Diacylglycerol Lipase α Knockout Mice Demonstrate Metabolic and Behavioral Phenotypes Similar to Those of Cannabinoid Receptor 1 Knockout Mice

Abstract

After creating >4,650 knockouts (KOs) of independent mouse genes, we screened them by high-throughput phenotyping and found that cannabinoid receptor 1 (Cnr1) KO mice had the same lean phenotype published by others. We asked if our KOs of DAG lipase α or β (Dagla or Daglb), which catalyze biosynthesis of the endocannabinoid (EC) 2-arachidonoylglycerol (2-AG), or Napepld, which catalyzes biosynthesis of the EC anandamide, shared the lean phenotype of Cnr1 KO mice. We found that Dagla KO mice, but not Daglb or Napepld KO mice, were among the leanest of 3651 chow-fed KO lines screened. In confirmatory studies, chow- or high fat diet-fed Dagla and Cnr1 KO mice were leaner than wild-type (WT) littermates; when data from multiple cohorts of adult mice were combined, body fat was 47 and 45% lower in Dagla and Cnr1 KO mice, respectively, relative to WT values. By contrast, neither Daglb nor Napepld KO mice were lean. Weanling Dagla KO mice ate less than WT mice and had body weight (BW) similar to pair-fed WT mice, and adult Dagla KO mice had normal activity and VO2 levels, similar to Cnr1 KO mice. Our Dagla and Cnr1 KO mice also had low fasting insulin, triglyceride, and total cholesterol levels, and after glucose challenge had normal glucose but very low insulin levels. Dagla and Cnr1 KO mice also showed similar responses to a battery of behavioral tests. These data suggest: (1) the lean phenotype of young Dagla and Cnr1 KO mice is mainly due to hypophagia; (2) in pathways where ECs signal through Cnr1 to regulate food intake and other metabolic and behavioral phenotypes observed in Cnr1 KO mice, Dagla alone provides the 2-AG that serves as the EC signal; and (3) small molecule Dagla inhibitors with a pharmacokinetic profile similar to that of Cnr1 inverse agonists are likely to mirror the ability of these Cnr1 inverse agonists to lower BW and improve glycemic control in obese patients with type 2 diabetes, but may also induce undesirable neuropsychiatric side-effects.

Rapid and profound rewiring of brain lipid signaling networks by acute diacylglycerol lipase inhibition

“…Although most lipid changes were consistent between DAGL inhibitortreated and DAGLα −/− mice, we did find that DAGLα −/− mice showed reductions in triglycerides, that were not observed in animals treated with DAGL inhibitors (Dataset S2). These alterations in triglycerides may thus require chronic, long-term inactivation of DAGLα, which is also known to cause significant reductions in total body weight and fat (15). These studies, taken together, demonstrate that acute pharmacological blockade of DAGLs produces a rapid and dramatic reorganization of lipid signaling networks in the mammalian brain that largely mirrors the myriad lipid changes observed in the brains of DAGLα −/− mice.…”

“…In support of this premise, the enzymes that produce several classes of lipid transmitters, including lysophospholipids (6), eicosanoids (7), and endocannabinoids (8,9), are highly expressed in the nervous system and play important roles in brain development, synaptic plasticity, and the modulation of complex behaviors. For example, the diacylglycerol (DAG) lipase enzymes DAGLα and DAGLβ (10) produce the endocannabinoid 2-arachidonoylglycerol (2-AG) (11,12), and the constitutive genetic disruption of DAGLα lowers brain 2-AG and arachidonic acid (AA) content (13,14), resulting in impaired synaptic plasticity (13,14), hypophagia (15), enhanced anxiety and fear responses (16,17), and propensity for spontaneous seizures (15).…”

The Endocannabinoid System: Pivotal Orchestrator of Obesity and Metabolic Disease

“…Interestingly, it has been shown that the compound O-7460, an inhibitor of the DAG lipase (DAGL)-/, the enzyme regulating the synthesis of 2-AG, acutely reduces high-fat diet intake and body weight in mice [114]. In agreement with these data, mice lacking DAGL-/ are hypophagic and lean, and phenotypically and metabolically resemble CB 1 knockout mice [115,116]. Finally, the ECS could be targeted in combination with other systems that are also potential targets for therapy, such as the gastrointestinal hormones peptide YY (PYY) and oxyntomodulin, the MCH system [117,118], or other systems.…”

Blockade of cannabinoid 1 receptor improves GLP-1R mediated insulin secretion in mice

“…A very recent study reported a comparable phenotype in mice lacking DAGLα, a lipase responsible for 2-AG biosynthesis, suggesting 2-AG as the EC responsible for regulating body weight and not AEA (Powell et al, 2015). Similarly, the blockade of peripheral CB1 in both genetic and diet-induced obese mice results in decreased plasma insulin concentrations (Nam et al, 2012; Tam et al, 2012, 2010).…”