Lotte Bjerre Knudsen

Technical University of Denmark, Copenhagen, Capital Region, Denmark

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Publications (57)258.19 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Glucagon-like peptide-1 (GLP-1) is released from endocrine L-cells lining the gut in response to food ingestion. However, GLP-1 is also produced in the nucleus of the solitary tract (NTS) where it acts as an anorectic neurotransmitter and key regulator of many autonomic and neuroendocrine functions. The expression and projections of GLP-1-producing neurons is highly conserved between rodent and primate brain, although a few key differences have been identified. The GLP-1 receptor (GLP-1R) has been mapped in the rodent brain, but no studies have described the distribution of GLP-1Rs in the nonhuman primate central nervous system. Here, we characterized the distribution of GLP-1R mRNA and protein in the adult macaque brain using in situ hybridization, radioligand receptor autoradiography and immunohistochemistry with a primate specific GLP-1R antibody. Immunohistochemistry demonstrated that the GLP-1R is localized to cell bodies and fiber terminals in a very selective distribution throughout the brain. Consistent with the functional role of the GLP-1R system, we find the highest concentration of GLP-1R-immunoreactivity present in select hypothalamic and brainstem regions that regulate feeding including the paraventricular and arcuate hypothalamic nuclei, as well as the area postrema, NTS, and dorsal motor nucleus of the vagus. Together, our data demonstrate that GLP-1R distribution is highly conserved between rodent and primate although a few key species differences were identified including the amygdala where GLP-1R expression is much higher in primate than in rodent.
    Endocrinology 11/2014; · 4.72 Impact Factor
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    ABSTRACT: Liraglutide is a glucagon-like peptide-1 (GLP-1) analog marketed for the treatment of type 2 diabetes. Besides lowering blood glucose, liraglutide also reduces body weight. It is not fully understood how liraglutide induces weight loss or to what degree liraglutide acts directly in the brain. Here, we determined that liraglutide does not activate GLP-1–producing neurons in the hindbrain, and liraglutide-dependent body weight reduction in rats was independent of GLP-1 receptors (GLP-1Rs) in the vagus nerve, area postrema, and paraventricular nucleus. Peripheral injection of fluorescently labeled liraglutide in mice revealed the presence of the drug in the circumventricular organs. Moreover, labeled liraglutide bound neurons within the arcuate nucleus (ARC) and other discrete sites in the hypothalamus. GLP-1R was necessary for liraglutide uptake in the brain, as liraglutide binding was not seen in Glp1r–/– mice. In the ARC, liraglutide was internalized in neurons expressing proopiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART). Electrophysiological measurements of murine brain slices revealed that GLP-1 directly stimulates POMC/CART neurons and indirectly inhibits neurotransmission in neurons expressing neuropeptide Y (NPY) and agouti-related peptide (AgRP) via GABA-dependent signaling. Collectively, our findings indicate that the GLP-1R on POMC/CART-expressing ARC neurons likely mediates liraglutide-induced weight loss.
    Journal of Clinical Investigation 10/2014; 124(10):0-0. · 13.77 Impact Factor
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    Alan Charles Moses, Lotte Bjerre Knudsen, Claus Bo Svendsen
    Pancreas 05/2014; 43(4):657. · 3.01 Impact Factor
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    ABSTRACT: Increased pancreas mass and glucagon-positive adenomas have been suggested to be a risk associated with sitagliptin or exenatide therapy in humans. Novo Nordisk has conducted extensive toxicology studies including data on pancreas weight and histology in Cynomolgus monkeys dosed with two different human GLP-1 receptor agonists. In a 52-week study with liraglutide, a dose-related increase in absolute pancreas weight, in female monkeys only, was observed. Such dose-related increase was not found in studies of 4, 13 or 87 weeks' duration. No treatment-related histopathological abnormalities were observed in any of the studies. Quantitative histology of the pancreas from the 52-week study showed an increase in the exocrine cell mass in liraglutide-dosed animals, with normal composition of both endocrine and exocrine cellular compartments. Proliferation rate of the exocrine tissue was low and comparable between groups. Endocrine cell mass and proliferation rate were unaltered by liraglutide treatment. Semaglutide showed no increase in pancreas weight and no treatment related histopathological findings in the pancreas after 13 or 52 weeks' dosing. Overall, based on 138 nonhuman primates, there were no histopathological changes in the pancreas associated with liraglutide or semaglutide, two structurally different GLP-1 receptor agonists.
    Diabetes 03/2014; · 7.90 Impact Factor
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    ABSTRACT: Glucagon-like peptide 1 (GLP-1) analogues are increasingly used in treatment of type 2 diabetes. While it is clear that these drugs lower blood glucose through an increase in insulin secretion and a lowering of glucagon secretion, they also lower body weight and systolic blood pressure and increase heart rate. Using a new monoclonal antibody for immunohistochemistry (IHC) we detected GLP-1 receptor (GLP-1R) in important target organs in humans and monkeys. In the pancreas, GLP-1R was predominantly localized in beta-cells with a markedly weaker expression in acinar cells. Pancreatic ductal epithelial cells did not express GLP-1R. In the kidney and lung GLP-1R was exclusively expressed in smooth muscle cells in the wall of arteries and arterioles. In the heart, GLP-1R was localized in myocytes of the sinoatrial node. In the gastrointestinal tract, the highest GLP-1R expression was seen in Brunner's gland in the duodenum, with lower level expression in parietal cells and smooth muscle cells in the muscularis externa in the stomach, and in myenteric nerve plexus neurons throughout the gut. No GLP-1R was seen in primate liver and thyroid. GLP-1R expression seen with IHC was confirmed by functional expression using in situ ligand binding (ISLB) with (125)I-GLP-1. In conclusion, these results give important new insight into the molecular mode of action of GLP-1 analogues by identifying the exact cellular localization of GLP-1R.
    Endocrinology 01/2014; · 4.72 Impact Factor
  • Diabetes care 12/2013; 36(12):e213. · 7.74 Impact Factor
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    ABSTRACT: The glucagon-like peptide-1 receptor (GLP-1R) belongs to family B of the G-protein coupled receptors (GPCRs), and has become a promising target for the treatment of type 2 diabetes. Here we describe the development and characterization of a fully functional cysteine-deprived and C-terminally truncated GLP-1R. Single cysteines were initially substituted with alanine, and functionally redundant cysteines were subsequently changed simultaneously. Our results indicate that Cys(174), Cys(226), Cys(296) and Cys(403) are important for the GLP-1-mediated response, whereas Cys(236), Cys(329), Cys(341), Cys(347), Cys(438), Cys(458) and Cys(462) are not. Extensive deletions were made in the C-terminal tail of GLP-1R in order to determine the limit for truncation. As for other family B GPCRs, we observed a direct correlation between the length of the C-terminal tail and specific binding of (125)I-GLP-1, indicating that the membrane proximal part of the C-terminal is involved in receptor expression at the cell surface. The results show that seven cysteines and more than half of the C-terminal tail can be removed from GLP-1R without compromising GLP-1 binding or function.
    Peptides 09/2013; · 2.61 Impact Factor
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    Regulatory Peptides 03/2013; 182:59–61. · 2.01 Impact Factor
  • Charles Pyke, Lotte Bjerre Knudsen
    Endocrinology 01/2013; 154(1):4-8. · 4.72 Impact Factor
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    ABSTRACT: A possible association between glucagon-like peptide-1 (GLP-1) analogs and incidences of pancreatitis has been suggested based on clinical studies. In male and female diabetic Zucker diabetic fatty (ZDF) rats, we investigated the effects of continuous administration of liraglutide and exenatide on biochemical [lipase, pancreatic amylase (P-amylase)] and histopathological markers of pancreatitis. Male and female ZDF rats were dosed for 13 wk with liraglutide (0.4 or 1.0 mg·kg(-1)·day(-1) sc once daily) or exenatide (0.25 mg·kg(-1)·day(-1) sc, Alzet osmotic minipumps). P-amylase and lipase plasma activity were measured, and an extended histopathological and stereological (specific cell mass and proliferation rate) evaluation of the exocrine and the endocrine pancreas was performed. Expectedly, liraglutide and exenatide lowered blood glucose and Hb A(1c) in male and female ZDF rats, whereas β-cell mass and proliferation rate were increased with greatly improved blood glucose control. Whereas neither analog affected lipase activity, small increases in P-amylase activity were observed in animals treated with liraglutide and exenatide. However, concurrent or permanent increases in lipase and P-amylase activity were never observed. Triglycerides were lowered by both GLP-1 analogs. The qualitative histopathological findings did not reveal adverse effects of liraglutide. The findings were mainly minimal in severity and focal in distribution. Similarly, the quantitative stereological analyses revealed no effects of liraglutide or exenatide on overall pancreas weight or exocrine and duct cell mass or proliferation. The present study demonstrates that, in overtly diabetic male and female ZDF rats, prolonged exposure to GLP-1 receptor agonists does not affect biochemical or histopathological markers of pancreatitis, and whereas both exenatide and liraglutide increase β-cell mass, they have no effect on the exocrine pancreas. However, clinical outcome studies and studies using primate tissues and/or studies in nonhuman primates are needed to further assess human risk.
    AJP Endocrinology and Metabolism 05/2012; 303(2):E253-64. · 4.51 Impact Factor
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    ABSTRACT: Liraglutide and exenatide are glucagon-like peptide receptor (GLP-1R) agonists used in the treatment of type 2 diabetes. Both molecules have been associated with the development of thyroid C-cell tumors after lifetime exposure in rodents. Previously, it has been reported that these tumors are preceded by increased plasma calcitonin and C-cell hyperplasia. We can now document that the murine C-cell effects are mediated via GLP-1R. Thus, 13 wk of continuous exposure to GLP-1R agonists was associated with marked increases in plasma calcitonin and in the incidence of C-cell hyperplasia in wild-type mice. In contrast, similar effects were not seen in GLP-1R knockout mice. Human C-cell cancer is often caused by activating mutations in the rearranged-during-transfection (RET) protooncogene. We developed an immunohistochemical method to assess RET activation in tissues. Liraglutide dosing to mice was not found to activate RET. Further evaluation of the signaling pathways demonstrated that liraglutide increased ribosomal S6, but not MAPK kinase, phosphorylation. These observations are consistent with effects of GLP-1R agonists on rodent C cells being mediated via mammalian target of rapamycin activation in a RET- and MAPK-independent manner.
    Endocrinology 03/2012; 153(3):1538-47. · 4.72 Impact Factor
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    ABSTRACT: Glucagon-like peptide (GLP)-1 analogs have been implicated as a risk factor for pancreatitis in humans. We investigated whether liraglutide, the once-daily human GLP-1 analog, induces pancreatitis in rats, mice, and monkeys. Pancreata from mice, rats, and nonhuman primates were examined macro- and microscopically. Evaluation of preneoplastic proliferative lesions in the pancreata from nonhuman primates was performed. After 2 years of treatment, 3 of 79 male mice in the control group and 2, 1, 1, and 1 mice in the different liraglutide groups (of 67-79 mice per group) had pancreatitis based on microscopic criteria. For females, the numbers were 0 of 79 mice in the control group and 3 mice in all the liraglutide groups (of 66-76 mice per group). Pancreatitis was not the cause of death in any animals. There were no cases of pancreatitis, macroscopically or microscopically, in 400 rats. Neither pancreatitis nor preneoplastic proliferative lesions was found in monkeys dosed for 87 weeks, with plasma liraglutide exposure 60-fold higher than that observed in humans at the maximal clinical dose. In conclusion, liraglutide did not induce pancreatitis in mice, rats, or monkeys when dosed for up to 2 years and at exposure levels up to 60 times higher than in humans.
    Diabetes 02/2012; 61(5):1243-9. · 7.90 Impact Factor
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    ABSTRACT: Of the mammalian species, only the GLP-1 receptors of rat and human origin have been described and characterized. Here, we report the cloning of the homologous GLP-1 receptors from mouse, rabbit, pig, cynomolgus monkey and chimp. The GLP-1 receptor is highly conserved across species, thus underlining the physiological importance of the peptide hormone and its receptor across a wide range of mammals. We expressed the receptors by stable transfection of BHK cells, both in cell lines with high expression levels of the cloned receptors, as well as in cell lines with lower expression levels, more comparable to endogenous expression of these receptors. High expression levels of cloned GLP-1 receptors markedly increased the potency of GLP-1 and other high affinity ligands, whereas the K(d) values were not affected. For a low affinity ligand like the ago-allosteric modulator Compound 2, expression levels of the human GLP-1 receptor were important for maximal efficacy as well as potency. The two natural metabolites of GLP-1, GLP-1(9-37) and GLP-1(9-36)amide were agonists when tested on a cell line with high expression of the recombinant human GLP-1 receptor, whereas they behaved as (low potent) antagonists on a cell line that expressed the receptor endogenously, as well as cells expressing a moderate level of the recombinant human GLP-1 receptor. The amide form was a more potent agonist than the free acid from. In conclusion, receptor expression level is an important parametre for selecting cell lines with cloned GLP-1 receptors for functional characterization of physiological and pharmaceutical ligands.
    Regulatory Peptides 01/2012; 175(1-3):21-9. · 2.01 Impact Factor
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    ABSTRACT: Previous studies with the novel once daily glucagon-like peptide-1 (GLP-1) analogue liraglutide and the GLP-1 receptor agonist exenatide have revealed profound insulinotrophic and antidiabetic effects, but also potent effects on gastric emptying (GE) and long-term and lasting reductions in body weight. In this study, we examined the acute and chronic effects of two different GLP-1 analogues with different pharmacokinetic profiles on GE, food intake and body weight. On the basis of a series of dose-finding studies, the doses of exenatide and liraglutide with similar acute anorectic effects were identified. GE was assessed using a standard acetaminophen release assay. After the acute test, rats were dosed bi-daily for 14 days in which period food intake and body weight was monitored. On day 14, the GE rate was reassessed. While both compounds exerted robust acute reductions in GE, the effect was markedly diminished following 14 days of dosing with liraglutide. In contrast, exenatide-treated rats still displayed a profound reduction in GE at the 14-day time-point. Both compounds exerted similar effects on body weight. The data suggest that the 'gastric inhibitory' GLP-1 receptors in rats are subject to desensitization/tachyphylaxis but that this effect is dependent on full 24-h exposure as obtained by liraglutide. The body weight-lowering effects of GLP-1 receptor stimulation are not subject to desensitization. These data indicate that regulation of appetite signals in the brain, and not GE, is the main mechanism for liraglutide-induced weight loss.
    Diabetes Obesity and Metabolism 01/2012; 14(6):531-8. · 5.18 Impact Factor
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    ABSTRACT: Glucagon-like peptide-1 (GLP-1) activates the GLP-1 receptor (GLP-1R), which belongs to family B of the G-protein-coupled receptors. We previously identified a selective small molecule ligand, compound 2, that acted as a full agonist and allosteric modulator of GLP-1R. In this study, the structurally related small molecule, compound 3, stimulated cAMP production from GLP-1R, but not from the homologous glucagon receptor (GluR). The receptor selectivity encouraged a chimeric receptor approach to identify domains important for compound 3-mediated activation of GLP-1R. A subsegment of the GLP-1R transmembrane domain containing TM2 to TM5 was sufficient to transfer compound 3 responsiveness to GluR. Therefore, divergent residues in this subsegment of GLP-1R and GluR are responsible for the receptor selectivity of compound 3. Functional analyses of other chimeric receptors suggested that the existence of a helix-helix interface between TM1 and TM7 is important for the compound 3 response. Furthermore, site-directed mutagenesis revealed that a Phe195-Leu substitution in TM2 and a Thr391-Ala substitution in TM7 increased and decreased the efficacy of compound 3 without disturbing the potency or efficacy of GLP-1. Collectively, differential effects of receptor mutations suggest that TM2 and/or TM7 are important for compound 3-mediated activation of GLP-1R.
    Pharmacology 11/2011; 88(5-6):340-8. · 1.58 Impact Factor
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    ABSTRACT: The efficacy of liraglutide, a human glucagon-like peptide-1 (GLP-1) analog, to prevent or delay diabetes in UCD-T2DM rats, a model of polygenic obese type 2 diabetes, was investigated. At 2 months of age, male rats were divided into three groups: control, food-restricted, and liraglutide. Animals received liraglutide (0.2 mg/kg s.c.) or vehicle injections twice daily. Restricted rats were food restricted to equalize body weights to liraglutide-treated rats. Half of the animals were followed until diabetes onset, whereas the other half of the animals were killed at 6.5 months of age for tissue collection. Before diabetes onset energy intake, body weight, adiposity, and liver triglyceride content were higher in control animals compared with restricted and liraglutide-treated rats. Energy-restricted animals had lower food intake than liraglutide-treated animals to maintain the same body weights, suggesting that liraglutide increases energy expenditure. Liraglutide treatment delayed diabetes onset by 4.1 ± 0.8 months compared with control (P < 0.0001) and by 1.3 ± 0.8 months compared with restricted animals (P < 0.05). Up to 6 months of age, energy restriction and liraglutide treatment lowered fasting plasma glucose and A1C concentrations compared with control animals. In contrast, liraglutide-treated animals exhibited lower fasting plasma insulin, glucagon, and triglycerides compared with both control and restricted animals. Furthermore, energy-restricted and liraglutide-treated animals exhibited more normal islet morphology. Liraglutide treatment delays the development of diabetes in UCD-T2DM rats by reducing energy intake and body weight, and by improving insulin sensitivity, improving lipid profiles, and maintaining islet morphology.
    Diabetes 10/2010; 59(10):2653-61. · 7.90 Impact Factor
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    L B Knudsen
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    ABSTRACT: To review the differences between the human glucagon-like peptide-1 (GLP-1) molecule and the analogue liraglutide, and to summarise key data from the liraglutide preclinical study programme showing the therapeutic promise of this new agent. Liraglutide is a full agonist of the GLP-1 receptor and shares 97% of its amino acid sequence identity with human GLP-1. Unlike human GLP-1, however, liraglutide binds reversibly to serum albumin, and thus has increased resistance to enzymatic degradation and a longer half-life. In preclinical studies, liraglutide demonstrated good glycaemic control, mediated by the glucose-dependent stimulation of insulin and suppression of glucagon secretion and by delayed gastric emptying. Liraglutide also had positive effects on body weight, beta-cell preservation and mass, and cardiac function. The therapeutic promise of liraglutide is evident from preclinical data. Liraglutide showed the potential to provide good glycaemic control without increasing the risk of hypoglycaemia and, as with exenatide, but not dipeptidyl peptidase-4 inhibitors, to mediate weight loss. Although these benefits have subsequently been studied clinically, beta-cell mass can be directly studied only in animal models. In common with other incretin-based therapies, liraglutide showed the potential to modulate the progressive loss of beta-cell function that drives the continuing deterioration in glycaemic control in patients with type 2 diabetes. Body weight was lowered by a mechanism involving mainly lowered energy intake, but also potentially altered food preference and maintained energy expenditure despite weight loss.
    International journal of clinical practice. Supplement 10/2010;
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    ABSTRACT: The availability of useful animal models reflecting the human obesity syndrome is crucial in the search for novel compounds for the pharmacological treatment of obesity. In the current study, we have performed an extensive characterization of the obesity syndrome in a polygenetic animal model, namely the selectively bred diet-induced obese (DIO) and diet-resistant (DR) rat strains. We show that they constitute useful models of the human obesity syndrome. DIO and DR rats were fed either a high-energy (HE) or a standard chow (Chow) diet from weaning to 9 months of age. Metabolic characterization including blood biochemistry and glucose homeostasis was examined at 2, 3, 6, and 9 months of age. Furthermore, in 6-month-old HE-fed DIO rats, the anti-obesity effects of liraglutide and sibutramine were examined in a 28-day study. Only HE-fed DIO rats developed visceral obesity, hyperleptinemia, hyperinsulinemia, and dyslipidemia, and showed a worsening of glucose tolerance over time. In line with the hyperlipidemic profile, a severe hepatic fat infiltration was observed in DIO rats at 6 months of age. The effects of liraglutide and sibutramine were tested in 6-month-old DIO rats. Both compounds effectively reduced food intake and body weight in DIO rats. Liraglutide furthermore improved glucose tolerance when compared with sibutramine. Our data highlights the usefulness of a polygenetic animal model for screening of compounds affecting food intake, body weight, and glucose homeostasis. Furthermore, the results underscore the effectiveness of GLP-1 mimetics both as anti-diabetes and anti-obesity agents.
    Journal of Endocrinology 09/2010; 206(3):287-96. · 3.59 Impact Factor
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    ABSTRACT: Liraglutide is a glucagon-like peptide-1 (GLP-1) analog developed for type 2 diabetes. Long-term liraglutide exposure in rodents was associated with thyroid C-cell hyperplasia and tumors. Here, we report data supporting a GLP-1 receptor-mediated mechanism for these changes in rodents. The GLP-1 receptor was localized to rodent C-cells. GLP-1 receptor agonists stimulated calcitonin release, up-regulation of calcitonin gene expression, and subsequently C-cell hyperplasia in rats and, to a lesser extent, in mice. In contrast, humans and/or cynomolgus monkeys had low GLP-1 receptor expression in thyroid C-cells, and GLP-1 receptor agonists did not activate adenylate cyclase or generate calcitonin release in primates. Moreover, 20 months of liraglutide treatment (at >60 times human exposure levels) did not lead to C-cell hyperplasia in monkeys. Mean calcitonin levels in patients exposed to liraglutide for 2 yr remained at the lower end of the normal range, and there was no difference in the proportion of patients with calcitonin levels increasing above the clinically relevant cutoff level of 20 pg/ml. Our findings delineate important species-specific differences in GLP-1 receptor expression and action in the thyroid. Nevertheless, the long-term consequences of sustained GLP-1 receptor activation in the human thyroid remain unknown and merit further investigation.
    Endocrinology 03/2010; 151(4):1473-86. · 4.72 Impact Factor
  • P. Madsen, C. L. Brand, J. J. Holst, L. B. Knudsen
    ChemInform 01/2010; 31(2).

Publication Stats

2k Citations
258.19 Total Impact Points


  • 2013
    • Technical University of Denmark
      • Department of Chemistry
      Copenhagen, Capital Region, Denmark
  • 1998–2013
    • Novo Nordisk
      • • Department of Insulin and Incretin Biology
      • • Diabetes Research Unit
      København, Capital Region, Denmark
  • 2007
    • Pfizer Inc.
      • Department of Medicinal Chemistry
      New York City, New York, United States
    • IT University of Copenhagen
      København, Capital Region, Denmark