Leptin and cholesterol levels are low in major depressive disorder, but high in schizophrenia

Abstract

Background

Appetite, food intake and weight are frequently altered in psychiatric disorders such as major depression and schizophrenia. Leptin is an adipocyte hormone, as the product of the ob gene, regulating food intake and energy balance providing the hypothalamus with information on the amount of body fat. Leptin seems to be strongly associated with lipid metabolism. Moreover, leptin is involved in the control of other behaviors and in brain development. There are few studies about the amounts of plasma leptin in mood disorder and schizophrenia with inconsistent findings. The relationship between leptin and major depressive disorder is still unknown. We planned to investigate the relationship of the serum leptin concentration, cholesterol, and BMI between patients with major depressive disorder, schizophrenic patients and healthy control subjects.

Methods

In the present study, the BMI, plasma cholesterol and leptin levels, BDI, and BPRS were compared in 69 patients with major depressive disorder, 78 schizophrenic patients, and 51 healthy controls.

Results

The major findings of our study included (1) leptin and cholesterol levels were low in patients with major depressive disorder, but high in schizophrenic patients; (2) negative correlations between BDI scores and serum cholesterol or leptin levels in the patients with major depressive disorder; (3) an inconsistently positive correlation between mean leptin levels, cholesterol, and BMI among different groups; (4) positive correlations between serum cholesterol or leptin levels and the length of illness in the schizophrenic patients.

Conclusions

In this study, our results indicate that that leptin and cholesterol might play differently important pathophysiological roles in these psychiatric disorders.

Introduction

Leptin is a fat cell-derived hormone that signals nutrition status to the hypothalamus weight and sexual behavior (Prolo et al., 1998), and has been discovered as the product of the obese (ob) gene (Zhang and Friedman, 1994). Plasma levels of leptin are found to have strong correlation with body mass index (BMI) and body fat percentage. It has been reported that leptin affects the intracellular lipid concentration via a decrease in the synthesis of fatty acid and cholesterol and an increase in lipid oxidation (Atmaca et al., 2002b, Auwerx and Steals, 1998). Leptin administration has been shown to reduce food intake and weight, suggesting its role in weight regulation (Halaas et al., 1995, Pelleymounter et al., 1995). Recently, many studies focused on leptin levels in psychiatric disorders (bipolar disorder, depression, suicidal attempters, borderline personality disorder) and psychotropic drug use (especially antipsychotics and valproate), but showed inconsistent findings (Kraus et al., 2001, Atmaca et al., 2002a, Atmaca et al., 2002b, Atmaca et al., 2003a, Atmaca et al., 2003b, Atmaca et al., 2003c). Besides, a positive correlation has been shown between serum leptin concentration and total cholesterol, triglyceride, and percentage body fat (Kaplan, 1998). Further, an interaction between leptinergic and serotonergic systems in the central nervous system has been demonstrated (Leibowitz and Alexander, 1998).

Low cholesterol values have been associated with the expression of aggressive and impulsive behavior in a variety of psychiatric disorders, e.g. intermittent explosive disorder (Virkkuncn and Penttinen, 1984) and antisocial personality disorder (Freedman et al., 1995). In depressed patients, low (Glueck et al., 1994, Maes et al., 1997) and high (Apter et al., 1999) cholesterol levels compared with healthy controls have been found. Recently studies have reported that schizophrenic patients using physical violence had lower serum cholesterol levels than those not using physical violence although the difference was not statistically significant (Huang and Wu, 2000). There were few studies systematically evaluating the relationship between different symptomatology, leptin, cholesterol, and BMI. In the present study, the BMI, plasma cholesterol and leptin levels, BDI (Beck Depression Inventory), and BPRS (Brief Psychiatric Rating Scale) were compared in 69 patients with major depressive disorder, 78 schizophrenic patients, and 51 healthy controls. The purpose of this study is to test the hypothesis that the leptin, BMI, and cholesterol should show different relationship among three groups because of different psychiatric status.