TY - JOUR A1 - Schell, Mareike A1 - Wardelmann, Kristina A1 - Kleinridders, Andre T1 - Untangling the effect of insulin action on brain mitochondria and metabolism JF - Journal of neuroendocrinology N2 - The regulation of energy homeostasis is controlled by the brain and, besides requiring high amounts of energy, it relies on functional insulin/insulin-like growth factor (IGF)-1 signalling in the central nervous system. This energy is mainly provided by mitochondria in form of ATP. Thus, there is an intricate interplay between mitochondrial function and insulin/IGF-1 action to enable functional brain signalling and, accordingly, propagate a healthy metabolism. To adapt to different nutritional conditions, the brain is able to sense the current energy status via mitochondrial and insulin signalling-dependent pathways and exerts an appropriate metabolic response. However, regional, cell type and receptor-specific consequences of this interaction occur and are linked to diverse outcomes such as altered nutrient sensing, body weight regulation or even cognitive function. Impairments of this cross-talk can lead to obesity and glucose intolerance and are linked to neurodegenerative diseases, yet they also induce a self-sustainable, dysfunctional 'metabolic triangle' characterised by insulin resistance, mitochondrial dysfunction and inflammation in the brain. The identification of causal factors deteriorating insulin action, mitochondrial function and concomitantly a signature of metabolic stress in the brain is of utter importance to offer novel mechanistic insights into development of the continuously rising prevalence of non-communicable diseases such as type 2 diabetes and neurodegeneration. This review aims to determine the effect of insulin action on brain mitochondrial function and energy metabolism. It precisely outlines the interaction and differences between insulin action, insulin-like growth factor (IGF)-1 signalling and mitochondrial function; distinguishes between causality and association; and reveals its consequences for metabolism and cognition. We hypothesise that an improvement of at least one signalling pathway can overcome the vicious cycle of a self-perpetuating metabolic dysfunction in the brain present in metabolic and neurodegenerative diseases. KW - brain KW - energy homeostasis KW - inflammation KW - insulin signalling KW - metabolism KW - mitochondrial function Y1 - 2021 U6 - https://doi.org/10.1111/jne.12932 SN - 0953-8194 SN - 1365-2826 VL - 33 IS - 4 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Wei, Xiaoyan A1 - Franke, Julia A1 - Ost, Mario A1 - Wardelmann, Kristina A1 - Börno, Stefan A1 - Timmermann, Bernd A1 - Meierhofer, David A1 - Kleinridders, Andre A1 - Klaus, Susanne A1 - Stricker, Sigmar T1 - Cell autonomous requirement of neurofibromin (Nf1) for postnatal muscle hypertrophic growth and metabolic homeostasis JF - Journal of cachexia, sarcopenia and muscle N2 - Background Neurofibromatosis type 1 (NF1) is a multi-organ disease caused by mutations in neurofibromin 1 (NF1). Amongst other features, NF1 patients frequently show reduced muscle mass and strength, impairing patients' mobility and increasing the risk of fall. The role of Nf1 in muscle and the cause for the NF1-associated myopathy are mostly unknown. Methods To dissect the function ofNf1in muscle, we created muscle-specific knockout mouse models for NF1, inactivatingNf1in the prenatal myogenic lineage either under the Lbx1 promoter or under the Myf5 promoter. Mice were analysed during prenatal and postnatal myogenesis and muscle growth. Results Nf1(Lbx1)and Nf1(Myf5)animals showed only mild defects in prenatal myogenesis. Nf1(Lbx1)animals were perinatally lethal, while Nf1(Myf5)animals survived only up to approximately 25 weeks. A comprehensive phenotypic characterization of Nf1(Myf5)animals showed decreased postnatal growth, reduced muscle size, and fast fibre atrophy. Proteome and transcriptome analyses of muscle tissue indicated decreased protein synthesis and increased proteasomal degradation, and decreased glycolytic and increased oxidative activity in muscle tissue. High-resolution respirometry confirmed enhanced oxidative metabolism in Nf1(Myf5)muscles, which was concomitant to a fibre type shift from type 2B to type 2A and type 1. Moreover, Nf1(Myf5)muscles showed hallmarks of decreased activation of mTORC1 and increased expression of atrogenes. Remarkably, loss of Nf1 promoted a robust activation of AMPK with a gene expression profile indicative of increased fatty acid catabolism. Additionally, we observed a strong induction of genes encoding catabolic cytokines in muscle Nf1(Myf5)animals, in line with a drastic reduction of white, but not brown adipose tissue. Conclusions Our results demonstrate a cell autonomous role for Nf1 in myogenic cells during postnatal muscle growth required for metabolic and proteostatic homeostasis. Furthermore, Nf1 deficiency in muscle drives cross-tissue communication and mobilization of lipid reserves. KW - neurofibromatosis KW - NF1 KW - myopathy KW - muscle atrophy KW - muscle metabolism KW - muscle fibre type KW - AMPK Y1 - 2020 U6 - https://doi.org/10.1002/jcsm.12632 SN - 2190-5991 SN - 2190-6009 VL - 11 IS - 6 SP - 1758 EP - 1778 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Castro, Jose Pedro A1 - Wardelmann, Kristina A1 - Grune, Tilman A1 - Kleinridders, Andre T1 - Mitochondrial Chaperones in the Brain BT - safeguarding Brain Health and Metabolism? JF - Frontiers in Endocrinology N2 - The brain orchestrates organ function and regulates whole body metabolism by the concerted action of neurons and glia cells in the central nervous system. To do so, the brain has tremendously high energy consumption and relies mainly on glucose utilization and mitochondrial function in order to exert its function. As a consequence of high rate metabolism, mitochondria in the brain accumulate errors over time, such as mitochondrial DNA (mtDNA) mutations, reactive oxygen species, and misfolded and aggregated proteins. Thus, mitochondria need to employ specific mechanisms to avoid or ameliorate the rise of damaged proteins that contribute to aberrant mitochondrial function and oxidative stress. To maintain mitochondria homeostasis (mitostasis), cells evolved molecular chaperones that shuttle, refold, or in coordination with proteolytic systems, help to maintain a low steady-state level of misfolded/aggregated proteins. Their importance is exemplified by the occurrence of various brain diseases which exhibit reduced action of chaperones. Chaperone loss (expression and/or function) has been observed during aging, metabolic diseases such as type 2 diabetes and in neurode-generative diseases such as Alzheimer's (AD), Parkinson's (PD) or even Huntington's (HD) diseases, where the accumulation of damage proteins is evidenced. Within this perspective, we propose that proper brain function is maintained by the joint action of mitochondrial chaperones to ensure and maintain mitostasis contributing to brain health, and that upon failure, alter brain function which can cause metabolic diseases. KW - insulin signaling KW - brain KW - chaperones KW - mitochondria homeostasis KW - mitochondrial dysfunction KW - neurodegeneration Y1 - 2018 U6 - https://doi.org/10.3389/fendo.2018.00196 SN - 1664-2392 VL - 9 PB - Frontiers Research Foundation CY - Lausanne ER - TY - JOUR A1 - Wardelmann, Kristina A1 - Rath, Michaela A1 - Castro, José Pedro A1 - Blümel, Sabine A1 - Schell, Mareike A1 - Hauffe, Robert A1 - Schumacher, Fabian A1 - Flore, Tanina A1 - Ritter, Katrin A1 - Wernitz, Andreas A1 - Hosoi, Toru A1 - Ozawa, Koichiro A1 - Kleuser, Burkhard A1 - Weiß, Jürgen A1 - Schürmann, Annette A1 - Kleinridders, André T1 - Central acting Hsp10 regulates mitochondrial function, fatty acid metabolism and insulin sensitivity in the hypothalamus JF - Antioxidants N2 - Mitochondria are critical for hypothalamic function and regulators of metabolism. Hypothalamic mitochondrial dysfunction with decreased mitochondrial chaperone expression is present in type 2 diabetes (T2D). Recently, we demonstrated that a dysregulated mitochondrial stress response (MSR) with reduced chaperone expression in the hypothalamus is an early event in obesity development due to insufficient insulin signaling. Although insulin activates this response and improves metabolism, the metabolic impact of one of its members, the mitochondrial chaperone heat shock protein 10 (Hsp10), is unknown. Thus, we hypothesized that a reduction of Hsp10 in hypothalamic neurons will impair mitochondrial function and impact brain insulin action. Therefore, we investigated the role of chaperone Hsp10 by introducing a lentiviral-mediated Hsp10 knockdown (KD) in the hypothalamic cell line CLU-183 and in the arcuate nucleus (ARC) of C57BL/6N male mice. We analyzed mitochondrial function and insulin signaling utilizing qPCR, Western blot, XF96 Analyzer, immunohistochemistry, and microscopy techniques. We show that Hsp10 expression is reduced in T2D mice brains and regulated by leptin in vitro. Hsp10 KD in hypothalamic cells induced mitochondrial dysfunction with altered fatty acid metabolism and increased mitochondria-specific oxidative stress resulting in neuronal insulin resistance. Consequently, the reduction of Hsp10 in the ARC of C57BL/6N mice caused hypothalamic insulin resistance with acute liver insulin resistance. KW - brain insulin signaling KW - mitochondria KW - oxidative stress KW - fatty acid metabolism Y1 - 2021 U6 - https://doi.org/10.3390/antiox10050711 SN - 2076-3921 VL - 10 IS - 5 PB - MDPI CY - Basel ER - TY - JOUR A1 - Wardelmann, Kristina T1 - Hormonal regulation of neuronal mitochondrial unfolded protein response and its impact on metabolism N2 - The hypothalamus is the main brain area of central regulation of whole body metabolism through impacting food intake and energy expenditure. For the complex regulation, high amounts of energy are needed and mainly provided by mitochondria. Hence, mitochondrial function is crucial for cell homeostasis and modulates central insulin sensitivity. Thus, mitochondrial dysfunction is associated with insulin resistance in the brain and therefore is involved in the pathogenesis of type-2 diabetes (T2D). Mitochondrial health and protein homeostasis is propagated by mitochondrial stress responses like e.g. mitochondrial unfolded protein response (UPRmt). Therefore, studies regarding the regulation of mitochondrial homeostasis are crucial for understanding its effects on the central nervous system (CNS) for the progression of metabolic and nutrition-dependent disorders. One main aim of this thesis was to investigate the metabolic regulation of mitochondrial stress responsiveness in the hypothalamus. The observed results showed that functional ERK-dependent insulin signaling is needed for regulation of mitochondrial stress response (MSR) genes and positively impacted the metabolism by controlling mitochondrial proteostasis without affecting mitochondrial biogenesis. To further explore the role of MSR genes for brain cell homeostasis and its consequences for the metabolism, one of the key players - the mitochondrial chaperone heat shock protein 10 (Hsp10) – was studied in detail. Hsp10 expression was decreased in insulin-resistant, hyperglycemic db/db mice brains along with increased protein oxidation. Leptin, another key hormone in regulating metabolism, was able to induce Hsp10 in neurons. Appropriately, lentiviral-mediated knock down (KD) of Hsp10 introduced into hypothalamic CLU-183 cells induced mitochondrial dysfunction, altered mitochondrial dynamics and increased contact sites between mitochondria and endoplasmic reticulum (ER). In addition, Hsp10 KD caused cellular insulin resistance along with increasing oxidative stress specifically in mitochondrial fraction. Interestingly, acute Hsp10 KD in the arcuate nucleus of the hypothalamus in C57BL/6N male mice did not change body weight or food intake, but it increased plasma leptin concentrations suggesting an effect on global leptin signaling. It increased hepatic markers of gluconeogenesis and hepatic insulin resistance along with features of low-grade inflammation. Long-term studies of hypothalamic Hsp10 KD mice revealed unaltered systemic insulin sensitivity. The demonstrated increase in markers of hepatic gluconeogenesis of acute Hsp10 KD was still exhibited after 13 weeks, but insulin resistance in the liver was no longer observed. In conclusion, hypothalamic insulin action regulates MSR and ensures proper mitochondrial function which positively affects metabolism. In addition, hypothalamic Hsp10 acts as a modulator of both insulin and leptin signaling and is identified as pivotal for the regulation of central mitochondrial function as well as insulin sensitivity in the brain and it impacts liver function. It may present a regulator of brain-liver crosstalk influencing hepatic gluconeogenesis and insulin sensitivity through a novel regulatory signaling mechanism. N2 - Die zentrale Regulation des Metabolismus wird vom Hypothalamus gesteuert, indem diese Hirnregion die Nahrungsaufnahme sowie den Energieverbrauch reguliert. Dieser komplexe Regulations-Mechanismus benötigt eine enorme Menge an Energie, die hauptsächlich von Mitochondrien produziert wird. Somit ist die mitochondriale Funktion existenziell für die Zell-Homöostase und in einigen Studien konnte gezeigt werden, dass diese Funktion ebenfalls mit der zentralen Insulin-Sensitivität zusammenhängt. Mitochondriale Dysfunktion hingegen ist mit Insulin-Resistenz im Gehirn assoziiert und damit an der Pathogenese und Progression von Diabetes Typ 2 beteiligt. Mitochondriale Stressantworten wie zum Beispiel die mitochondriale ungefaltete Proteinantwort (mitochondrial unfolded stress response) ermöglichen die Protein-Homöostase und einwandfreie Funktion der Mitochondrien. Folglich sind Untersuchungen der Regulation der mitochondrialen Funktion von großer Bedeutung für das Verständnis der zentralnervösen Auswirkungen auf die Entwicklung ernährungsbedingter Störungen des Metabolismus. Eine der Zielstellungen dieser Doktorarbeit war die Untersuchung der metabolischen Regulation der hypothalamische Stressantwort der Mitochondrien. Die hier durchgeführten Studien zeigten, dass die funktionelle Insulin Signalkaskade für die Regulierung der mitochondrialen Stressantwort (MSR) benötigt wird und dies durch die Kontrolle der Proteostase der Mitochondrien positive Effekte auf den Metabolismus hat. Zur genaueren Klärung der Aufgabe der mitochondrialen Stressantwort für die Homöostase der Gehirnzelle und dessen Auswirkungen für den Metabolismus wurde eines der Mitglieder dieser Stressantwort, das mitochondriale Chaperon Hitzeschock-Protein 10 (Hsp10), näher untersucht. Zunächst konnte dargelegt werden, dass die Expression von Hsp10 in Gehirnen von Insulin-resistenten, hyperglykämischen db/db Mäusen verringert ist. Diese Mäuse zeigen zusätzlich eine Erhöhung der Oxidation von Proteinen im Gehirn, ein weiteres Merkmal des Krankheitsbildes von Diabetes Typ 2. Darüber hinaus zeigten die vorliegenden Studien, dass Leptin, ein weiteres für die Regulation des Metabolismus wichtiges Hormon, die Expression von Hsp10 in Neuronen induzieren konnte. Der lentiviral-vermittelte knockdown von Hsp10 in der hypothalamischen, neuronalen Zelllinie CLU 183 hingegen verursacht mitochondriale Dysfunktion, sowie eine veränderte mitochondriale Dynamik einhergehend mit erhöhtem Kontakt von Mitochondrien mit dem endoplasmatischen Retikulum. Zusätzlich wurde Mitochondrien-spezifischer oxidativer Stress von der Reduzierung von Hsp10 verursacht und eine Insulin-Resistenz ausgelöst. Interessanterweise beeinflusste der akute knockdown der Hsp10 Expression im Nucleus Arcuatus des Hypothalamus in männlichen C57BL/6N Mäusen weder das Körpergewicht noch die Futteraufnahme, jedoch war die Plasma-Konzentration von Leptin erhöht. Dies deutet auf einen Effekt von zentralem Hsp10 auf die systemische Leptin-Signalwirkung hin. Außerdem wurde durch die akute Verringerung von hypothalamischen Hsp10 PEPCK in der Leber induziert, ein wichtiges Protein der Gluconeogenese, sowie eine hepatische Insulin-Resistenz ausgelöst, verbunden mit Anzeichen einer schwachen Inflammation dieses Gewebes. Bei verlängerter Reduktion der Expression von Hsp10 im Hypothalamus wurde die systemische Insulin-Sensitivität der Mäuse nicht verändert. Die hepatische Insulin-Resistenz war nach 13 Wochen des hypothalamischen knockdown von Hsp10 in C57BL/6N Mäusen nicht mehr zu beobachten, aber die Induktion des Gluconeogenese-Gens PEPCK in der Leber war weiterhin existent. Zusammenfassend zeigt diese Dissertation, dass die hypothalamische Insulin-Signalwirkung die mitochondriale Stressantwort reguliert und somit die Funktion der Mitochondrien gewährleistet, was den Metabolismus positiv beeinflusst. Des Weiteren deuten die diskutierten Ergebnisse darauf hin, dass Hsp10 im Hypothalamus ein Modulator der Insulin- sowie Leptinsignalwirkung des Körpers ist. Hsp10 ist entscheidend für die Regulierung der zentralen Funktion der Mitochondrien sowie der Insulin-Sensitivität in Gehirn und beeinflusst die Leberfunktion. Die Konsequenzen der Verringerung von Hsp10 im Hypothalamus modulieren die hepatische Gluconeogenese und Insulin-Sensitivität. Daraus folgend wird Hsp10 als neuer Regulator der Kommunikation zwischen Gehirn und Leber identifiziert, mit einem in diesem Falle noch unbekannten Mechanismus der Signalweiterleitung zwischen den beiden Organen. Y1 - 2019 ER - TY - JOUR A1 - Henkel, Janin A1 - Buchheim-Dieckow, Katja A1 - Castro, José Pedro A1 - Laeger, Thomas A1 - Wardelmann, Kristina A1 - Kleinridders, André A1 - Jöhrens, Korinna A1 - Püschel, Gerhard Paul T1 - Reduced Oxidative Stress and Enhanced FGF21 Formation in Livers of Endurance-Exercised Rats with Diet-Induced NASH JF - Nutrients N2 - Non-alcoholic fatty liver diseases (NAFLD) including the severe form with steatohepatitis (NASH) are highly prevalent ailments to which no approved pharmacological treatment exists. Dietary intervention aiming at 10% weight reduction is efficient but fails due to low compliance. Increase in physical activity is an alternative that improved NAFLD even in the absence of weight reduction. The underlying mechanisms are unclear and cannot be studied in humans. Here, a rat NAFLD model was developed that reproduces many facets of the diet-induced NAFLD in humans. The impact of endurance exercise was studied in this model. Male Wistar rats received control chow or a NASH-inducing diet rich in fat, cholesterol, and fructose. Both diet groups were subdivided into a sedentary and an endurance exercise group. Animals receiving the NASH-inducing diet gained more body weight, got glucose intolerant and developed a liver pathology with steatosis, hepatocyte hypertrophy, inflammation and fibrosis typical of NAFLD or NASH. Contrary to expectations, endurance exercise did not improve the NASH activity score and even enhanced hepatic inflammation. However, endurance exercise attenuated the hepatic cholesterol overload and the ensuing severe oxidative stress. In addition, exercise improved glucose tolerance possibly in part by induction of hepatic FGF21 production. KW - NAFLD KW - NASH KW - endurance exercise KW - FGF21 KW - glucose intolerance KW - cholesterol KW - oxidative stress Y1 - 2019 U6 - https://doi.org/10.3390/nu11112709 SN - 2072-6643 VL - 11 IS - 11 PB - MDPI CY - Basel ER -