Carnitine Concentrations Research Articles

The effect of long-term oral L-carnitine administration on insulin sensitivity, glucose disposal, plasma concentrations of leptin and acylcarnitines, and urinary acylcarnitine excretion in warmblood horses

Background: Insulin resistance in horses is an emerging field of interest as it is thought to be a contributing factor in the pathogenesis of many equine conditions.Objectives: The objectives of the present study were to determine the effects of long-term oral administration of L-carnitine on insulin sensitivity, glucose disposal, plasma leptin concentrations and acylcarnitine spectrum both in plasma and urine.Animals and methods: Six 3-year-old healthy warmblood geldings were used. In a double blind 2 × 2 Latin square design at a dosage of 100 mg/kg body weight (BW)/day for 28 days the effects of oral supplementation of L-carnitine (as fumarate) were assessed. Glucose disposal and insulin sensitivity were measured by means of the euglycemic-hyperinsulinemic clamp technique. Radioimmunoassays were used to determine plasma leptin and insulin concentrations. Electrospray tandem mass spectrometry was used to assess acylcarnitines both in plasma and urine. Statistical analysis was performed using a linear mixed-effects model and P values <0.05 were considered significant.Results: Long-term L-carnitine administration did not affect insulin sensitivity. Plasma leptin and free carnitine concentrations in plasma and urine increased significantly (P = 0.047 and 0.000, respectively) following L-carnitine administration as well as short-chain acylcarnitines in plasma and urinary excretion of short- and medium-chain acylcarnitines.Conclusion and clinical relevance: Given the effects of oral administration of L-carnitine further clinical study is necessary in order to assess the potential beneficial effects in equine patients suffering from metabolic myopathies such as acquired multiple acyl-CoA dehydrogenase deficiency.Impact for human medicine: The current study supports the treatment rationale of short-chain acyl-CoA dehydrogenase deficiency in humans with L-carnitine at an oral dosage of 100 mg/kg BW/day.

Protein ingestion impairs insulin‐stimulated net muscle carnitine uptake in healthy young men (LB812)

Carbohydrate ingestion promotes insulin‐mediated muscle carnitine accretion, but the effect of protein ingestion is unknown. Six healthy males (age 24 ± 5 yrs, BMI 23 ± 3 kg/m²) ingested 80g carbohydrate (CHO), 40g whey protein + 40g CHO (PRO), or flavoured water (CON) beverages (500 ml) 1 hr following ingestion of 3g L‐carnitine (0.1% ²H3‐L‐carnitine) on 3 randomised 3‐hr visits. The rate of disposal (Rd) and arterio‐venous (AV) forearm carnitine balance (determined from arterialised‐venous and venous plasma ²H3‐carnitine and carnitine concentrations), and brachial artery blood flow (BAF; Doppler ultrasound) were measured, together with serum insulin concentrations, at baseline and 20 min intervals for 3 hrs. Carnitine Rd at 100 min was 4.4 fold greater in CHO compared to CON (0.3 ± 0.1 vs 0.1 ± 0.1 µmol/min; P&lt;0.05), which coincided with peak serum insulin concentration in CHO (64 ± 10 mU/L). However, despite similar insulin responses in CHO and PRO (3‐hr area under curve [AUC] was 4.6 ± 0.8 and 3.9 ± 0.7 U/L•min, respectively) compared to CON (0.4 ± 0.04 U/L•min; P&lt;0.001) and increases in BAF (15 ± 3 and 12 ± 5%) above CON (P&lt;0.05), net carnitine balance AUC increased in CHO (P&lt;0.01), but not PRO, compared to CON (9.3 ± 4.0 and ‐3.9 ± 5.7 vs ‐1.2 ± 1.5 µmol•min, respectively) over the 2 hrs following beverage ingestion. Carbohydrate stimulates insulin mediated muscle carnitine balance, but protein may antagonise this process.

Similar metabolic responses in pigs and humans to breads with different contents and compositions of dietary fibers: a metabolomics study

In nutritional studies, pigs are often used as models for humans because of nutritional and physiologic similarities. However, evidence supporting similar metabolic responses to nutritional interventions is lacking. The objective was to establish whether pigs and humans respond similarly to a nutritional intervention. Using metabolomics, we compared the acute metabolic response to 4 test breads between conventional pigs (growing) and adult human subjects (with the metabolic syndrome). Six catheterized pigs and 15 human subjects were tested in a randomized crossover design with 4 breads: white-wheat bread low in dietary fiber, rye bread with whole-rye kernels, and 2 white-wheat breads supplemented with either wheat arabinoxylan or oat β-glucan. Blood samples drawn -15, 30, and 120 min postprandially were analyzed by untargeted liquid chromatography-mass spectrometry metabolomics. We found that the postprandial responses, as reflected in blood metabolomes, are similar in pigs and humans. Twenty-one of 26 identified metabolites that were found to be different between the species were qualitatively similar in response to the test breads, despite different basal metabolome concentrations in the plasma of pigs and humans. Humans had higher contents of phosphatidylcholines, oleic acid, and carnitine in plasma, possibly reflecting a higher intake of meats and fats. In pigs, betaine, choline, creatinine, tryptophan, and phenylalanine were higher, probably because of the higher doses of bread provided to the pigs (per kg body weight) and/or because of their growing status. Acute metabolic differences in these metabolites induced by the breads were, however, comparable between the 2 species. Our results indicate that pigs are a suitable model for human metabolic studies in food research. The human trial was registered at clinicaltrials.gov as NCT01316354. The animal experiment was conducted according to a license obtained by the Danish Animal Experiments Inspectorate, Ministry of Food, Agriculture and Fisheries, Danish Veterinary and Food Administration.

Metabolomic Biomarkers Reflect Usual Dietary Pattern: A Review

The composition of dietary intake plays an important role in metabolism, maintaining health and preventing chronic disease. Because we eat many foods every day and not just one nutrient or food, nutrition researchers began studying the whole diet by characterizing usual dietary intake as ‘diet patterns’, ‘diet quality’, diet scores, or diet indexes. Because self-report dietary intake is typically misreported, employing metabolomic biomarkers or a panel of biomarkers may better classify usual dietary intake or diet pattern than the use of self-reported dietary intake alone. We reviewed the current metabolomic literature with the aim of identifying relevant compounds among dietary pattern studies that may be useful in future dietary-metabolomic research. The most common diet patterns were the Western pattern (or high meat intake) and the plant-based pattern (or high in fruit and vegetables, and low in meat). Similar findings of greater carnitine and TMAO concentrations were demonstrated for the diet patterns high in meat. The plant-based diet patterns had higher glycerophosphatidylcholines and sphingolipids, but lower TMAO concentrations. However, the metabolomic pattern varied regardless of the common intake of high or low meat pattern. This may be partly explained by several methodologic differences in study design, which make comparison of the study findings difficult.

Serum carnitine as an independent biomarker of malnutrition in patients with impaired oral intake.

Carnitine is a vitamin-like compound that plays important roles in fatty acid β-oxidation and the control of the mitochondrial coenzyme A/acetyl-CoA ratio. However, carnitine is not added to ordinary enteral nutrition or total parenteral nutrition. In this study, we determined the serum carnitine concentrations in subjects receiving ordinary enteral nutrition (EN) or total parenteral nutrition (TPN) and in patients with inflammatory bowel diseases to compare its levels with those of other nutritional markers. Serum samples obtained from 11 EN and 11 TPN patients and 82 healthy controls were examined. In addition, 10 Crohn’s disease and 10 ulcerative colitis patients with malnutrition who were barely able to ingest an ordinary diet were also evaluated. Carnitine and its derivatives were quantified using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The carnitine concentrations in EN and TPN subjects were significantly lower compared with those of the control subjects. Neither the serum albumin nor the total cholesterol level was correlated with the carnitine concentration, although a significant positive correlation was found between the serum albumin and total cholesterol levels. Indeed, patients with CD and UC showed significantly reduced serum albumin and/or total cholesterol levels, but their carnitine concentrations remained normal. In conclusion, only a complete blockade of an ordinary diet, such as EN or TPN, caused a reduction in the serum carnitine concentration. Serum carnitine may be an independent biomarker of malnutrition, and its supplementation is needed in EN and TPN subjects even if their serum albumin and total cholesterol levels are normal.

真空調理時の加熱温度がシカ肉中のカルニチン含量および物性に及ぼす影響

本研究において，シカ肉の機能性食品としての活用を促進させるために，真空調理法を用いて，スチーム加熱の加熱温度の違いによるカルニチン含有量および物性への影響を検討した．80℃および100℃で真空調理を行った結果，80℃加熱の方が，温度上昇が緩やかであり，肉重量減少率が低かった．L-カルニチンとアセチルカルニチンは，80℃加熱の方が高い値を示し，その他のアシルカルニチン類は，100℃加熱の方が高い値を示した．L-カルニチンの過剰摂取がアテローム性動脈硬化を引き起こす可能性が報告されているが，通常の鹿肉の摂取量であれば，アテローム性動脈硬化を引き起こすリスクが生じることは考えにくい．脳機能向上などの機能性が示唆されているアセチルカルニチンは，80℃加熱の方が有意に多く含まれていた．また，物性測定において，100℃加熱と比較して，80℃加熱の方が有意に軟らかいことが示され，官能評価においても，80℃加熱の方が軟らかく好まれることが示された．うま味があり，総合的なおいしさが，80℃加熱において有意に好まれたことにより，嗜好性の向上にも繋がったと考えられる．これらの結果より，機能性・嗜好性のどちらにおいても，シカ肉の機能性食品としての活用を促進する上で，望ましいのは80℃加熱であると考えられる．

Biochemical evaluation of renal osteodystrophy in uraemic patients

Background/aim Renal osteodystrophy is a multifactorial disorder of bone remodelling that develops in patients with chronic renal failure (CRF). Biochemical markers of bone turnover have been proposed for the noninvasive diagnosis of renal osteodystrophy. The purpose of this study was to evaluate intact parathyroid hormone (iPTH) and some markers of bone disease in predialysis (preD) and haemodialysis (HD) CRF patients and correlate them with bone mineral density (BMD). Patients and methods Several biochemical markers were measured in the serum of 74 CRF patients (38 preD patients and 36 patients on regular HD). In addition, 30 healthy volunteers were included as controls. BMD of all patients was measured by means of calcaneal ultrasonography. Results BMD was measured by means of ultrasound. BMD was significantly decreased in both patient groups when compared with controls. Also, it was significantly lower in patients with osteoporosis than in those with osteopenia. iPTH, total alkaline phosphatase (ALP) and osteocalcin (OC) levels were significantly elevated in both patient groups when compared with controls. Ionized calcium (Ca 2+ ), free carnitine and insulin-like growth factor-1 (IGF-1) levels were significantly decreased in patients compared with controls. There was a significant inverse correlation of BMD with iPTH, ALP and OC and a significant positive correlation with Ca 2+ and IGF-1 in HD patients. PreD patients showed significant inverse correlation of BMD with iPTH and ALP and significant positive correlation with Ca 2+ . Conclusion The results of the present study suggested that ultrasound is a useful method for evaluating BMD and provides information about diverse regional skeletal changes in CRF patients. iPTH, ALP, OC and Ca 2+ can predict renal osteodystrophy in preD and HD CRF patients. PreD and HD CRF patients often have low serum concentrations of free carnitine and IGF-1.

Supplemental carnitine affects the microRNA expression profile in skeletal muscle of obese Zucker rats.

BackgroundIn the past, numerous studies revealed that supplementation with carnitine has multiple effects on performance characteristics and gene expression in livestock and model animals. The molecular mechanisms underlying these observations are still largely unknown. Increasing evidence suggests that microRNAs (miRNAs), a class of small non-coding RNA molecules, play an important role in post-transcriptional regulation of gene expression and thereby influencing several physiological and pathological processes. Based on these findings, the aim of the present study was to investigate the influence of carnitine supplementation on the miRNA expression profile in skeletal muscle of obese Zucker rats using miRNA microarray analysis.ResultsObese Zucker rats supplemented with carnitine had higher concentrations of total carnitine in plasma and muscle than obese control rats (P < 0.05). miRNA expression profiling in skeletal muscle revealed a subset of 152 miRNAs out of the total number of miRNAs analysed (259) were identified to be differentially regulated (adjusted P-value < 0.05) by carnitine supplementation. Compared to the obese control group, 111 miRNAs were up-regulated and 41 down-regulated by carnitine supplementation (adjusted P-value < 0.05). 14 of these miRNAs showed a log2 ratio ≥ 0.5 and 7 miRNAs showed a log2 ratio ≤ −0.5 (adjusted P-value < 0.05). After confirmation by qRT-PCR, 11 miRNAs were found to be up-regulated and 6 miRNAs were down-regulated by carnitine supplementation (P < 0.05). Furthermore, a total of 1,446 target genes within the validated miRNAs were revealed using combined three bioinformatic algorithms. Analysis of Gene Ontology (GO) categories and KEGG pathways of the predicted targets revealed that carnitine supplementation regulates miRNAs that target a large set of genes involved in protein-localization and -transport, regulation of transcription and RNA metabolic processes, as well as genes involved in several signal transduction pathways, like ubiquitin-mediated proteolysis and longterm depression, are targeted by the miRNAs regulated by carnitine supplementation.ConclusionThe present study shows for the first time that supplementation of carnitine affects a large set of miRNAs in skeletal muscle of obese Zucker rats suggesting a novel mechanism through which carnitine exerts its multiple effects on gene expression, which were observed during the past.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-512) contains supplementary material, which is available to authorized users.

Combined effect of sesamin and soybean phospholipid on hepatic fatty acid metabolism in rats.

We studied the combined effect of sesamin (1:1 mixture of sesamin and episesamine) and soybean phospholipid on lipid metabolism in rats. Male rats were fed diets supplemented with 0 or 2 g/kg sesamin, and containing 0 or 50 g/kg soybean phospholipid, for 19 days. Sesamin and soybean phospholipid decreased serum triacylglycerol concentrations and the combination of these compounds further decreased the parameter in an additive fashion. Soybean phospholipid but not sesamin reduced the hepatic concentration of triacylglycerol. The combination failed to cause a strong decrease in hepatic triacylglycerol concentration, presumably due to the up-regulation of Cd36 by sesamin. Combination of sesamin and soybean phospholipid decreased the activity and mRNA levels of hepatic lipogenic enzymes in an additive fashion. Sesamin strongly increased the parameters of hepatic fatty acid oxidation enzymes. Soybean phospholipid increased hepatic activity of 3-hydroxyacyl-CoA dehydrogenase although it failed to affect the activity of other enzymes involved in fatty acid oxidation. Sesamin strongly increased hepatic concentration of carnitine. Sesamin and soybean phospholipid combination further increased this parameter, accompanying a parallel increase in mRNA expression of carnitine transporter. These changes can account for the strong decrease in serum triacylglycerol in rats fed a diet containing both sesamin and soybean phospholipid.

Distribution, molecular structure and functional analysis of carnitine transporter (SLC22A5) in canine lens epithelial cells.

While carnitine has been reported to have an anti-oxidative role on the ocular surface, there has been no report on the existence of a carnitine transporter (SLC22A5) in the lens. Therefore, we investigated the carnitine transport activity of canine lens epithelial cells (LEC) and determined the molecular structure of canine SLC22A5. The carnitine transport activity was 7.16 ± 0.48 pmol/mg protein/30 min. Butyrobetaine, the analogue of carnitine, reduced 30% of the activity at 50 µM. A coding sequence of canine carnitine transporter was 1694 bp long and was predicted to encode 557 amino acid polypeptides. The deduced amino acid sequence of canine carnitine transporter showed >80% similarity to that of mouse and human. Western blot analysis detected the band at 60 kDa in the membrane of lens epithelial cells. The high content of carnitine in the lens is possibly transported from aqueous humor by SLC22A5.

Carnitine Deficiency and Improvement of Muscle Cramp by Administration of Carnitine in Patients with Liver Cirrhosis

Aim: We measured carnitine levels in patients with carnitine including dialysis patients, and examined whether administration of L-carnitine improved muscle symptoms. Methods: We measured carnitine levels in 27 patients with liver cirrhosis who were receiving treatment in our hospital, and administered L-carnitine (600 mg - 1800 mg) to patients having muscle cramps for approximately one month and examined the presence/absence of the symptom. We measured carnitine concentration before and after dialysis, before dialysis after the administration to eight dialysis patients, before and after the administration to 19 nondialytic patients. Results: The total carnitine levels before the dialysis of dialysis patients were an average of 42.2 μmol/L and fell to 17.7 μmol/L after more dialysis, but it was increased to 155 μmol/L after the administration of L-carnitine. In the nondialytic patients, the total carnitine levels were significantly increased from 71.7 μmol/L to 101.7 μmol/L after the administration of L-carnitine (P = 0.038). For symptomatic patients, significant improvement of muscle clamps was observed in the L-carnitine administrated group when compared with the non-administrated group (P = 0.0002). Conclusions: Total carnitine levels were low even before dialysis in the dialysis patients with liver cirrhosis in particular and they further decreased after the dialysis. Administration of L-carnitine increased the total carnitine levels and improved the symptom. Based on these results, we conclude that L-carnitine is useful for carnitine deficiency in patients with liver cirrhosis.

Serum Levels of Acylcarnitines Are Altered in Prediabetic Conditions

ObjectiveThe role of mitochondrial function in the complex pathogenesis of type 2 diabetes is not yet completely understood. Therefore, the aim of this study was to investigate serum concentrations of short-, medium- and long-chain acylcarnitines as markers of mitochondrial function in volunteers with normal, impaired or diabetic glucose control.MethodsBased on a 75 g oral glucose tolerance test, 1019 studied subjects were divided into a group with normal glucose tolerance (NGT; n = 636), isolated impaired fasting glycaemia (IFG; n = 184), impaired glucose tolerance (IGT; n = 87) or type 2 diabetes (T2D; n = 112). Serum concentrations of free carnitine and 24 acylcarnitines were measured by mass spectrometry.ResultsSerum levels of acetylcarnitine (C2), propionylcarnitine (C3), octanoylcarnitine (C8), malonylcarnitine/hydroxybutyrylcarnitine (C3DC+C4OH), hexanoylcarnitine (C6), octenoylcarnitine (C8:1), decanoylcarnitine (C10), decenoylcarnitine (C10:1), dodecanoylcarnitine (C12), tetradecenoylcarnitine (C14:1), tetradecadienylcarnitine (C14:2), hydroxytetradecanoylcarnitine (C14OH), hydroxyhexadecanoylcarnitine (C16OH) and octadecenoylcarnitine (C18:1) were significantly different among the groups (all p<0.05 adjusted for age, gender and BMI). Between the prediabetic states C14:1, C14:2 and C18:1 showed significantly higher serum concentrations in persons with IGT (p<0.05). Compared to T2D the IFG and the IGT subjects showed lower serum concentrations of malonylcarnitine/hydroxybutyrylcarnitine (C3DC+C4OH) (p<0.05).ConclusionAlterations in serum concentrations of several acylcarnitines, in particular tetradecenoylcarnitine (C14:1), tetradecadienylcarnitine (C14:2), octadecenoylcarnitine (C18:1) and malonylcarnitine/hydroxybutyrylcarnitine (C3DC+C4OH) are associated not only with T2D but also with prediabetic states.

Effect of carnitine, acetyl-, and propionylcarnitine supplementation on the body carnitine pool, skeletal muscle composition, and physical performance in mice

Pharmacokinetics and effects on skeletal muscle and physical performance of oral acetylcarnitine and propionylcarnitine are not well characterized. We therefore investigated the influence of oral acetylcarnitine, propionylcarnitine, and carnitine on body carnitine homeostasis, energy metabolism, and physical performance in mice and compared the findings to non-supplemented control animals. Mice were supplemented orally with 2 mmol/kg/day carnitine, acetylcarnitine, or propionylcarnitine for 4 weeks and studied either at rest or after exhaustive exercise. In the supplemented groups, total plasma and urine carnitine concentrations were significantly higher than in the control group receiving no carnitine, whereas the skeletal muscle carnitine content remained unchanged. The supplemented acylcarnitines were hydrolyzed in intestine and liver and reached the systemic circulation as carnitine. Bioavailability of carnitine and acylcarnitines, determined as the urinary excretion of total carnitine, was in the range of 19 %. Skeletal muscle morphology, including fiber-type composition, was not affected, and oxygen consumption by soleus or gastrocnemius fibers was not different between the groups. Supplementation with carnitine or acylcarnitines had no significant impact on the running capacity, but was associated with lower plasma lactate levels and a higher glycogen content in white skeletal muscle after exhaustive exercise. Oral supplementation of carnitine, acetylcarnitine, or propionylcarnitine in mice is associated with increased plasma and urine total carnitine concentrations, but does not affect the skeletal muscle carnitine content. Despite better preservation of skeletal muscle glycogen and lower plasma lactate levels, physical performance was not improved by carnitine or acylcarnitine supplementation.

Kinetics of Carnitine Palmitoyltransferase I (CPT I) in Chinese sucker (Myxocyprinus asiaticus) Change with its Development

The present study was conducted to evaluate the ontogeny and kinetic of CPT I in several tissues of the Chinese sucker Myxocyprinus asiaticus. To this end, liver, muscle and intestine tissues were examined at five various developmental stages of Chinese sucker: newly-hatched larvae, 68-day-old, 4-month-old, 1- and 2-year-old Chinese sucker, respectively. The total carnitine (TC) content in the liver increased from birth to 1-year-old Chinese sucker and then declined in the 2-year-old Chinese sucker. From the 68-day-old to the 1-year-old Chinese sucker, both free and total concentrations in muscle increased. Both acyl carnitine (AC) and TC concentrations in intestine were very variable at different stages. The ratio of AC to free carnitine (FC) in liver progressively increased from hatching to 4 months, and declined at the age of 1 year, and then increased by 2 years. In muscle, the highest and lowest ratios of AC/FC were observed at 68-days-old and 4 month-old Chinese sucker. The highest proportion of AC/FC in intestine was also observed at 68-day-old Chinese sucker. All the Chinese sucker larvae at hatching had a high value of the Michaelis constant (K(m)) for carnitine. Maximal velocity (V(max)) in intestine increased with age. V(max) in liver and muscle increased with age except a decrease at 4 months in liver and at 2 years in muscle. The FC concentration in the examined tissues at all developmental stages were less than the respective K(m), indicating that Chinese suckers require supplemental carnitine in their food to ensure that CPT I activity is not constrained by carnitine availability.

Differences in Circulating Carnitine Status of Preterm Infants Fed Fortified Human Milk or Preterm Infant Formula

The aim of the study was to compare plasma carnitine profiles in fortified human milk (HM)-fed preterm infants or formula-fed preterm infants. Plasma acylcarnitine concentrations were determined in 20 formula-fed and 18 HM-fed preterm infants (birth weights between 1000 and 2200 g) by isotope dilution ESI MS/MS technique on study days 0, 14, and 28. Concentrations of free carnitine (FC) and different acylcarnitines did not change during the 4 weeks of the study in infants fed HM. In contrast, in infants fed formula FC increased markedly (day 0: 29.989 [16.646] μmol/L, median [interquartile range], day 14: 43.972 [8.455], P < 0.05) along with increases of short-chain esters (C2 day 0: 5.300 [3.272], day 14: 6.773 [2.127], P < 0.05; C3 day 0: 0.070 [0.059], day 14: 0.110 [0.069], P < 0.05). In contrast, some medium-chain (C8:1, C12) and long-chain esters (C14, C16) decreased significantly in infant formula by day 14, whereas FC and C2 and C3 esters increased further by day 28 (FC: 47.672 [14.753], C2: 7.430 [4.688], C3: 0.107 [0.047]). The altered carnitine ester profile likely reflects active involvement of the carnitine molecule in the buffering, metabolism, and elimination of nonphysiological acyl moieties.

The effect of intake of lamb meat on energy metabolism of Sprague-Dawley rats: possible role of carnitine

The purpose of the present study was to determine whether carnitine was responsible for the increased energy metabolism observed in Sprague-Dawley rats following inclusion of lamb meat in their diet. This was tested by feeding one of the following three diets: a control diet (control) based on a standard formulation (AIN-93G), a carnitine-supplemented control diet (CD) and a lamb meat diet (LD). All diets were isocaloric (15.46 kJ/g DM) and contained 18.3% protein, 7.1% fat and 58.3% carbohydrate. The carnitine concentrations in the control diet, CD and LD were 29, 984 and 953 mg/kg, respectively. The expression of carnitine palmitoyltransferase-I(CPT-I)α and CTP-Iβ genes, Na,K-ATPase activities and the contents of fat, ATP and creatine phosphate (Cr.P) in liver and skeletal muscle tissues were measured on Days 7 and 14. Bodyweights, bodyweight gains and oxygen consumption rates (OCR) of rats were also measured. The rats fed the LD had higher OCR, ATP and Cr.P concentrations, expressions of CPT-I gene, Na,K-ATPase activities, and lower fat contents, bodyweights and bodyweight gains (P &lt; 0.05) than did the control-group rats. However, rats fed the CD were not significantly different from those fed the control diet, except for the higher CPT-Iα expression, ATP concentrations and lower fat contents in liver (P &lt; 0.05). We conclude that carnitine intake from lamb was not the main factor accounting for the significant effects of lamb consumption on energy metabolism. However, it is likely that carnitine intake by consumption of lamb meat in the LD partly contributed to lowering fat contents in liver, compared with the CD and the control diet groups.

Quantification of plasma carnitine and acylcarnitines by high-performance liquid chromatography-tandem mass spectrometry using online solid-phase extraction

Carnitine is an amino acid derivative that plays a key role in energy metabolism. Endogenous carnitine is found in its free form or esterified with acyl groups of several chain lengths. Quantification of carnitine and acylcarnitines is of particular interest for screening for research and metabolic disorders. We developed a method with online solid-phase extraction coupled to high-performance liquid chromatography and tandem mass spectrometry to quantify carnitine and three acylcarnitines with different polarity (acetylcarnitine, octanoylcarnitine, and palmitoylcarnitine). Plasma samples were deproteinized with methanol, loaded on a cation exchange trapping column and separated on a reversed-phase C8 column using heptafluorobutyric acid as an ion-pairing reagent. Considering the endogenous nature of the analytes, we quantified with the standard addition method and with external deuterated standards. Solid-phase extraction and separation were achieved within 8 min. Recoveries of carnitine and acylcarnitines were between 98 and 105 %. Both quantification methods were equally accurate (all values within 84 to 116 % of target concentrations) and precise (day-to-day variation of less than 18 %) for all carnitine species and concentrations analyzed. The method was used successfully for determination of carnitine and acylcarnitines in different human samples. In conclusion, we present a method for simultaneous quantification of carnitine and acylcarnitines with a rapid sample work-up. This approach requires small sample volumes and a short analysis time, and it can be applied for the determination of other acylcarnitines than the acylcarnitines tested. The method is useful for applications in research and clinical routine.

Changes in glucose and carnitine levels and their transporters in utero‐tubal junction in relation to sperm storage in the vespertilionid bat, Scotophilus heathi

Prolonged sperm storage over winter is a common feature of reproduction in some bats. In order to understand how sperm storage in the female genital tract of the vespertilionid bat, Scotophilus heathi (Greater yellow bat), is controlled, we compared concentrations of glucose and the fatty-acid carrier carnitine in the blood, and carnitine concentrations and levels of expression of the glucose transporters (GLUTs) and the carnitine transporter OCTN2 in the utero-tubal junction of females during non-storage (early winter) and sperm-storage periods (late winter-early spring). During the sperm-storage period (December-January) blood glucose concentrations declined, as did the expression of GLUT3 and GLUT5 in the utero-tubal junction. At the same time there were increases in the concentration of carnitine, and expression of OCTN2 and hormone-sensitive lipase (HSL) in the utero-tubal junction. These results suggest that prolonged sperm storage is enhanced by decreased glucose availability but increased free fatty acid availability at the site of sperm storage. Increases in expression of GLUT4 and GLUT8 in late winter suggest a role for these GLUTs in increasing sperm motility prior to fertilization.

Skeletal muscle carnitine loading increases energy expenditure, modulates fuel metabolism gene networks and prevents body fat accumulation in humans

Twelve weeks of daily l-carnitine and carbohydrate feeding in humans increases skeletal muscle total carnitine content, and prevents body mass accrual associated with carbohydrate feeding alone. Here we determined the influence of L-carnitine and carbohydrate feeding on energy metabolism, body fat mass and muscle expression of fuel metabolism genes. Twelve males exercised at 50% maximal oxygen consumption for 30 min once before and once after 12 weeks of twice daily feeding of 80 g carbohydrate (Control, n=6) or 1.36 g L-carnitine + 80 g carbohydrate (Carnitine, n=6). Maximal carnitine palmitolytransferase 1 (CPT1) activity remained similar in both groups over 12 weeks. However, whereas muscle total carnitine, long-chain acyl-CoA and whole-body energy expenditure did not change over 12 weeks in Control, they increased in Carnitine by 20%, 200% and 6%, respectively (P<0.05). Moreover, body mass and whole-body fat mass (dual-energy X-ray absorptiometry) increased over 12 weeks in Control by 1.9 and 1.8 kg, respectively (P<0.05), but did not change in Carnitine. Seventy-three of 187 genes relating to fuel metabolism were upregulated in Carnitine vs. Control after 12 weeks, with 'insulin signalling', 'peroxisome proliferator-activated receptor signalling' and 'fatty acid metabolism' as the three most enriched pathways in gene functional analysis. In conclusion, increasing muscle total carnitine in healthy humans can modulate muscle metabolism, energy expenditure and body composition over a prolonged period, which is entirely consistent with a carnitine-mediated increase in muscle long-chain acyl-group translocation via CPT1. Implications to health warrant further investigation, particularly in obese individuals who have a reduced reliance on muscle fat oxidation during low-intensity exercise.

L-Carnitine Consumption, Its Metabolism by Intestinal Microbiota, and Cardiovascular Health

arch, I n early April 2013, Koeth et al 1 published in Nature Medicine an original article providing evidence that ingested L-carnitine can encourage the growth of intestinal microbiota capable of converting carnitine to trimethylamine; the latter compound, on absorption, can be oxidized in the liver to trimethylamine-N-oxide (TMAO), which the authors suggested was likely to be a key mediator of the adverse impact of red meaterich diets on human vascular health. This report immediately gained attention in the nation’s media. For example, Koeth et al’s research was a highlighted story on the CBS Evening News With Scott Pelley on the evening of Friday, April 5, 2013, and by Sunday, April 7, Gina Kolata of the New York Times had cited this research in an article questioning the safety of carnitine. Within days of this report,Mayo Clinic Proceedings electronically published ahead of print a meta-analysis by DiNicolantonio et al of 13 placebo-controlled clinical trials enrolling 3629 patients that had evaluated the clinical impact of L-carnitine administration (as a supplement, not in red meat) in patients who had previously experienced amyocardial infarction. This meta-analysis concluded that carnitine administration was associated with clinical benefit: decreased mortality and reduced onset of cardiac arrhythmias and angina. The journal also issued a press release noting the findings of DiNicolantonio et al and their relevance to the report by Koeth et al. Other media sources seized on the seeming inconsistency of these reports, with websites such as Forbes.com, hearthealth.com, and junkscience.com offering commentary. This second wave of media reports was followed shortly thereafter by many hundreds of media stories on one or both of the L-carnitine studies. In publications focusing on choline, which, similar to carnitine, can be converted to trimethylamine by intestinal microbiota, Koeth and his colleagues have made a case that TMAO may be a mediating risk factor for atherosclerosis.