The American Academy of Pediatrics Committee on Nutrition presents an updated review of lactose intolerance in infants, children, and adolescents. Differences between primary, secondary, congenital, and developmental lactase deficiency that may result in lactose intolerance are discussed. Children with suspected lactose intolerance can be assessed clinically by dietary lactose elimination or by tests including noninvasive hydrogen breath testing or invasive intestinal biopsy determination of lactase (and other disaccharidase) concentrations. Treatment consists of use of lactase-treated dairy products or oral lactase supplementation, limitation of lactose-containing foods, or dairy elimination. The American Academy of Pediatrics supports use of dairy foods as an important source of calcium for bone mineral health and of other nutrients that facilitate growth in children and adolescents. If dairy products are eliminated, other dietary sources of calcium or calcium supplements need to be provided.

/pdf/lactose-intolerance-in-infants-children-and-adolescents-21abwqjj9t.pdf

Lactose Intolerance in Infants, Children, and Adolescents

The biosynthesis and maturation of the human intestinal lactase-phlorizin hydrolase (LPH; EC 3.2.1.23-3.2.1.62) has been studied in cultured intestinal biopsies and mucosal explants. Short time pulse labelling revealed on high mannose intermediate of Mr 215,000 which was converted upon endo-beta-N-acetylglucosaminidase H (endo-H) digestion to a polypeptide of Mr 200,000. The brush border form of LPH was revealed after longer pulse periods and has Mr 160,000. It possesses mainly complex oligosaccharide chains and, owing to its partial endo-H sensitivity, at least one chain of the high mannose type. Leupeptin partially inhibited the appearance of the Mr-160,000 polypeptide. Monensin treatment of biopsies resulted in the modification of the Mr-160,000 species to the Mr-140,000 molecule, which was endo-H sensitive. Pulse-chase analysis indicated a slow post-translational processing of the high mannose precursor (Mr 215,000) to yield the mature brush-border form (Mr 160,000) of LPH. Our results further indicate that LPH is synthesized as a single polypeptide precursor which is intracellularly cleaved to yield the mature brush border of LPH. The data presented suggest that this cleavage occurs during the translocation of the molecule across the Golgi complex.

Biosynthesis and maturation of lactase-phlorizin hydrolase in the human small intestinal epithelial cells.

There are at least 20 rare autosomal recessive disorders that are excessively common in Finland of which congenital lactase deficiency is one. During the last 17 years we have found 16 cases. In each case the mother noted watery diarrhoea, generally after the first feed of breast milk, and at the latest, by age 10 days. The lactose malabsorption was verified at a mean age of 36 (range 3-90) days, by which time the infants were dehydrated and 15 of them weighed less than at birth (mean weight for age was -2.8 SDs). On a lactose-free elimination diet (a group of 6 on Nutramigen and a group of 10 on soy-based formula) the children caught up in growth. One infant in each group showed allergic symptoms. While the infants were being breast fed their faeces contained 20 to 80 g/l lactose. In 24 peroral lactose tolerance tests, the greatest rise in blood glucose concentration was 0.8 mmol/l. Only 2 patients showed abnormal absorption when tested within a week of lactose elimination, and in each absorption tests became normal during the elimination period. Slight to partial villous atrophy of the jejunum was present in 4 early specimens, but in later ones the mean villous height was normal. The mean height of the epithelial cells was reduced and there were fewer intraepithelial lymphocytes in patients. The lactase activities in jejunal biopsy specimens were lower than in most patients with acquired lactase deficiency, with some overlap. The maltase and sucrase activities were normal.

https://adc.bmj.com/content/archdischild/58/4/246.full.pdf

Congenital lactase deficiency. A clinical study on 16 patients.

INTRODUCTION 475 LACTOSE 476 PHYSIOLOGY OF LACTOSE ABSORPTION 477 CHARACTERISTICS OF LACTASE 478 ONTOGENIC DEVELOPMENT OF LACTASE 479 Lactase Activity in the Fetus and Newborn .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 479 Lactase Adaptation.. .. . . . . . . ... .. . . ........ . . . . . . . . .. .... .... .... 480 Decline of Lactase Expression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 481 PATHOPHYSIOLOGY OF LACTOSE MALABSORPTION . .... 482 RELATIONSHIP BETWEEN MALABSORPTION AND INTOLERANCE 484 CLINICAL PRESENTATIONS OF LACTOSE MALABSORPTION 486 Congenital Lactase Deficiency. . . ... . . . . . . . . . . . ...... . . . . ... .. . . . . . . . . . ...... ....... . . . . . . . . ... 486 Primary Lactase Nonpersistence . . . . . . . . . . . ... . . ...... .. . . .. . . . . . ..... .... 486 Secondary Lactase Deficiency.... . . . . . . . . . . . . .... . .. . . .. .. . . . . . . ..... 487 Other Clinical Conditions ..... .. . . . . . . . . ..... ... ........ . . . . . . . . ..... . . . 489 DIAGNOSIS OF LACTOSE MALABSORPTION 490 MANAGEMENT OF LACTOSE MALABSORPTION 491 DIRECTIONS FOR THE FUTURE 494 GLOSSARY OF TERMS......... . ....... . ...... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494

Current concepts in lactose malabsorption and intolerance.

Enzymatic activity, biosynthesis, and maturation of lactasephlorizin hydrolase (LPH) were investigated in adult volunteers with suspected lactose intolerance. Mean LPH activity in jejunal biopsy homogenates of these individuals was 31% compared to LPH-persistent individuals, and was accompanied by a reduced level of LPH-protein. Mean sucrase activity in individuals with low LPH was increased to 162% and was accompanied by an increase in sucrase-isomaltase (SI)-protein. Biosynthesis of LPH, SI, and aminopeptidase N (APN) was studied in organ culture of small intestinal biopsy specimens. In individuals with LPH restriction, the rate of synthesis of LPH was drastically decreased, reaching just 6% of the LPH-persistent group after 20 h of culture, while the rate of synthesis of SI appeared to be increased. In addition, maturation of pro-LPH to mature LPH occurred at a slower rate in LPH-restricted tissue. Immunoelectron microscopy revealed an accumulation of immunoreactive LPH in the Golgi region of enterocytes from LPH-restricted individuals and reduced labeling of microvillus membranes. Therefore, lactose intolerance in adults is mainly due to a decreased biosynthesis of LPH, either at the transcriptional or translational level. In addition, intracellular transport and maturation is retarded in some of the LPH-restricted individuals, and this leads to an accumulation of newly synthesized LPH in the Golgi and a failure of LPH to reach the microvillus membrane.

/pdf/biogenesis-of-intestinal-lactase-phlorizin-hydrolase-in-n0jukrkbke.pdf

Biogenesis of intestinal lactase-phlorizin hydrolase in adults with lactose intolerance. Evidence for reduced biosynthesis and slowed-down maturation in enterocytes.

Brush-border membrane proteins of the small-bowel mucosa were separated on polyacrylamide gels from intestinal biopsy specimens obtained from four children with congenital lactose malabsorption and from two adults with specific hypolactasia. In three patients with the congenital type of lactase deficiency the protein band corresponding to brush-border lactase was reduced in intensity, but was never completely absent. No difference in gel patterns was detected when this pattern In congenital deficiency was compared to that obtained from the two patients with adult-type selective hypolactasia. In one patient with congenital lactose malabsorption the protein band corresponding to lactase activity was not detectable. The findings suggest that the mechanisms leading to low lactase activity in the congenital and adult forms of lactose intolerance are similar. (N Engl J Med 294:1030–1032, 1976)

https://www.nejm.org/doi/pdf/10.1056/NEJM197605062941903?listPDF=true

Protein patterns of brush-border fragments in congenital lactose malabsorption and in specific hypolactasia of the adult.

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Protein patterns of brush-border fragments in congenital lactose malabsorption and in specific hypolactasia of the adult.