Lactobacillus sp. improved microbiota and metabolite profiles of aging rats

https://doi.org/10.1016/j.phrs.2019.104312Get rights and content

Abstract

Aging is closely associated with altered gut function and composition, in which elderly were reported with reduced gut microbiota diversity and increased incidence of age-related diseases. Probiotics have been shown to exert beneficial health-promoting effects through modulation of intestinal microflora biodiversity, thus the effects of probiotics administration on D-galactose (D-gal) senescence-induced rat were evaluated based on the changes in gut microbiota and metabolomic profiles. Upon senescence induction, the ratio of Firmicutes/ Bacteroidetes was significantly lowered, while treatment with Lactobacillus helveticus OFS 1515 and L. fermentum DR9 increased the ratio at the phylum level (P < 0.05). Study on the genus level showed that L. paracasei OFS 0291 and L. helveticus OFS 1515 administration reduced Bacteroides, which are prominently opportunistic pathogens while L. fermentum DR9 treated rats promoted the proliferation of Lactobacillus compared to the aged rats (P < 0.05). Probiotics treatment did not alter fecal short-chain fatty acid (SCFA) profile, but an increase in acetate was observed in the D-gal rats. The analysis of fecal water-soluble metabolites showed that D-gal induced senescence caused great impact on amino acids metabolism such as urocanic acid, citrulline, cystamine and 5-oxoproline, which could serve as potential aging biomarkers. Treatment with probiotics ameliorated these metabolites in a strain-specific manner, whereby L. fermentum DR9 promoted antioxidative effect through upregulation of oxoproline, whereas both L. paracasei OFS 0291 and L. helveticus OFS 1515 restored the levels of reducing sugars, arabinose and ribose similar to the young rats. D-gal induced senescence did cause significant immunological alteration in the colon of aged rats however, all probiotic strains demonstrated immunomodulatory properties as L. paracasei OFS 0291, L. helveticus OFS 1515 and L. fermentum DR9 alleviated proinflammatory cytokines TNF-α, IFN-γ and IL-1β as well as IL-4 compared to the aged control (P < 0.05). Our study highlights the potential of probiotics as an anti-aging therapy through healthy gut modulation.

Introduction

Gut is one of the largest lymphoid organs in our body harbouring approximately 4 trillion of bacteria [1]. Weighing about 1–2 kg, the gut microbiota is constituted of 1000 bacterial species encoding not less than five million genes [2]. As gut microbiota control host physiology and survival, the roles of these bacteria in the aging process are indispensable. In human, gut microbiota are affected by dietary and health conditions but remain relatively stable after establishment as early as 3 years after birth [3]. However gut microbiota experience changes in composition and diversity in the elderly with lesser abundance of core bacterial families such as Bacteroidaceae, Ruminococcaceae and Lachnospiraceae, while certain health-associated species also become more prevalent [3]. Age-associated change in gut microbiota is reportedly affected by altered gut barrier integrity, intestinal immune homeostasis and various other old age-diseases [4].

Aging is irreversible and inevitable but the onset of age-related disorders can be delayed/ prevented through a healthy, balanced lifestyle- a term known as healthy aging. One of the approaches is through maintenance of balanced gut microbiota, be it via diet intervention and/or functional food supplementation. Probiotics, defined as live microorganisms which are beneficial for a healthy gut are well-known functional food used to improve and restore dysbiosis and gastrointestinal diseases [5]. Mainly comprised of lactic acid bacteria, probiotics were known to modulate the composition of gut microflora and subsequently gut barrier function [6]. Probiotics also present very high antioxidant and immunomodulatory activities by affecting cytokine production [7]. An enhanced gut integrity will lead to lower oxidative stress and inflammatory markers, both of which are the main culprit of aging [8]. Connecting all these findings, probiotics are in the limelight to be exploited as a putative target to mitigate aging.

In recent years, the study on gut microbiota composition can be achieved through next-generating sequencing (NGS) technologies [2]. With the emergence of DNA sequencing technology, the microbiome profile can be easily generated through PCR amplification of the universally conserved 16S rRNA genes, accompanied by high-throughput sequencing of the PCR products [9]. The study on gut could also be achieved via metabolomic profiling. It is a measure of metabolites which can represent the response to physiological (sex), pathophysiological (disease) and developmental stimuli (aging). The change in gut microbial diversity is also closely-correlated with an altered pattern of metabolites [10]. Thus, metabolomic profiling enables the identification of biomarkers for certain diseases and possible therapeutic interventions.

The present study aimed to determine the effect of probiotics strains L. fermentum DR9, L. paracasei OFS 0291 and L. helveticus OFS 1515 on the changes in gut microbial diversity and metabolites profiles of D-galactose senescence-induced rat.

Section snippets

Bacteria strains and culture

Two strains of lactic acid bacteria (LAB), Lactobacillus paracasei OFS 0291 and Lactobacillus helveticus OFS 1515 were obtained from School of Industrial Technology, Universiti Sains Malaysia (Penang, Malaysia). Lactobacillus fermentum DR9, isolated from fresh cow’s milk in Penang, was obtained via courtesy of Clinical Nutrition Intl (M) Sdn. Bhd., Malaysia. All stock cultures were preserved in 20% glycerol (-20 °C). Each strain was activated in sterile de Mann, Rogosa, Sharpe (MRS) broth

Diversity of gut microbiota

High-throughput Illumina Miseq sequencing on the V4 regions of 16S rRNA genes was used to evaluate the impact of senescence induction using D-galactose (D-gal) and administration of L. paracasei OFS 0291, L. helveticus OFS 1515 and L. fermentum DR9 on the gut microbiota composition upon 12 weeks of treatment. Based on the result, a total of 682323 number of reads were obtained, with a mean of 14215 reads per sample and a standard deviation of 3248 reads. Sequences above 97% similarity were

Discussions

Gut microbiota play an essential role in our body as they modulate health conditions and progression of diseases. Changes in gut microbiota occur throughout different life stages with most significant alteration during early birth and elderly phase. During aging, it was reported that gut microbiota diversity reduced [5]. At the same time, the increase tendency of age-associated diseases such as cardiovascular disease, diabetes, sarcopenia, osteoporosis and neurodegenerative diseases had led

Conclusions

In summary, the composition of microbiota significantly differed from the young rats upon D-gal senescence induction. Supplementation with L. fermentum DR9, L. paracasei OFS 0291 and L.helveticus OFS 1515 altered the gut microbiota profile by promoting proliferation of beneficial microbial community during aging. The metabolomic profile was augmented upon senescence induction and could serve as a tool to identify potential aging biomarkers. The changes in metabolomic profile by Lactobacillus

Declaration of Competing Interest

The authors declare no competing financial or conflict of interest.

Acknowledgements

This work was supported by the URICAS grant (1001/ PTEKIND/870030) and the MyBrain Scholarship provided by Ministry of Higher Education Malaysia, and funding by Clinical Nutrition Intl (M) Sdn. Bhd.

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