Intestinal dipeptidases and disaccharidases in children with malabsorption

Improved Starch Digestion of Sucrase-deficient Shrews Treated With Oral Glucoamylase Enzyme Supplements

BACKGROUND AND OBJECTIVE

Although named because of its sucrose hydrolytic activity, this mucosal enzyme plays a leading role in starch digestion because of its maltase and glucoamylase activities. Sucrase-deficient mutant shrews, Suncus murinus, were used as a model to investigate starch digestion in patients with congenital sucrase-isomaltase deficiency.Starch digestion is much more complex than sucrose digestion. Six enzyme activities, 2 α-amylases (Amy), and 4 mucosal α-glucosidases (maltases), including maltase-glucoamylase (Mgam) and sucrase-isomaltase (Si) subunit activities, are needed to digest starch to absorbable free glucose. Amy breaks down insoluble starch to soluble dextrins; mucosal Mgam and Si can either directly digest starch to glucose or convert the post-α-amylolytic dextrins to glucose. Starch digestion is reduced because of sucrase deficiency and oral glucoamylase enzyme supplement can correct the starch maldigestion. The aim of the present study was to measure glucogenesis in suc/suc shrews after feeding of starch and improvement of glucogenesis by oral glucoamylase supplements.

METHODS

Sucrase mutant (suc/suc) and heterozygous (+/suc) shrews were fed with C-enriched starch diets. Glucogenesis derived from starch was measured as blood C-glucose enrichment and oral recombinant C-terminal Mgam glucoamylase (M20) was supplemented to improve starch digestion.

RESULTS

After feedings, suc/suc and +/suc shrews had different starch digestions as shown by blood glucose enrichment and the suc/suc had lower total glucose concentrations. Oral supplements of glucoamylase increased suc/suc total blood glucose and quantitative starch digestion to glucose.

CONCLUSIONS

Sucrase deficiency, in this model of congenital sucrase-isomaltase deficiency, reduces blood glucose response to starch feeding. Supplementing the diet with oral recombinant glucoamylase significantly improved starch digestion in the sucrase-deficient shrew.

La maladie cœliaque de l’adulte : aspects nouveaux

INTRODUCTION

Celiac disease also known as gluten-sensitive enteropathy is a complex disorder where genetically susceptible individuals develop in typical cases signs of malabsorption after ingestion of cereals. Malabsorption is due to total or subtotal atrophy of the small intestinal mucosa regressing after adherence to a gluten-free diet. The only effective therapy is life-long strict abstinence from wheat, rye and barley.

CURRENT KNOWLEDGE AND KEY POINTS

During the last two decades spectrum of clinical features of adult celiac disease has been modified. About 60% of cases are now revealed by extraintestinal manifestations. Moreover, recent studies that used serological methods revealed existence of both latent and silent celiac sprue. The finding of the high frequency of atypical celiac sprue contributed to underestimation of the true prevalence of celiac disease until now, and explained that celiac disease could be unknown for a long time, with increased risk of nutritional deficiencies and malignancy. Concurrently, the finding that celiac disease is primarily associated to a few HLA class II molecules, and recent advent of tissue transglutaminase as the main auto-antigen eliciting anti-endomysial antibodies allowed to propose new pathogenesis hypothesis and efficient screening tests for celiac disease diagnosis.

FUTURE PROSPECTS AND PROJECTS

New epidemiological data concerning adult celiac disease must incite to a more systematic screening in patients with atypical but evocative features, or in at-risk subjects. Introduction of enzyme linked immunosorbent assays (ELISA) for the detection for anti-tissue transglutaminase antibodies allows to make use of a new available and efficient diagnosis parameter, which could constitute the main screening test in the near future.

Measurement of the 10,000-molecular weight calcium-binding protein in small-intestinal biopsy specimens from patients with malabsorption syndromes

Calcium-binding protein (CaBP) (molecular weight, 10,000) was measured in small-intestinal biopsy specimens from 36 patients with malabsorption syndromes: short-bowel syndrome (n = 13), untreated coeliac disease (n = 4), coeliac disease in remission (n = 7), patients with intestinal bypass owing to morbid obesity (n = 5), and in patients with chronic diarrhoea of unknown cause (n = 7). Twelve patients with no signs of malabsorption who had the irritable bowel syndrome were used as controls. Patients with small-bowel resections showed reduced concentrations of CaBP (p less than 0.01) and low intestinal calcium absorption (p less than 0.05). Small amounts of CaBP were found in intestinal specimens from patients with coeliac disease in remission (p less than 0.01), and CaBP was almost undetectable in patients with a newly diagnosed coeliac disease and avillous jejunal biopsy findings (p less than 0.001). Patients with chronic diarrhoea and patients with an intestinal bypass had CaBP concentrations comparable to those of the control group. A direct correlation was found between CaBP and the fractional calcium absorption in all patients (p less than 0.05). CaBP may therefore be considered an indicator of the efficiency of the small intestine to absorb calcium.

Intestinal peptidases and sucrase in coeliac disease

The activities of microvillus aminopeptidase (microsomal, EC 3.4.11.2), dipeptidyl peptidase IV (EC 3.4.14.-), glycyl-leucine dipeptidase (EC 3.4.13.11), proline dipeptidase (EC 3.4.13.9), sucrase (EC 3.2.1.48) and gamma-glutamyl transpeptidase (EC 2.3.2.2) were measured in peroral intestinal biopsies taken from patients with coeliac disease in the acute phase and in remission. A comparison with the amounts of corresponding activities from a reference group showed that all the measured activities were significantly decreased in the acute phase of the disease. In patients in remission only microvillus aminopeptidase and dipeptidyl dipeptidase IV displayed a substantial depression as compared to the reference group. It is suggested that a primary mucosal digestion defect will result in lack of substrate for other intestinal enzymes. This is a situation comparable to starvation and may explain the variation in the grade of restitution for the different enzymes.

A boy with severe infantile gastrogen lactose intolerance and acquired lactase deficiency

A 10-year-old boy with severe familial lactose intolerance in infancy (vomiting, failure to thrive, lactosuria (5.25 g/l), sucrosuria (12 g/l), and aminoaciduria. Intestinal disaccharidases (including lactase and sucrase) normal at age 6 and 20 weeks. Oral lactose tolerance test at this age resulted in lactosuria (4.6 g/l); sucrose tolerance test, in sucrosuria (18.5 g/l). In contrast, intraduodenal lactose tolerance test gave only low lactose excretion in urine (0.28 g/l). He improved rapidly and had no lactosuria on intraduodenal feeding with citric acid milk. The lactosuria diminished as age increased, but was still higher at age 6 years than that of controls. He tolerated normal disaccharide containing food after 1.5 years of age. At 5.5 to 6 years, he had symptoms of lactose malabsorption, and an isolated lactase deficiency was proved. At 10 years, he still tolerates only limited amounts of milk. The defect in severe familial infantile lactose intolerance seems to be localized in the gastric mucosa. Acquired lactase deficiency can appear later in childhood in this syndrome.

The activities of alanine aminopeptidase, leucine aminopeptidase, proline dipeptidase and prolyl dipeptidase in the mucosa of the small intestine. Investigations on normal children and patients with the malabsorption syndrome

Alanine aminopeptidase (EC 3.4.11.2), leucine aminopeptidase (EC 3.4.11.1), proline dipeptidase (EC 3.4.13.9), and prolyl dipeptidase (EC 3.4.13.8) have been investigated in small intestinal mucosa homogenates of normal children and children suffering from different degrees of villous damage. The activities of proline dipeptidase and prolyl dipeptidase could be shown to be significantly decreased in cases of subtotal and total villous atrophy, whereas the activities of alanine aminopeptidase and leucine aminopeptidase were not influenced. The results are discussed in view of the subcellular distribution of these enzymes.

[Intestinal disaccharidase and alkaline phosphatase activities of jejunal biopsies in small bowel diseases of children (author's transl)]

Intestinal disaccharidase activities were determined in 294 jejunal biopsies obtained from 254 children with various disorders of the small bowel, and alkaline phosphatase activity was measured in 251 biopsies. In normal mucosa a broad range of enzyme activity was found corresponding with the data in the literature. A primary disaccharidase deficiency was observed in 5 children with congenital sucrase-isomaltase deficiency and in a 12-year-old Egyptian boy with acquired lactase deficiency. A secondary generalized depression of disaccharidase activity and a diminution of alkaline phosphatase activity existed chiefly in patients who had severe or moderate mucosal damage, also in active coeliac disease and during gluten loading, in protracted diarrhoea of infancy, chronic malabsorption of unknown origin and agammaglobulinemia. During remissions enzyme activities recovered together with mucosal improvement. Low levels of enzyme activities were also seen in some cases of protracted diarrhoea of infancy and chronic malabsorption of unknown origin although only mild mucosal lesions were demonstrated.

Small bowel mucosal dysfunction in patients with cystic fibrosis

Jejunal biopsies were obtained from 37 children with cystic fibrosis, 16 with gluten-induced enteropathy, and 18 control subjects for the following studies: (1) disaccharidase activity, (2) L-ALA-L-Phe hydrolase activity, and (3) intestinal uptake of three 14C-labeled amino acids. Values were significantly reduced in the three determinations in patients with gluten-induced enteropathy as compared to control subjects. Lactase and L-ALA-L-Phe hydrolase activities were significantly reduced (p less than 0.01) in CF patients as compared to control subjects. Definite hypolactasia was also observed in 23% of the children with CF. Uptake of lysine was normal in CF patients whereas that of phenylalanine and cycloleucine was reduced as compared to control subjects. This study suggests an intestinal component to the malabsorption of patients with CF.