Diet, body clock, hormones, and metabolism: What's the link?

They used two groups of mice: one group was on a normal diet, and the other group was fed a high fat diet.The team also examined in detail what happened to the mice's 24-hour liver metabolism as a result of daily surges in glucocorticoid secretion.The methods that they used allowed them to show that the effects of glucocorticoids were different when the animals fasted during sleep, and while they fed when they were awake and active.The researchers found that the glucocorticoid receptor exerted these effects through time-sensitive binding with the genomes of the liver cells.In addition, it appears that the receptor, and therefore the associated stress hormones, help regulate nearly all circadian genes."Highlighting the dominant role [the glucocorticoid receptor] plays in synchronizing circadian amplitudes," write the authors, "we find that the majority of oscillating genes are bound by and depend on [the glucocorticoid receptor]."The researchers showed that the livers of mice that lacked the receptor did not control fat and sugar levels according to day and night.The team suggests that the findings reveal how the liver controls levels of sugar and fat in the blood differently during the day compared with nighttime.A further set of experiments also revealed that normal weight and obese mice responded differently to a glucocorticoid drug.The team believes that the study is the first to show that diet can alter the effect of hormones and drugs on metabolic tissues.The researchers suggest that their findings will help inform the emerging field of chronomedicine, which emphasizes the role of the biological clock in health and disease."We could describe a new link between lifestyle, hormones, and physiology at the molecular level, suggesting that obese people may respond differently to daily hormone secretion or to glucocorticoid drugs," says senior study author Nina Henriette Uhlenhaut, a professor at Helmholtz Zentrum München."Understanding how glucocorticoids control 24-hour cycles of gene activity in the liver and consequently blood levels of sugar and fat provides new insights into chronomedicine and the development of metabolic disease."Prof.