Obese individuals typically suffer more health related problems than their leaner counterparts. They are more likely to be diagnosed with insulin resistance, diabetes, increased stress hormones, hypothyroidism, and sleep apnea.
According to researchers at the Georgia Health Sciences University in Augusta, the potential for additional obesity risks related to circadian rhythms in the cardiovascular system were observed in mice.
In obese individuals, the natural "circadian rhythms" are believed to be disrupted.Scientists have observed that there is a molecular basis that precisely controls these day/night rhythms in a group of genes dubbed the circadian clock, including one molecule also aptly named 'Clock'.
Obese individuals frequently eat at irregular times, and especially late at night.
In addition, they often suffer from sleep apnea, which disturbs their sleep rhythm thus causing them to miss a good night's sleep.
Shift workers tend towards obesity because their physiological requirements are backwards (breakfast may start at 10:00 p.m.) and swing shift workers (who work a week on the day shift followed by a week on the night shift) are predisposed to obesity because their physiological cues "swing" back and forth thus interrupting the natural circadian rhythms.
The newest study reports that a master clock gene – which regulates the cardiovascular system – does not fluctuate regularly as it does in non-obese animals.
The study was conducted by examining 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.
In the lean animals they found evidence of a cardiovascular rhythm. Among the evidence was the presence of endothelial nitric oxide synthase (eNOS). This crucial enzyme helps coordinate blood flow and tends to be elevated at the end of the day and lower in the morning.
By contrast, they found this rhythm was lost in obese animals.
Researchers reported that eNOS had either shifted its pattern, peaked at the wrong time, or was flat overall.
The obese animals had thus lost their ability to control circadian variation of eNOS.
In a second phase of the study, researchers measured the acceleration of genes in blood vessels.
In the lean animals they found that a key regulator of circadian rhythm, a gene called Clock, was high at 7:00 a.m. and low at 7:00 p.m. In the obese animals the expression of the gene remained flat throughout the 24-hour cycle.
David Stepp, Ph.D., a senior researcher on the team, said "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."
Having identified that the Clock gene does not work in the presence of obesity, he says the team has new studies underway to help explain why.
