Author(s): TORRELLA, J.R., HIGUERA-CHAPARRO, Y.A., LORENZO, K., VILLAMIL-PARRA, W., CASTRO-ARIAS, M.E., ZÚÑIGA-VERGARA, P., VISCOR, G., TORRES, J.L., PAGÈS, T., MAGALHÃES, J., RAMOS-ROMERO, S., SANTOCILDES, G., Institution: UNIVERSITAT DE BARCELONA, Country: SPAIN, Abstract-ID: 1991

INTRODUCTION:
Chlorella is a marine microalga with bioactive macronutrients with antioxidant and anti-inflammatory activity meaning that consuming Chlorella improves aerobic exercise performance and reduces fatigue. To delve into the subjacent mechanisms responsible for Chlorella benefits in aerobic exercise, we aimed to assess the possible effects of a Chlorella-based diet on the fibre morphometry and capillarity of the anaerobic region of the muscle gastrocnemius (GAS) in exercised rats.
METHODS:
Twelve animals were trained 5 days/week for 10 weeks. Training was incrementally increased beginning at 15 cm/s for 15 min (first week) until achieving 45 cm/s for 1 h (last week). Depending on their diet, animals were divided into 2 groups: (1) STD, fed with a standard chow (Teklad Global 14% Protein Rodent Maintenance Diet); (2) ALG, fed with a mixture of 10% of Chlorella microalgae dry mass and omega-3 fatty acids (eicosapentaenoic and docosahexaenoic in 1:2 proportion). After the training period, GAS was excised, frozen and stored. Histological slides were cut in a cryostat and stained to demonstrate fibre oxidative and contractile properties of fast oxidative glycolytic (FOG), fast intermediate glycolytic (FIG) and fast glycolytic (FG) fibres. Fibre cross-sectional areas (FCSA), individual fibre capillarization index (CCA, ratio between number of capillaries and FCSA) and total capillary density (CD) were measured in the white zone of GAS.
RESULTS:
No significant differences were found in fibre type proportions between animals fed with the different diets (STD vs ALG, %±SD): FOG 9±3 vs 15±6; FIG 34±10 vs 24±11; FG 57±8 vs 61±8. Fibre sizes (FCSA) were also similar in both groups with the smallest areas found in FOG and the largest in FG (STD vs ALG, µm2±SD): FOG 2,953±278 vs 2,961±452; FIG 4,402±718 vs 4,591±195; FG 5,038±562 vs 5,242±597. Individual fibre capillarization (CCA) was greater in FOG and smaller in FG fibres showing similar values in both groups (STD vs ALG, capillaries per 1,000 µm2 FCSA±SD): FOG 2.57±0.41 vs 2.65±0.30; FIG 1.85±0.32 vs 1.83±0.18; FG 1.68±0.33 vs 1.80±0.34. Finally, the total capillarisation (capillaries·mm-2) of white GAS showed also no significant differences between groups with CD of 771±155 (STD) and 776±123 (ALG).
CONCLUSION:
Chlorella supplementation during a protocol of aerobic exercise did not induce significant changes in muscle fibre morphometry, capillarisation or fibre type proportions in the anaerobic zone of rat GAS muscle. The high percentage of FG fibres in white GAS and the low recruitment of this anaerobic zone of GAS during endurance exercise could explain these results. We are conducting additional work to elucidate if the eventual benefits of Chlorella supplementation on muscle structure and function could be restricted to the red or intermediate regions of the GAS. Further research seeking molecular and functional evidence is also underway.