Finding the Freshman 15

Do you remember the start of your higher education? For many of us, it was our first time away from home, our first time fending entirely for ourselves – and our first experience with the “freshman 15” – the weight gain (of an arbitrary 15 pounds) that affects so many university students during their first year. According to Patricia Cassano, Professor in Cornell University’s College of Human Ecology, the phenomenon affects about 75 percent of new students – but why? And is there any way to identify those at risk?

Figure 1. A chromatogram comparing signals in the pooled baseline blood samples for the incident central adiposity group (red line) and the stable adiposity group (black line). The arrow marks the signal for erythritol, and the much higher peak for this metabolite in the pool of participants with incident central adiposity gain is evident.

Cassano and her group are trying to answer those questions as part of Cornell’s EnHANCE project, an initiative that is trying to solve the medical mysteries of the post-secondary transition. The goal? To improve student health not just in their first year, but throughout their undergraduate education and even beyond. And now, the group may have cracked the code: erythritol, best known as an artificial sweetener, is strongly associated in the blood with an increase in weight and abdominal fat (see Figure 1). “We found that students who gained weight and abdominal fat over the course of the year had 15-fold 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,” says Cassano. Her study used a technique developed by senior co-author Karsten Hiller, Professor of Bioinformatics and Biochemistry at Technische Universität Braunschweig, Germany, to investigate how metabolites are generated and further metabolized: they had participants drink 13C-labeled glucose and followed its path through the body. To their surprise, the labeled atoms began to appear in circulating erythritol. Glucose metabolism, thought to be so well known, had a trick up its sleeve – a previously unknown product of its metabolism. In direct contrast to previous assumptions, erythritol can be both absorbed from food and synthesized by the body (1). Right now, those most impressed by the new biomarker are biochemists and molecular biologists. But one day, it may hold more significance for clinical laboratories, primary care doctors, and young adults heading off to start their university lives. “Our study raises the possibility that erythritol metabolism may play a role in weight gain and adiposity change,” says Cassano. The association between the biomarker and the physical outcomes must be confirmed and replicated; the metabolic pathway itself must be better understood and characterized; and the role of exogenous erythritol has yet to be factored into the equation. The Cornell researchers are working on animal and cell-based studies to decipher the exact biochemistry of the metabolic pathway from glucose to erythritol. “Once we know the exact mechanism, we will be able to shed more light on the link between elevated blood erythritol levels and weight gain,” says Cassano.

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References

1. KC Hootman et al., “Erythritol is a pentose-phosphate pathway metabolite and associated with adiposity gain in young adults”, Proc Natl Acad Sci USA, 114, E4233–E4240 (2017). PMID: 28484010.

About the Author(s)

Michael Schubert

While obtaining degrees in biology from the University of Alberta and biochemistry from Penn State College of Medicine, I worked as a freelance science and medical writer. I was able to hone my skills in research, presentation and scientific writing by assembling grants and journal articles, speaking at international conferences, and consulting on topics ranging from medical education to comic book science. As much as I’ve enjoyed designing new bacteria and plausible superheroes, though, I’m more pleased than ever to be at Texere, using my writing and editing skills to create great content for a professional audience.

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