Long-pulse gastric electrical stimulation protects interstitial cells of Cajal in diabetic rats via IGF-1 signaling pathway

Gastric and sacral electrical stimulation for motility disorders-A clinical perspective

BACKGROUND

Electrical stimulation of the gut has been investigated in recent decades with a view to treating various gastro-intestinal motility disorders including, among others, gastric electrical stimulation to relieve nausea and vomiting associated with gastroparesis and sacral neuromodulation to treat fecal incontinence and/or constipation. Although their symptomatic efficacy has been ascertained by randomized controlled trials, their mechanisms of action are not fully understood.

PURPOSE

This review summarizes the past year's literature on the mechanisms of action of gut electrical stimulation therapies, including their impact on the gut-brain axis.

Common Pathophysiological Mechanisms and Treatment of Diabetic Gastroparesis

Diabetic gastroparesis (DGP) is a common complication of diabetes mellitus, marked by gastrointestinal motility disorder, a delayed gastric emptying present in the absence of mechanical obstruction. Clinical manifestations include postprandial fullness and epigastric discomfort, bloating, nausea, and vomiting. DGP may significantly affect the quality of life and productivity of patients. Research on the relationship between gastrointestinal dynamics and DGP has received much attention because of the increasing prevalence of DGP. Gastrointestinal motility disorders are closely related to a variety of factors including the absence and destruction of interstitial cells of Cajal, abnormalities in the neuro-endocrine system and hormone levels. Therefore, this study will review recent literature on the mechanisms of DGP and gastrointestinal motility disorders as well as the development of prokinetic treatment of gastrointestinal motility disorders in order to give future research directions and identify treatment strategies for DGP.

Electroacupuncture Regularizes Gastric Contraction and Reduces Apoptosis of Interstitial Cells of Cajal in Diabetic Rats

Background/Aims

Gastric dysmotility is a frequent complication among patients with diabetes mellitus. Electroacupuncture (EA) has been empirically used to relieve gastrointestinal symptoms. The aims of this study were to investigate the effects of EA on gastric contraction and the mechanisms of interstitial cells of Cajal (ICC) involved.

Materials and Methods

Male Sprague–Dawley rats were randomized into the normal control, diabetes (DM), diabetic and sham EA (DM + SEA), diabetic and low-frequency EA (DM + LEA), and diabetic and high-frequency EA (DM + HEA) groups. Diabetic models were established and then treated with EA for 8 weeks. Body weight and blood glucose were recorded every 2 weeks. The spontaneous contractions of distal gastric strips were analyzed. Immunostaining and RT-PCR were used to test the apoptotic ICC, IGF-1/IGF-1R, and Nrf2/HO-1 pathways.

Results

The body weight in the DM + LEA and DM + HEA groups were increased compared with that of the DM group, though there was no effect on the blood glucose. The gastric contractions were obviously disordered in the DM group, but EA could regularize the contractions. The number of apoptotic ICC was dramatically increased in the DM group, but reduced with EA treatment. Meanwhile, the IGF-1/IGF-1R pathway was verified to be significantly altered in diabetic rats. The Nrf2/HO-1 pathway was not significantly increased in the DM group. EA with different frequencies efficiently improved the expression of IGF-1/IGF-1R signaling and activated the Nrf2/HO-1 pathway.

Conclusion

EA could improve gastric motility dysfunction and attenuate ICC apoptosis possibly through the regulation of IGF-1/IGF-1R and Nrf2/HO-1 pathways. EA may be a potential therapeutic method for diabetic gastric motility dysfunction.

Gastric Electrical Pacing Reduces Apoptosis of Interstitial Cells of Cajal via Antioxidative Stress Effect Attributing to Phenotypic Polarization of M2 Macrophages in Diabetic Rats

BACKGROUND

Gastric electrical pacing (GEP) could restore interstitial cells of Cajal in diabetic rats. M2 macrophages contribute to the repair of interstitial cells of Cajal injury though secreting heme oxygenase-1 (HO-1). The aim of the study is to investigate the effects and mechanisms of gastric electrical pacing on M2 macrophages in diabetic models.

METHODS

Sixty male Sprague-Dawley rats were randomized into control, diabetic (DM), diabetic with the sham GEP (DM+SGEP), diabetic with GEP1 (5.5 cpm, 100 ms, 4 mA) (DM+GEP1), diabetic with GEP2 (5.5 cpm, 300 ms, 4 mA) (DM+GEP2), and diabetic with GEP3 (5.5 cpm, 550 ms, 4 mA) (DM+GEP3) groups. The apoptosis of interstitial cells of Cajal and the expression of macrophages were detected by immunofluorescence technique. The expression levels of the Nrf2/HO-1 and NF-κB pathway were evaluated using western blot analysis or immunohistochemical method. Malonaldehyde, superoxide dismutase, and reactive oxygen species were tested to reflect the level of oxidative stress.

RESULTS

Apoptosis of interstitial cells of Cajal was increased in the DM group but significantly decreased in the DM+GEP groups. The total number of macrophages was almost the same in each group. In the DM group, M1 macrophages were increased and M2 macrophages were decreased. However, M2 macrophages were dramatically increased and M1 macrophages were reduced in the DM+GEP groups. Gastric electrical pacing improved the Nrf2/HO-1 pathway and downregulated the phosphorylation of NF-κB. In the DM group, the levels of malonaldehyde and reactive oxygen species were elevated and superoxide dismutase was lowered, while gastric electrical pacing reduced the levels of malonaldehyde and reactive oxygen species and improved superoxide dismutase.

CONCLUSION

Gastric electrical pacing reduces apoptosis of interstitial cells of Cajal though promoting M2 macrophages polarization to play an antioxidative stress effect in diabetic rats, which associates with the activated Nrf2/HO-1 pathway and the phosphorylation of NF-κB pathway.

Gastric Electrical Stimulation Has an Effect on Gastric Interstitial cells of Cajal (ICC) That is Associated With Mast Cells

Introduction

Gastric electrical stimulation (GES) is an emerging therapy for gastric motility disorders, showing improvement of gastroparesis related symptoms in previous studies. Interstitial cells of Cajal (ICC) and mast cells have been shown to have a relevant role in gastroparesis pathogenesis. However, the exact effects of GES in those cells is relatively unknown.

Methods

Full thickness biopsies (FTBx) of 20 patients with refractory gastroparesis were obtained at the time of GES placement and repeated when the device was exchanged (mean of 22.5 months between biopsies). A patient-reported outcomes survey was obtained during each office visit during this period. All biopsies were stained with cluster of differentiation 117 (CD117), S100, and mast cell tryptase antibodies and were analyzed.

Results

Half of the patients had a significant increase of ICC during the repeated biopsy compared with baseline (p=0.01) and the other half had significant decrease in ICC levels (p=0.006) but there was no noticeable difference in mast cells counts at baseline between groups. Mast cells analysis was performed in two different groups depending on ICC change from the baseline biopsy (CD117 increase vs CD117 decrease). There was only a significant increase of mast cells count within the CD117 worsened ICC group (p=0.007).

Conclusion

No significant increase in the number of mast cells count seen in patients who received a GES may indicate an improvement in overall inflammation in patients with refractory gastroparesis after GES placement.

Role of Gastric Electrical Stimulation in the Treatment of Gastroparesis

Introduction: Gastric electrical stimulation (GES) is a surgically implanted treatment option for drug refractory gastroparesis syndromes. Evidence supporting use of GES and the pathophysiology of gastroparesis syndromes is not widely known. We conducted a descriptive review to elucidate the pathophysiology of gastroparesis syndromes, with particular focus on gastrointestinal neuromodulation and the known mechanisms of action of GES. Methods: A descriptive review of PubMed, Web of Science and Cochrane Library was conducted using the keywords gastric electrical stimulation, gastroparesis, nausea, vomiting, neuromodulation, gastroparesis syndromes, central nervous system, gastric pacing and electrical stimulation. Results: 1040 potentially relevant articles were identified, of which 34 were included. These studies explored various central and peripheral effects of GES, as well as its effect on quality of life, hospital stay, mortality and health-related costs. Conclusion: Although evidence supporting gastrointestinal (GI) electrical stimulation and GI neuromodulation use is not widely known, GES does seem to offer significant improvement in symptom control, quality of life and other effects to many patients. GES exerts its effects through multiple central and peripheral mechanisms and has potential to modify the natural history of disease. Future work on gastroparetic syndromes and their treatment might be better focused in terms of pathophysiologic mechanisms. Improving outcomes with specific neuromodulation therapies, like GES, may offer improvements in health for many patients with refractory upper gastrointestinal symptoms.

Prokinetic effects of spinal cord stimulation and its autonomic mechanisms in dogs

BACKGROUND

Spinal cord stimulation (SCS) is widely used to treat chronic pain by inhibiting sympathetic activity; however, it is unknown whether it exerts a prokinetic effect on gastric motility. Our aim was to explore effects and possible mechanisms of SCS on glucagon-induced gastric dysmotility and dysrhythmia.

METHODS

Seven female dogs with electrodes chronically placed on the dorsal column of the spinal cord between T10 and T12 segments were studied in 2 randomized sessions (glucagon + sham-SCS, glucagon + SCS). SCS at T10 using a set of optimized stimulation parameters was performed for 30 minute immediately after glucagon injection. The antral manometry, electrogastrogram, and electrocardiogram were recorded to assess gastric contractions, gastric slow waves (GSW), and autonomic functions, respectively.

KEY RESULTS

(a) Compared to baseline, glucagon decreased antral motility index (MI) (6315 ± 565 vs 3243 ± 775, P < 0.001), reduced the percentage of normal GSW (89 ± 3% vs 58 ± 3%, P < 0.01), and increased sympathetic activity (0.25 ± 0 0.06 vs 0.60 ± 0.07, P < 0.01). (b) The sympathetic activity was negatively correlated with antral MI (r = -0.558; P < 0.01) and the percentage of gastric normal slow wave (r = -0.616; P < 0.01). (c) SCS prevented the glucagon-induced impairment in antral hypomotility (MI: 5770 ± 927 vs 5521 ± 1238, P > 0.05) and GSW abnormalities (% of normal waves: 84 ± 4% vs 79 ± 6%, P > 0.05) and sympathetic activity (0.27 ± 0.03 vs 0.33 ± 0.07, P > 0.05).

CONCLUSION

Spinal cord stimulation dramatically improves glucagon-induced impairment in gastric contractions and slow waves by inhibiting sympathetic activity.

Therapeutic effect of Huangqi Jianzhong decoction on diabetic gastroparesis in rats: Impact on SCF-Kit signaling pathway in the gastric antrum

AIM

To analyze the therapeutic effect of Huangqi Jianzhong decoction on diabetic gastroparesis (DGP) in rats and its impact on the stem cell factor (SCF)-Kit signaling pathway in the gastric antrum.

METHODS

Seventy-five male Wistar rats of SPF grade were randomly divided into five groups: model group, normal group, positive control group, low-dose Huangqi Jianzhong decoction group, and high-dose Huangqi Jianzhong decoction group (15 rats in each group). Except the normal group, DGP was induced in other groups. After DGP was induced, the rats in the positive control group were intra-gastrically administered with 0.78 g/mL of morphine suspension, and the two Huangqi Jianzhong decoction groups were intra-gastrically administered with 0.78 g/mL and 3.12 g/mL of Huangqi Jianzhong decoction. The normal group and the model group were given normal saline. The dose of each group was 10 mL/kg. After continuous administration for 6 wk, the general condition, body weight, gastric emptying rate, serum soluble SCF (sSCF), gastrin (GAS), motilin (MLT), and interstitial cells of Cajal (ICC) in the gastric antrum were observed. C-kit and membrane-bound SCF (mSCF) protein expression was detected.

RESULTS

Compared with the normal group, the blood glucose, GAS, and MLT levels in the model group increased, and the sSCF content and gastric emptying rate decreased. Compared with the model group, positive control group, and low dose Huangqi Jianzhong decoction group, the contents of blood glucose, GAS, and MLT significantly decreased, and the sSCF content and gastric emptying rate significantly increased in the high-dose group (P < 0.05). Compared with the normal group, the expression of c-kit and mSCF proteins in the gastric antrum decreased in the model group. Compared with the model group, the expression of c-Kit and mSCF proteins in the positive control group, low-dose and high-dose Huangqi Jianzhong decoction groups significantly increased (P < 0.05). Compared with the positive control group, the expression of c-Kit and mSCF proteins in the low-dose and high-dose Huangqi Jianzhong decoction groups increased, but the difference was not statistically significant (P > 0.05).

CONCLUSION

Huangqi Jianzhong decoction enhances the expression of mSCF protein and up-regulates the SCF-Kit signaling pathway, which increases the number of ICC in the gastric antrum of DGP rats, improves gastric pacing function, and enhances gastric motility.

Long-Pulse Gastric Electrical Stimulation Repairs Interstitial Cells of Cajal and Smooth Muscle Cells in the Gastric Antrum of Diabetic Rats

Background/Aims

The damage of interstitial cells of Cajal and smooth muscle cells has far-reaching implications in the pathogenesis of gastroparesis in diabetic patients. Gastric electrical stimulation (GES) is an efficient therapy for gastric motility disorders, but the mechanisms of GES require clarification.

Methods

Male rats were randomly divided into the control group, diabetic rat group (DM), diabetic rats with sham GES group (DM + SGES), and diabetic rats with different frequency GES group (DM + GES) (GES1: 5.5 cpm, 100 ms, 4 mA; GES2: 5.5 cpm, 300 ms, 4 mA; and GES3: 5.5 cpm, 550 ms, 2 mA). Gastric contractions were explored using the organ bath technique. The alterations of interstitial cells of Cajal, the SCF/c-kit pathway, and smooth muscle cells were also investigated.

Results

(1) Gastric contractions were significantly improved in the DM + GES group compared with those in the DM group. (2) The damage of interstitial cells of Cajal was prevented in the DM + GES group in contrast to the DM group. Moreover, long-pulse GES increased the expression of the SCF/c-kit pathway. More proliferated interstitial cells of Cajal in muscle layers were observed obviously in the DM + GES group. (3) The number of smooth muscle cells in the DM group was not significantly decreased compared with that in the control group. However, ultrastructural changes were distinctly damaged in the DM group. The application of GES protected against the alteration of the ultrastructures of smooth muscle cells.

Conclusions

Long-pulse GES improves gastric contraction possibly by enhancing the proliferation of interstitial cells of Cajal and restoring the injury of smooth muscle cells.

Yangyin Runchang Decoction Improves Intestinal Motility in Mice with Atropine/Diphenoxylate-Induced Slow-Transit Constipation

This study assessed the efficacy and mechanism of action of Yangyin Runchang decoction (YRD) in the treatment of slow-transit constipation (STC). ICR mice were randomly divided into four groups (n = 10/group) and treated with saline (normal control; NC), atropine/diphenoxylate (model control; MC; 20 mg/kg), or atropine/diphenoxylate plus low-dose YRD (L-YRD; 29.6 g/kg) or high-dose YRD (H-YRD; 59.2 g/kg). Intestinal motility was assessed by evaluating feces and the intestinal transit rate (ITR). The serum level of stem cell factor (SCF) and changes in interstitial cells of Cajal (ICCs) were also evaluated. Additionally, the expression of SCF and c-kit and the intracellular Ca²⁺ concentration [Ca²⁺]_I were investigated. Fecal volume and ITR were greater in the L-YRD and H-YRD groups than in the MC group. The serum SCF level was lower in the MC group than in the NC group; this effect was ameliorated in the YRD-treated mice. Additionally, YRD-treated mice had more ICCs and elevated expression of c-kit and membrane-bound SCF, and YRD also increased [Ca²⁺]_I in vitro in isolated ICCs. YRD treatment in this STC mouse model was effective, possibly via the restoration of the SCF/c-kit pathway, increase in the ICC count, and enhancement of ICC function by increasing [Ca²⁺]_i.