Electroacupuncture promotes the gastrointestinal motility of diabetic mice by CNP/NPR-B-cGMP and PDE3A-cGMP signaling

Electroacupuncture Promotes the Proliferation and Differentiation of Enteric Neural Precursor Cells via the PTEN/PI3K/Akt/mTOR Signaling Pathway in Diabetic Mice

BACKGROUND

Enteric neuronal loss significantly contributes to gastrointestinal (GI) motility disorders. Electroacupuncture (EA) can promote the regeneration of lost enteric neurons in diabetic mice, but its mechanisms are not fully understood. Nestin+/Ngfr+ cells can function as enteric neural precursor cells (ENPCs) to proliferate and differentiate into enteric neurons in adult mice. However, EA's effects on ENPCs remain unknown. The study aimed to investigate whether EA reversed enteric neuronal loss via regulation of ENPCs and its molecular basis.

MATERIALS AND METHODS

The study utilized conventional C57BL/6J mice and ENPC-tracing transgenic mice. Streptozotocin-induced type 1 diabetic mouse, PI3K inhibitor, and PTEN inhibitor models were used. GI motility was evaluated by defecation frequency, fecal water content, and whole gut transit test. The alterations of enteric neurons, ENPCs, and PTEN/PI3K/Akt/mTOR signaling were detected by Western blot and immunofluorescence.

RESULTS

EA increased defecation frequency and fecal water content, reduced whole gut transit time, and increased the number of enteric neurons. Notably, EA inhibited ENPC apoptosis and facilitated ENPC proliferation and differentiation with a preferential into ChAT enteric neurons. Additionally, PTEN was decreased and PI3K/Akt/mTOR signaling was activated with EA. However, LY294002 (PI3K inhibitor) inhibited EA's effects on ENPCs, while BpV(HOpic) (PTEN inhibitor) partially rescued these inhibitory effects.

CONCLUSIONS

EA alleviates diabetic enteric neuropathy by regulating ENPC dynamics through the PTEN/PI3K/Akt/mTOR signaling pathway. Notably, EA-mediated anti-apoptotic and pro-proliferative effects on ENPCs, and their preferential cholinergic differentiation establish EA as a multimodal therapy that bridges neuromodulation with precursor cell biology, offering an alternative strategy for GI motility disorders.

Low-intensity pulsed ultrasound combined with ST36 modulate gastric smooth muscle contractile marker expression via RhoA/Rock and MALAT1/miR-449a/DLL1 signaling in diabetic rats

BACKGROUND

Low-intensity pulsed ultrasound (LIPUS) combined with acupoint can promote gastric motility of diabetic rats. The switch of gastric smooth muscle cell (GSMCs) phenotype was related to the diabetes-induced gastric dysfunction, but the mechanism is not clearly elucidated. This study was aimed at exploring the underlying mechanism of LIPUS stimulation application in diabetic gastroparesis rats.

METHODS

In this study, Sprague-Dawley male rats were divided into three groups: control group (CON), diabetic gastroparesis group (DGP), and LIPUS-treated group (LIPUS). LIPUS irradiation was performed bilaterally at ST36 for 20 min per day for 4 weeks. The gastric emptying rate was measured by ultrasound examination. Contraction ability of GSMCs was assessed by muscle strip experiment. The expression of related proteins or mRNAs including α-SMA, SM22α, MHC, RhoA, Rock2, p-MYPT1, MYPT1, p-MLC, MLC, MALAT1, miR-449a, and DLL1 was detected by different methods such as western blotting, RT-qPCR, immunohistochemistry, and immunofluorescence staining, as appropriate.

KEY RESULTS

(a) LIPUS stimulation at ST36 could improve the gastric motility dysfunction of diabetic rats. (b) LIPUS increased RhoA, Rock2, p-MYPT1, and p-MLC expression level. (c) MALAT1 and DLL1 contents were decreased, but the level of miR-449a was increased in the LIPUS group.

CONCLUSIONS & INFERENCES

LIPUS may affect the contractile marker expression of gastric smooth muscle through the RhoA/Rock and MALAT1/miR-449a/DLL1 pathway to ameliorate DGP.

Chronic Electroacupuncture With High-Frequency at ST-36 Promotes Gastrointestinal Motility by Regulating Bone Morphogenetic Protein 2 Secretion of Muscularis Macrophages

BACKGROUND

Electroacupuncture (EA) at Zusanli (ST36) is an alternative treatment for several gastrointestinal motility disorders; however, the exact mechanism is unconfirmed. We aimed to show the potential effects of EA on muscularis macrophages (MMφ), the bone morphogenetic protein (BMP)/BMP receptor (BMPR)-Smad signal pathway, and enteric neurons in diabetic mice. This may provide fresh insight into ways EA affects gastrointestinal motility.

MATERIALS AND METHODS

C57BL/6J healthy adult male mice were randomly divided into five groups: regular control group, diabetes group, diabetes with sham EA group (acupuncture only), diabetes with low-frequency EA group (10 Hz), diabetes with high-frequency EA group (HEA) (100 Hz). The stimulation lasted eight weeks. Gastrointestinal motility was assessed. We identified M2-like MMφ in the layer of colonic muscle by flow cytometry. Western Blot, real-time polymerase chain reaction, and immunofluorescent staining were also used to determine the MMφ, molecules in the BMP2/BMPR-Smad pathway, and PGP9.5, neuronal nitric oxide synthase (nNOS) expression of enteric neurons in the colon of each group.

RESULTS

1) HEA improved the gastrointestinal motility (gastrointestinal transit time, defecation frequency) of diabetic mice. 2) HEA reversed the decreased proportion of M2-like MMφ and expression of the CD206 in the colon of diabetic mice. 3) HEA restored the downregulations of BMP2, BMPR1b, and Smad1 in the BMP2/BMPR-Smad pathway and increased downstream enteric neurons marked by PGP9.5, nNOS in the colon of diabetes mice.

CONCLUSIONS

HEA might promote gut dynamics by upregulating M2-like MMφ in the colon of diabetic mice, which in turn leads to the accumulation of molecules in the BMP2/BMPR-Smad signaling pathway and downstream enteric neurons.

Noninvasive electrical neuromodulation for gastrointestinal motility disorders

INTRODUCTION

Gastrointestinal motility disorders are highly prevalent without satisfactory treatment. noninvasive electrical neuromodulation is an emerging therapy for treating various gastrointestinal motility disorders.

AREAS COVERED

In this review, several emerging noninvasive neuromodulation methods are introduced, including transcutaneous auricular vagal nerve stimulation, percutaneous auricular vagal nerve stimulation, transcutaneous cervical vagal nerve stimulation, transcutaneous electrical acustimulation, transabdominal interference stimulation, tibial nerve stimulation, and translumbosacral neuromodulation therapy. Their clinical applications in the most common gastrointestinal motility are discussed, including gastroesophageal reflux disease, functional dyspepsia, gastroparesis, functional constipation, irritable bowel syndrome, and fecal incontinence. PubMed database was searched from 1995 to June 2023 for relevant articles in English.

EXPERT OPINION

Noninvasive neuromodulation is effective and safe in improving both gastrointestinal symptoms and dysmotility; it can be used when pharmacotherapy is ineffective. Future directions include refining the methodology, improving device development and understanding mechanisms of action.

Low-intensity pulsed ultrasound at ST36 improves the gastric motility by TNF-α/IKKβ/NF-κB signaling pathway in diabetic rats

BACKGROUND AND AIM

Low-intensity pulsed ultrasound (LIPUS) can effectively regulate the central and peripheral nervous system. However, whether LIPUS could act on acupuncture points to modulate the activity of peripheral nervous has rarely been studied. Our study aimed to investigate whether LIPUS at ST36 could improve gastric emptying in diabetic gastroparesis rats.

METHODS

Sprague-Dawley male rats were divided into three groups: control group (CON), diabetic gastroparesis group (DM), and diabetic gastroparesis LIPUS treated group (LIPUS). The body weight and blood glucose were recorded every week. Glucose tolerance, gastric emptying rate, and gastric motility were measured before and after treatment. Gastric motility was assessed by ultrasonic examination and Muscle strip experiment. The expression level of c-Kit was assessed by immunohistochemistry staining. Levels of TNF-α, p-NF-κB p-65, NF-κB p-65, and p-IKKβ, IKKβ were measured by western blot.

RESULTS

We reported LIPUS at an intensity of 0.88 W/cm2 exhibited significant differences in functional recovery of gastric delayed emptying in diabetic rats. Through ultrasound gastric motility functional testing and analysis of gastric antral smooth muscle strips indirectly and directly proved the effectiveness of LIPUS for the recovery of gastric delayed emptying. Pathological analysis and western blot indicated that the mechanism by which LIPUS applied to ST36 improved gastric motility may be partially attributed to the inhibition of the TNF-α/IKKβ/NF-κB signaling pathway, thereby rescuing the damaged interstitial cells of Cajal network.

CONCLUSION

LIPUS at ST36 improved the gastric motility and rescued the damaged networks of interstitial cells of Cajal. LIPUS may have a promising therapeutic potential for diabetic gastroparesis.

Electroacupuncture reduces blood glucose by regulating intestinal flora in type 2 diabetic mice

BACKGROUND

The development of diabetes is closely related to the gut microbiota in recent studies, which can be influenced by intestinal motility. A few studies report that electroacupuncture (EA) can lower blood glucose. EA can promote colonic motility and influence gut microbes. In this study, we explored the effect of the EA on blood glucose level in mice with type 2 diabetes (T2D) and its mechanism.

METHODS

The T2D mice model, fecal microbiota transplantation mice model, and Kit^W/Wv mice model （Point mutation of mouse W locus encoding kit gene）were used to investigate the effect of EA on blood glucose as well as the mechanism; The blood glucose and insulin resistance level and the intestinal flora were evaluated. The level of intestinal junction protein, inflammatory cytokines in the serum, interstitial cells of Cajal content, and colonic motility were detected. Lastly, the IKKβ/NF-κB-JNK-IRS-1-AKT pathway was explored.

RESULTS

EA lowered the blood glucose level, altered the gut microbiota, and promoted colonic motility in T2D mice. EA-altered microbiota decreased the blood glucose level and insulin resistance in the antibiotics-treated diabetic mice. EA increased tight junction protein, lowered inflammatory factors, and regulated the IKKβ/NF-κB-JNK-IRS-1-AKT pathway in the liver and muscles. EA could not reduce the blood glucose and regulated gut microbiota in the Kit^W/Wv mice model.

CONCLUSIONS

EA promoted intestinal motility to regulate the intestinal flora, thereby reducing the level of systemic inflammation, and ultimately lowering the blood glucose by the IKKβ/NF-κB-JNK-IRS-1-AKT signal pathway.

CD44 fucosylation on bone marrow-derived mesenchymal stem cells enhances homing and promotes enteric nervous system remodeling in diabetic mice

BACKGROUND

Diabetes can cause extensive enteric nervous system (ENS) injuries and gastrointestinal motility disorder. In developing possible treatments, researchers have engaged in tissue regeneration engineering with the very promising bone marrow-derived mesenchymal stem cells (BMSCs). However, BMSCs have poor homing ability to the targeted tissues after intravenous injection. Thus, we aimed to investigate whether enhancing the expression of E-selectin ligand on BMSCs could improve their homing ability and subsequently influence their role in ENS remodeling in diabetic mice.

METHODS

First, we constructed the fucosylation modification of CD44 on BMSCs through a fucosyltransferase VII (FTVII) system to generate a Hematopoietic Cell E-/L-selectin Ligand (HCELL) property, a fucosylated sialyllactosaminyl glycovariant of CD44 that potently binds E-selectin. Next, FTVII-modified and unmodified BMSCs labeled with green fluorescent protein (GFP) were injected into diabetic mice through the tail vein to compare their homing ability to the gastrointestinal tract and their effect on ENS remodeling, respectively. A bioluminescent imaging system was used to evaluate the homing ability of GFP-labeled BMSCs with and without FTVII modification, to the gastrointestinal tract. Gastrointestinal motility was assessed by gastrointestinal transient time, defecation frequency, stool water content and colon strips contractility. Immunofluorescence staining and western blotting were used to assess the expression levels of protein gene product 9.5 (PGP9.5), glial fibrillary acidic protein (GFAP) and glial cell line-derived neurotrophic factor (GDNF).

RESULTS

The FTVII-mediated α(1,3)-fucosylation modification of CD44 on BMSCs generated a HCELL property. Bioluminescent imaging assays showed that FTVII-modified BMSCs had enhanced homing ability to gastrointestinal tract, mainly to the colon, 24 h after injection through the tail vein. Compared with diabetic mice, FTVII-modified BMSCs significantly promoted the gastrointestinal motility and the ENS remodeling, including intestinal peristalsis (P < 0.05), increased feces excretion (P < 0.05) and the water content of the feces (P < 0.05), restored the spontaneous contraction of the colon (P < 0.05), and upregulated the protein expression levels of PGP9.5 (P < 0.01), GFAP (P < 0.001), and GDNF (P < 0.05), while unmodified BMSCs did not (P > 0.05).

CONCLUSIONS

CD44 fucosylation modification on murine BMSCs promotes homing ability to the gastrointestinal tract and ENS remodeling in diabetic mice.

Electroacupuncture accelerates the delayed intestinal transit in POI by suppressing M1 like muscularis macrophages and IL6 secretion

BACKGROUND

Electroacupuncture (EA) at ST-36 could accelerate the delayed gastrointestinal (GI) motility in many GI motility dysfunction models, but the definite effect and mechanisms are unclear. In this study, we intended to investigate the effects of EA on intestinal manipulation (IM) mice model and involved mechanisms.

METHODS

Male C57BL/6 mice were randomized into five groups: normal control, intestinal manipulation (IM), IM with sham EA (SEA), IM with high-frequency EA (HEA), and IM with low-frequency EA (LEA). The GI transit was evaluated. The infiltration of muscularis macrophages (MMφ) and its phenotype were analyzed with flow cytometry. Magnetic-activated cell sorting was applied to isolate MMφ, and the relationship between the MMφ and interstitial cells of Cajal (ICCs) was further investigated.

RESULTS

(1) Compared with the IM group, HEA and LEA attenuated the delayed intestinal transit. (2) Both the HEA and LEA obviously reduced the MMφ and suppressed the M1 activation of the MMφ in the ileum. (3) EA restored the disrupted ICC networks through inhibiting the release of IL6 by the MMφ.

CONCLUSION

(1) Electroacupuncture at acupoint ST-36 could accelerate the delayed intestinal transit in the IM murine model by restoring the ICC networks. (2) EA protected the ICCs through reducing the MMφ, inhibiting its M1 polarization and its IL6 secretion.

Defective development and microcirculation of intestine in Npr2 mutant mice

Intractable gastrointestinal (GI) diseases often develop during infancy. Our group previously reported that natriuretic peptide receptor B (NPR-B)-deficient Npr2^slw/slw mice exhibit severe intestinal dysfunction, such as stenosis and distention, which resembles the dysfunction observed in Hirschsprung’s disease-allied disorders. However, the root cause of intestinal dysfunction and the detailed of pathophysiological condition in the intestine are not yet clear. Here, we report that the intestine of preweaning Npr2^slw/slw mice showed bloodless blood vessels, and nodes were found in the lymphatic vessel. Additionally, the lacteals, smooth muscle, blood vessel, and nerves were barely observed in the villi of preweaning Npr2^slw/slw mice. Moreover, intramuscular interstitial cells of Cajal (ICC-IM) were clearly reduced. In contrast, villi and ICC-IM were developed normally in surviving adult Npr2^slw/slw mice. However, adult Npr2^slw/slw mice exhibited partially hypoplastic blood vessels and an atrophied enteric nervous. Furthermore, adult Npr2^slw/slw mice showed markedly reduced white adipose tissue. These findings suggest that the cause of GI dysfunction in preweaning Npr2^slw/slw mice is attributed to defective intestinal development with microcirculation disorder. Thus, it is suggested that NPR-B signaling is involved in intestinal development and control of microcirculation and fat metabolism. This report provides new insights into intractable GI diseases, obesity, and NPR-B signaling.

Signaling pathways underlying changes in the contractility of the stomach fundus smooth muscle in diabetic rats

Dysfunction of gastrointestinal (GI) motility is a common complication in patients with diabetes mellitus (DM). Studies related to changes in fundus contraction induced by inhibitors in DM are not well known. Therefore, this study aimed to investigate the signaling pathways involved in the changes in the contraction of fundus smooth muscle obtained from control and DM rats. DM was induced by injecting streptozotocin (65 mg/kg) into Sprague-Dawley rats. The rats were sacrificed after 14 days. Fundus smooth muscle contraction was stimulated using electrical field stimulation (amplitude, 50 V; duration, 1 min; frequency, 2-20 Hz) and acetylcholine (0.1 mM). The inhibitor-mediated cell membrane was pre-treated with atropine, verapamil, methysergide, ketanserin, ondansetron, and GR 113808. Inhibitors related to intracellular signaling, such as U73122, chelerythrine, L-NNA, were also used. ML-9 and Y-27632 were identified as inhibitors of factors of myosin light chain (MLC). The contractility was observed to be lower in the DM group than in the control group. Further, the activities of phospholipase C (PLC), protein kinase C (PKC), and myosin light chain kinase (MLCK) were decreased in the DM group. DM reduced the activity of PLC, PKC, and MLCK, which resulted in a decrease in the contractility of the fundus smooth muscle. Therefore, our results present the mechanism of this DM-mediated GI disorder.

Mechanism of CNP-mediated DG-PKC and IP4 signaling pathway in diabetic rats with gastric motility disorder

In the precedent research conducted by the same team, it concluded that the activities in C-type natriuretic peptide (CNP)/cyclic guanosine monophosphate (cGMP)/cyclic adenosine monophosphate (cAMP)/β-type phospholipase C (PLCβ) pathways of rat antral smooth muscle were changed due to diabetes, which was the key pathogenetic mechanism for diabetic gastric dysmotility. As the follow-on step, this study was designed to probe into the downstream signaling pathway of CNP/PLCβ. The results showed that level of α-type protein kinase C (PKCα),cell membrane to cytoplasm ratio of PKCα, cell membrane to cytoplasmic ratio of βI-type protein kinase C (PKCβI) and level of Phosphor-PKCα (P-PKCα) were significantly reduced in diabetes rat antral smooth muscle samples. The content of tetraphosphate inositol (IP4) in gastric antral smooth muscle of diabetic rats reduced, and the content of diacyl-glycerol (DG) was unchanged. CNP significantly decreased the content of IP4 and DG, this effect was more obvious in diabetic rats. Subsequent to the addition of protein kinase A (PKA) blocker N-[2- (p-Bromocin-namylamino)ethyl]-5 -isoquinolinesulfonamide dihydrochloride (H-89) before CNP treatment, the inhibitory effect of CNP was reduced; subsequent to the addition of protein kinase G (PKG) blocker KT5823 before CNP treatment, the inhibitory effect of CNP was also reduced. With the addition of the combination of H-89 and KT5823 before CNP treatment, the inhibition by CNP could be offset. These results were concluded that CNP inhibited the activity of PKC family in rat smooth muscle and reduced the levels of IP4 and DG through the PKG/PKA-PLCβ pathways, causing inhibited muscular contractions, which may be a key pathogenetic factor for diabetic gastroparesis.