Effectiveness of Magnolol, a Lignan from Magnolia Bark, in Diabetes, Its Complications and Comorbidities-A Review.

Diabetes mellitus is a chronic metabolic disease characterized by disturbances in carbohydrate, protein, and lipid metabolism, often accompanied by oxidative stress. Diabetes treatment is a complicated process in which, in addition to the standard pharmacological action, it is necessary to append a comprehensive approach. Introducing the aspect of non-pharmacological treatment of diabetes allows one to alleviate its many adverse complications. Therefore, it seems important to look for substances that, when included in the daily diet, can improve diabetic parameters. Magnolol, a polyphenolic compound found in magnolia bark, is known for its health-promoting activities and multidirectional beneficial effects on the body. Accordingly, the goal of this review is to systematize the available scientific literature on its beneficial effects on type 2 diabetes and its complications. Taking the above into consideration, the article collects data on the favorable effects of magnolol on parameters related to glycemia, lipid metabolism, or oxidative stress in the course of diabetes. After careful analysis of many scientific articles, it can be concluded that this lignan is a promising agent supporting the conventional therapies with antidiabetic drugs in order to manage diabetes and diabetes-related diseases.

Assessment of consumer awareness on the consumption of phytoestrogens in diet and their supplementation - survey studies.

INTRODUCTION: Phytoestrogens are plant-derived compounds with structural similarity to 17-ß-estradiol. They are considered safer substitutes for synthetic drugs, especially in the treatment of menopause related symptoms. They are delivered to the body with diet or as dietary supplements. AIM OF THE STUDY: The aim of the study was to assess consumer awareness of taking phytoestrogens with diet and supplements, as well as the benefits and risks of such supplementation. MATERIALS AND METHODS: An original survey form was created for the purpose of the study, 133 questionnaires were completed online, and 100 were distributed to random respondents in the Silesian Voivodship. The vast majority of the respondents (84.5%) was represented by women. The study group was diverse in terms of age, education and place of residence. RESULTS: Most of the respondents (67.4%) encountered the concept of phytoestrogens. Common plants as: flax, sunflower, pumpkin, European olive and hops were indicated as phytoestrogen main sources. A small group of respondents (6%) was convinced of the effectiveness of phytoestrogens and indicated their specific health-promoting activities, 49.4% said that not every therapy with their use would improve health and 42.9% declared lack of knowledge in this area. According to the survey outcomes, 16.7% of respondents unambiguously confirmed beneficial effect of phytoestrogens on menopause symptoms. Half of the respondents had no opinion whether phytoestrogens could be an effective replacement for synthetic drugs based therapies. CONCLUSIONS: Incomplete knowledge of society regarding the use of phytoestrogens indicates the need for raising awareness of patients/consumers in this area by medical staff and dietitians. Phytoestrogens, when taken responsibly, can have many benefits for human health.

Effect of Berberine on Glycation, Aldose Reductase Activity, and Oxidative Stress in the Lenses of Streptozotocin-Induced Diabetic Rats In Vivo-A Preliminary Study.

Diabetes mellitus affects the eye lens, leading to cataract formation by glycation, osmotic stress, and oxidative stress. Berberine, an isoquinoline alkaloid, is a natural compound that has been reported to counteract all these pathological processes in various tissues and organs. The goal of this study was to evaluate whether berberine administered at a dose of 50 mg/kg by oral gavage for 28 days to rats with streptozotocin-induced diabetes reveals such effects on the biochemical parameters in the lenses. For this purpose, the following lenticular parameters were studied: concentrations of soluble protein, non-protein sulfhydryl groups (NPSH), advanced oxidation protein products (AOPP), advanced glycation end-products (AGEs), thiobarbituric acid reactive substances (TBARS), and activities of aldose reductase (AR), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx). Diabetes induced unfavorable changes in the majority of the examined parameters. The administration of berberine resulted in an increased soluble protein level, decreased activity of AR, and lowered AOPP and AGEs levels. The results suggest that berberine administered orally positively affects the lenses of diabetic rats, and should be further examined with regard to its anticataract potential.

EFFECT OF GLABRIDIN AND GLYCYRRHIZIC ACID ON HISTOMORPHOMETRIC PARAMETERS OF BONES IN OVARIECTOMIZED RATS.

Licorice is a medicinal plant showing many therapeutic activities. Its roots contain numerous pharmacologically active compounds such as a triterpenoid saponin--glycyrrhizic acid and an isoflavan--glabridin. There are reports indicating that glabridin exhibits estrogen-like activity, therefore it can be classified into phytoestrogens, which may soothe menopause symptoms including postmenopausal osteoporosis. Due to this fact, the aim of the presented study was to evaluate the effect of glabridin and glycyrrhizic acid on histomorphometric parameters of bones in rats with ovariectomy-induced osteoporosis. The animals were divided into 6 group: (C)--control rats, (OVX)--ovariectomized rats, (OVX + E)--ovariectomized rats receiving estradiol at a dose of 0.1 mg/kg p.o., (OVX + G)--ovariectomized rats receiving genistein at a dose of 5 mg/kg p.o., (OVX + GL --ovariectomized rats treated with glabridin at a dose of 5 mg/kg p.o. and (OVX + GA)--ovariectomized rat administered with glycyrrhizic acid at a dose of 15 mg/kg p.o. Estradiol and genistein served as the positive controls in the study. Several macrometric and histomorphometric parameters were analyzed in the bones of tested rats. Obtained results indicate that glabridin shows slightly positive effect on osteoporotically changed bone tissue, and glycyrrhizic acid reveals meager influence on skeletal system with no preventive significance.

EFFECT OF DIETARY FLAVONOID NARINGENIN ON BONES IN RATS WITH OVARIECTOMY-INDUCED OSTEOPOROSIS.

Naringenin is a dietary flavanone which can be found in many products such as citrus fruits. This substance reveals multiple pharmacological activities such as antiinflammatory and antioxidative. During the menopause, the estrogen deficiency occurs, thus naringenin, which is also considered as a phytoestrogen, may be useful in the treatment of menopause-associated osteoporosis. The aim of the presented study was to examine the effect of naringenin on the mechanical properties, chemical composition and the histomorphological parameters of bones in the rats with ovariectomy-induced osteoporosis. The female Wistar rats were divided into 4 groups: sham-operated, ovariectomized, ovariectoiized treated with estradiol (0.2 mg/kg p.o.) and ovariectomized treated with naringenin (50 mg/kg p.o.), and the tested substances were administered for 4 weeks. The obtained results show that ovariectomy caused the characteristic changes in the skeletal system of rats - there was deterioration in mechanics, chemistry and histomorphometry. The estradiol administered to the rats served as positive control for the experiment. Administration of naringenin to the ovariectomized rats affected neither the bone chemical content nor the mechanical properties, however, there was a slight improvement in the bone microarchitecture in the tissue affected by osteoporosis. It can be concluded that the intake of naringenin in dietary products is not harmful and may even bring beneficial effect on the bones histomorphometry during postmenopausal osteoporosis.

BIOCHANIN A SHOWS NO EFFECT ON SKELETAL SYSTEM IN OVARIECTOMIZED RATS, WHEN ADMINISTERED IN MODERATE DOSE.

Biochanin A is a naturally occurring isoflavone. Its main sources are clover species such as Trifolium pretense, Trifolium subterraneum or Trifolium incarnatum. Phytoestrogens, including isoflavones, are plant-derived substances, which exhibit estrogen-like properties, thus they may be used as an alternative for hormonal replacement therapies and prevent postmenopausal osteoporosis. Therefore, the aim of the presented study, was to investigate the effect of biochanin A on chemistry and mechanical properties of skeletal system in rats with ovariectomy-induced osteoporosis. The animals were divided into 4 groups--(I) sham-operated rats, (II) ovariectomized rats, (III) ovariectomized rats receiving estradiol at a dose of 0.2 mg/kg p.o., which were a positive control, and (IV) ovariectomized rats receiving biochanin A at a dose of 5 mg/kg p.o. for four weeks. The administered dose of biochanin A is considered as moderate for human, which can be received in the dietary supplements, and was established using ten-fold conversion rate resulting from faster metabolism in rats. Obtained results showed that ovariectomy induced harmful changes in bone tissue, causing worsening in both chemistry and mechanical parameters in bones. Administration of biochanin A to ovariectomized rats did not affect any changes in bone tissue in comparison to the bones of untreated ovariectomized rats. There was neither improvement nor deterioration noted in chemical composition and mechanical properties in all analyzed bones. Basing on the results, it could be concluded, that biochanin A administered in a moderate dose shows no influence on bone tissue of rats with ovariectomy-induced osteoporosis.

Thalidomide affects the skeletal system of young rats.

Thalidomide has indications for the treatment of several immune-related, neoplastic, and inflammatory diseases, in both adults and children. Despite numerous therapeutic indications for the application of thalidomide, the influence of that drug upon skeletal system has not been recognized. The aim of the present study was to investigate the effects of thalidomide on the osseous tissue in young rats. The experiments were carried out on 5-week-old male Wistar rats. The animals were administered thalidomide in the doses of 15, 30 or 60 mg/kg p.o. over the period of 1, 3 or 6 weeks. The body mass gain, bone mass in the tibia, femur and L-4 vertebra, histomorphometric parameters of the femur (width of trabeculae, width of epiphyseal cartilage, the transverse cross-sectional area of the bone marrow cavity and the cortical bone) and the tibia (width of osteoid, diaphysis transverse growth, the transverse cross-sectional area of the bone marrow cavity and the cortical bone) were studied. The investigations carried out provide, for the first time, information concerning the influence of thalidomide upon bone remodeling processes in young rats. The effects of thalidomide on the skeletal system of young rats depended on the dose and upon application time. After administration of doses 15, 30 and 60 mg/kg p.o. for 1 and 3 weeks, no influence of thalidomide was noted upon the examined macrometric parameters and histomorphometric parameters of femur, tibia and L-4 vertebra in young rats. Significant disturbances of bone remodeling in young rats have been observed after 6 weeks of thalidomide application, while the progression of those changes increased with the increase of the dose administered. After administering the dose of 15 mg/kg p.o. for the period of 6 weeks, no significant changes were found, as regards the macrometric and histomorphometric parameters of bones. Thalidomide, applied 6 weeks in the dose of 30 mg/kg p.o., and in particular in the dose of 60 mg/kg p.o., turned out to disturb bone remodeling processes. In animals administered thalidomide in the dose of 60 mg/kg p.o., reduction mass of tibia, femur, and L-4 vertebra has been observed. In compact bone, thalidomide reduced the diaphysis transverse growth of tibia, reduced the width of osteoid, as well as reduced the transverse cross-sectional area of cortical bone, increased the transverse cross-sectional area of marrow cavity, and increased the transverse cross-sectional area of the marrow cavity/transverse cross-sectional area of the diaphysis ratio of tibia and femur. In cancellous bone, thalidomide reduced the width of bone trabeculae, and increased the width of epiphyseal cartilage. On the basis of the results obtained, one can conclude that thalidomide applied for 6 weeks in the dose of 60 mg/kg p.o. inhibited the bone formation processes and increased the bone resorption in young rats.

Alendronate prevents development of the skeletal changes induced by azathioprine in rats.

Immunosuppressive drugs are known to disturb bone remodeling. Azathioprine (AZA) is a potent immunosuppressive drug, but its effect on the skeletal system has not been reported so far. The aim of the present study was to investigate the effect of AZA on the rat bone remodeling, and the effect of alendronate on development of skeletal changes induced by AZA. The experiments were carried out on 3-month-old male Wistar rats, divided into the following groups: C - control rats (distilled water), AZA - azathioprine, ALN - alendronate, AZA + ALN - azathioprine and alendronate. Azathioprine (4 mg/kg po), alendronate (3 mg/kg po) and distilled water (2 ml/kg po) were administered once daily for 28 days. Bone remodeling was estimated based on quantitative and histomorphometric evaluation of the tibia and femur, and the mechanical properties of the femur and femoral neck. AZA at a dose of 4 mg/kg for 28 days induced bone remodeling disorders, inhibiting bone formation and mineralization. Alendronate prevented the development of skeletal changes caused by AZA administration, inhibiting bone resorption and increasing bone mineralization.

Effects of vigabatrin on the skeletal system of young rats.

Long-term administration of antiepileptic drugs may be connected with the risk of impairment of bone remodeling. Contrary to the reported unfavorable effect of classic antiepileptic drugs on bone metabolism, little is known about the effect of the next generation antiepileptics on bone remodeling. The aim of the present study was to investigate the effect of vigabatrin, as a representative of new antiepileptics, on the skeletal system of young rats, in comparison with conventional drugs--phenytoin and valproic acid. The experiments were carried out on 4-week-old male Wistar rats, divided into the control rats, and rats receiving vigabatrin (250 mg/kg p.o. daily), phenytoin (20 mg/kg p.o. daily) or valproic acid (250 mg/kg p.o. daily). The drugs were administered for 28 days. Histomorphometric parameters of the tibia and femur, mechanical properties of the femur, and bone length, diameter, mass, content of mineral substances and calcium were examined. After administration of phenytoin or valproic acid, the investigated bone parameters did not significantly differ from those observed in the control rats. Administration of vigabatrin caused profound impairment of bone accrual with impairment of bone histomorphometric parameters, along with the significant decrease in the body mass gain.

Bone remodeling after administration of proton pump (H+/K+-ATPase) inhibitors and alendronate in ovariectomized rats.

During osteoporosis therapy with alendronate, esophagitis and stomach ulceration may occur, requiring the concurrent use of drugs which decrease gastric juice production. The aim of the present study was to investigate the effect of concurrent administration of proton pump (H+/K+ATP-ase) inhibitors: omeprazole or pantoprazole and alendronate on bone remodeling in ovariectomized rats. The experiments were carried out on 3-month-old Wistar rats, divided into following groups (n = 8-10): NOVX - non-ovariectomized control rats; OVX - ovariectomized control rats; OVX + alendronate; OVX + omeprazole; OVX + omeprazole + alendronate; OVX + pantoprazole; OVX + pantoprazole + alendronate. The drugs were administered for 28 days: alendronate (3 mg/kg p.o.), omeprazole or pantoprazole (3 mg/kg i.p.). Bone remodeling was estimated based on histomorphometric evaluation of the tibia (endosteal and periosteal transverse growth and the osteoid width, transverse cross-section surface of the diaphysis and of the marrow cavity) and the femur (width of trabeculae in the distal epiphysis and metaphysis). Bone mass/100 g body mass and mass of bone mineral/100 mg bone mass in the tibia and femur were also determined. Pantoprazole stronger than omeprazole intensified bone remodeling disorders caused by estrogen deficiency in ovariectomized rats. Bone remodeling disorders were the result of intensification of bone resorption with concurrent inhibition of bone formation and mineralization. Pantoprazole, and to lesser extent omeprazole, weakened the preventive effect of alendronate on bone remodeling in ovariectomized rats.

Silymarin from Milk Thistle Fruits Counteracts Selected Pathological Changes in the Lenses of Type 1 Diabetic Rats.

Diabetes is a metabolic disease affecting many tissues and organs. The main etiological factor for diabetic complications is hyperglycemia and subsequent pathologies, such as oxidative stress. One of the organs susceptible to the development of diabetic complications is the eye with all of its elements, including the lens. The aim of this study was to evaluate the effect of silymarin, an extract obtained from milk thistle fruit husks, on the oxidative stress markers in the lenses of type 1 diabetic rats. The study was performed on male rats in which type 1 diabetes was induced with 60 mg/kg streptozotocin injection. Diabetic animals were treated via an intragastric tube with silymarin at 50 and 100 mg/kg doses for four weeks. Multiple oxidative stress and polyol pathway-related parameters were measured in the lenses, and auxiliary biochemical tests in the serum were conducted. Diabetes induced severe pathological changes both in the lenses and the serum, and silymarin counteracted several of them. Nevertheless, the qualitative analyses encompassing all tested parameters indicate that silymarin slightly improved the overall state of diabetic animals. Upon the obtained results, it can be concluded that silymarin reveals a faint positive effect on the lenses in type 1 diabetic rats.

Chrysin Reduces Oxidative Stress but Does Not Affect Polyol Pathway in the Lenses of Type 1 Diabetic Rats.

Prolonged hyperglycemia is one of the main causes of reactive oxygen species and free radicals generation in diabetes which may affect various organs, including the eye. Oxidative damage to proteins and lipids in the eye lens could lead to cataract formation. To cope with oxidative stress, the endogenous antioxidative system may be supported by the supplementation of exogenous antioxidants. The aim of this study was to evaluate the effect of chrysin, a natural flavonoid, on oxidative stress and polyol pathway-related markers in the lenses of streptozotocin-induced type 1 male diabetic rats. Chrysin at doses of 50 and 100 mg/kg was administered by gavage for 28 days. This treatment resulted in a decrease in antioxidative enzymes activity and oxidative stress index. Moreover, chrysin administration elevated the reduced glutathione level in the lenses. A decrease in the markers linked to oxidative damage to proteins and lipids in the lenses was noted, especially after treatment with 50 mg/kg of chrysin. Neither of the chrysin doses affected glycemia-related markers in the serum or altered parameters related to the polyol pathway and advanced glycation end-products level in the lenses of diabetic rats. Upon obtaining results, it can be concluded that chrysin reveals antioxidative activity in the lenses but shows no antihyperglycemic or antiglycation properties.

Circadian Profile of Salivary Melatonin Secretion in Hypoxic Ischemic Encephalopathy.

PURPOSE: In the present study, the salivary melatonin secretion in the hypoxic ischemic encephalopathy (HIE) children was measured. The logit model was fitted to the data to obtain the salivary dim light melatonin onsets (DLMOs), and the results were compared with the values estimated from the classic threshold method with a linear interpolation and those previously published for the blood measurements. MATERIALS AND METHODS: 9 patients suffering from HIE aged from 65 to 80 months were included in the study. The melatonin levels were assessed by a radioimmunoassay (RIA). The diurnal melatonin secretion was estimated using a nonlinear least squares method. Student's t-test and the Mann-Whitney U test were used for the comparisons of the obtained parameters. RESULTS: The circadian profiles of the melatonin secretion for both calculation methods do not differ statistically. The DLMO parameters obtained in the blood and saliva samples in children with hypoxic ischemic encephalopathy were similar.

Thalidomide affects the skeletal system of ovariectomized rats.

Apart from having written an inglorious chapter in the history of medicine, thalidomide is currently being intensely studied because of its multidimensional activity. The aim of this study was to examine the effects of thalidomide on the skeletal system in ovariectomized and non-ovariectomized rats. The experiments were carried out with female Wistar rats, divided into eight groups: sham-operated control rats; sham-operated rats receiving thalidomide at doses of 15, 30 or 60 mg/kg, po; ovariectomized control rats; ovariectomized rats receiving thalidomide at doses of 15, 30 or 60 mg/kg, po. The drug was administered for 4 weeks. Body mass gain and the mass of the uterus, liver, spleen and thymus were studied. Macrometric parameters and content of mineral substances, calcium and phosphorus in the femur, tibia and L-4 vertebra and histomorphometric parameters of the femur and tibia were examined. In the femur, the mechanical properties of the whole bone and of the femoral neck were examined. Thalidomide did not affect the skeletal system of the non-ovariectomized rats. Bilateral ovariectomy induced osteoporotic skeletal changes in mature female rats. The effects of thalidomide on the skeletal system of ovariectomized rats depended on the dose used. With a dose of 15 mg/kg, po, thalidomide counteracted some osteoporotic changes induced by estrogen deficiency. With a dose of 60 mg/kg, po, thalidomide intensified the destructive effects of estrogen deficiency on the rat skeletal system.

Effect of low-dose tacrolimus coadministered with raloxifene on the skeletal system in male rats.

Tacrolimus is an immunosuppressive drug, used to prevent organ transplant rejection. Immunosuppresants are known to unfavorably affect the osseous system. However, in our previous study on bone histomorphometric parameters we observed that low-dose tacrolimus intensified bone formation. The aim of the present study was to investigate the effects of low-dose tacrolimus on bone mechanical properties and mineralization in male rats. The effects of concurrent administration of tacrolimus and raloxifene were also studied. Raloxifene is a selective estrogen receptor modulator, used in the prevention and treatment of postmenopausal osteoporosis. In male rats raloxifene induces moderate intensification of bone mineralization. The experiments were carried out on mature male Wistar rats. The animals were divided into four groups (n = 7): control rats, rats treated with tacrolimus (0.3 mg/kg po), rats treated with raloxifene hydrochloride (5 mg/kg po) and rats treated with tacrolimus and raloxifene hydrochloride concurrently at abovementioned doses. The drugs were administered daily for 4 weeks. Body mass, bone mass and bone mineral content in the tibia, femur and L-4 vertebra, as well as mechanical properties of the whole femur (extrinsic stiffness, ultimate and breaking load, deformation caused by the applied load) and the femoral neck (load at fracture) were examined. Administration of tacrolimus at a dose of 0.3 mg/kg po for 4 weeks did not affect bone mechanical properties and mineralization. Concurrent administration of tacrolimus and raloxifene resulted in changes similar to those caused by raloxifene alone (statistically significant increases in the bone mass/body mass ratio, bone mineral content/body mass ratio and bone mineral content/bone mass ratio in comparison with the control rats, and no effect on bone mechanical properties). Results of the present study do not support the hypothesis that tacrolimus may be useful as a drug stimulating bone formation in skeletal diseases.

Rosmarinic and Sinapic Acids May Increase the Content of Reduced Glutathione in the Lenses of Estrogen-Deficient Rats.

Oxidative stress is believed to be associated with both postmenopausal disorders and cataract development. Previously, we have demonstrated that rosmarinic and sinapic acids, which are diet-derived antioxidative phenolic acids, counteracted some disorders induced by estrogen deficiency. Other studies have shown that some phenolic acids may reduce cataract development in various animal models. However, there is no data on the effect of phenolic acids on oxidative stress markers in the lenses of estrogen-deficient rats. The study aimed to investigate whether administration of rosmarinic acid and sinapic acid affects the antioxidative abilities and oxidative damage parameters in the lenses of estrogen-deficient rats. The study was conducted on three-month-old female Wistar rats. The ovariectomized rats were orally treated with rosmarinic acid at doses of 10 and 50 mg/kg or sinapic acid at doses of 5 and 25 mg/kg, for 4 weeks. The content of reduced glutathione (GSH), oxidized glutathione and amyloid ß1-42, as well as products of protein and lipid oxidation, were assessed. Moreover, the activities of superoxide dismutase, catalase, and some glutathione-related enzymes in the lenses were determined. Rosmarinic and sinapic acids in both doses resulted in an increase in the GSH content and glutathione reductase activity. They also improved parameters connected with protein oxidation. Since GSH plays an important role in maintaining the lens transparency, the increase in GSH content in lenses after the use of rosmarinic and sinapic acids seems to be beneficial. Therefore, both the investigated dietary compounds may be helpful in preventing cataract.

Effect of Rosmarinic Acid on the Serum Parameters of Glucose and Lipid Metabolism and Oxidative Stress in Estrogen-Deficient Rats.

Rosmarinic acid is found in medicinal and spice plants such as rosemary, lemon balm, and mint. The aim of the study was to investigate the effect of rosmarinic acid on parameters of glucose and lipid metabolism and parameters of oxidative stress in rats in the early phase of estrogen deficiency. The study was carried out on mature female Wistar rats divided into the following groups: sham-operated control rats, ovariectomized control rats, and ovariectomized rats treated orally with rosmarinic acid at a dose of 10 mg/kg or 50 mg/kg daily for 28 days. The concentration of sex hormones, parameters related to glucose and lipid metabolism as well as parameters of antioxidant abilities and oxidative damage were determined in the blood serum. In the ovariectomized control rats, the homeostasis model assessment of insulin resistance (HOMA-IR) index and cholesterol concentration increased, the superoxide dismutase activity increased, and the reduced glutathione concentration decreased. Administration of rosmarinic acid at both doses induced decreases in the fructosamine concentration and HOMA-IR, an increase in the concentration of reduced glutathione, and a decrease in the concentration of advanced oxidation protein products in ovariectomized rats. Moreover, rosmarinic acid at a dose of 50 mg/kg induced a decrease in the total cholesterol and triglyceride concentrations. The results indicate that rosmarinic acid may be useful in the prevention of metabolic disorders associated with estrogen deficiency, however further studies are necessary.

Effect of Rosmarinic Acid and Sinapic Acid on Oxidative Stress Parameters in the Cardiac Tissue and Serum of Type 2 Diabetic Female Rats.

Cardiovascular diseases are one of the most common complications of type 2 diabetes. They are considered the leading cause of death among diabetics. One of the mechanisms underlying diabetic cardiovascular complications is oxidative stress. Many phenolic acids are regarded as antioxidants. The aim of the study was to investigate the effect of rosmarinic acid (RA) and sinapic acid (SA) on oxidative stress parameters in the cardiac tissue and serum of type 2 diabetic female rats. Additionally, the effect of these compounds on glucose homeostasis and lipid profile in the serum was evaluated. Type 2 diabetes was induced with high-fat diet and streptozotocin. RA at the doses of 10 and 50 mg/kg and SA at the doses of 5 and 25 mg/kg were administrated orally for 28 days. Untreated diabetic rats exhibited unfavorable changes in glucose metabolism and lipid profile. Changes in the enzymatic and non-enzymatic markers indicated the onset of oxidative stress in these animals. The results showed that the higher doses of the tested phenolic acids-50 mg/kg of RA and 25 mg/kg of SA-revealed beneficial effects on oxidative stress in the cardiac tissue of diabetic rats.

Effect of caffeine on biomarkers of oxidative stress in lenses of rats with streptozotocin-induced diabetes.

INTRODUCTION: One of the major causes of cataract in diabetes is oxidative stress induced by reactive oxygen species (ROS). Nowadays, new substances with antioxidative properties that may prevent cataract development are needed. One such substance is caffeine - an alkaloid with well-documented antioxidative activity. MATERIAL AND METHODS: The study was conducted on lenses obtained from female rats, divided into 3 groups: control rats; diabetic rats; diabetic rats treated with caffeine at a dose of 20 mg/kg p.o. Type 1 diabetes was induced by streptozotocin (60 mg/kg i.p.). After 4 weeks of caffeine administration, the rats were sacrificed, and the lenses were collected, weighed and homogenized in PBS. The homogenate was used for analysis of protein content, glutathione (GSH) concentration, advanced oxidation protein product (AOPP) concentration, malondialdehyde (MDA) concentration and the activity of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx). RESULTS: The SOD, CAT and GPx activities were found to be higher in the lenses of diabetic rats. There were also increased MDA and AOPP concentrations as well as decreased GSH concentration. The administration of caffeine resulted in decreased activity of SOD, CAT and GPx. The treatment with caffeine also caused an increase of GSH concentration and a decrease of MDA and AOPP concentrations. CONCLUSIONS: The results of the present study may be of relevance in determining the effect of caffeine on the processes induced by ROS in vivo. Further, they can be an indication for clinical observations aiming at the assessment of both preventive and therapeutic effects of caffeine in cataract.

Antioxidative effect of flavonoid naringenin in the lenses of type 1 diabetic rats.

Oxidative stress arising during diabetes may lead to cataract formation. Thus, in order to prevent oxidative stress development, antioxidants could be considered helpful agents. Naringenin, a flavonoid with a well-documented antioxidative activity, can be found in many plant-derived products, especially citrus fruits. The aim of the study was to examine the effect of naringenin on oxidative stress markers in the lenses of type 1 diabetic rats. The study was conducted on 3-month-old male Wistar rats with streptozotocin-induced type 1 diabetes. The rats were treated orally with naringenin at the doses of 50 and 100 mg/kg for 4 weeks. In the lenses obtained from the animals, enzymatic and non-enzymatic parameters connected with oxidative stress were measured. The enzymatic parameters included superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and glucose-6-phosphate dehydrogenase activity. For non-enzymatic parameters, the total thiol groups, reduced and oxidized glutathione, protein carbonyl groups, advanced oxidation protein products, malondialdehyde and vitamin C level were assayed. Oral administration of naringenin counteracted most of the unfavorable changes induced by diabetes, including reduction of elevated antioxidative enzymes activity and amelioration of oxidative damage in proteins and lipids. Naringenin administered orally reduces oxidative stress markers in the lenses of type 1 diabetic rats.