SUMMARY Here we report the identification and verification of a β-hydroxybutyrate-derived protein modification, lysine β-hydroxybutyrylation (Kbhb), as a new type of histone mark. Histone Kbhb marks are dramatically induced in response to elevated β-hydroxybutyrate levels in cultured cells, and in livers from mice subjected to prolonged fasting or streptozotocin-induced diabetic ketoacidosis. In total, we identified 44 histone Kbhb sites, a figure comparable to the known number of histone acetylation sites. By ChIP-seq and RNA-seq analysis, we demonstrate that histone Kbhb is a mark enriched in active gene promoters, and that the increased H3K9bhb levels that occur during starvation are associated with genes up-regulated in starvation-responsive metabolic pathways. Histone β-hydroxybutyrylation thus represents a new epigenetic regulatory mark that couples metabolism to gene expression, offering a new avenue to study chromatin regulation and the diverse functions of β-hydroxybutyrate in the context of important human pathophysiological states, including diabetes, epilepsy, and neoplasia.

OBJECTIVE-Berberine (BBR) activates AMP-activated protein kinase (AMPK) and improves insulin sensitivity in rodent models of insulin resistance. We investigated the mechanism of activation of AMPK by BBR and explored whether derivatization of BBR could improve its in vivo efficacy. RESEARCH DESIGN AND METHODS-AMPK phosphorylation was examined in L6 myotubes and LKB1 Ϫ/Ϫ cells, with or without the Ca 2ϩ /calmodulin-dependent protein kinase kinase (CAMKK) inhibitor STO-609. Oxygen consumption was measured in L6 myotubes and isolated muscle mitochondria. The effect of a BBR derivative, dihydroberberine (dhBBR), on adiposity and glucose metabolism was examined in rodents fed a high-fat diet. RESULTS-We have made the following novel observations: 1) BBR dose-dependently inhibited respiration in L6 myotubes and muscle mitochondria, through a specific effect on respiratory complex I, similar to that observed with metformin and rosiglitazone; 2) activation of AMPK by BBR did not rely on the activity of either LKB1 or CAMKK␤, consistent with major regulation at the level of the AMPK phosphatase; and 3) a novel BBR derivative, dhBBR, was identified that displayed improved in vivo efficacy in terms of counteracting increased adiposity, tissue triglyceride accumulation, and insulin resistance in high-fat-fed rodents. This effect is likely due to enhanced oral bioavailability. CONCLUSIONS-Complex I of the respiratory chain represents a major target for compounds that improve whole-body insulin sensitivity through increased AMPK activity. The identification of a novel derivative of BBR with improved in vivo efficacy highlights the potential importance of BBR as a novel therapy for the treatment of type 2 diabetes.

RK. Intermittent peripheral tissue ischemia during coronary ischemia reduces myocardial infarction through a K ATP-dependent mechanism: first demonstration of remote ischemic perconditioning. Am J Physiol Heart Circ Physiol 292: H1883-H1890, 2007. First published December 15, 2006; doi:10.1152/ajpheart.00617.2006.-Remote ischemic preconditioning reduces myocardial infarction (MI) in animal models. We tested the hypothesis that the systemic protection thus induced is effective when ischemic preconditioning is administered during ischemia (PerC) and before reperfusion and examined the role of the K ϩ -dependent ATP (K ATP) channel. Twenty 20-kg pigs were randomized (10 in each group) to 40 min of left anterior descending coronary artery occlusion with 120 min of reperfusion. PerC consisted of four 5-min cycles of lower limb ischemia by tourniquet during left anterior descending coronary artery occlusion. Left ventricular (LV) function was assessed by a conductance catheter and extent of infarction by tetrazolium staining. The extent of MI was significantly reduced by PerC (60.4 Ϯ 14.3 vs. 38.3 Ϯ 15.4%, P ϭ 0.004) and associated with improved functional indexes. The increase in the time constant of diastolic relaxation was significantly attenuated by PerC compared with control in ischemia and reperfusion (P ϭ 0.01 and 0.04, respectively). At 120 min of reperfusion, preload-recruitable stroke work declined 38 Ϯ 6% and 3 Ϯ 5% in control and PerC, respectively (P ϭ 0.001). The force-frequency relation was significantly depressed at 120 min of reperfusion in both groups, but optimal heart rate was significantly lower in the control group (P ϭ 0.04). There were fewer malignant arrhythmias with PerC during reperfusion (P ϭ 0.02). These protective effects of PerC were abolished by glibenclamide. Intermittent limb ischemia during myocardial ischemia reduces MI, preserves global systolic and diastolic function, and protects against arrhythmia during the reperfusion phase through a K ATP channeldependent mechanism. Understanding this process may have important therapeutic implications for a range of ischemia-reperfusion syndromes. remote preconditioning; cardioprotection REPERFUSION STRATEGIES are well established for the treatment of evolving clinical ischemia-reperfusion (I/R) syndromes. Recent approaches to further improve outcomes after myocardial infarction (MI) have focused on strategies to protect the myocardium during the ischemic and reperfusion phases, such as sodium-hydrogen pump inhibitors, glucose/insulin infusions, and anti-complement therapy, although these have shown no major additional benefits (15,16,26).One successful approach in the experimental setting is ischemic preconditioning, whereby prior sublethal I/R induces a state of protection against a subsequent prolonged ischemic episode (18). However, ischemic preconditioning has not translated into the clinical setting, not only because it is impossible to predict clinical acute coronary syndromes, but also, even in the setting of predictable I/R injury ...