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Mitochondrial Genome Variation and Metabolic Traits in a Maori Community

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posted on 10.11.2021, 04:22 by Benton, Miles Clifford

The mitochondrion is the energy producing factory of cells and it has long been thought that disruption to mitochondrial systems is linked to energy metabolism dysfunction. Sequence variants in the mitochondrial genome are plausible candidate risk factors for numerous human diseases, and research has identified specific mitochondrial DNA (mtDNA) variants associated with metabolic disorders such as obesity and type-2 diabetes. As part of the Rakaipaaka Health and Ancestry Study (RHAS) it has been observed that the Maori community of Nuhaka (Ngati Rakaipaaka) have a high incidence of certain metabolic diseases, namely obesity and diabetes. The reason for this is not well understood, but is likely to be a combination of both current lifestyle (e.g. dietary) and ancestral genetic factors. This study set out to sequence the entire mitochondrial genome in a sample of RHAS Maori participants. The aim was to discover genetic variation that might be specific to this Maori community and test whether such variants are associated with diabetes and other metabolic traits. This study used a novel RFLP assay to screen the mtDNA control region for Polynesian mtDNA ancestry. This established an initial group (n=30) with high levels of Maori mtDNA. Hypervariable (HVRI) sequencing was then used to generate a large dataset of sequences (n=94). This dataset was representative of individuals showing high Maori ancestry and aided the selection of 20 mtDNA's for Mitochip analysis. Combining the RHAS Maori HVRI sequences with those from previous studies indicated elevated variation in Maori mtDNA. Haplotype analysis identified 17 unique Maori haplotypes, 10 more than previously recorded. Mitochip resequencing has provided the first complete Maori mtDNA sequences to date. When compared to other mtDNA sequences it was identified that RHAS Maori share similar haplotype markers with Polynesians. Seven novel undocumented variants were found, as well as four variants that had previously been associated with various metabolic disorders. Mitochip analysis of mtDNA sequences revealed three variants which created a RHAS Maori specific signature; C1185T, G4769A, and T16126C. These variants also defined 3 unique mtDNA haplotypes within RHAS Maori, which are the first Maori specific haplotypes reported. Variant genotyping and correlation with metabolic traits identified significant associations within the wider RHAS Maori community. It was identified that RHAS Maori with T16189C showed elevation in both vitamin B12 levels and mean diastolic blood pressure. Individuals with the G4769A variant were shown to have significant increases in specific metabolic risk factors for cardiovascular disease. Conversely individuals with the more common A4769G variant were 2 times less likely to be diagnosed with diabetes. The findings from this study have identified a series of potential markers of metabolic disease within the RHAS Maori community. The goal now is to understand how these markers interact with environmental variables to increase the risk of metabolic syndrome. Such an outcome may open the way to designing personalised intervention strategies (e.g. dietary) to increase the health and well-being of at risk individuals.

History

Copyright Date

01/01/2009

Date of Award

01/01/2009

Publisher

Te Herenga Waka—Victoria University of Wellington

Rights License

Author Retains Copyright

Degree Discipline

Biomedical Science

Degree Grantor

Te Herenga Waka—Victoria University of Wellington

Degree Level

Masters

Degree Name

Master of Biomedical Science

Victoria University of Wellington Item Type

Awarded Research Masters Thesis

Language

en_NZ

Victoria University of Wellington School

School of Biological Sciences

Advisors

Macartney, Donia; Chambers, Geoff; Lea, Rod