Metabolic remodelling in obesity and type 2 diabetes: pathological or protective mechanisms in response to nutrient excess?

Altered metabolism in tissues such as the liver, skeletal muscle and adipose tissue is observed in metabolic diseases characterized by nutrient excess and energy imbalance, such as obesity and type 2 diabetes. These alterations in metabolism can include resistance to the hormone insulin, lipid accumulation, mitochondrial dysfunction and transcriptional remodelling of major metabolic pathways. The underlying assumption has been that these same alterations in metabolism are fundamental to the pathogenesis of metabolic diseases. An alternative view is that these alterations in metabolism occur to protect cell and tissue viability in the face of constant positive energy balance. This speculative review presents evidence that many of the metabolic adaptations that occur in metabolic diseases characterized by nutrient excess can be viewed as protective in nature, rather than pathogenic per se for disease progression. Finally, we also briefly discuss the usefulness and potential pitfalls of therapeutic approaches that attempt to correct these same metabolic defects when energy balance is not altered, and the potential links between metabolic survival responses and other chronic diseases such as cancer.