Carnitine deficiency in children and adolescents with type 1 diabetes

Nutritional status and extended metabolic screening in Egyptian children with uncomplicated type 1 diabetes

Nutritional status assessment, including amino acids, carnitine, and acylcarnitine profile, is an important component of diabetes care management, influencing growth and metabolic regulation. A designed case-control research included 100 Egyptian participants (50 T1DM and 50 healthy controls) aged 6 to 18 years old. The participants' nutritional status was assessed using the Body Mass Index (BMI) Z-score. Extended metabolic screening (EMS) was performed using a high-performance liquid chromatography-electrospray ionization-mass spectroscopy system to evaluate the levels of 14 amino acids, free carnitine, and 27 carnitine esters. T1DM children had considerably lower anthropometric Z-scores than the control group, with 16% undernutrition and 32% short stature. Total aromatic amino acids, phenylalanine, phenylalanine/tyrosine ratio, proline, arginine, leucine, isoleucine, free carnitine, and carnitine esters levels were considerably lower in the diabetic group, suggesting an altered amino acid and carnitine metabolism in type 1 diabetes. BMI Z-score showed a significant positive correlation with Leucine, Isoleucine, Phenylalanine, Citrulline, Tyrosine, Arginine, Proline, free carnitine, and some carnitine esters (Acetylcarnitine, Hydroxy-Isovalerylcarnitine, Hexanoylcarnitine, Methylglutarylcarnitine, Dodecanoylcarnitine, Tetradecanoylcarnitine, and Hexadecanoylcarnitine). HbA1c% had a significant negative correlation with Total aromatic amino acids, Branched-chain amino acid/Total aromatic amino acids ratio, Glutamic Acid, Citrulline, Tyrosine, Arginine, Proline, and certain carnitine esters (Propionylcarnitine, Methylglutarylcarnitine, Decanoylcarnitine, Octadecanoylcarnitine and Octadecenoylcarnitine), suggest that dysregulated amino acid and carnitine metabolism may be negatively affect the glycaemic control in children with TIDM. In conclusion, regular nutritional assessments including EMS of T1DM patients are critical in terms of diet quality and protein content for improved growth and glycemic management.

Dietary l-carnitine regulates liver lipid metabolism via simultaneously activating fatty acid β-oxidation and suppressing endoplasmic reticulum stress in large yellow croaker fed with high-fat diets

Dietary l-carnitine (LC) is a nutritional factor that reduces liver lipid content. However, whether dietary LC can improve lipid metabolism via simultaneous activation of mitochondrial fatty acid (FA) β-oxidation and suppression of endoplasmic reticulum (ER) stress is still unknown. Large yellow croaker were fed with a high-fat diet (HFD) supplemented with dietary LC at 0, 1·2 or 2·4 ‰ for 10 weeks. The results indicated that a HFD supplemented with LC reduced the liver total lipid and TAG content and improved serum lipid profiles. LC supplementation administered to this fish increased the liver antioxidant capacity by decreasing serum and liver malondialdehyde levels and enhancing the liver antioxidant capacity, which then relieved the liver damage. Dietary LC increased the ATP dynamic process and mitochondrial number, decreased mitochondrial DNA damage and enhanced the protein expression of mitochondrial β-oxidation, biogenesis and mitophagy. Furthermore, dietary LC supplementation increased the expression of genes and proteins related to peroxisomal β-oxidation and biogenesis. Interestingly, feeding fish with LC-enriched diets decreased the protein levels indicative of ER stress, such as glucose-regulated protein 78, p-eukaryotic translational initiation factor 2a and activating transcription factor 6. Dietary LC supplementation downregulated mRNA expression relative to FA synthesis, reduced liver lipid and relieved liver damage through regulating β-oxidation and biogenesis of mitochondria and peroxisomes, as well as the ER stress pathway in fish fed with HFD. The present study provides the first evidence that dietary LC can improve lipid metabolism via simultaneously promoting FA β-oxidation capability and suppressing the ER stress pathway in fish.

The association between plasma carnitines and duration of diabetic ketoacidosis treatment in children with type 1 diabetes

OBJECTIVES

The aim of this study is to determine the plasma free carnitine and acyl-carnitine levels at the time of diabetic ketoacidosis (DKA) diagnosis, and at the end of DKA treatment and to investigate their association with the duration of DKA treatment in children with DKA.

METHODS

A total of 40 children with DKA who were treated consecutively in a tertiary health center for DKA were included in the study. The median age of the children was 11.3 years (1.1-17.5) and 25 of them (62.5%) were girls. In addition to routine blood tests, plasma free carnitine and acyl-carnitine levels were measured just before the start of intravenous insulin therapy and at the time of discontinuation of intravenous insulin therapy when DKA therapy was completed.

RESULTS

There was no difference in plasma free carnitine and acyl-carnitine levels before and after DKA treatment (p=0.776 and p=0.743 respectively). However, while the frequency of low plasma free carnitine was 30% at the beginning of the treatment, it was observed that this frequency was 20% at the end of the DKA treatment. There was no correlation between duration of DKA treatment and plasma free carnitine or acyl-carnitine levels at admission (p=0.497, r=-0.111 and p=0.474, r=0.116 respectively).

CONCLUSIONS

There is no a relationship between duration of DKA treatment and plasma free carnitine or acyl-carnitine level at admission in children with DKA.

Determination of carnitine ester profile in the children with type 1 diabetes: a valuable step towards a better management

Objective: This study is designed to investigate the levels of carnitine and acylcarnitines (ACs) in the children with diabetes type 1 compared to the healthy subjects.Methods: Forty-two type 1 diabetic children and healthy subjects were recruited in the study, respectively. In addition to FBS and Hb A1C, free carnitine and ACs in butyl-ester form in the fasting blood samples were assessed by isotope dilution mass spectrometry for all diabetics and controls using the tandem mass spectrometry system.Results: Diabetic patients had a higher level of C, C4, C6, C14, C18:2, and C18:2OH. Females had elevated C14:2 compared to the males. The C18:2 and C18:2OH levels were elevated as the Hb A1C level increased. The C18:2, C14OH were mostly increased in the prediabetic and diabetic patients, respectively.Conclusion: Increased ACs level indicates the increased acyl-CoA intermediates for the fatty acids and amino acids oxidation.

Carnitines as Mitochondrial Modulators of Oocyte and Embryo Bioenergetics

Recently, the importance of bioenergetics in the reproductive process has emerged. For its energetic demand, the oocyte relies on numerous mitochondria, whose activity increases during embryo development under a fine regulation to limit ROS production. Healthy oocyte mitochondria require a balance of pyruvate and fatty acid oxidation. Transport of activated fatty acids into mitochondria requires carnitine. In this regard, the interest in the role of carnitines as mitochondrial modulators in oocyte and embryos is increasing. Carnitine pool includes the un-esterified l-carnitine (LC) and carnitine esters, such as acetyl-l-carnitine (ALC) and propionyl-l-carnitine (PLC). In this review, carnitine medium supplementation for counteracting energetic and redox unbalance during in vitro culture and cryopreservation is reported. Although most studies have focused on LC, there is new evidence that the addition of ALC and/or PLC may boost LC effects. Pathways activated by carnitines include antiapoptotic, antiglycative, antioxidant, and antiinflammatory signaling. Nevertheless, the potential of carnitine to improve energetic metabolism and oocyte and embryo competence remains poorly investigated. The importance of carnitine as a mitochondrial modulator may suggest that this molecule may exert a beneficial role in ovarian disfunctions associated with metabolic and mitochondrial alterations, including PCOS and reproductive aging.

The Effects of Streptozotocin-Induced Diabetes and Insulin Treatment on Carnitine Biosynthesis and Renal Excretion

Carnitine insufficiency is reported in type 1 diabetes mellitus. To determine whether this is accompanied by defects in biosynthesis and/or renal uptake, liver and kidney were obtained from male Sprague-Dawley rats with streptozotocin-induced diabetes. Diabetic rats exhibited the metabolic consequences of type 1 diabetes, including hypoinsulinemia, hyperglycemia, and increased urine output. Systemic hypocarnitinemia, expressed as free carnitine levels, was evident in the plasma, liver, and kidney of diabetic rats. Compared to control rats, the low free carnitine in the plasma of diabetic rats was accompanied by decreased expression of γ-butyrobetaine hydroxylase in liver and kidney, suggesting impaired carnitine biosynthesis. Expression of organic cation transporter-2 in kidney was also reduced, indicating impaired renal reabsorption, and confirmed by the presence of elevated levels of free carnitine in the urine of diabetic rats. Insulin treatment of diabetic rats reversed the plasma hypocarnitinemia, increased the free carnitine content in both kidney and liver, and prevented urinary losses of free carnitine. This was associated with increased expression of γ-butyrobetaine hydroxylase and organic cation transporter-2. The results of our study indicate that type 1 diabetes induced with streptozotocin disrupts carnitine biosynthesis and renal uptake mechanisms, leading to carnitine insufficiency. These aberrations in carnitine homeostasis are prevented with daily insulin treatment.

Comparative study of the efficacy of captopril, simvastatin, and L-carnitine as cardioprotective drugs in children with type 1 diabetes mellitus: a randomised controlled trial

OBJECTIVES

To assess the efficacy and safety of captopril, simvastatin, and L-carnitine as cardioprotective drugs in children with type 1 diabetes mellitus on different echocardiographic parameters, electrocardiographic parameter, lipid profile, and carotid intima-media thickness.

METHODS

This randomised controlled trial was conducted on 100 children with type 1 diabetes mellitus for more than 3 years during the period from September 2018 to June 2020. Fifty healthy children of matched age and sex served as a control group. The patients were randomly assigned into four groups (25 children each): no-treatment group who received no cardioprotective drug, simvastatin group who received simvastatin (10-20 mg/day), captopril group who received captopril (0.2 mg/kg/day), and L-carnitine group who received L-carnitine (50 mg/kg/day) for 4 months. Lipid profile, serum troponin I, carotid intima-media thickness, and echocardiographic examinations were performed on all included children before and after the treatment.

RESULTS

Total cholesterol and low-density lipoprotein were significantly decreased in children who received simvastatin or L-carnitine. Triglycerides significantly decreased only in children who received simvastatin. High-density lipoprotein significantly increased in simvastatin and L-carnitine groups only. Serum troponin I decreased significantly in all the three treatment groups. Carotid intima-media thickness showed no significant change in all treatment groups. Echocardiographic parameters significantly improved in simvastatin, L-carnitine, and captopril groups.

CONCLUSION

Captopril, simvastatin, and L-carnitine have a significant beneficial effect on cardiac functions in children with type 1 diabetes mellitus. However, only simvastatin and L-carnitine have a beneficial effect on the lipid profile. The drugs were safe and well tolerated.Clinical trial registration: The clinical trial was registered at www.clinicaltrial.gov (NCT03660293).

Phospholipid Levels at Seroconversion Are Associated With Resolution of Persistent Islet Autoimmunity: The Diabetes Autoimmunity Study in the Young

Reversion of islet autoimmunity (IA) may point to mechanisms that prevent IA progression. We followed 199 individuals who developed IA during the Diabetes Autoimmunity Study in the Young. Untargeted metabolomics was performed in serum samples following IA. Cox proportional hazards models were used to test whether the metabolites (2,487) predicted IA reversion: two or more consecutive visits negative for all autoantibodies. We conducted a principal components analysis (PCA) of the top metabolites; |hazard ratio (HR) >1.25| and nominal P < 0.01. Phosphatidylcholine (16:0_18:1(9Z)) was the strongest individual metabolite (HR per 1 SD 2.16, false discovery rate (FDR)-adjusted P = 0.0037). Enrichment analysis identified four clusters (FDR P < 0.10) characterized by an overabundance of sphingomyelin (d40:0), phosphatidylcholine (16:0_18:1(9Z)), phosphatidylcholine (30:0), and l-decanoylcarnitine. Overall, 63 metabolites met the criteria for inclusion in the PCA. PC1 (HR 1.4, P < 0.0001), PC2 (HR 0.85, P = 0.0185), and PC4 (HR 1.28, P = 0.0103) were associated with IA reversion. Given the potential influence of diet on the metabolome, we investigated whether nutrients were correlated with PCs. We identified 20 nutrients that were correlated with the PCs (P < 0.05). Total sugar intake was the top nutrient. Overall, we identified an association between phosphatidylcholine, sphingomyelin, and carnitine levels and reversion of IA.

The Association Between Serum Carnitine Level, Glucose Regulation, Body Fat and Nutrient Intake in Diabetic Individuals

Carnitine (β-hydroxy-γ-trimethyl amino butyrate) is, a vitamin-like substance carrying long-chain fatty acids into the mitochondrial matrix. Due to its effect in energy metabolism, carnitine plays an important role in controlling diabetes and its complications. Studies on this topic have often focused on carnitine supplementation. This study was planned to investigate the relationship between serum carnitine level, glucose regulation and body fat in diabetic patients. A total of 64 people between the ages of 30-5, 32 patients with type 2 diabetes and 32 healthy subjects, were included in the study. Individual lipid profiles, glucose, insulin and serum carnitine levels were analyzed, anthropometric measurements were taken and 24-hour recall food consumption was recorded. As a result, blood glucose, insulin, triglyceride, VLDL-C, HDL-C and HOMA-IR were found to be higher in diabetic individuals than healthy group (p<0,05). Serum carnitine levels were found to be significantly lower in diabetic male (50,6±20,83 nmol/mL) than in healthy male (59,5±17,25 nmol/mL)(p<0,05). This difference was not statistically significant among female (p>0,05). It has been observed that intake of energy and macronutrients of diabetic individuals is generally lower than that of healthy individuals. Serum carnitine level was positively associated with polyunsaturated fatty acids and omega-6 fatty acid intake in male in the healthy group showed a negative correlation with fiber intake in female in the healthy group (p<0,05). There were negative correlations between serum carnitine level with body weight, body mass index and body fat mass in female in the healthy group (p<0,05). Individuals with diabetes are predisposed to dyslipidemia and insulin resistance. As a result; food consumption, and body fat affect individuals’ serum carnitine levels in type-2 diabetes. Since there is not enough study evaluating the relationship between anthropometric measurements of individuals and serum carnitine levels, it is thought that this result will guide future studies.

L-Carnitine Stimulates In Vivo Carbohydrate Metabolism in the Type 1 Diabetic Heart as Demonstrated by Hyperpolarized MRI

The diabetic heart is energetically and metabolically abnormal, with increased fatty acid oxidation and decreased glucose oxidation. One factor contributing to the metabolic dysfunction in diabetes may be abnormal handling of acetyl and acyl groups by the mitochondria. L-carnitine is responsible for their transfer across the mitochondrial membrane, therefore, supplementation with L-carnitine may provide a route to improve the metabolic state of the diabetic heart. The primary aim of this study was to use hyperpolarized magnetic resonance imaging (MRI) to investigate the effects of L-carnitine supplementation on the in vivo metabolism of [1-¹³C]pyruvate in diabetes. Male Wistar rats were injected with either vehicle or streptozotocin (55 mg/kg) to induce type-1 diabetes. Three weeks of daily i.p. treatment with either saline or L-carnitine (3 g/kg/day) was subsequently undertaken. In vivo cardiac function and metabolism were assessed with CINE and hyperpolarized MRI, respectively. L-carnitine supplementation prevented the progression of hyperglycemia, which was observed in untreated streptozotocin injected animals and led to reductions in plasma triglyceride and ß-hydroxybutyrate concentrations. Hyperpolarized MRI revealed that L-carnitine treatment elevated pyruvate dehydrogenase flux by 3-fold in the diabetic animals, potentially through increased buffering of excess acetyl-CoA units in the mitochondria. Improved functional recovery following ischemia was also observed in the L-carnitine treated diabetic animals.

Organic Cation Transporters in Health and Disease

The organic cation transporters (OCTs) OCT1, OCT2, OCT3, novel OCT (OCTN)1, OCTN2, multidrug and toxin exclusion (MATE)1, and MATE kidney-specific 2 are polyspecific transporters exhibiting broadly overlapping substrate selectivities. They transport organic cations, zwitterions, and some uncharged compounds and operate as facilitated diffusion systems and/or antiporters. OCTs are critically involved in intestinal absorption, hepatic uptake, and renal excretion of hydrophilic drugs. They modulate the distribution of endogenous compounds such as thiamine, L-carnitine, and neurotransmitters. Sites of expression and functions of OCTs have important impact on energy metabolism, pharmacokinetics, and toxicity of drugs, and on drug-drug interactions. In this work, an overview about the human OCTs is presented. Functional properties of human OCTs, including identified substrates and inhibitors of the individual transporters, are described. Sites of expression are compiled, and data on regulation of OCTs are presented. In addition, genetic variations of OCTs are listed, and data on their impact on transport, drug treatment, and diseases are reported. Moreover, recent data are summarized that indicate complex drug-drug interaction at OCTs, such as allosteric high-affinity inhibition of transport and substrate dependence of inhibitor efficacies. A hypothesis about the molecular mechanism of polyspecific substrate recognition by OCTs is presented that is based on functional studies and mutagenesis experiments in OCT1 and OCT2. This hypothesis provides a framework to imagine how observed complex drug-drug interactions at OCTs arise. Finally, preclinical in vitro tests that are performed by pharmaceutical companies to identify interaction of novel drugs with OCTs are discussed. Optimized experimental procedures are proposed that allow a gapless detection of inhibitory and transported drugs.

The Importance of the Fatty Acid Transporter L-Carnitine in Non-Alcoholic Fatty Liver Disease (NAFLD)

L-carnitine transports fatty acids into the mitochondria for oxidation and also buffers excess acetyl-CoA away from the mitochondria. Thus, L-carnitine may play a key role in maintaining liver function, by its effect on lipid metabolism. The importance of L-carnitine in liver health is supported by the observation that patients with primary carnitine deficiency (PCD) can present with fatty liver disease, which could be due to low levels of intrahepatic and serum levels of L-carnitine. Furthermore, studies suggest that supplementation with L-carnitine may reduce liver fat and the liver enzymes alanine aminotransferase (ALT) and aspartate transaminase (AST) in patients with Non-Alcoholic Fatty Liver Disease (NAFLD). L-carnitine has also been shown to improve insulin sensitivity and elevate pyruvate dehydrogenase (PDH) flux. Studies that show reduced intrahepatic fat and reduced liver enzymes after L-carnitine supplementation suggest that L-carnitine might be a promising supplement to improve or delay the progression of NAFLD.

Mass Spectrometric Analysis of L-carnitine and its Esters: Potential Biomarkers of Disturbances in Carnitine Homeostasis

PURPOSE

After a golden age of classic carnitine research three decades ago, the spread of mass spectrometry opened new perspectives and a much better understanding of the carnitine system is available nowadays. In the classic period, several human and animal studies were focused on various distinct physiological functions of this molecule and these revealed different aspects of carnitine homeostasis in normal and pathological conditions. Initially, the laboratory analyses were based on the classic or radioenzymatic assays, enabling only the determination of free and total carnitine levels and calculation of total carnitine esters' amount without any information on the composition of the acyl groups. The introduction of mass spectrometry allowed the measurement of free carnitine along with the specific and sensitive determination of different carnitine esters. Beyond basic research, mass spectrometry study of carnitine esters was introduced into the newborn screening program because of being capable to detect more than 30 metabolic disorders simultaneously. Furthermore, mass spectrometry measurements were performed to investigate different disease states affecting carnitine homeostasis, such as diabetes, chronic renal failure, celiac disease, cardiovascular diseases, autism spectrum disorder or inflammatory bowel diseases.

RESULTS

This article will review the recent advances in the field of carnitine research with respect to mass spectrometric analyses of acyl-carnitines in normal and various pathological states.

CONCLUSION

The growing number of publications using mass spectrometry as a tool to investigate normal physiological conditions or reveal potential biomarkers of primary and secondary carnitine deficiencies shows that this tool brought a new perspective to carnitine research.

Poor Efficacy of L-Acetylcarnitine in the Treatment of Asthenozoospermia in Patients with Type 1 Diabetes

Introduction. In recent years, research has focused on the impact that diabetes mellitus (DM) has on male reproductive function. The available evidence has mainly considered type 2 DM (DM2). However, we have previously shown that type 1 DM (DM1) also affects male reproductive health. Given the efficacy of carnitine in the treatment of male infertility, a topic that merits further investigation is its role in the treatment of infertile patients with DM1. Aim. To investigate the efficacy of carnitines for the treatment of asthenozoospermia in DM1 patients. Methods. This was a two-arm single-blind, randomized control trial. The patients enrolled in this study were assigned to the group receiving L-acetylcarnitine (LAC) (1.5 g daily for 4 months) or to the group receiving LAC (same dosage) plus L-carnitine (LC) (2 g daily for 4 months). Serum-glycated hemoglobin levels did not differ significantly after either of the two treatments given. Administration of LAC plus LC showed greater efficacy on progressive sperm motility than single therapy (increase 14% vs. 1% after treatment, respectively). Discussion. The results of this study showed that the administration of LAC plus LC is more effective than the administration of LAC alone. The lower efficacy of LAC alone could be due to the lower overall administered dosage. Alternatively, a selective defect of carnitine transporters at an epididymal level could be hypothesized in patients with DM1. Further studies are needed to clarify this point.

OCTN: A Small Transporter Subfamily with Great Relevance to Human Pathophysiology, Drug Discovery, and Diagnostics

OCTN is a small subfamily of membrane transport proteins that belongs to the larger SLC22 family. Two of the three members of the subfamily, namely, OCTN2 and OCTN1, are present in humans. OCTN2 plays a crucial role in the absorption of carnitine from diet and in its distribution to tissues, as demonstrated by the occurrence of severe pathologies caused by malfunctioning or altered expression of this transporter. These findings suggest avoiding a strict vegetarian diet during pregnancy and in childhood. Other roles of OCTN2 are related to the traffic of carnitine derivatives in many tissues. The role of OCTN1 is still unclear, despite the identification of some substrates such as ergothioneine, acetylcholine, and choline. Plausibly, the transporter acts on the control of inflammation and oxidative stress, even though knockout mice do not display phenotypes. A clear role of both transporters has been revealed in drug interaction and delivery. The polyspecificity of the OCTNs is at the base of the interactions with drugs. Interestingly, OCTN2 has been recently exploited in the prodrug approach and in diagnostics. A promising application derives from the localization of OCTN2 in exosomes that represent a noninvasive diagnostic tool.

Exosomes in inflammation and role as biomarkers

Exosomes are endosomal-derived nano-vesicles. They are considered vehicles through which donor cells transfer proteins, lipids and nucleic acids to target cells thus influencing their metabolism. Exosomes are involved in inflammatory processes that play a pivotal role in a large number of pathologic states including cancer, inflammatory bowel diseases, type 2 diabetes, obesity, rheumatoid arthritis and neurodegenerative diseases. The association between inflammation and change in nature or expression level of some exosomal cargos is the fundamental step for identifying possible novel biomarkers of inflammatory-based diseases. A novel interesting exosome cargo is the SLC22A5 transport protein whose level in exosomes is regulated by the pro-inflammatory cytokine INF-γ. The advantage of using exosomes as a biomarker vehicle consists of their ease of collection from body fluids such as urine and saliva as they may represent a non-invasive means for screening human pathology.

Effect of L-carnitine on diabetes-induced changes of skeletal muscles in rats

BACKGROUND

Patients with diabetes mellitus (DM) are at risk of experiencing chronic complications such as retinopathy, nephropathy and myopathy. We aimed to evaluate the effects of L-carnitine on type II DM (T2DM)-induced biochemical, contractile and pathological changes in skeletal muscles of rats.

METHODS

Thirty-two male Sprague Dawley rats were divided into the control, control+L-carnitine, T2DM and T2DM+L-carnitine groups. Plasma levels of glucose, insulin, malondialdehyde and antioxidants such as reduced glutathione, catalase and superoxide dismutase, haemoglobin A1c (HbA1c), insulin sensitivity index (ISI) as well as the contractile properties of the gastrocnemius muscle were measured. Also, histopathological studies and immunohistochemical examination of the gastrocnemius muscle using the MuRF1 (muscle RING-finger protein-1) marker were performed.

RESULTS

In diabetic rats, malondialdehyde, glucose, insulin, HbA1c and MuRF1 were increased, whereas ISI and antioxidants were decreased and the contractile properties deteriorated. L-carnitine decreased malondialdehyde, glucose, insulin, HbA1c and MuRF1 and increased ISI and antioxidants. Also, L-carnitine improves the contractile properties in diabetic rats. Histopathological studies confirm our data.

CONCLUSIONS

We conclude that L-carnitine exhibits protective effects on skeletal muscles of T2DM rats through its hypoglycemic and antioxidant actions as well as its inhibitory effect on protein degradation.

Characterization of Exosomal SLC22A5 (OCTN2) carnitine transporter

Exosomes are extracellular vesicles involved in cell-to-cell communication. Previous large scale proteomics revealed that they contain SLC proteins. However, no data on the function of exosomal SLCs is available, so far. An SLC localized in exosomes was here characterized for the first time: the carnitine transporter OCTN2 (SLC22A5). The protein was detected by Western Blot analysis in HEK293 exosomes. To investigate the functional properties of the exosomal OCTN2, the proteins extracted from vesicles were reconstituted into proteolipsomes and the transport function was measured as uptake of ³H-carnitine. Transport was stimulated by sodium and was dependent on pH. ³H-carnitine uptake was inhibited by Acetyl-carnitine, but not by Asn, Gln and Arg thus excluding interference by ATB^0,+, an amino acid transporter which also recognizes carnitine. Cardiolipin failed to stimulate transport, excluding the activity of the mitochondrial Carnitine/acylcarnitine transporter. Increased level of exosomal OCTN2 was induced by treatment of HEK293 with the pro-inflammatory cytokine INFγ. All data concurred to demonstrate that OCTN2 present in exosomes is fully functional and is in its native conformation. Functional OCTN2 was detected also in human urinary exosomes, thus suggesting the OCTN2 exosomal protein as a candidate biomarker for inflammation related pathologies.

Children who develop type 1 diabetes early in life show low levels of carnitine and amino acids at birth: does this finding shed light on the etiopathogenesis of the disease?

BACKGROUND

Children and adolescents with overt type 1 diabetes (T1D) have been found to show an altered carnitine profile. This pattern has not previously been analyzed in neonates before onset of the disease.

MATERIALS AND METHODS

Fifty children who developed T1D during the first 6 years of life, born and living in the Tuscany and Umbria Regions of Italy, were identified and 200 controls were recruited into the study. All newborns were subjected to extended neonatal screening by mass spectrometry at 48-72 h of life. Four controls for each of the 50 index cases were taken randomly and blinded in the same analytical batch. The panel used for neonatal screening consists of 13 amino acids, free carnitine, 33 acyl-carnitines and 21 ratios. All Guthrie cards are analyzed within 2 days of collection.

RESULTS

Total and free carnitine were found to be significantly lower in neonates who later developed T1D compared with controls. Moreover, the concentrations of the acyl-carnitines - acetyl-L-carnitine (C2), proprionylcarnitine (C3), 3-hydroxyisovalerylcarnitine (C5OH), miristoylcarnitine (C4), palmitoylcarnitine (C16) and stearoylcarnitine (C18) - were also significantly low in the cases vs controls. Furthermore, total amino-acid concentrations, expressed as the algebraic sum of all amino acids tested, showed a trend toward lower levels in cases vs controls.

CONCLUSIONS

We found that carnitine and amino-acid deficit may be evident before the clinical appearance of T1D, possibly from birth. The evaluation of these metabolites in the neonatal period of children human leukocyte antigen genetically at 'risk' to develop T1D, could represent an additional tool for the prediction of T1D and could also offer the possibility to design new strategies for the primary prevention of the disease from birth.

Similarities in serum acylcarnitine patterns in type 1 and type 2 diabetes mellitus and in metabolic syndrome

BACKGROUND/AIMS

In type 1 diabetes (T1D), type 2 diabetes (T2D) and metabolic syndrome (MetS), the associated complex metabolomic changes in the involvement of carnitine metabolism in total carnitine ester level has already been documented; here we extended the investigations to the individual acylcarnitines.

METHODS

The fasting serum acylcarnitine concentrations were determined in 49 T1D, 38 T2D and 38 MetS patients and 40 controls by isotope dilution electrospray ionization tandem mass spectrometry.

RESULTS

The acylcarnitine profiles of the 3patient groups shared elements with the controls. Considerably higher levels of almost all short-chain acylcarnitines (p < 0.05) and lower levels of some long-chain acylcarnitines were detected in T2D and MetS patients. The amounts of C3 and C4 carnitine were higher and most of the medium-chain and long-chain acylcarnitine levels were lower (p < 0.05) in T1D and MetS patients than in the controls. In T1D and T2D, the levels of C3 and C4 acylcarnitines were markedly elevated and some long-chain acylcarnitines were lower than the controls (p < 0.05). Moreover, significantly lower concentrations of free- and total carnitine were observed in T1D patients (p < 0.05).

CONCLUSIONS

Profound alterations were detected in acylcarnitine profiles in the 3 patient groups. Similarities in the patterns suggest different degrees of involvement of the same metabolic systems in a systems biology approach.

Resveratrol ameliorates metabolic disorders and muscle wasting in streptozotocin-induced diabetic rats

Diabetes mellitus (DM) is characterized by dysregulated energy metabolism. Resveratrol (RSV) has been shown to ameliorate hyperglycemia and hyperlipidemia in diabetic animals. However, its overall in vivo effects on energy metabolism and the underlying mechanism require further investigation. In the present study, electrospray ionization-tandem mass spectrometry was employed to characterize the urine and plasma metabolomes of control, streptozotocin-induced DM and RSV-treated DM rats. Using principal component analysis (PCA) and heat map analysis, we discovered significant differences among control and experimental groups. RSV treatment significantly reduced the metabolic abnormalities in DM rats. Compared with the age-matched control rats, the level of carnitine was lower, and the levels of acetylcarnitine and butyrylcarnitine were higher in the urine and plasma of DM rats. RSV treatment ameliorated the deranged carnitine metabolism in DM rats. In addition, RSV treatment attenuated the diabetic ketoacidosis and muscle protein degradation, as evidenced from the attenuation of elevated urinary methyl-histidine and plasma branched-chain amino acids levels in DM rats. The beneficial effects of RSV in DM rats were correlated with activation of hepatic AMP-activated protein kinase and SIRT1 expression, increase of hepatic and muscular mitochondrial biogenesis and inhibition of muscle NF-κB activities. We concluded that RSV possesses multiple beneficial metabolic effects in insulin-deficient DM rats, particularly in improving energy metabolism and reducing protein wasting.

Effect of L-carnitine on the synthesis of nitric oxide in RAW 264·7 murine macrophage cell line

L-Carnitine (β-hydroxy-γ-trimethyl aminobutyric acid) plays a critical role in inflammatory diseases by modulating inflammatory cell functions. Inducible nitric oxide synthase (iNOS), a proinflammatory enzyme responsible for the generation of nitric oxide (NO), has been implicated in the pathogenesis of inflammatory diseases. Mechanism of action of L-carnitine on inflammation via iNOS and nuclear factor κB (NF-κB) is unclear. In this study, we aimed to investigate the effect of L-carnitine on nitric oxide synthesis in lipopolysaccharide (LPS)-stimulated RAW 264·7 macrophage cells. For this purpose, cells were pretreated with various concentrations of L-carnitine and subsequently incubated with LPS (1 µg·ml(-1) ). NO levels, iNOS protein expression, and NF-κB activity were determined using colorimetric detection, Western blotting and transfection assays. Our results showed that treatment with L-carnitine suppressed nitric oxide production, iNOS protein expression and NF-κB activity. We demonstrated that inhibitory effect of L-carnitine on iNOS protein expression is at transcriptional level. This study may contribute to understanding the anti-inflammatory effect of L-carnitine.

Noninvasive assessment of exercise-related intramyocellular acetylcarnitine in euglycemia and hyperglycemia in patients with type 1 diabetes using ¹H magnetic resonance spectroscopy: a randomized single-blind crossover study

OBJECTIVE

Intramyocellular acetylcarnitine (IMAC) is involved in exercise-related fuel metabolism. It is not known whether levels of systemic glucose influence IMAC levels in type 1 diabetes.

RESEARCH DESIGN AND METHODS

Seven male individuals with type 1 diabetes performed 120 min of aerobic exercise at 55-60% of Vo(2max) randomly on two occasions (glucose clamped to 5 or 11 mmol/l, identical insulinemia). Before and after exercise, IMAC was detected by ¹H magnetic resonance spectroscopy in musculus vastus intermedius.

RESULTS

Postexercise levels of IMAC were significantly higher than pre-exercise values in euglycemia (4.30 ± 0.54 arbitrary units [a.u.], P < 0.001) and in hyperglycemia (2.44 ± 0.53 a.u., P = 0.01) and differed significantly according to glycemia (P < 0.01). The increase in exercise-related levels of IMAC was significantly higher in euglycemia (3.97 ± 0.45 a.u.) than in hyperglycemia (1.71 ± 0.50 a.u.; P < 0.01).

CONCLUSIONS

The increase in IMAC associated with moderate aerobic exercise in individuals with type 1 diabetes was significantly higher in euglycemia than in hyperglycemia.

Ameliorating effects of L-carnitine on diabetic podocyte injury

High glucose levels can change podocyte gene expression and subsequently induce podocyte damage through altered glucose metabolism. l-Carnitine is known to play a beneficial role in diabetes; however, there are no studies on the effects of l-carnitine on podocyte alteration under high glucose conditions. This study investigated whether l-carnitine can attenuate diabetic podocyte injury through the prevention of loss of slit diaphragm proteins. The l-carnitine treatment group showed increased glucose uptakes compared to the control group, suggesting that glucose utilization in the podocytes was increased by l-carnitine. l-Carnitine treatment also prevented decreased mRNA expressions of nephrin and podocin in the high glucose-stimulated podocytes. However, mRNA expressions of CD2AP and α-actinin-4 were not significantly changed by the high glucose conditions. When these data are taken together, l-carnitine can increase glucose uptake in podocytes under high glucose conditions, and its mechanism may be at least partly related to the up-regulation of nephrin and podocin. Our results help clarify the beneficial effects of l-carnitine in diabetic nephropathy.

L-carnitine supplementation to diet: a new tool in treatment of nonalcoholic steatohepatitis--a randomized and controlled clinical trial

OBJECTIVES

Nonalcoholic steatohepatitis (NASH) is a known metabolic disorder of the liver. No treatment has been conclusively shown to improve NASH or prevent disease progression. The function of L-carnitine to modulate lipid profile, glucose metabolism, oxidative stress, and inflammatory responses has been shown. The aim of this study was to evaluate the effects of L-carnitine's supplementation on regression of NASH.

METHODS

In patients with NASH and control subjects, we randomly dispensed one 1-g L-carnitine tablet after breakfast plus diet and one 1 g tablet after dinner plus diet for 24 weeks or diet alone at the same dosage and regimen. We evaluated liver enzymes, lipid profile, fasting plasma glucose, C-reactive protein (CRP), tumor necrosis factor (TNF)-alpha, homeostasis model assessment (HOMA)-IR, body mass index, and histological scores.

RESULTS

At the end of the study, L-carnitine-treated patients showed significant improvements in the following parameters: aspartate aminotransferase (P=0.000), alanine aminotransferase (ALT) (P=0.000), gamma-glutamyl-transpeptidase (gamma-GT) (P=0.000), total cholesterol (P=0.000), low-density lipoprotein (LDL) (P=0.000), high-density lipoprotein (HDL) (P=0.000), triglycerides (P=0.000), glucose (P=0.000), HOMA-IR (P=0.000), CRP (P=0.000), TNF-alpha (P=0.000), and histological scores (P=0.000).

CONCLUSIONS

L-carnitine supplementation to diet is useful for reducing TNF-alpha and CRP, and for improving liver function, glucose plasma level, lipid profile, HOMA-IR, and histological manifestations of NASH.

Inspiratory muscle strength is correlated with carnitine levels in type 2 diabetes

INTRODUCTION

Plasma carnitine insufficiency has been known to cause muscle weakness. Carnitine levels and pulmonary functions were lower in patients with diabetes.

PATIENTS AND METHODS

To determine whether pulmonary functions are correlated with carnitine levels in patients with type 2 diabetes. In this study, we evaluated pulmonary functions and carnitine concentrations in 49 patients with type 2 diabetes and 34 healthy controls.

RESULTS

Carnitine levels were lower in type 2 diabetes group than control group (52.56 +/- 12.38 and 78.96 +/- 10.66 hmol/mL, respectively, p < 0.0001). Pulmonary functions were not significantly different between groups. Carnitine levels were not correlated with age, duration of diabetes, fasting blood glucose levels, and glycemic control (HbA1c%) in patients with type 2 diabetes. However, carnitine levels in patient group were correlated with % forced vital capacity (FVC%) (r = 0.35, p = 0.016), % forced expiratory volume in 1 s (FEV1%) (r = 0.318, p= 0.029), FEV1/FVC (r= 0.302, p= 0.039), inspiratory muscle strength (PImax) (r = 0.407, p = 0.023), and PImax% (r = 0.423, p= 0.018).

CONCLUSION

This study suggests that low carnitine levels may be associated with lower PImax and PImax% in type 2 diabetes.

Serum carnitine levels in childhood leukemia

In patients with malignancies, the system of carnitine seems abnormally expressed. The serum total, free, and acyl carnitine levels in 40 children and adolescents with acute leukemia were determined using electrospray tandem mass spectrometry in 4 different phases of the disease: at the diagnosis, 1 year after the initiation of chemotherapy, at the end of treatment, and 2.4+/-1.668 years after the completion of chemotherapy. The age, sex, hemoglobin values, serum biochemistry, somatometric features of the patients, and the risk group of the disease were examined. Although the carnitine levels were found higher in patients compared with the control group from diagnosis to treatment completion, statistically significant decrease in carnitine levels was observed in patients within different phases of the disease especially during induction and consolidation treatment (phase A to B) for both free and total (P=0.023) carnitine. In addition, a statistically significant recovery in carnitine levels was observed between phase B (end of intensive chemotherapy) and D (some years after the completion of treatment) for free and total carnitine (P=0.054 and 0.035, respectively). No statistical correlation was documented between the carnitine levels and somatometric parameters or other variables studied. In conclusion, a significant transient decrease in the levels of carnitine during the treatment was observed in children with acute leukemia. Further studies are required to clarify the role of carnitine status in patients with malignancies and possibly the necessity of carnitine supplementation during chemotherapy administration.

Targeting neuroprotection as an alternative approach to preventing and treating neuropathic pain

Neuropathic pain syndromes arise from dysfunction of the nerve itself, through traumatic or nontraumatic injury. Unlike acute pain syndromes, the pain is long-lasting and does not respond to common analgesic therapies. Drugs that disrupt nerve conduction and transmission or central sensitization, currently the only effective treatments, are only modestly effective for a portion of the patients suffering from neuropathic pain and come with the cost of serious adverse effects. Neurodegeneration, as a reaction to nerve trauma or chronic metabolic or chemical intoxication, appears to be an underlying cause of neuropathic pain. Identifying mechanisms of neurodegeneration and designing neuroprotective therapies is an ambitious goal toward treating or even preventing the development of these disabling disorders.

L-carnitine: implications in the treatment of the metabolic syndrome and Type 2 diabetes

The metabolic syndrome (MS) is a conglomeration of inter-related common clinical disorders, including obesity, glucose intolerance, hypertension and dyslipidemia, which predispose to Type 2 diabetes (T2D) and cardiovascular diseases. Hyperinsulinemia, per se, and insulin resistance are the pathogenic factors associated with the metabolic risk factors. Since these risk factors are the most frequent causes for mortality among patients with T2D and the MS, treatments targeting normalization of both lipid and glucose homeostasis are of interest. The crucial role of L-carnitine (CA) as a regulator of lipid and glucose metabolism has raised considerable interest in its use as a potential tool for therapeutic intervention in the MS. Several clinical studies have, therefore, been undertaken to examine the efficacy and other benefits in the treatment of T2D and the MS. Studies from rodent models of MS have also shown the positive effects of CA on several components of the syndrome. CA, being an endogenous water-soluble nutrient, could be a safe adjunct and a relevant future drug for the MS. This review provides an overview on the importance of CA in T2D and the MS and the need for further evaluation of its inclusion in treatment protocols.

Role of acetyl-L-carnitine in the treatment of diabetic peripheral neuropathy

OBJECTIVE

To examine the role of acetyl-L-carnitine (ALC) in the treatment of diabetic peripheral neuropathy (DPN).

DATA SOURCES

A MEDLINE search (1966-April 2008) of the English-language literature was performed using the search terms carnitine, diabetes, nerve, and neuropathy. Studies identified were then cross-referenced for their citations.

STUDY SELECTION AND DATA EXTRACTION

The search was limited to clinical trials, meta-analyses, and reviews addressing the use of ALC for the treatment of DPN. Studies that included other disease states that could cause peripheral neuropathy were excluded. Two large clinical studies that used ALC for the treatment of DPN were identified. No case studies were identified.

DATA SYNTHESIS

The results from 2 published clinical trials involving 1679 subjects were included. Subjects who received at least 2 g daily of ALC showed decreases in pain scores. One study showed improvements in electrophysiologic factors such as nerve conduction velocities, while the other did not. Patients who had neuropathic pain reported reductions in pain using a visual analog scale. Nerve regeneration was documented in one trial. The supplement was well tolerated. A proprietary form of ALC was used in both studies.

CONCLUSIONS

Data on treatment of DPN with ALC support its use. It should be recommended to patients early in the disease process to provide maximal benefit. Further studies should be conducted to determine the effectiveness of ALC in the treatment and prevention of the worsening symptoms of DPN.

The protective effect of L-carnitine on ischemia-reperfusion heart

To investigate the protective effect of L-carnitine on myocardial ischemia-reperfusion injury in rat heart,all harvested isolated hearts were perfused on Langendorff apparatus with oxygenized K-H solution for 20 min. The hearts were then exposed to ischemia for 30 min. Following the ischemia the hearts were re-perfused with K-H solution for 120 min to serve as the control group A. Either 5 or 10 mmol/L of L-carnitine was added into the K-H solution for 20 min at the beginning of reperfusion to generate group B and group C, respectively. The derivatives of the intraventricular pressure curve (DP/DT), left ventricular developed pressure (LVDP), and coronary flux were monitored during the entire experiment. The levels of ATP, hepatin, malondialdehyde (MDA), and superoxide dismutase (SOD) in tissue, and lactic dehydrogenase (LDH), creatine phosphate kinase (CPK), malondialdehyde (MDA), and superoxide dismutase (SOD) concentration in the coronary efflux were all measured. Compared with the control group, the treatment with L-carnitine resulted in better results, i. e., higher DP/DTmax and LVDP. At the same time, ventricular fibrillation was reduced, and the levels of ATP, hepatin and SOD were all elevated. However, the concentrations of MDA, CPK and LDH were all reduced. In conclusion, L-carnitine has a protective effect on ischemia-reperfusion injury, which is partly due to its prevention of energy loss and its antioxidant activity.

L-Carnitine inhibits protein glycation in vitro and in vivo: evidence for a role in diabetic management

Glycation-initiated changes in tissue proteins are suggested to play an important role in the development of diabetes-related pathological changes. The purpose of this study was to examine the anti-glycating effect of L-carnitine (CA) in vivo in the high-fructose diet-fed rat and to determine the potential of CA to inhibit in vitro glycation. Additionally the glucose-disposal efficiency of CA in the rat diaphragm was investigated. High-fructose diet (60 g/100 g diet)-fed rats were treated with CA (300 mg/kg/day i.p.) for 60 days. The effect of CA on glucose, fructose and fructosamine in plasma, methyl glyoxal and glycated haemoglobin in whole blood and skin and tail tendon collagen glycation were determined. The inhibitory effect of CA on the glycation of bovine serum albumin in vitro was compared with that of aminoguanidine (AG), a known antiglycation agent. Glucose utilisation induced by insulin in the control rat diaphragm was monitored in the presence and absence of CA. High-fructose feeding induced hyperglycaemia and glycation of haemoglobin and skin and tail tendon collagen. In CA-administered fructose-fed rats glycation was significantly reduced. In vitro glycation and accumulation of advanced glycation end products were mitigated by CA. CA was more effective than AG in inhibiting glycation in vitro. CA also enhanced the utilisation of glucose in the rat diaphragm. The findings of the study reveal that CA not only has antiglycation effect but also enhances glucose disposal in the rat diaphragm. These findings provide evidence for the therapeutic utility of CA in diabetes and associated complications.

Fructose-induced hepatic gluconeogenesis: Effect of l-carnitine

High fructose feeding (60 g/100 g diet) in rodents induces alterations in both glucose and lipid metabolism. The present study was aimed to evaluate whether intraperitoneal carnitine (CA), a transporter of fatty acyl-CoA into the mitochondria, could attenuate derangements in carbohydrate metabolizing enzymes and glucose overproduction in high fructose-diet fed rats. Male Wistar rats of body weight 150-160 g were divided into 4 groups of 6 rats each. Groups 1 and 4 animals received control diet while the groups 2 and 3 rats received high fructose-diet. Groups 3 and 4 animals were treated with CA (300 mg/Kg body weight/day, i.p.) for 30 days. At the end of the experimental period, levels of carnitine, glucose, insulin, lactate, pyruvate, glycerol, triglycerides and free fatty acids in plasma were determined. The activities of carbohydrate metabolizing enzymes and glycogen content in liver and muscle were assayed. Hepatocytes isolated from liver were studied for the gluconeogenic activity in the presence of substrates such as pyruvate, lactate, glycerol, fructose and alanine. Fructose-diet fed animals showed alterations in glucose metabolizing enzymes, increased circulating levels of gluconeogenic substrates and depletion of glycogen in liver and muscle. There was increased glucose output from hepatocytes of animals fed fructose-diet alone with all the gluconeogenic substrates. The abnormalities associated with fructose feeding such as increased gluconeogenesis, reduced glycogen content and other parameters were brought back to near normal levels by CA. Hepatocytes from these animals showed significant inhibition of glucose production from pyruvate (74.3%), lactate (65.4%), glycerol (69.6%), fructose (56.2%) and alanine (63.6%) as compared to CA untreated fructose-fed animals. The benefits observed could be attributed to the effect of CA on fatty acyl-CoA transport.

Evidence for the association of the SLC22A4 and SLC22A5 genes with type 1 diabetes: a case control study

Background

Type 1 diabetes (T1D) is a chronic, autoimmune and multifactorial disease characterized by abnormal metabolism of carbohydrate and fat. Diminished carnitine plasma levels have been previously reported in T1D patients and carnitine increases the sensitivity of the cells to insulin. Polymorphisms in the carnitine transporters, encoded by the SLC22A4 and SLC22A5 genes, have been involved in susceptibility to two other autoimmune diseases, rheumatoid arthritis and Crohn's disease. For these reasons, we investigated for the first time the association with T1D of six single nucleotide polymorphisms (SNPs) mapping to these candidate genes: slc2F2, slc2F11, T306I, L503F, OCTN2-promoter and OCTN2-intron.

Methods

A case-control study was performed in the Spanish population with 295 T1D patients and 508 healthy control subjects. Maximum-likelihood haplotype frequencies were estimated by applying the Expectation-Maximization (EM) algorithm implemented by the Arlequin software.

Results

When independently analyzed, one of the tested polymorphisms in the SLC22A4 gene at 1672 showed significant association with T1D in our Spanish cohort. The overall comparison of the inferred haplotypes was significantly different between patients and controls (χ² = 10.43; p = 0.034) with one of the haplotypes showing a protective effect for T1D (rs3792876/rs1050152/rs2631367/rs274559, CCGA: OR = 0.62 (0.41–0.93); p = 0.02).

Conclusion

The haplotype distribution in the carnitine transporter locus seems to be significantly different between T1D patients and controls; however, additional studies in independent populations would allow to confirm the role of these genes in T1D risk.

The use of levo-carnitine in children with renal disease: a review and a call for future studies

Carnitine is an amino acid derivative that has a key role in the regulation of fatty acid metabolism and ATP formation. Carnitine deficiency has been described in various conditions, including chronic kidney disease (CKD) and end stage renal disease (ESRD). The deficiency of this micronutrient is postulated to lead to adverse effects across multiple organ systems. There is a paucity of information on carnitine deficiency and its effects in the pediatric CKD and ESRD populations. Currently, there is no evidence supporting the routine use of carnitine supplementation in children with ESRD. In this article, we review the pathophysiology, pharmacokinetics and the potential effects of levo-carnitine supplementation with a focus on the pediatric CKD and ESRD populations. Finally, potential future directions of research are discussed.

Cardio-protective effects of carnitine in streptozotocin-induced diabetic rats

BACKGROUND

Streptozotocin-induced diabetes (STZ-D) in rats has been associated with carnitine deficiency, bradycardia and left ventricular enlargement.

AIM

The purpose of this study was to determine whether oral carnitine supplementation would normalize carnitine levels and cardiac function in STZ-D rats.

METHODS

Wistar rats (48) were made hyperglycemic by STZ at 26 weeks of age. Same age normal Wistar rats (24) were used for comparison. Echocardiograms were performed at baseline 2, 6, 10, and 18 weeks after STZ administration in all animals. HbA1c, serum carnitine and free fatty acids (FFA) were measured at the same times. Since STZ-D rats become carnitine deficient, 15 STZ-D rats received supplemental oral carnitine for 16 weeks.

RESULTS

The heart rates for the STZ-D rats (290 +/- 19 bpm) were less than control rats (324 +/- 20 bpm) (p < 0.05). After 4 weeks of oral carnitine supplementation, the serum carnitine and heart rates of the STZ-D rats returned to normal. Dobutamine stress increased the heart rates of all study animals, but the increase in STZ-D rats (141 +/- 8 bpm) was greater than controls (79 +/- 8 bpm) (p < 0.05). The heart rates of STZ-D rats given oral carnitine, however, were no different than controls (94 +/- 9 bpm). The left ventricular mass/body weight ratio (LVM/BW) in the diabetic animals (2.7 +/- 0.5) was greater than control animals (2.2 +/- 0.3) (p < 0.05) after 18 weeks of diabetes. In contrast, the LVM/BW (2.3 +/- .2) of the STZ-D animals receiving supplemental carnitine was the same as the control animals at 18 weeks.

CONCLUSION

Thus, supplemental oral carnitine in STZ-D rats normalized serum carnitine, heart rate regulation and left ventricular size. These findings suggest a metabolic mechanism for the cardiac dysfunction noted in this diabetic animal model.