From mice to men: insights into the insulin resistance syndromes

The insulin resistance syndrome refers to a constellation of findings, including glucose intolerance, obesity, dyslipidemia, and hypertension, that promote the development of type 2 diabetes, cardiovascular disease, cancer, and other disorders. Defining the pathophysiological links between insulin resistance, the insulin resistance syndrome, and its sequelae is critical to understanding and treating these disorders. Over the past decade, two approaches have provided important insights into how changes in insulin signaling produce the spectrum of phenotypes associated with insulin resistance. First, studies using tissue-specific knockouts or tissue-specific reconstitution of the insulin receptor in vivo in mice have enabled us to deconstruct the insulin resistance syndromes by dissecting the contributions of different tissues to the insulin-resistant state. Second, in vivo and in vitro studies of the complex network of insulin signaling have provided insight into how insulin resistance can develop in some pathways whereas insulin sensitivity is maintained in others. These data, taken together, give us a framework for understanding the relationship between insulin resistance and the insulin resistance syndromes.