‘Obesity may disrupt circadian clock in cardio system’

But in obese individuals,who frequently eat at irregular times,the natural circadian rhythms are believed to be disrupted and it may lead to several metabolic disorders like hormonal imbalance,psychological and sleep disorders,as well as cancer. People working in shifts are likely to suffer from such problem.

With obesity known to affect at least the eat/sleep cycles,a team at the Georgia Health Sciences University in Augusta in the US set out to determine whether obesity might also affect the molecular components of the clock that governs the vascular system — the system of the heart and blood vessels that are responsible for blood movement in the body.

Their research,presented at the Experimental Biology 2011 meeting in Washington,was conducted in two phases.

In phase one,they examined the circadian variation in the cardiovascular chamber of three groups of mice (lean,obese and diabetic) at three time intervals: early morning,mid-day and evening,and measured the gene expression in the cardiovascular genes during these times.

Evidence of a cardiovascular rhythm was found in the lean animals. Among the evidence was the presence of endothelial nitric oxide synthase (eNOS),an enzyme helps coordinate blood flow,thus tends to be elevated at the end of the day and lower in the morning.

But,the researchers found this rhythm was lost in obese animals. For example,eNOS had either shifted its pattern,peaked at the wrong time,or was flat overall. Thus,the obese animals had lost their ability to control circadian variation of eNOS.

In phase two,the team used the data to examine whether the lack of rhythmic response could translate into a cardiovascular defect. They did so by examining a series of specific molecules from the cardiovascular clock genes and by measuring the acceleration of the genes in the blood vessels.

While in the lean animals they found that a key regulator of circadian rhythm,a gene called Clock,was high in morning and low in evening,the expression of the gene remained flat throughout the 24-hour cycle in the obese animals.

Dr David Stepp,a senior researcher on the team,summed up the findings by saying,”Based on the results of this study we now know that obesity impairs the clock machinery of the vasculature system and that correlates with a variation in expression of cardiovascular genes and their loss of the circadian rhythm.”