Puberty modifies sulpiride effects on body weight in rats

Dopamine D2 receptor antagonist counteracts hyperglycemia and insulin resistance in diet-induced obese male mice

Obesity leads to insulin resistance (IR) and type 2 diabetes. In humans, low levels of the hormone prolactin (PRL) correlate with IR, adipose tissue (AT) dysfunction, and increased prevalence of T2D. In obese rats, PRL treatment promotes insulin sensitivity and reduces visceral AT adipocyte hypertrophy. Here, we tested whether elevating PRL levels with the prokinetic and antipsychotic drug sulpiride, an antagonist of dopamine D2 receptors, improves metabolism in high fat diet (HFD)-induced obese male mice. Sulpiride treatment (30 days) reduced hyperglycemia, IR, and the serum and pancreatic levels of triglycerides in obese mice, reduced visceral and subcutaneous AT adipocyte hypertrophy, normalized markers of visceral AT function (PRL receptor, Glut4, insulin receptor and Hif-1α), and increased glycogen stores in skeletal muscle. However, the effects of sulpiride reducing hyperglycemia were also observed in obese prolactin receptor null mice. We conclude that sulpiride reduces obesity-induced hyperglycemia by mechanisms that are independent of prolactin/prolactin receptor activity. These findings support the therapeutic potential of sulpiride against metabolic dysfunction in obesity.

Effects of sub-chronic antipsychotic drug treatment on body weight and reproductive function in juvenile female rats

RATIONALE

Weight gain caused by some antipsychotics is not only confined to adults but can also adversely affect both children and adolescents. Indeed, olanzapine and risperidone have been associated with extreme weight gain in adolescents even greater than that reported in adults. We have recently shown substantial weight gain in adult female rats following treatment with olanzapine and risperidone but not ziprasidone.

OBJECTIVES

The aim of the present study was to compare the effects of several antipsychotics on weight gain and reproductive function in juvenile (aged 7 weeks) female hooded Lister rats.

METHODS

Olanzapine (4 mg/kg), risperidone (0.5 mg/kg), ziprasidone (2.5 mg/kg), sulpiride (10 mg/kg), haloperidol (0.5 mg/kg) or vehicle was administered i.p. once per day for 21 days. Body weight, food and water intake were measured daily, in addition to the determination of stage of the oestrous cycle.

RESULTS

Sub-chronic administration of olanzapine, risperidone, sulpiride and haloperidol, but not ziprasidone, significantly increased body weight compared to vehicle-treated animals during weeks 1-3. Sulpiride significantly increased food and water intake. Significantly increased percentage intra-abdominal fat weight was observed in olanzapine, risperidone, sulpiride and haloperidol, but not ziprasidone-treated animals. Marked disruption of the oestrous cycle was observed in all but the ziprasidone-treated group, which continued to have regular 4-day oestrous cycles.

CONCLUSIONS

Weight gain observed in these juvenile animals was 1.5-2 times greater than that previously observed in adult rats. These findings have important implications for the use of antipsychotics in children and adolescent patients.

Effects of chronic neuroleptic treatments on nutrient selection, body weight, and body composition in the male rat under dietary self-selection

New antipsychotic drugs often increase weight and produce metabolic disturbances in treated patients. However, the mechanisms by which neuroleptics induce these undesirable side effects in humans are not known. Studies have shown that antipsychotics can increase body weight in female but not in male rats. However, no studies investigated changes in macronutrient selection during chronic treatments with antipsychotics in male rats, and no studies investigated precisely body composition after such treatments. In the present work, we studied in male rats the effects of long-term administration of two neuroleptics: haloperidol, a classical neuroleptic which has a moderate effect on weight gain in humans, and olanzapine, an atypical neuroleptic which has a more important effect on weight gain. Treatments (both 1 mg/kg) were given orally for 6 weeks, and the animals were allowed to self-select food among carbohydrates, lipids and proteins. Food selection was measured throughout the study, and body composition was measured by dissection and weighing of the main organs and tissues. Circulating leptin, insulin and glucose were also assayed at the end of the study on blood collected at the time of carcass analysis. The results show that none of the neuroleptic treatments modified caloric intake, food selection, body weight, and body composition. Olanzapine produced a statistically non-significant increase in subcutaneous fat tissue. It is concluded that a 6-week olanzapine or haloperidol treatment in male rats under dietary macronutrient selection does not significantly affect energy regulation.

Chronic treatment with antipsychotics in rats as a model for antipsychotic-induced weight gain in human

Several clinical reports have demonstrated that most antipsychotics of the new generation, but not the typical antipsychotic haloperidol, induce weight gain in schizophrenic patients. Since weight gain induces serious health complications in humans, it is crucial to test upcoming antipsychotic compounds in an animal model of weight gain. With the aim of evaluating whether the rat can be used as a model for antipsychotic-induced weight gain, we have investigated the effect of chronic treatment (3 weeks) with one antipsychotic drug inducing weight gain in clinic (olanzapine) and one antipsychotic not inducing weight gain in clinic (haloperidol), on food and water intake and body weight gain in rats. We included both female and male rats in this study. To reduce spontaneous high food intake in rats, and to be able to evaluate the treatment effect on a potential increase of food intake or metabolic changes, we allowed animal to receive only low-palatability chow. In male rats, none of the two compounds induced weight gain, but in female rats, both compounds induced weight gain. Consequently, the effect observed in rats does not match the clinical situation, and Wistar rats in this set-up cannot be considered a relevant model for antipsychotic-induced weight gain in humans.

Comparative effects of the antipsychotics sulpiride or risperidone in rats. I: bodyweight, food intake, body composition, hormones and glucose tolerance

Obesity and related metabolic disorders are important side effects of some antipsychotic drugs (APs). The currently available animal model of AP-induced bodyweight gain (BWG) in rats is based on administration of sulpiride (SUL). However, this model has important limitations. For example, SUL is a pure dopamine antagonist, whereas most APs in current clinical use interact with multiple neurotransmitter receptors involved in food intake (FI) and metabolism regulation. Therefore, we evaluated the effects of risperidone (RIS, 0.125, 0.25 or 0.5 mg/kg during 16 days) on BWG and FI in male and female rats. Comparison between RIS (0.5 mg/kg), SUL (20 mg/kg) and vehicle (VEH) during 12 days was also conducted in females. In male rats, RIS did not significantly affect BWG, FI, glucose tolerance or leptin levels, even though prolactin and corticosterone were significantly elevated. In females, both APs significantly increased BWG and FI, but the effect was stronger with SUL. The BWG was significantly associated with an increase in body fat. Serum leptin levels were increased only in SUL-treated rats. The area under the curve for glucose (AUGC) was significantly lower in the SUL group, but it was similar for insulin in all treatment groups. The area under the curve for insulin (AUIC) and BWG positively correlated only in the RIS group. Prolactin and corticosterone were significantly increased by both APs. Serum estradiol levels were significantly increased by RIS but not by SUL, but progesterone levels were similar in both groups. The observed positive correlation between BWG and the AUIC during RIS administration suggests that this agent may represent a better model of AP administration in humans. The animal model of RIS-induced obesity in rats might be improved by testing other doses, route of administration and type of diet.

The antipsychotic drug sulpiride does not affect bodyweight in male rats. Is insulin resistance involved?

Previous studies have shown that prolonged administration of antipsychotic drugs induces obesity in female but not in male rats. To explore the mechanisms involved in this sex-dependent effect, we administered the dopamine antagonist sulpiride (20 mg/kg i.p.) or vehicle (0.1 N HCl) to adult male rats during 21 days and daily assessed bodyweight and food intake. Then, we evaluated the glucose tolerance and the serum levels of insulin, leptin, total testosterone, dehydroepiandrosterone-sulfate (DHEA-S), thyroid hormones and blood lipids. In another experiment, food intake and water intake were assessed after acute injections of sulpiride or vehicle into the perifornical lateral hypothalamus. Lastly, the dopamine metabolites dihydroxyphenylacetic acid (DOPAC) and homovanilic acid (HVA) in the lateral hypothalamus were assessed by in vivo microdialysis after acute systemic injections of sulpiride and vehicle. Chronic sulpiride administration did not affect bodyweight gain and food intake. However, prolactin levels and the area under the glucose and insulin curves were significantly elevated. Acute sulpiride significantly increased food intake, water intake, DOPAC and HVA levels. The acute effects of sulpiride show that this drug is active at the perifornical lateral hypothalamus, which is a brain area where blockade of dopamine receptors stimulates feeding. However, after prolonged administration, sulpiride did not affect body weight. This lack of effect may be related to the impairment of insulin sensitivity, which may prevent body weight gain, and counteract other effects of sulpiride that promote adiposity such as hyperprolactinemia. These findings noticeably contrast with those observed in sulpiride-treated female rats that appear to display enhanced insulin sensitivity. The changes in insulin sensitivity do not appear related to a decrease in androgenic activity, because testosterone and DHEA-S levels were not affected by sulpiride. However, these results should be considered as preliminary because other relevant endocrine variables such as free testosterone, steroid binding globulin and pituitary gonadotrophin levels were not evaluated. Since the same sex-dependent effect on body weight and food intake in rats has been observed during administration of risperidone, which has a different pharmacological profile than sulpiride, future studies must evaluate other neurotransmitters involved in food intake regulation such as serotonin, noradrenaline and histamine.

Naltrexone does not prevent the weight gain and hyperphagia induced by the antipsychotic drug sulpiride in rats

Few pharmacological tools are currently available to counteract the excessive body weight gain often observed during prolonged administration of antipsychotic drugs. Most antipsychotic drugs block dopamine receptors, and both the brain dopaminergic and opioid systems appear to be involved in initiation and maintenance of feeding behavior, respectively. We evaluated whether the opioid antagonist naltrexone (NAL, 0.5-16 mg/kg/ip for 21 days) (a) affects body weight and food intake in gonadally-intact and drug-free female rats, (b) prevents obesity, hyperphagia, hyperprolactinemia and vaginal cycle disruption induced by long-term administration of the antipsychotic drug sulpiride (SUL, 20 mg/kg/ip for 21 days), or (c) reverses the acute hyperphagia induced by SUL (15 microg bilaterally), when directly applied in the perifornical lateral hypothalamus (PFLH). In drug-free rats, only NAL doses above 4 mg/kg, significantly decreased weight gain and food intake. Even though NAL (1 and 8 mg/kg) significantly attenuated SUL-induced hyperphagia and hyperprolactinemia, it did not reverse at any dose the weight gain and permanent diestrous induced by SUL. In addition, local NAL did not prevent the hyperphagia and polidypsia observed after acute intrahypothalamic SUL. Unexpectedly, the cumulative and 24 h food intake in SUL-treated rats was significantly increased by NAL. Collectively, these results do not support a role for endogenous opiates in the neural and endocrine mechanisms involved in weight gain during prolonged antipsychotic drug administration in rats.

Antipsychotic drug-induced obesity in rats: correlation between leptin, insulin and body weight during sulpiride treatment

Sulpiride (SUL, 20 mg kg-1 day-1) induces weight gain, hyperphagia, hyperprolactinemia, hypogonadism, and perhaps increased insulin sensitivity in rats. Leptin seems to signal the brain about the size of body fat stores and nutrient metabolism. We evaluated the basal serum leptin levels in rats after acute (1 h) or prolonged SUL or vehicle administration (10, 20 and 30 days). At days 10 and 30 leptin was also assessed during a glucose overload test. As the maximal weight gain during SUL administration is observed at days 10-15 of treatment, leptin was measured in a comparison group of insulin-treated rats (5 IU day-1 for 10 days). SUL-treated rats significantly gained weight. However, leptin levels were not significantly increased at any time-point of treatment. SUL did not affect insulin levels either. By contrast, leptin levels were significantly elevated after insulin administration, along with weight gain and hyperinsulinemia. An opposite correlation was also observed at day 10: leptin and insulin correlated negatively in the SUL group and positively in the insulin group. In addition, leptin and the magnitude of weight gain tended to correlate positively after SUL treatment, but negatively after insulin administration. SUL-treated rats, thus, appear to exhibit an unusual type of weight gain, characterized by normal circulating leptin and insulin levels. Such a particular leptin profile may be related to hyperprolactinemia, hypogonadism or lack of hyperinsulinemia. Molecular Psychiatry (2000) 5, 70-76.

Body weight gain induced by antipsychotic drugs: mechanisms and management

Long-term administration of typical and atypical antipsychotic drugs (AP) induces excessive weight gain which afflicts up to 50% of patients, impairs health and interferes with treatment compliance. Basic and clinical research has shown that AP may affect body weight through diverse mechanisms. Increased appetite is probably related to the interaction of AP with neuronal receptors to dopamine, serotonin and histamine. Additional metabolic-endocrine disruption of weight regulation may be related to the effects of AP-induced hyperprolactinaemia on gonadal-adrenal steroids and insulin sensitivity. In humans, programmed physical activity, dietary restriction, anorectic agents, and drugs that counteract hyperprolactinaemia have been shown to be successful in a limited number of studies. Two novel strategies could expand the available therapeutic options. First, in preclinical experiments in female rats the estradiol antagonist/agonist drug tamoxifen or estradiol itself have been shown to completely prevent the obesity provoked by the AP sulpiride, and to induce an endocrine-metabolic milieu that seems to counteract AP-induced obesity. Secondly, it has also been shown that oral antihyperglycaemic agents such as metformin may decrease body weight and counteract insulin resistance and hyperinsulinaemia which is correlated with several metabolic abnormalities in obese subjects. Lastly, estradiol replacement, tamoxifen and/or antihyperglycaemic agents are not devoid of significant side-effects, and these drugs have not been tested in obese psychiatric patients. Therefore, further research is needed before their clinical use may be recommended.

Glucose tolerance and serum insulin levels in an animal model of obesity induced by sub-acute or chronic administration of antipsychotic drugs

1. To assess the role of insulin in the development of the obesity induced by antipsychotic drugs, a glucose tolerance test was conducted in female rats after 0 or 30 days of sulpiride administration. 2. At day 10, the area under the glucose curve did not differ between sulpiride and vehicle-treated rats, however, the area under the insulin curve was significantly decreased by sulpiride. At day, 30 the insulin response was similar in both groups, but the area under the glucose curve was significantly lower in the sulpiride-treated rats. 3. The results suggest that insulin resistance and hyperinsulinemia are not involved in the development and maintenance of the obesity induced by sulpiride. Contrarily, these findings may be related to an increased insulin sensitivity. 4. The absence of hyperinsulinemia and insulin resistance indicates important differences between primary obesity in humans and rodents and this model of drug-induced excessive weight gain.

Glucose tolerance and serum insulin levels in an animal model of obesity induced by the antipsychotic drug, sulpiride

To assess the role of insulin in the development of obesity induced by antipsychotic drugs, a glucose tolerance test was conducted in 40 female rats during the peak of sulpiride-induced weight gain and in 40 vehicle-treated animals. The glucose area under the curve did not differ between the groups (P = 0.24), however, the area under the insulin curve was significantly decreased by sulpiride (55.2 +/- 2.8 versus 115.6 +/- 18.9, P = 0.007). The results suggest that insulin resistance and hyperinsulinaemia are not involved in the excessive weight gain observed in this animal model of drug-induced obesity. Alternatively, the insulin-dampened response observed in the sulpiride-treated rats may be related to increased insulin sensitivity, which may promote weight gain as proposed by Ravussin (1995).

Mechanism of the neuroleptic-induced obesity in female rats

1. Obesity is an undesirable side effect of neuroleptics which affects 50% approximately of patients under a program of chronic administration. 2. An animal model of neuroleptic-induced obesity and hyperphagia has been developed in female rats treated chronically with sulpiride (20 mg/Kg/ip. for 21 days). However, it is unknown whether or not the hyperphagia is essential for the development of this type of obesity. 3. Sulpiride or vehicle was administered in two experimental conditions: in the first one, food was available in an amount which was three times the previous individual daily food intake; in the second one, the daily food provision was maintained at the individual daily average before starting the treatments. This way hyperphagia was prevented in half of the groups. Besides the body weight gain measurement in all the groups, the serum levels of estradiol, prolactin, glucose and lipids were assessed in the groups with unrestricted food intake. 4. Food restriction prevented the sulpiride-induced weight gain, even though the rats displayed a permanent diestrus which suggests an hyperprolactinemia-induced impairment in the balance of the reproductive hormones that may promote weight gain. However, the basal levels of estradiol were not affected by sulpiride. 5. The high density cholesterol was significantly increased by sulpiride, and the serum glucose levels were significantly decreased, however these changes were only detected during the first week of treatment. 6. The decrease in the serum glucose levels may be an early consequence of hyperinsulinemia. 7. Neuroleptic-induced obesity in rats appears to mimic energy intake, endocrine status and carbohydrate metabolism in humans under chronic neuroleptic administration. However, these rodents did not display the typical changes in blood lipids observed in human obesity.

Tamoxifen prevents sulpiride-induced weight gain in female rats

To evaluate its potential utility in counteracting neuroleptic-induced obesity, the effects of long-term administration of tamoxifen (TAM) on body weight (BW) and food intake (FI) of gonadally intact and sulpiride-treated (SUL) female rats were assessed. In addition, estradiol and prolactin serum levels were measured in rats treated with SUL. SUL plus TAM and SUL plus bromocriptine (BR). TAM, at doses of 10, 50 and 100 micrograms, significantly decreased BW gain: FI was significantly reduced at the doses of 50 and 100 micrograms. In addition, doses of TAM ranging from 5-100 micrograms completely prevented SUL-induced BW gain and hyperphagia. BR also prevented SUL effects on BW and FI. In contrast to BR, concomitant administration of TAM did not prevent SUL-induced hyperprolactinemia. Estradiol levels were not modified by SUL alone or SUL plus BR, but they were significantly increased in the animals treated with TAM plus SUL. Neuroleptic-induced obesity in female rats might be related to an alteration in gonadal steroid balance secondary to hyperprolactinemia. While BR might counteract neuroleptic-induced weight gain by preventing hyperprolactinemia, TAM might directly interact with estrogen receptors, or indirectly increase estradiol levels. The use of TAM in preventing neuroleptic-induced obesity in humans warrants further investigation.

Enhancement of amphetamine anorexia after chronic administration of sulpiride in rats

Long-term administration of sulpiride induces hyperphagia and obesity in female rats. After sulpiride withdrawal, a significant hypophagia has been observed. The hyperphagia could be related to the blockade and the hypophagia to supersensitivity of dopamine D2 receptors, in particular those D2 receptors located in the perifornical hypothalamus. If this were the case, an enhancement of anorexia induced by amphetamine and dopamine should be observed after interruption of long-term sulpiride treatment. Two doses of systemic sulpiride (20 or 200 mg/kg) and one dose of intrahypothalamic sulpiride (15 micrograms) were tested. Amphetamine was administered by systemic or intrahypothalamic infusion. Dopamine was administered in the hypothalamus. After withdrawal of systemic administration of sulpiride (200 mg/kg), an enhancement of anorexia induced by systemic amphetamine was observed. However, the anorexia induced by intrahypothalamic injections of amphetamine or dopamine was not affected by the interruption of the sulpiride treatment. These results suggest that the hypophagia following chronic sulpiride treatment is not due to supersensitivity of D2 dopamine receptors in the lateral hypothalamus. Moreover, the change in the response to amphetamine might be related to supersensitivity of extrahypothalamic D2 receptors.

Effects of long-term administration of clozapine on body weight and food intake in rats

Previous reports have shown that long-term administration of typical and atypical neuroleptics induced obesity in female but not in male rats. It has been suggested that impaired ovarian steroidogenesis related to neuroleptic-induced hyperprolactinemia is necessary to observe the body weight changes. This hypothesis was tested with clozapine, an atypical neuroleptic that produces in rats a shorter increase in serum prolactin levels than do other neuroleptics. The effects of clozapine on body weight and food intake were assessed in female and male rats under treatment with any of the following doses: 0.5, 1, 2.5, 5, 10, and 20 mg/kg IP for 21 days. Vaginal cycle under clozapine treatment, as an indirect indicator of ovarian steroidogenesis, was also assessed. Obesity was not observed in any group. By contrast, clozapine at the doses of 10 and 20 mg/kg significantly decreased body weight and feeding in male rats. Clozapine at the doses of 5 and 10 mg/kg IP induced permanent diestrus. The failure of clozapine to induce obesity in female rats, despite impaired vaginal cycle, can be considered indirect evidence that drug-induced hyperprolactinemia is not sufficient to observe neuroleptic-induced obesity in rats.

Systemic sulpiride increases dopamine metabolites in the lateral hypothalamus

In rats with microdialysis probes in the perifornical lateral hypothalamus (PFH) a single injection of the D2 receptor blocker 1-sulpiride (20 mg/kg IP) significantly increased extracellular dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), but not 5-hydroxyindoleacetic acid (5-HIAA). This suggests that sulpiride crosses the blood-brain barrier and blocks D2 dopamine receptors in the PFH leading to increased dopamine turnover reflected in increased extracellular DOPAC and HVA. We conclude that D2 blockade in the hypothalamus could play a role in the hyperphagia and body weight gain observed in female rats under chronic administration of the antipsychotic drug, sulpiride.