Effect of long-chain fatty acids on the binding of thyroxine and triiodothyronine to human thyroxine-binding globulin

Biochim Biophys Acta. 1986 Apr 11;881(2):292-6. doi: 10.1016/0304-4165(86)90016-4.

Abstract

The effect of long-chain fatty acids on the binding of thyroxine to highly purified human thyroxine-binding globulin has been studied by equilibrium dialysis performed at pH 7.4 and 37 degrees C. At a fixed molar ratio of 2000:1 of fatty acid to thyroxine-binding globulin, the degree of binding inhibition based on the percent change in nK value relative to the control as determined from Scatchard plots was: palmitic, 0%; stearic, 0%; oleic, 76%; linoleic, 69%; and linolenic, 61%. At a 500:1 molar ratio of oleic acid to thyroxine-binding globulin, equivalent to 0.125 mM free fatty acid in serum, thyroxine binding was inhibited by 18%, increasing to 93% at a 4500:1 molar ratio. At molar ratios of oleic acid to thyroxine-binding globulin of 1000:1, 2000:1 and 4000:1, the degree of inhibition of triiodothyronine binding was 24%, 41% and 76%, respectively. The results indicate that the unsaturated long-chain fatty acids are potent inhibitors of thyroxine binding to thyroxine-binding globulin, whereas the saturated fatty acids have little or no effect on thyroxine binding.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Fatty Acids / pharmacology*
  • Humans
  • Kinetics
  • Linoleic Acid
  • Linoleic Acids / pharmacology
  • Linolenic Acids / pharmacology
  • Molecular Weight
  • Oleic Acid
  • Oleic Acids / pharmacology
  • Palmitic Acid
  • Palmitic Acids / pharmacology
  • Stearic Acids / pharmacology
  • Structure-Activity Relationship
  • Thyroxine / metabolism*
  • Thyroxine-Binding Proteins / metabolism*
  • Triiodothyronine / metabolism*
  • alpha-Linolenic Acid

Substances

  • Fatty Acids
  • Linoleic Acids
  • Linolenic Acids
  • Oleic Acids
  • Palmitic Acids
  • Stearic Acids
  • Thyroxine-Binding Proteins
  • Triiodothyronine
  • alpha-Linolenic Acid
  • Oleic Acid
  • Palmitic Acid
  • stearic acid
  • Linoleic Acid
  • Thyroxine