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      In Alzheimer’s Disease, 6-Month Treatment with GLP-1 Analog Prevents Decline of Brain Glucose Metabolism: Randomized, Placebo-Controlled, Double-Blind Clinical Trial

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          In animal models, the incretin hormone GLP-1 affects Alzheimer’s disease (AD). We hypothesized that treatment with GLP-1 or an analog of GLP-1 would prevent accumulation of Aβ and raise, or prevent decline of, glucose metabolism (CMR glc) in AD. In this 26-week trial, we randomized 38 patients with AD to treatment with the GLP-1 analog liraglutide ( n = 18), or placebo ( n = 20). We measured Aβ load in brain with tracer [ 11C]PIB (PIB), CMR glc with [ 18F]FDG (FDG), and cognition with the WMS-IV scale ( NCT01469351). The PIB binding increased significantly in temporal lobe in placebo and treatment patients (both P = 0.04), and in occipital lobe in treatment patients ( P = 0.04). Regional and global increases of PIB retention did not differ between the groups ( P ≥ 0.38). In placebo treated patients CMR glc declined in all regions, significantly so by the following means in precuneus ( P = 0.009, 3.2 μmol/hg/min, 95% CI: 5.45; 0.92), and in parietal ( P = 0.04, 2.1 μmol/hg/min, 95% CI: 4.21; 0.081), temporal ( P = 0.046, 1.54 μmol/hg/min, 95% CI: 3.05; 0.030), and occipital ( P = 0.009, 2.10 μmol/hg/min, 95% CI: 3.61; 0.59) lobes, and in cerebellum ( P = 0.04, 1.54 μmol/hg/min, 95% CI: 3.01; 0.064). In contrast, the GLP-1 analog treatment caused a numerical but insignificant increase of CMR glc after 6 months. Cognitive scores did not change. We conclude that the GLP-1 analog treatment prevented the decline of CMR glc that signifies cognitive impairment, synaptic dysfunction, and disease evolution. We draw no firm conclusions from the Aβ load or cognition measures, for which the study was underpowered.

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          Most cited references 38

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          An anti-diabetes agent protects the mouse brain from defective insulin signaling caused by Alzheimer's disease- associated Aβ oligomers.

          Defective brain insulin signaling has been suggested to contribute to the cognitive deficits in patients with Alzheimer's disease (AD). Although a connection between AD and diabetes has been suggested, a major unknown is the mechanism(s) by which insulin resistance in the brain arises in individuals with AD. Here, we show that serine phosphorylation of IRS-1 (IRS-1pSer) is common to both diseases. Brain tissue from humans with AD had elevated levels of IRS-1pSer and activated JNK, analogous to what occurs in peripheral tissue in patients with diabetes. We found that amyloid-β peptide (Aβ) oligomers, synaptotoxins that accumulate in the brains of AD patients, activated the JNK/TNF-α pathway, induced IRS-1 phosphorylation at multiple serine residues, and inhibited physiological IRS-1pTyr in mature cultured hippocampal neurons. Impaired IRS-1 signaling was also present in the hippocampi of Tg mice with a brain condition that models AD. Importantly, intracerebroventricular injection of Aβ oligomers triggered hippocampal IRS-1pSer and JNK activation in cynomolgus monkeys. The oligomer-induced neuronal pathologies observed in vitro, including impaired axonal transport, were prevented by exposure to exendin-4 (exenatide), an anti-diabetes agent. In Tg mice, exendin-4 decreased levels of hippocampal IRS-1pSer and activated JNK and improved behavioral measures of cognition. By establishing molecular links between the dysregulated insulin signaling in AD and diabetes, our results open avenues for the investigation of new therapeutics in AD.
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            Brain glucose metabolism in the early and specific diagnosis of Alzheimer's disease. FDG-PET studies in MCI and AD.

             Lisa Mosconi (2005)
            The demographics of aging suggest a great need for the early diagnosis of dementia and the development of preventive strategies. Neuropathology and structural MRI studies have pointed to the medial temporal lobe (MTL) as the brain region earliest affected in Alzheimer's disease (AD). MRI findings provide strong evidence that in mild cognitive impairments (MCI), AD-related volume losses can be reproducibly detected in the hippocampus, the entorhinal cortex (EC) and, to a lesser extent, the parahippocampal gyrus; they also indicate that lateral temporal lobe changes are becoming increasingly useful in predicting the transition to dementia. Fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) imaging has revealed glucose metabolic reductions in the parieto-temporal, frontal and posterior cingulate cortices to be the hallmark of AD. Overall, the pattern of cortical metabolic changes has been useful for the prediction of future AD as well as in distinguishing AD from other neurodegenerative diseases. FDG-PET on average achieves 90% sensitivity in identifying AD, although specificity in differentiating AD from other dementias is lower. Moreover, recent MRI-guided FDG-PET studies have shown that MTL hypometabolism is the most specific and sensitive measure for the identification of MCI, while the utility of cortical deficits is controversial. This review highlights cross-sectional, prediction and longitudinal FDG-PET studies and attempts to put into perspective the value of FDG-PET in diagnosing AD-like changes, particularly at an early stage, and in providing diagnostic specificity. The examination of MTL structures, which has so far been exclusive to MRI protocols, is then examined as a possible strategy to improve diagnostic specificity. All told, there is considerable promise that early and specific diagnosis is feasible through a combination of imaging modalities.
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              Glucagon-like peptide-1 receptor is involved in learning and neuroprotection.

              Glucagon-like peptide-1 (GLP-1) is a gut peptide that, together with its receptor, GLP-1R, is expressed in the brain. Here we show that intracerebroventricular (i.c.v.) GLP-1 and [Ser(2)]exendin(1-9) (HSEGTFTSD; homologous to a conserved domain in the glucagon/GLP-1 family) enhance associative and spatial learning through GLP-1R. [Ser(2)]exendin(1-9), but not GLP-1, is also active when administered peripherally. GLP-1R-deficient mice have a phenotype characterized by a learning deficit that is restored after hippocampal Glp1r gene transfer. In addition, rats overexpressing GLP-1R in the hippocampus show improved learning and memory. GLP-1R-deficient mice also have enhanced seizure severity and neuronal injury after kainate administration, with an intermediate phenotype in heterozygotes and phenotypic correction after Glp1r gene transfer in hippocampal somatic cells. Systemic administration of [Ser(2)]exendin(1-9) in wild-type animals prevents kainate-induced apoptosis of hippocampal neurons. Brain GLP-1R represents a promising new target for both cognitive-enhancing and neuroprotective agents.

                Author and article information

                Front Aging Neurosci
                Front Aging Neurosci
                Front. Aging Neurosci.
                Frontiers in Aging Neuroscience
                Frontiers Media S.A.
                24 May 2016
                : 8
                1Institute of Biomedicine, Aarhus University Aarhus, Denmark
                2Department of Nuclear Medicine and PET Center, Aarhus University Hospital Aarhus, Denmark
                3Department of Neuroscience and Pharmacology, University of Copenhagen Copenhagen, Denmark
                4Dementia Clinic, Department of Neurology, Aarhus University Hospital Aarhus, Denmark
                5Department of Endocrinology, Aarhus University Hospital Aarhus, Denmark
                6Department of Clinical Biochemistry, Aarhus University Hospital Aarhus, Denmark
                7Center for Diabetes Research and Department of Clinical Pharmacology, Copenhagen University Hospital Gentofte and Rigshospitalet Copenhagen, Denmark
                Author notes

                Edited by: Naoyuki Sato, Osaka University, Japan

                Reviewed by: Christian Hölscher, Lancaster University, UK; Ramesh Kandimalla, Emory University, USA

                *Correspondence: Jørgen Rungby, jr@
                Copyright © 2016 Gejl, Gjedde, Egefjord, Møller, Hansen, Vang, Rodell, Brændgaard, Gottrup, Schacht, Møller, Brock and Rungby.

                This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

                Page count
                Figures: 2, Tables: 4, Equations: 1, References: 48, Pages: 10, Words: 0
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