Serum leptin levels increase rapidly after initiation of ... - Nature

Molecular Psychiatry (1998) 3, 76–80  1998 Stockton Press All rights reserved 1359–4184/98 $12.00

ORIGINAL RESEARCH ARTICLE

Serum leptin levels increase rapidly after initiation of clozapine therapy ¨ T Bromel1, WF Blum2,3, A Ziegler4, E Schulz1, M Bender5, C Fleischhaker1, H Remschmidt1, J-C Krieg5 and J Hebebrand1 1

Clinical Research Group, Department of Child and Adolescent Psychiatry of the University of Marburg; 2 Children’s Hospital of the University of Gieben; 3Lilly Deutschland GmbH; 4Institute of Medical Biometry and Epidemiology of the University of Marburg; 5Department of Psychiatry of the University of Marburg, Germany Keywords: body weight regulation; neuroleptics; cytokines; overeating; binge-eating; weight gain Weight gain is a major side-effect of treatment with clozapine. In order to investigate the influence of the atypical neuroleptic clozapine on leptin secretion, serum leptin levels were measured in 12 patients at baseline and for a 10-week period after initiation of treatment. Serum clozapine levels and levels of its metabolites were simultaneously assessed. Alterations of body weight and body composition were determined. During the 10-week observation period leptin levels differed significantly from the levels determined at baseline (P , 0.0001). During the first 2 weeks of treatment serum leptin levels at least doubled in eight of the 12 patients. The maximal relative increase over baseline was 536%. Low doses of clozapine were sufficient to induce this effect. Within a 10-week period mean body weight, mean body mass index, mean fat mass and mean lean body mass all increased. Based on the results we suggest that in predisposed individuals clozapine induces an increased appetite; overeating and weight gain can ensue, which in turn underlie elevated leptin secretion.

Weight gain is a relevant side-effect of treatment with the atypical neuroleptic drug clozapine.1–6 Weight gain under clozapine apparently exceeds that observed upon use of typical neuroleptics.7,8 The mechanisms are poorly understood, but some hypotheses have been suggested.9 Patients frequently report an inability to suppress appetite after a full meal, suggesting a change in satiety perception.3 An increase in appetite and carbohydrate craving have also been reported.10 In some studies weight gain has been associated with a positive psychopathological outcome.3,6 Clozapine binds with different affinities to diverse serotonin receptors and dopamine receptors. Binding also occurs to histamine, muscarinic and alpha-adrenergic receptors.11 Accordingly, one or more of these neurotransmitter systems are presumably involved in the weight gain related to clozapine. Leptin is a hormone synthesized by adipocytes.12,13

Serum leptin levels are correlated with the body mass index (BMI; kg m−2) and percent body fat.14,15 Leptin is presumed to signal the size of the adipose depot to brain and peripheral tissues.16 Leptin secretion is also influenced by fasting and overeating on a short-term basis prior to alterations of fat mass or body weight.17– 19 Overeating for a single day (100 kcal kg−1) is associated with a 40% elevation of circulating leptin levels. A 10% increase in body weight achieved within 5 weeks and maintained for an additional 2 weeks results in a 300–400% increase.17 In this study which included 12 patients with schizophrenia we determined serum leptin levels prior to and after initiation of treatment with clozapine. We hypothesized that initiation of treatment is accompanied by an alteration in leptin secretion. If that were the case, we planned to address its relationship to changes in body weight and body composition and to clozapine dosages and serum levels of clozapine and its metabolites. In accordance with our hypothesis the 12 patients’ leptin levels prior to initiation of clozapine treatment differed significantly from levels measured afterwards (x2 = 977.31; 9 d.f.; P , 0.0001). The majority of patients showed increments of their serum leptin levels that were already evident 1 week after initiation of clozapine treatment (Figure 1). In relation to baseline the mean relative increase in leptin levels remained elevated throughout the 10-week observation period. Interindividual variation was apparent. Leptin concentrations in eight of the 12 patients had at least doubled by week 2. The maximal increase up to week 2 was 536%. A single patient showed a comparably late increase of leptin secretion (.100%) not evident until week 4. In three patients leptin levels remained similar to baseline throughout the observation span (relative increases at week 1 ,35%). None of these three patients had a relative increase at any time point in excess of 55% despite the fact that they received high maximal daily doses of clozapine (600– 900 mg day−1). The four patients in whom clozapine treatment was intermittently discontinued deserve special consideration. At week 1 three of these patients had relative increases of their leptin levels of 109%, 198% and 318%, respectively, while the fourth patient had a decrease of 15%. Upon discontinuation of clozapine, leptin levels of all patients dropped to or below baseline. After treatment was reinitiated leptin levels again increased in only those three patients who had already shown the initial increase. Statistical analyses revealed that the patients’ mean body weight, mean BMI, mean fat mass and mean lean body mass increased during the observation span (all nominal P-values ,0.01; Table 1). The net differences in weight, BMI, and fat mass between baseline and weeks 1 and 2, respectively, revealed correlations between 0.3 and 0.75 to the relative increases in serum leptin levels at weeks 1 and 2 (Table 2). Correlation coefficients between these increases and lean body mass were negative.

Serum leptin levels increase after clozapine therapy ¨ T Bromel et al

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Figure 1 Mean relative increases of serum leptin levels in 12 patients during treatment with clozapine in relation to the baseline (pretreatment) level (bars indicate 95% confidence intervals). A single patient each was not available for blood sampling at weeks 1 and 2. The four patients in whom clozapine treatment was intermittently discontinued at week 3 or 4 were subsequently excluded. All P-values (two-sided non-randomized Wilcoxon-test) are nominal. Table 1 Mean ± standard deviations and ranges of anthropometric measurements performed in 11 patients prior to and after initiation of treatment with clozapine (the patient discharged at week 7 is excluded) Baseline n = 11

Week 1 n = 11

Week 2 n = 11

Week 10 n = 11

Body weight (kg) mean ± s.d. range

79.3 ± 19.3 55.5–115.5

79.8 ± 19.4 55.0–117.3

80.3 ± 19.5 55.0–118.0

83.5 ± 20.1 55.5–123.0

Body mass index (kg m−2) mean ± s.d. range

25.2 ± 4.8 19.4–35.7

25.4 ± 4.9 19.3–35.8

25.5 ± 4.9 19.3–36.0

26.5 ± 5.0 19.4–37.5

Fat mass (kg)* mean ± s.d. range

23.0 ± 10.6 9.6–41.0

23.5 ± 10.6 10.9–41.5

23.9 ± 10.3 11.9–42.1

25.9 ± 10.5 14.6–46.1

Lean body mass (kg)* mean ± s.d. range

60.6 ± 13.1 43.0–80.8

60.7 ± 12.9 42.5–79.4

61.0 ± 13.4 42.1–81.4

62.7 ± 13.8 43.3–82.3

Bioelectrical impedance analyses were carried out in nine patients (*). Within the 10-week observation period, mean body weight, mean body mass index, mean fat mass and mean lean body mass increased (all nominal P-values , 0.01).

Nine of the 12 patients reported an increased appetite and/or hunger. These patients reported an increased desire for sweets and soft drinks (n = 7), salty crackers (n = 1) or sandwiches (n = 1). Two patients developed binge-eating episodes as specified in the DSM-IV research

criteria for binge-eating disorder. The binge-eating commenced within the first week of treatment. In one of the two patients these episodes ceased upon intermittent discontinuation of clozapine treatment and recommenced after reinitiation. Both patients gained weight rapidly.


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Table 2 Pearson’s correlation coefficients between relative increases of serum leptin levels and increments in body weight, body mass index (BMI), fat mass and lean body mass Relative leptinincrease between baseline and week 1 Weight gain (kg) between baseline and week 1 week 2 BMI gain (kg m−2) between baseline and week 1 week 2 Fat mass gain (kg) between baseline and week 2 Lean body mass gain (kg) between baseline and week 2

*

Relative leptinincrease between baseline and week 2

0.67 0.61

0.41 0.30

0.69 0.42

0.62 0.30

0.75

0.50

−0.42

−0.62

*

* *

*

Correlations were calculated at weeks 1 and 2. Body composition was determined in nine patients only. * = Nominal P-values , 0.05.

A single patient without an increase in leptin levels and who gained 3 kg (as fat-free mass only) during the observation span did not report an alteration of his hunger sensation. It was not possible to reliably delineate any alterations of hunger sensations in the two other patients (weight gains of 0 and 1.1 kg over the 10-week period), whose leptin levels also remained within the baseline range throughout the observation period. Pretreatment did not seem to have an effect on the clozapine-induced increase in leptin secretion because all three non-pretreated patients showed the initial increase at weeks 1 and 2. All of the four patients who received no co-medication during the observation span (mean weight gain: 5.15 kg) showed the initial leptin increase; this group included the patient with the highest weight gain during the observation span (8.2 kg). Statistical analyses also revealed that the initial increase in relative leptin levels at week 1 or 2 was seemingly not strongly related to mean daily doses of clozapine or to serum levels of clozapine and its metabolites (all correlation coefficients ,0.4). Even the patient with the lowest dose (50 mg day−1 throughout the whole observation period) showed an increase of circulating leptin levels at week 1. The major finding of this study is that leptin secretion is altered upon initiation of clozapine treatment in a substantial proportion of patients. In our study group secretion increased rapidly in eight out of

12 patients (Figure 1). Small doses of the drug are apparently sufficient for induction of this phenomenon. Despite the fact that other factors could have influenced leptin secretion after initiation of clozapine treatment the magnitude of the increase and its rapid reversal upon discontinuation of treatment clearly indicate that clozapine directly or indirectly causes the increase in leptin secretion. The recently discovered pulsatility of leptin secretion20 cannot be responsible for the systematic changes observed. Most patients reported an increased hunger and/or appetite. The validity of the subjective reports of increased sensations of hunger are underscored by the fact that body weight and fat mass indeed increased (Table 1) throughout the observation span. Presently, only very limited information is available on the effects of overeating and subsequent weight gain on leptin levels. Increments of approximately 40% and 350% after a single day of overeating and after a 10% weight gain, respectively, have been reported.17 In patients with anorexia nervosa both the magnitude and the rate of weight gain affect leptin levels.21 Based on the rapid and longer-term17,21 effects of overeating and weight gain on leptin secretion, we assume that in predisposed individuals central effects of clozapine induce increased appetite and/or hunger and as a consequence overeating and in extreme cases binge-eating. Both overeating and the ensuing gain in fat mass induce the increased leptin secretion. The correlations at weeks 1 and 2 between relative increase in leptin levels and weight or fat mass gain (Table 2) support this interpretation. In order to test whether the rise is indeed only due to overeating and subsequent gain in fat mass, we would have had to precisely control the food intake of the patients and have a group of controls, matched for BMI and percent body fat, also raise their energy intake by a similar percentage. Even then direct comparisons would presumably be rendered difficult by individual variation of the leptin response to overeating and weight gain. Increased leptin secretion might signal the attempt of the organism to counter-regulate the increased energy intake through an increase in energy expenditure. As long as the effects of clozapine on energy intake override the counterregulation, the energy balance is positive and as a result weight gain ensues until energy intake and expenditure reach a new balance. We cannot exclude that another mechanism – alternative to or in addition to the effect brought about by an increased energy intake – is involved in the up-regulation of leptin. Interestingly, clozapine increases the plasma levels of tumor necrosis factor-a, soluble TNF receptors p55 and p75, and interleukin-2.22 Weight changes were not reported in that study. Leptin itself is related in structure to the family of helical cytokines.23,24 In conclusion, despite some limitations of this study including the small case number, the lack of a washout phase, co-medication in some patients and the lack of an adequate control group and of a standardised protocol for the assessment of the patients’ eating


behavior, we have clearly shown that clozapine can alter leptin secretion. In individual patients serum leptin levels increase more than five-fold over baseline. Based on our data we assume that this increase is related to overeating and subsequent weight gain induced by clozapine. The implications of these findings for the effects of clozapine on energy intake, weight regulation and psychopathology merit further consideration.

determined with a sensitive radioimmunoassay;27 serum levels of clozapine and its metabolites were measured with high performance liquid chromatography.28 During clozapine treatment ten patients were questioned as to alterations of their energy intake and of their eating behavior using a semi-structured questionnaire on a weekly basis. Two patients were not able to adequately reflect their eating behavior.

Sample and methods

Statistical analyses Our hypothesis was that leptin secretion is altered by initiation of clozapine treatment. We investigated this hypothesis under the assumption of normally distributed relative serum leptin levels. Detailed formulas of the applied linear model and the robust Wald statistic are given by Arminger29 (p 127, Eqns (3.231), (3.234) and (3.237)). All other statistical analyses were of an exploratory nature. All calculations were performed with the statistical software package STATISTICA for Windows 5.0. The four patients in whom clozapine treatment was intermittently discontinued in weeks 3 or 4 were subsequently excluded from the weekly calculations of the mean relative increase in serum leptin levels over baseline (Figure 1). The relative increases in mean leptin levels at weeks 1–10 in relation to baseline were exploratorily assessed with a two-sided non-randomized Wilcoxon-test (Figure 1). All patients excluding the patient who was discharged at week 7 were included in the descriptive analysis of the relevant anthropometric data at baseline and weeks 1, 2 and 10 (Table 1). Pearson’s correlation coefficients were used to descriptively assess the influence of the anthropometric variables (Table 2) and of the mean daily doses of clozapine, serum levels of clozapine and its metabolites on leptin secretion.

This prospective study assessed body mass index (BMI; kg m−2), body composition, serum leptin levels, serum levels of clozapine and of two metabolites in 12 consecutively ascertained psychiatric inpatients before and after initiation of treatment with clozapine. These six males and six females had diagnoses of schizophrenia (n = 9) or schizoaffective disorder (n = 3) according to the DSM-IV criteria25 with a variety of subtypes. Mean age (± s.d.) of the total group was 31 ± 7.1 (range 22–44) years. All 12 patients gave written informed consent; the study was approved by the Ethics Committee of the University of Marburg. Eleven patients were followed-up for 10 weeks upon initiation of treatment with clozapine; one patient was discharged in week 7. During the observation period (70 days), clozapine therapy was intermittently discontinued in four patients in the third or fourth week of treatment for 6, 7, 11 and 26 days, respectively, due to serious side-effects including fever and diarrhea (n = 3) and binge-eating episodes associated with rapid weight gain (n = 1). In 11 patients clozapine dosage was raised gradually during the first treatment stage and subsequently adjusted to clinical requirements; the mean clozapine dose (± s.d.) was 273 ± 142.3 (range 81–475) mg day−1. One patient received 50 mg day−1 throughout the 70 days. Nine patients had been pretreated with diverse neuroleptics and/or other psychopharmacologically active drugs directly prior to initiation of clozapine treatment. During the observation span four patients received clozapine only; eight were additionally treated with other neuroleptics (n = 3), benzodiazepines (n = 5) and/or antidepressants (n = 4). All patients were blood sampled on the day preceding initiation of clozapine treatment (baseline: week 0) and subsequently on a weekly basis for up to 10 weeks. A single patient each was not available for sampling at weeks 1 and 2. Blood sampling was routinely performed after an overnight fast at 8 am prior to intake of medication. Baseline body weight and height were also measured on the day preceding initiation of clozapine treatment. Weight was subsequently measured in parallel to the blood samplings. Fat mass was calculated from biweekly measured impedance (2000-S; DataInput, Frankfurt) according to gender-specific equations for normal weight individuals.26 Three acutely psychotic patients refused bioelectrical impedance analyses (BIA). Serum concentrations of leptin were

Acknowledgements We are indebted to the patients who participated in ¨ this study. We thank Ms Hanitsch (Gieben), Ms Stohr and Ms Finkenstein (Marburg) for their excellent technical assistance. This study was supported by the Deutsche Forschungsgemeinschaft.

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Correspondence: Professor J Hebebrand, Clinical Research Group, Department of Child and Adolescent Psychiatry of the University of Marburg, Hans-Sachs-Str 6, D-35033 Marburg, Germany. E-mail: HebebranKpost.med.uni-marburg.de Received 15 July 1997; revised and accepted 16 October 1997