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G polymorphism of the leptin gene and olanzapine-induced weight gain
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Progress in Neuro-Psychopharmacology & Biological Psychiatry 32 (2008) 160 – 163 www.elsevier.com/locate/pnpbp
Possible association between the −2548A/G polymorphism of the leptin gene and olanzapine-induced weight gain Seung-Gul Kang a , Heon-Jeong Lee a,b,⁎, Young-Min Park c , Jung-Eun Choi a,b , Changsu Han a , Yong-Ku Kim a , Seung-Hyun Kim a , Min-Soo Lee a , Sook-Haeng Joe a , In-Kwa Jung a , Leen Kim a b
a Department of Psychiatry, Korea University College of Medicine, Seoul, South Korea Division of Brain Korea 21 Biomedical Science, Korea University College of Medicine, Seoul, South Korea c Department of Psychiatry, Inje University College of Medicine, Goyang City, Gyeonggi-do, South Korea
Received 6 April 2007; received in revised form 6 August 2007; accepted 6 August 2007 Available online 14 August 2007
Abstract Antipsychotic-induced weight gain has important effects on treatment compliance and long-term health. Several reports have indicated that a −2548A/G single-nucleotide polymorphism (SNP) of the leptin gene is associated with antipsychotic-induced weight gain. We hypothesized that there is a similar relationship between the −2548A/G SNP and olanzapine-induced weight gain. A total of 74 Korean schizophrenic patients were examined. Their weight was measured before starting olanzapine and after long-term treatment lasting for at least 3 months. The weight gain was significantly higher for patients with the AG genotype than for those with the AA genotype ( p = 0.029). Analysis of covariance also showed the difference of weight gain was still significant when adjusted for sex and treatment duration ( p = 0.046). This finding supports the presence of a relationship between the − 2548A/G SNP of the leptin gene and weight gain in Korean schizophrenic patients receiving olanzapine treatment. © 2007 Elsevier Inc. All rights reserved. Keywords: Leptin gene; Olanzapine; Polymorphism; Schizophrenia; Weight gain
1. Introduction Atypical antipsychotics are favored among clinicians as the first-line treatment for schizophrenia, and are gradually replacing typical antipsychotics. Most researchers agree that extrapyramidal side effects and tardive dyskinesia are less common when taking atypical antipsychotics. However, atypical-antipsychotic-induced weight gain has important physical and psychological consequences. The use of antipsychotics can result in not only excessive weight gain, but also in metabolic sequelae, such as dyslipidemia, glucose dysregulation, and the metabolic syndrome. These sequelae exacerbate the already elevated risk of
Abbreviations: ANCOVA, analysis of covariance; BMI, body mass index; DSM-IV, Diagnostic and Statistical Manual of Mental Disorders—fourth edition; PCR, polymerase chain reaction; SNP, single-nucleotide polymorphism. ⁎ Corresponding author. Department of Psychiatry, Anam Hospital, Korea University College of Medicine, Anam-dong 5-ga, Seongbuk-gu, Seoul 136705, South Korea. Tel.: +82 2 9205815; fax: +82 2 9297679. E-mail address: [email protected] (H.-J. Lee). 0278-5846/$ - see front matter © 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.pnpbp.2007.08.002
cardiovascular disease and diabetes in this patient group (Casey, 2005). Substantial weight gain may also adversely affect selfesteem, social functioning, and physical activity. In addition, weight gain is one of the major reasons for the discontinuation of or noncompliance with atypical antipsychotics. Among the atypical antipsychotics, clozapine and olanzapine may in particular induce profound weight gain, although few of the other classical and atypical antipsychotics are free of this side effect (Allison et al., 1999). Olanzapine is associated with significant weight gain comparable to that produced by clozapine (Lund and Perry, 2000). Most such weight gain occurs during the first 6–8 weeks of olanzapine therapy and reaches a plateau by the end of the 1st year of treatment (Nasrallah, 2003). The underlying mechanisms by which these medications cause weight gain remain unclear. However, there appears to be considerable variability among patients with regard to their propensity to develop an antipsychotic-induced weight gain. It is likely that this variability is influenced by biological susceptibility, including genetic factors. Theisen et al. (2001) and Wehmeier et al. (2005) illustrated that the body weights achieved and
S.-G. Kang et al. / Progress in Neuro-Psychopharmacology & Biological Psychiatry 32 (2008) 160–163
maintained with clozapine treatment are similar in monozygotic twin pairs and thereby suggested that the antipsychotic-induced weight gain is under strong genetic control. The candidate genes that were found to be significantly associated with antipsychoticinduced weight gain are the 5-hydroxytryptamine 2C receptor gene (Reynolds et al., 2002), the cytochrome P450 2D6 gene (Ellingrod et al., 2002), the α2a-adrenergic receptor gene (Park et al., 2006), synaptosomal-associated protein of 25 kDa (SNAP-25) gene (Müller et al., 2005), the G protein beta3 subunit gene (Wang et al., 2005), and the leptin gene (Templeman et al., 2005; Zhang et al., 2003). Leptin is a 16-kDa protein hormone that plays an important role in regulating body weight (Friedman and Halaas, 1998; Halaas et al., 1995). The serum leptin concentration is positively correlated with body mass index (BMI) and percentage of body fat (Considine et al., 1996; Escobar et al., 2000). Leptin enters the central circulation after being released by adipocytes, and when it reaches the hypothalamus it functions as a feedback mechanism by signaling the amount of peripheral adipose tissue to the central nervous system. Leptin is catabolic in nature, with increases in plasma leptin concentration or direct administration of the hormone to the brain significantly inhibiting food intake and fat storage, while promoting energy expenditure (Campfield et al., 1995; Jequier, 2002; Weigle et al., 1995). The leptin gene, which is located at chromosome 7q31.3, encodes a 3.5-kb cDNA and has three exons and two introns (Gong et al., 1996). Many single-nucleotide polymorphisms (SNPs) of the leptin gene have been studied extensively. The −2548A/G polymorphism is found in the promoter region and was first described by Mammès et al. although at that time it was wrongly designated as −2549C/A (Mammès et al., 2000, 1998). Recent studies involving French (Mammès et al., 2000) and North American (Li et al., 1999) populations found that a polymorphism in the promoter region (−2548A/G) of the leptin gene was associated with obesity. In both studies, the −2548G allele was more prevalent in the overweight group. The aim of the present study was to investigate the association between the −2548A/G SNP of the leptin gene and olanzapineinduced weight gain in Korean schizophrenic patients.
was approved by the Ethics Committee of the Korea University Medical Center. Other findings from some of these subjects have been reported previously (Park et al., 2006). Body weight and height were measured prior to starting olanzapine and again after long-term treatment lasting at least 3 months. We controlled the use of drugs other than olanzapine. Medications such as other antipsychotics, mood stabilizers, and antidepressants were avoided during the study because of their potential effects on weight change. However, we combined the use of benzodiazepines or anticholinergics as needed. No subject had received olanzapine or clozapine prior to the current study. The dose and duration of olanzapine treatment at the end-point examination were 14.0 ± 5.1 mg (mean ± SD) and 453 ± 289 days, respectively. The mean duration of illness among subjects was 19.7 ± 8.1 years. Other clinical variables measured in the study were gender and age. Changes in body weight and BMI during the treatment were also calculated. 2.2. Genotyping Genotyping of the leptin gene promoter − 2548A/G SNP was carried out using a modification of a previously described method (Templeman et al., 2005). Using the polymerase chain reaction (PCR), a 242-bp genomic fragment corresponding to the promoter in the human leptin gene sequence, containing the − 2548A/G polymorphism, was amplified. The resulting 242bp PCR product was digested with CfoI for 3 h at 37 °C, and the digestion products were separated by electrophoresis on 10% polyacrylamide gels and stained with ethidium bromide. The restriction enzyme digestion pattern was − 2548G (181- and 61-bp products) or − 2548A (242-bp product). Investigators who were involved in rating the data were blind to the genotype status.
Table 1 Demographic and clinical variables of 74 schizophrenia patients in the two genotype groups AA (n = 61)
2. Methods and materials 2.1. Subjects A total of 98 schizophrenic inpatients were enrolled from the three collaborating hospitals of Korea University Hospital. All subjects were examined by trained psychiatrists using the Korean version of the Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders—fourth edition (DSM-IV), leading to a diagnosis based on DSM-IV criteria (American Psychiatric Association, 1994). Exclusion criteria included evidence of other psychiatric, medical, or neurological illness, a family history of diabetes or eating disorder, and age over 65 years or under 18 years. These criteria resulted in the exclusion of 24 patients. All of the participating patients were of Korean ethnicity. Written informed consent to participate in the study was obtained from all patients, and the study protocol
161
AG (n = 13)
t-test
Age (years) Sex (M/F) Baseline body weight (kg)
48.1 ± 11.4 43.0 ± 12.2 t = 1.44 40/21 10/3 χ2 = 0.63 65.0 ± 12.5 63.4 ± 12.2 t = 0.42
Weight change (kg)
4.4 ± 6.4
8.6 ± 5.3
t = −2.22 F = 4.14
p = 0.029 p = 0.046 ⁎
Baseline BMI (kg/m2) Increase in BMI Treatment duration (day) Olanzapine dosage (mg/day) Previous antipsychotics (mg/day) a
23.8 ± 3.7 1.66 ± 2.50 435 ± 299 14.3 ± 5.1 699 ± 418
22.4 ± 3.7 3.06 ± 1.96 538 ± 230 12.8 ± 5.0 721 ± 496
t = 1.24 t = −1.90 t = −1.16 t = 0.96 t = −0.157
p = 0.220 p = 0.062 p = 0.248 p = 0.342 p = 0.876
The values are means ± SD. Bold represents p b 0.05. BMI: Body Mass Index. a Chlorpromazine equivalents. ⁎ ANCOVA test adjusted for sex and treatment duration.
p = 0.154 p = 0.427 p = 0.675
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S.-G. Kang et al. / Progress in Neuro-Psychopharmacology & Biological Psychiatry 32 (2008) 160–163
Table 2 Comparison of the genotypes and allele frequencies of leptin gene −2548A/G polymorphism between weight gain ≥7% and weight gain b7% Genotypes Weight gain ≥7% Weight gain b7%
AA
AG
29 32
10 3
Allele Frequencies χ2 = 3.71 p = 0.054
A
G
0.87 0.96
0.13 0.04
χ2 = 3.35 p = 0.067
2.3. Statistical analyses The association between genotype and weight gain and change in BMI was tested by independent t-test. To adjust the potential confounding factors (treatment duration and sex), the difference in weight gain was also tested using analysis of covariance (ANCOVA). Differences in genotype and allele frequencies between cohorts with different body-weight changes were evaluated by a chi-square analysis. The analysis was performed using standard software (SPSS for Windows), and p values smaller than 0.05 were considered statistically significant. 3. Results Out of 74 patients, the − 2548 AA genotype was found in 82.4% (n = 61) and the AG genotype in 17.6% (n = 13). Although our sample contained no patients with the GG genotype, the genotype frequencies did not deviate from Hardy–Weinberg equilibrium (χ2 = 0.69, p = 0.407). Table 1 lists the demographic and clinical variables of our sample. There were no differences in sociodemographics, initial body weight, initial BMI, previous antipsychotics dosage, and olanzapine dosage and duration between the two genotype groups (Table 1). The weight gain was significantly greater in patients with the AG genotype than for those with the AA genotype (t = 2.22, p = 0.029). ANCOVA also showed the difference of weight gain was still significant when adjusted for sex and treatment duration (F = 4.14, p = 0.046). There was a marginally significant difference in the genotype distribution ( p = 0.054) and allele frequencies ( p = 0.067) between subjects with a clinically significant weight gain (more than 7% weight gain from baseline) and those without a significant weight gain (less than 7%; Table 2). These findings show that body weight gain during olanzapine treatment was more prevalent in patients with the AG genotype than in those with the AA genotype. 4. Discussion A few previous studies have examined the association of the − 2548A/G SNP of the leptin gene with antipsychotic-induced weight gain. Zhang et al. (2003) reported that the − 2548 AA genotype may be a genetic risk factor for the development of antipsychotic-induced weight gain after 10 weeks of treatment in 128 Chinese Han schizophrenic patients who have not been treated previously. In contrast, Templeman et al. (2005) investigated the same association in 73 Spanish Caucasian patients with first-episode schizophrenia and found that patients with the GG genotype of the − 2548A/G SNP tended to exhibit a greater
change in BMI than those with the AA or AG genotype after 9 months of treatment. They could not find any significant association at 6 weeks nor at 3 months. They considered that racial variations could affect the relationship between the leptin gene polymorphism and weight gain. The possibility of ethnic difference in antipsychotics-induced weight gain and diabetes have been commented previously (Ananth et al., 2005). Ryu et al. (2006) examined the association in 71 Korean schizophrenic patients, and found no association after 4 and 8 weeks of treatment with various antipsychotics. They mentioned that the duration of exposure to the antipsychotics was somewhat short for evaluation of the genetic effect on druginduced weight gain and allowing for switching antipsychotics during study might have influenced their results in their discussion section. Recently, Ellingrod et al. (2007) investigated the relationship between polymorphisms of the leptin gene −2548A/G and leptin receptor Q223R SNP and olanzapineinduced weight gain in schizophrenics. Genotypes and alleles for each locus were not associated with olanzapine-induced weight gain, however, changes in BMI from baseline increased significantly in persons with olanzapine plasma levels N20.6 ng/mL for subjects carrying at least one G allele at both candidate loci compared to those who did not have a G allele at each ( p = 0.049). Therefore, the association between the −2548A/G SNP and antipsychotic-induced weight gain has been equivocal. The overall distribution of genotypes in our study was similar to that of a previous Korean study (Ryu et al., 2006), in which the result showed the AA genotype was the most common and the GG genotype was extremely rare (only one patient had the GG genotype). The allele distribution was not different between two studies (Ryu et al., 2006 A 0.83, G 0.17 vs our study A 0.91, G 0.09; p = 0.110). However, contrary to that study, our results demonstrate a possible association between the −2548A/G SNP and olanzapine-induced weight gain. Interestingly, our results also differ from those of Zhang et al. (2003) and Templeman et al. (2005). These discrepancies could be explained by differences in ethnicity, in duration of illness and treatment, or in the type of the antipsychotics prescribed. One of the strengths of our study is that all participants took only olanzapine, thereby removing the confounding factor — the use of different antipsychotics by different patients, or by individual patients, during the study period. Our result is consistent with those of previous studies which found the − 2548G allele was related with obesity (Li et al., 1999; Mammès et al., 2000). Li et al. (1999) identified six frequent sequence variants within the 5′ flanking region of leptin gene, and reported that the largest differences in allele frequency between obese and average-weight groups occurred at − 2548. They reported that − 2548G allele was more frequently found in the overweight. Mammès et al. (2000) also noted that the G allele is associated with overweight. Hoffstedt et al. (2002) found that the − 2548 A allele of this variant was associated with increased leptin messenger RNA (mRNA) levels and increased adipose tissue leptin secretion rate. Since leptin is known as a mediator of long-term regulation of energy balance, high leptin level tends to suppress food intake and thereby induce weight loss. This study has several limitations. First, due to the nature of this natural long-term study, we did not completely control the
S.-G. Kang et al. / Progress in Neuro-Psychopharmacology & Biological Psychiatry 32 (2008) 160–163
use of the antipsychotic, including the duration and dosage of olanzapine. This factor could have influenced our results, but this is unlikely to be significant because there was no difference in the duration and dosage of olanzapine treatment between the genotype groups. ANCOVA result showed that the difference of weight gain was still significant when adjusted for sex and treatment duration. Second, we could not control age, initial body weight and BMI between the two genotype groups. Although the differences of these factors between the two groups were not statistically significant, we cannot exclude the possibility of them having potential confounding effect. Third, we did not control or assess food intake (e.g., caloric counts and meal refusal), exercise, or the patients’ metabolic rates due to the long-term nature of this study. All of these factors could affect the weight gain. Fourth, the relatively small sample size might limit the generalization of our findings. This represents the first report of an association between the − 2548A/G SNP of the leptin gene and olanzapine-induced weight gain. Thus, it may aid clinical psychiatrists when they choose the most appropriate antipsychotic to administer to a particular patient, depending upon his or her genetic tolerance to weight gain. To test the possibility of ethnicity differences, our results need to be replicated in future studies involving other races. Another important area for future study would be a comprehensive investigation of associations among drug level of antipsychotics, antipsychotics-induced weight gain, and other candidate genes. References Allison DB, Mentore JL, Heo M, Chandler LP, Cappelleri JC, Infante MC, et al. Antipsychotic-induced weight gain: a comprehensive research synthesis. Am J Psychiatry 1999;156:1686–96. American Psychiatric Association. Diagnostic and statistical manual of mental disorders: DSM-IV. Washington, DC: American Psychiatric Press; 1994. Ananth J, Kolli S, Gunatilake S, Brown S. Atypical antipsychotic drugs, diabetes and ethnicity. Expert Opin Drug Saf 2005;4:1111–24. Campfield LA, Smith FJ, Guisez Y, Devos R, Burn P. Recombinant mouse OB protein: evidence for a peripheral signal linking adiposity and central neural networks. Science 1995;269:546–9. Casey DE. Metabolic issues and cardiovascular disease in patients with psychiatric disorders. Am J Med 2005;118(Suppl 2):S15–22. Considine RV, Sinha MK, Heiman ML, Kriauciunas A, Stephens TW, Nyce MR, et al. Serum immunoreactive-leptin concentrations in normal-weight and obese humans. N Engl J Med 1996;334:292–5. Ellingrod VL, Miller D, Schultz SK, Wehring H, Arndt S. CYP2D6 polymorphisms and atypical antipsychotic weight gain. Psychiatr Genet 2002;12:55–8. Ellingrod VL, Bishop JR, Moline J, Lin YC, del Miller D. Leptin and leptin receptor gene polymorphisms and increases in body mass index (BMI) from olanzapine treatment in persons with schizophrenia. Psychopharmacol Bull 2007;40:57–62. Escobar L, Freire JM, Giron JA, Vazquez JM, Pajares M, Ortego J, et al. Plasma levels of insulin and leptin in patients with morbid obesity and anorexia nervosa after weight loss or gain, respectively. Rev Esp Med Nucl 2000;19:199–206.
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Friedman JM, Halaas JL. Leptin and regulation of body weight in mammals. Nature 1998;395:763–70. Gong DW, Bi S, Pratley RE, Weintraub BD. Genomic structure and promoter analysis of the human obese gene. J Biol Chem 1996;23:3971–4. Halaas JL, Gajiwala KS, Maffei M, Cohen SL, Chait BT, Rabinowitz D, et al. Weight-reducing effects of the plasma protein encoded by the obese gene. Science 1995;269:543–6. Hoffstedt J, Eriksson P, Mottaui-Tabar S, Arner P. A polymorphism in the leptin promotor region (− 2548 G/A) influences gene expression and adipose tissue secretion of leptin. Horm Metab Res 2002;34:355–9. Jequier E. Leptin signaling, adiposity, and energy balance. Ann N Y Acad Sci 2002;967:379–88. Li WD, Reed DR, Lee JH, Xu W, Kilker RL, Sodam BR, et al. Sequence variants in the 5′ flanking region of the leptin gene are associated with obesity in women. Ann Hum Genet 1999;63:227–34. Lund BC, Perry PJ. Olanzapine: an atypical antipsychotic for schizophrenia. Expert Opin Pharmacother 2000;1:305–23. Müller DJ, Klempan TA, De Luca V, Sicard T, Volavka J, Czobor P, et al. The SNAP-25 gene may be associated with clinical response and weight gain in antipsychotic treatment of schizophrenia. Neurosci Lett 2005;379:81–9. Mammès O, Betoulle D, Aubert R, Giraud V, Tuzet S, Petiet A, et al. Novel polymorphisms in the 5′ region of the LEP gene: association with leptin levels and response to low-calorie diet in human obesity. Diabetes 1998;47:487–9. Mammès O, Betoulle D, Aubert R, Herbeth B, Siest G, Fumeron F. Association of the G-2548A polymorphism in the 50 region of the LEP gene with overweight. Ann Hum Genet 2000;64:391–4. Nasrallah H. A review of the effect of atypical antipsychotics on weight. Psychoneuroendocrinology 2003;28(Suppl 1):S83–96. Park YM, Chung YC, Lee SH, Lee KJ, Kim H, Byun YC, et al. Weight gain associated with the 2a-adrenergic receptor − 1291 C/G polymorphism and olanzapine treatment. Am J Med Genet B Neuropsychiatr Genet 2006;141: 394–7. Reynolds GP, Zhang ZJ, Zhang XB. Association of antipsychotic drug-induced weight gain with a 5-HT2C receptor gene polymorphism. Lancet 2002;359: 2086–7. Ryu SH, Jang WS, Cho EY, Kim SK, Lee DS, Hong KS. Association study of − 2548A/G polymorphism of leptin gene with antipsychotics-induced weight gain. Korean J Psychopharmacol 2006;17:423–38. Templeman LA, Reynolds GP, Arranz B, San L. Polymorphisms of the 5-HT2C receptor and leptin genes are associated with antipsychotic drug-induced weight gain in Caucasian subjects with a first-episode psychosis. Pharmacogenet Genomics 2005;15:195–200. Theisen FM, Cichon S, Linden A, Martin M, Remschmidt H, Hebebrand J. Clozapine and weight gain. Am J Psychiatry 2001;158:816. Wang YC, Bai YM, Chen JY, Lin CC, Lai IC, Liou YJ. C825T polymorphism in the human G protein beta3 subunit gene is associated with long-term clozapine treatment-induced body weight change in the Chinese population. Pharmacogenet Genomics 2005;15:743–8. Wehmeier PM, Gebhardt S, Schmidtke J, Remschmidt H, Hebebrand J, Theisen FM. Clozapine: weight gain in a pair of monozygotic twins concordant for schizophrenia and mild mental retardation. Psychiatry Res 2005;133:273–6. Weigle DS, Bukowski TR, Foster DC, Holderman S, Kramer JM, Lasser G, et al. Recombinant ob protein reduces feeding and body weight in the ob/ob mouse. J Clin Invest 1995;96:2065–70. Zhang ZJ, Yao ZJ, Mou XD, Chen JF, Zhuk RX, Liu W, et al. Association of −2548G/A functional polymorphism in the promoter region of leptin gene with antipsychotic agent-induced weight gain. Zhonghua Yi Xue Za Zhi 2003;25:2119–23.
Progress in Neuro-Psychopharmacology & Biological Psychiatry 32 (2008) 160 – 163 www.elsevier.com/locate/pnpbp
Possible association between the −2548A/G polymorphism of the leptin gene and olanzapine-induced weight gain Seung-Gul Kang a , Heon-Jeong Lee a,b,⁎, Young-Min Park c , Jung-Eun Choi a,b , Changsu Han a , Yong-Ku Kim a , Seung-Hyun Kim a , Min-Soo Lee a , Sook-Haeng Joe a , In-Kwa Jung a , Leen Kim a b
a Department of Psychiatry, Korea University College of Medicine, Seoul, South Korea Division of Brain Korea 21 Biomedical Science, Korea University College of Medicine, Seoul, South Korea c Department of Psychiatry, Inje University College of Medicine, Goyang City, Gyeonggi-do, South Korea
Received 6 April 2007; received in revised form 6 August 2007; accepted 6 August 2007 Available online 14 August 2007
Abstract Antipsychotic-induced weight gain has important effects on treatment compliance and long-term health. Several reports have indicated that a −2548A/G single-nucleotide polymorphism (SNP) of the leptin gene is associated with antipsychotic-induced weight gain. We hypothesized that there is a similar relationship between the −2548A/G SNP and olanzapine-induced weight gain. A total of 74 Korean schizophrenic patients were examined. Their weight was measured before starting olanzapine and after long-term treatment lasting for at least 3 months. The weight gain was significantly higher for patients with the AG genotype than for those with the AA genotype ( p = 0.029). Analysis of covariance also showed the difference of weight gain was still significant when adjusted for sex and treatment duration ( p = 0.046). This finding supports the presence of a relationship between the − 2548A/G SNP of the leptin gene and weight gain in Korean schizophrenic patients receiving olanzapine treatment. © 2007 Elsevier Inc. All rights reserved. Keywords: Leptin gene; Olanzapine; Polymorphism; Schizophrenia; Weight gain
1. Introduction Atypical antipsychotics are favored among clinicians as the first-line treatment for schizophrenia, and are gradually replacing typical antipsychotics. Most researchers agree that extrapyramidal side effects and tardive dyskinesia are less common when taking atypical antipsychotics. However, atypical-antipsychotic-induced weight gain has important physical and psychological consequences. The use of antipsychotics can result in not only excessive weight gain, but also in metabolic sequelae, such as dyslipidemia, glucose dysregulation, and the metabolic syndrome. These sequelae exacerbate the already elevated risk of
Abbreviations: ANCOVA, analysis of covariance; BMI, body mass index; DSM-IV, Diagnostic and Statistical Manual of Mental Disorders—fourth edition; PCR, polymerase chain reaction; SNP, single-nucleotide polymorphism. ⁎ Corresponding author. Department of Psychiatry, Anam Hospital, Korea University College of Medicine, Anam-dong 5-ga, Seongbuk-gu, Seoul 136705, South Korea. Tel.: +82 2 9205815; fax: +82 2 9297679. E-mail address: [email protected] (H.-J. Lee). 0278-5846/$ - see front matter © 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.pnpbp.2007.08.002
cardiovascular disease and diabetes in this patient group (Casey, 2005). Substantial weight gain may also adversely affect selfesteem, social functioning, and physical activity. In addition, weight gain is one of the major reasons for the discontinuation of or noncompliance with atypical antipsychotics. Among the atypical antipsychotics, clozapine and olanzapine may in particular induce profound weight gain, although few of the other classical and atypical antipsychotics are free of this side effect (Allison et al., 1999). Olanzapine is associated with significant weight gain comparable to that produced by clozapine (Lund and Perry, 2000). Most such weight gain occurs during the first 6–8 weeks of olanzapine therapy and reaches a plateau by the end of the 1st year of treatment (Nasrallah, 2003). The underlying mechanisms by which these medications cause weight gain remain unclear. However, there appears to be considerable variability among patients with regard to their propensity to develop an antipsychotic-induced weight gain. It is likely that this variability is influenced by biological susceptibility, including genetic factors. Theisen et al. (2001) and Wehmeier et al. (2005) illustrated that the body weights achieved and
S.-G. Kang et al. / Progress in Neuro-Psychopharmacology & Biological Psychiatry 32 (2008) 160–163
maintained with clozapine treatment are similar in monozygotic twin pairs and thereby suggested that the antipsychotic-induced weight gain is under strong genetic control. The candidate genes that were found to be significantly associated with antipsychoticinduced weight gain are the 5-hydroxytryptamine 2C receptor gene (Reynolds et al., 2002), the cytochrome P450 2D6 gene (Ellingrod et al., 2002), the α2a-adrenergic receptor gene (Park et al., 2006), synaptosomal-associated protein of 25 kDa (SNAP-25) gene (Müller et al., 2005), the G protein beta3 subunit gene (Wang et al., 2005), and the leptin gene (Templeman et al., 2005; Zhang et al., 2003). Leptin is a 16-kDa protein hormone that plays an important role in regulating body weight (Friedman and Halaas, 1998; Halaas et al., 1995). The serum leptin concentration is positively correlated with body mass index (BMI) and percentage of body fat (Considine et al., 1996; Escobar et al., 2000). Leptin enters the central circulation after being released by adipocytes, and when it reaches the hypothalamus it functions as a feedback mechanism by signaling the amount of peripheral adipose tissue to the central nervous system. Leptin is catabolic in nature, with increases in plasma leptin concentration or direct administration of the hormone to the brain significantly inhibiting food intake and fat storage, while promoting energy expenditure (Campfield et al., 1995; Jequier, 2002; Weigle et al., 1995). The leptin gene, which is located at chromosome 7q31.3, encodes a 3.5-kb cDNA and has three exons and two introns (Gong et al., 1996). Many single-nucleotide polymorphisms (SNPs) of the leptin gene have been studied extensively. The −2548A/G polymorphism is found in the promoter region and was first described by Mammès et al. although at that time it was wrongly designated as −2549C/A (Mammès et al., 2000, 1998). Recent studies involving French (Mammès et al., 2000) and North American (Li et al., 1999) populations found that a polymorphism in the promoter region (−2548A/G) of the leptin gene was associated with obesity. In both studies, the −2548G allele was more prevalent in the overweight group. The aim of the present study was to investigate the association between the −2548A/G SNP of the leptin gene and olanzapineinduced weight gain in Korean schizophrenic patients.
was approved by the Ethics Committee of the Korea University Medical Center. Other findings from some of these subjects have been reported previously (Park et al., 2006). Body weight and height were measured prior to starting olanzapine and again after long-term treatment lasting at least 3 months. We controlled the use of drugs other than olanzapine. Medications such as other antipsychotics, mood stabilizers, and antidepressants were avoided during the study because of their potential effects on weight change. However, we combined the use of benzodiazepines or anticholinergics as needed. No subject had received olanzapine or clozapine prior to the current study. The dose and duration of olanzapine treatment at the end-point examination were 14.0 ± 5.1 mg (mean ± SD) and 453 ± 289 days, respectively. The mean duration of illness among subjects was 19.7 ± 8.1 years. Other clinical variables measured in the study were gender and age. Changes in body weight and BMI during the treatment were also calculated. 2.2. Genotyping Genotyping of the leptin gene promoter − 2548A/G SNP was carried out using a modification of a previously described method (Templeman et al., 2005). Using the polymerase chain reaction (PCR), a 242-bp genomic fragment corresponding to the promoter in the human leptin gene sequence, containing the − 2548A/G polymorphism, was amplified. The resulting 242bp PCR product was digested with CfoI for 3 h at 37 °C, and the digestion products were separated by electrophoresis on 10% polyacrylamide gels and stained with ethidium bromide. The restriction enzyme digestion pattern was − 2548G (181- and 61-bp products) or − 2548A (242-bp product). Investigators who were involved in rating the data were blind to the genotype status.
Table 1 Demographic and clinical variables of 74 schizophrenia patients in the two genotype groups AA (n = 61)
2. Methods and materials 2.1. Subjects A total of 98 schizophrenic inpatients were enrolled from the three collaborating hospitals of Korea University Hospital. All subjects were examined by trained psychiatrists using the Korean version of the Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders—fourth edition (DSM-IV), leading to a diagnosis based on DSM-IV criteria (American Psychiatric Association, 1994). Exclusion criteria included evidence of other psychiatric, medical, or neurological illness, a family history of diabetes or eating disorder, and age over 65 years or under 18 years. These criteria resulted in the exclusion of 24 patients. All of the participating patients were of Korean ethnicity. Written informed consent to participate in the study was obtained from all patients, and the study protocol
161
AG (n = 13)
t-test
Age (years) Sex (M/F) Baseline body weight (kg)
48.1 ± 11.4 43.0 ± 12.2 t = 1.44 40/21 10/3 χ2 = 0.63 65.0 ± 12.5 63.4 ± 12.2 t = 0.42
Weight change (kg)
4.4 ± 6.4
8.6 ± 5.3
t = −2.22 F = 4.14
p = 0.029 p = 0.046 ⁎
Baseline BMI (kg/m2) Increase in BMI Treatment duration (day) Olanzapine dosage (mg/day) Previous antipsychotics (mg/day) a
23.8 ± 3.7 1.66 ± 2.50 435 ± 299 14.3 ± 5.1 699 ± 418
22.4 ± 3.7 3.06 ± 1.96 538 ± 230 12.8 ± 5.0 721 ± 496
t = 1.24 t = −1.90 t = −1.16 t = 0.96 t = −0.157
p = 0.220 p = 0.062 p = 0.248 p = 0.342 p = 0.876
The values are means ± SD. Bold represents p b 0.05. BMI: Body Mass Index. a Chlorpromazine equivalents. ⁎ ANCOVA test adjusted for sex and treatment duration.
p = 0.154 p = 0.427 p = 0.675
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Table 2 Comparison of the genotypes and allele frequencies of leptin gene −2548A/G polymorphism between weight gain ≥7% and weight gain b7% Genotypes Weight gain ≥7% Weight gain b7%
AA
AG
29 32
10 3
Allele Frequencies χ2 = 3.71 p = 0.054
A
G
0.87 0.96
0.13 0.04
χ2 = 3.35 p = 0.067
2.3. Statistical analyses The association between genotype and weight gain and change in BMI was tested by independent t-test. To adjust the potential confounding factors (treatment duration and sex), the difference in weight gain was also tested using analysis of covariance (ANCOVA). Differences in genotype and allele frequencies between cohorts with different body-weight changes were evaluated by a chi-square analysis. The analysis was performed using standard software (SPSS for Windows), and p values smaller than 0.05 were considered statistically significant. 3. Results Out of 74 patients, the − 2548 AA genotype was found in 82.4% (n = 61) and the AG genotype in 17.6% (n = 13). Although our sample contained no patients with the GG genotype, the genotype frequencies did not deviate from Hardy–Weinberg equilibrium (χ2 = 0.69, p = 0.407). Table 1 lists the demographic and clinical variables of our sample. There were no differences in sociodemographics, initial body weight, initial BMI, previous antipsychotics dosage, and olanzapine dosage and duration between the two genotype groups (Table 1). The weight gain was significantly greater in patients with the AG genotype than for those with the AA genotype (t = 2.22, p = 0.029). ANCOVA also showed the difference of weight gain was still significant when adjusted for sex and treatment duration (F = 4.14, p = 0.046). There was a marginally significant difference in the genotype distribution ( p = 0.054) and allele frequencies ( p = 0.067) between subjects with a clinically significant weight gain (more than 7% weight gain from baseline) and those without a significant weight gain (less than 7%; Table 2). These findings show that body weight gain during olanzapine treatment was more prevalent in patients with the AG genotype than in those with the AA genotype. 4. Discussion A few previous studies have examined the association of the − 2548A/G SNP of the leptin gene with antipsychotic-induced weight gain. Zhang et al. (2003) reported that the − 2548 AA genotype may be a genetic risk factor for the development of antipsychotic-induced weight gain after 10 weeks of treatment in 128 Chinese Han schizophrenic patients who have not been treated previously. In contrast, Templeman et al. (2005) investigated the same association in 73 Spanish Caucasian patients with first-episode schizophrenia and found that patients with the GG genotype of the − 2548A/G SNP tended to exhibit a greater
change in BMI than those with the AA or AG genotype after 9 months of treatment. They could not find any significant association at 6 weeks nor at 3 months. They considered that racial variations could affect the relationship between the leptin gene polymorphism and weight gain. The possibility of ethnic difference in antipsychotics-induced weight gain and diabetes have been commented previously (Ananth et al., 2005). Ryu et al. (2006) examined the association in 71 Korean schizophrenic patients, and found no association after 4 and 8 weeks of treatment with various antipsychotics. They mentioned that the duration of exposure to the antipsychotics was somewhat short for evaluation of the genetic effect on druginduced weight gain and allowing for switching antipsychotics during study might have influenced their results in their discussion section. Recently, Ellingrod et al. (2007) investigated the relationship between polymorphisms of the leptin gene −2548A/G and leptin receptor Q223R SNP and olanzapineinduced weight gain in schizophrenics. Genotypes and alleles for each locus were not associated with olanzapine-induced weight gain, however, changes in BMI from baseline increased significantly in persons with olanzapine plasma levels N20.6 ng/mL for subjects carrying at least one G allele at both candidate loci compared to those who did not have a G allele at each ( p = 0.049). Therefore, the association between the −2548A/G SNP and antipsychotic-induced weight gain has been equivocal. The overall distribution of genotypes in our study was similar to that of a previous Korean study (Ryu et al., 2006), in which the result showed the AA genotype was the most common and the GG genotype was extremely rare (only one patient had the GG genotype). The allele distribution was not different between two studies (Ryu et al., 2006 A 0.83, G 0.17 vs our study A 0.91, G 0.09; p = 0.110). However, contrary to that study, our results demonstrate a possible association between the −2548A/G SNP and olanzapine-induced weight gain. Interestingly, our results also differ from those of Zhang et al. (2003) and Templeman et al. (2005). These discrepancies could be explained by differences in ethnicity, in duration of illness and treatment, or in the type of the antipsychotics prescribed. One of the strengths of our study is that all participants took only olanzapine, thereby removing the confounding factor — the use of different antipsychotics by different patients, or by individual patients, during the study period. Our result is consistent with those of previous studies which found the − 2548G allele was related with obesity (Li et al., 1999; Mammès et al., 2000). Li et al. (1999) identified six frequent sequence variants within the 5′ flanking region of leptin gene, and reported that the largest differences in allele frequency between obese and average-weight groups occurred at − 2548. They reported that − 2548G allele was more frequently found in the overweight. Mammès et al. (2000) also noted that the G allele is associated with overweight. Hoffstedt et al. (2002) found that the − 2548 A allele of this variant was associated with increased leptin messenger RNA (mRNA) levels and increased adipose tissue leptin secretion rate. Since leptin is known as a mediator of long-term regulation of energy balance, high leptin level tends to suppress food intake and thereby induce weight loss. This study has several limitations. First, due to the nature of this natural long-term study, we did not completely control the
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use of the antipsychotic, including the duration and dosage of olanzapine. This factor could have influenced our results, but this is unlikely to be significant because there was no difference in the duration and dosage of olanzapine treatment between the genotype groups. ANCOVA result showed that the difference of weight gain was still significant when adjusted for sex and treatment duration. Second, we could not control age, initial body weight and BMI between the two genotype groups. Although the differences of these factors between the two groups were not statistically significant, we cannot exclude the possibility of them having potential confounding effect. Third, we did not control or assess food intake (e.g., caloric counts and meal refusal), exercise, or the patients’ metabolic rates due to the long-term nature of this study. All of these factors could affect the weight gain. Fourth, the relatively small sample size might limit the generalization of our findings. This represents the first report of an association between the − 2548A/G SNP of the leptin gene and olanzapine-induced weight gain. Thus, it may aid clinical psychiatrists when they choose the most appropriate antipsychotic to administer to a particular patient, depending upon his or her genetic tolerance to weight gain. To test the possibility of ethnicity differences, our results need to be replicated in future studies involving other races. Another important area for future study would be a comprehensive investigation of associations among drug level of antipsychotics, antipsychotics-induced weight gain, and other candidate genes. References Allison DB, Mentore JL, Heo M, Chandler LP, Cappelleri JC, Infante MC, et al. Antipsychotic-induced weight gain: a comprehensive research synthesis. Am J Psychiatry 1999;156:1686–96. American Psychiatric Association. Diagnostic and statistical manual of mental disorders: DSM-IV. Washington, DC: American Psychiatric Press; 1994. Ananth J, Kolli S, Gunatilake S, Brown S. Atypical antipsychotic drugs, diabetes and ethnicity. Expert Opin Drug Saf 2005;4:1111–24. Campfield LA, Smith FJ, Guisez Y, Devos R, Burn P. Recombinant mouse OB protein: evidence for a peripheral signal linking adiposity and central neural networks. Science 1995;269:546–9. Casey DE. Metabolic issues and cardiovascular disease in patients with psychiatric disorders. Am J Med 2005;118(Suppl 2):S15–22. Considine RV, Sinha MK, Heiman ML, Kriauciunas A, Stephens TW, Nyce MR, et al. Serum immunoreactive-leptin concentrations in normal-weight and obese humans. N Engl J Med 1996;334:292–5. Ellingrod VL, Miller D, Schultz SK, Wehring H, Arndt S. CYP2D6 polymorphisms and atypical antipsychotic weight gain. Psychiatr Genet 2002;12:55–8. Ellingrod VL, Bishop JR, Moline J, Lin YC, del Miller D. Leptin and leptin receptor gene polymorphisms and increases in body mass index (BMI) from olanzapine treatment in persons with schizophrenia. Psychopharmacol Bull 2007;40:57–62. Escobar L, Freire JM, Giron JA, Vazquez JM, Pajares M, Ortego J, et al. Plasma levels of insulin and leptin in patients with morbid obesity and anorexia nervosa after weight loss or gain, respectively. Rev Esp Med Nucl 2000;19:199–206.
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