A genetic variant that significantly increases a smoker’s preference for cigarettes containing menthol has been found in people of African descent. The variant of MRGPRX4 gene is found to be five to eight times more frequent among smokers who use menthol cigarettes than other smokers, according to an international group of researchers supported by the U.S. Food and Drug Administration and the National Institutes of Health.
According to achieves from FDA nearly 20 million people in the United States smoke menthol cigarettes, which are particularly popular among African-American smokers and teen smokers. 86% of African-American smokers in the US, use menthol cigarettes, compared to less than 30 percent of smokers of European descent. In addition, menthol cigarettes may be harder to quit than other cigarettes.
The research team, led by Dennis Drayna, conducted detailed genetic analyses on 1,300 adults. In the initial analyses, researchers at the University of Texas Southwestern Medical Center, Dallas (UT Southwestern), used data from a multi-ethnic, population-based group of smokers from the Dallas Heart Study and from an African-American group of smokers from the Dallas Biobank.
The researchers said that 5 to 8 % of the African-American study participants had the gene variant. None of the participants of European, Asian, or Native American descent had the variant.
Identifying the genetic variant pointed the researchers in an unexpected direction, leading them to provide the first characterisation of this naturally-occurring MRGPRX4 variant in humans. The gene codes for a sensor, or receptor, that is believed to be involved in detecting and responding to irritants from the environment in the lungs and airways.
"We expected to find genes that relate to taste receptors since menthol is a flavour additive," said Drayna. "Instead, we discovered a different kind of signaling molecule that appears to be involved in menthol preference."
Another team at the University of North Carolina (UNC), Chapel Hill, then worked with the research team to look more closely at the effect of the African-specific variant on the function of the MRGPRX4 receptor. They found that the variant alters a specific type of cell signaling, and that menthol alters this further. Additional studies confirmed that this sensor is found in the airways, suggesting that menthol is likely to affect how we sense irritation in the airways.
