HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Frank, N. Articles by Latour, M. A. Search for Related Content PubMed PubMed Citation Articles by Frank, N. Articles by Latour, M. A.

Effect of hypothyroidism on the blood lipid response to higher dietary fat intake in mares^1,2

N. Frank^*,3, J. E. Sojka^* and M. A. Latour

^* Department of Veterinary Clinical Sciences, and and Department of Animal Sciences, Purdue University, West Lafayette, IN 47907

³ Correspondence: Dept. of Large Anim. Clin. Sci., Univ. of Tennessee, Knoxville 37996-4545 (e-mail: nfrank{at}utk.edu).

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 thyroidectomized 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 and P = 0.017, respectively) were detected in mares that were on the high-fat diet (2.66 ± 0.91 µmol FA•mL^–1•h^–1 and 2.95 ± 0.49 µmol FA•mL^–1•h^–1, respectively) vs. a low-fat diet (1.75 ± 0.55 µmol FA•mL^–1•h^–1 and 2.27 ± 0.59 µmol FA•mL^–1•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.

Key Words: Cholesterol • Hypothyroidism • Lipase • Thyroidectomy • Very Low Density Lipoprotein

This article has been cited by other articles:

				N. Frank, F. M. Andrews, S. B. Elliott, J. Lew, and R. C. Boston Effects of rice bran oil on plasma lipid concentrations, lipoprotein composition, and glucose dynamics in mares J Anim Sci, November 1, 2005; 83(11): 2509 - 2518. [Abstract] [Full Text] [PDF]