Prevalence of mitochondrial diabetes in southwestern Finland: a molecular epidemiological study

Incidence and prevalence of mtDNA-related adult mitochondrial disease in Southwest Finland, 2009-2022: an observational, population-based study

Background

Mitochondrial diseases are common inherited metabolic disorders. Due to improved case ascertainment and diagnosis methods, the detection of new diagnoses of mitochondrial disease can be expected to increase. In December 2009, the prevalence of mitochondrial DNA (mtDNA)-related mitochondrial disease was 4.6/100 000 (95% CI, 2.7 to 7.2) in the adult population of Southwest Finland. We investigated the number of new diagnoses and the incidence of mitochondrial disease in Southwest Finland between December 2009 and December 2022.

Methods

We collected data on all adult patients from Southwest Finland diagnosed with mitochondrial disease on 31 December 2009 and 31 December 2022. Most patients had been diagnosed at the Turku University Hospital (TUH) neurology outpatient clinic. Patients were also identified by searching the TUH electronic patient database for relevant International Classification of Diseases, Tenth Revision codes and conducted mtDNA analyses.

Results

42 new patients were diagnosed giving a mean annual rate of 3.2 new diagnoses. In 2022, the minimum prevalence estimate of adult mtDNA-related mitochondrial disease was 9.2/100 000 (95% CI, 6.5 to 12.7). The prevalence of adult mtDNA disease associated with m.3243A>G was 4.2/100 000 (95% CI, 2.5 to 6.7), and that with large-scale mtDNA deletions was 1.3/100 000 (95% CI, 0.4 to 2.9). During the 13-year period, the annual incidence of adult mtDNA disease was 0.6/100 000 and that of adult m.3243A>G-related disease 0.3/100 000.

Conclusion

Our results suggest that improved means of diagnostics and dedicated effort increase the detection of mitochondrial disease.

Mitochondrial genome variations, mitochondrial-nuclear compatibility, and their association with metabolic diseases

Two genomes regulate the energy metabolism of eukaryotic cells: the nuclear genome, which codes for most cellular proteins, and the mitochondrial genome, which, together with the nuclear genome, coregulates cellular bioenergetics. Therefore, mitochondrial genome variations can affect, directly or indirectly, all energy-dependent cellular processes and shape the metabolic state of the organism. This review provides a current and up-to-date overview on how codependent these two genomes are, how they appear to have coevolved, and how variations within the mitochondrial genome might be associated with the manifestation of metabolic diseases. This review summarizes and structures results obtained from epidemiological studies that identified links between mitochondrial haplogroups and individual risks for developing obesity and diabetes. This is complemented by findings on the compatibility of mitochondrial and nuclear genomes and cellular bioenergetic fitness, which have been acquired from well-controlled studies in conplastic animal models. These elucidate, more mechanistically, how single-nucleotide variants can influence cellular metabolism and physiology. Overall, it seems that certain mitochondrial genome variations negatively affect mitochondrial-nuclear compatibility and are statistically linked with the onset of metabolic diseases, whereas, for others, greater uncertainty exists, and additional research into this exciting field is required.

Mitochondrial DNA variation in sudden cardiac death: a population-based study

Cardiomyopathy and cardiac conduction defects are common manifestations of mitochondrial disease. Previous studies suggest that clinically asymptomatic individuals harbouring pathogenic mitochondrial DNA (mtDNA) mutations in the cardiac muscle may have sudden cardiac death (SCD) as the first manifestation of mitochondrial disease. We investigated the contribution of pathogenic mtDNA point mutations and mtDNA haplogroups in cardiac muscle in a cohort of 280 Finnish subjects that had died from non-ischaemic SCD with the median age of death at 59 years and in 537 population controls. We did not find any common or novel pathogenic mutations, but the frequency of haplogroup H1 was higher in the SCD subjects than that in 537 population controls (odds ratio: 1.76, confidence interval 95%: 1.02-3.04). We conclude that, at the population level, pathogenic point mutations in mtDNA do not contribute to non-ischaemic SCD, but natural variation may modify the risk.

Mitochondrial DNA associations with East Asian metabolic syndrome

Mitochondrial dysfunction has repeatedly been reported associated with type 2 diabetes mellitus (T2DM) and metabolic syndrome (MS), as have mitochondrial DNA (mtDNA) tRNA and duplication mutations and mtDNA haplogroup lineages. We identified 19 Taiwanese T2DM and MS pedigrees from Taiwan, with putative matrilineal transmission, one of which harbored the pathogenic mtDNA tRNALeu(UUR) nucleotide (nt) 3243A>G mutation on the N9a3 haplogroup background. We then recruited three independent Taiwanese cohorts, two from Taipei (N = 498, mean age 52 and N = 1002, mean age 44) and one from a non-urban environment (N = 501, mean age 57). All three cohorts were assessed for an array of metabolic parameters, their mtDNA haplogroups determined, and the haplogroups correlated with T2DM/MS phenotypes. Logistic regression analysis revealed that mtDNA haplogroups D5, F4, and N9a conferred T2DM protection, while haplogroups F4 and N9a were risk factors for hypertension (HTN), and F4 was a risk factor for obesity (OB). Additionally, the 5263C>T (ND2 A165V) variant commonly associated with F4 was associated with hypertension (HTN). Cybrids were prepared with macro-haplogroup N (defined by variants m.ND3 10398A (114T) and m.ATP6 8701A (59T)) haplogroups B4 and F1 mtDNAs and from macro-haplogroup M (variants m.ND3 10398G (114A) and m.ATP6 8701G (59A)) haplogroup M9 mtDNAs. Additionally, haplogroup B4 and F1 cybrids were prepared with and without the mtDNA variant in ND1 3394T>C (Y30H) reported to be associated with T2DM. Assay of mitochondria complex I in these cybrids revealed that macro-haplogroup N cybrids had lower activity than M cybrids, that haplogroup F cybrids had lower activity than B4 cybrids, and that the ND1 3394T>C (Y30H) variant reduced complex I on both the B4 and F1 background but with very different cumulative effects. These data support the hypothesis that functional mtDNA variants may contribute to the risk of developing T2DM and MS.

Mitochondrial DNA sequence context in the penetrance of mitochondrial t-RNA mutations: A study across multiple lineages with diagnostic implications

Mitochondrial DNA (mtDNA) mutations are well recognized as an important cause of inherited disease. Diseases caused by mtDNA mutations exhibit a high degree of clinical heterogeneity with a complex genotype-phenotype relationship, with many such mutations exhibiting incomplete penetrance. There is evidence that the spectrum of mutations causing mitochondrial disease might differ between different mitochondrial lineages (haplogroups) seen in different global populations. This would point to the importance of sequence context in the expression of mutations. To explore this possibility, we looked for mutations which are known to cause disease in humans, in animals of other species unaffected by mtDNA disease. The mt-tRNA genes are the location of many pathogenic mutations, with the m.3243A>G mutation on the mt-tRNA-Leu(UUR) being the most frequently seen mutation in humans. This study looked for the presence of m.3243A>G in 2784 sequences from 33 species, as well as any of the other mutations reported in association with disease located on mt-tRNA-Leu(UUR). We report a number of disease associated variations found on mt-tRNA-Leu(UUR) in other chordates, as the major population variant, with m.3243A>G being seen in 6 species. In these, we also found a number of mutations which appear compensatory and which could prevent the pathogenicity associated with this change in humans. This work has important implications for the discovery and diagnosis of mtDNA mutations in non-European populations. In addition, it might provide a partial explanation for the conflicting results in the literature that examines the role of mtDNA variants in complex traits.

Rapid Detection of the mt3243A > G Mutation Using Urine Sediment in Elderly Chinese Type 2 Diabetic Patients

OBJECTIVE

In this study, we aimed to identify mt3243A > G mutation carriers in a group of Chinese elderly type 2 diabetic patients by a rapid and noninvasive diagnostic system.

METHODS

DNA was extracted from blood, saliva, and urine sediment samples. The mutation screening and quantitation of heteroplasmy were performed by high-resolution melting (HRM) curve and pyrosequencing, respectively. Patients with mt3243A > G mutation underwent a detailed audiometric, ophthalmologic, neurological, and cardiac examination.

RESULTS

Two patients (2/1041) carrying the mt3243A > G mutation were detected among all type 2 diabetic patients. In patient 1, the heteroplasmy was 0.8%, 2.8%, and 14.7% in peripheral blood leukocytes, saliva, and urine sediment, respectively. In patient 2, the heteroplasmy was 5.3%, 8.4%, and 37.7% in peripheral blood leukocytes, saliva, and urine sediment, respectively. Both of the two patients showed hearing impairment. Abnormal ophthalmologic conditions and hyperintensity on T2-weighted magnetic resonance images were showed in patient 1.

CONCLUSION

The occurrence of mt3243 A > G mutation was 0.2% in Chinese elderly type 2 diabetic patients. Moreover, detection of mt3243 A > G mutation in urine sediment with high-resolution melting (HRM) curve and pyrosequencing is feasible in molecular genetic diagnosis.

Asthma related medication use and exacerbations in children and adolescents with type 1 diabetes

OBJECTIVES

To investigate the use of asthma medication and occurrence of asthma exacerbations up to 5 years before and after the onset of type 1 diabetes mellitus (T1DM) in children and adolescents.

METHODS

Children and adolescents younger than 19 years with at least 2 insulin prescriptions between 1999 and 2009 classified as T1DM cohort (n = 915) and a 4 times larger reference cohort (n = 3,590) with the same age and gender were identified from the Dutch PHARMO Record Linkage System. The date of first insulin dispensing was selected as the index date.

RESULTS

The 5-year prevalence rate of asthma medication use in the T1DM cohort (23.2%) was significantly higher than the reference cohort (18.3%) after the onset of diabetes. No statistically significant difference between the two cohorts was observed in the use of specific types of asthma medication except for short acting muscarinic antagonists that were significantly more used in the T1DM cohort (5.5%) compared with the reference cohort (0.62%) after the onset of diabetes. The incidence rate of asthma medication use declined over time with a peak in the T1DM cohort the 1st year after the onset of diabetes. Furthermore, 1 year after the index date there was a peak in incidence rate of asthma exacerbations in both T1DM (7.8 per 1,000 person year) and reference (6.8 per 1,000 person year) cohorts.

CONCLUSIONS

T1DM is associated with statistically significantly higher asthma medication use after the onset of T1DM, especially in the 1st year after the onset of diabetes. Pediatr Pulmonol. 2016;51:1113-1121. © 2016 Wiley Periodicals, Inc.

Cardiovascular medication use and cardiovascular disease in children and adolescents with type 1 diabetes: a population-based cohort study

OBJECTIVES

To investigate the 5-yr prevalence and incidence rates of cardiovascular medication and cardiovascular disease before and after onset of type 1 diabetes (T1D) in children and adolescents.

METHODS

Children and adolescents (<19 yr) with T1D (n = 925), defined as those who received at least two insulin prescriptions, and a four times larger reference cohort (n = 3591) with the same age and gender in the Dutch PHARMO Record Linkage System (RLS) were studied in a retrospective cohort study between 1999 and 2009. The date of first insulin dispensing was selected as the index date.

RESULTS

The overall prevalence rate of cardiovascular medication use was substantially higher in the T1D cohort before (2.2 vs. 1.0%, p < 0.001) and after (9.2 vs. 3.2%, p < 0.001) the index date. After the index date angiotensin-converting enzyme inhibitors (2.0%) and statins (1.5%) were the most prevalent cardiovascular medications in the T1D cohort. The highest incidence rate of cardiovascular medication use was observed in the first year after the index date [28.1 per 1000 person years (PY)]. Furthermore, three type 1 diabetic patients were hospitalized due to cardiomyopathy (n = 2) and heart failure (n = 1) and one child from the reference group was hospitalized due to cardiomyopathy in the 5 yr after the index date.

CONCLUSIONS

Children with T1D were more likely to use cardiovascular medications in the years before and after the onset of diabetes. Our study emphasizes the importance of routine screening tests and timely treatment of CVD risk factors in the pediatric population with diabetes.

Increasing trends in the incidence and prevalence rates of type 1 diabetes among children and adolescents in the Netherlands

OBJECTIVE

To assess the trends in the incidence and prevalence rates of type 1 diabetes (T1D) among children and adolescents in the Netherlands.

METHODS

A population-based cohort study was conducted in the Dutch PHARMO record linkage system (1998-2011). All children and adolescents aged ≤19 yr with at least one insulin dispensing (as a proxy for T1D) were identified and the numbers of incident and prevalent cases (numerators) were calculated. Overall age-adjusted (0-19 yr) incidence and prevalence rates together with age- and sex-specific rates of T1D and their 95% confidence intervals (CI) were calculated using data from the Dutch Central Bureau of Statistics as denominator. Trends over time were assessed using Joinpoint regression software (National Cancer Institute, Bethesda, MD, USA).

RESULTS

In 2011, the overall age-adjusted incidence and prevalence rates of T1D were 25.2/100 000 (95% CI, 23.7-26.8) person-years (PY) and 174.4/100 000 (95% CI, 170.2-178.5) children, respectively. The average annual percentage change (AAPC) in the overall age-adjusted incidence and prevalence rate was 3.7% (95% CI, 1.8-5.7) and 3.8% (95% CI, 2.4-5.2), respectively. While during the study period the largest increases in the incidence and prevalence rates of T1D were observed for the oldest age groups (10-14 and 15-19 yr), a decreasing trend was detected for the 0- to 4-yr-old category (with AAPCs of -1.8 (95% CI, -9.9 to 7.1) and -6.9% (95% CI, -11.5 to -2.1) for incidence and prevalence, respectively).

CONCLUSION

Age-adjusted incidence (1999-2011) and prevalence rates (1998-2011) of T1D in Dutch children (aged 0-19 yr) continued to increase and a shift was observed to a later onset of the disease.

Chronic comorbidities in children with type 1 diabetes: a population-based cohort study

OBJECTIVE

To determine the incidence of chronic comorbidities among children with type 1 diabetes (T1D) and to compare incidences with a group of children without diabetes.

DESIGN

Population-based cohort study.

SETTING

Dutch PHARMO database (1998-2010).

PATIENTS

All patients (<19 years old) with T1D between 1999 and 2009 (T1D cohort) and a group of age- and sex-matched (ratio: 1-4) children without diabetes (reference cohort).

MAIN OUTCOME MEASURE

The incidence of nine common chronic comorbidities was assessed on the basis that they were treated pharmacologically and/or resulted in hospital admission. Cox proportional hazard analysis was used to estimate the strength of the association between T1D and comorbidities, expressed as HRs and 95% CIs.

RESULTS

A total of 915 patients with T1D and 3590 children in the reference cohort (51% boys, mean age of 10.1 (SD 4.5) years) were included. T1D was associated with an increased risk (HR; 95% CI) of hospitalisation for any comorbidity (3.7; 2.5 to 5.5), thyroid disease (14.2; 6.7 to 31.0), non-infectious enteritis and colitis (5.9; 3.0 to 11.5), cardiovascular disorders (3.1; 2.3 to 4.2), mental disorders (2.0; 1.4 to 3.1), epilepsy (2.0; 1.1 to 3.7) and (obstructive) pulmonary disease (1.5; 1.2 to 2.0). There was no significant difference in the incidences of other comorbidities (malignant disorders, anaemia and migraine) between the two cohorts.

CONCLUSIONS

Our longitudinal study showed that incidences of six chronic diseases were significantly higher in T1D children during the early years of developing this disease compared with the reference children.

Association of mitochondrial DNA haplogroups and vascular complications of diabetes mellitus: A population-based study

We investigated whether mitochondrial (mtDNA) haplogroups and maternal family history of diabetes mellitus were associated with vascular diabetes mellitus complications in a population-based cohort of 299 Finnish diabetes mellitus patients with disease onset in young adult age. We found that haplogroup U was more prevalent among patients with no vascular diabetes mellitus complications than among those with at least one complication (p = 0.038). Haplogroup U was also more prevalent among the patients who reported maternal family history of diabetes mellitus than among those who did not (p = 0.0013). Furthermore, haplogroup U was more prevalent among patients with maternal family history of diabetes mellitus but no vascular diabetes mellitus complications than among those with at least one vascular diabetes mellitus complication but no maternal family history of diabetes mellitus (p = 0.0003 for difference). These findings suggest that different mtDNA-related factors may influence the risk of diabetes mellitus per se and the risk of vascular diabetes mellitus complications. Further studies are, however, warranted to replicate and elaborate on these results.

The genetics of diabetic pregnancy

Advancements in molecular technology coupled with a greater awareness of the human genome and epigenome have broadened our understanding of the genetic contributions to the diabetic pregnancy. There are multiple genes and pathways that can result in a hyperglycemic environment for the fetus. Exposure to this environment in utero has an impact on the risk of adult-onset chronic diseases. How identification of an individual's genetic variants will impact clinical care and outcomes will continue to evolve as our understanding grows.

Population-based cohort study of anti-infective medication use before and after the onset of type 1 diabetes in children and adolescents

A population-based cohort study was conducted in the Dutch PHARMO database to investigate prevalence and patterns of anti-infective medication use in children and adolescents with type 1 diabetes (T1D) before and after the onset of this disease. All patients <19 years with at least 2 insulin prescriptions (1999 to 2009) were identified (T1D cohort) and compared with an age- and sex-matched (ratio: 1 up to 4) diabetes-free reference group. The prevalence and average number of anti-infective use was studied from (up to) 8 years before until a maximum of 4 years after the onset of T1D. A total of 925 patients with T1D and 3,591 children and adolescents in the reference cohort (51% boys, mean age of 10.1 [standard deviation, 4.5] years) were included. The overall prevalence of anti-infective use (62.6 compared to 52.6%, P < 0.001) and average number of prescriptions (2.71 compared to 1.42 per child, P < 0.001) in the T1D cohort were significantly higher than those in the reference cohort after the onset of diabetes. This pattern was consistent across sex and age categories and already observed in the year before the onset of type 1 diabetes. Patients in the T1D cohort received more antibacterials (49.8 compared to 40%, P < 0.001), antimycotics (4.0 compared to 1.3%, P < 0.001), antivirals (2.5 compared to 0.4%, P < 0.001), and second-line antibiotics, such as aminoglycosides, quinolones, and third-generation cephalosporins and carbapenems. Our findings that elevated anti-infective use in the T1D cohort exists in the period before the onset of type 1 diabetes and the consumption of more second-line anti-infective compounds in this time period warrant further research.

Disease history and medication use as risk factors for the clinical manifestation of type 1 diabetes in children and young adults: an explorative case control study

Background

There is a highly variable asymptomatic period of beta cell destruction prior to the clinical presentation of type1 diabetes. It is not well known what triggers type 1 diabetes to become a clinically overt disease. This explorative study aimed to identify the association between disease history/medication use and the clinical manifestation of type 1 diabetes.

Methodology/Principal Findings

An explorative case control study was conducted in the Dutch PHARMO Record Linkage System. Cases (n  = 1,107) were younger than 25 years and had at least 2 insulin prescriptions between 1999 and 2009. For each case, up to 4 controls (without any prescription for the glucose lowering medications (n  = 4,424)) were matched by age and sex. Conditional logistic regression analysis was used to evaluate the association between disease history/medication use in the year prior to the diagnosis of type1 diabetes and clinical manifestation of this disease. Type1 diabetes was significantly associated with a history of mental disorder (odds ratio (OR) 8.0, 95% confidence interval (CI) 1.5–43.7), anemia (OR 5.1, 95% CI 1.1–22.9), and disease of digestive system (OR 2.6, 95% CI 1.2–5.5). The following drug exposures were significantly associated with the clinical manifestation of type 1 diabetes: “systemic hormonal preparations” (OR 1.7, 95% CI 1.1–2.6), medications for “blood and blood forming organs” (OR 1.6, 95% CI 1.1–2.6), “alimentary tract and metabolism” (OR 1.3, 95% CI 1.1–1.6), and “anti-infectives for systemic use” (OR 1.2, 95% CI 1.01–1.4).

Conclusions

Our explorative study demonstrated that in the year prior to the presentation of type1 diabetes in children and young adults, hospitalization for a diverse group of diseases and drug exposures were significantly more prevalent compared with age- and sex-matched diabetes-free controls.

WFS1 variants in Finnish patients with diabetes mellitus, sensorineural hearing impairment or optic atrophy, and in suicide victims

Mutations in the wolframin gene, WFS1, cause Wolfram syndrome, a rare recessive neurodegenerative disorder. The clinical features include early-onset bilateral optic atrophy (OA), diabetes mellitus (DM), diabetes insipidus, hearing impairment, urinary tract abnormalities and psychiatric illness, and, furthermore, WFS1 variants appear to be associated with non-syndromic DM and hearing impairment. Variation of WFS1 was investigated in Finnish subjects consisting 182 patients with DM, 117 patients with sensorineural hearing impairment (SNHI) and 44 patients with OA, and in 95 suicide victims. Twenty-two variants were found in the coding region of WFS1, including three novel nonsynonymous variants. The frequency of the p.[His456] allele was significantly higher in the patients with SNHI (11.5%; corrected P=0.00008), DM (6.6%; corrected P=0.036) or OA (9.1%; corrected P=0.043) than that in the 285 controls (3.3%). The frequency of the p.[His611] allele was 55.8% in the patients with DM being higher than that in the controls (47%; corrected P=0.039). The frequencies of p.[His456] and p.[His611] were similarly increased in an independent group of patients with DM (N=299). The results support previous findings that genetic variation of WFS1 contributes to the risk of DM and SNHI.

Juvenile parkinsonism, hypogonadism and Leigh-like MRI changes in a patient with m.4296G>A mutation in mitochondrial DNA

Leigh syndrome is a mitochondrial disease with considerable clinical and genetic variation. We present a 16-year-old boy with Leigh-like syndrome and broad developmental retardation, parkinsonism and hypogonadism. Sequencing of the entire mitochondrial DNA from blood revealed the m.4296G>A mutation in the MT-TI gene. The mutation was heteroplasmic with a 95% proportion of the mutant genome, while the proportion was 58% in the blood of the patient's clinically healthy mother. Our results suggest that m.4296G>A is pathogenic in humans, and that the phenotype related to this change includes Leigh-like syndrome in adolescence with parkinsonism and hypogonadism, in addition to the previously reported early infantile Leigh syndrome.