Plasma carnitine levels in children with protein-calorie malnutrition before and after rehabilitation

Secondary carnitine deficiency during refeeding in severely malnourished patients with eating disorders: a retrospective cohort study

BACKGROUND

Secondary carnitine deficiency in patients with anorexia nervosa has been rarely reported. This study aimed to investigate the occurrence of carnitine deficiency in severely malnourished patients with eating disorders during refeeding and assess its potential adverse effects on treatment outcomes.

METHOD

In a cohort study of 56 female inpatients with eating disorders at a single hospital from March 2010 to December 2020, we measured plasma free carnitine (FC) levels and compared to those of a healthy control group (n = 35). The patients were categorized into three groups based on FC levels: FC deficiency (FC< 20 µmol/L), FC pre-deficiency (20 µmol/L ≤ FC< 36 µmol/L), and FC normal (36 µmol/L ≤ FC).

RESULTS

Upon admission, the patients had a median age of 26 years (interquartile range [IQR]: 21-35) and a median body mass index (BMI) of 13.8 kg/m2 (IQR: 12.8-14.8). Carnitine deficiency or pre-deficiency was identified in 57% of the patients. Hypocarnitinemia was associated with a decline in hemoglobin levels during refeeding (odds ratio [OR]: 0.445; 95% confidence interval [CI]: 0.214-0.926, p = 0.03), BMI at admission (OR: 0.478; 95% CI: 0.217-0.874, p = 0.014), and moderate or greater hepatic impairment at admission (OR: 6.385; 95% CI: 1.170-40.833, p = 0.032).

CONCLUSIONS

Hypocarnitinemia, particularly in cases of severe undernutrition (BMI< 13 kg/m2 at admission) was observed in severely malnourished patients with eating disorders during refeeding, a critical metabolic transition phase. Moderate or severe hepatic impairment at admission was considered a potential indicator of hypocarnitinemia. Although hypocarnitinemia was not associated with any apparent adverse events other than anemia during refeeding, the possibility that carnitine deficiency may be a risk factor for more serious complications during sudden increases in energy requirements associated with changes in physical status cannot be denied. Further research on the clinical significance of hypocarnitinemia in severely malnourished patients with eating disorders is warranted.

Effects of L-Carnitine Supplementation on the Rate of Weight Gain and Biomarkers of Environmental Enteric Dysfunction in Children with Severe Acute Malnutrition: A Double-Blind Randomized Controlled Clinical Trial

BACKGROUND

Severe acute malnutrition (SAM) is a major public health concern among low- and middle-income countries, where the majority of the children encountering this acute form of malnutrition suffer from environmental enteric dysfunction (EED). However, evidence regarding the effects of L-carnitine supplementation on the rate of weight gain and EED biomarkers in malnourished children is limited.

OBJECTIVES

We aimed to investigate the role of L-carnitine supplementation on the rate of weight gain, duration of hospital stays, and EED biomarkers among children with SAM.

METHODS

A prospective, double-blind, placebo-controlled, randomized clinical trial was conducted at the Nutritional Rehabilitation Unit (NRU) of Dhaka Hospital, International Centre for Diarrheal Disease Research, Bangladesh. Children with SAM aged 9-24 mo were randomly assigned to receive commercial L-carnitine syrup (100 mg/kg/d) or placebo for 15 d in addition to standard of care. A total of 98 children with Weight-for-Length-z-score (WLZ) < -3 Standard deviation were enrolled between October 2021 and March 2023. Analyses were conducted on an intention-to-treat basis.

RESULTS

The primary outcome variable, "rate of weight gain," was comparable between L-carnitine and placebo groups (2.09 ± 2.23 compared with 2.07 ± 2.70; P = 0.973), which was consistent even after adjusting for potential covariates (age, sex, Weight-for-Age z-score, asset index, and WASH practices) through linear regression [ß: 0.37; 95% confidence interval (CI): -0.63,1.37; P = 0.465]. The average hospital stay was ∼4 d. The results of adjusted median regression showed that following intervention, there was no significant difference in the EED biomarkers among the treatment arms; Myeloperoxidase (ng/mL) [ß: -1342.29; 95% CI: -2817.35, 132.77; P = 0.074], Neopterin (nmol/L) [ß: -153.33; 95% CI: -556.58, 249.91; P = 0.452], alpha-1-antitrypsin (mg/mL) [ß: 0.05; 95% CI: -0.15, 0.25; P = 0.627]. Initial L-carnitine (μmol/L) levels (median, interquartile range) for L-carnitine compared with placebo were 54.84 (36.0, 112.9) and 59.74 (45.7, 96.0), whereas levels after intervention were 102.05 (60.9, 182.1) and 105.02 (73.1, 203.7).

CONCLUSIONS

Although our study findings suggest that L-carnitine bears no additional effect on SAM, we recommend clinical trials with a longer duration of supplementation, possibly with other combinations of interventions, to investigate further into this topic of interest. This trial was registered at clinicaltrials.gov as NCT05083637.

Role of L-Carnitine supplementation on rate of weight gain and biomarkers of Environmental Enteric Dysfunction in children with severe acute malnutrition: A protocol for a double-blinded randomized controlled trial

BACKGROUND

Severe acute malnutrition (SAM) and environmental enteric dysfunction (EED) are highly prevalent among children residing in resource-limited countries like Bangladesh. L-carnitine may play a role in improving the growth and ameliorating the EED among nutritionally vulnerable children.

OBJECTIVE

To investigate the role of L-carnitine supplementation on the rate of weight gain, duration of hospital stays, and EED biomarkers among children with severe acute malnutrition.

METHODS

This study is a double-blinded, placebo-controlled, randomized clinical trial aiming to enroll diarrheal children with SAM between 9-24 months of both sexes attending the nutritional rehabilitation unit (NRU) of Dhaka Hospital of icddr,b. It is an ongoing trial including two arms where one arm receives L-carnitine supplementation, and the other arms receive a placebo for 15 days in addition to the existing standard treatment of SAM. The primary outcome is the rate of weight gain, and the secondary outcomes include duration of hospital stay and EED biomarkers. Outcomes are assessed at baseline and 15 days of post-intervention. We hypothesize that the L- carnitine supplementation for 15 days in children with SAM will improve the rate of weight gain and biomarkers of EED.

TRIAL REGISTRATION

ClinicalTrials.gov # NCT05083637. Date of registration: October 19, 2021.

Newborn Metabolic Profile Associated with Hyperbilirubinemia With and Without Kernicterus

Our objective was to assess the relationship between hyperbilirubinemia with and without kernicterus and metabolic profile at newborn screening. Included were 1,693,658 infants divided into a training or testing subset in a ratio of 3:1. Forty‐two metabolites were analyzed using logistic regression (odds ratios (ORs), area under the receiver operating characteristic curve (AUC), 95% confidence intervals (CIs)). Several metabolite patterns remained consistent across gestational age groups for hyperbilirubinemia without kernicterus. Thyroid stimulating hormone (TSH) and C‐18:2 were decreased, whereas tyrosine and C‐3 were increased in infants across groupings. Increased C‐3 was also observed for kernicterus (OR: 3.17; 95% CI: 1.18–8.53). Thirty‐one metabolites were associated with hyperbilirubinemia without kernicterus in the training set. Phenylalanine (OR: 1.91; 95% CI: 1.85–1.97), ornithine (OR: 0.76; 95% 0.74–0.77), and isoleucine + leucine (OR: 0.63; 95% CI: 0.61–0.65) were the most strongly associated. This study showed that newborn metabolic function is associated with hyperbilirubinemia with and without kernicterus.

Global Metabolomic Identification of Long-Term Dose-Dependent Urinary Biomarkers in Nonhuman Primates Exposed to Ionizing Radiation

Due to concerns surrounding potential large-scale radiological events, there is a need to determine robust radiation signatures for the rapid identification of exposed individuals, which can then be used to guide the development of compact field deployable instruments to assess individual dose. Metabolomics provides a technology to process easily accessible biofluids and determine rigorous quantitative radiation biomarkers with mass spectrometry (MS) platforms. While multiple studies have utilized murine models to determine radiation biomarkers, limited studies have profiled nonhuman primate (NHP) metabolic radiation signatures. In addition, these studies have concentrated on short-term biomarkers (i.e., <72 h). The current study addresses the need for biomarkers beyond 72 h using a NHP model. Urine samples were collected at 7 days postirradiation (2, 4, 6, 7 and 10 Gy) and processed with ultra-performance liquid chromatography (UPLC) quadrupole time-of-flight (QTOF) MS, acquiring global metabolomic radiation signatures. Multivariate data analysis revealed clear separation between control and irradiated groups. Thirteen biomarkers exhibiting a dose response were validated with tandem MS. There was significantly higher excretion of l-carnitine, l-acetylcarnitine, xanthine and xanthosine in males versus females. Metabolites validated in this study suggest perturbation of several pathways including fatty acid β oxidation, tryptophan metabolism, purine catabolism, taurine metabolism and steroid hormone biosynthesis. In this novel study we detected long-term biomarkers in a NHP model after exposure to radiation and demonstrate differences between sexes using UPLC-QTOF-MS-based metabolomics technology.

Oedema in kwashiorkor is caused by hypoalbuminaemia

It has been argued that the oedema of kwashiorkor is not caused by hypoalbuminaemia because the oedema disappears with dietary treatment before the plasma albumin concentration rises. Reanalysis of this evidence and a review of the literature demonstrates that this was a mistaken conclusion and that the oedema is linked to hypoalbuminaemia. This misconception has influenced the recommendations for treating children with severe acute malnutrition. There are close pathophysiological parallels between kwashiorkor and Finnish congenital nephrotic syndrome (CNS) pre-nephrectomy; both develop protein-energy malnutrition and hypoalbuminaemia, which predisposes them to intravascular hypovolaemia with consequent sodium and water retention, and makes them highly vulnerable to develop hypovolaemic shock with diarrhoea. In CNS this is successfully treated with intravenous albumin boluses. By contrast, the WHO advise the cautious administration of hypotonic intravenous fluids in kwashiorkor with shock, which has about a 50% mortality. It is time to trial intravenous bolus albumin for the treatment of children with kwashiorkor and shock.

Carnitine and acylcarnitines: pharmacokinetic, pharmacological and clinical aspects

L-Carnitine (levocarnitine) is a naturally occurring compound found in all mammalian species. The most important biological function of L-carnitine is in the transport of fatty acids into the mitochondria for subsequent β-oxidation, a process which results in the esterification of L-carnitine to form acylcarnitine derivatives. As such, the endogenous carnitine pool is comprised of L-carnitine and various short-, medium- and long-chain acylcarnitines. The physiological importance of L-carnitine and its obligatory role in the mitochondrial metabolism of fatty acids has been clearly established; however, more recently, additional functions of the carnitine system have been described, including the removal of excess acyl groups from the body and the modulation of intracellular coenzyme A (CoA) homeostasis. In light of this, acylcarnitines cannot simply be considered by-products of the enzymatic carnitine transfer system, but provide indirect evidence of altered mitochondrial metabolism. Consequently, examination of the contribution of L-carnitine and acylcarnitines to the endogenous carnitine pool (i.e. carnitine pool composition) is critical in order to adequately characterize metabolic status. The concentrations of L-carnitine and its esters are maintained within relatively narrow limits for normal biological functioning in their pivotal roles in fatty acid oxidation and maintenance of free CoA availability. The homeostasis of carnitine is multifaceted with concentrations achieved and maintained by a combination of oral absorption, de novo biosynthesis, carrier-mediated distribution into tissues and extensive, but saturable, renal tubular reabsorption. Various disorders of carnitine insufficiency have been described but ultimately all result in impaired entry of fatty acids into the mitochondria and consequently disturbed lipid oxidation. Given the sensitivity of acylcarnitine concentrations and the relative carnitine pool composition in reflecting the intramitochondrial acyl-CoA to free CoA ratio (and, hence, any disturbances in mitochondrial metabolism), the relative contribution of L-carnitine and acylcarnitines within the total carnitine pool is therefore considered critical in the identification of mitochondria dysfunction. Although there is considerable research in the literature focused on disorders of carnitine insufficiency, relatively few have examined relative carnitine pool composition in these conditions; consequently, the complexity of these disorders may not be fully understood. Similarly, although important studies have been conducted establishing the pharmacokinetics of exogenous carnitine and short-chain carnitine esters in healthy volunteers, few studies have examined carnitine pharmacokinetics in patient groups. Furthermore, the impact of L-carnitine administration on the kinetics of acylcarnitines has not been established. Given the importance of L-carnitine as well as acylcarnitines in maintaining normal mitochondrial function, this review seeks to examine previous research associated with the homeostasis and pharmacokinetics of L-carnitine and its esters, and highlight potential areas of future research.

Role of carnitine in disease

Carnitine is a conditionally essential nutrient that plays a vital role in energy production and fatty acid metabolism. Vegetarians possess a greater bioavailability than meat eaters. Distinct deficiencies arise either from genetic mutation of carnitine transporters or in association with other disorders such as liver or kidney disease. Carnitine deficiency occurs in aberrations of carnitine regulation in disorders such as diabetes, sepsis, cardiomyopathy, malnutrition, cirrhosis, endocrine disorders and with aging. Nutritional supplementation of L-carnitine, the biologically active form of carnitine, is ameliorative for uremic patients, and can improve nerve conduction, neuropathic pain and immune function in diabetes patients while it is life-saving for patients suffering primary carnitine deficiency. Clinical application of carnitine holds much promise in a range of neural disorders such as Alzheimer's disease, hepatic encephalopathy and other painful neuropathies. Topical application in dry eye offers osmoprotection and modulates immune and inflammatory responses. Carnitine has been recognized as a nutritional supplement in cardiovascular disease and there is increasing evidence that carnitine supplementation may be beneficial in treating obesity, improving glucose intolerance and total energy expenditure.

Lipid kinetic differences between children with kwashiorkor and those with marasmus

BACKGROUND

It has been hypothesized that one factor associated with poor prognosis in kwashiorkor, but not in marasmus, is impaired lipid catabolism, which limits the supply of energy that is essential for survival when dietary intake is inadequate. However, this hypothesis has not been tested.

OBJECTIVE

The objective was to measure lipid kinetics in malnourished children with kwashiorkor or marasmus.

DESIGN

Glycerol concentration and flux (index of total lipolysis), palmitate concentration and flux (index of net lipolysis), and palmitate oxidation rate (index of fatty acid oxidation) were measured in 8 children (n = 5 boys and 3 girls) with kwashiorkor and 7 (n = 4 boys and 3 girls) with marasmus, aged 4-20 mo, in the postabsorptive state. The measurements were made approximately 3 d after admission, when the children were malnourished, and after the children attained normal weight-for-length, ie, at recovery.

RESULTS

The glycerol concentration was higher in the malnourished stage than at recovery for the marasmus and kwashiorkor groups combined. Glycerol flux tended to be lower (P = 0.067) and palmitate flux significantly lower (P < 0.05) in the kwashiorkor group than in the marasmus group. Palmitate oxidation was significantly lower in the malnourished stage than at recovery in the kwashiorkor group but not in the marasmus group. In the malnourished stage, palmitate oxidation was slower in the kwashiorkor group than in the marasmus group, but no significant differences between groups were observed at recovery.

CONCLUSIONS

Children with kwashiorkor break down fat and oxidize fatty acids less efficiently than do children with marasmus; this factor may explain the better survival rate in marasmus.

Hypocarnitinemia in lysinuric protein intolerance

Carnitine deficiency in lysinuric protein intolerance (LPI) has been reported only in a single case. We describe hypocarnitinemia in a 11 year-old male patient with LPI and relate its development to intake, biosynthesis, and uptake of carnitine.

Plasma and liver carnitine status of children with chronic liver disease and cirrhosis

BACKGROUND

Carnitine is an essential cofactor in the transfer of long-chain fatty acids across the inner mitochondrial membrane for oxidation. As its synthesis is performed in the liver, alterations in carnitine metabolism is expected in liver diseases, especially in cirrhosis.

METHODS

In this study, we investigated plasma and liver carnitine concentrations of 68 children with chronic liver disease, 36 of whom had cirrhosis as well. Carnitine level was determined by enzymatic method.

RESULTS

Plasma and liver carnitine concentrations were not correlated. Mean plasma carnitine level of cirrhotic children was significantly lower than that of the control group (P<0. 0001). While there was no difference between liver carnitine concentrations of children with chronic liver disease and cirrhosis (P>0.05), mean plasma level of cirrhotics were lower (P<0.05). Plasma carnitine was correlated with albumin, triglyceride and gamma glutamyl transpeptidase (GGT) in patients with chronic liver disease (P<0.05). Liver carnitine was correlated with GGT in cirrhotic patients (P<0.005). Children with malnutrition had higher plasma and liver carnitine levels (P<0.05). The highest plasma and liver carnitine levels were detected in children with biliary atresia and criptogenic cirrhosis, respectively. Both the lowest plasma and liver carnitine levels were detected in Wilson's disease.

CONCLUSION

Children with cirrhosis have low plasma carnitine concentrations. This finding is prominent in children with Wilson's disease. As carnitine is an essential factor in lipid metabolism, the carnitine supplementation for patients with cirrhosis in childhood, especially with Wilson's disease, seems to be mandatory.

Ketosis resistance in fibrocalculous pancreatic diabetes: II. Hepatic ketogenesis after oral medium-chain triglycerides

A majority of patients with fibrocalculous pancreatic diabetes (FCPD) do not become ketotic even in adverse conditions. It is not clear whether this ketosis resistance is due to reduced fatty acid release from adipose tissue or to impaired hepatic ketogenesis. We tested hepatic ketogenesis in FCPD patients using a ketogenic challenge of oral medium-chain triglycerides (MCTs) and compared it with that in matched insulin-dependent diabetes mellitus (IDDM) patients and healthy controls. After oral MCTs, FCPD patients showed only a mild increase in blood 3-hydroxybutyrate (3-HB) concentrations (median: fasting, 0.13 mmol/L; peak, 0.52) compared with IDDM patients (fasting, 0.44; peak, 3.39) and controls (fasting, 0.04; peak, 0.75). Plasma nonesterified fatty acid (NEFA) concentrations were comparable in the two diabetic groups (FCPD: fasting, 0.50 mmol/L; peak, 0.79; IDDM: fasting, 0.91; peak, 1.04). Plasma C-peptide concentrations were low and comparable in the two diabetic groups. Plasma glucagon concentrations were higher in IDDM patients in the fasting state, but declined to levels comparable to those in FCPD patients after oral MCTs. Plasma carnitine concentrations were comparable in the two groups of patients. It is concluded that the failure to stimulate ketogenesis under these conditions could be partly due to inhibition of a step beyond fatty acid entry into the mitochondria.

Carnitine metabolism in chronic liver disease

The liver is a central organ for carnitine metabolism and for the distribution of carnitine to the body. It is therefore not surprising that carnitine metabolism is impaired in patients and experimental animals with certain types of chronic liver disease. In this review, the changes in carnitine metabolism associated with chronic liver disease and the role of carnitine as a therapeutic agent in some of these conditions are discussed.

Neuromyopathic complications in a patient with anorexia nervosa and vitamin C deficiency

A 19-year-old female patient with anorexia nervosa developed profound weight loss over 1 year associated with vegetarianism and excessive exercise. There was severe wasting and proximal muscle weakness in the legs and bilateral weakness of eye closure. A purpuric rash developed due to vitamin C deficiency. This case demonstrates a new neurological sign in anorexia nervosa indicating a weakness of the orbicularis oculi muscles as part of a more general myopathy. The myopathic and scorbutic features may have a common pathogenesis.

The ketosis-resistance in fibro-calculous-pancreatic-diabetes. 1. Clinical observations and endocrine-metabolic measurements during oral glucose tolerance test

We measured circulating levels of C-peptide, pancreatic glucagon, cortisol, growth hormone and metabolites (glucose, non-esterified fatty acids, glycerol and 3-hydroxybutyrate) in fibro-calculous-pancreatic diabetic (FCPD, n = 28), insulin-dependent diabetic (IDDM, n = 28) and non-diabetic control (n = 27) subjects during an oral glucose tolerance test. There was no difference in the two diabetic groups in age (FCPD 24 +/- 2, IDDM 21 +/- 2 years, mean +/- SEM), BMI (FCPD 16.0 +/- 0.6, IDDM 15.7 +/- 0.4 kg/m2), triceps skinfold thickness (FCPD 8 +/- 1, IDDM 7 +/- 1 mm), glycaemic status (fasting plasma glucose, FCPD 12.5 +/- 1.5, IDDM 14.5 +/- 1.2 mmol/l), fasting plasma C-peptide (FCPD 0.13 +/- 0.03, IDDM 0.08 +/- 0.01 nmol/l), peak plasma C-peptide during OGTT (FCPD 0.36 +/- 0.10, IDDM 0.08 +/- 0.03 nmol/l) and fasting plasma glucagon (FCPD 35 +/- 4, IDDM 37 +/- 4 ng/l). FCPD patients, however, showed lower circulating concentrations of non-esterified fatty acids (0.73 +/- 0.11 mmol/l), glycerol (0.11 +/- 0.02 mmol/l) and 3-hydroxybutyrate (0.15 +/- 0.03 mmol/l) compared to IDDM patients (1.13 +/- 0.14, 0.25 +/- 0.05 and 0.29 +/- 0.08 mmol/l, respectively). This could be due to enhanced sensitivity of adipose tissue lipolysis to the suppressive action of circulating insulin and possibly also to insensitivity of hepatic ketogenesis to glucagon. Our results also demonstrate preservation of alpha-cell function in FCPD patients when beta-cell function is severely diminished, suggesting a more selective beta-cell dysfunction or destruction than hitherto believed.

Prevalence of carnitine depletion in critically ill patients with undernutrition

The aim of this study was to evaluate to what extent secondary carnitine deficiency may exist based on the prevalence of subnormal carnitine status in patients with critical illness and abnormal nutritional state. Healthy control patients (n = 12) were investigated and compared with patients with possible secondary carnitine deficiency, ie, patients with overt severe protein-energy malnutrition (PEM, n = 28), postoperative long-term (greater than 14 days) parenteral glucose feeding (250 g glucose/d, n = 7), severe liver disease (n = 10), renal insufficiency (n = 7), and sustained septicemia with increased metabolic rate (n = 8). Nutritional status, energy expenditure, creatinine excretion, and blood biochemical tests were measured in relationship to free and total carnitine concentrations in plasma and skeletal muscle tissue, as well as urinary excretion of free and total carnitine. The overall mortality rate was 48% within 30 days of the investigation in study patients with the highest mortality in liver disease (90%). The hospitalization range was 14 to 129 days in study patients. Most study patients had lost weight (4% to 19%) and had abnormal body composition. Patients with liver disease, septicemia, renal insufficiency, and those on long-term glucose feeding had significantly higher than predicted metabolic rate (+25% +/- 3%), while patients with severe malnutrition had decreased metabolic rate compared with controls. Patients with liver disease had increased plasma concentrations of free (96 +/- 16 mumol/L) and total (144 +/- 27 mumol/L) carnitine compared with controls (45 +/- 3, 58 +/- 7 mumol/L, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Improved methodology to assay carnitine and levels of free and total carnitine in human plasma

Carnitine, once known as vitamin Bt, is intrinsic to human tissue and is biochemically established as being acylated with fatty acids by Acyl-CoA to give Acyl-carnitines which then are transported to the inner mitochondrial membrane by a translocase. Carnitine is of increasing clinical interest and importance, and endomyocardial deficiencies of carnitine have been reported for patients in heart failure. Consequently, a reproducible and accurate analysis of human tissue specimens for levels of free carnitine and Acyl-carnitine to guide and to support continuing clinical studies of disease states is needed. We have devised an analytical method which utilizes 5,5'-dithiobis-2-nitro-benzoate and demonstrated recovery, reproducibility and precision. Hydrolysis of a specimen at 90 degrees C for 15 min, and control of pH below 6.0 are critical steps. The mean levels of free carnitine and total carnitine in 17 ordinary subjects were 50.6 +/- 9.7 nmol./ml and 62.6 +/- 11.7 nmol./ml. respectively.

Effect of food restriction on tissue carnitine concentration in rats

The effect of feeding different amounts of a standard laboratory pellet diet on tissue carnitine concentration was studied in four groups of rats. Group I was fed ad libitum, whereas food intake was restricted to 25, 20, and 15g protein/kg body weight/day in group II, III, and IV, respectively. The intake of food, protein, energy and carnitine was constant and adjusted to actual body weight in groups 2-4. Six weeks food restriction had no effect on muscle carnitine. Restricted diet caused lowered concentrations of carnitine in serum (group I, fed ad libitum, total 95.0 +/- 13.8, free 80.2 +/- 2.7; group II total 78.4 +/- 8.4, free 56.9 +/- 4.7; group III total 81.7 +/- 8.8, free 66.0 +/- 8.8; and group IV total 73.8 +/- 8.7, free 59.5 +/- 7.6 micromol/l) and urinary carnitine excretion (group I, total 7.1 +/- 3.3, free 6.3 +/- 3.1; group II, total 2.5 +/- 0.7, free 2.2 +/- 0.7; group III, total 1.9 +/- 0.8, free 1.6 +/- 0.8; and group IV, total 1.3 +/- 0.4 free 1.1 +/- 0.3 micromol/day). In contrast, the liver carnitine tended to increase when dietary intake was reduced (group I total 1.1 +/- 0.1, free 1.0 +/- 0.1; group II total 1.5 +/- 0.2, free 1.4 +/- 0.2; group III total 1.3 +/- 0.1, free 1.1 +/- 0.1; and group IV total 1.5 +/- 0.2, free 1.4 +/- 0.2 micromol/g dry wt). The highest liver carnitine concentrations were observed during the lowest dietary intake when also the serum and urine carnitine were lowest. We conclude that the amount of food intake has a direct impact on carnitine concentrations in the liver, serum, and urine while muscle carnitine concentration remains relatively stable despite wide variations in food intake.

Serum carnitine levels in bone marrow transplant recipients

This study investigated plasma carnitine levels in patients undergoing allogenic bone marrow transplantation. The patients received fat-based TPN (50% fat, 50% CHO; calorie: nitrogen ratio 125:1) for an average of 33 +/- 7.5 days. TPN was started before transplantation and stopped when patients were able to eat. Caloric needs were estimated using the Harris-Benedict equation; 150% of the estimated BEE was given for the first two weeks after transplantation. The amount of TPN was gradually decreased as patients resumed their oral intake. All patients had low-normal serum carnitine levels before transplantation. There was no significant change in total or free serum carnitine levels during the course of TPN. However, in patients who had symptoms of graft vs. host reaction (GVH), the highest carnitine values during GVH (total 72.3 +/- 6.5 and free 61.2 +/- 12.4 mumol/l) were significantly higher (p < 0.001) than the baseline values (total 27.1 +/- 9.3 and free 24.9 +/- 9.6 mumol/l) or the highest non GVH values after transplantation (total 32.0 +/- 10.7 and free 29.0 +/- 10.7 mumol/l, respectively). The serum triglyceride, total cholesterol, and HDL cholesterol remained within normal range. In conclusion, bone marrow transplant patients receiving fat-based TPN have normal circulating levels of carnitine. GVH reaction caused an increase in the carnitine levels, which was probably due to increased tissue catabolism.

Secondary carnitine deficiency in handicapped patients receiving valproic acid and/or elemental diet

We examined serum-free carnitine (SFC) concentrations and serum acylcarnitine (SAC)/SFC ratios in 40 severely handicapped patients, aged 2 to 36 years, and 69 age-matched control subjects. SFC levels in the patients treated with valproic acid (VPA) and/or receiving carnitine-deficient elemental diets (ED) were significantly lower, and their SAC/SFC ratios were significantly higher than in the other patients or in control subjects. There were 6 patients whose SFC levels were less than the -2SD level (15.8 +/- 6.7 microM, range 6.3-25.5) of those in control subjects (52.1 +/- 11.5 microM). They had no clinical symptoms of carnitine deficiency such as non-ketotic hypoglycemia, hepatomegaly, muscle weakness or cardiac function impairment, and showed normal transaminase, lipid and ammonia levels. In two cases (SFC = 11.0, 13.4 microM), the ketogenic responses to intravenous administration of fat-emulsion were impaired, but they were restored after D-,L-carnitine supplementation (30 mg/kg/day, po) for 1 month. However, in one case with the lowest SFC level (6.3 microM), the ketogenic responses to fat-emulsion infusion or fasting were normal, and dicarboxylic aciduria was not detected. These results indicate that 1) SFC levels are reduced in handicapped patients receiving VPA and/or ED, although clinical symptoms of carnitine deficiency do not easily develop, 2) some of these hypocarnitinemic cases show a subclinical impairment of hepatic fatty acid metabolism, not always correlated with the degree of SFC reduction, which can be restored by exogenous carnitine supplements, and therefore 3) in patients with acquired hypocarnitinemia, carnitine therapy should be considered, although a low SFC level alone may not imply an immediate indication.

Liver function in protein-energy malnutrition measured by cinnamic acid tolerance and benzoic acid tolerance: effect of carnitine supplementation

1. Rats fed on a protein-depleted diet for 8 weeks were repleted for 5 weeks on high-protein (HP), high-protein + 20 g DL-carnitine/kg (HP + C), or low-protein + 20 g DL-carnitine/kg (LP + C) diets. At 4 and 8 weeks of depletion, and 1 and 5 weeks of repletion, rats from each treatment group were given a benzoic acid tolerance test (BATT) or a cinnamic acid tolerance test (CATT) as a measure of liver function. 2. BATT and CATT measured the molar percentage of a test dose (1 mmol/kg body-weight) of benzoic acid or cinnamic acid excreted in the urine as hippuric acid within 24 h. Liver weight, liver lipid levels, and carnitine concentration in plasma and liver were also measured following liver-function testing. 3. BATT and CATT were severely impaired in protein-depleted rats, but returned rapidly to control levels following protein refeeding. Correlations of BATT and CATT with liver lipid concentration were high (r -0.49 and -0.62 respectively), and both tests show promise as clinical tests for liver function in protein-energy malnutrition. 4. Carnitine supplementation was required to return liver carnitine concentration of protein-depleted rats to control levels during repletion, but was not associated with accelerated reduction in liver fat concentration in protein-repleted rats.

Carnitine supplementation vs. medium-chain triglycerides in postburn nutritional support

The effect of dietary supplementation of carnitine on protein metabolism was studied in a burned guinea-pig model. Animals bearing a 30 per cent total body surface area burn were enterally infused with three isocaloric and isonitrogenous diets via gastrostomy feeding tubes for 14 days. Two diets contained safflower oil (long-chain triglycerides, LCT) and another diet contained medium-chain triglycerides (MCT) as their lipid sources (30 per cent of total calories as lipid). L-Carnitine was added to one of the two diets containing safflower oil. There were no significant differences in nitrogen balance, urinary excretion, serum albumin or transferrin among the three groups. However, the use of MCT in place of LCT appeared to increase liver weight and liver nitrogen. In this model, carnitine supplementation did not enhance the nitrogensparing effect of fat following burn injury.

Whole body fat oxidation before and after carnitine supplementation in uremic patients on chronic haemodialysis

This study has evaluated whether uremic patients on chronic haemodialysis with subnormal plasma levels of free carnitine show any alterations in whole body fat oxidation before and after one week with carnitine supplementation (60 mg/kg/day). Carnitine plasma levels changed from subnormal to supranormal levels of both free and total carnitine concentrations. This increase was not associated with any alteration in either oxygen uptake, carbon dioxide production, respiratory quotient or blood substrate levels such as glucose, glycerol, free fatty acids and lactate. The fractional oxidation of an intravenously infused fat emulsion (Intralipid) was 17% before and 19% after carnitine supplementation. No side effects were observed in spite of the rather high dose of carnitine administration. This study failed to demonstrate any impact on net whole body fat oxidation in carnitine substituted uremic patients with initially subnormal levels of free plasma carnitine.

Carnitine plasma concentrations in 353 metabolically healthy children

Carnitine plasma concentrations were determined by an enzymatic radioisotopic method in 353 metabolically healthy children and in 41 adults. There was a positive correlation between total and free carnitine plasma concentrations and the age of the children. Both free and acylcarnitine concentrations were elevated on the 1st day of life, reflecting an increased rate of fatty acid oxidation. Carnitine plasma concentrations decreased after the 1st day and subsequently increased during the 1st year. From the 2nd year of life until adulthood, no further change was noted. Up to 17 years of age no differences were seen between male and female individuals. However, adult males had higher carnitine concentrations in plasma than adult females. Total carnitine concentrations were higher in 10- to 17-year-old females and lower in 10- to 17-year-old males compared with adults of the same sex, indicating a possible role for sex hormones in the regulation of carnitine plasma concentrations.

Serum carnitine in children with kwashiorkor

Concentrations of free and acylcarnitine were measured in serum of children with kwashiorkor and compared with those obtained for well nourished children of similar age. The mean values (S.E.) for both free and acylcarnitine were significantly lower in the kwashiorkor group [32.6 (6.2) and 8.1 (2.2), respectively] than in the controls [53.2 (2.9) and 13.8 (3.1), respectively]. Serum albumin was also low in kwashiorkor patients, but there was no significant correlation with carnitine values.

Carnitine levels in skeletal muscle of malnourished patients before and after total parenteral nutrition

Carnitine is necessary for the transport of long-chain fatty acids across the mitochondrial membrane. Carnitine is derived from the diet and from endogenous synthesis from lysine and methionine. About 98% of the body's carnitine pool is located in skeletal muscle tissue. Skeletal muscle carnitine levels were determined in two groups of malnourished patients, eight patients with anorexia nervosa with a weight loss of 32.4% +/- 1.8 (mean +/- SEM) and six surgical patients with major gastrointestinal disorders and a weight loss of 15.2% +/- 2.7. Their hepatic and kidney functions were normal. On admission, the muscle carnitine levels were 16.9 +/- 4.0 mumol/g dry weight (mean +/- SD) for the surgical patients and 20.8 +/- 5.0 mumol/g dry weight for the anorexia nervosa patients, which corresponded to carnitine levels seen in healthy subjects. No statistical significance was found between the two groups. Total parenteral nutrition was given to the surgical patients for 2 weeks and to the anorexia nervosa patients for 3-5 weeks. No statistical difference in muscle carnitine levels was found in either group after nutritional support. These malnourished patients had no decreased muscle carnitine levels on admission and maintained them during several weeks of total parenteral nutrition.

Carnitine: an overview of its role in preventive medicine

Carnitine (beta-hydroxy-gamma-N-trimethylaminobutyric acid) is required for transport of long-chain fatty acids into the inner mitochondrial compartment for beta-oxidation. Widely distributed in foods from animal, but not plant, sources, carnitine is also synthesized endogenously from two essential amino acids, lysine and methionine. Human skeletal and cardiac muscles contain relatively high carnitine concentrations which they receive from the plasma, since they are incapable of carnitine biosynthesis themselves. Since the discovery of a primary genetic carnitine deficiency syndrome in 1973, carnitine has become the subject of extensive research. It is now recognized that carnitine deficiency may also occur secondary to genetic disorders of intermediary metabolism as well as to a variety of clinical disorders, including renal disease treated by hemodialysis, the renal Fanconi syndrome, cirrhosis, untreated diabetes mellitus, malnutrition, Reye's syndrome, and certain disorders of the endocrine, neuromuscular, and reproductive systems. Administration of the anticonvulsant valproic acid and total parenteral nutrition may also induce hypocarnitinemia. In many instances, the physiological implications of secondary carnitine deficiency have not been resolved. However, evidence for a specific carnitine requirement for the newborn, especially if preterm, is accumulating. Moreover, carnitine administration may have a favorable effect on some forms of hyperlipoproteinemia. Carnitine, now recognized as a conditionally essential nutrient, is a significant factor in preventive medicine.

Tropical or malnutrition-related diabetes: a real syndrome?

The syndrome known as tropical diabetes seems to be distinct from the two main types common in developed countries. Major pancreatic exocrine disease may or may not be present, and within these two groups there are clinical and biochemical variants. For these conditions the term malnutrition-related diabetes has been proposed. Although malnutrition is a plausible unifying factor, there is a good case for retaining the term tropical diabetes until there is more information on clinical and biochemical features and on aetiology.

Carnitine deficiency

Carnitine is an essential cofactor in the transfer of long-chain fatty acids across the inner mitochondrial membrane. Carnitine is metabolized from lysine, trimethyllysine and butyrobetaine. Butyrobetaine undergoes hydroxylation in the liver, brain and kidney to form carnitine which in turn is transported via the plasma to the heart and skeletal muscle where it is important for allowing beta oxidation of fatty acids. Three clinical forms of carnitine deficiency have been described: myopathic, systemic and mixed forms. Carnitine deficiency results in accumulation of neutral lipid within skeletal muscle, myocardium and liver. Ultrastructurally, myofibrils are disrupted and there is an accumulation of large aggregates of mitochondria and lipid deposits within the skeletal muscle and myocardium. Carnitine therapy has been effective in the treatment of the myopathic and some cases of systemic and mixed forms. Several syndromes of secondary carnitine deficiency have been described; these may be secondary to genetic defects of intermediary metabolism and to other conditions, particularly following hemodialysis.

Carnitine metabolism and inborn errors

Current knowledge of the metabolic role, biosynthesis, cellular uptake, excretion and turnover of carnitine is reviewed. The clinical spectrum and possible aetiology of the primary muscle and primary systemic carnitine deficiency syndromes are considered and the various genetic defects of intermediary metabolism which can give rise to secondary carnitine deficiency are indicated.

Urinary excretion of carnitine in multiply injured patients on different regimens of total parenteral nutrition

Carnitine derives from intake of preformed exogenous carnitine and synthesis from lysine and methionine, but is absent in parenteral fluids. Urinary excretions of carnitine and its derivatives was measured in 30 patients 2-8 days after severe multiple injuries and compared with controls. The patients received five different isocaloric parenteral nutritional regimens;group 1 glucose and fat, group 2 glucose, fat and amino acids, group 3 glucose and insulin, group 4 glucose and amino acids, and group 5 branched-chain amino acids. The mean total carnitine excretion in healthy men was 420 mumol/24 h +/- 57 (SEM), and in women 266 mumol/24 h +/- 29, 41% of which was free carnitine. Mean excretion of total carnitine during days 2-8 after trauma for the five groups was: 900 +/- 100, 1169 +/- 112, 1251 +/- 102, 1023 +/- 117, and 668 +/- 128 mumol/24 h, being significantly higher in groups 1-4 than in healthy men. The free carnitine fraction in the patients was significantly higher than in controlled healthy subjects. Total carnitine excretion was unaffected by different nutritional regimens in the very first days. During days 6-8, group 5, receiving branched-chain amino acids had lower excretion of total carnitine (compared to groups 2-4) and free carnitine (compared to groups 3-4). Groups 3 and 4 excreted a higher percentage as free carnitine compared to the other groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Carnitine in human nutrition

The oxidation of long-chain fatty acids is carnitine-dependent. Indeed, only when they are bound to carnitine, in the form of acyl-carnitines, do fatty acids penetrate into the mitochondria to be oxidized. To meet the need for carnitine, animals depend on both endogenous synthesis and an exogenous supply. A diet rich in meat supplies a lot of carnitine, while vegetables, fruits, and grains furnish relatively little. Although it has a low molecular weight and acts at low doses in a vital metabolic pathway, carnitine should not be considered a vitamin, but rather a nutritive substance. Indeed, it seems that the diet of the adult human need not necessarily furnish carnitine: the healthy organism, given a balanced nutrition (sufficiently rich in lysine and methionine), may well be able to meet all its needs. Furthermore, it seems that a reduction of the exogenous supply of carnitine results in a lowering of its elimination in the urine. However, dietary carnitine is more important during the neonatal period. The transition from fetal to extrauterine life is accompanied by an increased role of lipids in meeting energy needs. This change is accompanied by a rise in the body of the levels of carnitine, which is mainly supplied in the maternal milk. Finally, this review briefly surveys the illnesses in which a dietary carnitine supplement proves useful.

Urinary carnitine excretion in surgical patients on total parenteral nutrition

Urinary free and total carnitine excretions were measured in 41 normal adults and seven surgical patients on fat-free total parenteral nutrition for 8 to 45 days. The means (+/-SEM) of urinary free and total carnitine excretion in normal adults were 162 +/- 19 and 328 +/- 28 micrometers/days, respectively. All of the patients exhibited protein-calorie malnutrition with a mean carnitine intake of 11.6 +/- 1.5 micrometers/day. Under this stringent carnitine economy with the adequate supply of lysine and methionine, urinary total carnitine excretion significantly reduced to 127 to 162 micrometers/day. This probably reflects the carnitine biosynthetic rate. However, during the periods of operation and/or infection, urinary total carnitine excretion significantly increased 2- to 7-fold that of normal levels. Significant positive correlation was found between the two forms of urinary carnitine and total nitrogen excretions. Serum free and total carnitine levels in patients were significantly higher than normal adults. Such findings can be explained by the endocrine responses to the stress phenomenon and indicate a catabolic response of skeletal muscle in which most of the body carnitine resides. This can impair their carnitine status.

Carnitine deficiency induced during intermittent haemodialysis for renal failure

Carnitine concentration was measured in plasma, muscle, and dialysate before and after haemodialysis in patients with renal failure and in plasma and muscle of healthy controls. In eight of the nine patients carnitine concentration in muscle after haemodialysis was only 10% of the concentration in controls. Plasma-carnitine varied in patients before dialysis and in all of them was reduced by dialysis. The loss of carnitine into the dialysate (190--2100 mumol/treatment) greatly exceeded the normal loss in urine for most of patients, and was only partly compensated for. In some patients normal or high plasma-carnitine and low concentrations in muscle indicated that the carnitine-concentrating mechanisms in the muscle cell had failed. The reduction in carnitine will interfere seriously with normal cellular functions and this may help to explain the clinical syndrome of cardiomyopathy and cardiac failure which has been observed in some patients treated for a long time with intermittent haemodialysis.