Life lines 17

BONES, FAT, AGING, AND VIBRATION

Dr. Clinton Rubin is the Chair of the Biomedical Engineering Department at Stony Brook University. His research is on the relation of stem cells to the formation of fat cells and bone cells and how these two types of cells respond to mechanical stimulation. For most people mechanical stimulation means exercise. And for most people exercise, unless they like it, means running, bending, squatting, pushing, or engaging in games that require such effort. For those who live a sedentary life and exercise is at best walking from a parking lot to a store, a consequence of the lack of mechanical stimulation is an increase in the size and number of fat cells and a decrease in the number and size of bone cells. That means as we age we get fatter and as we age we get more brittle bones that break when we fall. In fact, Rubin claims after age 35 we lose about 2 percent of our bone cells per decade (in my case an 8 percent loss of bone cells). About 35 percent of adults in the United States are obese. I guess I would belong to that category because when my wife looks at my buttoned shirt as I sit, she calls me Wimpy, Popeye’s friend (for those whose memories go back to Smilin’ Jack, think, too, of his sidekick, Fat Stuff).

A few years ago, a thought occurred to Dr. Rubin. If both fat cells and bone cells have a common cell origin from mesenchymal stem cells, would there be a similar response in these two cells to mechanical stimulation? Instead of exercise he tried something different. He used a very mild vibration (the sort of pleasant thrumming in a vibrator chair) and found that it isn’t how hard you exercise but how much total vibration you get that gives you a maximum effect of mechanical stimulation. This is a couch potato’s dream – press the vibrator, munch the chips, and watch football or other diversions and slim down. Before you fellow fatties get too carried away, Rubin suggests some common sense. It isn’t so much what you eat; it is how much you eat that counts for making the fat that goes into your fat cells. Few people stop at one pretzel or one fistful of potato chips. Few people push away the plate after a sliver of pie. Few people allow one glass of beer as the day’s limit.

The surprise to Dr. Rubin was the beneficial effect vibration had on bone. In mice he studied, it prevented loss of bone cells and that means it could reduce the risk of osteoporosis. The story, as usual in science, is more complex than our desire to make it simple. In a high fat (or high calorie) diet, mice suppress mesenchymal stem cell formation. This not only leads to obesity and bone loss, it also diminishes the immune system and it diminishes muscle cells. While “buzz your bones,” as Rubin calls it, in moderation is a good idea, excess buzzing is damaging. In moderation Rubin finds his buzzed mice (90 cycles per second) cannot feel the buzz but their fat diminished 25-30 percent compared to non-buzzed mice. Dr. Rubin’s work is on going and he intends to use human volunteers to test out his buzzing therapy as an approach to regulating fat, bone and muscle growth. Lots of problems remain. A tennis player’s racket arm has 30 percent more muscle than his or her throwing arm. This implies that vibration in one part of the body may not do the job for the rest of the body.