Bitter taste and blood glucose are not involved in the suppressive effect of dietary histidine on food intake

Neurosci Lett. 2007 Jun 13;420(2):106-9. doi: 10.1016/j.neulet.2007.03.074. Epub 2007 Apr 25.

Abstract

Histamine decreases food intake by activating histaminergic neurons in the hypothalamus. Histamine is synthesized by histidine decarboxylase (HDC) from histidine. The purpose of this three-part animal study was to clarify the mechanism underlying the suppressive effect of dietary histidine on food intake. In experiment 1, we attempted to distinguish palatability from a direct effect of dietary histidine because histidine tastes slightly bitter to humans. We measured food intake every hour for 24 h in rats fed with a histidine-enriched diet or one of various quinine diets (0.001-0.8% quinine), also bitter. In experiment 2, we measured changes in blood glucose levels in rats fed with a standard or histidine-enriched diet because blood glucose is known to decrease food intake. In experiment 3, we intraperitoneally injected fluoromethylhistidine (FMH), an antagonistic inhibitor of HDC, in rats fed with a histidine-enriched diet. In experiment 1, food intake was almost the same in rats fed with the histidine-enriched diet as that in rats fed with the 0.01% quinine diet until 6 h, but food intake was low in other groups compared with that in the histidine-enriched diet group. After 6 h, food intake did not increase in rats fed with the histidine-enriched diet. In experiment 2, the blood glucose level rose quickly and then began to decrease at approximately 2 h in both groups of rats. However, it decreased more dramatically in rats fed with the histamine-enriched diet and reaches a significant difference from the decrease in the standard-diet group by 6 h. In experiment 3, food intake increased significantly in FMH-injected rats fed with the histidine-enriched diet compared with in non-FMH injected rats. Our results suggest that dietary histidine suppresses food intake by activating histaminergic neurons in the hypothalamus, independently bitter taste and blood glucose level.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blood Glucose / drug effects*
  • Blood Glucose / physiology
  • Body Weight / drug effects
  • Body Weight / physiology
  • Eating / drug effects*
  • Eating / physiology
  • Enzyme Inhibitors / pharmacology
  • Food, Formulated
  • Histamine / metabolism*
  • Histidine / pharmacology*
  • Histidine Decarboxylase / antagonists & inhibitors
  • Histidine Decarboxylase / metabolism
  • Hypothalamus / drug effects*
  • Hypothalamus / metabolism
  • Male
  • Neurons / drug effects
  • Neurons / metabolism
  • Obesity / drug therapy
  • Obesity / metabolism
  • Obesity / physiopathology
  • Quinine / pharmacology
  • Rats
  • Rats, Wistar
  • Taste / drug effects*
  • Taste / physiology
  • Time Factors

Substances

  • Blood Glucose
  • Enzyme Inhibitors
  • Histidine
  • Histamine
  • Quinine
  • Histidine Decarboxylase