Healthy Atlantic bottlenose dolphins (Tursiops truncatus) have been demonstrated to have a natural, prolonged glucose tolerance curve and a paradoxical increase in postprandial glucagon, similar to humans with diabetes mellitus.18,19 Previous studies conducted at the U.S. Navy Marine Mammal Program have also shown that the amount of glucagon released during the postprandial period in dolphins is dose-dependent with the amount of protein ingested (unpublished data). The evolutionary purpose for this metabolic process in healthy bottlenose dolphins may be to ensure readily-available blood glucose for a highly active brain during anticipated periods of fasting.3,6,7,11,15,20
To assess other blood-based changes that may occur during fasting and non-fasting states in bottlenose dolphins, a retrospective study involving 1,161 blood samples collected from 52 healthy animals during 1998-2005 was conducted to compare hematological and serum biochemical values in fasted versus non-fasted dolphins, controlling for age and sex. In addition to higher serum glucose levels, healthy dolphins fasted for 10 to 14 hours were more likely to have lower serum uric acid; higher platelet counts; and higher serum gamma-glutamyl transpeptidase (GGT) and alkaline phosphatase compared to non-fasted dolphins. Similar changes have been associated with the level of glucose control in humans with diabetes mellitus.1,5,10,13,14,16,17,21 There is a need to further investigate potential associations between high protein doses and diabetes-associated syndromes, including uric acid nephrolithiasis2,9, hemochromatosis8, and chronic hepatitis12, in dolphin populations.
The authors would like to thank GS Patton and GL Searle for their early unpublished work on insulin and glucagon in bottlenose dolphins. We also thank the U.S. Navy Marine Mammal Program management and veterinary team for their support of this work.
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