title: The relationship between alkaline phosphatase activity and intracellular lipid accumulation in murine 3T3-L1 cells and human preadipocytes.
abstract: Alkaline phosphatase (ALP) is expressed in 3T3-L1 preadipocytes, and its activity increases during adipogenesis. The purpose of this study was to determine whether ALP activity could be used as a measure of intracellular lipid accumulation in human preadipocytes and 3T3-L1 cells and which of the factors that induce adipogenesis are responsible for stimulating ALP activity. Adipogenesis was initiated in 3T3-L1 cells by incubation with differentiation medium containing insulin, dexamethasone, and 3-isobutyl-1-methylxanthine. The effect of leaving out each of the differentiation medium components was studied. Adipogenesis was also assessed in human preadipocytes and 3T3-L1 cells in the presence of the ALP inhibitor histidine. ALP activity was measured using an automated colorimetric assay and intracellular lipid accumulation was measured using the lipid-specific dye oil red O. Removal of insulin or dexamethasone from the differentiation medium had little effect on either ALP activity or lipid accumulation in 3T3-L1 cells, while removal of IBMX blocked both. Histidine inhibited ALP activity and adipogenesis in human preadipocytes and 3T3-L1 cells. Pearson univariate correlation analysis demonstrated strong correlations between ALP activity and lipid accumulation in human preadipocytes (r=0.78, n=69) and in 3T3-L1 cells (r=0.92, n=27). These data suggest that ALP and fat storage are tightly linked during preadipocyte maturation and that the measurement of ALP activity may be a novel technique for the quantification of intracellular lipid accumulation that is more sensitive and rapid than currently used methods.
authors.affiliation: Department of Chemical Pathology, National Health Laboratory Service, University of Witwatersrand Medical School, Parktown 2193, South Africa.
authors.forename: Aus T
authors.initials: AT
authors.lastname: Ali
authors.forename: Clem B
authors.initials: CB
authors.lastname: Penny
authors.forename: Janice E
authors.initials: JE
authors.lastname: Paiker
authors.forename: George
authors.initials: G
authors.lastname: Psaras
authors.forename: Faisel
authors.initials: F
authors.lastname: Ikram
authors.forename: Nigel J
authors.initials: NJ
authors.lastname: Crowther
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D041721:3T3-L1 Cells; D017667:Adipocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D050156:Adipogenesis / Q000187:drug effects / Q000502:physiology; D000469:Alkaline Phosphatase / Q000378:metabolism*; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D003470:Culture Media; D003907:Dexamethasone / Q000494:pharmacology; D006639:Histidine / Q000494:pharmacology; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D007424:Intracellular Fluid / Q000378:metabolism; D050356:Lipid Metabolism; D051379:Mice
chemical_list: D003470:Culture Media; D007328:Insulin; D006639:Histidine; D003907:Dexamethasone; D000469:Alkaline Phosphatase; D015056:1-Methyl-3-isobutylxanthine