After evaluating the prevalence of early endothelial dysfunction, as measured by means of reactive hyperemia in adolescents with type 1 diabetes, we started a 6-month, double-blind, randomized trial to test the efficacy of an antioxidant diet (± alpha-lipoic acid supplementation) to improve endothelial dysfunction. Seventy-one children and adolescents, ages 17 ± 3.9 yrs, with type 1 diabetes since 9.5 ± 5.3 yrs, using intensified insulin therapy, were randomized into 3 arms: (a) antioxidant diet 10.000 ORAC + alpha-lipoic acid; (b) antioxidant diet 10.000 ORAC + placebo; (c) controls. BMI, blood pressure, fasting lipid profile, HbA1c, insulin requirement, dietary habits, and body composition were determined in each patient. An antioxidant diet significantly improved endothelial dysfunction when supplemented with alpha-lipoic acid, unlike diet with placebo or controls. A significant reduction in bolus insulin was also observed. We speculate that alpha-lipoic acid might have an antioxidant effect in pediatric diabetes patients by reducing insulin.
Atherosclerosis and its vascular damage are the leading cause of mortality and morbidity in patients with diabetes. Recently, several studies have shown that cardiovascular diseases are the first cause of premature death among individuals with type 1 diabetes, demonstrating that although there have been substantial improvements in survival during the past 50 years, still challenges remain [
Although diabetes-related vascular complications are uncommon in the pediatric age, early functional and structural abnormalities may be present just a few years after the onset of type 1 diabetes [
A surrogate marker of cardiovascular disease is endothelial dysfunction [
In a previous study [
Endothelial cells have got numerous functions crucial for maintaining intravascular homeostasis: they play an important role in vascular tone regulation, hemostasis, and fibrinolysis and in the production of several substances [
Alpha-lipoic acid is a potent mitochondrial antioxidant agent that acts by multiple mechanisms promoting anti-inflammatory and antithrombotic pathways and positively influencing the nitric oxide mediated vasodilatation [
In most European countries alpha-lipoic acid is licensed and used as treatment in patients with neuropathic symptoms [
The hypothesis is that alpha-lipoic acid may improve the endothelial function. This hypothesis is based on similar results obtained either in animal models or in patients with diabetes mellitus, especially type 2 diabetes [
Therefore, the aim of our study was to investigate the effect of alpha-lipoic acid on endothelial dysfunction in youth with type 1 diabetes. This pilot study is a 6-month, double-blind, randomized controlled trial to test the efficacy of an antioxidant diet plus alpha-lipoic acid versus an antioxidant diet alone in improving endothelial dysfunction in adolescents with type 1 diabetes.
This study was a 6-month, prospective, randomized, double-blind, controlled trial conducted in pediatric patients with type 1 diabetes, performed at the Pediatric Department of the University of Milano. The trial was reviewed and approved by the “Luigi Sacco” Hospital Ethics Committee.
The trial was performed in accordance with the Declaration of Helsinki. Before any trial-related activities signed informed consent was obtained from all participants aged 16 years or older and from parents or guardians of participants aged younger than 16 years (assent was obtained from minors).
Patients with type 1 diabetes were referred for study participation from the outpatient clinic of the University of Milano between January 2013 and December 2013. Seventy-one patients who had been previously evaluated for the presence of endothelial dysfunction [
Inclusion criteria were type 1 diabetes (diabetes onset was defined according to ADA criteria), more than 1 year from diagnosis or confirmed C-peptide negative, age between 12 and 19 years, insulin requirement more than or equal to 0.5 U/kg/day, blood glucose checks more the 3 times per day, and insulin intensive therapy ongoing. Exclusion criteria were preexisting cardiovascular diseases or inflammatory systemic diseases, hypertension and prehypertension (BP ≥ 90th percentile for age, sex, and height), eating disorders, obesity (defined as BMI ≥ 95th percentile per age and sex in the 2000 CDC growth chart), celiac disease, inflammatory bowel disease or other significant gastrointestinal conditions, systemic glucocorticoid use (1-month cumulative use during last year) or ongoing treatment with glucocorticoid use, anemia, significant multiple food allergies, uncontrolled hypothyroidism or hyperthyroidism, significant mental illness, and pregnancy.
Clinical history and physical examination, nutritional records, and biochemical sample were collected at baseline, after 3 months, and after 6 months; endothelial dysfunction was evaluated at baseline and after 6 months.
Height was measured to the nearest centimeter using a rigid stadiometer. Weight was measured unclothed to the nearest 0.1 kg using a calibrated balance scale. Body mass index (BMI) was calculated for each patient. The pubertal developmental stage was determined according to Marshall and Tanner scale. Blood pressure was measured using a mercury sphygmomanometer, according to the National High Blood Pressure Education Program Working Group. Moreover, 24 h blood pressure was recorded in all patients.
All patients were in intensive insulin therapy, with either multiple daily injections or insulin pump therapy. Daily insulin requirement was calculated as total dose and as basal and bolus rates.
Blood sampling was performed in the fasting state at 8 a.m. Levels of lipids including triglycerides (TG), total cholesterol (TC), LDL-cholesterol, and HDL-cholesterol were evaluated in all subjects with standard laboratory methods.
Blood was drawn for HbA1c analysis using a fully automated high-performance liquid chromatography system (Variant II, Bio-Rad Laboratories, Munich, Germany).
At baseline and 3 and 6 months a nutritional visit was performed by the registered dietitian of the Pediatric Department of the “Luigi Sacco” Hospital. Three-day dietary records with nutrition data were evaluated using dedicated software (Metadieta, MeTeDa, San Benedetto del Tronto, AP, Italy). Data on dietary intake, reporting the types and amounts of all food and beverages consumed, with data on insulin doses and algorithms used at home, blood glucose results, and physical activity were collected. During the study period a dietary recall was collected every month; moreover a nutritional assessment was performed at 3 and 6 months to check the patients’ compliance to the dietary plan assigned.
Moreover, registered dietitian evaluated the body composition using Tanita BC-418, IL, USA.
Peripheral endothelium-dependent vasodilator capacity was estimated by assessing the RHI by means of the EndoPAT 2000 system (Itamar Medical Ltd., Caesarea, Israel) [
After the clinical assessment at baseline, each patient was randomly assigned to one of the three double-blind, study arms: 10.000 oxygen radical absorbance capacity units (ORAC) antioxidant diet plus alpha-lipoic acid (
Supplementation with 400 mg of slow-release alpha-lipoic acid or placebo, both in a lyophilized formulation, was furnished by the RA of the Pediatric Department. Patients were advised to melt the lyophilized solution in a glass of water and to get it twice a day at least 1 hour before lunch and dinner, for 6 months. The compliance with the antioxidant diet was monitored by monthly dietary recalls and a full nutritional assessment was repeated, after 3 and 6 months.
Both patients treated with antioxidant diet plus alpha-lipoic acid (
A similar dietary plan was assigned to patients enrolled in the control group (
Prior to data analysis, all metric variables were checked for normality by using Shapiro-Wilk test. Data were normally distributed. We used unpaired
All the 71 patients enrolled completed the 6-month study period and no one dropped out of study before completing it. Moreover no severe side effects have been reported by either alpha-lipoic acid group or placebo. Either severe hypoglycemic events or DKA episodes occurred during the 6-month study. Three patients of the alpha-lipoic acid group and 2 patients of the control group reported mild abdominal pain over the first 4 weeks of the study, with no need to withdraw from the study.
Baseline and 6-month clinical characteristics are summarized in Table
Clinical characteristics of the three study groups at baseline and after 3 and 6 months of follow-up.
Group 1 |
Group 2 |
Group 3 |
All |
| |
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Sex (M/F) | 15/10 | 16/11 | 11/8 | 42/29 | 0.699 |
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Age (years) | 16.1 ± 3.1 | 16.0 ± 3.4 | 16.5 ± 4.3 | 16.3 ± 3.4 | 0.916 |
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Diabetes duration (years) | 7.7 ± 4.9 | 8.2 ± 5.6 | 8.8 ± 5.7 | 8.1 ± 5.2 | 0.743 |
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BMI (kg/m2) | 21 ± 2 | 22 ± 3 | 21 ± 3 | 21 ± 3 | 0.911 |
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Insulin requirement (U/kg/day) | 0.83 ± 0.26 | 0.85 ± 0.31 | 0.77 ± 0.33 | 0.83 ± 0.29 | 0.775 |
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Insulin requirement (U/kg/day) after 3 months | 0.74 ± 0.18 |
0.86 ± 0.27 | 0.86 ± 0.19 | 0.82 ± 0.21 | 0.211 |
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Insulin requirement (U/kg/day) after 6 months | 0.85 ± 0.30 |
0.83 ± 0.29 | 0.89 ± 0.19 | 0.86 ± 0.26 | 0.887 |
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Basal dose (U/day - %) | 25.5 ± 8.6 |
25.4 ± 7.6 |
28.4 ± 12.2 |
26.4 ± 9.5 |
0.733 |
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Basal dose (U/day - %) |
25.9 ± 9.4 |
25.4 ± 8.0 |
29.4 ± 10.7 |
27.0 ± 9.4 |
0.513 |
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Basal dose (U/day - %) |
25.8 ± 9.4 |
25.6 ± 8.3 |
29.6 ± 11.3 |
27.2 ± 9.7 |
0.513 |
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Bolus dose (U/day - %) | 26.3 ± 10.8 |
25.6 ± 13.2 |
24.4 ± 9.0 |
25.4 ± 11.0 |
0.916 |
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Bolus dose (U/day - %) |
22.0 ± 9.4 |
25.8 ± 11.9 |
25.9 ± 6.4 |
24.6 ± 9.2 |
0.401 |
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Bolus dose (U/day - %) |
25.9 ± 13.3 |
24.1 ± 12.4 |
25.9 ± 6.1 |
25.3 ± 10.6 |
0.864 |
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HbA1c (%) | 7.97 ± 1.19 | 7.96 ± 1.04 | 7.91 ± 0.76 | 7.96 ± 1.04 | 0.856 |
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Reactive hyperemia index | 1.40 ± 0.68 | 1.39 ± 0.41 | 1.58 ± 0.64 | 1.47 ± 0.59 | 0.349 |
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Reactive hyperemia index |
1.72 ± 0.66 |
1.58 ± 0.40 | 1.54 ± 0.42 | 1.62 ± 0.51 |
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ORAC in the diet | 8872,43 ± 5378,22 | 9771,96 ± 6266,26 | 9503,25 ± 9973,67 | 9382,55 ± 7206,05 | 0.638 |
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ORAC in the diet at 3 months | 11844,09 ± 5603,01 | 12874,04 ± 7165,52 | 8489,71 ± 6946,57 | 11069,28 ± 6571,53 |
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ORAC in the diet at 6 months | 12518,70 ± 5908,64 | 15496,83 ± 6897,98 | 11306,83 ± 11737,31 | 13107,45 ± 8181,31 | 0.098 |
BMI = body mass index; HbA1c = glycosylated hemoglobin; ORAC = oxygen radical absorbance capacity.
These results are supported by data collected during the nutritional assessment. Indeed, dietary recall to evaluate patients’ compliance to the dietary plan showed a significant increase of ORAC intake at month 3 in both arms (treatment and placebo) but not in controls. After 6 months, ORAC consumption decreased in the treatment group but not in the placebo group, as reported in Table
Endothelial dysfunction was tested as RHI score in all groups at baseline and after 6 months.
As described in a previous study [
Endothelial function as RH-PAT score at baseline (■) and after 6-month follow-up (□); dotted line represents the normal value for the test.
The analyses performed on the other clinical parameters collected showed no differences at baseline and after 3 and 6 months among the three groups: BMI, 24 h blood pressure, lipid profile, HbA1c, dietary habits, and body composition resulted any different among the three groups and over the study period.
To the best of our knowledge, this is the first study analyzing the effects of a dietary supplementation in improving the endothelial dysfunction in youth with type 1 diabetes.
In this randomized, placebo controlled double-blind trial, we found a relationship between the consumption of an antioxidant diet plus alpha-lipoic acid and the improvement in endothelial dysfunction in youth with type 1 diabetes. In particular an antioxidant diet (10000 ORAC) plus alpha-lipoic acid (800 mg/day) seems to be effective in reducing insulin requirement and daily bolus rate after 3 months and in improving endothelial dysfunction after 6 months.
The efficacy of alpha-lipoic acid in improving glucose disposal has been previously described in animal models [
In our small study, a supplementation with 800 mg/day of alpha-lipoic acid for 3 months effectively resulted in reducing insulin requirement. The mechanisms of action are not completely clear, since, in our knowledge, studies having pediatric type 1 diabetes patients as target are lacking. However, as reported for type 2 diabetes, we hypothesize that alpha-lipoic acid can use nicotinamide adenine dinucleotide molecules (NADH) for the reduction to dihydrolipoic acid, resulting in an increased ratio of nicotinamide adenine dinucleotide (NAD+) to NADH and thus stimulating the glycolysis pathway [
In our study the alpha-lipoic beneficial effect on insulin requirement and thus on glucose uptake is reported at 3 months but it is not confirmed at 6 months. In our opinion this can be explained by a decreased compliance to the dietary supplementation, as confirmed by dietary recall and by data collected during the nutritional assessments.
We also demonstrated for the very first time the power of alpha-lipoic acid in improving endothelial dysfunction in youths with type 1 diabetes. In our cohort of patients, the prevalence of endothelial dysfunction is largely represented, despite the pediatric age and the quite good metabolic control [
Thus, during the last decades, many studies have been conducted to investigate the role of inflammation in diabetes onset and in diabetes-related complications. The opportunity for an early detection of endothelial dysfunction can lead to new insights into the very first steps of the cardiovascular complications. Indeed, endothelial cells play a wide spectrum of different functions, as regulating coagulation, leukocyte adhesion, and trafficking, modifying the tone of the vessel, and participating in the smooth-muscle growth [
Alpha-lipoic acid is reported to be effective in most of these reactions, getting the role of antioxidant, anti-inflammatory molecule. Indeed, although it is well defined as a therapy for preventing diabetic polyneuropathies and it is used in the management of diabetic peripheral neuropathy in both patients with type 1 and type 2 diabetes, alpha-lipoic acid has many biochemical functions. It acts as metal chelator, as scavenger of free radicals, and as reducer of the oxidized forms of other antioxidant agents such as vitamins C and E and it regulates several signal transductions [
Supported by this evidence, we can speculate that a 6-month supplementation with alpha-lipoic acid 800 mg/day can positively impact endothelial dysfunction, decreasing oxidative stress and inflammation in type 1 diabetes, even in pediatrics.
Despite this, these data must be carefully weighed against the lack of consensus regarding the most appropriate supplementation method for alpha-lipoic acid, dosage, and treatment duration.
However, in a paper recently published a 3-month treatment with 600 mg of alpha-lipoic acid was demonstrated to provide significant beneficial changes in VEGF, bFGF, MCO-1, and IL-10 serum levels in type 2 diabetic patients, confirming the efficacy of low-period treatment on endothelial outcomes [
The strength of our study is the evidence for the first time of a positive association between alpha-lipoic administration and decreased endothelial dysfunction in pediatric patients with type 1 diabetes. Nevertheless the trial has some limitations, and we strongly advise a larger sample and a long-term follow-up to confirm these results. Moreover, the effects of alpha-lipoic acid on glycemic control need to be investigated as well, both as glycemic variability and hypo- and hyperglycemic events.
The authors declare that there is no conflict of interests regarding the publication of this paper.
Andrea Scaramuzza conceived the study, collected data, wrote the paper, contributed to discussion, and is the guarantor of the study; Elisa Giani contributed to analyzing of data, writing of the paper, and discussion; Francesca Redaelli, Saverio Ungheri, and Matteo Ferrari collected data and contributed to discussion; Alessandra Bosetti supervised diet, collected data regarding diet composition, and contributed to discussion; Gian Vincenzo Zuccotti contributed to discussion and reviewing of the paper.
The authors want to thank all patients participating in the trial. They also would like to thank Laborest S.p.A., Italy, for providing both alpha-lipoic acid and placebo free of charge.