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PubMed2005

Lipoic acid improves glucose utilisation and prevents protein glycation and AGE formation.

The present study investigates the antiglycating effect of alpha-lipoic acid (LA) in high fructose-fed rats in vivo and its potential to inhibit the process of glycation in vitro. In addition, the effect of LA on glucose utilisation in rat diaphragm was also studied. Rats fed a high fructose diet (60% total calories) were administered with 35 mg/kg b.w, lipoic acid (LA) intraperitoneally for 20 days. The effects of LA on plasma glucose, fructosamine, protein glycation and glycated haemoglobin in high fructose rats and on in vitro glycation were studied. In vitro utilization of glucose was carried out in normal rat diaphragm in the presence and absence of insulin in which LA was used as an additive. The contents of glucose, glycated protein, glycated haemoglobin and fructosamine were significantly lowered on LA administration to high fructose-fed rats. LA prevented in vitro glycation and the accumulation of advanced glycation end products. Further LA enhanced glucose utilization in the rat diaphragm. This effect was additive to that of insulin and did not interfere with the action of insulin. The findings provide evidence for the therapeutic utility of lipoic acid in diabetes and its complications.

Albumins↗
PubMed2003

Vitamin C, glutathione, or lipoic acid did not decrease brain or kidney mercury in rats exposed to mercury vapor.

UNLABELLED: Some medical practitioners prescribe GSH and vitamin C alone or in combination with DMPS or DMSA for patients with mercury exposure that is primarily due to the mercury vapor emitted by dental amalgams. HYPOTHESIS: This study tested the hypothesis that GSH, vitamin C, or lipoic acid alone or in combination with DMPS or DMSA would decrease brain mercury. METHODS: Young rats were exposed to elemental mercury by individual nose cone, at the rate of 4.0 mg mercury per m3 air for 2 h per day for 7 consecutive days. After a 7-day equilibrium period, DMPS, DMSA, GSH, vitamin C, lipoic acid alone, or in combination was administered for 7 days and the brain and kidneys of the animals removed and analyzed for mercury by cold vapor atomic absorption. RESULTS: None of these regimens reduced the mercury content of the brain. Although DMPS or DMSA was effective in reducing kidney mercury concentrations, GSH, vitamin C, lipoic acid alone, or in combination were not. CONCLUSION: One must conclude that the palliative effect, if any, of GSH, vitamin C, or lipoic acid for treatment of mercury toxicity due to mercury vapor exposure does not involve mercury mobilization from the brain and kidney.

Administration, Inhalation↗
PubMed2003

The influence of lipoic acid on adriamycin-induced hyperlipidemic nephrotoxicity in rats.

Adriamycin widely used in the treatment of neoplastic conditions is nephrotoxic. In the present study the protective effect of lipoic acid was investigated in adriamycin-induced nephrotoxicity in adult male albino Wistar rats. Adriamycin-induced nephrotoxicity was characterized by hyperlipidemia, proteinuria, and hypoproteinemia, by decreased activities of the enzymes N-acetyl-beta-D-glucosaminidase and cathepsin D, by increased lipid peroxidation and decreases in serum catalase and glutathione activities, and by increased urinary and serum urea, creatinine and urinary glycosaminoglycans. Pretreatment with lipoic acid restored the changes, indicating that lipoic acid is renoprotective in adriamycin nephrotoxicity.

Acetylglucosaminidase↗
PubMed1998

alpha-Lipoic acid: a metabolic antioxidant which regulates NF-kappa B signal transduction and protects against oxidative injury.

Although the metabolic role of alpha-lipoic acid has been known for over 40 years, it is only recently that its effects when supplied exogenously have become known. Exogenous alpha-lipoic acid is reduced intracellularly by at least two and possibly three enzymes, and through the actions of its reduced form, it influences a number of cell process. These include direct radical scavenging, recycling of other antioxidants, accelerating GSH synthesis, and modulating transcription factor activity, especially that of NF-kappa B (Fig. 12). These mechanisms may account for the sometimes dramatic effects of alpha-lipoic acid in oxidative stress conditions (e.g., brain ischemia-reperfusion), and point the way toward its therapeutic use.

Animals↗
PubMedDate not supplied

Stability study of lipoic acid in the presence of vitamins A and E in o/w emulsions for cosmetic application.

The effectiveness of any cosmetic product containing a functional ingredient is determined by the skin delivery of the active molecule, which is influenced by the type of carrier and the molecule itself. Furthermore, the functional ingredient should be stable in the formulation. The purpose of this paper is to study the stability of lipoic acid in the presence of vitamins A (as palmitate) and E (as acetate) in semisolids for cosmetic use. The systems formulated were studied in regard to their aspect, pH, stability under centrifugation, and rheological behavior. The chemical analyses of lipoic acid and vitamins A and E were carried out by HPLC after studying the specificity of the method employed in each case. The quantitation of the active principles was performed by HPLC with C18 (5 microm) columns. The mobile phase was methanol for the vitamins, with spectrophotometric detection at 325 nm for vitamin A and 230 nm for vitamin E. The mobile phase for lipoic acid was methanol:water (80:20) and phosphoric acid at pH 3.0, with spectrophotometric detection at 332 nm. All systems were stable to centrifugation, and no significant modification of rheological behavior was observed in relation to the base emulsion used as control. The chemical studies performed indicated that although lipoic acid is not very stable in these formulations, the presence of vitamin A favors its chemical stability.

Centrifugation↗
PubMed2004

Alpha-lipoic acid in the treatment of autonomic diabetic neuropathy (controlled, randomized, open-label study).

AIM: to evaluate the effect of alpha-lipoic acid in autonomic diabetic neuropathy in a controlled, randomized, open-label study. MATERIAL AND METHODS: 46 patients with type 1 diabetes and different forms of autonomic neuropathy, of mean age 38.1 +/- 12.5 years and mean duration of diabetes 16.8 +/- 8.9 years were treated with alpha-lipoic acid for 10 days 600mg daily iv, thereafter one film tablet of 600mg daily for 50 days. 29 type 1 diabetic patients with autonomic diabetic neuropathy, of mean age 40.2 +/- 9.3 years and mean duration of diabetes 15.4 +/- 7.9 years served as a control group. We have followed-up patients' complaints, Ewing's tests, laboratory parameters of oxidative stress. RESULTS: There was a significant improvement after treatment in the score for severity of cardiovascular autonomic neuropathy--from 6.43 +/- 0.9 to 4.24 +/- 1.8 (p<0.001), while in the control group it worsened from 6.18 +/- 1.3 to 6.52 +/- 0.9 (p>0.1). We found improvement in the Valsalva manoeuvre after treatment - from 1.05 +/- 0.04 to 1.13 +/- 0.08 (p<0.001); in the deep-breathing test -from 3.4 +/- 2.8 to 10.4 +/- 5.7 (p<0.001); and in the lying-to-standing test--from 0.99 +/- 0.01 to 1.01 +/- 0.02 (p>0.1), while in the control group there was no improvement. There was a beneficial effect of treatment on the change of systolic blood pressure at the lying-to-standing test--from 22.7 +/- 11.5 to 9.8 +/- 7.9 (p<0.001), while in the control group the change was 20.5 +/- 11.1 mmHg and 19.7 +/- 12.9 mmHg (p>0.1), respectively. We found improvement in diabetic enteropathy in six patients; in the complaints of dizziness, instability upon standing in six patients; in neuropathic edema of the lower extremities in four patients and in erectile dysfunction in four patients after treatment, while in the control group no change was reported in the symptoms and signs of autonomic neuropathy by the end of the follow-up period. There were changes in the laboratory parameters of oxidative stress after therapy--total serum antioxidant capacity increased from 20.42 +/- 1.8 to 22.96 +/- 2.3 microgH2O2/ml/min (p<0.05), serum SOD activity - from 269.8 +/- 31.1 to 319.8 +/- 29.IU/l (p=0.02) and erythrocyte SOD--from 0.89 +/- 0.10 to 1.11 +/- 0.09 U/gHb (p=0.04). CONCLUSION: Our results demonstrate that alpha-lipoic acid (Thiogamma) appears to be an effective drug in the treatment of the different forms of autonomic diabetic neuropathy.

Adult↗
PubMed1997

Cytosolic and mitochondrial systems for NADH- and NADPH-dependent reduction of alpha-lipoic acid.

In cellular, tissue, and organismal systems, exogenously supplied alpha-lipoic acid (thioctic acid) has a variety of significant effects, including direct radical scavenging, redox modulation of cell metabolism, and potential to inhibit oxidatively-induced injury. Because reduction of lipoate to dihydrolipoate is a crucial step in many of these processes, we investigated mechanisms of its reduction. The mitochondrial NADH-dependent dihydrolipoamide dehydrogenase exhibits a marked preference for R(+)-lipoate, whereas NADPH-dependent glutathione reductase shows slightly greater activity toward the S(-)-lipoate stereoisomer. Rat liver mitochondria also reduced exogenous lipoic acid. The rate of reduction was stimulated by substrates which increased the NADH content of the mitochondria, and was inhibited by methoxyindole-2-carboxylic acid, a dihydrolipoamide dehydrogenase inhibitor. In rat liver cytosol, NADPH-dependent reduction was greater than NADH, and lipoate reduction was inhibited by glutathione disulfide. In rat heart, kidney, and brain whole cell-soluble fractions, NADH contributed more to reduction (70-90%) than NADPH, whereas with liver, NADH and NADPH were about equally active. An intact organ, the isolated perfused rat heart, reduced R-lipoate six to eight times more rapidly than S-lipoate, consistent with high mitochondrial dihydrolipoamide dehydrogenase activity and results with isolated cardiac mitochondria. On the other hand, erythrocytes, which lack mitochondria, somewhat more actively reduced S- than R-lipoate. These results demonstrate differing stereospecific reduction by intact cells and tissues. Thus, mechanisms of reduction of alpha-lipoate are highly tissue-specific and effects of exogenously supplied alpha-lipoate are determined by tissue glutathione reductase and dihydrolipoamide dehydrogenase activity.

Animals↗
PubMed1999

Neuroprotective effects of alpha-lipoic acid and its positively charged amide analogue.

Elevated levels of extracellular glutamate have been linked to reactive oxygen species mediated neuronal damage and brain disorders. Lipoic acid is a potent antioxidant that has previously been shown to exhibit neuroprotection in clinical studies. A new positively charged water soluble lipoic acid amide analog, 2-(N,N-dimethylamine) ethylamido lipoate HCl (LA-plus), with a better cellular reduction and retention of the reduced form was developed. This novel antioxidant was tested for protection against glutamate induced cytotoxicity in a HT4 neuronal cell line. Glutamate treatment for 12 h resulted in significant release of LDH from cells to the medium suggesting cytotoxicity. Measurement of intracellular peroxides showed marked (up to 200%) increase after 6 h of glutamate treatment. Compared to lipoic acid, LA-plus was more effective in (1) protecting cells against glutamate induced cytotoxicity, (2) preventing glutamate induced loss of intracellular GSH, and (3) disallowing increase of intracellular peroxide level following the glutamate challenge. The protective effect of LA-plus was found to be independent of its stereochemistry. The protective function of this antioxidant was synergistically enhanced by selenium. These results demonstrate that LA-plus is a potent protector of neuronal cells against glutamate-induced cytotoxicity and associated oxidative stress.

Animals↗
PubMedDate not supplied

Effect of alpha lipoic acid, melatonin and trans resveratrol on intracerebroventricular streptozotocin induced spatial memory deficit in rats.

In the present study, the effect of antioxidants-alpha lipoic acid, melatonin and trans resveratrol were studied against intracerebroventricular streptozotocin induced spatial memory deficit. Male Wistar rats were injected with intracerebroventricular streptozotocin bilaterally. The rats were treated chronically with alpha lipoic acid (200 mg/kg, po), melatonin (20 mg/kg, ip) and trans resveratrol (20 mg/kg, ip) for 18 days starting from day 1 of streptozotocin injection in separate groups. The spatial memory was evaluated using the Morris water maze task. The intracerebroventricular streptozotocin rats treated with antioxidants showed significantly less spatial memory deficit both in the acquisition and probe trials as compared to the vehicle treated rats. The study demonstrated the effectiveness of alpha lipoic acid, melatonin and trans resveratrol in preventing spatial memory deficit induced by intracerebroventricular streptozotocin and it's potential in age related neurodegenerative disorders where oxidative stress is involved such as Alzheimer's disease.

Animals↗
PubMedDate not supplied

[Effect of lipoic acid, biotin and pyridoxine on blood content of saturated and unsaturated fatty acids in ischemic heart disease and hypertension].

Gas liquid chromatography was used to examine the effect of treatment on the blood content of saturated and unsaturated fatty acids in 75 patients with coronary heart disease and essential hypertension. There were three groups of patients. The first group (30 subjects) received lipoic acid, whereas the second one (30 subjects) were given biotin nd pyridoxine. Fifteen patients (controls) did not receive any vitamins. Lipoic acid was found to raise the content of linoleic and arachidonic acids and to decrease the content of myristic acid. Meanwhile administration of biotin and pyridoxine led to an increase in the content of eicosatriene and arachidonic acids and to a reduction in the concentration of myristic and stearic acids. In the 15 patients who did not receive any vitamins, the blood content of fatty acids remained unchanged. Comparatively, the preference is given to lipoic acid that raises the blood content of linoleic acid playing an important part in the prophylaxis of atherosclerosis.

Adult↗
PubMed2001

Effect of DL-alpha-lipoic acid on mitochondrial enzymes in aged rats.

Mitochondrial dysfunction appears to contribute to some of the loss of function accompanying ageing. Mitochondria from aged tissue use oxygen inefficiently impairing ATP synthesis and results in increased oxidant production. A high flux of oxidants not only damages mitochondria, but other important cell biomolecules as well. In the present investigation, the levels of lipid peroxidation, oxidized glutathione, non-enzymatic antioxidants and the activities of mitochondrial enzymes were measured in liver and kidney mitochondria of young and aged rats before and after lipoic acid supplementation. In both liver and kidney increase in the levels of mitochondrial lipid peroxidation and oxidized glutathione and decrease in the levels of antioxidants and the activities of mitochondrial enzymes were observed in aged rats. DL-alpha-lipoic acid supplemented aged rats showed a decrease in the levels of lipid peroxidation and oxidized glutathione and increase in the levels of reduced glutathione, vitamins C and E and the activities of mitochondrial enzymes like isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase, succinate dehydrogenase, NADH-dehydrogenase and cytochrome-c-oxidase. Thus, lipoic acid reverses the age-associated decline in endogenous low molecular weight antioxidants and mitochondrial enzymes and, therefore, may lower the increased risk of oxidative damage that occurs during ageing. From our results it can be concluded that lipoic acid supplementation enhances the activities of mitochondrial enzymes and antioxidant status and thereby protects mitochondria from ageing.

Aging↗
PubMed1993

Polymerizable phospholipids with lipoic acid as head group: synthesis and phase properties.

Lipoic acid-substituted phospholipids were synthesized from phosphatidyl cholines by exchanging the choline residue with a glycol group using phospholipase D, forming phosphatidylglycols, and coupling of lipoic acid (1,2-dithiolane-3-pentanoic acid) to the residual glycol hydroxyl group by esterification. The thermotropic properties of aqueous dispersions of the phosphatidylglycols and the phosphatidylglycolipoates with different chain lengths were studied by differential scanning calorimetry (DSC) and differential scanning densitometry (DSD). The exchange of choline with glycol increases the phase transition temperature Tm for the gel to liquid-crystalline phase transition by approximately 5 degrees, independent of the chain length. Consecutive esterification of the glycol residue with lipoic acid causes a decrease of the transition temperature Tm by approximately 22 degrees compared with the phosphatidylglycols. Polymerization of vesicles prepared from phosphatidylglycolipoates was induced by the addition of dithiothreitol and followed by DSC and DSD. Polymerization has only slight influence on the transition behavior, indicating that the polymer chain in the head group is effectively decoupled from the hydrocarbon region. Polymerized vesicles show increased stability towards aggregation and fusion.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2003

Alpha-lipoic acid and cardiovascular disease.

Alpha-lipoic acid (ALA) has been identified as a powerful antioxidant found naturally in our diets, but appears to have increased functional capacity when given as a supplement in the form of a natural or synthetic isolate. ALA and its active reduced counterpart, dihydrolipoic acid (DHLA), have been shown to combat oxidative stress by quenching a variety of reactive oxygen species (ROS). Because this molecule is soluble in both aqueous and lipid portions of the cell, its biological functions are not limited solely to one environment. In addition to ROS scavenging, ALA has been shown to be involved in the recycling of other antioxidants in the body including vitamins C and E and glutathione. Not only have the antioxidant qualities of this molecule been studied, but there are also several reports pertaining to its blood lipid modulating characteristics, protection against LDL oxidation and modulation of hypertension. Therefore, ALA represents a possible protective agent against risk factors of cardiovascular disease (CVD). The objective of this review is to examine the literature pertaining to ALA in relation to CVD and describe the most powerful actions and potential uses of this naturally occurring antioxidant. Despite the numerous studies on ALA, many questions remain relating to the use of ALA as a supplement. There is no consensus on dosage, dose frequency, form of administration, and/or preferred form of ALA. However, collectively the literature increases our understanding of the potential uses for supplementation with ALA and identifies key areas for future research.

Antioxidants↗
PubMed2001

Protection against oxidative stress-induced insulin resistance in rat L6 muscle cells by mircomolar concentrations of alpha-lipoic acid.

In diabetic patients, alpha-lipoic acid (LA) improves skeletal muscle glucose transport, resulting in increased glucose disposal; however, the molecular mechanism of action of LA is presently unknown. We studied the effects of LA on basal and insulin-stimulated glucose transport in cultured rat L6 muscle cells that overexpress GLUT4. When 2-deoxy-D-glucose uptake was measured in these cells, they were more sensitive and responsive to insulin than wild-type L6 cells. LA, at concentrations < or = 1 mmol/l, had only small effects on glucose transport in cells not exposed to oxidative stress. When cells were exposed to glucose oxidase and glucose to generate H2O2 and cause oxidative stress, there was a marked decrease in insulin-stimulated glucose transport. Pretreatment with LA over the concentration range of 10-1,000 pmol/l protected the insulin effect from inhibition by H2O2. Both the R and S isomers of LA were equally effective. In addition, oxidative stress caused a significant decrease (approximately 50%) in reduced glutathione concentration, along with the rapid activation of the stress-sensitive p38 mitogen-activated protein kinase. Pretreatment with LA prevented both of these events, coincident with protecting insulin action. These studies indicate that in muscle, the major site of insulin-stimulated glucose disposal, one important effect of LA on the insulin-signaling cascade is to protect cells from oxidative stress-induced insulin resistance.

Animals↗
PubMed1997

alpha-Lipoic acid corrects neuropeptide deficits in diabetic rats via induction of trophic support.

This study compared the effects of treatment of diabetic rats with either alpha-lipoic acid (100 mg/kg/day i.p. 5 days/week) or with recombinant human nerve growth factor (rhNGF; 0.2 mg/kg s.c. 3 days/week) on NGF-like immunoreactivity (NGFLI) and neuropeptide Y-like immunoreactivity (NPYLI) levels in the sciatic nerve and on the release of substance P-like immunoreactivity (SPLI) from the spinal cord in response to electrical stimulation of the dorsal roots in vitro. Diabetic rats showed depletion of NGFLI and NPYLI, together with reduced release of SPLI. Treatment with NGF increased the sciatic nerve NGFLI (to four times that seen in untreated diabetic rats) and normalised stimulus-evoked release of SPLI, but did not affect the sciatic nerve NPYLI. Treatment with alpha-lipoic acid caused a small non-significant increase in sciatic nerve NGFLI, but normalised both NPYLI levels and stimulus-evoked release of SPLI. These findings indicate that alpha-lipoic acid can boost neurotrophic support in diabetic rats, with effects beyond those related to NGF.

Animals↗
PubMed2004

Alpha-lipoic acid, an anti-obesity agent?

Obesity shortens life expectancy and is a risk factor for hypertension and Type 2 diabetes. When added to the standard chow of Sprague-Dawley or Otsuka Long-Evans Tokushima Fatty rats, alpha-lipoic acid (0.5% weight/weight) reduced body weight and food intake. Alpha-lipoic acid also increased whole-body energy expenditure. It exerts its effects by suppressing hypothalamic AMP-activated protein kinase. Long-term studies to determine whether these anti-obesity effects are maintained in animals are required before alpha-lipoic acid is considered for clinical trial in human obesity.

AMP-Activated Protein Kinases↗
PubMed1995

Dose/response curves of lipoic acid R-and S-forms in the working rat heart during reoxygenation: superiority of the R-enantiomer in enhancement of aortic flow.

Micromolar concentrations of lipoic acid racemate added to a working rat heart during hypoxia have been previously found to improve aortic flow during subsequent reoxygenation. Since the R-form represents the naturally occurring form of lipoic acid, and the S-form does not reveal a positive influence on ATP synthesis in isolated mitoplasts, a dose/response curve of both enantiomers has been performed in working rat hearts. After the end of perfusion mitochondria were isolated and further analysed. At a concentration of 0.05-0.1 mumol of the R-enantiomer, aortic flow rises precipitously during reoxygenation, reaching over 70% of normoxic values compared to 50% of the controls. By contrast, with the S-enantiomer a value of about 60% is attained at 1 mumol, only. Accordingly, ATPase activity in mitochondria isolated from rat hearts previously treated with 0.05-0.1 mumol of the R- or S-enantiomer was significantly decreased or increased respectively. Consequently, whereas mitochondrial ATP synthesis was increased when the R-enantiomer was previously added to the working heart at 0.05-0.1 mumol concentration, with the S-enantiomer ATP synthesis remained within the control range. Mitochondrial membrane fluidity, measured with diphenylhexatriene, revealed a trend towards increase with the R- and decrease with the S-enantiomer. The total amount of thiol added at 0.1 mumol concentration is consistent with a value of 2 nmol/mg mitochondrial protein. This value has previously been found to be connected with -SH groups which add oligomycin-sensitivity to the ATPase complex. It is suggested that oligomycin-sensitive mitochondrial -SH groups contribute to the overall efficiency of low concentrations of lipoic acid R-enantiomer to enhance aortic flow.

Adenosine Triphosphatases↗
PubMed2005

Alpha-lipoic acid protects against cholecystokinin-induced acute pancreatitis in rats.

AIM: Alpha-lipoic acid (ALA) has been used as an antioxidant. The aim of this study was to investigate the effect of alpha-lipoic acid on cholecystokinin (CCK)-octapeptide induced acute pancreatitis in rats. METHODS: ALA at 1 mg/kg was intra-peritoneally injected, followed by 75 microg/kg CCK-octapeptide injected thrice subcutaneously after 1, 3, and 5 h. This whole procedure was repeated for 5 d. We checked the pancreatic weight/body weight ratio, the secretion of pro-inflammatory cytokines and the levels of lipase, amylase of serum. Repeated CCK octapeptide treatment resulted in typical laboratory and morphological changes of experimentally induced pancreatitis. RESULTS: ALA significantly decreased the pancreatic weight/body weight ratio and serum amylase and lipase in CCK octapeptide-induced acute pancreatitis. However, the secretion of IL-1beta, IL-6, and TNF-alpha were comparable in CCK octapeptide-induced acute pancreatitis. CONCLUSION: ALA may have a protective effect against CCK octapeptide-induced acute pancreatitis.

Acute Disease↗