Gender and estradiol as major factors in the expression and dimerization of nNOSα in rats with experimental diabetic gastroparesis

Huanglian-banxia promotes gastric motility of diabetic rats by modulating brain-gut neurotransmitters through MAPK signaling pathway

BACKGROUND

Gastric motility disorder is an increasingly common problem among people with diabetes. Neurotransmitters have been recognized as critical regulators in the process of gastric motility. Previous study has shown that herb pair huanglian-banxia (HL-BX) can improve gastric motility, but the underlying mechanism is still unclear. The aim of this study was to further investigate the role of HL-BX in modulating brain-gut neurotransmission to promote gastric motility in diabetic rats, and to explore its possible mechanism.

METHODS

The diabetic rats were divided into five groups. Gastric emptying rate, intestinal propulsion rate, body weight, and average food intake were determined. Substance P (SP), 5- hydroxytryptamine (5-HT), and glucagon-like peptide -1 (GLP-1) in the serum were measured by enzyme-linked immunosorbent assay. Dopamine (DA) and norepinephrine (NE) in the brain were analyzed by high-pressure liquid chromatography with a fluorescence detector. Protein expression of the tissues in the stomach and brain was determined by Western blot.

KEY RESULTS

HL-BX reduced average food intake significantly, increased body weight, and improved gastric emptying rate and intestinal propulsion rate. HL-BX administration caused a significant increase in SP, GLP-1, and 5-HT, but a significant decrease in DA and NE. Interestingly, HL-BX regulated simultaneously the different expressions of MAPK and its downstream p70S6K/S6 signaling pathway in the stomach and brain. Moreover, berberine exhibited a similar effect to HL-BX.

CONCLUSIONS

These results indicated that HL-BX promoted gastric motility by regulating brain-gut neurotransmitters through the MAPK signaling pathway. HL-BX and MAPK provide a potential therapeutic option for the treatment of gastroparesis.

Nitric Oxide Regulates Estrus Cycle Dependent Colonic Motility in Mice

Women are more susceptible to functional bowel disorders than men and the severity of their symptoms such as diarrhea, constipation, abdominal pain and bloating changes over the menstrual cycle, suggesting a role for sex hormones in gastrointestinal function. Nitric oxide (NO) is a major inhibitory neurotransmitter in the gut and blockade of nitric oxide synthase (NOS; responsible for NO synthesis) increases colonic motility in male mice ex vivo. We assessed the effects of NOS inhibition on colonic motility in female mice using video imaging analysis of colonic motor complexes (CMCs). To understand interactions between NO and estrogen in the gut, we also quantified neuronal NOS and estrogen receptor alpha (ERα)-expressing myenteric neurons in estrus and proestrus female mice using immunofluorescence. Mice in estrus had fewer CMCs under control conditions (6 ± 1 per 15 min, n = 22) compared to proestrus (8 ± 1 per 15 min, n = 22, One-way ANOVA, p = 0.041). During proestrus, the NOS antagonist N-nitro-L-arginine (NOLA) increased CMC numbers compared to controls (189 ± 46%). In contrast, NOLA had no significant effect on CMC numbers during estrus. During estrus, we observed more NOS-expressing myenteric neurons (48 ± 2%) than during proestrus (39 ± 1%, n = 3, p = 0.035). Increased nuclear expression of ERα was observed in estrus which coincided with an altered motility response to NOLA in contrast with proestrus when ERα was largely cytoplasmic. In conclusion, we confirm a cyclic and sexually dimorphic effect of NOS activity in female mouse colon, which could be due to genomic effects of estrogens via ERα.

Effect of Oral CNSA-001 (sepiapterin, PTC923) on gastric accommodation in women with diabetic gastroparesis: A randomized, placebo-controlled, Phase 2 trial

AIMS

Diabetic gastroparesis may be associated with impaired nitric oxide metabolism and reduced tetrahydrobiopterin (BH₄) synthesis. Oral treatment with CNSA-001 (sepiapterin, currently known as PTC923) increased BH₄ levels in humans in a previous study. This Phase 2 study evaluated CNSA-001 in women with diabetic gastroparesis.

METHODS

Non-pregnant diabetic women with moderate/severe symptomatic gastroparesis, delayed gastric emptying, and impaired gastric accommodation (nutrient satiety testing) were randomized to 10mg/kg BID CNSA-001 or matching placebo for 14days. The primary endpoint was change in gastric accommodation (maximal tolerated liquid meal volume) at 14- and 28-days' follow-up.

RESULTS

Gastric accommodation improved in CNSA-001-treated vs. placebo-treated subjects at 28days (least squares mean [LSM] difference: 98 [95% CI 36 to 161], p=0.0042). Subjects' ratings of bloating, fullness, nausea, and pain were lower vs. baseline in the CNSA-001 group at 14 and 28days, though these improvements were not observed consistently in placebo-treated subjects. There were no significant group differences in upper gastrointestinal symptom scores, and in gastric emptying breath test parameters. CNSA-001 was well tolerated, with no withdrawals for adverse events.

CONCLUSIONS

CNSA-001 improved gastric accommodation in women with diabetic gastroparesis. Further evaluation of CNSA-001 in gastroparesis is warranted; ClinicalTrials.gov number, NCT03712124.

Decreased Level of Neuropeptide Y Is Associated With Gastroparesis in Male Diabetic Rats

Background

Substance P (SP) and neuropeptide Y (NPY), excitatory and inhibitory neuropeptides, respectively, may impact gastric motility in patients with diabetic mellitus (DM). We investigated these neuropeptide levels, NPY receptors, total nitric oxide synthase (NOS) levels, and neuronal NOS alpha (nNOSα) activation status and levels in streptozotocin-induced type I diabetes in male rats.

Methods

Rats were grouped based on serum glucose and gastric emptying time: normal untreated control (CM), diabetic (DM) and diabetic gastroparesis (DM + GP). Neuropeptide serum levels were determined by enzyme-linked immunosorbent assay (ELISA). Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and western blotting measured NPY receptors, Y1 and Y2, and nNOSα expression. Low-temperature SDS-PAGE followed by western blotting was used to measure the dimerization of nNOSα. An NOS colorimetric assay kit was used to measure total NOS activity.

Results

SP levels were significantly decreased (P < 0.05) in DM and DM + GP compared to CM. NPY levels were significantly decreased (P < 0.05) in DM compared to CM, and DM + GP had a more significantly decreased NPY when compared to both DM and CM. Protein levels of neuropeptide receptor Y1 (NPY-Y1) in the smooth muscle of pylorus were significantly increased in DM, but not in DM + GP when compared to CM. Neuropeptide receptor Y2 (NPY-Y2) was not detected. Changes in nNOSα activity and their protein levels, as well as total NOS activity, among the groups were insignificant.

Conclusions

Increased expression of pylorus NPY-1R and decreased serum NPY are present in diabetes. A more pronounced decreased serum NPY with no NPY-1R upregulation in pyloric smooth muscle is associated with gastroparesis. NPY levels show no relationship with nNOSα levels, their activation status, or total NOS activity in pyloric smooth muscle. These data suggest a pathophysiological role of severely depleted NPY and absence of NPY-Y1 upregulation for gastroparesis phenotype.

Nitric oxide signalling in the brain and its control of bodily functions

Nitric oxide (NO) is a versatile molecule that plays key roles in the development and survival of mammalian species by endowing brain neuronal networks with the ability to make continual adjustments to function in response to moment-to-moment changes in physiological input. Here, we summarize the progress in the field and argue that NO-synthetizing neurons and NO signalling in the brain provide a core hub for integrating sensory- and homeostatic-related cues, control key bodily functions, and provide a potential target for new therapeutic opportunities against several neuroendocrine and behavioural abnormalities.

Efficacy and safety of complementary and alternative medicine therapy for gastroparesis: A protocol for systematic review and meta-analysis

BACKGROUND

Gastroparesis affects the quality of life of many patients, but there is no effective treatment. Now, complementary and alternative medicine originated from China is gradually accepted by the world because of its unique treatment principles and relatively safe treatment methods. However, at present, there is still a lack of more definitive clinical application evidence for the treatment of gastroparesis with complementary and alternative medicine to confirm the safety and efficacy of complementary and alternative medicine in the treatment of gastroparesis caused by various causes. More comprehensive and stronger evidence-based medicine evidence is needed.

METHODS

We will retrieve literatures using Medline, Embase, the Cochrane Library database, Web of science, CNKI, VIP, CBM, and WanFang. We will look for RCTs or CCTs on the use of complementary and alternative medicine in the treatment of gastroparesis, and extract relevant data into the excel sheet. The whole retrieval and data extraction process were carried out by 2 researchers independently. Then we will use meta-analysis to make statistical analysis of all the results and make a systematic review of all the included literatures.

RESULTS

All results and safety data were analyzed for a comprehensive evaluation and/or descriptive analysis of the efficacy and safety of complementary and alternative therapies for gastroparesis.

CONCLUSION

This study will provide more comprehensive clinical evidence for the treatment of gastroparesis with complementary and alternative therapies.

REGISTRATION

The research has been registered and approved on the INPLASY.COM website. The registration number is INPLASY2020100033.

Comparison of the Status of Interstitial Cells of Cajal in the Smooth Muscle of the Antrum and Pylorus in Diabetic Male and Female Patients with Severe Gastroparesis

Females dominate in the area of gastroparesis (GP), making up to 70–80% of these patients. One attractive hypothesis is that females have less smooth muscle reserve and thus less resilience to recover from an insult. Our aim was to investigate if there are gender differences in the number of interstitial cells of Cajal (ICC) in the antral and pyloric smooth muscle of diabetic (DM) patients with severe gastroparesis refractory to standard medical management. Full thickness antral and pyloric biopsies were obtained during surgery to implant a gastric electrical stimulation system and perform a pyloroplasty. Thirty-eight DM patients (66% females, n = 25; mean age 44) who failed medical therapies provided antral biopsies. Pyloric tissue samples were also collected from 29 of these patients (65% females, n = 19). Tissues were stained with H&E and c-Kit for the presence of ICC. ICC depletion was defined as less than 10 cells/HPF. In the antrum, 40% of females had significant ICC depletion, similar to 38% in males. In the pylorus, 68% of females had depletion of ICC, compared to 80% depletion in males. When combining both antral and pyloric smooth muscle regions, ICC depletion was similar in males (40%) when compared to females (38%). In diabetic patients with severe GP, females and males showed similar degrees of reduction in antral ICC, while more males had depletion of pyloric smooth muscle ICC compared to their female counterparts. Future larger studies should focus on whether differences in other smooth muscle biomarkers can be identified between males and females.

Supplementation of 17β-Estradiol Normalizes Rapid Gastric Emptying by Restoring Impaired Nrf2 and nNOS Function in Obesity-Induced Diabetic Ovariectomized Mice

Gastroparesis (Gp) is a multifactorial condition commonly observed in females and is characterized by delayed or rapid gastric emptying (GE). The role of ovarian hormones on GE in the pathogenesis of obesity induced type 2 diabetes mellitus (T2DM) is completely unknown. The aims of our study are to investigate whether supplementation of 17β-estradiol (E2) or progesterone (P4) restores impaired nuclear factor erythroid 2-related factor 2 (Nrf2, an oxidative stress-responsive transcription factor) and nitric oxide (NO)-mediated gastric motility in ovariectomized (OVX) mice consuming a high-fat diet (HFD, a model of T2DM). Groups of OVX+HFD mice were administered daily subcutaneous doses of either E2 or P4 for 12 weeks. The effects of E2 and P4 on body weight, metabolic homeostasis, solid GE, gastric antrum NO-mediated relaxation, total nitrite levels, neuronal nitric oxide synthase (nNOSα), and its cofactor expression levels were assessed in OVX+HFD mice. HFD exacerbated hyperglycemia and insulinemia while accelerating GE (p < 0.05) in OVX mice. Exogenous E2, but not P4, attenuated rapid gastric emptying and restored gastric nitrergic relaxation, total nitrite levels, nNOSα, and cofactor expression via normalizing Nrf2-Phase II enzymes, inflammatory response, and mitogen-activated protein kinase (MAPK) protein expression in OVX+HFD mice. We conclude that E2 is beneficial in normalizing metabolic homeostasis and gastric emptying in obese, diabetic OVX mice consuming a fat-rich diet.

Hypoganglionosis in the gastric antrum causes delayed gastric emptying

BACKGROUND

Enteric nervous system (ENS) abnormalities have been implicated in delayed gastric emptying but studies exploring potential treatment options are limited by the lack of an experimental animal model. We examined the ENS abnormalities in the mouse stomach associated with aging, developed a novel model of gastroparesis, and established a new approach to measure gastric emptying.

METHODS

A modified gastric emptying assay was developed, validated in nNOS ^-/- mice, and tested in mice at multiple ages. Age-related changes in ENS structure were analyzed by immunohistochemistry. Gastric aganglionosis was generated in Wnt1-iDTR mice using focal administration of diphtheria toxin (DT) into the anterior antral wall.

KEY RESULTS

Older mice (>5 months) exhibit hypoganglionosis in the gastric antrum and a decreased proportion of nNOS neurons as compared to younger mice (age 5-7 weeks). This was associated with a significant age-dependent decrease in liquid and solid gastric emptying. A novel model of gastric antrum hypoganglionosis was established using neural crest-specific expression of diphtheria toxin receptor. In this model, a significant reduction in liquid and solid gastric emptying is observed.

CONCLUSIONS & INFERENCES

Older mice exhibit delayed gastric emptying associated with hypoganglionosis and a reduction in nNOS-expressing neurons in the antrum. The causal relationship between antral hypoganglionosis and delayed gastric emptying was verified using a novel experimental model of ENS ablation. This study provides new information regarding the pathogenesis of delayed gastric emptying and provides a robust model system to study this disease and develop novel treatments.

Gastroparesis

Gastroparesis is a disorder characterized by delayed gastric emptying of solid food in the absence of a mechanical obstruction of the stomach, resulting in the cardinal symptoms of early satiety, postprandial fullness, nausea, vomiting, belching and bloating. Gastroparesis is now recognized as part of a broader spectrum of gastric neuromuscular dysfunction that includes impaired gastric accommodation. The overlap between upper gastrointestinal symptoms makes the distinction between gastroparesis and other disorders, such as functional dyspepsia, challenging. Thus, a confirmed diagnosis of gastroparesis requires measurement of delayed gastric emptying via an appropriate test, such as gastric scintigraphy or breath testing. Gastroparesis can have idiopathic, diabetic, iatrogenic, post-surgical or post-viral aetiologies. The management of gastroparesis involves: correcting fluid, electrolyte and nutritional deficiencies; identifying and treating the cause of delayed gastric emptying (for example, diabetes mellitus); and suppressing or eliminating symptoms with pharmacological agents as first-line therapies. Several novel pharmacologic agents and interventions are currently in the pipeline and show promise to help tailor individualized therapy for patients with gastroparesis.

Reactive oxygen species overproduction and MAP kinase phosphatase-1 degradation are associated with gastroparesis in a streptozotocin-induced male diabetic rat model

BACKGROUND

Diabetic gastroparesis in human and animal models suggest different developmental causes in females vs males. Previously, we demonstrated that although male and female diabetic gastroparetic rats exhibited similarity in disease pathology, molecular mechanisms were different: slow gastric emptying in male diabetic gastroparetic rats was not associated with the level of expression and dimerization of neuronal nitric oxide synthase α in gastric tissues, as was demonstrated in females. Male gastroparesis may involve other mechanisms, such as oxidative stress. We hypothesize that sustained increased reactive oxygen species (ROS) and degradation of MAP kinase phosphatase-1 with subsequent unregulated activation of c-Jun N-terminal kinase and p38MAP kinase pathways are associated with gastroparesis in a male diabetic rat model.

METHODS

Using a male rat model of diabetic gastroparesis, we analyzed serum and pyloric tissue for ROS and antioxidant enzyme levels using ELISA; MAP kinase phosphatase-1, c-Jun N-terminal kinases, and p38MAP kinase levels utilized western blotting techniques and phospho-specific antibodies.

KEY RESULTS

Both diabetic and diabetic gastroparetic rats demonstrated overproduction of ROS. However, loss of MAP kinase phosphatase-1, a MAP kinase pathway negative regulator, with subsequent activation of c-Jun N-terminal kinase 2 and p38MAP kinase pathways, were observed only in diabetic gastroparetic rats. Diabetic rats without gastroparesis had no significant pathway activation.

CONCLUSIONS & INFERENCES

These results suggest that sustained, increased ROS and degradation of MAP kinase phosphatase-1, with subsequent unregulated activation of c-Jun N-terminal kinase and p38MAP kinase pathways, are likely to be factors in diabetic gastroparesis phenotype in a male diabetic rat model.

Critical Evaluation of Animal Models of Gastrointestinal Disorders

Preclinical research remains an important tool for discovery and validation of novel therapeutics for gastrointestinal disorders. While in vitro assays can be used to verify receptor-ligand interactions and test for structural activity of new compounds, only whole-animal studies can demonstrate drug efficacy within the gastrointestinal system. Most major gastrointestinal disorders have been modeled in animals; however the translational relevance of each model is not equal. The purpose of this chapter is to provide a critical evaluation of common animal models that are being used to develop pharmaceuticals for gastrointestinal disorders. For brevity, the models are presented for upper gastrointestinal disorders involving the esophagus, stomach, and small intestine and lower gastrointestinal disorders that focus on the colon. Particular emphasis is used to explain the face and construct validity of each model, and the limitations of each model, including data interpretation, are highlighted. This chapter does not evaluate models that rely on surgical or other non-pharmacological interventions for treatment.

Increased Expression of Pyloric ERβ Is Associated With Diabetic Gastroparesis in Streptozotocin-Induced Male Diabetic Rats

BACKGROUND

Gastroparesis is a significant co-morbidity affecting up to 50% of patients with diabetes and is disproportionately found in women. Prior studies have suggested that loss of interstitial cells of Cajal, hyperglycemia, and nitric oxide dysfunction are potential causes of gastroparesis. Since diabetic gastroparesis affects more women than men, we performed an exploratory study with a diabetic rat model to determine if sex hormone signaling is altered in those where gastroparesis develops.

METHODS

We injected male rats with streptozotocin (STZ) to model type I diabetes, as confirmed by blood glucose levels. Gastroparesis was determined by acetaminophen gavage and serum acetaminophen levels. Rats were grouped based on acetaminophen and blood glucose data: diabetic (DM), diabetic and gastroparetic (DM + GP), and control (CM). Serum levels of testosterone, estrogen, and insulin were determined as well as aromatase expression in pyloric tissue and serum. Androgen receptor and estrogen receptor α (ERα) and β (ERβ) were also measured in the pylorus.

RESULTS

Compared to CM, estrogen increased and testosterone decreased in both DM and DM + GP rats. Sex hormone levels were not different between DM and DM + GP. Serum aromatase was increased in DM and DM + GP rats; however, pyloric tissue levels were not significantly different from controls. ERα was unchanged and androgen receptor decreased in DM and DM + GP. ERβ was increased only in DM + GP animals.

CONCLUSION

Our study implicates increased pyloric ERβ in the development of gastroparesis in STZ-induced male diabetic rats. Increased serum aromatase is likely responsible for altered sex hormone levels. Our study supports the implication of sex hormone signaling in diabetic development and demonstrates a potential unique role for pyloric ERβ in male diabetic gastroparesis.

Role of estrogen in diabetic gastroparesis

Gastroparesis is a highly prevalent chronic disorder of the stomach, which is characterized by delayed gastric emptying and accompanied by a series of upper gastrointestinal symptoms. Diabetic gastroparesis (DGP) is one of the severe complications of diabetes, seriously affecting the patient's quality of life. At present, the pathogenesis of DGP is still unclear. The majority of DGP patients are women, and women's symptoms change with the fluctuation of the level of estrogen. Therefore, we speculate that estrogen may play an vital role in the stomach motility. Gastric emptying is an objective index for the diagnosis of gastroparesis. This article reviews the role of estrogen in DGP and the possible mechanisms.

A Hypothesis for Examining Skeletal Muscle Biopsy-Derived Sarcolemmal nNOSμ as Surrogate for Enteric nNOSα Function

The pathophysiology of gastrointestinal motility disorders is controversial and largely unresolved. This provokes empiric approaches to patient management of these so-called functional gastrointestinal disorders. Preliminary evidence demonstrates that defects in neuronal nitric oxide synthase (nNOS) expression and function, the enzyme that synthesizes nitric oxide (NO), the key inhibitory neurotransmitter mediating mechano-electrical smooth muscle relaxation, is the major pathophysiological basis for sluggishness of oro-aboral transit of luminal contents. This opinion is an ansatz of the potential of skeletal muscle biopsy and examining sarcolemmal nNOSμ to provide complementary insights regarding nNOSα expression, localization, and function within enteric nerve terminals, the site of stimulated de novo NO synthesis. The main basis of this thesis is twofold: (a) the molecular similarity of the structures of nNOS α and μ, similar mechanisms of localizations to “active zones” of nitrergic synthesis, and same mechanisms of electron transfers during NO synthesis and (b) pragmatic difficulty to routinely obtain full-thickness biopsies of gastrointestinal tract, even in patients presenting with the most recalcitrant manifestations of stasis and delayed transit of luminal contents. This opinion attempts to provoke dialog whether this approach is feasible as a surrogate to predict catalytic potential of nNOSα and defects in nitrergic neurotransmission. This discussion makes an assumption that similar molecular mechanisms of nNOS defects shall be operant in both the enteric nerve terminals and the skeletal muscles. These overlaps of skeletal and gastrointestinal dysfunction are largely unknown, thus meriting that the thesis be validated in future by proof-of-principle experiments.

Combination of symptoms, syndrome and disease: Treatment of refractory diabetic gastroparesis

AIM: To assess effect of combination of symptoms, syndrome and disease on treatment of diabetic gastroparesis with severe nausea and vomiting.

METHODS: Professor Tong Xiaolin’s clinical electronic medical records of patients who were treated between January 1, 2006 and October 1, 2012 were used as a database. Patients who met the inclusion criteria were enrolled. General information (name, sex and age), symptoms and blood glucose levels were obtained from the clinic electronic medical record, which was supplemented by a telephone interview. The patient-rated Gastroparesis Cardinal Symptom Index (GCSI) was used to evaluate the severity of the symptoms of gastroparesis. The effects of the treatment were assessed by the change in the severity of the symptoms of gastroparesis and the change in blood glucose between the baseline levels and the post-treatment levels at 1, 2, 4, 8 and 12 wk.

RESULTS: Forty-five patients had a mean GCSI nausea and vomiting severity score of 4.21 ± 0.67 and a total GCSI score of 2.77 ± 0.63 before treatment. There was a significant improvement in the nausea and vomiting score at every return visit compared with the baseline score (1 wk: 3.02 ± 1.04 vs 4.18 ± 0.71, P < 0.001; 2 wk: 2.32 ± 1.25 vs 4.16 ± 0.73, P < 0.001; 4 wk: 2.12 ± 1.26 vs 4.12 ± 0.73, P < 0.001; 8 wk: 1.79 ± 1.09 vs 4.24 ± 0.77, P < 0.001; 12 wk: 0.69 ± 0.92 vs 4.25 ± 0.70, P < 0.001). Twenty-five of the 45 patients had complete resolution of vomiting during the observation period (mean time to resolution was 37.9 ± 27.3 d). The postprandial fullness and early satiety subscale, bloating subscale and total GCSI scores were also improved. Finally, the blood glucose levels improved after treatment, although the change was not significant.

CONCLUSION: Use of the combination of symptoms, syndrome and disease to treat diabetic gastroparesis with refractory nausea and vomiting may be a new treatment option.

Chronic estrogen deficiency causes gastroparesis by altering neuronal nitric oxide synthase function

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 BH4 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.

Ghrelin microinjected into the hypothalamic arcuatus nucleus regulates gastric motility in a diabetic rat model

AIM: To study the effect of Ghrelin microinjected into the hypothalamic arcuatus nucleus (ARC) on gastric motility in rats with diabetic gastroparesis (DGP).

METHODS: Two hundred and forty Wistar rats were randomly divided into 10 groups: control group (C), saline group (NS), low-dose Ghrelin group (L), high-dose Ghrelin group (H), high-dose Ghrelin plus D-Lys6-GHRP-6 (DLS) group (H+D), DGP group (DGP), saline-treated DGP group (DGP+NS), low-dose Ghrelin-treated DGP group (DGP+L), high-dose Ghrelin-treated DGP group (DGP+H), high-dose Ghrelin plus D-Lys6-GHRP-6 (DLS)-treated DGP group (DGP+H+D). A rat diabetic model was established by intraperitoneal injection of streptozotocin (STZ). Fluorescent immunohistochemistry, reverse transcription-polymerase chain reaction (RT-PCR) and real-time quantitative polymerase chain reaction (real-time PCR) were performed to evaluate the protein and mRNA expression of Ghrelin receptor (GHS-R) in the ARC of rats. The effect of Ghrelin injection into ARC on gastric motility was observed.

RESULTS: The number of GHS-R immunoreactive neurons and the relative level of GHS-R mRNA/β-actin in the ARC of normal rats were 10.0/mm² ± 2.1/mm² and 0.48 ± 0.13, while in DGP rats the values decreased to 3.0/mm² ± 0.7/mm² and 0.21 ± 0.10 (both P < 0.05). Microinjection of 0.05 or 0.5 nmol Ghrelin into the ARC could increase the amplitude of gastric motility in a dose-dependent manner (L: 14.6 g ± 2.2 g vs NS: 8.14 g ± 1.58 g, P < 0.05; H: 22.28 g ± 4.10 g vs NS: 8.14 g ± 1.58 g, P < 0.01; NS: 8.14 g ± 1.58 g vs L: 14.6 g ± 2.2 g, P < 0.05), and the frequency of gastric motility was also increased significantly (L: 7.45/min ± 0.87/min vs NS: 5.18/min ± 0.61/min, P < 0.05; H: 10.98/min ± 1.03/min vs NS: 5.18/min ± 0.61/min, P < 0.01; H: 10.98/min ± 1.03/min vs L: 7.45/min ± 0.87/min, P < 0.05). In DGP rats, gastric motility decreased with an enhanced amplitude (2.21 g ± 0.89 g vs 8.14 g ± 1.58 g, P < 0.05) and an increased frequency (1.81/min ± 0.2/min vs 5.18/min ± 0.61/min, P < 0.05). The administration of 0.5 mmol Ghrelin into the ARC could increase gastric motility in DGP rats (amplitude: DGP + H: 5.04 g ± 1.11 g vs DGP + NS: 2.14 g ± 0.23 g or DGP + L: 3.58 g ± 1.11 g, P < 0.05; frequency: DGP + H: 3.81/min ± 0.43/min vs DGP + NS: 1.8/min ± 0.19/min or DGP + L: 2.3/min ± 0.29/min, P < 0.05). The GHS-R antagonist, D-Lys3-GHRP-6, could totally block the effects of Ghrelin.

CONCLUSION: Gastric motility disorder in diabetic rats is partly caused by decreased expression of GHS-R in the hypothalamus. Ghrelin could regulate the genesis of DGP through the GHS-R in the ARC.