Cyanidin Stimulates Insulin Secretion and Pancreatic β-Cell Gene Expression through Activation of l-type Voltage-Dependent Ca2+ Channels

Cyanidin is a natural anthocyanidin present in fruits and vegetables with anti-diabetic properties including stimulation of insulin secretion. However, its mechanism of action remains unknown. In this study, we elucidated the mechanisms of cyanidin for stimulatory insulin secretion from pancreatic β-cells. Rat pancreatic β-cells INS-1 were used to investigate the effects of cyanidin on insulin secretion, intracellular Ca2+ signaling, and gene expression. We detected the presence of cyanidin in the intracellular space of β-cells. Cyanidin stimulated insulin secretion and increased intracellular Ca2+ signals in a concentration-dependent manner. The Ca2+ signals were abolished by nimodipine, an l-type voltage-dependent Ca2+ channel (VDCC) blocker or under extracellular Ca2+ free conditions. Stimulation of cells with cyanidin activated currents typical for VDCCs and up-regulated the expression of glucose transporter 2 (GLUT2), Kir6.2, and Cav1.2 genes. Our findings indicate that cyanidin diffuses across the plasma membrane, leading to activation of l-type VDCCs. The increase in intracellular Ca2+ stimulated insulin secretion and the expression of genes involved in this process. These findings suggest that cyanidin could be used as a promising agent to stimulate insulin secretion

Protective effect of cyanidin against glucose- and methylglyoxal-induced protein glycation and oxidative DNA damage

Cyanidin, a natural anthocyanin abundant in fruits and vegetables, has shown the health benefits due to its pharmacological properties. However, there was no evidence regarding anti-glycation activity of cyanidin. The aim of the study was to investigate the inhibitory effect of cyanidin on methylglyoxal (MG)- and glucose-induced protein glycation in bovine serum albumin (BSA) as well as oxidative DNA damage. Free radical scavenging activity and the MG-trapping ability of cyanidin were also investigated. The results demonstrated that cyanidin (0.125-1mM) significantly inhibited the formation of fluorescent and non-fluorescent AGEs in BSA/MG and BSA/glucose systems. There was a significantly improved protein thiol in BSA/MG and BSA/glucose when incubated with cyanidin. Correspondingly, cyanidin decreased the level of protein carbonyl content in BSA/glucose system. Moreover, cyanidin (0.5-1mM) prevented lysine/MG-mediated oxidative DNA damage in the absence or presence of copper ion. The results demonstrated that cyanidin showed the MG-trapping ability in a concentration-dependent manner. Cyanidin also reduced superoxide anion and hydroxyl radical generation in lysine/MG system. The mechanism by which cyanidin inhibited protein glycation was the MG-trapping ability and the free radical scavenging activity. The present study suggests that cyanidin might be a promising antiglycation agent for preventing or ameliorating AGEs-mediated diabetic complications

Cyanidin Attenuates Methylglyoxal-Induced Oxidative Stress and Apoptosis in INS-1 Pancreatic β-Cells by Increasing Glyoxalase-1 Activity

Recently, the mechanisms responsible for anti-glycation activity of cyanidin and its derivatives on the inhibition of methylglyoxal (MG)-induced protein glycation and advanced glycation-end products (AGEs) as well as oxidative DNA damage were reported. In this study, we investigated the protective effect of cyanidin against MG-induced oxidative stress and apoptosis in rat INS-1 pancreatic β-cells. Exposure of cells to cytotoxic levels of MG (500 µM) for 12 h caused a significant reduction in cell viability. However, the pretreatment of cells with cyanidin alone (6.25–100 μM) for 12 h, or cotreatment of cells with cyanidin (3.13–100 μM) and MG, protected against cell cytotoxicity. In the cotreatment condition, cyanidin (33.3 and 100 μM) also decreased MG-induced apoptosis as determined by caspase-3 activity. Furthermore, INS-1 cells treated with MG increased the generation of reactive oxygen species (ROS) during a 6 h exposure. The MG-induced increase in ROS production was inhibited by cyanidin (33.3 and 100 μM) after 3 h stimulation. Furthermore, MG diminished the activity of glyoxalase 1 (Glo-1) and its gene expression as well as the level of total glutathione. In contrast, cyanidin reversed the inhibitory effect of MG on Glo-1 activity and glutathione levels. Interestingly, cyanidin alone was capable of increasing Glo-1 activity and glutathione levels without affecting Glo-1 mRNA expression. These findings suggest that cyanidin exerts a protective effect against MG-induced oxidative stress and apoptosis in pancreatic β-cells by increasing the activity of Glo-1

Cyanidin Attenuates Methylglyoxal-Induced Oxidative Stress and Apoptosis in INS-1 Pancreatic β-Cells by Increasing Glyoxalase-1 Activity

Recently, the mechanisms responsible for anti-glycation activity of cyanidin and its derivatives on the inhibition of methylglyoxal (MG)-induced protein glycation and advanced glycation-end products (AGEs) as well as oxidative DNA damage were reported. In this study, we investigated the protective effect of cyanidin against MG-induced oxidative stress and apoptosis in rat INS-1 pancreatic β-cells. Exposure of cells to cytotoxic levels of MG (500 µM) for 12 h caused a significant reduction in cell viability. However, the pretreatment of cells with cyanidin alone (6.25-100 μM) for 12 h, or cotreatment of cells with cyanidin (3.13-100 μM) and MG, protected against cell cytotoxicity. In the cotreatment condition, cyanidin (33.3 and 100 μM) also decreased MG-induced apoptosis as determined by caspase-3 activity. Furthermore, INS-1 cells treated with MG increased the generation of reactive oxygen species (ROS) during a 6 h exposure. The MG-induced increase in ROS production was inhibited by cyanidin (33.3 and 100 μM) after 3 h stimulation. Furthermore, MG diminished the activity of glyoxalase 1 (Glo-1) and its gene expression as well as the level of total glutathione. In contrast, cyanidin reversed the inhibitory effect of MG on Glo-1 activity and glutathione levels. Interestingly, cyanidin alone was capable of increasing Glo-1 activity and glutathione levels without affecting Glo-1 mRNA expression. These findings suggest that cyanidin exerts a protective effect against MG-induced oxidative stress and apoptosis in pancreatic β-cells by increasing the activity of Glo-1

Anthocyanin-Enriched Riceberry Rice Extract Inhibits Cell Proliferation and Adipogenesis in 3T3-L1 Preadipocytes by Downregulating Adipogenic Transcription Factors and Their Targeting Genes

Riceberry rice (Oryza sativa L.) is a new pigmented variety of rice from Thailand. Despite its high anthocyanin content, its effect on adipogenesis and adipocyte function remains unexplored. We investigated whether Riceberry rice extract (RBE) impacted cell proliferation by examining viability and cell cycle, using preadipocyte 3T3-L1 cells. To test RBE’s effect on adipocyte formation, cells were cultured in adipogenic medium supplemented with extract and adipocyte number and triglyceride levels were quantified. Furthermore, Akt1 phosphorylation along with RT-qPCR and intracellular calcium imaging were performed to obtain an insight into its mechanism of action. The effect of RBE on adipocyte function was investigated using glucose uptake and lipolysis assays. Treatment of cells with RBE decreased preadipocyte number without cytotoxicity despite inducing cell cycle arrest (p < 0.05). During adipogenic differentiation, RBE supplementation reduced adipocyte number and triglyceride accumulation by downregulating transcription factors (e.g., PPARγ, C/EBPα, and C/EBPβ) and their target genes (p < 0.05). The Akt1 phosphorylation was decreased by RBE but insignificance, however, the extract failed to increase intracellular calcium signals. Finally, the treatment of adipocytes with RBE reduced glucose uptake by downregulating Glut4 mRNA expression and enhanced isoproterenol-induced lipolysis (p < 0.05). These findings suggest that RBE could potentially be used in the treatment of obesity by inhibiting adipocyte formation and proliferation

Telomere Shortening and Increased Oxidative Stress in Lumbar Disc Degeneration

Lumbar disc degeneration (LDD) contributes to low back pain. This study aimed to determine relative telomere length (RTL), oxidative stress status, and antioxidant levels and examine the relationships between RTL, oxidative stress, and the severity in LDD patients. A total of 100 subjects, 50 LDD patients and 50 healthy controls, were enrolled in the case–control study. Blood leukocyte RTL was analyzed using quantitative real-time polymerase chain reaction. Lipid peroxidation was determined by malondialdehyde (MDA) assay. Plasma 8-hydroxy 2′-deoxyguanosine (8-OHdG) values were determined using enzyme-linked immunosorbent assay. Total antioxidant capacity (TAC) and ferric reducing antioxidant power (FRAP) in plasma were also measured. The LDD patients had significantly shorter telomeres than the healthy controls (p = 0.04). Blood leukocyte RTL was inversely correlated with the LDD severity (r = −0.41, p = 0.005). Additionally, plasma MDA and 8-OHdG levels were markedly greater in LDD patients than in the controls (p = 0.01 and p = 0.002, respectively). Furthermore, the plasma MDA level showed a positive correlation with the radiographic severity (r = 0.49, p = 0.001). There was a positive correlation between plasma 8-OHdG and the severity (r = 0.60, p < 0.001). Moreover, plasma TAC and FRAP levels were significantly lower in LDD patients than in the controls (p = 0.04). No significant differences in plasma TAC and FRAP were observed among the three groups of LDD severity. We found that RTL was negatively correlated with the severity while plasma MDA and 8-OHdG levels were positively correlated with the severity. These findings suggest that blood leukocyte RTL, plasma MDA, and 8-OHdG may have potential as noninvasive biomarkers for the assessment of severity in LDD

Anthocyanin-Enriched Riceberry Rice Extract Inhibits Cell Proliferation and Adipogenesis in 3T3-L1 Preadipocytes by Downregulating Adipogenic Transcription Factors and Their Targeting Genes

Riceberry rice ( L.) is a new pigmented variety of rice from Thailand. Despite its high anthocyanin content, its effect on adipogenesis and adipocyte function remains unexplored. We investigated whether Riceberry rice extract (RBE) impacted cell proliferation by examining viability and cell cycle, using preadipocyte 3T3-L1 cells. To test RBE\u27s effect on adipocyte formation, cells were cultured in adipogenic medium supplemented with extract and adipocyte number and triglyceride levels were quantified. Furthermore, Akt1 phosphorylation along with RT-qPCR and intracellular calcium imaging were performed to obtain an insight into its mechanism of action. The effect of RBE on adipocyte function was investigated using glucose uptake and lipolysis assays. Treatment of cells with RBE decreased preadipocyte number without cytotoxicity despite inducing cell cycle arrest ( \u3c 0.05). During adipogenic differentiation, RBE supplementation reduced adipocyte number and triglyceride accumulation by downregulating transcription factors (e.g., PPARγ, C/EBPα, and C/EBPβ) and their target genes ( \u3c 0.05). The Akt1 phosphorylation was decreased by RBE but insignificance, however, the extract failed to increase intracellular calcium signals. Finally, the treatment of adipocytes with RBE reduced glucose uptake by downregulating Glut4 mRNA expression and enhanced isoproterenol-induced lipolysis ( \u3c 0.05). These findings suggest that RBE could potentially be used in the treatment of obesity by inhibiting adipocyte formation and proliferation

Effect of vitamin E on oxidative stress level in blood, synovial fluid, and synovial tissue in severe knee osteoarthritis: a randomized controlled study

Abstract Background This study was performed to evaluate the antioxidative and anti-inflammatory effects of vitamin E on oxidative stress in the plasma, synovial fluid, and synovial tissue of patients with knee osteoarthritis. Methods Seventy-two patients with late-stage knee osteoarthritis scheduled for total knee arthroplasty were randomized to take oral placebo (Group A) or 400 IU of vitamin E (Group B) once a day for 2 months before undergoing surgery. The blood levels of endpoints indicating oxidative stress or antioxidant capacity, Knee Society Score (KSS), Western Ontario and McMaster Universities Osteoarthritis Index score (WOMAC), and adverse effects were compared before and after the intervention between the two groups. At surgery, these redox endpoints and histological findings were compared between the synovial fluid and synovial tissue. Results In blood samples, the pre-intervention of oxidative stress and antioxidative capacity were not different between Group A and Group B. In post-intervention blood samples, the Malondialdehyde (Group A 1.34 ± 0.10, Group B 1.00 ± 0.09, p < 0.02), Alpha tocopherol (Group A 15.92 ± 1.08, Group B 24.65 ± 1.47, p < 0.01) and Trolox equivalent antioxidant capacity (Group A 4.22 ± 0.10, Group B 5.04 ± 0.10, 0 < 0.01) were significantly different between Group A and Group B. In synovial fluid samples, the Malondialdehyde (Group A 1.42 ± 0.12, Group B 1.06 ± 1.08, p 0.01), Alphatocopherol (Group A 4.51, Group B 7.03, p < 0.01), Trolox equivalent antioxidant capacity (Group A, 1.89 ± 0.06, Group B 2.19 ± 0.10) were significantly different between Group A and Group B. The pre-intervention WOMAC score and KSS score were not different between Group A and Group B. The post-intervention WOMAC score was significantly improved in all categories in Group B (Pain: Group A 27.26 ± 0.89, Group B 19.19 ± 1.43, p < 0.01; Stiffness: Group A 8.23 ± 0.79, Group B 5.45 ± 0.73, p 0.01; Function: Group A 94.77 ± 4.22, Group B 72.74 ± 6.55, p < 0.01). The post-intervention KSS score was significantly improved in all categories in Group B (Clinical: Group A 25.31 ± 14.33, Group B 33.52 ± 16.96, p < 0.01; Functional: Group A 41.43 ± 16.11, Group B 51.61 ± 19.60, p 0.02). Significantly fewer synovial tissue cells were stained with nitrotyrosine and hematoxylin–eosin in Group B than in Group A. There were no differences in adverse effects or surgical complications between the groups. Conclusion Vitamin E is an effective antioxidant that can improve clinical symptoms and reduce oxidative stress conditions in patients with late-stage knee osteoarthritis. Trial registration This research project had been approved for registration at Thai Clinical Trials Registry (TCTR) since 2016–08-28 11:26:32 (Retrospective registered). The TCTR identification number is TCTR20160828001

Cyanidin Stimulates Insulin Secretion and Pancreatic β-Cell Gene Expression through Activation of l-type Voltage-Dependent Ca2+ Channels

Cyanidin is a natural anthocyanidin present in fruits and vegetables with anti-diabetic properties including stimulation of insulin secretion. However, its mechanism of action remains unknown. In this study, we elucidated the mechanisms of cyanidin for stimulatory insulin secretion from pancreatic β-cells. Rat pancreatic β-cells INS-1 were used to investigate the effects of cyanidin on insulin secretion, intracellular Ca2+ signaling, and gene expression. We detected the presence of cyanidin in the intracellular space of β-cells. Cyanidin stimulated insulin secretion and increased intracellular Ca2+ signals in a concentration-dependent manner. The Ca2+ signals were abolished by nimodipine, an l-type voltage-dependent Ca2+ channel (VDCC) blocker or under extracellular Ca2+ free conditions. Stimulation of cells with cyanidin activated currents typical for VDCCs and up-regulated the expression of glucose transporter 2 (GLUT2), Kir6.2, and Cav1.2 genes. Our findings indicate that cyanidin diffuses across the plasma membrane, leading to activation of l-type VDCCs. The increase in intracellular Ca2+ stimulated insulin secretion and the expression of genes involved in this process. These findings suggest that cyanidin could be used as a promising agent to stimulate insulin secretion

Cyanidin-3-rutinoside stimulated insulin secretion through activation of L-type voltage-dependent Ca channels and the PLC-IP pathway in pancreatic β-cells

Cyanidin-3-rutinoside (C3R) is an anthocyanin with anti-diabetic properties found in red-purple fruits. However, the molecular mechanisms of C3R on Ca-dependent insulin secretion remains unknown. This study aimed to identify C3R\u27s mechanisms of action in pancreatic β-cells. Rat INS-1 cells were used to elucidate the effects of C3R on insulin secretion, intracellular Ca signaling, and gene expression. The results showed that C3R at 60, 100, and 300 µM concentrations significantly increased insulin secretion via intracellular Ca signaling. The exposure of cells with C3R concentrations up to 100 μM did not affect cell viability. Pretreatment of cells with nimodipine (voltage-dependent Ca channel (VDCC) blocker), U73122 (PLC inhibitor), and 2-APB (IP receptor blocker) inhibited the intracellular Ca signals by C3R. Interestingly, C3R increased intracellular Ca signals and insulin secretion after depletion of endoplasmic reticulum Ca stores by thapsigargin. However, insulin secretion was abolished under extracellular Ca-free conditions. Moreover, C3R upregulated mRNA expression for Glut2 and Kir genes. These findings indicate that C3R stimulated insulin secretion by promoting Ca influx via VDCCs and activating the PLC-IP pathway. C3R also upregulates the expression of genes necessary for glucose-induced insulin secretion. This is the first study describing the molecular mechanisms by which C3R stimulates Ca-dependent insulin secretion from pancreatic β-cells. These findings contribute to our understanding on how anthocyanins improve hyperglycemia in diabetic patients