Visceral adiposity and expression of clock genes in peripheral blood mononuclear cells: A pilot study

Increasing evidence suggests a close interrelationship between disrupted circadian rhythms and obesity and metabolic disturbances. In particular, abdominal obesity, which contributes to the pathogenesis of metabolic disease, is associated with disrupted clock gene expression. However, little is known about the relationship between clock gene expression and accurate computed tomography (CT)-based measurements of visceral adiposity. Therefore, we examined the relationship between expression of clock genes in peripheral blood mononuclear cells (PBMCs) with visceral and subcutaneous adiposity in 75 healthy overweight or obese individuals. PBMCs were obtained from blood samples collected at 8 AM, and gene expression was analyzed by real-time reverse transcription polymerase chain reaction. Visceral and subcutaneous adiposity were measured by CT. Our results showed that visceral fat area was significantly positively correlated with BMAL1 and CRY1 mRNA levels and significantly negatively correlated with CLOCK, PER2, PER3 and CRY2 mRNA levels. In contrast, subcutaneous fat area was not correlated with the expression of any of the clock genes analyzed. After adjusting for multiple variables, visceral fat area was significantly associated with the expression of BMAL1, PER2 and CRY1. Taken together, our results indicate that visceral adiposity, but not subcutaneous adiposity, correlates with expression of clock genes in PBMCs.