Increased Infarct Size and Lack of Hyperphagic Response after Focal Cerebral Ischemia in Peroxisome Proliferator-Activated Receptor β-Deficient Mice

Abstract

Peroxisome proliferator-activated receptors (PPARs) are involved in energy expenditure, regulation of inflammatory processes, and cellular protection in peripheral tissues. Among the different types of PPARs, PPARβ is the only one to be widely expressed in cortical neurons. Using PPARβ knockout (KO) mice, we report here a detailed investigation of the role of PPARβ in cerebral ischemic damage, associated inflammatory and antioxidant processes as well as food intake regulation after middle cerebral artery occlusion (MCAO). The PPARβ KO mice had a two-fold increase in infarct size compared with wild-type (WT) mice. Brain oxidative stress was dramatically enhanced in these KO mice, as documented by an increased content of malondialdehyde, decreased levels of glutathione and manganese superoxide dismutase, and no induction of uncoupling protein 2 (UCP2) mRNA. Unlike WT mice, PPARβ KO mice showed a marked increase of prooxidant interferon-gamma but no induction of nerve growth factor and tumor necrosis factor alpha after MCAO. In WT mice, MCAO resulted in inflammation-specific transient hyperphagia from day 3 to day 5 after ischemia, which was associated with an increase in neuropeptide Y (NPY) mRNA. This hyperphagic phase and NPY mRNA induction were not observed in PPARβ KO mice. Furthermore, our study also suggests for the first time that UCP2 is involved in MCAO food intake response. These data indicate that PPARβ plays an important role in integrating and regulating central inflammation, antioxidant mechanisms, and food intake after MCAO, and suggest that the use of PPARβ agonists may be of interest for the prevention of central ischemic damage.