Tenofovir alafenamide compared to tenofovir disoproxil fumarate, induces dysglycemia, and dyslipidemia in Wistar rats.

OBJECTIVES: To determine the metabolic effects of tenofovir alafenamide (TAF) compared to tenofovir disoproxil fumarate (TDF) in vivo . DESIGN AND METHODS: Male Wistar rats ( Rattus novergicus , 250-300 g body weight) were divided into three groups ( n  = 8) and orally treated daily with 1.0 ml distilled water (group 1), TAF (0.42 mg/kg) (group 2), or TDF (5.0 mg/kg) (group 3), respectively, for 56 days. Glucose tolerance tests were done before the animals were sacrificed by halothane overdose, and blood was collected by cardiac puncture for the analysis of plasma lipids, electrolytes, and insulin. The kidney and pancreatic tissues were excised and homogenized to measure oxidative stress. Compartmentation of TAF and TDF was determined in NRK-52 and peripheral blood mononuclear cells (PBMCs). RESULTS: There were no significant differences in weight gain among controls, TAF- or TDF-treated rats. TAF-treated rats had significantly increased fasting blood glucose (FBG), fasting plasma insulin (FPI), insulin resistance, impaired glucose tolerance, and dyslipidemia compared to control or TDF-treated rats, respectively. There was increased lipid peroxidation in the pancreas of TAF-treated compared to TDF-treated or control animals, respectively. TDF- treated rats presented with symptoms of Fanconi syndrome compared to TAF-treated or control animals, respectively. Kidney homogenates from TDF-treated animals had significantly reduced antioxidant enzyme activity compared to TAF-treated animals or controls, respectively. Intracellular concentrations of TAF were significantly higher than TDF in both NRK-52E cells and PBMC, respectively. CONCLUSIONS: TAF treatment is weight-neutral and causes dysglycemia, and dyslipidemia but not Fanconi syndrome compared to TDF.

The link between relative stability constant of DNA- and BSA-chromenopyrimidine complexes and cytotoxicity towards human breast cancer cells (MCF-7).

In this study, we synthesized and characterized ten chromenopyrimidine derivatives using analytical and spectroscopic methods. Studies on DNA and albumin binding affinity, as well as cytotoxicity tests on human breast cancer (MCF-7) cells, of the chromenopyrimidines, were conducted. The natural logarithm of the relative stability constant of DNA- and BSA-chromenopyrimidine complexes [ln(KDNA/KBSA)] was used as a criterion for selecting compounds for cytotoxicity studies. We found that ln(KDNA/KBSA) was inversely related to IC50 values of the compounds in MCF-7 cells. The antiproliferative effects of the compounds were found to induce apoptosis in MCF-7 cells, which is a desired mechanism of cell death. Correlations between the DNA and albumin binding affinities of chromenopyrimidines were established. We propose that this relationship approach can, for a given set of compounds, assist in predicting the cytotoxicity of potential drug candidates towards MCF-7 cells based on their experimentally determined CT-DNA and BSA binding affinities.

Potential Role of Polyphenolic Flavonoids as Senotherapeutic Agents in Degenerative Diseases and Geroprotection.

Cellular senescence, a hallmark of ageing, contributes to tissue or organ dysfunction and the pathophysiology of diverse age-related diseases (ARD) by various mechanisms. Targeting it by selective elimination of senescent cells (SCs) or blocking senescence-associated secretory phenotypes (SASP) with natural or synthetic compounds has been suggested to improve lifespan. Dietary phytochemicals possess a broad spectrum of biochemical and pharmacological effects that are beneficial to human health. Flavonoids, which are widely consumed in fruits and vegetables worldwide, are emerging as potential therapeutic agents to mitigate senescence. Naringenin, hesperetin, hesperidin, quercetin, fisetin, kaempferol, rutin, apigenin, luteolin, nobiletin, tangeretin, genistein, wogonin, epigallocatechin gallate (EGCG), theaflavin-3-gallate (TF2A), and procyanidin C1 possess potent antisenescence effects. A single biochemical process may not explain their pleiotropic pharmacological impact. Flavonoids directly modulate underlying cellular senescence processes or interact with molecular targets that regulate ageing-related pathways. This review discusses the potential use of flavonoids to mitigate senescence and consequently delay the onset of ageing-related diseases. We also highlight the underlying mechanisms of action of flavonoids as potential senotherapeutics and reflect on future perspectives and possible strategies to optimize and increase the translatability from bench to bedside in senotherapy.

The role of microRNAs in the pathophysiology, diagnosis, and treatment of diabetic cardiomyopathy.

INTRODUCTION: Diabetic cardiomyopathy (DCM) is an end-point macrovascular complication associated with increased morbidity and mortality in 12% of diabetic patients. MicroRNAs (miRNAs) are small noncoding RNAs that can act as cardioprotective or cardiotoxic agents in DCM. METHODS: We used PubMed as a search engine to collect and analyse data in published articles on the role of miRNAs on the pathophysiology, diagnosis and treatment of DCM. RESULTS: MiRNAs play an essential role in the pathophysiology, diagnosis and treatment of DCM due to their distinct gene expression patterns in diabetic patients compared to healthy individuals. Advances in gene therapy have led to the discovery of potential circulating miRNAs, which can be used as biomarkers for DCM diagnosis and prognosis. Furthermore, targeted miRNA therapies in preclinical and clinical studies, such as using miRNA mimics and anti-miRNAs, have yielded promising results. Application of miRNA mimics and anti-miRNAs via different nanodrug delivery systems alleviate hypertrophy, fibrosis, oxidative stress and apoptosis of cardiomyocytes. CONCLUSION: MiRNAs serve as attractive potential targets for DCM diagnosis, prognosis and treatment due to their distinctive expression profile in DCM development.

Synergism Potentiates Oxidative Antiproliferative Effects of Naringenin and Quercetin in MCF-7 Breast Cancer Cells.

Breast cancer (BC) is the most frequently diagnosed type of cancer as of 2020. Quercetin (Que) and Naringenin (Nar) are predominantly found in citrus fruits and vegetables and have shown promising antiproliferative effects in multiple studies. It is also known that the bioactive effects of these flavonoids are more pronounced in whole fruit than in isolation. This study investigates the potential synergistic effects of Que and Nar (CoQN) in MCF-7 BC cells. MCF-7 cells were treated with a range of concentrations of Que, Nar or CoQN to determine cell viability. The IC50 of CoQN was then used to investigate caspase 3/7 activity, Bcl-2 gene expression, lipid peroxidation and mitochondrial membrane potential to evaluate oxidative stress and apoptosis. CoQN treatment produced significant cytotoxicity, reduced Bcl-2 gene expression and increased caspase 3/7 activity compared to either Nar or Que. Furthermore, CoQN significantly increased lipid peroxidation and reduced mitochondrial membrane potential (MMP) compared to either Nar or Que. Therefore, CoQN treatment has potential pharmacological application in BC chemotherapy by inducing oxidative stress and apoptosis in MCF-7 BC cells. The results of this study support the increased consumption of whole fruits and vegetables to reduce cell proliferation in cancer.

Antidiabetic effects of Psidium x durbanensis Baijnath & Ramcharun ined. (Myrtaceae) leaf extract on streptozotocin-induced diabetes in rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Psidium guajava L. leaves are used to treat diabetes in South African folkloric medicine and in other parts of the world. Psidium x durbanensis Baijnath & Ramcharun ined. (PD) is a natural sterile hybrid and congener of Psidium guajava that is expected to share the medicinal properties of the genus Psidium and is widely distributed in South Africa. AIM OF THE STUDY: This study investigates the antioxidant, antidiabetic effects, and mechanisms of action of hydro-methanolic leaf extracts of PD on streptozotocin-induced diabetes in rats. MATERIAL AND METHODS: Phytochemical constituents of hydro-methanolic extract of PD were analyzed by gas chromatography-mass spectrometry (GC-MS). Male Wistar rats 250-300 g body weight (BW) were rendered diabetic after a single intraperitoneal injection with streptozotocin, 45 mg/kg BW. The diabetic rats were treated with hydro-methanolic (20:80 v/v) leaf extracts of PD (400 mg/kg/BW) or subcutaneous injections of regular insulin (2.0U/kg/BW, bid) for 56 days. The body weights of the animals were recorded daily. Fasting blood glucose, glucose tolerance tests, and insulin resistance index were measured. The effects of the extracts on total superoxide dismutase, catalase, and reduced glutathione activities, histopathology, and gene expression of insulin receptor substrate 1 and glucose transporter 4 were determined in the liver, pancreas, and gastrocnemius muscles of the rats. RESULTS: In the acute toxicity studies, there were no signs of toxicity observed for PD up to 2000 mg/kg BW doses. Diabetic animals showed significant weight loss, elevated and reduced fasting blood glucose and insulin, respectively, impaired glucose tolerance and diminished antioxidant enzymes' activities compared to controls. Treatment with PD hydro-methanolic leaf extracts improved body weight, glucose tolerance, insulin resistance, and antioxidant enzymes but not plasma insulin in diabetic animals compared to controls, respectively. GC-MS analysis identified organic acids, alcohols, vitamins, terpenoids, and esters in the extracts. Treatment with PD improved glucose uptake by stimulating mRNA expression of GLUT 4 in gastrocnemius muscles of diabetic animals compared to the untreated control and also restored histological aberrations in the pancreas and liver of diabetic rats compared with the untreated control rats. CONCLUSION: Collectively, the present study suggests that treatment with PD leaf extracts significantly ameliorated diabetes symptoms and oxidative stress in rats, and these effects may be linked to the bioactive phytoconstituents present in the plant. This study further suggests that PD improves insulin resistance by increasing glucose uptake in gastrocnemius muscles in an insulin-independent manner.

Metformin turns 62 in pharmacotherapy: Emergence of non-glycaemic effects and potential novel therapeutic applications.

Metformin is the most commonly prescribed oral antidiabetic medication. Direct/indirect activation of Adenosine Monophosphate-activated protein kinase (AMPK) and non-AMPK pathways, amongst others, are deemed to explain the molecular mechanisms of action of metformin. Metformin is an established insulin receptor sensitising antihyperglycemic agent, is highly affordable, and has superior safety and efficacy profiles. Emerging experimental and clinical evidence suggests that metformin has pleiotropic non-glycemic effects. Metformin appears to have weight stabilising, renoprotective, neuroprotective, cardio-vascular protective, and antineoplastic effects and mitigates polycystic ovarian syndrome. Anti-inflammatory and antioxidant effects of metformin seem to qualify it as an adjunct therapy in treating infectious diseases such as tuberculosis, viral hepatitis, and the current novel Covid-19 infections. So far, metformin is the only prescription medicine relevant to the emerging field of senotherapeutics. Non-glycemic effects of metformin favourable to its repurposing in therapeutic use are hereby discussed.

By reducing oxidative stress, naringenin mitigates hyperglycaemia-induced upregulation of hepatic nuclear factor erythroid 2-related factor 2 protein.

OBJECTIVES: Antioxidant and anti-inflammatory properties of naringenin could confer hepatoprotective effects. METHODS: Chang cells in culture media were maintained at 37°C and treated with increased concentrations of glucose (5.5-50 mm) and/or naringenin (25-100 µm), respectively, for 24 h. The cells were harvested and carbonyl proteins, antioxidant enzymes and proteins measured in cell lysates. Sprague Dawley rats were divided into 5 groups (n = 7) and orally treated daily for 56 days with 3.0 ml/kg per body weight (BW) distilled water (group 1), 60 mg/kg BW of naringenin (groups 2 and 4), respectively. Groups 3, 4 and 5 were given single 60 mg/kg per BW intraperitoneal injections of streptozotocin or insulin (2.0 IU/kg BW bid), (group 5 only). KEY FINDINGS: Cell viability was significantly decreased in response to increased hyperglycaemia but naringenin dose-dependently, significantly reversed this compared to controls, respectively. However, antioxidant enzyme activities were reduced due to increased and reduced oxidative stress, respectively. Naringenin further significantly reduced hepatic oxidative stress and nuclear factor erythroid 2-related factor 2 (Nrf2) protein expression and liver : body weight ratios in diabetic compared to controls rats. CONCLUSIONS: Naringenin confers hepatoprotective antioxidant effects by initially preventing upregulation of Nrf2 protein expression and its downstream antioxidant enzymes.

Citrus fruit-derived flavonoid naringenin and the expression of hepatic organic cation transporter 1 protein in diabetic rats treated with metformin.

Naringenin possesses many pharmacological effects and may modulate metformin disposition. The purpose of this study was to evaluate the role of naringenin on hepatic expression of organic cation transporter 1 (OCT1) protein and its associated effects on metformin-associated hyperlactataemia in diabetes. Forty-nine male Sprague Dawley rats randomly assigned to seven groups (n = 7) were orally treated daily with 3.0 mL/kg body-weight (BW) of distilled water (group 1) or 60 mg/kg BW of naringenin (groups 2 and 5) or 250 mg/kg BW of metformin (groups 3 and 6), respectively, dissolved in distilled water. Similarly, group 7 was given metformin and naringenin. Groups 4, 5, 6 and 7 were administered intraperitoneally with streptozotocin at a single dose of 60 mg/kg BW to induce diabetes. Glucose tolerance tests were performed. The animals were killed after 8 weeks of treatment, blood was collected, and livers excised for further biochemical analysis. Lowered body-weight, increased polydipsia and reduced hepatic glycogen concentrations were observed in diabetic rats compared to controls. Naringenin only significantly decreased plasma lactate levels, while metformin only or with naringenin significantly increased plasma lactate levels in diabetic compared to non-treated diabetic animals. Metformin only but not naringenin significantly increased plasma lactate levels in non-diabetic compared to control rats. Furthermore, naringenin with or without metformin but not metformin only significantly increased hepatic organic cation transporter 1 (OCT1) expression in diabetic compared to non-treated diabetic rats. Contrastingly, metformin only but not naringenin significantly increased hepatic OCT1 expression in non-diabetic rats compared to controls. Diabetic rats treated with metformin exhibited significantly increased plasma metformin concentrations compared to non-diabetic but naringenin significantly dropped this parameter. Conversely, hepatic metformin concentrations were significantly lower in diabetic rats treated with metformin compared to non-diabetic rats but significantly increased when naringenin was added. These results suggest that naringenin ameliorated hyperglycaemia-induced reduction in hepatic OCT1 expression leading to metformin accumulation and increased lactic acid production.

Mapping the evidence of hepatoprotective properties of Moringa oleifera from sub-Saharan African countries: a systematic review protocol.

BACKGROUND: One of the most challenging health problems is liver disease, which can be caused by medications, toxic substances, and excessive consumption of alcohol. Liver problems can be also caused by infections, autoimmune disorders, and food. This study aims to establish evidence of the use of Moringa oleifera in sub-Saharan African countries to manage liver damage conditions in animals. METHODS: In vivo studies will include those in which the activity of the serum levels of hepatic enzymes alanine transaminase (ALT) or serum glutamate-pyruvate transaminase (SGPT), aspartate transaminase (AST) or serum glutamic oxaloacetic transaminase (SGOT), gamma-glutamyltransferase (GGT), alkaline phosphatase (ALP), superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), and malondialdehyde (MDA) were measured after administering substances that induced liver injury as a primary outcome. The secondary outcome will include studies that measure the serum levels of hepatic enzymes (ALT, AST, GGT and ALP, SOD, CAT, and GR), free radical formation represented by MDA after administering the sub-Saharan Moringa oleifera, and decreases in their levels indicating the improvement of their activity. Search engines will include MEDLINE, CINAHL, PubMed, Google Scholar, SABINET, EBSCO, and WHO/African Index Medicus. The screened results will be grouped according to any noteworthy grouping variable, such as study characteristics. Data will be analyzed using Stata statistical software (Stata Corp V.14, TX, USA). Study data will be quantitatively synthesized by first assessing heterogeneity to examine whether the estimates from included studies could be pooled. Heterogeneity will be assessed by the chi-squared test on Cochran's Q statistic, which will be quantified by I 2 values. DISCUSSION: Results from this protocol will give new insights into the Moringa oleifera plant for developing effective hepatoprotective drugs against liver damage. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42018084698 .

DNA polymerase-γ hypothesis in nucleoside reverse transcriptase-induced mitochondrial toxicity revisited: A potentially protective role for citrus fruit-derived naringenin?

Nucleoside reverse transcriptase inhibitors (NRTIs) form the backbone in combination antiretroviral therapy (cARVs). They halt chain elongation of the viral cDNA by acting as false substrates in counterfeit incorporation mechanism to viral RNA-dependent DNA polymerase. In the process genomic DNA polymerase as well as mitochondrial DNA (mtDNA) polymerase-γ (which has a much higher affinity for these drugs at therapeutic doses) are also impaired. This leads to mitochondrial toxicity that manifests clinically as mitochondrial myopathy, peripheral neuropathy, hyperlactatemia or lactic acidosis and lipoatrophy. This has led to the revision of clinical guidelines by World Health Organization to remove stavudine from first-line listing in the treatment of HIV infections. Recent reports have implicated oxidative stress besides mtDNA polymerase-γ hypothesis in NRTI-induced metabolic complications. Reduced plasma antioxidant concentrations have been reported in HIV positive patients on cARVs but clinical intervention with antioxidant supplements have not been successful either due to low efficacy or poor experimental designs. Citrus fruit-derived naringenin has previously been demonstrated to possess antioxidant and free radical scavenging properties which could prevent mitochondrial toxicity associated with these drugs. This review revisits the controversy surrounding mtDNA polymerase-γ hypothesis and evaluates the potential benefits of naringenin as a potent anti-oxidant and free radical scavenger which as a nutritional supplement or therapeutic adjunct could mitigate the development of mitochondrial toxicity associated with these drugs.

Genetic polymorphisms of organic cation transporters 1 (OCT1) and responses to metformin therapy in individuals with type 2 diabetes mellitus: a systematic review protocol.

BACKGROUND: Metformin is one of the most commonly used drugs for type 2 diabetes mellitus (T2DM). Despite its efficacy and safety, metformin is frequently associated with highly variable glycemic responses, which is hypothesized to be the result of genetic variations in its transport by organic cation transporters (OCTs). This systematic review aims to highlight and summarize the overall effects of OCT1 polymorphisms on therapeutic responses to metformin and to evaluate their potential role in terms of interethnic differences with metformin responses. METHODS/DESIGN: We will systematically review observational studies reporting on the genetic association between OCT1 polymorphisms and metformin responses in T2DM patients. A comprehensive search strategy formulated with the help of a librarian will be used to search MEDLINE via PubMed, Embase, and CINAHL for relevant studies published between January 1990 and July 2017. Two review authors will independently screen titles and abstracts in duplicate, extract data, and assess the risk of bias with discrepancies resolved by discussion or arbitration of a third review author. Mined data will be grouped according to OCT1 polymorphisms, and their effects on therapeutic responses to metformin will be narratively synthesized. If sufficient numbers of homogeneous studies are scored, meta-analyses will be performed to obtain pooled effect estimates. Funnel plots analysis and Egger's test will be used to assess publication bias. This study will be reported according to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines. DISCUSSION: This review will summarize the genetic effects of OCT1 polymorphisms associated with variabilities in glycemic responses to metformin. The findings of this study could help to develop genetic tests that could predict a person's response to metformin treatment and create personalized drugs with greater efficacy and safety. SYSTEMATIC REVIEW REGISTRATION: Registration number: PROSPERO, CRD42017079978.

Genetic polymorphisms of organic cation transporter 1 (OCT1) and responses to metformin therapy in individuals with type 2 diabetes: A systematic review.

BACKGROUND: Metformin is one of the most commonly used drugs for the treatment of type 2 diabetes mellitus (T2DM). Despite its widespread use, there are considerable interindividual variations in metformin response, with about 35% of patients failing to achieve initial glycemic control. These variabilities that reflect phenotypic differences in drug disposition and action may indeed be due to polymorphisms in genes that regulate pharmacokinetics and pharmacodynamics of metformin. Moreover, interethnic differences in drug responses in some cases correspond to substantial differences in the frequencies of the associated pharmacogenomics risk allele. AIM: This study aims to highlight and summarize the overall effects of organic cation transporter 1(OCT1) polymorphisms on therapeutic responses to metformin and to evaluate the potential role of such polymorphisms in interethnic differences in metformin therapy. METHODS: We conducted a systematic review according to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines. We searched for PubMed/MEDLINE, Embase, and CINAHL, relevant studies reporting the effects of OCT1 polymorphisms on metformin therapy in T2DM individuals. Data were extracted on study design, population characteristics, relevant polymorphisms, measure of genetic association, and outcomes. The presence of gastrointestinal side effects, glycated hemoglobin A1 (HbA1c) levels, fasting plasma glucose (FPG), and postprandial plasma glucose (PPG) concentrations after treatment with metformin were chosen as measures of the metformin responses. This systematic review protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO). RESULTS: According to the data extracted, a total of 34 OCT1 polymorphisms were identified in 10 ethnic groups. Significant differences in the frequencies of common alleles were observed among these groups. Met408Val (rs628031) variant was the most extensively explored with metformin responses. Although some genotypes and alleles have been associated with deleterious effects on metformin response, others indeed, exhibited positive effects. CONCLUSION: Genetic effects of OCT1 polymorphisms on metformin responses were population specific. Further investigations in other populations are required to set ethnicity-specific reference for metformin responses and to obtain a solid basis to design personalized therapeutic approaches for T2DM treatment.

Cardioprotective Effects of Metformin.

Metformin, routinely used as first-line drug in the treatment of type 2 diabetes, has been shown to have cardioprotective effects beyond its glycemic control. These have been attributed to increases in Akt concentrations and activation of protein kinases in the RISK pathways, which prevent the mPTP from opening and rupturing it and therefore, protects myocyte viability. In myocardial infarction and subsequent reperfusion, metformin activation of AMPK promotes glycolysis and keeps the mPTP closed. Given as a preconditioning and/or postconditioning agent, metformin has been shown to decrease infarct size and improve survival rates after myocardial infarction. Metformin has further been reported to restore depleted PGC-1α levels and improve mitochondrial biogenesis by increasing phosphorylation of eNOSser1177, which produces NO and leads to reduced vascular inflammation and myocardial injury after ischemia. There is strong evidence suggesting that metformin improves cardiovascular outcomes by influencing metabolic signal transduction pathways. There are growing calls for metformin use to be expanded off-label beyond the traditional glycemic control. We review experimental evidence for metformin's impact on cardiovascular disease and its underlying molecular mechanisms of action and also discuss why significant gains made in experimental conditions have not translated into significant therapeutic applications.

Naringin prevents HIV-1 protease inhibitors-induced metabolic complications in vivo.

BACKGROUND: Insulin resistance, glucose intolerance and overt diabetes are known metabolic complications associated with chronic use of HIV-Protease Inhibitors. Naringin is a grapefruit-derived flavonoid with anti-diabetic, anti-dyslipidemia, anti-inflammatory and anti-oxidant activities. OBJECTIVES: The study investigated the protective effects of naringin on glucose intolerance and impaired insulin secretion and signaling in vivo. METHODS: Male Wistar rats were divided into six groups (n = 6) and were daily orally treated with distilled water {3.0 ml/kg body weight (BW)}, atazanavir (133 mg/kg BW), saquinavir (333 mg/kg BW) with or without naringin (50 mg/kg BW), respectively for 56 days. Body weights and water consumption were recorded daily. Glucose tolerance tests were carried out on day 55 of the treatment and thereafter, the rats were sacrificed by halothane overdose. RESULTS: Atazanavir (ATV)- or saquinavir (SQV)-treated rats exhibited significant weight loss, polydipsia, elevated Fasting blood glucose (FBG), reduced Fasting Plasma Insulin (FPI) and expression of phosphorylated, Insulin Receptor Substrate-1 (IRS-1) and Akt proteins, hepatic and pancreatic glucokinase levels, and also increasing pancreatic caspase-3 and -9 as well as UCP2 protein expressions compared to controls, respectively. These effects were completely reversed by naringin treatment. CONCLUSION: Naringin prevents PI-induced glucose intolerance and impairment of insulin signaling and as nutritional supplement it could therefore alleviate metabolic complications associated with antiretroviral therapy.

Metformin-like antidiabetic, cardio-protective and non-glycemic effects of naringenin: Molecular and pharmacological insights.

Metformin is a widely used drug for the treatment of type 2 diabetes (T2D). Its blood glucose-lowering effects are initially due to inhibition of hepatic glucose production and increased peripheral glucose utilization. Metformin has also been shown to have several beneficial effects on cardiovascular risk factors and it is the only oral antihyperglycaemic agent thus far associated with decreased macrovascular complications in patients with diabetes. Adenosine Monophosphate Activated-Protein Kinase (AMPK) is a major cellular regulator of lipid and glucose metabolism. Recent evidence shows that pharmacological activation of AMPK improves blood glucose homeostasis, lipid profiles, blood pressure and insulin-resistance making it a novel therapeutic target in the treatment of T2D. Naringenin a flavonoid found in high concentrations as its glycone naringin in citrus fruits, has been reported to have antioxidant, antiatherogenic, anti- dyslipidemic and anti-diabetic effects. It has been shown that naringenin exerts its anti-diabetic effects by inhibition of gluconeogenesis through upregulations of AMPK hence metformin-like effects. Naringin has further been shown to have non-glycemic affects like metformin that mitigate inflammation and cell proliferation. This review evaluates the potential of naringenin as anti-diabetic, anti-dyslipidemic anti-inflammatory and antineoplastic agent similar to metformin and proposes its further development for therapeutic use in clinical practice.

Naringin protects against HIV-1 protease inhibitors-induced pancreatic ß-cell dysfunction and apoptosis.

INTRODUCTION: The protective effects of grapefruit-derived naringin against HIV-1 Protease Inhibitors (PIs)-associated oxidative damage to pancreatic ß-cells and apoptosis were investigated in RIN-5F cells in culture. METHODS: Cells in culture medium were challenged with 11-25 mM glucose with or without nelfinavir (1-10 µM), saquinavir (1-10 µM) and atazanavir (5-20 µM), respectively for 24 h to determine insulin secretion. The cells were further treated with nelfinavir (10 µM), saquinavir (10 µM), atazanavir (20 µM) with and without naringin or glibenclamide (10 µM) for 24 h to determine insulin secretion, lipid peroxidation, Superoxide Dismutase (SOD) activity, glutathione (GSH) levels, ATP production and caspase-3 and-9 activities, respectively. RESULTS: Glucose-dependent insulin secretion was significantly reduced by PIs in a concentration-dependent manner. Treatment with either naringin or glibenclamide significantly reduced lipid peroxidation, Superoxide Dismutase (SOD) activities and also increased glutathione (GSH) and ATP levels in the cells that were treated with PIs. Furthermore, naringin or glibenclamide significantly reduced caspase-3 and caspase-9 activities in cells that were treated with PIs. CONCLUSIONS: PIs impair ß-cell functions by increasing oxidative stress and apoptosis. Treatment with naringin protected RIN-5F cells from PI-induced oxidative damage and apoptosis. Our results therefore suggest that nutritional supplements with naringin could prevent pancreatic ß-cell dysfunction and the attendant metabolic complications caused by PIs in patients on antiretroviral therapy.

Grapefruit Derived Flavonoid Naringin Improves Ketoacidosis and Lipid Peroxidation in Type 1 Diabetes Rat Model.

BACKGROUND: Hypoglycemic effects of grapefruit juice are well known but the effects of naringin, its main flavonoid on glucose intolerance and metabolic complications in type 1 diabetes are not known. OBJECTIVES: To investigate the effects of naringin on glucose intolerance, oxidative stress and ketonemia in type 1 diabetic rats. METHODS: Sprague-Dawley rats divided into 5 groups (n = 7) were orally treated daily with 3.0 ml/kg body weight (BW)/day of distilled water (group 1) or 50 mg/kg BW of naringin (groups 2 and 4, respectively). Groups 3, 4 and 5 were given a single intra-peritoneal injection of 60 mg/kg BW of streptozotocin to induce diabetes. Group 3 was further treated with subcutaneous insulin (4.0 IU/kg BW) twice daily, respectively. RESULTS: Stretozotocin (STZ) only-treated groups exhibited hyperglycemia, polydipsia, polyuria, weight loss, glucose intolerance, low fasting plasma insulin and reduced hepatic glycogen content compared to the control group. Furthermore they had significantly elevated Malondialdehyde (MDA), acetoacetate, ß-hydroxybutyrate, anion gap and significantly reduced blood pH and plasma bicarbonate compared to the control group. Naringin treatment significantly improved Fasting Plasma Insulin (FPI), hepatic glycogen content, malondialdehyde, ß-hydroxybutyrate, acetoacetate, bicarbonate, blood pH and anion gap but not Fasting Blood Glucose (FBG) compared to the STZ only-treated group. CONCLUSIONS: Naringin is not hypoglycemic but ameliorates ketoacidosis and oxidative stress. Naringin supplements could therefore mitigate complications of diabetic ketoacidosis.

Naringin Reduces Hyperglycemia-Induced Cardiac Fibrosis by Relieving Oxidative Stress.

INTRODUCTION: Hyperglycemia promotes myocardial fibrotic lesions through upregulation of PKC and p38 in response to redox changes. The effects of naringin on hyperglycemia-induced myocardial fibrotic changes and its putative effects on PKC-ß and p38 protein expression in type 1 rat model of diabetes are hereby investigated. METHODS: Male Sprague-Dawley rats were divided into six groups I-VI. Groups I and II, were orally treated with distilled water {3.0 ml/kg body weight (BW)} and naringin (50 mg/kg BW), respectively. Groups III, IV, V and VI were rendered diabetic by a single intraperitoneal injection of streptozotocin (60 mg/kg, BW) and were similarly treated with subcutaneous insulin (8.0 I.U/kg BW, twice daily), naringin (50 mg/kg BW), distilled water (3.0 ml/Kg BW) and ramipril (3.0 mg/kg/BW), respectively. The animals were sacrificed after 56 days by halothane overdose; blood and heart samples removed for further analysis. RESULTS: The untreated diabetic rats exhibited significantly increased oxidative stress, NADPH oxidase activity, increased cardiac fibrosis, PKC-ß and p38 mitogen activated protein kinase expression compared to controls. Naringin treatment significantly ameliorated these changes in diabetic rats compared to the untreated diabetic controls. CONCLUSIONS: Naringin's amelioration of myocardial fibrosis by modulating p38 and PKC-ß protein expression possibly through its known antioxidant actions and may therefore be useful in retarding the progression of fibrosis in a diabetic heart.