Pharmacodynamic effects of orally administered dexlipotam on endothelial function in type 2-diabetic patients.

OBJECTIVE: Diabetic endotheliopathy is the result of hyperglycemia and the production of oxygen-free radicals. In vitro and in vivo data have shown beneficial effects of dexlipotam (DEX), a tromethamine salt of R(+)-alpha-lipoic acid, on oxidative stress in hyperglycemic states, but no data are available on the effects of this agent on endothelial function. The purpose of this pilot study was to evaluate the impact of DEX on endothelial function in patients with type 2 diabetes (DM2) and to estimate the safety and tolerability of DEX. MATERIAL AND METHODS: DEX 960 mg and DEX 1,920 mg were investigated in DM2 patients over a period of 4 weeks using a randomized, placebo- (PLA) controlled, double-blinded study with 3 parallel groups. The marker of arterial function after 4-week therapy with DEX was the maximum percentage change versus baseline in the flow-mediated dilation of the brachial artery (FMD) after reperfusion. RESULTS: A total of 114 diabetic patients were randomized to the three study groups. DEX was safe and well tolerated. Dyspepsia appeared to be the most relevant side effect of DEX treatment. Systolic (p = 0.078) and diastolic blood pressure (p = 0.059) tended to be lower in patients treated with DEX at a dose of 1,920 mg. There were no significant differences in FMD between the placebo- and the DEX-treated groups. In patients with poorer glucose control (HbA1c > 6.5% Hb), FMD increased significantly after 4-week treatment with DEX: PLA -1.51 +/- 2.98%, DEX 960 mg +1.22 +/- 3.22, p = 0.027, DEX 1,920 mg +1.47 +/- 3.78, p= 0.012. The magnitude of the mean change compared to placebo was 2.73% (DEX 920) and 2.98% (DEX 1,920) in patients with HbAlc > 7.5% Hb (DEX 960, p = 0.007, DEX 1,920, p = 0.032). The effects of treatment were usually statistically significant in subgroups with more severe vascular stress (longer duration of disease, pretreatment history, higher LDL-C, higher blood pressure). CONCLUSION: DEX therapy appears to reduce endothelial dysfunction in DM2, especially in men with long history of DM2 and having poor glucose control. These findings will be useful in patient selection in future prospective clinical trials with drugs to treat vascular stress.

Diabetes-associated sustained activation of the transcription factor nuclear factor-kappaB.

Activation of the transcription factor nuclear factor-kappaB (NF-kappaB) has been suggested to participate in chronic disorders, such as diabetes and its complications. In contrast to the short and transient activation of NF-kappaB in vitro, we observed a long-lasting sustained activation of NF-kappaB in the absence of decreased IkappaBalpha in mononuclear cells from patients with type 1 diabetes. This was associated with increased transcription of NF-kappaBp65. A comparable increase in NF-kappaBp65 antigen and mRNA was also observed in vascular endothelial cells of diabetic rats. As a mechanism, we propose that binding of ligands such as advanced glycosylation end products (AGEs), members of the S100 family, or amyloid-beta peptide (Abeta) to the transmembrane receptor for AGE (RAGE) results in protein synthesis-dependent sustained activation of NF-kappaB both in vitro and in vivo. Infusion of AGE-albumin into mice bearing a beta-globin reporter transgene under control of NF-kappaB also resulted in prolonged expression of the reporter transgene. In vitro studies showed that RAGE-expressing cells induced sustained translocation of NF-kappaB (p50/p65) from the cytoplasm into the nucleus for >1 week. Sustained NF-kappaB activation by ligands of RAGE was mediated by initial degradation of IkappaB proteins followed by new synthesis of NF-kappaBp65 mRNA and protein in the presence of newly synthesized IkappaBalpha and IkappaBbeta. These data demonstrate that ligands of RAGE can induce sustained activation of NF-kappaB as a result of increased levels of de novo synthesized NF-kappaBp65 overriding endogenous negative feedback mechanisms and thus might contribute to the persistent NF-kappaB activation observed in hyperglycemia and possibly other chronic diseases.

The role of oxidative stress in the onset and progression of diabetes and its complications: a summary of a Congress Series sponsored by UNESCO-MCBN, the American Diabetes Association and the German Diabetes Society.

This review summarises the results and discussions of an UNESCO-MCBN supported symposium on oxidative stress and its role in the onset and progression of diabetes. There is convincing experimental and clinical evidence that the generation of reactive oxygen species (ROI) is increased in both types of diabetes and that the onset of diabetes is closely associated with oxidative stress. Nevertheless there is controversy about which markers of oxidative stress are most reliable and suitable for clinical practice. There are various mechanisms that contribute to the formation of ROI. It is generally accepted that vascular cells and especially the endothelium become one major source of ROI. An important role of oxidative stress for the development of vascular and neurological complications is suggested by experimental and clinical studies. The precise mechanisms by which oxidative stress may accelerate the development of complications in diabetes are only partly known. There is however evidence for a role of protein kinase C, advanced glycation end products (AGE) and activation of transcription factors such as NF kappa B, but the exact signalling pathways and the interactions with ROI remain a matter of discussion. Additionally, results of very recent studies suggest a role for ROI in the development of insulin resistance. ROI interfere with insulin signalling at various levels and are able to inhibit the translocation of GLUT4 in the plasma membrane. Evidence for a protective effect of antioxidants has been presented in experimental studies, but conclusive evidence from patient studies is missing. Large-scale clinical trials such as the DCCT Study or the UKPDS Study are needed to evaluate the long-term effects of antioxidants in diabetic patients and their potential to reduce the medical and socio-economic burden of diabetes and its complications.

Effect of alpha-lipoic acid on the progression of endothelial cell damage and albuminuria in patients with diabetes mellitus: an exploratory study.

Oxidative stress plays a central role in the pathogenesis and progression of late microangiopathic complications (diabetic nephropathy) in diabetes mellitus. Previous studies suggested that treatment of diabetic patients with the antioxidant alpha-lipoic acid reduce oxidative stress and urinary albumin excretion. In this prospective, open and non-randomized study, the effect of alpha-lipoic acid on the progression of endothelial cell damage and the course of diabetic nephropathy, as assessed by measurement of plasma thrombomodulin and urinary albumin concentration (UAC), was evaluated in 84 patients with diabetes mellitus over 18 months. Forty-nine patients (34 with Type 1 diabetes, 15 with Type 2 diabetes) had no antioxidant treatment and served as a control group. Thirty-five patients (20 with Type 1 diabetes, 15 with Type 2 diabetes) were treated with 600 mg alpha-lipoic acid per day. Only patients with an urinary albumin concentration <200 mg/l were included into the study. After 18 months of follow up, the plasma thrombomodulin level increased from 35.9+/-9.5 to 39.7+/-9.9 ng/ml (P<0.05) in the control group. In the alpha-lipoic acid treated group the plasma thrombomodulin level decreased from 37.5+/-16.2 to 30.9+/-14.5 ng/ml (P<0.01). The UAC increased in patients without alpha-lipoic acid treatment from 21.2+/-29.5 to 36.9+/-60.6 ng/l (P<0.05), but was unchanged with alpha-lipoic acid. It is postulated that the significant decrease in plasma thrombomodulin and failure of UAC to increase observed in the alpha-lipoic acid treated group is due to antioxidative effects of alpha-lipoic acid, and if so that oxidative stress plays a central role in the pathogenesis of diabetic nephropathy. Furthermore, progression of the disease might be inhibited by antioxidant drugs. A placebo-controlled study is needed.

Cataract development in diabetic sand rats treated with alpha-lipoic acid and its gamma-linolenic acid conjugate.

BACKGROUND: Diabetes commonly leads to long-term complications such as cataract. This study investigated the effects of alpha-lipoic acid (LPA) and its gamma-linolenic acid (GLA) conjugate on cataract development in diabetic sand rats. METHODS: Two separate experiments were conducted. In Experiment 1, sand rats were fed a "high-energy" diet (70% starch), an acute model of Type 2 diabetes, and injected with LPA. In Experiment 2, the animals received a "medium-energy" diet (59% starch), a chronic diabetic model, and were intubated with LPA or its GLA conjugate. Throughout the experiments, blood glucose levels and cataract development were measured. At the termination of the experiments, lens aldose reductase (AR) activity and lenticular reduced glutathione (GSH) levels were analyzed. RESULTS: LPA injection significantly inhibited cataract development and reduced blood glucose levels in rats fed the "high-energy" diet. Lens AR activity tended to be lower, while lenticular GSH levels increased. In sand rats fed a "medium-energy" diet (59% starch), LPA intubation had no effect on blood glucose levels and cataract development but GSH levels were increased. In contrast, sand rats intubated with GLA conjugate showed the highest blood glucose levels and accelerated cataract development. The conjugate treatment also decreased lenticular GSH content. CONCLUSIONS: The hypoglycemic effects of LPA are beneficial in the prevention of acute symptoms of Type 2 diabetes. It remains to be shown that the antioxidant activity of LPA is responsible for prevention or inhibition of cataract progression in sand rats.

Antioxidant alpha-lipoic acid and protein turnover in insulin-resistant rat muscle.

We have shown previously that the antioxidant alpha-lipoic acid (ALA) can stimulate glucose transport and can enhance the stimulation of this process by insulin in skeletal muscle from insulin-resistant obese Zucker rats. As insulin can also acutely activate general protein synthesis and inhibit net protein degradation in skeletal muscle, we hypothesized that ALA could directly affect protein turnover and also increase the effect of insulin on protein turnover in isolated skeletal muscle from developing obese Zucker rats. In epitrochlearis muscles isolated from obese Zucker rats, insulin (2 mU/ml) significantly (p < 0.05) increased in vitro protein synthesis (phenylalanine incorporation into protein) and decreased net protein degradation (tyrosine release), whereas a racemic mixture of ALA (2 mM) had no effect on either process. Interestingly, rates of protein synthesis in muscle from obese Zucker rats were substantially lower compared to those values observed in age-matched insulin-sensitive Wistar rats, whereas rates of protein degradation were comparable. Obese Zucker rats were also treated chronically with either vehicle or ALA (50 mg/kg/d for 10 d). Again, insulin significantly increased net protein synthesis and decreased net protein degradation in epitrochlearis muscles isolated from vehicle-treated obese Zucker rats; however, this stimulatory effect of insulin was not improved by prior in vivo ALA treatment. These results indicate that the previously described effect of the antioxidant ALA to increase insulin-stimulated glucose transport in skeletal muscle of obese, insulin-resistant rats does not apply to another important insulin-regulatable process, protein turnover. These findings imply that the cellular mode of action for ALA is restricted to signaling factors unique to the activation of glucose transport, and does not involve the pathway of stimulation of general protein synthesis and net protein degradation.

Effects of alpha-lipoic acid on microcirculation in patients with peripheral diabetic neuropathy.

Diabetic polyneuropathy is a serious complication in patients with diabetes mellitus. In addition to the maintenance of a sufficient metabolic control, alpha-lipoic acid (ALA) (Thioctacid, Asta Medica) is known to have beneficial effects on diabetic polyneuropathy although the exact mechanism by which ALA exerts its effect is unknown. In order to study the effect of ALA on microcirculation in patients with diabetes mellitus and peripheral neuropathy one group of patients (4 female, 4 male, age 60+/-3 years, diabetes duration 19+/-4 years, BMI 24.8+/-1.3 kg/m2) received 1200 mg ALA orally per day over 6 weeks (trial 1). A second group of patients (5 female, 4 male, age 65+/-3 years, diabetes duration 14+/-4 years, BMI 23.6+/-0.7 kg/m2) was studied before and after they had received 600 mg ALA or placebo intravenously over 15 minutes in order to investigate whether ALA has an acute effect on microcirculation (trial 2). Patients were investigated by nailfold video-capillaroscopy. Capillary blood cell velocity was examined at rest and during postreactive hyperemia (occlusion of the wrist for 2 minutes, 200 mmHg) which is a parameter of the perfusion reserve on demand. The oral therapy with ALA resulted in a significant decrease in the time to peak capillary blood cell velocity (tpCBV) during postocclusive hyperemia (trial 1: 12.6+/-3.1 vs 35.4+/-10.9 s, p<0.05). The infusion of ALA also decreased the tpCBV in patients with diabetic neuropathy (trial 2: before: 20.8+/-4,5, ALA: 11.74+/-4.4, placebo: 21.9-5.0 s, p<0.05 ALA vs both placebo and before infusions) indicating that ALA has an acute effect on microcirculation. Capillary blood cell velocity at rest (rCBV), hemodynamic parameters, hemoglobinA1c and local skin temperature remained unchanged in both studies. These results demonstrate that in patients with diabetic polyneuropathy ALA improves microcirculation as indicated by an increased perfusion reserve on demand. The observed effects are apparently acute effects. With the restriction of the pilot character of this investigation the findings support the assumption that ALA might exert its beneficial effects at least partially by improving microcirculation which is likely to occur also at the level of the vasa nervorum.

Engagement of the insulin-sensitive pathway in the stimulation of glucose transport by alpha-lipoic acid in 3T3-L1 adipocytes.

AIMS/HYPOTHESIS: A natural cofactor of mitochondrial dehydrogenase complexes and a potent antioxidant, alpha-lipoic acid improves glucose metabolism in people with Type II (non-insulin-dependent) diabetes mellitus and in animal models of diabetes. In this study we investigated the cellular mechanism of action of alpha-lipoic acid in 3T3-L1 adipocytes. METHODS: We treated 3T3-L1 adipocytes with 2.5 mmol/l R (+) alpha-lipoic acid for 2 to 60 min, followed by assays of: 2-deoxyglucose uptake; glucose transporter 1 and 4 (GLUT1 and GLUT4) subcellular localization; tyrosine phosphorylation of the insulin receptor or of the insulin receptor substrate-1 in cell lysates; association of phosphatidylinositol 3-kinase activity with immunoprecipitates of proteins containing phosphotyrosine or of insulin receptor substrate-1 using a in vitro kinase assay; association of the p85 subunit of phosphatidylinositol 3-kinase with phosphotyrosine proteins or with insulin receptor substrate-1; and in vitro activity of immunoprecipitated Akt1. The effect of R (+) alpha-lipoic acid was also compared with that of S(-) alpha-lipoic acid. RESULTS: Short-term treatment of 3T3-L1 adipocytes with R (+) alpha-lipoic acid rapidly stimulated glucose uptake in a wortmannin-sensitive manner, induced a redistribution of GLUT1 and GLUT4 to the plasma membrane, caused tyrosine phosphorylation of insulin receptor substrate-1 and of the insulin receptor, increased the antiphosphotyrosine-associated and insulin receptor substrate-1 associated phosphatidylinositol 3-kinase activity and stimulated Akt activity. CONCLUSION/INTERPRETATION: These results indicate that R (+) alpha-lipoic acid directly activates lipid, tyrosine and serine/threonine kinases in target cells, which could lead to the stimulation of glucose uptake induced by this natural cofactor. These properties are unique among all agents currently used to lower glycaemia in animals and humans with diabetes.

Effects of a unique conjugate of alpha-lipoic acid and gamma-linolenic acid on insulin action in obese Zucker rats.

The purpose of this study was to assess the individual and interactive effects of the antioxidant alpha-lipoic acid (LPA) and the n-6 essential fatty acid gamma-linolenic acid (GLA) on insulin action in insulin-resistant obese Zucker rats. LPA, GLA, and a unique conjugate consisting of equimolar parts of LPA and GLA (LPA-GLA) were administered for 14 days at 10, 30, or 50 mg. kg body wt(-1). day(-1). Whereas LPA was without effect at 10 mg/kg, at 30 and 50 mg/kg it elicited 23% reductions (P < 0.05) in the glucose-insulin index (the product of glucose and insulin areas under the curve during an oral glucose tolerance test and an index of peripheral insulin action) that were associated with significant increases in insulin-mediated (2 mU/ml) glucose transport activity in isolated epitrochlearis (63-65%) and soleus (33-41%) muscles. GLA at 10 and 30 mg/kg caused 21-25% reductions in the glucose-insulin index and 23-35% improvements in insulin-mediated glucose transport in epitrochlearis muscle. The beneficial effects of GLA disappeared at 50 mg/kg. At 10 and 30 mg/kg, the LPA-GLA conjugate elicited 29 and 38% reductions in the glucose-insulin index. These LPA-GLA-induced improvements in whole body insulin action were accompanied by 28-63 and 38-57% increases in insulin-mediated glucose transport in epitrochlearis and soleus muscles and resulted from the additive effects of LPA and GLA. At 50 mg/kg, the metabolic improvements due to LPA-GLA were substantially reduced. In summary, these results indicate that the conjugate of the antioxidant LPA and the n-6 essential fatty acid GLA elicits significant dose-dependent improvements in whole body and skeletal muscle insulin action on glucose disposal in insulin-resistant obese Zucker rats. Moreover, these actions of LPA-GLA are due to the additive effects of its individual components.

The role of oxidative stress and NF-kappaB activation in late diabetic complications.

A common endpoint of hyperglycemia dependent cellular changes is the generation of reactive oxygen intermediates (ROIs) and the presence of elevated oxidative stress. Therefore, oxidative stress is supposed to play an important role in the development of late diabetic complications. Formation of advanced glycation end products (AGE's) due to elevated nonenzymatic glycation of proteins, lipids and nucleic acids is accompanied by oxidative, radical-generating reactions and thus represents a major source for oxygen free radicals under hyperglycemic conditions. Once formed, AGE's can influence cellular function by binding to several binding sites including the receptor for AGE's, RAGE. Binding of AGE's (and other ligands) to RAGE results in generation of intracellular oxidative stress and subsequent activation of the redox-sensitive transcription factor NF-kappaB in vitro and in vivo. Consistently, activation of NF-kappaB in diabetic patients correlates with the quality of glycemic control and can be reduced by treatment with the antioxidant alpha-lipoic acid. The development of techniques allowing for a tissue culture independent measurement of NF-kappaB activation in patients with diabetes mellitus gives insights into the molecular mechanisms linking diabetes mellitus and hyperglycemia with formation of advanced glycated endproducts and generation of oxidative stress finally resulting in oxidative stress mediated cellular activation.

Alpha-lipoic acid: effect on glucose uptake, sorbitol pathway, and energy metabolism in experimental diabetic neuropathy.

The peripheral nerve of experimental diabetic neuropathy (EDN) is reported to be ischemic and hypoxic, with an increased dependence on anaerobic metabolism, requiring increased energy substrate stores. When glucose stores become reduced, fiber degeneration has been reported. We evaluated glucose uptake, nerve energy metabolism, the polyol pathway, and protein kinase C (PKC) activity in EDN induced by streptozotocin. Control and diabetic rats received lipoic acid (0, 10, 25, 50, 100 mg/kg). Duration of diabetes was 1 month, and alpha-lipoic acid was administered intraperitoneally 5 times per week for the final week of the experiment. Nerve glucose uptake was reduced to 60, s 37, and 30% of control values in the sciatic nerve, L5 dorsal root ganglion, and superior cervical ganglion (SCG), respectively, in rats with EDN. Alpha-lipoic acid supplementation had no effect on glucose uptake in normal nerves at any dose, but reversed the deficit in EDN, with a threshold between 10 and 25 mg/kg. Endoneurial glucose, fructose, sorbitol, and myo-inositol were measured in sciatic nerve. Alpha-lipoic acid had no significant effect on either energy metabolism or polyol pathway of normal nerves. In EDN, endoneurial glucose, fructose, and sorbitol were significantly increased, while myo-inositol was significantly reduced. Alpha-lipoic acid had a biphasic effect: it dose-dependently increased fructose, glucose, and sorbitol, peaking at 25 mg/kg, and then fell beyond that dose, and it dose-dependently increased myo-inositol. Sciatic nerve cytosolic PKC was increased in EDN. ATP, creatine phosphate, and lactate were measured in sciatic nerve and SCG. Alpha-lipoic acid prevented the reduction in SCG creatine phosphate. We conclude that glucose uptake is reduced in EDN and that this deficit is dose-dependently reversed by alpha-lipoic acid, a change associated with an improvement in peripheral nerve function.

Oral administration of RAC-alpha-lipoic acid modulates insulin sensitivity in patients with type-2 diabetes mellitus: a placebo-controlled pilot trial.

Alpha-lipoic acid (ALA), a naturally occuring compound and a radical scavenger was shown to enhance glucose transport and utilization in different experimental and animal models. Clinical studies described an increase of insulin sensitivity after acute and short-term (10 d) parenteral administration of ALA. The effects of a 4-week oral treatment with alpha-lipoic acid were evaluated in a placebo-controlled, multicenter pilot study to determine see whether oral treatment also improves insulin sensitivity. Seventy-four patients with type-2 diabetes were randomized to either placebo (n = 19); or active treatment in various doses of 600 mg once daily (n = 19), twice daily (1200 mg; n = 18), or thrice daily (1800 mg; n = 18) alpha-lipoic acid. An isoglycemic glucose-clamp was done on days 0 (pre) and 29 (post). In this explorative study, analysis was done according to the number of subjects showing an improvement of insulin sensitivity after treatment. Furthermore, the effects of active vs. placebo treatment on insulin sensitivity was compared. All four groups were comparable and had a similar degree of hyperglycemia and insulin sensitivity at baseline. When compared to placebo, significantly more subjects had an increase in insulin-stimulated glucose disposal (MCR) after ALA treatment in each group. As there was no dose effect seen in the three different alpha-lipoic acid groups, all subjects receiving ALA were combined in the "active" group and then compared to placebo. This revealed significantly different changes in MCR after treatment (+27% vs. placebo; p < .01). This placebo-controlled explorative study confirms previous observations of an increase of insulin sensitivity in type-2 diabetes after acute and chronic intravenous administration of ALA. The results suggest that oral administration of alpha-lipoic acid can improve insulin sensitivity in patients with type-2 diabetes. The encouraging findings of this pilot trial need to be substantiated by further investigations.

Treatment of diabetic polyneuropathy with the antioxidant thioctic acid (alpha-lipoic acid): a two year multicenter randomized double-blind placebo-controlled trial (ALADIN II). Alpha Lipoic Acid in Diabetic Neuropathy.

Short-term trials with the antioxidant thioctic acid (TA) appear to improve neuropathic symptoms in diabetic patients, but the long-term response remains to be established. Therefore, Type 1 and Type 2 diabetic patients with symptomatic polyneuropathy were randomly assigned to three treatment regimens: (1) 2 x 600(mg of TA (TA 1200), (2) 600)mg of TA plus placebo (PLA) (TA 600) or (3) placebo and placebo (PLA). A trometamol salt solution of TA of 1200 or 600 mg or PLA was intravenously administered once daily for five consecutive days before enrolling the patients in the oral treatment phase. The study was prospective, PLA-controlled, randomized, double-blind and conducted for two years. Severity of diabetic neuropathy was assessed by the Neuropathy Disability Score (NDS) and electrophysiological attributes of the sural (sensory nerve conduction velocity (SNCV), sensory nerve action potential (SNAP)) and the tibial (motor nerve conduction velocity (MNCV), motor nerve distal latency (MNDL)) nerve. Statistical analysis was performed after independent reviewers excluded all patients with highly variable data allowing a final analysis of 65 patients (TA 1200: n = 18, TA 600: n = 27; PLA: n = 20). At baseline no significant differences were noted between the groups regarding the demographic variables and peripheral nerve function parameters for these 65 patients. Statistically significant changes after 24 months between TA and PLA were observed (mean +/- SD) for sural SNCV: +3.8 +/- 4.2 m/s in TA 1200, +3.0+/-3.0m/s in TA 600, -0.1+/-4.8m/s in PLA (p < 0.05 for TA 1200 and TA 600 vs. PLA); sural SNAP: +0.6+/-2.5 microV in TA 1200, +0.3+/-1.4 microV in TA 600, -0.7 +/- 1.5 microV in PLA (p = 0.076 for TA 1200 vs. PLA and p < 0.05 for TA 600 vs. PLA), and in tibial MNCV: +/- 1.2 +/- 3.8 m/s in TA 1200, -0.3 +/- 5.2 m/s in TA 600, 1.5 +/- 2.9 m/s in PLA (p < 0.05 for TA 1200 vs. PLA). No significant differences between the groups after 24 months were noted regarding the tibial MNDL and the NDS. We conclude that in a subgroup of patients after exclusion of patients with excessive test variability throughout the trial, TA appeared to have a beneficial effect on several attributes of nerve conduction.

alpha-Lipoic acid decreases oxidative stress even in diabetic patients with poor glycemic control and albuminuria.

In the present cross-sectional study, the influence of alpha-lipoic acid on markers of oxidative stress, assessed by measurement of plasma lipid hydroperoxides (ROOHs), and on the balance between oxidative stress and antioxidant defence, determined by the ratio ROOH/(alpha-tocopherol/cholesterol), was examined in 107 patients with diabetes mellitus. Patients receiving alpha-lipoic acid (600 mg/day for > 3 months) had significant lower ROOHs and a lower ROOH/(alpha-tocopherol/cholesterol) ratio than those without alpha-lipoic acid treatment [ROOH: 4.76 +/- 2.49 vs. 7.16 +/- 3.22 mumol/l; p < .0001] and [ROOH/(alpha-tocopherol/cholesterol): 1.37 +/- 0.72 vs. 2.16 +/- 1.17; p < 0.0001]. In addition, the influence of glycemic control and albuminuria on ROOHs and on the ratio of ROOH/(alpha-tocopherol/cholesterol) was examined in the presence and absence of alpha-lipoic acid treatment. Patients were subdivided into three groups based on (1) their HbA1 levels (< 7.5, 7.5-9.5, and > 9.5%) and (2) their urinary albumin concentrations (< 20, 20-200, and > 200 mg/l). Neither poor glycemic control, nor the presence of micro- or macroalbuminuria prevented the antioxidant effect of alpha-lipoic acid. Using stepwise multiple regression analysis, alpha-lipoic acid was found to be the only factor significantly predicting low ROOHs and a low ratio of ROOH/(alpha-tocopherol/cholesterol). These data provide evidence that treatment with alpha-lipoic acid improves significantly the imbalance between increased oxidative stress and depleted antioxidant defence even in patients with poor glycemic control and albuminuria.

Alpha-lipoic acid provides neuroprotection from ischemia-reperfusion injury of peripheral nerve.

BACKGROUND: Reperfusion aggravates nerve ischemic fiber degeneration, likely by the generation of reduced oxygen species. We therefore evaluated if racemic alpha-lipoic acid (LA), a potent antioxidant, will protect peripheral nerve from reperfusion injury, using our established model of ischemia-reperfusion injury. METHODS: We used male SD rats, 300+/-5 g. Ischemia was produced by the ligature of each of the supplying arteries to the sciatic-tibial nerve of the right hind-limb for predetermined periods of time (either 3 or 5 h), followed by the release of the ligatures, resulting in reperfusion. LA was given intraperitoneally daily for 3 days for both pre- and post-surgery. Animals received either LA, 100 mg/kg/day, or the same volume of saline intraperitoneally. Clinical behavioral score and electrophysiology of motor and sensory nerves were obtained at 1 week after ischemia-reperfusion. After electrophysiological examination, the sciatic-tibial nerve was fixed in situ and embedded in epon. We evaluated for ischemic fiber degeneration (IFD) and edema, as we described previously. RESULTS: Distal sensory conduction (amplitude of sensory action potential and sensory conduction velocity (SCV) of digital nerve) was significantly improved in the 3-h ischemia group, treated with LA (P<0.05). LA also improved IFD of the mid tibial nerve (P=0.0522). LA failed to show favorable effects if the duration of ischemia was longer (5-h ischemia). CONCLUSION: These results suggest that alpha-lipoic acid is efficacious for moderate ischemia-reperfusion, especially on distal sensory nerves.

alpha-Lipoic acid treatment decreases serum lactate and pyruvate concentrations and improves glucose effectiveness in lean and obese patients with type 2 diabetes.

OBJECTIVE: We examined the effect of lipoic acid (LA), a cofactor of the pyruvate dehydrogenase complex (PDH), on insulin sensitivity (SI) and glucose effectiveness (SG) and on serum lactate and pyruvate levels after oral glucose tolerance tests (OGTTs) and modified frequently sampled intravenous glucose tolerance tests (FSIGTTs) in lean (n = 10) and obese (n = 10) patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: FSIGTT data were analyzed by minimal modeling technique to determine SI and SG before and after oral treatment (600 mg, twice a day, for 4 weeks). Serum lactate and pyruvate levels of diabetic patients after glucose loading were compared with those of lean (n = 10) and obese (n = 10) healthy control subjects in which SI and SG were also determined from FSIGTT data. RESULTS: Fasting lactate and pyruvate levels were significantly increased in patients with type 2 diabetes. These metabolites did not exceed elevated fasting concentrations after glucose loading in lean patients with type 2 diabetes. However, a twofold increase of lactate and pyruvate levels was measured in obese diabetic patients. LA treatment was associated with increased SG in both diabetic groups (lean 1.28 +/- 0.14 to 1.93 +/- 0.13; obese 1.07 +/- 0.11 to 1.53 +/- 0.08 x 10(-2) min-1, P < 0.05). Higher SI and lower fasting glucose were measured in lean diabetic patients only (P < 0.05). Lactate and pyruvate before and after glucose loading were approximately 45% lower in lean and obese diabetic patients after LA treatment. CONCLUSIONS: Treatment of lean and obese diabetic patients with LA prevents hyperglycemia-induced increments of serum lactate and pyruvate levels and increases SG.

Lipoic acid acutely induces hypoglycemia in fasting nondiabetic and diabetic rats.

Lipoic acid (LA) is a unique antioxidant that increases peripheral glucose utilization in diabetic patients. This study was conducted to investigate whether the inhibition of glucose production could be an additional mechanism for the action of LA. Intravenous (i.v.) LA injection (100 or 60 mg/kg body weight) to fasting nondiabetic or streptozotocin (STZ)-induced diabetic rats caused a rapid reduction in blood glucose with no effect on circulating insulin levels. In vivo conversion of fructose to glucose was not inhibited by LA, whereas the gluconeogenesis flux from alanine was completely prevented. Reduced liver pyruvate carboxylase (PC) activity in vivo is suggested by the finding that LA induced a decrease in liver coenzyme A (CoA) content (44% and 28% reduction in nondiabetic and diabetic rats, respectively, compared with vehicle-treated animals) and liver acetyl CoA content (80% and 67% reduction in nondiabetic and diabetic rats, respectively). A reduction in plasma free carnitine (42% and 22% in nondiabetic and diabetic rats, respectively) was observed in LA-treated animals, and acylcarnitine levels were increased twofold. This could be attributed to elevated levels of C16 and C18 acylcarnitine, without a detectable accumulation of lipoylcarnitine. Under such conditions, a significant increase in the plasma free fatty acid (FFA) concentration (204% in nondiabetic and 151% in diabetic animals) with no elevation in beta-hydroxybutyrate levels was noted. In conclusion, this study suggests that short-term administration of LA at high dosage to normal and diabetic rats causes an inhibition of gluconeogenesis secondary to an interference with hepatic fatty acid oxidation. This may render LA an antihyperglycemic agent for the treatment of diabetic subjects, who display glucose overproduction as a major metabolic abnormality.

Increased oxidative damage to all DNA bases in patients with type II diabetes mellitus.

Gas chromatography-mass spectrometry was used to measure the oxidative DNA damage in diabetic subjects and controls. Levels of multiple DNA base oxidation products, but not DNA base de-amination or chlorination products, were found to be elevated in white blood cell DNA from patients with type II diabetes as compared with age-matched controls. The chemical pattern of base damage is characteristic of that caused by an attack on DNA by hydroxyl radical. An increased formation of the highly reactive hydroxyl radical could account for many of the reports of oxidative stress in diabetic subjects. There was no evidence of an increased DNA damage by reactive nitrogen or chlorine species.

Peripheral blood mononuclear cells isolated from patients with diabetic nephropathy show increased activation of the oxidative-stress sensitive transcription factor NF-kappaB.

Increased oxidative stress and subsequent activation of the transcription factor NF-kappaB has been linked to the development of late diabetic complications. To determine whether oxidative stress dependent NF-kappaB activation is evident in patients with diabetic nephropathy we used an Electrophoretic Mobility Shift Assay based semiquantitative detection system which enabled us to determine NF-kappaB activation in ex vivo isolated peripheral blood mononuclear cells. We examined 33 patients with diabetes mellitus (Type I and Type II). Patients with diabetic nephropathy showed higher NF-kappaB binding activity in Electrophoretic Mobility Shift Assays and stronger immunohistological staining for activated NF-kappaBp65 than patients without renal complications. NF-kappaB binding activity correlated with the degree of albuminuria (r = 0.316) and with thrombomodulin plasma concentrations (r = 0.33), indicative for albuminuria associated endothelial dysfunction. In a 3 day intervention study in which 600 mg of the antioxidant thioctic acid (alpha-lipoic acid) per day were given to nine patients with diabetic nephropathy oxidative stress in plasma samples was decreased by 48% and NF-kappaB binding activity in ex vivo isolated peripheral blood mononuclear cells by 38%. In conclusion, activation of the transcription factor NF-kappaB in ex vivo isolated peripheral blood mononuclear cells of patients with diabetes mellitus correlates with the degree of diabetic nephropathy. NF-kappaB activation is at least in part dependent on oxidative stress since thioctic acid (alpha-lipoic acid) reduced NF-kappaB binding activity.