A new study conducted by researchers at Lehman College, and recently published in the American Heart Association’s journal Hypertension, shows conclusively that overfeeding causes increases in sympathetic nerve activity (SNA)—part of the fight or flight reflex—which can lead to the development of high blood pressure. Dr. Martin Muntzel (Biology), an expert on diet, Type 2 diabetes and high blood pressure, led the study.
For years, scientists have known that obesity and weight gain are the major causes of high blood pressure, but they haven’t been able to determine how this happens. To find out, Dr. Muntzel and his team implanted radiotelemetry devises into fourteen female Wistar rats to monitor SNA, heart rate and arterial pressure. This experiment marks the first successful use of radiotelemetry technology in rats.
Over a three-week period, the researchers fed seven of the rats a diet high in fat that included vanilla wafers, crackers, buttered popcorn, cheetos and other high-caloric nutrients, while the other seven rats were fed a low-fat diet. The results were immediate—within fifteen days the rats consuming the high-fat diet gained weight and their fat mass doubled, activating lumbar SNA, which in turn caused their heart rate and blood pressure to rise.
“One thing that really surprised me through the course of this experiment is that just two weeks of consuming junk food doubled the subject’s fat mass,” says Dr. Muntzel. The team chose the cafeteria-style diet not only for its palatability and high caloric content, but also because they knew that it would have precisely the effect they wanted, which was rapid weight gain.
“None of this would have been possible had we not been able to attain the radiotelemetry technology,” explains Dr. Muntzel. Telemetry-based devices, specifically the kind that records SNA, have been in use for only four years. “There are a number of researchers from around the world that are using this, but our group was the first to actually make it work in rats,” he adds proudly.
This research was funded through a four-year National Institute of Health (NIH) grant aimed at increasing minority participation in biomedical research. Dr. Muntzel worked with Dr. Omar Ali S. Al-Naimi, a medical doctor from Iraq, and two now former Lehman students: Alicia Barclay, who is completing her first year of medical school in Ohio, and David Ajasin, now a Ph.D. student at the Einstein College of Medicine.
Dr. Muntzel joined the faculty at Lehman in 1994, and has authored a number of articles on diet and its effects on the cardiovascular system.