Modelo preclínico de obesidad basado en alimentos altamente procesados y de alta palatabilidad / Preclinical model of obesity based on ultra-processed and highly palatable foods

Resumen Introducción: el alarmante incremento de la obesidad en todo el mundo y en Costa Rica responde principalmente a modificaciones en la composición de la dieta habitual de las personas. La presente investigación tuvo como objetivo implementar un protocolo de alimentación formulado a partir de alimentos altamente procesados y de alta palatabilidad (APAP) consumidos por la población costarricense para, luego, evaluar sus efectos en la conducta alimentaria y en parámetros biométricos y bioquímicos. Metodología: ratas adultas macho Wistar se asignaron a dos grupos. Al primero se le administró alimento estándar para roedores (grupo DC) y al segundo, alimentos APAP (grupo APAP), durante ocho semanas. Resultados: a lo largo de ese periodo, los animales expuestos a los APAP exhibieron mayor ingesta y energía, caracterizadas por un alto consumo de grasas y uno menor de proteínas y fibra; además, mostraron un incremento significativo en los diversos parámetros de obesidad (e. g., peso corporal y ganancia de peso, índice de Lee y adiposidad central) y niveles descriptivamente superiores de glucosa y triglicéridos en sangre, pero notablemente menores de colesterol total. Conclusiones: los resultados indican que una dieta basada en los alimentos APAP más frecuentes en la población costarricense es capaz de inducir hiperfagia y obesidad. Así, este modelo constituye una herramienta prometedora para ahondar en el estudio de las factores neurobiológicos y metabólicos relacionados con la obesidad por el sobreconsumo de alimentos APAP.

Abstract Introduction. The alarming increase in obesity both worldwide and in Costa Rica is mainly due to changes in the composition of the usual diet of the population. The goal of our research was to implement a feeding protocol formulated from ultra-processed and highly palatable foods (UPHP) consumed by the Costa Rican population and to evaluate the effects of the UPHP diet on eating behavior and biometric and biochemical parameters. Methods: Adult male Wistar rats were assigned to two groups. One group was given standard rodent chow (DC group) while the other group received UPHP foods (UPHP group) for eight weeks. Results: Throughout this period, animals exposed to the UPHP diet exhibited higher food and energy intake characterized by high consumption of fat and lower consumption of protein and fiber. Animals in the UPHP group also showed a significant increase in obesity parameters (e.g., body weight and bodyweight gain, Lees index, and central adiposity). Furthermore, the UPHP group had descriptively higher levels of blood glucose and triglycerides and significantly lower levels of total cholesterol. Conclusions: Our results indicate that a feeding protocol based on the most frequent food choices of the Costa Rican population is capable of inducing hyperphagia and obesity. This model constitutes a promising tool to delve into the study of the neurobiological and metabolic factors related to obesity induced by overconsumption of UPHP foods.

Fat Intake and Obesity-related Parameters Predict Striatal BDNF Gene Expression and Dopamine Metabolite Levels in Cafeteria Diet-fed Rats.

Modern westernized diet is a major risk factor associated with the current obesity epidemic. To study the effects of dietary choices of Western societies, the cafeteria diet has been validated as a preclinical model of obesity. We aimed to investigate the behavioral and metabolic alterations induced by a cafeteria diet on gene expression and neurotransmitter contents involved in neural plasticity and reward processing. Male Wistar rats were exposed to either standard or cafeteria diet for 9 weeks. Food intake and body weight were scored daily. Behavioral effects were assessed in the elevated plus-maze (EPM) and open field (OFT) tests. Serum biochemical parameters, brain monoamines, and BDNF, TrkB, CRF, CREB, and Dnmt3A mRNA levels were analyzed in reward-related brain regions. We found that cafeteria-diet rats consumed more energy and food than the control group, leading to increased body weight gain and adiposity. The cafeteria-diet rats showed an anxiolytic-like effect in the OFT, but not in the EPM. The cafeteria diet increased BDNF expression in the dorsal striatum (DS), and norepinephrine, 5-HT, TrkB, CREB, and Dnmt3A levels in the hippocampus. Additionally, multiple regression analysis showed that accumbal DOPAC and BDNF mRNA levels were robustly predicted by hyperphagia, fat mass accumulation, and body weight gain only in the cafeteria group. Overall, cafeteria diet-induced hyperphagia could lead to alterations in hedonic and motivational control of food intake through changes in dopamine metabolism and BDNF signaling in the nucleus accumbens and the DS.