Diabetes and apoptosis: lipotoxicity

Christine M. Kusminski, Shoba Shetty, Lelio Orci, Roger H. Unger, Philipp E. Scherer

Obesity is an established risk factor in the pathogenesis of insulin resistance, type 2 diabetes mellitus and cardiovascular disease; all components that are part of the metabolic syndrome. Traditionally, insulin resistance has been defined in a glucocentric perspective. However, elevated systemic levels of fatty acids are now considered significant contributors towards the pathophysiological aspects associated with the syndrome. An overaccumulation of unoxidized long-chain fatty acids can saturate the storage capacity of adipose tissue, resulting in a lipid 'spill over' to non-adipose tissues, such as the liver, muscle, heart, and pancreatic-islets. Under these circumstances, such ectopic lipid deposition can have deleterious effects. The excess lipids are driven into alternative non-oxidative pathways, which result in the formation of reactive lipid moieties that promote metabolically relevant cellular dysfunction (lipotoxicity) and programmed cell-death (lipoapoptosis). Here, we focus on how both of these processes affect metabolically significant cell-types and highlight how lipotoxicity and sequential lipoapoptosis are as major mediators of insulin resistance, diabetes and cardiovascular disease.