Postprandial changes in plasma ketone body and carnitine levels in normal and non-insulin-dependent diabetic subjects

Prolonged Use of Carnitine-Orotate Complex (Godex®) Is Associated with Improved Mortality: A Nationwide Cohort Study

Despite its hepatoprotective effects and favorable metabolic effects, the association between carnitine-orotate complex (Godex®) intake and mortality has never been investigated. We enrolled 13,413 adults who underwent national health examination and were prescribed the carnitine-orotate complex. Subjects were classified into three groups based on duration of using carnitine-orotate complex: <30, 30−180, and ≥180 days and were followed-up until 2019. Hazard ratios (HRs) and 95% confidence intervals (CIs) for all-cause mortality were estimated using Cox proportional hazards regression. During the follow-up period, 708 deaths were documented. Adjusted HR of mortality was 0.69 (95% CI 0.51−0.92) in those who used carnitine-orotate complex for ≥180 days compared to those who used it for <30 days. Use of carnitine-orotate complex for ≥180 days was associated with significantly reduced mortality in individuals with metabolic risk factors such as obesity, metabolic syndrome, dyslipidemia, and fatty liver than the shorter period of use. A significant interaction was observed in individuals with type 2 diabetes (HR 0.43, 95% CI 0.29−0.63, p-value 0.001). In this nationwide study, longer use of carnitine-orotate complex was associated with improved mortality compared to a shorter period of use, and the risk reductions were prominent in individuals with metabolic risk factors.

Relationship Between Acylcarnitine and the Risk of Retinopathy in Type 2 Diabetes Mellitus

OBJECTIVE

Diabetic retinopathy is a common complication of type 2 diabetes mellitus (T2DM). Due to the limited effectiveness of current prevention and treatment methods, new biomarkers are urgently needed for the prevention and diagnosis of DR. This study aimed to explore the relationships between plasma acylcarnitine with DR in T2DM.

METHODS

From May 2015 to August 2016, data of 1032 T2DM patients were extracted from tertiary hospitals. Potential non-linear associations were tested by binary logistic regression models, and ORs and 95% CIs of the research variables were obtained. Correlation heat map was used to analyze the correlation between variables. The change of predictive ability was judged by the area under the receiver operating characteristic curve.

RESULTS

Of the 1032 patients with T2DM, 162 suffered from DR. After adjusting for several confounding variables, C2 (OR:0.55, 95%CI:0.39-0.76), C14DC (OR:0.64, 95%CI:0.49-0.84), C16 (OR:0.64, 95%CI:0.49-0.84), C18:1OH (OR:0.51, 95%CI:0.36-0.71) and C18:1 (OR:0.60, 95%CI:0.44-0.83) were negatively correlated with DR. The area under the curve increased from 0.794 (95% CI 0.745 to 0.842) to 0.840 (95% CI 0.797 to 0.833) when C2, C14DC, C18:1OH and C18:1 added to the traditional risk factor model.

CONCLUSION

There was a negative correlation between C2, C14DC, C16, C18:1OH, and C18:1 and the risk of retinopathy in patients with T2DM. C2, C14DC, C18:1OH, and C18:1 may be new predictors and diagnostic markers of DR.

The Renal Safety of L-Carnitine, L-Arginine, and Glutamine in Athletes and Bodybuilders

One of the major concerns about taking amino acid supplements is their potential adverse effects on the kidney as a major organ involved in the metabolism and excretion of exogenous substances. The aim of this study is to review available data about renal safety of the most prominent amino acid supplements including L-arginine, glutamine and also L-carnitine as well as creatine (as amino acid derivatives) in athletes and bodybuilders. The literature was searched by keywords such as "L-carnitine", "L-arginine", "glutamine", and "kidney injury" in databases such as Scopus, Medline, Embase, and ISI Web of Knowledge. Articles published from 1950 to December 2017 were included. Among 3171, 5740, and 1608 records after primary search in the relevant databases, 8, 7, and 5 studies have been finally included, respectively, for L-carnitine, L-arginine, and glutamine in this review. Arginine appears to have both beneficial and detrimental effects on kidney function. However, adverse effects are unlikely to occur with the routine doses (from 3 to >100 g/day). The risks and benefits of L-carnitine on the athletes' and bodybuilders' kidney have not been evaluated yet. However, L-carnitine up to 6000 mg/day is generally considered to be a safe supplement at least in healthy adults. Both short-term (20-30 g within a few hours) and long-term (0.1 g/kg four times daily for 2 weeks) glutamine supplementation in healthy athletes were associated with no significant adverse effects, but it can cause glomerulosclerosis and serum creatinine level elevation in the setting of diabetic nephropathy. Creatine supplementation (ranged from 5 to 30 g/day) also appears to have no detrimental effects on kidney function of individuals without underlying renal diseases. More clinical data are warranted to determine the optimal daily dose and intake duration of common supplemental amino acids associated with the lowest renal adverse effects in sportsmen and sports women.

Significance of l-carnitine for human health

Carnitine acyltransferases catalyze the reversible transfer of acyl groups from acyl-coenzyme A esters to l-carnitine, forming acyl-carnitine esters that may be transported across cell membranes. l-Carnitine is a wáter-soluble compound that humans may obtain both by food ingestion and endogenous synthesis from trimethyl-lysine. Most l-carnitine is intracellular, being present predominantly in liver, skeletal muscle, heart and kidney. The organic cation transporter-2 facilitates l-carnitine uptake inside cells. Congenital dysfunction of this transporter causes primary l-carnitine deficiency. Carnitine acetyltransferase is involved in the export of excess acetyl groups from the mitochondria and in acetylation reactions that regulate gene transcription and enzyme activity. Carnitine octanoyltransferase is a peroxysomal enzyme required for the complete oxidation of very long-chain fatty acids and phytanic acid, a branched-chain fatty acid. Carnitine palmitoyltransferase-1 is a transmembrane protein located on the outer mitochondrial membrane where it catalyzes the conversion of acyl-coenzyme A esters to acyl-carnitine esters. Carnitine acyl-carnitine translocase transports acyl-carnitine esters across the inner mitochondrial membrane in exchange for free l-carnitine that exits the mitochondrial matrix. Carnitine palmitoyltransferase-2 is anchored on the matrix side of the inner mitochondrial membrane, where it converts acyl-carnitine esters back to acyl-coenzyme A esters, which may be used in metabolic pathways, such as mitochondrial β-oxidation. l-Carnitine enhances nonoxidative glucose disposal under euglycemic hyperinsulinemic conditions in both healthy individuals and patients with type 2 diabetes, suggesting that l-carnitine strengthens insulin effect on glycogen storage. The plasma level of acyl-carnitine esters, primarily acetyl-carnitine, increases during diabetic ketoacidosis, fasting, and physical activity, particularly high-intensity exercise. Plasma concentration of free l-carnitine decreases simultaneously under these conditions. © 2017 IUBMB Life, 69(8):578-594, 2017.

Similarities in serum acylcarnitine patterns in type 1 and type 2 diabetes mellitus and in metabolic syndrome

BACKGROUND/AIMS

In type 1 diabetes (T1D), type 2 diabetes (T2D) and metabolic syndrome (MetS), the associated complex metabolomic changes in the involvement of carnitine metabolism in total carnitine ester level has already been documented; here we extended the investigations to the individual acylcarnitines.

METHODS

The fasting serum acylcarnitine concentrations were determined in 49 T1D, 38 T2D and 38 MetS patients and 40 controls by isotope dilution electrospray ionization tandem mass spectrometry.

RESULTS

The acylcarnitine profiles of the 3patient groups shared elements with the controls. Considerably higher levels of almost all short-chain acylcarnitines (p < 0.05) and lower levels of some long-chain acylcarnitines were detected in T2D and MetS patients. The amounts of C3 and C4 carnitine were higher and most of the medium-chain and long-chain acylcarnitine levels were lower (p < 0.05) in T1D and MetS patients than in the controls. In T1D and T2D, the levels of C3 and C4 acylcarnitines were markedly elevated and some long-chain acylcarnitines were lower than the controls (p < 0.05). Moreover, significantly lower concentrations of free- and total carnitine were observed in T1D patients (p < 0.05).

CONCLUSIONS

Profound alterations were detected in acylcarnitine profiles in the 3 patient groups. Similarities in the patterns suggest different degrees of involvement of the same metabolic systems in a systems biology approach.

High L-carnitine concentrations do not prevent late diabetic complications in type 1 and 2 diabetic patients

Increased intake of L-carnitine, a cofactor in cellular energy metabolism, is recommended for diabetic patients with late complications. However, its clinical benefits remain controversial. We hypothesized that patients with low L-carnitine levels would have an increased rate of diabetic complications. To test this hypothesis, we evaluated the relationship of L-carnitine concentrations in blood with the prevalence and severity of late diabetic complications in type 1 and 2 diabetic patients. Human blood samples were collected from 93 and 87 patients diagnosed as having type 1 or type 2 diabetes, respectively, and 122 nondiabetic individuals. The determination of free L-carnitine concentrations in whole blood lysates was performed using ultra-performance liquid chromatography with tandem mass spectrometry. In diabetic patients, diabetic complications such as neuropathy, retinopathy, nephropathy, or hypertension were recorded. The average L-carnitine concentration in the blood of control subjects was 33 ± 8 nmol/mL, which was not significantly different from subgroups of patients with type 1 (32 ± 10 nmol/mL) or type 2 diabetes (36 ± 11 nmol/mL). Patients with low (<20 nmol/mL) l-carnitine levels did not have increased occurrences of late diabetic complications. In addition, patient subgroups with higher L-carnitine concentrations did not have decreased prevalence of late diabetic complications. Our results provide evidence that higher L-carnitine concentrations do not prevent late diabetic complications in type 1 and 2 diabetic patients.

Role of carnitine in the regulation of glucose homeostasis and insulin sensitivity: evidence from in vivo and in vitro studies with carnitine supplementation and carnitine deficiency

BACKGROUND

Although carnitine is best known for its role in the import of long-chain fatty acids (acyl groups) into the mitochondrial matrix for subsequent β-oxidation, carnitine is also necessary for the efflux of acyl groups out of the mitochondria. Since intracellular accumulation of acyl-CoA derivatives has been implicated in the development of insulin resistance, carnitine supplementation has gained attention as a tool for the treatment of insulin resistance. More recent studies even point toward a causative role for carnitine insufficiency in developing insulin resistance during states of chronic metabolic stress, such as obesity, which can be reversed by carnitine supplementation.

METHODS

The present review provides an overview about data from both animal and human studies reporting effects of either carnitine supplementation or carnitine deficiency on parameters of glucose homeostasis and insulin sensitivity in order to establish the less well-recognized role of carnitine in regulating glucose homeostasis.

RESULTS

Carnitine supplementation studies in both humans and animals demonstrate an improvement of glucose tolerance, in particular during insulin-resistant states. In contrast, less consistent results are available from animal studies investigating the association between carnitine deficiency and glucose intolerance. The majority of studies dealing with this question could either find no association or even reported that carnitine deficiency lowers blood glucose and improves insulin sensitivity.

CONCLUSIONS

In view of the abovementioned beneficial effect of carnitine supplementation on glucose tolerance during insulin-resistant states, carnitine supplementation might be an effective tool for improvement of glucose utilization in obese type 2 diabetic patients. However, further studies are necessary to explain the conflicting observations from studies dealing with carnitine deficiency.

Emerging perspectives on essential amino acid metabolism in obesity and the insulin-resistant state

Dysregulation of insulin action is most often considered in the context of impaired glucose homeostasis, with the defining feature of diabetes mellitus being elevated blood glucose concentration. Complications arising from the hyperglycemia accompanying frank diabetes are well known and epidemiological studies point to higher risk toward development of metabolic disease in persons with impaired glucose tolerance. Although the central role of proper blood sugar control in maintaining metabolic health is well established, recent developments have begun to shed light on associations between compromised insulin action [obesity, prediabetes, and type 2 diabetes mellitus (T2DM)] and altered intermediary metabolism of fats and amino acids. For amino acids, changes in blood concentrations of select essential amino acids and their derivatives, in particular BCAA, sulfur amino acids, tyrosine, and phenylalanine, are apparent with obesity and insulin resistance, often before the onset of clinically diagnosed T2DM. This review provides an overview of these changes and places recent observations from metabolomics research into the context of historical reports in the areas of biochemistry and nutritional biology. Based on this synthesis, a model is proposed that links the FFA-rich environment of obesity/insulin resistance and T2DM with diminution of BCAA catabolic enzyme activity, changes in methionine oxidation and cysteine/cystine generation, and tissue redox balance (NADH/NAD+).

Inspiratory muscle strength is correlated with carnitine levels in type 2 diabetes

INTRODUCTION

Plasma carnitine insufficiency has been known to cause muscle weakness. Carnitine levels and pulmonary functions were lower in patients with diabetes.

PATIENTS AND METHODS

To determine whether pulmonary functions are correlated with carnitine levels in patients with type 2 diabetes. In this study, we evaluated pulmonary functions and carnitine concentrations in 49 patients with type 2 diabetes and 34 healthy controls.

RESULTS

Carnitine levels were lower in type 2 diabetes group than control group (52.56 +/- 12.38 and 78.96 +/- 10.66 hmol/mL, respectively, p < 0.0001). Pulmonary functions were not significantly different between groups. Carnitine levels were not correlated with age, duration of diabetes, fasting blood glucose levels, and glycemic control (HbA1c%) in patients with type 2 diabetes. However, carnitine levels in patient group were correlated with % forced vital capacity (FVC%) (r = 0.35, p = 0.016), % forced expiratory volume in 1 s (FEV1%) (r = 0.318, p= 0.029), FEV1/FVC (r= 0.302, p= 0.039), inspiratory muscle strength (PImax) (r = 0.407, p = 0.023), and PImax% (r = 0.423, p= 0.018).

CONCLUSION

This study suggests that low carnitine levels may be associated with lower PImax and PImax% in type 2 diabetes.

Determination of free L-carnitine levels in type II diabetic women with and without complications

BACKGROUND

Studies on the determination of carnitine levels and nutritional status in patients of type II diabetes.

OBJECTIVE

We designed this study to determine changes of serum-free L-carnitine in type II diabetic women.

DESIGN

A cross-sectional study (case-control study).

SETTING

Clinical of Endocrinology and Metabolism, Sina Hospital, Pharmacological Research Center, Tabriz Medical university, Iran.

PATIENTS AND METHODS

Taking into account the importance of the control of diabetes, in the present case-control study, the levels of serum-free L-carnitine, blood glucose and lipids, systolic and diastolic blood pressure, body mass index (BMI) and nutritional status assessed in the case and control groups which were selected by the simple sampling method. The control group (n=18) included patients with no complications and the case group (n=33) was grouped into three subgroups including patients with retinopathy, hyperlipidemia and neuropathy.

RESULTS

Study results indicated that the mean serum-free L-carnitine concentration in the case group was significantly lower than its mean concentration level in the control group, 39.63+/-8.99 vs 53.42+/-0.93 micromol/l, respectively (P<0.001). Serum-free L-carnitine in retinopathy, hyperlipidemia and neuropathy case subgroups were 39.03+/-9.89, 39.63+/-8.99 and 40.44+/-12.50 micromol/l, respectively (P>0.05). No significant difference was found between the serum-free carnitine levels of the case subgroups. The mean blood glucose, triglycerides, total cholesterol, low-density lipoprotein cholesterol, very low-density lipoprotein cholesterol levels and systolic and diastolic blood pressure were significantly higher in the case group than in the control group.

CONCLUSION

In this study, the mean serum-free L-carnitine levels in diabetic patients with complications was almost 25% lower than in diabetic patients with no complications. On the basis of the study results, carnitine supplementation in diabetic patients, especially in patients with diabetes complications, might be useful.

Evidence for the association of the SLC22A4 and SLC22A5 genes with type 1 diabetes: a case control study

Background

Type 1 diabetes (T1D) is a chronic, autoimmune and multifactorial disease characterized by abnormal metabolism of carbohydrate and fat. Diminished carnitine plasma levels have been previously reported in T1D patients and carnitine increases the sensitivity of the cells to insulin. Polymorphisms in the carnitine transporters, encoded by the SLC22A4 and SLC22A5 genes, have been involved in susceptibility to two other autoimmune diseases, rheumatoid arthritis and Crohn's disease. For these reasons, we investigated for the first time the association with T1D of six single nucleotide polymorphisms (SNPs) mapping to these candidate genes: slc2F2, slc2F11, T306I, L503F, OCTN2-promoter and OCTN2-intron.

Methods

A case-control study was performed in the Spanish population with 295 T1D patients and 508 healthy control subjects. Maximum-likelihood haplotype frequencies were estimated by applying the Expectation-Maximization (EM) algorithm implemented by the Arlequin software.

Results

When independently analyzed, one of the tested polymorphisms in the SLC22A4 gene at 1672 showed significant association with T1D in our Spanish cohort. The overall comparison of the inferred haplotypes was significantly different between patients and controls (χ² = 10.43; p = 0.034) with one of the haplotypes showing a protective effect for T1D (rs3792876/rs1050152/rs2631367/rs274559, CCGA: OR = 0.62 (0.41–0.93); p = 0.02).

Conclusion

The haplotype distribution in the carnitine transporter locus seems to be significantly different between T1D patients and controls; however, additional studies in independent populations would allow to confirm the role of these genes in T1D risk.

Asymptomatic cardiomyopathy in children and adolescents with type 1 diabetes mellitus: association of echocardiographic indicators with duration of diabetes mellitus and metabolic parameters

This study was designed to determine the relationship of dimensions, wall thickness and function of the left ventricle with diabetes duration, fasting blood glucose, lipid profile, beta-OH-butyrate, free fatty acids (FFA) and carnitine levels in children and adolescents with type 1 diabetes mellitus (DM1) who had no cardiovascular complications. Thirty-five patients with DM1 (18 F/17 M, mean age: 12.0 years) and age matched control children (n = 24) were enrolled in the study. Patients with DM1 were subdivided into Group I (mean DM1 duration 3.5 years, n = 14), and Group II (mean DM1 duration 8.2 years, n = 21). Dimensions, wall thickness and systolic functions of the left ventricle were normal in all patients with DM1. Diastolic functions were normal in Group I. In Group II, peak A wave velocity (AVEL) (p = 0.004), velocity-time integral of A wave (AVTI) (p = 0.007) and isovolumetric relaxation time corrected by heart rate (cIVRT) (p = 0.048) were high, and peak E wave velocity (EVEL) and velocity-time integral of E wave (EVTI) were normal. E/A (p < 0.0001) and EVTI/AVTI (p = 0.001) were low in this group. In Group I, systolic and diastolic blood pressure, HDL-cholesterol and FFA values were normal; total cholesterol (p = 0.047), LDL-cholesterol (p = 0.017), beta-OH-butyrate (p = 0.003), and acetyl carnitine (p = 0.006) levels were high. In Group II, diastolic blood pressure (p = 0.008), total cholesterol (p < 0.0001) and LDL-cholesterol (p < 0.0001) were increased; and total carnitine (p = 0.019), free carnitine (p = 0.002) and HDL-cholesterol (p = 0.039) were decreased. Correlations were detected between total carnitine and AVEL and HR; free carnitine and AVEL, E/A and HR; HbA1c and EVTI/AVTI and cIVRT; LDL-cholesterol and E/A, EVTI/AVTI ratios and cIVRT; HDL-cholesterol and AVEL; FFA and LVDD, IVSD, LVPWD, LVmass and CO; metabolic parameters and DM1 duration and echocardiographic findings such as AVEL, EVEL, EVTI, VmaxAV and CO. In conclusion, left ventricular dimensions, wall thickness and systolic functions were normal in children and adolescents with DM1 who had no obvious cardiovascular complications. Left ventricular diastolic functions were abnormal in patients of Group II. Left ventricular diastolic function abnormalities were associated with glycemic control, free and total carnitine, and LDL- and HDL-cholesterol levels.

Carnitine deficiency in children and adolescents with type 1 diabetes

Carnitine is essential for the lipid and carbohydrate metabolism, and proper metabolic control in type 1 diabetes has potential impact on long-term complications. The plasma total, free, and acylcarnitine levels in 47 children and adolescents with type 1 diabetes were determined by a radioisotopic assay and compared to the values of a series of anthropometric measurements and metabolic parameters, including blood glycosylated hemoglobin Alc, serum cholesterol and triglycerides, and urine microalbumin levels. Plasma values for total, free, and acylcarnitine were 30.1+/-7.26, 20.0+/-4.50, and 10.2+/-6.47 micromol/l, respectively. Acyl/free carnitine ratio was 0.544+/-0.369. Individuals with type 1 diabetes had significantly lower total and free carnitine levels and significantly higher acyl/free carnitine ratios than controls (P<.001). Plasma total and free carnitine levels were inversely correlated to the duration of diabetes (P=.036 and P=.071, respectively). No statistical relationship was documented between carnitine levels and the remaining anthropometric and metabolic variables. In conclusion, total and free carnitine levels are decreased in children and adolescents with type 1 diabetes. This reduction is time related and may have potential interactions with the long-term complications of type 1 diabetes. Larger studies are required for final conclusions to be drawn on the precise role of carnitine and the possible benefit, if any, of carnitine supplementation in diabetic patients.

Acute gliclazide administration enhances glucose and ketone body utilization in the perfused hind limb of normal and streptozotocin-diabetic rats

Sulfonylureas are the most commonly used oral hypoglycemic agents. Their hypoglycemic actions are produced not only by stimulating insulin secretion but also by extrapancreatic mechanisms. Some groups have already demonstrated the extrapancreatic actions of sulfonylureas on carbohydrate metabolism in the liver, fat and muscle. In this study, we showed in an in situ perfused hind limb preparation of STZ-diabetic rats that gliclazide has an acute effect on ketone body and glucose utilization.

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.