Acute and long-term effects of psilocybin on energy balance and feeding behavior in mice

This mice study finds brain changes (prefrontal cortex transcriptome) but no acute nor long-lasting effects on food intake or bodyweight in obese mice after psilocybin administration. Though it’s difficult to translate to humans, the study suggests no non-psychological route through which psychedelics (psilocybin) can help with eating disorders.

Abstract

“Psilocybin and other serotonergic psychedelics have re-emerged as therapeutics for neuropsychiatric disorders, including addiction. Psilocybin induces long-lasting effects on behavior, likely due to its profound ability to alter consciousness and augment neural connectivity and plasticity. Impaired synaptic plasticity in obesity contributes to ‘addictive-like’ behaviors, including heightened motivation for palatable food, and excessive food seeking and consumption. Here, we evaluate the effects of psilocybin on feeding behavior, energy metabolism, and as a weight-lowering agent in mice. We demonstrate that a single dose of psilocybin substantially alters the prefrontal cortex transcriptome but has no acute or long-lasting effects on food intake or body weight in diet-induced obese mice or in genetic mouse models of obesity. Similarly, sub-chronic microdosing of psilocybin has no metabolic effects in obese mice and psilocybin does not augment glucagon-like peptide-1 (GLP-1) induced weight loss or enhance diet-induced weight loss. A single high dose of psilocybin reduces sucrose preference but fails to counter binge-like eating behavior. Although these preclinical data discourage clinical investigation, there may be nuances in the mode of action of psychedelic drugs that are difficult to capture in rodent models, and thus require human evaluation to uncover.”

Authors: Nicole Fadahunsi, Jens Lund, Alberte W. Breum, Cecilie V. Mathiesen, Isabella B. Larsen, Gitte M. Knudsen, Anders B. Klein & Christoffer Clemmensen

Summary

INTRODUCTION

Psilocybin, a serotonergic psychedelic, is systemically metabolized to psilocin, which activates the serotonin 2A receptor (5-HT2AR), altering perception to induce its hallucinogenic effect. This leads to enduring effects on behavior, for example, long-lasting improvement in depressive symptoms.

Psilocybin, a serotonin receptor agonist, reduces food intake in rats and dogs and has anti-inflammatory effects in a mouse model of cardiovascular disease. Self-reported data from psychedelic users shows that one-time use of a classic psychedelic reduces the risks of becoming obese. In the present study, psilocybin failed to affect body weight or food intake in mouse models of genetic obesity, diet-induced obesity, and binge-eating disorder. However, further clinical investigation might shed light on the use of psychedelics for the treatment of human obesity.

MATERIALS AND METHODS Animals

Mice were kept under normal room temperature (22 °C) on a standard 12 h light – dark cycle, and were either lean or obese. They were sham injected with isotonic saline in the 3 days preceding study start, and were block-randomized into groups.

Head-twitch response

17-week-old male C57BL/6J mice were injected with psilocybin and placed into their own new cages. Their behavior was recorded for 20 min and the number of head twitches was counted by two observers blinded to the experimental conditions.

Open field test

Fourteen-week-old male C57BL/6J mice were given a single intraperitoneal injection of 3 mg/kg psilocybin or isotonic saline, and their locomotor activity was recorded for 20 min using a ceiling-mounted Logitech C920 camera.

Voluntary running

Ten-week-old male C57BL/6J mice were single-housed in cages equipped with running wheels, and their running distance was measured on days 2 and 1. They were then injected intraperitoneally with either psilocybin or isotonic saline, and their running distance was measured again.

Metabolic assessment

9-week-old male C57BL/6J mice were single-housed in indirect calorimetry chambers and were injected intraperitoneally with psilocybin or isotonic saline on day 0. The automatic 20 min-interval measurements of oxygen consumption, carbon dioxide release, and food intake continued for 4 days.

Body temperature

Body temperature was assessed in 8-week-old male C57BL/6J mice after psilocybin injection and at 15, 30, 60, 120, 180, 360 min, and 24 h following treatments.

Blood biochemistry

8-week-old male C57BL/6J mice were randomized to receive either 3 mg/kg psilocybin or isotonic saline. Blood samples were drawn before treatment (0 h), 3 and 24 h following treatment, and were used to measure corticosterone, cholesterol, triglycerides, and insulin.

Food intake and body weight studies

Male DIO C57BL/6J mice were divided into two groups based on body weight and received a single intraperitoneal injection of psilocybin or isotonic saline.

21-week-old leptin-deficient ob/ob mice received 3 mg/kg psilocybin or isotonic saline, and food intake and body weight were measured daily.

Dietary intervention study

Group 1 mice were given a chow diet and high-fat diet, and were treated with isotonic saline on day 0 to determine baseline food intake and body weight following injection stress. Group 2 mice were given psilocybin on day 0 to stimulate diet-induced weight loss.

Binge eating paradigm

Mice that were fed a high-fat diet intermittently developed a binge-like phenotype, while mice that were fed a high-fat diet continuously developed a normal phenotype.

Mice were randomized to groups for pharmacological evaluation of the model. After two binge cycles, mice received either fluoxetine (30 mg/kg), psilocybin (3 mg/kg), or isotonic saline (n = 6 per group).

Sucrose preference test

Fourteen-week-old male C57BL/6J mice were acclimated to the presence of two water bottles in their home cage, and were subsequently injected intraperitoneally with psilocybin or isotonic saline. The water and sucrose intake over two study days were averaged.

Bulk RNA sequencing

Group 1 received 3 mg/kg psilocybin, Group 2 received isotonic saline, and Group 4 received 3 mg/kg psilocybin followed by tissue harvest 4 weeks after treatment.

On the day of the experiment, mice received a single intraperitoneal injection and were sacrificed. Their brains were dissected and flash frozen on dry ice, and RNA was isolated.

Gene expression analysis (qPCR)

Brown adipose tissue was dissected from all mice used in the bulk RNA seq study and cDNA was synthesised using RNeasy Minikit (Qiagen). qPCR was performed using SYBR green and gene expression analysis was normalized to housekeeping gene 36b4.

Transcriptomic analysis by RNA sequencing

Total RNA was isolated using an RNeasy mini kit, messenger RNA sequencing libraries were prepared using the Illumina TruSeq Stranded mRNA protocol, and 2.7 billion reads were generated using a NovaSeq 6000.

Bioinformatic analyses

Fastq files were generated and aligned to the GRCm38 primary assembly using STAR v. 2.7.2b, and then counted against the same gene model using featureCounts v. 1.6.2. Differential expression was calculated using limma v. 3.44.0 and contrasts were found using the camera function.

Statistical analyses

All statistical analyses were performed in GraphPad Prism version 9. P values 0.05 were considered statistically significant.

Establishing a psychoactive dose of psilocybin for metabolic studies

In order to test the bioactivity of psilocybin and determine an appropriate dose, we measured the head-twitch response following a single administration of 0.3 mg/kg, 1 mg/kg, 3 mg/kg or vehicle (isotonic saline). We performed an open-field test on mice and found that 3 mg/kg psilocybin was sufficient to induce a ‘psychoactive’ effect. The increased thigmotaxis (time spent close to the walls) following psilocybin-treatment could be interpreted as anxiogenic, but in this instance seems to relate to reduced total locomotion.

Psilocybin does not affect energy metabolism in mice

In a study assessing alcohol consumption following psychedelic use, alongside recidivism, participants reported an increase in exercise. Psilocybin did not affect voluntary physical activity or whole-body energy metabolism in male C57BL/6J mice injected with a single dose of psilocybin (3 mg/kg) or vehicle. Psilocybin administration did not affect body temperature, blood glucose or plasma corticosterone in mice. However, plasma cortisol was increased following the administration of both psilocybin and LSD in humans.

Psilocybin does not affect body weight or food intake in mouse models of obesity

Mice treated with the selective 5-HT2AR agonists DOI and TCB-2 exhibit hypophagia, but psilocybin, an agonist of 5-HT2ARs, had no effect on body weight or food intake in a mouse model of diet-induced obesity.

We wanted to assess the effect of psilocybin on leptin-deficient ob/ob mice, which have impaired metabolism and a depressive phenotype. However, a single dose of 3 mg/kg psilocybin had no effect on body weight or food intake.

We investigated the effect of a microdosing-like strategy on body weight in DIO mice, and in an MC4R KO mouse model. No significant effect was observed on food intake or body weight using this approach.

Psilocybin has no effect on body weight or food intake in combination with dietary or pharmacological interventions

Studies have shown that psilocybin can enhance cognitive flexibility, facilitating revision of long-held patterns of behavior. However, psilocybin did not enhance the efficacy of a dietary intervention in obese mice, nor did it enhance the weight loss effect of liraglutide.

Psilocybin does not alter binge-eating behavior, but reduces sucrose preference in lean mice

Early research showed that psilocybin could be used as a treatment for tobacco and alcohol dependence. More recent work has shown that psilocybin targets a neural circuit involved in craving, highlighting its potential as a treatment for addiction.

After successfully establishing the binge-eating phenotype in two consecutive cycles, psilocybin failed to ameliorate the binge-eating phenotype, but did lower sucrose preference in a single injection. This finding suggests that psilocybin may be of benefit for treating compulsive-reward-seeking behavior or excessive consumption of sweet foods.

Psilocybin causes acute transcriptional changes in the prefrontal cortex, but not in the hypothalamus

We found that psilocybin causes significant changes in gene expression in the prefrontal cortex (PFC) of mice, which persists even after a month. These changes include genes associated with cognition, neuronal growth, plasticity and obesity.

DISCUSSION

A single high dose of psilocybin significantly altered the transcriptomes of the hypothalamus and prefrontal cortex in lean mice. The effect of psilocybin was sustained over time, with the highest effects observed 3 hours after administration.

Homeostatic mechanisms defend the elevated body weight, hindering weight loss efforts, and requiring a chronic treatment regime for weight loss maintenance.

The psychedelic renaissance has sparked new hope for the treatment of many behavioral and neuropsychiatric conditions, including obesity. We conducted the first preclinical evaluation of psilocybin for obesity and binge-like eating behavior in mouse models of genetic and diet-induced obesity.

Psilocybin is used to treat depression, disorders with compulsive symptomatology, and eating disorders. It may also be useful for the treatment of compulsive behavior or dampening excessive consumption of sugar and sweet foods in susceptible individuals.

Rodent models may be applicable for translational evaluation of 5-HT2AR-targeting psychedelics as tools for weight management and eating disorders, and clinical trials are starting to assess the use of psilocybin for the treatment of obesity and disordered eating in humans.

Psilocybin, a 5-HT2AR agonist, had no impact on food intake or body weight in the wide variety of conditions tested, but did affect transcriptional programs in the prefrontal cortex. This suggests that psilocybin may be a novel approach for altering executive function to reduce impulsive food intake behavior.

Psilocybin did not reduce body weight and food intake in obese mice, but did lower the preference for sucrose in lean mice. However, a single high-dose was not sufficient to reduce body weight and food intake, nor to attenuate binge eating behavior.

ACKNOWLEDGEMENTS

The authors thank several people for their help, including Charlotte Sashi Aier Svendsen, Lars Roed Ingerslev, Mie Mechta, and The Single-Cell Omics platform at the Novo Nordisk Foundation Center for Basic Metabolic Research.

ADDITIONAL INFORMATION

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