Adiponectin multimer distribution, not absolute amount of plasma, correlates with depression severity in healthy elderly subjects

Adiponectin is an adipocyte-specific secretory protein that circulates in serum as three oligomeric complexes known as the high, medium and low molecular weight form (HMW, MMW and LMW). HMW adiponectin has been suggested to be a better predictor of metabolic variables, and it was recently reported that the ratio of HMW to total adiponectin or to LMW, not the absolute amount of plasma adiponectin, might be crucial in determining insulin sensitivity. Insulin resistance (IR) is considered to be a primary component of vascular risk factors. Although the association of depression with atherosclerotic vascular diseases has been well documented, the contribution of IR to the evolution and progression of depression-associated vascular morbidity and mortality remains unknown. The current preliminary study showed that the ratio of HMW to total adiponectin or to LMW, not the absolute amount of plasma adiponectin, was negatively associated with depression severity in healthy elderly subjects without metabolic syndrome. This pilot study supports a promising role of adiponectin multimer distribution for clarifying the pathophysiological mechanism by which depression is associated with increased risk for IR, leading to cardiovascular disease, metabolic syndrome or type 2 diabetes.