Publications by authors named "Katrin Pfuhlmann"

14 Publications

  • Page 1 of 1

Cannabis use of patients with inflammatory bowel disease in Germany: a cross-sectional survey.

Z Gastroenterol 2021 Jun 22. Epub 2021 Jun 22.

Department for Internal and Integrative Medicine, Sozialstiftung Bamberg, Bamberg, Germany.

Background And Aims:  Progressive legalization and increasing utilization of medical cannabis open up potential new applications, including for inflammatory bowel disease (IBD). This study aimed to collect current figures on the use of and experience with cannabis among IBD patients in Germany.

Methods:  A 71-item questionnaire was mailed to a randomly selected representative sample of 1000 IBD patients.

Results:  Questionnaires were returned by 417 patients (mean age 49.1 ± 17.0 years; 55.8 % women; 43.4 % ulcerative colitis and 54.7 % Crohn's disease). Seventy-three respondents (17.5 %) stated past cannabis use for recreational purposes, while 12 users mentioned usage at the time the questionnaire was completed (2.9 %). Seventeen patients (4.1 %) indicated past use of cannabis, and 18 participants (4.3 %) reported current use of cannabis to treat IBD. Perceived benefits of cannabis use by its users included reduced abdominal pain, improved sleep quality, and relief of unease and worry. They reported lower quality of life and higher levels of anxiety or depression than non-users. Of notice, 52.9 % of cannabis users obtained their cannabis from the black market. A total of 76.5 % of former and 50 % of current users did not report their cannabis use to the physician.

Conclusion:  This survey reveals the largest data set on cannabis use among IBD patients in Germany, with the potential for further research. Cannabis is mainly procured from the black market, with unknown quality.
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http://dx.doi.org/10.1055/a-1400-2768DOI Listing
June 2021

Type 2 diabetes risk gene Dusp8 regulates hypothalamic Jnk signaling and insulin sensitivity.

J Clin Invest 2020 11;130(11):6093-6108

Neurobiology of Stress Resilience, Max Planck Institute of Psychiatry, Munich, Germany.

Recent genome-wide association studies (GWAS) identified DUSP8, encoding a dual-specificity phosphatase targeting mitogen-activated protein kinases, as a type 2 diabetes (T2D) risk gene. Here, we reveal that Dusp8 is a gatekeeper in the hypothalamic control of glucose homeostasis in mice and humans. Male, but not female, Dusp8 loss-of-function mice, either with global or corticotropin-releasing hormone neuron-specific deletion, had impaired systemic glucose tolerance and insulin sensitivity when exposed to high-fat diet (HFD). Mechanistically, we found impaired hypothalamic-pituitary-adrenal axis feedback, blunted sympathetic responsiveness, and chronically elevated corticosterone levels driven by hypothalamic hyperactivation of Jnk signaling. Accordingly, global Jnk1 ablation, AAV-mediated Dusp8 overexpression in the mediobasal hypothalamus, or metyrapone-induced chemical adrenalectomy rescued the impaired glucose homeostasis of obese male Dusp8-KO mice, respectively. The sex-specific role of murine Dusp8 in governing hypothalamic Jnk signaling, insulin sensitivity, and systemic glucose tolerance was consistent with functional MRI data in human volunteers that revealed an association of the DUSP8 rs2334499 risk variant with hypothalamic insulin resistance in men. Further, expression of DUSP8 was increased in the infundibular nucleus of T2D humans. In summary, our findings suggest the GWAS-identified gene Dusp8 as a novel hypothalamic factor that plays a functional role in the etiology of T2D.
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http://dx.doi.org/10.1172/JCI136363DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7598066PMC
November 2020

Profound weight loss induces reactive astrogliosis in the arcuate nucleus of obese mice.

Mol Metab 2019 06 3;24:149-155. Epub 2019 Apr 3.

Research Unit Neurobiology of Diabetes, Helmholtz Zentrum München, 85764, Neuherberg, Germany; Institute for Diabetes and Obesity, Helmholtz Zentrum München, 85764, Neuherberg, Germany; German Center for Diabetes Research (DZD), 85764, Neuherberg, Germany. Electronic address:

Objective: Obesity has been linked to an inflammation like state in the hypothalamus, mainly characterized by reactive gliosis (RG) of astrocytes and microglia. Here, using two diet models or pharmacological treatment, we assessed the effects of mild and drastic weight loss on RG, in the context of high-fat diet (HFD) induced obesity.

Methods: We subjected HFD-induced obese (DIO) male C57BL/6J mice to a weight loss intervention with a switch to standard chow, calorie restriction (CR), or treatment with the Glp1 receptor agonist Exendin-4 (EX4). The severity of RG was estimated by an ordinal scoring system based on fluorescence intensities of glial fibrillary acidic protein, ionized calcium-binding adapter molecule 1 positive (Iba1), cell numbers, and morphological characteristics.

Results: In contrast to previous reports, DIO mice fed chronically with HFD showed no differences in microglial or astrocytic RG, compared to chow controls. Moreover, mild or profound weight loss had no impact on microglial RG. However, astrocyte RG was increased in CR and EX4 groups compared to chow fed animals and strongly correlated to body weight loss. Profound weight loss by either CR or EX4 was further linked to increased levels of circulating non-esterified free fatty acids.

Conclusions: Overall, our data demonstrate that in a chronically obese state, astrocyte and microglial RG is indifferent from that observed in age-matched chow controls. Nonetheless, profound acute weight loss can induce astrocyte RG in the hypothalamic arcuate nucleus, possibly due to increased circulating NEFAs. This suggests that astrocytes may sense acute changes to both the dietary environment and body weight.
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http://dx.doi.org/10.1016/j.molmet.2019.03.009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6977167PMC
June 2019

Celastrol Promotes Weight Loss in Diet-Induced Obesity by Inhibiting the Protein Tyrosine Phosphatases PTP1B and TCPTP in the Hypothalamus.

J Med Chem 2018 12 7;61(24):11144-11157. Epub 2018 Dec 7.

Institute of Structural Biology , Helmholtz Zentrum München , 85764 Neuherberg , Germany.

Celastrol is a natural pentacyclic triterpene used in traditional Chinese medicine with significant weight-lowering effects. Celastrol-administered mice at 100 μg/kg decrease food consumption and body weight via a leptin-dependent mechanism, yet its molecular targets in this pathway remain elusive. Here, we demonstrate in vivo that celastrol-induced weight loss is largely mediated by the inhibition of leptin negative regulators protein tyrosine phosphatase (PTP) 1B (PTP1B) and T-cell PTP (TCPTP) in the arcuate nucleus (ARC) of the hypothalamus. We show in vitro that celastrol binds reversibly and inhibits noncompetitively PTP1B and TCPTP. NMR data map the binding site to an allosteric site in the catalytic domain that is in proximity of the active site. By using a panel of PTPs implicated in hypothalamic leptin signaling, we show that celastrol additionally inhibited PTEN and SHP2 but had no activity toward other phosphatases of the PTP family. These results suggest that PTP1B and TCPTP in the ARC are essential for celastrol's weight lowering effects in adult obese mice.
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http://dx.doi.org/10.1021/acs.jmedchem.8b01224DOI Listing
December 2018

Fluorescent blood-brain barrier tracing shows intact leptin transport in obese mice.

Int J Obes (Lond) 2019 06 3;43(6):1305-1318. Epub 2018 Oct 3.

Research Unit Neurobiology of Diabetes, Helmholtz Zentrum München, 85764, Neuherberg, Germany.

Background/objectives: Individuals carrying loss-of-function gene mutations for the adipocyte hormone leptin are morbidly obese, but respond favorably to replacement therapy. Recombinant leptin is however largely ineffective for the vast majority of obese individuals due to leptin resistance. One theory underlying leptin resistance is impaired leptin transport across the blood-brain-barrier (BBB). Here, we aim to gain new insights into the mechanisms of leptin BBB transport, and its role in leptin resistance.

Methods: We developed a novel tool for visualizing leptin transport using infrared fluorescently labeled leptin, combined with tissue clearing and light-sheet fluorescence microscopy. We corroborated these data using western blotting.

Results: Using 3D whole brain imaging, we display comparable leptin accumulation in circumventricular organs of lean and obese mice, predominantly in the choroid plexus (CP). Protein quantification revealed comparable leptin levels in microdissected mediobasal hypothalami (MBH) of lean and obese mice (p = 0.99). We further found increased leptin receptor expression in the CP (p = 0.025, p = 0.0002) and a trend toward elevated leptin protein levels in the MBH (p = 0.17, p = 0.078) of obese mice undergoing weight loss interventions by calorie restriction or exendin-4 treatment.

Conclusions: Overall, our findings suggest a crucial role for the CP in controlling the transport of leptin into the cerebrospinal fluid and from there to target areas such as the MBH, potentially mediated via the leptin receptor. Similar leptin levels in circumventricular organs and the MBH of lean and obese mice further suggest intact leptin BBB transport in leptin resistant mice.
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http://dx.doi.org/10.1038/s41366-018-0221-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6760579PMC
June 2019

Celastrol-Induced Weight Loss Is Driven by Hypophagia and Independent From UCP1.

Diabetes 2018 11 28;67(11):2456-2465. Epub 2018 Aug 28.

Research Unit Neurobiology of Diabetes, Helmholtz Zentrum München, Neuherberg, Germany

Celastrol, a plant-derived constituent of traditional Chinese medicine, has been proposed to offer significant potential as an antiobesity drug. However, the molecular mechanism for this activity is unknown. We show that the weight-lowering effects of celastrol are driven by decreased food consumption. Although young Lep mice respond with a decrease in food intake and body weight, adult Lep and Lep mice are unresponsive to celastrol, suggesting that functional leptin signaling in adult mice is required to elicit celastrol's catabolic actions. Protein tyrosine phosphatase 1 (PTP1B), a leptin negative-feedback regulator, has been previously reported to be one of celastrol's targets. However, we found that global PTP1B knockout (KO) and wild-type (WT) mice have comparable weight loss and hypophagia when treated with celastrol. Increased levels of uncoupling protein 1 (UCP1) in subcutaneous white and brown adipose tissue suggest celastrol-induced thermogenesis as a further mechanism. However, diet-induced obese UCP1 WT and KO mice have comparable weight loss upon celastrol treatment, and celastrol treatment has no effect on energy expenditure under ambient housing or thermoneutral conditions. Overall, our results suggest that celastrol-induced weight loss is hypophagia driven and age-dependently mediated by functional leptin signaling. Our data encourage reconsideration of therapeutic antiobesity strategies built on leptin sensitization.
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http://dx.doi.org/10.2337/db18-0146DOI Listing
November 2018

Calcineurin A beta deficiency ameliorates HFD-induced hypothalamic astrocytosis in mice.

J Neuroinflammation 2018 Feb 8;15(1):35. Epub 2018 Feb 8.

Research Unit NeuroBiology of Diabetes, Helmholtz Diabetes Center, Helmholtz Zentrum München, 85764, Neuherberg, Germany.

ᅟ: Astrocytosis is a reactive process involving cellular, molecular, and functional changes to facilitate neuronal survival, myelin preservation, blood brain barrier function and protective glial scar formation upon brain insult. The overall pro- or anti-inflammatory impact of reactive astrocytes appears to be driven in a context- and disease-driven manner by modulation of astrocytic Ca homeostasis and activation of Ca/calmodulin-activated serine/threonine phosphatase calcineurin. Here, we aimed to assess whether calcineurin is dispensable for astrocytosis in the hypothalamus driven by prolonged high fat diet (HFD) feeding. Global deletion of calcineurin A beta (gene name: Ppp3cb) led to a decrease of glial fibrillary acidic protein (GFAP)-positive cells in the ventromedial hypothalamus (VMH), dorsomedial hypothalamus (DMH), and arcuate nucleus (ARC) of mice exposed chronically to HFD. The concomitant decrease in Iba1-positive microglia in the VMH further suggests a modest impact of Ppp3cb deletion on microgliosis. Pharmacological inhibition of calcineurin activity by Fk506 had no impact on IBA1-positive microglia in hypothalami of mice acutely exposed to HFD for 1 week. However, Fk506-treated mice displayed a decrease in GFAP levels in the ARC. In vivo effects could not be replicated in cell culture, where calcineurin inhibition by Fk506 had no effect on astrocytic morphology, astrocytic cell death, GFAP, and vimentin protein levels or microglia numbers in primary hypothalamic astrocytes and microglia co-cultures. Further, adenoviral overexpression of calcineurin subunit Ppp3r1 in primary glia culture did not lead to an increase in GFAP fluorescence intensity. Overall, our results point to a prominent role of calcineurin in mediating hypothalamic astrocytosis as response to acute and chronic HFD exposure. Moreover, discrepant findings in vivo and in cell culture indicate the necessity of studying astrocytes in their "natural" environment, i.e., preserving an intact hypothalamic microenvironment with neurons and non-neuronal cells in close proximity.
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http://dx.doi.org/10.1186/s12974-018-1076-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5806488PMC
February 2018

Dual specificity phosphatase 6 deficiency is associated with impaired systemic glucose tolerance and reversible weight retardation in mice.

PLoS One 2017 5;12(9):e0183488. Epub 2017 Sep 5.

Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, Neuherberg, Germany.

Here, we aimed to investigate the potential role of DUSP6, a dual specificity phosphatase, that specifically inactivates extracellular signal-regulated kinase (ERK), for the regulation of body weight and glucose homeostasis. We further assessed whether metabolic challenges affect Dusp6 expression in selected brain areas or white adipose tissue. Hypothalamic Dusp6 mRNA levels remained unchanged in chow-fed lean vs. high fat diet (HFD) fed obese C57Bl/6J mice, and in C57Bl/6J mice undergoing prolonged fasting or refeeding with fat free diet (FFD) or HFD. Similarly, Dusp6 expression levels were unchanged in selected brain regions of Lepob mice treated with 1 mg/kg of leptin for 6 days, compared to pair-fed or saline-treated Lepob controls. Dusp6 expression levels remained unaltered in vitro in primary adipocytes undergoing differentiation, but were increased in eWAT of HFD-fed obese C57Bl/6J mice, compared to chow-fed lean controls. Global chow-fed DUSP6 KO mice displayed reduced body weight and lean mass and slightly increased fat mass at a young age, which is indicative for early-age weight retardation. Subsequent exposure to HFD led to a significant increase in lean mass and body weight in DUSP6 deficient mice, compared to WT controls. Nevertheless, after 26 weeks of high-fat diet exposure, we observed comparable body weight, fat and lean mass in DUSP6 WT and KO mice, suggesting overall normal susceptibility to develop obesity. In line with the increased weight gain to compensate for early-age weight retardation, HFD-fed DUSP6 KO displayed increased expression levels of anabolic genes involved in lipid and cholesterol metabolism in the epididymal white adipose tissue (eWAT), compared to WT controls. Glucose tolerance was perturbed in both chow-fed lean or HFD-fed obese DUSP6 KO, compared to their respective WT controls. Overall, our data indicate that DUSP6 deficiency has limited impact on the regulation of energy metabolism, but impairs systemic glucose tolerance. Our data are in conflict to earlier reports that propose protection from diet-induced obesity and glucose intolerance in DUSP6 deficient mice. Reasons for the discrepancies remain elusive, but may entail differential genetic backgrounds, environmental factors such as the type and source of HFD, or alterations in the gut microbiome between facilities.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0183488PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5584967PMC
October 2017

Alterations in neuronal control of body weight and anxiety behavior by glutathione peroxidase 4 deficiency.

Neuroscience 2017 08 13;357:241-254. Epub 2017 Jun 13.

Research Unit NeuroBiology of Diabetes, Helmholtz Diabetes Center, Helmholtz Zentrum München, Neuherberg 85764, Germany; Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, Neuherberg 85764, Germany; German Center for Diabetes Research (DZD), Neuherberg 85764, Germany. Electronic address:

Elevated levels of oxidative stress and neuronal inflammation in the hypothalamus or ventral midbrain, respectively, represent common denominators for obesity and Parkinson's Disease (PD). However, little is known about defense mechanisms that protect neurons in these regions from oxidative damage. Here, we aimed to assess whether murine Gpx4, a crucial antioxidant enzyme that protects neurons from membrane damage and ferroptosis, is critical for the protection from neuronal inflammation in two distinct pathophysiologic diseases, namely metabolic dysfunction in diet-induced obesity or PD. Gpx4 was deleted from either AgRP or POMC neurons in the hypothalamus, essential for metabolic homeostasis, or from dopaminergic neurons in the ventral midbrain, governing behaviors such as anxiety or voluntary movement. To induce a pro-inflammatory environment, AgRP and POMC neuron-specific Gpx4 knockout mice were subjected to high-fat high-sucrose (HFHS) diet. To exacerbate oxidative stress in dopaminergic neurons of the ventral midbrain, we systemically co-deleted the PD-related gene DJ-1. Gpx4 was dispensable for the maintenance of cellular health and function of POMC neurons, even in mice exposed to obesogenic conditions. In contrast, HFHS-fed mice with Gpx4 deletion from AgRP neurons displayed increased body adiposity. Gpx4 expression and activity were diminished in the hypothalamus of HFHS-fed mice compared to standard diet-fed controls. Gpx4 deletion from dopaminergic neurons induced anxiety behavior, and diminished spontaneous locomotor activity when DJ-1 was co-deleted. Overall, these data suggest a physiological role for Gpx4 in balancing metabolic control signals and inflammation in AgRP but not POMC neurons. Moreover, Gpx4 appears to constitute an important rheostat against neuronal dysfunction and PD-like symptoms in dopaminergic circuitry within the ventral midbrain.
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http://dx.doi.org/10.1016/j.neuroscience.2017.05.050DOI Listing
August 2017

Direct Substrate Delivery Into Mitochondrial Fission-Deficient Pancreatic Islets Rescues Insulin Secretion.

Diabetes 2017 05 7;66(5):1247-1257. Epub 2017 Feb 7.

Helmholtz Diabetes Center, Helmholtz Zentrum München, Neuherberg, Germany

In pancreatic β-cells, mitochondrial bioenergetics control glucose-stimulated insulin secretion. Mitochondrial dynamics are generally associated with quality control, maintaining the functionality of bioenergetics. By acute pharmacological inhibition of mitochondrial fission protein , we demonstrate in this study that mitochondrial fission is necessary for glucose-stimulated insulin secretion in mouse and human islets. We confirm that genetic silencing of increases mitochondrial proton leak in MIN6 cells. However, our comprehensive analysis of pancreatic islet bioenergetics reveals that does not control insulin secretion via its effect on proton leak but instead via modulation of glucose-fueled respiration. Notably, pyruvate fully rescues the impaired insulin secretion of fission-deficient β-cells, demonstrating that defective mitochondrial dynamics solely affect substrate supply upstream of oxidative phosphorylation. The present findings provide novel insights into how mitochondrial dysfunction may cause pancreatic β-cell failure. In addition, the results will stimulate new thinking in the intersecting fields of mitochondrial dynamics and bioenergetics, as treatment of defective dynamics in mitochondrial diseases appears to be possible by improving metabolism upstream of mitochondria.
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http://dx.doi.org/10.2337/db16-1088DOI Listing
May 2017

Hypothalamic leptin action is mediated by histone deacetylase 5.

Nat Commun 2016 Feb 29;7:10782. Epub 2016 Feb 29.

Helmholtz Diabetes Center, Helmholtz Zentrum München, 85764 Neuherberg, Germany.

Hypothalamic leptin signalling has a key role in food intake and energy-balance control and is often impaired in obese individuals. Here we identify histone deacetylase 5 (HDAC5) as a regulator of leptin signalling and organismal energy balance. Global HDAC5 KO mice have increased food intake and greater diet-induced obesity when fed high-fat diet. Pharmacological and genetic inhibition of HDAC5 activity in the mediobasal hypothalamus increases food intake and modulates pathways implicated in leptin signalling. We show HDAC5 directly regulates STAT3 localization and transcriptional activity via reciprocal STAT3 deacetylation at Lys685 and phosphorylation at Tyr705. In vivo, leptin sensitivity is substantially impaired in HDAC5 loss-of-function mice. Hypothalamic HDAC5 overexpression improves leptin action and partially protects against HFD-induced leptin resistance and obesity. Overall, our data suggest that hypothalamic HDAC5 activity is a regulator of leptin signalling that adapts food intake and body weight to our dietary environment.
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http://dx.doi.org/10.1038/ncomms10782DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4773494PMC
February 2016

Calcineurin Links Mitochondrial Elongation with Energy Metabolism.

Cell Metab 2015 Nov 24;22(5):838-50. Epub 2015 Sep 24.

Helmholtz Diabetes Center, Helmholtz Zentrum München, 85764 Neuherberg, Germany; Division of Metabolic Diseases, Technische Universität München, 80333 Munich, Germany. Electronic address:

Canonical protein phosphatase 3/calcineurin signaling is central to numerous physiological processes. Here we provide evidence that calcineurin plays a pivotal role in controlling systemic energy and body weight homeostasis. Knockdown of calcineurin in Drosophila melanogaster led to a decrease in body weight and energy stores, and increased energy expenditure. In mice, global deficiency of catalytic subunit Ppp3cb, and tissue-specific ablation of regulatory subunit Ppp3r1 from skeletal muscle, but not adipose tissue or liver, led to protection from high-fat-diet-induced obesity and comorbid sequelæ. Ser637 hyperphosphorylation of dynamin-related protein 1 (Drp1) in skeletal muscle of calcineurin-deficient mice was associated with mitochondrial elongation into power-cable-shaped filaments and increased mitochondrial respiration, but also with attenuated exercise performance. Our data suggest that calcineurin acts as highly conserved pivot for the adaptive metabolic responses to environmental changes such as high-fat, high-sugar diets or exercise.
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http://dx.doi.org/10.1016/j.cmet.2015.08.022DOI Listing
November 2015
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