It is not well-understood how type 1 diabetes (T1DM) affects skeletal muscle histological phenotype, particularly capillarisation. This study aimed to analyze skeletal muscle myosin heavy chain (MyHC) fibre type changes and 3D capillary network characteristics in experimental T1DM mice. Female C57BL/6J-OlaHsd mice were categorized into streptozotocin (STZ)-induced diabetic (n = 12) and age-matched non-diabetic controls (n =12). The muscle fibre phenotype of the soleus, gluteus maximus, and gastrocnemius muscles were characterized based on the expression of MyHC isoforms, while capillaries of the gluteus maximus were assessed with immunofluorescence staining, confocal laser microscopy and 3D image analysis. STZ-induced diabetic mice exhibited elevated glucose levels, reduced body weight, and prolonged thermal latency, verifying the T1DM phenotype. In both T1DM and non-diabetic mice, the gluteus maximus and gastrocnemius muscles predominantly expressed fast-twitch type 2b fibers, with no significant differences noted. However, the soleus muscle in non-diabetic mice had a greater proportion of type 2a fibers and comparable type 1 fiber densities (26.2 ± 14.6% vs 21.9 ± 13.5%) relative to diabetic mice. T1DM mice showed reduced fiber diameters (P = 0.026), and the 3D capillary network analysis indicated a higher capillary length per muscle volume in the gluteus maximus of diabetic mice compared to controls (P < 0.05). Overall, T1DM induced significant changes in the skeletal muscle, including shifts in MyHC fibre types, decreased fibre diameters, and increased relative capillarisation, possibly due to muscle fibre atrophy. Our findings emphasize the superior detail provided by the 3D analytical method for characterizing skeletal muscle capillary architecture, highlighting caution in interpreting 2D data for capillary changes in T1DM.

• MeSH
• diabetes mellitus 1. typu metabolismus   patologie   MeSH
• experimentální diabetes mellitus * metabolismus   patologie   MeSH
• kapiláry * patologie   metabolismus   MeSH
• kosterní svaly * metabolismus   patologie   krevní zásobení   MeSH
• myši inbrední C57BL MeSH
• myši MeSH
• streptozocin MeSH
• těžké řetězce myosinu * metabolismus   MeSH
• zobrazování trojrozměrné MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• streptozocin MeSH
• těžké řetězce myosinu * MeSH

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.

• Klíčová slova
• 3D analysis, Capillary network, Fibre type, Insulin resistance, Obesity, Skeletal muscle,
• MeSH
• inzulinová rezistence MeSH
• kapiláry chemie   metabolismus   MeSH
• kosterní svaly chemie   metabolismus   MeSH
• myši inbrední C57BL MeSH
• myši MeSH
• obezita metabolismus   patologie   MeSH
• těžké řetězce myosinu analýza   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• těžké řetězce myosinu MeSH

Capillary network characteristics are invaluable for diagnostics of muscle diseases. Biopsy material is limited in size and mostly not accessible for intensive research. Therefore, especially in human tissue, studies are performed on autopsy material. To approach the problem whether it is reliable to deduce hypotheses from autopsy material to explain physiological and pathological processes, we studied capillarity in pig soleus muscle 1 and 24 hr after death. Capillaries and muscle fibers were immunofluorescently marked, and images were acquired with a confocal microscope. Characteristics of the capillary network were estimated by image analysis methods using several plugins of the Ellipse program. Twenty-four hours after death, the measured characteristics of the capillary network differ by up to 50% when compared with samples excised 1 hr after death. Muscle fiber diameter, the measured capillary length, and tortuosity were reduced, and capillary network became more anisotropic. The main postmortem change that affects capillaries is evidently geometric deformation of muscle tissue. In conclusion, when comparing results from biopsy samples with those from autopsy samples, the effect of postmortem changes on the measured parameters must be carefully considered.

• Klíčová slova
• capillaries, confocal microscopy, image analysis, pig, postmortem changes, skeletal muscle,
• MeSH
• kapiláry patologie   ultrastruktura   MeSH
• konfokální mikroskopie metody   MeSH
• kosterní svaly krevní zásobení   patologie   MeSH
• počítačové zpracování obrazu metody   MeSH
• posmrtné změny MeSH
• prasata MeSH
• zvířata MeSH
• Check Tag
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

The aim of this study was to determine whether capillarity in the denervated and reinnervated rat extensor digitorum longus muscle (EDL) is scaled by muscle fiber oxidative potential. We visualized capillaries adjacent to a metabolically defined fiber type and estimated capillarity of fibers with very high oxidative potential (O) vs fibers with very low oxidative potential (G). Capillaries and muscle fiber types were shown by a combined triple immunofluorescent technique and the histochemical method for NADH-tetrazolium reductase. Stacks of images were captured by a confocal microscope. Applying the Ellipse program, fibers were outlined, and the diameter, perimeter, cross-sectional area, length, surface area, and volume within the stack were calculated for both fiber types. Using the Tracer plug-in module, capillaries were traced within the three-dimensional (3D) volume, the length of capillaries adjacent to individual muscle fibers was measured, and the capillary length per fiber length (Lcap/Lfib), surface area (Lcap/Sfib), and volume (Lcap/Vfib) were calculated. Furthermore, capillaries and fibers of both types were visualized in 3D. In all experimental groups, O and G fibers significantly differed in girth, Lcap/Sfib, and Lcap/Vfib, but not in Lcap/Lfib. We conclude that capillarity in the EDL is scaled by muscle fiber size and not by muscle fiber oxidative potential.

• MeSH
• denervace svalu MeSH
• histocytochemie MeSH
• kapiláry anatomie a histologie   MeSH
• konfokální mikroskopie MeSH
• kosterní svalová vlákna metabolismus   MeSH
• kosterní svaly krevní zásobení   inervace   metabolismus   MeSH
• krysa rodu Rattus MeSH
• oxidace-redukce MeSH
• potkani Wistar MeSH
• zobrazování trojrozměrné MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH