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

Cow’s milk-induced gastrointestinal disorders: From infancy to adulthood

Milk is related to many gastrointestinal disorders from the cradle to the grave due to the many milk ingredients that can trigger gastrointestinal discomfort and disorders. Cow’s milk protein allergy (CMPA) is the most common food allergy, especially in infancy and childhood, which may persist into adulthood. There are three main types of CMPA; immunoglobulin E (IgE)-mediated CMPA, non-IgE-mediated CMPA, and mixed type. CMPA appears before the first birthday in almost all cases. Symptoms may start even during the neonatal period and can be severe enough to simulate neonatal sepsis. CMPA (often non-IgE mediated) can present with symptoms of gastroesophageal reflux, eosinophilic esophagitis, hemorrhagic gastritis, food protein-induced protein-losing enteropathy, and food protein-induced enterocolitis syndrome. Most CMPAs are benign and outgrown during childhood. CMPA is not as common in adults as in children, but when present, it is usually severe with a protracted course. Lactose intolerance is a prevalent condition characterized by the development of many symptoms related to the consumption of foods containing lactose. Lactose intolerance has four typical types: Developmental, congenital, primary, and secondary. Lactose intolerance and CMPA may be the underlying pathophysiologic mechanisms for many functional gastrointestinal disorders in children and adults. They are also common in inflammatory bowel diseases. Milk consumption may have preventive or promoter effects on cancer development. Milk may also become a source of microbial infection in humans, causing a wide array of diseases, and may help increase the prevalence of antimicrobial resistance. This editorial summarizes the common milk-related disorders and their symptoms from childhood to adulthood.

The importance of lactose intolerance in individuals with gastrointestinal symptoms

Lactose intolerance is a condition with an elevated prevalence worldwide, especially in Latin American, Asian, and African countries. The aim of the present narrative review was to highlight the importance of accurately diagnosing lactose intolerance to prevent self-diagnosis that results in the unnecessary elimination of milk and dairy products from the diet and the consequent deprivation of nutrients that could be essential at certain stages of life. The pathophysiologic mechanism of deficient lactose absorption in the intestine can be primary, secondary to other enteropathies, or coexistent with other intestinal diseases with similar symptoms, such as irritable bowel syndrome, bacterial overgrowth syndrome, or celiac disease, causing confusion in relation to diagnosis and treatment. Lactose intolerance consists of a set of symptoms attributed to the consumption of milk and dairy products that are assumed to be due to deficient digestion of that disaccharide. A wide range of tests have been validated to detect deficient digestion that include blood tests, genetic mutation analyses, breath tests, and recently, a urine test, all of which are described in the present article. Nevertheless, there are few validated questionnaires for symptom evaluation and measurement, partly due to the heterogeneity of concepts and the subjectivity of each of the symptoms.

Metabolism and Pharmacokinetics of Phytochemicals in the Human Body

Background:

Phytochemicals are obtained from various plants and used for the treatment of diseases as both traditional and modern medicines. Poor bioavailability of phytochemicals is a major concern in applying phytochemicals as a therapeutic agent. It is, therefore, necessary to understand the metabolism and pharmacokinetics of phytochemicals for its implication as a therapeutic agent.

Methods:

Articles on the metabolism of phytochemicals from the PubMed database. The articles were classified into the digestion, absorption, metabolism, excretion, toxicity, and bioavailability of phytochemicals and the effect of gut microbiota on the metabolism of phytochemicals.

Results:

The metabolism of each phytochemical is largely dependent on the individual's digestive ability, membrane transporters, metabolizing enzymes and gut microbiota. Further, the form of the phytochemical and genetic make-up of the individual greatly influences the metabolism of phytochemicals.

Conclusion:

The metabolism of phytochemicals is mostly depended on the form of phytochemicals and individualspecific variations in the metabolism of phytochemicals. Understanding the metabolism and pharmacokinetics of phytochemicals might help in applying plant-based medicines for the treatment of various diseases.

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).

Analytical Validation of a New Enzymatic and Automatable Method for d-Xylose Measurement in Human Urine Samples

Hypolactasia, or intestinal lactase deficiency, affects more than half of the world population. Currently, xylose quantification in urine after gaxilose oral administration for the noninvasive diagnosis of hypolactasia is performed with the hand-operated nonautomatable phloroglucinol reaction. This work demonstrates that a new enzymatic xylose quantification method, based on the activity of xylose dehydrogenase from Caulobacter crescentus, represents an excellent alternative to the manual phloroglucinol reaction. The new method is automatable and facilitates the use of the gaxilose test for hypolactasia diagnosis in the clinical practice. The analytical validation of the new technique was performed in three different autoanalyzers, using buffer or urine samples spiked with different xylose concentrations. For the comparison between the phloroglucinol and the enzymatic assays, 224 urine samples of patients to whom the gaxilose test had been prescribed were assayed by both methods. A mean bias of −16.08 mg of xylose was observed when comparing the results obtained by both techniques. After adjusting the cut-off of the enzymatic method to 19.18 mg of xylose, the Kappa coefficient was found to be 0.9531, indicating an excellent level of agreement between both analytical procedures. This new assay represents the first automatable enzymatic technique validated for xylose quantification in urine.

Acute and Chronic Effects of Dietary Lactose in Adult Rats Are not Explained by Residual Intestinal Lactase Activity

Neonatal rats have a high intestinal lactase activity, which declines around weaning. Yet, the effects of lactose-containing products are often studied in adult animals. This report is on the residual, post-weaning lactase activity and on the short- and long-term effects of lactose exposure in adult rats. Acutely, the postprandial plasma response to increasing doses of lactose was studied, and chronically, the effects of a 30% lactose diet fed from postnatal (PN) Day 15 onwards were evaluated. Intestinal lactase activity, as assessed both in vivo and in vitro, was compared between both test methods and diet groups (lactose vs. control). A 50%–75% decreased digestive capability towards lactose was observed from weaning into adulthood. Instillation of lactose in adult rats showed disproportionally low increases in plasma glucose levels and did not elicit an insulin response. However, gavages comprising maltodextrin gave rise to significant plasma glucose and insulin responses, indicative of a bias of the adult GI tract to digest glucose polymers. Despite the residual intestinal lactase activity shown, a 30% lactose diet was poorly digested by adult rats: the lactose diet rendered the animals less heavy and virtually devoid of body fat, whereas their cecum tripled in size, suggesting an increased bacterial fermentation. The observed acute and chronic effects of lactose exposure in adult rats cannot be explained by the residual intestinal lactase activity assessed.

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.

Phase I and phase IB clinical trials for the noninvasive evaluation of intestinal lactase with 4-galactosylxylose (gaxilose)

GOALS AND BACKGROUND

Hypolactasia is widespread, yet reliable diagnostic tests are lacking. A new test based on oral administration of 4-galactosylxylose (gaxilose) and urine or serum measurement of D-xylose after cleavage by intestinal lactase is under clinical development. We investigated the optimal dose of gaxilose and calculate cutoff values of D-xylose for that dose.

STUDY

In the randomized, dose-finding, phase I study, urine and serum pharmacokinetics of D-xylose were determined after oral administration of 6 ascending doses of gaxilose (and placebo) to 12 healthy adult volunteers. In the open, parallel, phase Ib study, 30 volunteers received the doses established for the urine and blood tests and D-xylose was measured. Cutoff values were calculated as 1.96 × SD below the mean value. Safety was assessed through reporting of adverse events.

RESULTS

Gaxilose administration showed a progressive, dose-dependent increase in D-xylose in urine and serum. An optimal gaxilose dose of 0.45 g and urine collection periods of 4 and 5 hours were selected for further studies. For the blood test, a 2.7 g dose was selected and C max measured at 90 minutes. The calculated cutoff values of D-xylose for normal lactase activity were 27.58 and 37.87 mg for the 4- and 5-hour urine tests, respectively, and 0.97 mg/dL for the blood test. There were no treatment-related adverse events.

CONCLUSIONS

The methodology described provides a simple, safe test for the evaluation of lactase activity in vivo. Further evaluation of the test as a noninvasive diagnosis of hypolactasia is ongoing in patients with lactose intolerance.

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.