Routine disaccharidase testing: are we there yet?

PURPOSE OF REVIEW

Disaccharidase testing, as applied to the evaluation of gastrointestinal disturbances is available but it is not routinely considered in the diagnostic work-up. The purpose of this review was to determine if disaccharidase testing is clinically useful and to consider how the results could alter patient management.

RECENT FINDINGS

Indicate that carbohydrate maldigestion could contribute functional bowel disorders and negatively impact the fecal microbiome. Diagnostic techniques include enzyme activity assays performed on random endoscopically obtained small intestinal biopsies, immunohistochemistry, stable isotope tracer and nonenriched substrate load breath testing, and genetic testing for mutations. More than 40 sucrase--isomaltase gene variants coding for defective or reduced enzymatic activity have been reported and deficiency conditions are more common than previously thought.

SUMMARY

The rationale for disaccharidase activity testing relates to a need to fully assess unexplained recurrent abdominal discomfort and associated symptoms. All disaccharidases share the same basic mechanism of mucosal expression and deficiency has far reaching consequences. Testing for disaccharidase expression appears to have an important role in symptom evaluation, but there are accuracy and logistical issues that should be considered. It is likely that specific recommendations for patient management, dietary modification, and enzyme supplementation would come from better testing methods.

Maternal protein restriction affects gene expression and enzyme activity of intestinal disaccharidases in adult rat offspring

This study investigated the consequences of intrauterine protein restriction on the gastrointestinal tract and particularly on the gene expression and activity of intestinal disaccharidases in the adult offspring. Wistar rat dams were fed isocaloric diets containing 6% protein (restricted, n = 8) or 17% protein (control, n = 8) throughout gestation. Male offspring (n = 5-8 in each group) were evaluated at 3 or 16 weeks of age. Maternal protein restriction during pregnancy produced offspring with growth restriction from birth (5.7 ± 0.1 vs 6.3 ± 0.1 g; mean ± SE) to weaning (42.4 ± 1.3 vs 49.1 ± 1.6 g), although at 16 weeks of age their body weight was similar to control (421.7 ± 8.9 and 428.5 ± 8.5 g). Maternal protein restriction also increased lactase activity in the proximal (0.23 ± 0.02 vs 0.15 ± 0.02), medial (0.30 ± 0.06 vs 0.14 ± 0.01) and distal (0.43 ± 0.07 vs 0.07 ± 0.02 U·g-1·min-1) small intestine, and mRNA lactase abundance in the proximal intestine (7.96 ± 1.11 vs 2.38 ± 0.47 relative units) of 3-week-old offspring rats. In addition, maternal protein restriction increased sucrase activity (1.20 ± 0.02 vs 0.91 ± 0.02 U·g-1·min-1) and sucrase mRNA abundance (4.48 ± 0.51 vs 1.95 ± 0.17 relative units) in the duodenum of 16-week-old rats. In conclusion, the present study shows for the first time that intrauterine protein restriction affects gene expression of intestinal enzymes in offspring.

Effects of crude red kidney bean lectin (phytohemagglutinin) exposure on performance, health, feeding behavior, and gut maturation of pigs at weaning1

The aim of this study was to obtain information that could help to ease the weaning transition in commercial pig production. Before weaning, phytohemagglutinin (PHA) in the form of a crude preparation of red kidney bean lectin was fed by gavage to 24 crossbred [(Swedish Landrace x Yorkshire) x Hampshire] piglets, whereas 24 control piglets were fed alpha-lactalbumin by gavage, to study the effect on growth, occurrence of postweaning diarrhea, feeding behavior, and some anatomical and physiological traits of the gastrointestinal tract. Within the litter, piglets were randomly assigned to PHA treatment or control and remained in the same pen from the beginning (PHA exposure at 7 d before weaning) until the end of the experiment (14 d post-weaning). Weaning took place at the age of 31 to 34 d. Pigs treated with PHA grew faster (P = 0.013) during the first week postweaning and tended to have lower total diarrhea scores (P = 0.10) than did control pigs. On d 5 after weaning, piglets treated with PHA spent more time eating (P = 0.028) than control pigs. No immunostimulating effect of PHA, measured by plasma immunoglobulin G, could be detected. An increase in the intestinal barrier properties before weaning, as a response to PHA treatment, was demonstrated in intestinal absorption studies using Na-fluorescein and BSA as gavage-fed markers. Less uptake (measured as plasma concentrations) of the marker molecule Na-fluorescein occurred during a 24-h study period, and numerically lower levels of BSA were observed compared with studies in control pigs of the same age. A total of 12 pigs (6 control, 6 PHA-treated) were euthanized on the day of weaning for analyses of gastrointestinal properties. The PHA-treated pigs tended to have a longer total small intestinal length (P = 0.063) than that of the control pigs. The enzyme profile of the jejunal epithelium responded to PHA exposure with a decrease in lactase activity and an increase in maltase and sucrase activities, which is similar to changes normally observed after weaning. No differences were found in the size of the pancreas or in its contents of trypsin and amylase. In conclusion, exposing piglets to crude, red kidney bean lectin for 3 d during the week before weaning led to changes in performance and small intestinal functional properties that would be expected to contribute to a more successful weaning.

Phenotypic flexibility in the intestinal enzymes of the African clawed frog Xenopus laevis

The intestinal plasticity of digestive enzymes of amphibian species is poorly known. The goal of this study was to characterize digestive enzyme profiles along the small intestine of adult frogs, Xenopus laevis, in response to an experimental diet. We acclimated adult X. laevis for 30 days either to carbohydrate-rich or protein-rich diets, and determined the morphology and digestive enzymes of the small intestine. We found a significant difference of aminopeptidase-N activity between carbohydrate-rich and protein-rich acclimated animals. We also found a little variation in the expression of maltase activity, which contrast with the proposed hypothesis about the existence of digestive tradeoff in vertebrates. This finding supports the adaptive modulation hypothesis and suggests that caution is called for when analyzing physiological data regarding assumed discrete trophic category of species.

Comparison of duodenal and jejunal disaccharidase levels in patients with non ulcer dyspepsia

AIMS

This study was conducted to compare the duodenal and jejunal disaccharidase levels in the same individual with duodenal ulcer or non ulcer dyspepsia.

METHODS

Thirty seven patients (duodenal ulcer--11, non-ulcer dyspepsia--26) were included in the study. Endoscopic biopsy samples were obtained from jejunum and duodenum using pediatric colonofibroscope.

RESULTS

Levels of jejunal disaccharidases were significantly higher than the duodenal disaccharidases.

CONCLUSIONS

An estimate of jejunal disaccharidases can be had by multiplication of duodenal disaccharidased by a factor 1.48 for lactase, 1.50 for sucrase and 1.56 for maltase.

Chemotherapy for cancer causes apoptosis that precedes hypoplasia in crypts of the small intestine in humans

BACKGROUND AND AIMS

The mechanism of gastrointestinal damage (mucositis) induced by cancer chemotherapy remains uncertain. The aims of this study were to define the time course and mechanism of small intestinal damage following chemotherapy in humans.

METHODS

Patients receiving chemotherapy underwent upper gastrointestinal endoscopy (a maximum of two per patient) with duodenal biopsy prior to chemotherapy and again at 1, 3, 5, and 16 days after chemotherapy. Tissue was taken for morphometry, disaccharidase assays, electron microscopy, and for assessment of apoptosis using the Tdt mediated dUTP-biotin nick end labelling (TUNEL) method. Villus area, crypt length, and mitotic index were measured by a microdissection technique.

RESULTS

Apoptosis increased sevenfold in intestinal crypts at one day, and villus area, crypt length, mitotic count per crypt, and enterocyte height decreased at three days after chemotherapy. Disaccharidase activities remained unchanged. Electron microscopy showed increased open tight junctions of enterocytes at day 3, consistent with more immature cells. All indices improved by 16 days.

CONCLUSION

Small intestinal mucositis is associated with apoptosis in crypts that precedes hypoplastic villous atrophy and loss of enterocyte height.

Relation of the disaccharidases in the small intestine of the rat to the degree of experimentally induced iron-deficiency anemia

Hypolactasia associated with severe iron-deficiency anemia has been reported in several studies. The objective of the present study was to determine whether hypolactasia is associated with the degree and duration of iron-deficiency anemia. Newly weaned male Wistar rats were divided into a control group receiving a diet supplemented with iron (C) and an experimental group (E) receiving a diet not supplemented with iron (iron-deficiency diet). The animals were studied on the 3rd, 5th, 7th, 14th, 21st, 28th and 35th days of the experiment, when overall and iron nutritional status and disaccharidase activity in the small intestine were determined by the Dahlqvist method. A reduction in weight occurred in the anemic animals starting on the 5th day of the study. Anemia was present in the experimental animals, with a progressive worsening up to the 14th day (hemoglobin: C = 13.27 and E = 5.37) and stabilizing thereafter. Saccharase and maltase activities did not differ significantly between groups, whereas lactase showed a significant reduction in total (TA) and specific activity (SA) in the anemic animals starting on the 21st day of the study. Median lactase TA for the C and E groups was 2.27 and 1.25 U on the 21st day, 2.87 and 1. 88 U on the 28th day, and 4.20 and 1.59 U on the 35th day, respectively. Median lactase SA was 0.31 and 0.20 U/g wet weight on the 21st day, 0.39 and 0.24 U/g wet weight on the 28th day, and 0.42 and 0.23 U/g wet weight on the 35th day, respectively. These findings suggest a relationship between the enzymatic alterations observed and both the degree and duration of the anemic process. Analysis of other studies on intestinal disaccharidases in anemia suggests that the mechanism of these changes may be functional, i.e., that the enterocytes may suffer a reduction in their ability to synthesize these enzymes.

Modification of disaccharidase activity measurement in rat bowel

This study describes a modification of the existing disaccharidase assay in rat small bowel in which whole bowel, rather than mucosa, is utilized. In addition, the use of total vs. specific activity as a more accurate unit of measurement of disaccharidase activity is discussed.

Disaccharidase activities in children: normal values and comparison based on symptoms and histologic changes

BACKGROUND

The relationship between symptoms, intestinal mucosal histology, and disaccharidase activities is not well defined. An analysis of disaccharidase activities was performed in children grouped by age, symptoms, and intestinal mucosal histology and normal values established.

METHODS

Disaccharidase activities and histology of 246 endoscopically obtained duodenal biopsies in 232 patients (121 girls; age range, 0.08-17 years; mean, 5.9 years) in a 3-year period were reviewed. Patients were divided into two groups based on absence (group 1; n = 142) or presence (group 2; n = 90) of diarrhea and were subdivided by age into, less than 24 months of age and 24 months of age or more. Histologic changes within groups were classified as (A) normal, (B) mild, or (C) moderate to severe based on villus height abnormalities. A questionnaire was sent to 34 patients with hypolactasia to assess the efficacy of lactose avoidance and/or lactase supplementation.

RESULTS

All group 1 patients had normal findings in analysis of mucosal specimens, and their disaccharidase activities showed normal values because they had no diarrhea. The geometric means (95% confidence interval) in children aged less than 24 months are (in micromoles of substrate hydrolyzed per minute at 37 degrees C per gram protein) (units [U]) lactase, 36.7 (13.4-100.4); maltase, 178.5 (88.9-356.3); palatinase, 12.7 (3.8-41.5); and sucrase 60.0 (24.0-148.1). In children 24 months of age or more, the values are 23.2 (3.9-108.1), 167.6 (78.8-355.9), 12.7 (4.9-32.9), and 51.0 (20.5-126.0), respectively. Only lactase activity decreased with age (p < 0.05). No differences in disaccharidase activities were noted in patients with and without diarrhea if the mucosal histology was normal (group 1A vs. 2A). In patients with diarrhea, values were commensurate with the degree of mucosal injury, especially in the older group. Twenty-two of 27 patients (81%) who responded to the questionnaire had benefited from lactase supplementation and/or lactose avoidance.

CONCLUSIONS

We have established normal values for disaccharidase activities in the pediatric population. Although the disaccharidase activities correlate more with degree of intestinal mucosal injury than with symptoms, their activities are difficult to predict accurately based on these criteria. If required, disaccharidase activities should be measured biochemically.

Disaccharidase levels in normal epithelium of the small intestine of rats with iron-deficiency anemia

Iron-deficiency anemia is the nutritional deficiency most frequently occurring throughout the world, which manifests as a complex systemic disease involving all cells, affecting enzyme activities and modifying protein synthesis. In view of these considerations, the objective of the present study was to determine the effects of iron-deficiency anemia on disaccharidases and on the epithelial morphokinetics of the jejunal mucosa. Newly weaned male Wistar rats were divided into 4 groups of 10 animals each: C6w received a standard ration containing 36 mg elemental iron per kg ration for 6 weeks; E6w received an iron-poor ration (5-8 mg/kg ration) for 6 weeks; C10w received an iron-rich ration (36 mg/kg ration) for 10 weeks; E10w received an iron-poor ration for 6 weeks and then an iron-rich ration (36 mg/kg) for an additional 4 weeks. Jejunal fragments were used to measure disaccharidase content and to study cell proliferation. The following results were obtained: 1) a significant reduction (P < 0.001) of animal weight, hemoglobin (Hb), serum iron and total iron-binding capacity (TIBC) in group E6w as compared to C6w; reversal of the alterations in Hb, serum iron and TIBC with iron repletion (E10w = C10w); animal weights continued to be significantly different in groups E10w and C10w. 2) Sucrase and maltase levels were unchanged; total and specific lactase levels were significantly lower in group E6w and this reduction was reversed by iron repletion (E10w = C10w). 3) The cell proliferation parameters did not differ between groups. On the basis of these results, we conclude that lactase production was influenced by iron deficiency and that this fact was not related to changes in cell population and proliferation in the intestinal mucosa.

Total intestinal lactase and sucrase activities are reduced in aged rats

Lactase-phlorizin hydrolase (LPH) and sucrase-isomaltase (SI) are intestinal microvillus membrane hydrolases that play important roles in carbohydrate digestion. Although the expression of these enzymes during postnatal development has been characterized, the effect of old age on disaccharidase activity is poorly understood. In the present investigation, we examined the effect of aging on lactase and sucrase activities and their mRNA levels in the small intestines of 3-, 12- and 24- mo-old rats by sampling from nine equidistant segments of small intestine. Total intestinal disaccharidase activity or mRNA abundance was determined from areas under the proximal-to-distal curves. Rats 24 mo of age had total intestinal lactase and sucrase activities that were 12 and 38% lower, respectively, than the 3-mo-old animals (P < 0.05). In contrast, total LPH and SI mRNA abundance did not change significantly. Thus, total intestinal lactase and sucrase activities decrease with age in a manner that likely involves a posttranscriptional process. The age-related decline in disaccharidase activity, if extrapolated to humans, may have important implications for the digestion of carbohydrate contained in the diet of the elderly.

A total parenteral nutrition solution supplemented with a nucleoside and nucleotide mixture sustains intestinal integrity, but does not stimulate intestinal function after massive bowel resection in rats

The effects of supplementing a total parenteral nutrition solution with a nucleoside and nucleotide mixture on mucosal adaptive processes after massive bowel resection were studied. Male Wistar rats (n=30) underwent 80% small intestine resection, were randomized into two groups and received either standard total parenteral nutrition (TPN) or TPN supplemented with a nucleoside and nucleotide mixture (2.5 mL.kg-1.d-1). An additional five rats, fed a nonpurified diet and not resected, were used as controls. After 4 or 7 d, rats were killed and samples were collected for mucosal indices and intestinal enzymatic activities (disaccharidases and diamine oxidase). After massive small bowel resection and TPN, residual jejunal mucosal wet weights, villus heights, protein and RNA contents on d 4 and 7, and total wet weights and DNA contents on d 7 were significantly lower than in the control group. Administration of the nucleoside and nucleotide mixture resulted in significantly higher residual jejunal total and mucosal weights, proteins, DNA, RNA contents, and the ratio of proliferating cell nuclear antigen positive cells per crypt than did the standard TPN solution on d 7. However, disaccharidase and diamine oxidase activities were not affected by supplementation with the nucleoside and nucleotide mixture. Our data suggest the supplementation of a nucleoside and nucleotide mixture to a TPN solution can attenuate the initial mucosal atrophy and improve intestinal cell turnover after massive bowel resection, but the supplementation has little effect on enterocyte enzymatic activities.

Mosaic regulation of lactase in human adult-type hypolactasia

BACKGROUND/AIMS

We have previously shown that in the proximal-jejunum of hypolactasic humans, just a few villus enterocytes express lactase protein and activity. In the present study, we compared the distribution of lactase messenger RNA (mRNA), protein, and activity in villus enterocytes in tissues obtained from subjects with persistent high lactase activity and those with hypolactasia.

METHODS

Immunohistochemical and enzymohistochemical staining was performed on closely adjacent sections of human proximal jejunum from 5 individuals with persistent high lactase activity and 32 with hypolactasia. In all the persistent and in 9 hypolactasic samples, in situ hybridization was also performed using a digoxygenin-labeled RNA probe.

RESULTS

In persistent tissues, lactase mRNA, protein, and activity were present in all villus enterocytes. In hypolactasic tissues, lactase mRNA was detected only in some villus enterocytes; some of them also expressed protein and activity, whereas others did not. In 8 of these hypolactasic samples, a variable number of villus enterocytes with lactase mRNA and protein did not express lactase activity.

CONCLUSIONS

Various types of enterocytes are present even on a single villus from individuals with adult-type hypolactasia. These results show that different mechanisms control lactase expression in enterocytes on the same villus.

The polymorphic expression of lactase in adults is regulated at the messenger RNA level

BACKGROUND/AIMS

Lactase phlorizin hydrolase (LPH) activity is high in infants but declines 80%-90% before adulthood in most mammals, including humans. However, 95% of whites show autosomal dominant inheritance of a lifelong high lactose digesting capacity (LDC). This study attempted to clarify the molecular mechanism(s) of this phenomenon (posttranslational vs. pretranslational).

METHODS

A race- and sex-balanced cohort (n = 20) was studied, and lactose tolerance and levels of jejunal lactase protein, activity, and messenger RNA (mRNA) were measured.

RESULTS

These data confirm that black heritage predicts low LDC, and white heritage predicts high LDC. Lactase breath hydrogen and determination of lactase/sucrase ratio (L/S) from jejunal biopsy specimens divide the group by high and low LDC phenotypes concordantly. All subjects with an L/S ratio > 0.5 had immunodetectable LPH protein and measurably higher LPH mRNA levels than the remaining subjects. LPH mRNA levels are highly correlated with lactase specific activity (r = 0.80) and L/S ratio (r = 0.88).

CONCLUSIONS

The direct correlation between LPH mRNA levels and lactase expression argues that the gene responsible for the human lactase polymorphism regulates the level of LPH mRNA.

Diagnosis of hypolactasia and lactose malabsorption

The article briefly describes the various methods that are available for diagnosing hypolactasia. Special attention is drawn to the fact that different methods are useful at different levels of the health care organization. When the test result indicates lactose malabsorption, general malabsorption should be excluded by a glucose-galactose tolerance test, for example. If the glucose-galactose tolerance test produces a normal result, it can be assumed that the patient has primary adult-type selective lactose malabsorption. The possibility of secondary lactose malabsorption must be excluded according to the principles described by Villako & Maaroos (104).

Diurnal variation and increase of disaccharidase activity in diabetic rats

The small intestinal disaccharidase activity and its daily variation in the diabetic rat have not been well described. Therefore, the small intestinal disaccharidase (maltase, lactase and sucrase) activity and its daily profile were studied in streptozotocin-induced diabetic rats under physiological conditions. In diabetic rats, a similar pattern of diurnal variation of disaccharidase activity to control rats was observed, while the relationships between daily change of disaccharidase activity and that of food consumption suggested that there was a different mechanism of diurnal variation in diabetic rats. On the other hand, a significant increase of mean 24-h lactase and sucrase activities was noted in diabetic rats, while that of maltase was not significant. Using the in vitro incubation method, a significant correlation between glucose concentration and lactase or sucrase activity but not maltase activity was observed. However, insulin showed no effect on disaccharidase activity. Thus we clarified the presence of a diurnal variation of disaccharidase activity and an increase in its activity in diabetic rats. This change was suggested to be derived from high plasma glucose level.

Disaccharidase activity in the small intestine of susceptible and resistant mice after primary and challenge infections with Giardia muris

The activities of four disaccharidases were examined in resistant (C57Bl/6) and susceptible (C3H/HeN) mice during the primary infection with Giardia muris and after challenge with either trophozoite extract or cysts. Significant decreases in lactase, sucrase, trehalase, and maltase activities in C57Bl/6 mice and lactase and sucrase activities in C3H/HeN mice in the anterior 25% of the small intestine were observed on day 10 after infection. The activities of maltase, sucrase, trehalase, and lactase in the jejunum of C3H/HeN mice were significantly reduced after challenge with trophozoite extract, when compared with the uninfected or infected, but not challenged animals. Decreases in enzyme activities of C3H/HeN mice were evident as early as 12 hours after challenge with the extract. The resistant C57Bl/6 mice showed little change in disaccharidase activity after challenge with trophozoite extract. On the other hand, challenge with cysts resulted in a few decreases in disaccharidase activities in both strains of mice: C57Bl/6 mice showed decreases in the duodenum, while disaccharidases of C3H/HeN mice had lower activity more posteriorly. Thus, challenge with parasite antigen results in a more severe disaccharidase deficiency in susceptible hosts when compared with resistant ones.

Early prenatal development of the brush border enzymes in the embryonal intestine

Standard methods were used for the study of the activity of brush border enzymes in the epithelium of the intestine of 45 human embryos aged from 4 to 22 weeks of the intrauterine life. Enzymes of the peptidase group (DPP IV, APM, APA, GGT, BBEP), of the phosphatase group (ALP, ACP, AMP, ATP), and of the disaccharidase group (saccharose, lactase, trehalase) were studied. In the embryonal developmental period (to week 8), the activity of proteases was mainly detected on the luminal surface of the primitive pseudostratified columnar epithelium of the intestine anlage. The highest activity was displayed by DPP IV. In the period from the 8th week, villi are formed from the duodenum up to the ileum. After week 9, differentiation of Lieberkühn crypts was observed. The activity of proteases was very high (DPP IV especially) in the differentiating microvillous zone of primitive enterocytes. Gradient of apex-base activity of the villus was maximal on the apex of villi. After week 12 of the intrauterine life, the activity of disaccharidases ALP and AMP occurs in the differentiating brush border, and a low activity of BBEP of the protease group is present.

[Comparative studies of the activity of disaccharidases in the mucosa of the small intestines in dystrophic, formerly hypotrophic-born young children and of patients with flat mucosa of various etiology]

The disaccharidase activities of the mucous membrane of the small intestine were determined in formerly hypotrophic children who showing a dystrophy with a morphological normal mucosa (n = 36), patients with a flat mucosa caused by enteral protein intolerances of different genesis (n = 27), patients with a morphologically and functionally normal mucosa (n = 51). In about half of the former small-for-date children were shown activities lower than the simple standard deviation of the normal value, for lactase n = 17, for sucrase n = 14, for maltase n = 12. Some children showed pathologically reduced activities even below the double standard deviation for the normal value: lactase n = 8, sucrase n = 5, maltase n = 3.

Mucosal immune activation and maturation of the small intestine at weaning in the hypothymic (nude) rat

Activation of the mucosal immune system peaks at weaning on days 21 and 22 of life in the rat. We have investigated activation in the gut associated lymphoid tissue and maturation of intestinal mucosa in hypothymic (nude) and in phenotypically normal heterozygous CBH rats at 22 days of life. Intestinal maturation, as assessed by villus area, crypt length, crypt cell production rate and disaccharidase activity, was similar in hypothymic and normal rats, and indices of mucosal immune function were elevated in both groups at this time. The proportion of mononuclear cells from the mesenteric lymph node expressing IL-2R was 11% in heterozygous and 14% in hypothymic rats as determined by flow cytometry. Immunoperoxidase staining of MLN sections confirmed the presence of IL-2R+ cells in the T-dependent interfollicular areas. However, the number of T-cells was considerably depleted in hypothymic rats. Intraepithelial lymphocyte counts and serum rat mucosal mast cell protease II concentrations were similar in the two groups, while counts of jejunal mucosal mast cells and eosinophils were paradoxically increased in hypothymic animals. As T lymphocyte function is thought to be impaired in hypothymic rats, the intact mucosal immune activity in hypothymic rats could be due to activation of intrinsic "thymic independent" T lymphocytes in hypothymic rats, or to engraftment with extrinsic maternal milk-derived lymphocytes and their activation in the infant rat gut.

Histologic findings are not correlated with disaccharidase activities in infants with protracted diarrhea

Histologic assessment as well as information about the disaccharidase activity of the small intestinal mucosa can be useful in the management of patients with small intestinal mucosal damage. In an effort to determine whether the degree of small intestinal mucosal damage would be reflected in a corresponding reduction in disaccharidase activity, we compared small intestinal mucosal histology with the results of disaccharidase activity measured in per oral suction small intestinal biopsies obtained from 21 infants with protracted diarrhea. The degree of small intestinal mucosal damage was graded using a subjective score (i.e., 0 to 4+ damage) by a pathologist (P) and by a computer-assisted digitizing system (to assess villus surface area, VSA, and villus/crypt ratio, V/C) in a blinded fashion. The mean (+/- SD) age of the infants was 2.5 +/- 1.5 months, and the duration of diarrhea was 25.2 +/- 11.5 days. There was good correlation between the results obtained from the digitizing system and from the pathologist: VSA versus P, r = 0.695; V/C versus P, r = 0.791; p = 0.0004. All infants demonstrated some degree of small intestinal mucosal damage. The mean (+/- SD) values for P, VSA, and V/C were 2.2 +/- 1.3, 2.9 +/- 0.9, and 0.9 +/- 0.5, respectively. The mean values for lactase, sucrase, and maltase were 17.1 +/- 17.0, 71.1 +/- 54.0, and 224.3 +/- 233 mumol/min/g protein, respectively. No correlation was observed between the histologic scoring results and lactase, sucrase, or maltase measurements. Expressing the disaccharidase activities per unit wet weight of tissue did not improve the correlations. Log transformation of the data also failed to improve the correlations.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of jejunal function in Wolman's disease

Findings in a 1-month-old male infant with Wolman's disease, a rare autosomal defect characterized by intractable diarrhea and severe malabsorption, are described. Investigations in this case focused on the digestive and absorptive functions of the jejunum using histological, biochemical, and electrophysiological methods. The intestinal villi were found to be distorted and club-shaped as a result of the infiltration of foam cells into the lamina propria of the mucosa. The microvilli of the epithelial cells were found on electron microscopy to be markedly shortened and irregular, and had a severe impairment of disaccharidase activity. Documentation of the loss of the sugar- and amino acid-evoked potential differences in the jejunum confirmed the severity of intestinal malabsorption. These observations indicate that the intestinal damage in Wolman's disease is so severe as virtually to exclude the absorption of any form of enteral nutrition. Despite the administration of i.v. hyperalimentation, the infant died of hepatic failure at the age of 6 months.

[Current diagnostic method for saccharose-isomaltose malabsorption]

The authors present the cases of 4 children who suffered from saccharose-isomaltose malabsorption. The clinical symptoms developed following artificial feeding. The diagnosis was made by the histological examination of small intestine samples and with the simultaneous measurement of disaccharide enzyme activity. The histological picture and activity of lactase enzyme were practically normal. The saccharose H2 breath test gave only in 1 case positive result. The treatment of the children required saccharose-free diet. The tolerance showed no improvement during the treatment.

Possible biological growth factors in breast milk and postnatal development of the gastrointestinal tract

To investigate as to whether or not biological growth factors known to be present in natural milks could influence postnatal development of gastrointestinal (GI) tract, tests were made to determine the enteric mucosal, protein and DNA contents, alkaline phosphatase and disaccharidase activities in mongrel puppies at birth and after four days of both mother-reared and artificial reared. Microvilli of the jejunal segment were also investigated histologically by electron microscopy. Similar increases in body weight over the first four days of life were obtained and mucosal protein and DNA contents in the small intestine were greater in the mother-reared animals than in the newborn animals but neither mucosal protein content nor DNA content of the artificially reared animals was different from that of the newborn animals. Alkaline phosphatase activity was greater in both the mother-reared and artificially reared animals than that of the newborn animals. The disaccharidase activities were not different among the three groups. The jejunal microvilli of the mother-reared animals were more elaborately grown in the structure than those of the artificially reared or newborn animals. Therefore, this study demonstrated that the mother rearing over the first four days of life resulted in acceleration of the enteric mucosal growth, and the result indicates that breast feeding plays an important role in the development of the GI tract during the neonatal period.

Monitoring of intestinal transplant rejection

Our results show that maltase, sucrase, and lactase activity are present at a normal level in nonrejecting small bowel transplants after an initial postoperative decline. This confirms that the disaccharide absorbing capacity of these grafts is intact. In allogeneic bowel, however, the levels of maltase and sucrase decline as histologic rejection occurs. These results suggest that serial maltase, sucrase, and possibly lactase levels in allogeneic intestinal transplants may serve as a useful adjunct in the monitoring of small bowel transplant rejection.

Giardia lamblia infection in immunosuppressed animals causes severe alterations to brush border membrane enzymes

NMRI mice immunosuppressed with dexamethasone followed by challenge intraesophageally with axenic Giardia lamblia (Portland I) trophozoites had severe infection in terms of the trophozoite counts in the jejunum. Although the immunosuppressive treatment with cortisone itself resulted in a deleterious effect on brush border membrane enzymes, the decline in disaccharidases (sucrase, maltase, and lactase) and alkaline phosphatase was highly significant (P less than 0.001) following G. lamblia infection. The alterations in enzymatic activity in immune intact but infected animals demonstrated the potential of the parasite itself to cause damage to the brush border membrane. We believe that individuals with underlying immunodeficiency, upon infection with G. lamblia, may have increased damage of the brush border membrane, leading to severe malabsorption.

Combined effects of glutamine and epidermal growth factor on the rat intestine

Glutamine (GLN) is an important fuel and epidermal growth factor (EGF) is a potent mitogen for intestinal mucosa cells. GLN-enriched parenteral nutrition was administered to male Wistar rats, and subcutaneous injections of EGF were given for 3, 6, and 7 days. Control animals were fed a non-GLN-containing solution. Other groups of animals received GLN or EGF alone. Mucosal samples were obtained from the jejunum, ileum, and colon for measurement of weight, DNA, protein, and mucosal thickness. Disaccharidase activity was measured in the jejunum. After 3 days, only animals that received both GLN and EGF had a significant increase in small-bowel mucosal protein and thickness relative to controls. A similar pattern was observed in the colon, where animals that received both agents had a greater mucosal thickness, DNA, and protein content than controls. At 7 days, animals that received EGF or GLN had greater nitrogen retention. In addition, animals that were treated with EGF had elevated sucrase and maltase activity compared with GLN-fed animals at this time. Animals treated with GLN and EGF tended to have increased sucrase activity relative to controls. GLN feeding was associated with increased mucosal DNA and protein contents throughout the intestine for the combined series. EGF increased mucosal DNA and protein in the small intestine but not in the colon. The effect of EGF on the protein content of the small-bowel mucosa was dose dependent. The effects of GLN and EGF on the small bowel and colonic mucosa were additive. These studies suggest that specific nutrients and hormones may be used in combination to decrease the mucosal atrophy that commonly occurs after gut disuse or disease.

Small intestinal function and structure in patients with chronic renal failure

We studied 24 patients with end-stage chronic renal failure not treated with hemodialysis (CRF1) and 16 patients on regular hemodialysis (CRF2), to investigate the digestive, absorptive and morphological aspects of the small intestinal mucosa. Serum d-xylose test and biochemical parameters of absorption (serum calcium and proteins) were determined. Jejunal mucosal biopsies were obtained and tissue homogenates assayed for disaccharidases (sucrase, maltase and lactase) and dipeptidases (glycyl-glycinase, leucyl-glycinase and leucyl-aminopeptidase). Histological changes were classified according to the severity of abnormality and compared with biopsies obtained from control subjects. Serum d-xylose test, calcium and proteins were normal in patients with CRF. Maltase specific activity was higher in CRF1 than in controls (p less than 0.05). Lactase and leucyl-aminopeptidase showed a tendency to decrease in CRF, but this difference did not reach statistical significance. Sucrase, glycyl-glycinase and leucyl-glycinase specific activity in CRF was similar to the control group. Histological changes of the small intestinal mucosa of mild to moderate degree were noted in 68% of patients with CRF vs 36% in control subjects (p less than 0.01). No significant difference was noted in the incidence of absorptive, enzymatic (with the exception of maltase) and histological changes between the two groups of patients with CRF. These changes are not influenced by hemodialysis, a long-term treatment averaging 6 months, they appear to represent primary manifestations of CRF and may be related to the nutritional status of patients with CRF.

'Normal' disaccharidase levels in children

Results of disaccharidase assays in small bowel biopsies from 887 children over a 3 year period were analysed to establish normal values. Abnormal histology, the presence of giardia trophozoites or total absence of sucrase and isomaltase were found in 307 cases and these were excluded from further consideration. The results for maltase, sucrase and lactase from the remaining 580 children have been graphed as percentiles at various ages. They represent results which are as close to normal as it is possible ethically to obtain.

Effect of restricting a balanced diet on rat intestinal disaccharidase activity and intestinal architecture

The effects of malnutrition on the gastrointestinal tract have been previously investigated in animal models using dietary protein restriction. Because malnutrition is clinically a consequence of reduced dietary intake of all macronutrients, we investigated the effect of restricting a balanced diet on intestinal disaccharidases and histologic conditions of rats. Our diet-restricted animals gained less weight (13 +/- 9 gm) than the control animals (158 +/- 27 gm) over the 5-week study. The proximal, middle, and distal small intestinal segments from the experimental animals had reduced mucosal protein content (15 +/- 4 mg vs. 24 +/- 7 mg). In these segments the total amount of maltase was slightly decreased, whereas sucrase and lactase activities were normal or increased. The intestinal villus/crypt ratios were similar in the experimental and control animals. Mucosal cell height was significantly reduced in the diet-restricted groups; however, cell width was normal. We conclude that severely diet-restricted animals have mucosal protein loss caused in part by reduced cell height, but that the disaccharidase enzyme activities are normal. Diet-restricted animals appear to have sufficient intestinal enzymes to support a normal amount of disaccharide hydrolysis.

Prenatal detection of intestinal obstructions, aneuploidy syndromes, and cystic fibrosis by microvillar enzyme assays (disaccharidases, alkaline phosphatase, and glutamyltransferase) in amniotic fluid

Microvillar enzymes (disaccharidases, alkaline phosphatase, and gamma-glutamyltransferase) were assayed in amniotic fluid from pregnancies with normal and abnormal fetuses to determine their specificity and reliability for the prenatal detection of intestinal obstructions and cystic fibrosis. All fetuses with imperforate anus, duodenal atresia, jejuno-ileal atresia, multiple intestinal atresia, or other forms of intestinal obstructions, with or without associated ventral wall defect or aneuploidy syndrome, showed diminished microvillar enzyme activities below the normal range of control amniotic fluid samples. The exclusively intestinal hydrolases maltase, sucrase, palatinase, and alkaline phosphatase were the most reliable and sensitive markers to detect intestinal obstructions whereas more widely distributed trehalase and gamma-glutamyltransferase activities were less sensitive. The combination of intestinal disaccharidase maltase, sucrase or palatinase and ALP assays is more accurate for prenatal diagnosis of CF than a combination of intestinal ALP and GGTF assays.

Gastrointestinal toxicity of chemotherapy and the influence of hyperalimentation

The effect of combination chemotherapy on human small intestinal morphology and disaccharidase activities and their relation with clinical and chemical (fecal wet weight and K-excretion) parameters for gastrointestinal toxicity were evaluated in patients with disseminated malignant melanoma receiving enteral normoalimentation (NA). Also evaluated were the supposed protective effects on gastrointestinal toxicity of enteral hyperalimentation (HA) with an elemental diet. After chemotherapy, a comparable decrease in villus height, total mucosal height, and mitotic index was found in jejunal biopsy specimens of both groups. However, in the NA group, the crypt depth decreased (in contrast to the HA group), whereas the disaccharidase activities in the HA group deteriorated to lower values than in the NA group. The authors found no correlation between disaccharidase levels and mucosal morphology, nor was there a correlation between these variables, fecal parameters and clinical diarrhea, suggesting that diarrhea occurring after chemotherapy was not due to loss of mucosal tissue or decrease in enzyme activities. A protective effect of HA with an elemental diet on gastrointestinal toxicity could not be established.

Aristotle revisited: the function of pyloric caeca in fish

The function of the pyloric caeca of fish has been uncertain since their detailed description in 345 B.C. by Aristotle. He suggested three hypotheses about their function: "to store up the food," "putrify it up," and "concoct it" (i.e., storage, fermentation, and digestion). Our results for trout, cod, largemouth bass, and striped bass support the third but not the first or second of Aristotle's theories. In all four species, the caeca prove to be a major site of sugar, amino acid, and dipeptide uptake, contributing more uptake than the entire remaining alimentary tract in trout and cod. Caecal brush-border membranes contain hydrolytic enzymes. X-ray plates taken at various times after trout had ingested radioopaque marker, and observations of trout fed blue dye plus glass beads of graded sizes, show that caeca fill and empty of food with the same time course as proximal intestine. Thus, whereas the caeca of mammals and birds serve as fermentation chambers, fish caeca are an adaptation to increase gut surface area.

Does zinc deficiency affect intestinal protein content or disaccharidase activity?

Zinc deficiency has been associated with impared carbohydrate absorption in patients with intestinal disease; however, it is not known whether the carbohydrate malabsorption is caused by the zinc abnormality. Because zinc is needed for protein synthesis, we investigated the effect of zinc deficiency on the total and specific activities of the intestinal glycoprotein disaccharidases. We found that zinc deficiency impairs total body growth and causes marked reductions in intestinal mucosal protein content and disaccharidase activity. However, the protein content and disaccharidase activities were reduced to a similar degree, and both were proportional to the final total body weight. We also found zinc deficiency to have no effect on intestinal villus height or crypt depth. We conclude that zinc deficiency inhibits somatic growth but does not disproportionately affect intestinal mucosal protein content, disaccharidase activity, or intestinal architecture.

Disaccharidase deficiency in amniotic fluid from cases of cystic fibrosis

The activities of the disaccharidases maltase and sucrase in 4 amniotic fluid from cystic fibrosis (CF) pregnancies have been compared to those of 120 non CF-pregnancies. Very low levels were found in 3 of the CF-fluids. The fourth CF-fluid was normal in all measured microvillar enzyme activities. Elevated levels of disaccharidases in meconium from one of the patients born with CF, supports the idea that these enzymes are trapped in the intestinal cavity by sticky meconium.

Amniotic fluid disaccharidases in the prenatal detection of cystic fibrosis

Intestinal disaccharidases in amniotic fluid were studied in 41 pregnancies with a recurrence risk for cystic fibrosis (CF). In 11 out of 13 pregnancies with CF fetuses the maltase and sucrase activities were either below the control range (8 cases) or below the 10th percentile of control values (3 cases). Trehalase and lactase were slightly less informative indicators of CF. Of the other 28 pregnancies 3 had low amniotic fluid activities of several intestinal enzymes and were terminated, 12 resulted in the birth of a healthy child and 13 are continuing. The findings in fetal CF suggest an impairment of the defaecation of intestinal contents into the amniotic fluid. Reduced or low amniotic fluid disaccharidase activities were also found in other fetal disorders with demonstrated or presumed intestinal anomalies: e.g. anal atresia (2 cases), anencephaly (3 our of the 7 cases), trisomy 13 (5 cases), trisomy 18 (3 of the 5 cases) and trisomy 21 (19 of the 22 cases). Reduced amniotic fluid disaccharidase activities, although not specific for CF, are highly informative in pregnancies at high risk for CF. Using the 10th percentile of the normal range for amniotic fluid disaccharidase activities as an action line, the sensitivity of CF detection is estimated at 80 to 90 per cent, which could in high risk pregnancies reduce the risk of having another affected child from 1 in 4 to 1 in 20.

The role of the small intestine in cystic fibrosis patients

A survey is given of the morphological and biochemical lesions of the small intestine that can be found in cystic fibrosis patients. The available data on the structure and function of the small intestine in CF patients favour the hypothesis that the small intestine itself might contribute to the malabsorption of nutrients in this disease. The most pronounced lesions, i.e. meconium ileus and absent active transport of bile salts are found in the ileum. It might be remembered that the ileum is also the site of intensive exchange of chloride and bicarbonate, a function that is heavily disturbed in the pancreas of CF patients. For this reason, further studies on the ileal function in cystic fibrosis are warranted.

Rapid test for determination of disaccharidase activities in endoscopic biopsy specimens from the small intestine

We have developed a new and rapid semiquantitative method of demonstrating disaccharidase activities in biopsy specimens obtained endoscopically from the jejunum. Biopsy samples are placed in sucrose or lactose solutions. Sucrase and lactase activities are detected by testing glucose in the solutions using commercial urine glucose detection strips.

Prenatal detection of the congenital nephrotic syndrome (Finnish type) by trehalase assay in amniotic fluid

We report relatively high trehalase activity in the amniotic fluid of two fetuses affected with the congenital nephrotic syndrome of the Finnish type. The results suggest that prenatal detection of this condition can be done on this basis in conjunction with the alpha-fetoprotein and acetylcholinesterase tests in amniotic fluid.

[Endoscopic exploration of the small intestine]

The development of Japanese enteroscopes, mot of which are still prototypes, has made it possible to explore the entire small bowel. These instruments are either introduced into the jejunum like an ordinary endoscope, or pushed along a guidewire, or weighted with mercury, like a Miller-Abbott probe. A simplified study of the adult malabsorption syndrome can be performed by proximal jejunoscopy, usually carried out in Europe with a paediatric colonoscope. Perendoscopic forceps biopsy of the jejunum can replace probe sampling and is well suited to measurements of disaccharidase activity. In cases with "blind loop syndrome", bacteriological examination of the intestinal juice, endoscopically collected in sterile conditions, usefully supplements the visual and bioptic information. Since several investigations can be performed during one single enteroscopic examination, this method will be increasingly used in the study of small bowel diseases.

[Disaccharidase activity as a diagnostic criterion for the mucosa of the small intestine]

Activities of lactase, sucrase, and maltase were determined in small intestinal biopsies of 125 children with coeliac disease, cow's milk protein intolerance, transient gluten intolerance, nonspecific enteropathies, and controls. Four cases of primary disaccharidase deficiencies could be identified. In the enteropathies, morphometric data were more closely correlated to the degree of the mucosal lesion (r = -0.92 for crypt depth) than were disaccharidase activities (r = 0.61 for lactase). In a stepwise discriminant analysis of the patient groups, based upon immunological, morphometric, and biochemical variables, lactase activity was a valuable secondary criterion, ranking third among the variables used.