Effect of L-carnitine on acetyl-CoA content and activity of blood platelets in healthy and diabetic persons

L-carnitine contributes to enhancement of viability and quality of platelet concentrates through changing the apoptotic and anti-apoptotic associated microRNAs

BACKGROUND

Micro RNAs are known as the main regulator of messenger RNA translation in platelets and have a vital role in process of apoptosis during platelet storage. Our pervious study revealed that the expression of miR-145 and miR-326 changed significantly in platelets under maintenance conditions. This study aimed to evaluate the effect of L-carnitine (LC) as an additive to augment platelet quality by changing the microRNA expression.

METHODS

We used ten platelet concentrate (PC) bags and divided each into two equal parts, LC- treated, and LC free PC. The expression of miR-145 and miR-326 were determined using real-time PCR. Moreover, we measured platelet count, platelet aggregation, platelet viability, and lactate dehydrogenase activity in all samples.

RESULTS

The miR-326 expression significantly increased during platelet storage with mean fold changes of 3.2 for the control and 2.5 for LC- treated PC. The mean fold changes in miR-145 expression was less in the control PC (0.52) compared to the LC- treated PC (0.79). Increased levels of platelet count, platelet aggregation, and platelet viability were found in the LC-treated compared to the untreated PC.

CONCLUSION

LC has a protective effect on platelet apoptosis, reduces the expression of apoptotic microRNA, and prevents the reduction of anti-apoptotic microRNA.

Development of targeted hydrophilic interaction liquid chromatography-tandem mass spectrometry method for acyl-Coenzyme A covering short- to long-chain species in a single analytical run

Acyl-CoAs play a significant role in numerous physiological and metabolic processes making it important to assess their concentration levels for evaluating metabolic health. Considering the important role of acyl-CoAs, it is crucial to develop an analytical method that can analyze these compounds. Due to the structural variations of acyl-CoAs, multiple analytical methods are often required for comprehensive analysis of these compounds, which increases complexity and the analysis time. In this study, we have developed a method using a zwitterionic HILIC column that enables the coverage of free CoA and short- to long-chain acyl-CoA species in one analytical run. Initially, we developed the method using an LC-QTOF instrument for the identification of acyl-CoA species and optimizing their chromatography. Later, a targeted HILIC-MS/MS method was created in scheduled multiple reaction monitoring mode using a QTRAP MS detector. The performance of the method was evaluated based on various parameters such as linearity, precision, recovery and matrix effect. This method was applied to identify the difference in acyl-CoA profiles in HepG2 cells cultured in different conditions. Our findings revealed an increase in levels of acetyl-CoA, medium- and long-chain acyl-CoA while a decrease in the profiles of free CoA in the starved state, indicating a clear alteration in the fatty acid oxidation process.

Effect of moxa smoke on sperm parameters and oxidative stress in rats with asthenozoospermia

Asthenozoospermia is a leading cause of male infertility, characterized by reduced sperm motility. In this study, we determined sperm motility and the activities of antioxidant enzymes and oxidation products in the testis of rats with ornidazole (ORN)-induced asthenozoospermia and further examined and compared the differential effects of moxa smoke (MS) and cigarette smoke (CS) on sperm motility and oxidative stress (OS) of asthenozoospermic rats. The smoke intervention was initiated 11 days after intragastric administration of ORN, followed by the examination of testis index, sperm parameters, OS-related gene levels, and testicular histopathology. Sperm motility and antioxidant enzyme activities, as well as oxidation products significantly decreased in ORN-induced rats compared with MS-treated rats (p < .05-.001). MS treatment restored the reduced sperm motility and activities of glutathione peroxidase, superoxide dismutase, and catalase, but increased the malondialdehyde and nitric oxide synthetase levels in ORN-induced rats (p < .05-.001). Also, the histopathological changes in the testis of ORN-induced rats were improved by MS treatment. The study highlighted that MS was an effective factor in moxibustion therapy, which notably improved the sperm motility of asthenozoospermic rats by inhibiting OS in the reproductive system.

Resveratrol Inhibits Metabolism and Affects Blood Platelet Function in Type 2 Diabetes

Chronic hyperglycemia contributes to vascular complications in diabetes. Resveratrol exerts anti-diabetic and anti-platelet action. This study aimed to evaluate the effects of resveratrol on metabolism and the function of blood platelets under static and in in vitro flow conditions in patients with type 2 diabetes. Blood obtained from 8 healthy volunteers and 10 patients with type 2 diabetes was incubated with resveratrol and perfused over collagen-coated capillaries. Isolated blood platelets were incubated with resveratrol and activated by collagen to assess platelet function, metabolism, ATP release, TXA₂ production, lipid peroxidation, and gluthatione content. In the type 2 diabetes group, plasma glucose and fructosamine concentrations were significantly higher than in the healthy group. In in vitro studies, collagen-induced thrombi formation in the blood of diabetic patients was 33% higher than in the healthy group. Resveratrol reduced thrombi by over 50% in the blood of healthy and diabetic patients. TXA₂ production was 47% higher in diabetic platelets than in the healthy group. Resveratrol reduced TXA₂ release by 38% in healthy platelets and by 79% in diabetic platelets. Resveratrol also reduced the activities of enzymes responsible for glycolysis and oxidative metabolism in the platelets of both groups. These data indicate that the resveratrol-induced inhibition of platelet metabolism and TXA₂ release may lead to a reduction of platelet function and thrombus formation in patients with type 2 diabetes. Therefore, resveratrol may be beneficial to prevent vascular complications as a future complementary treatment in aspirin-resistant diabetic patients.

Inhibition of pyruvate dehydrogenase complex activity by 3-bromopyruvate affects blood platelets responses in type 2 diabetes

BACKGROUND

Hyperactivation of blood platelets is an essential factor in the pathomechanism of diabetes-evoked angiopathies. The aim of this work was to investigate whether blood platelets hyperactivation resulting from type 2 diabetic hyperglycaemia-increased pyruvate dehydrogenase complex activity and excessive acetyl-CoA accumulation may be brought to the normal range by the enzyme inhibitors.

METHODS

Platelets were isolated from the blood of 9 type 2 diabetic patients and 10 healthy donors. Effects of 3-bromopyruvate and 3-nitropropionate on pyruvate dehydrogenase complex (PDHC) and succinate dehydrogenase activities, as well as levels of acetyl-CoA, ATP, thiobarbituric acid reactive species and aggregation were assessed in non-activated and thrombin-activated platelets.

RESULTS

In type 2 diabetic patients fasting plasma glucose and fructosamine levels were 61 and 64% higher, respectively, than in the healthy group (p < 0.001). In non-activated diabetic platelets PDHC activity, PDHC-E2, acetyl-CoA and ATP levels were 66, 70, 68 and 60%, higher, respectively, than in platelets from healthy controls (p < 0.01). 3-bromopyruvate (0.1 mM) decreased pyruvate dehydrogenase activity in healthy and diabetic platelets by 42% and 59%, respectively. Similar inhibitory effects were observed for acetyl-CoA and ATP levels, aggregation and TBARS accumulation rates. Succinate dehydrogenase activity was inhibited by 3-nitropropionate (10 mM) to 38 and 41% of control values in healthy and diabetic platelets, respectively, but affected neither function nor acetyl-CoA metabolism in platelets of both groups.

CONCLUSIONS

These data indicate that inhibition of pyruvate dehydrogenase excessive activity in diabetic platelets by 3-bromopyruvate may normalise their functional parameters through adjustment of acetyl-CoA/ATP levels to control values. Platelets from blood of diabetic patients display higher activities of pyruvate dehydrogenase complex (PDHC), higher levels of dihydrolipoate transacetylase (DLAT, E2 subunit of PDHC) as well as higher levels of acetyl-CoA yielding greater ATP/ADP accumulation than in platelets of normoglycemic subjects. Therefore, in diabetic platelets, thrombin caused higher release of ATP/ADP triggering excessive production of reactive oxygen species (ROS) and stronger aggregation compared to control platelets. In diabetic platelets, relative excess of DLAT in PDHC made them highly susceptible to 3-bromopyruvate (3BrP) inhibition. Resulting limitation of acetyl-CoA provision by 3-BrP normalised activity of diabetic platelets.

Determination of acetyl coenzyme A in human whole blood by ultra-performance liquid chromatography-mass spectrometry

Acetyl coenzyme A is involved in several key metabolic pathways. Its concentration can vary considerably in response to physiological or pathological conditions making it a potentially valuable biomarker. However, little information about the measurement and concentration of acetyl CoA in human whole blood is found in the literature. The aim of this study was the development of an accurate method for the determination of acetyl CoA in human whole blood by LC-MS/MS. The method, involving extraction from whole blood by a rapid protein precipitation procedure was thoroughly validated: limit of quantitation was 3.91 ng mL^-1. Accuracy and precision were calculated at five concentrations and were within ±15%. The average endogenous level of acetyl CoA in human whole blood was determined in 17 healthy individuals to be 220.9 ng mL^-1 (ranging from 124.0 to 308.0 ng mL^-1). This represents, to our knowledge, the first report of acetyl CoA levels in human whole blood, and the first practical and reliable method for its determination.

Higher mitochondrial potential and elevated mitochondrial respiration are associated with excessive activation of blood platelets in diabetic rats

AIMS

The high glucose concentration observed in diabetic patients is a recognized factor of mitochondrial damage in various cell types. Its impact on mitochondrial bioenergetics in blood platelets remains largely vague. The aim of the study was to determine how the metabolism of carbohydrates, which has been impaired by streptozotocin-induced diabetes may affect the functioning of platelet mitochondria.

MATERIALS AND METHODS

Diabetes was induced in Sprague Dawley rats by intraperitoneal injection of streptozotocin. Platelet mitochondrial respiratory capacity was monitored as oxygen consumption (high-resolution respirometry). Mitochondrial membrane potential was assessed using a fluorescent probe, JC-1. Activation of circulating platelets was monitored by flow cytometry measuring of the expressions of CD61 and CD62P on a blood platelet surface. To determine mitochondrial protein density in platelets, Western Blot technique was used.

KEY FINDINGS

The results indicate significantly elevated mitochondria mass, increased mitochondrial membrane potential (ΔΨm) and enhanced respiration in STZ-diabetic animals, although the respiration control ratios appear to remain unchanged. Higher ΔΨm and elevated mitochondrial respiration were closely related to the excessive activation of circulating platelets in diabetic animals.

SIGNIFICANCE

Long-term diabetes can result in increased mitochondrial mass and may lead to hyperpolarization of blood platelet mitochondrial membrane. These alterations may be a potential underlying cause of abnormal platelet functioning in diabetes mellitus and hence, a potential target for antiplatelet therapies in diabetes.

Experimental Research on Therapeutic Efficacy of Traditional Chinese Medicine Shengjing Capsule Extracts in Treating Spermatogenesis Impairment Induced by Oxidative Stress

BACKGROUND

To investigate antioxidant effects of traditional Chinese Shengjing capsule extracts (sperm-producing capsule, with functions of tonifying kidney and invigorating kidney essence) on testes, epididymides, and sperms of rats.

MATERIAL/METHODS

We randomly divided 50 rats into 5 groups. G1: normal control group (treated with saline); G2: cadmium chloride group; G3: cadmium chloride+ low doses of drugs; G4: cadmium chloride + medium doses of drugs; and G5: cadmium chloride + high doses of drugs (equivalent dose: 0.45 g/kg). In addition to the normal control group, the other 4 groups started receiving intraperitoneal injection of cadmium chloride (1 mg/kg, i.p.). Testicular glutathione peroxidase (GSH-PX), superoxide dismutase (SOD), and malondialdehyde aldehyde (MDA) were measured by ELISA; epididymis histopathological examination was performed; testis serum testosterone (T) was measured; specimens of the epididymal semen were analyzed for sperm concentration, morphology, vitality, and DNA fragmentation rate.

RESULTS

Sperm count and activity of rats in the model control group decreased significantly; their MDA concentration of testicular and epididymal homogenates increased greatly; while the vitality of SOD and GSH-Px dropped sharply. All indexes mentioned above were significantly different from those of the blank control group (P<0.05); the sperm count and activity of rats treated with Shengjing capsule (sperm-producing capsule) decreased, but were still significantly higher than those of the model group (P<0.05). MDA level of rats treated with Shengjing capsule were significantly lower than that of the model group (P<0.05), while their SOD and GSH-Px activity were significantly higher than the model group (P<0.05). The normal morphology rate and DNA integrity rate of groups treated with Shengjing capsule were significantly higher than those of the model group (P<0.05).

CONCLUSIONS

Shengjing can enhance the activity of antioxidant enzymes and inhibit oxidative stress. It can also repair testicular and epididymal pathological damages, protect spermatogenesis, increase sperm count and activity, and improve normal morphology rate of sperm.

Lysine acetyltransfer supports platelet function

BACKGROUND AND OBJECTIVES

The reversible acetylation of protein lysine ε-amino groups, catalyzed by lysine acetyltransferases and deacetylases, serves as a molecular switch in the orchestration of diverse cellular activities. Here, we aimed to investigate the role of lysine acetyltransfer in platelet function.

METHODS AND RESULTS

Proteomics methods identified 552 acetyllysine (acK) modifications on 273 platelet proteins that serve as candidate substrates for lysine acetyltransferases. Bioinformatics analyses of the identified acK-modified platelet proteins supported roles for the lysine acetyltransferase p300 in the regulation of actin-mediated platelet processes. Biochemical experiments showed that platelets express p300, which is activated in an Src kinase-dependent manner upon platelet stimulation with the platelet glycoprotein VI agonist collagen-related peptide (CRP). Inhibition of platelet p300 abrogated CRP-stimulated lysine acetylation of actin, filamin, and cortactin, as well as F-actin polymerization, integrin activation, and platelet aggregation. Super-resolution visualization of platelet actin-rich adhesion structures revealed abundant acK protein colocalized with platelet actin cytoskeletal proteins. Inhibition of p300 blocked platelet filopodium formation and the spreading of platelets on fibrinogen and collagen surfaces. In whole blood, p300 inhibition prevented the formation of platelet aggregates under shear, suggesting a physiologic role for lysine acetyltransferase activity in platelet function.

CONCLUSION

Together, our findings reveal lysine acetyltransfer to be a potential regulator of platelet actin dynamics, and potential roles for lysine acetylation in the molecular coordination of platelet activation and function.

A novel functional site in the PB2 subunit of influenza A virus essential for acetyl-CoA interaction, RNA polymerase activity, and viral replication

The PA, PB1, and PB2 subunits, components of the RNA-dependent RNA polymerase of influenza A virus, are essential for viral transcription and replication. The PB2 subunit binds to the host RNA cap (7-methylguanosine triphosphate (m(7)GTP)) and supports the endonuclease activity of PA to "snatch" the cap from host pre-mRNAs. However, the structure of PB2 is not fully understood, and the functional sites remain unknown. In this study, we describe a novel Val/Arg/Gly (VRG) site in the PB2 cap-binding domain, which is involved in interaction with acetyl-CoA found in eukaryotic histone acetyltransferases (HATs). In vitro experiments revealed that the recombinant PB2 cap-binding domain that includes the VRG site interacts with acetyl-CoA; moreover, it was found that this interaction could be blocked by CoA and various HAT inhibitors. Interestingly, m(7)GTP also inhibited this interaction, suggesting that the same active pocket is capable of interacting with acetyl-CoA and m(7)GTP. To elucidate the importance of the VRG site on PB2 function and viral replication, we constructed a PB2 recombinant protein and recombinant viruses including several patterns of amino acid mutations in the VRG site. Substitutions of the valine and arginine residues or of all 3 residues of the VRG site to alanine significantly reduced the binding ability of PB2 to acetyl-CoA and its RNA polymerase activity. Recombinant viruses containing the same mutations could not be replicated in cultured cells. These results indicate that the PB2 VRG sequence is a functional site that is essential for acetyl-CoA interaction, RNA polymerase activity, and viral replication.

Serum carnitine level and its associated factors in patients with chronic viral hepatitis

ABSTRACT: 

Aim: Serum carnitine level and its associated factors have been evaluated in patients with chronic viral hepatitis. Methods: Patients with confirmed chronic viral hepatitis based on the serological markers and liver biopsy were included. In total, 86 volunteers and 86 patients with chronic viral hepatitis completed the study. Demographic data, type of treatment regimen and nutritional status of the patients were recorded and one blood sample was collected from each patient after an overnight fasting. A double antibody sandwich ELISA kit was used to measure carnitine serum level. Results: Mean ± standard deviation of serum carnitine level in the case and control groups were 34.3 ± 15.3 and 55.7 ± 28.4 μmol/l, respectively (p = 0.001). Regarding carnitine deficiency definition, 64 out of 86 patients (74.4%) and 21 out of 86 (24.5%) healthy individuals suffered from carnitine deficiency (p < 0.001). Carnitine dietary intake was significantly lower (p < 0.001). Compared with patients with chronic hepatitis C infection, a more severe form of carnitine deficiency was detected in patients with chronic hepatitis B infection (18.39 ± 15.68 μmol/l vs 42.30 ± 32.92 μmol/l; p = 0.03). In addition, serum carnitine level (41.1 ± 14.8 μmol/l) was significantly higher in the cirrhotic than noncirrhotic patients (31.60 ± 13.2 μmol/l; p = 0.04). Conclusion: Although the cirrhotic patients had higher serum carnitine level compared with noncirrhotic patients, serum carnitine level in the patients with chronic hepatitis was significantly lower than the healthy individuals. Also compared with the defined cut-off point for normal carnitine serum level, carnitine deficiency was common in Iranian patients with chronic hepatitis.

Effects of warfarin and L-carnitine on hemostatic function and oxidative stress in streptozotocin-induced diabetic rats

Diabetes mellitus (DM) is a complex progressive disease characterized by hyperglycemia and a high risk of atherothrombotic disorders affecting the coronary, cerebral, and peripheral arterial trees. Oxidative stress is reported in diabetic patients. We investigated the hemostatic functions and oxidative stress in streptozotocin (STZ)-induced diabetic rats and the effects of warfarin and L-carnitine on those parameters. Forty male Sprague-Dawley rats were divided into four groups: control, DM, and DM received warfarin or L-carnitine. In all rats, blood glucose, insulin, hemoglobin A1c (HbA1c), fibrinogen, factor VII (FVII), plasminogen activator inhibitor-1 (PAI-1), fibrin degradation products (FDP), protein C, antithrombin III (ATIII), malondialdehydes (MDA), and antioxidants (superoxide dismutase, catalase, glutathione peroxidase, glutathione) were measured. Also, prothrombin time (PT), activated partial thromboplastin time (aPTT), coagulation time, and platelet aggregation were evaluated. In diabetic rats, plasma glucose, HbA1c, MDA, fibrinogen, FVII, FDP, PAI-1, and platelet aggregation increased while insulin, PT, aPTT, coagulation time, protein C, ATIII, and antioxidants decreased. Warfarin administration to diabetic rats decreased FVII and FDP and increased PT, aPTT, and coagulation time with no effect on MDA, antioxidants, PAI-1, protein C, ATIII, and platelet aggregation. On the other hand, L-carnitine decreased fibrinogen, FVII, FDP, PAI-1, MDA, and platelet aggregation and increased PT, aPTT, coagulation time, protein C, ATIII, and antioxidants in diabetic rats. Therefore, we concluded that hyperglycemia plays an important role in hypercoagulation state and oxidative stress in STZ-induced DM. While L-carnitine improves oxidative stress and decreases the hypercoagulation state in DM, warfarin normalizes the hypercoagulation state with no effect on oxidative stress.

L-carnitine supplementation improves hematological pattern in patients affected by HCV treated with Peg interferon-α 2b plus ribavirin

AIM: To evaluate the efficacy of L-carnitine on alleviating anemia, thrombocytopenia and leukopenia, and minimizing dose reductions in patients with chronic hepatitis C virus (HCV) in treatment with Interferon α (IFN-α) plus ribavirin.

METHODS: Sixty-nine patients with chronic hepatitis C were enrolled in the study and divided into two groups. group A (n = 35) received Peg-IFN-α 2b plus ribavirin plus L-carnitine, and group B (n = 34) received Peg-IFN-α and ribavirin for 12 mo. All patients underwent laboratory investigations including: red cell count, hemoglobin, white cell count, platelets, bilirubin, alanine aminotransferase (ALT), aspartate aminotransferase (AST), and viremia.

RESULTS: After 12 mo in group A compared to group B we observed significant differences in AST 108.8 vs 76.8 (IU/L; P < 0.001), ALT 137.9 vs 112.3 (IU/L; P < 0.001), viremia 4.04 vs 2.36 (× 10⁶ copies/mL; P < 0.001), Hb 1 vs 3.5 (g/dL; P < 0.05), red blood cells 0.3 vs 1.1 (× 10¹²/L; P < 0.001), white blood cells 1.5 vs 3 (× 10⁹/L; P < 0.001) and platelets 86 vs 85 (× 10⁹/L; P < 0.001). The end treatment responders were 18 vs 12 (60% vs 44%) and the non responders were 12 vs 15 (40% vs 50%) [odds ratio (OR) 1.65, 95% CI = 0.65-5.37, P < 0.05]. In group A compared to group B there was a significant improvement of sustained virological response in 15 vs 7 patients (50% vs 25%), while the relapsers were 3 vs 5 (10% vs 18%) (OR 3.57, 95% CI = 0.65-19.3, P < 0.001).

CONCLUSION: L-carnitine supplementations modulate erythropoiesis, leucopoiesis and thrombocytopoiesis, and may be useful in patients treated for HCV. L-carnitine treatment offers the possibility of achieving a sustained virological response while preventing overtreatment.

Proteome of platelets in patients with coronary artery disease

OBJECTIVE

This study aimed at investigating the protein patterns of platelets from patients with stable or acute coronary atherosclerosis (CAD), in which platelets play a key role.

MATERIALS AND METHODS

A proteomic approach was adopted to investigate specific protein patterns in platelets of patients with non-ST elevation acute coronary syndrome, stable angina, or of subjects with no history of CAD.

RESULTS

Six differentially expressed proteins were identified: two involved in energy metabolism (2-oxoglutarate dehydrogenase [OGDH], and lactate dehydrogenase [LDH]); three were associated with cytoskeleton-based processes (gamma-actin, coronin 1B, and pleckstrin); and one involved in protein degradation (proteasome subunit type 8). Expression levels of OGDH and a cleaved form of gamma-actin were significantly higher in the platelets of patients than in controls, whereas that of LDH was higher only in the platelets of patients with acute coronary disease. The increases in protein expression of OGDH and LDH are paralleled by changes in their functional activities. Coronin and proteasome subunit type 8 were less expressed in the platelets of patients, as were the basic isoforms of pleckstrin.

CONCLUSION

The platelet proteome is altered in CAD patients with stable or acute coronary syndrome possibly because of the ongoing atherosclerotic process. The identified protein changes not previously connected with CAD were an increase in the energy metabolism enzymes and alterations in the proteins associated with cytoskeleton-based processes, both of which indicate platelet activation.

Platelets of type 2 diabetic patients are characterized by high ATP content and low mitochondrial membrane potential

Platelet dysfunction plays a critical role in vascular complications of type 2 diabetes mellitus (T2DM). But the relationship between platelet hyperactivity and its energy metabolic process remains unclear. This study was designed to explore alterations of platelet mitochondrial ATP production and the possible mechanism. A total of 39 T2DM patients without macrovascular and microvascular complications and 32 normal controls were fasting sampled. Platelet ATP content was measured by a high performance liquid chromatograph (HPLC). The flow cytometry technique was adopted to evaluate mitochondrial membrane potential (DeltaPsim), the stored force for platelet ATP production. Consequently, T2DM patients exhibited obvious hyperglycemia, hyperlipidemia and hypertension, but normal platelet morphology. Platelet ATP content was significantly higher in T2DM (0.032 +/- 0.010 micromol/10(9) platelets versus 0.017 +/- 0.006 micromol/10(9) platelets, p < 0.001) than in the control group. Interestingly, DeltaPsim was markedly decreased in T2DM patients (0.79 +/- 0.18 versus 2.70 +/- 1.03, p < 0.001) compared with normal controls. For whole subjects, a stepwise regression showed that plasma glycated hemoglobin A1c (HbA1c) level positively correlated to platelet ATP content (beta = 0.552, 95% CI = 0.072-1.451), and fasting plasma glucose (FPG) level was negatively correlated to DeltaPsim (beta = -0.372, 95% CI = -0.471 to -0.089). These data support that hyperglycemia of T2DM promotes platelet mitochondria to generate more ATP, but decreases platelet mitochondrial potential. The discordance between them requires further researches to elucidate.

L-carnitine modulates blood platelet oxidative stress

The oxidative stress induced by acute exertion may interfere with blood platelet activation. The beneficial effect of L-carnitine (gamma-trimethylamino-beta-hydroxybutyric acid) on oxidative stress in blood platelets has not been fully investigated; however, different studies indicate that this compound modulates platelet functions. The aim of our study was to assess the effects of L-carnitine on platelet activation and oxidative/nitrative protein damage (determined by the levels of protein carbonyl groups, thiol groups, and 3-nitrotyrosine residues) in resting blood platelets or platelets treated with peroxynitrite (ONOO(-), a strong physiological oxidant) in vitro. We also investigated the effects of L-carnitine on the level of platelet glutathione and on the formation of superoxide anion radicals O2(-*), lipid peroxidation measured by thiobarbituric acid reactive substances (TBARS) in blood platelets stimulated by thrombin (a strong physiological agonist), and platelet aggregation induced by adenosine diphosphate (a strong physiological stimulator). We have observed that carnitine decreases platelet activation (measured by platelet aggregation, the generation of O2(-*), and TBARS production). Moreover, our results in vitro demonstrate that carnitine may protect against oxidation of thiol groups induced by ONOO(-). Thus, carnitine may have some protectory effects against oxidative changes induced in blood platelets.

Alterations of adenine nucleotide metabolism and function of blood platelets in patients with diabetes

Increased activity of blood platelets contributes to vascular complications in patients with diabetes. The aim of this work was to investigate whether persisting hyperglycemia in diabetic patients generates excessive accumulation of ATP/ADP, which may underlie platelet hyperactivity. Platelet ATP and ADP levels, thiobarbituric acid-reactive species synthesis, and aggregation of platelets from patients with diabetes were 18-82% higher than in platelets from healthy participants. In patients with diabetes, platelet stimulation with thrombin caused about two times greater release of ATP and ADP than in the healthy group while decreasing intraplatelet nucleotide content to similar levels in both groups. This indicates that the increased content of adenylate nucleotides in the releasable pool in the platelets of diabetic patients does not affect their level in metabolic cytoplasmic/mitochondrial compartments. Significant correlations between platelet ATP levels and plasma fructosamine, as well as between platelet ATP/ADP and platelet activities, have been found in diabetic patients. In conclusion, chronic hyperglycemia-evoked elevations of ATP/ADP levels and release from blood platelets of patients with diabetes may be important factors underlying platelet hyperactivity in the course of the disease.

Experimental colitis: decreased Octn2 and Atb0+ expression in rat colonocytes induces carnitine depletion that is reversible by carnitine-loaded liposomes

Carnitine transporters have recently been implicated in susceptibility to inflammatory bowel disease (IBD). Because carnitine is required for beta-oxidation, it was suggested that decreased carnitine transporters, and hence reduced carnitine uptake, could lead to impaired fatty acid oxidation in intestinal epithelial cells, and to cell injury. We investigated this issue by examining the expression of the carnitine transporters OCTN2 and ATB0+, and butyrate metabolism in colonocytes in a rat model of IBD induced by trinitrobenzene sulfonic acid (TNBS). We found that Octn2 and Atb0+ expression was decreased in inflammatory samples at translational and functional level. Butyrate oxidation, evaluated based on CO2 production and acetyl-coenzyme A synthesis, was deranged in colonocytes from TNBS-treated rats. Treatment with carnitine-loaded liposomes corrected the butyrate metabolic alterations in vitro and reduced the severity of colitis in vivo. These results suggest that carnitine depletion in colonocytes is associated with the inability of mitochondria to maintain normal butyrate beta-oxidation. Our data indicate that carnitine is a rate-limiting factor for the maintenance of physiological butyrate oxidation in colonic cells. This hypothesis could also explain the contradictory therapeutic efficacy of butyrate supplementation observed in clinical trials of IBD.