European Journal of Biomedical and Pharmaceutical Sciences

PHASE SHIFT IN BMAL1 MRNA CIRCADIAN RHYTHM INCREASES CHOLESTEROL AND TRIGLYCERIDES IN MALE RATS MAINTAINED UNDER ALTERED LIGHT-DARK CYCLE

Rehab E. El-Hennamy* and Mona Abdel-Rahman

ABSTRACT

Advances in technology and modern life style cause a production of 24h society, that accompanied by increased exposure to light at night. This phenomenon may have harmful effects on human health that result from disruption of the body circadian rhythm. The present study aimed to examine the effect of altered light-dark cycle on the circadian rhythm of Bmal 1 gene expression in liver as well as the changes in serum cholesterol, and triglycerides concentrations and their daily profiles. Rats were divided into two groups, a control group kept under normal 12-12 light –dark cycle and a group exposed to 12 hours phase delay of the light-dark cycle followed by altered light-dark cycle for one week. The daily profiles of cholesterol, triglycerides and Bmal1 mRNA after one week of the study, were shifted in the altered light-dark cycle group as compared with control. Cholesterol and triglycerides levels were increased significantly in the altered light-dark cycle group than control. It is concluded from the present study that the shift in the clock gene Bmal1 expression in liver cause alteration in the daily profile of cholesterol and triglycerides and increase in their concentration which may be due to its action on the metabolic genes.

Keywords: circadian rhythm, light- dark cycle, cholesterol, triglycerides, Bmal1 gene.