The metabolic syndrome: The question of balance between the pro-inflammatory effect of macronutrients and the anti-inflammatory effect of insulin

The common occurrence of the combination of obesity, insulin resistance, hypertension, hypertriglyceridemia, low HDL cholesterol, and hyperinsulinemia was first described by Reaven as insulin resistance syndrome or metabolic syndrome. The syndrome was recognized as a pro-atherogenic risk causing coronary heart disease (CHD). More recently, other features like elevated plasma PAI-1 and CRP have been added to the combination. In view of recent data demonstrating that insulin exerts an anti-inflammatory effect while macronutrients exert pro-inflammatory effects, we are in a better position to explain why an insulin-resistant state such as metabolic syndrome is pro-inflammatory and also explain how it develops. This focused review discusses the relevance of these recent observations, puts into perspective the pathogenesis of various features of metabolic syndrome, and also predicts some features that may be incorporated into it in the future.