Paper short abstract:

Human cold adaptation was important for survive during ice age. mtDNA haplogroup is suggested to relate cold adaptation. We try to discuss the relationship between modern human cold adaptability and mtDNA haplogroup.

Paper long abstract:

Human cold adaptability is affected by various factors; seasonal change, lifestyle, and genetic factor. However, genetic factor is still unclear. mtDNA haplogroup which determined by mtDNA polymorphism is one of genetic factor. Since mitochondria functions closely relate to human thermogenesis involving shivering thermogenesis (ST) and non-shivering thermogenesis (NST) to maintain body temperature, some previous studies suggested that mtDNA polymorphism shaped by cold climate and some polymorphism relate to human cold adaptation. We already reported haplogroup D had higher body temperature during severe cold (10 C°) in summer, but no difference in winter. The purpose of present study was to the interaction between mtDNA haplogroup and seasonal variation that contributes to cold adaptability under mild cold, focusing on NST and haplogroup D in Japanese. Seventeen university students (eight haplotype D participants and nine haplotype non-D participants) participated in the present study in the summer and winter. The climate chamber used was programmed so that ambient temperature dropped from 28 °C to 16°C over the course of an 80 min period. Oxygen intake, rectal temperature, skin temperature of participants was recorded during experiments. Results show that, in summer, there was no significant difference between D and non-D group. In winter, the increase in energy expenditure calculated by oxygen intake was higher in the haplogroup D than in the haplogroup non-D group. Because shivering was not occurred during experiment, this increase of energy expenditure was considered to be NST. Thus, present study suggests that mitochondrial haplogroup affects cold adaptability, and haplogroup D have higher NST in winter.