Determination of L-carnitine, acylcarnitine and total carnitine levels in plasma and tissues of camel (Camelus dromedarius)

Effects of low and high doses of fenofibrate on protein, amino acid, and energy metabolism in rat

A feared adverse effect of dyslipidaemia therapy by fibrates is myopathy. We examined the effect of fenofibrate (FF) on protein and amino acid metabolism. Rats received a low (50 mg/kg, LFFD) or high (300 mg/kg, HFFD) dose of FF or vehicle daily by oral gavage. Blood plasma, liver, and soleus and extensor digitorum longus muscles were analysed after 10 days. The FF-treated rats developed hepatomegaly associated with increased hepatic carnitine and ATP and AMP concentrations, decreased protein breakdown, and decreased concentrations of DNA and triglycerides. HFFD increased plasma ALT and AST activities. The weight and protein content of muscles in the HFFD group were lower compared with controls. In muscles of the LFFD group there were increased ATP and decreased AMP concentrations; in the HFFD group AMP was increased. In both FF-treated groups there were increased glycine, phenylalanine, and citrulline and decreased arginine and branched-chain keto acids (BCKA) in blood plasma. After HFFD there were decreased levels of branched-chain amino acids (BCAA; valine, leucine and isoleucine), methionine, and lysine and increased homocysteine. Decreased arginine and increased glycine concentrations were found in both muscles in FF-treated animals; in HFFD-treated animals lysine, methionine, and BCAA were decreased. We conclude that FF exerts protein-anabolic effects on the liver and catabolic effects on muscles. HFFD causes signs of hepatotoxicity, impairs energy and protein balance in muscles, and decreases BCAA, methionine, and lysine. It is suggested that increased glycine and decreased lysine and methionine levels are due to activated carnitine synthesis; decreased BCAA and BCKA levels are due to increased BCAA oxidation.

Ontogeny and kinetics of carnitine palmitoyltransferase I in hepatopancreas and skeletal muscle of grass carp (Ctenopharyngodon idella)

The ontogeny and kinetics of carnitine palmitoyltransferase I (CPT I) were investigated in hepatopancreas and muscle throughout four developmental stages (newly hatched larvae, 1-month-old juvenile, 3-month-old, and 6-month-old, respectively) of grass carp Ctenopharyngodon idella. In hepatopancreas, the maximal velocity (Vmax) significantly increased from hatching to 1-month-old grass carp and then gradually declined at 6-month-old grass carp. In muscle, CPT I activity was the highest at 1-month-old grass carp, nearly twofold higher than that at hatching (P < 0.05). The Michaelis constant (Km) value was also the highest for 1-month-old in both tested tissues. Carnitine concentrations (FC, AC and TC) were the lowest for 3-month-old grass carp and remained relatively constant in both tissues from fish under the other developmental stages. The FC concentration in hepatopancreas and muscle at four developmental stages were less than the respective Km, indicating that grass carp required supplemental carnitine in their food to ensure that CPT I activity was not constrained by carnitine availability.

Effects of waterborne copper exposure on carnitine composition, kinetics of carnitine palmitoyltransferases I (CPT I) and mRNA levels of CPT I isoforms in yellow catfish Pelteobagrus fulvidraco

The present study was conducted to determine the effect of waterborne copper (Cu) exposure on carnitine concentration, carnitine palmitoyltransferases I (CPT I) kinetics, and expression levels of four CPT I isoforms in the liver, muscle and heart of yellow catfish Pelteobagrus fulvidraco. Yellow catfish were exposed to four waterborne copper (Cu) concentrations (2 (control), 24 (low), 71 (medium), 198 (high) μg Cu/l, respectively) for 6weeks. Waterborne Cu exposure increased maximal reaction rates (Vmax) in the liver and muscle, but not in the heart. Michaelis-Menten constants (Km) tended to increase in the liver, but decreased in the heart after Cu exposure. The contents of total carnitine (TC) and acylcarnitine (AC) in the liver, and free carnitine (FC) in the muscle increased with increasing waterborne Cu concentrations, while FC content in the muscle declined with the increase of Cu levels. Waterborne Cu exposure also significantly influenced carnitine composition and profiles in heart. The mRNA expression of CPT Iα1a, CPT Iα1b and CPT Iα2a in the liver, and CPT Iα1a, CPT Iα1b and CPT Iβ in the muscle as well as CPT Iα1a in the heart were up-regulated by Cu exposure. Additionally, correlations were observed in the expression levels of CPT I isoforms and Km for carnitine, and between CPT I isoform expression and CPT I activity. To our knowledge, for the first time, the present study provided evidence that waterborne Cu exposure could influence carnitine composition, CPT I kinetics and mRNA levels of four CPT I isoforms in yellow catfish, which served to increase our understanding of the mechanisms underlying lipid catabolism during Cu exposure.

Differential effects of dietary Cu deficiency and excess on carnitine status, kinetics and expression of CPT I in liver and muscle of yellow catfish Pelteobagrus fulvidraco

The present study was conducted to determine the effect of dietary Cu deficiency and excess on carnitine status, kinetics and expression of CPT I in the liver and muscle of juvenile yellow catfish Pelteobagrus fulvidraco. To this end, yellow catfish were fed 0.76 (Cu deficiency), 4.18 (adequate Cu) and 92.45 (Cu excess) mg Cu kg(-1) diet, respectively, for 8 weeks. In the liver, Cu deficiency did not significantly affect the contents of FC, TC and AC, and the ratios of AC/FC and FC/TC. However, Cu excess reduced FC, TC and AC contents, and the ratio of AC/FC, but increased FC/TC ratio. In the muscle, dietary Cu levels showed no significant effects on the contents of FC, TC and AC as well as the ratio of FC/TC, but Cu excess significantly increased the ratio of AC/FC. Compared to the adequate Cu group, dietary Cu deficiency did not significantly affect the Vmax and Km values, and the ratio of Vmax/Km in the liver and muscle. However, Cu excess decreased Vmax and Vmax/Km ratio in the liver, and increased Vmax in the muscle. The mRNA expression of CPT Iα1a, CPT Iα1b, CPT Iα2a and CPT Iβ in the liver and muscle was influenced by dietary Cu levels. To our knowledge, the present study provided, for the first time, evidence that dietary Cu deficiency and excess differentially influenced carnitine status, kinetics and expression profiles of CPT I of yellow catfish, which would extend our understanding on Cu nutrition in fish.

Differential effects of dietary Cu deficiency and excess on carnitine status, kinetics and expression of CPT I in liver and muscle of yellow catfish Pelteobagrus fulvidraco

The present study was conducted to determine the effect of dietary Cu deficiency and excess on carnitine status, kinetics and expression of CPT I in the liver and muscle of juvenile yellow catfish Pelteobagrus fulvidraco. To this end, yellow catfish were fed 0.76 (Cu deficiency), 4.18 (adequate Cu) and 92.45 (Cu excess) mg Cu kg(-1) diet, respectively, for 8 weeks. In the liver, Cu deficiency did not significantly affect the contents of FC, TC and AC, and the ratios of AC/FC and FC/TC. However, Cu excess reduced FC, TC and AC contents, and the ratio of AC/FC, but increased FC/TC ratio. In the muscle, dietary Cu levels showed no significant effects on the contents of FC, TC and AC as well as the ratio of FC/TC, but Cu excess significantly increased the ratio of AC/FC. Compared to the adequate Cu group, dietary Cu deficiency did not significantly affect the Vmax and Km values, and the ratio of Vmax/Km in the liver and muscle. However, Cu excess decreased Vmax and Vmax/Km ratio in the liver, and increased Vmax in the muscle. The mRNA expression of CPT Iα1a, CPT Iα1b, CPT Iα2a and CPT Iβ in the liver and muscle was influenced by dietary Cu levels. To our knowledge, the present study provided, for the first time, evidence that dietary Cu deficiency and excess differentially influenced carnitine status, kinetics and expression profiles of CPT I of yellow catfish, which would extend our understanding on Cu nutrition in fish.

Dietary l-carnitine supplementation increases lipid deposition in the liver and muscle of yellow catfish (Pelteobagrus fulvidraco) through changes in lipid metabolism

Carnitine has been reported to improve growth performance and reduce body lipid content in fish. Thus, we hypothesised that carnitine supplementation can improve growth performance and reduce lipid content in the liver and muscle of yellow catfish (Pelteobagrus fulvidraco), a commonly cultured freshwater fish in inland China, and tested this hypothesis in the present study. Diets containing l-carnitine at three different concentrations of 47 mg/kg (control, without extra carnitine addition), 331 mg/kg (low carnitine) and 3495 mg/kg (high carnitine) diet were fed to yellow catfish for 8 weeks. The low-carnitine diet significantly improved weight gain (WG) and reduced the feed conversion ratio (FCR). In contrast, the high-carnitine diet did not affect WG and FCR. Compared with the control diet, the low-carnitine and high-carnitine diets increased lipid and carnitine contents in the liver and muscle. The increased lipid content in the liver could be attributed to the up-regulation of the mRNA levels of SREBP, PPARγ, fatty acid synthase (FAS) and ACCa and the increased activities of lipogenic enzymes (such as FAS, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and malic enzyme) and to the down-regulation of the mRNA levels of the lipolytic gene CPT1A. The increased lipid content in muscle could be attributed to the down-regulation of the mRNA levels of the lipolytic genes CPT1A and ATGL and the increased activity of lipoprotein lipase. In conclusion, in contrast to our hypothesis, dietary carnitine supplementation increased body lipid content in yellow catfish.

Nutritional Characteristics and Active Components in Liver from Wagyu×Qinchuan Cattle

We investigated nutritional characteristics and active components in the liver of Wagyu×Qinchuan cattle and Qinchuan cattle produced in Shaanxi (China). We observed significant differences (p<0.05) in the proximate composition of protein, fat, carbohydrate, total energy, and glycogen. Wagyu×Qinchuan cattle liver showed higher (p<0.05) sodium, iron, zinc, and selenium concentrations than Qinchuan cattle liver. The amino acid composition of Wagyu×Qinchuan cattle liver was richer (p<0.05) in 13 types of amino acids, with the exception of Asp (10.06%), Val (5.86%), and Met (1.72%). Total essential amino acids accounted for almost half the composition (39.69%) in Wagyu×Qinchuan cattle liver. Wagyu×Qinchuan cattle liver had lower (p<0.05) levels of monounsaturated fatty acids (18.2%), but higher (p<0.05) levels of polyunsaturated fatty acids (35.11%), compared with Qinchuan cattle liver (23.29% and 28.11%, respectively). The thrombogenic index was higher in Qinchuan cattle liver (0.86) than in Wagyu×Qinchuan cattle liver (0.70), and the glutathione (38.0 mg/100g) and L-carnitine (2.12 μM/g) content was higher (p<0.05) in Wagyu×Qinchuan cattle liver than in Qinchuan cattle liver (29.8 mg/100g and 1.41 μM/g, respectively). According to the results obtained, the liver of Wagyu×Qinchuan cattle, which is insufficiently used, should be increasingly utilized to improve its commercial value.

Differential effects of the chronic and acute zinc exposure on carnitine composition, kinetics of carnitine palmitoyltransferases I (CPT I) and mRNA levels of CPT I isoforms in yellow catfish Pelteobagrus fulvidraco

The present study is conducted to determine the effect of acute and chronic zinc (Zn) exposure on carnitine concentration, carnitine palmitoyltransferases I (CPT I) kinetics, and expression levels of CPT I isoforms in liver, muscle and heart of yellow catfish Pelteobagrus fulvidraco. To this end, yellow catfish are subjected to chronic waterborne Zn exposure (0.05 mg Zn L(-1), 0.35 mg Zn L(-1) and 0.86 mg Zn L(-1), respectively) for 8 weeks and acute Zn exposure (0.05 mg Zn L(-1) and 4.71 mg L(-1)Zn, respectively) for 96 h, respectively. Reduced Michaelis-Menten constants (Km) and maximal reaction rates (Vmax) values in liver and muscle are observed in fish exposed to chronic Zn concentration. In contrast, Vmax and Km values in heart increase with increasing Zn concentration. Chronic Zn exposure also significantly influences the contents of free carnitine (FC), total carnitine (TC) and acylcarnitine (AC) in liver and heart, but not in muscle. The acute Zn exposure significantly increases FC, AC, TC contents in liver and muscle, but reduces their contents in heart. The chronic and acute Zn exposure influences the mRNA levels of four CPT I isoforms (CPT Iα1b, CPT Iβ, CPT Iα2a and CPT Iα1a) in liver, muscle and heart. Furthermore, correlations are observed in the mRNA levels between CPT I isoforms and Km, and between isoforms expression and activity of CPT I. Thus, chronic and acute Zn exposure shows differential effects on carnitine content, CPT I kinetics and mRNA levels of four CPT I isoforms in yellow catfish, which provides new mechanism for Zn exposure on lipid metabolism and also novel insights into Zn toxicity in fish.

Influence of acetate and bicarbonate dialysate on blood short- and long-chain acyl carnitine in adult pyelonephritis patients

The effect of acetate and bicarbonate haemodialysis (HD) on the concentrations of erythrocyte, whole-blood and plasma total carnitine (TC), free carnitine (FC), short- (SC) and long-chain acylcarnitine (LC) and acylcarnitine (AC) as well as the ratio of AC to FC was investigated in 30 healthy subjects (15 men and 15 women) and 27 patients (10 men and 17 women) with chronic pyelonephritis (CPN) undergoing chronic HD. Fourteen patients (5 men and 9 women) used acetate HD and the remainder (5 men and 8 women) used bicarbonate HD. The mean predialysis erythrocyte, whole-blood and plasma concentrations of TC, FC, SC, LC and AC as well as the ratio of AC to FC were not significantly different from those in healthy controls (P > 0.05). However, after acetate or bicarbonate HD, a significant decrease in erythrocyte, whole-blood and plasma concentrations of TC, FC, SC, LC and AC were found, compared with either predialysis or healthy control values (P < 0.001). Furthermore, the ratio of AC to FC was significantly higher following acetate HD as compared with either acetate or bicarbonate predialysis values (P < 0.001). The observed variations in response between acetate and bicarbonate HD may be due to enhanced formation of acetyl-coenzyme A and fatty acid synthesis during acetate HD.

Investigation of the effect of theophylline administration on total, free, short-chain acyl and long-chain acyl carnitine distributions in rat renal tissues

This study is conducted to investigate the effect of oral theophylline administration on total (TC), free (FC), short-(SC), long-chain acyl (LC), acyl (AC) carnitine distributions as well as the ratio of acyl to free carnitine (AC/FC) in rat renal tissues. Theophylline was administrated at 100 mg kg-1 body weight day-1, and effects were monitored after a treatment period that lasted between 1 week and 5 weeks. The results indicated that theophylline administration leads to significantly higher concentrations of TC, FC, SC, L and AC in renal tissues as compared to those of control and placebo groups (P < 0.001). Moreover, the ratio of AC/FC was significantly increased (P < 0.001) as compared to either control or placebo groups. These changes may result from theophylline-enhanced mobilization of lipids from adipose tissues, which consequently stimulates an increased carnitine transport into the renal tissues to form acylcarnitines for subsequent beta-oxidation inside the renal mitochondria.

Influence of sex and chronic haemodialysis treatment on total, free and acyl carnitine concentrations in human serum

The influence of sex and haemodialysis treatment on serum total, free and acyl carnitine concentrations in healthy controls and chronic renal failure patients has been investigated. Patients on regular haemodialysis treatment generally displayed significantly decreased serum carnitine levels. The mean predialysis serum carnitine levels were not significantly different from the mean healthy control values. However, after dialysis a significant decrease in serum carnitine levels was observed compared to the predialysis and healthy control values. Moreover, serum ratio of acylated to free carnitine was significantly higher after haemodialysis as compared to both healthy controls and predialysis patients. Sex-related changes in serum total, free and acyl carnitine levels and ratios of acylated to free carnitine have been observed in healthy controls and patients on chronic haemodialysis treatment.

Investigations of the effects of theophylline administration on carnitine acetyltransferase activity of rat heart

The effects of oral theophylline administration (100 mg/kg b.w./day) on the activity of carnitine acetyltransferase (CAT) of rat heart for five-week interval treatment were studied. The result indicated that the body weights of placebo groups were not significantly changed as compared to control groups (P < 0.1), but theophylline treatment caused a significant decrease in the body weights of rat (P < 0.01) as compared to either control or placebo groups throughout the five-week interval treatments. Daily administration of theophylline to rats did not significantly affect heart weights as compared to either control or placebo groups (P < 0.1) for the five week-interval treatments. Our data indicated that the activity of CAT was not significantly changed in placebo groups as compared to control groups (P < 0.1), however, there was a significant increase in the activity of CAT in heart of theophylline-treated groups (P < 0.01) as compared to either control or placebo groups. The increase in the activity of CAT was noticed in the first three weeks of theophylline treatments followed by a gradual return toward normal activity by the fourth and fifth weeks of continued treatment. The observed changes in activity of CAT of heart might be due to theophylline-enhanced mobilization of lipid from adipose tissues which consequently stimulated increased L-carnitine transport into the heart tissues to form fatty acyl-carnitine groups for subsequent beta-oxidation inside the heart mitochondria. Accumulations of acyl-carnitine groups in heart mitochondria may increase the catalytic action of CAT and possible mechanisms are discussed.

Study of the effects of theophylline-related changes in total, free, short- chain acyl and long-chain acyl carnitine concentrations in rat heart

This study is conducted to investigate the effect of oral theophylline administration on total (TC), free (FC), short-(SC), long-chain acyl (LC), acyl (AC) carnitine concentrations and acyl to free carnitine (AC/FC) ratio in rat heart. Theophylline was administrated at 100 mg/kg wt/day, and effects were monitored after a treatment period that lasted between a week and five weeks. The results indicated that theophylline feeding leads to significantly higher concentrations of TC, FC, SC, LC and AC in heart tissue as compared to those of control and placebo groups (P < 0.001). Moreover, the ratio of AC/FC was significantly increased (P < 0.001) as compared to either control or placebo groups. These changes may result from theophylline-enhanced mobilization of lipids from adipose tissues, which consequently stimulates an increased carnitine transport into the heart tissues to form fatty acylcarnitines for subsequent beta-oxidation inside the heart mitochondria.

Kinetic properties of purified carnitine acetyltransferase from the skeletal muscle of Arabian camel (Camelus dromedarius)

The kinetic properties of carnitine acetyltransferase from the skeletal muscle of the Arabian camel (Camelus dromedarius) were studied. The enzyme showed an optimum pH between 7.2 and 8.2. Reciprocal plots of data obtained by varying one substrate concentration while keeping the other constant revealed lines that converged on the abscissa, indicating that the enzyme possible follows a random mechanism of catalysis. The Kms for L-carnitine and acetyl-coenzyme A were 244 and 44 microM respectively, while those for acetyl-DL-carnitine and coenzyme A (Co A) were 307 and 39 microM respectively. The Km for one substrate was found to be independent of the concentration of the second substrate used. Corresponding Vmax values for L-CA, acetyl-Co A, acetyl-DL-carnitine and Co A are 98, 98, 102 and 100 mumol min-1 mg-1 protein respectively. The low Km obtained for acetyl-DL-carnitine suggests an adaptive mechanism in this desert species for enduring prolonged dry spells without food and water.