Increases in VO2max and metabolic markers of fat oxidation by caffeine, carnitine, and choline supplementation in rats.

We have previously shown that the combination of caffeine, carnitine, and choline supplementation decreased body fat and serum leptin concentration in rats and was attributed to increased fat utilization for energy. As a result, it was hypothesized that the supplements may augment exercise performance including physiological and biochemical indexes. Twenty 7-week-old male Sprague-Dawley rats were given free access to a nonpurified diet with or without supplementation of caffeine, carnitine, and choline at concentrations of 0.1, 5, and 11.5 g/kg diet, respectively. One half of each dietary group was exercised on a motor-driven treadmill for 3 weeks and maximal aerobic power (VO(2)max) was determined on the 18th day of exercise. Rats were killed 24-hr postexercise, and blood, regional fat pads, and skeletal muscle were collected. The VO(2)max was increased (P < 0.05) in the supplemented/exercised group; however, the respiratory quotient (RQ) was not affected. Postexercised concentrations of serum triglycerides were decreased but beta-hydroxybutyrate, acylcarnitine, and acetylcarnitine were increased in the supplemented animals. The changes in serum metabolites were complemented by the changes in the muscle and urinary metabolites. The magnitude of increase in urinary acylcarnitines (34-45-fold) is a unique effect of this combination of supplements. Cumulative evidence indicates enhanced beta-oxidation of fatty acids without a change in the RQ because acetyl units were excreted in urine as acetylcarnitine and not oxidized to carbon dioxide. For this phenomenon, we propose the term "fatty acid dumping." We conclude that supplementation with caffeine, carnitine, and choline augments exercise performance and promotes fatty acid oxidation as well as disposal in urine.

Caffeine, carnitine and choline supplementation of rats decreases body fat and serum leptin concentration as does exercise.

The effect of a combination of caffeine, carnitine and choline with or without exercise on changes in body weight, fat pad mass, serum leptin concentration and metabolic indices was determined in 20 male, 7-wk-old Sprague-Dawley rats. They were given free access to a nonpurified diet without or with caffeine, carnitine and choline at concentrations of 0.1, 5 and 11.5 g/kg diet, respectively. In a 2x2 factorial design, one-half of each dietary group was exercised, and the other half was sedentary. Body weight and food intake of all rats were measured every day for 28 d. Rats were killed and blood and tissue samples were collected and analyzed for biochemical markers. Food intake of the groups was not different, but the body weight was significantly reduced by exercise in both dietary groups. Fat pad weights and total lipids of epididymal, inguinal and perirenal regions were significantly reduced by the supplements as well as by exercise. Regardless of exercise, supplements significantly lowered triglycerides in serum but increased levels in skeletal muscle. Serum leptin concentrations were equally lowered by supplements and exercise. Serum leptin was correlated with body weight (r = 0.55, P< or =0.01), fat pad weight (r = 0.82, P< or =0.001) and serum glucose (r = 0.51, P< or =0.05). We conclude that the indices of body fat loss due to dietary supplements were similar to those due to mild exercise, and there were no interactive effects of the two variables.

Choline supplementation reduces urinary carnitine excretion in humans.

Two experiments were conducted to determine the effects of supplementary choline and/or pantothenate on the carnitine and lipid status of free-living humans. Analyses of carnitine and cholesterol fractions, triacylglycerols, and creatinine were determined in serum and/or urine. In experiment 1, adults receiving 13.5 mmol choline plus 1.4 mmol pantothenate/d had a significant decline in urinary carnitine excretion and renal clearance with nonesterfied carnitine (NEC) declining the most dramatically, 84%. Additionally, serum NEC and total carnitine concentrations decreased significantly. No changes were observed in any of the serum lipids examined. In experiment 2, subjects took 0.20 mmol and 0.02 mmol/kg choline or pantothenate, respectively. Choline, but not pantothenate, supplementation significantly decreased urinary carnitine excretion, renal clearance, and fractional clearance of NEC. We conclude that supplementary choline maintained serum carnitine concentrations by conserving urinary carnitine. Moreover, these observations merit additional investigation to determine metabolic and functional consequences of choline and carnitine interactions in humans.

A randomised, double-blind, placebo-controlled trial of L-carnitine in suspected acute myocardial infarction.

In a randomised, double-blind placebo-controlled trial, the effects of the administration of oral L-carnitine (2 g/day) for 28 days were compared in the management of 51 (carnitine group) and 50 (placebo group) patients with suspected acute myocardial infarction. At study entry, the extent of cardiac disease, cardiac enzymes and lipid peroxides were comparable between the groups, although both groups showed an increase in cardiac enzymes and lipid peroxides. At the end of the 28-day treatment period, the mean infarct size assessed by cardiac enzymes showed a significant reduction in the carnitine group compared to placebo. Electrocardiographic assessment of infarct size revealed that the QRS-score was significantly less in the carnitine group compared to placebo (7.4 +/- 1.2 vs 10.7 +/- 2.0), while serum aspartate transaminase and lipid peroxides showed significant reduction in the carnitine group. Lactate dehydrogenase measured on the sixth or seventh day following infarction showed a smaller rise in the carnitine group compared to placebo. Angina pectoris (17.6 vs 36.0%), New York Heart Association class III and IV heart failure plus left ventricular enlargement (23.4 vs 36.0%) and total arrhythmias (13.7 vs 28.0%) were significantly less in the carnitine group compared to placebo. Total cardiac events including cardiac deaths and nonfatal infarction were 15.6% in the carnitine group vs 26.0% in the placebo group. It is possible that L-carnitine supplementation in patients with suspected acute myocardial infarction may be protective against cardiac necrosis and complications during the first 28 days.

Choline supplementation alters carnitine homeostasis in humans and guinea pigs.

We have previously shown that supplementary choline causes significant decreases in urinary excretion of carnitine in humans. The objectives of the present work were to study this interaction in a different human population and on other body pools of carnitine in an animal model. In young adult women, daily choline supplementation (20 mg/kg body wt) resulted in a 75% lower urinary carnitine excretion than in controls, without significantly altering plasma carnitine concentrations. Supplementary choline was added to the ground diet of Sprague-Dawley rats (2.5 g/kg diet) and guinea pigs (3 g/kg diet). Choline supplementation had no effect on plasma concentrations or urinary excretion of carnitine in the rats. In guinea pigs, however, choline supplementation resulted in a significantly lower urinary excretion and higher plasma total carnitine concentrations. The skeletal muscle carnitine concentration was higher in the choline-supplemented guinea pigs, but not significantly higher in other tissues. These studies demonstrated that choline supplementation results in decreased urinary excretion of carnitine in young adult women, that guinea pigs are a suitable animal model for studying the effect of choline supplementation on carnitine status in humans, and that choline results in a conservation of carnitine in guinea pigs and perhaps in humans.

Carnitine prolongs the half-life of ethanol in broilers.

The object was to determine if carnitine attenuated ethanol metabolism in broilers similar to that reported in the rats. Two groups (n = 5) of 5-week-old broilers were given for 10 days the feed with or without 0.5% L-carnitine supplement. A single oral dose of ethanol on day 8 was followed by serial blood samples which were analysed for ethanol. Another dose of ethanol was given on day 10 and 2 hr later, plasma and liver were collected and analysed for ethanol, total lipid, triglycerides and carnitine. The carnitine supplemented diet prolonged the half-life of ethanol due to attenuation of ethanol metabolism which is similar to that reported earlier in rodents. The increases in plasma and hepatic acylcarnitines indicate that supplementary carnitine lessens the load of free acyl groups in the liver by eventual oxidation or excretion.

Acetylcarnitine inhibits alcohol dehydrogenase.

Carnitine and acetylcarnitine are used as dietary supplements and as therapeutic agents. Carnitine attenuates ethanol metabolism in intact animals but the in vitro activities of alcohol dehydrogenase (ADH), microsomal ethanol oxidizing system (MEOS) or catalase are not significantly altered by carnitine. Since acetylcarnitine was a far more potent inhibitor of ethanol oxidation than carnitine in hepatocytes, the activities of rat liver ADH and MEOS were determined with or without acetylcarnitine. The activity of ADH, not MEOS, was significantly inhibited by acetylcarnitine at NAD: acetylcarnitine < or = 1. The inhibition is of a competitive nature where acetylcarnitine competes with NAD+ (Ki = 135 mumol.L-1). This finding is unique in that this is the first report of this function of acetylcarnitine and it is a novel interaction between two important nutrients, niacin and carnitine.

Opposite effects of dietary saturated and unsaturated fatty acids on ethanol-pharmacokinetics, triglycerides and carnitines.

OBJECTIVE: The objective of this study was to determine the effects of saturated fatty acid (SFA) and unsaturated fatty acid (UFA) diets on ethanol pharmacokinetics. Hepatic ADH and plasma carnitines were also evaluated as possible indicators of the mechanism involved. METHODS: Sprague-Dawley male rats were fed modified AIN76 diets containing 10% coconut oil (SFA) or corn oil (UFA) for 120 days. A single dose (3 g/kg bw) of ethanol (13% solution) was orally administered using a gastric canula on day 30, 90, 105 and 120. Tail vein blood samples were collected at various intervals following ethanol dose and were analyzed for blood-ethanol concentration (BEC). In an analogous trial rats were given these diets for 70 days and blood samples were collected on day 35 and 63 for triglycerides, cholesterol and carnitine determination. The animals were killed on day 70 to collect liver for ADH determination. RESULTS: Compared to the UFA group, the SFA group exhibited significantly higher BEC, larger area under the curve, longer half-life of ethanol, and lower rates of ethanol elimination. Plasma carnitines were also higher in the SFA vs UFA group. However, hepatic ADH activity was not different between the groups. CONCLUSION: Dietary SFA protects liver from alcohol injury by retarding ethanol metabolism, and carnitine may be involved.

Effects of diet restriction and carnitine on carbon tetrachloride toxicity in the rat.

Male Sprague Dawley rats were fed a semisynthetic diet ad libitum, 55% of ad libitum (45% restriction), or supplemented with 1% L-carnitine for 68 days. The LD50 dose of CCl4 was orally administered, and mortality and hepatic lipids were determined. The CCl4-induced mortality was significantly increased by feed restriction but not by carnitine. Carnitine prevented hepatic lipid accumulation caused by CCl4 under these conditions.

Suppression of aflatoxin B1-induced lipid abnormalities and macromolecule-adduct formation by L-carnitine.

The fatty liver and hypolipidemia caused by aflatoxin B1 (AFB1) were studied in male Sprague-Dawley rats fed Purina Rat Chow with or without L-carnitine supplement for 6 weeks. In Experiment 1, the rats (n = 20) were divided into four groups, i.e., nonsupplemented control (NSC), nonsupplemented AFB1 (NSA), carnitine supplemented control (CSC), and carnitine supplemented AFB1 (CSA). The NSA and CSA groups were given an oral dose of [3H]AFB1 (1 mg/kg) 6 hr before kill. In Experiment 2 (n = 10) there were only NSA and CSA groups and they were killed 24 hr post-AFB1 administration. Hepatic and plasma concentrations of total lipid, triglycerides, AFB1-macromolecules adducts and urinary excretion of AFB1 were determined. Carnitine supplementation ameliorated AFB1-induced hepatic steatosis and hypolipidemia. Supplementary carnitine reduced covalent binding of AFB1 to hepatic DNA, RNA, and protein. The carnitine effect was more pronounced after 24 hr than after 6 hr of AFB1 treatment. We conclude that supplementary carnitine suppressed AFB1-induced fatty liver and AFB1-macromolecule adduct formation in the rat.

Effects of L-carnitine on carbon tetrachloride-induced changes in serum and liver lipids and acylcarnitines.

Effects of 0.5% L-carnitine-supplemented diet on carbon tetrachloride-induced alterations of hepatic and serum lipids were examined in male rats. Treatment with carbon tetrachloride significantly increased hepatic total lipids, triglycerides, and total carnitine, but these were not significantly altered by 0.5% L-carnitine supplementation. However, in plasma, supplementary carnitine significantly decreased nonesterified fatty acids and increased acylcarnitines. These suggest that carnitine may soften hepatic lipid load by releasing acylcarnitines in blood.

Attenuation of ethanol metabolism by supplementary carnitine in rats.

The purpose of this study was to examine the effect of supplementary D,L-carnitine on blood-ethanol levels and ascertain if the effect was a result of altered absorption or metabolism of ethanol. Mature male Sprague-Dawley rats were fed Purina Rat Chow as such or supplemented with various levels of D,L-carnitine. First it was established that supplementing carnitine at 1% (w/w) level produced steady state concentrations of carnitine in blood after 3 days of feeding. When a single dose of ethanol was given orally after 5 days of carnitine supplementation, the blood levels of ethanol remained significantly elevated for 2-8 hours in the carnitine supplemented animals. Time course of blood-ethanol concentrations revealed that carnitine did not affect the rates of ethanol absorption and therefore, the effect must be due to the attenuation of ethanol clearance from the blood.

Dose-dependent lipotropic effect of carnitine in chronic alcoholic rats.

The objective of this study was to determine if the lipotropic effect of supplementary DL-carnitine was dose dependent. Male Sprague-Dawley rats were fed for 45 d a liquid ethanol diet in which 36% of the total energy was derived from ethanol. The ethanol diet, containing 1.27 g L-carnitine per g of the diet, was fed as such or was supplemented with 0.1%, 0.4%, 0.8%, 1.2%, or 1.6% (wt/wt) DL-carnitine. Results showed a definite inverse relationship between the concentrations of lipids and those of carnitine fractions in both plasma and liver. The concentrations of total lipids and triglycerides were significantly lower with increasing levels of supplementary carnitine, whereas those of carnitine fractions were significantly higher than in controls up to 0.8% supplemental carnitine. The changes in the plasma and hepatic concentrations of various classes of lipid and carnitine were inversely related and were found to be progressive up to 0.8% DL-carnitine supplementation. Therefore, it was concluded that the lipotropic effect of dietary carnitine is dose dependent, and that the optimal supplementary level is 0.8% DL-carnitine.

Distribution of carnitine and acylcarnitine in small intestine of carnitine-supplemented and fasted rats.

Distribution of carnitine and acylcarnitine in lumen flush and tissue of the small intestine was examined in four groups of male Sprague-Dawley rats fed either a nonpurified diet (groups 1, 2) or the same supplemented with 1% DL-carnitine (groups 3, 4). One group of animals under each dietary regimen (groups 2, 4) was fasted for 24 h prior to killing. Carnitine and acylcarnitines were present in higher concentrations in tissue of the small intestine than in the lumen flush. Even though the diets contained only traces of acid-soluble acylcarnitine, it was present in high concentrations both in tissue of the small intestine and lumen flush. Proximal segments of small intestine tended to concentrate carnitine and acylcarnitines under all conditions of treatment. Carnitine supplementation increased the amounts of carnitines in tissue; however, there was only a minor alteration in the pattern of distribution of carnitine and acylcarnitines.

Ameliorating effects of carnitine and its precursors on alcohol-induced fatty liver.

The lipid-lowering effect of carnitine and its precursors, namely lysine plus methionine, was examined in male Sprague-Dawley rats fed ethanol as 36% of the total calories. Ethanol caused typical hepatic steatosis characterized by significant accumulation of total lipids, triglycerides, cholesterols, phospholipids, and free fatty acids. Supplementation of the ethanol diet with 1% DL-carnitine, 0.5% L-lysine, and 0.2% L-methionine significantly lowered ethanol-induced increases of various lipid fractions, with the exception of free fatty acids. The lipid-lowering effect of carnitine was superior to that of its precursors and their effect together was no greater than that of carnitine alone. The triglyceride contents of liver and plasma were related inversely to the levels of carnitine and acyl carnitines. It is concluded that dietary carnitine more effectively than its precursors prevented alcohol-induced hyperlipemia and accumulation of fat in livers. Thus, a deficiency of functional carnitine may indeed exist in chronic alcoholic cases.