Growth and Gastrointestinal Tolerance in Healthy Term Infants Fed Milk-Based Infant Formula Supplemented with Five Human Milk Oligosaccharides (HMOs): A Randomized Multicenter Trial.

Background: Five of the most abundant human milk oligosaccharides (HMOs) in human milk are 2'-fucosyllactose (2'-FL), 3-fucosyllactose (3-FL), lacto-N-tetraose (LNT), 3'-sialyllactose (3'-SL) and 6'-sialyllactose (6'-SL). Methods: A randomized, double-blind, controlled parallel feeding trial evaluated growth in healthy term infants fed a control milk-based formula (CF; n = 129), experimental milk-based formula (EF; n = 130) containing five HMOs (5.75 g/L; 2'-FL, 3-FL, LNT, 3'-SL and 6'-SL) or human milk (HM; n = 104). Results: No significant differences (all p ≥ 0.337, protocol evaluable cohort) were observed among the three groups for weight gain per day from 14 to 119 days (D) of age, irrespective of COVID-19 or combined non-COVID-19 and COVID-19 periods. There were no differences (p ≥ 0.05) among the three groups for gains in weight and length from D14 to D119. Compared to the CF group, the EF group had more stools that were soft, frequent and yellow and were similar to the HM group. Serious and non-serious adverse events were not different among groups, but more CF-fed infants were seen by health care professionals for illness from study entry to D56 (p = 0.044) and D84 (p = 0.028) compared to EF-fed infants. Conclusions: The study demonstrated that the EF containing five HMOs supported normal growth, gastrointestinal (GI) tolerance and safe use in healthy term infants.

Three-Dimensional-Printed Uterine Model for Surgical Planning of a Cesarean Delivery Complicated by Multiple Myomas.

BACKGROUND: Uterine myomas encountered at cesarean delivery increase the complexity and risk of the procedure. Preoperative planning of such deliveries may help optimize patient outcomes. The application of three-dimensional printing technology is rapidly expanding in many surgical specialties. We created a three-dimensional-printed model from the magnetic resonance images (MRIs) of a gravid uterus with multiple myomas for surgical planning of cesarean delivery. INSTRUMENT: A three-dimensional-printed uterine model from MRIs of a pregnant patient with multiple uterine myomas as a tool for planning cesarean delivery. EXPERIENCE: A 33-year-old woman with a myomectomy history presented to our institution for prenatal care. Initial ultrasound imaging revealed multiple uterine myomas. A three-dimensional-printed uterine model, based on subsequent MRI, was created for presentation at an obstetric multidisciplinary meeting. The model accurately represented the number, size, and locations of uterine myomas, aiding surgical planning, including skin and uterine incisions. At the time of cesarean delivery, the model was directly correlated with patient anatomy to further determine the optimal placement of uterine incision. Maternal and fetal outcomes were excellent. CONCLUSION: Three-dimensional-printed models, through improved surgical planning, could optimize outcomes for patients with uterine myomas undergoing cesarean delivery.

Lutein as an Ingredient in Pediatric Nutritionals.

Lutein is a xanthophyll carotenoid that can be found in a variety of fruits and vegetables that may be limiting in the pediatric diet, which makes it an attractive nutrient for addition to supplemental nutritional products. Including lutein in the diet from a young age may provide protective benefits during a critical time of ocular and cognitive development. Lutein accumulation in eye and brain has led to research to better define the physiological role of this nutrient. Infants are exposed to lutein primarily through the consumption of breast milk or infant formulas containing lutein. The ingredient has been evaluated to be safe by many scientific and regulatory authorities for the addition to food, including formulated nutritional products. Nonhuman primates have been important in the investigation of the role dietary lutein in eye and brain function. Studies examining diets low or absent in lutein have revealed the impact on brain and eye function. Diets low in lutein may compromise neural tissues such as those found in the eye, which are susceptible to oxidation from blue wavelength light. No dietary recommendations have been established for lutein; however, several publications have highlighted the accumulating evidence that lutein provides long-term benefits when incorporated in adequate amounts in the diet.

Soy protein-based infant formulas with supplemental fructooligosaccharides: gastrointestinal tolerance and hydration status in newborn infants.

Unlike milk-based infant formulas, soy-based infant formulas containing supplemental fructooligosaccharides (FOS) have not been clinically evaluated. A randomized, double-blind, 28 day parallel feeding trial compared gastrointestinal (GI) tolerance and hydration in healthy term newborn infants fed either a commercialized soy formula (with history of safe use) containing sucrose as 20% of total carbohydrate, no supplemental short-chain FOS (scFOS) and no mixed carotenoids (lutein, lycopene, beta-carotene) as a control (CF, n = 62 infants) or one of two experimental soy-based formulas, EF1 (n = 64) and EF2 (n = 62) containing scFOS (2.5 g/L) and mixed carotenoids. EF1 differed from EF2 by containing sucrose. Results indicated no significant study group differences (p > 0.05) in study completion rates (CF = 81, EF1 = 86, & EF2 = 87%), growth, mean rank stool consistency, stool frequency, formula intake, spit-up/vomit, and safety measures (urine specific gravity, USG; hydration status and adverse events). Mean USGs for study groups were normal (<1.03). The EF1 > CF group in percent yellow stools (p < 0.01 at age 14 days). In conclusion, the study suggested that term infants fed soy-based formulas supplemented with scFOS and mixed carotenoids, with or without sucrose in the 1st 35 days of infancy demonstrated good tolerance and hydration comparable to the control soy-based formula with history of safe use.

Tolerance of formulas containing prebiotics in healthy, term infants.

OBJECTIVE: The aim of the study was to compare infants' gastrointestinal tolerance of formulas supplemented with 2 different levels of galacto-oligosaccharides (GOS) versus a control formula (CF) or human milk. METHODS: Healthy, full-term infants (n = 180) were enrolled in this 3-group controlled, double-blind, multicenter study, and a concurrently enrolled, nonrandomized human milk-fed group (HM) by 8 days of age. Infants were randomized to be fed formula supplemented with either 4 g (EF4) or 8 g (EF8) GOS/L or a CF until day of life (DOL) 119. Infants were to be seen at DOL 14, 35, 56, 84, and 119. Parents were to record detailed 24-hour information about intake, tolerance to feedings, and stool patterns and consistency each day from enrollment to DOL 35, and for 3 days before DOL 56, 84, and 119. Stool consistency was scored on a 5-point scale as watery (1), loose/mushy, soft, formed, or hard (5). RESULTS: The mean stool consistency score was higher in the CF group throughout the study (CF >  EF8 and CF > HM for all study periods and CF > EF4 from DOL 15 to 35, P < 0.05). There was a significantly higher percentage of watery stools in the EF8 versus the CF group from study day 1 (SD 1) to DOL 14 (P < 0.05), but no differences between the groups in number of stools per day. The percentage of feedings with spit up and/or vomiting within 1 hour after feeding was significantly lower for HM versus EF8 and CF from SD 1 to DOL 14 (P < 0.05). CONCLUSIONS: In this clinical study, milk-based term infant formula (Similac Advance) with 4 g GOS/L was well-tolerated in terms of stool consistency and additional measures of gastrointestinal tolerance by newborn infants through the first 4 months of life.

Plasma carotenoid concentrations of infants are increased by feeding a milk-based infant formula supplemented with carotenoids.

BACKGROUND: Human milk is the gold standard of infant nutrition and is a source of important substances, including carotenoids. Infant formulas are designed to mimic the composition and/or performance of human milk, although currently carotenoids are not routinely added to US infant formulas. The aim of this study was to assess plasma concentrations of ß-carotene, lutein and lycopene 56 days after feeding infants milk-based infant formula without (CTRL) or with different concentrations of added carotenoids (L1 and L2). RESULTS: Plasma carotenoid concentrations increased in infants fed carotenoid-supplemented formulas as compared with the control formula with no added carotenoids. At study day 56, infants fed the supplemented formulas (L1 and L2) had mean plasma lutein, ß-carotene and lycopene concentrations that were within the range of a concurrent group of human milk-fed infants (HM). Anthropometric measurements were comparable among all study groups. CONCLUSION: Plasma carotenoid concentrations of infants fed the supplemented formulas were within the range of the HM group and are consistent with reported plasma carotenoid ranges in human milk-fed infants. The experimental formulas were well tolerated and anthropometric measurements were comparable among all study groups.

Is the macronutrient intake of formula-fed infants greater than breast-fed infants in early infancy?

Faster weight gain early in infancy may contribute to a greater risk of later obesity in formula-fed compared to breast-fed infants. One potential explanation for the difference in weight gain is higher macronutrient intake in formula-fed infants during the first weeks of life. A systematic review was conducted using Medline to assess the macronutrient and energy content plus volume of intake in breast-fed and formula-fed infants in early infancy. All studies from healthy, term, singleton infants reporting values for the composition of breast milk during the first month of life were included. The energy content of colostrum (mean, SEM: 53.6 ± 2.5 kcal/100 mL), transitional milk (57.7 ± 4.2 kcal/100 mL), and mature milk (65.2 ± 1.1 kcal/100 mL) was lower than conventional infant formula (67 kcal/100 mL) on all days analyzed. The protein concentration of colostrum (2.5 ± 0.2 g/100 mL) and transitional milk (1.7 ± 0.1 g/100 mL) was higher than formula (1.4 g/100 mL), while the protein content of mature milk (1.3 ± 0.1 g/100 mL) was slightly lower. Formula-fed infants consume a higher volume and more energy dense milk in early life leading to faster growth which could potentially program a greater risk of long-term obesity.

A curriculum to teach and evaluate resident skills in the management of postpartum hemorrhage.

AIM: The aim of this study was the development of a curriculum for the management of postpartum hemorrhage and an objective assessment of technical skills (OSATS) for uterine compression sutures. METHOD: Twenty-two residents participated in the study. Evaluations included the global rating scale, task-specific checklist, and pass/fail rating for the OSATS and task-specific checklist for the hemorrhage drill. The reliability and validity of the evaluation tools were calculated. RESULTS: The inter-rater reliability was 0.98 for the hemorrhage drill checklist, 0.77 for the global rating scale, and 0.93 for the uterine suture checklist. Construct validity evaluation revealed senior residents performed superiorly to junior residents on the global rating scale (P=0.006) and on the uterine suture checklist (P=0.04). There was an improvement in performance on the post-test in comparison to the pretest (P=0.001). CONCLUSION: We present an inexpensive, reliable, and valid curriculum to teach and evaluate the medical and surgical management of postpartum hemorrhage.

Utility of ultrasound and MRI in prenatal diagnosis of placenta accreta: a pilot study.

OBJECTIVE: The purpose of this study was to evaluate transabdominal pelvic ultrasound and MRI for the prenatal diagnosis of placenta accreta. MATERIALS AND METHODS: A historical cohort pilot study was performed at our institution to identify women at risk of placenta accreta who had undergone both prenatal ultrasound and MRI. Findings at ultrasound and MRI were compared with the final diagnosis, which was established with clinical findings at delivery and pathologic examination of specimens. Volume measurements were made of low-signal-intensity intraplacental bands on T2-weighted MR images. Risk factors for placental insufficiency were recorded. RESULTS: Thirteen patients at risk of placenta accreta underwent both sonography and MRI. Nine of these patients had abnormal placentation. With ultrasound, abnormal placentation was correctly identified in six of nine patients (67%) and the absence of accreta in two of four patients (50%). With MRI, abnormal placentation was correctly identified in seven of nine patients (78%) and the absence of accreta in three of four patients (75%). The volumes of low-signal-intensity bands were significantly different in the patients with abnormal placentation and those without placenta accreta (p = 0.047), and band volumes were significantly different among patients with accreta, increta, and percreta (p < 0.0005). CONCLUSION: The accuracy of MRI may improve if volumes of low-signal-intensity bands are calculated, MRI is performed before 30 weeks' gestation, and risk factors for placental insufficiency are recognized.

Vitamin B-6 deficiency suppresses the hepatic transsulfuration pathway but increases glutathione concentration in rats fed AIN-76A or AIN-93G diets.

The transsulfuration pathway, which aids in regulating homocysteine concentration and mediates cysteine synthesis, may be sensitive to vitamin B-6 status because cystathionine beta-synthase (CBS) and cystathionine gamma-lyase (CGL) require pyridoxal 5'-phosphate (PLP). To assess relations between vitamin B-6 and transsulfuration, we evaluated the effects of dietary pyridoxine (PN) on the hepatic concentration of relevant metabolites and in vitro activity of CBS and CGL. Growing rats were fed AIN-93G- or AIN-76A-based diets that ranged from adequate to deficient in vitamin B-6 (2, 1, 0.5, 0.1, or 0 mg of PN/kg diet, n = 5). This design allowed assessment of the effects of supplemental methionine (AIN-76A) vs. cysteine (AIN-93G) in common research diets over a range of vitamin B-6 levels. CBS activity, assayed in the presence or absence of added S-adenosylmethionine, was independent of diet type and PN level. CGL activity was independent of diet type but proportional to dietary PN. Rats fed deficient (0 and 0.1 mg PN/kg) diets exhibited only approximately 30% of the CGL activity of those fed the 2 mg PN/kg diets. Hepatic cystathionine increased from 20 to 30 nmol/g for the 1-2 mg PN/kg diets to approximately 85 nmol/g for the 0 mg PN/kg diet; however, cysteine was reduced only in B-6-deficient rats consuming the AIN-93G diet (means of 30-40 nmol/g for adequate to 11.6 nmol/g for 0 mg PN/kg AIN-76A diet). In spite of these effects, hepatic glutathione concentration increased in vitamin B-6 deficiency. These results suggest that vitamin B-6-dependent changes in transsulfuration do not limit hepatic glutathione production.

Changes in intestinal morphology and permeability in the biobreeding rat before the onset of type 1 diabetes.

OBJECTIVE: Type 1 diabetes is an autoimmune disorder that occurs in genetically susceptible individuals. It has been hypothesized that the disease could be triggered by environmental agents that gain entry into the body through small intestinal absorption. Increased intestinal permeability has been reported both in spontaneous animal models of type 1 diabetes and human type 1 diabetes. In these studies, we examined both the physical and functional permeability characteristics of the small intestine in diabetes-prone and control rats. METHODS: In a series of studies, BioBreeding diabetes-prone(n = 31), BioBreeding diabetes-resistant (n = 20) and control Wistar (n = 25) rats were examined at intervals from 21 to 125 days of age. RESULTS: The percentage of goblet cells and the mucosal crypt depth were significantly greater in BioBreeding diabetes-prone than BioBreeding diabetes-resistant rats (P < 0.001 and P = 0.01, respectively). BioBreeding diabetes-prone and BioBreeding diabetes-resistant rats expressed less of the tight junction protein claudin (P < 0.05) and exhibited greater intestinal permeability (P < 0.001) than did Wistar rats. Intestinal permeability measured both in vivo and ex vivo decreased in all rat strains as age increased (P < 0.001). CONCLUSIONS: In a genetically susceptible rodent model of diabetes, early increased intestinal permeability might allow unregulated passage of environmental antigens that could potentially trigger the autoimmune response leading to type 1 diabetes.

Activities of hepatic cytosolic and mitochondrial forms of serine hydroxymethyltransferase and hepatic glycine concentration are affected by vitamin B-6 intake in rats.

Serine hydroxymethyltransferase (SHMT) is a pyridoxal phosphate (PLP)-dependent enzyme that exists as cytosolic and mitochondrial isozymes that catalyze the reversible interconversion of serine and tetrahydrofolate (THF) to glycine and 5,10-methyleneTHF. SHMT is a major source of one-carbon units for cellular metabolism, but its sensitivity to various degrees of altered vitamin B-6 nutritional status has not been determined. In this study, cytosolic and mitochondrial SHMT activities were measured in liver from rats fed dietary pyridoxine (PN) ranging from adequate to deficient levels (2, 1, 0.5, 0.1, and 0 mg PN/kg diet; n = 10 per group). Both mitochondrial and cytosolic SHMT activities increased (P < 0.001) with increasing dietary PN over this range, and activities were a linear function of liver PLP concentration. Mitochondrial SHMT comprised approximately 70% of total activity. Assays conducted with and without in vitro addition of PLP indicated that total SHMT (apo- and holoenzyme forms) varied with dietary PN for each isoform, but that the proportion of each present as the apoenzyme was not affected by PN intake. This aspect of SHMT nutritional regulation differs from that of many other PLP-dependent enzymes. Hepatic glycine concentration was inversely related to vitamin B-6 intake (P < 0.05), which suggests a functional effect of altered SHMT activity. Overall these results demonstrate the potential for disruption of SHMT-mediated one-carbon metabolism by inadequate vitamin B-6 intake.

Substitutes for glutamine in proliferation of rat intestinal epithelial cells.

OBJECTIVES: Glutamine (Gln) is important for intestinal epithelial proliferation. The purpose of this study was to determine whether glutamate (Glu), a mixture of nucleotide monophosphates, arginine, or glucosamine could support proliferation of rat intestinal crypt cells (IEC-6) in the absence of Gln. METHODS: Glu with added ammonia acetate, glucosamine, arginine, and nucleotide monophosphates were tested at concentrations that were isonitrogenous with respect to Gln. To determine whether de novo synthesis of Gln was affected by these nutrients, a duplicate set of treatment groups was also tested with 1.0 mM/L of methionine sulfoximine, an inhibitor of Gln synthetase. RESULTS: Gln + methionine sulfoximine-treated cells showed suboptimal proliferation below 0.6 mM/L but normal proliferation between 0.6 and 4.0 mM/L of Gln. In the absence of exogenous Gln, isonitrogenous concentrations of Glu, glucosamine, arginine, or nucleotide monophosphates yielded similar proliferation as Gln. Cells treated with Glu, glucosamine, arginine, or nucleotide monophosphate mixture showed a decrease in proliferation compared with cells treated with Gln across all treatment doses (P < 0.03). CONCLUSIONS: The importance of these results is that, in the presence of active Gln synthetase, these nutrients can maintain intestinal epithelial proliferation similar to that observed with Gln.

Uptake, hydrolysis, and metabolism of pyridoxine-5'-beta-D-glucoside in Caco-2 cells.

An important dietary source of vitamin B-6, pyridoxine-5'-beta-D-glucoside (PNG), exhibits only partial bioavailability, which is limited by the extent of enzymatic cleavage of the beta-glucosidic bond to release metabolically available pyridoxine (PN). This laboratory showed that the intestinal hydrolysis of PNG is catalyzed by cytosolic PNG hydrolase (PNGH) and brush border lactase-phlorizin hydrolase (LPH). LPH-catalyzed PNG hydrolysis in vitro is competitively inhibited by lactose. In the present study, the uptake and hydrolysis of PNG were examined in Caco-2 human colon carcinoma cells, which express a functional LPH but exhibit no PNGH activity. PNG uptake at 37 degrees C was linear over 5-500 micromol/L PNG. Uptake was not significantly reduced when Na(+) was substituted with K(+), Li(+), or Tris in the medium. Increasing PNG concentration in the medium did not change intracellular concentrations of PN, pyridoxamine (PM), pyridoxamine 5'-phosphate (PMP), or pyridoxal 5'-phosphate (PLP); however, intracellular pyridoxal (PL) concentration increased. Intracellular PNG concentration was not significantly reduced in the presence of lactose, but the concentration of PL declined in proportion to extracellular lactose (P = 0.01). These results indicate that PNG can be absorbed intact in a Na(+)-independent process and is taken up by passive diffusion. The presence of lactose in this in vitro model of intestinal uptake reduced the enzymatic hydrolysis of PNG by lactase.

Folate deprivation reduces homocysteine remethylation in a human intestinal epithelial cell culture model: role of serine in one-carbon donation.

Little is known about homocysteine metabolism in intestine. To address this question, we investigated homocysteine metabolism under conditions of folate adequacy and folate deprivation in the Caco-2 cell line, a model of human intestinal mucosal cells. Caco-2 cells were cultured in media enriched with [3-(13)C]serine and [U-(13)C(5)]methionine tracers, and enrichments of intracellular free amino acid pools of these amino acids as well as homocysteine, cystathionine, and cysteine were measured by using gas chromatography/mass spectrometry. Homocysteine transsulfuration plus folate-dependent and total remethylation were quantified from these amino acid enrichments. Homocysteine remethylation accounted for 19% of the intracellular free methionine pool in cells cultured with supplemental folate, and nearly all one-carbon units used for remethylation originated from the three carbon of serine via folate-dependent remethylation. Labeling of cystathionine and cysteine indicated the presence of a complete transsulfuration pathway in Caco-2 cells, and this pathway produced 13% of the intracellular free cysteine pool. Appearance of labeled homocysteine and cystathionine in culture medium suggests export of these metabolites from intestinal cells. Remethylation was reduced by one-third in folate-restricted cell cultures (P < 0.001), and only approximately 50% of the one-carbon units used for remethylation originated from the three carbon of serine under these conditions. In conclusion, the three carbon of serine is the primary source of one-carbon units used for homocysteine remethylation in folate-supplemented Caco-2 cell cultures. Remethylation is reduced as a result of folate restriction in this mucosal cell model, and one-carbon sources other than the three carbon of serine contribute to remethylation under this condition.

Hydrolytic activity toward pyridoxine-5'-beta-D-glucoside in rat intestinal mucosa is not increased by vitamin B-6 deficiency: effect of basal diet composition and pyridoxine intake.

Pyridoxine-5'-beta-D-glucoside (PNG), a glycosylated form of dietary vitamin B-6, is partially hydrolyzed in the small intestine by the cytosolic enzyme pyridoxine-5'-beta-D-glucoside hydrolase (PNG hydrolase) and by the brush border enzyme lactase phlorizin hydrolase (LPH) to release free pyridoxine (PN). This laboratory has previously shown that PNG hydrolase activity is inversely related to dietary vitamin B-6 in rats and guinea pigs. The current investigation was done to examine the effect of dietary PN on PNG hydrolytic activity and its distribution. Nutrient compositional differences between the AIN-76A and AIN-93G purified diets that were unrelated to vitamin B-6 were also examined in relation to PNG hydrolysis in rat small intestinal mucosa. Study one included rats (n = 29) that were fed the AIN-93G diet providing a range of PN concentrations for 5 wk. Rats (n = 49) in study two were fed either AIN-76A or AIN-93G each with graded concentrations of PN. In both studies, rat growth and plasma and liver pyridoxal 5'-phosphate (PLP) concentrations increased (P < 0.05) with increasing concentrations of dietary PN. PNG hydrolytic activity localized to the brush border membrane was five times that measured in the cytosol. Cytosolic PNG hydrolytic activity increased significantly with increasing dietary PN concentration in rats fed the AIN-76A, but not AIN-93G diet. Activity in the mucosal total membrane fraction did not increase in proportion to dietary PN concentration for either diet. Regardless of dietary PN concentration, the basal nutrient composition of the diets affected growth and PNG hydrolytic activity in intestinal mucosa. In contrast to previous results from this laboratory, intestinal hydrolytic activity toward PNG did not increase in vitamin B-6-deficient rats.

Intestinal brush border membrane catalyzes hydrolysis of pyridoxine-5'-beta-D-glucoside and exhibits parallel developmental changes of hydrolytic activities toward pyridoxine-5'-beta-D-glucoside and lactose in rats.

Pyridoxine-5'-beta-D-glucoside (PNG) is a major form of vitamin B-6 in plant foods that exhibits partial bioavailability as vitamin B-6 in humans. We previously identified an intestinal mucosal cytosolic PNG hydrolase that catalyzes the partial hydrolysis of PNG absorbed without prior deglycosylation. Recent observations that the brush border membrane also catalyzes PNG hydrolysis led to the hypothesis that PNG hydrolysis may be another function of the beta-glucosidase lactase-phlorizin hydrolase (LPH) and, thus, brush border PNG hydrolysis would undergo a developmental decline similar to that of lactose hydrolysis. In this study, the relationships among hydrolytic activities in small intestinal cytosolic and brush border fractions in rats (n = 9 per group) of various ages (1-2 d and 2, 4, 8, 12 and 24 wk) were examined. In vitro specific activities toward PNG and lactose were greater in brush border than cytosol, and these were greater in newborn rats than in all other age groups (P < 0.01). Brush border activities toward PNG and lactose and were closely correlated (r = 0.84; P < 0.0001). These findings suggest that the hydrolysis of PNG is catalyzed at least partially at the brush border and that the bioavailability of PNG may be influenced by the residual LPH activity in children and adults.

Enzymatic hydrolysis of pyridoxine-5'-beta-D-glucoside is catalyzed by intestinal lactase-phlorizin hydrolase.

An obligatory step in the mammalian nutritional utilization of pyridoxine-5'-beta-D-glucoside (PNG) is the intestinal hydrolysis of its beta-glucosidic bond that releases pyridoxine (PN). This laboratory previously reported the purification and partial characterization of a novel cytosolic enzyme, designated PNG hydrolase, which hydrolyzed PNG. An investigation of the subcellular distribution of intestinal PNG hydrolysis found substantial hydrolytic activity in the total membrane fraction, of which 40-50% was localized to brush border membrane. To investigate the possible role of a brush border beta-glucosidase in the hydrolysis of PNG, lactase phlorizin hydrolase (LPH) was purified from rat small intestinal mucosa. LPH hydrolyzed PNG with a K(m) of 1.0 +/- 0.1 mm, a V(max) of 0.11 +/- 0.01 micromol/min.mg protein, and a k(cat) of 1.0 s(-1). LPH-catalyzed PNG hydrolysis was inhibited by glucose, lactose, and cellobiose but not by PN. Specific blockage of the phlorizin hydrolase site of LPH using 2',4'-dintrophenyl-2-fluoro-2-deoxy-beta-D-glucopyranoside did not reduce PNG hydrolysis. Evidence of transferase activity was also obtained. Reaction mixtures containing LPH, PNG, and lactose yielded the formation of another PN derivative that was identified as a pyridoxine disaccharide. These results indicate that LPH may play an important role in the bioavailability of PNG, but further characterization is needed to assess its physiological function.