Polydatin Alleviates Diabetes-Induced Hyposalivation through Anti-Glycation Activity in db/db Mouse

BuZhong YiQi Formula Alleviates Diabetes-Caused Hyposalivation by Activating Salivary Secretion Pathway in the Parotid and Submandibular Glands of Rats

Background/Objectives: BuZhong Yiqi Formula (BZYQF) has significant ameliorative effects on type 2 diabetes mellitus (T2DM). However, its efficacy in alleviating the hyposalivation caused by T2DM needs to be confirmed, and its mechanism is unclear. Methods: Network pharmacology and molecular docking were combined to analyze the molecular mechanism by which BZYQF alleviates T2DM-caused hyposalivation. A T2DM rat model was induced to evaluate the efficacy of BZYQF. The total saliva before and after acid stimulation was collected to determine the salivary flow rate and salivary alpha-amylase (sAA) activity. The parotid (PG) and submandibular glands (SMG) of experimental rats were removed to perform histopathology observation, biochemical indicator determination, and expression detection of signaling molecules in the salivary secretion pathway. Results: The present study screened out 1014 potential targets of BZYQF regarding the treatment of T2DM. These targets were mainly involved in the formation of the receptor complex, exercising the neurotransmitter receptor activity and regulating secretion. They were significantly enriched in the salivary secretion pathway of β1-AR/PKA/AMY1 and CHRM3/IP3R/AQP5. Furthermore, in BZYQF, nine validated compounds were able to dock into the active site of β1-AR, and three validated compounds were able to dock into the active site of CHRM3. Animal experiments confirmed that BZYQF significantly reduces fasting blood glucose, total cholesterol and triglyceride levels; enhances insulin level and HOMA-IS (p < 0.05); and increases salivary flow rate (Basal: increase from 21.04 ± 14.31 to 42.65 ± 8.84 μL/min, effect size of Cohen's d = 6.80, p = 0.0078; Stimulated: increase from 36.88 ± 17.48 to 72.63 ± 17.67 μL/min, effect size of Cohen's d = 7.61, p = 0.0025) and sAA activity (Basal: increase from 0.68 ± 0.32 to 2.17 ± 0.77 U/mL, effect size of Cohen's d = 9.49, p = 0.0027; Stimulated: increase from 1.15 ± 0.77 to 4.80 ± 1.26 U/mL, effect size of Cohen's d = 13.10, p = 0.0001) in basal and stimulated saliva in T2DM rats. Further mechanistic studies revealed that BZYQF reduces glucose and lipid accumulation, enhances acetylcholine content, improves pathological lesions and inflammation, and significantly increases the expression of salivary secretion pathway signaling molecules, including PKA, IP3R, β1-AR, AQP5, CHRM3, and AMY1 in the PG and SMG of T2DM rats (p < 0.05). Conclusions: The present study demonstrated that BZYQF is able to alleviate T2DM-caused hyposalivation by improving glucose metabolism and activating the salivary secretion pathway in the PG and SMG of T2DM rats. This study might provide a novel rationale and treatment strategy for BZYQF in diabetes-induced hyposalivation in a clinical setting.

Polydatin protects against DSS-induced ulcerative colitis via Nrf2/Slc7a11/Gpx4-dependent inhibition of ferroptosis signalling activation

Introduction

Ulcerative colitis (UC), a form of inflammatory irritable bowel disease, is characterized by a recurrent and persistent nonspecific inflammatory response. Polydatin (PD), a natural stilbenoid polyphenol with potent properties, exhibits unexpected beneficial effects beyond its well-documented anti-inflammatory and antioxidant activities. In this study, we presented evidence that PD confers protection against dextran sodium sulfate (DSS)-induced ulcerative colitis.

Methods

The protective effect of PD on colitis was examined in cultured caco-2 cells and DSS-induced colitis mouse model. Bulk RNA sequencing and differential gene expression analysis were used to investigate the protective mechanism of PD on DSS-induced colitis. Ferroptosis was determined by MDA levels, SOD levels, mitochondrial iron accumulation and ROS production. Ferroptosis-related proteins Slc7a11, Nrf2 and Gpx4 levels were measured by western blot, immunohistochemical and immunofluorescence staining.

Results

PD mitigated the DSS-induced increases in pro-inflammatory cytokines (IL-6, TNF-α, and IL-1β), alleviated colon length shortening, reduced morphological damage to the intestinal mucosa, and preserved tight junction proteins (TJ) occludin and Zonula occludens-1 (ZO-1) in both caco-2 cells and murine models of colitis. Mechanistically, PD reversed the reduction of Nrf2, Slc7a11 and Gpx4, the degree of nuclear translocation of Nrf2 induced by DSS in vitro and in vivo significantly. Moreover, the protective effect of PD is attenuated by erastin and resembled that of Fer-1 in caco-2 cells model.

Discussion

Our study suggested that PD protects against DSS-induced ulcerative colitis via Nrf2/Slc7a11/Gpx4-dependent inhibition of ferroptosis signalling activation. Further investigation into the precise mechanisms underlying this phenomenon is warranted. The findings presented herein indicated that PD may serve as a potential therapeutic agent for patients with UC.

Agmatine alleviates diabetic-induced hyposalivation in rats: A histological and biochemical study

Diabetic patients commonly experience hyposalivation, which can cause challenges with eating, swallowing, dry mouth, and speaking. It also raises the likelihood of developing periodontal disease. This study aimed to evaluate if agmatine could improve the rate of salivation in rats with hyposalivation induced by streptozotocin (STZ). Five groups of Wistar rats were utilized with 10 animals in each group. They were classified as follows; Negative control group (G1), agmatine (G2) group, and Nicotinamide (NA)-STZ (G3) group; received a single intraperitoneal dose of 65 mg/kg of STZ after NA injection. NA was administered to protect residual β cells and enhance their insulin secretion; NA-STZ + Metformin (G4) Metformin-treated diabetic group; at day 10 diabetic rats received 50mg/kg orally for 28 days, and NA-STZ + Agmatine (G5) at day 10 diabetic rats received a daily intraperitoneal dose of 300 mg/kg Agmatine for 28 days. The salivary flow rate was assessed weekly. Then, the animals were euthanized, both parotid (PG) and submandibular (SMG) salivary glands were dissected, and the following parameters were assessed; salivary glands' histopathology, aquaporin 5 (AQP5), caspase-3, E-cadherin expressions, inflammatory markers and finally, salivary glands' oxidative stress status. Agmatine has alleviated the salivary glands' dysfunction in STZ-induced diabetic rats. It normalized diabetes mellitus-associated salivary glands' abnormalities including histopathological abnormalities, decreased AQP5 and E-cadherin expressions, increased caspase-3 expression, and oxidative stress and inflammatory parameters. Agmatine alleviates diabetes mellitus-associated hyposalivation. It can promote PGs and SMGs function through its histological and AQP5 expression improvements.

Improvement effect of gemigliptin on salivary gland dysfunction in exogenous methylglyoxal-injected rats

The symptom of hyposalivation associated with hypofunction of the salivary glands is a common feature of diabetes. Inadequate saliva production can cause tissue damage in the mouth, making it susceptible to infections and leading to oral health diseases. Previous studies have highlighted the harmful effects of methylglyoxal (MGO) and MGO-derived advanced glycation end products (AGEs) in diabetes. In this study, we investigated the protective effects of gemigliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, against MGO-induced salivary gland dysfunction. MGO treatment of immortalized human salivary gland acinar cells induced apoptosis via reactive oxygen species (ROS)-mediated pathways, but this effect was mitigated by gemigliptin. In vivo experiments involved the simultaneous administration of MGO (17.25 mg/kg) with aminoguanidine (100 mg/kg) and gemigliptin (10 and 100 mg/kg) daily to rats for two weeks. Gemigliptin increased the saliva volume and amylase levels in MGO-injected rats. Gemigliptin reduced the DPP-4 activity in both the salivary glands and serum of MGO-injected rats. Furthermore, gemigliptin exerted anti-glycation effects by reducing the accumulation of AGEs in the saliva, salivary glands, and serum and suppressing the expression of the receptor for AGEs. These actions protected the salivary gland cells from ROS-mediated apoptosis. Overall, gemigliptin protected the salivary gland cells from ROS-mediated cell death, reduced the accumulation of amylase and mucins in the salivary glands, and enhanced the salivary function by upregulating aquaporin 5 expression, and it exerted protective effects against MGO-induced salivary gland dysfunction by enhancing the anti-glycation, antioxidant, and salivary secretion activities. Our findings suggest gemigliptin as a potential therapeutic for patients with salivary gland dysfunction caused by the complications of diabetes.

Gemigliptin Improves Salivary Gland Dysfunction in D-Galactose-Injected Aging Rats

Oral dryness is among the most common conditions experienced by the elderly. As saliva plays a crucial role in maintaining oral health and overall quality of life, the condition is increasingly taking its toll on a rapidly growing aging population. D-galactose (D-gal) stimulates their formation, which in turn cause oxidative stress and accelerate age-related decline in physical function. In this study, we observed a reduction in salivary secretion and amylase levels in aged rats injected with D-gal, confirming salivary gland dysfunction. Treatment with gemigliptin increased DPP-4 inhibition and GLP-1 levels in the salivary glands of aging rats and reduced the expression of AGEs and receptors for advanced glycation end products (RAGE). This effect was caused by the presence of additional reactive oxygen species (ROS) in the salivary glands of the examined rats. Gemigliptin's cytoprotective effect reduced amylase and mucin accumulation and increased AQP5 expression, which are important indicators of salivary gland function. In sum, gemigliptin was shown to improve D-gal-induced decline in the salivary gland function of aged rats through its anti-glycation and antioxidant activities. Gemigliptin shows promise as a treatment strategy for patients experiencing decreased salivary function associated with their advancing age.

A Possible Novel Protective Effect of Piceatannol against Isoproterenol (ISO)-Induced Histopathological, Histochemical, and Immunohistochemical Changes in Male Wistar Rats

Dry mouth is characterized by lower saliva production and changes in saliva composition. In patients with some salivary gland function remaining, pharmaceutical treatments are not recommended; therefore, new, more effective methods of promoting saliva production are needed. Hence, this study aimed to provide an overview of the histological changes in the salivary gland in the model of isoproterenol (ISO)-induced degenerative changes in male Wistar rats and to evaluate the protective effect of piceatannol. Thirty-two male Wistar rats were randomly divided into four groups: the control group, the ISO group, and the piceatannol (PIC)-1, and -2 groups. After the third day of the experiment, Iso (0.8 mg/100 g) was injected intraperitoneally (IP) twice daily into the animals. PIC was given IP in different daily doses (20 and 40 mg/kg) for three days before ISO and seven days with ISO injection. The salivary glands were rapidly dissected and processed for histological, histochemical, immunohistochemical (Ki-67), and morphometric analysis. Upon seven days of treatment with ISO, marked hypertrophy was observed, along with an increased number of positive Ki-67 cells. Proliferation was increased in some endothelial cells as well as in ducts themselves. Despite the significant decrease in proliferation activity, the control group did not return to the usual activity level after treatment with low-dose PIC. Treatment with a high dose of PIC reduced proliferative activity to the point where it was substantially identical to the results seen in the control group. An ISO-driven xerostomia model showed a novel protective effect of piceatannol. A new era of regenerative medicine is dawning around PIC’s promising role.

Current Strategies and Potential Prospects for Nanoparticle-Mediated Treatment of Diabetic Nephropathy

Diabetic nephropathy (DN), a severe microvascular complication of diabetes mellitus (DM), is the most common form of chronic kidney disease (CKD) and a leading cause of renal failure in end-stage renal disease. No currently available treatment can achieve complete cure. Traditional treatments have many limitations, such as painful subcutaneous insulin injections, nephrotoxicity and hepatotoxicity with oral medication, and poor patient compliance with continual medication intake. Given the known drawbacks, recent research has suggested that nanoparticle-based drug delivery platforms as therapeutics may provide a promising strategy for treating debilitating diseases such as DN in the future. This administration method provides multiple advantages, such as delivering the loaded drug to the precise target of action and enabling early prevention of CKD progression. This article discusses the development of the main currently used nanoplatforms, such as liposomes, polymeric NPs, and inorganic NPs, as well as the prospects and drawbacks of nanoplatform application in the treatment of CKD.