Excess energy intake causes
obesity, which leads to
insulin resistance and various other complications of
metabolic syndrome, including diabetes,
atherosclerosis,
dyslipidemia, and
nonalcoholic fatty liver disease. Although recent studies have depicted altered lipid metabolism as an underlying feature, the detailed mechanisms are still unclear. Here we describe a possible role in high-fat diet (HFD)-induced
obesity for
monoacylglycerol lipase (MGL), an
enzyme that is also known to hydrolyze the
endocannabinoid 2-arachidonoylglycerol in brain. MGL-deficient [MGL-knockout (KO)] mice fed a HFD gained less
body weight than wild-type mice and were protected from
insulin resistance and hepatic steatosis. Food intake and energy expenditure were not altered in MGL-KO mice, but blood
triglyceride levels after oral
olive oil gavage were suppressed, indicating a role for MGL in intestinal fat absorption. Experiments with
cannabinoid receptor type 1 (CB1)/MGL double-KO mice revealed that these phenotypes may include mechanisms that are independent of CB1-receptor-mediated
endocannabinoid functions. We also noted that MGL-KO mice had less preference for HFD over normal chow diet. Oral but not intraperitoneal
lipid administration strongly suppressed the appetites of MGL-KO and CB1/MGL double-KO mice, but not of wild-type and CB1-KO mice. Appetite suppression was reversed by
vagotomy, suggesting involvement of MGL in the gut-brain axis regulation of appetite. Our results provide mechanistic insights of MGL's role in diet-induced
obesity,
lipid metabolic disorder, and regulation of appetite.-Yoshida, K., Kita, Y., Tokuoka, S. M., Hamano, F., Yamazaki, M., Sakimura, K., Kano, M., Shimizu, T.
Monoacylglycerol lipase deficiency affects diet-induced
obesity, fat absorption, and feeding behavior in
CB1 cannabinoid receptor-deficient mice.