Nicotine increases cortisol levels, encourages insulin resistance, study finds.
The nicotine in cigarette smoke may promote insulin resistance and lead to a condition known as prediabetes, new research shows.
The finding, could explain why smokers are at higher risk for diabetes. The same team of researchers was able to partially reverse nicotine’s effect on insulin in mice by giving the rodents the nicotine-blunting drug mecamylamine.
In a society news release, study author Dr. Theodore Friedman, chief of the division of endocrinology, metabolism and molecular medicine at Charles R. Drew University of Medicine and Science in Los Angeles, noted that smokers tend to face a higher diabetes risk, even though "smoking causes weight loss, which should protect against heart disease."
But prior studies have shown smokers to be more insulin-resistant, which leads to higher blood-sugar levels. Some studies had suggested that the key factor at work was nicotine’s effect on the stress hormone cortisol, since, as Friedman said, "Cortisol excess is known to induce insulin resistance."
In their study, the team gave adult mice twice-daily injections of nicotine for 14 days. The mice displayed higher levels of cortisol in the blood. They also ate less and lost weight compared to mice that did not receive the shots but nonetheless developed insulin resistance and prediabetes.
Treating the mice with the nicotine-agonist drug mecamylamine blocked this process somewhat, the researchers noted.
"Our results suggest that reducing tissue glucocorticoid levels or decreasing insulin resistance may reduce the heart disease seen in smokers," said Friedman. "We anticipate that in the future there will be drugs to specifically block the effect of nicotine on glucocorticoids [such as cortisol] and insulin resistance."