The effects of an obesogenic diet on behavior and cognition in zebrafish (Danio rerio): Trait average, variability, repeatability, and behavioral syndromes

Abstract

The obesity epidemic, largely driven by the accessibility of ultra‐processed high‐energy foods, is one of the most pressing public health challenges of the 21st century. Consequently, there is increasing concern about the impacts of diet‐induced obesity on behavior and cognition. While research on this matter continues, to date, no study has explicitly investigated the effect of obesogenic diet on variance and covariance (correlation) in behavioral traits. Here, we examined how an obesogenic versus control diet impacts means and (co‐)variances of traits associated with body condition, behavior, and cognition in a laboratory population of ~160 adult zebrafish ( Danio rerio ). Overall, an obesogenic diet increased variation in several zebrafish traits. Zebrafish on an obesogenic diet were significantly heavier and displayed higher body weight variability; fasting blood glucose levels were similar between control and treatment zebrafish. During behavioral assays, zebrafish on the obesogenic diet displayed more exploratory behavior and were less reactive to video stimuli with conspecifics during a personality test, but these significant differences were sex‐specific. Zebrafish on an obesogenic diet also displayed repeatable responses in aversive learning tests whereas control zebrafish did not, suggesting an obesogenic diet resulted in more consistent, yet impaired, behavioral responses. Where behavioral syndromes existed (inter‐class correlations between personality traits), they did not differ between obesogenic and control zebrafish groups. By integrating a multifaceted, holistic approach that incorporates components of (co‐)variances, future studies will greatly benefit by quantifying neglected dimensions of obesogenic diets on behavioral changes.

Obesity Impairs Cognitive Function with No Effects on Anxiety-like Behaviour in Zebrafish

“…In the present study, the AB strain was used as it is commonly accepted to study obesity and obesity-related processes [15]. The increase in the feeding rate in OIO fish resulted in increased W, L, and BMI, in addition to elevated total fat percentage compared to control animals (~60%), supporting the obese condition of OIO fish, as previously reported [15][16][17]19]. The growth dynamic in the sexes appears to be different, with the result that females are more adept at increasing energy density when overfed than males, likely due to increased oocyte production.…”

“…Therefore, DIO exhibits consistent effects on both STM and LTM, whereas OIO had no effect on LTM and controversial effects on STM (Ref. [17] vs. the present study). Since diet composition appears to be critical for obesity-induced cognitive and behavioural impairment, the aforementioned controversy may stem from the dietary components involved in generating obesity by overfeeding.…”

“…The manner in which obesity is induced in zebrafish seems to have effects on behavioural responses and particularly anxiety-like responses. Zebrafish, either larvae or adult specimens, fed obesogenic diets containing high fat levels exhibit anxiety-like behaviours [14,21]; however, obese fish on regular diets at high ratios failed to exhibit such behaviour [17,18]. Due to the wide spectrum of behavioural responses displayed in NTDT by zebrafish [22][23][24], it was decided to enlarge the behavioural variables to corroborate previous results and study the activation of the central monoaminergic circuitry.…”

“…The existence of STM and LTM has been demonstrated in zebrafish [31], and the effects of DIO on STM [13] and LTM have previously been studied [21]. DIO induced impairment of both STM and LTM, but OIO protocols had no effect on STM formation [17], although intergenerational effects of obesity have been reported [18]. Unfortunately, OIO effects on LTM response have not been studied.…”

“…However, overfeeding-induced obesity (OIO) with commercial food does induce deleterious effects on brain homeostasis and neuronal plasticity, thus promoting anxiety-like responses in zebrafish [16]. Nevertheless, similar experiments following an analogous approach to generating OIO in zebrafish were not able to replicate anxiety-like responses or find differences in aversive learning assays [17,18]. In the face of such controversy, the effects of OIO on anxiety-like behaviour and short-and long-term memory using aversive learning tests in zebrafish were explored.…”