Protein lets mice eat fat, stay thin

Black mouse 2330tgm gorged himself on a high-fat, “Supersize Me” diet of mouse chow for 20 straight weeks.

He liked it so much that flying mouse chow dust coated his whiskers and fur.

But 2330tgm had a man-made twist in his genes that kept him lean. Or at least leaner than his brothers, who – with normal, unaltered mouse genes – ate the same diet.

The twist? Higher levels of interleukin-15. Known in the biomedical field as IL-15, the protein molecule is naturally secreted in minute amounts into the bloodstream by the muscles of mice – and humans.

The study, conducted in the laboratory at the Veterans Administration Hospital at American Lake in Lakewood, marks a notable biomedical discovery with potential commercial and health benefits for:

 • Controlling human obesity.

 • Restoring muscle strength in frail senior citizens.

 • Breeding cattle and pigs for leaner cuts of meat.

And you can bet your flabby abs that once IL-15 makes its anticipated debut in pill form in a few years after more animal and human studies, the bodybuilding industry will latch onto it like a mouse on cheese.

“Everything we do in the field gets picked up by the bodybuilders,” said Dr. LeBris “Lee” Quinn, the University of Washington School of Medicine researcher who led the four-year IL-15 study.

But the funders of the study – the Veterans Administration and the U.S. Department of Agriculture’s Cooperative State Research, Education, and Extension Service – foresee greater benefits.

Maybe you’ve heard about a not-so-little-thing called the obesity epidemic in America? The U.S. Centers for Disease Control and Prevention’s latest report categorizes 33.3 percent of adult men as obese, 35.3 percent of women and 16.3 percent of children aged 2 to 19.

Tagging along with obesity comes a host of unwelcome associates – some cancers, diabetes, high blood pressure, heart disease, stroke, cartilage degeneration, sleep apnea.

Quinn believes IL-15 can help, eventually.

For her study, her team created artificial genes designed to secrete higher amounts of IL-15, injected the genes into fertilized mouse eggs, then implanted the eggs in female mice. DNA tests separated each litter into those with normal genes and those with the enhanced IL-15 genes.

Then the eating began. The study included healthy diets, normal diets and diets that Quinn equated with “the typical American fast food diet.”

The results? Male IL-15 mice stayed leaner but didn’t add muscle. Female IL-15 mice added more muscle but didn’t stay as lean.

While IL-15 promises to help us fight the battles of our bulges, the VA sees the potential for IL-15 to improve the welfare of and care for veterans.

“For aging veterans – and for baby boomers,” Quinn said, “geriatric research is thought to provide the biggest public benefit.”

Imagine a frail senior citizen who falls and breaks a hip. For some, it means a downward death spiral as the full body of muscles atrophy while the hip heals. But with IL-15, the theory goes, the muscles could regain strength to help in the recovery, Quinn said.

So far, Quinn said, the research indicates that IL-15, when given to a mouse in distress – like an injured senior citizen – noticeably increases muscle strength.

Her team already has started on its next study to determine if maintaining youthful levels of IL-15 in mice, as they age, will keep them healthier.

Meanwhile, the Agriculture Department has an interest in IL-15’s potential to decrease the fat in cattle and pigs. So when those leaner meat cuts enter the food supply, they won’t fatten us up as much.

In 2025, perhaps, when you sit your trim self down for a nice Angus beef, 24-ounce Porterhouse at El Gaucho, you’ll know you can enjoy it guilt- and fat-free thanks in part to Quinn, her research team and black mouse 2330tgm.

Dan Voelpel: 253-597-8785

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