The isomers of thioctic acid alter C-deoxyglucose incorporation in rat basal ganglia

Alpha-lipoic acid and its protective role in fructose induced endocrine-metabolic disturbances

In recent decades a worldwide increase has been reported in the consumption of unhealthy high calorie diets associated with marked changes in meal nutrient composition, such as a higher intake of refined carbohydrates, which leads to the speculatation that changes in food habits have contributed to the current epidemic of obesity and type 2 diabetes. Among these refined carbohydrates, fructose has been deeply investigated and murine models of high fructose diet have emerged as useful tools to study dietary-induced insulin resistance, impaired glucose tolerance, dyslipidemia and alterations in glucose metabolism. Since oxidative stress has been demonstrated to play a key pathogenic role in the alterations described above, several lines of research have focused on the possible preventive effects of antioxidant/redox state regulation therapy, among which alpha-lipoic acid has been extensively investigated. The following references discussed support the fact that co-administration of alpha-lipoic acid normalized the changes generated by fructose rich diets, thereby making this compound a good therapeutic tool, also administered as a food supplement, to prevent endocrine-metabolic disturbances triggered by high fructose associated with obesity and type 2 diabetes at an early stage of development (prediabetes).

Ameliorative role of antioxidant supplementation on sodium-arsenite induced adverse effects on the developing rat cerebellum

Background

Arsenic is an environmental contaminant of global concern. Consumption of ground water contaminated with inorganic arsenic (iAs) continues to be the major source of its exposure. The developing nervous system is especially vulnerable to environmental insults due to its higher rate of oxygen consumption and provision of weaker antioxidant (AOX) machinery.

Objective

Since oxidative stress has been reported as one of the major factors underlying iAs induced toxicity, the aim of the present study is to study the effect of two AOXs i.e., Alpha Lipoic Acid (ALA) and Curcumin (Cur) in developing cerebellum of rats exposed to arsenic during postnatal period.

Materials and Methods

The study was carried out on mother reared neonatal rat pups grouped as normal (Ia) and sham (vehicle) controls (Ib,c,d), while the experimental groups IIa/ IIb received sodium arsenite (NaAsO2) [(1.5/2.5 mg/kg body weight (bw)] alone or along with ALA (70 mg/kg bw)- IIIa/ IIIb or along with Cur (150 mg/kg bw)- IVa/ IVb. Behavioural, biochemical and immunohistochemical procedures were carried out to understand the underlying mechanisms.

Results

The observations indicated deficits in locomotor function, accumulation of iAs, increased levels of oxidative stress markers along with downregulation of the expression of proteins closely associated with synaptic functioning (Synaptophysin and Postsynaptic density protein95) in the cerebellum of iAs treated animals. Substantial recovery in all these parameters was observed in AOX co-treated groups.

Conclusion

Our results support the potential of ALA and Cur in amelioration of iAs induced developmental neurotoxicity. ALA and Cur can be proposed as dietary adjuvants amongst populations inhabiting areas with high iAs contamination as a safe and cost effective antidotes.

Potential of nonoral α-lipoic acid aqueous formulations to reduce ocular microvascular complications in a streptozotocin-induced diabetic rat model

PURPOSE

α-Lipoic acid (LA) aqueous formulations were studied for nonoral administration, including intravitreal and intraperitoneal preparations and topical eyedrops. The potential retinoprotective effects of these LA preparations were also evaluated in streptozotocin (STZ)-induced diabetic rats for screening better delivery systems of LA.

METHODS

Four LA liquid preparations were prepared and investigated. The short-term accelerated stabilities of LA preparations were investigated at 3 temperatures: 50°C, 70°C, and 90°C. The time courses of LA degradation in the preparations were determined by high-performance liquid chromatography. Furthermore, the potential therapeutic effects of LA preparations in a STZ-induced diabetic rat model were assessed by vitreous fluorophotometry to evaluate the fluorescein leakage from ocular vascular vessels into the vitreous. Capillary lesion in the retina was also examined using hematoxylin-eosin-stained microsections.

RESULTS

LA in an aqueous solution was rapidly degraded with the activation energy of 10.4 kcal/mol. The 3 LA preparations had shelf lives of ∼1 month at 25°C. These formulations significantly reduced the vitreous fluorescein level in STZ-induced diabetic rats as evaluated by the fluorescein leakage after tail vein injection. Capillary lesions in the retina of the diabetic rats were remarkably reduced by nonoral administration, particularly the intraperitoneal injection (30 mg/kg/day).

CONCLUSIONS

LA could be developed as aqueous preparations with suitable stability for short-term use in nonoral administration. LA preparations could be administered intravitreally or intraperitoneally to reduce ocular microvascular complications, such as retinopathy, in diabetic patients.

Assessment of a standardized ROS production profile in humans by electron paramagnetic resonance

Despite the growing interest in the role of reactive oxygen species (ROS) in health and disease, reliable quantitative noninvasive methods for the assessment of oxidative stress in humans are still lacking. EPR technique, coupled to a specific spin probe (CMH: 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine) is here presented as the method of choice to gain a direct measurement of ROS in biological fluids and tissues. The study aimed at demonstrating that, differently from currently available “a posteriori” assays of ROS-induced damage by means of biomolecules (e.g., proteins and lipids) spin-trapping EPR provides direct evidence of the “instantaneous” presence of radical species in the sample and, as signal areas are proportional to the number of excited electron spins, lead to absolute concentration levels. Using a recently developed bench top continuous wave system (e-scan EPR scanner, Bruker) dealing with very low ROS concentration levels in small (50 μL) samples, we successfully monitored rapid ROS production changes in peripheral blood of athletes after controlled exercise and sedentary subjects after antioxidant supplementation. The correlation between EPR results and data obtained by various enzymatic assays (e.g., protein carbonyls and thiobarbituric acid reactive substances) was determined too. Synthetically, our method allows reliable, quick, noninvasive quantitative determination of ROS in human peripheral blood.

Protective role of exogenous α-lipoic acid (ALA) on hippocampal antioxidant status and memory function in rat pups exposed to sodium arsenite during the early post-natal period

The present work focussed on the effect of exogenous α-lipoic acid (ALA) administration on retention memory and oxidative stress markers in the hippocampus subsequent to early post-natal exposure of rat pups to sodium arsenite (NaAsO(2)). Wistar rat pups were divided into the control groups receiving either no treatment (Ia) or distilled water by intraperitoneal route (i.p.) (Ib) and the experimental groups receiving either NaAsO(2) alone (1.5 and 2.0 mg/kg body wt.) (IIa, IIb) or NaAsO(2) (1.5 and 2.0 mg/kg body wt.) followed by ALA (70 mg/kg body wt.) (IIIa, IIIb) (i.p.) from post-natal day (PND) 4-15. The initial and retention transfer latency (ITL and RTL) was determined on PND 14 and 15 using elevated plus maze. The animals were sacrificed by cervical decapitation (PND 16) and the brains were obtained. The dissected out hippocampus was processed for estimation of oxidative stress markers, glutathione (GSH), and superoxide dismutase (SOD). NaAsO(2) exposure resulted in longer RTL in animal groups IIa and IIb, thereby suggestive of arsenic-induced impairment in retention memory. RTL was significantly shorter in animal groups (IIIa, IIIb) receiving ALA following NaAsO(2), thereby suggestive of improvement in retention memory. GSH and SOD levels were significantly decreased in animals receiving NaAsO(2) alone as against group Ib and administration of ALA following NaAsO(2) increased the levels of hippocampal GSH and SOD. These observations are suggestive of the role of exogenous ALA in ameliorating the adverse effects induced by NaAsO(2) exposure of rat pups on retention memory and oxidative stress markers.

Structural, chemical and biological aspects of antioxidants for strategies against metal and metalloid exposure

Oxidative stress contributes to the pathophysiology of exposure to heavy metals/metalloid. Beneficial renal effects of some medications, such as chelation therapy depend at least partially on the ability to alleviate oxidative stress. The administration of various natural or synthetic antioxidants has been shown to be of benefit in the prevention and attenuation of metal induced biochemical alterations. These include vitamins, N-acetylcysteine, alpha-lipoic acid, melatonin, dietary flavonoids and many others. Human studies are limited in this regard. Under certain conditions, surprisingly, the antioxidant supplements may exhibit pro-oxidant properties and even worsen metal induced toxic damage. To date, the evidence is insufficient to recommend antioxidant supplements in subject with exposure to metals. Prospective, controlled clinical trials on safety and effectiveness of different therapeutic antioxidant strategies either individually or in combination with chelating agent are indispensable. The present review focuses on structural, chemical and biological aspects of antioxidants particularly related to their chelating properties.

Brain regional responses in antioxidant system to α-lipoic acid in arsenic intoxicated rat

Impaired antioxidant defense mechanisms and oxidative stress are implicated in the pathogenesis of arsenic toxicity. Our study was designed to determine whether alpha-lipoic acid, which has been shown to have substantial antioxidant properties, when administered (70 mg/kg body weight) once daily for 60 days along with arsenic (100 ppm sodium arsenite mixed in drinking water) would prevent arsenic-induced changes in antioxidant defense system, superoxide dismutase (SOD-total SOD, Mn SOD, Cu/Zn SOD), catalase (CAT) and glutathione peroxidase (GSH-PX) in rat brain regions such as cortex, hypothalamus, striatum, cerebellum and hippocampus. The present study also examined the effect of alpha-lipoic acid over arsenic-induced oxidant production and lipid peroxidation level (LPO) in discrete brain regions of rats. The cortex, striatum and hippocampus showed greater decreases in GSH-Px enzyme activity than cerebellum and hypothalamus with arsenic exposure. Striatum had the greatest percentage of decreased activities of total SOD and Mn SOD, whereas cortex had the greatest percentage decrease in the activity of Cu/Zn SOD in arsenic-alone treated rats. Hypothalamus and cerebellum exhibited the lowest catalase activity among all tested regions in arsenic-only treated rats. Rate of dichlorofluorescin oxidation, an indication of reactive oxygen species and other intracellular oxidants production was increased with arsenic exposure in all brain regions studied. Cortex, hippocampus and striatum exhibited greater increase of LPO levels than cerebellum and hypothalamus. SOD, CAT, GSH-Px activities were upregulated in arsenic plus lipoic acid treated versus arsenic-only treated rats. Also, simultaneous lipoic acid treatment along with arsenic proved to be sufficient in reducing oxidant production and LPO level in all rat brain regions. Our results demonstrate that arsenic-induced deficits in antioxidant enzyme activities and increase in oxidant production and lipid peroxidation level in brain regions can be overcome through simultaneous treatment with lipoic acid.

The protective role of DL-?-lipoic acid in the oxidative vulnerability triggered by A?-amyloid vaccination in mice

Recent reports indicate that beta-amyloid peptide (Abeta) vaccine based therapy for Alzheimer's disease (AD) may be on the horizon. There are however, concerns about the safety of this approach. Immunization with Abeta has several disadvantages, because it crosses the blood brain barrier and cause inflammation and neurotoxicity. The present work is aimed to study the protective effective of alpha-lipoic acid (LA) in the oxidative vulnerability of beta-amyloid in plasma, liver, spleen and brain, when Abeta fibrils are given intraperitoneally in inflammation induced mice. Result shows that reactive oxygen species (ROS) in the astrocytes of inflammation induced mice along with Abeta (IA) has shown 2.5-fold increase when compared with LA treated mice. The increased level of lipid peroxidase (LPO) (p < 0.05) and decreased antioxidant status (p < 0.05) were observed in the plasma, liver, spleen and brain of LA induced mice when compared with LA treated mice. Data shows that there were no significant changes observed between the control and LA treated mice. Our biochemical and histological results highlight that significant oxidative vulnerability was observed in IA treated mice, which was prevented by LA therapy. Our findings suggest that the antioxidant effect of LA when induced with Abeta may serve as a potent therapeutic tool for inflammatory AD models.

Arsenic intoxication-induced reduction of glutathione level and of the activity of related enzymes in rat brain regions: reversal by dl-?-lipoic acid

The purpose of this study was to examine the effects of DL: -alpha-lipoic acid (LA) on arsenic (As) induced alteration of glutathione (GSH) level and of the activity of glutathione-related enzymes-glutathione peroxidase (GSH-Px), glutathione reductase (GR), and glucose-6-phosphate dehydrogenase (G6PDH)-in rat brain regions (cortex, hypothalamus, striatum, cerebellum and hippocampus). Male Wistar rats of 150+/-10 g weight were divided into four groups: control and three experimental groups supplemented with arsenic (sodium arsenite) alone (100 ppm mixed in drinking water), lipoic acid alone (70 mg kg(-1) body weight), arsenic plus lipoic acid (100 ppm arsenic in drinking water plus 70 mg lipoic acid kg(-1) body weight). The arsenic content of brain regions was found to increase with the administration of sodium arsenite. Arsenic exposure elicited a significant decline in glutathione content and in the activity of related enzymes, with the greatest decreases seen in the cortex, striatum, and hippocampus, whereas there were no significant differences between control rats and the group treated with lipoic acid alone. Highly elevated content of the thiobarbituric acid-reactive substance malondialdehyde (MDA) in the brain regions of arsenic-exposed rats reflected extensive lipid peroxidation (LPO) processes. Simultaneous lipoic acid treatment was effective in reducing brain regional arsenic levels and lipid peroxidation and in increasing the glutathione content and the activity of its related enzymes. Lipoic acid, by acting as an alternative sulfhydryl nucleophile to glutathione, prevents its oxidation to glutathione disulfide in detoxifying reactions against reactive oxygen species and consequently increases the activity of glutathione-related enzymes.

Influence of alpha-lipoic acid on lipid peroxidation and antioxidant defence system in blood of insulin-resistant rats

BACKGROUND

High fructose feeding induces insulin resistance and hyperinsulinaemia in rats. A role for oxidative stress in the occurrence of insulin resistance has been suggested by several workers.

AIM

The aim of this study was to investigate the effect of alpha-lipoic acid (LA) on oxidant-antioxidant balance in rats fed on a high-fructose diet that showed characteristic features of insulin resistance.

METHODS

Male Wistar rats weighing 150-170 g were divided into seven groups. The control group received the control diet containing starch. The fructose group was given a high-fructose diet (>60% of total calories). The third and fourth groups were given fructose diet and were administered two different doses of LA at a low dose (35 mg/kg body weight) and high dose (70 mg/kg body weight) using olive oil as vehicle. The fifth group received fructose diet and olive oil. The sixth group received control diet and was administered LA (70 mg/kg body weight). And, the seventh group received the control diet and olive oil. Products of lipid peroxidation and activities of enzymic antioxidants, namely superoxide dismutase, catalase, glutathione peroxidase, glutathione-S-transferase and glutathione reductase, in red blood cells were assayed. Levels of non-enzymic antioxidants alpha-tocopherol, ascorbic acid and reduced glutathione were determined in plasma.

RESULTS

The levels of lipid peroxides, diene conjugates and thiobarbituric acid-reactive substances were significantly higher in fructose-fed rats. Inadequate antioxidant system was observed in high-fructose-fed rats. Treatment of fructose rats mitigated the imbalance between peroxidation and antioxidant defence system at both the doses tested. Increases in glucose, triglycerides, free fatty acids, insulin and insulin resistance were observed in fructose-fed rats. LA administration prevented these alterations and improved insulin sensitivity. Significant positive correlations were obtained between insulin resistance and lipid peroxidation indices.

CONCLUSIONS

Increased lipid peroxidation and deficient antioxidant system are observed in high-fructose-fed rats. LA administration preserves the antioxidant system and lowers lipid peroxidation. The findings suggest an interrelationship between lipid peroxidation and insulin resistance.

Clinical pharmacology and neuroprotection in Parkinson's disease

There has been significant progress in the study of the causes, the pathogenesis, and the mechanism of cell death in Parkinson's disease (PD). Mutations in single genes have been shown to cause PD, and accumulation of alpha-synuclein seems to be a clue to the pathogenesis of neurodegeneration. However, mutations of single genes account for only a small number of cases. Environmental factors seem to play a large role in the majority of cases of sporadic PD. Genetic factors may predispose patients to develop PD if combined with other gene mutations or environmental toxins. In an attempt to design a neuroprotective therapy, the pathogenesis of neurodegeneration, and the mechanism of cell death have been studied. Aggregation of insoluble alpha-synuclein, oxidant stress, mitochondrial dysfunction, excitotoxicity, and glia and inflammatory processes are all thought to contribute to the cell death process and agents that interfere with these events may be neuroprotective. The final culmination of these events is supposed to be the induction of apoptosis in nigral dopaminergic neurons and this too offers opportunities for providing neuroprotection. A large number of different approaches are under discussion in the hope of developing a neuroprotective therapy, using clinical indices and neuroimaging markers of nigral dopaminergic neurons. Conventional approaches to studies that use large numbers of patients in search of small effects are costly and time consuming, and it would be impossible to test all the potentially valuable neuroprotective agents because of a lack of time, money, or subjects. As a translational research, it is more profitable to test agents in a small number of selected patients in search of a more neuroprotective effect. Well designed translational research might allow us to reduce the risk of missing a powerful neuroprotective treatment.

Neurochemical changes related to ageing in the rat brain and the effect of DL-alpha-lipoic acid

Age-related impairments of cognitive and motor function have been linked to a number of deleterious morphological and functional changes involving different areas of the brain. Loss of neurotransmitters, their receptors and responsiveness to neurotransmitters are key manifestations of neurological ageing and age-related disorders. In the present investigation we have evaluated the effect of DL-alpha-lipoic acid on neurotransmitters in discrete brain regions of young and aged rats. The levels of neurotransmitters were found to be lowered in aged rats. Moreover, DL-alpha-lipoic acid treated aged rats showed a increase in the status of dopamine, serotonin and norepinephrine. The results of this study provide evidence that DL-alpha-lipoic acid (a potent antioxidant) treatment can improve neurotransmitters during ageing. Hence, it can be concluded that DL-alpha-lipoic acid act as a potent neuromodulator in the brain of aged rats.

Effect of DL-alpha-lipoic acid on the status of lipid peroxidation and protein oxidation in various brain regions of aged rats

Free radicals have been implicated in the development of many acute and chronic diseases and in conditions involving brain or neurological tissue. The primary genetic material is subjected to damage by endogenous and exogenous agents, which may lead to instability and transcriptional infidelity. In the present study, we evaluated the protective effect of DL-alpha-lipoic acid, a metabolic antioxidant on lipid peroxidation, protein carbonyl content in various brain regions of aged rats when compared to brain regions of young rats. DL-alpha-lipoic acid was administered intraperitoneally (100mg/kg body weight/day) to experimental rats. Nucleic acid and protein content were low whereas thiobarbituric acid reactive substances and protein carbonyl content (markers of free radical damage) were high in cortex, striatum, hippocampus and hypothalamus followed by cerebellum of aged rat brain. Lipoate administration for 14 days in aged rats increased the levels of nucleic acid and protein and reduced lipid peroxidation and protein oxidation. These results demonstrate that lipoic acid is a potent antioxidant for neuronal cells against age associated oxidative damage.

Role of free radicals in the neurodegenerative diseases: therapeutic implications for antioxidant treatment

Free radicals and other so-called 'reactive species' are constantly produced in the brain in vivo. Some arise by 'accidents of chemistry', an example of which may be the leakage of electrons from the mitochondrial electron transport chain to generate superoxide radical (O2*-). Others are generated for useful purposes, such as the role of nitric oxide in neurotransmission and the production of O2*- by activated microglia. Because of its high ATP demand, the brain consumes O2 rapidly, and is thus susceptible to interference with mitochondrial function, which can in turn lead to increased O2*- formation. The brain contains multiple antioxidant defences, of which the mitochondrial manganese-containing superoxide dismutase and reduced glutathione seem especially important. Iron is a powerful promoter of free radical damage, able to catalyse generation of highly reactive hydroxyl, alkoxyl and peroxyl radicals from hydrogen peroxide and lipid peroxides, respectively. Although most iron in the brain is stored in ferritin, 'catalytic' iron is readily mobilised from injured brain tissue. Increased levels of oxidative damage to DNA, lipids and proteins have been detected by a range of assays in post-mortem tissues from patients with Parkinson's disease, Alzheimer's disease and amyotrophic lateral sclerosis, and at least some of these changes may occur early in disease progression. The accumulation and precipitation of proteins that occur in these diseases may be aggravated by oxidative damage, and may in turn cause more oxidative damage by interfering with the function of the proteasome. Indeed, it has been shown that proteasomal inhibition increases levels of oxidative damage not only to proteins but also to other biomolecules. Hence, there are many attempts to develop antioxidants that can cross the blood-brain barrier and decrease oxidative damage. Natural antioxidants such as vitamin E (tocopherol), carotenoids and flavonoids do not readily enter the brain in the adult, and the lazaroid antioxidant tirilazad (U-74006F) appears to localise in the blood-brain barrier. Other antioxidants under development include modified spin traps and low molecular mass scavengers of O2*-. One possible source of lead compounds is the use of traditional remedies claimed to improve brain function. Little is known about the impact of dietary antioxidants upon the development and progression of neurodegenerative diseases, especially Alzheimer's disease. Several agents already in therapeutic use might exert some of their effects by antioxidant action, including selegiline (deprenyl), apomorphine and nitecapone.

The alpha-ketoglutarate dehydrogenase complex in neurodegeneration

Altered energy metabolism is characteristic of many neurodegenerative disorders. Reductions in the key mitochondrial enzyme complex, the alpha-ketoglutarate dehydrogenase complex (KGDHC), occur in a number of neurodegenerative disorders including Alzheimer's Disease (AD). The reductions in KGDHC activity may be responsible for the decreases in brain metabolism, which occur in these disorders. KGDHC can be inactivated by several mechanisms, including the actions of free radicals (Reactive Oxygen Species, ROS). Other studies have associated specific forms of one of the genes encoding KGDHC (namely the DLST gene) with AD, Parkinson's disease, as well as other neurodegenerative diseases. Reductions in KGDHC activity can be plausibly linked to several aspects of brain dysfunction and neuropathology in a number of neurodegenerative diseases. Further studies are needed to assess mechanisms underlying the sensitivity of KGDHC to oxidative stress and the relation of KGDHC deficiency to selective vulnerability in neurodegenerative diseases.

Thioctic acid does not restore glutathione levels or protect against the potentiation of 6-hydroxydopamine toxicity induced by glutathione depletion in rat brain

Decreased reduced glutathione (GSH) levels are an early marker of nigral cell death in Parkinson's disease. Depletion of rat brain GSH by intracerebroventricular administration of buthionine sulphoximine (BSO) potentiates the toxicity of 6-hydroxydopamine (6-OHDA) to the nigrostriatal pathway. We have investigated whether thioctic acid can replenish brain GSH levels following BSO-induced depletion and/or prevent 6-OHDA induced toxicity. Administration of BSO (2 x 1.6 mg i.c.v.) to rats depleted striatal GSH levels by upto 75%. BSO treatment potentiated 6-OHDA (75 micrograms i.c.v.) toxicity as judged by striatal dopamine content and the number of tyrosine hydroxylase immunoreactive cells in substantia nigra. Repeated treatment with thioctic acid (50 or 100 mg/kg i.p.) over 48h had no effect on the 6-OHDA induced loss of dopamine in striatum or nigral tyrosine hydroxylase positive cells in substantia nigra. Also thioctic acid treatment did not reverse the BSO induced depletion of GSH or prevent the potentiation of 6-OHDA neurotoxicity produced by BSO. Thioctic acid (50 mg or 100 mg/kg i.p.) alone or in combination with BSO did not alter striatal dopamine levels but increased dopamine turnover. Striatal 5-HT content was not altered by thioctic acid but 5-HIAA levels were increased. Under conditions of inhibition of GSH synthesis, thioctic acid does not replenish brain GSH levels or protect against 6-OHDA toxicity. At last in this model of Parkinson's disease, thioctic acid does not appear to have a neuroprotective effect.