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Query: UMLS:C0024523 (malabsorption)
 7,319 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cobalamin (Cbl; vitamin B(12)) malabsorption in pancreatic insufficiency can be partially corrected by bicarbonate and completely corrected by pancreatic proteases but the mechanisms involved are unknown. Because saliva contains enough R-type Cbl-binding protein (R protein) to bind all of the dietary and biliary Cbl, it is possible that R protein acts as an inhibitor of Cbl absorption and that pancreatic proteases are required to alter R protein and prevent such inhibition. To test this hypothesis we studied the ability of R protein and intrinsic factor (IF) to compete for Cbl binding and ability of pancreatic proteases to alter this competition. Human salivary R protein bound Cbl with affinities that were 50- and 3-fold higher than those of human IF at pH 2 and 8, respectively. Cbl bound to IF was transferred to an equal amount of R protein with t((1/2))'s of 2 and 90 min at pH 2 and 8, respectively, and within several hours respective ratios of R protein-Cbl/IF-Cbl of 50 and 2 were observed. Cbl bound to R protein was not transferred to IF at either pH 2 or 8. Incubation of R protein with pancreatic proteases at pH 8 led to a 150-fold decrease in its affinity for Cbl. Incubation of R protein-Cbl with pancreatic proteases led to complete transfer of Cbl to IF within 10 min. Gel filtration studies with R protein-[(57)Co]Cbl and (125)I-R protein showed that pancreatic proteases partially degraded R protein. Pancreatic proteases differed in their ability to effect these changes with trypsin > chymotrypsin > elastase. Pancreatic proteases did not alter IF in any of the parameters mentioned above. Pepsin failed to alter either R protein or IF. THESE STUDIES SUGGEST THE FOLLOWING: (a) that Cbl is bound almost exclusively to R protein in the acid milieu of the stomach, rather than to IF as has been assumed previously; (b) that Cbl remains bound to R protein in the slightly alkaline environment of the intestine until pancreatic proteases partially degrade R protein and enable Cbl to become bound exclusively to IF; and (c) that the primary defect in Cbl absorption in pancreatic insufficiency is a lack of pancreatic proteases and a failure to alter R protein and effect the transfer of Cbl to IF. These studies also suggest that the partial correction of Cbl malabsorption observed with bicarbonate is due to neutralization of gastric HCl, since at slightly alkaline, pH IF can partially compete with R protein for the initial binding and retention of Cbl.
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PMID:Effect of proteolytic enzymes on the binding of cobalamin to R protein and intrinsic factor. In vitro evidence that a failure to partially degrade R protein is responsible for cobalamin malabsorption in pancreatic insufficiency. 2 56

1. Vitamin B12 absorption was measured in 18 patients with tropical malabsorption. 2. Absorption was particularly impaired in patients with severe mucosal lesions. 3. Sequential measurements with 57Co- and 58Co-labelled vitamin B12 were made before and 48 h after the start of tetracycline therapy. A rapid improvement (on average 22% increase in absorption) occurred in four of six patients with marked mucosal lesions. Further improvement occurred in four of five patients measured after 4 weeks' tetracycline, including the two who failed to improve initially. 4. These rapid changes in vitamin B12 absorption after antibiotics occur too early to be due to mucosal recovery and suggest that bacterial metabolism is an important factor in the malabsorption in these patients.
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PMID:Assessment of early and delayed responses in vitamin B12 absorption during antibiotic therapy in tropical malabsorption. 28 45

A patient with granulomatous gastritis is described. Two years after the presentation of his gastric disease he developed pernicious anemia. Lack of intrinsic factor production secondary to Crohn's disease of the stomach is felt to be the cause of his Vitamin B12 malabsorption.
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PMID:Pernicious anemia caused by Crohn's disease of the stomach. 43 4

In animal experiments (20 mongrel dogs) malabsorption was induced by resection of 100 cm ileum. Subsequently the influence of the ileocoecal valve (Valvula Bauhini) in absorption was studied. In one group of animals intestinal continuity was reestablished by ileoileostomy, in a second by ileocolostomy. The results of the absorption studies were compared with a healthy control group. After ileoileostomy animals do not lose weight, serum cholesterol and protein remain normal. Oral tolerance tests with Triolein-iodine-131 and Cyanocobalamine show results identical with those of the control group. After ileocolostomy all these parameters are lowered--partially to a pathological level. It is concluded that in all operations in the area of the terminal ileum and colon the Valvula Bauhini should be retained if possible.
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PMID:[Resection of the valvula bauhini and its effect on the metabolism. An experimental study in animals (author's transl)]. 48 Oct 32

Malabsorption tests were studied in 52 patients with multiple sclerosis. The stools were examined microscopically for fat and undigested meat fibers and were found to be abnormal in 41.6 and 40.9% respectively. Abnormally low five hour excretion of d-xylose was demonstrated in 26.6% cases. Malabsorption of Vitamin B12 was found in 11.9% cases. The jejunal mucosa was examined histologically and by tissue immune technic including viral studies. Histology showed normal mucosa in all except seven patients in whom an increased inflammatory infiltrate was present. Fluorescent antibody studies revealed the presence of measles virus antigen in all patients and immunofluorescent studies showed a variable degree of immune reaction in the majority of cases. The significance of these findings in the pathogenesis of multiple sclerosis is discussed.
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PMID:Multiple sclerosis and malabsorption. 61 12

Sixty-three unselected cases of giardiasis, with no evidence of other systemic disease, were screened for evidence of steatorrhoea. No patient had any evidence of protein-energy malnutrition. Seventeen (27%) of the cases had steatorrhoea; three (17-8%) of the 17 patients having steatorrhoea also had D-xylose malabsorption. Vitamin B12 absorption was normal in all. Bacterial culture and qualitative analysis of bile salt in jejunal fluid was carried out in all the 17 cases having steatorrhoea as well as 13 cases with normal absorptive parameters (eight cases of irritable bowel syndrome and five cases of giardia infection) who served as controls. All the patients showing bacterial overgrowth had free bile acids in their duodenal aspirate. Free bile acids could also be detected in jejunal aspirates of five of the seven patients having no bacterial overgrowth. Two control cases of giardia infection with normal small bowel function and sterile duodenal aspirate showed evidence of bile salt deconjugation. The significance of these findings is discussed in relation to the pathogenesis of steatorrhoea in patients with giardiasis. The possible role of giardia in bile salt deconjugation is suggested.
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PMID:Mechanism of malabsorption in giardiasis: a study of bacterial flora and bile salt deconjugation in upper jejunum. 85 75

Since vitamin B12malabsorption has been described in diabetics on biguanides and inhibition of bile acid absorption found in rat ileum the effect of treatment with different biguanides (phenformin, buformin, metformin) on bile acid metabolism and vitamin B12 absorption was assessed in maturity onset diabetics. Biguanides did not alter faecal weight or faecal fat excretion, but they decreased faecal bile acid excretion. All biguanides tested increased deconjugation of glycocholic acid, as determined by a simple breath test technique. Vitamin B12 malabsorption was most prominent in patients on metformin. Discontinuation of biguanide treatment, or administration of antibiotics, normalized or improved the increased deconjugation of bile acids and the Schilling test. Decreased faecal bile acid excretion, positive 14C-glycocholate breath tests, pathological Schilling tests and the reversal of pathological tests by antibiotic treatment suggest that small intestinal bacterial overgrowth, leading to binding of the intrinsic-factor-vitamin B12-complex to bacteria, is responsible for the previously observed pathological Schilling tests in diabetics on biguanides. Bile acid malabsorption, possibly responsible for the cholesterol-lowering effect of biguanides, does not occur in diabetics on biguanides. Whether qualitative changes in small intestinal bile acid composition might affect cholesterol metabolism remains to be determined.
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PMID:Alteration of bile acid metabolism and vitamin-B12-absorption in diabetics on biguanides. 87 86

Tropical enteropathy, which may be related to tropical sprue, has been described in many developing countries including parts of Africa. The jejunal changes of enteropathy are seen in Rhodesians of all social and racial categories. Xylose excretion, however, is related to socioeconomic status, but not race. Upper socioeconomic Africans and Europeans excrete significantly more xylose than lower socioeconomic Africans. Vitamin B12 and fat absorption are normal, suggesting predominant involvement of the proximal small intestine. Tropical enteropathy in Rhodesia is similar to that seen in Nigeria but is associated with less malabsorption than is found in the Caribbean, the Indian subcontinent, and South East Asia. The possible aetiological factors are discussed. It is postulated that the lighter exposure of upper class Africans and Europeans to repeated gastrointestinal infections may accound for their superior xylose absorption compared with Africans of low socioeconomic circumstances. It is further suggested that the milder enteropathy seen in Africa may be explained by a lower prevalence of acute gastroenteritis than in experienced elsewhere in the tropics.
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PMID:Tropical enteropathy in Rhodesia. 100 78

Bile acid and vitamin B12 malabsorption were evaluated in 34 cases of ulcerative colitis. Twenty-four patients were non-operated and 10 patients were colectomized. The postprandial duodenal bile acid concentration was abnormally low in 13 of 24 non-operated cases and found to be correlated to the activity of the disease. Two of six patients subjected to colectomy had a reduced bile acid concentration. Bile acid absorption was assessed by the cholyl-glycine-1-14C breath test combined with faecal analysis. The 14C-excretion in breath was abnormally elevated in only one of the patients in the total material. The faecal 14C-output was related to the disease activity in the non-operated group. Patients colectomized for ulcerative colitis had an extremely high excretion of isotope in the ileal effluent, from 15 to 81 per cent of the dose given. The faecal 14C-output was correlated with the duration of the ileostomy and the mass of ileal discharge. Vitamin B12 malabsorption was only present in five patients. It is concluded that patients with ulcerative colitis during the active phase of the disease have bile acid malabsorption, and patients colectomized for ulcerative colitis have an abnormal high bile acid deconjugation in the ileal effluent.
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PMID:Bile acid metabolism and vitamin B12 absorption in ulcerative colitis. 100 50

Vitamin B12 absorption was studied in 34 patients, 10 months to 6 years after construction of a continent ileostomy. Normal Schilling test values (greater than 10 percent) were obtained in 21 of the cases after a single determination. Repeated tests showed a normal B12 absorption in 8 of the 13 patients who had revealed a Schilling test value below 10 percent at the first determination. In the remaining 5 patients, repeated Schilling tests showed borderline values (5-10 percent) in 4 cases and a low value (mean 4.5 percent) in one case. One of the patients with borderline values had previously undergone resection of 80 cm of the terminal ileum. When vitamin B12-intrinsic factor complex was instilled directly into the reservoir in 3 patients, it was found that the vitamin was absorbed by the mucous membrane of the reservoir. The construction of a continent ileostomy reservoir thus does not appear to expose the patient to an increased risk of developing vitamin B12 malabsorption.
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PMID:Vitamin B12 absorption in patients with continent ileostomy. 112 47


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