Publications by authors named "Tamiko Ishizu"

8 Publications

  • Page 1 of 1

Effects of Different Exercise Training Protocols on Gene Expression of Rac1 and PAK1 in Healthy Rat Fast- and Slow-Type Muscles.

Front Physiol 2020 19;11:584661. Epub 2020 Nov 19.

Turku PET Centre, Turku University Hospital, University of Turku, Turku, Finland.

Purpose: Rac1 and its downstream target PAK1 are novel regulators of insulin and exercise-induced glucose uptake in skeletal muscle. However, it is not yet understood how different training intensities affect the expression of these proteins. Therefore, we studied the effects of (HIIT) and (MICT) on Rac1 and PAK1 expression in fast-type (, GC) and slow-type (, SOL) muscles in rats after HIIT and MICT swimming exercises.

Methods: The mRNA expression was determined using qPCR and protein expression levels with reverse-phase protein microarray (RPPA).

Results: HIIT significantly mRNA expression in GC compared to MICT ( = 0.003) and to the control group (CON) ( = 0.001). At the protein level Rac1 was in GC in both training groups, but only the difference between HIIT and CON was significant ( = 0.02). HIIT caused significant of mRNA expression in GC compared to MICT ( = 0.007) and to CON ( = 0.001). At the protein level, HIIT increased PAK1 expression in GC compared to MICT and CON (by ∼17%), but the difference was not statistically significant ( = 0.3, = 0.2, respectively). There were no significant differences in the Rac1 or PAK1 expression in SOL between the groups.

Conclusion: Our results indicate that HIIT, but not MICT, Rac1 and PAK1 mRNA expression and the protein expression of especially Rac1 but only in fast-type muscle. These exercise training findings may reveal new therapeutic targets to treat patients with metabolic diseases.
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http://dx.doi.org/10.3389/fphys.2020.584661DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7711069PMC
November 2020

Alendronate-induced disruption of actin cytoskeleton and inhibition of migration/invasion are associated with cofilin downregulation in PC-3 prostate cancer cells.

Oncotarget 2018 Aug 24;9(66):32593-32608. Epub 2018 Aug 24.

University of Turku, Institute of Biomedicine, FI-20520 Turku, Finland.

Bisphosphonates are used for prevention of osteoporosis and metastatic bone diseases. Anti-invasive effects on various cancer cells have also been reported, but the mechanisms involved are not well-understood. We investigated the effects of the nitrogen-containing bisphosphonate alendronate (ALN) on the regulation of actin cytoskeleton in PC-3 cells. We analyzed the ALN effect on the organization and the dynamics of actin, and on the cytoskeleton-related regulatory proteins cofilin, p21-associated kinase 2 (PAK2), paxillin and focal adhesion kinase. Immunostainings of cofilin in ALN-treated PC-3 cells and xenografts were performed, and the role of cofilin in ALN-regulated F-actin organization and migration/invasion in PC-3 cells was analyzed using cofilin knockdown and transfection. We demonstrate that disrupted F-actin organization and decreased cell motility in ALN-treated PC-3 cells were associated with decreased levels of total and phosphorylated cofilin. PAK2 levels were also lowered but adhesion-related proteins were not altered. The knockdown of cofilin similarly impaired F-actin organization and decreased invasion of PC-3 cells, whereas in the cells transfected with a cofilin expressing vector, ALN treatment did not decrease cellular cofilin levels and migration as in mock transfected cells. ALN also reduced immunohistochemical staining of cofilin in PC-3 xenografts. Our results suggest that reduction of cofilin has an important role in ALN-induced disruption of the actin cytoskeleton and inhibition of the PC-3 cell motility and invasion. These data also support the idea that the nitrogen-containing bisphosphonates could be efficacious in inhibition of prostate cancer invasion and metastasis, if delivered in a pharmacological formulation accessible to the tumors.
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http://dx.doi.org/10.18632/oncotarget.25961DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6135693PMC
August 2018

[F]FMPEP-d PET imaging shows age- and genotype-dependent impairments in the availability of cannabinoid receptor 1 in a mouse model of Alzheimer's disease.

Neurobiol Aging 2018 09 18;69:199-208. Epub 2018 May 18.

MediCity Research Laboratory, University of Turku, Turku, Finland; PET Preclinical Laboratory, Turku PET Centre, University of Turku, Turku, Finland.

Contradictory findings on the role of the type 1 cannabinoid receptor (CBR) during the pathogenesis of Alzheimer's disease (AD) have been reported. Here, we evaluated the CBR brain profile in an AD mouse model using longitudinal positron emission tomography with an inverse agonist for CBR, [F]FMPEP-d. APP/PS1-21 and wild-type (n = 8 in each group) mice were repeatedly imaged between 6 to 15 months of age, accompanied by brain autoradiography, western blot, and CBR immunohistochemistry with additional mice. [F]FMPEP-d positron emission tomography demonstrated lower (p < 0.05) binding ratios in the parietotemporal cortex and hippocampus of APP/PS1-21 mice compared with age-matched wild-type mice. Western blot demonstrated no differences between APP/PS1-21 and wild-type mice in the CBR abundance, whereas significantly lower (p < 0.05) receptor expression was observed in male than female mice. The results provide the first demonstration that [F]FMPEP-d is a promising imaging tool for AD research in terms of CBR availability, but not expression. This finding may further facilitate the development of novel therapeutic approaches based on endocannabinoid regulation.
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http://dx.doi.org/10.1016/j.neurobiolaging.2018.05.013DOI Listing
September 2018

Two weeks of moderate-intensity continuous training, but not high-intensity interval training, increases insulin-stimulated intestinal glucose uptake.

J Appl Physiol (1985) 2017 May 9;122(5):1188-1197. Epub 2017 Feb 9.

Turku PET Centre, University of Turku, Turku, Finland;

Similar to muscles, the intestine is also insulin resistant in obese subjects and subjects with impaired glucose tolerance. Exercise training improves muscle insulin sensitivity, but its effects on intestinal metabolism are not known. We studied the effects of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on intestinal glucose and free fatty acid uptake from circulation in humans. Twenty-eight healthy, middle-aged, sedentary men were randomized for 2 wk of HIIT or MICT. Intestinal insulin-stimulated glucose uptake and fasting free fatty acid uptake from circulation were measured using positron emission tomography and [F]FDG and [F]FTHA. In addition, effects of HIIT and MICT on intestinal GLUT2 and CD36 protein expression were studied in rats. Training improved aerobic capacity ( = 0.001) and whole body insulin sensitivity ( = 0.04), but not differently between HIIT and MICT. Insulin-stimulated glucose uptake increased only after the MICT in the colon (HIIT = 0%; MICT = 37%) ( = 0.02 for time × training) and tended to increase in the jejunum (HIIT = -4%; MICT = 13%) ( = 0.08 for time × training). Fasting free fatty acid uptake decreased in the duodenum in both groups (HIIT = -6%; MICT = -48%) ( = 0.001 time) and tended to decrease in the colon in the MICT group (HIIT = 0%; MICT = -38%) ( = 0.08 for time × training). In rats, both training groups had higher GLUT2 and CD36 expression compared with control animals. This study shows that already 2 wk of MICT enhances insulin-stimulated glucose uptake, while both training modes reduce fasting free fatty acid uptake in the intestine in healthy, middle-aged men, providing an additional mechanism by which exercise training can improve whole body metabolism. This is the first study where the effects of exercise training on the intestinal substrate uptake have been investigated using the most advanced techniques available. We also show the importance of exercise intensity in inducing these changes.
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http://dx.doi.org/10.1152/japplphysiol.00431.2016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5451533PMC
May 2017

Toll-like receptor 9 expression is associated with breast cancer sensitivity to the growth inhibitory effects of bisphosphonates in vitro and in vivo.

Oncotarget 2016 Dec;7(52):87373-87389

Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL, U.S.A.

Bisphosphonates are standard treatments for bone metastases. When given in the adjuvant setting, they reduce breast cancer mortality and recurrence in bone but only among post-menopausal patients. Optimal drug use would require biomarker-based patient selection. Such biomarkers are not yet in clinical use. Based on the similarities in inflammatory responses to bisphosphonates and Toll-like receptor (TLR) agonists, we hypothesized that TLR9 expression may affect bisphosphonate responses in cells. We compared bisphosphonate effects in breast cancer cell lines with low or high TLR9 expression. We discovered that cells with decreased TLR9 expression are significantly more sensitive to the growth-inhibitory effects of bisphosphonates in vitro and in vivo. Furthermore, cancer growth-promoting effects seen with some bisphosphonates in some control shRNA cells were not detected in TLR9 shRNA cells. These differences were not associated with inhibition of Rap1A prenylation or p38 phosphorylation, which are known markers for bisphosphonate activity. However, TLR9 shRNA cells exhibited increased sensitivity to ApppI, a metabolite that accumulates in cells after bisphosphonate treatment. We conclude that decreased TLR9-expression sensitizes breast cancer cells to the growth inhibitory effects of bisphosphonates. Our results suggest that TLR9 should be studied as a potential biomarker for adjuvant bisphosphonate sensitivity among breast cancer patients.
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http://dx.doi.org/10.18632/oncotarget.13570DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5349995PMC
December 2016

64Cu- and 68Ga-labelled [Nle(14),Lys(40)(Ahx-NODAGA)NH2]-exendin-4 for pancreatic beta cell imaging in rats.

Mol Imaging Biol 2014 Apr;16(2):255-63

Turku PET Centre, University of Turku, Turku, Finland.

Purpose: Glucagon-like peptide-1 receptor (GLP-1R) is a molecular target for imaging of pancreatic beta cells. We compared the ability of [Nle(14),Lys(40)(Ahx-NODAGA-(64)Cu)NH2]-exendin-4 ([(64)Cu]NODAGA-exendin-4) and [Nle(14),Lys(40)(Ahx-NODAGA-(68)Ga)NH2]-exendin-4 ([(68)Ga]NODAGA-exendin-4) to detect native pancreatic islets in rodents.

Procedures: The stability, lipophilicity and affinity of the radiotracers to the GLP-1R were determined in vitro. The biodistribution of the tracers was assessed using autoradiography, ex vivo biodistribution and PET imaging. Estimates for human radiation dosimetry were calculated.

Results: We found GLP-1R-specific labelling of pancreatic islets. However, the pancreas could not be visualised in PET images. The highest uptake of the tracers was observed in the kidneys. Effective dose estimates for [(64)Cu]NODAGA-exendin-4 and [(68)Ga]NODAGA-exendin-4 were 0.144 and 0.012 mSv/MBq, respectively.

Conclusion: [(64)Cu]NODAGA-exendin-4 might be more effective for labelling islets than [(68)Ga]NODAGA-exendin-4. This is probably due to the lower specific radioactivity of [(68)Ga]NODAGA-exendin-4 compared to [(64)Cu]NODAGA-exendin-4. The radiation dose in the kidneys may limit the use of [(64)Cu]NODAGA-exendin-4 as a clinical tracer.
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http://dx.doi.org/10.1007/s11307-013-0691-2DOI Listing
April 2014

Synthesis and preclinical characterization of [64Cu]NODAGA-MAL-exendin-4 with a Nε-maleoyl-L-lysyl-glycine linkage.

Nucl Med Biol 2013 Nov 8;40(8):1006-12. Epub 2013 Aug 8.

Turku PET Centre, University of Turku and Turku University Central Hospital, FI-20520 Turku, Finland; Department of Organic Chemistry, University of Turku, FI-20014 Turku, Finland. Electronic address:

Introduction: Renal localization of high radioactivity levels during targeted imaging compromises tissue visualization in the kidney region and limits diagnostic accuracy. Radioiodinated antibody fragments with a renal enzyme-cleavable N(ε)-maleoyl-L-lysyl-glycine (MAL) linkage demonstrated low renal radioactivity levels in mice, from early postinjection times. This study tested the hypothesis whether a (64)Cu-labeled NODAGA-exendin-4 peptide with a MAL linkage ([(64)Cu]NODAGA-MAL-exendin-4) could decrease kidney radioactivity levels in rats, compared to a [(64)Cu]NODAGA-exendin-4 reference, without impairing the radioactivity levels in the target tissue.

Methods: NODAGA-MAL-exendin-4 was synthesized in a two-phase approach using solid support to prepare maleoyl-derivatized NODAGA followed by Michael addition to cysteine-derivatized exendin-4 in solution. Radiolabeling was performed in buffered aqua with [(64)Cu]CuCl2, which was produced via the (64)Ni(p,n)(64)Cu nuclear reaction. The in vitro and in vivo stability, lipophilicity, and distribution kinetics in major rat organs for [(64)Cu]NODAGA-MAL-exendin-4 were studied and compared to [(64)Cu]NODAGA-exendin-4. Labeling of pancreatic islets was assessed using autoradiography.

Results: NODAGA-MAL-exendin-4 was synthesized, with an overall yield of 9%, and radiolabeled with (64)Cu with high specific radioactivity. Serum incubation studies showed high stability for [(64)Cu]NODAGA-MAL-exendin-4. Similar tissue distribution kinetics was observed for [(64)Cu]NODAGA-MAL-exendin-4 and [(64)Cu]NODAGA-exendin-4, with high kidney radioactivity levels.

Conclusions: The incorporated MAL linkage in [(64)Cu]NODAGA-MAL-exendin-4 was unable to reduce kidney radioactivity levels, compared to [(64)Cu]NODAGA-exendin-4. The applicability of metabolizable linkages in the design of kidney-saving exendin-4 analogs requires further investigation.
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http://dx.doi.org/10.1016/j.nucmedbio.2013.06.012DOI Listing
November 2013

Assessment of islet specificity of dihydrotetrabenazine radiotracer binding in rat pancreas and human pancreas.

J Nucl Med 2010 Sep 18;51(9):1439-46. Epub 2010 Aug 18.

Turku PET Centre, University of Turku, Turku, Finland.

Unlabelled: Vesicular monoamine transporter 2 (VMAT2) is a putative molecular target for the quantitative imaging of pancreatic beta-cell mass by PET. The VMAT2 PET tracer (11)C-dihydrotetrabenazine ((11)C-DTBZ) exhibits high pancreatic uptake that is reduced in type 1 diabetes. The aim of this study was to assess the islet and VMAT2 specificity of DTBZ binding in the pancreas.

Methods: The biodistribution of (11)C-DTBZ in rats was determined 10 and 60 min after injection. The localization of DTBZ radioactivity in rat and human pancreatic tissue sections was investigated by autoradiography. Saturation and competition binding assays were performed with (3)H-DTBZ and sections of rat pancreatic and control tissues. The binding of (11)C-DTBZ in pancreatic sections from rats with streptozotocin-induced diabetes was compared with that in control rats.

Results: The values for the pancreatic uptake of (11)C-DTBZ (percentage injected dose per gram of tissue) were 3.0 at 10 min and 2.7 at 60 min. At 10 min, pancreatic radioactivity was heterogeneously distributed, with higher levels toward the head of the pancreas (head-to-tail ratio, 1.7). No such gradient was observed in pancreatic sections incubated with (11)C-DTBZ and (3)H-DTBZ in vitro. In rats, (11)C-DTBZ and (3)H-DTBZ binding in pancreatic islets did not exceed binding in the exocrine pancreas. Saturable (3)H-DTBZ binding was observed in the rat brain striatum (dissociation constant [K(d)], 1.3 nM) and the bovine adrenal medulla (K(d), 3.3 nM), whereas in the rat pancreas, (3)H-DTBZ binding was nonsaturable. Competition binding with (3)H-DTBZ and VMAT2 antagonists also indicated that DTBZ binding in the rat pancreas was nonspecific and did not represent binding to VMAT2. Nonspecific pancreatic (11)C-DTBZ binding was lower in rats with streptozotocin-induced diabetes than in control rats. In sections of human pancreas, a subset of pancreatic islets were weakly but VMAT2-specifically labeled with (3)H-DTBZ.

Conclusion: The results showed that the pancreatic uptake of (11)C-DTBZ is mainly due to nonspecific binding in the exocrine pancreas and suggested that the reduction in pancreatic (11)C-DTBZ binding observed in type 1 diabetes is not specific for the loss of beta-cell mass.
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http://dx.doi.org/10.2967/jnumed.109.074492DOI Listing
September 2010