Tetrahydrobiopterin (BH4), a cofactor for nNOS, restores gastric emptying and nNOS expression in female diabetic rats.
Am J Physiol Gastrointest Liver Physiol
; 298(5): G692-9, 2010 May.
Article
in En
| MEDLINE
| ID: mdl-20185690
ABSTRACT
Gastroparesis is a debilitating disease predominantly affecting young women. Recently, dysregulation of neuronal nitric oxide synthase (nNOS) in myenteric plexus neurons has been implicated for delayed solid gastric emptying/gastroparesis in diabetic patients. In this study, we have explored the role of tetrahydrobiopterin (BH4), a major cofactor for nNOS activity and NO synthesis in diabetic gastroparesis. Diabetes was induced with single injection of streptozotocin (55 mg/kg body wt, ip) in female rats, with experiments performed on week 3 or 9 following induction, with or without 3-wk BH4 supplementation. Gastric pyloric BH4 levels were significantly decreased in diabetic female rats compared with control (18.6 +/- 1.45 vs. 31.0 +/- 2.31 pmol/mg protein). In vitro studies showed that 2,4-diamino-6-hydroxypyrimidine (DAHP), an inhibitor of BH4 synthesis, significantly decreased gastric NO release and nitrergic relaxation. Three-week dietary supplementation of BH4 either from day 1 or week 6 significantly attenuated diabetes-induced delayed gastric emptying for solids (3 wk BH4, 67 +/- 6.7 vs. diabetic, 36.05 +/- 7.09; 9 wk BH4, 57 +/- 8.45 vs. diabetic, 33 +/- 9.91) and diabetes-induced reduction in pyloric nNOS-alpha protein expression in female rats. Supplementation of BH4 significantly restored gastric nNOS-alpha dimerization in 9-wk-old diabetic female rats. In addition, BH4 treatment reversed (17.23 +/- 5.81 vs. 42.0 +/- 2.70 mmHg x s) the diabetes-induced changes in intragastric pressures (IGP) and gastric pyloric nitrergic relaxation (-0.62 +/- 0.01 vs. -0.22 +/- 0.07). BH4 deficiency plays a critical role in diabetes-induced alterations including delayed solid gastric emptying, increased IGP, reduced pyloric nitrergic relaxation, and nNOS-alpha expression in female rats. Supplementation of BH4 accelerates gastric emptying by restoring nitrergic system in diabetic female rats. Therefore, BH4 supplementation is a potential therapeutic option for female patients of diabetic gastroparesis.
Full text:
1
Database:
MEDLINE
Main subject:
Biopterins
/
Diabetes Mellitus, Experimental
/
Nitric Oxide Synthase Type I
/
Gastric Emptying
Limits:
Animals
Language:
En
Journal:
Am J Physiol Gastrointest Liver Physiol
Journal subject:
FISIOLOGIA
/
GASTROENTEROLOGIA
Year:
2010
Type:
Article
Affiliation country:
United States