“DEPRESSION AND ANXIETY AS OBESITY-RELATED COMORBIDITIES: POSSIBLE PROTECTIVE EFFECTS OF ACYLETHANOLAMIDES”

Obesity, whose primary cause is overconsumption of high-palatable caloric-dense food, has been linked to increased risk of depression and anxiety disorders. Indeed, diet restriction and abstinence from high-palatable food exacerbate these comorbidities. Considering the biological functions of endocannabinoids, such as anandamide, and related lipid signals, such as oleoylethanolamide and palmitoylethanolamide in the modulation of the reward system and mood tone; they might play a key role in modulating all the neurobehavioral components of this scenario. The aim of this study was to explore whether the abstinence from a palatable diet, after a long-term ad libitum consumption of high palatable food, might produce alterations of the emotional reactivity and mood tone and whether the pharmacological inhibition of fatty acid amide hydrolase (FAAH) by PF-3845 treatment (which causes an increase of acylethanolamide tone) could ameliorate such alterations. We used a rat model of diet-induced obesity based on hedonic overfeeding of a cafeteria-style diet (consisting of bacon, sausage, chocolate, cookies, etc) for 40 days. A control group of rats with ad libitum access only to standard chow and water was maintained. After the first 40 days of cafeteria diet, rats underwent an abstinence period of 28 days, with no longer access to the cafeteria diet but still ad libitum access to standard chow. During the abstinence period, animals were treated either with the FAAH inhibitor PF-3845 (10 mg/kg, sc.) or its vehicle administered every other day. At the end of the abstinence period, half of the rats were subjected to behavioral analyses such as the open field test, the elevated plus maze and the forced swimming test. The second half were sacrificed, their brains collected and micro-dissected for HPLC analyses of monoamines, western blot analysis of different proteins involved in the synthesis and degradation of acylethanolamides (monoacylglicerol lipase or MAGL; N-acyl phosphatidylethanolamine-specific phospholipase D or NAPE-PLD; diacylglycerol lipase alpha and beta or DAGL-α, DAGL-β; FAAH) and linked to inflammatory processes (cyclooxygenase 2 or COX2, CX3C chemokine receptor 1 or CX3CR1, allograft inflammatory factor 1or IBA-1, glial fibrillary acidic protein or GFAP). The preliminary results obtained from the behavioural studies showed that the prolonged abstinence from the cafeteria-diet was associated to anxiety-like behaviour in both the open-field and the elevated-plus-maze tests and depressive-like behaviour in the forced-swimming-test. The pharmacological treatment with PF-3845 was able to revert the depressive-like phenotype and to dampen the anxiety-like behaviour. Interestingly the altered behaviour was accompanied by modifications of monoaminergic tissue levels in key brain areas regulating eating; the treatment with PF-3845 was able to ameliorate such alterations. The results obtained from the western blotting analyses showed that the abstinence from the cafeteria diet reduced the expression of DAGL-β in the hypothalamus, NAPE-PLD and GFAP in medial prefrontal cortex. The treatment with PF-3845 was able to decrease the expression of CB1, NAPE-PLD and DAGL-α within the hypothalamus and reduce the expression of GFAP in medial prefrontal cortex. Overall the results obtained from the present study further support the role of the endocannabinoid system as a valid pharmacological target for the development of treatments for the neurofunctional alterations related to obesity.