학술논문
Chronic Estrogen Deficiency Causes Gastroparesis by Altering Neuronal Nitric Oxide Synthase Function
Original Article
Original Article
Document Type
Academic Journal
Author
Source
Digestive Diseases and Sciences. June 2013, Vol. 58 Issue 6, p1507, 9 p.
Subject
Language
English
ISSN
0163-2116
Abstract
Author(s): K. Ravella [sup.1], A. Al-Hendy [sup.2] [sup.3], C. Sharan [sup.2] [sup.3], A. B. Hale [sup.4], K. M. Channon [sup.4], S. Srinivasan [sup.5], P. R. Gangula [sup.1] [sup.2] Author Affiliations: [...]
Background Gastroparesis affects predominantly females; however, the biological basis for this gender bias is completely unknown. Several lines of evidence suggest that nitrergic dependent stomach motility function is reduced in diabetic gastroparesis and that nNOS is estrogen-regulated. Aims The purpose of this study was to investigate whether reduced levels of estradiol-17[beta] (E.sub.2) down-regulates tetrahydrobiopterin (BH.sub.4, a cofactor for nNOS dimerization and enzyme activity) biosynthesis and therefore nNOS mediated gastric motility would be impaired in a mouse model of chronic estrogen deficiency, follicle stimulating hormone receptor knock-out female mice (FORKO). Methods In-bred 12-week-old female FORKO mice were obtained from our FORKO breeding colony. Gastric emptying was measured in overnight fasting mice. Nitrergic relaxation (AUC/mg tissue) was measured at 2 Hz through electric field stimulation using gastric antrum strips prepared from WT and FORKO mice. Protein expression for nNOS[alpha], BH.sub.4 biosynthesis enzymes (GCH-1, DHFR) and estrogen receptors ([alpha], [beta]) were measured in gastric antrum by western blotting. Levels of BH.sub.4 and oxidized BH.sub.2, B biopterin levels were determined by HPLC. Results In FORKO, compared to wild type (WT) stomachs we indentified (1) reduced (%) gastric emptying (64 ± 2.5 vs. 77.6 ± 0.88), (2) greater reduction in nitregic relaxation (-0.13 ± 0.012 vs. -0.28 ± 0.012), (3) increased nNOS dimerization (0.48 ± 0.02 vs. 0.34 ± 0.05), (4) decreased NO release whether measured at 24 h (0.6 ± 0.04 vs. 1.7 ± 0.22, p < 0.05) or at 48 h (3.4 ± 0.26 vs. 5.0 ± 0.15, p < 0.05) of incubation, (5) decreased GCH-1 (1.9 ± 0.06 vs. 2.3 ± 0.04), DHFR (1.8 ± 0.14 vs. 2.4 ± 0.07) and ER[alpha] (2.7 ± 0.4 vs. 3.9 ± 0.4) and (6) increased oxidized biopterin levels and decreased ratio of BH.sub.4 versus BH.sub.2 + B. Conclusion We conclude that chronic estrogen deficiency negatively modifies the function of both BH.sub.4 and nNOS thereby contributing to the development of gastroparesis in a FORKO mouse model.
Background Gastroparesis affects predominantly females; however, the biological basis for this gender bias is completely unknown. Several lines of evidence suggest that nitrergic dependent stomach motility function is reduced in diabetic gastroparesis and that nNOS is estrogen-regulated. Aims The purpose of this study was to investigate whether reduced levels of estradiol-17[beta] (E.sub.2) down-regulates tetrahydrobiopterin (BH.sub.4, a cofactor for nNOS dimerization and enzyme activity) biosynthesis and therefore nNOS mediated gastric motility would be impaired in a mouse model of chronic estrogen deficiency, follicle stimulating hormone receptor knock-out female mice (FORKO). Methods In-bred 12-week-old female FORKO mice were obtained from our FORKO breeding colony. Gastric emptying was measured in overnight fasting mice. Nitrergic relaxation (AUC/mg tissue) was measured at 2 Hz through electric field stimulation using gastric antrum strips prepared from WT and FORKO mice. Protein expression for nNOS[alpha], BH.sub.4 biosynthesis enzymes (GCH-1, DHFR) and estrogen receptors ([alpha], [beta]) were measured in gastric antrum by western blotting. Levels of BH.sub.4 and oxidized BH.sub.2, B biopterin levels were determined by HPLC. Results In FORKO, compared to wild type (WT) stomachs we indentified (1) reduced (%) gastric emptying (64 ± 2.5 vs. 77.6 ± 0.88), (2) greater reduction in nitregic relaxation (-0.13 ± 0.012 vs. -0.28 ± 0.012), (3) increased nNOS dimerization (0.48 ± 0.02 vs. 0.34 ± 0.05), (4) decreased NO release whether measured at 24 h (0.6 ± 0.04 vs. 1.7 ± 0.22, p < 0.05) or at 48 h (3.4 ± 0.26 vs. 5.0 ± 0.15, p < 0.05) of incubation, (5) decreased GCH-1 (1.9 ± 0.06 vs. 2.3 ± 0.04), DHFR (1.8 ± 0.14 vs. 2.4 ± 0.07) and ER[alpha] (2.7 ± 0.4 vs. 3.9 ± 0.4) and (6) increased oxidized biopterin levels and decreased ratio of BH.sub.4 versus BH.sub.2 + B. Conclusion We conclude that chronic estrogen deficiency negatively modifies the function of both BH.sub.4 and nNOS thereby contributing to the development of gastroparesis in a FORKO mouse model.