lower triglyceride levels, we also see a small drop in blood pressure. These
HDL2B results, combined with previous findings from our lab showing better
glucose tolerance and insulin sensitivity (which should predict lower
incidence of diabetes), lower body temperature, and other such biomarkers
suggesting that caloric restriction may exert beneficial effects in primates
similar to those previously observed in rodents. These results may someday serve as a model
for human studies."
One interesting aspect of this particular study is that neither the control
monkeys nor the calorically restricted monkeys eat much fat or cholesterol as
part of their diets. Thus the study demonstrates that even in non-obese
monkeys, a reduction in calorie intake can benefit cholesterol, triglycerides and blood
pressure. This research presents an important contrast to studies that usually look at
obesity and how weight loss from that level can benefit health.
It is demonstrated here for the first time that caloric restriction can lead to changes in
HDLs and other lipid profiles that may be associated with health benefits for both
those animals that are lean as well as those that are heavier.
Recent research under the direction of Mark Lane, Ph.D., Senior Staff Fellow
at the NIH's Animal Center, has turned up an interesting added benefit to
caloric restriction. In addition to boosting good cholesterol and reducing
triglycerides, monkeys on caloric restricted diets experience a favorable
redistribution of fat away from their central regions thus reinforcing the
current finding about reduction in cardiovascular risk with caloric restriction.
The second study from Drs. Roth, Lane, and Donald Ingram at NIA and Dr.
Sheldon Ball at the University of San Francisco-Fresno, appeared in the July
1997 issue of the Journal of Clinical Endocrinology and Metabolism (Vol. 82,
No. 7, pp. 2093-2096). In this study, monkeys whose calorie intake was
restricted by 30 percent showed a slower decline in DHEAS (dehydroepi-androsterone sulfate) and DHEA (the unsulfated form) levels than those observed in control monkeys.
Dr. Lane, principal investigator of this study, says, "DHEA levels are of great
interest to us, not because we believe that DHEA is the fountain of youth, but
rather because it gives us a very good marker to measure the rates of aging in
control versus calorically restricted monkeys. It is important to distinguish
between levels of DHEA that occur naturally in the body and decline with age
and levels that are seen in people who pop DHEA pills to pharmacologically
raise their natural levels in hope of extending their lives. These artificially
higher levels may or may not give them any benefit. Controlled clinical trials
are needed before this question can be answered." Dr. Ingram adds, "It is
important to develop markers such as DHEAS which can be used to determine
the effects of various interventions, such as diet and exercise, on aging."
According to Dr. Roth, "this study shows that monkeys eating a calorically
restricted diet which contains little fat maintain higher DHEA levels in their
bodies. In this setting, DHEA is a marker of aging. We do not yet know if
DHEA plays a role in slowing the aging process."
Until NIA initiated studies in rhesus monkeys in 1987, the phenomena of
longer life and better health and vigor through caloric restriction had never
been investigated in longer-lived primate species. These studies will continue
for many more years with the goal of eventually giving a more precise
understanding of the mechanisms of how caloric restriction extends life.
The National Institute on Aging, one of the 18 Institutes which make up the
National Institutes of Health, leads the Federal effort supporting basic,
clinical, epidemiological and social research on aging and the special needs of
older people. A brochure, "Pills, Patches and Shots: Can Hormones Prevent
Aging?" is available from the NIA by calling 1-800-222-2225 or by visiting
the NIA's website at http://www.nih.gov/nia
Note: Video B-roll/VNR on betacam and 8x10 color stills of the monkeys in this study
are available for broadcast or print use by calling (301)496-1752.