Effect of hypothyroidism on the blood lipid response to higher dietary fat intake in mares.
Abstract: Blood lipid and lipoprotein concentrations were measured and compared between euthyroid and thyroidectomized mares on low-fat or high-fat diets to test the hypothesis that hypothyroidism alters the blood lipid response to higher dietary fat intake. Four healthy adult mares and four adult mares that had been thyroidectomized 3 to 6 mo earlier were placed on low-fat or high-fat diets according to a replicated 2 x 2 Latin square design consisting of two 5-wk feeding periods separated by a 2-wk washout interval. Plasma lipid concentrations were measured at 0, 3, 4, and 5 wk, and plasma lipase activities were measured at the end of each 5-wk feeding period. Compared with euthyroid mares (0.46 ng/mL [range 0.34 to 0.68 ng/mL T3], and 21.5 ng/mL [range 18.1 to 25.1 ng/mL T4], respectively), median serum concentrations of T3 and T4 were lower (P = 0.029 and P = 0.021, respectively) in thyroid-ectomized mares (0.26 ng/mL [range 0.23 to 0.26 ng/ mL T3], and undetectable T4). Serum T4 concentrations were below the limits of detection in thyroidectomized horses. Alterations in body weight over 5 wk did not differ between groups. Mean plasma very low density lipoprotein (VLDL) and triglyceride (TG) concentrations were higher (P = 0.045 and 0.034, respectively) in hypothyroid mares (55.42 +/- 35.05 mg/dL and 52.83 +/- 34.46 mg/dL, respectively) compared with euthyroid mares (28.28 +/- 13.76 mg/dL and 23.53 +/- 9.84 mg/dL, respectively). Mean plasma total cholesterol (TC) concentrations increased from 88.73 +/- 25.49 mg/dL at baseline to 103.93 +/- 24.42 mg/dL after 5 wk on the low-fat diet, but increased by a greater magnitude (P = 0.006 diet +/- time interaction) in mares that were on the high-fat diet (81.05 +/- 17.24 mg/dL and 123.84 +/- 32.27 mg/ dL, respectively). Mean plasma TC concentrations were higher (P = 0.099) in hypothyroid mares (116.16 +/- 32.89 mg/dL) than in euthyroid mares (89.56 +/- 14.45 mg/ dL). Higher post-heparin plasma lipoprotein lipase and hepatic lipase activities (P = 0.012 andP = 0.017, respectively) were detected in mares that were on the high-fat diet (2.66 +/- 0.91 micromol FA x mL(-1) x h(-1) and 2.95 +/- 0.49 micromol FA x mL(-1) x h(-1), respectively) vs. a low-fat diet (1.75 +/- 0.55 micromol FA x mL(-1) x h(-1) and 2.27 +/- 0.59 micromol FA x mL(-1) x h(-1), respectively). We conclude that plasma VLDL and TG concentrations are elevated in hypothyroid mares, but the blood lipid response to higher dietary fat intake is not influenced by hypothyroidism.
Publication Date: 2004-09-28 PubMed ID: 15446481DOI: 10.2527/2004.8292640xGoogle Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research study investigates the impact of hypothyroidism on how mares’ blood lipid levels respond to increasing fat in their diets. The findings demonstrate hypothyroid mares have higher plasma triglyceride and very low-density lipoprotein levels, but their blood lipid reaction to a higher fat diet remains unaltered.
Study Design and Participants
- The study was conducted using a total of eight adult mares, four of which were healthy (euthyroid mares), and the other four had been thyroidectomized 3 to 6 months prior (hypothyroid mares).
- The research was designed using a replicated 2 x 2 Latin square design, comprised of two 5-week feeding periods separated by a 2-week washout interval. This design was chosen to accurately measure and compare the effects of low-fat and high-fat diets on euthyroid and hypothyroid mares.
Study Measurements
- Over the 5-week period, plasma lipid concentrations were measured at weeks 0, 3, 4, and 5, and plasma lipase activities were assessed at the end of each feeding stage.
- The researchers primarily examined the concentrations of very low-density lipoprotein (VLDL), triglycerides (TG), and total cholesterol (TC) in the plasma, as well as the activities of lipoprotein lipase and hepatic lipase enzymes.
- In addition, the concentrations of thyroid-related hormones T3 and T4 were also measured in the mares. Hypothyroid mares showed significantly lower levels of these hormones when compared to euthyroid mares, as hypothesized.
Study Findings
- The findings showed that hypothyroid mares had significantly elevated mean plasma VLDL and TG levels when compared to euthyroid mares.
- The total cholesterol (TC) concentrations in plasma increased more in mares on a high-fat diet than in those on a low-fat diet.
- Although this increase was observed irrespective of the mares’ thyroid status, hypothyroid mares had slightly higher mean plasma TC levels than euthyroid mares.
- High-fat diets resulted in increased plasma post-heparin lipoprotein lipase and hepatic lipase activities when compared to low-fat diets. These are key enzymes involved in the breakdown of lipids (fats).
- Despite the impact of hypothyroidism on blood lipids, the study found that hypothyroidism did not affect the blood lipid response to a high-fat diet intake.
Conclusions
- The study concluded that while hypothyroidism increases VLDL and TG levels in mares, it does not influence the blood lipid response to a higher dietary fat intake.
- These findings may have implications for the dietary management of horses and potentially other animals with hypothyroidism, suggesting that the dietary fat intake does not need to be reduced in these animals as a specific response to the condition.
Cite This Article
APA
Frank N, Sojka JE, Latour MA.
(2004).
Effect of hypothyroidism on the blood lipid response to higher dietary fat intake in mares.
J Anim Sci, 82(9), 2640-2646.
https://doi.org/10.2527/2004.8292640x Publication
Researcher Affiliations
- Department of Veterinary Clinical Sciences, Purdue University, West Lafayette, IN 47907, USA. nfrank@utk.edu
MeSH Terms
- Animals
- Cholesterol / blood
- Cross-Over Studies
- Dietary Fats / administration & dosage
- Female
- Horse Diseases / blood
- Horse Diseases / metabolism
- Horses
- Hypothyroidism / blood
- Hypothyroidism / metabolism
- Hypothyroidism / veterinary
- Lipase / metabolism
- Lipids / blood
- Lipoproteins, VLDL / blood
- Random Allocation
- Thyroidectomy / veterinary
- Triglycerides / blood
Citations
This article has been cited 1 times.- Dhingra S, Bansal MP. Attenuation of LDL receptor gene expression by selenium deficiency during hypercholesterolemia.. Mol Cell Biochem 2006 Jan;282(1-2):75-82.
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