Proceedings of The Physiological Society

The Royal Society (ME 2012) (2012) Proc Physiol Soc 29, PC32

Poster Communications

Transcriptomic profiles in epididymal, inguinal, and brown adipose depots

S. Naknukool1, T. Goto1, N. Takahashi1, T. Kawada1, S. Seno2, H. Daiyasu2, H. Matsuda2

1. Food science and biotechnology, Kyoto University, Kyoto, Japan. 2. Bioinformatic engineering, Osaka University, Osaka, Japan.

[Introduction]: Fat tissues have been classified as either white adipose tissue (WAT) or brown adipose tissue (BAT). WAT accumulates excess energy in form of triglyceride. Conversely, BAT dissipates excess energy through adaptive thermogenesis by brown adipocyte-specific uncoupling protein (UCP) 1. Recently, a third type of adipocyte, name brite has been identified in WAT. These brite cells express many of genes specifically expressed in brown adipocytes, including Ucp1. Some WAT depots are more prone to induction of brite adipocytes. This study aimed to identify genes whose might be a key factor related to the difference in brite inducing ability of WAT depots. [Methods]: Epididymal WAT (EWAT), inguinal WAT (IWAT), and interscapular BAT were obtained from 6-wk-old C57BL/6 mice that were kept at 4°C or 26°C for 16 days. . All mice were anesthetized with seroflurane and then killed by cervical dislocation before harvesting adipose depots. The difference in brite inductive activity of each depot was determined by western blotting of UCP1. Gene expression was measured using Agilent SurePrint G3 Mouse microarray. Validity the cDNA microarray was determined by qRT-PCR. Microarray data was analyzed by Rank products method (n=3). [Results]: Cold accumulation did not significantly affect body weight of mice. However, elevating in BAT weight and decreasing in IWAT and EWAT weights were observed (p<0.05). Significant induction of UCP1 protein expression was found in BAT (1.8 times) and IWAT (25 times) (p<0.05). No UCP1 protein expression in EWAT was observed. Gene expressing profiles of IWAT and EWAT were similar to each other and much different from that of BAT, even when these tissues were taken from cold exposed mice. EWAT was found to exhibit 100 and 3000 times lower Ucp1 than that in IWAT and BAT. Up-regulation of Ucp1 in IWAT and BAT responding to cold exposure was detected, while the level of Ucp1 expression in EWAT was not altered. The expressions of brown fat-specific genes were highest in BAT and their expression level elevated after cold exposure in all tissues, except Pgc1α. Elevation of adipogenic gens aP2 and Pparg was detected in all tissues of cold exposed mice. Number of genes that their expression levels were significantly up-regulated (> 2 fold, false discovery rate < 20%) by cold-exposure is 1474 genes. Within this group of genes, 12 genes are receptor genes. By comparing between tissues, there were 22 receptor genes that are higher express in IWAT than EWAT. After gene expression validity by PCR, eight genes were selected for study their function related to Ucp1 expression. The highly expressing and significantly inducible by cold exposure genes (especially receptor gene), in IWAT and BAT, but not in EWAT, identified in this study might be used as a target in a strategy for increase energy expenditure that may also provide opportunities for the development of new therapeutics for obesity.

Where applicable, experiments conform with Society ethical requirements