L-carnitine treatment in the hyperlipidemic rabbit

Dietary choline, but not L-carnitine, increases circulating lipid and lipoprotein concentrations, without affecting body composition, energy expenditure or respiratory quotient in lean and obese male cats during weight maintenance

Introduction

Due to the involvement in one-carbon metabolism and lipid mobilization, choline and L-carnitine supplementation have been recommended to minimize hepatic lipid accumulation and support fat oxidation, respectively. This study investigated the lipotropic benefits of choline or L-carnitine supplementation in lean and obese cats maintaining body weight (BW).

Methods

Lean [n = 9; body condition score (BCS): 4-5/9] and obese (n = 9; BCS: 8-9/9) adult male neutered colony cats were used in a replicated 3 x 3 complete Latin square design. Treatments included choline (378 mg/kg BW0.67), L-carnitine (200 mg/kg BW) and control (no supplement). Treatments were supplemented to the food for 6 weeks each, with a 2-week washout between treatments. Cats were fed once daily to maintenance energy requirements, and BW and BCS were assessed weekly. Fasted blood collection, indirect calorimetry, and dual-energy X-ray absorptiometry occurred at the end of each treatment period. Serum was analyzed for cholesterol (CHOL), high-density lipoprotein CHOL (HDL-C), triglycerides (TAG), non-esterified fatty acids (NEFA), glucose, creatinine (CREAT), urea, alkaline phosphatase (ALP) and alanine aminotransferase (ALT). Very low-density lipoprotein CHOL (VLDL) and low-density lipoprotein CHOL (LDL-C) were calculated. Data were analyzed using proc GLIMMIX, with group and period as random effects, and treatment, body condition, and their interaction as fixed effects, followed by a Tukey's post-hoc test when significance occurred.

Results

Cats supplemented choline had lower food intake (P = 0.025). Treatment did not change BW, BCS and body composition (P > 0.05). Obese cats had greater ALP, TAG, and VLDL, and lower HDL-C compared to lean cats (P < 0.05). Choline resulted in greater CHOL, HDL-C, LDL-C and ALT (P < 0.05). L-carnitine resulted in lower CREAT (P = 0.010). Following the post-hoc test, differences between treatment means were not present for ALP (P = 0.042). No differences were found for glucose, urea or NEFA (P > 0.05). Obese cats had a lower fed respiratory quotient (RQ), regardless of treatment (P = 0.045). Treatment did not affect fed or fasted RQ and energy expenditure (P > 0.05).

Discussion

Choline appeared to increase circulating lipid and lipoprotein concentrations regardless of body condition, likely through enhanced lipid mobilization and hepatic elimination. Neither dietary choline or L-carnitine altered body composition or energy metabolism in the lean or obese cats, as compared to control.

Probio-X Relieves Symptoms of Hyperlipidemia by Regulating Patients' Gut Microbiome, Blood Lipid Metabolism, and Lifestyle Habits

Hyperlipidemia is a key risk factor for cardiovascular disease, and it is associated with lipid metabolic disorders and gut microbiota dysbiosis. Here, we aimed to investigate the beneficial effects of 3-month intake of a mixed probiotic formulation in hyperlipidemic patients (n = 27 and 29 in placebo and probiotic groups, respectively). The blood lipid indexes, lipid metabolome, and fecal microbiome before and after the intervention were monitored. Our results showed that probiotic intervention could significantly decrease the serum levels of total cholesterol, triglyceride, and low-density lipoprotein cholesterol (P < 0.05), while increasing the levels of high-density lipoprotein cholesterol (P < 0.05) in patients with hyperlipidemia. Probiotic recipients showing improved blood lipid profile also exhibited significant differences in their lifestyle habits after the 3-month intervention, with an increase in daily intake of vegetable and dairy products, as well as weekly exercise time (P < 0.05). Moreover, two blood lipid metabolites (namely, acetyl-carnitine and free carnitine) significantly increased after probiotic supplementation cholesterol (P < 0.05). In addition, probiotic-driven mitigation of hyperlipidemic symptoms were accompanied by increases in beneficial bacteria like Bifidobacterium animalis subsp. lactis and Lactiplantibacillus plantarum in patients' fecal microbiota. These results supported that mixed probiotic application could regulate host gut microbiota balance, lipid metabolism, and lifestyle habits, through which hyperlipidemic symptoms could be alleviated. The findings of this study urge further research and development of probiotics into nutraceuticals for managing hyperlipidemia. IMPORTANCE The human gut microbiota have a potential effect on the lipid metabolism and are closely related to the disease hyperlipidemia. Our trial has demonstrated that 3-month intake of a mixed probiotic formulation alleviates hyperlipidemic symptoms, possibly by modulation of gut microbes and host lipid metabolism. The findings of the present study provide new insights into the treatment of hyperlipidemia, mechanisms of novel therapeutic strategies, and application of probiotics-based therapy.

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 effects of supplementation with L-carnitine on apolipoproteins: A systematic review and meta-analysis of randomized trials

Randomized controlled trials (RCTs) have reported that L-carnitin may change serum apolipoproteins. However, the results of RCTs are contradictory. Our objective was to conduct a systematic review and meta-analysis to summarize earlier RCTs on the effects of L-carnitine supplementation on apolipoproteins B100 and AI. ISI web of science, Ovid, PubMed/Medline, Scopus, and Google Scholar were searched from inception to January 2019 using relevant keywords. Treatment effects were considered as weighted mean difference (MD) and the corresponding 95% confidence interval in concentrations of serum apolipoproteins. Random-effects model (Dersimonian-Liard) was used to estimate the overall summary effect. This meta-analysis was performed on fourteen trials. Our results indicated that L-carnitine supplementation has a non-significant effect on Apo B100 (mean difference (MD): 1.820 mg/dl; 95% CI: -3.367 to 7.006, p = 0.492) and Apo AI (MD: -0.119 mg/dl; 95% CI: -4.425 to 4.186, p = 0.957). We also found body mass index, L-carnitine dosage; health condition and intervention duration could change the results. We conclude that L-carnitine does not change Apo B100 and Apo AI concentration. Further trials with sufficient sample size are needed to confirm these findings.

Systemic regulation of L-carnitine in nutritional metabolism in zebrafish, Danio rerio

Excess fat accumulation has been observed widely in farmed fish; therefore, efficient lipid-lowering factors have obtained high attention in the current fish nutrition studies. Dietary L-carnitine can increase fatty acid β-oxidation in mammals, but has produced contradictory results in different fish species. To date, the mechanisms of metabolic regulation of L-carnitine in fish have not been fully determined. The present study used zebrafish to investigate the systemic regulation of nutrient metabolism by dietary L-carnitine supplementation. L-carnitine significantly decreased the lipid content in liver and muscle, accompanied by increased concentrations of total and free carnitine in tissues. Meanwhile, L-carnitine enhanced mitochondrial β-oxidation activities and the expression of carnitine palmitoyltransferase 1 mRNA significantly, whereas it depressed the mRNA expression of adipogenesis-related genes. In addition, L-carnitine caused higher glycogen deposition in the fasting state, and increased and decreased the mRNA expressions of gluconeogenesis-related and glycolysis-related genes, respectively. L-carnitine also increased the hepatic expression of mTOR in the feeding state. Taken together, dietary L-carnitine supplementation decreased lipid deposition by increasing mitochondrial fatty acid β-oxidation, and is likely to promote protein synthesis. However, the L-carnitine-enhanced lipid catabolism would cause a decrease in glucose utilization. Therefore, L-carnitine has comprehensive effects on nutrient metabolism in fish.

Protective role of L-carnitine and vitamin E on the testis of atherosclerotic rats

Atherosclerosis is a condition caused by lipid build-up and inflammation in the arteries, so hyperlipidemia is the major reason for atherosclerosis. Testis was found to be negatively affected by hyperlipidemia which leads to its impaired functions. Vitamin E and l-carnitine have well-known lipid-lowering and antioxidative activities. Triton WR 1339 is a non-ionic detergent, which induces severe hyperlipidemia by inhibition of lipoprotein lipase. The present study evaluates the protective role of vitamin E and l-carnitine on the testis in atherosclerosis and detects the most effective choice for protection against atherosclerosis; vitamin E, l-carnitine or a combination of both. A total of 80 albino male rats were divided into eight groups (10 rats for each group): control (G1), triton (G2), l-carnitine (G3), triton + l-carnitine (G4), vitamin E (G5), triton + vitamin E (G6), l-carnitine + vitamin E (G7) and triton + l-carnitine + vitamin E (G8). Data showed a significant increase in the levels of total cholesterol (TC), triglycerides (TGs), low-density lipoprotein cholesterol (LDL-C), 17 beta hydroxysteroid dehydrogenase (17 β HSD), testicular catalase and malondialdehyde (MDA) in G2 when compared with G1, whereas high-density lipoprotein cholesterol (HDL-C), serum testosterone, testicular 17 ketosteroid reductase (17 KSR), total thiol and glutathione- S-transferase (GST) data showed a significant decrease in G2 when compared with G1. Treatment with l-carnitine or/and vitamin E helps in improving the adverse effect of triton; also the histological changes confirm this finding. So the present study recommends all people to include l-carnitine and vitamin E in their diet to be protected against atherosclerosis.

A combination of (ω-3) polyunsaturated fatty acids, polyphenols and L-carnitine reduces the plasma lipid levels and increases the expression of genes involved in fatty acid oxidation in human peripheral blood mononuclear cells and HepG2 cells

BACKGROUND

Hyperlipidemia and obesity are associated with metabolic syndrome and increased risk in developing diabetes and cardiovascular disease. Nutritional supplements, e.g. L-carnitine and polyunsaturated fatty acids (PUFAs), exert lipid-lowering effects. Hence, the hypothesis that dietetic intervention reduces plasma lipid levels and metabolic enzymes in overweight hyperlipidemic subjects was tested.

SUBJECTS AND METHODS

In a prospective placebo-controlled double-blind study in 22 moderately hyperlipidemic obese humans consuming low-fat yoghurt enriched with a combination of low-dose PUFAs, polyphenols and L-carnitine (PPC) twice a day for 12 weeks were compared to 20 matching participants ingesting low-fat yoghurt. The effects on plasma lipids and expression of enzymes involved in regulation of fatty acid oxidation in peripheral blood mononuclear cells (PBMCs) and HepG2 cells were evaluated.

RESULTS

PPC consumption led to significantly reduced plasma free fatty acid (-29%) and triglyceride (-24%) concentrations (each p < 0.05). PPC application increased significantly peroxisome proliferator-activated receptor α (PPARα) mRNA abundances and those of PPARα target genes (carnitine palmitoyltransferases-1, CPT1A and CPT1B, carnitine acetyltransferase and organic cation transporter 2; each p < 0.05) in PBMCs. In controls, plasma lipid levels and PBMC gene expression did not change. These findings were substantiated by the results of cell culture experiments in HepG2 cells.

CONCLUSION

Supplementation of PPC had marked lipid-lowering effects and PBMC gene expression profiles seemed to reflect nutrition-related metabolic changes.

PDZ adaptors: their regulation of epithelial transporters and involvement in human diseases

Homeostasis in the body is at least partially maintained by mechanisms that control membrane permeability, and thereby serve to control the uptake of essential substances (e.g., nutrients) and the efflux of unwanted substances (e.g., xenobiotics and metabolites) in epithelial cells. Various transporters play fundamental roles in such bidirectional transport, but little is known about how they are organized on plasma membranes. Protein-protein interactions may play a key role: several transporters in epithelial cells interact with the so-called adaptor proteins, which are membrane anchored and interact with both transporters and other membranous proteins. Although most of the evidences for transporter-adaptor interaction has been obtained in vitro, recent studies suggest that adaptor-mediated transporter regulation does occur in vivo and could be relevant to human diseases. Thus, protein-protein interaction is not only associated with the formation of macromolecular complexes but is also involved in various cellular events, and may provide transporters with additional functionality by forming transporter networks on plasma membranes. Interactions between xenobiotic transporters and PSD95/Dlg/ZO1 (PDZ) adaptors were previously reviewed by Kato and Tsuji (2006. Eur J Pharm Sci 27:487-500); the present review focuses on the latest findings about PDZ adaptors as regulators of transporter networks and their potential role in human diseases.

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.

L-carnitine and taurine synergistically inhibit the proliferation and osteoblastic differentiation of vascular smooth muscle cells

AIM

To investigate the synergistic action of L-carnitine (LC) and taurine (TAU) on the proliferation and osteoblastic differentiation of vascular smooth muscle cells (VSMCs).

METHODS

DNA and protein synthesis of VSMCs were assessed using scintillation counting. Alkaline phosphatase (ALP) activity and calcium content were determined to investigate the effects of LC and TAU on the osteoblastic differentiation and mineralization of VSMCs. TAU uptake by VSMCs was assayed. RNA interference was used to down-regulate the expression of the TAU transporter (TAUT) in rat VSMCs.

RESULTS

LC and TAU synergistically inhibited the proliferation and beta-glycerophosphate (beta-GP)-induced osteoblastic differentiation of VSMCs as evidenced by the decreased [(3)H]thymidine incorporation, ALP activity and calcium deposition. Furthermore, LC stimulated the TAU uptake and TAUT expression in VSMCs. Suppression of TAUT with short hairpin RNA (shRNA) abolished the synergistic action of LC and TAU in VSMCs.

CONCLUSION

The synergistic inhibitory action of LC and TAU on the proliferation and osteoblastic differentiation of VSMCs is attributable to the up-regulation of TAUT expression and TAU uptake by LC.

L-Carnitine supplementation reduces oxidized LDL cholesterol in patients with diabetes

BACKGROUND

Patients with type 2 diabetes are under high oxidative stress, and levels of hyperglycemia correlate strongly with levels of LDL oxidation. Carnitine favorably modulates oxidative stress.

OBJECTIVE

This objective of this study was to evaluate the efficacy of L-carnitine on the reduction of oxidized LDL cholesterol in patients with type 2 diabetes.

DESIGN

Eighty-one patients with diabetes were randomly assigned to 1 of 2 treatment groups for 3 mo. The 2 groups received either 2 g L-carnitine once daily (n = 41) or placebo (n = 40). The following variables were assessed at baseline, after washout, and at 1, 2, and 3 mo of treatment: body mass index, fasting plasma glucose, glycosylated hemoglobin, total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides, apolipoprotein A1, apolipoprotein B-100, oxidized LDL cholesterol, thiobarbituric acid-reactive substances, and conjugated dienes.

RESULTS

At the end of the study period, the L-carnitine-treated patients showed significant improvements compared with the placebo group in the following markers: oxidized LDL levels decreased by 15.1 compared with 3.0 U/L (P < 0.001); LDL cholesterol decreased by 0.45 compared with 0.16 mmol/L (P < 0.05); triglycerides decreased by 1.02 compared with 0.09 mmol/L (P < 0.001); apolipoprotein A1 concentrations decreased by 0.12 compared with 0.03 mg/dL (P < 0.05); apolipoprotein B-100 concentrations decreased by 0.13 compared with 0.04 mg/dL (P < 0.05); thiobarbituric acid-reactive substance concentrations decreased by 1.92 compared with 0.05 (P < 0.001), and conjugated diene concentrations decreased by 0.72 compared with 0.11 in the placebo group (P < 0.001).

CONCLUSION

Our study indicates that oral administration of L-carnitine reduces oxidized LDL cholesterol levels in patients with type 2 diabetes.

Efficacy and tolerability of combined treatment with L-carnitine and simvastatin in lowering lipoprotein(a) serum levels in patients with type 2 diabetes mellitus

Lipoprotein(a) [Lp(a)] concentration is generally related to coronary artery disease (CAD) and cerebrovascular disease. However, at present, few interventions are available to lower Lp(a) concentrations. We investigated the effects of l-carnitine, co-administered with simvastatin, on hyper-Lp(a) in patients with type 2 diabetes mellitus. We conducted an open, randomised, parallel-group study, in one investigational center (University hospital). Fifty-two patients with type 2 diabetes mellitus, a triglyceride serum levels <400mg/dL (<4.5 mmol/L), and Lp(a) serum levels >20mg/dL (0.71 mmol/L) were randomised to receive simvastatin alone (n=26) or simvastatin plus l-carnitine (n=26) for 60 days. Simvastatin was administered, in both groups, at a dosage of 20 mg/day, while l-carnitine was administered at a dosage of 2g/day once daily. Both treatments were given orally. Serum levels of triglycerides, total cholesterol, LDL cholesterol, high-density lipoprotein (HDL) cholesterol, non-HDL cholesterol (total cholesterol minus HDL cholesterol), apolipoprotein B, and Lp(a) were measured at baseline and 60 days after starting treatment. No difference in time by groups (simvastatin and simvastatin plus l-carnitine) were observed in the reduction of LDL cholesterol, non-HDL cholesterol, and apoB serum levels. On the other hand, Lp(a) serum levels increase from baseline to 60 days in the simvastatin group alone versus a significant decrease in the combination group. Our findings provide support for a possible role of combined treatment with l-carnitine and simvastatin in lowering Lp(a) serum levels in patients with type 2 diabetes mellitus than with simvastatin alone. Our results strongly suggest that l-carnitine may have a role among lipid-lowering strategies.

Strategies for designing novel functional meat products

In recent years, much attention has been paid to physiological functions of foods due to increasing concerns for health. Although there has been limited information of physiological functions of meat until recently, several attractive meat-based bioactive compounds, such as carnosine, anserine, l-carnitine, conjugated linoleic acid, have been studied. Emphasizing these activities is one possible approach for improving the health image of meat and developing functional meat products. This article provides potential benefits of representative meat-based bioactive compounds on human health and an overview of meat-based functional products. Strategies for designing novel functional meat products utilizing bioactive peptides and/or probiotic bacteria, is also discussed. This article focuses particularly on the possibility of meat protein-derived bioactive peptides, such as antihypertensive peptides. There are still some hurdles in developing and marketing novel functional meat products since such products are unconventional and consumers in many countries recognize meat and meat products to be bad for health. Along with accumulation of scientific data, there is an urgent need to inform consumers of the exact functional value of meat and meat products including novel functional foods.

Mitochondrial dysfunction in NASH: causes, consequences and possible means to prevent it

Calorie-enriched diet and lack of exercise are causing a worldwide surge of obesity, insulin resistance and lipid accretion in liver (i.e. hepatic steatosis), which can lead to steatohepatitis. Steatosis and nonalcoholic steatohepatitis (NASH) can also be induced by drugs such as amiodarone, tamoxifen and some antiretroviral drugs, including stavudine and zidovudine. There is accumulating evidence that mitochondrial dysfunction (more particularly respiratory chain deficiency) plays a key role in the physiopathology of NASH whatever its initial cause. In contrast, the mitochondrial beta-oxidation of fatty acids can be either increased (as in insulin resistance-associated NASH) or decreased (as in drug-induced NASH). However, in both circumstances, generation of reactive oxygen species (ROS) by the damaged respiratory chain can be augmented. ROS generation in an environment enriched in lipids in turn induces lipid peroxidation which releases highly reactive aldehydic derivatives (e.g. malondialdehyde) that have diverse detrimental effects on hepatocytes and other hepatic cells. In hepatocytes, ROS, reactive nitrogen species and lipid peroxidation products further impair the respiratory chain, either directly or indirectly through oxidative damage to the mitochondrial genome. This consequently leads to the generation of more ROS and a vicious cycle occurs. Mitochondrial dysfunction can also lead to apoptosis or necrosis depending on the energy status of the cell. ROS and lipid peroxidation products also increase the generation of several cytokines (TNF-alpha, TGF-beta, Fas ligand) playing a key role in cell death, inflammation and fibrosis. Recent investigations have shown that some genetic polymorphisms can significantly increase the risk of steatohepatitis and that several drugs can prevent or even reverse NASH. Interestingly, most of these drugs could exert their beneficial effects by improving directly or indirectly mitochondrial function in liver. Finding a drug, which could fully prevent oxidative stress and mitochondrial dysfunction in NASH is a major challenge for the next decade.

The effect of oral L-carnitine supplementation on the lipid profiles of hyperlipidaemic children

AIM

To investigate the carnitine status and the effect of carnitine supplementation on serum lipid profiles in children with hyperlipoproteinaemia, a clinical open trial was conducted at Hacettepe University Ihsan Dogramaci Children's Hospital, Section of Nutrition and Metabolism.

METHODS

Patients were given carnitine at a dose of 100 mg/kg/d for 12 wk. Blood samples for the determination of lipid profile and carnitine levels and urine samples for carnitine levels were obtained on admission, at week 4 and week 12 of the study period.

RESULTS

A total of 41 children were enrolled in the study: 20 patients had type II heterozygotes, eight patients had type II homozygotes, three patients had type III, six patients had type V and four patients had secondary hyperlipidaemias. Serum and urine carnitine levels were within normal limits on admission. No significant correlations were found between serum carnitine levels and serum lipid profiles. Serum HDL and apolipoprotein A-I decreased significantly during the 12 wk of intervention in type II heterozygotes. In type II homozygotes, total cholesterol and LDL levels at weeks 4 and 12 increased significantly compared to initial levels. No significant change was noted for lipid parameters in hyperlipoproteinaemia type V.

CONCLUSION

The results of this trial demonstrated that carnitine supplementation was of no benefit for children with hyperlipidaemias, especially in primary hyperlipoproteinaemia type II heterozygotes, homozygotes and type V.

Effect of L-carnitine on plasma glycemic and lipidemic profile in patients with type II diabetes mellitus

OBJECTIVE

We designed this study to investigate the effects of oral L-carnitine administration on fasting plasma glucose (FPG), glycosylated hemoglobin (HbA1c) and lipid parameters in patients with diabetes mellitus type II.

PATIENTS AND METHODS

The effect of L-carnitine on FPG and lipid parameters was investigated in 22 male and 13 female type II diabetic patients; the mean age +/- s.d. was 51.3 +/- 3.7 y. The patients were randomly allocated to two groups (L-carnitine and placebo group) and 1 g of L-carnitine or of placebo was given orally three times a day for a period of 12 weeks.

RESULTS

FPG in the L-carnitine group decreased significantly from 143 +/- 35 to 130 +/- 33 mg/dl (P = 0.03), and we observed a significant increase of triglycerides (TG) from 196+/-61 to 233+/-12 mg/dl (P = 0.05), of Apo A1 from 94 +/- 20 to 103 +/- 23 mg/dl (P = 0.02), and of Apo B100 from 98 +/- 18 to 108 +/- 22 mg/dl (P = 0.02) after 12 weeks of treatment. There was no significant change in LDL-C, HDL-C, HbA1C, LP(a) or total cholesterol.

CONCLUSION

L-Carnitine significantly lowers FPG but increases fasting triglyceride in type II diabetic patients.

Acetyl-l-carnitine supplementation restores decreased tissue carnitine levels and impaired lipid metabolism in aged rats

The effects of long-term carnitine supplementation on age-related changes in tissue carnitine levels and in lipid metabolism were investigated. The total carnitine levels in heart, skeletal muscle, cerebral cortex, and hippocampus were approximately 20% less in aged rats (22 months old) than in young rats (6 months old). On the contrary, plasma carnitine levels were not affected by aging. Supplementation of acetyl-l-carnitine (ALCAR; 100 mg/kg body weight/day for 3 months) significantly increased tissue carnitine levels in aged rats but had little effect on tissue carnitine levels in young rats. Plasma lipoprotein analyses revealed that triacylglycerol levels in VLDL and cholesterol levels in LDL and in HDL were all significantly higher in aged rats than in young rats. ALCAR treatment decreased all lipoprotein fractions and consequently the levels of triacylglycerol and cholesterol. The reduction in plasma cholesterol contents in ALCAR-treated aged rats was attributable mainly to a decrease of cholesteryl esters rather than to a decrease of free cholesterol. Another remarkable effect of ALCAR was that it decreased the cholesterol content and cholesterol-phospholipid ratio in the brain tissues of aged rats. These results indicate that chronic ALCAR supplementation reverses the age-associated changes in lipid metabolism.

L-carnitine alleviates alcohol-induced liver damage in rats: role of tumour necrosis factor-alpha

AIMS

Excessive alcohol intake induces hepatic fatty infiltration, which has been suggested to sensitize the liver to further damage. To test this hypothesis, L-carnitine, a constitutional lipotropic compound, was administered to rats chronically treated with ethanol by liquid diet feeding for 10 weeks.

RESULTS

Ethanol administration caused marked steatosis, mild inflammation and elevated plasma alanine aminotransferase and tumour necrosis factor alpha (TNF-alpha) concentrations. Dietary supplementation with L-carnitine significantly reduced all these parameters as well as the hepatic concentration of thiobarbituric acid reactive substances, an indicator of lipid peroxidation products. Pretreatment with L-carnitine also significantly blunted ethanol-induced stimulation of TNF-alpha release by isolated Kupffer cells.

CONCLUSIONS

This study provides direct support for the notion that steatosis sensitizes the liver to further damage and suggests an involvement of TNF-alpha in this process.

L-carnitine prevents the progression of atherosclerotic lesions in hypercholesterolaemic rabbits

This study has been initiated to investigate, in hypercholesterolaemic rabbits, whether L-carnitine deficiency could be an additional risk factor in atherosclerosis, and if so, whether L-carnitine supplementation could prevent the progression of atherosclerosis. Hypercholesterolaemia was induced by feeding rabbits 2% cholesterol-enriched diet for 28 days, whereas, carnitine deficiency was induced by daily i.p. administration of 250 mg kg(-1) of D-carnitine for 28 days. Histopathological examination of aorta and coronaries from hypercholesterolaemic rabbits revealed severe atherosclerotic lesions, intimal plaques and foam cell formation. Also, hypercholesterolaemic diet resulted in a significant 53 and 43% decrease in reduced glutathion (GSH) levels and a significant (1.87-fold) and (14.1-fold) increase in malonedialdhyde (MDA) levels in aorta and cardiac tissues, respectively. Daily administration of L-carnitine (250 mg kg(-1)) for 28 days, completely prevented the progression of atherosclerotic lesions induced by hpercholesterolaemia in both aorta and coronaries. Conversely, daily administration of D-carnitine (250 mg kg(-1)) for 28 days increased the progression of atherosclerotic lesions with the appearance of foam cells and apparent intimal plaques which are even larger than that seen in hypercholesterolaemic rabbits. Both L-carnitine and D-carnitine produced similar effects on the lipid profile, GSH and MDA which may point to the conclusion that: (1) L-carnitine prevents the progression of atherosclerotic lesions by another mechanism in addition to its antioxidant and lipid-lowering effects; (2) endogenous carnitine depletion and/or carnitine deficiency should be viewed as an additional risk factor in atherogenesis.

Protective role of L-carnitine on liver and heart lipid peroxidation in atherosclerotic rats

Lipid peroxides are considered to be the initiation factor for atherosclerosis. Present study depicts that L-carnitine treatment (300 mg/kg body weight/day) for 7 and 14 days caused significant reduction in the tissue lipid peroxidations. It also shows marked improvement in the antioxidant status. By this way carnitine maintain the normal function of the cells.

L-Carnitine effects on chemical composition of plasma lipoproteins of rabbits fed with normal and high cholesterol diets

L-Carnitine plays an important role in the mitochondrial uptake of long-chain fatty acids in mammals. It has recently been shown that this compound has a marked hypo-cholesterolemic effect when used in conjunction with lipid-rich diets. The aim of this study was to investigate the effects of L-carnitine on the fatty acid composition of plasma lipoproteins in rabbits fed with different diets. Four different groups were investigated: group I (standard diet), group II (standard diet supplemented with L-carnitine at 80 mg/kg), group III (standard diet supplemented with 0.5% cholesterol), and group IV (standard diet supplemented with 0.5% cholesterol plus L-carnitine at 80 mg/kg). The feeding period was 126 d. Total plasma cholesterol was indistinguishable in groups I and II, but increased nearly 40-fold in group III. This increment was reduced by 50% in group IV. Correspondingly, total cholesterol content in lipoprotein fractions [very low density lipoprotein (VLDL), low density lipoprotein (LDL), high density lipoprotein (HDL) separated by agarose gel chromatography was the same for groups I and II, while for animals fed a cholesterol-rich diet (III) total cholesterol in VLDL + LDL increased nearly 100-fold when compared with groups I and II but, again, the increment was reduced by 50% in group IV. In contrast, total cholesterol in HDL increased only fivefold for both groups III and IV when compared with groups I and II, indicating no effects of L-carnitine on this parameter. The reduction of total cholesterol in VLDL + LDL particles in animals fed a cholesterol-rich diet plus L-carnitine was associated with a marked decrease in the ratio of cholesteryl ester to free cholesterol and a dramatic increase in their phospholipid content; opposite effects were observed for HDL. L-Carnitine induced a marked decrease in the saturated to unsaturated C16 + C18 fatty acid ratio in cholesteryl esters associated with VLDL and LDL from animals fed with both normal and cholesterol-rich diets. The opposite effect (a large increase in the saturated to unsaturated fatty acid ratio) was observed for both cholesteryl esters and phospholipids associated with HDL in animals fed with both diets. The results suggested that the hypocholesterolemic effects of L-carnitine could be associated with increased systemic breakdown of cholesteryl esters, a probable increase in reverse cholesterol transport, and the stabilization of a phospholipid-based structure of VLDL + LDL particles.

Carnitine deficiency in diabetes mellitus complications

In this study, the serum total, free and ester carnitine levels in 24 type II diabetes mellitus (DM) patients with complications and 15 type II DM patients with no complications were investigated. The patients were investigated in four groups; the control group included the patients with no complications (group 1), the groups including the patients with retinopathy (group 2), hyperlipidemia (group 3), and neuropathy (group 4). In addition, patients were grouped into two. The first group included 10 patients who took insulin by injection (group 5), and the second group included 29 patients using antidiabetic drugs orally (OAD) (group 6). Free and ester carnitine levels were determined by using Boehringer Manheim UV-enzymatic L-carnitine kit. Statistical analysis results showed that both the plasma total and free carnitine levels of groups 2, 3, and 4 were found to be low when compared to the levels of group 1 (p < 0.05). It was observed that the plasma total and free carnitine levels of group 5 were lower when compared to group 6. No significant difference was observed between the plasma ester carnitine levels of all the groups investigated. As a result of this study, it has been thought that carnitine plays an important role in diabetes mellitus complications.

Effect of L-carnitine treatment on very low density lipoprotein kinetics in the hyperlipidemic rabbit

This study examined the hypolipidemic effect of 4 weeks of L-carnitine treatment (170 mg/kg b.w./day) in New Zealand White rabbits fed a high fat diet (5% corn oil/0.5% cholesterol). Specifically, [3H] glycerol and [125I] very low density lipoprotein (VLDL) turnover studies were conducted to examine the effect of treatment on VLDL kinetics. The masses of plasma VLDL-triglycerides (VLDL-TG) and VLDL-apoprotein B (VLDL-apoB) were significantly increased by the high-fat diet. Four weeks of treatment with L-carnitine significantly reduced these masses. Kinetic analysis indicated that fat feeding reduced the fractional catabolic rates (FCRs) of VLDL-TG and VLDL-apoB relative to chow-fed controls. The transport of these VLDL components was not altered by the diet. L-carnitine treatment had no effect on the FCRs of VLDL-TG and VLDL-apoB or on the transport of VLDL-apoB. Yet, treatment significantly lowered the transport of VLDL-TG. These data indicate that the lipid-lowering effect of L-carnitine in this animal model was due, in part, to a decrease in the transport and not due to an alteration in the fractional catabolic rate of VLDL-TG.

Natural products and the athlete: facts and folklore

OBJECTIVE

To contrast scientific facts with suggested manufacturers' claims regarding food supplements (natural products) marketed for enhanced athletic prowess.

DATA SOURCES

A MEDLINE search was performed to obtain documentation supporting the claims of natural-product manufacturers. In addition, several references pertaining to pharmacognosy, natural products, herbs, pharmacy practice, and sports medicine were reviewed. Claims were obtained from promotional advertisements in bodybuilding magazines, product labels, and fact sheets for sales representatives in nutrition and health-food stores.

DATA EXTRACTION

We reviewed all of the clinical trials, published between 1966 and 1992, relative to the manufacturers' claims regarding these products.

DATA SYNTHESIS

Pertinent human and/or animal studies supporting each natural product were compared with the manufacturers' claims.

CONCLUSIONS

We found that there was no published scientific evidence to support the promotional claims for a large proportion of the products (8/19, 42 percent). Only 4 of 19 products (21 percent) were associated with any documented human clinical trials supporting their promotional claims. Six of 19 agents (32 percent) had some scientific documentation to support their promotional claims; however, these products were judged to be marketed in a misleading manner.