TY - JOUR
T1 - Chronic estrogen deficiency causes gastroparesis by altering neuronal nitric oxide synthase function
AU - Ravella, K.
AU - Al-Hendy, A.
AU - Sharan, C.
AU - Hale, A. B.
AU - Channon, K. M.
AU - Srinivasan, S.
AU - Gangula, P. R.
N1 - Funding Information:
Acknowledgments We thank Dr. Ayman Al-Hendy for the FORKO and SVE129 mice, and Dr. Diana Marver for review of the manuscript. Financial support for the original research was provided by NIH-NIDDK R21DKO76704 (PG), P60DK020593 pilot project funds (PG), and RCMI G12RR03032 (PG) start-up funds at Meharry Medical College, Nashville, TN, USA.
PY - 2013/6
Y1 - 2013/6
N2 - 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-17β (E2) down-regulates tetrahydrobiopterin (BH4, 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 nNOSα, BH4 biosynthesis enzymes (GCH-1, DHFR) and estrogen receptors (α, β) were measured in gastric antrum by western blotting. Levels of BH4 and oxidized BH2, 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 ERα (2.7 ± 0.4 vs. 3.9 ± 0.4) and (6) increased oxidized biopterin levels and decreased ratio of BH 4 versus BH2 + B. Conclusion: We conclude that chronic estrogen deficiency negatively modifies the function of both BH4 and nNOS thereby contributing to the development of gastroparesis in a FORKO mouse model.
AB - 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-17β (E2) down-regulates tetrahydrobiopterin (BH4, 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 nNOSα, BH4 biosynthesis enzymes (GCH-1, DHFR) and estrogen receptors (α, β) were measured in gastric antrum by western blotting. Levels of BH4 and oxidized BH2, 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 ERα (2.7 ± 0.4 vs. 3.9 ± 0.4) and (6) increased oxidized biopterin levels and decreased ratio of BH 4 versus BH2 + B. Conclusion: We conclude that chronic estrogen deficiency negatively modifies the function of both BH4 and nNOS thereby contributing to the development of gastroparesis in a FORKO mouse model.
KW - Biopterins
KW - Estrogen
KW - Follicle stimulating hormone
KW - Gastroparesis
KW - Nitric oxide
KW - nNOS dimerization
UR - http://www.scopus.com/inward/record.url?scp=84879503659&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84879503659&partnerID=8YFLogxK
U2 - 10.1007/s10620-013-2610-4
DO - 10.1007/s10620-013-2610-4
M3 - Article
C2 - 23504347
AN - SCOPUS:84879503659
SN - 0163-2116
VL - 58
SP - 1507
EP - 1515
JO - Digestive Diseases and Sciences
JF - Digestive Diseases and Sciences
IS - 6
ER -
