Association of Plasma Lipid Levels With Atherosclerosis Prevalence in Psittaciformes

Abstract

The prevalence of atherosclerosis is high in the captive psittacine population and increases with age and female sex. The genera Psittacus, Amazona, and Nymphicus are predisposed to atherosclerosis, whereas the genera Cacatua and Ara are less susceptible. Plasma cholesterol and lipoprotein abnormalities have been suggested as risk factors in the development of atherosclerosis as observed in mammals. To investigate whether the psittacine genera susceptibility to atherosclerosis and the known risk factors of age and sex could be associated with differences in the lipid profile, a retrospective analysis was conducted on blood lipid values from 5625 birds. Prevalence values were obtained from a previously published, large, case-control study and were compared with identified trends in plasma lipid profiles. Genus-specific differences were identified in plasma total cholesterol values that corresponded to observed trends in the prevalence of clinically important atherosclerotic lesions, which were also highly correlated. The effect of age was significant but was mild and may not account for the dramatic increase in atherosclerosis prevalence observed with age. In addition, Quaker parrots ( Myiopsitta monachus ), which were used as experimental models for psittacine atherosclerosis and dyslipidemia, were found to have the highest values in all lipid profile parameters. The results of this study suggest that the differences observed in prevalence among species of the psittacine genera may partly be explained by differences in plasma total cholesterol levels. Results also support the use of Quaker parrots as models for studying atherosclerosis and dyslipidemia.

EFFECTS OF EXERCISE ON THE PLASMA LIPID PROFILE IN HISPANIOLAN AMAZON PARROTS (AMAZONA VENTRALIS) WITH NATURALLY OCCURRING HYPERCHOLESTEROLEMIA

“…The median HDL : TC ratio in this study was 0.477, which is similar to other Amazon parrots and indicates that just under half of the plasma cholesterol is contained in HDL particles. 7,38,41 This is low compared with many other avian species, including other psittacines, for which HDL : TC ratios are commonly 0.6-0.8. [1][2][3]7,17,25,[29][30][31][32] Low HDL-C and low HDL : TC ratio are associated with increased cardiovascular disease risk in humans.…”

“…Automated biochemical assays for TC, HDL-C, and triglycerides have been used extensively in avian species, including Amazon parrots. 4,7,15,16,38,41 It is common to estimate LDL-C concentration by using the Friedewald equation, which relies on an assumed 5 : 1 ratio of triglyceride to cholesterol in very-low-density lipoprotein (VLDL) particles in human plasma. 19 However, this assumption is known to be inaccurate in humans with triglyceride concentrations .150 mg/dl, 37 and 8 of 10 parrots in this study had triglyceride concentrations above that value.…”

“…are popular companion and zoologic collection birds, and are among the avian genera particularly susceptible to naturally occurring hypercholesterolemia and atherosclerosis. 6,7,40 The research colony of Hispaniolan Amazon parrots (Amazona ventralis) at the University of California, Davis, has a chronic history of hypercholesterolemia. The range of total cholesterol (TC) concentrations measured over 6 yr, using two independent clinical laboratories, was 350-550 mg/dl; this is well above published normal ranges of approximately 100-350 mg/dl for Ama-zon parrots.…”

“…The range of total cholesterol (TC) concentrations measured over 6 yr, using two independent clinical laboratories, was 350-550 mg/dl; this is well above published normal ranges of approximately 100-350 mg/dl for Ama-zon parrots. 7,20,28,41 None of the parrots was exhibiting signs of cardiovascular disease at the time of the study. Antemortem diagnosis of subclinical cardiovascular disease is challenging in avian species and has not been undertaken for these parrots.…”

“…However, chronic hypercholesterolemia has been established as a risk factor for development of clinically significant disease. 7,40 The persistence of hypercholesterolemia, despite a speciesappropriate formulated diet, motivated an investigation of other modifiable lifestyle factors.…”