# Cold Exposure Induces Swine Brown Adipocytes to Display an Island-like Distribution with Atypical Characteristics

## TL;DR

This study reveals that pigs have brown adipocytes with unique features and explores their response to cold exposure.

## Contribution

The discovery of brown adipocytes in pigs and their atypical characteristics fills a research gap in animal fat metabolism.

## Key findings

- Swine brown adipocytes display island-like distribution and have small lipid droplets and numerous mitochondria.
- Expression of EBF2 and ATP2B4 confirms brown adipocyte identity in pigs.
- High miR-10383 expression enhances UCP3 thermogenic efficiency during cold exposure.

## Abstract

The original purpose of this study was to compare human and pig scRNA-seq data to determine why pigs do not have brown adipocytes. However, during the experiment, we identified brown adipocytes in pigs. Therefore, we aimed to confirm that these adipocytes were brown adipocytes via a comparative analysis using typical mouse brown adipose tissue sections. We found that swine brown adipocytes were distributed in an island-like pattern, with three typical characteristics: (1) numerous mitochondria and small lipid droplets, (2) a cellular volume smaller than that of white adipocytes, and (3) expression of specific marker genes (EBF2 and ATP2B4). The expression levels of the thermogenesis-related genes UCP2/3 were not significantly increased. Thus, we conducted ceRNA network analysis, revealing that high expression of the key microRNA miR-10383 increased the thermogenic efficiency of UCP3 in the cold exposure group. In addition, the epigenetic memory of UCP3 was disrupted. Chromatin accessibility and Whole-Transcriptome Sequencing of Groin Adiposesibility results revealed peaks in the promoter regions of the UCP2/3 genes. In our discussion of the study’s limitations, we explain how to repeat the experiment to significantly increase the UCP2/3 protein content. This study fills a research gap regarding brown fat in pigs and can provide a reference for future studies on fat metabolism.