We measured the effects of a diet in which D-β-hydroxybutyrate-(R)-1,3 butanediol monoester [ketone ester (KE)] replaced equicaloric amounts of carbohydrate on 8-wk-old male C57BL/6J mice. Diets contained equal amounts of fat, protein, and micronutrients. The KE group was fed ad libitum, whereas the control (Ctrl) mice were pair-fed to the KE group. Blood d-β-hydroxybutyrate levels in the KE group were 3-5 times those reported with high-fat ketogenic diets. Voluntary food intake was reduced dose dependently with the KE diet. Feeding the KE diet for up to 1 mo increased the number of mitochondria and doubled the electron transport chain proteins, uncoupling protein 1, and mitochondrial biogenesis-regulating proteins in the interscapular brown adipose tissue (IBAT). [(18)F]-Fluorodeoxyglucose uptake in IBAT of the KE group was twice that in IBAT of the Ctrl group. Plasma leptin levels of the KE group were more than 2-fold those of the Ctrl group and were associated with increased sympathetic nervous system activity to IBAT. The KE group exhibited 14% greater resting energy expenditure, but the total energy expenditure measured over a 24-h period or body weights was not different. The quantitative insulin-sensitivity check index was 73% higher in the KE group. These results identify KE as a potential antiobesity supplement.

Three groups of male Wistar rats were pair fed NIH-31 diets for 14 days to which were added 30% of calories as corn starch, palm oil, or R-3-hydroxybutyrate-R-1,3-butanediol monoester (3HB-BD ester). On the 14th day, animal brains were removed by freeze-blowing, and brain metabolites measured. Animals fed the ketone ester diet had elevated mean blood ketone bodies of 3.5 mM and lowered plasma glucose, insulin, and leptin. Despite the decreased plasma leptin, feeding the ketone ester diet ad lib decreased voluntary food intake 2-fold for 6 days while brain malonyl-CoA was increased by about 25% in ketone-fed group but not in the palm oil fed group. Unlike the acute effects of ketone body metabolism in the perfused working heart, there was no increased reduction in brain free mitochondrial [NAD ؉ ]/[NADH] ratio nor in the free energy of ATP hydrolysis, which was compatible with the observed 1.5-fold increase in brain uncoupling proteins 4 and 5. Feeding ketone ester or palm oil supplemented diets decreased brain L-glutamate by 15-20% and GABA by about 34% supporting the view that fatty acids as well as ketone bodies can be metabolized by the brain.The metabolism of ketone bodies in the working perfused heart increased the supply of mitochondrial NADH and the ⌬G of ATP hydrolysis (1). Other than the observation that ketone bodies can replace glucose as the major energy substrate in brain (2), little is known about the precise effects of ketone metabolism in brain in vivo. The elevation of ketone bodies (3-hydroxybutyrate and acetoacetate) and free fatty acids through ketogenic diets have been used for almost a century to treat drug refractory epilepsy (3, 4). In addition, it has been suggested that mild ketosis might be an effective treatment for a number of neurodegenerative and other diseases (5-7). We therefore undertook a broad survey of the effects of a ketone ester-and a fat-supplemented diet on several of the pathways of intermediary and energy metabolism in rat brain.Prevention of postmortal changes, necessary for the accurate determination of in vivo redox and phosphorylation states in brain, require rapid inactivation of tissue, which was accomplished by freeze-blowing (8, 9 Elevation of blood ketone bodies, by either fasting or high fat diets, results in elevation of both blood ketone bodies and free fatty acids. Therefore, prior to this report, it has not been possible to investigate ketone body metabolism in brain independent of the effects induced by elevation of plasma free fatty acids.More recently, ketogenic diets have been used in the treatment of obesity where it has been shown that high protein, low carbohydrate diets decreased appetite, sensation of hunger, and food intake in hospitalized patients(10). The intraventricular infusion of 3-hydroxybutyrate (11, 12) or intravenous administration of its precursor 1,3-butanediol (13), have previously been shown to decrease food intake in the rat as has intraperitoneal injections of 3-hydroxybutyrate or 1,3-butanediol in the pigmy goat (14). Subcutaneo...

We studied the toxicological responses of a human hepatoblastoma cell line (HepG2/C3A) to various free fatty acids (FFA) in order to identify the relation between reactive oxygen species (ROS) production and mitochondrial permeability transition (MPT). Exposure to the saturated FFA, palmitate, led to a time-dependent ROS production and hydrogen peroxide release as well as a loss of mitochondrial potential. The cytotoxicity of palmitate was significantly reduced by treating with scavengers of hydrogen peroxide, hydroxyl radical and the spin trap alpha-(4-pyridyl-1-oxide)-N-tert-butyl nitrone (POBN). Superoxide dismutase (SOD) mimics, nitric oxide scavenger, and inhibitor of de novo ceramide synthesis had no effect on the toxicity. MPT-inhibitor, cyclosporine, prevented the loss of mitochondrial potential but did not reduce the cytotoxicity. In contrast, inhibiting mitochondrial complexes I and III reduced the early potential loss and the cytotoxicity. These results suggest that palmitate-cytotoxicity to hepatoma cells is mediated through the production of H2O2 and *OH and independent of MPT.