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Kõks S. Genomics of Wolfram Syndrome 1 (WFS1). Biomolecules 2023; 13:1346. [PMID: 37759745 PMCID: PMC10527379 DOI: 10.3390/biom13091346] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 08/30/2023] [Accepted: 09/02/2023] [Indexed: 09/29/2023] Open
Abstract
Wolfram Syndrome (WFS) is a rare, autosomal, recessive neurogenetic disorder that affects many organ systems. It is characterised by diabetes insipidus, diabetes mellites, optic atrophy, and deafness and, therefore, is also known as DIDMOAD. Nearly 15,000-30,000 people are affected by WFS worldwide, and, on average, patients suffering from WFS die at 30 years of age, usually from central respiratory failure caused by massive brain atrophy. The more prevalent of the two kinds of WFS is WFS1, which is a monogenic disease and caused by the loss of the WFS1 gene, whereas WFS2, which is more uncommon, is caused by mutations in the CISD2 gene. Currently, there is no treatment for WFS1 to increase the life expectancy of patients, and the treatments available do not significantly improve their quality of life. Understanding the genetics and the molecular mechanisms of WFS1 is essential to finding a cure. The inability of conventional medications to treat WFS1 points to the need for innovative strategies that must address the fundamental cause: the deletion of the WFS1 gene that leads to the profound ER stress and disturbances in proteostasis. An important approach here is to understand the mechanism of the cell degeneration after the deletion of the WFS1 gene and to describe the differences in these mechanisms for the different tissues. The studies so far have indicated that remarkable clinical heterogeneity is caused by the variable vulnerability caused by WFS1 mutations, and these differences cannot be attributed solely to the positions of mutations in the WFS1 gene. The present review gives a broader overview of the results from genomic studies on the WFS1 mouse model.
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Affiliation(s)
- Sulev Kõks
- Perron Institute for Neurological and Translational Science, 8 Verdun Street, Nedlands, WA 6009, Australia;
- Centre for Molecular Medicine and Innovative Therapeutics, Murdoch University, Perth, WA 6150, Australia
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Devakumar D, Grijalva-Eternod C, Cortina-Borja M, Williams J, Fewtrell M, Wells J. Disentangling the associations between parental BMI and offspring body composition using the four-component model. Am J Hum Biol 2016; 28:524-33. [PMID: 26848813 PMCID: PMC4957621 DOI: 10.1002/ajhb.22825] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Revised: 08/15/2015] [Accepted: 12/08/2015] [Indexed: 12/12/2022] Open
Abstract
Objectives This study sets out to investigate the intergenerational associations between the body mass index (BMI) of parents and the body composition of their offspring. Methods The cross‐sectional data were analyzed for 511 parent–offspring trios from London and south‐east England. The offspring were aged 5–21 years. Parental BMI was obtained by recall and offspring fat mass and lean mass were obtained using the four‐component model. Multivariable regression analysis, with multiple imputation for missing paternal values was used. Sensitivity analyses for levels of non‐paternity were conducted. Results A positive association was seen between parental BMI and offspring BMI, fat mass index (FMI), and lean mass index (LMI). The mother's BMI was positively associated with the BMI, FMI, and LMI z‐scores of both daughters and sons and of a similar magnitude for both sexes. The father's BMI showed similar associations to the mother's BMI, with his son's BMI, FMI, and LMI z‐scores, but no association with his daughter. Sensitivity tests for non‐paternity showed that maternal coefficients remained greater than paternal coefficients throughout but there was no statistical difference at greater levels of non‐paternity. Conclusions We found variable associations between parental BMI and offspring body composition. Associations were generally stronger for maternal than paternal BMI, and paternal associations appeared to differ between sons and daughters. In this cohort, the mother's BMI was statistically significantly associated with her child's body composition but the father's BMI was only associated with the body composition of his sons. Am. J. Hum. Biol. 28:524–533, 2016. © 2016 The Authors American Journal of Human Biology Published by Wiley Periodicals, Inc.
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Affiliation(s)
- Delan Devakumar
- UCL Institute for Global Health, London, WC1N 1EH, United Kingdom
| | | | - Mario Cortina-Borja
- Clinical Epidemiology, Nutrition and Biostatistics Section, UCL Institute of Child Health, London, WC1N 1EH, United Kingdom
| | - Jane Williams
- Childhood Nutrition Research Centre, UCL Institute of Child Health, London, WC1N 1EH, United Kingdom
| | - Mary Fewtrell
- Childhood Nutrition Research Centre, UCL Institute of Child Health, London, WC1N 1EH, United Kingdom
| | - Jonathan Wells
- Childhood Nutrition Research Centre, UCL Institute of Child Health, London, WC1N 1EH, United Kingdom
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Sedman T, Rünkorg K, Krass M, Luuk H, Plaas M, Vasar E, Volke V. Exenatide Is an Effective Antihyperglycaemic Agent in a Mouse Model of Wolfram Syndrome 1. J Diabetes Res 2016; 2016:9239530. [PMID: 27069934 PMCID: PMC4812441 DOI: 10.1155/2016/9239530] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Accepted: 02/22/2016] [Indexed: 01/13/2023] Open
Abstract
Wolfram syndrome 1 is a very rare monogenic disease resulting in a complex of disorders including diabetes mellitus. Up to now, insulin has been used to treat these patients. Some of the monogenic forms of diabetes respond preferentially to sulphonylurea preparations. The aim of the current study was to elucidate whether exenatide, a GLP-1 receptor agonist, and glipizide, a sulphonylurea, are effective in a mouse model of Wolfram syndrome 1. Wolframin-deficient mice were used to test the effect of insulin secretagogues. Wolframin-deficient mice had nearly normal fasting glucose levels but developed hyperglycaemia after glucose challenge. Exenatide in a dose of 10 μg/kg lowered the blood glucose level in both wild-type and wolframin-deficient mice when administered during a nonfasted state and during the intraperitoneal glucose tolerance test. Glipizide (0.6 or 2 mg/kg) was not able to reduce the glucose level in wolframin-deficient animals. In contrast to other groups, wolframin-deficient mice had a lower insulin-to-glucose ratio during the intraperitoneal glucose tolerance test, indicating impaired insulin secretion. Exenatide increased the insulin-to-glucose ratio irrespective of genotype, demonstrating the ability to correct the impaired insulin secretion caused by wolframin deficiency. We conclude that GLP-1 agonists may have potential in the treatment of Wolfram syndrome-related diabetes.
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Affiliation(s)
- Tuuli Sedman
- Department of Physiology, Institute of Biomedicine and Translational Medicine, University of Tartu, 19 Ravila Street, 50411 Tartu, Estonia
- Centre for Translational Medicine, Institute of Biomedicine and Translational Medicine, University of Tartu, 19 Ravila Street, 50411 Tartu, Estonia
| | - Kertu Rünkorg
- Department of Physiology, Institute of Biomedicine and Translational Medicine, University of Tartu, 19 Ravila Street, 50411 Tartu, Estonia
- Centre for Translational Medicine, Institute of Biomedicine and Translational Medicine, University of Tartu, 19 Ravila Street, 50411 Tartu, Estonia
| | - Maarja Krass
- Department of Physiology, Institute of Biomedicine and Translational Medicine, University of Tartu, 19 Ravila Street, 50411 Tartu, Estonia
- Centre for Translational Medicine, Institute of Biomedicine and Translational Medicine, University of Tartu, 19 Ravila Street, 50411 Tartu, Estonia
| | - Hendrik Luuk
- Department of Physiology, Institute of Biomedicine and Translational Medicine, University of Tartu, 19 Ravila Street, 50411 Tartu, Estonia
- Centre for Translational Medicine, Institute of Biomedicine and Translational Medicine, University of Tartu, 19 Ravila Street, 50411 Tartu, Estonia
| | - Mario Plaas
- Laboratory Animal Centre, Institute of Biomedicine and Translational Medicine, University of Tartu, 19 Ravila Street, 50411 Tartu, Estonia
| | - Eero Vasar
- Department of Physiology, Institute of Biomedicine and Translational Medicine, University of Tartu, 19 Ravila Street, 50411 Tartu, Estonia
- Centre for Translational Medicine, Institute of Biomedicine and Translational Medicine, University of Tartu, 19 Ravila Street, 50411 Tartu, Estonia
| | - Vallo Volke
- Department of Physiology, Institute of Biomedicine and Translational Medicine, University of Tartu, 19 Ravila Street, 50411 Tartu, Estonia
- Centre for Translational Medicine, Institute of Biomedicine and Translational Medicine, University of Tartu, 19 Ravila Street, 50411 Tartu, Estonia
- Tartu University Hospital, 8 L. Puusepa Street, 51014 Tartu, Estonia
- *Vallo Volke:
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Ho J, Pacaud D, Rakic M, Khan A. Diabetes in pediatric patients with Kearns-Sayre syndrome: clinical presentation of 2 cases and a review of pathophysiology. Can J Diabetes 2015; 38:225-8. [PMID: 25092642 DOI: 10.1016/j.jcjd.2014.04.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 04/04/2014] [Accepted: 04/07/2014] [Indexed: 10/24/2022]
Abstract
Kearns-Sayre syndrome (KSS), resulting from a mitochondrial DNA deletion, is a rare cause of diabetes in children. We report 2 pediatric cases of KSS associated with diabetes that presented with hyperosmolar hyperglycemia with minimal ketosis. Both patients were treated initially with isotonic fluid resuscitation followed by intravenous insulin infusion. The first case was a boy of Blackfoot Aboriginal ancestry who presented with failure to thrive, developmental delay and Fanconi syndrome and was diagnosed with KSS at 3 years of age. At 4 years he presented with a cough and left upper lobe lung infiltrate as well as a hyperosmolar hyperglycemic episode. He subsequently required multiple daily insulin injections. This patient developed cardiomyopathy and died at the age of 10 years. The second case was a 6-year-old boy of Asian ancestry who presented with ataxia exacerbated by intercurrent illnesses, decreased exercise tolerance, gross motor and fine motor delays, anorexia and recurrent episodes of vomiting associated with dehydration, and he was subsequently diagnosed with KSS. At 11 years of age, the patient developed hyperosmolar hyperglycemia, and after treatment for it, he required multiple daily insulin injections. He died of end stage congestive heart failure secondary to cardiomyopathy at 13 years of age. These 2 cases are presented to describe the possible pathophysiology of mitochondrial diabetes and to emphasize the need to monitor for the development of diabetes in patients with known mitochondrial disease and also to be aware of possible mitochondrial disease in pediatric patients who present with hyperglycemia in the context of multisystem involvement.
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Affiliation(s)
- Josephine Ho
- Division of Pediatric Endocrinology, Department of Pediatrics, University of Calgary, Calgary, Alberta, Canada
| | - Danièle Pacaud
- Division of Pediatric Endocrinology, Department of Pediatrics, University of Calgary, Calgary, Alberta, Canada
| | - Maja Rakic
- University of Calgary, Bachelor of Health Sciences Program, Faculty of Medicine, Calgary, Alberta, Canada
| | - Aneal Khan
- Metabolic Clinic, Department of Medical Genetics and Pediatrics, University of Calgary, Calgary, Alberta, Canada.
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Byrne EM, McRae AF, Duffy DL, Zhao ZZ, Martin NG, Whitfield JB, Visscher PM, Montgomery GW. Family-based mitochondrial association study of traits related to type 2 diabetes and the metabolic syndrome in adolescents. Diabetologia 2009; 52:2359-2368. [PMID: 19760390 DOI: 10.1007/s00125-009-1510-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2008] [Accepted: 07/06/2009] [Indexed: 01/06/2023]
Abstract
AIMS/HYPOTHESIS There has been much focus on the potential role of mitochondria in the aetiology of type 2 diabetes and the metabolic syndrome, and many case-control mitochondrial association studies have been undertaken for these conditions. We tested for a potential association between common mitochondrial variants and a number of quantitative traits related to type 2 diabetes in a large sample of >2,000 healthy Australian adolescent twins and their siblings, many of whom were measured on more than one occasion. METHODS To the best of our knowledge, this is the first mitochondrial association study of quantitative traits undertaken using family data. The maternal inheritance pattern of mitochondria means established association methodologies are unsuitable for analysis of mitochondrial data in families. We present a methodology, implemented in the freely available program Sib-Pair for performing such an analysis. RESULTS Despite our study having the power to detect variants with modest effects on these phenotypes, only one significant association was found after correction for multiple testing in any of four age groups. This was for mt14365 with triacylglycerol levels (unadjusted p = 0.0006). This association was not replicated in other age groups. CONCLUSIONS/INTERPRETATION We find little evidence in our sample to suggest that common European mitochondrial variants contribute to variation in quantitative phenotypes related to diabetes. Only one variant showed a significant association in our sample, and this association will need to be replicated in a larger cohort. Such replication studies or future meta-analyses may reveal more subtle effects that could not be detected here because of limitations of sample size.
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Affiliation(s)
- E M Byrne
- Queensland Statistical Genetics, Queensland Institute of Medical Research, 300 Herston Road, Brisbane, QLD, 4029, Australia.
- Queensland Statistical Genetics, Queensland Institute of Medical Research, 300 Herston Road, Brisbane, QLD, 4029, Australia.
- School of Medicine, University of Queensland, Brisbane, QLD, Australia.
| | - A F McRae
- Queensland Statistical Genetics, Queensland Institute of Medical Research, 300 Herston Road, Brisbane, QLD, 4029, Australia
- Queensland Statistical Genetics, Queensland Institute of Medical Research, 300 Herston Road, Brisbane, QLD, 4029, Australia
| | - D L Duffy
- Genetic Epidemiology, Queensland Institute of Medical Research, Brisbane, QLD, Australia
| | - Z Z Zhao
- Genetic Epidemiology, Queensland Institute of Medical Research, Brisbane, QLD, Australia
| | - N G Martin
- Genetic Epidemiology, Queensland Institute of Medical Research, Brisbane, QLD, Australia
| | - J B Whitfield
- Genetic Epidemiology, Queensland Institute of Medical Research, Brisbane, QLD, Australia
| | - P M Visscher
- Queensland Statistical Genetics, Queensland Institute of Medical Research, 300 Herston Road, Brisbane, QLD, 4029, Australia
- Queensland Statistical Genetics, Queensland Institute of Medical Research, 300 Herston Road, Brisbane, QLD, 4029, Australia
| | - G W Montgomery
- Genetic Epidemiology, Queensland Institute of Medical Research, Brisbane, QLD, Australia
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Waterfield T, Gloyn AL. Monogenic β-cell dysfunction in children: clinical phenotypes, genetic etiology and mutational pathways. ACTA ACUST UNITED AC 2008. [DOI: 10.2217/17455111.2.4.517] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Monogenic diabetes accounts for 1–2% of all cases of diabetes mellitus and presentation is often in childhood. Recognizing the clinical features of monogenic β-cell dysfunction prevents misdiagnosis and allows for more effective management and genetic counseling. Monogenic β-cell dysfunction is a diverse collection of clinical phenotypes underpinned by common mutational pathways. Mutations affecting the glycolytic glucokinase enzyme, the mitochondria, the KATP channels and transcription factors have been known for some time. Until recently, the role of endoplasmic reticulum stress was underestimated in the pathogenesis of diabetes. It is becoming increasingly clear that endoplasmic reticulum stress is an important etiological factor in the development of monogenic and polygenic diabetes. In this article, we aim to define the etiology of pediatric monogenic β-cell dysfunction and provide guidance on the investigation and management of children presenting with monogenic β-cell dysfunction.
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Affiliation(s)
- Thomas Waterfield
- Diabetes Research Laboratories, Oxford Centre for Diabetes Endocrinology & Metabolism, Churchill Hospital, Old Road, Headington, Oxford, OX3 7LJ, UK
| | - Anna L Gloyn
- Diabetes Research Laboratories, Oxford Centre for Diabetes Endocrinology & Metabolism, Churchill Hospital, Old Road, Headington, Oxford, OX3 7LJ, UK
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Abstract
The development of personalized pluripotent stem cells for research and for possible therapies holds out great hope for patients. However, such cells will face significant technical and regulatory challenges before they can be used as therapeutic reagents. Here we consider two possible sources of personalized pluripotent stem cells: embryonic stem cells derived from nuclear transfer (NT-ESCs) and induced pluripotent stem cells (iPSCs) derived from direct reprogramming of adult somatic cells. Both sources of personalized pluripotent stem cells face unique regulatory hurdles that are in some ways significantly higher than those facing stem cells derived from embryos produced by fertilization (ESCs). However, the outstanding long-term potential of iPSCs and their relative freedom from the ethical concerns raised by both ESCs and NT-ESCs makes direct reprogramming an exceptionally promising approach to advancing research and providing therapies in the field of regenerative medicine.
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Affiliation(s)
- Maureen L Condic
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah 84132-3401, USA.
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Mathis S, Paquis V, Mesnage V, Balaboï I, Gil R, Gilbert B, Neau JP. Ataxie cérébelleuse révélant un syndrome de Wolfram. Rev Neurol (Paris) 2007; 163:197-204. [PMID: 17351539 DOI: 10.1016/s0035-3787(07)90391-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
INTRODUCTION Wolfram syndrome is a genetic disease with recessive autosomic transmission, associating early-onset diabetes mellitus and bilateral optical atrophy. CASE REPORT We report the case of a 47-year-old patient for whom we diagnosed a Wolfram syndrome in view of a late neurological syndrome in association with ataxia and bilateral horizontal nystagmus. The brain resonance magnetic imaging revealed a major atrophy of the brainstem and cerebellum. CONCLUSION Wolfram syndrome is a rare pathology, with fatal consequences before the age of 50. The association of diabetes mellitus and optical atrophy, especially when there are other symptoms (ataxia, deafness, diabetes insipidus, neuropsychiatric manifestations or urinary tract disorders) should lead to this diagnosis and to carry out a genetic confirmation.
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Affiliation(s)
- S Mathis
- Clinique Neurologique, CHU La Milétrie, Poitiers
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Saxena R, de Bakker PIW, Singer K, Mootha V, Burtt N, Hirschhorn JN, Gaudet D, Isomaa B, Daly MJ, Groop L, Ardlie KG, Altshuler D. Comprehensive association testing of common mitochondrial DNA variation in metabolic disease. Am J Hum Genet 2006; 79:54-61. [PMID: 16773565 PMCID: PMC1474138 DOI: 10.1086/504926] [Citation(s) in RCA: 153] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2005] [Accepted: 03/24/2006] [Indexed: 12/13/2022] Open
Abstract
Many lines of evidence implicate mitochondria in phenotypic variation: (a) rare mutations in mitochondrial proteins cause metabolic, neurological, and muscular disorders; (b) alterations in oxidative phosphorylation are characteristic of type 2 diabetes, Parkinson disease, Huntington disease, and other diseases; and (c) common missense variants in the mitochondrial genome (mtDNA) have been implicated as having been subject to natural selection for adaptation to cold climates and contributing to "energy deficiency" diseases today. To test the hypothesis that common mtDNA variation influences human physiology and disease, we identified all 144 variants with frequency >1% in Europeans from >900 publicly available European mtDNA sequences and selected 64 tagging single-nucleotide polymorphisms that efficiently capture all common variation (except the hypervariable D-loop). Next, we evaluated the complete set of common mtDNA variants for association with type 2 diabetes in a sample of 3,304 diabetics and 3,304 matched nondiabetic individuals. Association of mtDNA variants with other metabolic traits (body mass index, measures of insulin secretion and action, blood pressure, and cholesterol) was also tested in subsets of this sample. We did not find a significant association of common mtDNA variants with these metabolic phenotypes. Moreover, we failed to identify any physiological effect of alleles that were previously proposed to have been adaptive for energy metabolism in human evolution. More generally, this comprehensive association-testing framework can readily be applied to other diseases for which mitochondrial dysfunction has been implicated.
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Affiliation(s)
- Richa Saxena
- Center for Human Genetic Research, Massachusetts General Hospital, Boston, 02114, USA
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10
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Mohlke KL, Jackson AU, Scott LJ, Peck EC, Suh YD, Chines PS, Watanabe RM, Buchanan TA, Conneely KN, Erdos MR, Narisu N, Enloe S, Valle TT, Tuomilehto J, Bergman RN, Boehnke M, Collins FS. Mitochondrial polymorphisms and susceptibility to type 2 diabetes-related traits in Finns. Hum Genet 2005; 118:245-54. [PMID: 16142453 DOI: 10.1007/s00439-005-0046-4] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2004] [Accepted: 07/12/2005] [Indexed: 12/29/2022]
Abstract
Mitochondria play an integral role in ATP production in cells and are involved in glucose metabolism and insulin secretion, suggesting that variants in the mitochondrial genome may contribute to diabetes susceptibility. In a study of Finnish families ascertained for type 2 diabetes mellitus (T2DM), we genotyped single nucleotide polymorphisms (SNPs) based on phylogenetic networks. These SNPs defined eight major haplogroups and subdivided groups H and U, which are common in Finns. We evaluated association with both diabetes disease status and up to 14 diabetes-related traits for 762 cases, 402 non-diabetic controls, and 465 offspring of genotyped females. Haplogroup J showed a trend toward association with T2DM affected status (OR 1.69, P=0.056) that became slightly more significant after excluding cases with affected fathers (OR 1.77, P=0.045). We also genotyped non-haplogroup-tagging SNPs previously reported to show evidence for association with diabetes or related traits. Our data support previous evidence for association of T16189C with reduced ponderal index at birth and also show evidence for association with reduced birthweight but not with diabetes status. Given the multiple tests performed and the significance levels obtained, this study suggests that mitochondrial genome variants may play at most a modest role in glucose metabolism in the Finnish population. Furthermore, our data do not support a reported maternal inheritance pattern of T2DM but instead show a strong effect of recall bias.
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Affiliation(s)
- Karen L Mohlke
- Department of Genetics, University of North Carolina, 4109-F Neurosciences Research Building, 103 Mason Farm Road, CB#7264, 27599-7264, Chapel Hill, NC, USA.
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Smigrodzki RM, Khan SM. Mitochondrial microheteroplasmy and a theory of aging and age-related disease. Rejuvenation Res 2005; 8:172-98. [PMID: 16144471 DOI: 10.1089/rej.2005.8.172] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
We implicate a recently described form of mitochondrial mutation, mitochondrial microheteroplasmy, as a candidate for the principal component of aging. Microheteroplasmy is the presence of hundreds of independent mutations in one organism, with each mutation usually found in 1-2% of all mitochondrial genomes. Despite the low abundance of single mutations, the vast majority of mitochondrial genomes in all adults are mutated. This mutational burden includes inherited mutations, de novo germline mutations, as well as somatic mutations acquired either during early embryonic development or later in adult life. We postulate that microheteroplasmy is sufficient to explain the pathomechanism of several age-associated diseases, especially in conditions with known mitochondrial involvement, such as diabetes (DM), cardiovascular disease, Parkinson's disease (PD), and Alzheimer's disease (AD) and cancer. The genetic properties of microheteroplasmy reconcile the results of disease models (cybrids, hypermutable PolG variants and mitochondrial toxins), with the relatively low levels of maternal inheritance in the aforementioned diseases, and provide an explanation of their delayed, progressive course.
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Porter JR, Barrett TG. Monogenic syndromes of abnormal glucose homeostasis: clinical review and relevance to the understanding of the pathology of insulin resistance and beta cell failure. J Med Genet 2005; 42:893-902. [PMID: 15772126 PMCID: PMC1735963 DOI: 10.1136/jmg.2005.030791] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Type 2 diabetes mellitus is caused by a combination of insulin resistance and beta cell failure. The polygenic nature of type 2 diabetes has made it difficult to study. Although many candidate genes for this condition have been suggested, in most cases association studies have been equivocal. Monogenic forms of diabetes have now been studied extensively, and the genetic basis of many of these syndromes has been elucidated, leading to greater understanding of the functions of the genes involved. Common variations in the genes causing monogenic disorders have been associated with susceptibility to type 2 diabetes in several populations and explain some of the linkage seen in genome-wide scans. Monogenic disorders are also helpful in understanding both normal and disordered glucose and insulin metabolism. Three main areas of defect contribute to diabetes: defects in insulin signalling leading to insulin resistance; defects of insulin secretion leading to hypoinsulinaemia; and apoptosis leading to decreased beta cell mass. These three pathological pathways are reviewed, focusing on rare genetic syndromes which have diabetes as a prominent feature. Apoptosis seems to be a final common pathway in both type 1 and type 2 diabetes. Study of rare forms of diabetes may help ion determining new therapeutic targets to preserve or increase beta cell mass and function.
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Affiliation(s)
- J R Porter
- Birmingham Children's Hospital, Birmingham B4 6NH, UK.
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13
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Abstract
Type II diabetes is a common, complex and heterogeneous group of disorders of growing public health concern. Paradoxically, rare monogenic forms of diabetes mellitus have been the most informative regarding diabetes pathophysiology to date. We discuss disappointing results of genetic approaches thus far, emphasizing the genetic heterogeneity underlying the common phenotypic endpoint of elevated blood glucose level and the phenotypic misclassification in large studies resulting from this admixture and from the obligatory use of epidemiological or clinical surrogate measures. We suggest that novel approaches that take explicit account of the phenotypic, environmental and genetic complexities of type II diabetes are needed and discuss some principles that might underlie such approaches.
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Affiliation(s)
- A B Jenkins
- Department of Biomedical Science, University of Wollongong, Wollongong, NSW
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14
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Bolander FF. Molecular Bases of Endocrinopathies. Mol Endocrinol 2004. [DOI: 10.1016/b978-012111232-5/50017-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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McBain SC, Morgan NG. Functional effects of expression of wolframin-antisense transcripts in BRIN-BD11 beta-cells. Biochem Biophys Res Commun 2003; 307:684-8. [PMID: 12893278 DOI: 10.1016/s0006-291x(03)01243-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Wolfram syndrome is a rare condition in which the pancreatic beta-cells of patients are selectively deleted during the early years of life by a non-autoimmune-mediated mechanism. The condition is associated with mutations in the gene encoding wolframin, suggesting that this protein exerts a critical, but currently unknown, function in beta-cells. We have used an antisense strategy to modulate the expression of wolframin in insulin-secreting BRIN-BD11 cells to study its function. Stably transfected clones were established expressing full-length human wolframin antisense transcripts. These cells exhibited a dramatic reduction in cell proliferation rate and changes in morphology, although insulin secretion was not modified. The results imply that wolframin expression is required to sustain normal rates of beta-cell proliferation.
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Affiliation(s)
- Stuart C McBain
- School of Life Sciences, Keele University, Staffs ST5 5BG, UK
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Owen KR, Stride A, Ellard S, Hattersley AT. Etiological investigation of diabetes in young adults presenting with apparent type 2 diabetes. Diabetes Care 2003; 26:2088-93. [PMID: 12832318 DOI: 10.2337/diacare.26.7.2088] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVE Young adults with newly diagnosed apparent type 2 diabetes present the clinician with a wide differential diagnosis of possible etiology, including autoimmune and genetic causes as well as young-onset type 2 diabetes (YT2D). The characteristics of these groups have been described, but it is not known in which subjects investigation for etiology may be beneficial. RESEARCH DESIGN AND METHODS A total of 268 unselected U.K. Caucasian subjects diagnosed at ages 18-45 years and not treated with permanent insulin for < or =6 months were studied. All subjects underwent clinical assessment and screening for GAD antibodies (GADA) and tyrosine phosphatase IA-2 antibodies (IA-2A). Screening for a common mutation in the hepatocyte nuclear factor-1 alpha (HNF-1 alpha) gene and the common mitochondrial mutation was performed in the antibody-negative subjects. Subjects without insulin resistance were selected for sequencing of the HNF-1 alpha gene. RESULTS A specific etiology was defined in 11.6% of the 268 subjects and in 24.7% of the lean subjects. Twenty-six subjects (9.7%) were positive for a beta-cell antibody, one subject had familial partial lipodystrophy and the lamin A/C mutation R482W, and two subjects had the mitochondrial mutation A3243G. Two of 15 selected subjects had HNF-1 alpha mutations, the novel missense mutation A501T, and the previously reported R583Q. CONCLUSIONS This unselected series shows that there is considerable heterogeneity in apparent YT2D. beta-Cell autoantibodies should be performed in all those presenting at ages 18-45 years. Genetic investigations can be targeted to phenotypically defined subjects. The finding of a specific etiology will allow individualization of management and give patients valuable information about their condition.
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Affiliation(s)
- Katharine R Owen
- Peninsula Medical School, Department of Diabetes and Vascular Medicine, Exeter, Devon, UK.
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Abstract
Type 2 diabetes (T2DM) is a serious disease with severe complications. Around one in 10 people alive today suffer from type 2 diabetes or are destined to develop it before they die. Inheritance plays an important role in the cause of type 2 diabetes. A considerable amount of research is devoted to defining the genes involved in the aetiology of this widespread disease. This information is crucial if we are to improve our methods of preventing and treating diabetes. Over the last 25 years there have been considerable advances in our understanding of the genetics of diabetes. Important discoveries have been made in dissecting the genes involved in rare monogenic forms of type 2 diabetes which has become a paradigm for genetic studies of type 2 diabetes. This review focuses on the main approaches currently adopted and our current understanding of the genes involved in susceptibility to type 2 diabetes.
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Affiliation(s)
- Anna L Gloyn
- Department of Diabetes & Vascular Medicine, Peninsular Medical School, Barrack Road, Exeter EX2 5AX, UK.
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