Tetrahydrocurcumin ameliorates diabetes profiles of db/db mice by altering the composition of gut microbiota and up-regulating the expression of GLP-1 in the pancreas

Tetrahydrocurcumin alleviates di-(2-ethylhexyl) phthalate-induced adipose tissue dysfunction and testicular toxicity in adult mice: possible involvement of adiponectin-adipoR signaling in the testis

Widespread exposure to endocrine disruptors is associated with metabolic dysfunction and reproductive toxicity. Tetrahydrocurcumin (THC) has attracted attention as it offers protection against obesity and metabolic disorders due to its potent antioxidative and diverse biological properties but its influence and underlying mechanism of action on adipose tissue function and DEHP-induced testicular injury remain unknown. Our results showed that THC (100 mg kg-1 day-1) administration for 27 weeks enlarged adipocytes while attenuating macrophage infiltration and IL-6 expression in the adipose tissue of male C57BL/6J mice exposed to 5 mg kg-1 day-1 of DEHP. Moreover, THC ameliorated DEHP-induced deregulation of adiponectin but not leptin. DEHP caused testicular histological damage, spermatogenesis impairment, apoptosis, inflammation, and AGE, which were improved by THC. THC treatment elevated Nrf2/HO-1 and decreased Glut1 in interstitial Leydig cells, which may contribute to its beneficial effects on the testis. Our results further demonstrated that THC also ameliorated circulating adiponectin and testicular adipoR1-AMPK signaling, partially accounting for the improvement of DEHP-caused testicular dysfunction. The finding of this study revealed that THC is a promising candidate for improving adipose and testicular dysfunction caused by DEHP.

Promotion of healthy aging through the nexus of gut microbiota and dietary phytochemicals

Aging is associated with the decline of tissue and cellular functions, which can promote the development of age-related diseases like cancer, cardiovascular disease, neurodegeneration, and disorders of the musculoskeletal and immune systems. Healthspan is the length of time an individual is in good health and free from chronic diseases and disabilities associated with aging. Two modifiable factors that can influence healthspan, promote healthy aging, and prevent the development of age-related diseases, are the diet and microbiota in the gastrointestinal tract (gut microbiota). This review will discuss how dietary phytochemicals and gut microbiota can work in concert to promote a healthy gut and healthy aging. First an overview is provided of how the gut microbiota influences healthy aging through its impact on gut barrier integrity, immune function, mitochondria function and oxidative stress. Next, the mechanisms by which phytochemicals effect gut health, inflammation, and nurture a diverse and healthy microbial composition are discussed. Lastly, the gut microbiota can directly influence health by producing bioactive metabolites from phytochemicals in food like urolithin A, equol, hesperetin and sulforaphane. These and other phytochemical derived microbial metabolites that may promote healthspan are discussed. Importantly, an individual's capacity to produce health promoting microbial metabolites from cruciferous vegetables, berries, nuts, citrus and soy products will be dependent on the specific bacteria present in the individual's gut.

Natural pigments in the food industry: Enhancing stability, nutritional benefits, and gut microbiome health

Natural pigments are increasingly favored in the food industry for their vibrant colors, fewer side effects and potential health benefits compared to synthetic pigments. However, their application in food industry is hindered by their instability under harsh environmental conditions. This review evaluates current strategies aimed at enhancing the stability and bioactivity of natural pigments. Advanced physicochemical methods have shown promise in enhancing the stability of natural pigments, enabling their incorporation into food products to enhance sensory attributes, texture, and bioactive properties. Moreover, recent studies demonstrated that most natural pigments offer health benefits. Importantly, they have been found to positively influence gut microbiota, in particular their regulation of the beneficial and harmful flora of the gut microbiome, the reduction of ecological dysbiosis through changes in the composition of the gut microbiome, and the alleviation of systemic inflammation caused by a high-fat diet in mice, suggesting a beneficial role in dietary interventions.

Managing Type 2 Diabetes Mellitus via the Regulation of Gut Microbiota: A Chinese Medicine Perspective

BACKGROUND

Type 2 Diabetes Mellitus (T2DM) is a metabolic disorder characterized by insulin resistance and inadequate insulin production. Given the increased frequency of T2DM and the health issues it can cause, there is an increasing need to develop alternative T2DM management strategies. One such approach is Chinese Medicine (CM), a complementary therapy widely used in T2DM treatment. Given the emphasis on gut microbiota in current research, studying CM in the treatment of T2DM via gut microbiota modulation could be beneficial. Scope and approach: The use of various CM methods for managing T2DM via gut microbiota modulation is highlighted in this review. Following an introduction of the gut microbiota and its role in T2DM pathogenesis, we will review the potential interactions between gut microbiota and T2DM. Thereafter, we will review various CM treatment modalities that modulate gut microbiota and provide perspectives for future research. Key findings and discussion: In T2DM, Akkermansia, Bifidobacterium, and Firmicutes are examples of gut microbiota commonly imbalanced. Studies have shown that CM therapies can modulate gut microbiota, leading to beneficial effects such as reduced inflammation, improved metabolism, and improved immunity. Among these treatment modalities, Chinese Herbal Medicine and acupuncture are the most well-studied, and several in vivo studies have demonstrated their potential in managing T2DM by modulating gut microbiota. However, the underlying biomolecular mechanisms of actions are not well elucidated, which is a key area for future research. Future studies could also investigate alternate CM therapies such as moxibustion and CM exercises and conduct large-scale clinical trials to validate their effectiveness in treatment.

Curcumin and Gut Microbiota: A Narrative Overview with Focus on Glycemic Control

Turmeric is a spice widely used in China, Southeast Asia, and in traditional Ayurvedic medicine. Its safety profile and efficacy as an antioxidant, anti-inflammatory, antimicrobial, antitumor, antidiabetic, and anti-obesity agent have led to extensive research into its potential role in preventing and treating metabolic diseases. The active compound in turmeric is curcumin, which exhibits low systemic bioavailability after oral administration. However, it is detectable in the gut, where it bidirectionally interacts with the gut microbiota (GM), which plays a crucial role in maintaining host health. The favorable effects of curcumin, particularly its hypoglycemic properties, are linked to alteration in intestinal dysbiosis observed in type 2 diabetes mellitus and metabolic syndrome patients. Restoration of the eubiotic GM may contribute to glycemic homeostasis. Preclinical and clinical studies have demonstrated the involvement of the GM in the regulation of glucose and lipid metabolism. Although the underlying mechanism remains incompletely understood, intestinal dysbiosis is associated with insulin resistance, hyperglycemia, and low-grade inflammation. In the present overview, we summarize the biological properties of curcumin, focusing on its link with GM and, therefore, on its potential role in metabolic diseases.

The role of tetrahydrocurcumin in disease prevention and treatment

In recent decades, natural compounds derived from herbal medicine or dietary sources have played important roles in prevention and treatment of various diseases and have attracted more and more attention. Curcumin, extracted from the Curcumae Longae Rhizoma and widely used as food spice and coloring agent, has been proven to possess high pharmacological value. However, the pharmacological application of curcumin is limited due to its poor systemic bioavailability. As a major active metabolite of curcumin, tetrahydrocurcumin (THC) has higher bioavailability and stability than curcumin. Increasing evidence confirmed that THC had a wide range of biological activities and significant treatment effects on diseases. In this paper, we reviewed the research progress on the biological activities and therapeutic potential of THC on different diseases such as neurological disorders, metabolic syndromes, cancers, and inflammatory diseases. The extensive pharmacological effects of THC involve the modulation of various signaling transduction pathways including MAPK, JAK/STAT, NF-κB, Nrf2, PI3K/Akt/mTOR, AMPK, Wnt/β-catenin. In addition, the pharmacokinetics, drug combination and toxicology of THC were discussed, thus providing scientific basis for the safe application of THC and the development of its dietary supplements and drugs.

Gut-Brain Axis in Focus: Polyphenols, Microbiota, and Their Influence on α-Synuclein in Parkinson's Disease

With the recognition of the importance of the gut-brain axis in Parkinson's disease (PD) etiology, there is increased interest in developing therapeutic strategies that target α-synuclein, the hallmark abhorrent protein of PD pathogenesis, which may originate in the gut. Research has demonstrated that inhibiting the aggregation, oligomerization, and fibrillation of α-synuclein are key strategies for disease modification. Polyphenols, which are rich in fruits and vegetables, are drawing attention for their potential role in this context. In this paper, we reviewed how polyphenols influence the composition and functional capabilities of the gut microbiota and how the resulting microbial metabolites of polyphenols may potentially enhance the modulation of α-synuclein aggregation. Understanding the interaction between polyphenols and gut microbiota and identifying which specific microbes may enhance the efficacy of polyphenols is crucial for developing therapeutic strategies and precision nutrition based on the microbiome.

Ameliorative Effects of Curcumin on Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM), a multifactorial and complicated metabolic disorder, is a growing public health problem. Numerous studies have indicated that bioactive compounds from herbal medicine have beneficial effects on T2DM prevention and treatment, owing to their numerous biological properties. Curcumin, the major curcuminoid of turmeric, is one of the most studied bioactive components of herbal supplements, and has a variety of biological activities. Clinical trials and preclinical research have recently produced compelling data to demonstrate the crucial functions of curcumin against T2DM via several routes. Accordingly, this review systematically summarizes the antidiabetic activity of curcumin, along with various mechanisms. Results showed that effectiveness of curcumin on T2DM is due to it being anti-inflammatory, anti-oxidant, antihyperglycemic, anti-apoptotic, and antihyperlipidemic, among other activities. In light of these results, curcumin may be a promising prevention/treatment choice for T2DM.

Hyperglycemia effect of Pinctada martensii hydrolysate in diabetic db/db mice

ETHNOPHARMACOLOGICAL RELEVANCE

Pinctada martensii (Dunker) and other marine shellfish flesh have been traditionally used in China as folk remedies regulate blood sugar.

AIM OF THE STUDY

To investigate the main active constituents and the pharmacological mechanism of Pinctada martensii flesh enzymatic hydrolysate (PMH) against T2DM.

MATERIALS AND METHODS

The hypoglycemic activity of enzymolysis peptides from Pinctada martensii was evaluated by using db/db mice, through the influence of glycemic index, blood lipid and key protein expression of PI3K-Akt pathway. In addition, label-free quantitative proteomics was used to screen the key proteins for Pinctada martensii hydrolysate (PMH) to improve T2DM, and Western blot and qRT-PCR were used to verify the expression difference of differential proteins at protein and mRNA levels between different groups.

RESULTS

PMH were prepared and characterized. In vivo investigations revealed that the PMH could regulate blood glucose and improve glucose tolerance and insulin tolerance, reduced serum total cholesterol, triglyceride, low-density lipoprotein cholesterol levels and increase high-density lipoprotein cholesterol levels in db/db mice. Western blot results showed that PMH could up-regulate IRS-1, P-PI3K/PI3K and P-Akt/Akt levels in db/db mice. Label-free quantitative proteomic approach was used to analyze the proteome in db/db mouse liver, 231 proteins were reversed significantly (p < 0.05), and these proteins were involved in oxidative phosphorylation, glycolysis/gluconeogenesis and other pathways. Further screened 15 proteins with FC > 1.2 could be enriched in the retinol metabolic pathway, and the proteins in this pathway were also verified.

CONCLUSIONS

PMH has hypoglycemic effect and can be used as a potential natural T2DM intervener. The hypoglycemic activity of PMH is related to its regulation of the PI3K/AKT pathway. The PI3K/AKT pathway and the retinol pathway are considered as another potential pathway for PMH to exert hypoglycemic effects.

Crosstalk between glucagon-like peptide 1 and gut microbiota in metabolic diseases

Gut microbiota exert influence on gastrointestinal mucosal permeability, bile acid metabolism, short-chain fatty acid synthesis, dietary fiber fermentation, and farnesoid X receptor/Takeda G protein-coupled receptor 5 (TGR5) signal transduction. The incretin glucagon-like peptide 1 (GLP-1) is mainly produced by L cells in the gut and regulates postprandial blood glucose. Changes in gut microbiota composition and function have been observed in obesity and type 2 diabetes (T2D). Meanwhile, the function and rhythm of GLP-1 have also been affected in subjects with obesity or T2D. Therefore, it is necessary to discuss the link between the gut microbiome and GLP-1. In this review, we describe the interaction between GLP-1 and the gut microbiota in metabolic diseases. On the one hand, gut microbiota metabolites stimulate GLP-1 secretion, and gut microbiota affect GLP-1 function and rhythm. On the other hand, the mechanism of action of GLP-1 on gut microbiota involves the inflammatory response. Additionally, we discuss the effects and mechanism of various interventions, such as prebiotics, probiotics, antidiabetic drugs, and bariatric surgery, on the crosstalk between gut microbiota and GLP-1. Finally, we stress that gut microbiota can be used as a target for metabolic diseases, and the clinical application of GLP-1 receptor agonists should be individualized.

Exploring the gut microbiota: lifestyle choices, disease associations, and personal genomics

The gut microbiota is a rich and dynamic ecosystem that actively interacts with the human body, playing a significant role in the state of health and disease of the host. Diet, exercise, mental health, and other factors have exhibited the ability to influence the gut bacterial composition, leading to changes that can prevent and improve, or favor and worsen, both intestinal and extra-intestinal conditions. Altered gut microbial states, or 'dysbiosis', associated with conditions and diseases are often characterized by shifts in bacterial abundance and diversity, including an impaired Firmicutes to Bacteroidetes ratio. By understanding the effect of lifestyle on the gut microbiota, personalized advice can be generated to suit each individual profile and foster the adoption of lifestyle changes that can both prevent and ameliorate dysbiosis. The delivery of effective and reliable advice, however, depends not only on the available research and current understanding of the topic, but also on the methods used to assess individuals and to discover the associations, which can introduce bias at multiple stages. The aim of this review is to summarize how human gut microbial variability is defined and what lifestyle choices and diseases have shown association with gut bacterial composition. Furthermore, popular methods to investigate the human gut microbiota are outlined, with a focus on the possible bias caused by the lack of use of standardized methods. Finally, an overview of the current state of personalized advice based on gut microbiota testing is presented, underlining its power and limitations.

Liposomes Co-Delivering Curcumin and Colistin to Overcome Colistin Resistance in Bacterial Infections

Antibiotic colistin is the last line of defense against multidrug-resistant (MDR) Gram-negative bacterial infections. Emergence of colistin resistance in microbes is a critical challenge. Herein, curcumin is discovered, for the first time, to reverse the resistance phenotype of colistin-resistant bacteria via a checkerboard assay. For the co-delivery of curcumin and colistin, negatively charged poly(ethylene glycol)-functionalized liposomes encapsulating both drugs (Lipo-cc) are prepared. Killing kinetics and live/dead assays confirm the antibacterial activity of Lipo-cc against colistin-resistant bacteria, which is more potent than that of the free curcumin and colistin combination. Mechanistical studies reveal that Lipo-cc restores the affinity of colistin for the bacterial membrane and improves the uptake of curcumin, which leads to reduced efflux pump activity, achieving a synergistic effect of colistin and curcumin. At the effective antibacterial dose, Lipo-cc does not exhibit any toxicity. The therapeutic efficacy of Lipo-cc is further demonstrated in an intestinal bacterial infection model induced with colistin-resistant Escherichia coli. Lipo-cc reduces the bacterial burden with over 6-log reduction and alleviated inflammation caused by infection. Importantly, unlike colistin, Lipo-cc does not affect the homeostasis of the intestinal flora. Taken together, Lipo-cc successfully overcame colistin resistance, indicating its potential for the treatment of colistin-resistant bacterial infections.

Statistical optimization of tetrahydrocurcumin loaded solid lipid nanoparticles using Box Behnken design in the management of streptozotocin-induced diabetes mellitus

In the past, curcumin was the go-to medication for diabetes, but recent studies have shown that tetrahydrocurcumin is more effective. The problem is that it's not very soluble in water or very bioavailable. So, our research aims to increase the bioavailability and anti-diabetic efficacy of tetrahydrocurcumin in streptozotocin-induced diabetic rats by synthesizing tetrahydrocurcumin-loaded solid lipid nanoparticles. Box Behnken Design was employed for the optimization of tetrahydrocurcumin-loaded solid lipid nanoparticles (THC-SLNs). The optimal formulation was determined by doing an ANOVA to examine the relationship between the independent variables (drug-to-lipid ratio, surfactant concentration, and co-surfactant concentration) and the dependent variables (particle size, percent entrapment efficiency, and PDI). Particle size, PDI, and entrapment efficiency all showed statistical significance based on F-values and p-values. The optimized batch was prepared using a drug-to-lipid ratio (1:4.16), 1.21% concentration of surfactant, and 0.4775% co-surfactant (observed with a particle size of 147.1 nm, 83.58 ± 0.838 % entrapment efficiency, and 0.265 PDI, and the values were found very close with the predicted ones. As the THC peak vanishes from the DSC thermogram of the improved formulation, this indicates that the drug has been transformed from its crystalline form into its amorphous state. TEM analysis of optimized formulation demonstrated mono-dispersed particles with an average particle size of 145 nm which are closely related to zetasizer's results. In-vitro release study of optimized formulation demonstrated burst release followed by sustained release up to 71.04% throughout 24 hrs. Increased bioavailability of the adjusted THC-SLN was found in an in vivo pharmacokinetics research with 9.47 folds higher AUC(0-t) compared to plain THC-suspension. Additionally, pharmacodynamic experiments of optimized formulation demonstrated a marked decrease in blood glucose level to 63.7% and increased body weight from 195.8 ± 7.223 to 231.2 ± 7.653 on the 28th day of the study and showed a better anti-diabetic effect than plain drug suspension. Results of stability studies revealed that formulation can be stored for longer periods at room temperature. Tetrahydrocurcumin can be effectively administered by SLN for the treatment of diabetes.

The role of curcumin in the liver-gut system diseases: from mechanisms to clinical therapeutic perspective

Natural products have provided abundant sources of lead compounds for new drug discovery and development over the past centuries. Curcumin is a lipophilic polyphenol isolated from turmeric, a plant used in traditional Asian medicine for centuries. Despite the low oral bioavailability, curcumin exhibits profound medicinal value in various diseases, especially liver and gut diseases, bringing an interest in the paradox of its low bioavailability but high bioactivity. Several latest studies suggest that curcumin's health benefits may rely on its positive gastrointestinal effects rather than its poor bioavailability solely. Microbial antigens, metabolites, and bile acids regulate metabolism and immune responses in the intestine and liver, suggesting the possibility that the liver-gut axis bidirectional crosstalk controls gastrointestinal health and diseases. Accordingly, these pieces of evidence have evoked great interest in the curcumin-mediated crosstalk among liver-gut system diseases. The present study discussed the beneficial effects of curcumin against common liver and gut diseases and explored the underlying molecular targets, as well as collected evidence from human clinical studies. Moreover, this study summarized the roles of curcumin in complex metabolic interactions in liver and intestine diseases supporting the application of curcumin in the liver-gut system as a potential therapeutic option, which opens an avenue for clinical use in the future.

Taraxasterol Inhibits Hepatic Gluconeogenesis and Increases Glycogen Synthesis via the PI3K/Akt Signaling Pathway

Objective: Taraxasterol (TS) is the main active compound of Taraxacum, which plays a significant role in the treatment of diabetes in many classic prescriptions. However, the mechanisms of TS in the treatment of diabetes remain unclear. This study aimed to investigate the underlying mechanism of TS in hepatic gluconeogenesis and glycogen synthesis in HepG2 cells with insulin resistance (IR). Methods: Molecular docking was conducted by using Discovery Studio (DS) to predict the target of TS in the treatment of diabetes. Then we treated HepG2 cells with glucosamine for 18 h. After the cells were treated with TS, the glucose consumption was examined. Oil red O staining was used to detect the lipid accumulation of HepG2 cells, and cellular glucose uptake levels were assessed using fluorescent 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) amino)-2-deoxy-D-glucose. The expression of the related proteins of the PI3K/Akt signaling pathway in the HepG2 cells was evaluated by western blot assay. Results: The molecular docking analysis revealed a good binding pose between the insulin receptor and TS. Furthermore, TS administration significantly enhanced glucose uptake and consumption, and reduced lipid accumulation in HepG2 cells with IR. The results of pharmacological mechanism study showed that TS up-regulated glycogenesis by PI3K/Akt/GSK3-motivated GS activation, and down-regulated gluconeogenesis by PI3K/Akt/FoxO1 expression of PEPCK and G6Pase in HepG2 cells with IR. Conclusions: Molecular docking and in vitro experimental results indicate that TS suppresses hepatic gluconeogenesis and augments glycogen synthesis by the PI3K/Akt signaling pathway, and it may have similar effects as insulin in regulating blood glucose.

Tetrahydrocurcumin regulates the tumor immune microenvironment to inhibit breast cancer proliferation and metastasis via the CYP1A1/NF-κB signaling pathway

The NF-κB signaling pathway is overactivated in tumor cells, and the activation of the NF-κB signaling pathway releases a large number of inflammatory factors, which enhance tumor immunosuppression and promote tumor metastasis. The cytochrome P450 (CYP450) system consists of important metabolic enzymes present in different tissues and progressive tumors, which may lead to changes in the pharmacological action of drugs in inflammatory diseases such as tumors. In this study, the anticancer effect of tetrahydrocurcumin (THC), an active metabolite of curcumin, on breast cancer cells and the underlying mechanism were investigated. Result showed that THC selectively inhibited proliferation and triggered apoptosis in breast cancer cells in a concentration- and time-dependent manner. Moreover, THC-induced cell apoptosis via a mitochondria-mediated pathway, as indicated by the upregulated ratio of Bax/Bcl-2 and reactive oxygen species (ROS) induction. In addition, THC could affect the CYP450 enzyme metabolic pathway and inhibit the expression of CYP1A1 and activation of the NF-κB pathway, thereby inhibiting the migration and invasion of breast cancer cells. Furthermore, after overexpression of CYP1A1, the inhibitory effects of THC on the proliferation, metastasis, and induction of apoptosis in breast cancer cells were weakened. The knockdown of CYP1A1 significantly enhanced the inhibitory effect of THC on the proliferation, metastasis, and apoptosis induction of breast cancer cells. Notably, THC exhibited a significant tumor growth inhibition and anti-pulmonary metastasis effect in a tumor mouse model of MCF-7 and 4T1 cells by regulating the tumor immunosuppressive microenvironment. Collectively, these results showed that TH could effectively trigger apoptosis and inhibit the migration of breast cancer cells via the CYP1A1/NF-κB signaling pathway, indicating that THC serves as a potential candidate drug for the treatment of breast cancer.

Gut microbiota: The key to the treatment of metabolic syndrome in traditional Chinese medicine - a case study of diabetes and nonalcoholic fatty liver disease

Metabolic syndrome mainly includes obesity, type 2 diabetes (T2DM), alcoholic fatty liver (NAFLD) and cardiovascular diseases. According to the ancient experience philosophy of Yin-Yang, monarch-minister compatibility of traditional Chinese medicine, prescription is given to treat diseases, which has the advantages of small toxic and side effects and quick effect. However, due to the diversity of traditional Chinese medicine ingredients and doubts about the treatment theory of traditional Chinese medicine, the mechanism of traditional Chinese medicine is still in doubt. Gastrointestinal tract is an important part of human environment, and participates in the occurrence and development of diseases. In recent years, more and more TCM researches have made intestinal microbiome a new frontier for understanding and treating diseases. Clinically, nonalcoholic fatty liver disease (NAFLD) and diabetes mellitus (DM) often co-occur. Our aim is to explain the mechanism of interaction between gastrointestinal microbiome and traditional Chinese medicine (TCM) or traditional Chinese medicine formula to treat DM and NAFLD. Traditional Chinese medicine may treat these two diseases by influencing the composition of intestinal microorganisms, regulating the metabolism of intestinal microorganisms and transforming Chinese medicinal compounds.

Effect of natural polyphenols in Chinese herbal medicine on obesity and diabetes: Interactions among gut microbiota, metabolism, and immunity

With global prevalence, metabolic diseases, represented by obesity and type 2 diabetes mellitus (T2DM), have a huge burden on human health and medical expenses. It is estimated that obese population has doubled in recent 40 years, and population with diabetes will increase 1.5 times in next 25 years, which has inspired the pursuit of economical and effective prevention and treatment methods. Natural polyphenols are emerging as a class of natural bioactive compounds with potential beneficial effects on the alleviation of obesity and T2DM. In this review, we investigated the network interaction mechanism of "gut microbial disturbance, metabolic disorder, and immune imbalance" in both obesity and T2DM and systemically summarized their multiple targets in the treatment of obesity and T2DM, including enrichment of the beneficial gut microbiota (genera Bifidobacterium, Akkermansia, and Lactobacillus) and upregulation of the levels of gut microbiota-derived metabolites [short-chain fatty acids (SCFAs)] and bile acids (BAs). Moreover, we explored their effect on host glucolipid metabolism, the AMPK pathway, and immune modulation via the inhibition of pro-inflammatory immune cells (M1-like Mϕs, Th1, and Th17 cells); proliferation, recruitment, differentiation, and function; and related cytokines (TNF-α, IL-1β, IL-6, IL-17, and MCP-1). We hope to provide evidence to promote the clinical application of natural polyphenols in the management of obesity and T2DM.

Antibacterial and Antiviral Properties of Tetrahydrocurcumin-Based Formulations: An Overview of Their Metabolism in Different Microbiotic Compartments

In this review, the basic metabolic characteristics of the curcuminoid tetrahydrocurcumin (THC) at the level of the intestinal microbiota were addressed. Special attention was given to the bactericidal effects of one of the THC-phospholipid formulations, which has shown greater bioavailability and activity than pure THC. Similarly, quinoline derivatives and amino acid conjugates of THC have also shown antibacterial effects in the gut. The microbial effect of pure THC is particularly pronounced in pathophysiological conditions related to the function of the intestinal microbiota, such as type II diabetes. Furthermore, the antiviral characteristics of Cur compared to those of THC are more pronounced in preventing the influenza virus. In the case of HIV infections, the new microemulsion gel formulations of THC possess high retention during preventive application in the vagina and, at the same time, do not disturb the vaginal microbiota, which is critical in maintaining low vaginal pH. Based on the reviewed literature, finding new formulations of THC which can increase its bioavailability and activity and emphasize its antibacterial and antiviral characteristics could be very important. Applying such THC formulations in preventing and treating ailments related to the microbiotic compartments in the body would be beneficial from a medical point of view.

Regulation of the intestinal flora: A potential mechanism of natural medicines in the treatment of type 2 diabetes mellitus

Diabetes mellitus comprises a group of heterogeneous disorders, which are usually subdivided into type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM). Both genetic and environmental factors have been implicated in the onset of diabetes. Type 1 diabetes primarily involves autoimmune insulin deficiency. In comparison, type 2 diabetes is contributed by the pathological state of insulin deficiency and insulin resistance. In recent years, significant differences were found in the abundance of microflora, intestinal barrier, and intestinal metabolites in diabetic subjects when compared to normal subjects. To further understand the relationship between diabetes mellitus and intestinal flora, this paper summarizes the interaction mechanism between diabetes mellitus and intestinal flora. Furthermore, the natural compounds found to treat diabetes through intestinal flora were classified and summarized. This review is expected to provide a valuable resource for the development of new diabetic drugs and the applications of natural compounds.

Gut Microbiota: The Potential Key Target of TCM's Therapeutic Effect of Treating Different Diseases Using the Same Method-UC and T2DM as Examples

Traditional Chinese herbal medicine often exerts the therapeutic effect of "treating different diseases with the same method" in clinical practice; in other words, it is a kind of herbal medicine that can often treat two or even multiple diseases; however, the biological mechanism underlying its multi-path and multi-target pharmacological effects remains unclear. Growing evidence has demonstrated that gut microbiota dysbiosis plays a vital role in the occurrence and development of several diseases, and that the root cause of herbal medicine plays a therapeutic role in different diseases, a phenomenon potentially related to the improvement of the gut microbiota. We used local intestinal diseases, such as ulcerative colitis, and systemic diseases, such as type 2 diabetes, as examples; comprehensively searched databases, such as PubMed, Web of Science, and China National Knowledge Infrastructure; and summarized the related studies. The results indicate that multiple individual Chinese herbal medicines, such as Rhizoma coptidis (Huang Lian), Curcuma longa L (Jiang Huang), and Radix Scutellariae (Huang Qin), and Chinese medicinal compounds, such as Gegen Qinlian Decoction, Banxia Xiexin Decoction, and Shenling Baizhu Powder, potentially treat these two diseases by enriching the diversity of the gut microbiota, increasing beneficial bacteria and butyrate-producing bacteria, reducing pathogenic bacteria, improving the intestinal mucosal barrier, and inhibiting intestinal and systemic inflammation. In conclusion, this study found that a variety of traditional Chinese herbal medicines can simultaneously treat ulcerative colitis and type 2 diabetes, and the gut microbiota may be a significant target for herbal medicine as it exerts its therapeutic effect of "treating different diseases with the same method".

Understanding the mechanism underlying the anti-diabetic effect of dietary component: a focus on gut microbiota

Diabetes has become one of the biggest non-communicable diseases and threatens human health worldwide. The management of diabetes is a complex and multifaceted process including drug therapy and lifestyle interventions. Dietary components are essential for both diabetes management and health and survival of trillions of the gut microbiota (GM). Herein, we will discuss the relationship between diets and GM, the mechanism linking diabetes and gut dysbiosis, and the effects of dietary components (nutrients, phytochemicals, probiotics, food additives, etc.) on diabetes from the perspective of modulating GM. The GM of diabetic patients differs from that of health individuals and GM disorder contributes to the onset and maintenance of diabetes. Studies in humans and animal models consolidate that dietary component is a key regulator of diabetes and increasing evidence suggests that the alteration of GM plays a salient role in dietary interventions for diabetes. Given that diabetes is a major public health issue, especially that diabetes is linked with a high risk of mortality from COVID-19, this review provides compelling evidence for that targeting GM by dietary components is a promising strategy, and offers new insights into potential preventive or therapeutic approaches (dietary and pharmacological intervention) for the clinical management of diabetes.

Dietary curcumin restores insulin homeostasis in diet-induced obese aged mice

Although aging is a physiological process to which all organisms are subject, the presence of obesity and type 2 diabetes accelerates biological aging. Recent studies have demonstrated the causal relationships between dietary interventions suppressing obesity and type 2 diabetes and delaying the onset of age-related endocrine changes. Curcumin, a natural antioxidant, has putative therapeutic properties such as improving insulin sensitivity in obese mice. However, how curcumin contributes to maintaining insulin homeostasis in aged organisms largely remains unclear. Thus, the objective of this study is to examine the pleiotropic effect of dietary curcumin on insulin homeostasis in a diet-induced obese (DIO) aged mouse model. Aged (18-20 months old) male mice given a high-fat high-sugar diet supplemented with 0.4% (w/w) curcumin (equivalent to 2 g/day for a 60 kg adult) displayed a different metabolic phenotype compared to mice given a high-fat high-sugar diet alone. Furthermore, curcumin supplementation altered hepatic gene expression profiling, especially insulin signaling and senescence pathways. We then mechanistically investigated how curcumin functions to fine-tune insulin sensitivity. We found that curcumin supplementation increased hepatic insulin-degrading enzyme (IDE) expression levels and preserved islet integrity, both outcomes that are beneficial to preserving good health with age. Our findings suggest that the multifaceted therapeutic potential of curcumin can be used as a protective agent for age-induced metabolic diseases.

Tetrahydrocurcumin Upregulates the Adiponectin-AdipoR Pathway and Improves Insulin Signaling and Pancreatic β-Cell Function in High-Fat Diet/Streptozotocin-Induced Diabetic Obese Mice

Impairment of adiponectin production and function is closely associated with insulin resistance and type 2 diabetes, which are linked to obesity. Studies in animal models have documented the anti-diabetic effects of tetrahydrocurcumin (THC). Although several possible mechanisms have been proposed, the contribution of adiponectin signaling on THC-mediated antihyperglycemic effects remains unknown. Here, we report that adiposity, steatosis, and hyperglycemia were potently attenuated in high-fat diet/streptozotocin-induced diabetic obese mice after they received 20 and 100 mg/kg THC for 14 weeks. THC upregulated UCP-1 in adipose tissue and elevated adiponectin levels in the circulation. THC upregulated the AdipoR1/R2-APPL1-mediated pathway in the liver and skeletal muscle, which contributes to improved insulin signaling, glucose utilization, and lipid metabolism. Furthermore, THC treatment significantly (p < 0.05) preserved islet mass, reduced apoptosis, and restored defective insulin expression in the pancreatic β-cells of diabetic obese mice, which was accompanied by an elevation of AdipoR1 and APPL1. These results demonstrated a potential mechanism underlying the beneficial effects of THC against hyperglycemia via the adiponectin-AdipoR pathway, and thus, may lead to a novel therapeutic use for type 2 diabetes.

Polyphenols as adjunctive treatments in psychiatric and neurodegenerative disorders: Efficacy, mechanisms of action, and factors influencing inter-individual response

The pathophysiology of psychiatric and neurodegenerative disorders is complex and multifactorial. Polyphenols possess a range of potentially beneficial mechanisms of action that relate to the implicated pathways in psychiatric and neurodegenerative disorders. The aim of this review is to highlight the emerging clinical trial and preclinical efficacy data regarding the role of polyphenols in mental and brain health, elucidate novel mechanisms of action including the gut microbiome and gene expression, and discuss the factors that may be responsible for the mixed clinical results; namely, the role of interindividual differences in treatment response and the potentially pro-oxidant effects of some polyphenols. Further clarification as part of larger, well conducted randomized controlled trials that incorporate precision medicine methods are required to inform clinical efficacy and optimal dosing regimens.

Curcumin, Quercetin, Catechins and Metabolic Diseases: The Role of Gut Microbiota

Polyphenols (PPs) are the naturally occurring bioactive components in fruits and vegetables, and they are the most abundant antioxidant in the human diet. Studies are suggesting that ingestion of PPs might be helpful to ameliorate metabolic syndromes that may contribute in the prevention of several chronic disorders like diabetes, obesity, hypertension, and colon cancer. PPs have structural diversity which impacts their bioavailability as they accumulate in the large intestine and are extensively metabolized through gut microbiota (GM). Intestinal microbiota transforms PPs into their metabolites to make them bioactive. Interestingly, not only GM act on PPs to metabolize them but PPs also modulate the composition of GM. Thus, change in GM from pathogenic to beneficial ones may be helpful to ameliorate gut health and associated diseases. However, to overcome the low bioavailability of PPs, various approaches have been developed to improve their solubility and transportation through the gut. In this review, we present evidence supporting the structural changes that occur after metabolic reactions in PPs (curcumin, quercetin, and catechins) and their effect on GM composition that leads to improving overall gut health and helping to ameliorate metabolic disorders.

Comparative Study of Curcumin and Its Hydrogenated Metabolites, Tetrahydrocurcumin, Hexahydrocurcumin, and Octahydrocurcumin, on Melanogenesis in B16F10 and MNT-1 Cells

Curcumin, a bioactive from Curcuma longa, has been shown to possess anti-melanogenic activity previously; however, the effects of its hydrogenated metabolites (HMs)—Tetrahydrocurcumin (THC), Hexahydrocurcumin (HHC), and Octahydrocurcumin (OHC)—on melanogenesis have not been sufficiently explored. We have studied and compared three HMs (THC, HHC, and OHC) with the parent compound, curcumin (PC), on melanin synthesis in B16F10 mouse and MNT-1 human melanoma cells. Our results demonstrated that all the HMs were nontoxic over the concentration range 5–40 µM, while PC was nontoxic at 5 µM but induced toxicity at 20 and 40 µM in B16F10 cells. All three HMs enhanced melanin synthesis, while PC (5 µM) inhibited it. THC (40 µM) significantly stimulated melanin synthesis to a greater degree than HHC and OHC in both B16F10 and MNT-1 cells; the order of melanogenesis stimulation was THC = OHC > HHC in B16F10 mouse cells, while it was THC > HHC > OHC in MNT-1 cells. HMs stimulated melanogenesis by pathways not involving tyrosinase, as neither the intracellular tyrosinase activity nor the protein levels of tyrosinase were affected. In addition, mushroom tyrosinase activity, using L-Dihydroxyphenylalanine (L-DOPA) as the substrate, showed no direct effects of HMs. In summary, our results demonstrate that the HMs enhanced melanogenesis, which establishes that the hydrogenation of the heptadiene moiety of curcumin leads to a loss of its anti-melanogenic activity and instead results in the stimulation of melanogenesis. This stimulation is not further enhanced upon hydrogenation of the β-diketone, which was noted in MNT-1 cells, although the correlation to the number of keto groups differed in B16F10 cells where HHC was the weakest stimulator of melanogenesis. Collectively, THC with both keto groups intact is the best stimulator. Moreover, our results also validate that the electrophilicity of curcumin is necessary for its anti-melanogenic activity, as the non-electrophilic HMs did not inhibit melanogenesis. Furthermore, our results suggest that THC might hold promise as a stimulator of melanogenesis for treatment of hypopigmentation disorders and anti-graying therapies. Future studies to probe the molecular signaling mechanisms and test whether the pro-melanogenic activity of HMs is retained in primary human melanocytes are warranted.