The research and development on the antioxidants in prevention of diabetic complications

Mohammad Rahimi-Madiseh， Afsaneh Malekpour-Tehrani， Mahmoud Bahmani， Mahmud Rafieian-kopaei?

1Medical Plants Research Center， Shahrekord University of Medical Sciences， Shahrekord， Iran

2Department of Social Medicine， Shahrekord University of Medical Sciences， Shahrekord， Iran

3Faculty of Medicine and Clinical Microbiology Research Center， Ilam

The research and development on the antioxidants in prevention of diabetic complications

Mohammad Rahimi-Madiseh1， Afsaneh Malekpour-Tehrani2， Mahmoud Bahmani3， Mahmud Rafieian-kopaei1?

1Medical Plants Research Center， Shahrekord University of Medical Sciences， Shahrekord， Iran

2Department of Social Medicine， Shahrekord University of Medical Sciences， Shahrekord， Iran

3Faculty of Medicine and Clinical Microbiology Research Center， Ilam

ARTICLE INFO

Article history:

Received 15 May 2016

Received in revised form 16 June 2016

Accepted 1 July 2016

Available online 20 September 2016

Diabetic nephropathy

Natural antioxidants

Diabetes complications

Nephropathy

Neuropathy

Retinopathy

Diabetes mellitus can damage the eyes， kidneys， nerves and heart. Microvascular and macrovascular disorders are the leading causes of morbidity and mortality in diabetic patients. Hyperglycemia can increase the indicators of lipid peroxidation and oxidative stress in which free radicals have the main role in the pathogenesis of these complications. Therefore，antioxidants which combat oxidative stress should be able to prevent and repair free radicals induced damages. Although free radicals contribute to kidney damage， atherosclerosis，diabetes， heart disease， nephrotoxicity and hepatotoxicity； however， clinical trials do not uniquely confirm a substantial impact on diabetic damage. It seems that antioxidants in vegetables， fruits and grains help preventing diabetes complications； however， there is little evidence that taking single antioxidants such as vitamin E or vitamin C protect these complications. The fi ndings about combination antioxidants are also complicated and not entirely clear. In this review paper we tried to present the role of oxidative stress on microvascular complications of type2 diabetes mellitus. Other objective of this paper is to review the new fi ndings about the role of various antioxidants on prevention and treatment of diabetes mellitus as well as its complications including retinopathy， nephropathy and neuropathy.

1. Introduction

The prevalence of diabetes among adults has been increased signif i cantly worldwide. It has been predicted that the number of adults with diabetes will increase from 135 million in 1995 to 30 million in 2025. The age range of diabetic patients in developing and developed countries is between 45-64 and 63- 65 years， respectively. Diabetes is the fourth leading cause of death globally and every 1 minute 6 persons die from the complications of diabetes ［1］.

Diabetic causes arterial diseases in conjunction with neuropathywhich accounts for more than 60% of all non-traumatic amputations in the United States. Diabetes mellitus and impaired glucose tolerance increase cardiovascular disease risk up to 8-fold ［2］. Furthermore， new blood vessel growth is impaired in response to ischemia in diabetic patients， resulting in decreased collateral vessel formation in ischemic hearts and in non-healing foot ulcers ［3］.

A high-fat diet has also been shown to release free radicals and contribute to impairment of β-cell function and also damage to mitochondrial DNA. Interesting studies have shown that hyperglycemia even in non-diabetic rats can increase muscle protein carbonyl content and increase the levels of malondialdehyde and 4-hydroxynonenal， indicators of lipid peroxidation and oxidative stress. These biomarkers of insulin resistance and oxidative stress suggest that free radicals have signif i cant role in the pathogenesis of insulin resistance and impaired insulin signaling ［4］. Therefore，antioxidants which combat oxidative stress should be able to prevent and repair free radical induced damages.

Free radicals are mainly reactive oxygen species （ROS） consisting of superoxide free radicals， hydrogen peroxide， singlet oxygen， nitric oxide （NO） and proxy nitrite. While on the one hand hyperglycemia increases free radical production， on the other hand it impairs the endogenous antioxidant defense system ［5，6］. Antioxidant defense mechanisms include both enzymatic and nonenzymatic strategies. Common antioxidants include vitamins A， C and E， glutathione， and the enzymes superoxide dismutase， catalase， glutathione reductase and also α-lipoic acid， coenzyme Q10， several bioflavonoids，cofactors （folic acid， vitamins B1， B2， B6， B12）， and antioxidant minerals （copper， zinc， selenium， and manganese） ［7］. Medicinal plants are the most important source of antioxidants which seem to act on various diseases better than the above mentioned ones［8-10］. So， the aim of this study was to present the ef f ect of oxidative stress on micro-vascular complications of type2 diabetes. Better knowledge in this field can facilitate designing interventional studies for preventing or averting micro-vascular complications in diabetic patients. Other objective of this paper is to review the available data about the impacts of these two kinds of antioxidants on vascular complications of diabetes mellitus including retinopathy，nephropathy and neuropathy.

2. The mechanisms of diabetes induced tissue damage

Hyperglycemia， and in diabetic microvasculature， intracellular hyperglycemia， have been shown to cause tissue damage through 5 major mechanisms:

（1） Increase in expression of the receptor for advanced glycation end products （AGEs） and its activating ligands；

（2） Increase in intracellular formation AGEs；

（3） Increase in fl ux of glucose and other sugars through the polyol pathway；

（4） Activation of protein kinase C isoforms；

（5） Overactivity of the hexosamine pathway.

All five mechanisms have been shown to be activated by mitochondrial overproduction of reactive oxygen species （ROS）. In contrast， diabetic macrovascular and heart damage， are resulted from increased oxidation of fatty acids， resulting from pathway-specif i c insulin resistance ［11］.

Many cellular pathways that cause insulin resistance and diabetic complications have linked to the production of free radicals and oxidative stress. Early effects of elevated glucose may increase the presence of potentially protective pathways but prolonged exposure of elevated glucose can cause formation of ROS and can be detrimental even after glucose control. Excessive levels of free radicals cause damage to cell lipid membranes， cell proteins and nucleic acids， which finally may cause cell death ［12，13］. Besides，elevation of ceruloplasmin during hyperglycemia is suggestive of elevated ROS. Oxidative stress can trigger the onset of diabetes mellitus by decreasing insulin sensitivity and damaging the β-cells of pancreas ROS can penetrate through β-cell membranes and destroy those cells ［12］.

Hyperglycemia can cause increased production of ROS in dif f erent cell types. For example with increase in age in type 2 DM in rat models， elevated levels of 8-hydroxy deoxy guanosine （8-OHdG）and hydroxynonenal （HNE）-modified proteins in pancreatic β-cells have been reported. Studies have shown that acute glucose surge in addition to chronic hyperglycemia can promote oxidative stress mechanisms during type 2 DM ［12］.

Oxidative stress and apoptotic cell death during disorders such as diabetes mellitus are signif i cantly associated with impairment in cellular energy maintenance and mitochondrial function. ROS exposure can lead to the opening of the mitochondrial membrane permeability transition pore， reduction of mitochondrial β-nicotinamide adenine dinucleotide （NAD+） stores， and thereby apoptotic cell injury. Free fatty acids also can lead to ROS release，mitochondrial DNA damage， and impaired pancreatic β-cell function ［14］.

ROS can oxidize the DNA， protein and lipid and have an important role of chronic diseases like diabetes ［15］. Elevated oxid-ative stress in diabetics is claimed to promote the development of myocardial injury， retinopathy， nephropathy， and neuropathy. The possible mechanisms of oxidative stress in developing these complications include glucose autoxidation， decreased tissue concentration of low molecular weight antioxidants like glutathione and vitamin E，and deteriorated activation of antioxidant defense enzymes such as catalase and superoxide dismutase （SOD） ［1］. Experimental and clinical studies indicate that increase in oxidative stress may be responsible for progressing risk of cardiovascular diseases in diabetic or insulinresistant states because of elevated levels of glucose ［16-18］. Common risk factors for cardiovascular diseases amongst non-diabetic， insulinresistant， and diabetic patients are reasonable because pathologies for cardiovascular diseases amongst these three groups of patients are very similar， although the progression and severity of the pathologies are not the same. However， it is not clear whether oxidative stress is causing micro-vascular pathologies because micro-vascular pathologies are noticed only in the diabetic state and are freely associated with hyperglycemia. In contrast， micro vascular pathologies such as predicate loss and meningeal expansion， which contribute to diabetic retinopathy and nephropathy， respectively， are not reported in the aging populations or insulin-resistant state in spite of the fact that they experience oxidative stress to a similar level as diabetes ［19］.

Thus， an increase in oxidative stress induced by free fatty acids，lipids， or other processes is not suffi cient to cause micro-vascular complications of diabetes. It is still possible that oxidative stress may promote the micro-vascular pathologies although it is unlikely that micro-vessel pathologies of diabetes are initiated by oxidative stress［15］. Lastly， the damage caused by oxidative stress is likely to be tissue specif i c because hyperglycemia appears to increase oxidant production in many cell types and tissues that do not manifest signif i cant pathologies ［19］.

3. Oxidative stress and diabetic retinopathy

Diabetic retinopathy is one of the most important causes of blindness in adults. The reasons of this complication are microvascular damage， swelling of blood vessels and fluid leak. If diabetic retinopathy not prevented， new vessels grow and fi nally retinal detachment will be occurred ［20］. The occurrence of this disease depends on the duration of diabetes and rarely develops in fi rst few years of diabetes but the incidence increases to 50% by 10 years and 90% by 25 years of diabetes. The increase in survival of diabetic patients has been lead to increase in prevalence of diabetic retinopathy. The retina has high content of polysaturated fatty acids and has the highest uptake of oxygen and also highest oxidation of glucose. As a result retina is more prone to oxidative stress. The correlation between hyperglycemia， oxidative stress and changes in the redox homeostasis is the main phenomenon in the pathogenesis of diabetic retinopathy. It has been suggested that oxidative stress contributes not only to the development of diabetic retinopathy but also in the resistance of it even after good glycemic control. The reason that diabetic retinopathy is resistant to reverse might be due to accumulation of damaged molecules and ROS that are not easily removed ［1，20］. It has been shown that membrane lipid peroxidation and oxidative damage to DNA （indicated by 8-hydroxy 2deoxyguanosine:8- Hodge）， the result of ROS-induced damage， are raised in the retina in diabetes ［21］.

Since oxidative stress shows an imbalance between excess formation andor impaired removal of ROS， the antioxidant defense system of the cell is crucial part of the overall oxidative stress experienced by a cell ［9，22］. In diabetes the activities of antioxidant defense enzymes responsible for scavenging free radicals and maintaining redox homeostasis such as SOD， glutathione reeducates，glutathione peroxidase， and catalase are decreased in retina ［23］. Further， the cell is equipped with intracellular antioxidant， GSH，that is the main defense of the cell. It can act as a scavenger of ROS and modulate intracellular redox state. The level of this intracellular antioxidant is diminished in the retina in diabetes and enzymes responsible for its metabolism are compromised ［24］. Not only this antioxidant defense， but also nonenzymatic antioxidants such as vitamin C， vitamin E andβ-carotene that exist biologically for the redox homeostasis regulation are also decreased during oxidative stress in hyperglycemic state ［25］. The high consumption of oxygen and exposure to visible light makes the retina highly susceptible to oxidative stress. Studies have consistently shown that photochemical injury is attributable to oxidative stress and the antioxidants like vitamin C， vitamin E and vitamin A protect against this type of injury ［25］. Hence for the early detection of diabetic retinopathy and its prevention it is advisable to estimate the markers of oxidative stress. Also， the diet of these patients should contain a recommended dietary allowance of vitamins to allow the non-enzymatic and enzymatic antioxidant systems to respond to oxidative stress which is observed in diabetic patients.

4. Oxidative stress and diabetic neuropathy

More than fifty percent of all patients with diabetes develop neuropathy， a progressive deterioration of nerves that leads to peripheral and autonomic nerve dysfunction. Diabetic neuropathy is the most common cause of amputation and failure of autonomous system ［26］. The lifelong chance of undergoing one or more amputation in a patient with diabetes mellitus is 15% ［27］. In diabetic state， accumulation of superoxide， increase in polio-pathway activity，advanced gyration end products （AGE） accumulation， protein kinase C （PKC） activity and hexamine flux trigger progressive cellular dysfunction. In nerve， the confluence of metabolic and vascular impairment result in neuron dysfunction and loss of neurotropic support， and in long term can mediate neuron， Schwann cell and glial cell apoptosis of the peripheral nervous system ［28］.

Animal studies with experimental diabetes have shown that nerve growth factor （NGF）， neurotrophin-3 （NT-3）， colliery neutrophil factor and insulin like growth factor-I （IGF-I） have been decreased and were correlated with presence of neuropathy ［29］.

Hedgehog proteins are essential for development of nervous system. Desert hedgehog is found exclusively in Schwann cells and is necessary in peripheral nerve patterning. After 10 weeks of experimental diabetes， a decrease in the expression of desert hedgehog gene was found. This decrease correlates with several established physiological biochemical markers of induced diabetes，including motor and sensory nerve conduction velocities， diminish in blood fl ow of nerve， decreased NGF and neuropeptide levels and decreased pain threshold in response to heat ［30］.

To prevent or avert the complications of diabetes including neuropathy， numerous studies have been done using antioxidant agents and some of them have shown promising results. High doses of singe-antioxidant agents like vitamin E or vitamin C may disturb the antioxidant-provident balance of cell systems. It has been suggested that mixture of antioxidant therapies possibly in combination with some trace elements and vitamins that improve metabolic processes can provide a better choice for treatment. Monitoring the patients antioxidant reserves also may clear development of defects that could be diminished by changing the therapeutic antioxidant regimen ［10，31］. Therefore， until we can completely control blood glucose level， therapies like antioxidants that are targeted against oxidative stress remain most promising way to prevent neuropathy and other diabetic complications.

5. Oxidative stress and diabetic nephropathy

As it was mentioned， ROS is permanently produced in physiological conditions and effectively eliminated by several intra and extracellular， antioxidant systems. Numerous studies on experimental models of both immune and nonimmune glomerular injury demonstrated ROS to be fi rst agent in the pathogenesis of these disorders and showed that the kidney is susceptible to oxidativestress ［32-36］. Hyperglycemia not only because of generation of more ROS but also because of attenuation of the scavenging enzymes is a pathogenetic factor of long-term complications of diabetes ［37-41］. In order to establish a role for oxidative stress in diabetic nephropathy it has been demonstrated that oxidative stress is elevated in diabetic kidney before the clinical signs of nephropathy. The halflife of ROS is extremely short and as a result direct measurement of ROS in tissue is diffi cult， so the endogenous end products of ROS have been measured to address the involvement of oxidative stress in a given pathologic state ［42-44］. Lipid peroxidation of unsaturated fatty acids， one of the radical reactions， has been an index of increased oxidative stress and cytotoxicity. Studies have shown that albuminuria that is a marker of glomerulopathy in diabetes has signif i cantly higher levels of lipid peroxides in plasma， urine and renal proximal tubes ［45-47］ and this fi nding suggests that oxidative stress are increased in diabetic kidneys ［48］.

Morevere， 8-hydroxy deoxyguanosine（8-OHdG ） which is an oxidized purine residue in DNA， has been accepted as a good marker of oxidative tissue injury.Formation of 8-OHdG was also elevated in the kidney and provided additional evidence that oxidative stress is the main cause of diabetic nephropathy ［48］.

Possible changes in the repair system for 8-OHdG in addition to an increased production of ROS， might play a role in such oxidative damage in the kidney of diabetic patients ［49］. Typical lesions of kidney affected by diabetes are seen in glumeruli and include thickening of capillary basement membrane with mesangium expansion， resulting in dif f use， nodular glomerulosclerosis ［50-52］. Expansion of the glomerular mesangium is one of the most important factors in the loss of fi ltration function. Glucose produced a dose-dependent increase in lipid peroxidation in cultured meningeal cells， which is supportive of increased lipid peroxidation in diabetic glomeruli ［53］. Hyperglycemia-induced oxidative stress plays a major role in expansion of extracellular matrix and glucose-induced collagen production was ef f ectively prevented by two antioxidants，taurine and vitamin E ［54］. Although increased superoxide generation in hyperglycemia is a key event in activation of other pathways， it is only a fi rst step in generating endothelial dysfunction ［55-57］.

Nitric oxide （NO） plays a central role in modulating endothelial function ［58，59］. Metabolism of L-arginine produces NO by nitric oxide synthase （NOS）， and has three isoforms: brain （bNOS），endothelia （eNOS） and inducible type （iNOS）. Hyperglycemia is a stimulating factor for inducing iNOS［60］ and mitochondrial-generated superoxide can inhibit eNOS. The superoxide anion can reduce NO，thereby diminishing the effi cacy of this strong endotheliom-derived vasodilator and during hyperglycemia， availability of NO is reduced［60］. When endothelial cells respond to high glucose， reactive nitrogen and oxygen species production occurs ［61，62］. These reactive agents trigger DNA single-strand breakage， and as it was mentioned above，increased amounts of 8-hydroxyguanine and 8-hydroxydeoxy guanosine （markers of DNA damage due to oxidative stress） can be found in both the plasma and tissues of diabetic rats. These concentrations are correlated and can be decreased by control of hyperglycemia and by using antioxidants probucol and vitamin E ［63］. As previously mentioned， convincing evidence is now available about the ef f ect of oxidative stress in the development of diabetic complications. However， clinical trials with antioxidants， especially with vitamin E have not demonstrated any benef i ts ［64］.

It has recently been suggested that treatment with antioxidants like vitamin E is limited to scavenging already-produced oxidants and should be considered more symptomatic rather than a routine therapy for vascular oxidative stress ［65］. New insights into the mechanisms leading to the oxidative stress generation in diabetes are now available and these fi ndings have led to more assessment of new antioxidant molecules that hopefully in the future may inhibit at an early stage， the mechanism leading to diabetic complications like diabetic nephropathy ［66-68］.

6. Medicinal plants antioxidants and diabetic complications

Sustained hyperglycemia can damage the eyes， kidneys， nerves and heart and antioxidants are able to reduce the diabetes and none diabetes damages ［69-71］. Microvascular （nephropathy and retinopathy） and macrovascular （atherosclerotic） disorders are the leading causes of morbidity and mortality in diabetic patients ［65］. As it was mentioned there is no preventive or curative method for diabetes mellitus. Therefore， there is a need to find out reliable treatments in slowing the progression of diabetic complications. Investigations on various approaches have shown promising results［72，73］ Recently some plants have shown benef i cial ef f ects not only on renal function in diabetes mellitus ［74，75］， but also on renal toxicities induced by some drugs or toxins ［76-77］.

Since time immemorial， mankind has searched for medications to cure or prevent various diseases. A 5000 year-old Sumerian clay slab has recently discovered describing the use of medicinal plants for the preparation of drugs ［78］. In the late 19th and early 20th centuries， there was a steady decline in the therapeutic use of herbal medicines. Nevertheless， currently， due to the potent side ef f ects of modern synthetic drugs and increasing contraindications to their usage， a popular resurgence has materialized for the use of medicinal plants ［79，80］. Medicinal plants， mostly with antioxidant activity， are the major source of drugs for the treatment of oxidative stress induced complications. Nowadays， about half of the available drugs are estimated to be originated from plants ［81］.

The rebirth of herbal medicine， particularly in developed countries，is chiefly centred on renewed interest by society and advancing scientif i c information regarding plants. In this context therefore， it is important that the momentum of research into medicinal plants is maintained or even escalated ［79］. Hence， studies with medicinal plants have shown promising ef f ects in several disease conditions including diabetes ［82，83］， hyperlipidemia ［84，85］， pain ［86，87］， amnesia［88，89］ and gastrointestinal ［90，91］ complications. Herbal preparations also have capacities to diminish drug and none drug inducedtoxicities ［92- 94］.

Out of the two types of diabetes， the incidence of non-insulin dependent diabetes mellitus （NIDDM） is much higher than the insulin dependent one. The sulphonyl urea and biguanide drugs are valuable treatment for hyperglycemia in non-insulin dependent diabetes mellitus， but other than having side ef f ects， they usually are unable to lower glucose level to within normal range ［80］.

Even insulin therapy does not reinstate a permanent normal pattern of glucose homeostasis， and carries an increased risk of hypoglycemia and atherogenesis. Medicinal plants have the advantage of having no or only few side ef f ects ［95-97］. Some of them have been used in traditional medicine from ancient times. Till today metformin is the only available drug derived from a medicinal plant Galega offi cina approved for the treatment of non-insulin dependent diabetes mellitus patients ［98］.

There are a lot of medicinal plants with anti-diabetic property；nearly all of them possess antioxidant activities. These plants might provide useful sources for the development of new drugs useful in the treatment of diabetes mellitus and its complications ［83］. Herbal medicines seem to be a reliable source for new drugs. This section of the article reviews and emphasis the benef i cial ef f ects of some medicinal plants in prevention and treatment of diabetes-associated complications ［98］. Current pre-clinical and clinical studies have demonstrated that many have benef i cial ef f ects on some processes in experimental animals. Modif i cation of risk factors in diabetes has an impressive impact on morbidity and mortality in diabetic patients ［99，100］.

Hyperglycemia leads to increased oxidative stress and activation of polyol pathway， which may cause inflammation and renal damage ［101］. Several plant extracts with hypoglycemic properties and protective activities against diabetes complications have been identified ［100］. It has been shown that metformin， a biguanide hypoglycemic compound from a herbal source （Galega offi cinalis），may be useful in the prevention of kidney injury ［73，98］. Some other herbal medicines such as curcumin from Curcuma longa， Panax quinquefolium， Vitisvinifera and glycosides from Stelechocarpus caulif l orus have also been shown to prevent diabete complications［100，101］. The active phytochemicals and the mechanisms responsible for activities of several herbal medicines have been identif i ed. Some herbal medicines have a positive impact on glucose homeostasis in diabetic patients. These plants have compounds ef f ective on diabetes mellitus or impaired glucose tolerance. Some plants lower blood pressure or improve the renal and cardiovascular functions， which are often seen in diabetic patients. The active agents identif i ed in these plants include polysaccharides， flavonoids， xanthones and peptides ［102，103］.

Increased activities and levels of antioxidants usually reduce diabetes complications. Antioxidants usually give electrons to free radicals. People with low intake of vegetables and fruits have been shown to beat greater risk for development of diabetes complications. Although free radicals contribute to kidney damage， atherosclerosis，diabetes， heart disease， nephrotoxicity and hepatotoxicity； however， clinical trials do not uniquely conf i rm a substantial impact on kidney damage ［9， 10］. It seems that antioxidant in vegetables， fruits and grains help preventing diabetes complications； however， there is little evidence that taking single antioxidants such as vitamin E or vitamin C protect against these complications. The fi ndings about combination antioxidants are also complicated and not entirely clear ［10，104］. Natural whole products， such as vegetables and fruits，seem to act as parts of elaborate networks and therefore， no single antioxidant can do the work of the whole ones ［10，105，106］.

7. Conclusion

Diabetes mellitus can damage the eyes， kidneys， nerves and heart. Microvascular and macrovascular disorders are the leading causes of morbidity and mortality in diabetic patients. Hyperglycemia increases oxidative stress in which ROS has the main role in the pathogenesis of these complications. Therefore， antioxidants which combat oxidative stress should be able to prevent and repair ROS induced damages. It seems that antioxidants in vegetables， fruits and grains help preventing diabetes complications； however， there is little evidence that taking single antioxidants such as vitamin E or vitamin C protect against these complications.

Conflict of interest statement

The author declares that there is no conf l ict of interest.

Acknowledgments

Hereby， we gratefully thank the Medical Plants Research Center staf f of Shahrekord University of Medical Sciences who helped us to conduct this study.

［1］ King H， Aubert RE， Herman WH. Global burden of diabetes， 1995-2025: prevalence， numerical estimates， and projections. Diabetes Care 1998；21（9）: 1414-1431.

［2］ Norhammar A， Tenerz A， Nilsson G， Hamsten A， Efendíc S， Ryde′n L， et al. Glucose metabolism in patients with acute myocardial infarction and no previous diagnosis of diabetes mellitus: a prospective study. Lancet 2002； 359（9324）: 2140-2144.

［3］ Abac? A ， O?uzhan A ， Kahraman S ， Eryol NK ， ü nal， Ar?n ? H ， et al. Ef f ect of diabetes mellitus on formation of coronary collateral vessels. Circulation 1999； 99（17）: 2239-2242.

［4］ Bahmani M， Zargaran A， Rafieian-Kopaei M， Saki M. Ethnobotanical study of medicinal plants used in the management of diabetes mellitus in the Urmia， Northwest Iran. Asian Pac J Trop Med 2014； 7（Suppl 1）: 348-354.

［5］ Nasri H， Raf i eian-Kopaei M. Protective ef f ects of herbal antioxidants on diabetic kidney disease. J Res Med Sci 2014； 19（1）: 82-83.

［6］ Nasri H， Raf i eian-Kopaei M. Tubular kidney protection by antioxidants. Iran. J. Public Health 2013； 42（10）: 1194-1196.

［7］ Rolo AP， Palmeira CM. Diabetes and mitochondrial function: role of hyperglycemia and oxidative stress. Toxicol Appl Pharmacol 2006； 212（2）: 167-178.

［8］ Bahmani M ， Sarrafchi A ， Shirzad H ， Rafieian-Kopaei M. Autism: Pathophysiology and promising herbal remedies. Curr Pharm Des 2016；22（3）: 277-285.

［9］ Rafieian-Kopaei M ， Baradaran A， Rafieian M. Oxidative stress and the paradoxical ef f ects of antioxidants. J Res Med Sci 2013； 18（7）: 628.

［10］ Raf i eian-Kopaie M， Baradaran A. Plants antioxidants: From laboratory to clinic. J Nephropathol 2013； 2（2）: 152-153.

［11］ Brownlee M. The pathobiology of diabetic complications: a unifying mechanism. Diabetes 2005； 54（6）:1615-1625.

［12］ Maritim A， Sanders R， Watkins III J. Diabetes， oxidative stress， and antioxidants: a review. J Biochem Mol Toxicol 2003； 17（1）: 24-38.

［13］ Sarrafchi A ， Bahmani M ， Shirzad H ， Rafieian-Kopaei M. Oxidative stress and Parkinson's disease: New hopes in treatment with herbal antioxidants. Curr Pharm Des 2016； 22（2）: 238-246.

［14］ Maiese K， Chong ZZ， Shang YC， Hou J. Novel avenues of drug discovery and biomarkers for diabetes mellitus. J Clin Pharmacol 2011； 51（2）: 128-152.

［15］ Evans JL， Goldf i ne ID， Maddux BA， Grodsky GM. Are oxidative stressactivated signaling pathways mediators of insulin resistance and β-cell dysfunction？ Diabetes 2003； 52（1）: 1-8.

［16］ Asgary S ， Sahebkar A， Afshani MR， Keshvari M ， Haghjooyjavanmard S， Raf i eian-Kopaei M. Clinical evaluation of blood pressure lowering，endothelial function improving， hypolipidemic and anti-inf l ammatory effects of pomegranate juice in hypertensive subjects. Phytother Res 2014； 28（2）: 193-199.

［17］ Gharipour M ， Ramezani MA ， Sadeghi M ， Khosravi A ， Masjedi M，Khosravi-Boroujeni H， et al. Sex based levels of creactive protein and white blood cell count in subjects with metabolic syndrome: Isfahan Healthy Heart Program. J Res Med Sci 2013； 18（6）: 467-472.

［18］ Khosravi-Boroujeni H， Mohammadifard N， Sarrafzadegan N， Sajjadi F，Maghroun M， Khosravi A， et al. Potato consumption and cardiovascular disease risk factors among Iranian population. Int J Food Sci Nutr 2012；63（8）: 913-920.

［19］ Scott JA ， King GL. Oxidative stress and antioxidant treatment in diabetes. Ann N Y Acad Sci 2004； 1031（1）: 204-213

［20］ Aylward G. Progressive changes in diabetics and their management. Eye 2005； 19（10）: 1115-1118.

［21］ Kowluru RA， Abbas SN. Diabetes-induced mitochondrial dysfunction in the retina. Invest Ophthalmol Vis Sci 2003； 44（12）: 5327-5334.

［22］ Baradaran A， Nasri H， Nematbakhsh M， Raf i eian-Kopaei M. Antioxidant activity and preventive ef f ect of aqueous leaf extract of Aloe Vera on gentamicin-induced nephrotoxicity in male Wistar rats. La Clin ter 2013；165（1）: 7-11.

［23］ Haskins K ， Bradley B， Powers K ， Fadok V， Flores S ， Ling X ， et al. Oxidative stress in type 1 diabetes. Ann N Y Acad Sci 2003； 1005（1）: 43-54.

［24］ Kowluru RA ， Kern TS ， Engerman RL. Abnormalities of retinal metabolism in diabetes or experimental galactosemia. IV. Antioxidant defense system. Free Radic Biol Med 1996； 22（4）: 587-592.

［25］ Ford ES， Mokdad AH， Giles WH， Brown DW. The metabolic syndrome and antioxidant concentrations. Diabetes 2003； 52（9）: 2346-2352.

［26］ Feldman E， Stevens M， Russell J， Greene D， Porte D， Sherwin R， et al. Somatosensory neuropathy. Ellenberg and rifkin's diabetes mellitus. New York: McGraw Hill； 2002， p.771-788.

［27］ Feldman E， Stevens M， Russell J. Diabetic peripheral and autonomic neuropathy. Contempl Endocrinol 2002； 1: 437-461.

［28］ Schmeichel AM， Schmelzer JD， Low PA. Oxidative injury and apoptosis of dorsal root ganglion neurons in chronic experimental diabetic neuropathy. Diabetes 2003； 52（1）:165-171.

［29］ Apfel SC. Neurotrophic factors and diabetic peripheral neuropathy. Eur Neurol 1999； 41（1）: 27-34.

［30］ Feldman EL. Oxidative stress and diabetic neuropathy: a new understanding of an old problem. J Clin Invest 2003； 111（4）: 431-433.

［31］ Vincent AM ， Russell JW， Low P， Feldman EL. Oxidative stress in the pathogenesis of diabetic neuropathy. Endocr Rev 2004； 25（4）: 612-628.

［32］ Rafieian-Kopaei M， Nasri H. Re: Erythropoietin ameliorates oxidative stress and tissue injury following renal ischemia/reperfusion in rat kidney and lung. Med Prin Pract 2013； 23（1）: 95.

［33］ Nasri H ， Tavakoli M ， Ahmadi A ， Baradaran A ， Nematbakhsh M， Raf i eian-Kopaei M. Ameliorative ef f ect of melatonin against contrast media induced renal tubular cell injury. Pak J Med Sci 2014； 30（2）: 261-265

［34］ Baradaran A， Nasri H， Raf i eian-Kopaei M. Comment on: Anti-oxidative stress activity of Stachys lavandulifolia aqueous extract in humans. Cell J 2013； 15（3）: 272-273.

［35］ Baradaran A， Madihi Y， Merrikhi A ， Rafieian-Kopaei M. Nematbakhsh M， Asgari， A. Khosravi Z， et al. Nephrotoxicity of hydroalcoholic extract of Teucrium polium in Wistar rats. Pak J Med Sci 2013. 29（ Suppl 1）: 329-333.

［36］ Nasri H ， Nematbakhsh M ， Ghobadi Sh ， Ansari R ， Shahinfard N ，Rafieiankopaei M. Preventive and curative effects of ginger extract against histopathologic changes of gentamicininduced tubular toxicity in rats. Int J Prev Med 2013； 4（ 3）: 316-321.

［37］ Nasri H ， Baradaran A， Ardalan MR， Mardani S， Momeni A ， Rafieian-Kopaei M. Bright renoprotective properties of metformin: beyond blood glucose regulatory ef f ects. Iran J Kidney Dis 2013； 7（6）: 423-428.

［38］ Rafieian-Kopaei M ， Nasri H. The ameliorative effect of Zingiber officinale in diabetic nephropathy. Iran Red Crescent Med J 2014；16（5）:1-2.

［39］ Baradaran A， Madihi Y， Merrikhi A， Raf i eian-Kopaei M， Nasri H. Serum lipoprotein （a） in diabetic patients with various renal function not yet on dialysis. Pak J Med Sci 2013； 29（Suppl 1）: 354-357.

［40］ Behradmanesh S， Horestani MK， Baradaran A， Nasri H. Association of serum uric acid with proteinuria in type 2 diabetic patients. J Res Med Sci 2013； 18: 44-46.

［41］ Nasri H， Madihi Y， Merrikhi A， Gheissari A， Baradaran A， Kheiri S， et al. Association of proteinuria with various clinical fi ndings and morphologic variables of Oxford classification in immunoglobulin A nephropathy patients. Int J Prev Med 2013； 4（5）: 546-551.

［42］ Setorki M ， Nazari B ， Asgary S ， Azadbakht L， Rafieian-Kopaei. Antiatherosclerotic ef f ects of verjuice on hypocholesterolemic rabbits. Afr J Pharm Pharmacol 2011； 5（8） 1038-1045.

［43］ Amini FG， Rafieian-Kopaei M， Nematbakhsh M， Baradaran A， Nasri H. Ameliorative ef f ects of metformin on renal histologic and biochemical alterations of gentamicin-induced renal toxicity in Wistar rats. J Res Med Sci 2012； 17（7）: 621-625.

［44］ Setorki M， Rafieian-Kopaei M， Merikhi A， Heidarian E ， Shahinfard N，Ansari R， et al. Suppressive impact of Anethum graveolens consumption on biochemical risk factors of atherosclerosis in hypercholesterolemic rabbits. Int J Prev Med 2013； 4（8）: 889-895.

［45］ Delfan B， Bahmani M ， Hassanzadazar H ， Saki K， Rafieian-Kopaei M. Identif i cation of medicinal plants af f ecting on headaches and migraines in Lorestan Province， West of Iran. Asian Pac J Trop Med 2014； 7（Suppl 1）: 376-379.

［46］ Ardalan MR， Nasri H， Raf i eianKopaei M. Comment on: Protective role of recombinant human erythropoietin in kidney and lung injury following renal bilateral. ischemiareperfusion in rat model. Int J Prev Med 2013；4（10）: 1226-1227.

［47］ Nasri H ， Rafieian-Kopaei M. Kidney tubular cell protection； recent fi ndings. Iran J Pediatr 2014； 24（6）: 781-783.

［48］ Ha H， Kim KH. Role of oxidative stress in the development of diabetic nephropathy. Kidney Int Suppl 1995； 51（3）: 18-21.

［49］ Nasri H， Ardalan MR， Rafieian-Kopaei M. Mechanistic Impacts of Medicinal Plants in Diabetic Kidney Disease. Iran J Public Health 2014 ；43（9）: 1311-1313.

[50] Rafieian-Kopaei M， Ghaed-Amini F， Nasri H. Erythropoietin has kidney protective effi cacy beyond stimulating erythropoiesis. J Isfahan Med Sch 2013； 31（235）:619-622.

［51］ Raf i eian-Kopaei M， Baradaran A， Nasri H. Signif i cance of extracapillary proliferation in IgA-nephropathy patients with regard to clinical and histopathological variable. Hippokratia 2013； 17（3）: 258-261.

［52］ Rafieian-Kopaei M， Nasri H. Re: Erythropoietin ameliorates oxidative stress and tissue injury following renal ischemia/reperfusion in rat kidney and lung. Med Princ Pract 2014； 23（1）: 95. Doi: 10.1159/000350842.

［53］ Ha H ， Lee SH ， Kim KH. Effects of rebamipide in a model of experimental diabetes and on the synthesis of transforming growth factor-β and fibronectin， and lipid peroxidation induced by high glucose in cultured mesangial cells. J Pharmacol Exp Ther 1997； 281（3）: 1457-1462.

［54］ Ha H ， Kim KH. Pathogenesis of diabetic nephropathy: The role of oxidative stress and protein kinase C. Diabetes Res Clin Pract 1999； 45（2）: 147-151.

［55］ Asgary S ， Keshvari M ， Sahebkar A ， Hashemi M ， Rafieian-Kopaei. Clinical investigation of the acute ef f ects of pomegranate juice on blood pressure and endothelial function in hypertensive individuals. ARYA Atheroscler 2013； 9（6）: 326-331.

［56］ Khosravi-Boroujeni H ， Sarrafzadegan N， Mohammadifard N， Sajjadi F， Maghroun M， Asgari S， et al. White rice consumption and CVD risk factors among Iranian population. J Health Popul Nutr 2013； 31（2）: 252-261.

［57］ Asgary S， Kelishadi R， Raf i eian-Kopaei M， Najaf i S， Najaf i M， Sahebkar A. Investigation of the lipid-modifying and antiinf l ammatory ef f ects of Cornus mas L. supplementation on dyslipidemic children and adolescents. Pediatr Cardiol 2013； 34（7）: 1729-1735.

［58］ Heidarian E， Raf i eian-Kopaei M， Ashraf i K. The ef f ect of hydroalcoholic extract of allium latifolium on the liver phosphatidate phosphatase and serum lipid prof i le in hyperlipidemic rats. J Babol Univ Med Sci 2013；15（4）: 37-46.

［59］ Asgary S， Rafieian-Kopaei M， Najafi S， Heidarian E， Sahebkar A. Antihyperlipidemic ef f ects of Sesamum indicum L. in rabbits fed a highfat diet. Sci World J 2013； 2013（4）: 365892

［60］ Baek KJ， Thiel B， Lucas S， Stuehr D. Macrophage nitric oxide synthase subunits. Purif i cation， characterization， and role of prosthetic groups and substrate in regulating their association into a dimeric enzyme. J Biol Chem1993； 268（28）: 21120-21129.

［61］ Heidarian E， Raf i eian-Kopaei M， Ashraf i K. The ef f ect of hydroalcoholic extract of allium latifolium on the liver phosphatidate phosphatase and serum lipid prof i le in hyperlipidemic rats. J Babol Univ Med Sci 2013；15（4）: 37-46

［62］ Nasri H， Shirzad H， Baradaran A， Raf i eian-Kopaei M. Antioxidant plants and diabetes mellitus. J Res Med Sci 2015； 20（5）: 491-502

［63］ Park KS， Kim JH ， Kim MS， Kim JM ， Kim SK ， Choi JY， et al. Effects of insulin and antioxidant on plasma 8-hydroxyguanine and tissue 8-hydroxydeoxyguanosine in streptozotocin-induced diabetic rats. Diabetes 2001； 50（12）: 2837-2841.

［64］ Marchioli R ， Schweiger C， Levantesi G ， Tavazzi L， Valagussa F. Antioxidant vitamins and prevention of cardiovascular disease: Epidemiological and clinical trial data. Lipids 2001； 36（Suppl ）: 53-63.

［65］ Ceriello A. New insights on oxidative stress and diabetic complications may lead to a “causal” antioxidant therapy. Diabetes Care 2003； 26（5）: 1589-1596.

［66］ Nasri H， Nematbakhsh M， Raf i eian-Kopaei M. Ethanolic extract of garlic for attenuation of gentamicin-induced nephrotoxicity in Wistar rats. Iran J Kidney Dis 2013 ； 7（5）: 376-382.

［67］ Ghaed F， Raf i eian-Kopaei M， Nematbakhsh M ， Baradaran A， Nasri H .Ameliorative ef f ects of metformin on renal histologic and biochemical alterations of gentamicin-induced renal toxicity in Wistar rats. J Res Med Sci 2012； 17（7）: 621-625.

［68］ Nasri H， Raf i eian-Kopaei M. Medicinal plants and new concerns in statin consumption. Iranian J Publ Health 2013； 42（9）: 1071-1072.

［69］ Behradmanesh S ， Derees F， Rafieian-Kopaei M. Effect of Salvia offi cinalis on diabetic patients. J Renal Inj Prev 2013； 2（2）: 51-54.

［70］ Asgari A. Herbal medicines and kidney ； friends or foes？ J Nephropharmacol 2014； 3（1）: 5-6.

［71］ Raf i eian-Kopaei M， Nasri H. Comment on: Is the renoprotective ef f ect of erythropoietin in chronic kidney disease a myth？ J Formos Med Assoc 2014 ； 113（1）:62.

［72］ Baradaran A， Nasri H， Rafieian-Kopaei M. Protection of Renal Tubular Cells by Antioxidants: Current Knowledge and New Trends. Cell J 2015；16（4）: 568-571.

［73］ Raf i eian-Kopaie M， Baradaran A. Combination of metformin with other antioxidants may increase its renoprotective effi cacy. J Renal Inj Prev 2013； 2（2）: 35-36.

［74］ Hasanpour Z ， Nasri H， Rafieian-Kopaei M ， Ahmadi A ， Baradaran A ，Nasri P， et al. Paradoxical ef f ects of atorvastatin on renal tubular cells anexperimental investigation. Iran J Kidney Dis 2015； 9（3）: 215-220.

［75］ Nasri H ， Hajian S， Ahmadi A， Baradaran A， Kohi G， Nasri P， et al. Ameliorative ef f ect of green tea against contrast-induced renal tubular cell injury. Iran J Kidney Dis 2015 ； 9（6）: 421-426.

［76］ Heidarian E， Raf i eian-Kopaei M. Amelioration of lead toxicity from rat liver with artichoke leaf extract. Toxicol Lett 2012； 211（3）: S142.

［77］ Heidarian E， Raf i eian-Kopaei M. Protective ef f ect of artichoke （Cynara scolymus） leaf extract against lead toxicity in rat. Pharm Biol 2013； 51（9）: 1104-1109.

［78］ Sewell RDE， Rafieian-Kopaei M. The history and ups and downs of herbal medicine usage. J Herbmed Pharmacol 2014； 3（1）: 1-3.

［79］ Nasri H， Shirzad H. Toxicity and safety of medicinal plants. J Herbmed Plarmacol 2013； 2（2）: 21-22.

［80］ Asadi-Samani M ， Bahmani M ， Rafieian-Kopaei M. The chemical composition， botanical characteristic and biological activities of Borago offi cinalis: a review. Asian Pac J Trop Med 2014； 7（Suppl 1）: 22-28.

［81］ Fabricant DS， Farnsworth NR. The value of plants used in traditional medicine for drug discovery. Environ Health Perspect 2001； 109 （Suppl 1）: 69-75.

［82］ Nasri H， Rafieian-Kopaei M. Comment on: The effects of green tea consumption on metabolic and anthropometric indices in patients with type 2 diabetes. J Res Med Sci 2014 ； 19（12）: 1203-1204.

［83］ Bahmani M， Zargaran A ， Rafieian-Kopaei M， Saki K. Ethnobotanical study of medicinal plants used in the management of diabetes mellitus in the Urmia， Northwest Iran. Asian Pac J Trop Med 2014； 7（Suppl）: 348-354.

［84］ Madihi Y， Merrikhi A， Baradaran A， Rafieian-kopaei M， Shahinfard N，Ansari R， et al. Impact of sumac on postprandial high-fat oxidative stress. Pak J Med Sci 2013； 29 （1）: 340-345.

［85］ Rafieian-kopaei M， Shahinfard N， Rouhi-Boroujeni H， Gharipour M，Darvishzadeh-Boroujeni P. Ef f ects of Ferulago angulata extract on serum lipids and lipid peroxidation. Evid-Based Compl Alt 2014； 2014（2014）: 1-5.

［86］ Delfan B， Bahmani M， Rafieian-Kopaei M， Delfan M ， Saki K. A review study on ethnobotanical study of medicinal plants used in relief of toothache in Lorestan Province， Iran. Asian Pac J Trop Dis 2014； 7（Suppl 2）: 879-884.

［87］ Bahmani M， Shirzad HA， Majlesi M， Shahinfard N， Rafieian-Kopaei M. A review study on analgesic applications of Iranian medicinal plants. Asian Pac J Trop Med 2014； 7（Suppl 1）: 43-53.

［88］ Rabiei Z， Rafieian-kopaei M ， Heidarian E ， Saghaei E， Mokhtari S. Ef f ects of Zizyphus jujube extract on memory and learning impairment induced by bilateral electric lesions of the nucleus Basalis of Meynert in rat. Neurochem Res 2014； 39（2）: 353-360.

［89］ Rahnama S， Rabiei Z， Alibabaei Z， Mokhtari S， Rafieian-kopaei M，Deris F. Anti-amnesic activity of Citrus aurantium fl owers extract against scopolamine-induced memory impairments in rats. Neurol Sci 2015；36（4）: 553-560.

［90］ Hosseini-asl K， Raf i eian-kopaei M. Can patients with active duodenal ulcer fast Ramadan？ Am J Gastroenterol 2002； 97（9）: 2471-2472.

［91］ Sedighi M ， Rafieian-Kopaei M ， Noori-Ahmadabadi M. Kelussia odoratissima Mozaf f arian inhibits ileum contractions through voltage dependent and beta adrenergic receptors. Life Sci J 2012； 9（4）: 1033-1038.

［92］ Kafash-Farkhad N， Asadi-Samani M， Rafieian-Kopaei M. A review on phytochemistry and pharmacological ef f ects of Prangos ferulacea （L.）Lindl. Life Sci J 2013； 10（8）: 360-367.

［93］ Heidarian E， Raf i eian-Kopaei M. Protective ef f ect of artichoke （Cynara scolymus） leaf extract against lead toxicity in rat. Pharm Biol 2013；51（9）: 1104-1109.

［94］ Shirzad H ， Burton RC ， Smart YC ， Rafieian-Kopaei M ， Shirzad M. Natural cytotoxicity of NC-2（+） cells against the growth and metastasis of WEHI-164 fi brosarcoma. Scand J Immunol 2011； 73（2）: 85-90.

［95］ Sedighi M ， Rafieian-Kopaei M， Noori-Ahmadabadi M. Kelussia odoratissima Mozaf f arian inhibits ileum contractions through voltage dependent and beta adrenergic receptors. Life Sci J 2012； 9（4）: 1033-1038.

［96］ Rafieian-Kopaei M ， Hosseini M ， Shirzad H. Comment on: Effect of pomegranate fl ower extract on cisplatin-induced nephrotoxicity in rats. J Nephropathol 2014； 3（4）: 121-123.

［97］ Oubre A， Carlson T， King S ， Reaven G. From plant to patient: an ethnomedical approach to the identification of new drugs for the treatment of NIDDM. Diabetologia 1997； 40（5）: 614-617.

［98］ Rahimi-Madiseh M， Bahmani M ， Karimian P， Rafieian-kopaei M. Herbalism in Iran: A systematic review. Der Pharma Chemica 2016； 8（2）: 36-42.

［99］ Raf i eian-Kopaie M， Baradaran A. Combination of metformin with other antioxidants may increase its renoprotective effi cacy. J Renal Inj Prev 2013； 2（2）: 35-36.

［100］ Nasri H， Raf i eian-Kopaei M. Metformin and diabetic kidney disease: a mini-review on recent fi ndings. Iran J Pediatr 2014； 24（5）: 565-568.

［101］ Khajehdehi P. Turmeric: Reemerging of a neglected Asian traditional remedy. J Nephropathol 2012； 1（1） :17-22.

［102］ Asadi SY， Parsaei P， Karimi M， Ezzati S， Zamiri A， Mohammadizadeh F， et al. Ef f ect of green tea （Camellia sinensis） extract on healing process of surgical wounds in rat. Int J Surg 2013； 11（4）: 332-337.

［103］ Asadbeigi M， Mohammadi T， Rafieian-Kopaei M ， Saki K ， Bahmani M， Delfan B. Traditional ef f ects of medicinal plants in the treatment of respiratory diseases and disorders: an ethnobotanical study in the Urmia. Asian Pac J Trop Med 2014； 7（Suppl 1）: 364-368.

［104］ Bahmani M， Rafieian-Kopaei M， Hassanzadazar H， Saki K ， Karamati SA， Delfan B. A review on most important herbal and synthetic antihelmintic drugs. Asian Pac J Trop Med 2014； 7（Suppl 1）: 29-33.

［105］ Parsaei P， Karimi M ， Asadi SY， Rafieian-kopaei M. Bioactive components and preventive ef f ect of green tea （Camellia sinensis） extract on post-laparotomy intra-abdominal adhesion in rats. Int J Surg 2013；11（9）: 811-815.

［106］ Asadi-Samani M ， Bahmani M， Rafieian-Kopaei M. The chemical composition， botanical characteristic and biological activities of Borago officinalis: a review. Asian Pac J Trop Med 2014； 7（Suppl 1）: 22-28.

10.1016/j.apjtm.2016.07.001

Mohammad Rahimi-Madiseh， Medical Plants Research Center，Shahrekord University of Medical Sciences， Shahrekord， Iran.

E-mail: m_rahimi7@yahoo.com

Tel/Fax: +98 33340709

?Corresponding author: Mahmud Raf i eian-kopaei， Medical Plants Research Center，Shahrekord University of Medical Sciences， Shahrekord， Iran.

E-mail: raf i eian@yahoo.com

Tel/Fax: +98 33340709