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[Intestinal malabsorption of glucose and galactose. Study of a family]
Insights
Congenital glucose-galactose malabsorption in a child was linked to significantly reduced intestinal glucose transport. Carrier parents showed normal glucose absorption, indicating a specific genetic defect.
Area of Science:
- Gastroenterology
- Human Genetics
- Molecular Biology
Context:
- Congenital glucose-galactose malabsorption (CGGM) is a rare inherited disorder.
- It results from defects in the sodium-glucose cotransporter 1 (SGLT1) in the small intestine.
Purpose:
- To investigate the molecular and physiological basis of CGGM in a pediatric patient.
- To differentiate the transport defect from carrier status in parents.
Summary:
- A child with CGGM exhibited positive hydrogen breath tests after glucose and galactose challenges, indicating malabsorption.
- In vitro studies revealed a selective decrease in active glucose accumulation and net glucose absorption, with reduced mucosal membrane permeability.
- Parents, presumed heterozygotes, showed normal glucose absorption and no detectable transport defects.
Impact:
- This study elucidates the specific transport defect in CGGM, highlighting reduced brush border permeability as the cause of malabsorption.
- It provides insights into the genetic basis of glucose transport and its clinical implications.
Abstract:
A girl with congenital glucose-galactose malabsorption and her two parents were studied. Hydrogen breath tests performed on the child during glucose and galactose tolerance tests (0.5 g/kg) were positive (increase in expired pH concentration of 21 p.p.m. and 32.5 p.p.m. from the basal level respectively). This was negative for fructose (2 g/kg). In vitro intestinal transport studies showed: 1) a selective decrease in active glucose accumulation (intracellular concentration 0.34 mM in 0.1 mM glucose bathing solution - controls: 1.58 +/- 0.56 (means +/- SD), and 12.1 mM in 10 mM bathing solution - controls: 38.4 +/- 12.4). 2) absence of net glucose absorption during in vitro Ussing chamber measurements with a marked decrease in mucosal membrane glucose permeability. For the parents, the hydrogen breath test was negative after glucose and galactose ingestion (2 g/kg) and intestinal transport was normal (father; intracellular concentration 1.32 mM and mother 2.04 for 0.1 mM bathing glucose concentration). The marked decrease in brush border permeability explains the absence of net glucose absorption in the child. The parents who are presumed to be heterozygotes did not exhibit any detectable transport defect.