Innovative Research With Pythons Offers New Insights
Into The Body’s Digestive Processes
Could the giant snake’s preference for a high protein
diet shed some light on the Atkins diet craze?
(February 3, 2003) - Bethesda, MD - Your diet
is primarily high protein, consisting of a wide range of mammals and
selected birds. The meals you eat avoid fat and cholesterol – your food
selections seem to be good for you, but is it healthy?
This is not a discussion of the millions who have now
adopted the high-protein, low-carbohydrate diet popularized by Dr. Robert
Atkins. The high protein diet described belongs to the Burmese python and
new findings based on research with animals reveal the physiological
processes that occur with digestion of a high protein fare. Accordingly,
this animal’s emergence as a laboratory animal may have contributed to an
earlier resolution in the heated debate that was carried on about the safety
of the high protein diet.
Background
The Burmese python (Python molurus) and its
unique feeding habit of eating at infrequent intervals (several times a
year), on large meals (often exceeding the creature’s body mass), are
associated with large intestinal responses. Specifically, within 24 to 48
hours after eating, the python experiences a 2.5 fold-increase in intestinal
mucosal mass, a six-fold increase in microvillus length, and 25 to 100-fold
increases in metabolic rate and plasma hormone and lipid levels. In total,
the overall gastrointestinal response is twice that of a mammal laboratory
animal, making this species ideal for study (the researchers selected the
python knowing that any conclusions reached would have to be tested in a
mammal subject).
Mice, rabbits, rats, and dogs have all served science
by taking their place as mammalian models for study of human physiological
processes. However, despite the use of live animal subjects, the digestive
process, or the gastrointestinal response to food, has remained unclear.
Essentially, these conventional laboratory animals feed frequently on small
meals and therefore are always constantly digesting and express only modest
activity of gastrointestinal performance.
The Study
The authors of “Luminal Nutrient Signals for Intestinal
Adaptations in Pythons” are Stephen M. Secor, John S. Lane, Edward E. Whang,
Stanley W. Ashley, and Jared Diamond, all from the University of
California-Los Angeles School of Medicine, Los Angeles, California. Their
findings appeared in the December 2002, edition of American Journal of
Physiology-Gastrointestinal and Liver Physiology.
Methodology
Burmese pythons are indigenous to the subtropical
regions of Southeast Asia and feed in the wild chiefly on birds and
mammals. They are one of the largest snake species, reaching lengths up to
six meters and masses to 100 kilograms. The reptiles used in this study
were secured from a commercial breeder and maintained on biweekly diet of
laboratory rats and water. Key stages of the experiment included:
Tests for luminal nutrient signal: Inserting a
rubber catheter in the small intestines of 21 pythons followed by a solution
allowed post-mortem examination of the organ’s mass, morphology, and
nutrient uptake values, and compared the findings against a control group.
Tests for signals other than luminal nutrients:
To determine the potential regulatory role of other signals, the researchers
(1) identified the cephalic (cranial) phase response on the small intestine;
and (2) measured small intestine stretching through placement of a balloon
catheter into the organ.
Results
Python intestine failed to respond
trophically or functionally to luminal infusions of saline, glucose,
lipid, or bile. Infusion of amino acids and peptides, with or
without glucose, induced an intermediate response. Infusion of
nutritionally complete liquid formula or natural diet induced
full intestinal response. Intact meals triggered full intestinal
responses without pancreatic or biliary secretions, whereas direct
cephalic and gastric stimulation failed to elicit any response.
Hence neither physical stimulation (cephalic, gastric, or intestinal)
nor the luminal presence of glucose, lipids, or bile can induce
intestinal response; instead, a combination of nutrients is required
(even without pancreaticobiliary secretions), the most important
being amino acids and peptides.
Significant is the finding that amino acids/peptides
play a significant response to ingested nutrients. This could be explained
that the giant snake’s natural meal of live birds and mammals provides a
high protein diet, with much less fat and few carbohydrates.
Conclusions
Advantages for using the python in gastrointestinal
studies included observance of the creature’s large regulatory span, the
ease of surgical procedures during the experiment, and the disassociation
between functional and trophic (nutritional) responses. The authors suggest
that additional experiments be conducted with pythons to determine nutrient
response to isolated intestinal loops, upstream or downstream induction of
intestinal adaptation, and regulation of intestinal function by
gastrointestinal peptides, and intestinal response to regulatory peptides.
The scientific community continues to debate the
efficacy and safety of recommended diets for millions of Americans who are
classified as obese. The answer to good health may lie in selecting food
that is effectively digested by our gastrointestinal system – and the
laboratory animal holding the key could be the python.
Source: December 2002, edition of
American Journal of Physiology-Gastrointestinal and Liver Physiology.
The journal is one of 14 published monthly by the American Physiological
Society (APS).
-end-
The American Physiological
Society (APS) was founded in 1887 to foster basic and applied science, much
of it relating to human health. The Bethesda, MD-based Society has more than
10,000 members and publishes 3,800 articles in its 14 peer-reviewed journals
every year.
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Editor’s Note: To set up
an interview with a member of the research team, please contact Donna Krupa
at 703.527.7357 (direct dial), 703.967.2751 (cell) or
djkrupa1@aol.com.
