Inflammation and insulin resistance: an old story with new ideas.

Years before insulin was discovered, anti-inflammatory sodium salicylate was used to treat diabetes in 1901. Intriguingly for many years that followed, diabetes was viewed as a disorder of glucose metabolism, and then it was described as a disease of dysregulated lipid metabolism. The diabetes research focused on the causal relationship between obesity and insulin resistance, a major characteristic of type 2 diabetes. It is only within the past 20 years when the notion of inflammation as a cause of insulin resistance began to surface. In obesity, inflammation develops when macrophages infiltrate adipose tissue and stimulate adipocyte secretion of inflammatory cytokines, that in turn affect energy balance, glucose and lipid metabolism, leading to insulin resistance. This report reviews recent discoveries of stress kinase signaling involving molecular scaffolds and endoplasmic reticulum chaperones that regulate energy balance and glucose homeostasis. As we advance from a conceptual understanding to molecular discoveries, a century-old story of inflammation and insulin resistance is re-born with new ideas.