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Study of the effect of a dietary intervention with wild-type lactic acid bacteria on the gut microbiome of animal models of obesity-hypercholesterolemia (Bachelor thesis)

Καρβούνη, Αναστασία/ Karvouni, Anastasia

Obesity and hypercholesterolemia are among the most common metabolic disorders of modern societies and are associated with an increased risk of cardiovascular diseases, type 2 diabetes mellitus, and other chronic inflammatory conditions. Nowadays, numerous studies have highlighted the important role of the gut microbiota in lipid metabolism regulation and in maintaining host homeostasis, leading the scientific community to focus on the investigation of potential probiotic microorganisms that may contribute to the maintenance or restoration of the normal intestinal microflora. The aim of the present undergraduate thesis was to investigate the effect of dietary intervention with the wild-type lactic acid bacterium Lactococcus cremoris FBMS_5810 on the gut microbiota of animal models of obesity and hypercholesterolemia. For this purpose, mice were divided into three experimental groups: a normal diet group (ND), a high-fat diet group (HFD), and a group that received high-fat diet fortified with freeze-diet free L. cremoris FBMS_5810 cells (LC). Microbiological analyses were performed on fecal samples collected at weeks 0, 4, and 8, as well as on intestinal fluid of cecum and colon. The results demonstrated that the high-fat diet induced significant alterations in the composition of the intestinal microbiota, negatively affecting the microbial balance and increasing the populations of Enterobacteriaceae, coliforms, Enterococcus spp., E. coli και Clostridium spp. In contrast, administration of L. cremoris FBMS_5810 partially counteracted these alterations compared to mice receiving only the high-fat diet. However, the populations of LAB and Bifidobacterium spp. remained lower than those observed in theh normal diet group. Furthermore, a significant increase in the Lactococcus spp. Population was observed in the LC groop during the first four weeks of the intervention, a finding that may be associated with the administration of the strain under study. A particularly notable finding was observed for the Clostridium spp. population, whose levels differed significantly among all three groups. In the colon, the HFD group showed the highest Clostridium spp. levels compared with the ND and LC groups, whereas in fecal samples, the LC group displayed significantly lower levels than both the HFD group and even the ND group. In conclusion, the findings of the present study suggest that administration of the L. cremoris FBMS_5810 strain may contribute to mitigating obesity- and hypercholesterolemia-associated intestinal dysbiosis, supporting the need for further investigation of its potential beneficial effects.