Simple and Practical Multigram Synthesis of d-Xylonate Using a Recombinant Xylose Dehydrogenase

An efficient multienzyme system for the preparative synthesis of d-xylonate, a chemical with versatile industrial applications, is described. The multienzyme system is based on d-xylose oxidation catalyzed by the xylose dehydrogenase from Calulobacter crescentus and the use of catalytic amounts of NAD⁺. The cofactor is regenerated in situ by coupling the reduction of acetaldehyde into ethanol catalyzed by alcohol dehydrogenase from Clostridium kluyveri. Excellent conversions (>95%) were obtained in a process that allows easy product isolation by simple evaporation of the volatile buffer and byproducts.

Phase IV noninferiority controlled randomized trial to evaluate the impact on diagnostic thinking and patient management and the test-retest reproducibility of the Gaxilose test for hypolactasia diagnosis

BACKGROUND

The diagnostic accuracy of the Gaxilose test (GT) for hypolactasia diagnosis has already been proved. The objectives of this clinical trial were to demonstrate the noninferiority of the GT compared to the hydrogen breath test (HBT) on the impact on diagnostic thinking and patient management, to evaluate the GT reproducibility with urine accumulated from 0 to 4 hours and from 0 to 5 hours and to assess test safety.

METHODS

We conducted a randomized, parallel, noninferiority clinical trial. Patients with clinical symptoms suggestive of lactose intolerance were screened for inclusion and randomly assigned to the GT arm or the HBT arm of the study. The impact on diagnostic thinking and patient management was analyzed with pretest and posttest questionnaires in which the investigators indicated their estimated probability of hypolactasia diagnosis and the intended management before and after the GT or the HBT (noninferiority margin: -10%). The primary outcome of the study was the impact on diagnostic thinking, expressed as the mean of the absolute values of the differences between the pretest and posttest probabilities of hypolactasia diagnosis. Patients randomized to the GT arm performed also the retest to evaluate the reproducibility of the GT.

RESULTS

A total of 147 patients were included in the intend-to-treat (ITT) population. Among them, 74 performed the HBT and 73 performed the GT. The results proved the noninferiority of the GT compared to the HBT on the impact on diagnostic thinking (ImpactGT = 31.74 ± 23.30%; ImpactHBT = 24.28 ± 19.87%; ΔGT-HBT = 7.46%; 95% confidence interval of ΔGT-HBT: 1.55%, infinite) and on patient management. The test-retest reproducibility was better for the GT with urine accumulated from 0 to 5 h: the intraclass correlation coefficient (ICC) was 0.5761, and the Kappa coefficient was 0.7548, indicative of substantial agreement between both tests. No serious adverse events were reported during the study.

CONCLUSIONS

The GT has an impact on diagnostic thinking and patient management noninferior to that of the HBT, is reproducible and well tolerated. These results prove the clinical benefit of its use in the clinical practice (ClinicalTrials.gov identifier: NCT02636413).

Development of a new method for d-xylose detection and quantification in urine, based on the use of recombinant xylose dehydrogenase from Caulobacter crescentus

The gene xylB from Caulobacter crescentus has been cloned and expressed in Escherichia coli providing a high yield of xylose dehydrogenase (XylB) production and excellent purity (97%). Purified recombinant XylB showed an absolute dependence on the cofactor NAD(+) and a strong preference for d-xylose against other assayed mono and disaccharides. Additionally, XylB showed strong stability when stored as freeze-dried powder at least 250days both at 4°C and room temperature. In addition, more than 80% of the initial activity of rehydrated freeze-dried enzyme remained after 150days of incubation at 4°C. Based on these characteristics, the capability of XylB in d-xylose detection and quantification was studied. The linearity of the method was maintained up to concentrations of d-xylose of 10mg/dL and the calculated limits of detection (LoD) and quantification (LoQ) of xylose in buffer were 0.568mg/dL and 1.89mg/dL respectively. Thus, enzymatic detection was found to be an excellent method for quantification of d-xylose in both buffer and urine samples. This method can easily be incorporated in a new test for the diagnosis of hypolactasia through the measurement of intestinal lactase activity.

Improvement and validation of d-xylose determination in urine and serum as a new tool for the noninvasive evaluation of lactase activity in humans

BACKGROUND

The phloroglucinol assay is the current method for d-xylose determination in urine/plasma/serum. However, its sensitivity is limited when low amounts of d-xylose are to be measured, such as in the noninvasive evaluation of intestinal lactase with 4-galactosylxylose (gaxilose). An improved assay was therefore needed.

METHODS

We developed and validated a modified version of the phloroglucinol-based assay for quantification of d-xylose in urine/serum samples. A method for gaxilose determination by gas chromatography (GC) was also optimized.

RESULTS

Linearity ranged from 0.125 to 5.0 mg/l (5-200 mg/l in original sample). Accuracy at LOQ (0.125 mg/l) was 0.97/2.49% in spiked urine/serum; for other quality controls (QC), it was <1.27%. Intra- and interassay precision at LOQ were 6.02% and 6.45% for urine, and 8.86% and 10.00%, respectively, for serum; for other QC, precision was <2.15%. Linearity of gaxilose determination by GC was 3.90-195.17 for urine and 9.75-195.17 mg/l for serum with acceptable sensitivity and reproducibility. The method proved adequate for the d-xylose determination in healthy and hypolactasic subjects after oral administration of gaxilose.

CONCLUSIONS

The modified method provides high sensitivity and robustness for d-xylose quantification in urine/serum for routine clinical use especially in the noninvasive diagnosis of intestinal lactase deficiency with the gaxilose test.

Photosynthesis limitations in three fern species

Maximum photosynthesis rates in ferns are generally lower than those of seed plants, but little is known about the limiting factors, which are crucial to understand the evolution of photosynthesis in land plants. To address this issue, a gas exchange/chlorophyll fluorescence analysis was performed in three fern species spanning high phylogenetic range within Polypodiopsida (Osmunda regalis, Blechnum gibbum and Nephrolepis exaltata) to determine their maximum net photosynthesis (AN ), stomatal (gs ) and mesophyll (gm ) conductances to CO2 , and the maximum velocity of carboxylation (Vc,max ). The in vitro Rubisco specificity factor (SC /O ) was also determined. All three species had values for SC /O similar to those typical of seed plants, but values of AN , gs , gm and Vc,max were within the lowest range of those observed in seed plants. In addition, gs was unresponsive to light and CO2 , as already described in other fern species. On the contrary, gm varied with changes CO2 . A quantitative photosynthesis limitation analysis suggested that early land plants (ferns) presented not only stomatal limitations-which were less adjustable to the environment-but also restricted gm and Vc,max , resulting in limited maximum photosynthesis rates.

The serum levels of the EGF-like homeotic protein dlk1 correlate with different metabolic parameters in two hormonally different children populations in Spain

BACKGROUND

The Dlk1 gene encodes for dlk1, a transmembrane protein belonging to the EGF-like repeat-containing family. Dlk1 has been shown to act as a regulator of adipogenesis. Fc-dlk1 transgenic mice show a decrease in adipose tissue and glucose tolerance, hypertriglyceridaemia and lower insulin sensitivity. Dlk1-deficient mice show growth retardation, increased serum lipid metabolites and develop obesity. These data advocate for a role of dlk1 in the maintenance of lipid homeostasis, and suggest that dlk1 levels may influence the development of cardiovascular disease.

AIM AND METHODS

In this study, we analysed whether dlk1 serum levels could be indicative of the different hormonal or metabolic status shown by two Spanish children populations (6-8 years-old), Orense and Murcia. We determined dlk1 serum levels by ELISA assay, using an antibody raised against the recombinant protein, and performed a correlation analysis against measurements of several hormonal and biochemical parameters in samples from 494 subjects.

RESULTS

We found a statistically significant positive correlation between serum levels of dlk1 and those of glucose (P < 0.05), total cholesterol (P < 0.01) and high-density lipoprotein-cholesterol (HDL-C) (P < 0.01) in children from Murcia, but not from Orense's population, where dehydroepiandrosterone-sulphate (DHEA-S) levels were significantly higher (P < 0.01) and dlk1 correlated positively with insulin (P < 0.01), homeostasis model assessment (HOMA) (P < 0.01) and free fatty acids (FFA) (P < 0.05).

CONCLUSIONS

dlk1 serum levels appear related to the anabolic status of the children in association with changes in the levels of DHEA-S, which have been associated with hyperinsulinaemia and diabetes. Monitoring dlk1 levels may be important to evaluate the metabolic and hormonal stage of child development.

Optimizing the enzymatic synthesis of β-d-galactopyranosyl-d-xyloses for their use in the evaluation of lactase activity in vivo

Disaccharides 2-O-, 3-O-, and 4-O-beta-D-galactopyranosyl-D-xyloses (2, 3, and 1, respectively) were obtained by beta-galactosidase-catalyzed reactions for their use in the evaluation of intestinal lactase activity in vivo. Their administration to suckling rats followed by determination of the derived D-xylose in the urine and measurement of lactase activity in intestinal homogenates showed 1 to be the most suitable disaccharide for a potential test of the deficiency of intestinal lactase. The synthesis of 1 was further studied by evaluating the effect of different variables on the yield and regioselectivity of the enzymatic galactosylation, and the purification process was optimized.

Noninvasive evaluation of intestinal lactase with 4-galactosylxylose: comparison with 3- and 2-galactosylxylose and optimization of the method in rats

BACKGROUND

Urinary excretion of D-xylose by suckling rats after ingestion of a mixture of 4-, 3-, and 2-galactosylxyloses reflects lactase activity in vivo. We aimed to select the most convenient of these disaccharides for detecting changes of the enzyme activity in vivo and to optimize the method.

METHODS

4-, 3-, and 2-galactosylxyloses were synthesized and purified, then orally administered to suckling rats of different ages. D-Xylose was measured colorimetrically by the phloroglucinol reaction in urine and plasma. Lactase activity was determined in extracts of small intestine mucosa with lactose, galactosylxyloses, and phlorizin as substrates.

RESULTS

D-Xylose appeared in the urine in a dose-dependent manner after ingestion of any of the 3 galactosylxylose disaccharides. Correlation between D-xylose elimination and intestinal lactase activity was highest with 4-galactosylxylose (r = 0.97; n = 24), lower with 2-galactosylxylose (r = 0.89; n = 24), and lowest with 3-galactosylxylose (r = 0.34; n = 23). The kinetic properties of intestinal lactase accounted for these differences. D-Xylose concentration in plasma after administration of 4-galactosylxylose also correlated with lactase activity (r = 0.93; n = 33).

CONCLUSIONS

4-Galactosylxylose is the most suitable compound for the evaluation of lactase activity in vivo. Measurement of the derived D-xylose in either urine or blood gives an estimate of the total lactose digestive capacity of the small intestine. The optimized method holds promise for development of a simple, low-cost, and reliable new test for the noninvasive diagnosis of hypolactasia.

Identification of C-terminal motifs responsible for transmission of inhibition by ATP of mammalian phosphofructokinase, and their contribution to other allosteric effects

Systematic deletions and point mutations in the C-terminal extension of mammalian PFK (phosphofructokinase) led us to identify Leu-767 and Glu-768 of the M-type isoform (PFK-M) as the motifs responsible for the role of this region in inhibition by MgATP. These amino acids are the only residues of the C-terminus that are conserved in all mammalian isoforms, and were found to have a similar function in the C-type isoenzyme. Both residues in PFK-C and Leu-767 in PFK-M were also observed to be critical for inhibition by citrate, which is synergistic with that by MgATP. Binding studies utilizing titration of intrinsic protein fluorescence indicated that the C-terminal part of the enzyme participates in the signal transduction route from the MgATP inhibitory site to the catalytic site, but does not contribute to the binding of this inhibitor, whereas it is essential for the binding of citrate. Mutations of the identified structural motifs did not alter either the action of other allosteric effectors that also interact with MgATP, such as the inhibitor phosphoenolpyruvate and the strong activator fructose 2,6-bisphosphate, or the co-operative effect of fructose 6-phosphate. The latter data provide evidence that activation by fructose 2,6-bisphosphate and fructose 6-phosphate co-operativity are not linked to the same allosteric transition as that mediating inhibition by MgATP.

Are twelve days of omeprazole, amoxicillin and clarithromycin better than six days for treating H. pylori infection in peptic ulcer and in non-ulcer dyspepsia?

BACKGROUND/AIMS

To evaluate whether omeprazole, amoxicillin and clarithromycin for 12 days is more effective for Helicobacter pylori eradication than the same regimen for only 6 days; and to verify whether these eradication regimens are more effective in peptic ulcer disease than in non-ulcer dyspepsia.

METHODOLOGY

We studied 411 patients in whom a gastroscopy was carried out due to symptoms related to the upper gastrointestinal tract and who were diagnosed with duodenal ulcer (175 patients, 43%), gastric ulcer (42 patients, 10%), or non-ulcer dyspepsia (194 patients, 47%), and concomitant infection by H. pylori. At endoscopy, biopsies were obtained for rapid urease test, and a 13C-urea breath test was carried out. Urea breath test was repeated four weeks after completing eradication treatment with 1) omeprazole (20 mg b.i.d.), amoxicillin (1 g b.i.d.) and clarithromycin (500 mg b.i.d.) for six days (239 patients), or 2) the same regimen for 12 days (172 patients).

RESULTS

H. pylori eradication was achieved in 73.6% (95% CI, 68-79%) of the patients treated during 6 days, and in 84.3% (79-90%) of those receiving 12 days of therapy (P < 0.01). The overall eradication rate with both regimens (6 plus 12 days), respectively in patients with duodenal ulcer, gastric ulcer and non-ulcer dyspepsia, was 84.6% (79-90%), 75.6% (61-86%), and 72.8% (67-79%) (P < 0.01 when comparing duodenal ulcer vs. non-ulcer dyspepsia). Twelve-day regimen was more effective than 6-day regimen only in non-ulcer dyspepsia (62% vs. 83%, P < 0.01), but not in duodenal or gastric ulcer. In the multivariate analysis the duration (6 vs. 12 days) of eradication therapy (odds ratio: 2.2; 1.3-3.7) and the type of disease (duodenal ulcer vs. non-ulcer dyspepsia; odds ratio: 2.3; 1.3-3.8) were the only variables which influenced on H. pylori eradication efficacy (chi 2 model, 17; P < 0.001).

CONCLUSIONS

Efficacy with omeprazole-amoxicillin-clarithromycin regimen in patients with duodenal ulcer is higher than in those patients with non-ulcer dyspepsia. The increase of H. pylori eradication rate by 21% in our non-ulcer dyspepsia patients justifies the prolongation from 6 to 12 days of omeprazole-amoxicillin-clarithromycin therapy, whilst the increase of cure rates in duodenal or gastric ulcer patients with a 12-day therapy would not be cost-effective.

6-mercaptopurine or methotrexate added to prednisone induces and maintains remission in steroid-dependent inflammatory bowel disease

BACKGROUND

As treatment of steroid-dependent patients with inflammatory bowel disease (IBD) is controversial, we analysed the efficacy and tolerance of 6-mercaptopurine (6-MP) and methotrexate (MTX) added to prednisone in increasing and maintaining the disease remission rate.

METHODS

Seventy-two steroid-dependent IBD patients, 34 with ulcerative colitis (UC) and 38 with Crohn's disease (CD), receiving treatment with prednisone were randomly assigned in a 2:2:1 ratio to additionally receive, orally, over a period of 30 weeks 1.5 mg/kg/day of 6-MP (group A) or 15 mg/week of MTX (group B), or 3 g/day of 5-aminosalicylic acid (5-ASA) (group C). All patients who achieved remission were included in a maintaining remission study for 76 weeks. Remission was defined after stopping prednisone as a CD activity index of <150 and normal serum orosomucoid concentration for CD patients and a Mayo Clinic score <7 for UC patients.

RESULTS

With regard to achieved remission, a significantly higher (P< 0.05) rate existed for UC patients in group A (78.6%) than in group C (25%), with no statistical differences in group B (58.3%) versus C. For CD patients, the rates were significantly higher (P< 0.001 and 0.01, respectively) in groups A (93.7%) and B (80%) versus C (14%). With regard to maintaining remission, UC patients in group A (63.6%) presented significantly higher rates (P < 0.0015 and P < 0.001, respectively) versus 14.3% in group B and none in group C. For CD patients, statistical differences (P < 0.001) existed when comparing rates in groups A (53.3%) and B (66.6%) versus none in group C. Noticeable side effects appeared in 13.3% of patients from group A and 11.5% from group B.

CONCLUSIONS

These results suggest that 6-MP or MTX added to prednisone could be effective in steroid sparing, as well as in achieving and maintaining remission in steroid-dependent IBD patients. MTX was less effective in maintaining remission in UC patients.

[Antibodies against Helicobacter pylori in saliva. Study of their validity versus breath test and its agreement with serology]

OBJECTIVES

To evaluate prospectively the validity of a new diagnostic method based on a saliva sample, taking as reference the breath test with 13C-marked urea, and to compare the results of this technique with another indirect method based on the detection of antibodies, "classical" serology using venous blood.

METHODS

48 individuals, 24 healthy volunteers and 24 consecutive patients with gastro-duodenal ulcer disease, were studied prospectively. Treatment during the previous month with gastro-erosive medication, antibiotics, proton-pump inhibitors or bismuth-derived drugs, prior treatment to eradicate H. pylori, gastric surgery and the presence of linked illnesses, were all considered criteria of exclusion from the study. For the diagnostic test in saliva a commercial enzyme-linked immunosorbent assay (ELISA, trademark Helisal) was used; and for blood serology, another commercial ELISA (Helico-G). The staff responsible for reading the saliva, serology and breath tests did not know the result of the other diagnostic methods. The result of the breath test with 13C-urea (TAU-kit) was taken as the reference standard for H. pylori infection.

RESULTS

The mean age of the healthy volunteers was 23 +/- 0.7 years; and of ulcer patients, 55 +/- 18. The prevalence of H. pylori infection, valued by the gold standard, was 79.2% in the ulcer patients and 54% in the volunteers. The sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of the saliva test in the ulcer patients were, respectively: 100% (95% CI, 79-99), 60% (17-93), 90% (68-98), 100% (31-97) and 92% (71-98). In the volunteers these figures were: 46% (20-74), 73% (39-93), 67% (31-91), 53% (27-78) and 58% (37-77). The serology results were better, with 100% sensitivity in both groups and outstanding diagnostic accuracy (92% and 96% for ulcer patients and volunteers, respectively). Concordance between serology and the saliva test in ulcer patients was perfect (kappa, 1). However, in asymptomatic individuals concordance was deficient (kappa, 0.28), and the prevalence of infection diagnosed with the two tests was not homogeneous (McNemar, 2.8; p < 0.05).

CONCLUSION

The diagnostic test for H. pylori infection in saliva is lacking in diagnostic accuracy in healthy individuals, which indicates that it cannot be used for screening infection in the asymptomatic population. The technique is more valuable in ulcer patients, although it does not reach the specificity desirable. For these reasons, the saliva test evaluated in this study cannot be recommended for diagnosis of H. pylori infection.

Estimated incidence of inflammatory bowel disease in Argentina and Panama (1987-1993)

AIM

to estimate the incidence of inflammatory bowel disease (IBD) in two areas from Panama and Argentina.

METHOD

during a 7-year period from 1987 to 1993 we surveyed IBD in two well-defined communities from Panama (District of Colón) and Argentina (Partido General Pueyrredón). The mean annual incidence of IBD was estimated from hospital-based registries. Records from the General Records Department and the endoscopy, radiology and pathology services were reviewed at the Hospital MA Guerrero in Colón and at two other hospitals in Partido General Pueyrredón to identify suspected cases of IBD. Cases were confirmed using standard criteria, and disease incidence rates were calculated by dividing the number of cases in which a positive diagnosis could be established by the population served by each hospital.

RESULTS

mean annual incidence of ulcerative colitis in Panama was 1.2/100 000 inhabitants/year, and no cases of Crohn's disease (CD) could be diagnosed. Mean annual incidence of IBD in Partido General Pueyrredón was 2.2/100 000 inhabitants/year, with only a single case of CD being identified. We argue that such figures could represent a good estimate of the incidence of IBD in each area, given the wide coverage of the population by the hospitals surveyed in each region.

CONCLUSION

according to these results, the incidence rates of IBD seem to be much lower than those published for other "Hispanic" communities outside Latin America. Factors such as population structure, environment or genetic determinants might account for these differences.

Significant increase in eradication rates of Helicobacter pylori infection with two consecutive dual therapies (omeprazole and amoxycillin or omeprazole and clarithromycin). A randomized study in 450 Spanish patients

Helicobacter pylori infection is associated with peptic ulcer disease and chronic gastritis, and eradication of the microorganism markedly reduces the recurrence of peptic ulcer. However, a major problem is the choice of a treatment that is effective, has high eradication rate, and is well tolerated by patients. We evaluated the eradication of H. pylori infection in patients with chronic gastritis (CG), duodenal ulcer (DU), and gastric ulcer (GU) after two dual therapies (omeprazole with either amoxycillin or clarithromycin). Of 450 patients initially included in the study, 207 had CG, 187 DU and 56 GU, and all presented with H. pylori infection. Diagnosis was made from endoscope examination, biopsy samples, rapid urease test and 13C-urea breath test (UBT). H. pylori infection was considered to be present when two of the tests had positive results. All patients were randomized to one of two regimens: (A) omeprazole (20 mg b.i.d.) plus amoxycillin (750 mg t.i.d.) or (B) omeprazole (40 mg b.i.d.) plus clarithromycin (500 mg t.i.d.). The duration of each of the regimens was 2 weeks. Fifty-eight patients who showed H. pylori infection after the first treatment (27 with CG, 24 with DU, and 7 with GU) were allocated to a second therapy. H. pylori eradication was assessed by UBT, 6 weeks after the end of the therapies; positive values were those higher than 5 delta units. A second consecutive dual therapy of omeprazole plus an antibiotic (amoxycillin or clarithromycin) not used in the first therapy improved on the eradication rates obtained with the first regimen. The overall eradication rates were also higher, but no significant differences were found between amoxycillin and clarithromycin. The best results were obtained in those patients with GU.

Rheumatic manifestations in human immunodeficiency virus positive and negative individuals: a study of 2 populations with similar risk factors

OBJECTIVE

Assess the impact of human immunodeficiency virus (HIV) infection on the onset of rheumatic manifestations in HIV+ patients, and to compare them with a control HIV- group with similar risk factors.

METHODS

We prospectively studied 74 consecutive HIV+ patients, looking for clinical and laboratory findings of rheumatic manifestations and compared them with 72 control subjects with similar risk factors for HIV who tested negative for HIV.

RESULTS

Rheumatic manifestations were more frequently observed in the HIV+ group than the HIV-group (p < 0.001): Arthralgias were found in 34 (45%), arthritis in 8 (10%), and Reiter's syndrome in 6 (8%). Laboratory findings revealed rheumatoid factor in 16 (21%) HIV+ vs 2 (2%) in HIV-, antinuclear antibodies in 13 (17%) HIV+ vs 0 in HIV-, IgG anticardiolipin antibodies in 70 (94%) HIV+ vs 7 (9%) in HIV- (p < 0.001). Hyperuricemia was found in 31 HIV+ patients (41%), and hypouricemia in 4 (5%), compared with none in the HIV- group (p < 0.0001). Neoplasia were identified in 13 HIV+ patients, in 7 associated with hyperuricemia and 3 with hypouricemia. Of interest, 2 patients had urate abnormalities before the diagnosis of neoplasia.

CONCLUSIONS

Our study suggests that rheumatic manifestations are more prevalent in HIV+ patients. In advanced HIV infection, hypo and hyperuricemia may be considered markers of neoplasia.