Hypothesis: Cryptochromes and Brown Fat are Essential for Adaptation and Affect Mood and Mood-Related Behaviors

Timo Partonen

doi:10.3389/fneur.2012.00157

Abstract

Solar radiation and ambient temperature have acted as selective physical forces among populations and thereby guided species distributions in the globe. Circadian clocks are universal and evolve when subjected to selection, and their properties contribute to variations in fitness within specific environments. Concerning humans, as compared to the remaining, the “evening owls” have a greater deviation from the 24 h cycle, are under a greater pressure to circadian desynchrony and more prone to a cluster of health hazards with the increased mortality. Because of their position in the hierarchy and repressive actions, cryptochromes are the key components of the feedback loops on which circadian clocks are built. Based on the evidence a new hypothesis is formulated in which brown adipocytes with their cryptochromes are responsive to a broad range of physical stimuli from the habitat and through their activity ensure adaptation of the individual. The over-activated brown adipose tissue with deficient cryptochromes might induce disrupted thermoregulation and circadian desynchrony, and thereby contribute to lowered mood and pronounced depressive behaviors.

Highlights

Darwin (1859) concluded that“each at some period of its life, during some season of the year, during each generation or at intervals, has to struggle for life, and to suffer great destruction
A common genetic variant in TRIP6 was associated with absolute latitude, and with minimum winter temperature (Hancock et al, 2011). This gene is known to interact with proteins that regulate resting metabolic rate, and the thyroid-regulated energy balance. These findings suggest that brown adipocytes and circadian clocks, of whose components the cryptochromes do react to ultraviolet radiation (Foley et al, 2011), are relevant to survival and adaptation, and targeted by natural selection
HEAT GENERATED BY BROWN FAT IS CENTRAL TO ALL OSCILLATIONS far, there is preliminary evidence demonstrating that brown adipose tissue was clearly over-activated in two suicide cases with depressive disorder (Huttunen and Kortelainen, 1990), but on the basis of these data it cannot be judged whether the finding was specific

Summary

Introduction

Darwin (1859) concluded that“each at some period of its life, during some season of the year, during each generation or at intervals, has to struggle for life, and to suffer great destruction. The over-activated brown adipose tissue with deficient cryptochromes might induce disrupted thermoregulation and circadian desynchrony, and thereby contribute to lowered mood and pronounced depressive behaviors.

Results

Conclusion