TY - JOUR

T1 - Sensing of triacylglycerol in the gut

T2 - different mechanisms for fatty acids and 2-monoacylglycerol

AU - Kleberg, Karen

AU - Jacobsen, Anne Katrine

AU - Ferreira, Jozelia G

AU - Windeløv, Johanne Agerlin

AU - Rehfeld, Jens F

AU - Holst, Jens Juul

AU - de Araujo, Ivan E

AU - Hansen, Harald S

N1 - © 2015 The Authors. The Journal of Physiology © 2015 The Physiological Society.

PY - 2015/1/16

Y1 - 2015/1/16

N2 - KEY POINTS: Digestion is required for intestinal sensing of triacylglycerol in this behavioural model. The hydrolysis products of triacylglycerol, fatty acids and 2-monoacylglycerol, regulate feeding via separate mechanisms. Sensing of long-chain fatty acids, but not of 2-monoacylglycerol, stimulated central dopaminergic signalling. Fatty acid chain length regulates behavioural responses to fatty acids.ABSTRACT: Sensing of dietary triacylglycerol in the proximal small intestine results in physiological, hormonal and behavioural responses. However, the exact physiological pathways linking intestinal fat sensing to food intake and the activation of brain circuits remain to be identified. In this study we examined the role of triacylglycerol digestion for intestinal fat sensing, and compared the effects of the triacylglycerol digestion products, fatty acids and 2-monoacylglycerol, on behavioural, hormonal and dopaminergic responses in behaving mice. Using an operant task in which mice are trained to self-administer lipid emulsions directly into the stomach, we show that inhibiting triacylglycerol digestion disrupts normal behaviour of self-administration in mice, indicating that fat sensing is conditional to digestion. When administered separately, both digestion products, 2-monoacylglycerol and fatty acids, were sensed by the mice, and self-administration patterns of fatty acids were affected by the fatty acid chain length. Peripheral plasma concentrations of the gut hormones GLP-1, GIP, PYY, CCK and insulin did not offer an explanation of the differing behavioural effects produced by 2-monoacylglycerol and fatty acids. However, combined with behavioural responses, striatal dopamine effluxes induced by gut infusions of oleic acid were significantly greater than those produced by equivalent infusions of 2-oleoylglycerol. Our data demonstrate recruitment of different signalling pathways by fatty acids and 2-monoacylglycerol, and suggest that the structural properties of fat rather than total caloric value determine intestinal sensing and the assignment of reward value to lipids.

AB - KEY POINTS: Digestion is required for intestinal sensing of triacylglycerol in this behavioural model. The hydrolysis products of triacylglycerol, fatty acids and 2-monoacylglycerol, regulate feeding via separate mechanisms. Sensing of long-chain fatty acids, but not of 2-monoacylglycerol, stimulated central dopaminergic signalling. Fatty acid chain length regulates behavioural responses to fatty acids.ABSTRACT: Sensing of dietary triacylglycerol in the proximal small intestine results in physiological, hormonal and behavioural responses. However, the exact physiological pathways linking intestinal fat sensing to food intake and the activation of brain circuits remain to be identified. In this study we examined the role of triacylglycerol digestion for intestinal fat sensing, and compared the effects of the triacylglycerol digestion products, fatty acids and 2-monoacylglycerol, on behavioural, hormonal and dopaminergic responses in behaving mice. Using an operant task in which mice are trained to self-administer lipid emulsions directly into the stomach, we show that inhibiting triacylglycerol digestion disrupts normal behaviour of self-administration in mice, indicating that fat sensing is conditional to digestion. When administered separately, both digestion products, 2-monoacylglycerol and fatty acids, were sensed by the mice, and self-administration patterns of fatty acids were affected by the fatty acid chain length. Peripheral plasma concentrations of the gut hormones GLP-1, GIP, PYY, CCK and insulin did not offer an explanation of the differing behavioural effects produced by 2-monoacylglycerol and fatty acids. However, combined with behavioural responses, striatal dopamine effluxes induced by gut infusions of oleic acid were significantly greater than those produced by equivalent infusions of 2-oleoylglycerol. Our data demonstrate recruitment of different signalling pathways by fatty acids and 2-monoacylglycerol, and suggest that the structural properties of fat rather than total caloric value determine intestinal sensing and the assignment of reward value to lipids.

U2 - 10.1113/jphysiol.2014.285635

DO - 10.1113/jphysiol.2014.285635

M3 - Journal article

C2 - 25639597

VL - 593

SP - 2097

EP - 2109

JO - The Journal of Physiology

JF - The Journal of Physiology

SN - 0022-3751

IS - 8

ER -