Biology subjects

Naneix, F.

Publications and source records attributed to Naneix, F..

8 recordsLinked to original sources

bioRxiv2026

Long lasting alterations of feeding by adolescent obesity

The prevalence of obesity is increasing worldwide, especially amongst younger populations. As both brain and body are still under development, numerous studies have shown that adolescence is an especially sensitive period for the impact of external insults including unbalanced diets. To better understand and prevent the vulnerability to obesity and maladaptive food choice, it is crucial to explore the long-term impact of adolescent exposure to obesogenic diets on different feeding behaviours. To address this, we gave mice access to an obesogenic diet with a very high-fat content (vHFD) specifically during adolescence and investigated the long-lasting impact on feeding at adulthood months after a switch to a healthy diet. Using specific feeding tests, we found that both males and females vHFD-exposed mice exhibited an increased intake of both standard food and palatable high-fat foods, without impacting preference for non-caloric food rewards. Importantly, these sex-dependent alterations are not fully correlated with diet-induced weight gain but may support long-term vulnerability to overeating and the development or maintenance of obesity.

neuroscience↗

bioRxiv2026

Adolescent obesity induces sex-specific alterations of action control

The prevalence of obesity is rising worldwide in young people and is associated with poor long-term health outcomes. To counter obesity, weight loss strategies especially involve changes in feeding behaviors and food choice. However, the high level of relapse to unhealthy dietary habits represents an important challenge, suggesting long-term alterations of decision-making and food-seeking processes. Previous studies showed that adolescence is critical for the development of decision-making functions. Thus, it is essential to understand the precise impact of the exposure to obesogenic diets during this life stage on the different processes underlying flexible control of food-seeking actions. To address this, we gave mice access to high-fat diets (HFDs) with different fat contents during adolescence and investigated the long-lasting impact on action control at adulthood after a switch to a healthy diet. We uncovered important sex differences. In both males and females, exposure to HFD with very high-fat content (60%) promoted habitual behavior, which is less flexible to adapt to changes in outcome value or action-outcome relationships. In contrast, exposure to HFD with lower fat content (45%) impaired action control based on the updating of outcome value in males only, while impairing action control based on the updating of action-outcome relationships in females only. These findings highlight how the consumption of obesogenic diets during adolescence has long-lasting, diet- and sex-dependent effects on decision-making processes, promoting habitual responses to food. These changes may support long-term vulnerability for mental and physiological health conditions. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=112 SRC="FIGDIR/small/702500v2_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@73aab1org.highwire.dtl.DTLVardef@1cb8110org.highwire.dtl.DTLVardef@1866a5dorg.highwire.dtl.DTLVardef@1b11d2c_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2025

Dietary protein restriction in rats leads to a rapid within-session preference for protein

Evolution has provided species with adaptive behavioural mechanisms that guarantee tight dietary protein regulation. However, an unsolved question is whether the well-established preference for protein-containing food manifested during states of protein restriction is innate or learned. Here, we tackled this problem by maintaining male rats on either a low-protein diet (5% protein, protein-restricted) or a control diet (22% protein, non-restricted) for 9-12 days, and then offered them two novel foods, a protein-containing solution (4% casein) and a carbohydrate-containing solution (4% maltodextrin) during a daily 60-minute free-choice test, repeated for 5 consecutive days. We assessed both the total and cumulative intake of each solution throughout each test, as well as the microstructure of licking behaviour as an index of the solutions palatability. In a second experiment, we exposed a different cohort of rats, before any behavioural test, to the same protein source (i.e., casein) that they would encounter during the free-choice tests, to assess whether familiarity with casein would drive subsequent casein intake even in non-restricted rats. We found that dietary protein restriction leads to a rapid preference (within 16 minutes of first exposure) for a casein-rich solution, and this preference is persistent over subsequent exposures. Increased palatability of protein during initial exposure correlated with protein preference in the restricted rats. Moreover, familiarity with casein did not lead to protein preference in non-restricted rats. This study demonstrates that, when in need of protein, protein preference is a rapid adaptation that requires minimal experience of protein. HighlightsO_LIProtein-restricted rats show a rapid preference for protein over carbohydrate C_LIO_LIThe preference emerges within 5 minutes of exposure to solutions C_LIO_LIIncreased palatability of casein is partially related to preference C_LIO_LIExposure to casein without protein restriction does not lead to preference C_LI

animal behavior and cognition↗

bioRxiv2022

Restriction of dietary protein in rats increases progressive-ratio motivation for protein

Low-protein diets can impact food intake and appetite, but it is not known if motivation for food is changed. In the present study, we used an operant behavioral task - the progressive ratio test - to assess whether motivation for different foods was affected when rats were maintained on a protein-restricted diet (REST, 5% protein diet) compared to non-restricted control rats (CON, 18% protein). Rats were tested either with nutritionally-balanced pellets (18.7% protein, Experiment 1) or protein-rich pellets (35% protein, Experiment 2) as reinforcers. Protein restriction increased breakpoint for protein-rich pellets, relative to CON rats, whereas no difference in breakpoint for nutritionally-balanced pellets was observed between groups. When given free access to either nutritionally-balanced pellets or protein-rich pellets, REST and CON rats did not differ in their intake. We also tested whether a previous history of protein restriction might affect present motivation for different types of food, by assessing breakpoint of previously REST animals that were subsequently put on standard maintenance chow (protein-repleted rats, REPL, Experiment 2). REPL rats did not show increased breakpoint, relative to their initial encounter with protein-rich pellets while they were protein-restricted. This study demonstrates that restriction of dietary protein induces a selective increased motivation for protein-rich food, a behavior that disappears once rats are not in need of protein.

neuroscience↗

bioRxiv2020

Chemogenetic silencing of hippocampus and amygdala reveals a double dissociation in periadolescent obesogenic diet-induced memory alterations

1In addition to numerous metabolic comorbidities, obesity is associated with several adverse neurobiological outcomes, especially learning and memory alterations. Obesity prevalence is rising dramatically in youth and is persisting in adulthood. This is especially worrying since adolescence is a crucial period for the maturation of certain brain regions playing a central role in memory processes such as the hippocampus and the amygdala. We previously showed that periadolescent exposure to obesogenic high-fat diet (HFD) had opposite effects on hippocampus- and amygdala-dependent memory, impairing the former and enhancing the latter. However, the causal role of these two brain regions in periadolescent HFD-induced memory alterations remains unclear. Here, we first showed that periadolescent HFD induced long-term, but not short-term, object recognition memory deficits, specifically when rats were exposed to a novel context. Using chemogenetic approaches to inhibit targeted brain regions, we then demonstrated that recognition memory deficits are dependent on the activity of the ventral hippocampus, but not the basolateral amygdala. On the contrary, the HFD-induced enhancement of conditioned odor aversion requires specifically amygdala activity. Taken together, these findings suggest that HFD consumption throughout adolescence impairs long-term object recognition memory through the overactivation of the ventral hippocampus during memory acquisition. Moreover, these results further highlight the bidirectional effects of adolescent HFD on hippocampal and amygdala functions.

neuroscience↗

bioRxiv2020

AGE DEPENDENT EFFECTS OF PROTEIN RESTRICTION ON DOPAMINE RELEASE

Despite the essential role of protein intake for health and development, very little is known about the impact of protein restriction on neurobiological functions, especially at different stages of the lifespan. The dopamine system is a central actor in the integration of food-related processes and is influenced by physiological state and food-related signals. Moreover, it is highly sensitive to dietary effects during early life periods such as adolescence due to its late maturation. In the present study, we investigated the impact of protein restriction either during adolescence or adulthood on the function of the mesolimbic (nucleus accumbens) and nigrostriatal (dorsal striatum) dopamine pathways using fast-scan cyclic voltammetry in rat brain slices. In the nucleus accumbens, protein restriction in adults increased dopamine release in response to low and high frequency trains of stimulation (1-20 Hz). By contrast, protein restriction performed at adolescence decreased nucleus accumbens dopamine release. In the dorsal striatum, protein restriction has no impact on dopamine release when performed at adulthood but in adolescent rats we observed frequency-dependent increases in stimulated dopamine release. Taken together, our results highlight the sensitivity of the different dopamine pathways to the effect of protein restriction, as well as their vulnerability to deleterious diet effects at different life stages.

neuroscience↗

bioRxiv2019

Protein appetite drives neural activity in the ventral tegmental area

Control of protein intake is essential for numerous biological processes as several amino acids cannot be synthesized de novo, however, its neurobiological substrates are still poorly understood. In the present study, we combined in vivo fiber photometry with nutrient-conditioned flavor in a rat model of protein appetite to record neuronal activity in the ventral tegmental area (VTA), a central brain region for the control of food-related processes. In adult male rats, protein restriction increased preference for casein (protein) over maltodextrin (carbohydrate). Moreover, protein consumption was associated with a greater VTA response relative to carbohydrate. After initial nutrient preference, a switch from a normal balanced diet to protein restriction induced rapid development of protein preference but required extensive exposure to macronutrient solutions to induce greater VTA responses to casein. Furthermore, prior protein restriction induced long-lasting food preference and VTA responses. This study reveals that VTA circuits are involved in protein appetite in times of need, a crucial process for all animals to acquire an adequate amount of protein in their diet. Significance StatementAcquiring insufficient protein in ones diet has severe consequences for health and ultimately will lead to death. In addition, a low level of dietary protein has been proposed as a driver of obesity as it can leverage up intake of fat and carbohydrate. However, much remains unknown about the role of the brain in ensuring adequate intake of protein. Here, we show that in a state of protein restriction a key node in brain reward circuitry, the ventral tegmental area, is activated more strongly during consumption of protein than carbohydrate. Moreover, although rats behavior changed to reflect new protein status, patterns of neural activity were more persistent and only loosely linked to protein status.

neuroscience↗

bioRxiv2019

Portion size does not influence food consumption in rats

In studies of eating behavior that have been conducted in humans, the tendency to consume more when given larger portions of food, known as the portion size effect (PSE), is one of the most robust and widely replicated findings. Despite this, the mechanisms that underpin it are still unknown. In particular, it is unclear whether the PSE arises from higher-order social and cognitive processes that are unique to humans or, instead, reflects more fundamental processes that drive feeding, such as conditioned food-seeking. Importantly, studies in rodents and other animals have yet to show convincing evidence of a PSE. In this series of studies, we used several methods to test for a PSE in adult male Sprague-Dawley rats. Our approaches included using visually identifiable portions of a palatable food; training on a plate cleaning procedure; providing portion sizes of food pellets that were signaled by auditory and visual food-predictive cues; providing food with amorphous shape properties; and providing standard chow diet portions in home cages. In none of these manipulations did larger portions increase food intake. In summary, our data indicate that a PSE does not appear to be present in rats or, if it is, it is more nuanced, dependent on experimental procedure and/or smaller in size than it is in humans. In turn, these findings suggest that the widely-replicated PSE in humans may be more likely to reflect higher-order cognitive and social processes than fundamental conditioned behaviors.\n\nHighlightsO_LIPortion size effect (PSE) refers to increased food intake induced by large portions.\nC_LIO_LIAlthough widely replicated in human feeding studies, it may not exist animals.\nC_LIO_LIPresence of a PSE in animals would shed light on mechanisms, which are not known.\nC_LIO_LIHere, we find no evidence of PSE in rats under a number of experimental conditions.\nC_LIO_LIThis suggests that the human PSE is more likely due to socio-cognitive processes.\nC_LI

animal behavior and cognition↗