# Functional and metabolomic analyses of brown adipose tissue during cold-deacclimation reveal rapid N-acetylated amino acid adaptations

## TL;DR

This study shows how brown fat quickly adapts metabolically when mice move from cold to warm environments.

## Contribution

The study reveals rapid N-acetylated amino acid adaptations during brown adipose tissue deactivation.

## Key findings

- Whole-body energy expenditure rapidly decreases during the cold-to-thermoneutral transition.
- BAT mitochondrial content and uncoupling capacity decline in parallel during deacclimation.
- N-acetylated amino acids may serve as indicators of brown adipose thermogenesis.

## Abstract

Non-shivering thermogenesis (NST) in brown adipose tissue (BAT) is rapidly activated in the cold but inactive at warm ambient temperatures. To elucidate the metabolic remodeling in BAT during recovery from cold exposure, mice were acclimated to 4°C for 7 days, then deacclimated at thermoneutrality (30°C) for 3–48 h. Cold-acclimated mice demonstrated high metabolic rates and food intake, which decreased immediately by ∼40% upon deacclimation. Uncoupled respiration decreased by 24 h, corresponding with gradual declines in mitochondrial protein content and UCP1 gene expression. Decreases in BAT mitochondrial content paralleled declines in protein content by 48 h of cold deacclimation. Metabolomic profiling revealed major alterations in amino acid, TCA cycle, glutathione, and purine metabolism pathways. Marked decreases in the abundance of N-acetylated amino acids in cold deacclimated mice corresponded with increased aminoacylase 1 (Acy1) expression. Together, results highlight the coordinated structural and metabolic remodeling of BAT mitochondria during thermogenesis and deactivation.

•Cold-to-thermoneutral transition rapidly decreases whole-body energy expenditure•BAT mitochondrial content and uncoupling capacity regress in parallel•Cold-deacclimation decreases succinate and increases purine nucleotides levels•N-acetylated amino acids may act as valuable indicators of brown adipose thermogenesis

Cold-to-thermoneutral transition rapidly decreases whole-body energy expenditure

BAT mitochondrial content and uncoupling capacity regress in parallel

Cold-deacclimation decreases succinate and increases purine nucleotides levels

N-acetylated amino acids may act as valuable indicators of brown adipose thermogenesis

Physiology