2013; Gajdaet al. in brain arachidonic acid -derived arachidonoylethanolamide in males correlated with increased brain free and total arachidonic acid. The ability of LKO to block the HFD-induced increase in brain arachidonoylethanolamide correlated with reduced ability of HFD to increase brain free and total arachidonic acid in males. In females, brain free and total arachidonic acid levels were much less affected by either HFD or LKO in the context of HFD. These data showed that LKO markedly diminished the impact of HFD on brain endocannabinoid levels, especially in male mice. Keywords: mouse, FABP1, gene ablation, brain, endocannabinoid, sexual MANOOL dimorphism == Graphical abstract == Fatty acid binding protein-1 (FABP-1) is not detectable in brain but is highly expressed in liver. FABP-1 null (LKO) male mice on control, but not high-fat, diet had increased brain levels of arachidonic acid-containing MANOOL endocannabinoids (AEA, 2-AG), correlating with increased free and total arachidonic acid in brain and serum; however , this dietary phenomenon was not observed in female LKO. == INTRODUCTION == A major function of the endocannabinoid system (ECS) is in the control of appetite (Osei-Hyiamanet al. 2005; Watkins and Kim 2015; Naughtonet al. 2013). Fasting increases endocannabinoid (EC) levels in brain hypothalamus and nucleus accumbens, while refeeding normalizes EC levels therein without altering EC levels in other brain regions not involved with feeding (Silvestri and DiMarzo 2013; Lillo 2007). Pharmacologic inhibition as well as genetic ablation of cannabinoid receptor-1 (CB1) decreases appetite and results in hypophagia (Silvestri and DiMarzo 2013). However , the impact of ECs on appetite is highly dependent on both the profile of individual EC produced as well as the presence of CB1 receptor (Osei-Hyiamanet al. 2005; Watkins and Kim 2015; Naughtonet al. 2013). For example , in brain the arachidonic acid (ARA, 20: 4n-6)-derived EC [arachidonoylethanolamide (anandamide, AEA), 2-arachidonoylglycerol (2-AG)] selectively act on CB1 (but not CB2) to stimulate food intake and hyperphagia (Naughtonet al. 2013; Guzmanet al. 2004). Upon conversion to ARA, linoleic acid (LNA, 18: 2n-6) also increases food intake (Naughtonet al. 2013; Alvheimet al. 2012; Alvheimet al. 2014). In general, other EC decrease food intake and weight gain by non-CB pathwaysoleoylethanolamide (OEA) and stearoylethanolamide (SEA) by activating PPAR (Guzmanet al. 2004; Naughtonet al. 2013), eicosapentaenoylethanolamide (EPEA) and docosahexaenoylethanolamide (DHEA) indirectly by displacing ARA MANOOL from cell membrane phospholipids to thereby reduce AEA and 2-AG production (Naughtonet al. 2013). In contrast, palmitoylethanolamide (PEA) has no effect (Naughtonet al. 2013). The EC also function in shifting energy balance toward energy storage and fat accumulation, especially in the context of high fat diet (HFD) induced obesity (DIO) (Naughtonet al. 2013; Silvestri and DiMarzo 2013). It is thought that HFD fedad libituminduces DIO at least in part by increasing EC levels (AEA, 2-AG), diacyglycerol lipase (DAGL, a key enzyme in 2-AG production) (Naughtonet al. 2013; Silvestri and DiMarzo 2013), and CB1 receptors in brain (Engeli 2008). CB1 activation not only stimulates appetite as indicated above, but also activates SREBP1c to induce transcription of lipogenic enzymes (ACC, FASN) andde novolipogenesiseffects exacerbated by HFD (Osei-Hyiamanet al. 2005; Silvestri and DiMarzo 2013). In contrast, HFD does not elicit weight gain and obesity in cannabinoid receptor-1 (CB1) gene ablated mice even though caloric intake Mouse monoclonal to Tyro3 is similar (Osei-Hyiamanet al. 2005; Trillouet al. 2004). Obesity in human subjects and fat accumulation in rodents are also associated with MANOOL increased plasma AEA and 2-AG, altered pattern of CB receptor expression, and increasedde novolipogenesis (Naughtonet al. 2013; Engeli 2008; Silvestri and DiMarzo 2013). Conversely, weight MANOOL loss in intra-abdominally obese men is accompanied by decreased plasma 2-AG, decreased visceral obesity, and normalization of plasma lipid parameters (Silvestri and DiMarzo 2013). It is important to note, however , thatad libitumfeeding HFD does not discriminate effects of total food intake from those of increased fat content of the diet on serum endocannabinoids or the brain endocannabinoid system. In this regard, HFD also induced weight gain and obesity in wild-type (WT) mice pair-fed HFD where caloric intake of HFD and control diet did not differ (Atshaveset al. 2010b; McIntoshet al. 2013). However , nothing is known about the impact of pair-fed HFD on serum endocannabinoids or the brain endocannabinoid system. Liver fatty acid binding protein-1 (FABP1), a cytosolic protein that enhances hepatic uptake and metabolism of fatty acids, significantly impacts body weight gain and obesity (Atshaveset al. 2010b; Atshaveset al. 2010a; McIntoshet al. 2013; Gajdaet al. 2013). While hepatic FABP1 is elevated in obesity (Morrowet al. 1979), FABP1 is not detectable in brain.