What Fat Monkeys Tell Scientists About Obesity Disease
Posted Feb 20 2011 7:25am
Meet Shiva, who sits around and eats too much rich, fatty foods and sips too many sugary drinks, with a pot belly to prove it. Only it's not your neighbor, it's a monkey.
Leah Nash for The New York Times
At 45 pounds Shiva weighs twice a normal monkey's weight. Like many people, he eats too much and gets barely any exercise, one of 150 monkeys who have been fattened up to help scientists study obesity and diabetes. The overweight monkeys also test new drugs aimed at treating those conditions.
The scientists admit, “We are trying to induce the couch-potato style, ”that mimics the health issues we face in the United States today.”
Experts say fat monkeys are more ideal than fat rats because monkeys more closely resemble humans not only physiologically but also in terms of feeding habits, i.e. it turns out that monkeys, like people, eat when they are bored, and eat even when they are not really hungry. But unlike human research subjects who 'fudge' when reporting their calorie intake and exercise, monkey subjects can have food intake measured perfectly accurately,
“Nonhuman primates don’t lie to you,” said neuroscientist Dr. Grove in the New York Times article on the Oregon primate center. “We know exactly how much they are eating.”
The monkeys have helped test experimental diet drugs and weight loss results from gastric bypass surgery as compared to forced dieting...scientists want to figure out the hormonal mechanisms by which the surgery can quickly resolve diabetes, so that drugs might one day be developed to have the same effect.
The study will do what cannot be done with people — kill some of the monkeys to examine their brains and pancreases.
The Oregon Health and Science University primate research center has more than 4,000 rhesus macaques monkies, and about 150 of them are the so-called rotund rhesuses. Some receive daily insulin shots to treat diabetes, and some have clogged arteries. One monkey died of a heart attack a few years ago at a fairly young age.
Shiva's daily diet has one-third of the calories coming from fat, similar to a typical American diet. She and the others can snack daily on a 300-calorie chunk of peanut butter, and are sometimes treated to popcorn or peanuts.
They also drink a fruit-flavored punch with the fructose equivalent of about a can of soda a day. In all, they might consume about twice as many calories as a normal-weight monkey.
Dr. Grove and researchers at some other centers say the high-fructose corn syrup appears to accelerate the development of obesity and diabetes.
It's unclear how much credence to put in lab results when you consider that Rinat Neuroscience had an experimental drug that sharply reduced appetite in rodents.... but obese baboons in San Antonio doubled or tripled their food intake when they got the drug.
Monkey studies can cost up to several million dollars because they are as difficult to do as human studies form an ethical standpoint.
For example in this study, the monkeys were (some say cruelly) kept animals separated at all times so they could snack between meals, since that is an important reason people gain weight. Allowing them outside, even one at a time, would mean they would exercise more, which defeated the purpose of studying the impact of a sedentary lifestyle with a calorically dense diet.
Perhaps not surprisingly, we see research labs making the same moves that pharmaceutical companies and patients have made - going abroad.
Apparently research money farms is a booming industry in China, where thousands of primates are caged for studies.
More research on obesity here. A good resource for bariatric surgery here.