Urolithin C increases glucose-induced ERK activation which contributes to insulin secretion

The flavonoid resokaempferol improves insulin secretion from healthy and dysfunctional pancreatic β-cells

BACKGROUND AND PURPOSE

The pharmacology of flavonoids on β-cell function is largely undefined especially in the context of defective secretion of insulin. We sought to identify flavonoids that increased the insulin-secreting function of β-cells and to explore the underlying mechanisms.

EXPERIMENTAL APPROACH

INS-1 β-cells in culture and islets of Langerhans isolated from control and diabetic male rats were used for insulin secretion experiments. Pharmacological and electrophysiological approaches were used for mechanistic studies.

KEY RESULTS

Among a set of flavonoids, exposure of INS-1 β-cells to resokaempferol (ResoK) enhanced glucose-stimulated insulin secretion and therefore we further characterised its activity and its pharmacological mechanism. ResoK glucose-dependently enhanced insulin secretion in INS-1 β-cells and pancreatic islets isolated from rats. Mechanistically, whole cell patch clamp recordings in INS-1 cells showed that ResoK rapidly and dose-dependently enhanced the L-type Ca2+ current whereas it was inactive towards T-type Ca2+ current. Accordingly, pharmacological inhibition of L-type Ca2+ current but not T-type Ca2+ current blocked the effects of ResoK on glucose-stimulated insulin secretion. ResoK was still active on dysfunctional β-cells as it ameliorated glucose-stimulated insulin secretion in glucotoxicity-induced dysfunctional INS-1 cells and in pancreatic islets isolated from diabetic rats.

CONCLUSION AND IMPLICATIONS

ResoK is a glucose-dependent activator of insulin secretion. Our results indicated that the effects of ResoK on insulin secretion involved its capacity to stimulate L-type Ca2+ currents in cultured β-cells. As ResoK was also effective on dysfunctional β-cells, our work provides a new approach to stimulating insulin secretion, using compounds based on the structure of ResoK.

Urolithin C suppresses colorectal cancer progression via the AKT/mTOR pathway

Urolithin families are gut-microbial metabolites of ellagic acid (EA). Although urolithin A (UA) and urolithin B (UB) were reported to have antiproliferative activities in cancer cells, the role and related mechanisms of urolithin C (UC) in colorectal cancer (CRC) have not yet been clarified. In this study, we assess the antitumor activities of UC in vitro and in vivo and further explore the underlying mechanisms in CRC cell lines. We found that UC inhibited the proliferation and migration of CRC cells, induced apoptosis, and arrested the cell cycle at the G2/M phase in vitro, and UC inhibited tumor growth in a subcutaneous transplantation tumor model in vivo. Mechanically, UC blocked the activation of the AKT/mTOR signaling pathway by decreasing the expression of Y-box binding protein 1(YBX1). The AKT agonist SC79 could reverse the suppression of cell proliferation in UC-treated CRC cells. In conclusion, our research revealed that UC could prevent the progression of CRC by blocking AKT/mTOR signaling, suggesting that it may have potential therapeutic values.

Pharmacological and phytochemical insights on the pancreatic β-cell modulation by Angelica L. roots

ETHNOPHARMACOLOGICAL RELEVANCE

Angelica roots are a significant source of traditional medicines for various cultures around the northern hemisphere, from indigenous communities in North America to Japan. Among its many applications, the roots are used to treat type 2 diabetes mellitus; however, this application is not mentioned often. Ethnopharmacological studies have reported the use of A. japonica var. hirsutiflora, A. furcijuga, A. shikokiana, and A. keiskei to treat diabetes symptoms, and further reports have demonstrated the three angelica roots, i.e., A. japonica var. hirsutiflora, A. reflexa, and A. dahurica, exhibit insulin secretagogue activity.

AIM OF THE STUDY

This study aimed to phytochemically characterize and compare angelica roots monographed in the European Pharmacopeia 11th, isolate major plant metabolites, and assess extracts and isolates' capability to modulate pancreatic β-cell function.

MATERIALS AND METHODS

Root extracts of Angelica archangelica, Angelica dahurica, Angelica biserrata, and Angelica sinensis were phytochemically profiled using liquid chromatography method coupled with mass spectrometry. Based on this analysis, simple and furanocoumarins were isolated using chromatography techniques. Extracts (1.6-50 μg/mL) and isolated compounds (5-40 μmol/L) were studied for their ability to modulate insulin secretion in the rat insulinoma INS-1 pancreatic β-cell model. Insulin was quantified by the homogeneous time-resolved fluorescence method.

RESULTS

Forty-one secondary metabolites, mostly coumarins, were identified in angelica root extracts. A. archangelica, A. dahurica, and A. biserrata root extracts at concentration of 12.5-50 μg/mL potentiated glucose-induced insulin secretion, which correlated with their high coumarin content. Subsequently, 23 coumarins were isolated from these roots and screened using the same protocol. Coumarins substituted with the isoprenyl group were found to be responsible for the extracts' insulinotropic effect.

CONCLUSIONS

Insulinotropic effects of three pharmacopeial angelica roots were found, the metabolite profiles and pharmacological activities of the roots were correlated, and key structures responsible for the modulation of pancreatic β-cell function were identified. These findings may have implications for the traditional use of angelica roots in treating diabetes. Active plant metabolites may also become lead structures in the search for new antidiabetic treatments.

Urolithin C alleviates pancreatic β-cell dysfunction in type 1 diabetes by activating Nrf2 signaling

AIMS

Type 1 diabetes (T1D) is an autoimmune disorder that destroys insulin-generating pancreatic β-cells. Preserving pancreatic β-cell function is important for treating T1D. Our study aims to explore the mechanism underlying urolithin C (UC)-mediated regulation of β-cell function.

METHODS

Non-obese diabetic (NOD) mice were administrated with UC to evaluate UC-mediated protection of T1D. The inflammation of the pancreas islets was examined by hematoxylin and eosin staining. Glucose-stimulated insulin secretion (GSIS) assay and oral glucose tolerance test were applied to evaluate the progression of T1D. MIN6 cells were treated with TNF-α, IL-1β and IFN-γ in the presence of UC. Cell viability was analyzed by CCK-8. Cell apoptosis, proliferation and DNA fragmentation were examined by Annexin V-FITC and PI staining, EdU incorporation and comet assays. Keap1, Nrf2, HO-1 and NQO1 were examined by western blot. Immunofluorescence staining was applied to detect Nrf2 and insulin.

RESULTS

UC administration significantly reduced diabetes incidence, attenuated insulitis, elevated insulin levels and GSIS and reduced blood glucose and AUC in NOD mice. Cytokine treatment suppressed MIN6 cell viability and proliferation but enhanced apoptosis and DNA damage, and these detrimental effects were relieved by UC treatment. Furthermore, UC administration inhibited Keap1 expression and promoted the expression of Nrf2, HO-1 and NQO1 in NOD mice. Nrf2 signaling has been reported to be implicated in preventing the onset of diabetes, and HO-1 and NQO1 are phase II antioxidant enzymes that are regulated by Nrf2 signaling. Cytokine treatment upregulated Keap1 and downregulated Nrf2, HO-1 and NQO1 in MIN6 cells, but it was reversed by UC. The nuclear translocation of Nrf2 was prevented by cytokine treatment, but UC promoted its nuclear translocation. UC-mediated upregulation of Nrf2, HO-1 and NQO1, decreased cell apoptosis and increased proliferation and insulin secretion were abolished by silencing of Nrf2.

CONCLUSION

UC improves pancreatic β-cell function by activating Nrf2 signaling, thereby alleviating T1D progression.

Health functions and related molecular mechanisms of ellagitannin-derived urolithins

Ellagitannins are vital bioactive polyphenols that are widely distributed in a variety of plant-based foods. The main metabolites of ellagitannins are urolithins, and current research suggests that urolithins provide a variety of health benefits. This review focused on the role of the gut bacteria in the conversion of ellagitannins to urolithins. Based on the results of in vitro and in vivo studies, the health benefits of urolithins, including antioxidant, anti-inflammatory, anti-cancer, anti-obesity, anti-diabetic, anti-aging, cardiovascular protective, neuroprotective, kidney protective, and muscle mass protective effects, were thoroughly outlined, with a focus on their associated molecular mechanisms. Finally, we briefly commented on urolithins' safety. Overall, urolithins' diverse health benefits indicate the potential utilization of ellagitannins and urolithins in the creation of functional foods and nutraceuticals to treat and prevent some chronic diseases.

Biocatalytic Approaches for an Efficient and Sustainable Preparation of Polyphenols and Their Derivatives

Many sectors of industry, such as food, cosmetics, nutraceuticals, and pharmaceuticals, have increased their interest in polyphenols due to their beneficial properties. These molecules are widely found in Nature (plants) and can be obtained through direct extraction from vegetable matrices. Polyphenols introduced through the diet may be metabolized in the human body via different biotransformations leading to compounds having different bioactivities. In this context, enzyme-catalyzed reactions are the most suitable approach to produce modified polyphenols that not only can be studied for their bioactivity but also can be labeled as green, natural products. This review aims to give an overview of the potential of biocatalysis as a powerful tool for the modification of polyphenols to enhance their bioaccessibility, bioavailability, biological activity or modification of their physicochemical properties. The main polyphenol transformations occurring during their metabolism in the human body have been also presented.

A mechanistic insight into the biological activities of urolithins as gut microbial metabolites of ellagitannins

Urolithins are the gut metabolites produced from ellagitannin-rich foods such as pomegranates, tea, walnuts, as well as strawberries, raspberries, blackberries, and cloudberries. Urolithins are of growing interest due to their various biological activities including cardiovascular protection, anti-inflammatory activity, anticancer properties, antidiabetic activity, and antiaging properties. Several studies mostly based on in vitro and in vivo experiments have investigated the potential mechanisms of urolithins which support the beneficial effects of urolithins in the treatment of several diseases such as Alzheimer's disease, type 2 diabetes mellitus, liver disease, cardiovascular disease, and various cancers. It is now obvious that urolithins can involve several cellular mechanisms including inhibition of MDM2-p53 interaction, modulation of mitogen-activated protein kinase pathway, and suppressing nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activity. Antiaging activity is the most appealing and probably the most important property of urolithin A that has been investigated in depth in recent studies, owing to its unique effects on activation of mitophagy and mitochondrial biogenesis. A recent clinical trial showed that urolithin A is safe up to 2,500 mg/day and can improve mitochondrial biomarkers in elderly patients. Regarding the importance of mitochondria in the pathophysiology of many diseases, urolithins merit further research especially in clinical trials to unravel more aspects of their clinical significance. Besides the nutritional value of urolithins, recent studies proved that urolithins can be used as pharmacological agents to prevent or cure several diseases. Here, we comprehensively review the potential role of urolithins as new therapeutic agents with a special focus on the molecular pathways that have been involved in their biological effects. The pharmacokinetics of urolithins is also included.

Roles of Gut Microbial Metabolites in Diabetic Kidney Disease

Diabetes is a highly prevalent metabolic disease that has emerged as a global challenge due to its increasing prevalence and lack of sustainable treatment. Diabetic kidney disease (DKD), which is one of the most frequent and severe microvascular complications of diabetes, is difficult to treat with contemporary glucose-lowering medications. The gut microbiota plays an important role in human health and disease, and its metabolites have both beneficial and harmful effects on vital physiological processes. In this review, we summarize the current findings regarding the role of gut microbial metabolites in the development and progression of DKD, which will help us better understand the possible mechanisms of DKD and explore potential therapeutic approaches for DKD.