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The role of anaplerotic metabolism of glucose and glutamine in insulin secretion : a model approach
Vladimir Grubelnik, Jan Zmazek, Marko Gosak, Marko Marhl, 2024, original scientific article

Abstract: We propose a detailed computational beta cell model that emphasizes the role of anaplerotic metabolism under glucose and glucose-glutamine stimulation. This model goes beyond the traditional focus on mitochondrial oxidative phosphorylation and ATP-sensitive K+ channels, highlighting the predominant generation of ATP from phosphoenolpyruvate in the vicinity of KATP channels. It also underlines the modulatory role of H2O2 as a signaling molecule in the first phase of glucose-stimulated insulin secretion. In the second phase, the model emphasizes the critical role of anaplerotic pathways, activated by glucose stimulation via pyruvate carboxylase and by glutamine via glutamate dehydrogenase. It particularly focuses on the production of NADPH and glutamate as key enhancers of insulin secretion. The predictions of the model are consistent with empirical data, highlighting the complex interplay of metabolic pathways and emphasizing the primary role of glucose and the facilitating role of glutamine in insulin secretion. By delineating these crucial metabolic pathways, the model provides valuable insights into potential therapeutic targets for diabetes.
Keywords: mathematical models, pancreatic beta cell, pyruvate-malate cycle
Published in DKUM: 06.06.2024; Views: 71; Downloads: 1
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Diversity and content of carotenoids and other pigments in the transition from the green to the red stage of Haematococcus pluvialis microalgae identified by HPLC-DAD and LC-QTOF-MS
Jaša Veno Grujić, Biljana Todorović, Roman Kranvogl, Terezija Ciringer, Jana Ambrožič-Dolinšek, 2022, original scientific article

Abstract: H. pluvialis is a unicellular freshwater alga containing many bioactive compounds, especially carotenoids, which are the strongest antioxidants among the pigments. This study evaluates the composition and content of carotenoids and other pigments in both stages of algae life cycle, especially in the green vegetative stage, less studied in comparison to the red stage. To determine the composition and content of carotenoids, a combination of HPLC-DAD and LC-QTOF-MS was used. The content of carotenoids in the green vegetative stage was significantly lower than in the red vegetative stage. In the green vegetative stage, 16 different carotenoids and other pigments were identified. Among the total 8.86 mg g−1 DW of pigments, 5.24 mg g−1 DW or 59% of them were chlorophyll a with its derivatives, and 3.62 mg g−1 DW or 41% of them were free carotenoids. After the transition from the green to the red stage, the carotenoid composition was replaced by secondary carotenoids, astaxanthin and its esters, which predominated in the whole carotenoid composition. In addition to free astaxanthin, 12 astaxanthin monoesters, 6 diesters and 13 other carotenoids were determined. The majority of 37.86 mg g−1 DW pigments were monoesters. They represented 82% of all pigments, and their content was about 5 times higher than both, diesters (5.91 mg g−1 DW or 12% of all) and free carotenoids (2.4 mg g−1 DW or 6% of all). The results of the study contribute to the data on the overall pigment composition and content of H. pluvialis algae and provide the basis for further improvement of cultivation of the H. pluvialis algae.
Keywords: antioxidants, astaxanthin, chlorophylls, bioactive compounds, algae, Haematococcus, life cycle, pigment composition, secondary carotenoids
Published in DKUM: 21.05.2024; Views: 90; Downloads: 2
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Lipotoxicity in a vicious cycle of pancreatic beta cell exhaustion
Vladimir Grubelnik, Jan Zmazek, Matej Završnik, Marko Marhl, 2022, original scientific article

Abstract: Hyperlipidemia is a common metabolic disorder in modern society and may precede hyperglycemia and diabetes by several years. Exactly how disorders of lipid and glucose metabolism are related is still a mystery in many respects. We analyze the effects of hyperlipidemia, particularly free fatty acids, on pancreatic beta cells and insulin secretion. We have developed a computational model to quantitatively estimate the effects of specific metabolic pathways on insulin secretion and to assess the effects of short- and long-term exposure of beta cells to elevated concentrations of free fatty acids. We show that the major trigger for insulin secretion is the anaplerotic pathway via the phosphoenolpyruvate cycle, which is affected by free fatty acids via uncoupling protein 2 and proton leak and is particularly destructive in long-term chronic exposure to free fatty acids, leading to increased insulin secretion at low blood glucose and inadequate insulin secretion at high blood glucose. This results in beta cells remaining highly active in the “resting” state at low glucose and being unable to respond to anaplerotic signals at high pyruvate levels, as is the case with high blood glucose. The observed fatty-acid-induced disruption of anaplerotic pathways makes sense in the context of the physiological role of insulin as one of the major anabolic hormones.
Keywords: diabetes, insulin secretion, lipids, PEP cycle, uncoupling proteins, mitochondrial dysfunction
Published in DKUM: 20.05.2024; Views: 66; Downloads: 2
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A game theoretic approach for plastic life cycle assessment
Chunyan Si, Yee Van Fan, Lidija Čuček, Monika Dokl, Petar Varbanov, 2023, original scientific article

Abstract: Plastic production and its end-of-life management pose a significant environmental footprint. The mitigation strategies of the plastic industry are comparatively attainable than the other hard-to-abate sector. However, the involvement of different stakeholders is needed. The life cycle analysis proposed in this study allocated the environmental footprint to stakeholders based on the game theory concept. It addresses the limitation of previous approaches that do not guarantee the stakeholders from different stages will participate in the initiatives with the lowest net environmental footprint due to the dissatisfaction or imbalance in the allocated unburdening footprint (benefit) and burdening footprint. The applicability of the proposed approach is demonstrated through a plastic recycling case study. An allocation of 82 % of environmental benefit to the producer, 14 % to the manufacturer, and 4 % to the user are suggested to achieve efficiency (lowest external interference) and stable cooperation (participation in recycling). This work serves as an initial assessment in demonstrating the integration of the game theory concept in environmental footprint allocation or Life Cycle Assessment.
Keywords: plastic production, environmental footprint, life cycle
Published in DKUM: 18.04.2024; Views: 97; Downloads: 3
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Organizational maturity and sustainability orientation influence on DMS life cycle : case analysis
Sandra Jordan, Simona Sternad Zabukovšek, 2023, original scientific article

Abstract: The topic of the article addresses the management of the document management system (DMS), which represents one of the important steps for organizations to speed up the implementation of business processes, achieve better control over documents, and ensure safer operations. When implementing and using DMS, the importance of the organization’s maturity shall not be forgotten, as it gives the organization a framework to evaluate and improve the overall effectiveness and efficiency of the organization’s DMS, which can contribute to better decision-making and increased productivity. On the other hand, sustainable-oriented organizations are likely to show interest in choosing, implementing, and using DMS. In the article, the impact of an organization’s maturity and the role of sustainability on the DMS lifecycle are researched. Results are presented based on a case analysis of Company X. Supporting the case analysis, structured interviews with the project leader on the clients’ and the project leader on the providers’ side have been performed, which shall give a deeper insight into DMS implementation and the importance of sustainability and organizational maturity, resulting in more successful DMS implementation and use.
Keywords: document management system (DMS), DMS life cycle, maturity model, sustainability, case analysis
Published in DKUM: 09.04.2024; Views: 107; Downloads: 7
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High-cycle fatigue behaviour of the aluminium alloy 5083-H111
Branko Nečemer, Franc Zupanič, Tomaž Vuherer, Srečko Glodež, 2023, original scientific article

Keywords: aluminium alloys, rolling direction, high-cycle fatigue, fracture analysis
Published in DKUM: 04.04.2024; Views: 128; Downloads: 13
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LCF behaviour of high strength aluminium alloys AA 6110A and AA 6086
Jernej Klemenc, Srečko Glodež, Matej Steinacher, Franc Zupanič, 2023, original scientific article

Abstract: The proposed research presents the comprehensive investigation of the Low Cycle Fatigue (LCF) behaviour of two high-strength aluminium alloys of series AA 6xxx: the conventional alloy AA 6110A and the newly developed alloy AA 6086. Both alloys were characterised in the as-cast condition after homogenisation, extrusion, and T6 heat treatment. The quasi-static strength and hardness of the aluminium alloy AA 6086 were found to be significantly higher if compared to the AA 6110A alloys, while the ductility was a little bit smaller. The LCF tests showed that the AA 6086 alloy is more suitable for the high-cycle fatigue regime. On the other hand, the engineering advantage of the AA 6110A alloy is only for low-cycle fatigue applications if less than 100 loading cycles are expected in the service life of the analysed structure. The fatigue cracks formed predominantly on the α-AlMnSi intermetallic particles in both alloys, and, during LCF tests, exhibited small crack propagation. The area of the fatigue crack growth was much smaller than the area of the forced fracture. At smaller amplitude strains the fatigue striations were present at the fracture surface, while, at higher amplitude strains, they were not present. The obtained experimental results represent a good basis for engineering design applications of the analysed alloys AA 6086 and AA 6110A.
Keywords: aluminijeve zlitine, malociklično utrujanje, eksperimentalno testiranje, fraktografija, aluminium alloys, low cycle fatigue, experimental testing, fractography
Published in DKUM: 29.03.2024; Views: 115; Downloads: 12
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Life Cycle Assessment of Pilot-Scale Bio-Refining of Invasive Japanese Knotweed Alien Plant towards Bio-Based Bioactive Compounds
Robert Hren, Katerina Naumoska, Urška Jug, Lidija Čuček, Blaž Likozar, Uroš Novak, Annamaria Vujanović, 2023, original scientific article

Abstract: Japanese knotweed is an invasive alien plant species with characteristic rapid expansion in Europe and North America and resistance to extermination. It displaces autochthonous biodiversity and causes major damage to infrastructure, thus causing global ecological and economic damage. The Japanese knotweed plant is usually eradicated using various chemical, biological, or mechanical techniques, which at a large scale include heavy equipment, usually followed by incineration. Therefore, excavation is preferred to eradication techniques, and as a biomass waste recovery method due to the extraction of high-value biocompounds. This is supported by the fact that the Japanese knotweed possesses various bioactive compounds with beneficial effects on human health. Its rhizome bark extract produces strong and stable antioxidant activity over time, as well as apoptotic, antibacterial, and other beneficial activities. In this work, an environmental impact assessment, including greenhouse gas footprint, acidification, eutrophication, and ecotoxicity for extraction route of the Japanese knotweed rhizome bark, is performed. A comparative case study between the lab-based and proposed pilot-scale production of active added-value extract was evaluated. The results show the pilot-scale production exhibits lower environmental burdens, mainly due to greater electricity requirements for the lab-scale alternative.
Keywords: Japanese knotweed rhizome bark extract, invasive alien plant species, bioactive compounds, lab-scale, pilot-scale, life cycle assessment (LCA), environmental burden assessment
Published in DKUM: 19.03.2024; Views: 163; Downloads: 9
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Managing document management systems’ life cycle in relation to an organization’s maturity for digital transformation
Simona Sternad Zabukovšek, Sandra Jordan, Samo Bobek, 2023, original scientific article

Abstract: Document management systems (DMS) have become an important topic regarding digital transformation in organizations because they enable paperless business, speed up processes, lower business costs, and support sustainability activities in organizations. DMSs should be considered as green technology and also as technology crucial for green digital transformation. Sustainability is becoming increasingly crucial for organizations and society, and DMSs, along with paperless business, can contribute to the sustainable orientation of organizations. However, the problem with DMS implementations is that they often fail and that DMS users often use DMSs at a basic level, which means that, among other things, they still prefer to print documents rather than use electronic documents. A framework that can contribute to a better implementation and a higher level of use of DMSs, which both lead to a more green digital transformation of the organization, represents an organization's maturity. We used the Process and Enterprise Maturity Model (PEMM) to assess the organization's maturity level concerning the DMS' life cycle. Findings are presented from the research study. The research study was based on a questionnaire and collected data from DMS users. The research study showed that an organization's maturity impacts the DMS' life cycle. Organizations that manage the DMS' life cycle will better cope with digital transformation and sustainability issues related to paperless business.
Keywords: digitalization of processes, document management system (DMS), organization maturity, process maturity, life cycle, digital transformation
Published in DKUM: 16.02.2024; Views: 306; Downloads: 11
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