Adiponectin is a metabolic link between obesity and bone mineral density



The Stowers Institute’s Baumann Lab has discovered an important step in the maturation pathway of telomerase, the enzyme that replenishes the sequences that are lost at chromosome ends with every cell division. The findings were published in the Advance Online Publication of Nature . Telomerase is viewed as a promising cancer treatment target because its

Full Post: Researchers identify key step in maturation pathway of telomerase

Researchers at the University of Toronto, Faculty of Medicine, Toronto, Canada, have discovered that adiponectin, a protein secreted from adipocytes, is a metabolic link that can explain, in part, the known positive relationship between obesity and both bone mineral density and reduced susceptibility to fractures.

This study appears in the December issue of Experimental Biology and Medicine. Circulating adiponectin levels are significantly lower in obese humans and rodent models than in lean controls. It is known that excess body weight and elevated body mass index are strongly correlated with high bone mineral density, and that weight loss is associated with loss of bone mineral density and increased risk of fractures. However, the mechanism for this relationship is unclear.

The research team, Dr. Michael C. Archer, Earle W. McHenry Professor and Chair, Dr. Wendy E. Ward, Associate Professor, Dr. Kafi Ealey, Postdoctoral Fellow and predoctoral student Jovana Kaludjerovic, in the Department of Nutritional Sciences, investigated whether adiponectin modulates bone development using transgenic mice that overexpress this protein. These mice were initially developed by Dr. P. Scherer’s research group at Albert Einstein College of Medicine, N.Y. Bone mineral density and biomechanical strength properties, surrogate measures of fracture risk at multiple skeletal sites, were the outcomes used to assess bone development. Female mice overexpressing adiponectin had weaker vertebra at 8 weeks of age than control mice and this delay in bone development persisted through to the end of the study period, representing early adulthood. The weaker vertebra model compression fractures of the lumbar spine in humans, among the most common type of fragility fracture associated with low bone mass and osteoporosis. The strength of the femur neck, representing the hip, was also weaker in both females and males overexpressing adiponectin. Serum adiponectin levels were inversely correlated with femur bone mineral content, further emphasizing that a high level of adiponectin impedes bone development at not only the lumbar spine but also the hip. Whether or not the delay in bone development resolves in later life or is sustained and leads to an increased risk of fragility fracture, particularly during aging when bone loss rapidly occurs due to declining levels of sex steroids, requires further investigation.

In summary, elevated circulating adiponectin was associated with lower bone mass and weaker bones in growing mice compared to control animals. Furthermore, these effects of adiponectin were observed in the absence of differences in body weight between the two groups of mice. Dr. Archer commented, “A unique and important feature of the adiponectin transgenic mice is that they exhibit significantly elevated circulating adiponectin but have similar body weights as control animals, thus eliminating obesity from confounding the study findings - mechanical load resulting from an obese state can modulate bone metabolism”. Moreover, Dr. Archer said, “female mice exhibited a stronger response than males, and this is likely due to the sexual dimorphism in these mice whereby females have significantly higher circulating levels than males”.

Dr. Steven R. Goodman, Editor-in-Chief of Experimental Biology and Medicine said ” These intriguing results form the University of Toronto team supplies significant insight into adiponectin secretion, from adipocytes, and loss of bone mineral density and resulting increased fractures. I consider this a major advance for this field of research.

http://www.sebm.org/

Link




Men who survived childhood leukemia treatment into adulthood were more likely to have low bone mineral density than other adults their age, putting them at risk of osteoporosis and bone fractures, according to a new study. The study, led by James G. Gurney, Ph.D., of the University of Michigan Comprehensive Cancer Center, found that 24

Full Post: Men who survive childhood leukemia have lower bone mineral density



Children and teenagers with even mild cases of anorexia exhibit abnormal bone structure, according to a new study appearing in the December issue of Radiology and presented at the annual meeting of the Radiological Society of North America (RSNA). “Adolescence is the most critical period for growth of bone mass, and the onset of anorexia

Full Post: Computed tomography technology shows anorexia impairs adolescent bone development



New research reveals that computed tomography (CT) colonography, also known as virtual colonoscopy, has the potential to screen for two diseases at once-colorectal cancer and osteoporosis, both of which commonly affect adults over age 50. Results of the study will be presented today at the annual meeting of the Radiological Society of North America (RSNA).

Full Post: Virtual colonoscopy has potential to screen for colorectal cancer and osteoporosis at same time



An interim analysis of a breast cancer prevention study using exemestane (Aromasin) finds an “acceptable” level of bone loss. The ongoing phase II study details reported, by Jennifer Eng-Wong, MD, a breast cancer specialist at Georgetown’s Lombardi Comprehensive Cancer Center at the San Antonio Breast Cancer Symposium, examines the use of exemestane in postmenopausal women

Full Post: Planned safety analysis of a breast cancer prevention study reveals encouraging news for Exemestane



When it comes to remodeling our bones-an ongoing process of break down and renewal that goes on throughout adulthood–researchers have new evidence that our guts play a surprisingly important role. The findings point toward novel methods for increasing bone mass in patients with diseases characterized by impaired bone formation, including postmenopausal osteoporosis, according to the

Full Post: Gut found to exert control over bone