MCG researchers study hormone that may prevent bone being lost in space

March 22, 2001

The reality of long-term space travel is raising questions about how to deal with the impact of long-term weightlessness on the body.

Medical College of Georgia researchers say that one of the destructive results B accelerated and significant loss of bone density B may be thwarted by a hormone secreted by the gut to help the body use food as fuel.

Their research on glucose-dependent insulinotropic peptide, or GIP, is funded by the National Space Biomedical Research Institute in Houston but it also holds promise for the down-to-earth problem of bone loss that inevitably comes with age.

Dr. Carlos M. Isales, endocrinologist, and Dr. Roni J. Bollag, developmental biologist, have developed a transgenic mouse that over-expresses GIP by about four times the normal rate; that equals the increase that occurs in the body after a meal.

"We think GIP is a signal the blood sends to your bones that says,
"We think the hormone may also act with insulin to make bones stronger," Dr. Isales said. As food is eaten, GIP and insulin levels both go up, but their secretion patterns are different: GIP levels don't return to baseline as quickly.

Rather GIP hangs around longer, stimulating osteoblasts to make bone and shutting down osteoclasts that break down bone. The balance of bone loss and production is uncoupled by weightlessness and by hormonal loss that occurs with age, Dr. Isales said. "You can break down bone, but you don't form it as well," without the natural force of gravity. Bone loss and production are constants in life, with the average person reforming his skeleton three or four times. Most people reach peak bone mass at age 25 and begin losing bone by age 40. A young space traveler would never reach peak bone mass without some intervention to re-establish the lost synergy, he said; an astronaut of any age would soon develop porous, weak bones.

But the researchers believe their transgenic mouse would fare much better in space, where they hope it will eventually land. For the time being, they are using a nearly $900,000, three-year grant to study the mice on earth, simulating periods of weightlessness in the animals that over-express GIP and measuring the impact of the loss of gravity on the bones. "We think that what will happen is that those mice who over-express GIP won't lose bone," Dr. Isales said.

If they are right, GIP levels could be increased by injecting a synthetic version already commercially available for research, but the simplest way might be designing an optimal diet, he said. Carbohydrates, protein and fat all stimulate GIP production. The current thinking is that heavier people have denser bones because of increased gravity, but increased GIP production likely plays a role as well, Dr. Isales said.

They also will look at the impact of GIP on early bone development. The researchers have a mouse that expresses GIP at 10 times the natural rate.

These high levels may not only impact bone sturdiness, but also may increase bone length, he said. "We think it's involved in bone formation in the growth plate," Dr. Isales said, which means GIP supplements might also treat growth problems.
-end-


Medical College of Georgia at Augusta University

Related Bone Density Articles from Brightsurf:

Romosozumab substantially builds bone density in hip and spine
New research presented at ACR Convergence, the American College Rheumatology's annual meeting, reveals that romosozumab, an osteoporosis drug, produces substantial gains in bone mineral density in the hip and lumbar spine within one year, and that transitioning patients to a potent antiresorptive drug can lead to even more bone density gains.

Bone density is associated with regular use, study finds
Researchers at the Beckman Institute at the University of Illinois Urbana-Champaign have found that bone density and frame size of women is associated with habitual use in tasks that involve domestic labor.

New guidelines for assessment of bone density and microarchitecture in vivo with HR-pQCT
There is an urgent need for guidance and consensus on the methods for, and reporting of, high-resolution peripheral quantitative computed tomography (HR-pQCT) imaging so that different studies can be compared to each other.

Adults with undiagnosed Celiac disease have lower bone density, says first study on topic
Research by George Mason University College of Health and Human Services found lower bone density in adults who are likely to have undiagnosed celiac disease, an autoimmune disease triggered by consuming gluten, despite this group consuming more calcium and phosphorous than the control group.

Family history of diabetes linked to increased bone mineral density
The association between type 2 diabetes and increased fracture risk is well documented.

Lower than expected risk of bone density decline with Truvada PrEP
Researchers have shown that among users of pre-exposure prophylaxis (PrEP) to prevent against AIDS that includes tenofovir (Truvada), those with daily use -- very high adherence -- had only about a 1% average decrease in bone mineral density in the spine and a 0.5% decline in the hip.

Sex-specific effects of DHEA on bone mineral density and body composition
Women 55 and older have an increased risk of bone and muscle loss but therapy with the hormone Dehydroepiandrosterone (DHEA) may help prevent bone loss and increase muscle mass in older women, according to a new study led by Catherine M.

Beyond bone mineral density: Additional bone traits predict risk for fracture
In the largest prospective study of its kind, researchers from Beth Israel Deaconess Medical Center (BIDMC) and the Institute for Aging Research at Hebrew SeniorLife used high-resolution tomography imaging to assess whether bone characteristics besides bone mineral density can predict risk of fracture.

A fracture anywhere reduces bone density everywhere
New studies from UC Davis Health are among the first to associate fractures with systemic bone loss.

More dairy associated with higher bone density and greater spine strength in men over 50
Researchers from Hebrew SeniorLife's Institute for Aging Research (IFAR), Wageningen University, Tilburg University, University of Reading, and Beth Israel Deaconess Medical Center (BIDMC) have discovered that higher intake of dairy foods, such as milk, yogurt, and cheese, is associated with higher volumetric bone mineral density and vertebral strength at the spine in men.

Read More: Bone Density News and Bone Density Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.