Determination of triglycerides in Caenorhabditis elegans fed lactobacilli

Abstract

Caenorhabditis (C.) elegans is regarded as a simple model to assess the in vivo effects of probiotics, especially concerning the study of fat metabolism due to its ability to store lipids in intestinal and skin-like hypodermal cells. The main constituents in fat droplets stored in this nematode are triglycerides (TG). The objective of this work was to evaluate TG levels in C. elegans feeding with lactobacilli alone or combined in different proportions. The strains used in this study are listed as follow: Lacticaseibacillus rhamnosus CRL1425, Lactiplantibacillus plantarum CRL1427, CRL1428, CRL1449, CRL1472, Lacticaseibacillus casei CRL1430, Limosilactobacillus fermentum CRL1446 y Lactobacillus delbrueckii subsp. bulgaricus CRL1447. The strains to the different mix were selected based on previous studied functional properties and were combined as follows: mixture 1 (Mix 1) was formed by CRL1446, CRL1449, and CRL1472; Mixture 2 (Mix 2) by CRL1446 and CRL1449, Mixture 3 (Mix 3) by CRL1446 and CRL1472, and Mixture 4 (Mix 4) by CRL1449 and CRL1472. Nematodes synchronized were fed Escherichia (E.) coli OP50 (controls nematodes) and OP50:Lactobacilli in a ratio of 0:100; 25:75; and 50:50 (nematodes treated) at 18 °C until they reached the L4/adult stage. Then, a 5% solution of Triton X-100 was added and sonicated. The lipids were solubilized at 90 ° C for 5 min, and the lysate was removed by centrifugation. TG was determined in the supernatant by enzymatic methods. At least 3 biological replicas were used for each or mixtures of strains. The results showed that the nematode development was slower in the 0: 100 OP50:Lactobacilli ratio, while the 50:50 OP50:Lactobacilli ratio was similar to the control. In a 25:75 ratio, all strains, except CRL1427 and CRL1428, showed a significant reduction in TG levels. The CRL1425, CRL1446, and CRL1447 strains hat the highest percentage of TG reduction (75, 70, and 75%, respectively). When the nematodes were fed with Mix 1, Mix2 and Mix3 presented a significantly lower TG content than the control, with a reduction percentage of 56, 49, 42%, respectively. However, no significant differences were observed between these mixes. Mix 4 did not induce any change compared with nematode control. In conclusion, C. elegans can be used as a screening method for strains with the ability to reduce TG content, which reports an anti-obesity effect of these strains.