Can jet lag make you fat?

Our waking and sleeping cycles—shaped over millions of years of evolution—have been turned upside down within a single century with the advent of electric lighting, air travel, and other demands of the modern era.

People now regularly disrupt their biological clocks. Think shift workers and frequent flyers, who have already been shown to be at high risk for such common metabolic diseases as obesity, diabetes, and heart disease.

A new study by Dr. Eran Elinav’s group in the Department of Immunology, published in Cell, reveals for the first time that our biological clocks work in tandem with the populations of bacteria residing in our intestines, and that these microorganisms vary their activities over the course of the day and night. And the bacteria do all this without cues from the sun and moon but rather in the total darkness of the digestive system, using the feeding cycles of the “host” to time their activities.

The study goes on to say that mice and humans with disrupted daily wake-sleep patterns exhibit changes in the composition and function of their gut bacteria, thereby increasing their risk for obesity and glucose intolerance. The study was done together with the lab of Prof. Eran Segal from the Department of Computer Science and Applied Mathematics and the Department of Molecular Cell Biology.

To determine whether the finding has any medical significance, the scientists created “jet-lagged” mice by exposing them to light and dark at different intervals, thereby altering their day-night rhythms. The jet-lagged mice stopped eating at regular times, and this interrupted the cyclic rhythms of their internal bacteria - leading to weight gain and high blood sugar levels. They then transferred bacteria from the jet-lagged mice into ordinary mice, or controls, and what they found was startling: The ordinary mice began gaining weight and developed high blood sugar levels.

The scientists then turned to humans. They collected bacterial samples from two people flying from the U.S. to Israel—once before the flight, once a day after landing when jet lag was at its peak, and once two weeks later when the jet lag had worn off. The researchers then implanted the bacteria from each of these stages into mice. And sure enough, the mice that received the jet-lagged humans’ bacteria exhibited significant weight gain and high blood sugar levels, while mice that received the bacteria from either before or after the jet lag had worn off remained their own trim and slim selves.

Dr. Eran Elinav is supported by the Abisch Frenkel Foundation for the Promotion of Life Sciences, the Benoziyo Endowment Fund for the Advancement of Science, the Gurwin Family Fund for Scientific Research, the Leona M. and Harry B. Helmsley Charitable Trust, the Adelis Foundation, Yael and Rami Ungar, Israel, the Crown Endowment Fund for Immunological Research, John L. and Vera Schwartz, Pacific Palisades, CA, the Rising Tide Foundation, Alan Markovitz, Canada, Andrew and Cynthia Adelson, Canada, the estate of Jack Gitlitz, the estate of Lydia Hershkovich, the European Research Council, the CNRS - Centre National de la Recherche Scientifique, the estate of Samuel and Alwyn J. Weber, and Mr. and Mrs. Donald L. Schwarz, Sherman Oaks, CA

He is the incumbent of the Rina Gudinski Career Development Chair.

http://www.weizmann.ac.il/immunology/elinav

Prof. Eran Segal is supported by the Kahn Family Research Center for Systems Biology of the Human Cell, the Cecil & Hilda Lewis Charitable Trust, the European Research Council, and Mr. and Mrs. Donald L. Schwarz, Sherman Oaks, CA

http://www.wisdom.weizmann.ac.il/~eran