Loss of PGC-1α causes depot-specific alterations in mitochondrial capacity, ROS handling and adaptive responses to metabolic stress in white adipose tissue

Abstract

White adipose tissue (WAT) delivers lipid-fueled metabolic support to systemic energy expenditure through control of lipolytic and re-esterifying regulatory pathways, facilitated by mitochondrial bioenergetic support. Mitochondria are important sources of reactive oxygen species (ROS) and oxidative damage may potentially derail adipocyte function when mitochondrial homeostasis is challenged by overproduction of ROS. Peroxisome proliferator-activated receptor-gamma coactivator (PGC)-1α is a transcriptional co-activator that in skeletal muscle plays a central role in mitochondrial biogenesis and function but whether PGC-1α is equally important for mitochondrial function and adaptations in white adipose tissue remains to be fully resolved. The aim of the present study was to characterize the necessity of adipocyte PGC-1α for adaptive regulation of mitochondrial function in distinct white adipose depots. PGC-1α adipose tissue-specific knockout (ATKO) and floxed littermate control mice (CTRL) were subjected to either 24 h of fasting or 48 h of cold exposure. Bioenergetics, ROS handling, basal and adaptive protein responses, markers of protein damage as well as lipid cycling capacity and regulation were characterized in distinct WAT depots.

ATKO mice demonstrated impairments in respiration as well as reduced OXPHOS protein content in fed and fasted conditions. Increased ROS emission in tandem with diminished mitochondrial antioxidant defense capacity resulted in increased protein oxidation in ATKO WAT. Adipose tissue PGC-1α knockout also led to changes in regulation of lipolysis and potentially triglyceride reesterification in WAT. In conclusion, PGC-1α regulates adipose tissue mitochondrial respiration and ROS balance as well as lipid cycling during metabolic challenges in a depot specific manner.