TY - JOUR A1 - Henkel, Janin A1 - Alfine, Eugenia A1 - Saín, Juliana A1 - Jöhrens, Korinna A1 - Weber, Daniela A1 - Castro, José Pedro A1 - König, Jeannette A1 - Stuhlmann, Christin A1 - Vahrenbrink, Madita A1 - Jonas, Wenke A1 - Kleinridders, André A1 - Püschel, Gerhard Paul T1 - Soybean Oil-Derived Poly-Unsaturated Fatty Acids Enhance Liver Damage in NAFLD Induced by Dietary Cholesterol JF - Nutrients N2 - While the impact of dietary cholesterol on the progression of atherosclerosis has probably been overestimated, increasing evidence suggests that dietary cholesterol might favor the transition from blunt steatosis to non-alcoholic steatohepatitis (NASH), especially in combination with high fat diets. It is poorly understood how cholesterol alone or in combination with other dietary lipid components contributes to the development of lipotoxicity. The current study demonstrated that liver damage caused by dietary cholesterol in mice was strongly enhanced by a high fat diet containing soybean oil-derived ω6-poly-unsaturated fatty acids (ω6-PUFA), but not by a lard-based high fat diet containing mainly saturated fatty acids. In contrast to the lard-based diet the soybean oil-based diet augmented cholesterol accumulation in hepatocytes, presumably by impairing cholesterol-eliminating pathways. The soybean oil-based diet enhanced cholesterol-induced mitochondrial damage and amplified the ensuing oxidative stress, probably by peroxidation of poly-unsaturated fatty acids. This resulted in hepatocyte death, recruitment of inflammatory cells, and fibrosis, and caused a transition from steatosis to NASH, doubling the NASH activity score. Thus, the recommendation to reduce cholesterol intake, in particular in diets rich in ω6-PUFA, although not necessary to reduce the risk of atherosclerosis, might be sensible for patients suffering from non-alcoholic fatty liver disease. KW - non-alcoholic fatty liver disease (NAFLD) KW - NASH KW - cholesterol KW - PUFA KW - inflammation KW - oxidative stress Y1 - 2018 U6 - https://doi.org/10.3390/nu10091326 SN - 2072-6643 VL - 10 IS - 9 SP - 1 EP - 17 PB - Molecular Diversity Preservation International (MDPI) CY - Basel ER - TY - GEN A1 - Henkel, Janin A1 - Alfine, Eugenia A1 - Saín, Juliana A1 - Jöhrens, Korinna A1 - Weber, Daniela A1 - Castro, José Pedro A1 - König, Jeannette A1 - Stuhlmann, Christin A1 - Vahrenbrink, Madita A1 - Jonas, Wenke A1 - Kleinridders, André A1 - Püschel, Gerhard Paul T1 - Soybean Oil-Derived Poly-Unsaturated Fatty Acids Enhance Liver Damage in NAFLD Induced by Dietary Cholesterol T2 - Nutrients N2 - While the impact of dietary cholesterol on the progression of atherosclerosis has probably been overestimated, increasing evidence suggests that dietary cholesterol might favor the transition from blunt steatosis to non-alcoholic steatohepatitis (NASH), especially in combination with high fat diets. It is poorly understood how cholesterol alone or in combination with other dietary lipid components contributes to the development of lipotoxicity. The current study demonstrated that liver damage caused by dietary cholesterol in mice was strongly enhanced by a high fat diet containing soybean oil-derived ω6-poly-unsaturated fatty acids (ω6-PUFA), but not by a lard-based high fat diet containing mainly saturated fatty acids. In contrast to the lard-based diet the soybean oil-based diet augmented cholesterol accumulation in hepatocytes, presumably by impairing cholesterol-eliminating pathways. The soybean oil-based diet enhanced cholesterol-induced mitochondrial damage and amplified the ensuing oxidative stress, probably by peroxidation of poly-unsaturated fatty acids. This resulted in hepatocyte death, recruitment of inflammatory cells, and fibrosis, and caused a transition from steatosis to NASH, doubling the NASH activity score. Thus, the recommendation to reduce cholesterol intake, in particular in diets rich in ω6-PUFA, although not necessary to reduce the risk of atherosclerosis, might be sensible for patients suffering from non-alcoholic fatty liver disease. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 479 KW - non-alcoholic fatty liver disease (NAFLD) KW - NASH KW - cholesterol KW - PUFA KW - inflammation KW - oxidative stress Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-419773 ER - TY - JOUR A1 - Kehm, Richard A1 - Jähnert, Markus A1 - Deubel, Stefanie A1 - Flore, Tanina A1 - König, Jeannette A1 - Jung, Tobias A1 - Stadion, Mandy A1 - Jonas, Wenke A1 - Schürmann, Annette A1 - Grune, Tilman A1 - Höhn, Annika T1 - Redox homeostasis and cell cycle activation mediate beta-cell mass expansion in aged, diabetes-prone mice under metabolic stress conditions: role of thioredoxin-interacting protein (TXNIP) JF - Redox Biology N2 - Overnutrition contributes to insulin resistance, obesity and metabolic stress, initiating a loss of functional beta-cells and diabetes development. Whether these damaging effects are amplified in advanced age is barely investigated. Therefore, New Zealand Obese (NZO) mice, a well-established model for the investigation of human obesity-associated type 2 diabetes, were fed a metabolically challenging diet with a high-fat, carbohydrate restricted period followed by a carbohydrate intervention in young as well as advanced age. Interestingly, while young NZO mice developed massive hyperglycemia in response to carbohydrate feeding, leading to beta-cell dysfunction and cell death, aged counterparts compensated the increased insulin demand by persistent beta-cell function and beta-cell mass expansion. Beta-cell loss in young NZO islets was linked to increased expression of thioredoxin-interacting protein (TXNIP), presumably initiating an apoptosis-signaling cascade via caspase-3 activation. In contrast, islets of aged NZOs exhibited a sustained redox balance without changes in TXNIP expression, associated with higher proliferative potential by cell cycle activation. These findings support the relevance of a maintained proliferative potential and redox homeostasis for preserving islet functionality under metabolic stress, with the peculiarity that this adaptive response emerged with advanced age in diabetesprone NZO mice. KW - aging KW - redox homeostasis KW - metabolic stress KW - beta-cells KW - cell cycle KW - thioredoxin-interacting protein Y1 - 2020 U6 - https://doi.org/10.1016/j.redox.2020.101748 SN - 2213-2317 VL - 37 PB - Elsevier CY - Amsterdam ER - TY - GEN A1 - Raupbach, Jana A1 - Ott, Christiane A1 - König, Jeannette A1 - Grune, Tilman T1 - Proteasomal degradation of glycated proteins depends on substrate unfolding BT - preferred degradation of moderately modified myoglobin T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - The Maillard reaction generates protein modifications which can accumulate during hyperglycemia or aging and may have inflammatory consequences. The proteasome is one of the major intracellular systems involved in the proteolytic degradation of modified proteins but its role in the degradation of glycated proteins is scarcely studied. In this study, chemical and structural changes of glycated myoglobin were analyzed and its degradation by 20S proteasome was studied. Myoglobin was incubated with physiological (5-10 mM), moderate (50-100 mM) and severe levels (300 mM) of glucose or methylglyoxal (MGO, 50 mM). Glycation increased myoglobin's fluorescence and surface hydrophobicity. Severe glycation generated crosslinked proteins as shown by gel electrophoresis. The concentration of advanced glycation endproducts (AGEs) N-epsilon-carboxymethyl lysine (CML), N-epsilon-carboxyethyl lysine (CEL), methylglyoxal-derived hydroimidazolone-1 (MG-H1), pentosidine and pyrraline was analyzed after enzymatic hydrolysis followed by UPLC-MS/MS. Higher concentrations of glucose increased all analyzed AGEs and incubation with MGO led to a pronounced increase of CEL and MG-H1. The binding of the heme group to apo-myoglobin was decreased with increasing glycation indicating the loss of tertiary protein structure. Proteasomal degradation of modified myoglobin compared to native myoglobin depends on the degree of glycation: physiological conditions decreased proteasomal degradation whereas moderate glycation increased degradation. Severe glycation again decreased proteolytic cleavage which might be due to crosslinking of protein monomers. The activity of the proteasomal subunit beta 5 is influenced by the presence of glycated myoglobin. In conclusion, the role of the proteasome in the degradation of glycated proteins is highly dependent on the level of glycation and consequent protein unfolding. KW - glycation KW - myoglobin KW - heme KW - advanced glycation endproducts KW - 20S proteasome Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-527570 SN - 1866-8372 SP - 516 EP - 524 ER - TY - JOUR A1 - Raupbach, Jana A1 - Ott, Christiane A1 - König, Jeannette A1 - Grune, Tilman T1 - Proteasomal degradation of glycated proteins depends on substrate unfolding: Preferred degradation of moderately modified myoglobin JF - Free radical biology and medicine : the official journal of the Oxygen Society, a constituent member of the International Society for Free Radical Research N2 - The Maillard reaction generates protein modifications which can accumulate during hyperglycemia or aging and may have inflammatory consequences. The proteasome is one of the major intracellular systems involved in the proteolytic degradation of modified proteins but its role in the degradation of glycated proteins is scarcely studied. In this study, chemical and structural changes of glycated myoglobin were analyzed and its degradation by 20S proteasome was studied. Myoglobin was incubated with physiological (5-10 mM), moderate (50-100 mM) and severe levels (300 mM) of glucose or methylglyoxal (MGO, 50 mM). Glycation increased myoglobin's fluorescence and surface hydrophobicity. Severe glycation generated crosslinked proteins as shown by gel electrophoresis. The concentration of advanced glycation endproducts (AGEs) N-epsilon-carboxymethyl lysine (CML), N-epsilon-carboxyethyl lysine (CEL), methylglyoxal-derived hydroimidazolone-1 (MG-H1), pentosidine and pyrraline was analyzed after enzymatic hydrolysis followed by UPLC-MS/MS. Higher concentrations of glucose increased all analyzed AGEs and incubation with MGO led to a pronounced increase of CEL and MG-H1. The binding of the heme group to apo-myoglobin was decreased with increasing glycation indicating the loss of tertiary protein structure. Proteasomal degradation of modified myoglobin compared to native myoglobin depends on the degree of glycation: physiological conditions decreased proteasomal degradation whereas moderate glycation increased degradation. Severe glycation again decreased proteolytic cleavage which might be due to crosslinking of protein monomers. The activity of the proteasomal subunit beta 5 is influenced by the presence of glycated myoglobin. In conclusion, the role of the proteasome in the degradation of glycated proteins is highly dependent on the level of glycation and consequent protein unfolding. KW - Glycation KW - Myoglobin KW - Heme KW - Advanced glycation endproducts KW - 20S KW - proteasome Y1 - 2020 U6 - https://doi.org/10.1016/j.freeradbiomed.2019.11.024 SN - 0891-5849 SN - 1873-4596 VL - 152 SP - 516 EP - 524 PB - Elsevier CY - New York ER - TY - JOUR A1 - König, Jeannette A1 - Grune, Tilman A1 - Ott, Christiane T1 - Assessing autophagy in murine skeletal muscle: current findings to modulate and quantify the autophagic flux JF - Current opinion in clinical nutrition and metabolic care N2 - Purpose of review In addition to the currently available lysosomotropic drugs and autophagy whole-body knockout mouse models, we provide alternative methods that enable the modulation and detection of autophagic flux in vivo, discussing advantages and disadvantages of each method. Recent findings With the autophagosome-lysosome fusion inhibitor colchicine in skeletal muscle and temporal downregulation of autophagy using a novel Autophagy related 5-short hairpin RNA (Atg5-shRNA) mouse model we mention two models that directly modulate autophagy flux in vivo. Furthermore, methods to quantify autophagy flux, such as mitophagy transgenic reporters, in situ immunofluorescent staining and multispectral imaging flow cytometry, in mature skeletal muscle and cells are addressed. To achieve clinical benefit, less toxic, temporary and cell-type-specific modulation of autophagy should be pursued further. A temporary knockdown as described for the Atg5-shRNA mice could provide a first insight into possible implications of autophagy inhibition. However, it is also important to take a closer look into the methods to evaluate autophagy after harvesting the tissue. In particular caution is required when experimental conditions can influence the final measurement and this should be pretested carefully. KW - autophagy flux KW - in vivo KW - skeletal muscle Y1 - 2019 U6 - https://doi.org/10.1097/MCO.0000000000000579 SN - 1363-1950 SN - 1473-6519 VL - 22 IS - 5 SP - 355 EP - 362 PB - Lippincott Williams & Wilkins CY - Philadelphia ER - TY - THES A1 - König, Jeannette T1 - Lipofuscin - Entstehung und Rolle in der Zellalterung Y1 - 2017 ER -