Measurement of the unfolded protein response to investigate its role in adipogenesis and obesity.

The endoplasmic reticulum (ER) is the cellular organelle responsible for the folding of proteins destined for secretion and the intramembrane system of the cell, biosynthesis of lipids, and storage of calcium for regulated release. Extracellular stimuli and changes in intracellular homeostasis can alter the protein-folding environment of the ER and cause the accumulation of misfolded or unfolded proteins, a stress condition called ER stress. To resolve protein misfolding, cells have evolved a collection of adaptive signaling pathways, called the unfolded protein response (UPR). It is now recognized that ER stress contributes to many pathophysiological conditions. Increasing lines of evidence suggest that obesity/insulin resistance and subsequent type 2 diabetes are associated with ER stress and UPR activation in adipose tissue. However, whether and/or how ER stress and the UPR contribute to the pathogenesis of metabolic syndrome and obesity is not entirely clear. In this section, we describe how the UPR may contribute to the pathology of obesity, methods to measure UPR induction, and approaches to investigate the role of the UPR during adipocyte differentiation and in mature adipose tissue.