Author(s): ZUÑIGA, P., HIGUERA-CHAPARRO, Y., LORENZO, K., VILLAMIL-PARRA, W., CASTRO-ARIAS, M., VISCOR, G., TORRES, J.L., PAGÈS, T., MAGALHÃES, J., RAMOS-ROMERO, S., TORRELLA, J.R., SANTOCILDES, G., Institution: UNIVERSITY OF BARCELONA, Country: SPAIN, Abstract-ID: 1783

INTRODUCTION:
Chlorella is a marine microalga rich in proteins and containing essential amino acids. It is an excellent dietary source of high-quality protein regarding physical exercise, since its macronutrients have antioxidant and anti-inflammatory activity. We aimed to analyse the effects of a Chlorella-based diet supplementation during a protocol of aerobic exercise on the most oxidative part of a predominantly anaerobic muscle, the rat extensor digitorum longus (EDL).
METHODS:
Twelve animals were trained 5 days/week for 10 weeks (beginning at 15 cm/s for 15 min and achieving 45 cm/s for 1 h the last week). Animals were divided into 2 groups: (1) STD, fed with standard chow (Teklad Global 14% Protein Rodent Maintenance Diet); (2) ALG, fed with a mixture of 10% of Chlorella dry mass and omega-3 fatty acids (eicosapentaenoic and docosahexaenoic in 1:2 proportion). Histological EDL slides were cut in a cryostat and stained to demonstrate the metabolic 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 medial EDL zone.
RESULTS:
After the exercise protocol, similar fibre type distributions were found in the animals fed with different diets (STD vs ALG, %±SD): SO: 4±1 vs 5±3; FOG 25±4 vs 23±1; FIG 27±6 vs 28±6; FG 44±8 vs 44±5. No statistical differences were found in FCSA between both groups, with the smallest areas found in oxidative fibres (SO and FOG) and the largest in FG (STD vs ALG, µm2±SD): SO: 1,474±273 vs 1,208±321; FOG 1,595±259 vs 1,541±219; FIG 2,552±222 vs 2,687±372; FG 4,205±799 vs 4,289±612. The CCA index was greater in oxidative fibres and smaller in the anaerobic ones but also showed similar values in both groups (STD vs ALG, capillaries per 1,000 µm2 FCSA±SD): SO: 4.45±0.67 vs 5.15±0.96; FOG 4.35±0.36 vs 4.26±0.56; FIG 2.98±0.24 vs 2.89±0.46; FG 2.37±0.41 vs 2.37±0.35. The CD of the whole medial EDL region (capillaries·mm-2) showed no significant differences between both groups: 1,010±179 (STD) and 918±135 (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 medial EDL rat muscle. Although with a great proportion of FG fibres, the medial EDL is thought to prioritise oxygen supply for oxidative demand whereas the lateral compartment is hypothesized to optimise for metabolite removal (J Anat 240:700-710, 2022). However, we could not demonstrate, after diet supplementation with Chlorella, any endurance improvement in the oxidative demand for one of the muscles involved in the dorsiflexion of the ankle. Further research is needed to elucidate if nutritional supplementation could affect muscle endurance or resistance to fatigue at molecular or functional levels.