Aspartate modulates the circadian patterns of a few biochemical variables in Wistar rats

D-aspartate was used to demonstrate possible sources of excitatory input to the suprachiasmatic nucleus (SCN) in rats. Aspartate (50 mg/kg bodyweight) was orally administrated chronically for 60 days to Wistar rats and 24 h rhythmic patterns of glucose, cholesterol, total protein and aspartate transaminase (AST) were studied under light - dark (LD 12:12 h) cycle. Our results showed acrophase advances in glucose and delays in cholesterol and AST rhythms. Increased mesor and altered amplitude values were found in all rhythms; aspartate levels in the brain were found to be significantly increased in aspartate treated animals. We hypothesised that the altered biochemical rhythms in aspartate treated rats could be due to (1) modulation of neurotransmission in SCN, (2) behavioural rhythms and (3) feeding rhythms.     

Influence of N-phthaloyl gamma-aminobutyric acid on circadian rhythms of lipid peroxidation products and antioxidants

N-Phthaloyl GABA was administrated daily (50 mg/kg body weight-i.p) to Wistar rats for 21 days and circadian rhythms of thiobarbituric acid reactive substances (TBARS) and antioxidants such as reduced glutathione (GSH), catalase (CAT) and superoxide dismutase (SOD) were studied. N-Phthaloyl GABA was found to delay TBARS and to advance GSH, CAT and SOD acrophases. Amplitude and mesor values of these rhythms were found to be altered during N-Phthaloyl GABA treatment. Since GABA is hypothesized to be involved in conveying dark information to clock, exogenous administration of P-GABA might alter the photic information received by the clock. Our study shows that P-GABA administration alters the temporal patterns of lipid peroxidation and antioxidants in Wistar rats. But the exact mechanism remains to be explored and further research is needed.     

Temporal variations of lipid peroxidation products, antioxidants and liver marker enzymes in experimental hyperammonemic rats

Circadian variations of lipid peroxidation products: thiobarbituric acid and reactive substances (TBARS), antioxidants: reduced glutathione (GSH), superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT) and liver marker enzymes such as transaminases (aspartate transaminase (AST) and alanine transaminase (ALT), alkaline phosphatase (ALP) and γ-Glutamyl transpeptidase (GGT) in circulation were analysed in control and ammonium chloride (AC) induced (100 mg/kg bodyweight) hyperammonemic rats. Elevated lipid peroxidation and liver marker enzymes (increased mesor of TBARS, AST, ALT, ALP and GGT) associated with decreased activities of antioxidants (decreased mesor of GPx, GSH, SOD and CAT) were found in hyperammonemic rats. Variations in acrophase, amplitude and r values were also found in between the control and hyperammonemic rats. These alterations clearly indicate that temporal liver marker enzymes and redox status are modulated during hyperammonemic conditions, which may also play a crucial role in disease development.     

Effect of oral methionine on blood lipid peroxidation and antioxidants in alloxan-induced diabetic rats

Supplementation of thiol compounds has been suggested to protect against the toxic effects of reduced oxygen species by contributing to the thiol pool of the cell. The present study was designed to determine whether supplementation of methionine in the diet of diabetic animals protected against the oxidative stress in diabetic pathology. Oral methionine was administered at a dosage of 330 mg/100 g feed to diabetic rats. The effect was compared with the effect of insulin administration. Levels of lipid peroxides were measured in plasma, erythrocytes, and erythrocyte membrane. Anti-oxidants were measured in plasma. Diabetic condition was associated with increased lipid peroxidation and depletion in antioxidant levels. Although methionine did not affect the level of blood glucose and some of the antioxidants, it lowered the lipid peroxide content in blood. Erythrocyte lipid peroxidation activity was unaffected by methionine treatment. Administration of insulin lowered both plasma and erythrocyte lipid peroxide levels.     

Constant light exposure aggravates POMC-mediated muscle wasting associated with hypothalamic alteration of circadian clock and SIRT1 in endotoxemia rats

Constant light exposure is widespread in the intensive care unit (ICU) and could increase the rate of brain dysfunction as delirium and sleep disorders in critical patients. And the activation of hypothalamic neuropeptides is proved to play a crucial role in regulating hypercatabolism, especially skeletal muscle wasting in critical patients, which could lead to serious complications and poor prognosis. Here we investigated the hypothesis that constant light exposure could aggravate skeletal muscle wasting in endotoxemia rats and whether it was associated with alterations of circadian clock and hypothalamic proopiomelanocortin(POMC) expression. Fifty-four adult male Sprague-Dawley rats were intraperitoneally injected with lipopolysaccharide(LPS) or saline, subjected to constant light or a 12:12?h light-dark cycle for 7 days. On day 8, rats were sacrificed across six time points in 24?h and hypothalamus tissues and skeletal muscle were obtained. Rates of muscle wasting were measured by 3-methylhistidine(3-MH) and tyrosine release as well as expression of two muscle atrophic genes, muscle ring finger 1(MuRF-1) and muscle atrophy F-box(MAFbx). The expression of circadian clock genes, silent information regulator 1(SIRT1), POMC and hypothalamic inflammatory cytokines were also detected. Results showed that LPS administration significantly increased hypothalamic POMC expression, inflammatory cytokine levels and muscle wasting rates. Meanwhile constant light exposure disrupted the circadian rhythm, declined the expression of SIRT1 as well as aggravated hypothalamic POMC overexpression and skeletal muscle wasting in rats with endotoxemia. Taken together, the results demonstrated that constant light exposure could aggravate POMC-mediated skeletal muscle wasting in endotoxemia rats, which is associated with alteration of circadian clocks and SIRT1 in the hypothalamus.     

Ontogenic profile of some antioxidants and lipid peroxidation in human placental and fetal tissues

Reactive oxygen species (ROS) pose a serious threat to maternal and fetal health during pregnancy. However, there is little information on the oxidative damage caused by ROS and its protection during prenatal life. The present study highlights the status of various antioxidants in human placental and fetal tissues at different phases of gestation. The activity profile of scavenging enzymes, superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase as well as the concentrations of non-enzymatic antioxidants, ascorbic acid, -tocopherol, bilirubin and glutathione have been determined in human placental whole homogenate, placental brush border membrane and fetal liver over gestational periods ranging from 6 weeks of pregnancy till birth. The ontogenic profile of lipid peroxidation, a marker of oxidative damage has also been investigated in the feto-placental system. Catalase, superoxide dismutase and glutathione reductase activities increased significantly, but glutathione peroxidase activity remained almost the same throughout development. Except - tocopherol and bilirubin, the concentrations of other non-enzymic scavengers followed a significant increasing trend with advancement of pregnancy. Results indicate that there is gradual suppression of lipoperoxide formation with the progress of gestation to protect the fetus against oxygen toxicity.     

Influence of monosodium glutamate on circadian rhythms of lipid peroxidation products and antioxidants in rats

Monosodium glutamate (MSG) was administrated subcutaneously for 60 days to Wistar rats and 24h rhythms of thiobarbituric acid reactive substances (TBARS) and antioxidants such as reduced glutathione, superoxide dismutase and catalase were studied. MSG treatment was found to advance TBARS and to delay the acrophases of GSH and catalase. Amplitude and mesor values of these rhythms were found to be altered during MSG treatment. As glutamate levels in brain were found to be significantly increased (in MSG), we hypothesize that increased glutamate levels in brain could alter these biochemical rhythms probaly by modulating the transmission in several areas/nuclei in brain.     

Effects of altered photoperiod on circadian clock and lipid metabolism in rats

Disruption of circadian clock timekeeping due to changes in the photoperiod enhances the risk of lipid metabolism disorders and metabolic syndrome. However, the effects of altered photoperiods on the circadian clock and lipid metabolism are not well understood. To explore the effects of altered photoperiods, we developed a rat model where rats were exposed to either short-day or long-day conditions. Our findings demonstrated that altered photoperiods mediated circadian clocks by partly disrupting rhythmicity and shifting phase values of clock genes. We also showed that compared to long-day conditions, rats under short-day conditions exhibited more photoperiodic changes in a variety of physiological outputs related to lipid metabolism, such as significant increases in serum triglyceride (TG), high-density lipoprotein, and leptin levels, as well as increased body weight, fat:weight ratio, and hepatic TG levels. These increments were gained possibly through upregulated expression of forkhead box O1 (FoxO1), which partly mediates the expression of peroxisome proliferator-activated receptorα (PPARα) to increase the expression of phosphoenolpyruvate carboxykinase (PEPCK), peroxisome proliferator-activated receptor-g coactivator-1β (PGC1β), and fatty acid synthase (Fasn). In addition, the oscillation rhythms of FoxO1, PEPCK, PGC1β, and Fasn expression levels in the livers of rats exposed to a short-day photoperiod were more robust than those exposed to a long-day photoperiod. These findings suggest that a change in photoperiod can partly disrupt the circadian rhythmcity of clock genes, impair lipid metabolism, and promote obesity.     

Effects of differences in the availability of light upon the circadian rhythms of institutionalized elderly

The aim of this study was to compare the availability of diurnal and nocturnal light in two residences for aged persons (R1 and R2, Palma de Mallorca, Illes Balears, Spain). We found that the R1 inmates were exposed to lower amounts of light during waking time and higher amounts during sleeping time. The main traits of the circadian rhythms and the quality of sleep in the inmates of the two residences were found to be positively related to the availability of light during waking time and negatively to the increased light exposure during bed time. In addition, the sleep of R1 inmates suffered higher disturbances as a consequence of the different policy for nocturnal diapers check and change. Altogether, these two factors may explain the differences observed in the two residences regarding the circadian rhythms, health status and quality of life. Two conclusions stem from these results: (1) the circadian rhythms of aged people are particularly sensitive to the contrast between diurnal and nocturnal light and (2) the nursing staff of institutions for aged people must receive specific formation on the best practices for maintaining the circadian health of aged people.     

Role of endogenous and exogenous antioxidants in the defence against functional damage and lipid peroxidation in rat liver mitochondria

Mitochondria are cellular organelles where the generation of reactive oxygen species may be high. They are, however, effectively protected by their high capacities of antioxidative systems, as enzymes and either water or lipid soluble low molecular weight antioxidants.These antioxidative defence systems can be effectively regenerated after or during an oxidative stress as long as the mitochondria are in an energized state. Energization of mitochondria mainly depends on the availability of suitable respiratory substrates which can provide hydrogen for the reduction of either the glutathione- or -tocopherol-system, since GSH is regenerated by glutathione reductase with the substrate NADPH and the -tocopheroxyl-radical likely by reduced coenzyme Q. It was shown that mitochondria do not undergo damages as long as they can keep a high energy state. The delicate balance between prooxidative/antioxidative activities can be shifted towards oxidation, if experimentally prooxidants were added. After exhaustion of the antioxidative defence systems damages of rnitochondrial functions become expressed followed by membrane injuries along with the oxidation and degradation of mitochondrial lipids and proteins leading finally to the total degradation of the mitoc hondria.Extramitochondrial antioxidants may assist the mitochondrial antioxidative defence systems in a complex way, whereby particularly ascorbic acid can act both as prooxidant and as antioxidant. (Mol Cell Biochem 174: 199–205, 1997)     

Studies on spice principles as antioxidants in the inhibition of lipid peroxidation of rat liver microsomes

Polyunsaturated fatty acids (PUFA) are vulnerable to peroxidative attack. Protecting PUFA from peroxidation is essential to utilize their beneficial effects in health and in preventing disease. The antioxidants vitamin E, t-butylhydroxy toluene (BHT) and t-butylhydroxy anisole (BHA) inhibited ascorbate/Fe²⁺-induced lipid peroxidation in rat liver microsomes. In addition, a number of spice principles, for example, curcumin (5–50 µM) from turmeric, eugenol (25–150 µM) from cloves and capsaicin (25–150 µM) from red chillies inhibited lipid peroxidation in a dose-dependent manner. Zingerone from ginger inhibited lipid peroxidation at high concentrations (> 150 µM) whereas linalool (coriander), piperine (black pepper) and cuminaldehyde (cumin) had only marginal inhibitory effects even at high concentrations (600 µM). The inhibition of lipid peroxidation by curcumin and eugenol was reversed by adding high concentrations of Fe²⁺.     

The influence of antioxidants in the thiyl radical induced lipid peroxidation and geometrical isomerization in micelles of linoleic acid

Abstract

The biomimetic model of micelles of linoleic acid containing 2-mercaptoethanol and the antioxidant was examined under gamma irradiation up to 400?Gy in aerobic or deoxygenated conditions where thiyl radicals are the main reactive species. Lipid peroxidation was retarded by ascorbic acid and α-tocopherol, whereas this process was strongly inhibited by resveratrol as effectively as the ascorbic acid/α-tocopherol mixture. Furthermore, antioxidants have a much stronger inhibitory effect on the peroxidation in the presence of 2-mercaptoethanol, and at the same time show protective properties of the double bond, decreasing the cis–trans isomerization. Under anaerobic conditions, cis–trans isomerization occurred and antioxidants efficiency increased along the series: resveratrol < α-tocopherol?<?ascorbic acid. This result is explained taking into account the double bond localization in the hydrophobic core of the micelle and the need of co-localization of the antioxidant in order to get an anti-isomerizing activity and protection of the natural lipid geometry.     

Combined efficacy of tamoxifen and coenzyme Q10 on the status of lipid peroxidation and antioxidants in DMBA induced breast cancer

An increasing amount of experimental and epidemiological evidence implicates the involvement of oxygen derived radicals in the pathogenesis of cancer development. It is well known that chemical carcinogenesis is multistage process. Free radicals are found to be involved in both initiation and promotion of multistage carcinogenesis. Tamoxifen (TAM) is a potent antioxidant and a non-steroidal antiestrogen drug most used in the chemotherapy and chemoprevention of breast cancer. Besides its anticarcinogenic potential, it also produces some adverse toxic side effects, while taken for a long time. In order to minimise the side effects and to improve the antioxidant efficacy of tamoxifen, coenzyme Q₁₀ (CoQ₁₀) was added. Hence the present study was designed to investigate the combined efficacy of TAM along with CoQ₁₀ in 7, 12 dimethyl benz(a)anthracene (DMBA) induced peroxidative damage in rat mammary carcinoma. The experimental setup comprised of one control and five experimental groups and it was carried out in adult female Sprague-Dawley rats. Mammary carcinoma was induced by oral administration of DMBA (25 mg kg^–1 body wt) and the treatment was started by the oral administration of TAM (10 mg kg^–1 body wt day^–1) and CoQ₁₀ (40 mg kg^–1 body wt day^–1) dissolved in olive oil and continued for 28 days. Rats induced with DMBA showed a decline in the thiol capacity of the cell accompanied by high malondialdehyde content levels along with lowered activities of antioxidant status (superoxide dismutase, catalase, glutathione peroxidase and reduced glutathione). In contrast, glutathione metabolising enzymes (glutathione reductase, glucose-6-phosphate dehydrogenase and glutathione-S-transferase) were increased significantly in chemically induced carcinoma bearing rats. Administration of TAM along with CoQ₁₀ restored the activities to a significant level thereby preventing cancer cell proliferation. This study highlights the increased antioxidant enzyme activities in relation to the susceptibility of cells to carcinogenic agents and the response of tumour cells to the chemotherapeutic agents.     

Ornithine alpha-ketoglutarate modulates the levels of antioxidants and lipid peroxidation products in ammonium acetate treated rats

The effects of ornithine alpha-ketoglutarate (OKG) on ammonium acetate induced hepatotoxicity were studied in experimental rats. The levels of urea, non-protein nitrogen and thiobarbituric acid reactive substances were significantly increased in ammonium acetate treated rats; but these levels were significantly decreased in ammonium acetate-OKG treated rats. Similar patterns were observed in the levels of free fatty acids, triglycerides and phospholipids. Furthermore, non-enzymatic (reduced glutathione) and enzymatic (glutathione peroxidase, superoxide dismutase and catalase) antioxidants were significantly decreased in ammonium acetate treated rats, when compared with control and were significantly increased in ammonium acetate-OKG treated rats compared to ammonium acetate treatment alone.     

Expression of circadian rhythmicity in Djungarian hamsters under constant light: Effects of light intensity and the circadian system's state

Summary Djungarian hamsters (Phodopus sungorus), were exposed to constant light with increasing intensities (20, 60, 350 lux), and wheel running activity was recorded. With increasing light intensity the percentage of hamsters showing a split in their daily activity pattern increased and the free running period was lengthened for both the unsplit and the split state. The fact that the free running period of both states depended on the light intensity together with the observation that the highest incidence of acircadian activity occurred under 350 lux, provoked the idea that the emergence of splitting or acircadian rhythmicity is a direct consequence of the light induced lengthening of the free running period. However, analysis of the data failed to support the idea that emergence of a split or acircadian activity is a threshold phenomenon with respect to the free running period.Due to differences in circadian function some Djungarian hamsters do not exhibit photoinduction following short day exposure. In these individuals splitting also occurred but required exposure to a higher light intensity than in photo-responsive hamsters. This observation is in accordance with the idea that the two phenotypes differ in the interaction of the two component oscillators underlying circadian rhythmicity.Abbreviations LD long day photoperiod - LL constant light - SD short day photoperiod - free running period     

In the presence of ferritin, visible light induces lipid peroxidation of the porcine photoreceptor outer segment

We studied the synergistic effect of visible light and ferritin on the lipid peroxidation on a fraction of porcine photoreceptor outer segment (POS). Reaction mixtures containing the POS fraction and horse spleen ferritin were irradiated under white fluorescent light mainly at 17,000 lx or incubated under dark conditions at 37°C. The lipid peroxidation was evaluated by both the thiobarbituric acid method and the ferrous oxidation/xylenol orange method. The irradiation-induced lipid peroxidation was affected by some experimental factors such as the irradiation dose and acidity of the material. When the irradiation was stopped, the lipid peroxidation was also stopped; thereafter, the re-irradiation induced lipid peroxidation. Moreover, this lipid peroxidation was inhibited by desferrioxamine, an iron chelator, or by dimethylthiourea, a hydroxyl radical scavenger, suggesting that the lipid peroxidation involves hydroxyl radicals generated via the Fenton reaction by iron ion released from ferritin. The lipid peroxidation did not take place under dark conditions or in the absence of ferritin. This study suggested the possibility that the visible light-induced lipid peroxidation of the POS fraction in the presence of ferritin may participate in the etiology of human retinal degenerative diseases as the human retina is exposed to light for life.     

Effect of DL-alpha-lipoic acid on the status of lipid peroxidation and antioxidants in mitochondria of aged rats

The life span of a species is thought to be determined by the rate of mitochondrial damage which in turn is inflicted by free radicals in the mitochondria during the course of normal metabolism. The level of lipid peroxidation and antioxidants were measured in liver and kidney mitochondria of young and aged rats before and after DL-alpha-lipoic acid supplementation. In both liver and kidney, mitochondrial lipid peroxidation increased with age and a decrease in the enzymatic and non-enzymatic antioxidants were observed. DL-alpha-lipoic acid treated aged rats showed a decrease in the level of lipid peroxides and an increase in the antioxidant status. Our results conclude that supplementation of lipoic acid restores the depleted mitochondrial antioxidant status and suggest that it could be an effective therapeutic agent in treatment of age-associated disorders where free radicals are the major causative factor.     

In the presence of ferritin,visible light induces lipid peroxidation of the porcine photoreceptor outer segment

We studied the synergistic effect of visible light and ferritin on the lipid peroxidation on a fraction of porcine photoreceptor outer segment (POS). Reaction mixtures containing the POS fraction and horse spleen ferritin were irradiated under white fluorescent light mainly at 17,000 lx or incubated under dark conditions at 37°C. The lipid peroxidation was evaluated by both the thiobarbituric acid method and the ferrous oxidation/xylenol orange method. The irradiation-induced lipid peroxidation was affected by some experimental factors such as the irradiation dose and acidity of the material. When the irradiation was stopped, the lipid peroxidation was also stopped; thereafter, the re-irradiation induced lipid peroxidation. Moreover, this lipid peroxidation was inhibited by desferrioxamine, an iron chelator, or by dimethylthiourea, a hydroxyl radical scavenger, suggesting that the lipid peroxidation involves hydroxyl radicals generated via the Fenton reaction by iron ion released from ferritin. The lipid peroxidation did not take place under dark conditions or in the absence of ferritin. This study suggested the possibility that the visible light-induced lipid peroxidation of the POS fraction in the presence of ferritin may participate in the etiology of human retinal degenerative diseases as the human retina is exposed to light for life.     

Sphingomyelin chain length influences the distribution of GPI-anchored proteins in rafts in supported lipid bilayers

Glycosyl-phosphatidylinositol (GPI)-anchored proteins are enriched in cholesterol- and sphingolipid-rich lipid rafts within the membrane. Rafts are known to have roles in cellular organization and function, but little is understood about the factors controlling the distribution of proteins in rafts. We have used atomic force microscopy to directly visualize proteins in supported lipid bilayers composed of equimolar sphingomyelin, dioleoyl-sn-glycero-3-phosphocholine and cholesterol. The transmembrane anchored angiotensin converting enzyme (TM-ACE) was excluded from the liquid ordered raft domains. Replacement of the transmembrane and cytoplasmic domains of TM-ACE with a GPI anchor (GPI-ACE) promoted the association of the protein with rafts in the bilayers formed with brain sphingomyelin (mainly C18:0). Association with the rafts did not occur if the shorter chain egg sphingomyelin (mainly C16:0) was used. The distribution of GPI-anchored proteins in supported lipid bilayers was investigated further using membrane dipeptidase (MDP) whose GPI anchor contains distearoyl phosphatidylinositol. MDP was also excluded from rafts when egg sphingomyelin was used but associated with raft domains formed using brain sphingomyelin. The effect of sphingomyelin chain length on the distribution of GPI-anchored proteins in rafts was verified using synthetic palmitoyl or stearoyl sphingomyelin. Both GPI-ACE and MDP only associated with the longer chain stearoyl sphingomyelin rafts. These data obtained using supported lipid bilayers provide the first direct evidence that the nature of the membrane-anchoring domain influences the association of a protein with lipid rafts and that acyl chain length hydrophobic mismatch influences the distribution of GPI-anchored proteins in rafts.     

Antioxidant effect of selenium on lipid peroxidation,hyperlipidemia and biochemical parameters in rats exposed to diazinon

Diazinon (DZN) is one of the most organophosphate insecticides that widely used in agriculture and industry. Selenium is generally recognized to be a trace mineral of great importance for human health, protecting the cells from the harmful effects of free radicals. Therefore, the present study was carried out to investigate the alterations in biochemical parameters, free radicals and enzyme activities induced by diazinon in male rat serum, and the role of selenium in alleviating the negative effects of DZN. Animals were divided into four groups of seven rats each; the first group was used as control. Groups 2, 3 and 4 were treated with selenium (Se; 200 μg/kg BW), diazinon (DZN; 10 mg/kg BW) and diazinon plus selenium, respectively. Rats were orally administered their respective doses daily for 30 days. Results obtained showed that DZN significantly induced thiobarbituric acid reactive substances (TBARS) and decreased the activities of glutathione S-transferase (GST), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) and the levels of reduced glutathione (GSH) in rat sera. Aminotransferases (AST, ALT), phosphatases (AlP, AcP) and lactate dehydrogenase (LDH) activities were significantly increased while acetylcholinesterase (AChE) activity was decreased due to DZN administration. Also, DZN treatment caused significant perturbations in lipids profile and serum biochemical parameters. On the other hand, Se alone significantly decreased the levels of TBARS, total lipids, cholesterol, urea and creatinine, while increased the activities of antioxidant enzymes and glutathione content, total protein (TP) and albumin. In addition, Se in combination with DZN partially or totally alleviated its toxic effects on the studied parameters. In conclusion, Se has beneficial effects and could be able to antagonize DZN toxicity.