Bioactive Components from Ginger, Tea and Apple Prevent Protein Glycation by Trapping Methylglyoxal with Potential in Alleviation of Diabetic Complications

Diabetes is the fifth-deadliest disease in the United States. Most diabetes patients die from diabetic complications, such as renal failure, heart attack or stroke. However, diabetic complications are still neither preventable nor curable. New strategies that can prevent, treat, or cure diabetic complications are needed. Increasing evidence has identified the formation of advanced glycation end products (AGEs) as a major pathogenic link between hyperglycemia and diabetes-related complications. In diabetes, formation of AGEs occurs at a higher rate when compared to non-diabetic normal individuals. Alpha-oxoaldehydes such as methylglyoxal (MGO) and glyoxal (GO), the reactive dicarbonyl intermediates generated during the non-enzymatic glycation between reducing sugars and amino groups of proteins, lipids, and DNA, are precursors of AGEs and exert direct toxicity to cells and tissues. Levels of MGO and GO were observed to be 2-6 times higher in diabetic patients' plasma as compared with healthy people's plasma. In addition, this is complicated by many food products and beverages representing exogenous sources of MGO and GO. It is likely that decreasing the levels of MGO and GO and inhibiting the formation of AGEs will form an important component of future therapy in patients with diabetes. Numerous studies have reported that bioactive components in ginger, tea and apple can prevent diabetes and its related complications. However, the underlying molecular mechanisms are still largely unknown. In this project, we investigated the effect of bioactive compounds in ginger ([6]-shogaol (6S) and [6]-gingerol (6G)), tea (epigallocatechin gallate (EGCG)) and apple (phloretin and phloridzin) to inhibit the formation of AGEs via trapping MGO. We demonstrated for the first time that both [6]-shogaol (6S) and [6]-gingerol (6G), the major active components in ginger, markedly trapped MGO in vitro and consequently formed mono-MGO adducts, 6S-MGO and 6G-MGO, which were purified from the respective chemical reaction and characterized as novel compounds by NMR experiments and LC-MS/MS approaches. We revealed that the ?-carbon of carbonyl group in the side chain of 6S or 6G is the major active site for trapping MGO. We also demonstrated that 6S and 6G could effectively inhibit the formation of MGO-induced AGEs via trapping MGO in a time-dependent manner in the human serum albumin (HSA)-MGO system. Mono-MGO adducts, 6S-MGO and 6G-MGO, were determined to be the major conjugates in 6S- and 6G-treated HSA-MGO assays, respectively, using LC-ESI/MS techniques. These findings showed the potential effects of 6S and 6G on the prevention of protein glycation, suggesting regular consumption of ginger root extract may attenuate the progression of MGO-associated diabetic complications in patients. Similarly, we found that both EGCG and phloretin could inhibit the formation of AGEs through the same pathways. In addition, we also studied whether these compounds could inhibit the formation of AGEs via trapping MGO in high fat diet treated mice. Two different doses of 6G, EGCG and phloretin (25 mg/kg and 75 mg/kg) were given to mice through oral gavage for 16 weeks. Plasma and tissue samples were collected from control and treated mice. The formation of MGO adducts of each compound were analyzed using our established LC/MS methods. The levels of MGO and AGEs were also quantified.qscienc

The Two-Way Relationship between Diabetes Mellitus and Periodontal Disease: A New Insight

Periodontal Disease and Diabetes Mellitus are two chronic systemic diseases that are intimately connected. A bidirectional relationship exists between the two; to study this unique relationship, they must be studied separately as independent malfunctions and in tandem. Patients that experience these conditions exhibit similar innate immune responses, which lead to aggravated dysfunction of specific body systems. In patients where both conditions exist simultaneously, Diabetes and Periodontal Disease can act in a synchronistic manner, worsening symptoms. In this chapter, the epidemiology of the diabetes mellitus and periodontal disease, presence of biomarkers have been reviewed, and the metabolic syndrome, clinical relevance and treatment modalities, complications of diabetes mellitus, and guidelines for the general dentists, primary care physician, periodontist have been discussed

In vitro and in vivo inhibition of aldose reductase and advanced glycation end products by phloretin, epigallocatechin 3-gallate and [6]-gingerol

Abstract Hyperglycemic stress activates polyol pathway and aldose reductase (AR) key enzyme responsible for generating secondary complications during diabetes. In this study the therapeutic potential of phloretin, epigallocatechin 3-gallate (EGCG) and [6]-gingerol were evaluated for anti-glycating and AR inhibitory activity in vitro and in vivo systems. Human retinal pigment epithelial (HRPE) cells were induced with high glucose supplemented with the phloretin, EGCG and [6]-gingerol. Aldose reductase activity, total advanced glycation end products (AGEs) and enzyme inhibitor kinetics were assessed. Male C57BL/6J mice were randomly assigned to one of the different treatments (bioactive compounds at 2 concentrations each) with either a low fat diet or high fat diet (HFD). After sixteen weeks, AGE accumulation and AR activity was determined in heart, eyes and kidney. High glucose induced toxicity decreased cell viability compared to the untreated cells and AR activity increased to 2–5 folds from 24 to 96h. Pre-treatment of cells with phloretin, EGCG and [6]-gingerol improved cell viability and inhibited AR activity. The enzyme inhibition kinetics followed a non-competitive mode of inhibition for phloretin and EGCG whereas [6]-gingerol indicated uncompetitive type of inhibition against AR. Data from the animal studies showed high plasma glucose levels in HFD group over time, compared to the low fat diet. HFD group developed cataract and AR activity increased to 4 folds compared to the group with low fat diet. Administration of EGCG, phloretin and [6]-gingerol significantly reduced blood sugar levels, AGEs accumulation, and AR activity. These findings could provide a basis to consider using the selected dietary components alone or in combination with other therapeutic approaches to prevent diabetes-related complications in humans.Qatar national Research Fun

Specific Bioactive Compounds from Ginger, Tea, and Apple Prevent Diabetes-Related Cataract Via Inhibition of Aldose Reducatse

North Carolina Research Campus, 500 Laureate Way, Kannapolis, NC 28081, United States Abstract Chronic hyperglycemia is an important risk factor involved in the onset and progression of secondary complications of diabetes. Aldose reductase (AR) has been implicated in the etiology of diabetic eye diseases, diabetic cardiomyopathy and/or nephropathy. High glucose levels activate AR, which is one of the key rate limiting enzymes to use NADPH to reduce glucose to sorbitol in the polyol pathway. The depletion of NADPH is correlated to the production of GSH which increases intercellular oxidative stress. Since inhibition of AR plays an important therapeutic value in preventing and or alleviating diabetic complications. At present there are many AR inhibitors such as Sorbinil, Dilantin, Epalrestat, Tolrestat, Zopolvestat and Minalrestat. However, most of these compounds have serious side effects such as Steven-Johnson syndrome and hypersensitivity reaction. In recent years nutraceuticals have garnered interest for their potential as dietary and natural health promoting properties. Hence, the purpose of this study was to investigate the inhibitory activity of phloretin from apple, ( − )-epigallocatechin 3-gallate (EGCG) from green tea and [6]-gingerol from ginger against aldose reductase as indicator or their potential in the alleviation of diabetic complications. These three compounds were selected out of 9 bioactive compounds based on their activity in cell culture assays. Human retinal pigment epithelial (HRPE) cells were subjected to different concentrations of glucose (10–100 mM) for 1 and 4 days during which cell viability and aldose reductase activity were evaluated. Results show that cell viability decreased to 93 ± 3%, 83 ± 6%, 65 ± 4% and 39 ± 3% at 10, 25, 50 and 100 mM of glucose on day 1 with further drastic decrease in cell viability to 73 ± 5%, 61 ± 3%, 35 ± 2%, and 11 ± 6%, respectively, on day 4 compared to the untreated cell. The activity of aldose reductase was found to increase 5 folds at 10 mM from day 1 to day 4, whereas at 25, 50 and 100 mM concentrations of glucose the AR activity was increased to almost 2 folds. The specific activity of aldose reductase was found to be 8.92 ± 1.6 U/mg protein at 100 mM glucose on day 4. The apparent Michaelis constant (Km) of the substrate glyceraldehyde and NADPH was estimated to be 4.5 mM and 68.96 μM, respectively. Pre-treatment of cells with phloretin, EGCG and [6]-gingerol at 25 μM improved cell viability to 72 ± 4%, 77 ± 5% and 78 ± 4%, at day 1 respectively, whereas EGCG further improved cell viability on day 4 to 89 ± 5%, but phloretin and [6]-gingerol could marginally increase to 76 ± 3%, 81 ± 4% when compared to the untreated cells. The three compounds could inhibit AR activity up to 90 % at 12.5 μM of phloretin, EGCG and [6]-gingerol with IC50 values of 4.1 μM, 3.7 μM, and 2.4 μM, respectively. The enzyme inhibition kinetics showed non-competitive mode of inhibition for phloretin and EGCG, since it did not alter the Km but the maximum velocity (Vmax) decreased in the presence of the compounds, whereas [6]-gingerol indicated uncompetitive type of inhibition against AR, where it decreased both Km and Vmax upon binding. The above cell culture findings were further validated in mouse model. Male C57BL/6J mice 5 weeks old, were divided into eight groups of 11 mice each. The animals had free access to food and water and were fed with either a standard laboratory diet (8604 Teklad Rodent diet, Harlan, TM) or a high fat diet (HFD) (TD 110716, Teklad Research Rodent Diet, Harlan, TM). Animals were randomly assigned to the different treatment groups (N = 11 / group): (i) Normal diet, (ii) HFD, (iii) HFD + EGCG 25 mg/kg, (iv) HFD + EGCG at 75 mg/kg, (v) HFD + phloretin 25 mg/kg, (vi) HFD + phloretin 75 mg/kg, (vii) HFD + [6]-gingerol 25 mg/kg, (viii) HFD + [6]-gingerol 75 mg/kg. All test solutions were prepared freshly every day prior to use and were administered intraperitoneal injection (i. p.), once daily and three times in a week over a period of sixteen weeks. Body weight was recorded every day, while blood glucose levels were determined weekly with a commercially available micro-draw blood monitoring system. After sixteen weeks, the animals were sacrificed; heart, eyes and kidney were examined for AR activity. The results shows that the HFD group had developed diabetes, with blood glucose levels 260 ± 27 mg/dL, whereas the control with normal diet showed about 130 ± 20 mg/dL. The groups treated with EGCG, phloretin and [6]-gingerol at 75 mg/kg significantly decreased blood sugar levels to 128 ± 8, 125 ± 15 and 132 ± 9 mg/dL, respectively. The groups treated with EGCG, phloretin and [6]-gingerol at 25 mg/kg also decreased the blood sugar levels to 198 ± 15, 180 ± 16 and 170 ± 19 mg/dL, respectively. The eye lens of the mice from HFD group had developed cataract and the AR activity increased to 4 fold compared to the group fed with normal diet. All the compounds at 75 mg/kg, prevented/delayed the formation of cataract by 80%, whereas dosing at 25 mg/kg showed signs of cataract but AR activity was decreased to two folds when compared to the HFD group. The HFD enhanced the aldose reductase activity to two and three folds in the heart and kidney. Data from this study suggest the promising potential of these dietary compounds in providing cytoprotection and inhibiting a key enzyme associated with the onset of diabetes-related complications. Upon validation of this benefit in vivo, such dietary compounds could be of interest to dietary supplements and pharmaceutical industry as complementary treatment of secondary complications in diabetic patients.qscienc

Specific bioactive compounds in ginger and apple alleviate hyperglycemia in mice with high fat diet-induced obesity via Nrf2 mediated pathway

Prolonged hyperglycemia activates the formation of advanced glycation end-products (AGEs). Major dicarbonyl compounds such as methylglyoxal or glyoxal are found to be the main precursors of AGEs and N(e)-(carboxymethyl)lysine (CML) found to be predominantly higher in the diabetic population. We hypothesized that phloretin from apple and [6]-gingerol from ginger inhibit formation of AGEs and suppress the receptor for advanced glycation end products (RAGE) via nuclear factor erythroid-2- related-factor-2 (Nrf2)-dependent pathway. Phloretin and [6]-gingerol were supplemented at two different doses to C57BL/6 mice on high fat diet or standard diet for a period of 17 weeks. Phloretin or [6]- gingerol supplementation significantly reduced plasma glucose, alanine aminotransferase, aspartate aminotransferase, AGEs and insulin levels. Phloretin and [6]-gingerol also decreased the levels of AGEs and CML levels, via Nrf2 pathway, enhancing GSH/GSSG ratio, heme oxygenase-1 and glyoxalase 1 in liver tissue. These results suggest that phloretin and [6]-gingerol are potential dietary compounds that can alleviate diabetes-induced complications.Qatar National research Fun

Supplementation of 17β-Estradiol Normalizes Rapid Gastric Emptying by Restoring Impaired Nrf2 and nNOS Function in Obesity-Induced Diabetic Ovariectomized Mice

Gastroparesis (Gp) is a multifactorial condition commonly observed in females and is characterized by delayed or rapid gastric emptying (GE). The role of ovarian hormones on GE in the pathogenesis of obesity induced type 2 diabetes mellitus (T2DM) is completely unknown. The aims of our study are to investigate whether supplementation of 17β-estradiol (E2) or progesterone (P4) restores impaired nuclear factor erythroid 2-related factor 2 (Nrf2, an oxidative stress-responsive transcription factor) and nitric oxide (NO)-mediated gastric motility in ovariectomized (OVX) mice consuming a high-fat diet (HFD, a model of T2DM). Groups of OVX+HFD mice were administered daily subcutaneous doses of either E2 or P4 for 12 weeks. The effects of E2 and P4 on body weight, metabolic homeostasis, solid GE, gastric antrum NO-mediated relaxation, total nitrite levels, neuronal nitric oxide synthase (nNOSα), and its cofactor expression levels were assessed in OVX+HFD mice. HFD exacerbated hyperglycemia and insulinemia while accelerating GE (p < 0.05) in OVX mice. Exogenous E2, but not P4, attenuated rapid gastric emptying and restored gastric nitrergic relaxation, total nitrite levels, nNOSα, and cofactor expression via normalizing Nrf2-Phase II enzymes, inflammatory response, and mitogen-activated protein kinase (MAPK) protein expression in OVX+HFD mice. We conclude that E2 is beneficial in normalizing metabolic homeostasis and gastric emptying in obese, diabetic OVX mice consuming a fat-rich diet

Bioactive compounds isolated from apple, tea, and ginger protect against dicarbonyl induced stress in cultured human retinal epithelial cells

Abstract BackgroundMethylglyoxal (MGO) is known to be a major precursor of advanced glycation end products (AGEs) which are linked to diabetes and its related complications. Naturally occurring bioactive compounds could play an important role in countering AGEs thereby minimizing the risk associated with their formation. MethodsIn this study, eight specific bioactive compounds isolated from apple, tea and ginger were evaluated for their AGEs scavenging activity using Human Retinal Pigment Epithelial (H-RPE) cells treated with MGO. ResultsAmong the eight specific compounds evaluated, (-)-epigallocatechin 3-gallate (EGCG) from tea, phloretin in apple, and [6]-shogaol and [6]-gingerol from ginger were found to be most effective in preventing MGO-induced cytotoxicity in the epithelial cells. Investigation of possible underlying mechanisms suggests that that these compounds could act by modulating key regulative detoxifying enzymes via modifying nuclear factor-erythroid 2-related factor 2 (Nrf2) function. MGO-induced cytotoxicity led to increased levels of AGEs causing increase in Nε-(Carboxymethyl) lysine (CML) and glutathione (GSH) levels and over expression of receptor for advanced glycation end products (RAGE). Data also showed that translocation of Nrf2 from cytosol to nucleus was inhibited, which decreased the expression of detoxifying enzyme like heme oxygenase-1 (HO-1). The most potent bioactive compounds scavenged dicarbonyl compounds, inhibited AGEs formation and significantly reduced carbonyl stress by Nrf2 related pathway and restoration of HO-1 expression. ConclusionsThese findings demonstrated the protective effect of bioactive compounds derived from food sources against MGO-induced carbonyl stress through activation of the Nrf2 related defense pathway, which is of significant importance for therapeutic interventions in complementary treatment/management of diabetes-related complications.Qatar National Research Fun