RSS Feeds
Rejuvenation in Older Adults Receiving Oral Ghrelin
- Ralf M. Nass, MD;
- Mary Lee Vance, MD; and
- Michael O. Thorner, MBBS, DSc
IN RESPONSE:
We appreciate the thoughtful comments in response to our article and offer some clarifications.
We believe that aging is not a disease but a complex multisystem decline that occurs over decades. It is likely that MK-677 acts at multiple sites, including the hypothalamus, the pituitary, and the periphery. We have no evidence that atherosclerosis impairs its action.
We did not perform other cancer screening in these healthy older adults. Women were carefully monitored with Papanicolaou smears and mammography, and prostate-specific antigen was monitored in men. Adverse effects were reported in the Results section. A study of this size cannot assess cancer risk; however, as of 20 July 2007, more than 600 adults had been exposed to MK-677 for 6 to 12 months. The combined incidence rate for malignant conditions in any MK-677 treatment group was similar to the incidence rate in the placebo groups in these studies (Papanicolaou DA. Personal communication.). The cancer risk of growth hormone and IGF-I administration is controversial and has been extensively reviewed (1).
As Dr. Webster points out, the benefits of exercise are well established and should always be recommended. However, physiologic studies show that the effects of resistance training on intramuscular metabolic changes achieved in elderly persons, as well as muscle growth response, are significantly less than those in younger study samples (2, 3). Additional data suggest that in men older than 80 years of age, the capacity to gain strength with resistance training is decreased because of limited myocellular adaptive response (4).
Furthermore, some elderly adults cannot exercise because of substantial muscle loss and frailty. Interventions that prevent or delay a decline in muscle mass would be desirable, given the expected demographic shift in the aging population. Our observations support a role for ghrelin mimetics to enhance growth hormone secretion; this resulted in both arrest of muscle mass loss as well as an increase in muscle mass. The increase in appetite also may be important. Recent data from the Health ABC (Dynamics of Health, Aging and Body Composition) Study demonstrate a significant association between change in lean mass in elderly persons and dietary protein intake (5).
Long-term studies comparing the effects of exercise with a ghrelin mimetic alone or in combination with exercise are certainly needed in elderly patients who are physically able to exercise. We emphasized that ours was a “proof-of-concept” study, and now definitive studies need to be designed and performed.
Ralf M. Nass, MD
Mary Lee Vance, MD
Michael O. Thorner, MBBS, DSc
University of Virginia Health System
Charlottesville, VA 22908
Article and Author Information
-
Potential Financial Conflicts of Interest: None disclosed.
