Activation of the AMP-activated protein kinase by the anti-diabetic drug metformin in vivo. Role of mitochondrial reactive nitrogen species

Metformin, one of the most commonly used drugs for the treatment of type II diabetes, was recently found to exert its therapeutic effects, at least in part, by activating the AMP-activated protein kinase (AMPK). However, the site of its action, as well as the mechanism to activate AMPK, remains elusive. Here we report how metformin activates AMPK. In cultured bovine aortic endothelial cells, metformin dose-dependently activated AMPK in parallel with increased detection of reactive nitrogen species (RNS). Further, either depletion of mitochondria or adenoviral overexpression of superoxide dismutases, as well as inhibition of nitric-oxide synthase, abolished the metformin-enhanced phosphorylations and activities of AMPK, implicating that activation of AMPK by metformin might be mediated by the mitochondria-derived RNS. Furthermore, administration of metformin, which increased 3-nitrotyrosine staining in hearts of C57BL6, resulted in parallel activation of AMPK in the aorta and hearts of C57BL6 mice but not in those of endothelial nitric-oxide synthase (eNOS) knockout mice in which metformin had no effect on 3-nitrotyrosine staining. Because the eNOS knockout mice expressed normal levels of AMPK-alpha that was activated by 5-aminoimidazole-4-carboxamide riboside, an AMPK agonist, these data indicate that RNS generated by metformin is required for AMPK activation in vivo. In addition, metformin significantly increased the co-immunoprecipitation of AMPK and its upstream kinase, LKB1, in C57BL6 mice administered to metformin in vivo. Using pharmacological and genetic inhibitors, we found that inhibition of either c-Src or PI3K abolished AMPK that was enhanced by metformin. We conclude that activation of AMPK by metformin might be mediated by mitochondria-derived RNS, and activation of the c-Src/PI3K pathway might generate a metabolite or other molecule inside the cell to promote AMPK activation by the LKB1 complex.     

Trends and variability in spectral diffuse attenuation of coral reef waters

Coral Reefs - Knowledge of water clarity is an essential component of coral reef ecology. While qualitative trends are well known, there are currently few published records of...     

Protein interactomes for plant lipid biosynthesis and their biotechnological applications

Plant lipids have essential biological roles in plant development and stress responses through their functions in cell membrane formation, energy storage and signalling. Vegetable oil, which is composed mainly of the storage lipid triacylglycerol, also has important applications in food, biofuel and oleochemical industries. Lipid biosynthesis occurs in multiple subcellular compartments and involves the coordinated action of various pathways. Although biochemical and molecular biology research over the last few decades has identified many proteins associated with lipid metabolism, our current understanding of the dynamic protein interactomes involved in lipid biosynthesis, modification and channelling is limited. This review examines advances in the identification and characterization of protein interactomes involved in plant lipid biosynthesis, with a focus on protein complexes consisting of different subunits for sequential reactions such as those in fatty acid biosynthesis and modification, as well as transient or dynamic interactomes formed from enzymes in cooperative pathways such as assemblies of membrane-bound enzymes for triacylglycerol biosynthesis. We also showcase a selection of representative protein interactome structures predicted using AlphaFold2, and discuss current and prospective strategies involving the use of interactome knowledge in plant lipid biotechnology. Finally, unresolved questions in this research area and possible approaches to address them are also discussed.     

Biological denitration of propylene glycol dinitrate byBacillus sp. ATCC 51912

In previous studies, bacterial cultures were isolated that had the ability to degrade the nitrate ester glyceryl trinitrate (i.e. nitroglycerin). The goal of the present study was to examine the ability of resting cells and cell-free extracts of the isolateBacillus sp. ATCC 51912 to degrade the more recalcitrant nitrate ester propylene glycol dinitrate (PGDN). It was observed that the PGDN-denitrating activity was expressed during growth even when cells were cultured in the absence of nitrate esters. This indicates that nitrate esters are not required for expression of denitration activity. Using cell-free extracts, PGDN was observed to be sequentially denitrated to propylene glycol mononitrate (PGMN) and propylene glycol with the second denitration step proceeding more slowly than the first. Also it was observed that dialysis of the cell-free extracts did not affect denitration activity indicating that regenerable cofactors [e.g. NAD(P)H or ATP] are not required for denitration.     

Timing and site selection of spawning in a landlocked population of rainbow smelt in Wisconsin

To study the site selection and timing of spawning by rainbow smelt, Osmerus modax, in a freshwater system, smelt were sampled with fyke nets during the spawning run in spring 2002 and 2003. The sex ratio of smelt favored males in the early and late segments of the run, with over 90% of smelt caught being male. At the peak in the catch, females comprised 57% of the smelt collected. The gonadosomatic index of males and females declined significantly on the day of peak catch, signaling the peak in spawning activity. Higher catches of smelt occurred on cobble-dominated substrates during the peak of the run, but no site selection was apparent earlier or later. Groundwater outflow did not appear to affect catches. Our study suggests that smelt come inshore but do not select specific spawning substrates prior to or after the peak in spawning. Smelt do select cobble sites during the highest rates of spawning. The relation between the peak in spawning and site selection could have application in planning removal strategies for the species.