PKA phosphorylates and inactivates AMPKα to promote efficient lipolysis

The mobilization of metabolic energy from adipocytes depends on a tightly regulated balance between hydrolysis and resynthesis of triacylglycerides (TAGs). Hydrolysis is stimulated by β‐adrenergic signalling to PKA that mediates phosphorylation of lipolytic enzymes, including hormone‐sensitive lipase (HSL). TAG resynthesis is associated with high‐energy consumption, which when inordinate, leads to increased AMPK activity that acts to restrain hydrolysis of TAGs by inhibiting PKA‐mediated activation of HSL. Here, we report that in primary mouse adipocytes, PKA associates with and phosphorylates AMPKα1 at Ser‐173 to impede threonine (Thr‐172) phosphorylation and thus activation of AMPKα1 by LKB1 in response to lipolytic signals. Activation of AMPKα1 by LKB1 is also blocked by PKA‐mediated phosphorylation of AMPKα1 in vitro. Functional analysis of an AMPKα1 species carrying a non‐phosphorylatable mutation at Ser‐173 revealed a critical function of this phosphorylation for efficient release of free fatty acids and glycerol in response to PKA‐activating signals. These results suggest a new mechanism of negative regulation of AMPK activity by PKA that is important for converting a lipolytic signal into an effective lipolytic response.     

Low fertility in contemporary humans and the mate value of their children: sex-specific effects on social status indicators

Evolutionary explanations of low fertility in modern affluent societies commonly state that low fertility is the outcome of high parental investments in the quality of their children. Although the empirical evidence that modern parents do face a quantity–quality trade-off is strong, two issues that are relevant from an evolutionary perspective have not received much attention. First, sex differences in the proximate aspects of quality have been largely ignored. Second, the relationship between the quantity of children and their reproductive success in contemporary low-fertility societies remains unclear. In this article, we study the quantity–quality trade-off as a trade-off between the number of children and the mate value and reproductive success of those children. We examine the trade-off in two steps. First, a lower number of children is expected to increase the mate value of these children. Second, greater mate value is expected to lead to greater reproductive success. Using sex-specific indicators of mate value, we test these hypotheses in a representative sample of the Dutch population aged 55–85 in 1992 (n=3229). This sample contains information on three successive generations in which the middle generation has completed fertility. We find support for the first hypothesis, but only partial support for the second hypothesis. A higher number of children is traded off against the mate value of the children, but not against their reproductive success. We conclude that the conditions under which the quantity of children is traded off against their reproductive success depend on the social environment.     

Life cycle assessment and eco-efficiency analysis of drinking cups used at public events

Background, aim, and scope  

At the request of the Public Waste Agency for the Flemish Region, the Flemish Institute for Technological Research performed a life cycle assessment (LCA), according to the International Organization for Standardization (ISO) 14040 procedures (ISO 1997, 1998, 2000, and ISO 2006), followed by an eco-efficiency analysis of four alternative types of drinking cups for use at public events. The results of the LCA study served as input for the eco-efficiency analysis in which the costs related to the four cup systems were studied and combined with the environmental impacts. The objective of this study was to gain insight into the current environmental impacts and costs related to existing systems for drinking cups at public events in Flanders (Belgium) in order to outline a well-founded policy with regard to this subject. Since the results of this comparative study are publicly available, a critical review was performed according to ISO 14040 (review by interested parties, using a review panel) after each stage (goal and scope, data inventory, impact analysis/interpretation, eco-efficiency analysis) during the study.     

Early signaling through the Arabidopsis pattern recognition receptors FLS2 and EFR involves Ca2+‐associated opening of plasma membrane anion channels

The perception of microbes by plants involves highly conserved molecular signatures that are absent from the host and that are collectively referred to as microbe‐associated molecular patterns (MAMPs). The Arabidopsis pattern recognition receptors FLAGELLIN‐SENSING 2 (FLS2) and EF‐Tu receptor (EFR) represent genetically well studied paradigms that mediate defense against bacterial pathogens. Stimulation of these receptors through their cognate ligands, bacterial flagellin or bacterial elongation factor Tu, leads to a defense response and ultimately to increased resistance. However, little is known about the early signaling pathway of these receptors. Here, we characterize this early response in situ, using an electrophysiological approach. In line with a release of negatively charged molecules, voltage recordings of microelectrode‐impaled mesophyll cells and root hairs of Col‐0 Arabidopsis plants revealed rapid, dose‐dependent membrane potential depolarizations in response to either flg22 or elf18. Using ion‐selective microelectrodes, pronounced anion currents were recorded upon application of flg22 and elf18, indicating that the signaling cascades initiated by each of the two receptors converge on the same plasma membrane ion channels. Combined calcium imaging and electrophysiological measurements revealed that the depolarization was superimposed by an increase in cytosolic calcium that was indispensable for depolarization. NADPH oxidase mutants were still depolarized upon elicitor stimulation, suggesting a reactive oxygen species‐independent membrane potential response. Furthermore, electrical signaling in response to either flg22 or elf 18 critically depends on the activity of the FLS2‐associated receptor‐like kinase BAK1, suggesting that activation of FLS2 and EFR lead to BAK1‐dependent, calcium‐associated plasma membrane anion channel opening as an initial step in the pathogen defense pathway.     

The peripheral blood mononuclear cell microRNA signature of coronary artery disease

Background

MicroRNAs are being used in the oncology field to characterize tumors and predict the survival of cancer patients. Here, we explored the potential of microRNAs as biomarkers for coronary artery disease (CAD) and acute coronary syndromes.

Methods and results

Using real-time PCR-based profiling, we determined the microRNA signature of peripheral blood mononuclear cells (PBMCs) from stable and unstable CAD patients and unaffected controls. 129 of 157 microRNAs measured were expressed by PBMCs and low variability between separate PBMC pools was observed. The presence of CAD in general coincided with a marked 5-fold increase (P < 0.001) in the relative expression level of miR-135a, while the expression of miR-147 was 4-fold decreased (P < 0.05) in PBMCs from CAD patients as compared to controls, resulting in a 19-fold higher miR-135a/miR-147 ratio (P < 0.001) in CAD. MicroRNA/target gene/biological function linkage analysis suggested that the change in PBMC microRNA signature in CAD patients is probably associated with a change in intracellular cadherin/Wnt signaling. Interestingly, unstable angina pectoris patients could be discriminated from stable patients based upon their relatively high expression level of a cluster of three microRNAs including miR-134, miR-198, and miR-370, suggesting that the microRNA signatures can be used to identify patients at risk for acute coronary syndromes.

Conclusions

The present study is the first to show that microRNA signatures can possibly be utilized to identify patients exhibiting atherosclerotic CAD in general and those at risk for acute coronary syndromes. Our findings highlight the importance of microRNAs signatures as novel tool to predict clinical disease outcomes.     

Triplet Imaging of Oxygen Consumption during the Contraction of a Single Smooth Muscle Cell (A7r5)

The measurement of tissue and cell oxygenation is important for understanding cell metabolism. We have addressed this problem with a novel optical technique, called triplet imaging, that exploits oxygen-induced triplet lifetime changes and is compatible with a variety of fluorophores. A modulated excitation of varying pulse widths allows the extraction of the lifetime of the essentially dark triplet state using a high-fluorescence signal intensity. This enables the monitoring of fast kinetics of oxygen concentration in living cells combined with high temporal and spatial resolution. First, the oxygen-dependent triplet-state quenching of tetramethylrhodamine is validated and then calibrated in an L-ascorbic acid titration experiment demonstrating the linear relation between triplet lifetime and oxygen concentration according to the Stern-Volmer equation. Second, the method is applied to a biological cell system, employing as reporter a cytosolic fusion protein of β-galactosidase with SNAP-tag labeled with tetramethylrhodamine. Oxygen consumption in single smooth muscle cells A7r5 during an [Arg⁸]-vasopressin-induced contraction is measured. The results indicate a consumption leading to an intracellular oxygen concentration that decays monoexponentially with time. The proposed method has the potential to become a new tool for investigating oxygen metabolism at the single cell and the subcellular level.     

Genetic diversity trends in twentieth century crop cultivars: a meta analysis

In recent years, an increasing number of papers has been published on the genetic diversity trends in crop cultivars released in the last century using a variety of molecular techniques. No clear general trends in diversity have emerged from these studies. Meta analytical techniques, using a study weight adapted for use with diversity indices, were applied to analyze these studies. In the meta analysis, 44 published papers were used, addressing diversity trends in released crop varieties in the twentieth century for eight different field crops, wheat being the most represented. The meta analysis demonstrated that overall in the long run no substantial reduction in the regional diversity of crop varieties released by plant breeders has taken place. A significant reduction of 6% in diversity in the 1960s as compared with the diversity in the 1950s was observed. Indications are that after the 1960s and 1970s breeders have been able to again increase the diversity in released varieties. Thus, a gradual narrowing of the genetic base of the varieties released by breeders could not be observed. Separate analyses for wheat and the group of other field crops and separate analyses on the basis of regions all showed similar trends in diversity.     

Cardiolipin clusters and membrane domain formation induced by mitochondrial proteins

We show in this study that mitochondrial creatine kinase promotes segregation and clustering of cardiolipin in mixed membranes, a phenomenon that has been proposed to occur at contact sites in the mitochondria. This property of mitochondrial creatine kinase is dependent on the native octameric structure of the protein and does not occur after heat-denaturation or with the native dimeric form of the protein. Cardiolipin segregation was demonstrated by differential scanning calorimetry using membranes containing cardiolipin and either dipalmitoylphosphatidylethanolamine or 1-palmitoyl-2-oleoylphosphatidylethanolamine. Addition of the ubiquitous form of mitochondrial creatine kinase leads to the formation of a phosphatidylethanolamine-rich domain as a result of the protein binding preferentially to the cardiolipin. Such phase separation does not occur if cardiolipin is replaced with dioleoyl phosphatidylglycerol. Lipid phase separation is observed with other cardiolipin-binding proteins, including cytochrome c and, to a very small extent, with truncated Bid (t-Bid), as well as with the cationic polypeptide poly-L-lysine, but among these proteins the octameric form of mitochondrial creatine kinase is by far the most effective in causing segregation and clustering of cardiolipin. The proteins included in this study are found at mitochondrial contact sites where they are known to associate with cardiolipin. Domains in mitochondria enriched in cardiolipin play an important role in apoptosis and in energy flux processes.