Hypoglycemic effect and mechanism of honokiol on type 2 diabetic mice

Exploring the associations between gut microbiota composition and SARS-CoV-2 inactivated vaccine response in mice with type 2 diabetes mellitus

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination is crucial for protecting vulnerable individuals, yet individuals with type 2 diabetes mellitus (T2DM) often exhibit impaired vaccine responses. Emerging evidence suggests that the composition of the host microbiota, crucial in immune regulation and development, influences vaccine efficacy. This study aimed to characterize the relationships between the SARS-CoV-2 inactivated vaccine and the host microbiota (specifically, gut and lung microbiota) of C57BL/6 mice with T2DM. Employing 16S rRNA metagenomic sequencing and ultra-high-performance liquid chromatography-mass spectrometry, we observed lower alpha diversity and distinct beta diversity in fecal microbiota before vaccination and in gut microbiota 28 days post-vaccination between T2DM mice and healthy mice. Compared with healthy mice, T2DM mice showed a higher Firmicutes/Bacteroidetes ratio 28 days post-vaccination. Significant alterations in gut microbiota composition were detected following vaccination, while lung microbiota remained unchanged. T2DM was associated with a diminished initial IgG antibody response against the spike protein, which subsequently normalized after 28 days. Notably, the initial IgG response positively correlated with fecal microbiota alpha diversity pre-vaccination. Furthermore, after 28 days, increased relative abundance of gut probiotics (Bifidobacterium and Lactobacillus) and higher levels of the gut bacterial tryptophan metabolite, indole acrylic acid, were positively associated with IgG levels. These findings suggest a potential link between vaccine efficacy and gut microbiota composition. Nonetheless, further research is warranted to elucidate the precise mechanisms underlying the impact of the gut microbiome on vaccine response. Overall, this study enhances our understanding of the intricate relationships among host microbiota, SARS-CoV-2 vaccination, and T2DM, with potential implications for improving vaccine efficacy.

IMPORTANCE

Over 7 million deaths attributed to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by 6 May 2024 underscore the urgent need for effective vaccination strategies. However, individuals with type 2 diabetes mellitus (T2DM) have been identified as particularly vulnerable and display compromised immune responses to vaccines. Concurrently, increasing evidence suggests that the composition and diversity of gut microbiota, crucial regulators of immune function, may influence the efficacy of vaccines. Against this backdrop, our study explores the complex interplay among SARS-CoV-2 inactivated vaccination, T2DM, and host microbiota. We discover that T2DM compromises the initial immune response to the SARS-CoV-2 inactivated vaccine, and this response is positively correlated with specific features of the gut microbiota, such as alpha diversity. We also demonstrate that the vaccination itself induces alterations in the composition and structure of the gut microbiota. These findings illuminate potential links between the gut microbiota and vaccine efficacy in individuals with T2DM, offering valuable insights that could enhance vaccine responses in this high-risk population.

Phytochemicals and their Potential Mechanisms against Insulin Resistance

Insulin's inception dates back to 1921 and was unveiled through a momentous revelation. Diabetes is a dangerous, long-term disease in which the body fails to generate enough insulin or utilize the insulin it creates adequately. This causes hyperglycemia, a state of high blood sugar levels, which can even put a person into a coma if not managed. Activation of the insulin receptor corresponds to two crucial metabolic functions, i.e., uptake of glucose and storage of glycogen. Type 2 diabetes mellitus (T2DM) exists as one of the most challenging medical conditions in the 21st century. The sedentary lifestyle and declining quality of food products have contributed to the rapid development of metabolic disorders. Hence, there is an urgent need to lay some reliable, significant molecules and modalities of treatment to combat and manage this epidemic. In this review, we have made an attempt to identify and enlist the major phytoconstituents along with the associated sources and existing mechanisms against insulin resistance. The conducted study may offer potential sustainable solutions for developing and formulating scientifically validated molecules and phytoconstituents as formulations for the management of this metabolic disorder.

Vascular endothelial growth factor B regulates insulin secretion in β cells of type 2 diabetes mellitus mice via PLCγ and the IP3R‑evoked Ca2+/CaMK2 signaling pathway

Vascular endothelial growth factor B (VEGFB) plays a crucial role in glucolipid metabolism and is highly associated with type 2 diabetes mellitus (T2DM). The role of VEGFB in the insulin secretion of β cells remains unverified. Thus, the present study aimed to discuss the effect of VEGFB on regulating insulin secretion in T2DM development, and its underlying mechanism. A high‑fat diet and streptozocin (STZ) were used for inducing T2DM in mice model, and VEGFB gene in islet cells of T2DM mice was knocked out by CRISPR Cas9 and overexpressed by adeno‑Associated Virus (AAV) injection. The effect of VEGFB and its underlying mechanism was assessed by light microscopy, electron microscopy and fluorescence confocal microscopy, enzyme‑linked immunosorbent assay, mass spectrometer and western blot analysis. The decrement of insulin secretion in islet β cell of T2DM mice were aggravated and blood glucose remained at a high level after VEGFB knockout (KO). However, glucose tolerance and insulin sensitivity of T2DM mice were improved after the AAV‑VEGFB186 injection. VEGFB KO or overexpression can inhibit or activate PLCγ/IP3R in a VEGFR1‑dependent manner. Then, the change of PLCγ/IP3R caused by VEGFB/VEGFR1 will alter the expression of key factors on the Ca2+/CaMK2 signaling pathway such as PPP3CA. Moreover, VEGFB can cause altered insulin secretion by changing the calcium concentration in β cells of T2DM mice. These findings indicated that VEGFB activated the Ca2+/CaMK2 pathway via VEGFR1‑PLCγ and IP3R pathway to regulate insulin secretion, which provides new insight into the regulatory mechanism of abnormal insulin secretion in T2DM.

Drug Discovery of Plausible Lead Natural Compounds That Target the Insulin Signaling Pathway: Bioinformatics Approaches

The growing smooth talk in the field of natural compounds is due to the ancient and current interest in herbal medicine and their potentially positive effects on health. Dozens of antidiabetic natural compounds were reported and tested in vivo, in silico, and in vitro. The role of these natural compounds, their actions on the insulin signaling pathway, and the stimulation of the glucose transporter-4 (GLUT4) insulin-responsive translocation to the plasma membrane (PM) are all crucial in the treatment of diabetes and insulin resistance. In this review, we collected and summarized a group of available in vivo and in vitro studies which targeted isolated phytochemicals with possible antidiabetic activity. Moreover, the in silico docking of natural compounds with some of the insulin signaling cascade key proteins is also summarized based on the current literature. In this review, hundreds of recent studies on pure natural compounds that alleviate type II diabetes mellitus (type II DM) were revised. We focused on natural compounds that could potentially regulate blood glucose and stimulate GLUT4 translocation through the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway. On attempt to point out potential new natural antidiabetic compounds, this review also focuses on natural ingredients that were shown to interact with proteins in the insulin signaling pathway in silico, regardless of their in vitro/in vivo antidiabetic activity. We invite interested researchers to test these compounds as potential novel type II DM drugs and explore their therapeutic mechanisms.

Review of the correlation between Chinese medicine and intestinal microbiota on the efficacy of diabetes mellitus

Diabetes mellitus is a serious metabolic disorder that can lead to a number of life-threatening complications. Studies have shown that intestinal microbiota is closely related to the development of diabetes, making it a potential target for the treatment of diabetes. In recent years, research on the active ingredients of traditional Chinese medicine (TCM), TCM compounds, and prepared Chinese medicines to regulate intestinal microbiota and improve the symptoms of diabetes mellitus is very extensive. We focus on the research progress of TCM active ingredients, herbal compounds, and prepared Chinese medicines in the treatment of diabetes mellitus in this paper. When diabetes occurs, changes in the abundance and function of the intestinal microbiota disrupt the intestinal environment by disrupting the intestinal barrier and fermentation. TCM and its components can increase the abundance of beneficial bacteria while decreasing the abundance of harmful bacteria, regulate the concentration of microbial metabolites, improve insulin sensitivity, regulate lipid metabolism and blood glucose, and reduce inflammation. TCM can be converted into active substances with pharmacological effects by intestinal microbiota, and these active substances can reverse intestinal microecological disorders and improve diabetes symptoms. This can be used as a reference for diabetes prevention and treatment.

Anti-Inflammatory and Antioxidant Properties of Carvacrol and Magnolol, in Periodontal Disease and Diabetes Mellitus

Periodontal disease and diabetes mellitus are two pathologies that are extremely widespread worldwide and share the feature of chronic inflammation. Carvacrol is a phenolic monoterpenoid, produced by a variety of herbs, the most well-known of which is Origanum vulgare. Magnolol is a traditional polyphenolic compound isolated from the stem bark of Magnolia officinalis, mainly used in Chinese medicine. The purpose of this paper is to review the therapeutic properties of these bioactive compounds, in the treatment of periodontitis and diabetes. Based on our search strategy we conducted a literature search in the PubMed and Google Scholar databases to identify studies. A total of one hundred eighty-four papers were included in the current review. The results show that carvacrol and magnolol have anti-inflammatory, antioxidant, antimicrobial, anti-osteoclastic, and anti-diabetic properties that benefit both pathologies. Knowledge of the multiple activities of carvacrol and magnolol can assist with the development of new treatment strategies, and the design of clinical animal and human trials will maximize the potential benefits of these extracts in subjects suffering from periodontitis or diabetes.

Plant Extracts in Obesity: A Role of Gut Microbiota

Obesity has become one of the most serious chronic diseases threatening human health. Its occurrence and development are closely associated with gut microbiota since the disorders of gut microbiota can promote endotoxin production and induce inflammatory response. Recently, numerous plant extracts have been proven to mitigate lipid dysmetabolism and obesity syndrome by regulating the abundance and composition of gut microbiota. In this review, we summarize the potential roles of different plant extracts including mulberry leaf extract, policosanol, cortex moutan, green tea, honokiol, and capsaicin in regulating obesity via gut microbiota. Based on the current findings, plant extracts may be promising agents for the prevention and treatment of obesity and its related metabolic diseases, and the mechanisms might be associated with gut microbiota.

Honokiol inhibits carotid artery atherosclerotic plaque formation by suppressing inflammation and oxidative stress

Honokiol is a natural active compound extracted from Chinese herbal medicine, Magnolia officinalis. In this study, the role of honokiol in the development of carotid artery atherosclerotic lesions was evaluated in an ApoE-/- mouse model fed with a normal diet (ND) or a Western-type diet (WD) for ten weeks. After first two weeks, a perivascular collar was surgically placed on the right common carotid arteries of the mice. Then, WD-fed mice were intraperitoneally injected with honokiol (10 or 20 mg/kg) or administrated with 10 mg/kg atorvastatin calcium by gavage once a day for eight weeks. After that, the right common carotid arteries were excised for further experiments. The result showed that honokiol substantially inhibited the development of atherosclerotic lesions. Furthermore, honokiol downregulated the expression of pro-inflammatory markers, like tumor necrosis factor-α, interleukin (IL)-6, and IL-1β. Additionally, honokiol treatment decreased reactive oxygen species level and enhanced superoxide dismutase activity. Nitric oxide level, inducible nitric oxide synthase (iNOS) expression, and aberrant activation of nuclear factor-κB pathway were also significantly inhibited by honokiol treatment. Together, these findings suggest that honokiol protects against atherosclerotic plaque formation in carotid artery, and may be an effective drug candidate for the treatment of carotid artery atherosclerotic stenosis.

Honokiol Restores Polymyxin Susceptibility to MCR-1-Positive Pathogens both In Vitro and In Vivo

The emergence of the plasmid-mediated colistin resistance gene mcr-1 has led to serious multidrug-resistant (MDR) Enterobacteriaceae infections, which are a great threat to the clinic. This study aims to find an inhibitor of MCR-1 to reestablish the use of polymyxins against MDR Enterobacteriaceae infections. Here, we determined that the natural compound honokiol could enhance the efficacy of polymyxins against MDR Enterobacteriaceae infections by a checkerboard MIC assay, a time-kill assay, a combined disk test, Western blotting, molecular simulation dynamics, and mouse infection models. The MIC results indicated that honokiol can recover the sensitivity of polymyxins against MCR-1-positive Klebsiella pneumoniae and Escherichia coli (with a fractional inhibitory concentration index ranging from 0.09 ± 0.00 to 0.27 ± 0.06). Based on time-kill curve analysis, all of the tested bacteria were killed within 1 h following the combined therapy with honokiol and polymyxins. Molecular simulation dynamics results suggested that honokiol directly binds to the MCR-1 active region, reducing the biological activity of MCR-1. The combination of honokiol and polymyxins could increase the 40% protection rate and reduce the bacterial load on the thigh muscles of mice. Our study indicates that honokiol is a predominant natural compound whose combination therapy with polymyxins is very promising in future treatment options for MCR-1-positive Enterobacteriaceae infections.IMPORTANCE In the present study, honokiol could effectively inhibit the activity of MCR-1 and showed almost no cytotoxicity to MH-S cells. According to our results, the combination of honokiol and polymyxin had a clear synergistic effect against MCR-1-positive Enterobacteriaceae in vitro Combination therapy also showed a powerful therapeutic effect in vivo, which can significantly improve mouse livability, reduced the load of bacteria, and reduced pathological change. This combined therapy of small molecule compounds and antibiotics may not continue to induce new bacterial resistance, due to the fact that MCR-1 targeted by honokiol is not indispensable for the bacterial viability; on the other hand, it can reduce the dosage of combined antibiotics, and it is also a promising alternative therapy for the treatment of drug-resistant infections in the future.

Honokiol Improves Insulin Resistance, Hepatic Steatosis, and Inflammation in Type 2 Diabetic db/db Mice

This study focuses on the effect of honokiol (HON) on glucose homeostasis, insulin resistance, dyslipidemia, hepatic steatosis, and inflammation in type 2 diabetic db/db mice. Male C57BL/KsJ-db/db mice were fed a normal diet with or without HON (0.02%, w/w) or pioglitazone (PIO, anti-diabetic agent, 0.01%, w/w) for 5 weeks. Blood biomarker, tissue morphology and enzymatic and genetic parameters were determined. PIO significantly decreased food intake, fasting blood glucose, and glycosylated hemoglobin (HbA1c) levels, but markedly increased body weight, adipose tissue weight, and plasma leptin levels. HON did not significantly affect food intake, body weight, or levels of plasma leptin and blood glucose. However, HON led to significant decreases in adipose tissue weight, plasma insulin, blood HbA1c and HOMA-IR levels and improved glucose tolerance. The anti-diabetic and anti-adiposity effects of HON were partially related to the inhibition of gluconeogenic enzymes and their mRNA expression in the liver; and the inhibition of lipogenic enzymes in adipose tissue, respectively. Unlike PIO, HON did not affect dyslipidemia, but ameliorated hepatic steatosis by inhibiting hepatic lipogenic enzymes activity. Moreover, HON exhibited anti-inflammatory effects similar to PIO. These results suggest that HON can protect against type 2 diabetes by improving insulin resistance, glucose and lipid metabolism, and inflammation.

PAXX Participates in Base Excision Repair via Interacting with Pol β and Contributes to TMZ Resistance in Glioma Cells

Non-homologous end joining (NHEJ) is one of the major DNA repair pathway in mammalian cell that can ligate a variety of DNA ends. However, how does all NHEJ factors communicate and organize together to achieve the final repair is still not clear. PAralog of XRCC4 and XLF (PAXX) was a new factor identified recently that play an important role in NHEJ. PAXX contributes to efficient NHEJ by interacting with Ku, which is a NHEJ key factor, and PAXX deficiency cause sensitivity to DNA double-strand break repair (DSBR). We observed that PAXX-deficient cells showed slight increase of homologous recombination (HR, which is another major DSBR repair pathways in mammalian cells). More importantly, we found that PAXX contributes to base excision repair pathway via interaction of polymerase beta (pol β). Temozolomide (TMZ) is one of the standard chemotherapies widely applied in glioblastoma. However, TMZ resistance and lack of potent chemotherapy agents can substitute TMZ. We observed that PAXX deficiency cause more sensitivity to TMZ-resistant glioma cells. In conclusion, the PAXX contributes to a variety of DNA repair pathways and TMZ resistance. Therefore, inhibition of PAXX may provide a promising way to overcome TMZ resistance and improve TMZ therapeutic effects in glioma treatment.

High, but not low, exercise volume shifts the balance of renin-angiotensin system toward ACE2/Mas receptor axis in skeletal muscle in obese rats

Metabolic syndrome is a cluster of metabolic risk factors that is linked to central obesity, elevated blood pressure, insulin resistance (IR), and dyslipidemia, where the renin-angiotensin system (RAS) may provide a link among them. This study aimed to evaluate volume exercise effects comparing low vs. high volume of chronic aerobic exercise on RAS axes in skeletal muscle in a diet-induced obesity (DIO) rat model. For this, male Wistar-Kyoto rats were fed a standard chow (SC) diet or a high-fat (HF) diet for 32 wk. Animals receiving the HF diet were randomly divided into low exercise volume (LEV, 150 min/wk) and high exercise volume (HEV, 300 min/wk) at the 20th week. After 12 wk of aerobic treadmill training, the body mass and composition, blood pressure, glucose and lipid metabolism, RAS axes, insulin signaling, and inflammatory pathway were performed. HEV slowed the body mass gain, reduced intra-abdominal fat pad and leptin levels, improved total and peripheral body composition and inflammatory cytokine, reduced angiotensin II type 1 receptor expression, and increased Mas receptor protein expression compared with the HF animals. Sedentary groups (SC and HF) presented lower time to exhaustion and maximal velocity compared with the LEV and HEV groups. Both exercise training groups showed reduced resting systolic blood pressure and heart rate, improved glucose tolerance, IR, insulin signaling, and lipid profile. We conclude that the HEV, but not LEV, shifted the balance of RAS toward the ACE2/Mas receptor axis in skeletal muscle, presenting protective effects against the DIO model.

Honokiol induces superoxide production by targeting mitochondrial respiratory chain complex I in Candida albicans

Background

Honokiol, a compound extracted from Magnolia officinalis, has antifungal activities by inducing mitochondrial dysfunction and triggering apoptosis in Candida albicans. However, the mechanism of honokiol-induced oxidative stress is poorly understood. The present investigation was designed to determine the specific mitochondrial reactive oxygen species (ROS)-generation component.

Methods/results

We found that honokiol induced mitochondrial ROS accumulation, mainly superoxide anions (O₂^•−) measured by fluorescent staining method. The mitochondrial respiratory chain complex I (C I) inhibitor rotenone completely blocked O₂^•− production and provided the protection from the killing action of honokiol. Moreover, respiratory activity and the C I enzyme activity was significantly reduced after honokiol treatment. The differential gene-expression profile also showed that genes involved in oxidoreductase activity, electron transport, and oxidative phosphorylation were upregulated.

Conclusions

The present work shows that honokiol may bind to mitochondrial respiratory chain C I, leading to mitochondrial dysfunction, accompanied by increased cellular superoxide anion and oxidative stress.

General significance

This work not only provides insights on the mechanism by which honokiol interferes with fungal cell, demonstrating previously unknown effects on mitochondrial physiology, but also raises a note of caution on the use of M. officinalis as a Chinese medicine due to the toxic for mitochondria and suggests the possibility of using honokiol as chemosensitizer.

4-O'-methylhonokiol protects from alcohol/carbon tetrachloride-induced liver injury in mice

Alcoholic liver disease (ALD) is a leading cause of liver cirrhosis, liver cancer, and related mortality. The endocannabinoid system contributes to the development of chronic liver diseases, where cannabinoid receptor 2 (CB2) has been shown to have a protecting role. Thus, here, we investigated how CB2 agonism by 4'-O-methylhonokiol (MHK), a biphenyl from Magnolia grandiflora, affects chronic alcohol-induced liver fibrosis and damage in mice. A combination of alcohol (10% vol/vol) and CCl4 (1 ml/kg) was applied to C57BL/6 mice for 5 weeks. MHK (5 mg/kg) was administered daily, and liver damage assessed by serum AST and ALT levels, histology, gene, and protein expression. Endocannabinoids (ECs) and related lipid derivatives were measured by liquid chromatography and mass spectrometry (LC-MS) in liver tissues. In vitro, MHK was studied in TGFβ1-activated hepatic stellate cells (HSC). MHK treatment alleviated hepatic fibrosis, paralleled by induced expression of matrix metalloproteinases (MMP)-2, -3, -9, and -13, and downregulation of CB1 mRNA. Necrotic lesions and hepatic inflammation were moderately improved, while IL-10 mRNA increased and IFNγ, Mcl-1, JNK1, and RIPK1 normalized by MHK. Hepatic anandamide (AEA) and related N-acetylethanolamines (NAEs) were elevated in MHK group, whereas fatty acid synthase and diacylglycerol O-acyltransferase 2 expression reduced. In vitro, MHK prevented HSC activation and induced apoptosis via induction of bak1 and bcl-2. To conclude, MHK revealed hepatoprotective effects during alcohol-induced liver damage through the induction of MMPs, AEA, and NAEs and prevention of HSC activation, indicating MHK as a potent therapeutic for liver fibrosis and ALD.

KEY MESSAGES

Methylhonokiol improves liver damage and survival. Methylhonokiol reduces hepatic fibrosis and necroinflammation. Methylhonokiol prevents myofibroblast activation and induces apoptosis. Methylhonokiol upregulates endocannabinoids and related N-acylethanolamines. Methylhonokiol contributes to lipid hydrolysis via PPARα/γ.

Honokiol induces reactive oxygen species-mediated apoptosis in Candida albicans through mitochondrial dysfunction

Objective

To investigate the effects of honokiol on induction of reactive oxygen species (ROS), antioxidant defense systems, mitochondrial dysfunction, and apoptosis in Candida albicans.

Methods

To measure ROS accumulation, 2′,7′-dichlorofluorescein diacetate fluorescence was used. Lipid peroxidation was assessed using both fluorescence staining and a thiobarbituric acid reactive substances (TBARS) assay. Protein oxidation was determined using dinitrophenylhydrazine derivatization. Antioxidant enzymatic activities were measured using commercially available detection kits. Superoxide dismutase (SOD) genes expression was measured using real time RT-PCR. To assess its antifungal abilities and effectiveness on ROS accumulation, honokiol and the SOD inhibitor N,N′-diethyldithiocarbamate (DDC) were used simultaneously. Mitochondrial dysfunction was assessed by measuring the mitochondrial membrane potential (mtΔψ). Honokiol-induced apoptosis was assessed using an Annexin V-FITC apoptosis detection kit.

Results

ROS, lipid peroxidation, and protein oxidation occurred in a dose-dependent manner in C. albicans after honokiol treatment. Honokiol caused an increase in antioxidant enzymatic activity. In addition, honokiol treatment induced SOD genes expression in C. albicans cells. Moreover, addition of DDC resulted in increased endogenous ROS levels and potentiated the antifungal activity of honokiol. Mitochondrial dysfunction was confirmed by measured changes to mtΔψ. The level of apoptosis increased in a dose-dependent manner after honokiol treatment.

Conclusions

Collectively, these results indicate that honokiol acts as a pro-oxidant in C. albicans. Furthermore, the SOD inhibitor DDC can be used to potentiate the activity of honokiol against C. albicans.

Extracts of Magnolia Species-Induced Prevention of Diabetic Complications: A Brief Review

Diabetic complications are the major cause of mortality for the patients with diabetes. Oxidative stress and inflammation have been recognized as important contributors for the development of many diabetic complications, such as diabetic nephropathy, hepatopathy, cardiomyopathy, and other cardiovascular diseases. Several studies have established the anti-inflammatory and oxidative roles of bioactive constituents in Magnolia bark, which has been widely used in the traditional herbal medicines in Chinese society. These findings have attracted various scientists to investigate the effect of bioactive constituents in Magnolia bark on diabetic complications. The aim of this review is to present a systematic overview of bioactive constituents in Magnolia bark that induce the prevention of obesity, hyperglycemia, hyperlipidemia, and diabetic complications, including cardiovascular, liver, and kidney.