Meeting Abstract

P2.143  Tuesday, Jan. 5  Timecourse for Metabolic Remodeling in Response to Cold Acclimation in Threespine Sticklebacks ORCZEWSKA, Julieanna I*; O’BRIEN, Kristin M; University of Alaska Fairbanks jiorczewska@alaska.edu

This study sought to determine the molecular basis of metabolic remodeling in response to cold acclimation in the threespine stickleback, Gasterosteus aculeatus. Animals were maintained at 20˚C for 12 wk, then acclimated to 8˚C for 9 wk or held at 20ºC for an additional 9 wk. Animals were harvested on days 1-4 and wks 1, 4 and 9 of cold acclimation. The extent of mitochondrial biogenesis was determined in oxidative pectoral adductor muscle and liver tissue by measuring mitochondrial volume density, the ratio of mitochondrial DNA-to-nuclear DNA, and both transcript levels and maximal activities of citrate synthase (CS) and cytochrome c oxidase (COX). Transcript levels of the known regulators of mitochondrial biogenesis in mammals, PGC-1α, PGC-1β, NRF-1 and TFAM were also measured. While the activity and mRNA levels of CS and COX increased in response to cold acclimation in both liver and oxidative muscle, mitochondrial volume density only significantly increased in oxidative muscle from 12.5% ± 1.8 to 23.7% ± 1.8 (P< 0.05). Transcript levels of PGC-1α and PGC-1β did not increase in oxidative muscle in response to cold acclimation, suggesting that these factors may not play a role in mitochondrial biogenesis in fishes. However, mRNA levels of TFAM and NRF-1 significantly increased in oxidative muscle on day 2 of cold acclimation and again after 9 wks at 8˚C. Transcript levels of PGC-1α, PGC-1β and TFAM increased in liver after 1 wk at 8˚C and although not triggering mitochondrial biogenesis, may be important for increasing the expression of COX subunits and the copy number of mitochondrial DNA. These results suggest that the response to cold acclimation differs among tissues and that only some components of the pathway regulating mitochondrial biogenesis are similar between fishes and mammals.