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Experimental Section
Gerontology 2008;54:168–172
DOI: 10.1159/000127415
Markedly Different Clinical Features in 2 Diabetes
Mellitus Patients with Extremely High Tissue Levels
of the Mitochondrial DNA A3243G Mutation
Shinji Harihara a Kenichi Nakamura c Mutsunori Fujiwara d Tomio Arai e
Motoji Sawabe e Fujio Takeuchi b Kaiyo Takubo c
a Department of Biological Sciences, Graduate School of Science, and b Department of Internal Medicine, Faculty of
Medicine, University of Tokyo, c Research Team for Geriatric Diseases, Tokyo Metropolitan Institute of Gerontology,
d Department of Laboratory Medicine, Tokyo Red Cross Medical Center, and e Departments of Anatomical and
Clinical Pathology, Tokyo Metropolitan Geriatric Medical Center, Tokyo , Japan
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. Copyright © 2008 S. Karger AG, Basel
Introduction
There have been many reports on human disorders
caused by mitochondrial DNA (mtDNA) mutations, most
of which are caused by point mutations [1] and some of
which are due to deletion [2] .
Among the point mutations of human mtDNA that
cause disorders or diseases, A3243G mutations are well
known and have been widely described. This mutation is
a major cause of several serious mitochondrial diseases
such as MELAS (mitochondrial myopathy, encephalopa-
thy, lactic acidosis and stroke-like episodes) [3, 4] , Leigh’s
syndrome [5] , myoclonic epilepsy with ragged red fiber
myopathy [6] , chronic progressive external ophthalmo-
plegia [7, 8] , hearing loss [9] and mitochondrial diabetes
mellitus (MDM) [10, 11] . In patients with these disorders,
mutated and normal mtDNA molecules coexist as het-
eroplasmy, and the incidence of the A3243G mutation is
much higher than in normal individuals.
Key Words
Mitochondrial DNA  mtDNA A3243G mutation  Diabetes
mellitus
Abstract
Background: Mitochondrial DNA (mtDNA) A3243G muta-
tion is one of the major causative factors of mitochondrial
diabetes mellitus. We found that tissues from 2 of 142 diabe-
tes 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 mu-
tation level and clinical features of the patients. Methods:
Patient 1 was a 51-year-old woman, diagnosed as having di-
abetes mellitus at the age of 17, and was admitted to hospi-
tal because of cerebral infarction. Patient 2 was an 82-year-
old woman who was admitted because of respiratory fail -
ure. mtDNA A3243G levels were measured in tissues collect -
ed 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 extreme-
ly high in all of the tissues surveyed (range 32–47%). Conclu-
sion: Although both patients showed high levels of the
Received: May 18, 2007
Accepted: January 24, 2008
Published online: April 16, 2008
Shinji Harihara
Department of Biological Sciences, Graduate School of Science
The University of Tokyo
Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033 (Japan)
Tel. +81 3 5841 4497, Fax +81 3 3818 7547, E-Mail harihara@biol.s.u-tokyo.ac.jp
© 2008 S. Karger AG, Basel
0304–324X/08/0543–0168$24.50/0
Accessible online at:
www.karger.com/ger

DM Patients with High mtDNA A3243G
Levels
Gerontology 2008;54:168–172 169
Position 3243, which is located in the tRNA (Leu) gene
of mtDNA, may cause a conformational change of the
tRNA (Leu) molecule, resulting in disordered synthesis
of the protein [12] . Yasukawa et al. [13] reported that the
presence of guanine at position 3243 blocked the base
modification of the anticodon in the RNA, possibly re-
sulting in mistranslation.
Recently, MDM has been intensively investigated and
most cases appear to be caused by the mtDNA A3243G
mutation [11, 14, 15] . Therefore, it is diagnostically im-
portant to measure the level of mtDNA A3243G in each
diabetes mellitus (DM) patient in order to identify pos-
sible MDM patients and investigate the mechanism of the
disease.
In this report, we describe the presence of the mtDNA
A3243G mutation in 142 cases of DM. We also focus on
2 DM patients whose tissues showed extremely high lev-
els of the mtDNA A3243G mutation, and discuss wheth-
er the mutation was the major factor responsible for the
disease in each individual.
Patients and Methods
First, we examined mtDNA mutations of the esophageal epi-
thelium in 142 autopsy cases (77 men, 65 women; age range 51–98
years; mean age 76 years). mtDNA mutation values in 140 of the
142 cases were less than 1%. These values were not different from
the mutation ratio observed in white blood cells from controls,
reported previously [16] . Corresponding values in the remaining
2 cases were 18.5% (patient 1) and 32.1% (patient 2). We therefore
examined mtDNA mutation in all of the tissues from these 2 pa-
tients.
Patient 1
A 51-year-old woman with a history of type I DM was admit-
ted to hospital because of cerebral infarction. She had been diag-
nosed as having DM at the age of 17 years. Although she had been
treated with insulin since 19 years of age, her disease had not been
well controlled. Due to heavy pleural effusion, she had been ad-
mitted to our hospital several times. By the age of 42 years, hem-
orrhage had occurred in her vitreous, and she had undergone he-
modialysis due to diabetic nephropathy for 6 years. Her left heel
had become gangrenous when she was 49 years old due to a DM-
related circulatory disease. Her close family members included no
other DM patients. The patient herself had not been diagnosed as
having MDM.
Three months after hospitalization, she died due to myocar-
dial infarction. At the time, her height was 157 cm and her weight
was 40.2 kg. Autopsy revealed multiple cerebral infarctions and
acute myocardial infarction superimposed on an old infarct. Her
left ventricle was hypertrophic, and her heart weighed 450 g. The
atrophic pancreas showed atrophy of the acini, interstitial fibro-
sis, and centroacinar and ductal dilatation. The cells of the islets
of Langerhans were markedly reduced in number, with mild am-
yloid deposition, although we considered this change not to be
specific to MDM. Diabetic nephropathy was observed and the
kidneys were atrophic, weighing 70 and 80 g, showing marked
hyalinization of glomeruli with mesangial and nodular sclerosis
and fibrin caps. Levels of arteriosclerosis with calcification of the
blood vessels were remarkable. The aorta showed atherosclerosis
with ulceration and calcification. Pulmonary edema was evident,
and the lungs weighed 527 and 725 g.
The patient’s family history was unknown, although her 2
sons, aged 20 and 22 years, were free of DM.
Patient 2
An 82-year-old woman was admitted to hospital because of
respiratory failure caused by a deformity in the vertebral column.
The patient’s blood sugar level was 265 mg/ml immediately after
admission. Although she had been diagnosed as having DM at the
age of 45 and admitted to hospital for instructions regarding self-
care, she did not show any strong clinical signs of DM, and MDM
had not been diagnosed.
She had not received any drugs for DM at any time in her life,
and dietetic treatment had been the only intervention. She began
using a hearing aid when she was 76 years old. She was admitted
to hospital due to the possibility of cancer in the head of the pan-
creas at the age of 79. When she was 80 years old, she developed
osteoporosis and was admitted again.
After her death, due to pneumonia after 3 months of hospital-
ization, an autopsy was performed. Extreme emaciation was evi-
dent (height 140 cm, weight 26 kg). Confluent pneumonia, prob-
ably aspiration pneumonia, was found in both lungs, which
weighed 365 and 325 g. The pancreas was atrophic, with a reduced
number of islet cells, and parts of the islets of Langerhans showed
hyalinization. The heart showed brown atrophy and weighed 220
g. The liver also showed brown atrophy. Spondylosis deformans
was observed in the vertebral column, and slight arteriolosclero-
sis was observed in the kidneys (weight 120 and 150 g).
The patient had 2 brothers and 1 sister, who were healthy. Al-
though she also had 2 sons and 2 daughters, 1 of her sons had died
in infancy. All of her surviving children (a son aged 53, and daugh-
ters aged 45 and 47) were healthy.
Sample Collection
Family members of both subjects signed written consent forms
for the educational and scientific use of the subjects’ organs, in-
cluding DNA analysis. The study protocol was approved by the
Tokyo Metropolitan Institute of Gerontology.
Tissues were collected at autopsy for pathological analysis.
The following fresh tissue samples were collected from patient 1:
kidney, liver, cerebral cortex, lung, esophageal epithelium, myo-
cardium, adrenal medulla, pancreas, thyroid gland, accessory
thyroid, skeletal muscle (quadriceps femoris), abdomen skin,
head skin, tongue, trigone of the bladder and upper side of the
bladder. The following tissue samples were collected from patient
2: kidney, esophageal epithelium, myocardium and liver.
Tissues from the patients were stored at –80 ° C until use. DNA
was extracted from each sample by the usual methods described
previously [17] .
Analysis of mtDNA A3243G Levels
Ratios of mtDNA A3243G variation were measured using the
methods described by Takeuchi et al. [16] and Harihara et al. [18] .