Demonstration of in vivo metabolic effects of 3,5-di-iodothyronine.

The objective of the present study was to test in vivo the metabolic effects of 3,5-di-iodothyronine (3,5-T2) in unanesthetized and unrestrained male Sprague-Dawley rats. Amino acid and lipid metabolisms were investigated by breath tests using as tracers the 13C-carboxyl-labeled molecules of leucine, alpha-ketoisocaproic acid (KIC) and octanoic acid, in four different groups of rats: hypothyroid animals (receiving propylthiouracil (PTU) and iopanoic acid), hypothyroid animals treated with either a daily i.p. injection of 3,5-T2 (25 micrograms/100 g body weight), or tri-iodothyronine (T3) (1 microgram/100 g body weight), and control euthyroid animals receiving equivalent volumes of the vehicle solutions. Energy expenditure was measured by continuous monitoring of O2 consumption and CO2 production in these different groups. Daily energy expenditure was decreased by 30% in PTU-treated rats. The chronic treatments with 3,5-T2 and T3 restored daily energy expenditure to the control level. 13CO2 recovered in breath following the i.v. injection of octanoic acid-[1-13C] was decreased in hypothyroid animals compared with control animals (P < 0.05) and restored to control values by T3 and 3,5-T2 treatments. The 13CO2 recovered in breath after i.v. injection of leucine-[1-13C] was increased in PTU-treated compared with control animals (P < 0.05). Chronic treatment with either 3,5-T2 or T3 restored 13CO2 to control values. Excretion of 13CO2 recovered in breath following the i.v. injection of KIC-[1-13C] was increased in PTU-treated compared with control animals. Chronic treatments with either 3,5-T2 or T3 did not restore KIC decarboxylation. These results suggest that 3,5-T2 exerts metabolic effects on energy expenditure, on both lipid beta-oxidation and leucine metabolism in hypothyroid rats. We conclude that 3,5-T2 is a metabolically active iodothyronine.

In situ regulation of lipolysis by insulin and norepinephrine: a microdialysis study during euglycemic-hyperinsulinemic clamp.

Lipolytic responsiveness of subcutaneous and epididymal adipose tissue to norepinephrine (NE) was measured by microdialysis before and during a euglycemic-hyperinsulinemic clamp in male Sprague-Dawley rats (280 +/- 7g, n = 8). Microdialysis probes were perfused with standard Krebs-Ringer buffer without (basal condition [BC]) or with NE 10(-6) mol/L to determine basal and stimulated rates of lipolysis. The dialysate concentration of glycerol was measured (lipolytic index). NE infusion resulted in 3.0- and 4.2-fold increases in glycerol release in abdominal subcutaneous and epididymal adipose tissues, respectively. A euglycemic-hyperinsulinemic clamp at 6 mU/kg.min increased by ninefold the insulinemia (120 +/- 9 U/L). Hyperinsulinemia suppressed basal glycerol release by 57% and 42% in subcutaneous and epididymal adipose depots, respectively (BC + I). Lipolytic responses to NE infusion during a euglycemic-hyperinsulinemic clamp (NE + I) were reduced by 45% and 33% in subcutaneous and epididymal adipose tissues, respectively, as compared with BC. Under BC, the lipolytic response to NE was greater in epididymal than in subcutaneous adipose tissue. Physiological levels of insulin regulated basal lipolysis and counteracted adrenergic stimulation of lipolysis to a similar extent in both superficial (subcutaneous) and intraabdominal (epididymal) adipose tissue. Our findings show that lipolysis is more responsive to NE in epididymal than in subcutaneous adipose tissue. The antilipolytic effects of insulin are similar in both superficial and deep intraabdominal adipose tissues. Furthermore, physiological plasma insulin levels cannot fully antagonize the lipolytic effects of NE.

Effect of growth hormone deficiency on hormonal control of hepatic glycogenolysis in hypophysectomized rat.

The present study was designed to investigate the hormonal regulation of rat liver glycogenolysis in growth hormone (GH) deficiency. To this end, hepatocytes were isolated from control, GH-deprived (hypophysectomized and treated with triiodothyronine [T3] and corticotropin), and 7-day GH-supplemented fed rats and incubated with glucagon and alpha 1-adrenergic agonist (phenylephrine) to measure the hormonal activation of both glycogen phosphorylase and glucose production from glycogen stores. GH deficiency induces a combined decrease of 50% of the glycogen content, the activity of glucose-6-phosphatase, and the maximal hormone-induced glycogen phosphorylase activity. Daily GH injections restore the levels of both glycogen phosphorylase and glucose-6-phosphatase. These enzymatic inductions occur without normalization of insulinemia. Despite the reduced levels of key enzymes of glycogenolysis, the stimulation of glucose production from glycogen in response to glucagon and phenylephrine is not modified in GH-deprived rats. An increase in the intrinsic activity of one or both of the enzymatic steps is postulated to compensate for the lower levels of enzymes, as indicated by the slopes of the correlation between glucose production and phosphorylase a activity (107 and 216 nmol glucose produced/min/U phosphorylase a [P < .001] in control and GH-deprived rats, respectively). GH replacement enhances maximal phosphorylase activity and brings the correlation toward the control value (slope, 128 nmol glucose produced/min/U phosphorylase a). Our findings demonstrate that glycogenolysis in hepatocytes isolated from GH-deprived rats is normal, despite a reduction of glycogen phosphorylase and glucose-6-phosphatase activities.(ABSTRACT TRUNCATED AT 250 WORDS)

Human hepatic macrovesicular steatosis: a noninvasive study of mitochondrial ketoisocaproic acid decarboxylation.

Differentiating between alcoholic and nonalcoholic hepatic steatosis is often a difficult clinical task. However, decreased fatty acid mitochondrial oxidation appears as the main factor for alcoholic steatosis, whereas nonalcoholic steatosis may be due to other causes. We studied mitochondrial function, based on a 13C-ketoisocaproic acid (13C-KIC) breath test, in nine alcoholic and 12 nonalcoholic steatosis patients and 10 healthy volunteers. Our results showed a 42% 13C-KIC decarboxylation decrease in alcoholic steatosis patients, but not in nonalcoholic steatosis patients. This noninvasive breath test appears helpful for the diagnostic work-up of hepatic steatosis.

Reversible and irreversible glucose disposal in dogs: influence of fasting and cold exposure.

Rates of total glucose entry rate, irreversible loss, and recycling were measured in unanesthetized dogs with indwelling arterial and venous catheters. Four experimental conditions were selected: 16 or 26 hr of fasting and neutral (+25 degrees C) or cold (-21 degrees C) ambient temperatures. A mixture of U 14C-glucose and 2-3H-glucose was used as a tracer, according to the primed infusion technique. No matter what the ambient temperature was, increase of fasting time from 16 to 26 hr induced a slight, but nonsignificant, decrease in both the total glucose entry rate and the irreversible loss. At neutral ambient temperature, the amount of glucose promptly recycled was less after 16 hr than after 26 hr of fasting, while an opposite pattern was observed during cold exposure. Thus, that part of hepatic glucose entry promptly recycled was significantly increased from 22% (16 hr of fasting) to 31% (26 hr of fasting) at neutral ambient temperature. It remained almost unchanged (20% and 18%) in cold. It was, therefore, suggested that this increase might be considered as an compensatory mechanism, exerting a sparing effect on glucose utilization. This mechanism does not occur in cold ambient temperature, thus, worsening a possible shortage in glucose supply.

Mechanism of carbon tetrachloride autoprotection: an in vivo study based on 13C-aminopyrine and 13C-galactose breath tests.

This study was conducted to evaluate in vivo the hepatotoxic effects of CCl4 administration to rats using 13C breath tests: aminopyrine breath test (ABT) was used to monitor CCl4-induced cytochrome P450 inactivation, and galactose breath test (GBT) to quantitatively measure the CCl4-induced decrease of liver function. The ABT results showed profound aminopyrine demethylation inhibition lasting for three days and complete recovery at day 7, while GBT results were decreased only one day after CCl4. The protection induced by a first CCl4 dose against a second one paralleled cytochrome P450 inactivation: a second CCl4 dose given three days after the first one induced no GBT decrease and a mild increase of serum transaminase activities. On the other hand, the second dose administered 7 days after the first one produced a GBT decrease similar to the one observed after the first one. These results should be taken into consideration to determine the optimal CCl4 dosing schedule in the rat CCl4-induced cirrhosis model.

Continuous monitoring of 13C-aminopyrine metabolism in rats: effects of cold exposure and noradrenaline.

A system was developed to allow constant monitoring of hepatic cytochrome P450 activity in awake and unrestrained rats. A continuous 13C-aminopyrine perfusion was performed, and breath samples obtained for endogenous CO2 production and 13C measurements, to calculate 13C O2 production due to aminopyrine demthylation. Increasing doses of 13C-aminopyrine produced a hyperbolic increase of expired 13CO2, compatible with an in vivo measurement of enzymatic activity. Acute-cold exposure of the rats during 13C-aminopyrine perfusion produced a two-fold increase of endogenous CO2 production, together with a 27% increased 13C-aminopyrine metabolism (p<0.05 vs basal conditions). In contrast, noradrenaline (20 microg/kg BW/min), despite a similar effect on energy expenditure, did not significantly change 13C-aminopyrine metabolism. Acute-cold exposure is known to stimulate both adrenal catecholamine secretion and the sympathetic nervous system. The observed difference in 13C-aminopyrine demthylation during cold exposure and nonadrenaline perfusion, therefore, could be due to a more specific effect of adrenal catecholamines on liver aminopyrine metabolism. These results suggest the possibility of prolonged in vivo monitoring of liver metabolism pathways such as aminopyrine demethylation, thus allowing the study of drug acute interactions with cytochrome P450 system.

Sleep changes in fasting rats.

The proportion and the distribution of wakefulness (W) slow-wave sleep (SWS) and paradoxical sleep (PS) were studied in 27-week-old rats over 24 hr periods, both in the fed state and after having been deprived of food for 2 to 3 weeks. In these rodents, prolonged fasting has been characterized by 3 successive metabolic phases which have been found to correspond to changes in protein metabolism. Sleep-waking changes were not studied during the first phase which was often of short duration (24 hr). During the second phase, i.e., when proteins were spared, the 24 hr proportions of W and sleep states remained unchanged. There were, however, profound changes in the daily mean episodic characteristics of each vigilance state (duration and frequency) except in the case of PS. During the phase II, the differences in the day/night proportions observed in each vigilance state were less than in the fed state. This reflected a lowering in the amplitude of their daily rhythms. In contrast, when protein use rose (phase III), W was increased sharply at the expense of SWS and PS, the latter being almost completely suppressed. During this last phase, which was also of short duration (by mean 3 days) alertness was greatly enhanced and the rats, which were typically nocturnal when fed, became diurnal. The changes in sleep and wakefulness were examined in relation to their effects on the homeostatic and cyclic components of sleep mechanisms and adaptive strategy to food deprivation in rat.

Fasting-induced rise in locomotor activity in rats coincides with increased protein utilization.

The aim of this study was to investigate the possible relation between the modifications in locomotor activity (on running wheel) which occur during prolonged fasting and changes in the utilization of energy reserves. In 18-week-old rats, we found that the rate of body mass loss reflects the changes in nitrogen excretion that occur over three phases of fasting: (I) initially decreasing, (II) maintained at a low level and (III) increasing. Locomotor activity started to increase during phase II without a change in its nycthemeral pattern. By contrast, the 10-fold higher daily locomotor activity that occurred in phase III was marked by a higher proportion of diurnal activity. Using 9-, 18-, and 33-week-old rats, in order to obtain a different timing in the metabolic changes during fasting, we could confirm the coincidence between the later rise in locomotor activity and the occurrence of phase III. Refeeding of rats of either age in phase III rapidly suppressed fasting-induced changes in locomotor activity. These data accord with the idea that behavioral changes reflecting the search for food are triggered by a later and reversible change in the utilization of body protein vs. lipid stores during prolonged fasting.

Comparison between lactulose-mannitol test and 51Cr-labelled ethylene diamine tetra-acetate test in inflammatory bowel diseases.

A direct comparison was made between mannitol-lactulose and EDTA tests in 10 control subjects and in 9 and 19 patients suffering, respectively, from ulcerative colitis or Crohn's disease. The markers were orally administered in a random order and urinary recoveries were measured. At group level, significant differences were only observed in EDTA test results between control subjects and Crohn's disease patients. At the individual level, these tests exhibited poor sensitivity in ulcerative colitis, both in the inactive and active forms of the disease. In contrast, in patients suffering from Crohn's disease, the lactulose and EDTA recoveries and lactulose/mannitol ratios reached interesting figures, particularly in the EDTA 24-hr-test where 63% of the results were abnormal. This percentage climbed to 75% when active forms of the disease were selected. More interestingly, addition of abnormal results obtained with sugar and/or EDTA tests provided a significant increase in sensitivity with figures up to 90% in the entire group and 92% in patients with active forms of the disease. It is suggested that a) Neither the lactulose-mannitol test nor the EDTA test is useful in ulcerative colitis even in the active forms, b) in Crohn's disease, the sensitivity of the EDTA test is greater than that of the sugar test, c) a combination, in the same patient, of the EDTA and sugar tests is able to provide an interesting percentage of sensitivity.

Effects of proximal gastric vagotomy on gastric secretory and plasma hormonal responses to sham feeding in patients with duodenal ulcers.

The effects of proximal gastric vagotomy on the gastric secretion of acid and pepsin, and on the release of gastrin and pancreatic polypeptide in response to sham feeding were assessed comparatively within 1-4 months after surgery in 32 male duodenal ulcer patients. Each test comprised three successive periods: basal, modified sham feeding (MSF) and pentagastrin stimulation. In each test period the acid output was strongly correlated with the corresponding pepsin output, both parameters being reduced to similar extents after vagotomy. The percentage of postoperative reduction of MSF-induced acid and pepsin outputs was positively correlated with the preoperative values. MSF resulted in a limited but significant release of gastrin, the response being significantly greater after surgery. The MSF-induced release of pancreatic polypeptide was significantly reduced by proximal gastric vagotomy, the reduction percentage being negatively correlated with the time elapsed since surgery. Neither pre- nor post-operatively did the gastrin and pancreatic polypeptide responses bear any relationship to the other parameters tested. We conclude that the study of sham feeding responses of pepsin, gastrin and pancreatic polypeptide provides no further information than does the measurement of acid secretion for the segregation of duodenal ulcer patients, especially with respect to follow-ups for ulcer recurrence.

Aminopyrine breath test: development of a 13C-breath test for quantitative assessment of liver function in humans.

BACKGROUND/AIM: 14C-aminopyrine breath test (ABT) has been shown to be well correlated to the severity of liver diseases, but its use is limited in countries where radioactive isotopes are severely controlled. The goal of this study was to develop a 13C-ABT based on a highly sensitive method to measure 13CO2 in breath samples. MATERIALS AND METHODS: The relevant parameters were studied in 26 controls and 27 patients: the 13CO2 enrichment of expired breath between t-10 and t+60 minutes was determined as the most simple and clinically useful parameter. The 13C-ABT was then prospectively compared to clinico-biological data and the galactose elimination capacity (GEC) in 82 patients. RESULTS: The 13C-ABT was well correlated to: i) the Child-Pugh classification; ii) GEC results; iii) the hepatic volume. The presence of ascites or alcoholic consumption did not alter significantly the results of the test. 13C-ABT appeared more sensitive than GEC to evaluate minor liver dysfunctions. CONCLUSIONS: The 13C-ABT is a simple and sensitive test to measure liver function. The use of the stable isotope 13C ensures the harmlessness of the test and the possibility to repeat it in a given patient.

Relationships between the extent of ileal lesion of resection and vitamin B12, bile salt and fat absorption.

Vitamin B12 Urinary excretion, stool weight, fecal fat excretion, fecal 14C glycocholate excretion and 14CO2 output after I-14C glycocholate ingestion, were measured in 13 patients with non-operated ileal Crohn's disease (NOC), 14 patients with ileal resection for ileal Crohn's disease, with or without right colectomy (RC), and 11 patients with ileal resection with or without right colectomy for pathology other than Crohn's disease (RNC). A positive linear relationship was found between stool weight and 14C glycocholate fecal excretion. The logs of fecal fat and 14C glycocholate excretions were related to the extent of the ileal lesion of resection; a similar but negative relationship was observed for vitamin B12 urinary excretion. Fecal fat excretion and respiratory 14CO2 output were significantly higher in patients with right colectomy.

[Ischemic preconditioning: concept of endogenous myocardial protection]. / Le préconditionnement ischémique: concept d'une protection myocardique endogène.

Preconditioning is a temporary tolerance to ischaemia acquired by the myocardium after a short period of ischaemia. It results in the limitation of the infarct size induced by prolonged coronary occlusion. The mechanism of this cytoprotection remains poorly understood. The A1 adenosine receptors, the ATP-sensitive potassium channels and protein-kinase C seem to play prominent roles. The effects of preconditioning on the complications of ischaemia/reperfusion such as myocardial stunning, ventricular arrhythmias or decreased coronary reserve are not well known. Several studies suggest that the cytoprotection resulting from preconditioning could be applied to human myocardium and constitute a preventive anti-ischaemic therapy during coronary angioplasty, cardiac surgery or the conservation of transplant grafts.

[13C-urea breath test for the diagnosis of Helicobacter pylori infection. Comparison with histology]. / Test respiratoire à l'urée-13C pour le diagnostic de l'infection à Helicobacter pylori. Comparaison avec l'histologie.

OBJECTIVE: This study was to evaluate the 13C-urea breath test for the diagnosis of Helicobacter pylori infection compared with pathological data of gastric antrum and fundus endoscopic biopsies. METHODS: In 95 patients, the results of the 13C-urea breath test were retrospectivally compared with histology (standard and Giemsa staining). RESULTS: Using a ROC curve, the best cut-off value for the 13C-urea breath test was determined at + 3 delta 0/00 of breath isotopic enrichment. Compared with histology, the diagnostic values of the 13C-urea breath test were: sensibility 90.3%, specificity 97%, positive predictive value 98.2%, negative predictive value 84%. The false negative results of the breath test (6 out of 95) were obtained in patients with few H. pylori present in antral biopsies, or in patients under omeprazole therapy. The urea breath test was well correlated with the inflammation of the gastric mucosa (P < 0.0001). The isotopic enrichment in breath was well correlated to the number of H. pylori estimated by histological analysis (P < 0.05). CONCLUSIONS: The 13C-urea breath test is a non invasive and non radioactive diagnostic tool for H. pylori infection. Its excellent positive predictive value and its good negative predictive value guarantee its usefulness in clinical practice, especially for the control of eradication after anti-H. pylori therapy.

[Effect of enprostil on the healing and the recurrence of duodenal ulcer. Comparison with ranitidine]. / Effect de l'enprostil sur la cicatrisation et la récidive des ulcéres duodénaux. Comparaison à la ranitidine.

Enprostil, a synthetic prostaglandin E2, has been shown to exert both antisecretory and mucoprotective activity. It is effective in duodenal ulcer healing. OBJECTIVE--This study was performed to compare the frequency and the delay of spontaneous duodenal ulcer relapse during a two-year follow up period after initial healing by enprostil (35 micrograms, twice a day) or ranitidine (300 mg per day). METHODS--This multicentric, double-blind, randomized study included 642 patients (324 in the enprostil group and 318 in the ranitidine group). Patients included in the follow up period were evaluated by an endoscopy at 6 months, one and two years after healing. RESULTS--After a 6 weeks treatment period, healing rate was 85% for ranitidine and 70% for enprostil, respectively (P < 0.001). Adverse effects, especially digestive ones, occurred more often with enprostil than with ranitidine (P < 0.001). After initial healing, there was no significant difference between the 2 groups concerning the cumulative rate of relapse, despite a non significant trend for a milder rate of relapse in the enprostil group (P = 0.08). Twenty-seven % of the patients randomized to treatment (intend-to-treat analysis) in the enprostil group and 29% in the ranitidine group had no ulcer recurrence 6 months after ulcer healing, and respectively 12% and 13% at 2 years (difference not statistically significant). CONCLUSIONS--It is concluded that a) ranitidine is more effective and has less adverse effects than enprostil for duodenal ulcer healing, b) after duodenal ulcer healing by enprostil, there is a non significant trend for a lower rate of relapse than after healing with ranitidine, c) there is the same proportion of patients without ulcer in the 2 groups after 6 months and 2 years.

[Variations of plasma gastrin (basal and postprandial) in ththtreatmentof duodenal ulcer with either enprostil or ranitidine. Correlations with rates of relapse]. / Variations de la gastrine plasmatique (basale et post-prandiale) au cours de traitements de l'ulcère duodénal par l'enprostil ou la ranitidine. Corrélations avec les taux de rechute.

Enprostil, a synthetic E2-prostaglandin efficacious for duodenal ulcer healing, presents both antisecretory and antigastrinic effects. This is at variance with the elevation of plasma gastrin observed with ranitidine. OBJECTIVE--This leads us to compare enprostil and ranitidine on the following points: a) variations of plasma gastrin (basal and postprandial) parameters over a 6-week conventional treatment; b) correlation studies between ulcer relapses (frequency and temporal evolution) after treatment discontinuation and various gastrinic criteria. METHODS--Among a group of 642 patients followed for ulcer relapse, 165 were considered for gastrin (78 of the "Enprostil" group and 87 of the "Ranitidine" group). RESULTS--Initially, both populations were comparable for clinical and plasma gastrin parameters. After 6 weeks of treatment, the increases in the various gastrin parameters (basal, postprandial, peak, integraded) were significantly greater and the absolute values higher (Wilcoxon, P < 0.001) with ranitidine than with enprostil. No correlation was found between relapse occurrence after drug discontinuation and these gastrin parameters. CONCLUSIONS--Ranitidine hypergastrinemia seems directly related to gastric hyposecretion whereas its absence with enprostil is likely more dependent upon a specific antigastrinic activity than on a reduced antisecretory activity. Those differences in mechanism of action have no consequence on the stability of ulcer obtained by either drug.

[Physiology of the digestive smooth muscle]. / Physiologie du muscle lisse digestif.

By comparison with striated muscle, the main features of digestive smooth muscle are richness, complexity and diversity specially with thanks to the enteric and prevertebral nervous neurons which add up their effects to those of the central nervous system. The morphological and molecular characteristics of the smooth muscle contractility begin to be unveiled, but a lot of basic knowledge is still needed for further pharmacological advances.

[Nervous control of intestinal motility]. / Contrôle nerveux de la motricité digestive.

Leaving aside hormonal factors which should not be underestimated, it is now clear that digestive motility is a unitary phenomenon mainly under control of the nervous system. This system includes three discrete and somewhat redundant integrative levels: the enteric nervous system located in the digestive wall; the prevertebral ganglia and finally the central nervous system operating through more classical parasympathetic (cholinergic or not) or sympathetic (adrenergic) pathways. Nowadays, interest is concentrated upon the enteric nervous system because of its ubiquity, its potentiality, (it is able to operate highly integrative motor functions), its complexity and its neurochemical diversity. This last feature will provide, in the future, numerous opportunities for pharmacology and therapeutics.