Effect of spermine on lipid profile and HDL functionality in the streptozotocin-induced diabetic rat model

Serum levels of advanced glycation end products negatively correlates with activity of Paraoxonase1 and Lecithin-Cholesterol Acyltransferase in diabetic retinopathy; A cross-sectional case-control study

BACKGROUND

Development of diabetic retinopathy (DR) is closely linked to oxidative stress triggered by various metabolic pathways. Paraoxonase 1 (PON1) and Lecithin-Cholesterol Acyltransferase (LCAT) have protective roles in DR that remain poorly understood. Higher AGEs levels and its role in vascular complications of type 2 diabetes has been shown in previous studies. This case-control study aimed to assess LCAT and PON1 activity and their correlation with advanced glycation end products (AGEs) in patients with diabetes with or without retinopathy.

METHOD

45 healthy individuals and 88 diabetic patients were enrolled, categorized as No Diabetic Retinopathy (NDR), Non-Proliferative Diabetic Retinopathy (NPDR), and Proliferative Diabetic Retinopathy (PDR).

RESULTS

PON1 and LCAT activity conversely correlated with serum levels of advanced glycation end products in patients with diabetic retinopathy. There was not such a correlation in patients without DR nor in controls. The correlation was stronger between PON1 and AGEs in comparison to LCAT. PON1 activity was significantly lower in type 2 diabetes patients compared to healthy controls (45.39 ± 16.48 and 203.75 ± 8.92, respectively, P < 0.001). Activity further decreased in NPDR and PDR compared to NDR (23.99 ± 9.79 and 21.28 ± 8.22, respectively, P < 0.001). LCAT activity was significantly lower in diabetic patients compared to controls (33.16 ± 5.98 and 44.35 ± 2.26, respectively, P < 0.001). However, LCAT activity was not lower in diabetic retinopathy compared to NDR (P > 0.05).

CONCLUSION

Serum PON1 activity negatively correlated with AGEs levels in patients with diabetes but not in controls. The LCAT-AGEs correlation however was only significant in PDR patients. These findings emphasize the potential importance of AGES and PON1 in diabetic retinopathy development and progression.

Absorption, anti-inflammatory, antioxidant, and cardioprotective impacts of a novel fasting mimetic containing spermidine, nicotinamide, palmitoylethanolamide, and oleoylethanolamide: A pilot dose-escalation study in healthy young adult men

This pilot dose-escalation study evaluated the absorption and metabolism of a novel fasting mimetic formulation containing spermidine, nicotinamide, palmitoylethanolamide (PEA), and oleoylethanolamide (OEA) taken as oral supplements in young adults. Five healthy men consumed a standardized breakfast, followed by control (wheat flour) or low, medium, or high doses of supplements containing spermidine, nicotinamide, PEA, and OEA 2 hours later. Blood was drawn at 0, 1, 2, and 4 hours after the supplement (2, 3, 4, and 6 hours postprandial). Plasma concentrations of spermidine, 1-methylnicotinamide, PEA and OEA were quantified by liquid chromatography-mass spectrometry. The secretion of tumor necrosis factor alpha and production of reactive oxygen species by stimulated macrophages incubated with plasma, and cholesterol efflux capacity of plasma were analyzed. Plasma 1-methylnicotinamide, PEA, and OEA concentrations increased after supplement intake (P < .05). Spermidine concentrations decreased in the control arm (P < .05) but not the supplement arms. Net incremental area under the curve for tumor necrosis factor alpha and reactive oxygen species in stimulated macrophages decreased when incubated with plasma following supplement intake (P < .05). Intake of the combined supplements showed they were bioavailable and increased in plasma in a dose-dependent manner and provide preliminary data showing enhanced plasma anti-inflammatory and antioxidant functions. This trial was registered at clinicaltrials.gov (NCT05017428).

Protective effects of spermidine levels against cardiovascular risk factors: An exploration of causality based on a bi-directional Mendelian randomization analysis

The study investigated the causal relationships between spermidine levels and CVD risk factors using a bi-directional MR approach. Employing genetic variants from extensive GWAS datasets as IVs, the study aimed to determine whether spermidine levels can influence CVD risk factors such as blood pressure, blood glucose, and lipid profiles, and vice versa. The findings suggest a protective role of elevated spermidine levels against hypertension, elevated blood glucose, and lipid profiles (LDL-C and HDL-C). Specifically, increased spermidine levels were significantly associated with lower risk of hypertension (IVW beta = -0.0013453913, p = 0.01597648) and suppression risk of elevated blood glucose (IVW beta = -0.08061330, p = 0.02450205). Additionally, there was a notable association with lipid modulation, showing a decrease in LDL-C (IVW beta = -0.01849161, p = 0.01086728) and an increase in HDL-C (IVW beta = 0.0044608332, P = 0.01760051). Conversely, the influence of CVD risk factors on spermidine levels was minimal, with the exception that elevated blood glucose levels resulted in reduced spermidine levels. (IVW beta = -0.06714391, P = 0.01096123). These results underline the potential of spermidine as a modifiable dietary target for the prevention and management of cardiovascular diseases. Further investigations are warranted to explore the underlying biological mechanisms and the applicability of these findings in broader and diverse populations.

Inhibition and Mechanism of Protein Nonenzymatic Glycation by Lactobacillus fermentum

Lactobacillus fermentum (L. fermentum) was first evaluated as a potential advanced glycation end-product (AGE) formation inhibitor by establishing a bovine serum albumin (BSA) + glucose (glu) glycation model in the present study. The results showed that the highest inhibition rates of pentosidine and total fluorescent AGEs by L. fermentum were approximately 51.67% and 77.22%, respectively, which were higher than that of aminoguanidine (AG). Mechanistic analysis showed that L. fermentum could capture methylglyoxal and glyoxal, inhibit carbonyl and sulfhydryl oxidation, reduce the binding of glucose and amino groups, increase total phenolic content and antioxidant activity, and release intracellular substances to scavenge free radicals; these abilities were the basis of the antiglycation mechanism of L. fermentum. In addition, L. fermentum significantly prevented conformational changes in proteins during glycation, reduced protein cross-linking by 35.67%, and protected the intrinsic fluorophore. Therefore, the inhibition of L. fermentum on glycation mainly occurs through antioxidation, the capture of dicarbonyl compounds, and the protection of the BSA structure. These findings collectively suggest that Lactobacillus is an inhibitor of protein glycation and AGE formation and has the potential for nutraceutical applications.

Effects of soda water on blood lipid and metabolic profiling of urine in hyperlipidemia rats using UPLC/Triple-TOF MS

The effects of a natural soda water (Shi Han Quan, SHQ) on hyperlipidemia and the changes of urine metabolic profiling by metabolomics techniques were investigate. Thirty six Wistar rats weighing 160-200 g were divided into control group, hyperlipidemia (HL) group, and hyperlipidemia + SHQ water (SHQ) group. The metabolites in urine were determined using ultra high performance liquid chromatography-triple-time of flight-mass spectrometry (UPLC/Triple-TOF MS). At the end of 1 month and 3 months, the total glyceride (TG) level was significantly lower in SHQ group compared to HL group. There was no significantly difference in total cholesterol (TC) levels in HL group compared with SHQ group. The results showed that dinking SHQ water can improve the TG, but with no effects on TC. After drinking SHQ water for 3 months, the rats in different groups could be classified into different clusters according to the metabolites in urine. Total 15 important metabolites were found and correlated with disturbance of amino acid, phospholipid, fatty acid and vitamin metabolism, which suggested the changes of metabolism in the body and possible mechanism by which SHQ improved the TG. These findings provide a new insight for the prevention and control of hyperlipidemia.

Nanoformulation of Seaweed Eisenia bicyclis in Albumin Nanoparticles Targeting Cardiovascular Diseases: In Vitro and In Vivo Evaluation

Natural products, especially those derived from seaweeds, are starting to be seen as effective against various diseases, such as cardiovascular diseases (CVDs). This study aimed to design a novel oral formulation of bovine albumin serum nanoparticles (BSA NPs) loaded with an extract of Eisenia bicyclis and to validate its beneficial health effects, particularly targeting hypercholesterolemia and CVD prevention. Small and well-defined BSA NPs loaded with Eisenia bicyclis extract were successfully prepared exhibiting high encapsulation efficiency. Antioxidant activity and cholesterol biosynthesis enzyme 3-hydroxy-3 methylutaryl coenzyme A reductase (HMGR) inhibition, as well as reduction of cholesterol permeation in intestinal lining model cells, were assessed for the extract both in free and nanoformulated forms. The nanoformulation was more efficient than the free extract, particularly in terms of HMGR inhibition and cholesterol permeation reduction. In vitro cytotoxicity and in vivo assays in Wistar rats were performed to evaluate its safety and overall effects on metabolism. The results demonstrated that the Eisenia bicyclis extract and BSA NPs were not cytotoxic against human intestinal Caco-2 and liver HepG2 cells and were also safe after oral administration in the rat model. In addition, an innovative approach was adopted to compare the metabolomic profile of the serum from the animals involved in the in vivo assay, which showed the extract and nanoformulation's impact on CVD-associated key metabolites. Altogether, these preliminary results revealed that the seaweed extract and the nanoformulation may constitute an alternative natural dosage form which is safe and simple to produce, capable of reducing cholesterol levels, and consequently helpful in preventing hypercholesterolemia, the main risk factor of CVDs.

Role of Polyamines and Hypusine in β Cells and Diabetes Pathogenesis

The polyamines-putrescine, spermidine, and spermine-are polycationic, low molecular weight amines with cellular functions primarily related to mRNA translation and cell proliferation. Polyamines partly exert their effects via the hypusine pathway, wherein the polyamine spermidine provides the aminobutyl moiety to allow posttranslational modification of the translation factor eIF5A with the rare amino acid hypusine (hydroxy putrescine lysine). The "hypusinated" eIF5A (eIF5Ahyp) is considered to be the active form of the translation factor necessary for the translation of mRNAs associated with stress and inflammation. Recently, it has been demonstrated that activity of the polyamines-hypusine circuit in insulin-producing islet β cells contributes to diabetes pathogenesis under conditions of inflammation. Elevated levels of polyamines are reported in both exocrine and endocrine cells of the pancreas, which may contribute to endoplasmic reticulum stress, oxidative stress, inflammatory response, and autophagy. In this review, we have summarized the existing research on polyamine-hypusine metabolism in the context of β-cell function and diabetes pathogenesis.

Polyamines in mammalian pathophysiology

Polyamines (PAs) are essential organic polycations for cell viability along the whole phylogenetic scale. In mammals, they are involved in the most important physiological processes: cell proliferation and viability, nutrition, fertility, as well as nervous and immune systems. Consequently, altered polyamine metabolism is involved in a series of pathologies. Due to their pathophysiological importance, PA metabolism has evolved to be a very robust metabolic module, interconnected with the other essential metabolic modules for gene expression and cell proliferation/differentiation. Two different PA sources exist for animals: PA coming from diet and endogenous synthesis. In the first section of this work, the molecular characteristics of PAs are presented as determinant of their roles in living organisms. In a second section, the metabolic specificities of mammalian PA metabolism are reviewed, as well as some obscure aspects on it. This second section includes information on mammalian cell/tissue-dependent PA-related gene expression and information on crosstalk with the other mammalian metabolic modules. The third section presents a synthesis of the physiological processes described as modulated by PAs in humans and/or experimental animal models, the molecular bases of these regulatory mechanisms known so far, as well as the most important gaps of information, which explain why knowledge around the specific roles of PAs in human physiology is still considered a "mysterious" subject. In spite of its robustness, PA metabolism can be altered under different exogenous and/or endogenous circumstances so leading to the loss of homeostasis and, therefore, to the promotion of a pathology. The available information will be summarized in the fourth section of this review. The different sections of this review also point out the lesser-known aspects of the topic. Finally, future prospects to advance on these still obscure gaps of knowledge on the roles on PAs on human physiopathology are discussed.

Prevention of α-crystallin glycation and aggregation using l-lysine results in the inhibition of in vitro catalase heat-induced-aggregation and suppression of cataract formation in the diabetic rat

The principle role of α-crystallin is chaperoning activity that protect s other proteins against different stresses. High glucose concentration induces the osmotic stress and results in biomacromolecules glycation, which is subsequently cause their conformational and functional changes. Here, the roles of l-lysine (Lys) on the prevention of α-crystallin glycation in both in vitro and in vivo conditions are investigated. The catalase (CAT) activity was considered as a marker of α-crystallin functionality in both conditions. Streptozotocin-induced diabetic rats were treated with 0.1% of the Lys in drinking water. The purified α-crystallin was also incubated with glucose, in the presence or absence of the Lys and its structure-function was compared. The results showed that the visual cataract score was significantly lower in the diabetic rats treated with Lys. After Lys treatment, CAT, superoxide dismutase, aldose reductase and other biochemical parameters in the lens and serum of the diabetic rats returned to the normal value. Formation of the advanced glycation endproducts (AGEs), protein cross-linking, and the hydrophobicity of α-crystallin were changed due to glycation, but they were reversed by Lys treatment. The glycated α-crystallin lost its chaperone activity against heat denatured-CAT, but in the presence of Lys, it preserved its activity and prevented CAT aggregation. In conclusion, Lys treatment significantly inhibited the progression of diabetic cataract in rats. These effects were due to the Lys antiglycating and antioxidant effects, in addition to its protective effect against α-crystallin chaperoning activity.

Dietary and Gut Microbiota Polyamines in Obesity- and Age-Related Diseases

The polyamines putrescine, spermidine, and spermine are widely distributed polycationic compounds essential for cellular functions. Intracellular polyamine pools are tightly regulated by a complex regulatory mechanism involving de novo biosynthesis, catabolism, and transport across the plasma membrane. In mammals, both the production of polyamines and their uptake from the extracellular space are controlled by a set of proteins named antizymes and antizyme inhibitors. Dysregulation of polyamine levels has been implicated in a variety of human pathologies, especially cancer. Additionally, decreases in the intracellular and circulating polyamine levels during aging have been reported. The differences in the polyamine content existing among tissues are mainly due to the endogenous polyamine metabolism. In addition, a part of the tissue polyamines has its origin in the diet or their production by the intestinal microbiome. Emerging evidence has suggested that exogenous polyamines (either orally administrated or synthetized by the gut microbiota) are able to induce longevity in mice, and that spermidine supplementation exerts cardioprotective effects in animal models. Furthermore, the administration of either spermidine or spermine has been shown to be effective for improving glucose homeostasis and insulin sensitivity and reducing adiposity and hepatic fat accumulation in diet-induced obesity mouse models. The exogenous addition of agmatine, a cationic molecule produced through arginine decarboxylation by bacteria and plants, also exerts significant effects on glucose metabolism in obese models, as well as cardioprotective effects. In this review, we will discuss some aspects of polyamine metabolism and transport, how diet can affect circulating and local polyamine levels, and how the modulation of either polyamine intake or polyamine production by gut microbiota can be used for potential therapeutic purposes.

Efficacy of a Methanolic Extract of Adansonia digitata Leaf in Alleviating Hyperglycemia, Hyperlipidemia, and Oxidative Stress of Diabetic Rats

Traditionally, in many countries, various parts of the Adansonia digitata (A. digitata) tree have been used in the treatment of many clinical ailments including diarrhea and dysentery. The phytochemical screening has indicated that the leaf extract of A. digitata contains flavonoids, saponins, mucilage, steroids, and alkaloids. Thus, this paper aims to evaluate the hyperglycaemic and hypolipidaemic effects of methanolic extract of A. digitata leaves (200 mg/kg and 400 mg/kg) in diabetic rats. The extract was administered orally for six weeks in the streptozotocin (STZ)-induced diabetic rats. The treatment with the extract caused a significant reduction in the blood glucose, glycosylated hemoglobin, cholesterol, triglycerides, low-density lipoprotein (LDL), interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-α), and malondialdehyde (MDA) levels by 46.7%, 46.15%, 48.91%, 43%, 60%, 66%, 45.45%, and 30.4%, respectively, as compared to the diabetic group after the sixth week of treatment. The leaf extract also mitigated the decline of high-density lipoprotein (HDL) level, RBCs count, hemoglobin level, packed cell volume (PCV %), and erythropoietin concentration in diabetic rats by 31%, 33.25%, 24.72%, 51.42%, and 220.68% with respect to the diabetic group. Also, the extract maintained the level of antioxidant enzymes, catalase (CAT) and superoxide dismutase (SOD), and reduced glutathione (GSH) in the diabetic rats. It also reduced the elevation in the white blood corpuscles (WBC) count in the STZ-induced diabetic rats. Our study, therefore, indicates that methanolic extract of A. digitata leaf exerts strong antidiabetic and hypolipidaemic properties in a dose-dependent manner by improving the hematological properties and redox parameters in the experimental diabetic rats.

Dietary methionine increased the lipid accumulation in juvenile tiger puffer Takifugu rubripes

Methionine (Met) is one of the most important amino acids in fish feed. The effects of dietary Met on lipid deposition in fish varied a lot among different studies. The present study was aimed at investigating the effects of dietary Met supplementation on the lipid accumulation in tiger puffer, which have a unique lipid storage pattern. Crystalline L-Met was supplemented to a low-fishmeal control diet to obtain two experimental diets with a low (1.1% of dry weight, L-MET) or high Met level (1.6% of dry weight, H-MET). A 67-day feeding trial was conducted with juvenile tiger puffer (average initial weight, 13.83 g). Each diet was fed to triplicate tanks (30 fish in each tank). The results showed that the total lipid contents in whole-body and liver significantly increased with increasing dietary Met levels. The hepatosomatic index, weight gain, and total bile acid content in serum showed similar patterns in response to dietary Met treatments, while the lipid content in muscle was not affected. The hepatic contents of 18-carbon fatty acids were elevated by dietary Met supplementation. The Hepatic mRNA expression of lipogenetic gene such as FAS, GPAT, PPARγ, ACLY, and SCD1 was down-regulated, while the gene expression of lipolytic genes ACOX1 and HSL, as well as that of ApoB100, were up-regulated by increasing dietary Met levels. The hepatic lipidomics of experimental fish was also analyzed. In conclusion, increasing dietary Met levels (0.61%, 1.10%, and 1.60%) increased the hepatic lipid accumulation in tiger puffer. The mechanisms involved warrant further studies.

Advanced glycation endproducts in food and their effects on health

Advanced glycation endproducts (AGEs) form by Maillard-reactions after initial binding of aldehydes with amines or amides in heated foods or in living organisms. The mechanisms of formation may include ionic as well as oxidative and radical pathways. The reactions may proceed within proteins to form high-molecular weight (HMW) AGEs or among small molecules to form low-molecular weight (LMW) AGEs. All free amino acids form AGEs, but lysine or arginine side chains dominate AGE formation within proteins. The analysis of AGEs in foods and body fluids is most often performed by ELISA or LC-MS; however, none of the methodologies cover all HMW and LMW AGEs. Most research is, therefore, carried out using 'representative' AGE compounds, most often N(ε)-carboxymethyl-lysine (CML). Only LMW AGEs, including peptide-bound forms, and carbonyls may be absorbed from the gut and contribute to the body burden of AGEs. Some AGEs interact with specific pro- or anti-inflammatory receptors. Most studies on the biological effects of AGEs have been carried out by administering heated foods. The pro-inflammatory and deteriorating biological effects of AGEs in these studies, therefore, need further confirmation. The current review points out several research needs in order to address important questions on AGEs in foods and health.

Effect of crocin on the insulin resistance and lipid profile of streptozotocin-induced diabetic rats

Crocin is the only water soluble carotenoid in nature, and it has a known powerful antioxidant activity. The aim of this work was to investigate the hypoglycemic and hypolipidemic effects of crocin in streptozotocin (STZ)-induced type 2 diabetic rats. Neonatal male Wistar rats (2-5 days old) were randomly divided into five groups. Three groups were intraperitoneally injected with STZ (90 mg/kg body weight). Among them, two groups were treated with intraperitoneal injection of crocin (50 or 100 mg/kg), and the third group was treated with vehicle only. Two control groups were also considered, and one of them was treated with crocin. After 5 months, their blood and urine samples were collected, and the animals were sacrified. The results indicate a significant lower body weight (P < 0.001) and abnormal parameters in the diabetic rats compared with the normal group. An administration of both doses of crocin significantly decreased the levels of serum glucose, advanced glycation end products, triglyceride, total cholesterol, and low-density lipoprotein and increased the high-density lipoprotein in the diabetic rats. The treatments were also effective in decreasing HbA1c and microalbuminuria, as well as homeostatic model assessment for insulin resistance as a measure of insulin resistance in the diabetic rats.

Aldehyde and xanthine oxidase activities in tissues of streptozotocin-induced diabetic rats: effects of vitamin E and selenium supplementation

Effects of vitamin E and selenium supplementation on aldehyde oxidase (AO) and xanthine oxidase (XO) activities and antioxidant status in liver, kidney, and heart of streptozotocin (STZ)-induced diabetic rats were examined. AO and XO activities increased significantly after induction of diabetes in rats. Following oral vitamin E (300 mg/kg) and sodium selenite (0.5 mg/kg) intake once a day for 4 weeks, XO activity decreased significantly. AO activity decreased significantly in liver, but remained unchanged in kidney and heart of vitamin E- and selenium-treated rats compared to the diabetic rats. Total antioxidants status, paraoxonase-1 (PON1) and erythrocyte superoxide dismutase activities significantly decreased in the diabetic rats compared to the controls, while a higher fasting plasma glucose level was observed in the diabetic animals. The glutathione peroxidase activity remained statistically unchanged. Malondialdehyde and oxidized low-density lipoprotein levels were higher in the diabetic animals; however, these values were significantly reduced following vitamin E and selenium supplementation. In summary, both AO and XO activities increase in STZ-induced diabetic rats, and vitamin E and selenium supplementation can reduce these activities. The results also indicate that administration of vitamin E and selenium has hypolipidemic, hypoglycemic, and antioxidative effects. It decreases tissue damages in diabetic rats, too.

Protective effects of beta glucan and gliclazide on brain tissue and sciatic nerve of diabetic rats induced by streptozosin

There have not been yet enough studies about effects of beta glucan and gliclazide on oxidative stress created by streptozotocin in the brain and sciatic nerve of diabetic rats. The aim of this paper was to investigate the antioxidant effects of gliclazide and beta glucan on oxidative stress and lipid peroxidation created by streptozotosin in brain and sciatic nerve. Total of 42 rats were divided into 6 groups including control, diabetic untreated (DM) (only STZ, diabetic), STZ (DM) + beta glucan, STZ (DM) + gliclazide, only beta glucan treated (no diabetic), and only gliclazide treated (no diabetic). The brain and sciatic nerve tissue samples were analyzed for malondialdehyde (MDA), total oxidant status (TOS), total antioxidant status (TAS), oxidative stress index (OSI), and paraoxonase (PON-1) levels. We found a significant increase in MDA, TOS, and OSI along with a reduction in TAS level, catalase, and PON-1 activities in brain and sciatic nerve of streptozotocin-induced diabetic rats. Also, this study shows that in terms of these parameters both gliclazide and beta glucan have a neuroprotective effect on the brain and sciatic nerve of the streptozotocin-induced diabetic rat. Our conclusion was that gliclazide and beta glucan have antioxidant effects on the brain and sciatic nerve of the streptozotocin-induced diabetic rat.

Effect of chemical chaperones on glucose-induced lysozyme modifications

Nonenzymatic glycation of biomacromolecules occurs due to the diabetes mellitus and ageing. A number of small molecules, known as chemical chaperones, stabilize protein conformation against thermal and chemically induced denaturation. These compounds are including: polyamines (e.g. spermine and spermidine), amino acids (e.g. lysine) and polyols (e.g. glycerol). In this study the effect of spermidine (Spd), spermine (Spm), and glycerol on glycation, structure and function of lysozyme (LZ), as an extra-cellular protein, by different techniques is investigated. LZ is incubated with or without glucose (50 or 100 mM) in the absence or presence of Spd/Spm/glycerol at 37 °C up to 16 weeks. All the observed changes of glycated-LZ in comparison with the native protein, including: increased fluorescence emission, alteration in the secondary and tertiary structure, and reduced electrophoretic mobility- indicate its structural changes that are accompanied with its reduced activity. Glucose in the presence or absence of Spd induces the protein dimerization, but glucose plus Spm induces its trimmerization. In contrast, glycerol inhibits the LZ glycation and prevents the large changes on its structure and function. Glucose binds lysine residues, decreases the protein positive charges and induces some alterations in its structure and activity. Polyamines also directly bind to LZ, increase its positive charges and hence induce more glycation; more conformational changes, oligomerization and its inactivation in the presence of glucose, but glycerol affect the protein environment and preserve protein from these harmful effects.

Ellagic acid attenuates oxidative stress on brain and sciatic nerve and improves histopathology of brain in streptozotocin-induced diabetic rats

The aim of this study was to investigate the possible effects of ellagic acid in brain and sciatic nerve tissues of diabetic rats. Also, the impact of ellagic acid on catalase and paraoxonase (PON-1) activities, total antioxidant status (TAS), total oxidant status (TOS), oxidative stress index (OSI), malondialdehyde (MDA) and nitric oxide (NO) were examined. The rats were randomly divided into four groups, with eight rats each: Normal controls (not diabetic), only ellagic acid treated (ellagic acid controls, not diabetic), Diabetic controls (streptozotocin, diabetic), ellagic acid-treated diabetic (streptozotocin + ellagic acid). After a 4 week experiment, rats were sacrificed, and biomarkers for oxidative stress in the brain and sciatic nerve tissues of the rats were measured. There was significant depletion in the PON-1, catalase, and TAS levels in the brain and sciatic nerve tissues compared to the control groups (for both parameters, p<0.05). The values of catalase, PON-1 and TAS reversed back to normal levels in ellagic acid-treated diabetic rats compared to untreated diabetic rats (for both parameters, p<0.05). The levels of MDA, TOS, NO and, OSI in the brain and sciatic nerve tissues were higher in untreated diabetic rats compared to control group (for both parameters p<0.05). However, MDA, TOS, OSI, and NO levels were found to be significantly reduced in the ellagic acid-treated diabetic group compared to the untreated diabetic group in these tissues (for both parameters, p<0.05). In conclusion, the results of the present study suggested that ellagic acid exhibits neuroprotective effects against oxidative damage in diabetic rats.

Effect of vitamin e and selenium supplement on paraoxonase-1 activity, oxidized low density lipoprotein and antioxidant defense in diabetic rats

INTRODUCTION

The aim of the present study was to assess the effects of vitamin E and selenium supplementation on serum paraoxonase (PON1) activity, lipid peroxidation and antioxidant defense in streptozotocin-induced diabetic rats.

METHODS

Thirty two female Sprague Dawley rats were divided into 3 groups: the control group (n=8) received a standard diet; streptozotocin (STZ)-induced diabetic rats (n=12), received corn oil and physiological solution; and vitamin E and selenium supplemented diabetic rats (n=12) were treated with oral administration of vitamin E (300 mg/kg) and sodium selenite (0.5 mg/kg) once a day for 4 weeks.

RESULTS

Significantly lower total antioxidant status (TAS), PON1and erythrocyte SOD activities and a higher fasting plasma glucose level were observed in the diabetic rats compared to the control. A significant increase in SOD and GPX activities in vitamin E and selenium supplemented diabetic group was observed after 5 weeks of the experiment. Compared to the normal rats, malondialdehyde (MDA) and oxidized LDL (Ox-LDL) levels were higher in the diabetic animals; however, these values reduced significantly following vitamin E and selenium supplementation.

CONCLUSION

Vitamin E and selenium supplementation in diabetic rats has hypolipidemic, hypoglycemic and antioxidative effects and may slow down the progression of diabetic complications through its protective effect on PON1 activity and lipoproteins oxidation.

The effect of hot-tub therapy on serum Hsp70 level and its benefit on diabetic rats: a preliminary report

PURPOSE

To carry out a preliminary study examining the efficacy of long-term hot-tub therapy (HTT) in the improvement of diabetic complications on streptozotocin-induced diabetic rats.

MATERIALS AND METHODS

Male Wistar rats were immersed mid-sternum in a circulating water bath (42 degrees C for 30 min) to obtain a core body temperature of 41 degrees C; this process was repeated three times a week for 5 months. The blood was collected every month. Multiple parameters were examined for all rats including heat shock protein (Hsp70) level, serum glucose and insulin concentrations, advanced glycation end product (AGE) and glycated haemoglobin (HbA1c) formation, lipid profile and antioxidant defence system. Additionally, the chaperoning capacity of glycated Hsp70 was evaluated based on in vitro studies in which the refolding of denatured luciferase was compared to refolding by native Hsp70.

RESULTS

HTT-treated diabetic rats showed a significant improvement in lipid profile, antioxidant capacity, insulin secretion and serum Hsp70 level and a significant decrease in AGE formation compared to the untreated diabetic rats. However, HTT had a borderline significant effect on weight and fasting blood glucose. Glycated Hsp70 lost its chaperoning ability to reactivate the denatured luciferase.

CONCLUSION

A decrease in complications in diabetic rats after hot-tub therapy is shown here. An increase in the extracellular Hsp70 level due to HTT was observed. This increase may serve to protect the structure of proteins (e.g. preventing AGE formation), and the observed beneficial effects may be related to it.