Pan J W, Rothman T L, Behar K L, Stein D T, Hetherington H P
Department of Medicine, Brookhaven National Laboratory, Upton, New York 11973, USA.
J Cereb Blood Flow Metab. 2000 Oct;20(10):1502-7. doi: 10.1097/00004647-200010000-00012.
Ketones are known to constitute an important fraction of fuel for consumption by the brain, with brain ketone content generally thought to be low. However, the recent observation of 1-mmol/L levels of brain beta-hydroxybutyrate (BHB) in children on the ketogenic diet suggests otherwise. The authors report the measurement of brain BHB and lactate in the occipital lobe of healthy adults using high field (4-T) magnetic resonance spectroscopy, measured in the nonfasted state and after 2- and 3-day fasting-induced ketosis. A 9-mL voxel located in the calcarine fissure was studied, detecting the BHB and lactate upfield resonances using a 1H homonuclear editing sequence. Plasma BHB levels also were measured. The mean brain BHB concentration increased from a nonfasted level of 0.05 +/- 0.05 to 0.60 +/- 0.26 mmol/L (after second day of fasting), increasing further to 0.98 +/- 0.16 mmol/L (after the third day of fasting). The mean nonfasted brain lactate was 0.69 +/- 0.17 mmol/L, increasing to 1.47 +/- 0.22 mmol/L after the third day. The plasma and brain BHB levels correlated well (r = 0.86) with a brain-plasma slope of 0.26. These data show that brain BHB rises significantly with 2- and 3-day fasting-induced ketosis. The lactate increase likely results from ketones displacing lactate oxidation without altering glucose phosphorylation and glycolysis.
已知酮类是大脑消耗燃料的重要组成部分，一般认为大脑中的酮含量较低。然而，最近对采用生酮饮食的儿童大脑中β-羟基丁酸（BHB）水平达到1 mmol/L的观察结果却并非如此。作者报告了使用高场（4-T）磁共振波谱法对健康成年人枕叶中的大脑BHB和乳酸进行测量的结果，测量在非禁食状态以及禁食2天和3天诱导酮症后进行。研究了位于距状裂的一个9 mL体素，使用1H同核编辑序列检测BHB和乳酸的高场共振。还测量了血浆BHB水平。大脑BHB平均浓度从非禁食状态下的0.05±0.05 mmol/L增加到禁食第二天后的0.60±0.26 mmol/L，在禁食第三天后进一步增加到0.98±0.16 mmol/L。非禁食状态下大脑乳酸平均水平为0.69±0.17 mmol/L，在禁食第三天后增加到1.47±0.22 mmol/L。血浆和大脑BHB水平相关性良好（r = 0.86），大脑-血浆斜率为0.26。这些数据表明，禁食2天和3天诱导酮症会使大脑BHB显著升高。乳酸增加可能是由于酮类取代了乳酸氧化，而未改变葡萄糖磷酸化和糖酵解。
