- Devrease of Mitochondrial DNA Content in Non-Insulin Dependent Diabetic Rats.
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Ji Hyun Song, Sun Hee Yim, Bok Ghee Han, Hong Kyu Lee, Young Mi Kim, Kyong Soo Park, S Suzuki
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Korean Diabetes J. 2000;24(2):202-215. Published online January 1, 2001
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 Abstract
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- BACKGROUND
Although genetic disorder in diabetes mellitus (DM) is not well understood, it has been suggested that the maternally inherited mitochondrial DNA which does not follow the Mendel's laws is a genetic factor for DM. It was reported that the mitochondrial DNA contents in DM patients were decreased compared to the normal control. Similar decrease in mitochondrial DNA content before DM development was tested in animal models. METHOD: The mitochondrial DNA (mtDNA) content in various tissues obtained from two types of non-insulin dependent diabetic rats, Goto-Kakizaki (GK) and Otsuka Long-Evans Tokushima Fatty (OLETF) rats at different ages were quantified. We also determined the quantity of hepatic COX subunit lll(COX III) mRNA, and the enzyme activities of succinate dehydrogenase (SDH) and cytochrome c oxidase (COX) in mitochondria isolated from liver and skeletal muscle were measured. RESULTS: At 6 weeks, mtDNA content of GK rat liver was 20% decreased compared to the Wistar control, The mtDNA content of Wistar rat liver was decreased to aging from 6 weeks to 24 weeks while mtDNA in GK rat liver remains relatively constant. In case of skeletal muscle, however, mtDNA contents in GK rats were 50% decreased compared to the control at 12 and 24 week old, Similarly, OLETF and LETO control rats showed the age-dependent decrease of mtDNA content in liver and pancreas. Especially the mtDNA contents in OLETF rat tissues were reduced at the younger age than the LETO control content. That is, at 6 weeks old mtDNA contents in OLETF rat pancreas and liver were only 50% of the control. The level of mitochondrial coded hepatic CDX subunit III mRNA tends to decrease with age. Despite the decrease of mtDNA content, hepatic COX lll mRNA level and COX activities and SDH activities were not altered significantly, implying that the change of mtDNA contents did not damage the mitochondrial gene transcription and mitochondrial function dramatically. CONCLUSIONS: This results suggest that mtDNA contents in pancreas and liver decrease age-dependently but it occurs at younger age in NIDDM. The decrease of mtDNA content at young age may be a cause of NIODM.
- Decreased Mitochondrial DNA Content in Peripheral Blood Leukocyte procedes the Development of Type 2 Diabetes Mellitus.
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Jae Joon Koh, Jong Ho Ahn, Soon Ja Kwon, Ji Hyun Song, Chan Soo Shin, Do Joon Park, Kyong Soo Park, Seong Yeon Kim, Hong Kyu Lee
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Korean Diabetes J. 1998;22(1):56-64. Published online January 1, 2001
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Abstract
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- BACKGROUND
Mitochondrial mutations and deletions, have been implicated in the pathogenesis of diabetes mellitus. This can explain only a very small proportion of the patients with diabetes mellitus. Mitochondrial DNA(mtDNA) is vulnerable to oxidative stress, resulting in both qualitative and quantitative changes. We reported that the amount of mtBNA decreased in the peripheral blood leukocyte of patients with NIDDM. In this study, we examined that decreased mtDNA content preceded the development of NIDDM{Non-insulin dependent diabetes mellitus) and correlated with various insulin resistance parameters.In this study, we demonstrated that the amount of mtDNA decreased in peripheral blood leukocyte of patients with NIDDM. Furthermore, we found that lower mtDNA levels preceded the development of diabetes mellitus. METHODS: We utilized the stored blood samples from two community-based survey conducted in Yonchon County, Korea in 1993 and 1995. We selected 23 newly diagnosed diabetic patients and 22 age- and sex-matched control subjects. The buffy coats of peripheral blood samples were used for the competitive PCR and the products pairs were separated by gel EP. The content of mtDNA was calculated with the densitometry. RESULTS: There were no difference in the initial anthropometric parameters, blood pressure and lipid profiles between subjects who became diabetic converters and non converters. The mean quantity of mtDNA was lower in the converters, with 102.8+ 41.5 copies/pg template DNA compared to 137.8+ 67.7 copies/pg template DNA of the controls(p 0.05). The significant inverse correlations were noted between mtDNA content and WHR(r=0.31, p<0.05) in the first, and fasting glucose level(r=-0.35, p<0.05), diastolic blood pressures(r=-0.36, p<0.05), and WHR(r=-0.40, p<0.01) in the second survey. The correlations with the serum levels of total and high density cholesterol, triglyceride, insulin and proinsulin were not statistically significant. CONCLUSION: Although a relationship between diabetes and mitochondrial dysfunction has been suspected. This study showed that decreased mtDNA content in peripheral blood proceded the development of NIDDM. This is the first study to demonstrate that quantitative changes in mtDNA precede the development of NIDDM.
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