Genetics and epidemiology of adult-type hypolactasia

Inferring ancestry with the hierarchical soft clustering approach tangleGen

Understanding the genetic ancestry of populations is central to numerous scientific and societal fields. It contributes to a better understanding of human evolutionary history, advances personalized medicine, aids in forensic identification, and allows individuals to connect to their genealogical roots. Existing methods, such as ADMIXTURE, have significantly improved our ability to infer ancestries. However, these methods typically work with a fixed number of independent ancestral populations. As a result, they provide insight into genetic admixture, but do not include a hierarchical interpretation. In particular, the intricate ancestral population structures remain difficult to unravel. Alternative methods with a consistent inheritance structure, such as hierarchical clustering, may offer benefits in terms of interpreting the inferred ancestries. Here, we present tangleGen, a soft clustering tool that transfers the hierarchical machine learning framework Tangles, which leverages graph theoretical concepts, to the field of population genetics. The hierarchical perspective of tangleGen on the composition and structure of populations improves the interpretability of the inferred ancestral relationships. Moreover, tangleGen adds a new layer of explainability, as it allows identifying the single-nucleotide polymorphisms that are responsible for the clustering structure. We demonstrate the capabilities and benefits of tangleGen for the inference of ancestral relationships, using both simulated data and data from the 1000 Genomes Project.

The detection, characterization, and quantification of dominant degradation products of nisin A and Z in selected dairy products by liquid chromatography-high-resolution mass spectrometry technique

Nisin, a bacteriocin produced through fermentation using bacterium Lactococcus lactis, has several commercial variants such as nisin A and nisin Z. Nisin serves as a natural preservative with antimicrobial properties in various food products, including dairy and beverages, for extending product shelf life. The efficacy and safety of nisin A as a bacteriocin has been well characterized. However, there is limited evidence regarding the efficacy, stability, and safety of nisin Z as a food preservative, as it has not undergone comprehensive regulatory reviews. In this work, we studied the stability of nisin A and Z in a selection of yogurt drinks and found nisin to be unstable, particularly in fruit-flavored yogurt drinks. Both nisin A and Z could experience significant degradation leading to the nisin parent ion peaks dropping below detectable level before the product's expiry date. Compared with nisin A, the formation of oxidized metabolite nisin Z+O appeared to be the predominant reaction for nisin Z. These findings highlight the need for further scientific research to understand the behavior of nisin Z under different application conditions, which is crucial for assessing the efficacy and safety of nisin Z under these conditions. One potential application of this knowledge is to optimize the formulation of yogurt-based drinks to stabilize nisin Z and sustain its biopreservative function throughout the product's shelf life. Additionally, the current study shows that for the testing of the presence of nisin A or nisin Z, it is imperative to cover both the parent and the main degradant(s) of nisin. This is especially true for nisin Z, for which the regulatory approval status may vary in different markets. As such, the confirmative identification of nisin Z and its key metabolites in commercial products would be essential.

Lactose malabsorption and intolerance: What is the correct management in older adults?

Lactose malabsorption is a very common condition due to intestinal lactase deficiency. Post weaning, a genetically programmed and irreversible reduction of lactase activity occurs in the majority of the world's population. Lactose malabsorption does not necessarily result in gastrointestinal symptoms, i.e. lactose intolerance, which occurs in approximately one third of those with lactase deficiency. In the absence of well-established guidelines, the common therapeutic approach tends to exclude milk and dairy products from the diet. However, this strategy may have serious nutritional disadvantages. Mainly in particular categories, such as the older adults, the approach to lactose malabsorption may deserve careful considerations. Milk and dairy products are an important supply of a wide range of nutrients that contribute to meet the nutritional needs in different life stages. Dietary composition can significantly impact the mechanisms leading to age-related loss of bone mineral density, skeletal muscle mass or function and overall risk of sarcopenia. Moreover, in the latest years, different lines of evidence have highlighted an association between dairy intake and prevention of chronic diseases as well as all-cause mortality. The aim of this opinion paper is to provide an overview of lactose malabsorption and intolerance in the older adults and their implications in clinical practice.

The Role of Bovine and Non-Bovine Milk in Cardiometabolic Health: Should We Raise the "Baa"?

Although causality is yet to be confirmed, a considerable volume of research has explored the relationships between cow milk consumption, type II diabetes, and cardiovascular disease. Contrastingly, it has not been comprehensively examined whether milk of non-bovine origin can provide cardiometabolic protection. This narrative review outlines the marked differences in macronutrient composition, particularly protein and lipid content, and discusses how whole milk product (and individual milk ingredients) from different species could impact cardiometabolic health. There is some data, although primarily from compositional analyses, animal studies, and acute clinical trials, that non-bovine milk (notably sheep and goat milk) could be a viable substitute to cow milk for the maintenance, or enhancement, of cardiometabolic health. With a high content of medium-chain triglycerides, conjugated linoleic acid, leucine, and essential minerals, sheep milk could assist in the prevention of metabolic-related disorders. Similarly, albeit with a lower content of such functional compounds relative to sheep milk, goat and buffalo milk could be plausible counterparts to cow milk. However, the evidence required to generate nutritional recommendations for ‘non-bovine milk’ is currently lacking. Longer-term randomised controlled trials must assess how the bioactive ingredients of different species’ milks collectively influence biomarkers of, and subsequently incidence of, cardiometabolic health.

Subjective, but not documented, lactose intolerance accompanies irritable bowel syndrome

Introduction

Lactose intolerance, due to lactase deficiency, may overlap with the symptoms of irritable bowel syndrome (IBS) or lead to an incorrect diagnosis of IBS. Identification of lactose intolerance and lactase deficiency enables targeted treatment to be implemented.

The aim of the study was to search for a frequency of a lactose intolerance symptoms in patients with IBS, depending on the results of hydrogen breath test (HBT).

Materials and Methods

The study involved 56 patients with IBS and 23 healthy people. Both, IBS patients and healthy controls, were asked to complete a survey about IBS symptoms and tolerance of lactose-containing products. A HBT was performed on all subjects.

Results

Lactase deficiency was diagnosed in 60.7% of patients with IBS and 43.5% of control group. The differences between the study groups were not statistically significant. No statistically significant differences were observed between the incidence of lactase deficiency depending on the type of IBS.

In the group of patients with IBS and normal HBT results, as well as in patients with IBS and lactase deficiency, there were no statistically significant differences in the frequency of lactose intolerance symptoms. However, among people with normal HBT results, patients with IBS reported symptoms of intolerance after consuming lactose-containing foods significantly more often compared to the control group (p<0.05).

Conclusions

Frequency of lactase deficiency does not differ between IBS patients and healthy individuals. Patients with IBS are more likely to report symptoms of lactose intolerance, regardless of the HBT result, compared to healthy individuals.

Compositional and functional properties of milk and dairy products derived from cows fed pasture or concentrate-based diets

Worldwide milk production is predominantly founded on indoor, high-concentrate feeding systems, whereas pasture-based feeding systems are most common in New Zealand and Ireland but have received greater attention recently in countries utilizing conventional systems. Consumer interest in 'pasture-fed' dairy products has also increased, arising from environmental, ethical, and nutritional concerns. A substantial body of research exists describing the effect of different feeding strategies on the composition of milk, with several recent studies focusing on the comparison of pasture- and concentrate-based feeding regimes. Significant variation is typically observed in the gross composition of milk produced from different supplemental feeds, but various changes in the discrete composition of macromolecular components in milk have also been associated with dietary influence, particularly in relation to the fatty acid profile. Changes in milk composition have also been shown to have implications for milk and dairy product processability, functionality and sensory properties. Methods to determine the traceability of dairy products or verify marketing claims such as 'pasture-fed' have also been established, based on compositional variation due to diet. This review explores the effects of feed types on milk composition and quality, along with the ultimate effect of diet-induced changes on milk and dairy product functionality, with particular emphasis placed on pasture- and concentrate-based feeding systems.

Relation of the C/T-13910 LCT Polymorphism with Body Composition Measures and Their Modulation by Dairy Products in a Caucasian Men

The C/T-13910 LCT is closely associated with lactase persistence and LCT has emerged as a new candidate gene for obesity, in particular in northern Europeans. The aim of this research is to investigate to what degree sex determines the association between the LCT variant and anthropometric traits in a cohort of healthy individuals. We recruited 1000 (500 males and 500 females aged 18-65 years) healthy blood donors. The C/T-13910 LCT polymorphism was genotyped using TaqMan assays. All individuals were phenotyped with respect to anthropometric characteristics. Prevalence of genotypes was 22.7% CC (lactase non-persistent, LNP), 58.6% CT, and 18.7% TT. LNP genotype was present less frequently among men p = .0005; OR 0.582 [0.425-0.794]. Therefore, in addition statistical calculations were performed separately for men and women. Additional analysis demonstrated an association between the CC genotypes and higher chest (p = .03), waist (p = .005), and forearm circumference (p = .0004) or more lean body mass (p = .04), than T-allele carriers in males. In females, they were not significantly different. Men consumed more milk (p = .003), while women ate more yoghurt (p = .001). Pearson's correlation analysis showed that the higher intake of milk and dairy products was associated with higher fat body mass among men with lactase persistence. In Caucasian men, the LNP genotype is associated with reduced milk intake and dairy products, but more fat-free mass and higher forearm circumference, which may be relevant to dietary management for lactose intolerant.

Do adults and older people follow current guidelines for milk consumption?

OBJECTIVE

To estimate the prevalence of frequent milk consumption (≥five times/week), the consumption of low-fat/skimmed milk and associated factors in adults and older people, evaluating adherence to current Brazilian guideline.

DESIGN

Population-based cross-sectional study involving the analysis of data from the 2015 Campinas Food Intake and Nutritional Status and 2015 Campinas Health Survey. The prevalence of milk consumption was analysed according to socio-economic characteristics, morbidities and health-related behaviours.

SETTING

City of Campinas, state of São Paulo, Brazil.

PARTICIPANTS

A sample of 1710 participants of the 2015 Campinas Nutritional and Health Surveys.

RESULTS

A total of 73·8 % of the population consumed milk, but the prevalence of frequent consumption was only 44·0 %. Frequent milk consumption was higher among women, older people and individuals with better diet quality. A total of 18·4 % of the individuals who consumed milk reported consuming low-fat/skimmed milk; this prevalence was higher among women, individuals with a higher socio-economic status, those with better diet quality and those with chronic diseases.

CONCLUSION

Despite the high nutritional quality of milk and the different types available on the market, adults and older people do not follow current recommendations regarding its consumption. Information on the nutritional quality of milk and current recommendations should be disseminated more at healthcare services.

Characterization of crystalline forms of gaxilose, a diagnostic drug

Lactose intolerance is a pathology caused by lactase enzyme deficiency, usually produced in the intestinal cells provoking symptoms as abdominal pain, bloating, diarrhea, gas and nausea. Gaxilose, 4-O-β-D galactopyranosyl-d-xylose, is used as a diagnostic drug for a non-invasive method for hypolactasia diagnosis. To date, no definitive guide for identifying gaxilose and distinguishing between crystalline forms is available. Data have been collected from a number of different analytical techniques in order to provide a full characterization of the compound and a simple method to discriminate between two solid forms.

Why and when was lactase persistence selected for? Insights from Central Asian herders and ancient DNA

The genetic adaptation of humans to the consumption of milk from dairying animals is one of the most emblematic cases of recent human evolution. While the phenotypic change under selection, lactase persistence (LP), is known, the evolutionary advantage conferred to persistent individuals remains obscure. One informative but underappreciated observation is that not all populations whose ancestors had access to milk genetically adapted to become lactase persistent. Indeed, Central Asian herders are mostly lactase nonpersistent, despite their significant dietary reliance on dairy products. Investigating the temporal dynamic of the -13.910:C>T Eurasian mutation associated with LP, we found that, after its emergence in Ukraine 5,960 before present (BP), the T allele spread between 4,000 BP and 3,500 BP throughout Eurasia, from Spain to Kazakhstan. The timing and geographical progression of the mutation coincides well with the migration of steppe populations across and outside of Europe. After 3,000 BP, the mutation strongly increased in frequency in Europe, but not in Asia. We propose that Central Asian herders have adapted to milk consumption culturally, by fermentation, and/or by colonic adaptation, rather than genetically. Given the possibility of a nongenetic adaptation to avoid intestinal symptoms when consuming dairy products, the puzzle then becomes this: why has LP been selected for at all?

Lactose intolerance in children and adults

Lactose is a disaccharide found in milk and dairy products. Children and adults with lactose intolerance are unable to tolerate significant amounts of lactose because of an inadequate amount of the enzyme lactase. The condition occurs in three main types: primary, secondary, and primary adult-type hypolactasia. The use of milk in the diet of these individuals may lead to appearance of the irritable bowel syndrome. In persons with lactose intolerance symptoms include diarrhoea, dominated by abdominal colic, loud peristaltic sounds, increased flatulence and meteorism. A diagnosis of lactose intolerance can usually be made with a careful history, elimination of lactose from the diet, lactose tolerance test, hydrogen breath test and genetic testing. In the absence of appropriate tests in patients with suspected primary adult-type hypolactasia, diagnosis can be made as in patients with food allergy. Treatment is based on the restriction of lactose intake with the use of fermented milk products. However, especially for children, if milk and dairy products are eliminated from the diet, it is important to ensure D vitamin and calcium supplementation.

Genetic and Oral Tests for the Diagnosis of Lactose Intolerance in Mixed-Ancestry Brazilians with Metabolic Syndrome

BACKGROUND/AIMS

Metabolic syndrome (MetS) comprises a cluster of physiological and anthropometric abnormalities. MetS has been linked to lactose intolerance (LI). The aim of this study was to compare the sensitivity and specificity to detect LI using 2 different tests: (1) a genetic test and (2) an oral lactose tolerance test (OLTT).

METHODS

Two hundred and fifty-four MetS patients, ≥20 years of age, of both genders, were recruited for this comparative study. Nine single nucleotide polymorphisms (SNPs) were selected for genetic investigation: rs182549and rs4988235(both considered "gold standard"); rs56064699; rs148142676; rs562211644; rs59533246; rs3754689; rs2278544,and rs10552864(as potential novel SNPs). Sensitivity and specificity, as well as positive and negative predictive values, were calculated for each genotype using WINPEPI version 11.65. Differences between positive and negative OLTT groups were considered statistically significant when p ≤ 0.05.

RESULTS

Among the selected SNPs, only rs182549(p < 0.001) and rs4988235(p < 0.001) gave similar results compared to an OLTT. The sensitivity of both SNPs to detect LI was 87 and 86%, and specificity was 83 and 82.5%, respectively.

CONCLUSION

Genetic tests using rs182549and rs4988235SNPs showed high agreement with OLTT. These genetic tests may be a good option to replace OLTT in MetS patients.

Comparison of Lactase Variant MCM6 -13910 C>T Testing and Self-report of Dairy Sensitivity in Patients With Irritable Bowel Syndrome

GOALS

To evaluate agreement of MCM6-13910 with self-report of dairy sensitivity (DS) and lactose hydrogen methane breath test (LHMBT) results in subjects with irritable bowel syndrome (IBS).

BACKGROUND

IBS is a functional gastrointestinal disorder with symptoms including abdominal pain, variable bowel habits, and bloating. Adult patients with lactose malabsorption may present with similar symptoms. Patients with lactose malabsorption have a lactase nonpersistent (LNP) phenotype. Recent studies found 2 single nucleotide polymorphisms associated with LNP: G/A-22018 and C/T-13910.

STUDY

Genotyping the MCM6-13910 variant of LNP in 538 IBS patients and 317 controls (without IBS). Subjects completed questionnaires pertaining to gastrointestinal problems and dietary consumption, with charts abstracted.

RESULTS

Self-reported DS was higher in IBS (45%) than controls (9.8%, odds ratio=6.46, P<0.001). The C/C-13910 genotype was similar in IBS cases and controls, 81 (15.1%) and 47 (14.8%). Among subjects reporting DS, 49 (18.0%) had the C/C genotype. Overall agreement between genotype and self-reported DS was 0.06 in IBS and 0.07 in controls. There were 20 subjects with LHMBT results; 3 had positive results, 17 were negative. LNP genotypes were found in all 3 of positive LHMBT results; 16 had negative LHMBT among the 17 who were lactase persistent. Agreement between C/C-13910 genotype and LHMBT was excellent with κ-statistic of 0.83 (0.50-1.00).

CONCLUSIONS

In IBS patients, self-report of lactose intolerance are highly prevalent but are a poor indicator of underlying C/C-13910 genotype. LHMBT had excellent agreement with C/C-13910 genotype.

A Cautionary Note on the Effects of Population Stratification Under an Extreme Phenotype Sampling Design

Extreme phenotype sampling (EPS) is a popular study design used to reduce genotyping or sequencing costs. Assuming continuous phenotype data are available on a large cohort, EPS involves genotyping or sequencing only those individuals with extreme phenotypic values. Although this design has been shown to have high power to detect genetic effects even at smaller sample sizes, little attention has been paid to the effects of confounding variables, and in particular population stratification. Using extensive simulations, we demonstrate that the false positive rate under the EPS design is greatly inflated relative to a random sample of equal size or a “case-control”-like design where the cases are from one phenotypic extreme and the controls randomly sampled. The inflated false positive rate is observed even with allele frequency and phenotype mean differences taken from European population data. We show that the effects of confounding are not reduced by increasing the sample size. We also show that including the top principal components in a logistic regression model is sufficient for controlling the type 1 error rate using data simulated with a population genetics model and using 1,000 Genomes genotype data. Our results suggest that when an EPS study is conducted, it is crucial to adjust for all confounding variables. For genetic association studies this requires genotyping a sufficient number of markers to allow for ancestry estimation. Unfortunately, this could increase the costs of a study if sequencing or genotyping was only planned for candidate genes or pathways; the available genetic data would not be suitable for ancestry correction as many of the variants could have a true association with the trait.

Genetic determinants of beverage consumption: Implications for nutrition and health

Beverages make important contributions to nutritional intake and their role in health has received much attention. This review focuses on the genetic determinants of common beverage consumption and how research in this field is contributing insight to what and how much we consume and why this genetic knowledge matters from a research and public health perspective. The earliest efforts in gene-beverage behavior mapping involved genetic linkage and candidate gene analysis but these approaches have been largely replaced by genome-wide association studies (GWAS). GWAS have identified biologically plausible loci underlying alcohol and coffee drinking behavior. No GWAS has identified variants specifically associated with consumption of tea, juice, soda, wine, beer, milk or any other common beverage. Thus far, GWAS highlight an important behavior-reward component (as opposed to taste) to beverage consumption which may serve as a potential barrier to dietary interventions. Loci identified have been used in Mendelian randomization and gene×beverage interaction analysis of disease but results have been mixed. This research is necessary as it informs the clinical relevance of SNP-beverage associations and thus genotype-based personalized nutrition, which is gaining interest in the commercial and public health sectors.

Inhibition of Maillard Reactions by Replacing Galactose with Galacto-Oligosaccharides in Casein Model Systems

Lactose reduced dairy products are more prone to Maillard reactions due to the presence of reactive monosaccharides. Conventional β-galactosidases, which are used for lactose hydrolysis in lactose-reduced dairy products, will lead to conversion of lactose into glucose and galactose, where especially galactose is very reactive during Maillard reactions. Some β-galactosidases have transgalactosylating activity and will thus convert lactose into galacto-oligosaccharides (GOS) and hereby limit the release of galactose. The aim of this study was to investigate the extent of participation of GOS in Maillard reactions in comparison to lactose, a 50:50 mixture of glucose and galactose, and galactose exclusively in sodium caseinate-based milk-like model systems heated at 130 and 75 °C at pH 6.8. The GOS system exhibited reduced loss of free amino groups; accumulated less furosine and less of the following advanced glycation end products (AGEs): N^ε-carboxyethyl lysine, methylglyoxal-derived hydroimidazolone isomers, glyoxal-derived lysine dimer, and methylglyoxal-derived lysine dimer; and also developed less browning compared to monosaccharide models. However, the GOS-caseinate system accumulated more 3-deoxyglucosone and 3-deoxygalactosone, which resulted in higher concentrations of 5-(hydroxymethyl)furfural and pyrraline. The results indicated that GOS overall participate less readily in Maillard reactions than the monosaccharides investigated but were more prone to degradation to C6 α-dicarbonyls species. Finally, relationship analysis indicated that C6 α-dicarbonyls seemed to primarily increase concentrations of 5-(hydroxymethyl)furfural instead of AGEs. Our results suggest that conversion of lactose into GOS instead of monosaccharides in milk by transgalactosylating β-galactosidases could be a useful strategy for production of lactose-free milk for people with lactose intolerance.

Lactose Intolerance, Dairy Avoidance, and Treatment Options

Lactose intolerance refers to symptoms related to the consumption of lactose-containing dairy foods, which are the most common source for this disaccharide. While four causes are described, the most common is the genetically-determined adult onset lactose maldigestion due to loss of intestinal lactase governed by control of the gene by a 14,000 kb promoter region on chromosome 2. Gastrointestinal symptoms from lactose have expanded to include systemic effects and have also been confounded by other food intolerances or functional gastrointestinal disorders. Partly because lactose maldigestion is often interpreted as lactose intolerance (symptoms), focus of therapy for these symptoms starts with lactose restriction. However, withholding of dairy foods completely is not appropriate due to a more favorable impact on health. Industrial efforts to substitute with plant-based products is not completely successful at this time. This narrative article reviews the complexities of the perception of lactose intolerance, its epidemiology, and pathogenesis. Treatments are discussed, including the inappropriateness of dairy avoidance. In conjunction, effects of dairy products on 19 common diseases are reviewed. Different methods of treatment, lactose-reduced products, plant-based dairy substitutes, adaptation, prebiotics, exogenous lactase, probiotics, and some other dietary interventions are further discussed.

Consistency of listed indications and contraindications between the U.S., the U.K., Japan, and Korea on prescription drug labels

Inclusion of indications and contraindications in drug labeling is essential for drug approval. Little is known regarding how well new drug information labels agree across countries. To compare the number of indications and contraindications on the labels of drugs in the U.S., U.K., Japan, and Korea, we selected 81 new drugs approved in these countries between 2008 and 2016 and assessed the number of indications and contraindications on each label. Average and median numbers with standard deviations were presented for the 81-drug set, and for subsets grouped according to drug class. Correlation analyses were conducted to estimate Pearson and concordance correlation coefficients. No significant difference was observed across countries in the number of indications, the average being 1.69, 1.67, 1.54, and 1.51 in the U.S., the U.K., Korea, and Japan (p = 0.31), respectively. By contrast, substantial variation was observed in the number of contraindications, the average being 1.54, 2.42, 3.53, and 3.00 in the U.S., the U.K., Korea, and Japan (p < 0.001), respectively. Pearson correlation coefficients comparing contraindications were 0.40, 0.48, and 0.47 for U.S.-U.K., U.S.-Korea, and U.S.-Japan, but 0.83, 0.73, and 0.71 for U.K.-Korea, U.K.-Japan, and Korea-Japan, respectively (p < 0.01). There is consistency in the number of indications, but a substantial discrepancy in contraindications listed in drug labeling across countries. Further study is warranted to improve global harmonization of contraindication listings.

Lactase deficiency and lactose intolerance in a multiracial Asian population in Malaysia

Background and Aims

There have been few reports on lactase deficiency (LD) and lactose intolerance (LI) in Malaysia, which has a peculiar mix of three distinct major Asian races-Malay, Chinese, and Indian. The aim of this study was to determine the prevalence of LD and LI in a young multiethnic Malaysian population.

Methods

Lactase activity was measured with a ¹³CO₂ lactose breath test using an infrared spectrometer. Each subject took 25 g of lactose naturally enriched in ¹³CO₂ together with 250 mL of water after an overnight fast. Breath samples were collected at baseline and at 15-min intervals for 180 min. Subjects were asked to report gastrointestinal (GI) symptoms following ingestion of the lactose test meal.

Results

Of the 248 subjects tested, 216 (87.1%) were lactase deficient. We found no significant differences in the presentation of LD between gender and races. LD was found in 87.5% of males and 86.8% of females (P = 0.975) and in different races: Chinese (88.5%) versus Malay (83.1%) (P = 0.399), Indian (90.5%) versus Malay (P = 0.295), and Chinese versus Indian (P = 0.902). LI was diagnosed in only 49 (19.8%) subjects; 35 patients had diarrhea, while the remainder had at least two other GI symptoms after the lactose meal.

Conclusion

The prevalence of LD was high in all three major ethnic groups-Malays, Chinese, and Indians. Ironically, the prevalence of LI was low overall.

Peroxisome proliferator-activated receptor gamma (PPARγ) regulates lactase expression and activity in the gut

Lactase (LCT) deficiency affects approximately 75% of the world's adult population and may lead to lactose malabsorption and intolerance. Currently, the regulation of LCT gene expression remains poorly known. Peroxisome proliferator activator receptorγ (PPARγ) is a key player in carbohydrate metabolism. While the intestine is essential for carbohydrate digestion and absorption, the role of PPARγ in enterocyte metabolic functions has been poorly investigated. This study aims at characterizing PPARγ target genes involved in intestinal metabolic functions. In microarray analysis, the LCT gene was the most upregulated by PPARγ agonists in Caco-2 cells. We confirmed that PPARγ agonists were able to increase the expression and activity of LCT both in vitro and in vivo in the proximal small bowel of rodents. The functional response element activated by PPARγ was identified in the promoter of the human LCT gene. PPARγ modulation was able to improve symptoms induced by lactose-enriched diet in weaned rats. Our results demonstrate that PPARγ regulates LCT expression, and suggest that modulating intestinal PPARγ activity might constitute a new therapeutic strategy for lactose malabsorption.

Analysis of LCT-13910 genotypes and bone mineral density in ancient skeletal materials

The relation of LCT-13910 genotypes and bone mineral density (BMD) has been the subject of modern-day human population studies, giving inconsistent results. In the present study we analyze for the first time a relation of LCT-13910 genotypes and BMD in historical skeletal individuals. Ancient population might be a model for testing this association due to elimination of non-natural factors affecting bone density. Among 22 medieval individuals from Sanok churchyard (South-Eastern Poland; dated from XIV to XVII c. AD) we identified 4 individuals with osteoporosis (mean BMD = 0.468 g/cm2, SD = 0.090), 10 individuals with osteopenia (mean BMD = 0.531 g/cm2, SD = 0.066) and 8 individuals with normal BMD values (mean BMD = 0,642 g/cm2, SD = 0.060). Analyses of BMD and LCT-13910 genotypes revealed that mean BMD was the highest (0.583 g/cm2, SD = 0.065) in the individuals with lactose tolerance genotypes (TT and CT). We also found possible association of lower BMD at the radius and CC genotypes due to higher but not statistically significant frequency of osteoporosis in the lactose intolerant group (p = 0.60). Statistically significant correlation was found between BMD and females aged 20-35 years, with tendency to reduce BMD with age (p = 0.02).

Breath Hydrogen Testing in East and Southeast Asia

Breath hydrogen tests are popular, noninvasive tests for the assessment of carbohydrate fermentation in patients with irritable bowel syndrome (IBS) and functional dyspepsia (FD). There is limited information regarding the utility of breath hydrogen and methane tests in IBS and FD patients in East and Southeast Asia. This review aims to summarize current literature about common indications of breath testing in this region, the genesis of functional gastrointestinal symptoms by provocative breath testing and provide suggestions for correct use. The most common testing indication is the assessment of lactose intolerance, followed by small intestinal bacterial overgrowth (SIBO) and differentiation of intestinal gas profiles in research setting. Studies in this region not only documented a high prevalence of lactose malabsorption but a population, both healthy and IBS, that is highly symptomatic to typical lactose intakes. Breath hydrogen assessment of other fermentable carbohydrates (FODMAPs) are fairly uncommon, whereas methane breath testing is almost nonexistent. Cumulative hydrogen production following lactulose was also not excessive in IBS patients compared with controls. The evidence however, for the detection of SIBO suggests limited reliability in the use of lactulose or glucose breath testing alone and inconclusive data on its correlation with symptoms. Conversely, little has been carried out in FD. In conclusion, breath testing should be limited in the predicting patients with SIBO for directing clinical management but can be considered in the objective assessment of lactose malabsorption within a low FODMAP diet. Recommendations to improve the interpretation of breath testing in research were also provided.

Weighted likelihood inference of genomic autozygosity patterns in dense genotype data

Background

Genomic regions of autozygosity (ROA) arise when an individual is homozygous for haplotypes inherited identical-by-descent from ancestors shared by both parents. Over the past decade, they have gained importance for understanding evolutionary history and the genetic basis of complex diseases and traits. However, methods to infer ROA in dense genotype data have not evolved in step with advances in genome technology that now enable us to rapidly create large high-resolution genotype datasets, limiting our ability to investigate their constituent ROA patterns.

Methods

We report a weighted likelihood approach for inferring ROA in dense genotype data that accounts for autocorrelation among genotyped positions and the possibilities of unobserved mutation and recombination events, and variability in the confidence of individual genotype calls in whole genome sequence (WGS) data.

Results

Forward-time genetic simulations under two demographic scenarios that reflect situations where inbreeding and its effect on fitness are of interest suggest this approach is better powered than existing state-of-the-art methods to infer ROA at marker densities consistent with WGS and popular microarray genotyping platforms used in human and non-human studies. Moreover, we present evidence that suggests this approach is able to distinguish ROA arising via consanguinity from ROA arising via endogamy. Using subsets of The 1000 Genomes Project Phase 3 data we show that, relative to WGS, intermediate and long ROA are captured robustly with popular microarray platforms, while detection of short ROA is more variable and improves with marker density. Worldwide ROA patterns inferred from WGS data are found to accord well with those previously reported on the basis of microarray genotype data. Finally, we highlight the potential of this approach to detect genomic regions enriched for autozygosity signals in one group relative to another based upon comparisons of per-individual autozygosity likelihoods instead of inferred ROA frequencies.

Conclusions

This weighted likelihood ROA inference approach can assist population- and disease-geneticists working with a wide variety of data types and species to explore ROA patterns and to identify genomic regions with differential ROA signals among groups, thereby advancing our understanding of evolutionary history and the role of recessive variation in phenotypic variation and disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-017-4312-3) contains supplementary material, which is available to authorized users.

Country, regional, and global estimates for lactose malabsorption in adults: a systematic review and meta-analysis

BACKGROUND

Studies have shown wide variation in the prevalence of lactose malabsorption across the world, but no systematic reviews or meta-analyses have recently assessed the prevalence of lactose malabsorption in different geographical areas. We aimed to present an updated systematic review and meta-analysis on the prevalence of lactose malabsorption in adults, by countries and regions, and to assess the variation between different testing methods.

METHODS

Studies reporting on prevalence of lactose malabsorption and lactase persistence were identified by searching MEDLINE and Embase from database inception to Nov 2, 2016. We evaluated studies presenting lactose malabsorption or lactase persistence prevalence data in adults and children aged 10 years or older, including cross-sectional and prospective studies, using genotyping, hydrogen breath tests, lactose tolerance tests, and other testing methods. We excluded studies in children younger than 10 years, studies using self-reported data, and studies including inpatients and outpatients at gastroenterological wards. Studies were screened by two authors (CLS and SKF) and data values were extracted by two authors (CLS and SKF) independently. The primary outcome was the prevalence of lactose malabsorption. This study is registered with PROSPERO, number CRD42017064802.

FINDINGS

We screened 2665 records, and 306 study populations from 116 full-text articles were included (primary sources); data for 144 additional study populations from 59 articles were obtained from review articles, because full-text primary articles could not be obtained (secondary sources). Of the 450 study populations included, 231 were assessed by genotyping, 83 by hydrogen breath tests, 101 by lactose tolerance tests, and 35 by other methods or methods that were not described sufficiently. The studies included 62 910 participants from 89 countries (covering 84% of the world's population). When standardising for country size, the global prevalence estimate of lactose malabsorption was 68% (95% CI 64-72), ranging from 28% (19-37) in western, southern, and northern Europe to 70% (57-83) in the Middle East. When assessing the global prevalence using genotyping data only, the estimate was 74% (69-80), whereas prevalence was 55% (46-65) using lactose tolerance test data, and 57% (46-67) using hydrogen breath test data. Risk of bias was assessed based on ten indicators; 12 of the articles had a score of ten, indicating low risk of bias, 76 had a score of nine, 26 a score of eight, and two articles a score of seven (indicating higher risk of bias). There was substantial heterogeneity between studies within most of the assessed countries.

INTERPRETATION

Lactose malabsorption is widespread in most of the world, with wide variation between different regions and an overall frequency of around two-thirds of the world's population. Acknowledging regional patterns of lactose malabsorption is important to guide management of gastrointestinal symptoms.

FUNDING

None.

Gastrointestinal Symptoms and FODMAP Intake of Aged-Care Residents from Christchurch, New Zealand

Studies on fermentable oligo-, di-, and monosaccharides as well as polyols (FODMAPs) intake in older adults are lacking. This study investigated the relationship between gastrointestinal (GI) symptoms and FODMAPs in aged care residents. The Gastrointestinal Symptom Rating Score questionnaire modified for patients with IBS (GSRS-IBS) was used to identify participants with IBS-like symptoms. Dietary intake was assessed for a subgroup of participants with highest total GSRS-IBS score (symptomatic cases) and age, sex, and level of care matched participants with low total GSRS-IBS score (asymptomatic controls). Seventy-four participants with a mean (SD) age of 86 (6.6) years completed the GSRS-IBS questionnaire and dietary data were collected using food diaries from a subsample of 27 symptomatic and 27 asymptomatic participants. The study found many older adults with functional gut symptoms. There were no differences between the groups for FODMAP intake and no significant relationship was found between FODMAP intake and total GSRS-IBS score. Lactose from milk and milk-based desserts was the biggest FODMAP contributor (16 g/day) and a significant relationship between total FODMAP intake and diarrhoea was found. A larger study sample in future studies is required to better capture symptomatic cases and manipulation of dietary FODMAPs may assist with the management of IBS in the elderly.

Lactase persistence in Tunisia as a result of admixture with other Mediterranean populations

Background

The ability to digest lactose after weaning, namely, lactase persistence (LP), is encoded by polymorphisms in the MCM6 gene and varies widely in frequency among different human populations. Although, evolution of LP-related genetic variants was investigated in many groups of Sub-Saharan African, Middle Eastern, and European ancestry, only few studies have focused on populations from North Africa and no data are especially available from the Tunisian one. For this reason, there is an urgent need to investigate the frequency patterns at these loci in Tunisia since this adaptive trait is implicated in health.

Methods

Forty SNPs covering the LCT/MCM6 genes and including the two functional variants − 13,910 C > T and − 22,018 G > A were genotyped in 117 Tunisian individuals using the Sequenom Mass Array technology. The observed nucleotide and haplotype patterns of variation were then compared with those of several African, European, and Mediterranean human groups for which comparable data were publicly available. Admixture analysis on a 5 Mb genomic region surrounding the LCT/MCM6 loci was also performed by extracting genotypes from a previously generated genome-wide dataset in order to deepen the reconstruction of the evolutionary history of these loci.

Results

We found that lactase non-persistence (LNP)-related alleles and haplotypes were predominantly present in the examined population. A clear differentiation between Tunisian, African, and North European/North Italian samples was found, while the Tunisian population showed more genetic affinity to Central and South Italian groups.

Conclusions

Our study provided a first report of LP-associated alleles and haplotypes in the Tunisian population. We highlighted a gradient followed by LP diffusion from Europe to North Africa. Based on the rich historic background of Tunisia, we suggest that this adaptive trait was introduced in that geographic region by a relatively recent gene flow.

Electronic supplementary material

The online version of this article (doi:10.1186/s12263-017-0573-3) contains supplementary material, which is available to authorized users.

Prevalence of abnormal lactose breath hydrogen tests in children with functional abdominal pain

OBJECTIVES

The study was undertaken to determine the prevalence of abnormal lactose breath hydrogen test in children with non-organic chronic abdominal pain.

METHODS

Children with chronic abdominal pain were examined and investigated for organic causes. All children without a known organic cause underwent lactose and glucose breath hydrogen test. After a standard dose of 2 g/kg of lactose to a maximum of 50 g, hydrogen in breath was measured at 15 min intervals for 3 h. A rise of 20 ppm above baseline was considered suggestive of lactose malabsorption.

RESULTS

Of 108 children screened, organic causes were found in 46 children. Sixty-two patients without any organic cause underwent hydrogen breath test. Lactose hydrogen breath test (HBT) was positive in 36 of 62 (58%), while 11 (17%) had positive HBT with glucose suggestive of small intestinal bacterial overgrowth (SIBO). Twenty out of 34 (59%) improved on lactose free diet while 8 out of 11 (72%) children of SIBO improved on antibiotics.

CONCLUSIONS

Lactose malabsorption was seen in 58% of children with non-organic chronic abdominal pain.

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.

Update on diagnostic value of breath test in gastrointestinal and liver diseases

In the field of gastroenterology, breath tests (BTs) are used intermittently as diagnostic tools that allow indirect, non-invasive and relatively less cumbersome evaluation of several disorders by simply quantifying the appearance in exhaled breath of a metabolite of a specific substrate administered. The aim of this review is to have an insight into the principles, methods of analysis and performance parameters of various hydrogen, methane and carbon BTs which are available for diagnosing gastrointestinal disorders such as Helicobacter pylori infection, small intestinal bacterial overgrowth, and carbohydrate malabsorption. Evaluation of gastric emptying is routinely performed by scintigraphy which is however, difficult to perform and not suitable for children and pregnant women, this review has abridged the 13C-octanoic acid test in comparison to scintigraphy and has emphasized on its working protocol and challenges. A new development such as electronic nose test is also highlighted. Moreover we have also explored the limitations and constraints restraining the wide use of these BT. We conclude that breath testing has an enormous potential to be used as a diagnostic modality. In addition it offers distinct advantages over the traditional invasive methods commonly employed.

Do patients with lactose intolerance exhibit more frequent comorbidities than patients without lactose intolerance? An analysis of routine data from German medical practices

Background

The increase in food intolerances poses a burgeoning problem in our society. Food intolerances not only lead to physical impairment of the individual patient but also result in a high socio-economic burden due to factors such as the treatment required as well as absenteeism. The present study aimed to explore whether lactose intolerant (LI) patients exhibit more frequent comorbidities than non-LI patients.

Methods

The study was conducted on a case-control basis and the results were determined using routine data analysis. Routine data from the IMS Disease Analyzer database were used for this purpose. A total of 6,758 data records were processed and analyzed.

Results

There were significant correlations between LI and the incidence of osteoporosis, changes in mental status, and the presence of additional food intolerances. Comparing 3,379 LI vs. 3,379 non-LI patients, 34.5% vs. 17.7% (P<0.0001) suffered from abdominal pain; 30.6% vs. 17.2% (P<0.0001) from gastrointestinal infections; and 20.9% vs. 16.0% (P=0.0053) from depression. Adjusted odds ratios (OR) were the highest for fructose intolerance (n=229 LI vs. n=7 non-LI; OR 31.06; P<0.0001), irritable bowel syndrome (n=247 LI vs. n=44 non-LI; OR 5.23; P<0.0001), and bloating (n=351 LI vs. n=68 non-LI; OR 4.94; P<0.0001).

Conclusion

The study confirms that LI should not be regarded as an isolated illness but considered a possible trigger for further diseases. Additional research is necessary to assert more precise statements.

The Interrelationships between Lactose Intolerance and the Modern Dairy Industry: Global Perspectives in Evolutional and Historical Backgrounds

Humans learned to exploit ruminants as a source of milk about 10,000 years ago. Since then, the use of domesticated ruminants as a source of milk and dairy products has expanded until today when the dairy industry has become one of the largest sectors in the modern food industry, including the spread at the present time to countries such as China and Japan. This review analyzes the reasons for this expansion and flourishing. As reviewed in detail, milk has numerous nutritional advantages, most important being almost an irreplaceable source of dietary calcium, hence justifying the effort required to increase its consumption. On the other hand, widespread lactose intolerance among the adult population is a considerable drawback to dairy-based foods consumption. Over the centuries, three factors allowed humans to overcome limitations imposed by lactose intolerance: (i) mutations, which occurred in particular populations, most notably in the north European Celtic societies and African nomads, in which carriers of the lactose intolerance gene converted from being lactose intolerant to lactose tolerant; (ii) the ability to develop low-lactose products such as cheese and yogurt; and (iii) colon microbiome adaptation, which allow lactose intolerant individuals to overcome its intolerance. However, in a few examples in the last decade, modern dairy products, such as the popular and widespread bio-cultured yogurts, were suspected to be unsuitable for lactose intolerant peoples. In addition, the use of lactose and milk-derived products containing lactose in non-dairy products has become widespread. For these reasons, it is concluded that it might be important and helpful to label food that may contain lactose because such information will allow lactose intolerant groups to control lactose intake within the physiological limitations of ~12 g per a single meal.

The Diverse Forms of Lactose Intolerance and the Putative Linkage to Several Cancers

Lactase-phlorizin hydrolase (LPH) is a membrane glycoprotein and the only β-galactosidase of the brush border membrane of the intestinal epithelium. Besides active transcription, expression of the active LPH requires different maturation steps of the polypeptide through the secretory pathway, including N- and O-glycosylation, dimerization and proteolytic cleavage steps. The inability to digest lactose due to insufficient lactase activity results in gastrointestinal symptoms known as lactose intolerance. In this review, we will concentrate on the structural and functional features of LPH protein and summarize the cellular and molecular mechanism required for its maturation and trafficking. Then, different types of lactose intolerance are discussed, and the molecular aspects of lactase persistence/non-persistence phenotypes are investigated. Finally, we will review the literature focusing on the lactase persistence/non-persistence populations as a comparative model in order to determine the protective or adverse effects of milk and dairy foods on the incidence of colorectal, ovarian and prostate cancers.

Prevalence of self-reported stomach symptoms after consuming milk among indigenous Sami and non-Sami in Northern- and Mid-Norway - the SAMINOR study

Objective

The main purpose of this work was to identify the prevalence of self-reported stomach symptoms after consuming milk among Sami and non-Sami adults.

Study design

A cross-sectional population-based study (the SAMINOR study). Data were collected by self-administrated questionnaires.

Method

SAMINOR is a population-based study of health and living conditions conducted in 24 municipalities in Northern Norway during 2003 and 2004. The present study included 15,546 individuals aged between 36 and 79, whose ethnicity was categorized as Sami (33.4%), Kven (7.3%) and Norwegian majority population (57.2%).

Results

Sami respondents had a higher prevalence of self-reported stomach symptoms after consuming milk than the Norwegian majority population. The reporting was highest among Sami females (27.1%). Consumption of milk and dairy products (yoghurt and cheese) was high among all the ethnic groups. However, significantly more Sami than non-Sami never (or rarely) consume milk or cheese, and individuals who reported stomach symptoms after consuming milk had an significant lower intake of dairy products than those not reporting stomach symptoms after consuming dairy products. Sami reported general abdominal pain more often than the majority population. The adjusted models show a significant effect of Sami ethnicity in both men and women on self-reported stomach symptoms after consuming milk. In females, the odds ratio (OR)=1.77 (p=0.001) and in males OR=1.64 (p=0.001).

Conclusion

Our study shows that the Sami population reported more stomach symptoms after consuming milk, suggesting a higher prevalence of milk intolerance among the Sami population than the Norwegian majority population.

Lactose intolerance and risk of lung, breast and ovarian cancers: aetiological clues from a population-based study in Sweden

Background:

Individuals with lactose intolerance are recommended to avoid milk or dairy products, which may affect the development of cancer.

Methods:

We identified individuals with lactose intolerance from several Swedish Registers linked to the Swedish Cancer Registry to calculate standardised incidence ratios (SIRs) for cancers in the breast, lung, and ovary.

Results:

A total of 22 788 individuals with lactose intolerance were identified, and their risks of lung (SIR=0.55), breast (SIR=0.79), and ovarian (SIR=0.61) cancers were significantly decreased. Cancer incidences in the siblings and parents of individuals with lactose intolerance were similar to those in the general population.

Conclusions:

In this large cohort study, people with lactose intolerance, characterised by low consumption of milk and other dairy products, had decreased risks of lung, breast, and ovarian cancers, but the decreased risks were not found in their family members, suggesting that the protective effects against these cancers may be related to their specific dietary pattern.

Lactose intolerance genetic testing: is it useful as routine screening? Results on 1426 south-central Italy patients

Adult-type hypolactasia is a widespread condition throughout the world, causing lactose malabsorption. Several studies suggested that the identification of C/T-13910 and G/A-22018 mutations, located upstream the gene encoding the lactase-phlorizin hydrolase (LPH), is a useful tool for the differential diagnosis of hypolactasia. We evaluated the frequencies of C/T-13910 and G/A-22018 variants in a central-south Italian population and the usefulness of lactase deficiency genetic testing in the clinic practice. The genomic DNA of 1426 patients and 1000 healthy controls from central-south Italy was isolated from peripheral whole blood and genotyped for the C/T-13910 and G/A-22018 polymorphisms by high-resolution melting analysis (HRMA) and sequencing. The frequencies of genotypes in the 1426 patients analysed were as follows: 1077 CC/GG (75.5%), 287 CT/GA (20.1%), 24 TT/AA (1.7%), 38 CC/GA (2.7%). Only 64 out of 1426 (4.5%) performed also L-BHT test, 29 of which were negative for L-BHT also in presence of different genotypes. Among the 35 individuals with L-BHT positive, 34 were CC/GG and only one CT/GA. Although lactose genetic test is a good predictor of persistence/non-persistence lactase in specific population, its use in the central-south Italy population should be limited given the high prevalence of the CCGG diplotype in normal individuals.

Lactose intolerance and other disaccharidase deficiency

Intolerance to foods which contain lactose can cause a range of intestinal and systemic symptoms. These symptoms are caused by Lactase deficiency which is encoded by a single gene (LCT) of ≈ 50 kb located on chromosome 2q21. In some food items, lactose has been missed because of "hidden" lactose due to inadequately labeled, confusing diagnosis of lactose intolerance based on dietary restriction of dairy foods. Two polymorphisms, C/T13910 and G/A22018, linked to hypolactasia, correlate with breath hydrogen and symptoms after lactose. The key in the management of lactose intolerance is the dietary removal of lactose. Patients diagnosed as lactose intolerant must be advised of "risk" foods, inadequately labeled, including processed meats, bread, cake mixes, soft drinks, and lagers. This review highlights the types, symptoms and management of lactose intolerance and also highlights differences from milk allergy which closely mimics the symptoms of lactose intolerance.

Retrospective and prospective perspectives on zoonotic brucellosis

Members of the genus Brucella are pathogenic bacteria exceedingly well adapted to their hosts. The bacterium is transmitted by direct contact within the same host species or accidentally to secondary hosts, such as humans. Human brucellosis is strongly linked to the management of domesticated animals and ingestion of their products. Since the domestication of ungulates and dogs in the Fertile Crescent and Asia in 12000 and 33000 ya, respectively, a steady supply of well adapted emergent Brucella pathogens causing zoonotic disease has been provided. Likewise, anthropogenic modification of wild life may have also impacted host susceptibility and Brucella selection. Domestication and human influence on wild life animals are not neutral phenomena. Consequently, Brucella organisms have followed their hosts’ fate and have been selected under conditions that favor high transmission rate. The “arm race” between Brucella and their preferred hosts has been driven by genetic adaptation of the bacterium confronted with the evolving immune defenses of the host. Management conditions, such as clustering, selection, culling, and vaccination of Brucella preferred hosts have profound influences in the outcome of brucellosis and in the selection of Brucella organisms. Countries that have controlled brucellosis systematically used reliable smooth live vaccines, consistent immunization protocols, adequate diagnostic tests, broad vaccination coverage and sustained removal of the infected animals. To ignore and misuse tools and strategies already available for the control of brucellosis may promote the emergence of new Brucella variants. The unrestricted use of low-efficacy vaccines may promote a “false sense of security” and works towards selection of Brucella with higher virulence and transmission potential.

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.

Noninvasive diagnosis of hypolactasia with 4-Galactosylxylose (Gaxilose): a multicentre, open-label, phase IIB-III nonrandomized trial

GOALS AND BACKGROUND

Hypolactasia affects over half of the world population. Diagnosis remains problematic as currently available tests, such as the hydrogen breath test, have low reliability and lactose intolerance symptoms are unspecific. We evaluated the diagnostic performance and safety of a new noninvasive diagnostic test based on urine or serum measurement of D-xylose after lactase cleavage of orally administered 4-galactosylxylose (gaxilose).

STUDY

In a multicentre, open-label, nonrandomized, phase IIb-III study, consecutive patients with symptoms suggestive of lactose intolerance sequentially underwent intestinal biopsy for direct measurement of lactase activity (reference standard), hydrogen breath test, and blood glucose test after lactose challenge, 4- and 5-hour urine-based gaxilose test, and blood-based gaxilose test. For the gaxilose tests, 0 to 4 and 4 to 5 hours urine samples were taken after a 0.45 g gaxilose dose, whereas serum samples were taken 90 minutes after a 2.7 g dose for D-xylose determination. Genetic testing of hypolactasia was also assessed.

RESULTS

Of the 222 patients enrolled, 203 completed all diagnostic tests; 108 were hypolactasic according to biopsy. The sensitivities and specificities and positive and negative predictive values of the gaxilose tests were all >90% versus 69% to 85% for the hydrogen breath test and the blood glucose test. The area under the ROC curve was significantly higher for the gaxilose tests (>0.9, P≤0.007). These tests also had higher sensitivity than genetic testing for hypolactasia and were well tolerated.

CONCLUSIONS

The diagnostic performance of the gaxilose tests is excellent and can substantially improve the diagnosis of hypolactasia.

The uncertain significance of low vitamin D levels in African descent populations: a review of the bone and cardiometabolic literature

Vitamin D levels in people of African descent are often described as inadequate or deficient. Whether low vitamin D levels in people of African descent lead to compromised bone or cardiometabolic health is unknown. Clarity on this issue is essential because if clinically significant vitamin D deficiency is present, vitamin D supplementation is necessary. However, if vitamin D is metabolically sufficient, vitamin D supplementation could be wasteful of scarce resources and even harmful. In this review vitamin D physiology is described with a focus on issues specific to populations of African descent such as the influence of melanin on endogenous vitamin D production and lactose intolerance on the willingness of people to ingest vitamin D fortified foods. Then data on the relationship of vitamin D to bone and cardiometabolic health in people of African descent are evaluated.