49Type 2 Diabetes (T2D) is an emerging public health problem in Asia. An Asian mitochondrial DNA 50 variation m.1382A>C (rs111033358) leads to a K14Q amino acid replacement in MOTS-c, an 51 insulin sensitizing mitochondrial-derived peptide. Meta-analysis of three cohorts (n=27,527, J-52 MICC, MEC, and TMM) showed that males but not females with the C-allele exhibit a higher 53 prevalence of T2D. Furthermore, in J-MICC, only males with the C-allele in the lowest tertile of 54 physical activity increased their prevalence of T2D, demonstrating a kinesio-genomic interaction.
55High-fat fed, male mice injected with MOTS-c showed reduced weight and improved glucose 56 tolerance, but not K14Q-MOTS-c treated mice. Like the human data, female mice were unaffected.
57Mechanistically, K14Q-MOTS-c leads to diminished insulin-sensitization in vitro. Thus, the 58 m.1382A>C polymorphism is associated with susceptibility to T2D in men, possibly interacting with 59 exercise, and contributing to the risk of T2D in sedentary males by reducing the activity of MOTS-c. 60 61 64 65The prevalence of type 2 diabetes mellitus (T2D) is growing dramatically. Over 400 million 66 individuals were diagnosed with T2D worldwide in 2015, and the International Diabetes Federation 67 projects that at least 600 million people will need to be treated for T2D by 2040 1 . However, treating 68 T2D is challenging because the disease etiology is genetically heterogeneous and varies among 69 ethnicities 2-4 . For example, a recent meta-analysis showed that T2D is 72% heritable (95% CI: 61-70 78%) 2 , and the Western Pacific Region -including China and Japan -makes up ~37% of the total 71 T2D diagnoses in the world 1 . This is particularly noteworthy because although East-Asian 72 populations have lower mean body mass index (BMI) than Caucasian populations, they have a 73 higher susceptibility to T2D compared to Caucasians 5 . Furthermore, when matched for BMI, East
74Asians have a greater percentage of body fat and a tendency for increased visceral adiposity 6 .
75T2D in Asian patients is characterized by early beta cell dysfunction, in contrast to Caucasian 76 populations that have more insulin resistance 7,8 . Thus, ethnicity-based DNA variations likely 77 influence the pathogenesis of T2D.
78While diabetes directly caused by mutations in mtDNA are extremely rare 9 , several genetic 79 analyses revealed that mtDNA polymorphisms contribute to T2D risk in both European and Asian 80 populations 10,11 . Notably, mtDNA sequences are more varied by ethnicity compared to nuclear 81 DNA sequences due to the 10-times higher mutation rate of mtDNA compared to nuclear DNA 82 12,13 . As a result, certain mtDNA polymorphisms could contribute to the T2D prevalence in different 83 ethnicities. The human mitochondrial genome consists of 16,569-base pairs and encodes 37 84 genes including 13 full size proteins involved in oxidative phosphorylation, 2 rRNA, and 22 tRNA 85 genes that are necessary for protein synthesis within the mitochondria. Genetic polymorphisms in 86 t...