Gain-of-Function R225W Mutation in Human AMPKγ3 Causing Increased Glycogen and Decreased Triglyceride in Skeletal Muscle

BACKGROUND: AMP-activated protein kinase (AMPK) is a heterotrimeric enzyme that is evolutionarily conserved from yeast to mammals and functions to maintain cellular and whole body energy homeostasis. Studies in experimental animals demonstrate that activation of AMPK in skeletal muscle protects against insulin resistance, type 2 diabetes and obesity. The regulatory gamma(3) subunit of AMPK is expressed exclusively in skeletal muscle; however, its importance in controlling overall AMPK activity is unknown. While evidence is emerging that gamma subunit mutations interfere specifically with AMP activation, there remains some controversy regarding the impact of gamma subunit mutations. Here we report the first gain-of-function mutation in the muscle-specific regulatory gamma(3) subunit in humans. METHODS AND FINDINGS: We sequenced the exons and splice junctions of the AMPK gamma(3) gene (PRKAG3) in 761 obese and 759 lean individuals, identifying 87 sequence variants including a novel R225W mutation in subjects from two unrelated families. The gamma(3) R225W mutation is homologous in location to the gamma(2)R302Q mutation in patients with Wolf-Parkinson-White syndrome and to the gamma(3)R225Q mutation originally linked to an increase in muscle glycogen content in purebred Hampshire Rendement Napole (RN-) pigs. We demonstrate in differentiated muscle satellite cells obtained from the vastus lateralis of R225W carriers that the mutation is associated with an approximate doubling of both basal and AMP-activated AMPK activities. Moreover, subjects bearing the R225W mutation exhibit a approximately 90% increase of skeletal muscle glycogen content and a approximately 30% decrease in intramuscular triglyceride (IMTG). CONCLUSIONS: We have identified for the first time a mutation in the skeletal muscle-specific regulatory gamma(3) subunit of AMPK in humans. The gamma(3)R225W mutation has significant functional effects as demonstrated by increases in basal and AMP-activated AMPK activities, increased muscle glycogen and decreased IMTG. Overall, these findings are consistent with an important regulatory role for AMPK gamma(3) in human muscle energy metabolism

Strategies of Eradicating Glioma Cells: A Multi-Scale Mathematical Model with MiR-451-AMPK-mTOR Control

The cellular dispersion and therapeutic control of glioblastoma, the most aggressive type of primary brain cancer, depends critically on the migration patterns after surgery and intracellular responses of the individual cancer cells in response to external biochemical and biomechanical cues in the microenvironment. Recent studies have shown that a particular microRNA, miR-451, regulates downstream molecules including AMPK and mTOR to determine the balance between rapid proliferation and invasion in response to metabolic stress in the harsh tumor microenvironment. Surgical removal of main tumor is inevitably followed by recurrence of the tumor due to inaccessibility of dispersed tumor cells in normal brain tissue. In order to address this multi-scale nature of glioblastoma proliferation and invasion and its response to conventional treatment, we propose a hybrid model of glioblastoma that analyses spatio-temporal dynamics at the cellular level, linking individual tumor cells with the macroscopic behaviour of cell organization and the microenvironment, and with the intracellular dynamics of miR-451-AMPK-mTOR signaling within a tumour cell. The model identifies a key mechanism underlying the molecular switches between proliferative phase and migratory phase in response to metabolic stress and biophysical interaction between cells in response to fluctuating glucose levels in the presence of blood vessels (BVs). The model predicts that cell migration, therefore efficacy of the treatment, not only depends on oxygen and glucose availability but also on the relative balance between random motility and strength of chemoattractants. Effective control of growing cells near BV sites in addition to relocalization of invisible migratory cells back to the resection site was suggested as a way of eradicating these migratory cells.Publisher PDFPeer reviewe

Toward a framework to assist servitization strategy implementation

Advice for manufacturing companies to increase their attention to opportunities downstream of production had grown loud by the mid 1990s. Accompanying this advice lay warnings of generic, implementation issues to be addressed in the journey downstream - new marketing and commercial capabilities to be acquired; fresh perspectives on appropriate performance measures; new relationships with customers; and adopt and nurture a service culture and supporting processes.In this exploratory paper we gather and critically analyse the increasing volume of research on servitization strategy implementation from the operations, marketing, and service literatures to summarize and structure current knowledge on the barriers to servitization for manufacturing companies. Contingencies like company size; competitive situation; and the extent of services provided were studied, however, the range of available research was not yet sufficient to draw useful conclusions. The paper therefore concentrates on identifying, assembling and structuring generic barriers to the implementation of servitization strategies from research over the last twenty years to provide researchers and practitioners with an appreciation of the wide scope and implications of a servitization strategy

Improving the aerospace supply chain: a preliminary assessment of an industry-level intervention

The objectives of the study were to 1. Evaluate the SC21 initiative in relation to the changing industry context and consequent customer company requirements; and current trends in supply chain management; 2.Examine the impact operating within a complex supply chain network through the experience of three customer and three supplier companies; 3.Assess the SC21 programme in terms of research on supplier development and the approach, success factors and challenges for case study examples of SC21 implementation; 4.Examine the changing definitions of customer value and challenges in transitioning from product to through-life service orientation; and finally; 5.Identify potential key questions, research partners and proposal outlines for future research.The research findings from the preliminary study will provide a focus for future research proposals

Implementing Lean in aerospace-challenging the assumptions and understanding the challenges

Lean manufacturing appears to hold considerable promise for addressing a range of simultaneous, competitive demands including high levels of process and product quality, low cost and reductions in lead times. These requirements have been recognised within the aerospace sector and efforts are now well established to implement Lean practices. Lean manufacturing was initiated within the automotive sector. However, since the publication of the influential book, The Machine That Changed the World (Womack et al., 1990) there has been a range of documented cases of Lean implementation in a variety of sectors. Despite this evidence, the perception remains that Lean manufacturing is to some degree, an ‘automotive idea’ and difficult to transfer to other sectors especially when there are major differences between them. In this paper we discuss the key drivers for Lean in aerospace and examine the assumption that cross-sector transfer may be difficult. A Lean implementation case comparison examines how difficulties that arise may have more to do with individual plant context and management than with sector specific factors