Mona F. Mahmoud

Quercetin Protects against Diabetes-Induced Exaggerated Vasoconstriction in Rats: Effect on Low Grade Inflammation

Vascular complications are the leading cause of morbidity and mortality in patients with diabetes. Quercetin is an important flavonoid with antioxidant and anti-inflammatory activity. Here, the effect of quercetin on diabetes-induced exaggerated vasoconstriction in insulin deficient and insulin resistant rat models was investigated. Insulin deficiency was induced by streptozotocin while, insulin resistance by fructose. Rats were left 8 weeks or 12 weeks after STZ or fructose administration respectively. Quercetin was daily administered in the last 6 weeks. Then, tail blood pressure (BP) was recorded in conscious animals; concentration-response curves for phenylephrine (PE) and KCl were studied in thoracic aorta rings. Non-fasting blood glucose level, serum insulin level, insulin resistance index, serum tumour necrosis factor-α (TNF-α) and serum C-reactive protein (CRP) were determined. Nuclear transcription factor-κB (NF-κB) was assessed by immunofluorescence technique. Histopathological examination was also performed. The results showed that quercetin protected against diabetes-induced exaggerated vasoconstriction and reduced the elevated blood pressure. In addition, quercetin inhibited diabetes associated adventitial leukocyte infiltration, endothelial pyknosis and increased collagen deposition. These effects were accompanied with reduction in serum level of both TNF-α and CRP and inhibition of aortic NF-κB by quercetin in both models of diabetes. On the other hand, quercetin did not affect glucose level in any of the used diabetic models. This suggests that the protective effect of quercetin is mediated by its anti-inflammatory effect rather than its metabolic effects. In summary, quercetin is potential candidate to prevent diabetic vascular complications in both insulin deficiency and resistance via its inhibitory effect on inflammatory pathways especially NF-κB signaling.

Anti-inflammatory effect of atorvastatin on vascular reactivity and insulin resistance in fructose fed rats

We investigated the possible protective effect of atorvastatin against vascular dysfunction associated with insulin resistance (IR) in fructose-fed model rats. The effect of atorvastatin (10 mg/kg/day for 8 weeks) on vascular reactivity, glucose, cholesterol, insulin, and the IR index in a well-established model of dietary hypertriglyceridemia, the fructose-fed rat, was investigated. Fructose feeding (10% fructose in drinking water for 8 weeks) induced hypercholesterolemia and hyperinsulinemia without any change in blood glucose levels. Fructose feeding also elevated serum tumor necrosis factor-alpha (TNF-α), the insulin resistance index, leukocyte infiltration, and endothelial cell pyknosis. Fructose feeding induced hyper-responsiveness to both phenylephrine (PE), KCl, and hyporesponsiveness to acetylcholine (Ach) but not to sodium nitroprusside-induced relaxation. Atorvastatin, given concurrently with fructose, reduced hypercholesterolemia, hyperinsulinemia, TNF-α level, and the IR index. It also reduced leukocyte infiltration and endothelial cell pyknosis and decreased hyper-responsiveness to both PE and KCl but did not affect hyporesponsiveness to Ach relaxation. In conclusion, atorvastatin protected against impairment in aortic vascular reactivity associated with insulin resistance, particularly increased contractility, but not reduced endothelium-dependent relaxation, by a mechanism involving a reduction in cholesterol and IR in addition to anti-inflammatory effects.

Caffeic acid phenethyl ester, a 5-lipoxygenase enzyme inhibitor, alleviates diabetic atherosclerotic manifestations: effect on vascular reactivity and stiffness.

Atherosclerosis is a major macrovascular complication of diabetes that increases the risks for myocardial infarction, stroke, and other vascular diseases. The effect of a selective 5-lipoxygenase enzyme inhibitor; caffeic acid phenethyl ester (CAPE) on diabetes-induced atherosclerotic manifestations was investigated. Insulin deficiency or resistance was induced by STZ or fructose respectively. Atherosclerosis developed when rats were left for 8 or 12 weeks subsequent STZ or fructose administration respectively. CAPE (30 mg kg(-1) day(-1)) was given in the last 6 weeks. Afterwards, blood pressure (BP) was recorded. Then, isolated aorta reactivity to KCl and phenylephrine (PE) was studied. Blood glucose level, serum levels of insulin, tumor necrosis factor α (TNF-α) as well as advanced glycation end products (AGEs) were determined. Moreover aortic haem oxygenase-1 (HO-1) protein expression and collagen deposition were also assessed. Insulin deficiency and resistance were accompanied with elevated BP, exaggerated response to KCl and PE, elevated serum TNF-α and AGEs levels. Both models showed marked increase in collagen deposition. However, CAPE alleviated systolic and diastolic BP elevations and the exaggerated vascular contractility to both PE and KCl in both models without affecting AGEs level. CAPE inhibited TNF-α serum level elevation, induced aortic HO-1 expression and reduced collagen deposition. CAPE prevented development of hyperinsulinemia in insulin resistance model without any impact on the developed hyperglycemia in insulin deficiency model. In conclusion, CAPE offsets the atherosclerotic changes associated with diabetes via amelioration of the significant functional and structural derangements in the vessels in addition to its antihyperinsulinemic effect in insulin resistant model.

Effect of Cordyceps sinensis and taurine either alone or in combination on streptozotocin induced diabetes.

The present study aimed to investigate the antidiabetic effects of Cordyceps sinensis, taurine and their combination in comparison with glibenclamide both in vivo and in vitro using streptozotocin rat model. The diabetic rats were orally given glibenclamide, C. sinensis, taurine or Cordyceps and taurine combination for 21 days. Their effects were studied both in vivo and in vitro. Oral administration of Cordyceps, taurine and their combination decreased serum glucose, fructosamine, total cholesterol, triglycerides levels, insulin resistance index and pancreatic malondialdehyde content. Cordyceps significantly increased serum insulin, HDL-cholesterol, total antioxidant capacity levels, β cell function percent, and pancreatic reduced glutathione (GSH) content. However, taurine was unable to elevate pancreatic GSH level to a significant level. These natural products and their combinations were more effective than glibenclamide in reducing insulin resistance index and they had stronger antioxidant properties. Cordyceps and taurine significantly enhanced glucose uptake by diaphragms of normal and diabetic rats in absence and presence of insulin. In conclusion, Cordyceps and taurine either alone or in combination have less potent hypoglycemic effects than glibenclamide; however, they have more ability to reduce insulin resistance and stronger antioxidant properties.

Limonin attenuates hepatocellular injury following liver ischemia and reperfusion in rats via toll-like receptor dependent pathway.

Limonin has been shown to exhibit anti-inflammatory and antioxidant properties in the settings of chemically induced hepatic injury. The current study aimed to investigate the protective effects of limonin on experimentally-induced hepatic ischemia reperfusion (I/R) injury in rats. Rats were injected IP with either DMSO or limonin (100 mg/kg BW), 30 min before submission to 45 min of ischemia, followed by 1 h of reperfusion. Limonin ameliorated the deleterious effects of I/R as indicated by improvement in liver function tests, reduction of lactate dehydrogenase, reduction of oxidative stress, decrease in hepatocyte degeneration, and pyknosis. Furthermore, pretreatment of I/R rats with limonin, induced a significant down regulation in the various elements of the toll like receptor (TLR)pathway including TLR-2 and TLR-4, myeloid differentiation factor 88 (MYD88) and toll/IR-1(TIR)-domain-containing adaptor protein inducing interferon-beta (TRIF) and the downstream effectors TNF-α, TNF-α/IL-10 ratio and nuclear factor-κB (NF-κB). It also increased the anti-inflammatory cytokine IL-10 and decreased the activity of the apoptotic marker, caspase-3. These data indicate that limonin exerts antioxidant and anti-inflammatory effects in ischemic liver, thus, protecting hepatocytes against I/R injury in rats. The mechanism of these hepatoprotective effects appears to be related to the antioxidant and anti-inflammatory potential of limonin mediated by the down regulation of TLR- signaling pathway.

Evaluation of the efficacy of ginger, Arabic gum, and Boswellia in acute and chronic renal failure.

This study was conducted to evaluate the effects of Zingiber officinale Roscoe (Ginger), Arabic gum (AG), and Boswellia on both acute and chronic renal failure (CRF) and the mechanisms underlying their effects. Acute renal failure was induced by 30 min ischemia followed by 24 h reperfusion, while CRF was induced by adenine feeding for 8 weeks. Prophylactic oral administration of ginger, AG, Boswellia, or vehicle (in control groups) was started 3 days before and along with adenine feeding in different groups or 7 days before ischemia–reperfusion. Ginger and AG showed renoprotective effects in both models of renal failure. These protective effects may be attributed at least in part to their anti-inflammatory properties as evident by attenuating serum C-reactive protein levels and antioxidant effects as evident by attenuating lipid peroxidation marker, malondialdehyde levels, and increasing renal superoxide dismutase activity. Ginger was more potent than AG in both models of renal failure. However, Boswellia showed only partial protective effect against both acute renal failure and CRF and it had no antioxidant effects. Finally, we can say that ginger and AG could be beneficial adjuvant therapy in patients with acute renal failure and CRF to prevent disease progression and delay the need for renal replacement therapy.

Role of cannabinoid receptors in hepatic fibrosis and apoptosis associated with bile duct ligation in rats.

This study assessed the effect of stimulation of CB2 receptors or CB1 blockade on fibrosis and apoptosis in rats subjected to bile duct ligation (BDL). It was performed in sham and BDL rats for four weeks. Fibrosis-induced rats received a CB2 receptor agonist β-caryophyllene, CB1 receptor antagonist, hemopressin, combination of β-caryophyllene and CB2 antagonist, AM630 or vehicle daily during the last 2 weeks of the BDL ligation. Transaminases activity, bilirubin levels, hepatic collagen content, hydroxyproline level, Bcl2 positive hepatocytes, and mRNA expression of CB1, CB2 receptors and matrix metalloproteinase-1 (MMP-1) genes were measured in all animals. Bile duct ligated rats showed increased bilirubin levels, elevated transaminases activity, increased hepatic collagen content, and hydroxyproline level, reduced Bcl2 positive hepatocytes and increased expression of the assessed messengers in comparison with sham rats. However, fibrotic rats treated with either β-caryophyllene or hemopressin had reduced hepatic collagen content, improved transaminase activity and reduced bilirubin level, ameliorated CB1 gene expression, and increased MMP-1 gene expression compared with untreated fibrotic rats. These results were associated with attenuated apoptosis with only β-caryophyllene administration. CB2 receptor blockade by AM630 prevents the effects of β-caryophyllene on CB1 receptor and MMP-1 genes expression. This study points out that either stimulation of CB2 receptors or CB1 blockade can attenuate hepatic fibrosis in bile duct ligated rats. The mechanisms underlying these incidents may open new avenues for attenuating fibrosis and apoptosis of cholestasis- induced liver diseases.

Baicalein protects against hypertension associated with diabetes: Effect on vascular reactivity and stiffness

The present work investigated the possible protective effect of baicalein, a natural lipoxygenase enzyme inhibitor, on both insulin deficiency (ID) and insulin resistance (IR)-induced macro-vascular impairment. ID and IR were induced by STZ or fructose for 8 or 12 weeks respectively while baicalein was administered in the last six weeks. Blood pressure (BP) was recorded and isolated aorta reactivity to phenylephrine (PE) and acetylcholine (ACh) were studied. Blood levels of glucose, insulin, advanced glycation end products (AGEs) and tumour necrosis factor-α (TNF-α) were determined. Aortic nuclear transcription factor-κB (NF-κB) activation was assessed. Both models resulted in elevated BP, increased vasoconstriction and impaired relaxation KCl, elevated TNF-α and AGEs, NF-κB activation, marked infiltration of leukocytes in the adventitia, pyknosis of endothelial cells and marked collagen deposition. Baicalein ameliorated elevations in BP in models, prevented exaggerated vasoconstriction IR model and improved relaxation in ID model. Baicalein reduced AGEs and TNF-α level, decreased NF-κB activation and inhibited histopathological changes in both models. Baicalein offsets the hypertensive and the vascular impairment associated with both diabetic models via ameliorating functional and structural derangements of blood vessels.

Interleukin-10 to tumor necrosis factor-alpha ratio is a predictive biomarker in nonalcoholic fatty liver disease: interleukin-10 to tumor necrosis factor-alpha ratio in steatohepatitis.

Objectives Fatty liver disease is commonly associated with diabetes mellitus (DM). Insulin resistance (IR) as an investigative biomarker is only concerned with fatty liver that results from DM type 2 associated with metabolic syndrome. Irrespective of IR, DM is generally characterized by overproduction of the proinflammatory cytokine tumor necrosis factor-alpha (TNF-&agr;), whereas action of the latter is modulated by the anti-inflammatory cytokine interleukin-10 (IL-10). The aim of this study was to investigate the efficacy of using TNF-&agr; alone or IL-10/TNF-&agr; ratio compared to IR, as a promising biomarker for fatty liver assessment in DM. Furthermore, we hypothesized that using garlic as an immunomodulator may decrease TNF-&agr; and increase IL-10 production to improve steatohepatitis. Methods DM was induced metabolically by a high-fat diet to bring about IR, or chemically by alloxan, producing insulin deficiency, in male albino rats. Garlic powder was supplemented (15 mg/kg per day) for 3 weeks. Fatty liver was depicted histologically and biochemically (aspartic aminotransferase, alanine aminotransferase, HOMA-IR, TNF-&agr;, IL-10, IL-10/TNF-&agr; ratio). Results We found that, in contrast to obese rats, garlic decreased IL-10/TNF-&agr; ratio, despite decreasing TNF-&agr; in alloxan diabetic rats in agreement with the histology, which revealed more prominent improvement in the obese group. Moreover, the effect of garlic was not linked to improvement of IR in obese rats. Conclusion We conclude that IL-10/TNF-&agr; ratio may be considered as a convenient biomarker for investigation of fatty liver of different grades, apart from being associated with IR, and immunomodulation of this ratio in favor of increasing it may exert significant improvement.

Hepatoprotective and hypoglycemic effects of a tannin rich extract from Ximenia americana var. caffra root

BACKGROUND Liver diseases and diabetes are serious health disorders associated with oxidative stress and ageing. Some plant polyphenols can lower the risk of these diseases. PURPOSE We investigated the phytochemical profiling of a root extract from Ximenia americana var. caffra using HPLC-PDA-ESI-MS/MS. The antioxidant activities in vitro were investigated. The hepatoprotective activities were studied in rat models with d-galactosamine (d-GaIN)-induced hepatotoxicity and the antidiabetic activities in STZ-diabetic rats were also investigated. MATERIALS AND METHODS HPLC-PDA-ESI-MS/MS was used to identify plant phenolics. The antioxidant activities in vitro were determined using DPPH and FRAP assays. The in vivo hepatoprotective activities were determined for d-GaIN-induced hepatotoxicity in rats. We determined the liver markers alanine aminotransferase (ALT), aspartate aminotransferase (AST) and gamma-glutamyltransferase (GGT), liver peroxidation product malondialdehyde (MDA), glutathione content (GSH), albumin and total bilirubin concentration. The histopathological changes in rat liver were also studied. The antidiabetic activities were also investigated in STZ-diabetic rats and serum glucose, serum insulin hormone, and lipid peroxides were determined. RESULTS The root extract is rich in tannins with 20 compounds including a series of stereoisomers of (epi)catechin, (epi)catechin-(epi)catechin, (epi)catechin-(epi)catechin-(epi)catechin, and their galloyl esters. Promising antioxidant potential was observed in vitro in DPPH assay with EC50 of 6.5 µg extract / 26 µg raw material and in FRAP assay with 19.54 mM FeSO4 compared with ascorbic acid (EC50 of 2.92 µg/ml) and quercetin (FeSO4 24.04 mM/mg), respectively. Significant reduction of serologic enzymatic markers and hepatic oxidative stress markers such as ALT, AST, MDA, GGT, and total bilirubin, as well as elevation of GSH and albumin were observed in rats with d-galactosamine-induced liver damage treated with the extract. These findings agree with a histopathological examination suggesting a hepatoprotective potential for the root extract. The root extract can mediate an antidiabetic effect by reducing elevated blood glucose and serum lipid peroxides levels and by increasing insulin in STZ-diabetic rats by -107, -31.1, +11.3%, respectively. CONCLUSIONS The results of this study suggest that the tannin-rich extract from Ximenia americana var. caffra could be an interesting candidate for the treatment of several health disorders associated with oxidative stress such as hepatocellular injury and diabetes.