May 9, 2017

Researchers ID biomarker for weight gain, fat-mass growth

A new study, led by Cornell University researchers in the Division of Nutritional Sciences and researchers at Braunschweig University of Technology, Germany, and the University of Luxembourg, has identified the sugar alcohol erythritol as a biomarker for increasing fat mass. In contrast to previous assumptions and research, erythritol can be metabolized by, and even produced in, the human body.

Erythritol occurs naturally in a variety of foods, such as pears and watermelon, but in recent years has increasingly become a common ingredient in low-calorie foods as a sugar replacement sweetener.

The study, published May 8 in the Proceedings of the National Academy of Sciences, was conducted as a discovery-based analysis to identity metabolomic markers associated with weight gain and increase in fat mass in young adults during the transition to college life.

Researchers found that students who gained weight and abdominal fat over the course of the year had fifteenfold higher blood erythritol at the start of the year compared with their counterparts who were stable or lost weight and fat mass over the academic year.

As part of Cornell’s EnHANCE project, an initiative of the Division of Nutritional Sciences that seeks to understand how the transition to college affects changes in diet, weight and metabolism, these findings advance knowledge on impacts to student health through the undergraduate years and beyond.

Each fall, more than 3 million high school graduates enroll in postsecondary education as first-time college freshmen, and this transition to a residential college environment is associated with weight gain.

“About 75 percent of this population experiences weight gain during the transition,” said Patricia Cassano, professor in the Division of Nutritional Sciences, a shared unit of Cornell’s College of Human Ecology and College of Agriculture and Life Sciences. “With this in mind, it is important to identify biomarkers of risk that could guide its understanding and prevention.”

For the study, data on 172 freshmen were collected at the beginning and end of the academic year. Student assessments included questionnaires, physical measurements and dual energy X-ray absorptiometry to measure lean and fat mass, and blood collection for measurement of biomarkers.

Senior co-author Karsten Hiller, professor of bioinformatics and biochemistry at TU Braunschweig and a leading scientist in cellular metabolism, noted: “We developed techniques to investigate how metabolites are generated and how they are further metabolized. These techniques can be applied to unknown metabolites as well.”

The study shows a novel metabolic pathway for dietary glucose with erythritol, an unrecognized product of glucose metabolism. Results found that erythritol is not only absorbed from food but is also produced by the body. By substituting carbon atoms in glucose with “heavy” carbon (13C), the researchers followed the route of glucose throughout metabolism in the body.

The result was surprising. When participants drank 13C-labeled glucose, the labeled carbon was metabolized and appeared in blood erythritol after some time.

“This result proves that the body can synthesize the sugar alcohol itself,” said Hiller. “Erythritol is not consumed and released from the body unchanged; it has an impact on the metabolism of our body. This finding is in contrast to all previous assumptions.”

According to Cassano, “With the finding of a previously unrecognized metabolism of glucose to erythritol and given the erythritol-weight gain association, further research is needed to understand whether and how this pathway contributes to weight-gain risk.”

The exact interplay between increased erythritol concentrations in blood and the development of weight gain and fat mass is not yet understood, she said. It is not clear whether endogenous erythritol and/or exposure from food contributes to the erythritol-weight gain association.

Future research is being planned to investigate the role of erythritol in human metabolism and to clarify its role in the context of weight gain.

Cornell’s Katie C. Hootman and University of Luxembourg’s Jean-Pierre Trezzi are co-first authors of the study, with co-authors Kristin A. Guertin, Lindsay S. Burwell, Patrick J. Stover and Patricia A. Cassano from Cornell University, Xiangyi Dong and Christian Jaeger from the University of Luxembourg, and Lisa Kraemer and Karsten Hiller from TU Braunschweig.

Stephen D'Angelo is assistant director of communications for the College of Human Ecology.