COMMENTARY

Small intestine

Changing genes; losing lactase

R J Grand¹, R K Montgomery¹, D K Chitkara¹, J N Hirschhorn²

¹ Divisions of Gastroenterology and Nutrition, Children’s Hospital Boston, and Department of Pediatrics, Harvard Medical School, Boston, MA 02115, USA
² Department of Genetics, Children’s Hospital Boston, and Department of Pediatrics, Harvard Medical School, Boston, MA 02115, USA

Correspondence to:
Correspondence to:
Dr R J Grand, Harvard Medical School, Division of Gastroenterology and Nutrition, The Children’s Hospital, 300 Longwood Avenue, Hunnewell G, Boston, MA 02115, USA;
richard.grand@tch.harvard.edu

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Transcriptional regulation of the lactase-phlorizin hydrolase (LPH) gene by polymorphisms is associated with persistence of high levels of intestinal lactase activity or non-persistence

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Keywords: adult-type hypolactasia; transcriptional regulation; lactase-phlorizin hydrolase gene; lactase-phlorizin hydrolase; polymorphism

The first 150 words of the full text of this article appear below.

Lactase-phlorizin hydrolase (LPH), an intestinal microvillus membrane enzyme that hydrolyses lactose, is a critical enzyme for neonatal nutrition. The developmental pattern of lactase expression in the human fetus is distinct from that of similar digestive enzymes. Before week 24 of gestation, intestinal lactase activity is low. It then begins to increase, and during the third trimester lactase activity increases markedly until levels in term neonates are at or above those of infants aged 2–11 months.¹ Lactase exhibits a characteristic proximal to distal pattern of expression in the small intestine; enzyme activity is greatest in the mid- jejunum, with decreasing activity both proximally and distally, resulting in minimal activity in the proximal duodenum and the terminal ileum.²

In most human populations, lactase activity decreases during mid-childhood (about five years of age), resulting in low levels from that age onwards. This pattern is similar to that seen in . . . [Full text of this article]

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