The effects of punicic acid on obesity in zebrafish

Obesity has truly emerged as a major health concern worldwide as it affects the quality of life and increases the risk for developing multiple and serious health conditions such as diabetes, heart disease and some cancers. Obesity is linked to at least 2.8 million deaths each year. The challenges to successful obesity management are numerous and, to date, treatments can include lifestyle changes, dietary modification, increased physical activity, the use of medications, and in some cases the recommendation for surgery. Among dietary changes, scientific evidence indicates that dietary fat plays a role in weight loss and maintenance. Several polyunsaturated fatty acids groups, including conjugated linoleic acids (CLAs) and conjugated linolenic acids (CLnAs), have demonstrated health benefits on obesity-related metabolic disorders. Among them, punicic acid (PunA; C18:3cis-9, trans-11, cis-13) is an omega-5 long chain PUFA and a CLnA isomer that can be found in natural sources, most notably the pomegranate seeds (Punica granatum L.). As evidence suggests that PunA possesses powerful preventive and even therapeutic properties regarding cancer and chronic diseases (obesity, type-2 diabetes, heart diseases), its addition to diets may be beneficial. The present work aimed to determine the effects of PunA on obesity using zebrafish as animal models. For that purpose, a first experiment, called “egg yolk feeding trial”, was conducted to test experimental and control egg yolks (from hens fed a diet enriched in pomegranate seed oil (PSO) or in olive oil) as a diet to feed 3-month-old zebrafish for 20 days. The aim of this feeding trial was also to observe the effects of PunA on zebrafish growth. Beside this, a second experiment, called “basal feed matrix (BFM) overfeeding trial”, was carried out to test whether a diet enriched in PunA reduced obesity using a lab-made basal feed matrix supplemented with PSO (experimental diet) or with olive oil (control diet). 8-month-old zebrafish were first overfed with the control diet for one month to increase their body mass and, subsequently, were separated into two groups and overfed for one additional month with either the control diet or the experimental diet. Changes in zebrafish growth parameters (weight and length) and fat composition were assessed within the two experiments. Results from the egg yolk feeding trial showed that, probably due to their vitamin and mineral deficiencies, egg yolks should not be utilized as a fish diet on their own, but rather as a supplement of another diet such as Artemia. Moreover, PunA did not demonstrate any beneficial effects on zebrafish body mass after 20 days of feeding. In contrast, the BFM overfeeding trial demonstrated that feeding zebrafish with BFM supplemented with PSO for 30 days decreased the zebrafish body mass compared to those fed with BFM supplemented with olive oil (control diet). These observations raise the interest in incorporating PunA into diets and in continuing to investigate the potential anti-obesity effects of this fatty acid.