Lipoic acid is 10 times more toxic in cats than reported in humans, dogs or rats

Alpha lipoic acid toxicosis in cats (2008-2016): Four cases

OBJECTIVE

To review clinical signs, treatments, and outcome of 4 cases in cats after ingestion of alpha lipoic acid.

CASE SERIES SUMMARY

Four cases with known alpha lipoic acid ingestions developed clinical signs. A consistent clinical sign in all cases was vomiting, while 2 of the 4 cases resulted in death.

NEW OR UNIQUE INFORMATION PROVIDED

This is the first reported case series of alpha lipoic acid ingestions in cats.

Cognitive Dysfunction in Cats: Update on Neuropathological and Behavioural Changes Plus Clinical Management

Cognitive dysfunction syndrome (CDS) is an established condition in cats that shares many similarities with human Alzheimer's disease (AD), where cognitive decline ultimately results in dementia. Cats with CDS display behavioural abnormalities, including excessive Vocalisation, altered Interaction with owners (increased affection/attention), altered Sleep-wake cycles, House-soiling, Disorientation (spatial and/or temporal), alterations in Activity, Anxiety, and/or Learning/memory deficits (i.e., VISHDAAL). These cats develop neuropathologies, such as accumulation of β-amyloid and hyperphosphorylated tau deposits. Because of its similarities to those in the brains of people with cognitive impairment and AD, the domestic cat could be a natural model for human dementia studies. It is important to diagnose CDS promptly in cats, ruling out other causes for these behavioural changes, to provide effective management. Interventions include environmental enrichment (e.g., easy access to key resources, calming pheromones), dietary supplementations (e.g., Senilife, Aktivait for cats, SAMe), specific diets (e.g., containing antioxidants, medium-chain triglycerides) and, potentially, medication (e.g., selegiline or propentofylline). This article reviews the literature about CDS in cats, its causes, neuropathology, clinical signs, diagnosis and potential management options. By doing so, it furthers our understanding of this condition and allows improved health, welfare and quality of life of affected cats.

The Effect of Alpha Lipoic Acid on the Recovery of Sciatic Nerve Injury in Rats: A Prospective Randomized Controlled Trial

OBJECTIVE

The aim of this study was to investigate the regenerative effects of alpha lipoic acid on the recovery of sciatic nerve crush injury (SNCI) in rats.

DESIGN

This was a randomized, experimental, and sham-controlled study. The sciatic nerves of 28 rats in four groups were traumatized for 60 secs: G1, sham operated + saline; G2, SNCI + saline; G3, SNCI + alpha lipoic acid 50 mg/kg/day; and G4, SNCI + alpha lipoic acid 100 mg/kg/day. Sciatic functional index values were measured on day 0, 1, 7, 14, 21, and 28. Sciatic nerve stimulation threshold values were recorded on day 1, 14, and 28. End-point histopathologic evaluation was conducted.

RESULTS

The mean sciatic functional index value of G2 but not G3/G4 on day 7 was significantly lower than on day 0 (P = 0.035, P = 0.447/P = 0.800). The mean sciatic functional index value of G2 but not G3/G4 increased significantly between day 7 and 14 (P = 0.035, P = 0.447/P = 0.438). The day 14 mean sciatic nerve stimulation threshold values of G3/G4 but not G2 were decreased significantly compared with those on day 1 (P = 0.022/P = 0.022, P = 0.933). The mean sciatic nerve stimulation threshold values of G3/G4 on day 14 were similar to those on day 0 (P = 0.106/P = 0.418). Regeneration in muscle and nerve connective tissues and nerve structures was observed in G3/G4. Inflammation in the muscle and nerve tissues of G4 was suppressed down to similar levels of G1. Myelinated nerve fibers were less degenerated in G3/G4.

CONCLUSION

Alpha lipoic acid has the potential to accelerate the process of nerve healing in the context of SNCI in rats.

Alpha-Lipoic Acid as a Nutritive Supplement for Humans and Animals: An Overview of Its Use in Dog Food

Simple Summary

A review of human and animal studies involving alpha-lipoic acid supplementation was conducted to determine the utility of alpha-lipoic acid in dog food. The present literature shows that alpha-lipoic acid has utility as a nutritive additive at concentrations of 2.7–4.94 mg/kg body weight/day and improves antioxidant capacity in dogs.

Abstract

Alpha-lipoic acid (a-LA) is used as a nutritive additive in dog food. Therefore, we performed a systematic review of studies published to date in PubMed, Google Scholar, Cochrane Library and MedlinePlus involving alpha-lipoic acid supplementation, which included human clinical trials as well as animal studies, to evaluate its utility as a supplement in foods for healthy, adult dogs. While an upper limit of alpha-lipoic acid intake in humans has not been conclusively determined, the levels for oral intake of a-LA have been better defined in animals, and distinct differences based on species have been described. The maximum tolerated oral dose of a-LA in dogs has been reported as 126 mg/kg body weight and the LD₅₀ as 400 to 500 mg/kg body weight. The antioxidant, anti-inflammatory and neuro-protective benefits of alpha-lipoic acid in dogs were observed at concentrations much lower than the maximum tolerated dose or proposed LD₅₀. At concentrations of 2.7–4.94 mg/kg body weight/day, alpha-lipoic acid is well tolerated and posed no health risks to dogs while providing improved antioxidant capacity. This review thereby supports the utility of alpha-lipoic acid as an effective nutritive additive in dog food.

Alpha-Lipoic Acid Is an Effective Nutritive Antioxidant for Healthy Adult Dogs

Simple Summary

A 6 month prospective, controlled clinical trial was conducted to determine the nutritive antioxidant activity of alpha-lipoic acid as a maintenance food for healthy adult (non-gestational, non-lactating) dogs. The results of the study showed that increasing concentrations of alpha-lipoic acid induced a significant increase in the concentrations of intracellular glutathione, an important biomarker of the antioxidant system.

Abstract

This study was designed to determine the effect of alpha-lipoic acid on the glutathione status in healthy adult dogs. Following a 15 month baseline period during which dogs were fed a food containing no alpha-lipoic acid, dogs were randomly allocated into four groups. Groups were then fed a nutritionally complete and balanced food with either 0, 75, 150 or 300 ppm of alpha-lipoic acid added for 6 months. Evaluations included physical examination, body weight, food intake, hematology, serum biochemistry profile and measurements of glutathione in plasma and erythrocyte lysates. Throughout, blood parameters remained within reference ranges, dogs were healthy and body weight did not change significantly. A significant increase of 0.05 ng/mL of total glutathione in red blood cell (RBC) lysate for each 1 mg/kg bodyweight/day increase in a-LA intake was observed. In addition, a significant increase was observed for GSH, GSSG and total glutathione in RBC lysate at Month 6. We conclude that alpha-lipoic acid, as part of a complete and balanced food, was associated with increasing glutathione activity in healthy adult dogs.

Toxicological Profile of the Pain-Relieving Antioxidant Compound Thioctic Acid in Its Racemic and Enantiomeric Forms

Thioctic acid is a multipotent antioxidant compound existing as dextrorotatory (+), eutomer and naturally occurring and levorotatory (-). It has been proven to help fight many pathologies and is sold as racemate. In agreement with studies claiming a greater biopotency of the eutomer compared to the levorotatory compound, we recently preclinically and clinically showed that (+) thioctic acid is a pain-reliever as effective as double-dosed racemate. We investigated acute and subchronical toxicity of (+/-) thioctic acid, (-) thioctic acid, (+) thioctic acid and (+) salt thioctic acid on Sprague-Dawley rats. For acute toxicity, compounds were administered intraperitoneally (i.p.) with a single-injection at 125, 240, 360, 480 µmol/kg, then rodents were tested for motorial coordination and minimum lethal dose (LDmin). A subtoxic dose (360 µmol/kg) was administered i.p. for 15 days and we finally evaluated motorial impairment, glycemia, organ toxicity, and apoptosis state. Acutely administered, the highest doses of all thioctic acid compounds negatively affected motorial ability and (-) thioctic acid LDmin resulted higher than the others. Subchronic administrations caused overall body weight loss, motorial impairment, mass loss in some organs. (+/-) and (-) thioctic acid injections enhanced caspase-3 activity in some organs, (-) enantiomer-treated animals displayed more marked organ toxicity signs. Together with our previous study on the biologic role of enantiomers, these data suggest a therapeutic use of (+) enantiomer-based formulations, thus lowering dose and toxicity without affecting the positive effects brought by the drug.

Effects of acetyl L-carnitine on zebrafish embryos: Phenotypic and gene expression studies

Acetyl L-carnitine (ALCAR), a dietary supplement and an antioxidant, plays a vital role in the bioenergetic process that produces ATP. Although there are reports on antioxidant toxicity, there is no information on the potential toxicity of ALCAR. Here, using zebrafish embryos, we explored whether ALCAR modulated ATP synthesis, generation of reactive oxygen species (ROS) and expression of specific genes related to major signaling pathways that control metabolism, growth, differentiation, apoptosis and oxidative stress. First, we show that ALCAR elicits a physiologic response, as ATP levels increased after ALCAR treatment. Simultaneously, an increase in the expression of ROS, a by-product of ATP synthesis, was observed in the ALCAR-treated embryos. Consistent with higher ROS expression, the level of cysteine, a precursor of glutathione, was significantly reduced. ALCAR did not have any drastic effect on overall development and heart rate. Polymerase chain reaction-based gene expression array analyses showed no significant change in the expression of 83 genes related to 10 major signaling pathways including: the transforming growth factor β (TGFβ), Wingless and Int-1 (Wnt), nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB), Janus kinase/signal transducers and activators of transcription (JAK/STAT), p53, Notch, Hedgehog, Peroxisome proliferator-activated receptor (PPAR), oxidative stress, and hypoxia pathways. Our results show that the expression of 83 genes related to these major signaling pathways did not change significantly.

Potential Causes of Increased Vocalisation in Elderly Cats with Cognitive Dysfunction Syndrome as Assessed by Their Owners

The objectives of this study were to explore owner perception of the causes of increased vocalisation in cats diagnosed with cognitive dysfunction syndrome (CDS) and consider what impact this vocalisation may have on the cat's household. Owners of cats diagnosed with CDS that presented with increased vocalisation were invited to complete an online survey. The survey consisted of 28 questions including the cat's signalment, its medical history, and questions pertaining to the owner's perception of what motivated their cat´s increased vocalisation. This was determined by looking at the cat's behaviour when vocalising, where it was looking when it was vocalising, and if the vocalisation stopped when the owner interacted with it, e.g., petting or feeding it. The owners were also asked how stressful they found their cat's vocalisation. There were 37 responses. The majority of owners reported that the main cause of their cat's vocalisation appeared to be disorientation (40.5%) or attention seeking (40.5%). Seeking a resource such as food was reported in 16.2%, and pain was perceived to be the cause in only 2.7% of cats. However, the majority of owners (64.8%) believed there was >1 cause of their cat's increased vocalisation. Importantly, when owners were asked how stressful they found their cat's increased vocalisation, 40.5% scored ≥3 (where 1 = not stressful; 5 = significantly stressful). This study provides novel insight into owner perception of feline CDS, as well as potential causes for increased vocalisation; this will allow veterinarians to better advise owners on how to manage their cat with CDS.

Pathophysiology and aetiology of hypoglycaemic crises

Hypoglycaemia is a common, life-threatening complication that occurs as a component of a wide variety of disease processes. Despite its frequent occurrence, information concerning the aetiology, characteristics and outcomes of hypoglycaemic crises in veterinary medicine is limited. This review summarises the current understanding of the pathophysiology of hypoglycaemia, the body's counter-regulatory response, underlying aetiologies, diagnosis and treatment. Disease mechanisms are discussed and published evidence in veterinary literature regarding prognostic indicators, prevalence, diagnosis and treatment is examined for hypoglycaemia-related disease processes including insulinoma, glucose-lowering toxins and medications.

Supplements for exotic pets

The use of supplements has become commonplace in an effort to complement traditional therapy and as part of long-term preventive health plans. This article discusses historical and present uses of antioxidants, vitamins, and herbs. By complementing traditional medicine with holistic and alternative nutrition and supplements, the overall health and wellness of exotic pets can be enhanced and balanced. Further research is needed for understanding the strengths and uses of supplements in exotic species. Going back to the animals' origin and roots bring clinicians closer to nature and its healing powers.

Pre-clinical and Clinical Safety Studies of CMX-2043: a cytoprotective lipoic acid analogue for ischaemia-reperfusion injury

CMX-2043 is an α-lipoic acid analogue targeted to reduction of cellular injury and organ damage due to ischaemia–reperfusion injury (IRI). It has been shown to be effective in a rat model of cardiac IRI. The studies here reported evaluate its safety and pharmacokinetic profile in preparation for human clinical studies in procedures associated with IRI. Safety and tolerability were tested in standard pre-clinical in vitro and animal models and in a Phase 1 human clinical trial. CMX-2043 did not bind to a wide range of receptors and specific targets at approximately 4 μg/mL (10 μM). It was not mutagenic by Ames assay, did not produce chromosome aberrations in Chinese hamster ovary (CHO) cells, and was negative for clastogenic potential. Toxicological studies in rats including both single and 14-day repeat intravenous doses and in dogs (single intravenous dose) with a 2-week recovery period were conducted. The NOAEL in rats and dogs was 30 and >10 mg/kg, respectively. No serious adverse events were reported in a placebo-controlled, sequential dose escalation Phase 1 clinical trial. The low toxicity in the pre-clinical studies and the absence of adverse events in the Phase 1 trial have supported investigation of CMX-2043 in a human efficacy trial.

Antioxidant and toxicological effects elicited by alpha-lipoic acid in aquatic organisms

Lipoic acid (LA) is a disulfide-containing compound derived from octanoic acid that is synthesized in mitochondria. This molecule acts as a co-factor for mitochondrial enzymes that catalyze oxidative decarboxylation reactions. Several antioxidant properties of LA enable it to be considered as an "ideal antioxidant", having diverse benefits that allow it to deal with environmental or biological stress. Some of the effects induced by LA in aquatic organisms render it suitable for use in aquaculture. However, it is necessary to determine the appropriate dose(s) to be used with different species and even organs to maximize the beneficial antioxidant and detoxifying effects and to minimize the pro-oxidant toxic effects. This review analyzes and compiles existing data from aquatic organisms in which both benefits and drawbacks of LA have been described.

Cognitive dysfunction in cats: clinical assessment and management

Increasing numbers of cats are living to become elderly and they commonly develop behavioral changes. The objectives of this article are to consider the possible causes and prevalence of behavioral problems in pet cats, to describe how cognitive dysfunction syndrome (CDS) typically presents, and how its diagnosis and management are often complicated by the concurrent presence of multiple interacting disease processes. The most frequently reported behavioral problems in old cats are loss of litter box training and crying out loudly at night. The most common causes of these problems are CDS, osteoarthritis, systemic hypertension (commonly secondary to chronic kidney disease or hyperthyroidism), hyperthyroidism (even without hypertension), deafness, and brain tumors. These conditions all occur frequently in older cats, many of which suffer from a number of concurrent interacting conditions. Owners and veterinary surgeons often mistake these for "normal aging changes," so many treatable conditions are neglected and go untreated. Almost one third of cats 11 to 14 years of age develop at least one geriatric-onset behavior problem that appears to relate to CDS, and this increases to over 50% for cats 15 years of age or older. For optimum management of elderly cats with behavioral problems, all interacting conditions need to be diagnosed and addressed concurrently with management for CDS.

Cognitive dysfunction in cats: a syndrome we used to dismiss as 'old age'

PRACTICAL RELEVANCE

Cognitive dysfunction syndrome (CDS) is a widely accepted diagnosis in dogs, with established treatment options. In cats, however, our understanding of cognitive dysfunction is still being shaped by ongoing research in the field, and limited treatment options are available. Recent clinical studies indicate that old age in the cat is accompanied by increased behavioural signs such as wandering, vocalization and night-time activity that are not attributable to identifiable medical problems. It is essential, therefore, that veterinarians include behavioural well-being in the routine care of senior cats.

PATIENT GROUP

While the exact age of onset is not established, studies suggest that age-related behavioural changes consistent with cognitive dysfunction are prevalent in cats as early as 10 years of age and that prevalence increases significantly in older cats.

CLINICAL CHALLENGES

The diagnosis of cognitive dysfunction requires the identification of geriatric behavioural changes that are not caused by other medical problems, although the two may not be mutually exclusive. Therefore, the practitioner must rely heavily on owner reports and history to ensure prompt diagnosis and treatment. The absence of any approved dietary or pharmaceutical interventions for cognitive dysfunction adds a further challenge, although several possibilities exist.

EVIDENCE BASE

This article draws on recent research that has produced neuropathological, cognitive and behavioural evidence for cognitive dysfunction in aging cats. As an impetus to further our understanding of this disease and potential treatment options, the authors propose a behavioural checklist that might aid in the clinical diagnosis of feline CDS and discuss treatment options that have proven successful in the canine counterpart of this disease.

Alpha-lipoic acid induces elevated S-adenosylhomocysteine and depletes S-adenosylmethionine

Lipoic acid is a disulfhydryl-containing compound used in clinical medicine and in experimental models as an antioxidant. We developed a stable isotope dilution capillary gas chromatography/mass spectrometry assay for lipoic acid. We assayed a panel of the metabolites of transmethylation and transsulfuration 30 min after injecting 100 mg/kg lipoic acid in a rat model. Lipoic acid values rose 1000-fold in serum and 10-fold in liver. A methylated metabolite of lipoic acid was also detected but not quantitated. Lipoic acid injection caused a massive increase in serum S-adenosylhomocysteine and marked depletion of liver S-adenosylmethionine. Serum total cysteine was depleted but liver cysteine and glutathione were maintained. Serum total homocysteine doubled, with increases also in cystathionine, N,N-dimethylglycine, and alpha-aminobutyric acid. In contrast, after injection of 2-mercaptoethane sulfonic acid, serum total cysteine and homocysteine were markedly depleted and there were no effects on serum S-adenosylmethionine or S-adenosylhomocysteine. We conclude that large doses of lipoic acid displace sulfhydryls from binding sites, resulting in depletion of serum cysteine, but also pose a methylation burden with severe depletion of liver S-adenosylmethionine and massive release of S-adenosylhomocysteine. These changes may have previously unrecognized deleterious effects that should be investigated in both human disease and experimental models.

Alpha-lipoic acid as a dietary supplement: molecular mechanisms and therapeutic potential

Alpha-lipoic acid (LA) has become a common ingredient in multivitamin formulas, anti-aging supplements, and even pet food. It is well-defined as a therapy for preventing diabetic polyneuropathies, and scavenges free radicals, chelates metals, and restores intracellular glutathione levels which otherwise decline with age. How do the biochemical properties of LA relate to its biological effects? Herein, we review the molecular mechanisms of LA discovered using cell and animal models, and the effects of LA on human subjects. Though LA has long been touted as an antioxidant, it has also been shown to improve glucose and ascorbate handling, increase eNOS activity, activate Phase II detoxification via the transcription factor Nrf2, and lower expression of MMP-9 and VCAM-1 through repression of NF-kappa B. LA and its reduced form, dihydrolipoic acid, may use their chemical properties as a redox couple to alter protein conformations by forming mixed disulfides. Beneficial effects are achieved with low micromolar levels of LA, suggesting that some of its therapeutic potential extends beyond the strict definition of an antioxidant. Current trials are investigating whether these beneficial properties of LA make it an appropriate treatment not just for diabetes, but also for the prevention of vascular disease, hypertension, and inflammation.

Dietary lipoic acid-dependent changes in the activity and mRNA levels of hepatic lipogenic enzymes in rats

Effects of dietary α-lipoic acid on hepatic and serum lipid concentrations and the activity and mRNA levels of lipogenic enzymes were examined in rats. Rats were fed experimental diets containing varying amounts of lipoic acid (0, 1, 2·5, 5 g/kg) for 21 d. Lipoic acid profoundly decreased serum and liver concentrations of TAG, and also lowered serum concentrations of phospholipid and NEFA, and the concentration of cholesterol in the liver. A hypoglycaemic effect of this compound was also observed. Lipoic acid dose-dependently decreased the activity and mRNA levels of fatty acid synthase, ATP-citrate lyase, glucose 6-phosphate dehydrogenase, malic enzyme and pyruvate kinase in the liver despite that reductions were considerably attenuated in the NADPH-producing enzymes. This compound also dose-dependently lowered the mRNA levels of spot 14, adiponutrin, stearoyl-CoA desaturase 1, and Δ5- and Δ6-desaturases. In addition, lipoic acid dose-dependently lowered serum concentrations of insulin and leptin, but increased those of adiponectin. Lipoic acid appeared to reduce hepatic lipogenesis and hence decreases serum and liver lipid levels. Alterations in serum concentrations of insulin and (or) adiponectin may trigger this consequence.

Cognitive dysfunction and the neurobiology of ageing in cats

With improvements in nutrition and veterinary medicine the life expectancy of pet cats is increasing. Accompanying this growing geriatric population there are increasing numbers of cats with signs of apparent senility. A recent study suggests that 28 per cent of pet cats aged 11 to 14 years develop at least one geriatric onset behavioural problem, and this increases to over 50 per cent for cats of 15 years of age or older. While behavioural changes may result from systemic illness, organic brain disease or true behavioural problems, the possibility of age-related cognitive dysfunction is often overlooked. Studies have revealed a number of changes in the brains of geriatric cats that showed signs of cognitive dysfunction, and potential causes include vascular insufficiency leading to hypoxia, increased free radical damage and the deposition of beta-amyloid plaques and/or the modification of other proteins. By recognising the importance of behavioural changes in old cats, investigating them fully for potentially treatable medical conditions, and instigating dietary and environmental modifications to meet their changing needs, we can make the lives of our geriatric cats much more comfortable and rewarding.

Antioxidants in veterinary nutrition

Nutritional antioxidants have experienced a surge in research and interest in the past 20 years. this surge may be attributed to the improved methodology for investigation as well as the focus on diseases and aging processes related to oxidative stress that lend themselves to opportunistic outcomes. As such, the field of veterinary nutritional antioxidant research is also beginning to yield some interesting results, albeit, small in number compared with laboratory animals and human beings. Nonetheless, this article updates the practitioner on recent advances in research involving nutritional antioxidant applications in companion animals.

Safety evaluation of alpha-lipoic acid (ALA)

The safety of the antioxidant alpha-lipoic acid (racemic form) (ALA), also called thioctic acid (CAS RN 1077-28-7) was assessed in acute and subchronic toxicity studies as well as in in vitro and in vivo mutagenicity/genotoxicity studies. ALA was not acutely toxic to rats (LD(50)>2000mg/kg bw, OECD method 425). Administration of 31.6 or 61.9mg ALA/kg bw/day for 4 weeks to male/female Wistar rats did not show any adverse effects. Specifically, there was no significant difference between control and treated animals at 31.6 or 61.9mg ALA/kg bw with regard to body weight gain, feed consumption, animal behaviour, or haematological and clinical chemistry parameters. Only the high-dose of 121mg ALA/kg bw was associated with slight alterations in liver enzymes as well as histopathological effects on the liver and mammary gland. ALA did not possess any mutagenic activity in the Ames assays conducted with various bacterial strains of Salmonella typhimurium. Moreover, there was no evidence of genotoxic activity in a mouse micronucleus assay. The results of these studies support the safety of ALA. The no-observed-adverse-effect level (NOAEL) is considered to be 61.9mg/kg bw/day.

Long-term safety of alpha-lipoic acid (ALA) consumption: A 2-year study

Alpha-lipoic acid (ALA) (CAS RN 1077-28-7), also referred to as thioctic acid, has been demonstrated to exhibit strong anti-oxidant properties. In order to test the long-term toxicity of ALA, groups of 40-50 male and female, 5-6-week-old, Sprague-Dawley rats were subjected to oral administration of 20, 60, or 180 mg/kg body weight (bw)/day ALA for 24 months. There was no significant difference between control animals and treated animals at 20 or 60 mg/kg bw/day with respect to body weight gain, food consumption, behavioural effects, haematological and clinical chemistry parameters, and gross and histopathological findings. In all treatment groups, mortality was slightly lower as compared to the control. The absolute weights of the heart (high-dose males), thymus (high-dose males), and left adrenal (mid-dose males), liver (high-dose females), and lungs (high-dose females) were decreased in comparison to controls. These changes were of no toxicological significance. The only notable finding in rats of both sexes dosed at 180 mg/kg bw/day was a reduction in food intake relative to the controls and a concomitant decrease in body weight. This decrease in body weight led to significant differences between the control and high-dose rats with respect to the absolute weights of certain organs. However, no gross or histopathological changes were associated with these findings. The no-observed-adverse-effect level (NOAEL) is considered to be 60 mg/kg bw/day.

Effects of dietary antioxidant supplementation before and after oral acetaminophen challenge in cats

OBJECTIVE

To determine effects of lipoic acid, vitamin E, and cysteine before and after oxidant challenge in cats.

ANIMALS

24 sexually intact adult cats.

PROCEDURE

Cats were allocated into 4 equal groups. For 25 weeks, group A was fed a control dry diet and groups B, C, and D received this diet supplemented with vitamin E (2200 U/kg [dry matter basis {DMB}]) plus cysteine (9.5 g/kg [DMB]), lipoate (150 mg/kg [DMB]), or all 3 antioxidants together, respectively. Weights were measured every 3 days and venous blood obtained every 5 weeks for CBC; serum biochemical analyses; lymphocyte blastogenesis; thiobarbituric acid reactive substances concentration; and concentrations of plasma protein carbonyl, 8-OH d-guanosine, blood glutathione, plasma amino acid, lipoate, and dihydrolipoate. At 15 weeks, all cats received acetaminophen (9 mg/kg, PO, once), clinical effects were observed, and methemoglobin concentrations were measured.

RESULTS

Lymphocyte blastogenesis increased transiently in group C and D cats. After acetaminophen administration, all groups had transient increases in methemoglobin within 4 hours and mild, brief facial edema; group C had decreased glutathione concentration and increased 8-OH d-guanosine concentration versus controls; and protein carbonyl concentration increased least for group B. Plasma lipoate and dihydrolipoate concentrations peaked by week 10 for groups C and D. Conclusions and Clinical Relevance-Lipoate, vitamin E, and cysteine did not have synergistic effects. Lipoate supplementation (150 mg/kg [DMB]) did not act as an antioxidant but appeared to enhance oxidant effects of acetaminophen. Vitamin E plus cysteine had protective effects.

Lipoic acid and ascorbic acid affect plasma free amino acids selectively in the teleost fish pacu (Piaractus mesopotamicus)

Most studies on the antioxidants, lipoic acid (LA) and ascorbic acid (AA), focused on species that, unlike teleost fish, are not scurvy-prone, and are able to synthesize AA. The antioxidant properties of LA may make it useful in aquaculture nutrition, but several effects must first be investigated, and we address here plasma free amino acids (FAA). In mammals, LA and AA in high doses were claimed to alter plasma FAA profile; to our knowledge, however, no data are available in fish. We therefore studied the effects of dietary LA and AA on plasma FAA in the South American teleost fish pacu, which is being used increasingly in aquaculture. LA treatment decreased concentrations of 18 of 23 individual FAA; specifically, dispensable and total FAA were significantly affected. Ornithine was elevated (+26%) in LA-treated fish and significantly decreased ratios of plasma [Arg]/[Orn] and other individual [FAA]/[Orn] were observed. LA and AA both affected sulfur FAA concentrations. Plasma cystine levels were significantly increased in the LA-supplemented groups. AA had little effect on most amino acids, and no interaction with LA was detected. AA supplementation did, however, significantly lower taurine (-42%) and cystathionine (-31%) levels in plasma. No effect on the branched chain:aromatic amino acid ratios was observed. The data indicate that at the dietary level studied, LA and AA independently affect selected plasma FAA in pacu, and suggest that any use of LA in particular as a dietary supplement should take into account an altered plasma FAA profile.