frequencies of the m.4216T > C and m.4917A > G variants are higher in diabetic patients than in control subjects. Moreover, haplogroups J (partially defined by the presence of the m.4216T > C variant only) and T (partially defined by the presence of both m.4216T > C and m.4917A > G variants) are more frequent in the type 2 diabetic group than in the control group. Patients belonging to the cluster J/T are more insulin resistant than patients of other haplogroups. In conclusion, our results indicate the association of the cluster J/T (as suggested by analyses of the m.4216T > C and m.4917A > G variants) with insulin resistance and type 2 diabetes.

Data-mining analysis suggests an epigenetic pathogenesis for type 2 diabetes

The etiological origin of type 2 diabetes mellitus (T2DM) has long been controversial. The body of literature related to T2DM is vast and varied in focus, making a broad epidemiological perspective difficult, if not impossible. A data-mining approach was used to analyze all electronically available scientific literature, over 12 million Medline records, for “objects” such as genes, diseases, phenotypes, and chemical compounds linked to other objects within the T2DM literature but were not themselves within the T2DM literature. The goal of this analysis was to conduct a comprehensive survey to identify novel factors implicated in the pathology of T2DM by statistically evaluating mutually shared associations. Surprisingly, epigenetic factors were among the highest statistical scores in this analysis, strongly implicating epigenetic changes within the body as causal factors in the pathogenesis of T2DM. Further analysis implicates adipocytes as the potential tissue of origin, and cytokines or cytokine-like genes as the dysregulated factor(s) responsible for the T2DM phenotype. The analysis provides a wealth of literature supporting this hypothesis, which—if true—represents an important paradigm shift for researchers studying the pathogenesis of T2DM.

The G1888A variant in the mitochondrial 16S rRNA gene may be associated with Type 2 diabetes in Caucasian-Brazilian patients from southern Brazil

AIM

To compare the frequencies of the G1888A variant in the mitochondrial 16S rRNA gene between patients with Type 2 diabetes and non-diabetic control subjects from southern Brazil.

METHODS

We analysed 520 Type 2 diabetic patients (389 Caucasian- and 131 African-Brazilians) and 530 control subjects (400 Caucasian- and 130 African-Brazilians). DNA samples were amplified by polymerase chain reaction and digested with the RsaI enzyme. Variant frequency in patients and control subjects was compared using chi2 test, Fisher's exact test or odds ratio test. We also investigated the frequency of the G1888A variant in a subgroup of the patients with a maternal history of Type 2 diabetes plus two or more features of maternally inherited diabetes and deafness.

RESULTS

The 1888A allele does not seem to be associated with Type 2 diabetes in African-Brazilians (frequency of 3.8% in patients and 0.8% in control subjects; PFisher=0.213). However, in Caucasian-Brazilians, the 1888A allele was significantly associated with diabetes (12.3% in patients vs. 3.5% in control subjects; OR=3.881; 95% CI 2.106-7.164; P<0.001) and also with higher levels of insulin resistance. The majority of the patients carrying the 1888A allele did not have clinical features of maternally inherited diabetes and deafness.

CONCLUSION

The present study indicates the association of the mitochondrial G1888A variant with Type 2 diabetes and insulin resistance in Caucasian-Brazilian patients from southern Brazil. However, further studies are required to confirm its effects on mitochondrial function and the role of these effects on the pathogenesis of Type 2 diabetes.

Mitochondrial polymorphisms and susceptibility to type 2 diabetes-related traits in Finns

Mitochondria play an integral role in ATP production in cells and are involved in glucose metabolism and insulin secretion, suggesting that variants in the mitochondrial genome may contribute to diabetes susceptibility. In a study of Finnish families ascertained for type 2 diabetes mellitus (T2DM), we genotyped single nucleotide polymorphisms (SNPs) based on phylogenetic networks. These SNPs defined eight major haplogroups and subdivided groups H and U, which are common in Finns. We evaluated association with both diabetes disease status and up to 14 diabetes-related traits for 762 cases, 402 non-diabetic controls, and 465 offspring of genotyped females. Haplogroup J showed a trend toward association with T2DM affected status (OR 1.69, P=0.056) that became slightly more significant after excluding cases with affected fathers (OR 1.77, P=0.045). We also genotyped non-haplogroup-tagging SNPs previously reported to show evidence for association with diabetes or related traits. Our data support previous evidence for association of T16189C with reduced ponderal index at birth and also show evidence for association with reduced birthweight but not with diabetes status. Given the multiple tests performed and the significance levels obtained, this study suggests that mitochondrial genome variants may play at most a modest role in glucose metabolism in the Finnish population. Furthermore, our data do not support a reported maternal inheritance pattern of T2DM but instead show a strong effect of recall bias.

Maternal inheritance in cyclic vomiting syndrome

Cyclic vomiting syndrome (CVS), characterized by severe discrete episodes of nausea, vomiting, and lethargy, is a fairly common, disabling, predominately-childhood condition most often associated with migraine and dysautonomic features. Our group recently reported that children with CVS and additional neuromuscular disease manifestations demonstrate strong maternal inheritance of multiple disease manifestations and abnormal urine organic acids, suggesting the presence of predisposing mitochondrial DNA (mtDNA) sequence variants. In order to determine if maternal inheritance is present in CVS in general, a clinical interview was administered regarding 80 unrelated individuals with CVS ascertained randomly from the database of the Cyclic Vomiting Syndrome Association (CVSA). Disease manifestations consistent with potential mitochondrial dysfunction were far more common in matrilineal (sharing the same mtDNA sequence) versus in non-matrilineal relatives, including mothers versus fathers (P = 3 x 10(-9)) and maternal versus paternal grandmothers (P = 2 x 10(-6)). Maternal inheritance is suggested in 52% of the 23 subjects with two or more neuromuscular abnormalities ("CVS+") and in 54% of the 44 subjects without any neuromuscular abnormalities ("CVS-"). In both the CVS+ and CVS- sub-groups, subjects, and affected matrilineal relatives of all ages suffer at a far higher incidence from several dysautonomic-related conditions, including migraine and irritable bowel, as well as depression and hypothyroidism, while neuromuscular and cognitive disorders such as hypotonia and ADHD are common only in affected children. We conclude that mtDNA sequences predispose towards the development of protean disease manifestations in CVS patients ascertained through a disease-specific association, as well as among their matrilineal relatives, whether or not neuromuscular disease is present in the proband. Since CVS was absent in all but one matrilineal relative of our probands, CVS is apparently a rare clinical presentation in individuals carrying the predisposing mtDNA sequences. The four conditions reported most frequently among the matrilineal relatives of our cases, migraine, depression, irritable bowel, and hypothyroidism, are known to segregate together in families, and our findings suggest that a common predisposing genetic factor is likely present on the mtDNA.

Assessing Maternal Genetic Associations

BACKGROUND

In utero exposures, including maternal phenotypes, are potential risk factors for both early-onset and adult-onset diseases. Two alternative study designs use maternal genotypes at polymorphic loci as biomarkers of an offspring's in utero exposure: (1) a traditional case-control study with logistic regression analysis, in which cases, controls, and mothers of both types of subjects are genotyped; and (2) a case-parent triad study with log-linear analysis, in which cases and both parents are genotyped.

METHODS

We used computer simulations to compare the operating characteristics of the log-linear approach to case-parent triad data and the case-control approach for assessing relative risks (RRs) associated with maternal genotypes.

RESULTS

For high-risk allele frequencies (chromosomal prevalence; f) between 0.20 and 0.75, both methods allowed for valid, unbiased estimates of maternal RRs. The case-parent triad approach, however, had 43% greater power, on average, than the case-control approach with an equal number of genotypes, and 13% greater power with an equal number of cases. For example, under dominant inheritance, to detect 2-fold maternal RRs with 200 (or 150) cases when allele prevalence is between 0.15 and 0.40, the case-parent triad and equal-genotype case-control designs had, on average, 87% and 62% power, respectively. As f approached 0 or 1, the power of both methods decreased sharply.

DISCUSSION

The greater efficiency of case-parent triads may be due to the inclusion of paternal genotype information, which allows for independent tests of disease association with maternal or offspring genotypes. These results highlight one potential advantage of case-parent triad data in assessing maternal genetics as risk factors for offspring disease. We discuss these findings and other considerations between the 2 methodological approaches.

Meta-analysis of three diabetes population studies: association of inactive ALDH2 genotype with maternal inheritance of diabetes

To date, there have been three population studies that examined the association of mitochondrial aldehyde dehydrogenase 2 (ALDH2) genotype with inheritance of diabetes. Here, we summarize the results by meta-analysis. The study 1 consisted of 212 type 2 diabetics who did not have renal failure. The study 2 consisted of 73 type 2 diabetics who had renal failure. The study 3 consisted of 230 type 1 diabetics. In total, 515 subjects were examined for the association of ALDH2 genotype with inheritance of diabetes. Out of 515 subjects, 307 (60%) had active ALDH2 (ALDH2*1/ALDH2*1) and 208 (40%) had inactive ALDH2 (175 had ALDH2*1/ALDH2*2 and 33 had ALDH2*2/ALDH2*2). As for family history, 25 subjects (8.1%) in the active ALDH2 group had a diabetic mother, compared with 43 (20.6%) in the inactive ALDH2 group. Twenty-nine subjects (9.4%) in the active ALDH2 group had a diabetic father, compared with 14 (6.7%) in the inactive ALDH2 group. The percentage of diabetic mother was higher in the inactive ALDH2 group, the differences were statistically significant (P < 0.0001). We hence speculate that diabetic patients with inactive ALDH2 genotype may have underlying background of mitochondria etiology, thereby showing maternal trait of diabetes inheritance. In conclusion, meta-analysis using three diabetes population studies strongly confirmed the association between ALDH2 inactivity and maternal inheritance.

Acquired non-type 1 diabetes in childhood: subtypes, diagnosis, and management

Over the past 30 years it has become apparent that not all diabetes presenting in childhood is autoimmune type 1. Increasingly type 2 diabetes, maturity onset diabetes of the young, iatrogenic diabetes, and rare syndromic forms of diabetes such as Wolfram's syndrome have been identified in children. This review is aimed at the general paediatrician looking after children with diabetes, and aims to provide an algorithm for assessment, investigation, and suggested management for the newly diagnosed child with suspected non-type 1 diabetes. This article will also be relevant to the child with atypical diabetes-that is, on low insulin doses outside the honeymoon period.

Is human Type 2 diabetes maternally inherited? Insights from an animal model

AIMS

Patients with Type 2 diabetes mellitus more often report a history of an affected mother than father. However, in the few studies where both parents and offspring have been directly tested, this apparent maternal excess has not been confirmed. Rodent models of diabetes have the advantage that all parents and offspring can undergo glucose tolerance testing at a specific age in adult life. The aim of this study was to gain insights into the inheritance of human Type 2 diabetes by using a rat model.

METHODS

Goto Kakizaki (GK) rats (a model of Type 2 diabetes) were mated with non-diabetic Wistar rats. Offspring were produced from 20 GK female vs. Wistar male and 20 Wistar female vs. GK male crosses. Fasting blood glucose was measured at 6 weeks and 3 months of age and an intravenous glucose tolerance test (0.8 g/kg) performed at 6 months of age.

RESULTS

Wistar mothers produced litters with almost twice as many viable offspring as GK mothers (14.1 vs. 7.4, P < 0.001). Despite the larger litter size, offspring in the two groups were of comparable weight at 6 weeks and 6 months of age. At 3 months of age, male offspring of Wistar mothers were heavier than offspring of GK mothers (415.7 g vs. 379.5 g, P = 0.016) but this difference was not sustained at 6 months of age. Fasting blood glucose at all ages and average blood glucose during the glucose tolerance test were similar in both groups.

CONCLUSIONS

We therefore conclude that there is no evidence for maternal transmission of diabetes in the GK rat. Mothers were able to adjust their supply of milk so that offspring attained similar weights independent of litter size. The weight of the offspring remained independent of litter size into adult life.

X-linked and lineage-dependent inheritance of coping responses to stress

Coping-or how one routinely deals with stress-is a complex behavioral trait with bearing on chronic disease and susceptibility to psychiatric disorders. This complexity is a result of not only underlying multigenic factors, but also important non-genetic ones. The defensive burying (DB) test, although originally developed as a test of anxiety, can accurately measure differences in coping strategies by assaying an animal's behavioral response to an immediate threat with ethological validity. Using offspring derived from reciprocal crosses of two inbred rat strains differing in DB behaviors, we provide convergent phenotypic and genotypic evidence that coping styles are inherited in an X-linked fashion. We find that first-generation (F(1)) males, but not females, show maternally derived coping styles, and second-generation (F(2)) females, but not males, show significant differences in coping styles when separated by grandmaternal lineage. By using a linear modeling approach to account for covariate effects (sex and lineage) in QTL analysis, we map three quantitative trait loci (QTL) on the X Chromosome (Chr) ( Coping-1, Approach-1, and Approach-2) associated with coping behaviors in the DB paradigm. Distinct loci were associated with different aspects of coping, and their effects were modulated by both the sex and lineage of the animals, demonstrating the power of the general linear modeling approach and the important interplay of allelic and non-allelic factors in the inheritance of coping behaviors.

Diabetes mellitus with mitochondrial gene mutations in Japan

Diabetes mellitus due to the mitochondrial DNA 3243(A-G) mutation is reported to represent 0.5-1% of the general diabetic population in Japan. To further elucidate the clinical symptoms and course of diabetes mellitus with the 3243 mutation, we undertook a nationwide cross-sectional case-finding study and observational study of a genetically defined subject group. One hundred sixteen Japanese diabetic patients with the mutation were registered and analyzed. The patients had a higher maternal inheritance of diabetes or deafness, short stature, thin habitus, and early middle-aged onset of diabetes or deafness. Eighty-six percent of the patients required insulin therapy because of progressive insulin secretory defect. Although half of the patients had the phenotype of type 1 diabetes or slowly progressive type 1 diabetes, the patients lacked the presence of autoantibodies to glutamic acid decarboxylase. Diabetes in the mothers was characterized by early middle-aged onset, reduction in the insulin secretory capacity, early requirement of insulin therapy, and increases in the daily insulin dose. The heteroplasmic ratio of the 3243 mutation in leukocytes was low. The patients had mitochondria-related complications such as sensorineural deafness, cardiomyopathy, cardiac conductance disorders, encephalomyopathy, macular pattern dystrophy, and mental disorders. The patients also had advanced microvascular complications. Thus, this study has revealed that (1) diabetes mellitus with the 3243 mutation is a subtype of diabetes mellitus with mitochondria-related complications and (2) insulin secretory ability is more severely impaired in the patients whose mothers were also diabetic.