FIGURE 3.

Modulation of Miox and Srebp1 expression by hyperlipidemia, palmitate/BSA, and insulin. Treatment of HK-2 cells with palmitate/BSA (Palm/BSA) (100 μm) increased Miox expression with a concomitant decrease in membrane-bound precursor form of pre-Srebp1 (pSrebp1, 120 kDa) in the cytoplasmic fraction and a simultaneous recruitment and cleavage mature form (mSrebp1, 68 kDa) translocated into the nucleus (A–C). No change in the expression of β-actin or laminB1 was observed. In view of the fact that Srebp1 is activated and is associated with excessive secretion of insulin, expression of Miox and mSrebp1 was determined. A dose-dependent increase in expression of Miox and mSrebp1 was observed following insulin (10–1,000 nm) treatment, suggesting a temporal relationship between the up-regulation of Miox and translocation/expression of mSrebp1 (D–G). Con, control. The in vivo results were similar to those seen in cultured cells exposed to palmitate/BSA. HFD administration over a period of 6 weeks to mice resulted in a time-dependent up-regulation of mSrebp1 (H). IHC studies confirmed the up-regulation of Srebp in renal proximal tubules, both in cytoplasmic and nuclear fractions (I and J, arrowheads). *, p < 0.01 versus control, n = 4.