Getting grip on glucocorticoid-induced metabolic derangements

Synthetische glucocorticoïden, zoals prednisolon, zijn krachtige ontsteking remmende medicijnen, die veel en wijdverspreid worden voorgeschreven in de behandeling van chronische ontstekingsziekten. Helaas hebben deze medicijnen ernstige bijwerkingen, waarvan vele symptomen doen denken aan het metabool syndroom, zoals hyperglycemie, insuline resistentie en dyslipidemie. Het werk beschreven in dit proefschrift behandelt de metabole bijwerkingen van prednisolon therapie in muizen en was gericht op het ontrafelen van de (moleculaire) mechanismen die ten grondslag liggen aan deze bijwerkingen met behulp van o.a. stabiele isotoop methoden. Allereerst werd er een nieuwe methode ontwikkeld om glucose metabolisme te bestuderen in een gevaste toestand met behulp van stabiele isotopen. Deze werd methode werd in meerdere muismodellen behandeld met prednisolon gebruikt. Ten eerste in conventionele muizen, ten tweede in muizen op een hoog vet dieet en ten derde in muizen met collageen geïnduceerde reuma. Echter, in deze diermodellen werd geen klassieke insuline resistentie ontdekt, ondanks dat ze duidelijke metabole afwijkingen vertoonden. Verschillende technieken gedurende verschillende condities werden gebruikt om te bevestigen dat in deze muizen insuline resistentie niet gedetecteerd kon worden. Daarnaast werd een nieuw medicijn bestudeerd dat verminderde metabole bijwerkingen had. Ter afsluiting werd in een muismodel met een mutatie in de glucocorticoid receptor dyslipidemie bestudeerd. De in vivo onderzoeken die in dit proefschrift beschreven staan, voorzien een diepgaande analyse van de effecten van glucocorticoïden op het glucose en lipiden metabolisme, en insuline resistentie in muizen. Het draagt bij aan een verbeterd begrip van glucocorticoïd geïnduceerde metabole bijwerkingen. Daarnaast levert het een belangrijke stap in de waardering van muismodel in het onderzoek naar bijwerkingen van prednisolon

Chronic Prednisolone Treatment Aggravates Hyperglycemia in Mice Fed a High-Fat Diet but Does Not Worsen Dietary Fat-Induced Insulin Resistance

textabstractSynthetic glucocorticoids such as prednisolone have potent antiinflammatory actions. Unfortunately, these drugs induce severe adverse effects in patients, many of which resemble features of the metabolic syndrome, such as insulin resistance. In this study, we investigated whether adverse effects of prednisolone on glucose homeostasis are aggravated in mice with compromised insulin sensitivity due to a high-fat diet by applying various methods to analyze changes in insulin sensitivity in mice. C57BL/6J micewerefed a high-fat diet for 6wkandtreated with either prednisolone (10 mg/kg · d) or vehicle for the last 7 d. Insulin sensitivity and blood glucose kinetics were analyzed with state-of-the-art stable isotope procedures in different experimental conditions. Prednisolone treatment aggravated fasting hyperglycemia and hyperinsulinemia caused by high-fat feeding, resulting in a higher homeostatic assessment model of insulin resistance. In addition, prednisolone-treated high-fat diet-fed mice appeared less insulin sensitive by detailed analysis of basal glucose kinetics. Remarkably, using hyperinsulinemic-euglycemic or hyperglycemic clamp techniques, neither hepatic nor peripheral insulin resistance was worsened in the group that was treated with prednisolone. Yet analysis of hepatic glucose metabolism revealed that prednisolone did alter glycogen balance by reducing glycogen synthase flux under hyperinsulinemic as well as hyperglycemic conditions. In addition to elevated insulin levels, prednisolone-treated mice showed a major rise in plasma leptin and fibroblast growth factor 21 levels. Our data indicate that prednisoloneinduced adverse effects on glucose metabolism in high-fat diet-fed mice do not reflect impaired insulin sensitivity but may be caused by other changes in the hormonal regulatory network controlling glucose metabolism such as fibroblast growth factor 21 and leptin. Copyrigh

Getting grip on glucocorticoid-induced metabolic derangements

Synthetische glucocorticoïden, zoals prednisolon, zijn krachtige ontsteking remmende medicijnen, die veel en wijdverspreid worden voorgeschreven in de behandeling van chronische ontstekingsziekten. Helaas hebben deze medicijnen ernstige bijwerkingen, waarvan vele symptomen doen denken aan het metabool syndroom, zoals hyperglycemie, insuline resistentie en dyslipidemie. Het werk beschreven in dit proefschrift behandelt de metabole bijwerkingen van prednisolon therapie in muizen en was gericht op het ontrafelen van de (moleculaire) mechanismen die ten grondslag liggen aan deze bijwerkingen met behulp van o.a. stabiele isotoop methoden. Allereerst werd er een nieuwe methode ontwikkeld om glucose metabolisme te bestuderen in een gevaste toestand met behulp van stabiele isotopen. Deze werd methode werd in meerdere muismodellen behandeld met prednisolon gebruikt. Ten eerste in conventionele muizen, ten tweede in muizen op een hoog vet dieet en ten derde in muizen met collageen geïnduceerde reuma. Echter, in deze diermodellen werd geen klassieke insuline resistentie ontdekt, ondanks dat ze duidelijke metabole afwijkingen vertoonden. Verschillende technieken gedurende verschillende condities werden gebruikt om te bevestigen dat in deze muizen insuline resistentie niet gedetecteerd kon worden. Daarnaast werd een nieuw medicijn bestudeerd dat verminderde metabole bijwerkingen had. Ter afsluiting werd in een muismodel met een mutatie in de glucocorticoid receptor dyslipidemie bestudeerd. De in vivo onderzoeken die in dit proefschrift beschreven staan, voorzien een diepgaande analyse van de effecten van glucocorticoïden op het glucose en lipiden metabolisme, en insuline resistentie in muizen. Het draagt bij aan een verbeterd begrip van glucocorticoïd geïnduceerde metabole bijwerkingen. Daarnaast levert het een belangrijke stap in de waardering van muismodel in het onderzoek naar bijwerkingen van prednisolon. Synthetic glucocorticoids such as prednisolone have potent anti-inflammatory actions and are widely prescribed for treatment of chronic inflammatory diseases. Unfortunately, these drugs can elicit severe adverse effects, many of which resemble features of the metabolic syndrome such as hyperglycemia, insulin resistance and dyslipidemia. The work described in this thesis focused on the metabolic adverse effects of prednisolone treatment in mice and aimed to unravel (molecular) mechanism that underlie these adverse effects in appropriate mouse models using stable isotope methodologies. A novel stable isotope method to evaluate glucose metabolism in a fasted state has been developed. This model has been used in multiple mouse models. Firstly, in conventional C57BL/6J mice treated with prednisolone, secondly in these mice fed a high fat diet and thirdly in mice with collagen-induced arthritis. However, in these models ‘classical insulin resistance’ was not detected, although these mice did display metabolic derangements. Many techniques were used to assess insulin resistance under different conditions, to ascertain that ‘classical insulin resistance’ was not detected. In addition, a novel compound that showed reduced metabolic derangements was examined. Finally, dyslipidemia was examined in mice with a dimerization defective glucocorticoid receptor. The in vivo studies described in this thesis provide in-depth analysis of the effects of glucocorticoids on glucose an lipid metabolism and insulin resistance in mice and contribute to an improved understanding of glucocorticoid-induced effects on glucose metabolism. The studies described in this thesis provide an important step in the recognition of the value of mice studies in glucocorticoid-related adverse effects.

Archaeal and Bacterial SecD and SecF Homologs Exhibit Striking Structural and Functional Conservation

The majority of secretory proteins are translocated into and across hydrophobic membranes via the universally conserved Sec pore. Accessory proteins, including the SecDF-YajC Escherichia coli membrane complex, are required for efficient protein secretion. E. coli SecDF-YajC has been proposed to be involved in the membrane cycling of SecA, the cytoplasmic bacterial translocation ATPase, and in the stabilizing of SecG, a subunit of the Sec pore. While there are no identified archaeal homologs of either SecA or SecG, many archaea possess homologs of SecD and SecF. Here, we present the first study that addresses the function of archaeal SecD and SecF homologs. We show that the SecD and SecF components in the model archaeon Haloferax volcanii form a cytoplasmic membrane complex in the native host. Furthermore, as in E. coli, an H. volcanii ΔsecFD mutant strain exhibits both severe cold sensitivity and a Sec-specific protein translocation defect. Taken together, these results demonstrate significant functional conservation among the prokaryotic SecD and SecF homologs despite the distinct composition of their translocation machineries

Prevalence and pathophysiology of early dumping in patients after primary Roux-en-Y gastric bypass during a mixed-meal tolerance test

BACKGROUND: Early dumping is a poorly defined and incompletely understood complication after Roux-en-Y gastric (RYGB). OBJECTIVE: We performed a mixed-meal tolerance test in patients after RYGB to address the prevalence of early dumping and to gain further insight into its pathophysiology. SETTING: The study was conducted in a regional hospital in the northern part of the Netherlands. METHODS: From a random sample of patients who underwent primary RYGB between 2008 and 2011, 46 patients completed the mixed-meal tolerance test. The dumping severity score for early dumping was assessed every 30 minutes. A sum score at 30 or 60 minutes of ≥5 and an incremental score of ≥3 points were defined as indicating a high suspicion of early dumping. Blood samples were collected at baseline, every 10 minutes during the first half hour, and at 60 minutes after the start. RESULTS: The prevalence of a high suspicion of early dumping was 26%. No differences were seen for absolute hematocrit value, inactive glucagon-like peptide-1, and vasoactive intestinal peptide between patients with or without early dumping. Patients at high suspicion of early dumping had higher levels of active glucagon-like peptide-1 and peptide YY. CONCLUSION: The prevalence of complaints at high suspicion of early dumping in a random population of patients after RYGB is 26% in response to a mixed-meal tolerance test. Postprandial increases in both glucagon-like peptide-1 and peptide YY are associated with symptoms of early dumping, suggesting gut L-cell overactivity in this syndrome

Prevalence of hypoglycaemia in a random population after Roux-en-Y gastric bypass after a meal test

OBJECTIVE: Roux-en-Y gastric bypass (RYGB) is an effective way to induce sustainable weight loss and can be complicated by postprandial hyperinsulinemic hypoglycaemia (PHH). To study the prevalence and the mechanisms behind the occurrence of hypoglycaemia after a mixed meal tolerance test (MMTT) in patients with primary RYGB. DESIGN: This is a cross-sectional study of patients four years after primary RYGB. METHODS: From a total population of 550 patients, a random sample of 44 patients completed the total test procedures. A standardized mixed meal was used as stimulus. Venous blood samples were collected at baseline, every 10 minutes during the first half hour and every 30 minutes until 210 minutes after the start. Symptoms were assessed by questionnaires. Hypoglycaemia defined as a blood glucose below 3.3 mmol/L. RESULTS: The prevalence of postprandial hypoglycaemia was 48% and was asymptomatic in all patients. Development of hypoglycaemia was more frequent in patients with lower weight at surgery (p = 0.045), with higher weight loss after surgery (p = 0.011), and with higher insulin sensitivity calculated by Homeostasis Model Assessment indexes (HOMA2-IR p = 0.014) and enhanced beta cell function (insulinogenic index at 20 minutes p = 0.001). CONCLUSION: In a randomly selected population four years after primary RYGB surgery 48% of patients developed a hypoglycemic event during a mixed meal tolerance test without symptoms, suggesting the presence of hypoglycaemia unawareness in these patients. The findings in this study suggest that the pathophysiology of PHH is multifactorial

Chronic Prednisolone Treatment Reduces Hepatic Insulin Sensitivity while Perturbing the Fed-to-Fasting Transition in Mice

Chronic glucocorticoid use for treatment of inflammatory diseases is accompanied by severeside effects in humans (e.g. hyperglycemia and insulin resistance). The present studies were conducted to characterize consequences of chronic treatment with the synthetic glucocorticoid prednisolone on insulin sensitivity and blood glucose kinetics in mice. Prednisolone treatment increased fasting blood glucose and plasma insulin concentrations, but this apparently reduced insulin sensitivity could not be confirmed in hyperinsulinemic euglycemic clamp studies. Therefore, a novel method to study whole body glucose kinetics was used. This method revealed that prednisolone-treated mice show an increased hepatic glucose production (HGP). The increased HGP was accompanied by elevated plasma insulin concentrations, indicating reduced insulin sensitivity of hepatic glucose metabolism in prednisolone-treated mice. Compared with vehicle, prednisolone-treated mice had lower blood glucose concentrations, higher plasma free fatty acids, and higher plasma fibroblast growth factor-21 concentrations in the fed condition, i.e. mimicking a fasting situation. Next, the effects of 24-h fasting on energy metabolism were studied. Compared with controls, fasted prednisolone-treated mice had higher blood glucose concentrations and lower plasma beta-hydroxybutyrate concentrations. In conclusion, these results indicate that chronic prednisolone treatment reduces insulin sensitivity of HGP, induces a fasting-like phenotype in fed mice, and perturbs the fed-to-fasting transition. (Endocrinology 151: 2171-2178, 2010

Prednisolone increases enterohepatic cycling of bile acids by induction of Asbt and promotes reverse cholesterol transport

Background &amp; Aims: Glucocorticoids, produced by the adrenal gland under control of the hypothalamic-pituitary-adrenal axis, exert their metabolic actions largely via activation of the glucocorticoid receptor (GR). Synthetic glucocorticoids are widely used as anti-inflammatory and immunosuppressive drugs but their application is hampered by adverse metabolic effects. Recently, it has been shown that GR may regulate several genes involved in murine bile acid (BA) and cholesterol metabolism, yet the physiological relevance hereof is controversial. The aim of this study is to provide a mechanistic basis for effects of prednisolone on BA and cholesterol homeostasis in mice.Methods: Male BALB/c mice were treated with prednisolone (12.5 mg/kg/day) for 7 days by subcutaneous implantation of slow-release pellets, followed by extensive metabolic profiling.Results: Sustained prednisolone treatment induced the expression of the apical sodium-dependent bile acid transporter (Asbt) in the ileum, which stimulated BA absorption. This resulted in elevated plasma BA levels and enhanced biliary BA secretion. Concomitantly, both biliary cholesterol and phospholipid secretion rates were increased. Enhanced BA reabsorption suppressed hepatic BA synthesis, as evident from hepatic gene expression, reduced plasma C4 levels and reduced fecal BA loss. Plasma HDL cholesterol levels were elevated in prednisolone-treated mice, which likely contributed to the stimulated flux of cholesterol from intraperitoneally injected macrophage foam cells into feces.Conclusions: Sustained prednisolone treatment increases entero-hepatic recycling of BA, leading to elevated plasma levels and reduced synthesis in the absence of cholestasis. Under these conditions, prednisolone promotes macrophage-derived reverse cholesterol transport. (C) 2014 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.</p