Potential utility of natural polyphenols for reversing fat-induced insulin resistance

Administration of silymarin in NAFLD/NASH: A systematic review and meta-analysis

INTRODUCTION AND OBJECTIVES

Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disease with a high prevalence worldwide and poses serious harm to human health. There is growing evidence suggesting that the administration of specific supplements or nutrients may slow NAFLD progression. Silymarin is a hepatoprotective extract of milk thistle, but its efficacy in NAFLD remains unclear.

MATERIALS AND METHODS

Relevant studies were searched in PubMed, Embase, the Cochrane Library, Web of Science, clinicaltrails.gov, and China National Knowledge Infrastructure and were screened according to the eligibility criteria. Data were analyzed using Revman 5.3. Continuous values and dichotomous values were pooled using the standard mean difference (SMD) and odds ratio (OR). Heterogeneity was evaluated using the Cochran's Q test (I2 statistic). A P<0.05 was considered statistically significant.

RESULTS

A total of 26 randomized controlled trials involving 2,375 patients were included in this study. Administration of silymarin significantly reduced the levels of TC (SMD[95%CI]=-0.85[-1.23, -0.47]), TG (SMD[95%CI]=-0.62[-1.14, -0.10]), LDL-C (SMD[95%CI]=-0.81[-1.31, -0.31]), FI (SMD[95%CI]=-0.59[-0.91, -0.28]) and HOMA-IR (SMD[95%CI]=-0.37[-0.77, 0.04]), and increased the level of HDL-C (SMD[95%CI]=0.46[0.03, 0.89]). In addition, silymarin attenuated liver injury as indicated by the decreased levels of ALT (SMD[95%CI]=-12.39[-19.69, -5.08]) and AST (SMD[95% CI]=-10.97[-15.51, -6.43]). The levels of fatty liver index (SMD[95%CI]=-6.64[-10.59, -2.69]) and fatty liver score (SMD[95%CI]=-0.51[-0.69, -0.33]) were also decreased. Liver histology of the intervention group revealed significantly improved hepatic steatosis (OR[95%CI]=3.25[1.80, 5.87]).

CONCLUSIONS

Silymarin can regulate energy metabolism, attenuate liver damage, and improve liver histology in NAFLD patients. However, the effects of silymarin will need to be confirmed by further research.

Polyphenols in Metabolic Diseases

Polyphenols (PPs) are a large group of phytochemicals containing phenolic rings with two or more hydroxyl groups. They possess powerful antioxidant properties, multiple therapeutic effects, and possible health benefits in vivo and in vitro, as well as reported clinical studies. Considering their free-radical scavenging and anti-inflammatory properties, these substances can be used to treat different kinds of conditions associated with metabolic disorders. Many symptoms of metabolic syndrome (MtS), including obesity, dyslipidemia, atherosclerosis, elevated blood sugar, accelerating aging, liver intoxication, hypertension, as well as cancer and neurodegenerative disorders, are substantially relieved by dietary PPs. The present study explores the bioprotective properties and associated underlying mechanisms of PPs. A detailed understanding of these natural compounds will open up new opportunities for producing unique natural PP-rich dietary and medicinal plans, ultimately affirming their health benefits.

Phytobioactive compound-based nanodelivery systems for the treatment of type 2 diabetes mellitus - current status

Type 2 diabetes mellitus (T2DM) is a major chronic disease that is prevalent worldwide, and it is characterized by an increase in blood glucose, disturbances in the metabolism, and alteration in insulin secretion. Nowadays, food-based therapy has become an important treatment mode for type 2 diabetes, and phytobioactive compounds have gained an increasing amount of attention to this end because they have an effect on multiple biological functions, including the sustained secretion of insulin and regeneration of pancreatic islets cells. However, the poor solubility and lower permeability of these phyto products results in a loss of bioactivity during processing and oral delivery, leading to a significant reduction in the bioavailability of phytobioactive compounds to treat T2DM. Recently, nanotechnological systems have been developed for use as various types of carrier systems to improve the delivery of bioactive compounds and thus obtain a greater bioavailability. Furthermore, carrier systems in most nanodelivery systems are highly biocompatible, with nonimmunologic behavior, a high degree of biodegradability, and greater mucoadhesive strength. Therefore, this review focuses on the various types of nanodelivery systems that can be used for phytobioactive compounds in treating T2DM with greater antidiabetic effects. There is also additional focus on improving the effects of various phytobioactive compounds through nanotechnological delivery to ensure a highly efficient treatment of type 2 diabetes.

Effects of Mediterranean diet supplemented with silybin-vitamin E-phospholipid complex in overweight patients with non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease is the most common liver disease worldwide.

AIM

The aim of this study is to compare the metabolic effects of the Mediterranean diet versus the diet associated with silybin, phosphatidylcholine and vitamin E complex in overweight patients with non-alcoholic fatty liver disease.

METHODS

Thirty Caucasian overweight patients were randomized into three groups of 10 (Groups A, B and C). A personalized Mediterranean diet was started in Group A and B patients. In association with the diet, Group B patients were given Realsil complex, daily, for 6 months. Group C patients refused any treatment.

RESULTS

We showed that the Mediterranean diet alone, or in association with the Realsil complex, led to the significant variation in BMI, waist circumference, total cholesterol and triglycerides. We also observed a statistically significant decrease in homeostasis model assessment technique in Group B patients.

Silibinin potentially attenuates arsenic-induced oxidative stress mediated cardiotoxicity and dyslipidemia in rats

Cardiac dysfunction is one of the major causes of mortality and morbidity throughout the world. Chronic exposure of arsenic (As) mainly leads to cardiotoxic effect. Cardiotoxicity was induced by the sodium arsenite as the source of As (5 mg/kg BW, PO) for 4 weeks. As intoxication significantly (p < 0.05) increased the serum cardiac markers, viz. creatine kinase-MB, lactate dehydrogenase, aspartate transaminase, alanine transaminase and alkaline phosphatase, oxidative stress markers in heart, plasma total cholesterol (TC), triglycerides (TG), phospholipids (PL), free fatty acids (FFA), low density lipoprotein cholesterol, very low density lipoprotein cholesterol as well as cardiac lipid profile (TC, TG and FFA) and significantly (p < 0.05) decreased the level of serum high density lipoprotein cholesterol, cardiac PL, mitochondrial enzymes such as ICDH, SDH, MDH, α-KDH and NADH dehydrogenase, levels of enzymatic antioxidant, nonenzymatic antioxidants and membrane-bound ATPases in heart. In addition, As-intoxicated rats showed a significant (p < 0.05) up-regulation of myocardial NADPH (NOX) oxidase sub units such as NOX2 and NOX4 as well as Keap-1 and down-regulation of Nrf2 and HO-1 protein expressions. Pre-administration of silibinin (SB) (75 mg/kg BW) remarkably recovered all these altered parameters to near normalcy in As-induced cardiotoxic rat. Moreover, the light microscopic and transmission electron microscopic study further supports the protective efficacy of SB on the heart mitochondria. In conclusion, our data demonstrate that SB has a potential to extenuate the arsenic-induced cardiotoxicity and dyslipidemia in rat.

The therapeutic potential of milk thistle in diabetes

Milk thistle has been known for more than 2.000 years as a herbal remedy for a variety of disorders. It has mainly been used to treat liver and gallbladder diseases. Silibum marianum, the Latin term for the plant, and its seeds contain a whole family of natural compounds, called flavonolignans. Silimarin is a dry mixture of these compounds; it is extracted after processing with ethanol, methanol, and acetone. Silimarin contains mainly silibin A, silibin B, taxifolin, isosilibin A, isosilibin B, silichristin A, silidianin, and other compounds in smaller concentrations. Apart from its use in liver and gallbladder disorders, milk thistle has recently gained attention due to its hypoglycemic and hypolipidemic properties. Recently, a substance from milk thistle has been shown to possess peroxisome proliferator-activated receptor γ (PPARγ) agonist properties. PPARγ is the molecular target of thiazolidinediones, which are used clinically as insulin sensitizers to lower blood glucose levels in diabetes type 2 patients. The thiazolidinedione type of PPARγ ligands is an agonist with a very high binding affinity. However, this ligand type demonstrates a range of undesirable side effects, thus necessitating the search for new effective PPARγ agonists. Interestingly, studies indicate that partial agonism of PPARγ induces promising activity patterns by retaining the positive effects attributed to the full agonists, with reduced side effects. In this review, the therapeutic potential of milk thistle in the management of diabetes and its complications are discussed.

Silibinin inhibits the toxic aggregation of human islet amyloid polypeptide

In type 2 diabetes mellitus (T2DM), misfolded human islet amyloid polypeptide (hIAPP) forms amyloid deposits in pancreatic islets. These amyloid deposits contribute to the dysfunction of β-cells and the loss of β-cell mass in T2DM patients. Inhibition of hIAPP fibrillization has been regarded as a potential therapeutic approach for T2DM. Silibinin, a major active flavonoid extracted from herb milk thistle (Silybum marianum), has been used for centuries to treat diabetes in Asia and Europe with unclear mechanisms. In this study, we tested whether silibinin has any effect on the amyloidogenicity of hIAPP. Our results provide first evidence that silibinin inhibits hIAPP fibrillization via suppressing the toxic oligomerization of hIAPP and enhances the viability of pancreatic β-cells, therefore silibinin may serve as a potential therapeutic agent for T2DM.

Blood pressure is reduced and insulin sensitivity increased in glucose-intolerant, hypertensive subjects after 15 days of consuming high-polyphenol dark chocolate

Flavanols from chocolate appear to increase nitric oxide bioavailability, protect vascular endothelium, and decrease cardiovascular disease (CVD) risk factors. We sought to test the effect of flavanol-rich dark chocolate (FRDC) on endothelial function, insulin sensitivity, beta-cell function, and blood pressure (BP) in hypertensive patients with impaired glucose tolerance (IGT). After a run-in phase, 19 hypertensives with IGT (11 males, 8 females; 44.8 +/- 8.0 y) were randomized to receive isocalorically either FRDC or flavanol-free white chocolate (FFWC) at 100 g/d for 15 d. After a wash-out period, patients were switched to the other treatment. Clinical and 24-h ambulatory BP was determined by sphygmometry and oscillometry, respectively, flow-mediated dilation (FMD), oral glucose tolerance test, serum cholesterol and C-reactive protein, and plasma homocysteine were evaluated after each treatment phase. FRDC but not FFWC ingestion decreased insulin resistance (homeostasis model assessment of insulin resistance; P < 0.0001) and increased insulin sensitivity (quantitative insulin sensitivity check index, insulin sensitivity index (ISI), ISI(0); P < 0.05) and beta-cell function (corrected insulin response CIR(120); P = 0.035). Systolic (S) and diastolic (D) BP decreased (P < 0.0001) after FRDC (SBP, -3.82 +/- 2.40 mm Hg; DBP, -3.92 +/- 1.98 mm Hg; 24-h SBP, -4.52 +/- 3.94 mm Hg; 24-h DBP, -4.17 +/- 3.29 mm Hg) but not after FFWC. Further, FRDC increased FMD (P < 0.0001) and decreased total cholesterol (-6.5%; P < 0.0001), and LDL cholesterol (-7.5%; P < 0.0001). Changes in insulin sensitivity (Delta ISI - Delta FMD: r = 0.510, P = 0.001; Delta QUICKI - Delta FMD: r = 0.502, P = 0.001) and beta-cell function (Delta CIR(120) - Delta FMD: r = 0.400, P = 0.012) were directly correlated with increases in FMD and inversely correlated with decreases in BP (Delta ISI - Delta 24-h SBP: r = -0.368, P = 0.022; Delta ISI - Delta 24-h DBP r = -0.384, P = 0.017). Thus, FRDC ameliorated insulin sensitivity and beta-cell function, decreased BP, and increased FMD in IGT hypertensive patients. These findings suggest flavanol-rich, low-energy cocoa food products may have a positive impact on CVD risk factors.

Emerging drugs for non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is a condition of emerging relevance that includes different forms of chronic liver damage, from a simple fatty infiltration (steatosis) of hepatocytes to steatohepatitis (NASH) with fibrosis. This last form may evolve to cirrhosis and hepatocellular carcinoma.

OBJECTIVE

To discuss therapeutic management of NAFLD. Theoretically, only patients with non-alcoholic steatohepatitis (NASH) need to be treated, as only NASH may evolve to cirrhosis. Differentiation between steatosis and NASH currently requires a liver biopsy.

METHODS

We discuss different therapeutic approaches proposed in literature for patients with NAFLD.

RESULTS

The treatment of associated conditions leads to an improvement of NAFLD and NASH. No specific drug is actually present to treat liver steatosis or NASH.

CONCLUSIONS

The treatment of NAFLD depends on the individual characteristics of each patient. Diet and physical exercise may be considered a basal universal approach. Future research will discover possible specific liver drugs.

Interrelation between the inhibition of glycolytic flux by silibinin and the lowering of mitochondrial ROS production in perifused rat hepatocytes

Silibinin, the most biologically active component of the polyphenolic extract from milk thistle seeds, is widely used to prevent many types of hepatobiliary disorders. Recent evidence suggests new applications for this ancient medication, notably for the treatment of type 2 diabetes owing to its antihyperglycemic properties. As we have lately demonstrated that silibinin lowered glucose production from various gluconeogenic substrates in perifused rat hepatocytes, the aim of this study was to examine the effect of silibinin on both oxidative glucose utilization and reactive oxygen species (ROS) generation since the release of ROS secondary to an increased mitochondrial metabolism may contribute to diabetic damage. We found that silibinin dose-dependently reduced glycolysis from carbohydrates in a cell perifusion system via an inhibitory effect targeted on pyruvate kinase activity. Furthermore, a dramatic effect upon oxidative phosphorylation was shown, as evidenced by a fall in ATP-to-ADP ratio, together with an increase in lactate-to-pyruvate ratio. The most attractive finding was that silibinin, at a concentration as low as 10 microM, fully mitigated the rise in metabolic flow-driven ROS formation. In addition, studies on isolated liver mitochondria revealed that this low dose of silibinin depressed ROS production linked to the electron transfer chain activity. From these results, one may tentatively suggest that interesting activities for silibinin, beyond its general antioxidant status, could be expected from its potential clinical use, especially in pathological conditions when mitochondrial ROS formation is severely enhanced.

Advanced glycation and lipoxidation end products--amplifiers of inflammation: the role of food

BACKGROUND

High levels of glycated and lipoxidated proteins and peptides in the body are repeatedly associated with chronic diseases. These molecules are strongly associated with activation of a specific receptor called RAGE and a long-lasting exaggerated level of inflammation in the body.

METHODS

PubMed reports over 5000 papers plus >13,500 articles about the related HbA(1c), most of them published in the past 5 years. Most of the available abstracts have been read and approximately 800 full papers have been studied.

RESULTS

RAGE, a member of the immunoglobulin superfamily of cell surface molecules and receptor for advanced glycation end products, known since 1992, functions as a master switch, induces sustained activation of nuclear factor kappaB (NFkappaB), suppresses a series of endogenous autoregulatory functions, and converts long-lasting proinflammatory signals into sustained cellular dysfunction and disease. Its activation is associated with high levels of dysfunctioning proteins in body fluids and tissues, and is strongly associated with a series of diseases from allergy and Alzheimers to rheumatoid arthritis and urogenital disorders. Heat treatment, irradiation, and ionization of foods increase the content of dysfunctioning molecules.

CONCLUSIONS

More than half of the studies are performed in diabetes and chronic renal diseases; there are few studies in other diseases. Most of our knowledge is based on animal studies and in vitro studies. These effects are worth further exploration both experimentally and clinically. An avoidance of foods rich in deranged proteins and peptides, and the consumption of antioxidants, especially polyphenols, seem to counteract such a development.

The effect of a silybin-vitamin e-phospholipid complex on nonalcoholic fatty liver disease: a pilot study

Oxidative stress leads to chronic liver damage. Silybin has been conjugated with vitamin E and phospholipids to improve its antioxidant activity. Eighty-five patients were divided into 2 groups: those affected by nonalcoholic fatty liver disease (group A) and those with HCV-related chronic hepatitis associated with nonalcoholic fatty liver disease (group B), nonresponders to treatment. The treatment consisted of silybin/vitamin E/phospholipids. After treatment, group A showed a significant reduction in ultrasonographic scores for liver steatosis. Liver enzyme levels, hyperinsulinemia, and indexes of liver fibrosis showed an improvement in treated individuals. A significant correlation among indexes of fibrosis, body mass index, insulinemia, plasma levels of transforming growth factor-beta, tumor necrosis factor-alpha, degree of steatosis, and gamma-glutamyl transpeptidase was observed. Our data suggest that silybin conjugated with vitamin E and phospholipids could be used as a complementary approach to the treatment of patients with chronic liver damage.

Review of clinical trials evaluating safety and efficacy of milk thistle (Silybum marianum [L.] Gaertn.)

Milk thistle extracts have been used as traditional herbal remedies for almost 2000 years. The extracts are still widely used to protect the liver against toxins and to control chronic liver diseases. Recent experimental and clinical studies suggest that milk thistle extracts also have anticancer, antidiabetic, and cardioprotective effects. This article reviews clinical trials of milk thistle conducted in the past 5 years including pharmacokinetic and toxicity studies, herb-drug interactions, and other safety issues. Several trials have studied the effects of milk thistle for patients with liver diseases, cancer, hepatitis C, HIV, diabetes, and hypercholesterolemia. Promising results have been reported in the protective effect of milk thistle in certain types of cancer, and ongoing trials will provide more evidence about this effect. In addition, new established doses and improvement on the quality and standardization of this herb will provide the much-awaited evidence about the efficacy of milk thistle in the treatment of liver diseases. Milk thistle extracts are known to be safe and well tolerated, and toxic or adverse effects observed in the reviewed clinical trials seem to be minimal. The future of milk thistle research is promising, and high-quality randomized clinical trials on milk thistle versus placebo may be needed to further demonstrate the safety and efficacy of this herb.

The Interleukin-6 inflammation pathway from cholesterol to aging--role of statins, bisphosphonates and plant polyphenols in aging and age-related diseases

We describe the inflammation pathway from Cholesterol to Aging. Interleukin 6 mediated inflammation is implicated in age-related disorders including Atherosclerosis, Peripheral Vascular Disease, Coronary Artery Disease, Osteoporosis, Type 2 Diabetes, Dementia and Alzheimer's disease and some forms of Arthritis and Cancer. Statins and Bisphosphonates inhibit Interleukin 6 mediated inflammation indirectly through regulation of endogenous cholesterol synthesis and isoprenoid depletion. Polyphenolic compounds found in plants, fruits and vegetables inhibit Interleukin 6 mediated inflammation by direct inhibition of the signal transduction pathway. Therapeutic targets for the control of all the above diseases should include inhibition of Interleukin-6 mediated inflammation.

Resveratrol inhibits firefly luciferase

The potential therapeutic value of resveratrol in age-related disease settings including cancer, diabetes, and Alzheimer's has emerged from a rapidly growing body of experimental evidence. Protection from oxidative stress appears to be a common feature of resveratrol that may be mediated through SirT1, though more specific molecular mechanisms by which resveratrol mediates its effects remain unclear. This has prompted an upsurge in cell-based mechanistic studies, often incorporating reporter assays for pathway elucidation in response to resveratrol treatment. Here, we report that resveratrol potently inhibits firefly luciferase with a K(i) value of 2microM, and caution that this confounding element may lead to compromised data interpretation.