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Page 20 of 35 Boyajian et al. Microbiome Res Rep 2024;3:29 https://dx.doi.org/10.20517/mrr.2024.05

L. reuteri is another bacterial species with promising potential for the treatment of obesity. Recent findings
[194]
reveal the anti-inflammatory activity of L. reuteri LM1071 in LPS-stimulated immune cells . Another
study found that the L. reuteri stress protein GroEL inhibits pro-inflammatory cytokines and promotes anti-
inflammatory activity in human macrophages, reduces LPS-induced colonic inflammation in human
biopsies, and inhibits dextran sulfate sodium (DSS)-induced colitis in murine models, likely through TLR4
[195]
signaling . In addition to immunomodulatory properties, L. reuteri produces antimicrobial molecules and
is able to strengthen the gut barrier to prevent microbial translocation . Earlier research showed reduced
[196]
cholesterol and increased Vitamin D serum levels in hypercholesterolemic adults after a nine-week
supplementation with L. reuteri NCIMB 30242 , while current, ongoing research is investigating the
[197]
impact of L. reuteri V3401 on plasma LPS levels, microbiota composition, and disease biomarkers in obese
[198]
patients diagnosed with MetS . However, other evidence reveals that L. reuteri may be associated with
obesity and correlated with a higher BMI . Further investigation may compare various subspecies of
[199]
L. reuteri and determine their mechanisms of action in relation to obesity. Other strains of Lactobacillus
have been discussed as potential agents for weight and fat mass loss in overweight and obese individuals,
such as L. casei, L. rhamnosus, and L. curvatus, as well as their combination with other Lactobacillus strains
or strains of the Bifidobacterium genera .
[200]

L. casei Shirota, a probiotic reported to improve muscle function in young adult mice, was recently
[201]
investigated in aged SAMP8 mice for its effects on age-related sarcopenia . Findings revealed that 12-week
supplementation with L. casei improves age-related decline in muscle mass and strength, decreases
inflammation and oxidative stress, recovers loss of SCFAs, and enriches the gut microbiota with genera
positively correlated with muscle ability, mitochondrial function, and anti-inflammatory cytokine, IL-10. As
observed with the other species, the effects of L. casei may be attributed to the gut-muscle axis, which refers
to the impact of the gut microbiota on muscle mass and function through inflammation and SCFA levels.
L. paracasei also holds promise as an anti-aging probiotic. A recent study reported that L. paracasei PS23
improves cognitive function in aging mice, including memory deficits, age-related motor impairment, and
[202]
anxiety behavior . The mechanisms of L. paracasei PS23 were attributed to an increase in serotonin levels,
antioxidant enzyme production, and beneficial gut modulation, such as an increase in Dubosiella, a
potential anti-inflammatory species. Chen et al. also explored the effects of L. paracasei PS23 on sarcopenia
and concluded that this strain attenuates age-related loss of muscle mass and strength by enhancing
mitochondrial function, reducing inflammation, and improving antioxidant enzyme levels in muscle
tissue . Similarly, long-term (43-week) supplementation with L. paracasei K71 led to enhanced cognition
[203]
and upregulated BDNF expression in senescence-accelerated mouse prone 8 (SAMP8) . However,
[204]
serotonin levels did not alter in response to treatment, compared to control, and the study did not assess gut
microbial composition.

Age-related decline in immunity may be improved by probiotic supplementation. A clinical trial conducted
in 2013 evaluated L. delbrueckii subsp. bulgaricus 8481 for immunomodulatory properties in elderly
individuals and found an improved immune risk profile, slowed aging of T cell subpopulations, and
[205]
decreased systemic levels of the pro-inflammatory cytokine, IL-8 . However, the benefits of the probiotic
supplementation ceased within six months of stopping probiotic intake, suggesting that continual
supplementation is required for sustained effects. Moreover, literature lacks recent clinical studies on
L. delbrueckii or similar probiotic strains. The use of Lactobacillus in delaying or improving the aging
process and its hallmarks is promising, yet requires additional research given the complex nature of aging
and the strain-specific effects of the probiotics.