Acta Neurol Scand DOI: 10.1111/ane.12313
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd ACTA NEUROLOGICA SCANDINAVICA
Insulin resistance in patients on valproic acid: relation to adiponectin Aly RH, Amr NH, Saad WE, Megahed AA. Insulin resistance in patients on valproic acid: relation to adiponectin. Acta Neurol Scand: DOI: 10.1111/ane.12313. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd. Objectives – To investigate the presence of insulin resistance in obese children with idiopathic epilepsy on valproic acid (VPA) monotherapy in comparison to obese otherwise healthy subjects. Secondary outcome was to explore the relation between adiponectin and insulin resistance among those patients. Materials and Methods – Fifty obese children with generalized idiopathic epilepsy on VPA monotherapy and a control group of 49 obese clinically healthy age and sexmatched children with simple obesity were recruited in the study. Anthropometric assessment, fasting plasma insulin (FI), fasting glucose (FG) and fasting adiponectin levels were measured. Fasting glucose insulin ratio (FGIR) and homoeostasis model assessment for insulin resistance (HOMA-IR) were calculated for both patients and control subjects. Measurement of serum VPA trough level was also performed in patients. Results – Patients had significantly higher fasting blood glucose, fasting insulin, lower FGIR and higher HOMA-IR values, compared to controls. Mean adiponectin level was significantly lower in patients compared to controls. The duration of treatment with valproic acid negatively correlated with adiponectin (r = 0.285, P = 0.045), but did not correlate with fasting glucose, insulin, FGIR or HOMA-IR. Total daily VPA dose significantly correlated with fasting insulin (r = 0.495, P < 0.001), FGIR (r = 0.525, P < 0.001) and HOMA-IR (r = 0.404, P = 0.004). Conclusion – This study ascertains the relationship between dose and duration of VPA therapy, insulin resistance and the adipocytokine axis. We are reporting the novel proposal that obese VPA-treated children are more insulin resistant and have lower adiponectin levels than obese and otherwise healthy children.
Introduction
Valproic acid is one of the most commonly used anti-epileptic drugs (1). Its use has been found to be associated with increase in body weight (2) and glucose-stimulated insulin secretion (3). Rates of valproic acid-associated obesity vary from 16% up to 71% among its users (4–6). High insulin levels have been observed in both lean and obese patients taking valproic acid, suggesting the role of factors others than excess adiposity in the pathogenesis of insulin resistance (7). Adiponectin is an adipocytokine secreted by adipose tissue and is described as a link between
R. H. Aly1, N. H. Amr1, W. E. Saad2, A. A. Megahed1 1 Department of Paediatrics, Faculty of Medicine, Ain Shams University, Cairo, Egypt; 2Department of Clinical Pathology, Faculty of Medicine, Ain Shams University, Cairo, Egypt
Key words: epilepsy; valproic acid; insulin resistance; adiponectin R. H. Aly, Department of Paediatrics, Ain Shams University, 2 El Sobky Street, Heliopolis, Cairo, Egypt Tel.: +20 12 23220859 Fax: +202 37600250 e-mail: [email protected] Accepted for publication August 27, 2014
glucose and lipid metabolism (8). Its levels correlate negatively with body weight, insulin resistance, cardiovascular risk factors and the metabolic syndrome (9, 10). In adult patients, valproate therapy was associated with lower adiponectin concentrations and weight gain (11). The interaction between valproic acid therapy, insulin resistance, weight gain and adiponectin remains unclear. The aim of this study was to investigate the presence of insulin resistance in obese children with idiopathic epilepsy on valproic acid monotherapy in comparison with obese otherwise healthy subject. Secondary outcome was to explore the relation between adiponectin and insulin resistance among those patients. 1
Aly et al. Materials and methods
Fifty obese children with primary genetic epilepsy following up in the Paediatric Neurology Clinic of Ain-Shams University Hospital were recruited in this cross-sectional study during the period from 1 April 2013 to 29 January 2014. Diagnosis of epilepsy and seizure type was established according to the guidelines of the International League Against Epilepsy (12). All patients had electro-encephalographic findings consistent with generalized epilepsy. All patients were receiving valproic acid (VPA) monotherapy. Patients were included if they were obese, on VPA therapy for at least 12 months, and the current dose was unchanged for at least 3 months prior to recruitment. Obesity was defined as body mass index (BMI) >95th percentile for age and sex (13). Exclusion criteria included patients with chronic diseases, patients with diseases known to affect adipokines such as diabetes, patients with neurological diseases other than epilepsy, genetic syndromes and patients on any other regular medication. Non-compliant patients were excluded from the study. A control group of 49 clinically healthy age and sexmatched children with simple obesity agreed to participate in the study. The control group was recruited from new patients attending the Pediatric Obesity Clinic of Ain-Shams University Hospital. The study protocol was approved by the local ethics committee of Ain-Shams University, and legal guardians signed an informed consent prior to the study. Clinical assessment
Clinical records of patients were reviewed to record the age of onset of epilepsy, duration of epilepsy and frequency of seizures in the last 6 months. Detailed neurological history was taken for the included patients with special emphasis on the history of the epilepsy disorder and therapeutic history. The severity of the seizure was rated according to Chalfont seizure severity scale (14). The therapeutic history was reviewed to check compliance and valproic acid dosage details. Total valproic acid dose in milligrams per day was calculated. All patients were given valproic acid preparation at a dose ranging between 10 and 60 mg/kg/day. None of the patients or the controls was enrolled in a structured weight-losing program. None of the patients had abnormal neurological findings on examination or abnormal neuroimaging studies. All patients had normal blood 2
count, serum electrolytes and liver and kidney function tests. Anthropometric assessment
Standing height was measured without shoes, to the nearest 0.1 cm, using Harpenden stadiometer (Holtain Ltd, Croswell, Crymych, UK), and weight was measured using a digital scale, to the nearest 0.1 kg, wearing light clothing and without shoes. Body mass index (BMI) was calculated using the formula kg/m2. Standard deviation scores (SDS) for weight, height and BMI were calculated (13, 15). Waist and hip circumferences were measured using a flexible tape to the nearest 0.1 cm. Waist circumference (WC) was measured at the end of expiration midway between the lower rib margin and the iliac crest (16), and standard deviation scores for WC were estimated (17). All measurements were taken twice. Laboratory assessment
After 12-h overnight fast, a venous blood sample was withdrawn and analysed for estimation of fasting plasma insulin (FI) and fasting glucose (FG). Blood glucose was measured with the glucose oxidase method (Glucose & Lactate Analyzer 2300 Stat Plus; Yellow Springs Instruments, Yellow Springs, OH, USA). Insulin was determined by commercially available chemiluminescent micro particle immunoassay kit (ARCHITECT system; Abbott Diagnostics, Irving, Texas, USA). Fasting glucose–insulin ratio was calculated by dividing fasting glucose by fasting insulin values. A ratio 2.7 (18). Measurement of adiponectin
Fasting venous blood samples were centrifuged and stored at 20°C. Serum adiponectin was measured by ELISA (AviBion, human adiponectin, Acrp30, Vantaa, Finland). Measurement of serum VPA trough level
VPA was assayed using fluorescence polarization immunoassay technology using TDxFLx system (Kit supplied by ABOTT laboratories, Irving,
Insulin resistance in epilepsy Texas, USA). The therapeutic range 50–100 lg/ ml was taken to suggest the therapeutic range of serum VPA. Statistical analysis
IBM SPSS statistics (version 22.0. Armonk, NY, USA: IBM Corp. 2013) was used for data analysis. Data is expressed as mean (SD) for quantitative parametric measures in addition to median percentiles for quantitative nonparametric measures and both number and percentage for categorized data. Student’s t-test was used for comparison between two independent mean groups for parametric data, Wilcoxon Rank Sum test for two independent groups for nonparametric data, ranked Spearman correlation test to study the possible association between each two variables among each group for nonparametric data. The probability of error at 0.05 was considered significant while at 0.01 and 0.001 were highly significant. Results
The mean (SD) age of patients was 8.2 (2.6), ranging between 4.95 and 15.61 years. They were 26 (52%) males and 24 (48%) females. The control group comprised 49 children; 26 males (53%) and 23 (47%) females, mean (SD) age 8.3 (2.5) years, ranging between 5.34 and 14.17 years. The mean (SD) age of onset of the epilepsy disorder was 54.7 (35.2) months. Mean (SD) disease duration was 47.2 (29) months. The mean (SD) seizure frequency in the last 6 months was 14(28.8) episodes and the mean (SD) seizure severity score in the last 6 months was 47.9 (39.2). EEG recordings of all patients showed different types of generalized epileptogenic activities. Table 1 shows the clinical and therapeutic characteristics of patients. Patients had significantly higher fasting blood glucose (P = 0.003), fasting insulin (P < 0.001),
lower FGIR (P < 0.001) and higher HOMA-IR values (P < 0.008), compared to controls. The mean HOMA-IR in patients exceeded the cut-off level for insulin resistance (Table 2). Twenty patients (40%) had FGIR below the cut-off level for insulin resistance and 39 (78%) had HOMAIR above the cut-off level for insulin resistance. Mean adiponectin level was significantly lower in patients compared to controls (1.3 (0.5) vs 2.2 (1), P < 0.001) (Table 2). The mean (SD) duration of treatment with VPA was 32.5 (13.6) months and the mean (SD) total VPA dose per day was 704.7 (296.8) mg (Table 1). The duration of treatment with valproic acid negatively correlated with adiponectin (r = 0.285, P = 0.045), but did not correlate with fasting glucose, insulin, FGIR or HPMA-IR (Fig. 1, Table 3). Both serum VPA and total daily valproic acid dose did not significantly correlate with adiponectin, although the correlation was positive with serum VPA and negative with total daily VPA dose, respectively (r = 0.174, P = 0.228 and r = 0.187, P = 0.194) (Table 3). Total daily VPA dose significantly correlated with fasting insulin (r = 0.495, P < 0.001), FGIR (r = 0.525, P < 0.001), and HOMA-IR (r = 0.404, P = 0.004) (Fig. 2). Total daily VPA dose further significantly correlated with duration of treatment (r = 0.368, P = 0.009). Adiponectin negatively correlated with weight SDS in patients (r = 0.351, P = 0.012), waist circumference SDS (r = 0.562, P < 0.001) and height SDS (r = 0.309, P = 0.029). The correlation with BMI SDS was negative but did not reach statistical significance (r = 0.195, P = 0.174). Adiponectin did not correlate significantly with fasting glucose (r = 0.124, P = 0.392),
Table 2 Comparison between cases and controls Cases (n = 50)
Table 1 Clinical and therapeutic characteristics of patients Mean (SD) Age of epilepsy onset (mo) Epilepsy duration (mo) Seizure frequency* Chalfont severity score SVPA (lg/ml) Rx duration (mo) Total VPA dose (mg/d)
54.7 47.2 14 47.9 79.7 32.5 704.7
(35.2) (29) (28.8) (39.2) (21.1) (13.6) (296.8)
Minimum–Maximum 9–159 12–132 0–180 0–104 29–113 11–50 280.6–1499.3
*In last 6 months. Mo, months; SVPA, serum valproic acid; Rx duration, duration of therapy; VPA, valproic acid; d, day.
Age (years) Height SDS Weight SDS BMI SDS Waist SDS Fasting glucose (mg/dl) Fasting insulin (lU/ml) FGIR HOMA-IR Adiponectin (lg/ml)
8.2 0.3 2.1 3 1.9 93.1 16.4 6.7 3.7 1.3
(2.6) (0.8) (0.8) (0.7) (1.2) (7.7) (6.2) (3.1) (1.4) (0.5)
Controls (n = 49) 8.3 0.2 2.4 2.9 2.1 87.3 11.9 8.9 2.5 2.2
(2.5) (0.7) (0.8) (0.7) (1.2) (11.3) (5) (4.4) (1) (1)
P value 0.624 0.002 0.09 0.836 0.554 0.003
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd ACTA NEUROLOGICA SCANDINAVICA
Insulin resistance in patients on valproic acid: relation to adiponectin Aly RH, Amr NH, Saad WE, Megahed AA. Insulin resistance in patients on valproic acid: relation to adiponectin. Acta Neurol Scand: DOI: 10.1111/ane.12313. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd. Objectives – To investigate the presence of insulin resistance in obese children with idiopathic epilepsy on valproic acid (VPA) monotherapy in comparison to obese otherwise healthy subjects. Secondary outcome was to explore the relation between adiponectin and insulin resistance among those patients. Materials and Methods – Fifty obese children with generalized idiopathic epilepsy on VPA monotherapy and a control group of 49 obese clinically healthy age and sexmatched children with simple obesity were recruited in the study. Anthropometric assessment, fasting plasma insulin (FI), fasting glucose (FG) and fasting adiponectin levels were measured. Fasting glucose insulin ratio (FGIR) and homoeostasis model assessment for insulin resistance (HOMA-IR) were calculated for both patients and control subjects. Measurement of serum VPA trough level was also performed in patients. Results – Patients had significantly higher fasting blood glucose, fasting insulin, lower FGIR and higher HOMA-IR values, compared to controls. Mean adiponectin level was significantly lower in patients compared to controls. The duration of treatment with valproic acid negatively correlated with adiponectin (r = 0.285, P = 0.045), but did not correlate with fasting glucose, insulin, FGIR or HOMA-IR. Total daily VPA dose significantly correlated with fasting insulin (r = 0.495, P < 0.001), FGIR (r = 0.525, P < 0.001) and HOMA-IR (r = 0.404, P = 0.004). Conclusion – This study ascertains the relationship between dose and duration of VPA therapy, insulin resistance and the adipocytokine axis. We are reporting the novel proposal that obese VPA-treated children are more insulin resistant and have lower adiponectin levels than obese and otherwise healthy children.
Introduction
Valproic acid is one of the most commonly used anti-epileptic drugs (1). Its use has been found to be associated with increase in body weight (2) and glucose-stimulated insulin secretion (3). Rates of valproic acid-associated obesity vary from 16% up to 71% among its users (4–6). High insulin levels have been observed in both lean and obese patients taking valproic acid, suggesting the role of factors others than excess adiposity in the pathogenesis of insulin resistance (7). Adiponectin is an adipocytokine secreted by adipose tissue and is described as a link between
R. H. Aly1, N. H. Amr1, W. E. Saad2, A. A. Megahed1 1 Department of Paediatrics, Faculty of Medicine, Ain Shams University, Cairo, Egypt; 2Department of Clinical Pathology, Faculty of Medicine, Ain Shams University, Cairo, Egypt
Key words: epilepsy; valproic acid; insulin resistance; adiponectin R. H. Aly, Department of Paediatrics, Ain Shams University, 2 El Sobky Street, Heliopolis, Cairo, Egypt Tel.: +20 12 23220859 Fax: +202 37600250 e-mail: [email protected] Accepted for publication August 27, 2014
glucose and lipid metabolism (8). Its levels correlate negatively with body weight, insulin resistance, cardiovascular risk factors and the metabolic syndrome (9, 10). In adult patients, valproate therapy was associated with lower adiponectin concentrations and weight gain (11). The interaction between valproic acid therapy, insulin resistance, weight gain and adiponectin remains unclear. The aim of this study was to investigate the presence of insulin resistance in obese children with idiopathic epilepsy on valproic acid monotherapy in comparison with obese otherwise healthy subject. Secondary outcome was to explore the relation between adiponectin and insulin resistance among those patients. 1
Aly et al. Materials and methods
Fifty obese children with primary genetic epilepsy following up in the Paediatric Neurology Clinic of Ain-Shams University Hospital were recruited in this cross-sectional study during the period from 1 April 2013 to 29 January 2014. Diagnosis of epilepsy and seizure type was established according to the guidelines of the International League Against Epilepsy (12). All patients had electro-encephalographic findings consistent with generalized epilepsy. All patients were receiving valproic acid (VPA) monotherapy. Patients were included if they were obese, on VPA therapy for at least 12 months, and the current dose was unchanged for at least 3 months prior to recruitment. Obesity was defined as body mass index (BMI) >95th percentile for age and sex (13). Exclusion criteria included patients with chronic diseases, patients with diseases known to affect adipokines such as diabetes, patients with neurological diseases other than epilepsy, genetic syndromes and patients on any other regular medication. Non-compliant patients were excluded from the study. A control group of 49 clinically healthy age and sexmatched children with simple obesity agreed to participate in the study. The control group was recruited from new patients attending the Pediatric Obesity Clinic of Ain-Shams University Hospital. The study protocol was approved by the local ethics committee of Ain-Shams University, and legal guardians signed an informed consent prior to the study. Clinical assessment
Clinical records of patients were reviewed to record the age of onset of epilepsy, duration of epilepsy and frequency of seizures in the last 6 months. Detailed neurological history was taken for the included patients with special emphasis on the history of the epilepsy disorder and therapeutic history. The severity of the seizure was rated according to Chalfont seizure severity scale (14). The therapeutic history was reviewed to check compliance and valproic acid dosage details. Total valproic acid dose in milligrams per day was calculated. All patients were given valproic acid preparation at a dose ranging between 10 and 60 mg/kg/day. None of the patients or the controls was enrolled in a structured weight-losing program. None of the patients had abnormal neurological findings on examination or abnormal neuroimaging studies. All patients had normal blood 2
count, serum electrolytes and liver and kidney function tests. Anthropometric assessment
Standing height was measured without shoes, to the nearest 0.1 cm, using Harpenden stadiometer (Holtain Ltd, Croswell, Crymych, UK), and weight was measured using a digital scale, to the nearest 0.1 kg, wearing light clothing and without shoes. Body mass index (BMI) was calculated using the formula kg/m2. Standard deviation scores (SDS) for weight, height and BMI were calculated (13, 15). Waist and hip circumferences were measured using a flexible tape to the nearest 0.1 cm. Waist circumference (WC) was measured at the end of expiration midway between the lower rib margin and the iliac crest (16), and standard deviation scores for WC were estimated (17). All measurements were taken twice. Laboratory assessment
After 12-h overnight fast, a venous blood sample was withdrawn and analysed for estimation of fasting plasma insulin (FI) and fasting glucose (FG). Blood glucose was measured with the glucose oxidase method (Glucose & Lactate Analyzer 2300 Stat Plus; Yellow Springs Instruments, Yellow Springs, OH, USA). Insulin was determined by commercially available chemiluminescent micro particle immunoassay kit (ARCHITECT system; Abbott Diagnostics, Irving, Texas, USA). Fasting glucose–insulin ratio was calculated by dividing fasting glucose by fasting insulin values. A ratio 2.7 (18). Measurement of adiponectin
Fasting venous blood samples were centrifuged and stored at 20°C. Serum adiponectin was measured by ELISA (AviBion, human adiponectin, Acrp30, Vantaa, Finland). Measurement of serum VPA trough level
VPA was assayed using fluorescence polarization immunoassay technology using TDxFLx system (Kit supplied by ABOTT laboratories, Irving,
Insulin resistance in epilepsy Texas, USA). The therapeutic range 50–100 lg/ ml was taken to suggest the therapeutic range of serum VPA. Statistical analysis
IBM SPSS statistics (version 22.0. Armonk, NY, USA: IBM Corp. 2013) was used for data analysis. Data is expressed as mean (SD) for quantitative parametric measures in addition to median percentiles for quantitative nonparametric measures and both number and percentage for categorized data. Student’s t-test was used for comparison between two independent mean groups for parametric data, Wilcoxon Rank Sum test for two independent groups for nonparametric data, ranked Spearman correlation test to study the possible association between each two variables among each group for nonparametric data. The probability of error at 0.05 was considered significant while at 0.01 and 0.001 were highly significant. Results
The mean (SD) age of patients was 8.2 (2.6), ranging between 4.95 and 15.61 years. They were 26 (52%) males and 24 (48%) females. The control group comprised 49 children; 26 males (53%) and 23 (47%) females, mean (SD) age 8.3 (2.5) years, ranging between 5.34 and 14.17 years. The mean (SD) age of onset of the epilepsy disorder was 54.7 (35.2) months. Mean (SD) disease duration was 47.2 (29) months. The mean (SD) seizure frequency in the last 6 months was 14(28.8) episodes and the mean (SD) seizure severity score in the last 6 months was 47.9 (39.2). EEG recordings of all patients showed different types of generalized epileptogenic activities. Table 1 shows the clinical and therapeutic characteristics of patients. Patients had significantly higher fasting blood glucose (P = 0.003), fasting insulin (P < 0.001),
lower FGIR (P < 0.001) and higher HOMA-IR values (P < 0.008), compared to controls. The mean HOMA-IR in patients exceeded the cut-off level for insulin resistance (Table 2). Twenty patients (40%) had FGIR below the cut-off level for insulin resistance and 39 (78%) had HOMAIR above the cut-off level for insulin resistance. Mean adiponectin level was significantly lower in patients compared to controls (1.3 (0.5) vs 2.2 (1), P < 0.001) (Table 2). The mean (SD) duration of treatment with VPA was 32.5 (13.6) months and the mean (SD) total VPA dose per day was 704.7 (296.8) mg (Table 1). The duration of treatment with valproic acid negatively correlated with adiponectin (r = 0.285, P = 0.045), but did not correlate with fasting glucose, insulin, FGIR or HPMA-IR (Fig. 1, Table 3). Both serum VPA and total daily valproic acid dose did not significantly correlate with adiponectin, although the correlation was positive with serum VPA and negative with total daily VPA dose, respectively (r = 0.174, P = 0.228 and r = 0.187, P = 0.194) (Table 3). Total daily VPA dose significantly correlated with fasting insulin (r = 0.495, P < 0.001), FGIR (r = 0.525, P < 0.001), and HOMA-IR (r = 0.404, P = 0.004) (Fig. 2). Total daily VPA dose further significantly correlated with duration of treatment (r = 0.368, P = 0.009). Adiponectin negatively correlated with weight SDS in patients (r = 0.351, P = 0.012), waist circumference SDS (r = 0.562, P < 0.001) and height SDS (r = 0.309, P = 0.029). The correlation with BMI SDS was negative but did not reach statistical significance (r = 0.195, P = 0.174). Adiponectin did not correlate significantly with fasting glucose (r = 0.124, P = 0.392),
Table 2 Comparison between cases and controls Cases (n = 50)
Table 1 Clinical and therapeutic characteristics of patients Mean (SD) Age of epilepsy onset (mo) Epilepsy duration (mo) Seizure frequency* Chalfont severity score SVPA (lg/ml) Rx duration (mo) Total VPA dose (mg/d)
54.7 47.2 14 47.9 79.7 32.5 704.7
(35.2) (29) (28.8) (39.2) (21.1) (13.6) (296.8)
Minimum–Maximum 9–159 12–132 0–180 0–104 29–113 11–50 280.6–1499.3
*In last 6 months. Mo, months; SVPA, serum valproic acid; Rx duration, duration of therapy; VPA, valproic acid; d, day.
Age (years) Height SDS Weight SDS BMI SDS Waist SDS Fasting glucose (mg/dl) Fasting insulin (lU/ml) FGIR HOMA-IR Adiponectin (lg/ml)
8.2 0.3 2.1 3 1.9 93.1 16.4 6.7 3.7 1.3
(2.6) (0.8) (0.8) (0.7) (1.2) (7.7) (6.2) (3.1) (1.4) (0.5)
Controls (n = 49) 8.3 0.2 2.4 2.9 2.1 87.3 11.9 8.9 2.5 2.2
(2.5) (0.7) (0.8) (0.7) (1.2) (11.3) (5) (4.4) (1) (1)
P value 0.624 0.002 0.09 0.836 0.554 0.003
