Circadian rhythmicity of plasma amino acid variations in healthy subjects.

The circadian periodicity of plasma amino acids (AA) was explored using Cosinor analysis. Six healthy subjects eating a standard diet (30 Kcal and 1 g of protein/Kg of body weight) were studied. Plasma samples for AA determination were taken at 07:00, 11:00, 15:00, 17:00, 21:00 and 24:00. The majority of AA showed an increment in the evening samples. This 24-h variability led to a circadian rhythmicity for all AA, except for taurine, threonine, glutamate, alanine, cystine, and total tryptophan. On average, the fluctuation was approximately 15% of the mesor and the acrophase timing was between 17:00 and 22:00.

Lactitol in prevention of recurrent episodes of hepatic encephalopathy in cirrhotic patients with portal-systemic shunt.

Recurrent episodes of hepatic encephalopathy (HE) frequently occur in surgically shunted cirrhotic patients. The prevention of these episodes is based mainly on the long-term use of lactulose. Recently, lactitol, a nonabsorbable disaccharide similar to lactulose, has been proposed as an alternative in the management of HE. It has the advantage of being better tolerated and producing a more predictable catharsis. The effects of the two agents were compared in a controlled randomized study lasting six months involving 31 cirrhotic patients with portal-systemic shunt, of whom 40% experienced HE. The PSE index (mental state, EEG, asterixis, Raitan test, and ammonia) was assessed in each patient on entry to the study and every three months during treatment. Episodes of HE, side effects, and the patients' comments on efficacy, tolerability, and palatability were recorded. The dose required to induce two bowel movements per day was 48 +/- 25 ml of lactulose syrup and 36 +/- 7 g of lactitol. During the study, the number of patients who had an episode of HE and the PSE index was similar in both groups. The patients judged lactitol better from the point of view of palatability. Meteorism and flatulence, experienced by patients treated with lactulose, was not reported by the lactitol group. We concluded that lactitol is as effective as lactulose in the long-term prevention of episodes of HE in cirrhotics with portal-systemic shunt and may be better tolerated.

Drawbacks in the use of 23-nor-deoxycholic acid standards.

23-Nor-deoxycholic acid is widely used as internal standard in gas-liquid chromatographic studies of bile acids. Two batches of this compound, submitted to conventional alkaline hydrolysis of bile acid conjugates, were found to be transformed into a product with chromatographic properties different from those of "authentic" 23-nor-deoxycholic acid. To identify this "new" product a comparison was made between chromatographic properties, mass spectra, and NMR spectra of 23-nor-deoxycholic acid before and after alkaline hydrolysis. The results indicate that the "new" compound is the true 23-nor-deoxycholic acid while the product present in the two batches examined is a monoacetate derivative.

Structure of biliary phosphatidylcholine in cholesterol gallstone patients.

The fatty acid composition of biliary phosphatidylcholine was analyzed in 13 patients with radiolucent gallstones undergoing elective cholecystectomy, and in 11 normolipemic patients without gallstone undergoing abdominal surgery. The only difference in the percentage fatty acid composition between the two groups was a significantly (p less than 0.05) higher percentage arachidonic acid in the first group. This acid was exclusively located in the sn-2 position of phosphatidylcholine (PC), accounting for 13.0 +/- 4.9% in the first group and 8.2 +/- 4.9% in the second (p less than 0.05). The percentage arachidonic acid of PC was negatively correlated (p less than 0.001) with the percentage biliary chenodeoxycholate in gallstone patients, but not in controls. Explanation of these findings is, at present, only speculative.

Sulfated bile acids in serum, bile, and urine of cirrhotic patients before and after portacaval anastomosis.

Sulfated and unsulfated bile acid composition was studied in serum and bile in 10 patients with alcoholic cirrhosis. Samples, collected before and 2 months after portacaval anastomosis, were analyzed using a gaschromatographic method. Mean total serum bile acid levels rose from 32.0 +/- 5.3 (SE) mumol/liter before to 87.4 +/- 13.3 mumol/liter after surgery (P less than 0.005). The increase in serum bile acid levels was significantly only with respect to the unsulfated fraction (22.7 +/- 3.0 mumol/liter to 67.6 +/- 8.1 mumol/liter, P less than 0.005). Thus the percent sulfation of total serum bile acid decreased from 24.6% to 19.2%. The sulfated bile acid fraction comprised mainly chenodeoxycholate both before and after surgery. Percent sulfation of individual bile acids was not modified after portacaval anastomosis. Bile acid sulfates were present in bile only in negligible amounts. The daily urinary excretion of bile acids, studied in 6 patients, increased significantly (P less than 0.05) after surgery, the increase being due only to the unsulfated compounds. Data from this study indicate that in cirrhotic patients no significant changes occur in serum with respect to sulfated bile acids after portacaval anastomosis, despite a definite increase in serum unsulfated bile acid levels. This is likely due to the lack of an efficient enterohepatic circulation of bile acid sulfates.