[Pharmacologic studies in thiamine deficiency. I. Changes in the catecholamine content of tissues]

Sleep and indolamine alterations induced by thiamine deficiency

Behavioral, polygraphic, biochemical and histological aspects of thiamine deficiency in rats induced by thiamine-deficient food and pyrithiamine treatment (40 mg/kg daily for 4 days) are described. Behavioral alterations were essentially characterized by ataxia, pilo-erection and paresis. Polygraphic data indicated an increase in slow-wave sleep (SWS) of 33% and decreases in paradoxical sleep (PS) and wakefulness (W), respectively, of 69% and 27%. These effects were reversed by complete food and thiamine administration, the reversal including an overshoot in PS. Biochemical assays, performed when the polygraphic data indicated a large effect, demonstrated a significant increase in serotonin (5-HT) and 5-hydroxyindolacetic-acid (5-HIAA). These effects were particularly evident in the raphe system and the locus coeruleus. Histological data from the raphe dorsalis displayed a notable increase in yellow fluorescence in pyrithiamine-treated animals over controls. We conclude from these experiments that a deficiency in thiamine affects the serotonergic system and that the subsequent effects on sleep are a consequence of this serotonergic change.

Effect of protein-calorie malnutrition on catecholamine levels and weight of heart in rats

Catecholamine levels and weight of heart were studied in rats subjected to protein-calorie malnutrition and after a period of nutritional rehabilitation. Rats given a protein deficient diet (4% protein) for periods of 6 and 12 weeks showed a severe restriction of body weight gain. Nevertheless, even though the measured heart weight of deficient rats was significantly lower than the respective controls (16% protein), the deficient rats incurred "real" cardiac enlargement since the mean heart weight of the equal body weight controls was significantly different from that of the deficient animals. The mean heart weight of rats fed a high-protein diet for 6 weeks thereupon a 6-week period of protein deprivation was still less than that of controls, and the heart ratio was still greater than that of controls. However, the heart weight of rehabilitated rats was not significantly different from that of equal body weight controls. Serum protein and albumin levels in dificient rats were significantly decreased in comparison to rats fed a high-protein diet. While the serum protein levels of rehabilitated rats were lower than those of controls, the albumin levels were not different. The protein-calorie malnourished rats, which received a low-protein diet for 6 and 12 weeks, showed a significant increase in myocardium noradrenaline concentration. After a period of nutritional rehabilitation this change did not persist. These catecholaminergic alterations in heart may be responsible, at least in part, for the different cardiac abnormalities described as a result of protein-calorie dietary deficiency. It may also explain the "real" cardiac enlargement observed in deficient rats, according to the hypothesis that noradrenaline may be the ultimate myocardial hypertrophy hormone.

Noradrenaline levels and morphologic alterations of myocardium in experimental protein-calorie malnutrition

Experimental protein-calorie malnutrition was produced in rats by giving them a low-protein diet for 6 weeks. Control animals were fed a high-protein diet. The deficient rats showed severe restriction of body weight gain, fatty liver and hypoproteinaemia. In addition the present study demonstrates that the experimentally induced protein-calorie malnutrition brings about marked pathological changes and increased catecholamine levels in the hearts of rats. Based on this demonstration, and considering the synchronism of morphological and biochemical data, we postulate that the nutritional stress to the heart raises the myocardium noradrenaline concentration and the continued exposure to high levels of catecholamines may play a role in the development of cardiac changes in protein-energy malnutrition.

Alcohol and malnutrition in the pathogenesis of experimental alcoholic cardiomyopathy

In this study, the morphology and the catecholamine levels of the myocardium in both well-nourished and malnourished alcohol-fed rats were examined. Alcohol has been administered to rats for 16 weeks. Rats fed a diet containing alcohol corresponding to 40 per cent. of total calorific intake and inadequate amounts of calories and nutrients developed morphological changes in the heart, while the controls did not. In addition, an increase in cardiac noradrenaline concentration and heart: body weight ratio could be observed. There were no differences in myocardial morphology and catecholamine concentration between well-nourished rats fed alcohol as 35 per cent. of the calorific intake and pair-fed controls. A dispute exists about whether alcohol is directly toxic to the heart or indirectly injurious due to associated dietary deficiency. The present results, taken together, make the theory of cardiotoxicity of alcohol an unlikely one, at least in the case of the rat; and they offer considerable support for the hypothesis that the association between chronic consumption of alcoholic beverages and cardiomyopathy is a result of a primary multifactorial nutritional deficiency, resulting from displacement of nutrient-associated calories by the "empty" calories--devoid of protein, vitamins, and minerals--of alcohol, and/or a secondary nutritional deficiency due to injurious effects of alcohol on the liver, pancreas and intestine. It is suggested that continued exposure to high levels of catecholamine, directly related to malnutrition, may play a role in the development of myocardial pathology.

Persistent erection in thiamine-deficient rats

Male Wistar rats, maintained on a thiamine-deficient diet, showed a significant weight loss, decrease in heart frequency, disturbance of urinary excretion, and symptoms of polyneuritis. Once persistent erection ocurred in these rats, it continued throughout the study and subsided in most cases after the administration of thiamine HCl.

Possible role of intestinal alkaline phosphatase activity in thiamine transport

Thiamine deficiency caused a marked decrease of intestinal alkaline phosphatase (al-Pase) activity, but had no effect on the Ca++-ATPase activity and Ca++-absorption in rats. The al-Pase activity was significantly decreased 1 h after oral administration of ethanol at 0.5 and 2.5 g/kg. In contrast, Mg++-, Ca++-and (Na+ + K+)-ATPase activities did not change after the administration of ethanol. These findings show that the al-Pase activity, unlike the Ca++-ATPase activity, is not related to Ca++-absorption. A possible role of al-Pase activity in the active transport of thiamine in the intestine was discussed.

Thiamine diphosphatase in rat small intestine

TDPase is located mostly in the proximal portion of the small intestine and its activity, like that of ALPase, decreased markedly in thiamine deficiency. The decreased enzyme activities were restored after thiamine or vitamin D3. Kinetic and other studies of the purified enzyme indicated the identity of the two enzymes.

Role of thiamine metabolism in the central nervous system. II. Effects of various agents on thiamine triphosphatase activity in rat brain

The effects of various agents on the activity of brain thiamine triphosphatase (TTPase) in vivo and in vitro were studied. Thiamine deficiency caused a significant increase in soluble TTPase activity and a decrease in membrane-associated TTPase activity. Insulin and a fasting state did not affect these enzyme activities. DL-Methamphetamine (10mg/kg i.p.) increased the activity of the soluble TTPase, whereas reserpine (2.5 mg/kg i.p.) caused no change in the enzyme activities. A single injection of chlopromazine (25 mg/kg s.c.) had no effect on the microsomal or soluble TTPase activities, but repeated injections reduced the activity of the microsomal enzyme. The effects of various neuroactive agents on microsomal TTPase activity were examined in vitro. Among the drugs tested, only chlorpromazine caused marked inhibition of the enzyme activity.

Glucose intolerance in thiamine-deficient rats

The mechanism of glucose intolerance in thiamine-deficient rats has been examined. Deficient rats showed marked glucose intolerance. However, the hypoglycaemic effect of insulin (1 i.u. kg−1, i.p.) was similar in the deficient, pair-fed and normal groups, though somewhat weaker in the normal group than in the other two groups. After injection of tolbutamide (40 mg kg−1, i.p.), the hypoglycaemic effects in the three groups were the same. Tyramine (10 mg kg−1, s.c.) restored the impaired glucose tolerance of deficient rats to normal, but not that of alloxan diabetic rats. Furthermore, tyramine did not restore the intolerance of deficient rats pretreated with alloxan. These results suggest that the main factor causing glucose intolerance in the deficient rats may be suppressed insulin secretion.

Monoamine oxidase activities in tissues of thiamine-deficient rats

The oxidation of monoamine by homogenates of tissues of thiamine-deficient rats was measured with noradrenaline as substrate. Monoamine oxidase activities were depressed in tissues in which the catecholamine content had previously been found raised during thiamine deficiency, with the exception in the cerebral cortex. The impaired enzyme activities were restored to the control level by repeated thiamine injections. An accumulation of pyruvic acid did not inhibit monoamine oxidase activity and thiamine pyrophosphate is not implicated as a co-factor in the oxidation of monoamine substrate.