The Molecular Basis of Glucose Galactose Malabsorption in a Large Swedish Pedigree.

Glucose-galactose malabsorption (GGM) is due to mutations in the gene coding for the intestinal sodium glucose cotransporter SGLT1 (SLC5A1). Here we identify the rare variant Gln457Arg (Q457R) in a large pedigree of patients in the Västerbotten County in Northern Sweden with the clinical phenotype of GGM. The functional effect of the Q457R mutation was determined in protein expressed in Xenopus laevis oocytes using biophysical and biochemical methods. The mutant failed to transport the specific SGLT1 sugar analog α-methyl-D-glucopyranoside (αMDG). Q457R SGLT1 was synthesized in amounts comparable to the wild-type (WT) transporter. SGLT1 charge measurements and freeze-fracture electron microscopy demonstrated that the mutant protein was inserted into the plasma membrane. Electrophysiological experiments, both steady-state and presteady-state, demonstrated that the mutant bound sugar with an affinity lower than the WT transporter. Together with our previous studies on Q457C and Q457E mutants, we established that the positive charge on Q457R prevented the translocation of sugar from the outward-facing to inward-facing conformation. This is contrary to other GGM cases where missense mutations caused defects in trafficking SGLT1 to the plasma membrane. Thirteen GGM patients are now added to the pedigree traced back to the late 17th century. The frequency of the Q457R variant in Västerbotten County genomes, 0.0067, is higher than in the general Swedish population, 0.0015, and higher than the general European population, 0.000067. This explains the high number of GGM cases in this region of Sweden.

Recombinant human growth hormone treatment, using two dose regimens in children with chronic renal failure--a report on linear growth and adverse effects.

The aim of this study was to study the efficiency and the adverse effects of 2 or 4 IU/m2/day of growth hormone (GH) in the first year and 4 IU/m2/day in the second. Of 29 growth-retarded children with chronic renal failure (CRF) (aged 3.4-15.1 years), 23 completed the first year of therapy, and 16 completed the second year. Height velocity SDS (HVSDS) increased in the first year in the low-dose group with 3.0, and 3.8 in the high-dose group. In the second year, HVSDS increased by 1.3 in the low-dose group and by 2.1 in high-dose group (p < 0.05). The IGF-I/IGFBP-3 ratio rose identically during the first year (p < 0.01). The retarded bone age did not advance inappropriately. The integrated insulin levels (AUC) increased significantly after 1 year of therapy in both groups. HbA1c, levels did not change. The number of adverse events was highest in the low-dose group, in which one patient developed overt insulin dependent diabetes mellitus. In conclusion, glucose metabolism should be monitored in children with CRF during rhGH-treatment. GH therapy in our patients resulted in a significant increase in height velocity with no inappropriate bone age progression and few serious adverse effects, all without relation to the dose of rhGH. The low start dose (2 IU/m2/ day) was of no advantage compared to the high dose.