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3D analysis of capillary network in skeletal muscle of obese insulin-resistant mice

Abstract

In obesity, the skeletal muscle capillary network regresses and the insulin-mediated capillary recruitment is impaired. However, it has been shown that in the early stage of advanced obesity, an increased functional vascular response can partially compensate for other mechanisms of insulin resistance. The present study aimed to investigate the changes in the capillary network around individual muscle fibres during the early stage of obesity and insulin resistance in mice using 3D analysis. Capillaries and muscle fibres of the gluteus maximus muscles of seven high-fat-diet-induced obese and insulin-resistant mice and seven age-matched lean healthy mice were immunofluorescently labelled in thick transverse muscle sections. Stacks of images were acquired using confocal microscope. Capillary network characteristics were estimated by methods of quantitative image analysis. Muscle fibre typing was performed by histochemical analysis of myosin heavy chain isoforms on thin serial sections of skeletal muscle. Capillary length per muscle fibre length and capillary length per muscle fibre surface were increased by 27% and 23%, respectively, around small muscle fibres in obese mice, while there were no significant comparative differences around large fibres of obese and lean mice. Furthermore, the capillarization was larger around small compared to large fibres and there was a shift toward fast type myosin heavy chain isoforms, with no significant changes in muscle fibre diameters, tortuosity and anisotropy in obese mice. Overall, the results show that obese insulin-resistant mice have selective increase in capillarization around small predominantly intermediate muscle fibres, which is most likely related to the impaired glucose metabolism characteristic of type 2 diabetes.

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Acknowledgements

We are thankful to David Vondrášek, Nataša Pollak Kristl, Ivan Blažinovič, Majda Črnak Maasarani, Friderik Štendler, Marko Slak, Andreja Vidmar, Stanko Kristl, Milan Števanec, Vesna Mrak and Liljana Markova for technical support, and to Miha Pintarič and Chiedozie K. Ugwoke for manuscript proofreading.

Funding

This study was funded by the Slovenian Research Agency (Grant Nos: P3-0043, P4-0220 and P3-0310), the Czech Ministry of Education Youth and Sports (LM2015062 Czech-BioImaging), the European Regional Development Fund (OPPK BrainView CZ.2.16/3.1.00/21544), the Operational program for Research Development and Education (CZ.02.1.01/0.0/0.0/16_013/0001775 Modernization and support of research activities of the national infrastructure for biological and medical imaging Czech-BioImaging) and the University Medical Centre Ljubljana Tertiary Funding.

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Correspondence to Nejc Umek.

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The authors declare that there is no conflict of interest, financial or otherwise regarding the publication of this paper.

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All applicable international, national, and/or institutional guidelines for the care and use of animals were followed. All procedures performed in studies involving animals were in accordance with the ethical standards of the institution or practice at which the studies were conducted. The Ethical Committee for laboratory animals of the Republic of Slovenia reviewed and approved all animal study protocols (Permit Number: U34401-21/2013/6).

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Umek, N., Horvat, S., Cvetko, E. et al. 3D analysis of capillary network in skeletal muscle of obese insulin-resistant mice. Histochem Cell Biol 152, 323–331 (2019). https://doi.org/10.1007/s00418-019-01810-7

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  • DOI: https://doi.org/10.1007/s00418-019-01810-7

Keywords

  • Obesity
  • Insulin resistance
  • Capillary network
  • 3D analysis
  • Skeletal muscle
  • Fibre type