Ancient Europeans farmed dairy-but couldn't digest milk.

Giant study of ancient pottery and DNA challenges common evolutionary explanation for lactase persistence.

Development of a novel SNP assay to detect lactase persistence associated genetic variants.

BACKGROUND: In adulthood the activity of the lactase enzyme is inherited as autosomal dominant form associated to Single nucleotide polymorphisms (SNPs). The present research was aimed to develop a novel genetic method to test lactase non persistence more powerfully. METHODS AND RESULTS: In our study, we selected eight different SNPs that are associated with lactase persistence from Caucasian, Arabian Bedouins, sub-Saharian Africans and Asian populations to set up an approach to detect all the eight different SNPs at the same time in the same sample. This technique is centred on the identification of SNPs with a single nucleotide primer extension method using Sanger sequencing and capillary electrophoresis. CONCLUSIONS: Our method allowed us to check the genotype asset of eight SNPs related to lactase persistence simultaneously and in a very efficient manner. It could be applied to a higher number of SNPs in a single reaction.

Clinical Utility of LCT Genotyping in Children with Suspected Functional Gastrointestinal Disorder.

Genetic testing is a good predictor of lactase persistence (LP) in specific populations but its clinical utility in children is less clear. We assessed the role of lactose malabsorption in functional gastrointestinal disorders (FGID) in children and the correlation between the lactase non-persistence (LNP) genotype and phenotype, based on exhaled hydrogen and gastrointestinal symptoms, during a hydrogen breath test (HBT). We also evaluate dairy consumption in this sample. We conducted a 10-year cross-sectional study in a cohort of 493 children with suspected FGID defined by Roma IV criteria. Distribution of the C/T-13910 genotype was as follows: CC, 46.0%; TT, 14.4% (LP allele frequency, 34.1%). The phenotype frequencies of lactose malabsorption and intolerance were 36.3% and 41.5%, respectively. We observed a strong correlation between genotype and both lactose malabsorption (Cramér's V, 0.28) and intolerance (Cramér's V, 0.54). The frequency of the LNP genotype (p = 0.002) and of malabsorption and intolerance increased with age (p = 0.001 and 0.002, respectively). In 61% of children, evaluated dairy consumption was less than recommended. No association was observed between dairy intake and diagnosis. In conclusion, we found a significant correlation between genotype and phenotype, greater in older children, suggesting that the clinical value of genetic testing increases with age.

Analysis of lactase in lactose intolerance supplements.

Lactase is the enzyme responsible for the digestion of the disaccharide lactose, and deficiency in this enzyme causes the prevalent medical condition lactose intolerance. Management of lactose intolerance can be achieved through the administration of lactase supplements. Lactase is an appropriate platform for advanced enzymatic study because its medical application is a motivator for student learning. The following is an upper-level biochemistry laboratory sequence that integrates student inquiry and exposure to advanced laboratory techniques. Students investigate three different lactase supplements through experimentation that includes the Bradford assay, SDS-PAGE, continuous and discontinuous kinetic assays, and zymography. Upon completion of this project, students compile their results and conclusions in a scientifically formatted paper comparing supplement protein content and activity. This safe and inexpensive laboratory project enriches student understanding of key biochemical concepts while mirroring work performed in a realistic research setting. © 2018 International Union of Biochemistry and Molecular Biology, 46(6):652-662, 2018.

Differences in DNA Methylation and Functional Expression in Lactase Persistent and Non-persistent Individuals.

In humans the expression of lactase changes during post-natal development, leading to phenotypes known as lactase persistence and non-persistence. Polymorphisms within the lactase gene (LCT) enhancer, in particular the -13910C > T, but also others, are linked to these phenotypes. We were interested in identifying dynamic mediators of LCT regulation, beyond the genotype at -13910C > T. To this end, we investigated two levels of lactase regulation in human intestinal samples obtained from New England children and adolescents of mixed European ancestry: differential expression of transcriptional regulators of LCT, and variations in DNA methylation, and their relation to phenotype. Variations in expression of CDX2, POU2F1, GATA4, GATA6, and HNF1α did not correlate with phenotype. However, an epigenome-wide approach using the Illumina Infinium HM450 bead chip identified a differentially methylated position in the LCT promoter where methylation levels are associated with the genotype at -13910C > T, the persistence/non-persistence phenotype and lactase enzymatic activity. DNA methylation levels at this promoter site and CpGs in the LCT enhancer are associated with genotype. Indeed, taken together they have a higher power to predict lactase phenotypes than the genotype alone.

Lactase persistence, milk intake, hip fracture and bone mineral density: a study of 97 811 Danish individuals and a meta-analysis.

BACKGROUND: Whether a causal relationship exists between milk intake and reduced risk of fractures is unclear. OBJECTIVES: We tested the hypothesis that genetically determined milk intake reduces the risk of fractures and increases bone mineral density (BMD). METHODS: We investigated the association between milk intake, LCT-13910 C/T (rs4988235), which is associated with lactase persistence (TT/TC) in Northern Europeans, and hip fractures in three Danish prospective studies (N = 97 811, age ≥20 years). We added meta-analyses of LCT-13910 and fractures and BMD from five published Northern European population studies. RESULTS: In the Danish studies, the adjusted hazard ratio (HR) for hip fracture per one glass per week higher milk intake was 1.00 (95% CI: 0.99-1.01). The per T-allele milk intake was 0.58 (0.49-0.68) glasses per week, but HR was 1.01 (0.94-1.09) for hip fracture. In meta-analyses of Danish studies with published Northern European population studies, the random effects odds ratio for any fracture was 0.86 (0.61-1.21; I2 = 73%) for TT vs. CC and 0.90 (0.68-1.21; I2 = 63%) for TC vs. CC. The standardized mean difference in femoral neck BMD was 0.10 (0.02-0.18; I2 = 0%) g cm-2 for TT vs. CC and 0.06 (-0.04 to 0.17; I2 = 17%) g cm-2 for TC vs. CC. There were no differences in lumbar spine or total hip BMD comparing TT or TC with CC. CONCLUSION: Genetically lifelong lactase persistence with high milk intake was not associated with hip fracture in Danish population-based cohorts. A meta-analysis combining Danish studies with published Northern European population studies also showed that lactase persistence was not associated with fracture risk. Genetic lactase persistence was associated with a higher femoral neck BMD, but not lumbar spine or total hip BMD.

Lactase persistence, milk intake, and mortality in the Danish general population: a Mendelian randomization study.

Meta-analyses have suggested no association between milk intake and mortality. Since only few studies have been conducted, we investigated the association between the lactase persistent genetic variant LCT-13910 C/T (rs4988235), a proxy for long-term low and high intake of milk, and mortality. We used two Danish population-based studies with self-reported intake of milk and genotyping for LCT-13910 C/T. We obtained information on all-cause and cause-specific mortality (cardiovascular and cancer) from the national Danish registries. We used multivariable adjusted Cox regression to assess the association between milk intake and mortality in 74,241 individuals, and both logistic and Cox-regression to assess the association between genetic lactase persistence and mortality in 82,964 individuals using a Mendelian randomization design. We applied per T-allele, co-dominant and dominant models. During a mean follow-up of 7 years, 9759 individuals died, 2166 from cardiovascular disease, and 2822 from cancer. Observationally, there was no association between intake of skimmed milk and all-cause or cardiovascular mortality, and we did not find any associations between intake of semi-skimmed or whole milk with all-cause or cause-specific mortality. Intake of skimmed milk was associated with lower cancer mortality with a hazard ratio of 0.97 (95% CI 0.96-1.00) per doubling in milk intake. Per T-allele, milk intake increased with 0.58 (0.50-0.68) glasses/week. Genetically, we found no associations between the lactase persistent LCT-13910 C/T genotype and all-cause or cause-specific mortality; per T-allele OR (95% CI) for all-cause mortality was 1.02 (0.97-1.06). Our study did not provide strong evidence of observational or genetic associations between milk intake and all-cause or cause-specific mortality.

World-wide distributions of lactase persistence alleles and the complex effects of recombination and selection.

The genetic trait of lactase persistence (LP) is associated with at least five independent functional single nucleotide variants in a regulatory region about 14 kb upstream of the lactase gene [-13910*T (rs4988235), -13907*G (rs41525747), -13915*G (rs41380347), -14009*G (rs869051967) and -14010*C (rs145946881)]. These alleles have been inferred to have spread recently and present-day frequencies have been attributed to positive selection for the ability of adult humans to digest lactose without risk of symptoms of lactose intolerance. One of the inferential approaches used to estimate the level of past selection has been to determine the extent of haplotype homozygosity (EHH) of the sequence surrounding the SNP of interest. We report here new data on the frequencies of the known LP alleles in the 'Old World' and their haplotype lineages. We examine and confirm EHH of each of the LP alleles in relation to their distinct lineages, but also show marked EHH for one of the older haplotypes that does not carry any of the five LP alleles. The region of EHH of this (B) haplotype exactly coincides with a region of suppressed recombination that is detectable in families as well as in population data, and the results show how such suppression may have exaggerated haplotype-based measures of past selection.

Lactase Non-persistence and Lactose Intolerance.

PURPOSE OF REVIEW: To evaluate the clinical and nutritional significance of genetically determined lactase non-persistence and potential lactose and milk intolerance in 65-70% of the world's adult population. RECENT FINDINGS: Milk consumption is decreasing in the USA and is the lowest in countries with a high prevalence of lactase non-persistence. The dairy industry and Minnesota investigators have made efforts to minimize the influence of lactose intolerance on milk consumption. Some lactose intolerant individuals, without co-existent irritable bowel syndrome, are able to consume a glass of milk with a meal with no or minor symptoms. The high frequency of lactase persistence in offspring of Northern European countries and in some nomadic African tribes is due to mutations in the promoter of the lactase gene in association with survival advantage of milk drinking. Educational and commercial efforts to improve calcium and Vitamin D intake have focused on urging consumption of tolerable amounts of milk with a meal, use of lowered lactose-content foods including hard cheeses, yogurt, and lactose-hydrolyzed milk products.

Recent advances on lactose intolerance: Tolerance thresholds and currently available answers.

The genetically programmed reduction in lactase activity during adulthood affects 70% of the world adult population and can cause severe digestive disorders, which are the sign of lactose intolerance. Lactose intolerance symptoms vary depending on the residual lactase activity, the small bowel transit time, and especially the amount of ingested lactose. To formulate dairy products suitable for the vast majority of lactose intolerants, it is essential to define lactose intolerance threshold. A recent meta-analysis permitted to show that almost all lactose intolerants tolerate 12 g of lactose in one intake and approximately 18 g of lactose spread over the day. The prevalence and severity of lactose intolerance are probably overestimated by the general public. This misconception usually leads to an unnecessary reduction of dairy foodstuff consumption. Nevertheless, dairy products are essential for health mainly due to their calcium content and the positive influence of probiotic bacteria. The formulation of dairy products suitable for most intolerant and suspicious subjects seems necessary. The use of exogenous enzyme preparations, as well as the consumption of lactose-free products or products rich in probiotic bacteria are proposed as symptom-reducing strategies.

Lactase nonpersistence is directed by DNA-variation-dependent epigenetic aging.

The inability to digest lactose, due to lactase nonpersistence, is a common trait in adult mammals, except in certain human populations that exhibit lactase persistence. It is not known how the lactase gene is dramatically downregulated with age in most individuals but remains active in some individuals. We performed a comprehensive epigenetic study of human and mouse small intestines, by using chromosome-wide DNA-modification profiling and targeted bisulfite sequencing. Epigenetically controlled regulatory elements accounted for the differences in lactase mRNA levels among individuals, intestinal cell types and species. We confirmed the importance of these regulatory elements in modulating lactase mRNA levels by using CRISPR-Cas9-induced deletions. Genetic factors contribute to epigenetic changes occurring with age at the regulatory elements, because lactase-persistence and lactase-nonpersistence DNA haplotypes demonstrated markedly different epigenetic aging. Thus, genetic factors enable a gradual accumulation of epigenetic changes with age, thereby influencing phenotypic outcome.

Lactase persistence versus lactose intolerance: Is there an intermediate phenotype?

BACKGROUND: According to the prevailing theory about the genetic background to lactose intolerance, there are three genotypes but only two adult physiological phenotypes: lactase persistence in individuals with the CT and TT genotypes and lactase non-persistence in individuals with the CC genotype. However, analysis of lactase activity from intestinal biopsies has revealed three distinct levels of activity, suggesting that an intermediate physiological phenotype may exist. AIM: To assess possible disparities between different genotypes with regard to biomarkers of lactase activity and physical symptoms during an oral lactose load test. METHODS: A retrospective study using an oral lactose load test (n=487). Concentrations of hydrogen in exhaled air and blood glucose were measured. Afterwards, subjects were asked to provide oral mucosa samples for genotyping and answer a questionnaire (participation rate 56%, n=274). RESULTS: Mean hydrogen levels in exhaled air at 120min were significantly higher in the CT genotype than in the TT genotype. There was no significant difference in blood glucose levels between the two groups. Reported symptoms, with the possible exception of abdominal pain, were equally prevalent in both groups. CONCLUSIONS: Subjects with the CT and TT genotypes, hitherto classified as lactase-persistent, differ in their physiological response to lactose intake, indicating differences in phenotype which could have clinical significance.

Lactose intolerance.

Lactose is the main carbohydrate in infant feeding, but its impact decreases as the child gets older and consumes less milk and dairy products. Congenital lactose intolerance is a very rare condition. However, lactase activity may be low and need to mature during the first weeks of life in many infants. However, the evidence that unabsorbed lactose is causing infantile crying and colic is contradictory. Unabsorbed lactose has a bifidogenic effect and improves calcium absorption. Lactose malabsorption may occur secondary and thus temporally to other etiologies such as infectious gastroenteritis, cow's milk allergy and celiac disease. One the cause is treated, lactase activity will gradually return to normal. The vast majority of Asian children will develop late onset congenital lactase deficiency. However, this entity only exceptionally causes symptoms before the age of 4-5 years. Symptoms are abdominal cramps, flatulence and watery, acid stools, and decrease the quality of life but lactose intolerance is not associated with "true disease". The diagnosis is made on clinical grounds and confirmed with a lactose breath test, if needed. These patients need to have a lifetime long reduced lactose intake to improve their quality of life.

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

Lactase-phlorizin hydrolase (LPH) is a membrane glycoprotein and the only ß-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.

Milk Intolerance, Beta-Casein and Lactose.

True lactose intolerance (symptoms stemming from lactose malabsorption) is less common than is widely perceived, and should be viewed as just one potential cause of cows' milk intolerance. There is increasing evidence that A1 beta-casein, a protein produced by a major proportion of European-origin cattle but not purebred Asian or African cattle, is also associated with cows' milk intolerance. In humans, digestion of bovine A1 beta-casein, but not the alternative A2 beta-casein, releases beta-casomorphin-7, which activates µ-opioid receptors expressed throughout the gastrointestinal tract and body. Studies in rodents show that milk containing A1 beta-casein significantly increases gastrointestinal transit time, production of dipeptidyl peptidase-4 and the inflammatory marker myeloperoxidase compared with milk containing A2 beta-casein. Co-administration of the opioid receptor antagonist naloxone blocks the myeloperoxidase and gastrointestinal motility effects, indicating opioid signaling pathway involvement. In humans, a double-blind, randomized cross-over study showed that participants consuming A1 beta-casein type cows' milk experienced statistically significantly higher Bristol stool values compared with those receiving A2 beta-casein milk. Additionally, a statistically significant positive association between abdominal pain and stool consistency was observed when participants consumed the A1 but not the A2 diet. Further studies of the role of A1 beta-casein in milk intolerance are needed.

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.

[THERAPY OF TRANSIENT LACTASE INSUFFICIENCY OF CHILDREN IN PECTORAL AGE].

Thus, we have discovered that the children of the first half-year of life have different degrees of severity of transient lactase insufficiency basing on the results of hydrogen respiratory test. It was set that the starting dose of enzyme lactase must depend on the degree of severity of displays of transient lactase insufficiency, taking into account the indexes of hydrogen respiratory test.

Congenital lactose intolerance is triggered by severe mutations on both alleles of the lactase gene.

BACKGROUND: Congenital lactase deficiency (CLD) is a rare severe autosomal recessive disorder, with symptoms like watery diarrhea, meteorism and malnutrition, which start a few days after birth by the onset of nursing. The most common rationales identified for this disorder are missense mutations or premature stop codons in the coding region of the lactase-phlorizin hydrolase (LPH) gene. Recently, two heterozygous mutations, c.4419C > G (p.Y1473X) in exon 10 and c.5387delA (p.D1796fs) in exon 16, have been identified within the coding region of LPH in a Japanese infant with CLD. METHODS: Here, we investigate the influence of these mutations on the structure, biosynthesis and function of LPH. Therefore the mutant genes were transiently expressed in COS-1 cells. RESULTS: We show that both mutant proteins are mannose-rich glycosylated proteins that are not capable of exiting the endoplasmic reticulum. These mutant proteins are misfolded and turnover studies show that they are ultimately degraded. The enzymatic activities of these mutant forms are not detectable, despite the presence of lactase and phlorizin active sites in the polypeptide backbone of LPH-D1796fs and LPH-Y1473X respectively. Interestingly, wild type LPH retains its complete enzymatic activity and intracellular transport competence in the presence of the pathogenic mutants suggesting that heterozygote carriers presumably do not show symptoms related to CLD. CONCLUSIONS: Our study strongly suggests that the onset of severe forms of CLD is elicited by mutations in the LPH gene that occur in either a compound heterozygous or homozygous pattern of inheritance.

[Small intestinal bacterial overgrowth as a cause of lactase deficiency].

AIM: To establish the rate of lactase deficiency (LD) in patients with post-infectious irritable bowel syndrome (PI-IBS), to define a role of enteric bacteria in the pathogenesis of hypolactasia, and to evaluate the efficiency of probiotic therapy. SUBJECTS AND METHODS: Examinations were made in 386 patients with PI-IBS, including 112 (79.4%) women; mean age 33.9 ± 9.1 years; disease duration 2.6 ± 1.4 years. Rapid tests of small intestinal mucosa (SIM) biopsy specimens obtained from the duodenal retrobulbar segment were used to diagnose LD. Bacterial growth was estimated by a hydrogen breath test using a H2 MICRO gas analyzer. RESULTS: The patients with PI-IBS were revealed to have moderate and severe LD in 25.6 and 10.9%, respectively. All the patients with LD were detected to have small intestinal (SI) bacterial overgrowth (BOG). An inverse correlation was found between LD and the degree of SI BOG (r = -0.53; p < 0.001). 73.7% of the patients with moderate LD showed a positive effect of probiotic therapy as regression of clinical symptoms of LD, a decrease of hydrogen levels in expired air from 72.4 ± 25.1 to 16.41 ± 3.2 ppm (p < 0.05), an increase of lactate activity in the SIM biopsy specimens and an improvement of quality of life from 2.69 ± 0.53 to 5.53 ± 0.64 scores according to the GCI scale. No improvement occurred in 73.8% of the patients with severe LD. CONCLUSION: LD was identified in 36.5% of the patients with PI-IBS. There was an inverse correlation between the degree of LD and SI BOG. The good therapeutic effect of probiotics in LD suggests that the symbiotic gut microflora positively affects the activity of lactase in the human SIM. No therapeutic effect of probiotics in patients with severe LN serves as the basis for a search for more active probiotic therapy.

Adult lactose digestion status and effects on disease.

BACKGROUND: Adult assimilation of lactose divides humans into dominant lactase-persistent and recessive nonpersistent phenotypes. OBJECTIVES: To review three medical parameters of lactose digestion, namely: the changing concept of lactose intolerance; the possible impact on diseases of microbial adaptation in lactase-nonpersistent populations; and the possibility that the evolution of lactase has influenced some disease pattern distributions. METHODS: A PubMed, Google Scholar and manual review of articles were used to provide a narrative review of the topic. RESULTS: The concept of lactose intolerance is changing and merging with food intolerances. Microbial adaptation to regular lactose consumption in lactase-nonpersistent individuals is supported by limited evidence. There is evidence suggestive of a relationship among geographical distributions of latitude, sunhine exposure and lactase proportional distributions worldwide. DISCUSSION: The definition of lactose intolerance has shifted away from association with lactose maldigestion. Lactose sensitivity is described equally in lactose digesters and maldigesters. The important medical consequence of withholding dairy foods could have a detrimental impact on several diseases; in addition, microbial adaptation in lactase-nonpersistent populations may alter risk for some diseases. There is suggestive evidence that the emergence of lactase persistence, together with human migrations before and after the emergence of lactase persistence, have impacted modern-day diseases. CONCLUSIONS: Lactose maldigestion and lactose intolerance are not synonymous. Withholding dairy foods is a poor method to treat lactose intolerance. Further epidemiological work could shed light on the possible effects of microbial adaptation in lactose maldigesters. The evolutionary impact of lactase may be still ongoing.