LOS ANGELESóResearchers at Charles Drew University of Medicine and Science in Los Angeles and Western University of Health Sciences in Pomona have discovered a reason why smoking increases the risk of heart disease and strokes.
The study, which will be presented Thursday, June 11 at The Endocrine Society's 91st annual meeting in Washington, D.C., found that nicotine in cigarettes promotes insulin resistance, a pre-diabetic condition that raises blood sugar levels higher than normal. People with pre-diabetes are at greater risk of developing cardiovascular disease.
Theodore Friedman, MD, Ph.D., chief of the endocrinology division at Charles Drew University, said the findings help explain a "paradox" that links smoking to heart disease.
Smokers experience a high degree of cardiovascular deaths, Friedman said. "This is surprising considering both smoking and nicotine may cause weight loss and weight loss should protect against cardiovascular disease."
The researchers studied the effects of twice-daily injections of nicotine on 24 adult mice over two weeks. The nicotine-injected mice ate less food, lost weight and had less fat than control mice that received injections without nicotine.
"Our results in mice show that nicotine administration leads to both weight loss and decreased food intake," Friedman said. "Mice exposed to nicotine have less fat. In spite of this, mice have abnormal glucose tolerance and are insulin resistant (pre-diabetes)."
Studies have shown that smokers who are pre-diabetic have blood glucose levels higher than normal, but not high enough for diabetes, a known risk factor for heart disease. Smokers also have higher rates of diabetes, but it is not directly clear whether smoking is the cause, because there could be other risk factors, Friedman said.
In the tests, however, the mice receiving nicotine developed pre-diabetes and also had high levels of the stress hormone cortisol, which increases blood pressure and blood sugar. The study's authors were able to partially reverse the harmful effects of pre-diabetes by treating the mice with a drug that blunts the action of nicotine.
"Our results suggest that decreasing insulin resistance may reduce the heart disease seen in smokers," Friedman said. "We anticipate that in the future there will be drugs to specifically block the effect of nicotine on insulin resistance."
New drugs are needed because those that are currently available are not specific enough to completely block nicotine's effects or they have bothersome side effects, said Friedman, whose study is one of 34 being featured at The Endocrine Society's 91st annual meeting..
ABOUT CHARLES DREW UNIVERSITY OF MEDICINE AND SCIENCE (CDU)
CDU is a private nonprofit, nonsectarian, minority-serving medical and health sciences institution. Located in the Watts-Willowbrook area of South Los Angeles, CDU has graduated over 550 medical doctors, 2,500 post-graduate physicians, more than 2,000 physician assistants and hundreds of other health professionals. The only dually designated Historically Black Graduate Institution and Hispanic Serving Health Professions School in the U.S. CDU is recognized as a leader in health inequities and translational research, specifically with respect to heart disease, diabetes, cancer, mental health, and HIV/AIDS. The University is among the top 7% of National Institutes of Health (NIH)-funded institutions and rated one of the top 50 private universities in research in the U.S. Recently, the CDU/UCLA medical program was named the "best performer" in the University of California System with respect to producing outstanding underrepresented minority physicians. For more information, visit http://www.cdrewu.edu.
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