Activation of AMP-activated protein kinase (AMPK) through inhibiting interaction with prohibitins.

5'-Adenosine monophosphate-activated protein kinase (AMPK) is a potential therapeutic target for various medical conditions. We here identify a small-molecule compound (RX-375) that activates AMPK and inhibits fatty acid synthesis in cultured human hepatocytes. RX-375 does not bind to AMPK but interacts with prohibitins (PHB1 and PHB2), which were found to form a complex with AMPK. RX-375 induced dissociation of this complex, and PHBs knockdown resulted in AMPK activation, in the cultured cells. Administration of RX-375 to obese mice activated AMPK and ameliorated steatosis in the liver. High-throughput screening based on disruption of the AMPK-PHB interaction identified a second small-molecule compound that activates AMPK, confirming the importance of this interaction in the regulation of AMPK. Our results thus indicate that PHBs are previously unrecognized negative regulators of AMPK, and that compounds that prevent the AMPK-PHB interaction constitute a class of AMPK activator.

Lower Body Mass Index is a Risk Factor for In-Hospital Mortality of Elderly Japanese Patients Treated with Ampicillin/sulbactam.

Objectives: A retrospective examination was conducted to identify risk factors for in-hospital mortality of elderly patients (65 years or older) treated with the beta-lactam/beta-lactamase inhibitor combination antibiotic, ampicillin/sulbactam (ABPC/SBT). Methods: Clinical data from 96 patients who were hospitalized with infectious diseases and treated with ABPC/SBT (9 g/day or 12 g/day) were analyzed. Risk factors examined included demographic and clinical laboratory parameters. Parameter values prior to treatment and changes after treatment were compared between survivors and non-survivors. Results: The study patients had an average age of 81.9±8.4 years (±SD) and body mass index (BMI) of 19.9±4.2 kg/m2. They were characterized by anemia (low hemoglobin and hematocrit levels), inflammation (high leukocyte count, neutrophil count, C-reactive protein level, and body temperature), and hepatic and renal dysfunction (high aspartate aminotransferase, alanine aminotransferase and blood urea nitrogen levels). The BMI of non-survivors, 16.2±2.9 kg/m2, was lower than that of survivors, 20.4±4.1 kg/m2. In addition, the hematological parameters deteriorated more remarkably, inflammation markers were not altered (or the decrease was marginal), and hepatic function was not improved, in non-survivors. Conclusions: A lower BMI value is a risk factor for in-hospital mortality of elderly patients treated with ABPC/SBT.

A novel JNK2/SREBP-1c pathway involved in insulin-induced fatty acid synthesis in human adipocytes.

Insulin plays important roles in apoptosis and lipid droplet (LD) formation, and it is one of the determinants involved in increasing fat mass. However, the mechanisms underlying insulin-induced enlargement of fat mass remain unclear. Our previous study suggested that insulin-induced increases in LDs are related to c-Jun N-terminal kinase (JNK)2-mediated upregulation of cell death-inducing DNA fragmentation factor-α-like effector (CIDE)C in human adipocytes. However, other genes involved in insulin/JNK2-induced LD formation are unknown. Here, we explored insulin/JNK2-regulated genes to clarify the mechanism of enlargement of LDs. Microarray analysis revealed that an insulin/JNK2 pathway mostly regulates expression of genes involved in lipid metabolism, including sterol regulatory element binding protein (SREBP)-1, a key transcription factor of lipogenesis. The JNK inhibitor SP600125 blocked insulin-induced upregulation of SREBP-1c expression. Small interfering RNA-mediated depletion of JNK2 suppressed insulin-induced nuclear accumulation of the active form of SREBP-1 protein and upregulation of SREBP-1c. Furthermore, depletion of JNK2 attenuated insulin-induced upregulation of SREBP-1c target lipogenic enzymes, leading to reduced de novo fatty acid synthesis. In addition, JNK2 coimmunoprecipitated with SREBP-1, reinforcing the correlation between JNK2 and SREBP-1. These results suggest that SREBP-1c is a novel insulin/JNK2-regulated gene and that the JNK2/SREBP-1c pathway mediates insulin-induced fatty acid synthesis, which may lead to enlargement of LDs in human adipocytes.

Suppression of FoxO1/cell death-inducing DNA fragmentation factor α-like effector A (Cidea) axis protects mouse ß-cells against palmitic acid-induced apoptosis.

Chronic exposure to free fatty acid (FFA) induces pancreatic ß-cell apoptosis, which may contribute to the development of type 2 diabetes. The cell death-inducing DNA fragmentation factor α-like effector (CIDE) family is involved in type 2 diabetes with obesity. In the present study, we found that only apoptosis-inducing FFA upregulated Cidea, and both apoptosis and Cidea were upregulated most strongly by palmitic acid, suggesting that the expression of Cidea is positively correlated with apoptosis. In contrast, there were weak correlations between Cideb and Cidec expression, and apoptosis. Furthermore, suppression of Cidea inhibited palmitic acid-induced apoptosis. Finally, suppression of FoxO1 inhibited palmitic acid-induced Cidea upregulation and apoptosis. These results indicate that Cidea is a critical regulator of FFA-induced apoptosis as a novel downstream target for FoxO1 in ß-cells, suggesting that suppression of Cidea is a potentially useful therapeutic approach for protecting against ß-cell loss in type 2 diabetes.

Differential regulation of CIDEA and CIDEC expression by insulin via Akt1/2- and JNK2-dependent pathways in human adipocytes.

Both insulin and the cell death-inducing DNA fragmentation factor-α-like effector (CIDE) family play important roles in apoptosis and lipid droplet formation. Previously, we reported that CIDEA and CIDEC are differentially regulated by insulin and contribute separately to insulin-induced anti-apoptosis and lipid droplet formation in human adipocytes. However, the upstream signals of CIDE proteins remain unclear. Here, we investigated the signaling molecules involved in insulin regulation of CIDEA and CIDEC expression. The phosphatidylinositol 3-kinase (PI3K) inhibitors wortmannin and PI-103 blocked both insulin-induced downregulation of CIDEA and upregulation of CIDEC. The Akt inhibitor API-2 and the c-Jun N-terminal kinase (JNK) inhibitor SP600125 selectively inhibited insulin regulation of CIDEA and CIDEC expression, respectively, whereas the MAPK/ERK kinase inhibitor U0126 and the p38 inhibitor SB203580 did not. Small interfering RNA-mediated depletion of Akt1/2 prevented insulin-induced downregulation of CIDEA and inhibition of apoptosis. Depletion of JNK2, but not JNK1, inhibited insulin-induced upregulation of CIDEC and lipid droplet enlargement. Furthermore, insulin increased both Akt and JNK phosphorylation, which was abrogated by the PI3K inhibitors. These results suggest that insulin regulates CIDEA and CIDEC expression via PI3K, and it regulates expression of each protein via Akt1/2- and JNK2-dependent pathways, respectively, in human adipocytes.

Nobiletin, a citrus flavonoid that improves memory impairment, rescues bulbectomy-induced cholinergic neurodegeneration in mice.

We have recently reported that nobiletin, a citrus flavonoid, improves impaired memory in olfactory-bulbectomized (OBX) mice, which have been widely utilized as a useful paradigm that shares some major clinical features of Alzheimer's disease. Here, we examined the effects of nobiletin on OBX-induced cholinergic neurodegeneration in mice. OBX mice showed reduced acetylcholinesterase (AChE) staining and choline acetyltransferase (ChAT) expression in the hippocampus. An 11-day administration of nobiletin rescued OBX-induced decrease in the density of AChE-staining and ChAT expression in the hippocampus. These results suggest that nobiletin rescues OBX-induced cholinergic neurodegeneration, accompanied by improvement of impaired memory in OBX mice.

Nobiletin and its related flavonoids with CRE-dependent transcription-stimulating and neuritegenic activities.

cAMP response element (CRE) transcription is dysregulated in neurodegenerative disorders in the central nervous system (CNS), including polyglutamine diseases. As the first step to find natural compounds with protective action against neurodegeneration in the CNS, we here examined whether six citrus flavonoids, namely nobiletin, 5-demethylnobiletin, tangeretin, sinensetin, 6-demethoxytangeretin, and 6-demethoxynobiletin, stimulated CRE-dependent transcription and induced neurite outgrowth in PC12D cells. Among the compounds, nobiletin most potently enhanced CRE-dependent transcription and neurite outgrowth by activating ERK/MAP kinase-dependent signalling to increase CREB phosphorylation. The transcription and neurite outgrowth were stimulated by nobiletin in a concentration-dependent manner, with a strong correlation between them. Furthermore, a 11-day oral administration of nobiletin rescued impaired memory in olfactory-bulbectomized mice documented to be accompanied by a cholinergic neurodegeneration. These results suggest that nobiletin with the activity to improve impaired memory may become a potential leading compound for drug development for neurodegenerative disorders exhibiting the dysregulated CRE-dependent transcription.