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PubMed1997

Regulation of sucrase and lactase in developing rats: role of nuclear factors that bind to two gene regulatory elements.

BACKGROUND & AIMS: Sucrase-isomaltase and lactase-phlorizin hydrolase expressions change remarkably during postnatal development in rats. The aim of this study was to explore the role of transacting nuclear proteins, proteins that bind to the SIF1 cis-regulatory element of the sucrase-isomaltase gene and to the CE-LPH1 cis-regulatory element of the lactase-phlorizin hydrolase gene, in this regulation. METHODS: Enzyme activity, Northern analysis, and electrophoretic mobility shift assays were used to study the relationship of these nuclear proteins to sucrase-isomaltase and lactase-phlorizin hydrolase gene expression in rats during development. RESULTS: A rapidly migrating low-molecular-weight SIF1-binding protein was found in suckling animals without sucrase-isomaltase messenger RNA (mRNA), and a higher-molecular-weight-binding protein was found in older animals with expression of sucrase-isomaltase mRNA. Supershift experiments and Western analysis showed that neither protein is Cdx-2, the only previously described SIF1-binding protein. CE-LPH1-binding protein was found only in adult animals (with low lactase activity), and there was no relationship between enzymatic activity and levels of lactase-phlorizin hydrolase mRNA. CONCLUSIONS: SIF1-binding proteins may regulate sucrase-isomaltase expression during postnatal development, but CE-LPH1-binding proteins do not seem to regulate lactase-phlorizin hydrolase expression during this period.

Age Factors↗
PubMed1987

A study of the molecular pathology of sucrase-isomaltase deficiency. A defect in the intracellular processing of the enzyme.

The intestinal brush-border enzyme sucrase-isomaltase splits sucrose into its component monosaccharides, glucose and fructose. A deficiency of the enzyme leads to sucrose intolerance. We studied the synthesis and intracellular processing of sucrase-isomaltase, using human intestinal explants in organ culture. Pulse-chase experiments with [35S]methionine followed by immunoprecipitation, sodium dodecyl sulfate-polyacrylamide-gel electrophoresis, and fluorography of labeled sucrase-isomaltase demonstrated that the molecule was initially recognized as a protein with a relative molecular weight (Mr) of 205,000. This was apparently converted to a species of 225,000 Mr within two hours. We studied the glycosylation of the protein using endo-beta-N-acetylglucosaminidase H and peptide-N4-(N-acetyl-beta-glucosaminyl)-asparagine amidase digestion of oligosaccharide side chains of the two forms of sucrase-isomaltase. The results showed that the early-appearing 205-kd (kilodalton) molecule contained high-mannose asparagine-linked oligosaccharides, and that the later-appearing, 225-kd molecule contained highly processed (mature) carbohydrate chains. Studies in a patient with primary sucrase-isomaltase deficiency demonstrated normal translation and high-mannose glycosylation of the precursor but a failure in further processing of the oligosaccharides, with subsequent intracellular degradation of the glycoprotein and undetectable enzymatic activity of intestinal sucrase. Abnormal intracellular processing of the enzyme was the probable mechanism of enzyme deficiency in this patient.

Adult↗
PubMed1990

Age-related changes in sucrase and lactase activity in the small intestine of 3- and 10-week-old obese mice (C57BL/6Jobob).

The relationship between obesity and the digestion of carbohydrates is poorly understood. Data in humans have provided conflicting results. Studies using the obese mouse (C57BL/6Jobob) suggest that obesity is associated with increased activity of intestinal alpha-disaccharidases. To evaluate the developmental pattern of these enzyme activities in obesity, we determined the activity of sucrase and lactase in the small intestine of genetically obese mice (C57BL/6Jobob) and lean littermates at 3 and 10 weeks of age. Sucrase and lactase activities were measured on intestinal homogenates from segments of the small intestine in mice maintained on standard laboratory diets during the postweaning period. Results were expressed as specific activity and total activity per intestinal segment. Obese mice did not differ from lean littermates in body weight at 3 weeks of age, but exhibited increased protein content in the proximal small intestine. Sucrase specific activity was significantly higher in the obese mice at 3 weeks of age in all intestinal segments. Sucrase total activity showed a similar pattern. At 10 weeks of age, body weights of obese mice were substantially greater than the lean littermates. Sucrase specific and total activities were also greater in the obese mice at 10 weeks of age. Lactase specific activity, however, was similar in both obese and lean mice at both ages studied. Lactase total activity was greater in the obese mice, consistent with their greater intestinal mass. These observations demonstrate that changes in the intestinal sucrase activity of the obese mouse precede the development of excessive body weight.

Age Factors↗
PubMed1986

Endogenous corticosterone rather than dietary sucrose as a modulator for intestinal sucrase activity in artificially reared rat pups.

The effects of sucrose and corticosterone on the expression of intestinal sucrase activity in preweanling rat pups were studied using an artificial rearing (AR) technique. When AR rat pups were isocalorically fed diets containing lactose or sucrose, or a carbohydrate-free diet from d 12-16, jejunal and ileal sucrase and maltase activities were induced to similar levels in all AR rats, whereas ileal lactase activity was precociously decreased. In separate experiments, enzyme activities were measured in ileal isografts subcutaneously implanted in littermates at birth. In AR rats fed the lactose diet, these isografts showed sucrase and maltase activities comparable with those of host ileum and also to isografts from AR rats fed the sucrose diet. In contrast, lactase activity was significantly higher in isografts than host ileum in all AR rats. Serum corticosterone levels were significantly elevated in AR rats for 24 h after intragastric cannular implantation. Precocious expression of ileal sucrase activity occurred in corticosterone treated, but not in untreated, adrenalectomized AR rats. In conclusion, dietary sucrose has no specific role in enhancing intestinal sucrase activity, and endogenous corticosterone is responsible for the induction of sucrase activity in AR rats.

Adrenalectomy↗
PubMed1982

Maturational effect of triiodothyronine and its analog 3,5-dimethyl-3'-isopropyl-L-thyronine on sucrase activity in the small intestine of the developing rat.

In this study we compared the effect of 3,5-dimethyl-3'-isopropyl-L-thyronine (DIMIT) with that of triiodothyronine (T3) on sucrase activity in the small intestine of the fetal and suckling rat. DIMIT (5 micrograms/100 g BW) was injected into pregnant Sprague--Dawley rats on days 17-20 of gestation and DIMIT (10 and 50 micrograms/100 g BW) and T3 (10 and 50 micrograms/100 g BW) were given subcutaneously to two groups of sucklings on days 4-7 and 11-14. Fetal animals were sacrificed on day 21 of gestation; sucklings on days 8 and 15. Sucrase activity in the proximal, middle, and distal small intestine was assayed. DIMIT and T3 suppressed serum thyroid-stimulating hormone (TSH) in the fetus and suckling. Sucrase activity was increased in all small intestinal segments in the fetal and older suckling groups. In the younger sucklings the effect was seen only in the middle and distal segments. In both fetal and suckling groups the sucrase response was dose related. Thus, DIMIT has a thyromimetic effect on development of sucrase activity. The lack of sucrase reactivity in the proximal segment of the younger (8-day-old) sucklings to the administration of either DIMIT or T3 is interesting but unexplained.

Animals↗
PubMed1985

Dietary regulation of intestinal lactase and sucrase in adult rats: quantitative comparison of effect of lactose and sucrose.

To characterize the mechanisms leading to dietary evoked increases of lactase and sucrase activities by carbohydrates, we performed a quantitative comparison of the effects of lactose and sucrose on the corresponding disaccharidases in the jejunum of 2-month-old rats. For 7-10 days the rats were fed a low-starch (5 cal%), high-fat (73 cal%) diet, and for various periods of time (3-72 h) were given an isocaloric sucrose or lactose (20, 40, or 70 cal%) diet. Lactase and sucrase activities in jejunal homogenates were significantly increased within 3 h after the initial feeding of the sucrose (40 cal%) diet. After 3 h of feeding the sucrose diet, sucrase activity gradually increased and reached its maximum at 24 h, whereas lactase activity did not exhibit further change. Increased intake of sucrose led to an increase of lactase and sucrase activity. Within a range of doses of digestible amounts of lactose, the effect of diet containing lactose on these disaccharidase activities was similar to the effect of the diet containing sucrose. This similarity suggests the important role of the common constituent sugar, i.e., glucose. Further, analyses of response to these disaccharides along the villus-crypt axis revealed that the increase of lactase activity occurs at a more apical and broader locus of cohort of epithelial cells along the height of the villus than that of sucrase, suggesting that different mechanisms are involved in dietary regulation of lactase and sucrase.

Animals↗
PubMed1992

Physiologic variation of sucrase activity and microbial counts in human saliva.

Quantitation of salivary sucrase activity has been proposed as a method for the estimation of the level of sucrose consumption. The purpose of the present study was to investigate the physiologic variability of the sucrase activity and microbial counts in paraffin-wax-stimulated saliva of subjects with sound sucrose consumption habits. Variation was analyzed by repeated sampling studies. Intraday variability was investigated by serial analyses of 16 individuals who gave eight samples at 2-h intervals on a single day. Interday variation was studied by analyzing the morning value of 24 individuals on three consecutive days. Interday variability of salivary mutans streptococci, lactobacilli, and yeasts was tested using semiquantitative commercial test kits. The diurnal variation of sucrase activity revealed that the activity in the morning was significantly higher than at noon or at later sampling times of the day. Interday variation was considerable in subjects with high sucrase values. The day-to-day variability of the salivary microbes was considerable for lactobacilli and relatively small for yeasts. A weak positive correlation ranging from 0.732 to 0.741 was found between high sucrase activity values and salivary lactobacilli. Salivary samples should be collected in the morning to differentiate between subjects with high and low sucrase activities.

Adult↗
PubMed1987

Epidermal growth factor selectively increases maltase and sucrase activities in neonatal piglet intestine.

1. Pig intestinal sucrase and maltase activities increase markedly, and lactase activity decreases, during the second week of post-natal life. Correlations noted between the time course describing these changes and that found previously to describe a decline in the ability of the pig intestine to take up macromolecules suggest that both events are subject to the same type of developmental control. 2. Injection of epidermal growth factor (EGF) into 3-day-old piglets increase sucrase and maltase activities measured 3 days later. These increases, which are not seen when measuring other hydrolase enzymes, are confined to the mid and distal regions of the small intestine. 3. Dexamethasone injected into 3-day-old piglets inhibits lactase and, on occasion, sucrase activities without affecting other intestinal hydrolases. Significant increases in sucrase and maltase activities also occur in distal intestine following injection of EGF plus dexamethasone into 3-day-old pigs. 4. Cytochemical analysis shows EGF effects on sucrase and maltase activities to be exerted in crypt and basal villus enterocytes produced post-natally. Dexamethasone inhibits lactase activity mainly by acting on mid and upper villus enterocytes produced before birth. 5. EGF appears to increase sucrase and maltase activities by extending the time during which young enterocytes continue to accumulate these enzymes in their brush-border membranes. Dexamethasone appears to cause a more fundamental change in the biochemistry of older enterocytes. accompanied by an increasing ability of these cells to transport neutral amino acids through a sodium-dependent mechanism (see James, Smith, Tivey & Wilson, 1987a).

Animals↗
PubMed1978

Development of the circadian rhythm of jejunal sucrase activity in the weanling rat.

In the adult rat, fed ad libitum, the activity of jejunal sucrase shows a diurnal rhythm with a peak during the dark period. Ontogenically, sucrase activity appears around the 16th postnatal day, then rises rapidly, and reaches adult levels by the 25th day. Our aim was to determine the developmental stage at which the diurnal rhythm appears and to elucidate its physiological basis. When sampled every 3 h on the 19th day, jejunal sucrase showed no discernible pattern with time. In contrast, at 22 days (1 day after completion of weaning) a circadian rhythm very similar to that of adults had appeared. Weights of stomach contents showed that the adult pattern of nocturnal feeding also matured between days 19 and 22. When weaning was prevented, no sucrase rhythm was detected on day 22, despite an imposed rhythm of suckling. Thus the sucrase rhythm is normally cued by some aspect of weaning other than rhythmic ingestion per se. Although corticosterone seemed a likely mediator of the sucrase rhythm, studies in adult rats showed that the rhythm persists in adrenalectomized animals.

Adrenalectomy↗
PubMed2005

Decreased sucrase and lactase activity in iron deficiency is accompanied by reduced gene expression and upregulation of the transcriptional repressor PDX-1.

Disaccharidases are important digestive enzymes whose activities can be reduced by iron deficiency. We hypothesise that this is due to reduced gene expression, either by impairment to enterocyte differentiation or by iron-sensitive mechanisms that regulate mRNA levels in enterocytes. Iron-deficient Wistar rats were generated by dietary means. The enzyme activities and kinetics of sucrase and lactase were tested as well as the activity of intestinal alkaline phosphatase (IAP)-II because it is unrelated to carbohydrate digestion. mRNA levels of beta-actin, sucrase, lactase, and the associated transcription factors pancreatic duodenal homeobox (PDX)-1, caudal-related homeobox (CDX)-2, GATA-binding protein (GATA)-4, and hepatocyte nuclear factor (HNF)-1 were measured by real-time PCR. Spatial patterns of protein and gene expression were assessed by immunofluorescence and in situ hybridization, respectively. It was found that iron-deficient rats had significantly lower sucrase (19.5% lower) and lactase (56.8% lower) but not IAP-II activity than control rats. Kinetic properties of both enzymes remained unchanged from controls, suggesting a decrease in the quantity of enzyme present. Sucrase and lactase mRNA levels were reduced by 44.5% and 67.9%, respectively, by iron deficiency, suggesting that enzyme activity is controlled primarily by gene expression. Iron deficiency did not affect the pattern of protein and gene expression along the crypt to villus axis. Expression of PDX-1, a repressor of sucrase and lactase promoters, was 4.5-fold higher in iron deficiency, whereas CDX-2, GATA-4, and HNF-1 levels were not significantly different. These data suggest that decreases in sucrase and lactase activities result from a reduction in gene expression, following from increased levels of the transcriptional repressor PDX-1.

Alkaline Phosphatase↗
PubMed1975

Studies on normal and precocious appearance of jejunal sucrase in suckling rats.

Some of the cellular and molecular events involved in the normal and precocious appearance of sucrase in jejunum of infant rats have been studied. Actinomycin D has been shown to inhibit (by 79%) the rise in sucrase activity usually seen after administration of hydrocortisone to 9-day-old rats. The precocious appearance of sucrase has also been studied with respect to the cytological localization of enzyme activity in the intestinal mucosa. Tissue was sectioned in a cryostat (transverse to the villi) and sucrase was assayed in homogenates prepared from the sections. By 24 h after administration of hydrocortisone to 9-day-old animals, sucrase was detectable only at the bases of the villi. During the subsequent 72 h the enzyme activity increased and spread along the villi at a rate consistent with that of cell migration. These data have lead to the conclusion that the action of glucocorticoids on enterocytes can occur only when the cells are in their proliferative phase. An ontogenic study of the ability of hydrocortisone to elicit jejunal sucrase showed that the tissue becomes increasingly responsive to the hormone with increasing age through the first and second postnatal weeks. Various hypotheses to explain this increase have been examined.

Age Factors↗
PubMed1980

Circadian rhythm of intestinal sucrase activity in rats. Mechanism of enzyme change.

Past investigation has revealed that the circadian rhythm of intestinal sucrase activity in rats is primarily cued by the time of feeding. We examined the mechanism of the circadian rhythm by methods involving quantitative immunoprecipitation of sucrase-isomaltase protein and study of decay of radioactively labeled protein. Rats were placed on a controlled feeding regimen (1000-1500 h) and then sacrificed at 3-h intervals over a 24-h period. Immunotitration experiments indicated that the circadian rhythm was the result of changes in the absolute amount of sucrase-isomaltase protein present and not of changes in the enzyme's catalytic efficiency. To study the mechanism of this circadian variation in sucrase-isomaltase mass, [(14)C]sodium carbonate was injected and, after maximum incorporation into brush border protein, the rats were sacrified at 3-h intervals. Sucrase-isomaltase protein was isolated by immunoprecipitation, and the decrease in total disintegrations per minute over time was used to study degradation of the protein. Enzyme degradation was not constant but exhibited a clear circadian rhythm. The period of increasing enzyme mass was characterized by virtual cessation of enzyme degradation (t((1/2)) of 38 h), and the period of declining enzyme mass by rapid degradation (t((1/2)) of 6 h or less). We found similar changes in enzyme degradation in fasted animals, demonstrating that the changes were not the result of decreased isotope reutilization during feeding. We found no evidence of a circadian rhythm in [(14)C]leucine incorporation into the protein, suggesting that enzyme synthesis was constant. These results indicate that the circadian rhythm of sucrase activity represents changes in the total amount of enzyme protein that are, at least in large part, secondary to changes in the enzyme's degradation rate.

Animals↗
PubMed1982

Relative importance of corticosterone and thyroxine in the postnatal development of sucrase and maltase in rat small intestine.

Both corticosterone and T4 have been previously implicated as causal factors in the ontogenic increases in jejunal sucrase and maltase activities during the third week of life in the rat. Furthermore, it is known that the administration of exogenous T4 during the developmental period causes significant increases in serum corticosterone concentrations. To determine whether the effects of T4 on sucrase and maltase are secondary to the corticosterone rise, we examined the effect of T4 administration in adrenalectomized (adX) pups. Serum corticosterone was measured in all operated animals. Some of the adX pups had substantial concentrations of circulating corticosterone. In adX pups with serum corticosterone levels below 0.1 microgram/dl, there was no effect of T4 on either maltase or sucrase activity. We also studied the effect of propylthiouracil-induced hypothyroidism on sucrase and maltase. At 21 days of age, both enzyme activities were significantly reduced in hypothyroid pups. Injections of either T4 or cortisone acetate were equally effective in restoring activities to normal. For sucrase, there was no further increase in activity when both hormones were administered. For maltase, the combined treatment gave activities that were significantly higher than those with either hormone alone. We conclude that for both sucrase and maltase, the effects of changes in thyroid status are primarily due to the accompanying changes in serum corticosterone. The normal rate of development of both enzymes appears to be principally under glucocorticoid control, although for maltase, T4 may have a facilitory action.

Adrenalectomy↗
PubMed1990

Sucrase activity in relation to other salivary factors and DMFS values of dental students.

Samples of stimulated whole saliva were collected from 176 dental students, and their teeth were examined both clinically and radiographically. Salivary flow; buffering capacity; numbers of lactobacilli, yeasts, and Streptococcus mutans; and DMFS and DS values were correlated to sucrase activity. The high flow-rate group had a lower (p = 0.0201*) sucrase activity than the low flow-rate group. The proportion of high (greater than or equal to 10 mumol/min x mg x 10(-3] sucrase activities among the highest density category of lactobacilli was 67%, whereas the corresponding proportion in the whole material was only 28%. Men had significantly (p = 0.0169*) higher sucrase activities than women. The other variables measured did not seem to have any significant effect on the sucrase activity values. In addition to sucrose consumption, other factors like the rate of salivary flow and the density of lactobacilli seem to influence the level of salivary sucrase activity.

Buffers↗
PubMed1987

Sucrase deficiency in Greenland. Incidence and genetic aspects.

The disaccharidase activities in small-intestinal surgical biopsy specimens from 97 Greenlanders were investigated. Five of the patients, or 5%, had sucrase deficiency. The diagnosis, sucrose malabsorption, was established by sucrose tolerance tests. In all parts of the world other than the arctic regions sucrase deficiency is a rare condition. The patients were divided into three separate groups in accordance with their sucrase activity. The middle group was considered to be heterozygote carriers of the sucrase-deficient gene. The number of people in the group corresponded to the theoretical number of heterozygotes in accordance with the Hardy-Weinberg equation, suggesting that sucrase deficiency is recessively inherited in a simple Mendelian fashion. Four of the five patients with sucrase deficiency had deficiency of lactase as well. The nutritional implications are discussed.

Adult↗
PubMed1993

In vivo sucrase-isomaltase and lactase-phlorizin hydrolase turnover in the fed adult rat.

We estimated in vivo turnover rates of sucrase-isomaltase and lactase-phlorizin hydrolase in adult rats. Fed animals received a primed continuous infusion of phenylalanine (300 microCi, 150 mumol Phe/100 g of body weight for 30 s, then 7.5 microCi, 3.75 mumol Phe/min for 10 to 140 min). Sucrase-isomaltase and lactase-phlorizin hydrolase were immunoprecipitated from jejunal mucosal membranes; isoforms were separated by SDS-polyacrylamide gel electrophoresis. Endoglycosidase H digestions and (for lactase-phlorizin hydrolase) N-terminal amino acid sequencing were performed on all isoforms. Specific radioactivity of prosucrase-isomaltase and prolactase-phlorizin hydrolase isoforms reached isotopic equilibrium by 60 and 90 min, respectively. Specific radioactivity of brush border sucrase and lactase did not reach steady state. The isotope kinetic, N-terminal amino acid sequencing, and endoglycosidase H digestion data suggested that one of the high molecular weight lactase isoforms is a dimer of mature lactase. Compartmental modeling of specific radioactivity demonstrated that mean intracellular residence time is 59 min for prosucrase-isomaltase isoforms and 68 min for prolactase-phlorizin hydrolase isoforms. Mean residence time in the brush border was 5.8 h for sucrase and 7.8 h for lactase. Fractional synthesis rates were 414%/day for sucrase and 307%/day for lactase. Thus, in vivo brush border sucrase and lactase turn over at similar rates in the adult rat.

Amino Acid Sequence↗
PubMed1993

Alkaline Phosphatase, Sucrase, and Insulin-like Growth Factor Receptors are Present in Atrophied Small Bowel 14 Years after Jejunoileal Bypass.

The authors obtained atrophied and hypertrophied small intestinal tissue from a patient undergoing jejunolleal (JI) bypass reversal. Tissue from both segments was examined for insulin, insulin-like growth factor-I (IGF-1) and IGF-11 receptors, and alkaline phosphatase and sucrase. We were interested in the potential of the atrophied segment to respond to luminal stimulation once the food train was re-established. Within the atrophic segment, flow cytometric evaluation of the receptors revealed (expressed as percent positive staining cells): insulin, 17.1%; IGF-1, 33.6%; and IGF-11, 60.8%, while the immunoreactive sucrase was 87.7% and alkaline phosphatase was 88.6%. Actual sucrase activity (expressed as glucose generated) in this segment was 17.9 ng/minl,ug protein and alkaline phosphatase was 28.0 U/L/µg protein as assessed by conventional methods. Receptor evaluation in the hypertrophic segment demonstrated 9.7% positive staining cells for insulin, 26.6% for IGF-I and 70.2% for IGF-11. Immunoreactive sucrase was 91.2% and alkaline phosphatase was 91.4%. Enzyme activity for sucrase was 10.4 ng/min/µg protein and for alkaline phosphatase was 59.4 U/L/µg protein. This data suggests that even in atrophied bowel insulin and IGF receptors as well as sucrase and alkaline phosphatase enzymes are present and may assist in the rapid recovery of the atrophied portion following reversal of the JI bypass.

Journal Article↗
PubMed1984

Effect of dietary sucrose on synthesis and degradation of intestinal sucrase.

Rates of synthesis and degradation of sucrase-isomaltase were measured along the crypt-villus unit of intestinal mucosa of rats fed either a high-sucrose or a carbohydrate-free diet. The objective of the study was to investigate i) the biochemical basis for the accumulation of sucrase during migration and differentiation of the enterocyte, leading to changes in distribution of activity of sucrase along the villus, and ii) the mechanism for the adaptation of sucrase activity to the amount of dietary carbohydrate. The results indicate that synthesis of sucrase is more rapid than degradation at the crypt-villus junction and in the lower part of the villus, producing a progressive accumulation of enzyme. The decreased activity at the tip of the villus is the consequence of a decided diminution of synthesis while the rate of degradation remains elevated. In rats fed a diet high in sucrose, the increased activity (3.25 times) is associated with much more rapid synthesis (2.6 times), while degradation is only slightly slower (0.8 times) than in those animals deprived of carbohydrate.

Animals↗