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It is estimated that between 0.5% to 2.8% of patients with diabetes have maternally inherited diabetes and deafness (MIDD), which is caused by a mutation at position 3243 of the mitochondrial DNA. The result of this mutation is reduced functional capacity of the respiratory enzyme complexes in mitochondria leading to reduced ATP generation. In the pancreatic beta cell, the altered ATP generation is thought to result in insulin deficiency, leading to diabetes. The diagnosis of MIDD is suspected based on the presence of one or more of 1) maternal heritability of diabetes or impaired glucose tolerance with a normal BMI, 2) hearing impairment and 3) maculopathy. Recognition is important as it allows tailored treatment and early detection, prevention and management of associated disorders in both the patient and their maternal relatives. We present two cases of MIDD and a review of the pathogenesis, clinical characteristics and management of this uncommon but under-recognised, monogenic form of diabetes.

Background In mitochondrial diabetes, apoptosis of β-cells caused by mitochondrial stress plays an important role in impaired insulin secretion. Several studies have reported that coenzyme Q10 (CoQ10) has therapeutic effects on mitochondrial diabetes, but no reports have examined the fundamental effectiveness or mechanism of CoQ10 in mitochondrial diabetes. We previously reported in a Japanese article that CoQ10 has protective effects on pancreatic β-cells against mitochondrial stress using mouse pancreatic β-cell line MIN6 and staurosporine (STS). Here, we report that CoQ10 protects MIN6 cells against apoptosis caused by STS and describe the more detailed apoptotic cascade. Methods Apoptosis of MIN6 cells was induced by 0.5 µM STS treatment for specific periods with or without 30 μM CoQ10. The apoptosis cascade in MIN6 cells was then investigated using WST-8 assays, annexin-V staining, western blotting, and DNA degradation analysis. Results Sixteen hours of 0.5 μM STS treatment led to 47% cell viability, but pretreatment with 30 μM CoQ10 resulted in significantly higher viability of 76% (P

Diabetes mellitus is a heterogeneous group of conditions defined by resultant chronic hyperglycemia. Given the increasing prevalence of diabetes mellitus and the increasing understanding of genetic etiologies, we present a broad review of rare genetic forms of diabetes that have differing diagnostic and/or treatment implications from type 1 and type 2 diabetes. Advances in understanding the genotype-phenotype associations in these rare forms of diabetes offer clinically available examples of evolving precision medicine where defining the correct genetic etiology can radically alter treatment approaches. In this review, we focus on forms of monogenic diabetes, mitochondrial diabetes, and syndromic diabetes.

A patient with mitochondrial diabetes mellitus developed diabetic ketoacidosis. During insulin treatment, although diabetic ketoacidosis improved, lactic acidosis unexpectedly worsened. This clinical course, named "switched metabolic acidosis," could reflect the unique pathophysiology of the mitochondrial disorder.

Mitochondrial diabetes (MD) is a heterogeneous disorder characterized by a chronic hyperglycemia and is maternally transmitted. Syndromic MD is a subgroup of MD including diabetic microangiopathy and macroangiopathy, in addition to extrapancreatic disorder. MD is caused by genetic mutations and deletions affecting mitochondrial DNA. This mitochondrial damage initiates apoptosis. In this study, we hypothesized that functional polymorphisms in genes involved in apoptotic pathway could be associated with the development of apoptosis in MD disease and increased its risk. Detection of apoptosis was confirmed on muscle biopsies taken from MD patients using the TUNEL method and the Cytochrome c protein expression level. We genotyped then 11 published SNPs from intrinsic and extrinsic apoptotic pathway and assessed the signification of these polymorphisms in 43 MD patients and 100 healthy controls. We found 10 selected polymorphisms (p53 (rs1042522 and rs17878362), BCL2 (rs2279115), BAX (rs1805419), BAK1 (rs210132 and rs2227925), CASP3 (rs1405937), CASP7 (rs2227310), CASP8 (rs1045485) and CASP10 (rs13006529)) with a potential apoptosis effect in MD patients compared to control population. Specifically, SNPs involved in the intrinsic pathway (p53, BCL2, BAK1 and CASP3) presented the highest risk of apoptosis. Our result proved that apoptosis initiated by mtDNA mutations, can be emphasized by a functional apoptotic polymorphisms associated with high expression of cytochrome c protein and more myofibers with apoptosis in syndromic MD subgroup compared with non-syndromic MD subgroup.

Introduction. Considering the urgent need to optimize the methods for preventing diabetes mellitus, it is important to find the methods of early diagnosis of carbohydrate metabolism disorders that precede the manifestation of type 2 diabetes mellitus and to promote the method of self-monitoring of carbohydrate metabolism available in Ukraine and abroad for each family. In connection with the peculiarities of energy metabolism, the expediency of studying the pyruvate dehydrogenase activity of blood for the purpose of early diagnosis of diabetes mellitus is obvious. Aim. To identify the persons with a hereditary predisposition to type 2 diabetes mellitus (with mitochondrial diabetes) in the population of the Prykarpattya region using the assessment of carbohydrate metabolism. To recommend the use of a bloodless visual method of studying the total content of α-ketoacids in the urine. Materials and methods. Into the study there were involved 292 practically healthy residents of the Prykarpattya region (166 men and 126 women aged 6 to 80 years) in which the blood glucose level did not exceed 5.6 mmol (100.8 mg%). The state of carbohydrate metabolism was evaluated using pyruvate dehydrogenase and α-ketoglutarate dehydrogenase tests. The monitoring was performed by indicators of pyruvate dehydrogenase activity in blood of healthy persons in the range of 8.01-16.30 μcat/l, as well as the 2-hour α-ketoneuria (6.4-11.4 mg, p

Mitochondrial diseases arise as a consequence of respiratory chain dysfunction caused by mutations in the mitochondrial genome (mtDNA) or nuclear-encoded mitochondrial genes. Multisystem involvement is a hallmark of many subtypes of mitochondrial disease in which energy-dependent organs including the brain, skeletal muscles, and heart are commonly affected. The most common mitochondrial genotype that causes diabetes mellitus is a single nucleotide substitution (m.3243A>G) in the mitochondrial tRNALeu(UUR) gene which is linked to a distinctive clinical phenotype - maternally inherited diabetes and deafness. Diabetes mellitus often arises insidiously as part of the clinical presentation associated with mitochondrial disease; however, there are unique clinical features and associated complications compared to other diabetes subtypes. Overall, the treatment of patients with mitochondrial diabetes is similar to those with other causes of diabetes but with additional emphasis on the screening and subsequent management of additional multiorgan involvement.

Background: Mitochondrial DNA (mtDNA) A3243G mutation is one of the major causative factors of mitochondrial diabetes mellitus. We found that tissues from 2 of 142 diabetes mellitus patients showed extremely high levels of the mutation. Objective: To investigate the level of the mutation in each tissue and to find the relationship between the mutation level and clinical features of the patients. Methods: Patient 1 was a 51-year-old woman, diagnosed as having diabetes mellitus at the age of 17, and was admitted to hospital because of cerebral infarction. Patient 2 was an 82-year-old woman who was admitted because of respiratory failure. mtDNA A3243G levels were measured in tissues collected at autopsy. Results: In patient 1, mtDNA A3243G levels were found to vary among the tissues. The patient’s highest mtDNA A3243G value was 42% and the lowest value was 9%, whereas the level in most individuals is usually less than 1%. Although patient 2 did not exhibit serious clinical symptoms of diabetes mellitus, the mtDNA A3243G level was extremely high in all of the tissues surveyed (range 32–47%). Conclusion: Although both patients showed high levels of the mtDNA A3243G mutation, their clinical conditions differed greatly. Thus, mitochondrial diabetes mellitus patients may show a wide variety of clinical features and large variations in life span.

Diabetes mitocondrial é freqüentemente associado à mutação mitocondrial A3243G. A prevalência desse subtipo de diabetes na população diabética varia de 0,5 a 3%, dependendo do grupo populacional estudado. OBJETIVO: Examinar a freqüência e o quadro clínico do diabetes associado com a mutação mitocondrial A3243G em pacientes brasileiros com tolerância a glicose alterada. MÉTODOS: A população estudada foi composta por 78 indivíduos portadores de diabetes mellitus tipo 1 (grupo I), 148 diabéticos tipo 2 (grupo II), 15 diabéticos tipo 1 ou tipo 2 portadores de disacusia (grupo III) e 492 indivíduos da comunidade nipo-brasileira com vários graus de intolerância a glicose. O DNA foi extraído de leucócitos do sangue periférico e a mutação A3243G foi determinada através da amplificação por PCR e digestão por Apa 1. Em alguns pacientes, o DNA também foi extraído da mucosa oral e folículo capilar. A mutação A3243G foi identificada em três indivíduos, todos do grupo III, resultando em uma prevalência de 0,4%. Os carreadores da mutação apresentavam diagnóstico do diabetes em idade jovem, índice de massa corpórea normal ou baixo e requerimento de insulina. CONCLUSÃO: Diabetes mitocondrial é um subtipo raro de diabetes em nossa população e deve ser investigado naqueles indivíduos portadores de diabetes e surdez. Maternal inherited diabetes and deafness (MIDD) has been related to an A to G transition in the mitochondrial RNA Leu (UUR) at base pair 3243. The prevalence of MIDD in the diabetes population ranges between 0.5-3.0% depending on the ethnic background. AIM: To examine the frequency and clinical features of diabetes associated with this mutation in Brazilian patients with glucose intolerance. METHODS: The study population comprised: 78 type 1 diabetic subjects (group I), 148 patients with type 2 diabetes (group II), 15 patients with either type 1 or type 2 diabetes and hearing loss (group III) and 492 Japanese Brazilians with varying degrees of glucose intolerance. DNA was extracted from peripheral blood leucocytes and the A3243G mutation was determined by PCR amplification and Apa 1 digestion. In some individuals DNA was also extracted from buccal mucosa and hair follicles. The 3243 bp mutation was found in three individuals, all from group III, resulting in a prevalence of 0.4%. These subjects had an early age of diagnosis of diabetes, low or normal body mass index and requirement of insulin therapy. In conclusion MIDD is rare in our population and should be investigate in patients with diabetes and deafness.

ZusammenfassungGene spielen bei der Pathogenese des Diabetes mellitus eine wichtige Rolle. Die häufigste Form bei Kindern und Jugendlichen ist der Diabetes mellitus Typ 1. Bei vorhandener genetischer Prädisposition kann durch verschiedene Umweltfaktoren eine Autoimmunreaktion ausgelöst werden, welche durch Zerstörung der Betazellen zum Insulinmangel und somit zum Diabetes mellitus Typ 1 führt. Beim Diabetes mellitus Typ 2, welcher bei der zunehmenden Adipositas im Kindes- und Jugendalter in den letzten Jahren in Deutschland häufiger zu beobachten ist, spielen genetische Faktoren eine entscheidende Rolle. Der Diabetes mellitus Typ 2 wird polygen vererbt. Bisher liegen jedoch nur unzureichende Daten vor, um eine genetische Diagnostik in der Praxis sinnvoll erscheinen zu lassen. Bei einer Reihe von weiteren Diabetestypen ist deren genetische Ursache in den letzten Jahrzehnten geklärt worden. Eine genetische Diagnostik ist in diesen Fällen notwendig und sinnvoll. Der Maturity Onset Diabetes of the Young (MODY) fällt meist durch seine im Vergleich zum Diabetes mellitus Typ 1 mildere Verlaufsform auf und wird mit einer Häufigkeit von 5–10% aller Diabetesformen beziffert. Der MODY Typ 2 wird durch eine Mutation im Glukokinase-Gen hervorgerufen, der MODY Typ 3 durch eine Mutation im HNF-1α-Gen. Der mitochondriale Diabetes mellitus wird aufgrund der häufig auftretenden Schwerhörigkeit auch als MIDD (Maternally Inherited Diabetes and Deafness) bezeichnet und durch Mutationen im mitochondrialen Genom hervorgerufen. Weiterhin wurden in den letzten Jahren verschiedene Genmutationen beim sehr seltenen neonatalen Diabetes mellitus (transienter und permanenter neonataler Diabetes mellitus) aufgeklärt.

Background Mitochondrial diabetes is a kind of rare diabetes caused by monogenic mutation in mitochondia. The study aimed to summarize the clinical phenotype profiles in mitochondrial diabetes withm.3243A>G mitochondrial DNA mutation and to investigate the mechanism in this kind of diabetes by analyzing the relationship among clinical phenotypes and peripheral leukocyte DNA telomere length. Methods Fifteen patients with maternally inherited diabetes in five families were confirmed as carrying the m.3243A>G mitochondrial DNA mutation. One hundred patients with type 2 diabetes and one hundred healthy control subjects were recruited to participate in the study. Sanger sequencing was used to detect the m.3243A>G mitochondrial DNA mutation. The peak height G/A ratio in the sequence diagram was calculated. Real-time polymerase chain reaction (PCR) was used to measure telomere length. Results The patients with mitochondrial diabetes all had definite maternally inherited history, normal BMI (19.5 ± 2.36 kg/m2), early onset of diabetes (35.0 ± 14.6 years) and deafness. The peak height G/A ratio correlated significantly and negatively with the age at onset of diabetes (≦25 years, 61.6 ± 20.17 %; 25–45 years, 16.59 ± 8.64 %; >45 years, 6.37 ± 0.59 %; p = 0.000). Telomere length was significantly shorter among patients with mitochondrial diabetes and type 2 diabetes than in the control group (1.28 ± 0.54 vs. 1.14 ± 0.43 vs. 1.63 ± 0.61; p = 0.000). However, there was no significant difference between patients with mitochondrial diabetes and those with type 2 diabetes. There was no correlation between telomere length and the peak height G/A ratio. Conclusion Deafness with definite maternal inheritance and normal BMI, associated with elevated blood lactic acid and encephalomyopathy, for the most part, suggest the diagnosis of mitochondrial diabetes . The peak height G/A ratio could reflect the spectrum of age at onset of the disease. Telomere length was shorter in patients with mitochondrial diabetes and those with type 2 diabetes, which suggests that the shorter telomere length is likely involved in the pathogenesis of diabetes but is not specific for this kind of diabetes.

Diabetes mellitus is an etiologically heterogeneous disorder. Monogenic forms of diabetes mellitus cover a heterogeneous group of diabetes which are uniformly caused by a single gene mutation and are characterized by impaired insulin secretion of the pancreatic beta cell. It is estimated that they account for up to 5% of all cases of diabetes mellitus, which are often not diagnosed or are misclassified as type 1 or 2 diabetes. However, accurate diagnosis is important because of the special implications for treatment, prognosis and family risk. The knowledge of typical clinical features such as mode of inheritance, age at diagnosis and impaired insulin secretion, as well as genetic testing establishes the diagnosis of MODY, mitochondrial diabetes and neonatal diabetes. In particular, diabetes occurring under 6 months of age—usually termed neonatal diabetes—appears to be predominantly monogenic.

West syndrome occurs in infancy and in early childhood. It is characterized by intractable seizures occurring almost daily, severe psychomotor retardation, poor prognosis and EEG abnormalities, known as hypsarrhythmia. We report here the case of a 28-year-old patient, who was diagnosed with West syndrome when he was 8 months old and with diabetes mellitus when he was 25 years old. Sequencing analyses and restriction analyses were suggestive of mitochondrial diabetes. Four years after the diagnosis of diabetes, this patient's diabetes is still controlled by diet and biguanides.

Os objetivos deste estudo foram investigar a prevalência de dez mutações conhecidas no DNA mitocondrial (mtDNA) em pacientes com diabetes tipo 2, e procurar por novas mutações em quatro genes mitocondriais em um subgrupo de pacientes com características de MIDD (Maternally Inherited Diabetes and Deafness). Estas mutações foram investigadas em 407 pacientes diabéticos tipo 2 sem características de diabetes mitocondrial (grupo de diabetes tipo 2 clássico) e em 38 pacientes com diabetes tipo 2 e com características sugestivas de MIDD. Através do seqüenciamento de quatro genes mitocondriais nos pacientes com MIDD, selecionou-se cinco outras mutações potencialmente patogênicas que também foram investigadas no restante dos pacientes. De uma forma geral, a freqüência total das 15 mutações analisadas foi de 36,8% no grupo de pacientes com MIDD e de 2,4% no grupo de diabetes tipo 2 clássico (p < 0,001). Em conclusão, nosso estudo reforça a importância de mutações mitocondriais na patogênese do MIDD. 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 fi ve others potentially pathogenic mutations that were also screened in the remaining patients. Overall, the frequency of the fi fteen 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.

Cardiac involvement and its clinical course in a diabetic patient with a mitochondrial tRNALeu(UUR) mutation at position 3243 is reported in a 54-year-old man with no history of hypertension. At age 46, an electrocardiogram showed just T wave abnormalities. At age 49, it fulfilled SV1 + RV5 or 6 >35 mm with strain pattern. At age 52, echocardiography revealed definite left ventricular (LV) hypertrophy, and abnormally increased mitochondria were shown in biopsied endomyocardial specimens. He was diagnosed as having developed hypertrophic cardiomyopathy associated with the mutation. However, at age 54, SV1 and RV5,6 voltages were decreased, and echocardiography showed diffuse decreased LV wall motion and LV dilatation. Because he had mitochondrial diabetes, the patient's heart rapidly developed hypertrophic cardiomyopathy, and then it seemed to be changing to a dilated LV with systolic dysfunction. Rapid progression of cardiomyopathy can occur in mitochondrial diabetes. (Jpn Circ J 1999; 63: 130 - 132)

Obraz kliniczny cukrzycy typu 2 jest uwarunkowany współistnieniem zaburzeń wydzielania insuliny i insulinooporności. Dzięki wysiłkom naukowców z całego świata wykazano związki między mutacjami i polimorfizmami niektórych genów a wieloczynnikowymi i monogenowymi formami cukrzycy typu 2. Formy monogenowe, mimo ich rzadkości, stanowią obszar, w którym dokonał się znaczący postęp w zrozumieniu molekularnego podłoża cukrzycy typu 2. Monogenowe formy cukrzycy typu 2 obejmują cukrzycę MODY (maturity onset diabetes of the young), cukrzycę mitochondrialną (MIDD, maternally inherited diabetes with deafness) oraz inne rzadkie zespoły związane głównie ze skrajnie nasiloną insulinoopornością. Prace nad identyfikacją genów odpowiedzialnych za częstszy, uwarunkowany wieloczynnikowo typ cukrzycy typu 2 były mało owocne. Złożona cukrzyca typu 2 wiąże się z interakcją wielu czynników środowiskowych i genetycznych, takich jak pewne częste polimorfizmy niektórych genów. Jak dotąd różnicom w sekwencji zaledwie kilku genów przypisano związek z patogenezą wielogenowej formy cukrzycy typu 2. Są to na przykład geny kalpainy 10, PPARg, KCNJ11 i insuliny. Należy mieć nadzieję, że w związku z coraz szerszym zakresem wiedzy o strukturze genomu ludzkiego i doskonaleniem metod biologii molekularnej kolejne lata przyniosą istotny postęp dotyczący poznania podłoża cukrzycy typu 2. Clinical picture of the type 2 diabetes (T2DM) is influenced by two major, coexisting conditions: impaired insulin secretion and insulin resistance. As a result of efforts of the scientists around the world mutations and polymorphisms in a number of genes were linked with monogenic and polygenic forms of T2DM. Monogenic forms, despite their rarity, were the field where a substantial progress has been achieved in recognising the molecular background of T2DM. The monogenic forms comprise MODY (maturity onset diabetes of the young), mitochondrial diabetes (MIDD - maternally inherited diabetes with deafness) and certain rare forms resulting mainly from severe insulin resistance. Efforts aiming to identify genes responsible for more common, polygenic form of T2DM were not so fruitful. The complex, polygenic form of T2DM occurs as an effect of interaction of many environmental and genetic factors, such as certain common gene polymorphisms. So far, only several sequence differences have been verified to play role in the pathogenesis of polygenic T2DM. These are the polymorphisms in genes of calpain 10, PPARg, KCNJ11 and insulin. It is expected that in the nearest future more T2DM susceptibility genes will be identified.

A heteroplasmic T to C transition at nucleotide position 14709 in the mitochondrial tRNA glutamic acid (tRNA(Glu)) gene has previously been associated with maternally inherited diabetes and deafness (MIDD). To investigate the pathogenic mechanism of the T14709C mutation, we have constructed transmitochondrial cell lines by transferring fibroblasts mitochondria from a patient with the mutation into human cells lacking mitochondrial DNA (mtDNA) (rho degrees cells). Clonal cybrid cell lines were obtained containing various levels of the heteroplasmic mutation, or exclusively mutated or wild-type mtDNA. Measurement of respiratory chain enzymatic activities failed to detect a difference between the homoplasmic mutant and homoplasmic wild-type cybrid cell lines. However, a subtle decrease in the steady-state levels of tRNA(Glu) transcripts in some mutant clones. Our studies suggest that the T14709C mutation is insufficient to lead impairment of mitochondrial function in homoplasmic osteosarcoma cybrid clones, and that we cannot exclude that the T14709C mutation affects mitochondrial function by a yet unidentified mechanism.