We all heard over and over that sleep deficiency could lead to obesity. One may wonder why it is the case. What sleep has to do with insulin insensitivity and metabolic syndrome?
Surprisingly, new study from Weizmann Institute of Science, Israel, suggests that alteration in sleep-wake rhythmicity leads to obesity through modification of gut microbiota.
This study, diurnal rhythmicity and a microbiome-dependent mechanism for common metabolic disturbances in humans, from Cell, examined how disruption of food intake rhythmicity due to time zone travel (jet-lag) affected development of metabolic syndrome.
First, the authors observed that there was rhythmic variation of gut microbiota composition wild-type mice due to dark-light cycle, that was lost in Per1/2−/− mice, which are deficient in a functional host clock genes. Interestingly, artificially modulating food availability could alleviate circadian clock deficiency in Per1/2−/− mice.
To mimic natural dark-light cycle disruption, the authors created experimental jet-lag condition for mice. Within 6 weeks, jet-lagged mice showed weight gain and glucose intolerance, hallmark of metabolic syndrome. Interestingly, antibiotic treatment of jet-lagged mice reversed signs of metabolic syndrome.
Finally, the authors examined gut microbiota composition from individuals undergoing jet-lag. Interestingly, during jet-lag phase there was an increase in Firmicutes which were linked to obesity in earlier studies. Moreover, gut flora taken collected during jet-lag phase but not before or after, could promote metabolic syndrome in germ-free mice.
In summary, this study showed that human circadian rhythm control gut microbiota composition which in turn influence development of metabolic syndrome (weight gain, type II diabetes). It shows that some of the effects of dark-light cycle disruption could be minimized by antibiotic treatment. Of course, in this case antibiotic treatment must be directed to specific gut microbiota species. In addition, this study indicates that modulating or restricting access to food to particular time periods could minimize effect of dark-light cycle disruption in humans.