Sure, smoking can cause lung cancer, but until I saw this paper in ACS’ Journal of Proteome Research (JPR), I had no idea it also can weaken bones. Apparently, I’m late to the game, as it’s been almost 20 years since scientists first figured that out.
Smoking is a risk factor for osteoporosis, a condition in which bones get thin and become less dense. That makes the bones brittle, and they can break easily (think of broken hips among the elderly). It’s often associated with a hump at the base of the neck or a stooped posture that’s caused by the spine bones, or vertebrae, weakening. People with the condition also lose height, becoming up to six inches shorter over time. The disease is more common in women than men, with about 1 in 5 of U.S. women developing the condition after age 50. It’s a major cause of disability among older people.
Of course, aside from osteoporosis, smoking is better known for increasing the risks of developing heart disease, stroke, emphysema and many cancers, including bladder, lung and pancreatic cancer.
But how could smoking cause osteoporosis?
In the JPR paper, Gary Guishan Xiao and colleagues point out that previous studies suggested that toxins in cigarette smoke weakened bones by affecting the activity of osteoblasts, cells that build new bone, and osteoclasts, which break down, old bone. But is one of these cell types more affected? How exactly does smoking make bones weak and brittle?
To shed light on how cigarette smoking weakens bones, the scientists analyzed differences in genetic activity in bone marrow cells of mice exposed to cigarette smoke and those not exposed to smoke. They also examined cells from human smokers and non-smokers.
They discovered that human smokers produce unusually large amounts of two proteins that trigger the production of bone-resorbing osteoclasts compared to non-smokers. The experiments with laboratory mice confirmed the finding.
(The researchers acknowledged funding from the Cancer and Smoking Related Disease Research Program and the Nebraska Tobacco Settlement Biomedical Research Program.)