“We should consider the type of sugar we are consuming, because different sugars behave differently in our body,” said Roshanak Rahimian, PharmD, MSc, PhD, professor of physiology and pharmacology. Dr. Rahimian, along with Sonali Shaligram ’17 and Farjana Akther ’19, collaborated on a study with researchers from University of Barcelona. “Our goal was to investigate the molecular mechanisms underlying the metabolic and vascular effects of these simple sugars and to determine whether these effects are exclusively related to increased calorie consumption or the type of sugar,” Dr. Rahimian explains.
The results of the study were published in the prestigious American Journal of Physiology – Heart and Circulatory Physiology, in the February 2017 issue. The article entitled “Type of supplemented simple sugar, not merely calorie intake, determines adverse effects on metabolism and aortic function in female rats,” was co-authored by Gemma Sangüesa; Sonali Shaligram; Farjana Akther; Núria Roglans, PharmD; Juan C. Laguna, PhD; Roshanak Rahimian, PharmD, MSc, PhD; and Marta Alegret, PharmD.
“Fructose is a monosaccharide, a simple sugar that is present in many fruits and vegetables,” Dr. Rahimian explains. “Although fructose has the same chemical formula (C6H12O6) as glucose, it differs in its chemical structure.” Shaligram adds, metabolism of fructose also differs from that of glucose. While both are metabolized by the liver, other tissues can uptake glucose. She quotes Robert H. Lustig, MD, professor of pediatrics at University of California, San Francisco, “Up to 80 percent of glucose can be metabolized by other tissues; in comparison 100 percent of fructose is metabolized by the liver.”
Their findings emphasize that the type of sugar consumed makes a difference. “Despite higher caloric intake in glucose-supplemented subjects, fructose caused worse metabolic and vascular responses,” Dr. Rahimian said. Although both sugar-fed groups consumed more calories than the control group, the total calorie intake of the glucose-fed subjects was higher than that of fructose. Also, despite this difference, only the fructose group exhibited a significant increase in final body weight. In addition, the fructose group showed more vascular and liver damages than those of glucose-fed group.
While studies have been done comparing glucose and fructose, the unique aspect of this study is the focus on investigating how specific genes are altered when the two sugars are metabolized. Dr. Rahimian adds, “Our collaborators at University of Barcelona had already published several articles on the adverse effect of fructose, but further studies should be done on the relative effects of glucose and fructose on vascular reactivity and the underlying mechanisms involved.”
Dr. Rahimian shares what drives her and her team to pursue this research: “Cardiovascular disease (CVD) is the number one cause of death worldwide. Macro and micro-vascular complications can lead to CVD. Unhealthy diet is one common factor responsible for developing obesity and CVD. The consumption of sugar sweetened beverages (SSB) are increasing very rapidly. Therefore, we were very interested in the topic of investigating different types of sugars and their effects on metabolic and vascular function.”
As stated in the article, “At present, there is an intense debate in the scientific community about whether the adverse cardiovascular and metabolic effects of SSB are mostly attributable to specific effects of the simple sugar used as sweeteners or are merely the consequence of the increase in caloric intake and weight gain in the population consuming large quantities of SSB.”
The study gave Pacific students the opportunity to be involved in the various stages of the research project, from planning to publishing. “The graduate students were fully involved in analyzing the data and giving intellectual input over the course of the study,” Dr. Rahimian shares. “We are so proud of this work. It provided my group the opportunity to experience an outstanding collaboration with the University of Barcelona group. We got a chance to work closely with each other. It is very rewarding to share research and knowledge with other groups.”
By Anne Marie H. Bergthold