Acetoacetate protects neuronal cells from oxidative glutamate toxicity

Abstract

Glutamate cytotoxicity contributes to neuronal degeneration in many central nervous system (CNS) diseases, such as epilepsy and ischemia. We previously reported that a high-fat and low-carbohydrate diet, the ketogenic diet (KD), protects against kainic acid-induced hippocampal cell death in mice. We hypothesized based on these findings that ketosis resulting from KD might inhibit glutamate cytotoxicity, resulting in inhibition of hippocampal neuronal cell death. Therefore, we investigated the role of ketone bodies [acetoacetate (AA) and beta-hydroxybutyrate (beta-OHB)] both in a mouse hippocampal cell line (HT22) and in rat primary hippocampal neurons. As a result, we found that pretreatment with 5 mM lithium AA and 4 mM Na beta-OHB protected the HT22 hippocampal cell line and primary hippocampal neuronal culture against 5 mM glutamate toxicity and that up to 2 hr of pretreatment with 5 mM AA had a protective effect against 5 mM glutamate toxicity in the HT22 cell line. Pretreatment with 5 mM AA decreased ROS production of HT22 cell line at 2 and 8 hr exposure of glutamate, and it decreased the appearance of annexin V-positive HT22 cells, which are indicative of an early stage of apoptosis, and propidium iodide-positive HT22 cells, which are indicative of necrosis.

Rapid Adaptation of Rat Brain and Liver Metabolism to a Ketogenic Diet: An Integrated Study Using 1H- and 13C-NMR Spectroscopy

“…A previous in vitro study showing that the addition of AcetoAc or β-HB protected neurons in culture against Glu cytotoxicity 37 supports our present results. We show here for the first time that, within 7 days, the KD had increased ketogenic BCAAs in the liver (Figure 4) and brain, especially Leu and ILeu.…”

Neuroprotective and disease-modifying effects of the ketogenic diet

“…Thus, acetoacetate has been shown to protect against glutamate-mediated toxicity in both primary hippocampal neuron cell cultures; however, a similar effect occurred in an immortalized hippocampal cell line (HT22) lacking ionotropic glutamate receptors (Noh et al, 2006). Acetoacetate also decreased the formation of early cellular markers of glutamate-induced apoptosis and necrosis, probably through the attenuation of glutamate-induced formation of ROS, as discussed below.…”

“…In fact, exogenous administration of β-hydroxybutyrate can reduce brain damage and improve neuronal function in models of brain hypoxia, anoxia, and ischemia (Cherian et al, 1994;Dardzinski et al, 2000;Suzuki et al, 2001Suzuki et al, , 2002Smith et al, 2005). In addition, the other ketone bodies, acetoacetate and acetone, which are β-hydroxybutyrate metabolites and can also serve as alternative energy sources, have similar neuroprotective effects (Garcia and Massieu, 2001;Massieu et al, 2001Massieu et al, , 2003Noh et al, 2006). Interestingly, in rats receiving a ketogenic diet, neuronal uptake of β-hydroxybutyrate is increased after cortical impact injury in comparison with animals receiving a standard diet (Prins et al, 2004).…”

Ketone Bodies as a Therapeutic for Alzheimer's Disease

“…When KB are used in cell culture systems or infused into animal models, numerous reports have indicated neuroprotective qualities (Table 1). For example, infusion of KB into rodents protects them from glutamate toxicity, 50 ischemia, 51 and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) toxicity. 33 This approach has been tested in a cell culture model of AD and in human trials.…”