The mitochondrial tRNALeu(UUR) A to G 3243 mutation is associated with insulin-dependent and...

ORIGINAL ARTICLES

The Mitochondrial tRNALeu(UUR) A to G3243 Mutation is Associated withInsulin-dependent and Non-insulin-dependent Diabetes in a ChinesePopulationP.R. Smith*1, M.J. Dronsfield1, C.H. Mijovic1, A.T. Hattersley2, V.T.F. Yeung3, C. Cockram3,J.C.N. Chan3, A.H. Barnett1, S.C. Bain1

1Department of Medicine, University of Birmingham, Birmingham,UK2Department of Vascular Medicine Diabetes Research, University ofExeter, Exeter, UK3Department of Medicine, Chinese University of Hong Kong, HongKong

The mitochondrial DNA tRNALeu(UUR) A to G 3243 mutation is associated with maternallyinherited diabetes in Caucasians and Japanese. In a Hong Kong Chinese population wehave detected the 3243 mutation in 2 of 74 unrelated subjects with well characterizedinsulin-dependent (Type 1) diabetes mellitus (IDDM) and 2 of 75 unrelated subjects withyoung onset (,35 years) non-insulin-dependent diabetes (NIDDM). The 3243 mutationhas only previously been associated with IDDM in Japanese. Racial differences inassociation of the mitochondrial 3243 mutation with IDDM suggest the influence of othergenes that may increase its diabetogenic pathogenicity in Oriental races. We also founda significant excess of maternal inheritance of diabetes in the young onset NIDDM cohort,with a ratio of diabetic mothers to fathers of 2.4:1, p , 0.005. The 3243 mutation,however, only accounts for a small proportion of the observed excess maternal inheritance,and further study is needed to search for other diabetes associated mitochondrial DNAmutations. 1997 by John Wiley & Sons, Ltd.

Diabet. Med. 14: 1026–1031 (1997)

No of Figures: 1. No of Tables: 3. No of Refs: 42

KEY WORDS Chinese; IDDM; NIDDM; mitochondrial DNA; genetics

Received 25 April 1997; revised 16 June 1997; accepted 20 June 1997

region on chromosome 6p, the insulin gene region onIntroductionchromosome 11p, and at least 12 other chromosomalregions contribute to the development of IDDM.1Diabetes mellitus is a common chronic disease affecting

1–5 % of subjects in different populations. Genetic factors Mutations in the glucokinase gene on chromosome 7p,the hepatocyte nuclear factor-4a gene on chromosomehave an important role in the aetiology of both insulin-

dependent (Type 1) diabetes (IDDM) and non-insulin- 20q and the hepatocyte nuclear factor-1a gene onchromosome 12q are causes of maturity-onset diabetesdependent (Type 2) diabetes (NIDDM). Recently, much

progress has been made in the identification or localiz- of the young (MODY).2–5

Mutations of the mitochondrial genome are alsoation of responsible genes. Genes within the HLAassociated with diabetes.6,7 Mitochondrial DNA (mtDNA)is 16 569 bases in length, circular in form, and has been

Abbreviations: mtDNA mitochondrial DNA; tRNALeu(UUR) transfer RNA fully sequenced.8 It codes for 13 enzyme subunits ofgene for leucine, mt3243 mitochondrial tRNALeu A to G mutation complexes in the respiratory chain, 22 transfer RNAsat base pair 3243, MELAS syndrome of mitochondrial myopathy,

(tRNAs), and 2 ribosomal RNAs (rRNAs). Most pathogenicencephalopathy, lactic acidosis and stroke-like episodes, CPEO chronicprogressive external ophthalmoplegia, rRNA ribosomal RNA, mRNA mutations of the mitochondrial genome are hetero-messenger RNA, OGTT oral glucose tolerance test, IGT impaired plasmic, i.e. affected cells contain a mixture of mutatedglucose tolerance, ICA islet cell antibodies.

and normal mtDNA. Inheritance of mtDNA, its mutations* Correspondence to: Dr P.R. Smith, Department of Medicine, Under-graduate Centre, Birmingham Heartlands Hospital, Bordesley Green and associated diseases is almost exclusively maternal.East, Brimingham, B9 5SS, UK Much of the initial interest in mutations of mtDNA as aSponsors: Lilly Industries UK; Medical Research Council (UK); British

cause for diabetes was prompted by an observed excessDiabetic Association; Hong Kong University Research Grants Council;Wellcome Trust of maternal inheritance in NIDDM.9,10

1026 CCC 0742–3071/97/141026–06$17.50 1997 by John Wiley & Sons, Ltd. DIABETIC MEDICINE, 1997; 14: 1026–1031

ORIGINAL ARTICLESThe mitochondrial mutation most frequently associated Patients and Methods

with diabetes is an A to G substitution within a tRNAgene for leucine, at base pair 3243 (mt3243). This Subjectsmutation is associated with a syndrome of maternally

All subjects were unrelated, of Chinese race and residentinherited diabetes and deafness,7,11,12 and with otherin Hong Kong at the time of the study. We studied 74disease phenotypes, including a syndrome of myopathy,patients with IDDM, 75 patients with young onset (,35encephalopathy, lactic acidosis, and stroke-like episodesyears) NIDDM, and 95 non-diabetic controls. IDDM was(MELAS), chronic progressive external ophthalmoplegiadiagnosed on the basis of an acute presentation of(CPEO), and myopathy alone.13 At a molecular level, indiabetes, with ketoacidosis or heavy ketonuria, and avitro studies have shown that the mutation causes severecontinuing requirement for treatment with insulin.defects of mitochondrial protein synthesis and oxidativeNIDDM was diagnosed using WHO criteria for diabetes;31

phosphorylation (OXPHOS).14 Possible mechanismspatients had been treated for a minimum of 1 year withinclude an imbalance in transcription of rRNA anddiet +/− oral hypoglycaemic therapy. Clinical data aremRNA genes, due to the mutation interfering with thesummarized in Table 1. Informed consent was obtainedbinding of a protein termination factor,14 and thefrom all participating patients and approval for the studyproduction of a unique RNA transcript which may disruptobtained from the responsible Hospital Ethical Commit-normal mitochondrial mRNA translation.15

tees.Possession of the mt3243 mutation is not invariablyassociated with a disease phenotype in affected pedigrees.

Screening of Diabetic Subjects for mt3243However screening of normal controls has been consist-ently negative in .600 Caucasian and Japanese subjects

DNA was extracted from peripheral blood leucocytes.reported in the literature.16–22 Screening of diabetic

The mitochondrial genome encompassing mt3243, frompopulations for mt3243 suggests racial differences in nucleotides 3029 to 3456 was amplified using theprevalence. Amongst Caucasians, screening was negative polymerase chain reaction (PCR) as described.7 Amplifiedin patients with familial IDDM (i.e. possessing a first DNA fragments underwent a final ‘hot’ cycle with thedegree relative with diabetes),23 but revealed a prevalence addition of (a33P)dATP, to prevent the proportion ofof |0.5% in an unselected group of patients with mutated mtDNA being underestimated as a consequenceNIDDM,24 and 1.5–2% in those with familial NIDDM.23

of heteroduplex formation.32 PCR products were digestedAmong Japanese, mt3243 was found in 0.9% of a large with ApaI (2 h at 37 °C) which in the presence ofunselected diabetic population,21 and may be responsible mt3243 cleaves the 427bp products into 214 and 213bpfor |6% of familial IDDM and |2% familial NIDDM.12

fragments. DNA products were then electrophoresed onMt3243 was not detected in a small cohort of South 8 % denaturing polyacrylamide gels and visualized usingIndian subjects with NIDDM.25 The significance of these autoradiography. To ensure assays were sufficientlyracial differences is unclear. They may reflect the sensitive, all amplifications, digestions, and gel runsinfluence of other genes, nuclear or mitochondrial, that included a sample known to contain mt3243 at a leveldetermine the frequency with which mt3243 occurs, and |2 % of wild type. Water controls were used to preventits pathogenicity in different tissues. MtDNA with mt3243 false positive results from product contamination ofhas been variously reported to be both at a replicative PCR reagents.advantage,26 and disadvantage to normal mtDNA.27

IDDM and NIDDM in the Chinese show different Statistical Analysischaracteristics from those seen in other racial groups.

Age and age of onset of diabetes data are given asIDDM has a comparatively low prevalence in Chinese28

median and range. Family history data was analysedand is unusual in not showing an overall associationusing the chi2 test.with HLA DR4 or with its sub-types.29 This suggests

there may be greater genetic heterogeneity in theaetiology of IDDM in Chinese compared with other Resultsraces. Young onset NIDDM has a high prevalence among

The mt3243 mutation was detected in 2 of 74 patientsChinese30 and mt3243 has been associated with an earlywith IDDM, and in 2 of 75 patients with young onsetage of onset of NIDDM.12 The aim of this study was toNIDDM, a similar prevalence (2.7 %) in each of theinvestigate the prevalence of mt3243 among Chinesegroups. Mt3243 was not detected in the 95 non-subjects with diabetes. We screened Chinese patientsdiabetic Chinese control subjects. An autoradiographwith well characterized IDDM and early onset NIDDMdemonstrating the presence of the mutation in the(diagnosed before the age of 35 years) for mt3243. Aaffected subjects is shown in Figure 1. The mutation wascohort of non-diabetic Chinese subjects was also includeddetected in heteroplasmic form in all 4 subjects, thein the study.level of mutated mtDNA varying from |1 % to 30 %,measured by photodensitometry. Clinical details on the

1027MITOCHONDRIAL DNA MUTATION IN CHINESE

1997 by John Wiley & Sons, Ltd. Diabet. Med. 14: 1026–1031 (1997)

ORIGINAL ARTICLESTable 1. Background data diabetic subjects in IDDM and NIDDM groups

Patient group Number of subjects Age (yr) Age at onset of diabetes Initial treatment Current treatment(M/F) (yr)

IDDM 74 (32/42) 24.5 (11–70) 20.5 (3–66) Insulin InsulinNIDDM 75 (26/49) 33 (16–45) 29 (6–35) Diet 22 Diet 21

OHA 53 OHA 46Insulin 8

Age data shown as median and range.

hearing loss. His sister developed diabetes at age 24,and is treated with insulin. His mother developed diabetesat age 50 and is treated with oral hypoglycaemic agents.His father concealed a diagnosis of NIDDM for morethan 10 years before dying from presumed diabeticnephropathy.

Patient 2A 35-year-old female developed diabetes at the age of

30, presenting with hyperglycaemia and heavy ketonuria.She was immediately commenced on insulin therapy.ICA were undetectable 2 years post-diagnosis. Mother,maternal grandmother, and paternal uncle all had dia-betes. Although not clinically deaf, audiometry, after

Figure 1. Autoradiograph ApaI digested aP33 dATP labelled detection of mt3243, revealed mild bilateral sensorineuralPCR product. Presence of mt3243 demonstrated by restriction hearing loss.of 427bp PCR product to 213/214bp fragments in samples leftto right from patients 1, 2, 4, and 3. No digestion demonstrated

Patient 3in samples from patient 3’s father, mother, son, and 2 sisters.Final lane contains a positive control (|2% mt3243) A 34-year-old female was diagnosed diabetic aged 32

years and treated with oral hypoglycaemic agents.Audiometry was normal. Mt3243 was not detected in4 subjects with mt3243 are given below and areleucocyte DNA from the patient’s mother, despite hersummarized in Table 2.having diabetes and sensorineural deafness. Mt3243 wasalso not found in either of her sisters, one of whom hasProfiles of the Affected SubjectsNIDDM, and the other impaired glucose tolerance (IGT)and sensorineural deafness. Nor was mt3243 detectablePatient 1in her non-diabetic son. A standard WHO 75 g oralA 30-year-old male had IDDM for 3 years. Heglucose tolerance test (OGTT) revealed IGT in her father,presented with diabetic ketoacidosis (pH 7.1, heavywho was also negative for the mutation.ketonuria). Islet cell antibodies (ICA) were not detectable

at diagnosis. He also suffers with bilateral sensorineural

Table 2. Summary of clinical characteristics of subjects with the mitochondrial 3243 mutation

Subject Sex Age (yr) Age at Diabetic relatives Ketosis Treatment Clinical Deafness ICA HLA DRonset of diagnosis JDF Typediabetes Units

(yr)

1 M 30 27 mother, father and sister + Insulin IDDM + ,5 DR4/12NIDDM

2 F 35 30 mother, maternal + Insulin IDDM + ,5 DR7/15grandmother and paternaluncle NIDDM

3 F 34 32 mother and sister NIDDM – OHA NIDDM – NT DR9/14father and sister IGT

4 M 24 22 mother NIDDM – OHA NIDDM NT NT DR10/?

NT, not tested; ? – unable to type.

1028 P.R. SMITH ET AL.

Diabet. Med. 14: 1026–1031 (1997) 1997 by John Wiley & Sons, Ltd.

ORIGINAL ARTICLESPatient 4 and reduced urinary C-peptide excretion.12 Insulin sensi-

tivity, however, appears to be normal.33 The subjectsA 24-year-old male developed diabetes at age 22 andis treated with oral hypoglycaemic agents. He has no with IDDM and mt3243 in this study did not have HLA

class II profiles typical of Chinese IDDM patientshistory of deafness. His mother has suffered with NIDDMand deafness for 12 years. (DR3 positive/DR3/4 heterozygosity)29 and ICAs were

undetectable. This suggests that autoimmune pancreaticTable 3 summarizes the data for the reported familyhistory of diabetes in first degree relatives of subjects in beta cell destruction is an unlikely cause of the diabetes.

It has been suggested that mitochondrial dysfunctionthe young onset NIDDM group. Forty-one of 75 patients(55%) had a diabetic parent, the number of affected causes insulin secretory failure by reducing ATP avail-

ability in beta cells. ATP derived from mitochondrialmothers exceeding that of affected fathers by 31 to 13(x2 = 10.42, df = 1, p , 0.005). OXPHOS is essential for the phosphorylation of glucose

by glucokinase, the rate limiting step in beta cellglucose sensing. The maintenance of high intracellularDiscussionconcentrations of ATP is also critical for cell membranedepolarization and consequent insulin release from theThis study shows that mt3243 is associated with both

insulin-dependent diabetes (2 of 74 subjects) and young beta cell.34 Although there is evidence of defectiveglucose sensing in subjects with mt3243,35 this wouldonset non-insulin-dependent diabetes (2 of 75 subjects)

in Chinese. The finding of mt3243 in the unselected not be sufficient in itself to cause IDDM. Anothersuggestion is that the insulinopaenia is due to beta cellIDDM patient cohort compares with uniformly negative

screening in unselected and familial Caucasian IDDM.23 loss. This is supported by histological reports of thepancreas of patients with mt3243 and other defects ofThe prevalence of mt3243 at 2.7% in the young onset

NIDDM cohort approximates to the 2–3% reported for mtDNA and diabetes, which have described smallpancreatic islets with reduced or absent beta cells.36Japanese and Caucasians with familial NIDDM.22,23 This

is perhaps unsurprising, since mt3243 has been associated In this study both subjects with IDDM and mt3243have a maternal family history of NIDDM implying thatwith an earlier age of onset than typical NIDDM.12

The finding of an association with IDDM is particularly mt3243 causes a spectrum of glucose intolerance inChinese. This can be explained by the extent of pancreaticsignificant. The acute presentation of diabetes and

tendency to ketosis is consistent with insulin dependency beta cell insufficiency which is probably determined bythe proportion of mutated mtDNA within those cells.in the two patients. Diabetic ketoacidosis has only

previously been reported in Japanese patients with Levels of mutated mtDNA are known to vary considerablybetween tissues due to replicative segregation (themt3243. Despite screening of several hundred Caucasians

with familial IDDM23 and numerous reports of Caucasian random partitioning of the mutated and normal mtDNAin mother cell cytoplasm prior to cell division). However,families with maternally inherited diabetes and mt3243

from the Netherlands, UK, France, and Australia (in the intrafamilial clustering of specific disease phenotypes(such as MELAS and CPEO) associated with the samewhich many of the diabetic members receive insulin

treatment), none have been described with a tendency mt3243 mutation implies that replicative segregationcannot be the entire explanation. Additional genetic, orto ketoacidosis. The association of IDDM and mt3243

in Chinese and Japanese suggests racial differences in non-genetic, factors must be important in determiningthe phenotype expressed in patients who carry thisthe diabetogenic pathogenicity of the mutation. Although

such differences may be the result of environmental mutation.37

The failure to detect mt3243 in the diabetic and deaffactors, it would appear more likely that there aregenetically determined factors which influence the dia- mother and affected siblings of patient 3 is not unusual,

similar observations having been made by other groupsbetic phenotype in Orientals. These genes may benuclear and/or mitochondrial. in subjects with myopathic disease37 and diabetes and

deafness.35 Although mt3243 is probably present, withThe pathophysiology of mt3243 diabetes is unknown.A number of studies have demonstrated defective beta- sufficient mutated mtDNA in the pancreatic beta cells

to cause diabetes/IGT, and in the inner ear to causecell function, with decreased first-phase insulin response33

deafness, levels in leucocytes are so low, as to beundetectable. Such extremes of heteroplasmic variationTable 3. Summary of reported family history of diabetes in the

young onset NIDDM patient group increase further with age, leucocyte levels of mt3243showing a decline, while levels in post-mitotic tissues (e.g.

n Subjects Diabetic Diabetic Both Diabetic muscle, pancreas, and brain) remain relatively stable.38

with mothers fathers parents siblings The high proportion of young onset NIDDM subjectsdiabetic diabetic

with a diabetic parent, 41 of 75 (55%), is, despitefirst degreerelatively small numbers, striking. The proportion ofrelativesthose with parental disease having a diabetic mother, at

75 45 31 13 3 28 70 %, is similar to the 68 % found by Alcolado and the66 % of the CODIAB study.9,10 Notwithstanding the

1029MITOCHONDRIAL DNA MUTATION IN CHINESE

1997 by John Wiley & Sons, Ltd. Diabet. Med. 14: 1026–1031 (1997)

ORIGINAL ARTICLESchromosome 7p to early-onset non-insulin-dependentrelatively high prevalence of mt3243 (2.7 %), most ofdiabetes mellitus [published erratum appears in Naturethe excess maternal inheritance in the young onset1992; 357(6379):607]. Nature 1992; 356: 162–164.

NIDDM group remains unexplained. Attempts at identifi- 3. Hattersley AT, Turner RC, Permutt MA, Patel P, Tanizawacation of other mtDNA mutations associated with dia- Y, Chiu KC, et al. Linkage of type 2 diabetes to thebetes, at a population level have hitherto been unproduc- glucokinase gene [see comments]. Lancet 1992; 339:

1307–1310.tive. Although duplications and deletions of mtDNA,39

4. Yamagata K, Furuta H, Oda N, Kaisaki PJ, Menzel S, Coxand the tRNALys 8344 mutation40 have been associatedNJ, et al. Mutations in the hepatocyte nuclear factor-4awith diabetes in individual families, screening of NIDDMgene in maturity-onset diabetes of the young (MODY1).

subjects for these defects has been negative.20Nature 1996; 384: 458–460.

While mitochondrial disease could be the only cause 5. Yamagata K, Oda N, Kaisaki PJ, Menzel S, Furuta H,of the observed excess maternal inheritance in NIDDM, Vaxillaire M, et al. Mutations in the hepatocyte nuclear

factor-1a gene in maturity-onset diabetes of the youngother explanations have been proposed. These include(MODY3). Nature 1996; 384: 455–458.maternal imprinting of diabetogenic genes, and maternal

6. Ballinger SW, Shoffner JM, Hedaya EV, Trounce I, Polakhyperglycaemia inducing metabolic changes in the fetus, MA, Koontz DA, et al. Maternally transmitted diabetespredisposing to the later development of diabetes.41 It is and deafness associated with a 10.4 kb mitochondrialalso likely that paternal diabetes is being underesti- DNA deletion. Nature Genetics 1992; 1: 11–15.

7. van den Ouweland JM, Lemkes HH, Ruitenbeek W,mated.42 The concealed diagnosis of NIDDM in theSandkuijl LA, de Vijlder MF, Struyvenberg PA, et al.father of patient 1, and discovery of IGT in patient 3’sMutation in mitochondrial tRNA(Leu)(UUR) gene in afather, only after she was found to have mt3243, supportslarge pedigree with maternally transmitted type II diabetesthis suggestion. mellitus and deafness. Nature Genetics 1992; 1: 368–371.

In conclusion, the mtDNA A to G 3243 tRNALeu8. Anderson S, Bankier AT, Barrell BG, de Bruijn MHL,

mutation is associated with the development of both Coulson AR, Drouin J, et al. Sequence and organisationof the human mitochondrial genome. Nature 1981; 290:insulin and young onset non-insulin-dependent diabetes457–465.in Chinese. IDDM in subjects with mt3243 shows no

9. Alcolado JC, Alcolado R. Importance of maternal historyfeatures of autoimmune disease, but may be a conse-of non-insulin dependent diabetic patients. Br Med J

quence of premature pancreatic beta cell loss. The 1991; 302: 1178–1180.association of the mutation with IDDM in Chinese and 10. Thomas F, Balkau B, Vauzelle-Kervroedan F, Papoz L,Japanese, but not Caucasians, suggests the influence of Group TC-I-ZS. Maternal effect and familial aggregation

in NIDDM. The CODIAB Study. Diabetes 1994; 43: 63–67.other genes, whether nuclear or mitochondrial, that11. Reardon W, Ross RJ, Sweeney MG, Luxon LM, Pembreyincrease its beta cell pathogenicity in Oriental races. An

ME, Harding AE, et al. Diabetes mellitus associated withexcess of maternal inheritance appears to be a featurea pathogenic point mutation in mitochondrial DNA [see

of young onset NIDDM in Chinese. If this excess is due comments]. Lancet 1992; 340: 1376–1379.to mutations of mtDNA, the prevalence of mt3243 only 12. Kadowaki T, Kadowaki H, Mori Y, Tobe K, Sakuta R,

Suzuki Y, et al. A subtype of diabetes mellitus associatedaccounts for a small proportion, and further study iswith a mutation of mitochondrial DNA. N Engl J Medneeded to search for other diabetes associated mtDNA1994; 330: 962–968.mutations.

13. Hammans SR, Sweeney MG, Hanna MG, BrockingtonM, Morgan-Hughes JA, Harding AE, The mitochondrialDNA transfer RNALeu(UUR) A→G(3243) mutation. A

Acknowledgements clinical and genetic study. Brain 1995; 118: 721–734.14. Chomyn A, Martinuzzi A, Yoneda M, Daga A, Hurko O,

Johns D, et al. MELAS mutation in mtDNA binding sitePRS is a Sheldon Fellow of West Midlands Health. Thisfor transcription termination factor causes defects inwork has received financial support from Lilly Industriesprotein synthesis and in respiration but no change inUK, Medical Research Council (UK). British Diabeticlevels of upstream and downstream mature transcripts.Association, Hong Kong University Research Grants Proc Natl Acad Sci USA 1992; 89: 4221–4225.

Council (Ref. RGC-CUHK 208/94M) and Wellcome Trust. 15. Schon EA, Koga Y, Davidson M, Moraes CT, King MP.We thank M.S.W. Lau for sample collection and A. Riaz, The mitochondrial tRNA(Leu)(UUR)) mutation in MELAS:C. Hunt, D. Dube, J. Heward, and M.A. Penny for a model for pathogenesis. Biochimica et Biophysica Acta

1992; 1101: 206–209.assistance with DNA extraction. We also thank J.A.16. Goto Y, Nonaka I, Haral S. A mutation in the tRNAMaasen and L.M.’t Hart for assistance in validating the

Leu(UUR) gene associated with the MELAS subgroup ofsensitivity of our radioactive mt3243 assay. mitochondrial encephalomyopathies. Nature 1990; 348:651–653.

17. Hammans SR, Sweeney MG, Brockington M, Morgan-Hughes JA, Harding AE. Mitochondrial encephalopathies:Referencesmolecular genetic diagnosis from blood samples. Lancet1991; 337: 1311–1313.1. Todd JA. Genetic analysis of type 1 diabetes using whole

18. Kobayashi Y, Momoi MY, Tominaga K, Shimoizumi H,genome approaches. Proc Nat Acad Sci USA 1995; 92:Nihei K, Yanagisawa M, et al. Respiration-deficient cells8560–8565.are caused by a single point mutation in the mitochondrial2. Froguel P, Vaxillaire M, Sun F, Velho G, Zouali H, Butel

MO, et al. Close linkage of glucokinase locus on tRNA-Leu (UUR) gene in mitochondrial myopathy,

1030 P.R. SMITH ET AL.

Diabet. Med. 14: 1026–1031 (1997) 1997 by John Wiley & Sons, Ltd.

ORIGINAL ARTICLESencephalopathy, lactic acidosis, and strokelike episodes 30. Chan JCN, Cheung CK, Swaminathan R, Nicholls MG,

Cockram CS. Obesity, albuminuria and hypertension(MELAS). Am J Hum Genet 1991; 49: 590–599.among Hong Kong Chinese with non-insulin-dependent19. Oka Y, Katagiri H, Yazaki Y, Murase T, Kobayashidiabetes. Postgraduate Medical Journal 1993; 69: 204–T. Mitochondrial gene mutation in islet-cell-antibody-210.positive patients who were initially non-insulin-dependent

31. WHO Study Group: Diabetes Mellitus: Report of a WHOdiabetics. Lancet 1993; 342: 527–538.Study Group. Geneva: WHO, 1985. (Tech. Rep. Ser 727).20. Alcolado JC, Majid A, Brockington M, Sweeney MG,

32. Shoffner JM, Lott MT, Lezza AM, Seibel P, Ballinger SW,Morgan R, Rees A, et al. Mitochondrial gene defects inWallace DC. Myoclonic epilepsy and ragged-red fiberpatients with NIDDM. Diabetologia 1994; 37: 372–376.disease (MERRF) is associated with a mitochondrial DNA21. Otabe S, Sakura H, Shimokawa K, Mori Y, Kadowaki H,tRNA Lys mutation. Cell 1990; 61: 931–937.Yasuda K, et al. The high prevalence of the diabetic

33. Walker M, Taylor RW, Stewart MW, Bindoff LA, Shearingpatients with a mutation in the mitochondrial gene inPA, Anyaoku V, et al. Insulin and proinsulin secretionJapan. J Clin Endocrinol Metab 1994; 79: 768–771.in subjects with abnormal glucose tolerance and a22. Kishimoto M, Hashiramoto M, Araki S, Ishida Y, Kazumimitochondrial tRNA Leu(UUR) mutation (Letter). DiabetesT, Kanda F, et al. Diabetes mellitus carying a mutationCare 1995; 18: 1507–1509.in the mitochondrial tRNA leu(UUR) gene. Diabetologia

34. Cook DL, Hales CN. Intracellular ATP directly blocks1995; 38: 193–200.K+ channels in pancreatic b-cells. Nature 1984; 311:23. Vionnet N, Passa P, Froguel P. Prevalence of mitochondrial271–273.gene mutations in families with diabetes mellitus (Letter).

35. Velho G, Byrne MM, Clement K, Sturis J, Pueyo ME,Lancet 1993; 342: 1429–1430.Blanche H, et al. Clinical phenotypes, insulin secretion,24. ’t Hart MT, Lemkes HHPJ, Heine RJ, Stolk RP, Feskensand insulin sensitivity in kindreds with maternally inheritedEJM, Jansen JJ, et al. Prevalence of maternally inheriteddiabetes and deafness due to mitochondrial tRNAdiabetes and deafness in diabetic populations in theLeu(UUR) gene mutation. Diabetes 1996; 45: 478–487.Netherlands (letter). Diabetologia 1994; 37: 1169–1170.

36. Poulton J, O’Rahilly S, Morten KJ, Clark A. Mitochondrial25. McCarthy M, Cassell P, Tran T, Mathias L, ’t Hart LM, DNA, diabetes and pancreatic pathology in Kearns-SayreMaasen JA, et al. Evaluation of the importance of maternal syndrome. Diabetologia 1995; 38: 868–871.history of diabetes and of mitochondrial variation in 37. Hammans SR, Sweeney MG, Hanna MG, Brockingtonthe development of NIDDM. Diabetic Med 1996; 13: M, Morgan-Hughes JA, Harding AE. The mitochondrial420–428. DNA transfer RNA Leu (UUR) A→G(3243) mutation: a

26. Yoneda M, Chomyn A, Martinuzzi A, Hurko O, Attardi clinical and genetic study. Brain 1995; 118: 721–734.G. Marked replicative advantage of human mtDNA 38. Poulton N, Morten K. Noninvasive diagnosis of the MELAScarrying a point mutation that causes the MELAS encephal- syndrome from blood DNA. Annals of Neurology 1993;omyopathy. Genetics – Proc Natl Acad Sci USA 1992; 34: 116.89: 11164–11168. 39. Ballinger SW, Shoffner JM, Gebhart S, Koontz DA,

27. Shoubridge EA. Segregation of mitochondrial DNAs carry- Wallace DC. Mitochondrial diabetes revisited (Letter).ing a pathogenic point mutation (tRNA(leu3243)) in cybrid Nature Genetics 1994; 7: 458–459.cells. Biochemical & Biophysical Research Communi- 40. Suzuki S, Hinokoi Y, Hiria S, Onoda M, Matsumoto M,cations 1995; 213: 189–195. Ohtomo M, et al. Diabetes with mitochondrial gene tRNA

28. Bao MZ, Wang JX, Dorman JS, Trucco M. HLA-DQb LYS mutation. Diabetes Care 1994; 17: 1428–1431.non-Asp57 allele and incidence of diabetes in China and 41. Pettitt DJ, Aleck KA, Baird HR, Carraher MJ, Bennett PH,the USA. Lancet 1989; II 497–498. Knowler WC. Congenital susceptibility to NIDDM: Role

29. Penny MA, Jenkins D, Mijovic C, Cookson CS, Hawkins of intrauterine environment. Diabetes 1988; 37: 622–628.BR, Fletcher JA, et al. Susceptibility to insulin dependent 42. Cox NJ. Maternal component in NIDDM transmission.diabetes in a Chinese population: role of HLA class II How large an effect? (Letter; Comment). Diabetes 1994;

43: 166–168.alleles. Diabetes 1992; 41: 914–919.

1031MITOCHONDRIAL DNA MUTATION IN CHINESE

1997 by John Wiley & Sons, Ltd. Diabet. Med. 14: 1026–1031 (1997)