Muscle metaboreflex attenuates spontaneous heart rate baroreflex sensitivity during dynamic exercise

Hypoperfusion of active skeletal muscle elicits a reflex pressor response termed the muscle metaboreflex. Dynamic exercise attenuates spontaneous baroreflex sensitivity (SBRS) in the control of heart rate (HR) during rapid, spontaneous changes in blood pressure (BP). Our objective was to determine whether muscle metaboreflex activation (MRA) further diminishes SBRS. Conscious dogs were chronically instrumented for measurement of HR, cardiac output, mean arterial pressure, and left ventricular systolic pressure (LVSP) at rest and during mild (3.2 km/h) or moderate (6.4 km/h at 10% grade) dynamic exercise before and after MRA (via partial reduction of hindlimb blood flow). SBRS was evaluated as the slopes of the linear relations (LRs) between HR and LVSP during spontaneous sequences of at least three consecutive beats when HR changed inversely vs. pressure (expressed as beats x min(-1) x mmHg(-1)). During mild exercise, these LRs shifted upward, with a significant decrease in SBRS (-3.0 +/- 0.4 vs. -5.2 +/- 0.4, P<0.05 vs. rest). MRA shifted LRs upward and rightward and decreased SBRS (-2.1 +/- 0.1, P<0.05 vs. mild exercise). Moderate exercise shifted LRs upward and rightward and significantly decreased SBRS (-1.2 +/- 0.1, P<0.05 vs. rest). MRA elicited further upward and rightward shifts of the LRs and reductions in SBRS (-0.9 +/- 0.1, P<0.05 vs. moderate exercise). We conclude that dynamic exercise resets the arterial baroreflex to higher BP and HR as exercise intensity increases. In addition, increases in exercise intensity, as well as MRA, attenuate SBRS.     

Spontaneous baroreflex control of heart rate during exercise and muscle metaboreflex activation in heart failure

In heart failure (HF), there is a reduced baroreflex sensitivity at rest, and during dynamic exercise there is enhanced muscle metaboreflex activation (MRA). However, how the arterial baroreflex modulates HR during exercise is unknown. We tested the hypothesis that spontaneous baroreflex sensitivity (SBRS) is attenuated during exercise in HF and that MRA further depresses SBRS. In seven conscious dogs we measured heart rate (HR), cardiac output, and left ventricular systolic pressure at rest and during mild and moderate dynamic exercise, before and during MRA (via imposed reductions of hindlimb blood flow), and before and after induction of HF (by rapid ventricular pacing). SBRS was assessed by the sequences method. In control, SBRS was reduced from rest with a progressive resetting of the baroreflex stimulus-response relationship in proportion to exercise intensity and magnitude of MRA. In HF, SBRS was significantly depressed in all settings; however, the changes with exercise and MRA occurred with a pattern similar to the control state. As in control, the baroreflex stimulus-response relationship showed an intensity- and muscle metaboreflex (MMR)-dependent rightward and upward shift. The results of this study indicate that HF induces an impairment in baroreflex control of HR at rest and during exercise, although the effects of exercise and MRA on SBRS occur with a similar pattern as in control, indicating the persistence of some vagal activity.     

Synthesis and structure-activity relationship of novel RXR antagonists: orally active anti-diabetic and anti-obesity agents

A series of diazepinylbenzoic acid derivatives were synthesized and tested in the inhibition assay of the transactivation of RXR. Oral treatment of cyano derivatives (16f) was found to show anti-diabetic and anti-obesity effects in KK-A(y) mice.     

Design, synthesis, and evaluation of isoindolinone-hydroxamic acid derivatives as histone deacetylase (HDAC) inhibitors

We designed and synthesized hydroxamic acid derivatives bearing a 4-(3-pyridyl)phenyl group as a cap structure, and found that they exhibit potent histone deacetylase (HDAC) inhibitory activity. A representative compound, 17a, showed more potent growth-inhibitory activity against pancreatic cancer cells and greater upregulation of p21(WAF1/CIP1) expression than the clinically used HDAC inhibitor suberoylanilide hydroxamic acid (Zolinza).     

BAK1 and BKK1 regulate brassinosteroid-dependent growth and brassinosteroid-independent cell-death pathways

Brassinosteroids (BRs) are phytosteroid hormones controlling various physiological processes critical for normal growth and development. BRs are perceived by a protein complex containing two transmembrane receptor kinases, BRASSINOSTEROID INSENSITIVE 1 (BRI1) and BRI1-ASSOCIATED RECEPTOR KINASE 1 (BAK1) [1-3]. BRI1 null mutants exhibit a dwarfed stature with epinastic leaves, delayed senescence, reduced male fertility, and altered light responses. BAK1 null mutants, however, only show a subtle phenotype, suggesting that functionally redundant proteins might be present in the Arabidopsis genome. Here we report that BAK1-LIKE 1 (BKK1) functions redundantly with BAK1 in regulating BR signaling. Surprisingly, rather than the expected bri1-like phenotype, bak1 bkk1 double mutants exhibit a seedling-lethality phenotype due to constitutive defense-gene expression, callose deposition, reactive oxygen species (ROS) accumulation, and spontaneous cell death even under sterile growing conditions. Our detailed analyses demonstrate that BAK1 and BKK1 have dual physiological roles: positively regulating a BR-dependent plant growth pathway, and negatively regulating a BR-independent cell-death pathway. Both BR signaling and developmentally controlled cell death are critical to optimal plant growth and development, but the mechanisms regulating early events in these pathways are poorly understood. This study provides novel insights into the initiation and crosstalk of the two signaling cascades.     

Rotenoids and flavonoids with anti-invasion of HT1080, anti-proliferation of U937, and differentiation-inducing activity in HL-60 from Erycibe expansa

Principal rotenoids (deguelin, tephrosin, rotenone, and 12a-hydroxyrotenone) (3-30microM) isolated from the stems of Erycibe expansa significantly inhibited invasion of human fibrosarcoma HT1080 cells through Matrigel-coated filters and release of proMMPs-2 and 9. In addition, deguelin and tephrosin showed differentiation-inducing activity in human promyelocytic leukemia HL-60 cells. Furthermore, effects of various constituents isolated from the ethyl acetate-soluble fraction on proliferation of human leukemia U937 cells were examined. As a result, most of isoflavones and several flavans as well as rotenoids showed moderate or substantial anti-proliferative activities.     

Synthesis and structure-activity relationship of RXR antagonists based on the diazepinylbenzoic acid structure

Synthesis and structure-activity relationship of RXR antagonists employing a diazepinylbenzoic acid scaffold are described. Of those antagonists, sulfonamide derivatives (6v and 6w) reveal a high antagonistic activity and good pharmacokinetic properties.     

Lead optimization of [(S)-gamma-(arylamino)prolyl]thiazolidine focused on gamma-substituent: Indoline compounds as potent DPP-IV inhibitors

Dipeptidyl peptidase IV (DPP-IV) inhibitors are looked to as a potential new antidiabetic agent class. A series of [(S)-gamma-(arylamino)prolyl]thiazolidine compounds in which the electrophilic nitrile is removed are chemically stable DPP-IV inhibitors. To discover a structure for the gamma-substituent of the proline moiety more suitable for interacting with the S(2) pocket of DPP-IV, optimization focused on the gamma-substituent was carried out. The indoline compound 22e showed a DPP-IV-inhibitory activity 100-fold more potent than that of the prolylthiazolidine 10 and comparable to that of NVP-DPP728. It also displayed improved inhibitory selectivity for DPP-IV over DPP8 and DPP9 compared to compound 10. Indoline compounds such as 22e have a rigid conformation with double restriction of the aromatic moiety by proline and indoline structures to promote interaction with the binding site in the S(2) pocket of DPP-IV. The double restriction effect provides a potent inhibitory activity which compensates for the decrease in activity caused by removing the electrophilic nitrile.