Dietary free fatty acids form alkaline phosphatase-enriched microdomains in the intestinal brush border membrane

TY - JOUR

T1 - Dietary free fatty acids form alkaline phosphatase-enriched microdomains in the intestinal brush border membrane

AU - Hansen, Gert H

AU - Rasmussen, Karina

AU - Niels-Christiansen, Lise-Lotte

AU - Danielsen, E Michael

PY - 2011/2/1

Y1 - 2011/2/1

N2 - Free fatty acids released during intralumenal digestion of dietary fat must pass through the enterocyte brush border membrane before triacylglycerol reassembly and subsequent chylomicron delivery to the lymph system. In the present work fluorescent BODIPY fatty acid analogs were used to study this membrane passage in organ cultured intestinal mucosal explants. We found that in addition to a rapid uptake into the cytoplasm, a fraction of the fatty acid analogs were inserted directly into the brush border membrane. Furthermore, a brief exposure of microvillar membrane vesicles to a fat mixture mimicking a physiological solution of dietary mixed micelles, rearranged the lipid raft microdomain organization of the membranes. Thus, the fat mixture generated a low-density subpopulation of microvillar detergent resistant membranes (DRMs) highly enriched in alkaline phosphatase (AP). Since this GPI-linked enzyme is the membrane protein in the brush border with the highest affinity for lipid rafts, this implies that free fatty acids selectively insert stably into these membrane microdomains. We have previously shown that absorption of dietary lipids transiently induce a selective endocytosis of AP from the brush border, and from work by others it is known that fat absorption is accompanied by a rise in serum AP and secretion of surfactant-like particles from enterocytes. We propose that these physiological processes may be triggered by the sequestering of dietary free fatty acids in lipid raft microdomains of the brush border.

AB - Free fatty acids released during intralumenal digestion of dietary fat must pass through the enterocyte brush border membrane before triacylglycerol reassembly and subsequent chylomicron delivery to the lymph system. In the present work fluorescent BODIPY fatty acid analogs were used to study this membrane passage in organ cultured intestinal mucosal explants. We found that in addition to a rapid uptake into the cytoplasm, a fraction of the fatty acid analogs were inserted directly into the brush border membrane. Furthermore, a brief exposure of microvillar membrane vesicles to a fat mixture mimicking a physiological solution of dietary mixed micelles, rearranged the lipid raft microdomain organization of the membranes. Thus, the fat mixture generated a low-density subpopulation of microvillar detergent resistant membranes (DRMs) highly enriched in alkaline phosphatase (AP). Since this GPI-linked enzyme is the membrane protein in the brush border with the highest affinity for lipid rafts, this implies that free fatty acids selectively insert stably into these membrane microdomains. We have previously shown that absorption of dietary lipids transiently induce a selective endocytosis of AP from the brush border, and from work by others it is known that fat absorption is accompanied by a rise in serum AP and secretion of surfactant-like particles from enterocytes. We propose that these physiological processes may be triggered by the sequestering of dietary free fatty acids in lipid raft microdomains of the brush border.

KW - Alkaline Phosphatase

KW - Digestion

KW - Electrophoresis, Polyacrylamide Gel

KW - Fatty Acids, Nonesterified

KW - Food

KW - Humans

KW - Intestinal Mucosa

KW - Lipid Bilayers

KW - Membrane Microdomains

KW - Microscopy, Electron

KW - Microscopy, Fluorescence

KW - Microvilli

KW - Organ Culture Techniques

U2 - 10.3109/09687688.2010.542552

DO - 10.3109/09687688.2010.542552

M3 - Journal article

C2 - 21166483

SN - 0968-7688

VL - 28

SP - 136

EP - 144

JO - Membrane Biochemistry

JF - Membrane Biochemistry

IS - 2

ER -