Central inhibition of HDAC6 re-sensitizes leptin signaling during obesity to induce profound weight loss.

Leptin resistance during excess weight gain significantly contributes to the recidivism of obesity to leptin-based pharmacological therapies. The mechanisms underlying the inhibition of leptin receptor (LepR) signaling during obesity are still elusive. Here, we report that histone deacetylase 6 (HDAC6) interacts with LepR, reducing the latter's activity, and that pharmacological inhibition of HDAC6 activity disrupts this interaction and augments leptin signaling. Treatment of diet-induced obese mice with blood-brain barrier (BBB)-permeable HDAC6 inhibitors profoundly reduces food intake and leads to potent weight loss without affecting the muscle mass. Genetic depletion of Hdac6 in Agouti-related protein (AgRP)-expressing neurons or administration with BBB-impermeable HDAC6 inhibitors results in a lack of such anti-obesity effect. Together, these findings represent the first report describing a mechanistically validated and pharmaceutically tractable therapeutic approach to directly increase LepR activity as well as identifying centrally but not peripherally acting HDAC6 inhibitors as potent leptin sensitizers and anti-obesity agents.

Aspirin cooperates with p300 to activate the acetylation of H3K9 and promote FasL-mediated apoptosis of cancer stem-like cells in colorectal cancer.

Cancer stem-like cells (CSCs) have been proposed as a key driving force of tumor growth and relapse in colorectal cancer (CRC), and therefore, they are promising targets for cancer therapy. Epidemiological evidence has suggested that the daily use of aspirin reduces overall mortality of CRC and the risk of distant metastasis. We investigated the effect and mechanism of aspirin on CSCs in CRC. Methods: The ratio of CSCs was analyzed after aspirin treatment both in a cell model and patient samples. Chemically modified aspirin and immunoprecipitation were adopted to detect the target proteins of aspirin. A locus-specific light-inducible epigenetic modification system based on CRISPR technology was constructed to verify the causal relationship in these molecular events. In vivo characterization was performed in a xenograft model. Results: We found that aspirin induces apoptosis in enriched colorectal CSCs, inhibits tumor progression, and enhances the anti-neoplastic effects of chemotherapeutic agents. Furthermore, aspirin directly interacts with p300 in the nucleus, promotes H3K9 acetylation, activates FasL expression, and induces apoptosis in colorectal CSCs. Notably, these effects of aspirin are absent in non-CSCs since H3K9 is hypermethylated in non-CSCs and the effects are not induced by other NSAIDs. In addition, aspirin can suppress oxaliplatin-enriched CSCs and serve as an adjuvant therapy. Conclusions: Taken together, we revealed a unique epigenetic and cox-independent pathway (p300-AcH3K9-FasL axis) by which aspirin eliminates colorectal CSCs. These findings establish an innovative framework of the therapeutic significance of aspirin.

Genetic identification of leptin neural circuits in energy and glucose homeostases.

Leptin, a hormone produced in white adipose tissue, acts in the brain to communicate fuel status, suppress appetite following a meal, promote energy expenditure and maintain blood glucose stability1,2. Dysregulation of leptin or its receptors (LEPR) results in severe obesity and diabetes3-5. Although intensive studies on leptin have transformed obesity and diabetes research2,6, clinical applications of the molecule are still limited 7 , at least in part owing to the complexity and our incomplete understanding of the underlying neural circuits. The hypothalamic neurons that express agouti-related peptide (AGRP) and pro-opiomelanocortin (POMC) have been hypothesized to be the main first-order, leptin-responsive neurons. Selective deletion of LEPR in these neurons with the Cre-loxP system, however, has previously failed to recapitulate, or only marginally recapitulated, the obesity and diabetes that are seen in LEPR-deficient Lepr db/db mice, suggesting that AGRP or POMC neurons are not directly required for the effects of leptin in vivo8-10. The primary neural targets of leptin are therefore still unclear. Here we conduct a systematic, unbiased survey of leptin-responsive neurons in streptozotocin-induced diabetic mice and exploit CRISPR-Cas9-mediated genetic ablation of LEPR in vivo. Unexpectedly, we find that AGRP neurons but not POMC neurons are required for the primary action of leptin to regulate both energy balance and glucose homeostasis. Leptin deficiency disinhibits AGRP neurons, and chemogenetic inhibition of these neurons reverses both diabetic hyperphagia and hyperglycaemia. In sharp contrast to previous studies, we show that CRISPR-mediated deletion of LEPR in AGRP neurons causes severe obesity and diabetes, faithfully replicating the phenotype of Lepr db/db mice. We also uncover divergent mechanisms of acute and chronic inhibition of AGRP neurons by leptin (presynaptic potentiation of GABA (γ-aminobutyric acid) neurotransmission and postsynaptic activation of ATP-sensitive potassium channels, respectively). Our findings identify the underlying basis of the neurobiological effects of leptin and associated metabolic disorders.

A Postsynaptic AMPK→p21-Activated Kinase Pathway Drives Fasting-Induced Synaptic Plasticity in AgRP Neurons.

AMP-activated protein kinase (AMPK) plays an important role in regulating food intake. The downstream AMPK substrates and neurobiological mechanisms responsible for this, however, are ill defined. Agouti-related peptide (AgRP)-expressing neurons in the arcuate nucleus regulate hunger. Their firing increases with fasting, and once engaged they cause feeding. AgRP neuron activity is regulated by state-dependent synaptic plasticity: fasting increases dendritic spines and excitatory synaptic activity; feeding does the opposite. The signaling mechanisms underlying this, however, are also unknown. Using neuron-specific approaches to measure and manipulate kinase activity specifically within AgRP neurons, we establish that fasting increases AMPK activity in AgRP neurons, that increased AMPK activity in AgRP neurons is both necessary and sufficient for fasting-induced spinogenesis and excitatory synaptic activity, and that the AMPK phosphorylation target mediating this plasticity is p21-activated kinase. This provides a signaling and neurobiological basis for both AMPK regulation of energy balance and AgRP neuron state-dependent plasticity.