Abstract
Troglitazone (Tro) and pioglitazone (Pio) activation of peroxisome proliferator-activated receptor (PPAR)-γ and PPAR-γ-independent pathways was studied in cell lines derived from porcine renal tubules. PPAR-γ-dependent activation of PPAR response element-driven luciferase gene expression was observed with Pio at 1 μM but not Tro at 1 μM. On the other hand, PPAR-γ-independent P-ERK activation was observed with 5 μM Tro but not with Pio (5-20 μM). In addition, Pio (1-10 μM) increased metabolic acid production and activated AMP-activated protein kinase (AMPK) associated with decreased mitochondrial membrane potential, whereas Tro (1-20 μM) did not. These results are consistent with three pathways through which glitazones may act in effecting metabolic processes (ammoniagenesis and gluconeogenesis) as well as cellular growth: 1) PPAR-γ-dependent and PPAR-γ-independent pathways, 2) P-ERK activation, and 3) mitochondrial AMPK activation. The pathways influence cellular acidosis and glucose and glutamine metabolism in a manner favoring reduced plasma glucose in vivo. In addition, significant interactions can be demonstrated that enhance some physiological processes (ammoniagenesis) and suppress others (ligand-mediated PPAR-γ gene expression). Our findings provide a model both for understanding seemingly opposite biological effects and for enhancing therapeutic potency of these agents.
Original language | English (US) |
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Pages (from-to) | C1137-C1146 |
Journal | American Journal of Physiology - Cell Physiology |
Volume | 292 |
Issue number | 3 |
DOIs | |
State | Published - Mar 2007 |
Keywords
- AMP-activated protein kinase
- Intracellular pH
- Mitochondria
- Na/H exchanger
- Peroxisome proliferator-activated receptor-γ
- Phospho-extracellular signal-regulated kinase
ASJC Scopus subject areas
- Physiology
- Cell Biology