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Bernstein HG, Keilhoff G, Dobrowolny H, Steiner J. The many facets of CD26/dipeptidyl peptidase 4 and its inhibitors in disorders of the CNS - a critical overview. Rev Neurosci 2023; 34:1-24. [PMID: 35771831 DOI: 10.1515/revneuro-2022-0026] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 05/10/2022] [Indexed: 01/11/2023]
Abstract
Dipeptidyl peptidase 4 is a serine protease that cleaves X-proline or X-alanine in the penultimate position. Natural substrates of the enzyme are glucagon-like peptide-1, glucagon inhibiting peptide, glucagon, neuropeptide Y, secretin, substance P, pituitary adenylate cyclase-activating polypeptide, endorphins, endomorphins, brain natriuretic peptide, beta-melanocyte stimulating hormone and amyloid peptides as well as some cytokines and chemokines. The enzyme is involved in the maintenance of blood glucose homeostasis and regulation of the immune system. It is expressed in many organs including the brain. DPP4 activity may be effectively depressed by DPP4 inhibitors. Apart from enzyme activity, DPP4 acts as a cell surface (co)receptor, associates with adeosine deaminase, interacts with extracellular matrix, and controls cell migration and differentiation. This review aims at revealing the impact of DPP4 and DPP4 inhibitors for several brain diseases (virus infections affecting the brain, tumours of the CNS, neurological and psychiatric disorders). Special emphasis is given to a possible involvement of DPP4 expressed in the brain.While prominent contributions of extracerebral DPP4 are evident for a majority of diseases discussed herein; a possible role of "brain" DPP4 is restricted to brain cancers and Alzheimer disease. For a number of diseases (Covid-19 infection, type 2 diabetes, Alzheimer disease, vascular dementia, Parkinson disease, Huntington disease, multiple sclerosis, stroke, and epilepsy), use of DPP4 inhibitors has been shown to have a disease-mitigating effect. However, these beneficial effects should mostly be attributed to the depression of "peripheral" DPP4, since currently used DPP4 inhibitors are not able to pass through the intact blood-brain barrier.
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Affiliation(s)
- Hans-Gert Bernstein
- Department of Psychiatry and Psychotherapy, Otto v. Guericke University Magdeburg, Leipziger Str. 44, D-39120 Magdeburg, Germany
| | - Gerburg Keilhoff
- Institute of Biochemistry and Cell Biology, Otto v. Guericke University Magdeburg, Leipziger Str. 44, D-39120 Magdeburg, Germany
| | - Henrik Dobrowolny
- Department of Psychiatry and Psychotherapy, Otto v. Guericke University Magdeburg, Leipziger Str. 44, D-39120 Magdeburg, Germany
| | - Johann Steiner
- Department of Psychiatry and Psychotherapy, Otto v. Guericke University Magdeburg, Leipziger Str. 44, D-39120 Magdeburg, Germany
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Mi Z, Abrahamson EE, Ryu AY, Malek-Ahmadi M, Kofler JK, Fish KN, Sweet RA, Villemagne VL, Schneider JA, Mufson EJ, Ikonomovic MD. Vesicular Glutamate Transporter Changes in the Cortical Default Mode Network During the Clinical and Pathological Progression of Alzheimer's Disease. J Alzheimers Dis 2023; 94:227-246. [PMID: 37212097 PMCID: PMC10994206 DOI: 10.3233/jad-221063] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
BACKGROUND Altered glutamatergic neurotransmission may contribute to impaired default mode network (DMN) function in Alzheimer's disease (AD). Among the DMN hub regions, frontal cortex (FC) was suggested to undergo a glutamatergic plasticity response in prodromal AD, while the status of glutamatergic synapses in the precuneus (PreC) during clinical-neuropathological AD progression is not known. OBJECTIVE To quantify vesicular glutamate transporter VGluT1- and VGluT2-containing synaptic terminals in PreC and FC across clinical stages of AD. METHODS Unbiased sampling and quantitative confocal immunofluorescence of cortical VGluT1- and VGluT2-immunoreactive profiles and spinophilin-labeled dendritic spines were performed in cases with no cognitive impairment (NCI), mild cognitive impairment (MCI), mild-moderate AD (mAD), or moderate-severe AD (sAD). RESULTS In both regions, loss of VGluT1-positive profile density was seen in sAD compared to NCI, MCI, and mAD. VGluT1-positive profile intensity in PreC did not differ across groups, while in FC it was greater in MCI, mAD, and sAD compared to NCI. VGluT2 measures were stable in PreC while FC had greater VGluT2-positive profile density in MCI compared to sAD, but not NCI or mAD. Spinophilin measures in PreC were lower in mAD and sAD compared to NCI, while in FC they were stable across groups. Lower VGluT1 and spinophilin measures in PreC, but not FC, correlated with greater neuropathology. CONCLUSION Frank loss of VGluT1 in advanced AD relative to NCI occurs in both DMN regions. In FC, an upregulation of VGluT1 protein content in remaining glutamatergic terminals may contribute to this region's plasticity response in AD.
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Affiliation(s)
- Zhiping Mi
- Department of Neurology, University of Pittsburgh School of
Medicine, Pittsburgh, PA, USA
- Geriatric Research Education and Clinical Center, VA
Pittsburgh Healthcare System, Pittsburgh, PA, USA
| | - Eric E. Abrahamson
- Department of Neurology, University of Pittsburgh School of
Medicine, Pittsburgh, PA, USA
- Geriatric Research Education and Clinical Center, VA
Pittsburgh Healthcare System, Pittsburgh, PA, USA
| | - Angela Y. Ryu
- Department of Neurology, University of Pittsburgh School of
Medicine, Pittsburgh, PA, USA
| | - Michael Malek-Ahmadi
- Banner Alzheimer’s Institute, Phoenix, AZ, USA
- Department of Biomedical Informatics, University of Arizona
College of Medicine, Phoenix, AZ, USA
| | - Julia K. Kofler
- Department of Pathology, University of Pittsburgh School of
Medicine, Pittsburgh, PA, USA
| | - Kenneth N. Fish
- Department of Psychiatry, University of Pittsburgh School
of Medicine, Pittsburgh, PA, USA
| | - Robert A. Sweet
- Department of Neurology, University of Pittsburgh School of
Medicine, Pittsburgh, PA, USA
- Department of Psychiatry, University of Pittsburgh School
of Medicine, Pittsburgh, PA, USA
| | - Victor L. Villemagne
- Department of Psychiatry, University of Pittsburgh School
of Medicine, Pittsburgh, PA, USA
| | - Julie A. Schneider
- Rush Alzheimer’s Disease Center, Rush University
Medical Center, Chicago, IL, USA
| | - Elliott J. Mufson
- Banner Alzheimer’s Institute, Phoenix, AZ, USA
- Departments of Translational Neurosciences and Neurology,
Barrow Neurological Institute, Phoenix, AZ, USA
| | - Milos D. Ikonomovic
- Department of Neurology, University of Pittsburgh School of
Medicine, Pittsburgh, PA, USA
- Geriatric Research Education and Clinical Center, VA
Pittsburgh Healthcare System, Pittsburgh, PA, USA
- Department of Psychiatry, University of Pittsburgh School
of Medicine, Pittsburgh, PA, USA
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