Upregulation of 25-hydroxyvitamin D3-1α-hydroxylase by butyrate in Caco-2 cells

Figure 1 Effects of 1α-25(OH)₂D₃, 25(OH)₂D₃ and butyrate on differentiation of Caco-2 cells as assessed by AP activity. Cells were treated for 48 h with a medium supplemented with 10^-6 mol/L 1α-25(OH)₂D₃, 10^-6 mol/L 25(OH)₂D₃, 3 mmol/L butyrate, or with one of the combinations of butyrate (3 mmol/L) and 1α-25(OH)₂D₃ (10^–6 mol/L) or butyrate (3 mmol/L) and 25(OH)₂D₃, (10^–6 mol/L). Values are expressed as milliunits of AP activity per milligram cellular protein. ^aP<0.05; ^bP<0.01; ^dP<0.001; NS: non significant.

Figure 2 Time-dependent effect of butyrate on 1α-25(OH)₂D₃ expression. A: Caco-2 cells were grown for 36 h in serum-free medium in the absence (lane 1) or presence of butyrate (3 mmol/L) (lanes 2-4). 1α-25(OH)₂D₃ mRNA was analyzed by semiquantitative RT-PCR with the fluorescent dye PicoGreen. B: Caco-2 cells were treated for 72 h in the absence (lane 1) or presence of butyrate (3 mmol/L) (lanes 2-4) and then harvested for immunoblot analysis. The band at approximately 55 ku corresponds to 1α-25(OH)₂D₃ protein. Quantitation of protein was performed using a luminescent image scanner. ^aP<0,05 vs control; NS: non significant.

Figure 3 Time-dependent effect of butyrate on 1α-25(OH)₂D₃ activity. Caco-2 cells were treated for 72 h in the absence (lane 1) or presence of butyrate (3 mmol/L) (lanes 2-4) and then harvested for ELISA. Values are expressed as pg/mL of 1α-25(OH)2D3. ^aP<0,05 vs control; NS, non significant.