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PubMed1999

Influence of lactose-citrate co-metabolism on the differences of growth and energetics in Leuconostoc lactis, Leuconostoc mesenteroides ssp. mesenteroides and Leuconostoc mesenteroides ssp. cremoris

The biodiversity of growth and energetics in Leuconostoc sp. has been studied in MRS lactose medium with and without citrate. On lactose alone, Ln. lactis has a growth rate double that of Ln. cremoris and Ln. mesenteroides. The pH is a more critical parameter for Ln. mesenteroides than for Ln. lactis or Ln. cremoris; without pH control Ln. mesenteroides is unable to acidify the medium under pH 4.5, while with pH control and as a consequence of a high Y(ATP) its growth is greater than Ln. lactis and Ln. cremoris. In general, lactose-citrate co-metabolism increases the growth rate, the biomass synthesis, the lactose utilisation ratio, and the production of lactate and acetate from lactose catabolism. The combined effect of the pH and the co-metabolism lactose-citrate on the two components of the proton motive force (deltap = deltapsi - ZdeltapH) has been studied using resting-cell experiments. At neutral pH deltap is nearly entirely due to the deltapsi, whereas at acidic pH the deltapH is the major component. On lactose alone, strains have a different aptitude to regulate their intracellular pH value, for Ln. mesenteroides it drastically decreases at acidic pH values (pH, = 5.2 for pH 4), while for Ln. lactis and Ln. cremoris it remains above pH 6. Lactose-citrate co-metabolism allows a better control of pH homeostasis in Ln. mesenteroides, consequently the pHi becomes homogeneous between the three strains studied, for pH 4 it is in an interval of 0.3 pH unit (from pHi = 6.4 to pHi = 6.7). In this metabolic state, and as a consequence of the variation in deltapH, and to some extent in the deltapsi, the difference of deltap between the three strains is restricted to an interval of 20 mV.

Journal Article↗
PubMed1983

Characterization of beta-galactosidase--lactose-permease chimaeras of Escherichia coli.

Escherichia coli strains have been isolated in which 3, 39 or 805 5'-end codons of lacZ, the gene for the cytoplasmic enzyme beta-galactosidase are fused to codon 9 of lacY, the gene for lactose permease. Lactose-permease-deficient cells, carrying the lacZ-Y fusions on F' lac pro episomes, are phenotypically positive on eosin/methylene blue/lactose or on melibiose plates, demonstrating that the beta-galactosidase--lactose-permease chimaeras transport lactose and melibiose in vivo. The apparent affinity for beta-D-galactopypanosyl 1-thio-beta-D-galactopyranoside (GalSGal) in cells is similar to that of the wild-type gene product. The maximum velocity of active GalSGal transport is reduced in all three fusion strains. Both lactose and p-nitrophenyl alpha-D-galactopyranoside inhibit GalSGal uptake. As demonstrated by immunoblot experiments the chimaeras cross-react with polyclonal antibodies directed against native lactose permease and they are present in the cell envelope fraction of homogenates. Their apparent molecular weights upon electrophoresis in NaDodSO4/polyacrylamide gels correspond to those expected from their respective primary sequences, taking into account the migration properties of wild-type lactose permease. It is proposed that substitution of eight N-terminal lactose permease residues by N-terminal beta-galactosidase residues neither prevents membrane incorporation of permease nor completely impairs the ability to transport galactosides actively. Alternative interpretations of the experimental results are discussed.

Biological Transport, Active↗
PubMed1976

Utilization of Lactose, Glucose, and Galactose by a Mixed Culture of Streptococcus thermophilus and Lactobacillus bulgaricus in Milk Treated with Lactase Enzyme.

The mechanism responsible for an increased rate of acid production when yogurt starter cultures are grown in milk treated with lactase enzyme was investigated by studying carbohydrate utilization and acid development by a pure culture of Streptococcus thermophilus and a mixed yogurt starter culture consisting of S. thermophilus and Lactobacillus bulgaricus. In milk containing glucose, galactose, and lactose, glucose and lactose (but not free galactose) were fermented. Fermentation of lactose in control milk was accompanied by the release of free galactose, with the result that carbohydrate utilization was less efficient than in treated milk. This phenomenon also occurred when lactose was fermented by S. thermophilus in broth culture. Carbohydrate utilization by the mixed yogurt culture was more rapid when the lactose in milk was partially prehydrolyzed. Our results suggest that the more rapid acid development that took place when a mixed yogurt starter culture was grown in milk containing prehydrolyzed lactose was the result of a more rapid and efficient utilization of carbohydrate by S. thermophilus when free glucose in addition to lactose was available for fermentation. The evidence presented also suggests that uptake and utilization of glucose and lactose by S. thermophilus are different in broth and milk cultures.

Journal Article↗
PubMed1989

Lactose transport system of Streptococcus thermophilus: a hybrid protein with homology to the melibiose carrier and enzyme III of phosphoenolpyruvate-dependent phosphotransferase systems.

The gene responsible for the transport of lactose into Streptococcus thermophilus (lacS) was cloned in Escherichia coli as a 4.2-kilobase fragment from an EcoRI library of chromosomal DNA by using the vector pKK223-3. From deletion analysis, the gene for lactose transport mapped to two HindIII fragments with a total size of 2.8 kilobases. The gene was transcribed in E. coli from its own promoter. Functional expression of lactose transport activity was shown by assaying for the uptake and exchange of lactose both in intact cells and in membrane vesicles. The nucleotide sequence of lacS and 200 to 300 bases of 3' and 5' flanking regions were determined. The gene was 1,902 base pairs long, encoding a 69,454-dalton protein with an NH2-terminal hydrophobic region and a COOH-terminal hydrophilic region. The NH2-terminal end was homologous with the melibiose carrier of E. coli (23% similarity overall; greater than 50% similarity for regions with at least 16 amino acids), whereas the COOH-terminal end showed 34 to 41% similarity with the enzyme III (domain) of three different phosphoenolpyruvate-dependent phosphotransferase systems. Among the conserved amino acids were two histidyl residues, of which one has been postulated to be phosphorylated by HPr. Since sugars are not phosphorylated during translocation by the lactose transport system, it is suggested that the enzyme III-like region serves a regulatory function in this protein. The lacS gene also appears similar to the partially sequenced lactose transport gene of Lactobacillus bulgaricus (lacL; greater than 60% similarity). Furthermore, the 3' flanking sequence of the S. thermophilus lactose transport gene showed approximately 50% similarity with the N-terminal portion of the beta-galactosidase gene of L. bulgaricus. In both organisms, the lactose transport gene and the beta-galactosidase appear to be separated by a 3-base-pair intercistronic region.

Amino Acid Sequence↗
PubMed1990

Beta-galactosidase tablets in the treatment of lactose intolerance in pediatrics.

Lactose-intolerant children manifest diminished or nonexistent intestinal lactase activity, resulting in flatulence, abdominal pain, and diarrhea. To assess the hydrolytic capability of lactase-containing tablets taken immediately before oral lactose challenge, we studied 18 children previously identified as being lactose intolerant and having no underlying organic gastrointestinal disease. Subjects had a mean (+/- SEM) age of 11.4 +/- 3.4 years; 72% were male. At time of the study, lactase-containing tablets or placebo tablets were ingested (double-blind) immediately before drinking a solution of lactose. Breath samples were obtained for hydrogen analysis at 30-minute intervals during a 2-hour period, and clinical symptoms were monitored. In lactose-intolerant patients, hydrogen production was significantly greater following placebo (maximum hydrogen excretion, approximately 60 ppm) compared with lactase-containing tablets (maximum hydrogen excretion, 7 ppm). Increased hydrogen production was associated with clinical symptoms including abdominal pain (89% of subjects following placebo ingestion), bloating (83%), diarrhea (61%), and flatulence (44%). These results indicate, therefore, that coingestion of lactose and lactase-containing tablets significantly reduces both breath hydrogen excretion and clinical symptoms associated with lactose intolerance.

Abdominal Pain↗
PubMed1984

Hydrogen breath test quantification and clinical correlation of lactose malabsorption in adult irritable bowel syndrome and ulcerative colitis.

Lactose malabsorption was studied, by hydrogen breath test, in 72 adults suffering from irritable bowel syndrome, in 20 ulcerative colitis patients, and in 69 healthy subjects. The minimum dose of lactose required to cause a positive breath test was determined, and the symptoms caused and the resulting hydrogen eliminated quantified. A high incidence of lactose malabsorption was shown at standard doses (up to 50 g) in both the healthy subjects (70%) and the patients (86% and 85%, respectively). In the irritable bowel syndrome and the ulcerative colitis groups, symptoms occurred with a smaller quantity of breath hydrogen, presumably in association with a greater individual sensitivity of the colon to distension. The threshold lactose dose was notably lower in the diseased subjects who registered as evidence a prevalence of malabsorption at a 20-g lactose load. The pathogenetic role of lactose malabsorption in the irritable bowel syndrome is emphasized, as is the importance of the personal lactose tolerance.

Adolescent↗
PubMed1994

The frequency distribution of lactose malabsorption among adult populations from the eastern and western Egyptian deserts.

The study consisted of 172 subjects belonging to ethnic groups from Sinai in the Eastern Desert and the New Valley in the Western Desert, with respective mean ages of 36.7 +/- 2.0 and 26.6 +/- 1.0 years. Lactose absorption was assessed by measurement of urinary galactose in pooled 2-hr urine samples following ingestion of an oral lactose dose of 40 g. Mean 2-hr excretion values after ingestion were 32.3 mg galactose in the Sinai and 7.7 mg in the New Valley. In the evaluation of lactose malabsorption, a diagnosis of lactose malabsorption is based upon a cutoff point of 0.075 mg/mg urinary galactose:creatinine ratio. The overall prevalence rate in those populations is 34.3%. The proportion of lactose malabsorbers was 11.1% in Sinai and 51.0% in the New Valley. Highly significant differences (chi 2 = 29.5, P < 0.0001) were found between the two ethnic groups with regard to the frequency distribution of lactose malabsorption. The existence of an east-west gradient of increasing frequencies of lactose malabsorption gene is suggested.

Adolescent↗
PubMed2005

Inverse dose effect of pretest dietary lactose intake on breath hydrogen results and symptoms in lactase nonpersistent subjects.

The aim of this study was to determine a relationship between pretest intake of lactose and outcome of lactose breath hydrogen test. Patients presented at a testing laboratory participated in the study. A 3-hour breath hydrogen, 50-g lactose challenge was carried out. Results were tabulated and patients completed a 3-day recall diet questionnaire. Daily lactose intake was independently calculated and was associated with breath hydrogen and total symptom score. Statistical analysis used Spearman's correlation, Mann-Whitney U-test and chi2 or Fisher exact test. Of 118 patients, 50% were lactose maldigesters. In these patients, measured breath hydrogen and symptom scores were significantly higher in the lowest intake group (< 5 g/d) than in the highest intake group (> 20 g/d) (P < .05). In the presumed lactose digesters, 59% experienced some symptoms during testing for unclear reasons. Pretest dietary intake of lactose inversely affects results of breath hydrogen.

Adolescent↗
PubMed1997

The impact of HIV infection on lactose absorptive capacity.

Forty HIV-infected adult patients at different disease stages and 44 healthy volunteers were evaluated for lactose malabsorption using the hydrogen breath test after 20 g lactose ingestion. All subjects were previously tested for breath hydrogen (H2) excretion after 12 g lactulose ingestion. The presence of intestinal superinfections, gastrointestinal symptoms and the intensity of clinical intolerance after lactose load were accurately searched in each patient. The cumulative H2 excretion after lactulose did not significantly differ between the different groups studied. The prevalence of lactose malabsorption turned out to be significantly higher (P < 0.001) in HIV-infected patients (70%) than in controls (34%). Moreover, in patients in more advanced disease stages the degree of lactose malabsorption was significantly greater than in patients at earlier disease stages, who did not differ from healthy volunteers. Furthermore the degree of lactose intolerance was significantly greater (P < 0.001) in symptomatic patients than in those without intestinal symptoms and in healthy volunteers, while no significant difference was observed between these latter groups. The results here demonstrate the negative impact of HIV infection on lactose absorptive capacity in adult patients, particularly marked in more advanced stages of the disease, suggesting that, in addition to the presence of the virus alone, other factors may contribute to determine the enterokinetic alterations responsible for lactase deficiency.

Adolescent↗
PubMed1997

Milk fat does not affect the symptoms of lactose intolerance.

OBJECTIVE: This study investigated the role of the fat content of milk on symptoms of lactose intolerance. DESIGN: Subjects recorded intolerance symptoms using a visual analogue scale (VAS) following ingestion of three test milks for varying fat content for a two-day period. SUBJECTS/SETTING: The subjects were thirty adult volunteers, patients of two Estonian out-patient clinics with diagnosed lactose intolerance. The study milks were drunk at home or at work. All thirty subjects completed the study protocol. INTERVENTION: Each subject drank, in random order, fat-free milk (4.9% lactose), high-fat milk (8% fat, 4.9% lactose), and a lactose-free and fat-free control milk. They drank 200 ml of the milk twice a day for two days, one milk type per session, with five days between sessions. The subjects noted their gastrointestinal symptoms during the test periods and during a 5 d milk-free period at the beginning of the study. The occurrence and severity of symptoms were compared. A global measure of the severity of symptoms was defined by computing the sum of the symptoms scores. RESULTS: The sum of symptoms was higher during all milk periods than during the milk-free period (P < 0.01). There were no statistically significant differences in the occurrence or severity of symptoms during the fat-free milk period compared with the high-fat milk period. CONCLUSIONS: Even a marked difference in the fat content of milk did not affect the symptoms of lactose intolerance. Consequently, there seems to be no case for recommending full-fat milk products in the treatment of lactose intolerance.

Adolescent↗
PubMed1992

[Lactose intolerance in chronic inflammatory bowel diseases].

In 124 patients with Crohn's disease (69 women, 55 men; mean age 33.7 [11-66] years) and 53 with ulcerative colitis (30 women, 23 men; mean age 36.2 [19-74] years) the incidence of lactose intolerance, as measured by the H2 breath test and blood sugar concentration, was determined prospectively. To exclude abnormal bacterial colonization of the small intestine or rapid small-intestine transit after partial resection of the small intestine as a cause of lactose intolerance, the oro-caecal transit time for lactulose (H2 breath test) was measured. While 21 of 124 patients with Crohn's disease (16.9%) had the expected incidence of lactose intolerance, this was present in only 2 of 53 patients with ulcerative colitis (3.8%; P < 0.05). The lactose intolerance was independent of the site of any inflammatory changes, disease activity and extent of small-intestine resection. Oro-caecal transit time for lactose was similar for all patients. There was no lactose intolerance in two patients with abnormal small-intestinal bacterial colonization.--Because of their considerable diagnostic and prognostic significance, tests for lactose intolerance should be performed routinely in all cases of Crohn's disease or ulcerative colitis.

Adolescent↗
PubMed2004

Lactose: the milk sugar from a biotechnological perspective.

Lactose is a very important sugar because of its abundance in the milk of humans and domestic animals. Lactose is a valuable asset as a basic nutrient and the main substrate in fermentative processes that led to the production of fermented milk products, such as yogurt and kefir. In some instances, lactose also can be a problem as the causative agent of some diseases, such as lactose intolerance and galactosemia, or for being a by-product generated in huge amounts by the cheese industry. The study of the biochemical reactions leading to the synthesis and assimilation of lactose has provided valuable models for the understanding of biosynthetic and catabolic processes. Lactose-hydrolyzing enzymes are structurally and phylogenetically related to different types of beta-galactosidases and bacterial cellobiases involved in the enzymatic degradation of cellulose. Biotransformation of lactose, by either enzymatic or fermentative procedures, is important for different types of industrial applications in dairy and pharmaceutical industries.

Animals↗
PubMed1976

Relationship of lactose intolerance to milk intolerance in young children.

The prevalence of lactose intolerance as revealed by the standard lactose tolerance test was compared with the occurrence of intolerance to graded amounts of milk in 69 black and 30 white children. Of the black children studied, 11% of those 4 to 5 years old, 50% of those 6 to 7 years old, and 72% of those 8 to 9 years old were found to be lactose-intolerant, yet no child was intolerant to 240 ml of milk. Symptom responses to greater amounts of milk did not suggest that the frequency of primary lactose intolerance might be a reason for limiting existing milk programs for young children. No significant differences were found between the milk intakes of black lactose-tolerant and black lactose-intolerant children, nor between milk intakes of 6- and 7-year-old black and white children in Boston. However, 8- to 9-year-old black children drank significantly less milk than 8- to 9-year-old white children did. The blood glucose response at 0, 20, and 45 min after the ingestion of 2 g lactose/kg (maximum 50 g) was unreliable as an indicator of an individual's symptomatic response to lactose.

Age Factors↗
PubMed1979

Lactose intolerance in Iran.

One hundred five Iranian subjects, ranging in age from 4 months to 25 years, were tested for lactose absorption and tolerance. After ingesting a lactose dose, on the basis of low blood glucose response, 68% of the subjects were malabsorbers. Prevalence of lactose malabsorption increased with age, i.e., 31% of the children less than 3 years of age malabsorbed lactose, whereas 86% of adults did so. Clinical manifestations of lactose intolerance were shown by 39% of all subjects; of those who were lactose malabsorbers, only 57% manifested clinical symptoms. Among the lactose malabsorbers, the lowest prevalence of clinical symptoms occurred among the children less than 3 years of age and the highest in adults.

Adolescent↗
PubMed1997

Lactose maldigestion in breast-feeding Gambian infants.

BACKGROUND: The ability of breast-feeding infants to utilize lactose, the major carbohydrate in breast-milk, is dependent on the presence of the enzyme lactase (E.C.3.2.1.108). Lactase is located in the brush border of the small intestine and because of its exposed position it is extremely vulnerable to pathogenic damage. Breast-fed Gambian infants have poor growth associated with intestinal damage beyond 3-4 months. The aim of this study was to assess the ability of Gambian infants aged 2-15 months (N = 113) to digest lactose and to see how this varied with age, intestinal permeability, and growth performance. METHODS: Lactose maldigestion was estimated by monthly measurements of urinary lactose and lactulose following an oral dose of the latter. RESULTS: Both urinary lactose excretion and lactulose maldigestion increased with age (p < 0.0001 ANOVA). Up to 6 months the mean urinary lactose: lactulose excretion ratio was within the quoted normal range (< 0.4). Beyond this age, mean values were hypolactasic. Lactose maldigestion was related to poor growth in both weight and length (r = -0.04, p < 0.0001, after age correction). Although a major part of this relationship was a reflection of the previously reported correlation between intestinal permeability and growth, more than 30% of the association was in addition to the permeability effect. Possible explanations are discussed. CONCLUSIONS: Moderate-to-severe hypolactasia does occur in breast-fed Gambian infants and is related to poorer-than-expected growth. However, this does not mean that breast milk intake should be reduced as the nutritional and immunological benefits of breast milk continue to outweigh any disadvantages.

Aging↗
PubMed2005

Systemic lactose intolerance: a new perspective on an old problem.

Intolerance to certain foods can cause a range of gut and systemic symptoms. The possibility that these can be caused by lactose has been missed because of "hidden" lactose added to many foods and drinks inadequately labelled, confusing diagnosis based on dietary removal of dairy foods. Two polymorphisms, C/T13910 and G/A22018, linked to hypolactasia, correlate with breath hydrogen and symptoms after lactose. This, with a 48 hour record of gut and systemic symptoms and a six hour breath hydrogen test, provides a new approach to the clinical management of lactose intolerance. The key is the prolonged effect of dietary removal of lactose. Patients diagnosed as lactose intolerant must be advised of "risk" foods, inadequately labelled, including processed meats, bread, cake mixes, soft drinks, and lagers. This review highlights the wide range of systemic symptoms caused by lactose intolerance. This has important implications for the management of irritable bowel syndrome, and for doctors of many specialties.

Asthma↗
PubMed2005

High prevalence of celiac disease in patients with lactose intolerance.

BACKGROUND/AIMS: Acquired lactase deficiency is a common cause of gastrointestinal symptoms but its etiology remains unclear. Celiac disease could lead to lactase deficiency and is much more common than previously suspected. Several studies have highlighted the prevalence of lactose intolerance in celiac disease, but studies assessing the prevalence of celiac disease in lactose intolerance are lacking. We evaluated the prevalence of celiac disease in patients with a positive H2-lactose breath test compared to a control group. METHODS: This retrospective study included 54 patients (15 males/39 females; mean age 37.8 +/- 7 years) from southern Italy, referred to the Gastroenterology Unit for bloating and diarrhea after the introduction of milk or dietary lactose. They had a positive H2-lactose breath test and a negative H2-glucose breath test. 50 blood donors were drawn from a similar population, matched for sex and age, and enrolled as a control group. All patients were screened for possible celiac disease by measuring the serum level of IgA antibodies to endomysium, anti-transglutaminase and total IgA. Patients positive for at least one of these markers were submitted to upper gastrointestinal endoscopy. RESULTS: None of the patients had a IgA deficiency. 24% of the patients showed positivity of celiac disease antibodies compared to 2% in the control group (p < 0.001). Histologic samples of these patients showed villous atrophy (53.8% Marsh type IIIa, 38.4% Marsh IIIb, and 7.6% with Marsh type IIIc) confirming the celiac disease, while in the control subjects duodenal biopsies were normal. CONCLUSIONS: A high prevalence of celiac disease was observed in patients with a positive H2-lactose breath test compared to healthy controls. In these subjects lactase deficiency seems to be the only manifestation of celiac disease. We suggest serologic screening for celiac disease in all patients with a positive H2-lactose breath test before beginning a milk-exclusion diet.

Adult↗
PubMed2001

Lactose intolerance and intestinal villi morphology in Thai people.

OBJECTIVE: To study the relationship of lactose intolerance and intestinal villi morphology in Thai people. MATERIAL AND METHOD: Subjects for this study were patients with functional dyspepsia who had no history of milk allergy and underwent gastroduodenoscopy. Two mucosal biopsy specimens were taken from beyond the distal end of the second part of the duodenum. The specimens were carefully orientated and were graded according to the following scheme: group I: finger shaped villi; group II: mixed finger and leaf shaped villi; group III: clubbing or blunting shaped villi. All subjects were tested for lactose malabsorption by breath hydrogen analysis after consuming 50 gram lactose. Breath hydrogen concentration was analyzed in samples collected intermittently by end-expiratory technique. A rise in breath hydrogen concentration of 20 PPM over baseline was considered evidence of lactose malabsorption. RESULTS: The twenty-five subjects were twenty females (80.0%) and five males (20.0%) who ranged in age from 18 to 53 years (mean 31 +/- 8.29). Sixteen subjects belonged to the finger shaped villi group (64.0%), five to the mixed finger and leaf shaped villi, group (20.0%) and four to the clubbing or blunting shaped villi group (16.0%). Results of breath hydrogen excretion test identified the prevalence of lactose intolerance in 68 per cent of the subjects: 15/16 (93.75%) of group I; 1/5 (20.0%) of group II and 1/4 (25%) of group III respectively (P<0.001). The symptom of diarrhea after lactose loading was correlated well in patients who had positive breath hydrogen analysis. CONCLUSION: As shown in this study, the lactose intolerance is not related to intestinal villi morphology. It is implied that primary lactase deficiency is more common in Thai people than secondary lactase deficiency.

Adolescent↗