Implications of oxidative stress in high sucrose low magnesium diet fed rats

STUDIES OF MAGNESIUM AND PHOSPHORUS COMBINED MEDICATION BASED ON CASEIN

Aim. The Department of Biochemistry and Physiology of Animals, named after Academician Guly NUBIP of Ukraine, developed magnesium and phosphorus combined medication based on casein. Our aim was to test its bioavailability based on the ability to be hydrolyzed by a mixture of pancreatic digestive enzymes trypsin and chymotrypsin, also check the absence of cytotoxic effects on cell cultures. Methods. To assess bioavailability, we used hydrolysis of the medication with a mixture of trypsin and chymotrypsin, followed by detection of hydrolysis products by polyacrylamide gel electrophoresis. A standard MTT-test performed on both MT-4 and Namalva cell lines was used to assess cytotoxic effects. Results. Based on electrophoresis data, it was found that despite chemical modifications of the natural casein, the medication based on it is characterized by a high ability to hydrolyze by digestive enzymes under the same conditions as casein. Also, an MTT-test demonstrates that the medication has no cytotoxic properties against cell lines MT-4 and Namalva. Conclusions. Since the negative effects of the drug associated with its digestibility and toxicity have not been observed, it is recommended to continue the study of its effects on living organisms.

Dietary supplementation with magnesium citrate may improve pancreatic metabolic indices in an alloxan-induced diabetes rat model

The purpose of the current study was to evaluate the protective properties of dietary magnesium supplementation on pancreatic tissue of rats with alloxan-induced diabetes mellitus. Twenty-five male Wistar rats were split into five groups (control, diabetes, diabetes with 100 mg Mg daily, diabetes with 250 mg Mg daily, diabetes with 500 mg Mg daily) with feeding supplementation starting on day 1, diabetes induction on day 21, and animal sacrifice on day 30. Fasting glucose in blood serum was measured on days 21, 25, 27, and day 30. Glucose metabolism enzymes, namely, lactate dehydrogenase and glucose-6-phosphate dehydrogenase, were measured in pancreatic tissue upon the sacrifice, as well as lipid peroxidation, antioxidant system protective enzymes (catalase and superoxide dismutase), and glutathione system components (glutathione reductase, glutathione peroxidase, and glutathione reduced). Pearson correlation coefficients showed strong negative correlation between serum glucose (control and diabetic animals) and glucose metabolism enzymes, catalase, superoxide dismutase, glutathione peroxidase in pancreatic tissue (r >-0.9, p <0.05), moderate negative correlation with reduced glutathione (r = -0.79, p <0.05), moderate positive correlation with lipid peroxidation index (r = +0.67, p <0.05), weak correlation with glutathione reductase (r = -0.57, p <0.05). Magnesium supplementation slowed down diabetes onset considering fasting glucose levels in rats (p <0.05), as well as partially restored investigated dehydrogenase levels in the pancreas of rats comparing to diabetes group (p <0.05). The lipid peroxidation index varied between treatments showing the dose-dependent influence of Mg2+. Magnesium supplementation partially restored catalase and superoxide dismutase activities in pancreatic tissue, as well as glutathione peroxidase and reduced glutathione levels (p <0.05), while glutathione reductase levels remained unaffected (p >0.05). The obtained results suggested a model, where magnesium ions may have a possible protective effect on pancreatic tissue against the negative influence of alloxan inside β cells of the pancreas.

Serum magnesium levels and risk of coronary artery disease: Mendelian randomisation study

BACKGROUND

Observational studies have shown that serum magnesium levels are inversely associated with risk of cardiovascular disease, but whether this association is causal is unknown. We conducted a Mendelian randomisation study to investigate whether serum magnesium levels may be causally associated with coronary artery disease (CAD).

METHODS

This Mendelian randomisation analysis is based on summary-level data from the CARDIoGRAMplusC4D consortium's 1000 Genomes-based genome-wide association meta-analysis of 48 studies with a total of 60,801 CAD cases and 123,504 non-cases. Six single-nucleotide polymorphisms associated with serum magnesium levels at genome-wide significance were used as instrumental variables.

RESULTS

A genetic predisposition to higher serum magnesium levels was inversely associated with CAD. In conventional Mendelian randomisation analysis, the odds ratio of CAD was 0.88 (95% confidence interval [CI] 0.78 to 0.99; P = 0.03) per 0.1-mmol/L (about 1 standard deviation) increase in genetically predicted serum magnesium levels. Results were consistent in sensitivity analyses using the weighted median and heterogeneity-penalised model averaging methods, with odds ratios of 0.84 (95% CI 0.72 to 0.98; P = 0.03) and 0.83 (95% CI 0.71 to 0.96; P = 0.02), respectively.

CONCLUSIONS

This study based on genetics provides evidence that serum magnesium levels are inversely associated with risk of CAD. Randomised controlled trials elucidating whether magnesium supplementation lowers the risk of CAD, preferably in a setting at higher risk of hypomagnesaemia, are warranted.

A novel mechanism underlies atrazine toxicity in quails (Coturnix Coturnix coturnix): triggering ionic disorder via disruption of ATPases

The widely used atrazine has been reported to exhibit extensive ecological hazards. Due to the biological accumulation, atrazine elicits widespread toxic effects on different organisms. However, true proof for the mechanism of atrazine-induced toxicity is lacking. To determine the potential mechanism by which atrazine exerted toxic effects, quails were treated with atrazine (0, 50, 250 and 500 mg/kg) by gavage administration for 45 days. Atrazine significantly increased the histological alterations and serum creatine kinase, lactate dehydrogenase and choline esterase levels. A marked disorder in ionic (Na+, K+, Ca2+ and Mg2+)contents and the decrease of ATPases (Na+-K+-ATPase, Ca2+-ATPase, Mg2+-ATPase and Ca2+-Mg2+-ATPase) activities were observed in the heart and liver of atrazine-exposed quails. Of note, it was also observed that atrazine suppressed the transcription of Na+, K+ transfer associated genes (Na+-K+-ATPase subunits) and Ca2+ transfer associated genes (Ca2+-ATPase subunits, solute carriers) in heart and liver. In conclusion, atrazine induced cardiac and hepatic damage via causing the ionic disorder, triggering the transcription of the ion transporters and leading the histopathological and functional alternations in the heart and liver of quails. This study demonstrated atrazine significantly induced the ionic disorder via decreasing the ATPases activities and disturbing the transcription of the ion transporters.

Evaluation of lipid peroxidation and antioxidant defense mechanisms in the bone of rats in conditions of separate and combined administration of vanadium (V) and magnesium (Mg)

The impact of vanadium (V) and magnesium (Mg) applied as sodium metavanadate (SMV, 0.125 mg V/ml) and magnesium sulfate (MS, 0.06 mg Mg/ml) on oxidative stress markers in bone of male Wistar rats was investigated. Some of them were also measured in the liver, e.g. l-ascorbic acid (hepatic L-AA). Additionally, relationships between selected indices determined in bone were examined. SMV alone (Group II) did not significantly alter the level of TBARS and the activity of SOD, compared with the control (Group I), but it slightly reduced the GR activity (by 13%) and the L-AA level (by 15.5%). It also markedly lowered the activity of CAT and GPx (by 34% and 29%), and to some degree elevated the activity of GST (by 16%) and the hepatic L-AA level (by 119%). MS alone (Group III) decreased the TBARS level (by 49%), slightly lowered the L-AA concentration (by 14%), and reduced the SOD, GPx, and GR activities (by 31%, 40%, and 28%), but did not change the activity of CAT, compared with the control. Additionally, it elevated the GST activity (by 56%) and the hepatic L-AA level (by 40%). In turn, the SMV + MS combination (Group IV) reduced the TBARS level (by 38%) and the SOD, CAT, GPx, and GR activities (by 61%, 58%, 72%, and 40%) but elevated the GST activity (by 66%), compared with the control. The activity of SOD and GPx in the rats in Group IV was also reduced, compared with Group II (by 61% and 61%) and Group III (by 44% and 54%). In turn, the activities of CAT and GR were decreased, compared with Group III (by 55%) and Group II (by 31%), and the L-AA level was lowered, in comparison with Groups II and III (by 53% and 54%). Further, the concentration of V in the bone of rats in Groups II and IV increased, whereas the concentration of Mg decreased, compared with Groups I and III, in which the V and Mg levels dropped and were not altered, respectively, compared with Group I. The total content of Fe in the bone of rats in Groups II and IV increased, compared with Group III, in which the total Fe content did not change, compared with Group I. In turn, the total bone Cu content significantly decreased in the rats in Groups III and IV, compared with Groups I and II, whereas the total Zn content and the Ca concentration did not change markedly. The results provided evidence that the concentration of V used as SMV did not enhance LPO in bone, whereas Mg, at the selected level, markedly reduced LPO in this tissue. On the other hand, both elements administered separately and in combination disrupted the antioxidant defense mechanisms and homeostasis of some metals in bone tissue, which consequently may have contributed to disturbances in the balance in the activities of osteoblastic and osteoclastic cells, and thereby negatively affected bone health.

Feeding on ripening and over-ripening fruit: interactions between sugar, ethanol and polyphenol contents in a tropical butterfly

In ripe fruit, energy mostly derives from sugar, while in over-ripe fruit, it also comes from ethanol. Such ripeness differences may alter the fitness benefits associated with frugivory if animals are unable to degrade ethanol when consuming over-ripe fruit. In the tropical butterfly Bicyclus anynana, we found that females consuming isocaloric solutions mimicking ripe (20% sucrose) and over-ripe fruit (10% sucrose, 7% ethanol) of the palm Astrocaryum standleyanum exhibited higher fecundity than females consuming a solution mimicking unripe fruit (10% sucrose). Moreover, relative to butterflies consuming a solution mimicking unripe fruit, survival was enhanced when butterflies consumed a solution mimicking either ripe fruit supplemented with polyphenols (fruit antioxidant compounds) or over-ripe fruit devoid of polyphenols. This suggests that (1) butterflies have evolved tolerance mechanisms to derive the same reproductive benefits from ethanol and sugar, and (2) polyphenols may regulate the allocation of sugar and ethanol to maintenance mechanisms. However, variation in fitness owing to the composition of feeding solutions was not paralleled by corresponding physiological changes (alcohol dehydrogenase activity, oxidative status) in butterflies. The fitness proxies and physiological parameters that we measured therefore appear to reflect distinct biological pathways. Overall, our results highlight that the energy content of fruit primarily affects the fecundity of B. anynana butterflies, while the effects of fruit consumption on survival are more complex and vary depending on ripening stage and polyphenol presence. The actual underlying physiological mechanisms linking fruit ripeness and fitness components remain to be clarified.

Neuroprotective Effect of Magnesium Acetyltaurate Against NMDA-Induced Excitotoxicity in Rat Retina

Glutamate excitotoxicity plays a major role in the loss of retinal ganglion cells (RGCs) in glaucoma. The toxic effects of glutamate on RGCs are mediated by the overstimulation of N-methyl-D-aspartate (NMDA) receptors. Accordingly, NMDA receptor antagonists have been suggested to inhibit excitotoxicity in RGCs and delay the progression and visual loss in glaucoma patients. The purpose of the present study was to examine the potential neuroprotective effect of Mg acetyltaurate (MgAT) on RGC death induced by NMDA. MgAT was proposed mainly due to the combination of magnesium (Mg) and taurine which may provide neuroprotection by dual mechanisms of action, i.e., inhibition of NMDA receptors and antioxidant effects. Rats were divided into 5 groups and were given intravitreal injections. Group 1 (PBS group) was injected with vehicle; group 2 (NMDA group) was injected with NMDA while groups 3 (pre-), 4 (co-), and 5 (post-) treatments were injected with MgAT, 24 h before, in combination or 24 h after NMDA injection respectively. NMDA and MgAT were injected in PBS at doses 160 and 320 nmol, respectively. Seven days after intravitreal injection, the histological changes in the retina were evaluated using hematoxylin & eosin (H&E) staining. Optic nerves were dissected and stained in Toluidine blue for grading on morphological neurodegenerative changes. The extent of apoptosis in retinal tissue was assessed by TUNEL assay and caspase-3 immunohistochemistry staining. The estimation of neurotrophic factor, oxidative stress, pro/anti-apoptotic factors and caspase-3 activity in retina was done using enzyme-linked immunosorbent assay (ELISA) technique. The retinal morphometry showed reduced thickness of ganglion cell layer (GCL) and reduction in the number of retinal cells in GCL in NMDA group compared to the MgAT-treated groups. TUNEL and caspase-3 staining showed increased number of apoptotic cells in inner retina. The results were further corroborated by the estimation of neurotrophic factor, oxidative stress, pro/anti-apoptotic factors, and caspase-3 activity in retina. In conclusion, current study revealed that intravitreal MgAT prevents retinal and optic nerve damage induced by NMDA. Overall, our data demonstrated that the pretreatment with MgAT was more effective than co- and posttreatment. This protective effect of MgAT against NMDA-induced retinal cell apoptosis could be attributed to the reduction of retinal oxidative stress and activation of BDNF-related neuroprotective mechanisms.

Risk of postprandial insulin resistance: the liver/vagus rapport

Ingestion of a meal is the greatest challenge faced by glucose homeostasis. The surge of nutrients has to be disposed quickly, as high concentrations in the bloodstream may have pathophysiological effects, and also properly, as misplaced reserves may induce problems in affected tissues. Thus, loss of the ability to adequately dispose of ingested nutrients can be expected to lead to glucose intolerance, and favor the development of pathologies. Achieving interplay of several organs is of upmost importance to maintain effectively postprandial glucose clearance, with the liver being responsible of orchestrating global glycemic control. This dogmatic role of the liver in postprandial insulin sensitivity is tightly associated with the vagus nerve. Herein, we uncover the behaviour of metabolic pathways determined by hepatic parasympathetic function status, in physiology and in pathophysiology. Likewise, the inquiry expands to address the impact of a modern lifestyle, especially one's feeding habits, on the hepatic parasympathetic nerve control of glucose metabolism.

Natural plant products and extracts that reduce immunoexcitotoxicity-associated neurodegeneration and promote repair within the central nervous system

Our understanding of the pathophysiological and biochemical basis of a number of neurological disorders has increased enormously over the last three decades. Parallel with this growth of knowledge has been a clearer understanding of the mechanism by which a number of naturally occurring plant extracts, as well as whole plants, can affect these mechanisms so as to offer protection against injury and promote healing of neurological tissues. Curcumin, quercetin, green tea catechins, balcalein, and luteolin have been extensively studied, and they demonstrate important effects on cell signaling that go far beyond their antioxidant effects. Of particular interest is the effect of these compounds on immunoexcitotoxicity, which, the authors suggest, is a common mechanism in a number of neurological disorders. By suppressing or affecting microglial activation states as well as the excitotoxic cascade and inflammatory mediators, these compounds dramatically affect the pathophysiology of central nervous system disorders and promote the release and generation of neurotrophic factors essential for central nervous system healing. We discuss the various aspects of these processes and suggest future directions for study.

The relation between hypomagnesaemia and vascular stiffness in renal transplant recipients

BACKGROUND

Arterial stiffness is a strong predictor of outcome. Hypomagnesaemia, by its association with arterial hypertension, endothelial dysfunction, dyslipidaemia and inflammation, might affect vascular stiffness. As hypomagnesaemia is common in renal transplant recipients (RTR), we examined its potential association with arterial stiffness.

METHODS

Cross-sectional analysis. Evaluation of vascular stiffness in 512 RTR from two university centres at a median of 72 months post-transplantation. Determination of carotid-femoral pulse wave velocity (PWV) (SphygmoCor). A multiple linear regression analysis was used to investigate the independent relationship between magnesium serum level and PWV with the following covariates: age, diabetes, smoking status, body mass index, blood pressure, heart rate (HR), C-reactive protein (CRP), high-density lipoprotein cholesterol, parathyroid hormone and use of angiotensin-converting enzyme inhibitors/angiotensin receptor blockers, diuretics, calcium channel blockers, statins and calcineurin inhibitors next to their drug levels.

RESULTS

Lower serum magnesium was independently associated with PWV (P = 0.018) in addition to age, CRP, HR, diabetes and mean arterial pressure (model R(2) = 0.45; P < 0.001). The relationship between magnesium and PWV was attenuated (P = 0.054) after adjustment for the use of sirolimus, which was associated with higher magnesium levels (P<0.001) and lower PWV (P = 0.013). In patients >55 years (median age), however (low), magnesium remained an independent predictor of PWV (P = 0.024) after accounting for the same covariates.

CONCLUSIONS

Serum magnesium is an independent predictor of arterial stiffness in RTR, especially in patients >55 years.

Magnesium, inflammation, and obesity in chronic disease

About 60% of adults in the United States do not consume the estimated average requirement for magnesium, but widespread pathological conditions attributed to magnesium deficiency have not been reported. Nevertheless, low magnesium status has been associated with numerous pathological conditions characterized as having a chronic inflammatory stress component. In humans, deficient magnesium intakes are mostly marginal to moderate (approximately 50% to <100% of the recommended dietary allowance). Animal experiments indicate that signs of marginal-to-moderate magnesium deficiency can be compensated or exacerbated by other factors influencing inflammatory and oxidative stress; recent studies suggest a similar happening in humans. This suggestion may have significance in obesity, which is characterized as having a chronic low-grade inflammation component and an increased incidence of a low magnesium status. Marginal-to-moderate magnesium deficiency through exacerbating chronic inflammatory stress may be contributing significantly to the occurrence of chronic diseases such as atherosclerosis, hypertension, osteoporosis, diabetes mellitus, and cancer.

Enhanced renal accumulation of cisplatin via renal organic cation transporter deteriorates acute kidney injury in hypomagnesemic rats

BACKGROUND

This study aimed to explore the effects of hypomagnesemia on cisplatin (CDDP)-induced acute kidney injury (AKI) in rats and the relation of hypomagnesemia to the regulation of organic cation transporters and renal accumulation of CDDP.

METHODS

Sprague-Dawley rats were given an Mg-deficient diet starting 7 days before treatment with CDDP. CDDP was administered intravenously to rats in the normal Mg-diet group and Mg-deficient-diet group at 3 mg/kg via the left jugular vein. At the specified periods after injection of CDDP, the amount of platinum in blood and organ samples was determined using inductively coupled plasma-mass spectrometry. Protein expression levels of renal organic cation transporters were determined. Uptake of tetraethylammonium (TEA) bromide in renal slices of rats was measured.

RESULTS

Rats fed a Mg-deficient diet showed a significant body weight decrease and a marked decrease in serum Mg levels compared with control rats fed an adequate Mg diet. Serum blood urea nitrogen and creatinine levels were unaltered after CDDP treatment in control rats, whereas these levels were markedly elevated in hypomagnesemic rats. Immunoblotting revealed up-regulation of the organic cation transporter rOCT2 in hypomagnesemic rats before CDDP administration, but not of rOCT1 or rat multidrug and toxin-extrusion 1. TEA uptake by renal slices from hypomagnesemic rats was significantly higher compared with that of control rats. Renal accumulation of CDDP was markedly increased in hypomagnesemic rats.

CONCLUSION

These results suggest that hypomagnesemia could cause dehydration and up-regulation of rOCT2, enhancing renal accumulation of CDDP and the deterioration of AKI.