cyclic-gmp and Abnormalities--Multiple

Gain-of-function mutations in guanylyl cyclase C (GCC) result in persistent diarrhea with perinatal onset. We investigated a specific GCC inhibitor, SSP2518, for its potential to treat this disorder.. We investigated the effect of SSP2518 on GCC-mediated intracellular cyclic guanosine monophosphate (cGMP) levels and on GCC-mediated chloride secretion in intestinal organoids from 3 patients with distinct activating GCC mutations and from controls, with and without stimulation of GCC with heat-stable enterotoxin.. Patient-derived organoids had significantly higher basal cGMP levels than control organoids, which were lowered by SSP2518 to levels found in control organoids. In addition, SSP2518 significantly reduced cGMP levels and chloride secretion in patient-derived and control organoids (P < 0.05 for all comparisons) after heat-stable enterotoxin stimulation.. We reported in this study that the GCC inhibitor SSP2518 normalizes cGMP levels in intestinal organoids derived from patients with GCC gain-of-function mutations and markedly reduces cystic fibrosis transmembrane conductance regulator-dependent chloride secretion, the driver of persistent diarrhea.

Topics: Abnormalities, Multiple; Cyclic GMP; Diarrhea; Gain of Function Mutation; Heterocyclic Compounds, 4 or More Rings; Humans; Metabolism, Inborn Errors; Receptors, Enterotoxin

Patients with leprechaunism have hyperinsulinemia and extreme insulin resistance. The mechanism of the insulin resistance has not been delineated. To examine postreceptor events in this unusual syndrome we have assayed the enzyme guanylate cyclase [E.C.4.6.12], which is modulated by insulin, and the concentration of the intracellular messenger cyclic GMP in liver from two children with leprechaunism and extreme insulin resistance. Both patients exhibited down regulation of the red blood cell insulin receptors, but normal insulin receptor binding to Ebstein-Barr transformed IM-9 lymphocytes and monocytes. There was no evidence of antireceptor or antiinsulin antibodies. Activity of liver guanylate cyclase expressed as pmol/mg protein/10 min incubation in the soluble and particulate fractions were, respectively, Ark-1 133 +/- 18, 25 +/- 6; Ark-2 129 +/- 17, 23 +/- 8; control children (six average) 287 +/- 16, 55 +/- 9. The concentration of cyclic GMP was also 50% lower (0.08 +/- 0.03 in Ark-1 and 0.07 +/- 0.04 in Ark-2), compared to 0.19 +/- 0.07 pmol/mg protein/min in the control livers. There was no change in adenylate cyclase activity in children with leprechaunism versus the control children. These data suggest an abnormality of a postreceptor event in this rare genetic disease. These data, however, do not rule out that in some cases of leprechaunism a receptor binding abnormality may be the primary defect. We speculate that a defect in insulin action distal to plasma membrane receptor binding may be etiological in this unusual syndrome.

Topics: Abnormalities, Multiple; Cyclic GMP; Face; Female; Guanylate Cyclase; Hirsutism; Humans; Infant, Newborn; Insulin Resistance; Liver; Receptor, Insulin