Influence of Age, Sex, and Diet on the Human Fecal Metabolome Investigated by 1H NMR Spectroscopy

Comparative analysis of gut microbiome-derived short-chain fatty acids in patients with severe mental disorder: Insights from schizophrenia and bipolar disorder

Both schizophrenia (SZ) and bipolar disorder (BD) are associated with disruptions in the gut microbiome. Short-chain fatty acids (SCFAs), such as acetate, propionate and butyrate, are key metabolites produced by gut bacteria that influence brain function, immune responses and behaviour. We conducted a cross-sectional observational study with 123 patients (86 with SZ and 37 with BD). We analysed faecal samples for SCFA and examined associations with clinical (psychopathology and cognition), metabolic and lifestyle factors. We performed analysis of covariance to find differences in SCFA levels between diagnostic groups, adjusting for covariates. Faecal SCFA levels were numerically higher in the SZ group than in the BD group. However, after adjusting for covariates, a significant sex-by-diagnosis interaction was observed only for acetate levels. Body mass index emerged as a key predictor of SCFA levels but we observed no significant associations with other metabolic or lifestyle variables, including diet, physical activity and blood inflammatory biomarkers. Additionally, SCFA levels showed no correlation with symptom severity or cognitive performance in either group. This study is the first to compare SCFA profiles between SZ and BD, highlighting potential differences in gut microbiota-derived metabolites between these disorders. These findings suggest greater disruption of the gut-brain axis in SZ, potentially reflecting distinct pathophysiological mechanisms involving metabolic and sex-related factors. Further research, including blood SCFA measurements, could better explain the role of SCFAs and explore microbiota-targeted therapeutic strategies for SZ and BD.

Type of diet has no major influence on inflammatory response in a Saddleback pig model

Fermentable carbohydrates and resulting short-chain fatty acids (SCFAs) received attention via modifying potential on obesity-associated systemic low-grade inflammation. However, their effects on inflammation remain poorly understood. In this study, the anti-inflammatory properties of pectin or inulin supplementation were investigated in an atherogenic-fed pig obesity model. Pigs were divided into three atherogenic-fed groups with or without 5% pectin/inulin supplementation (AD, ADp, ADi, n = 10) and a conventional-fed group (CD, n = 10) for a 15-week feeding period. We demonstrated that faecal SCFA concentrations decreased and faecal pH increased in all groups over the feeding period (P < 0.05). SCFA concentrations were comparable between colon and faeces in all groups. Liver inflammatory-marker expressions were on average < 1 in all groups, except TNF-α (AD < CD and ADi; P < 0.01). Inflammatory-marker expressions in abdominal adipose tissue exceeded subcutaneous marker expressions in all groups. AD showed significantly lower IL-1β and CD68 mRNA levels than CD (P < 0.03). Comparing the atherogenic diet groups, the IL-1β mRNA levels were higher in ADi versus AD and ADp (P = 0.02). Our data indicated that fermentable carbohydrates added to an atherogenic diet cannot resolve low-grade adipose tissue inflammatory associated with obesity.

Age, sex, and mitochondrial-haplotype influence gut microbiome composition and metabolites in a genetically diverse rat model

We evaluated the impact of sex and mitochondrial-haplotype on the age-related changes in the fecal gut microbiome of the genetically heterogeneous rodent model, the OKC-HETB/W rat. The age-related changes in the microbiome differed markedly between male and female rats. Five microbial species changed significantly with age in male rats compared to nine microbial species in female rats. Only three of these microbes changed with age in both male and female rats. The mitochondrial-haplotype of the rats also affected how aging altered the microbiome. Interestingly, most of the microbial species that changed significantly with age were mitochondrial-haplotype and sex specific, i.e., changing in one sex and not the other. We also discovered that sex and mitochondrial-haplotype significantly affected the age-related variations in content of fecal short-chain fatty acids and plasma metabolites that influence or are regulated by the microbiome, e.g., tryptophan derived metabolites and bile acids. This study demonstrates that the host's sex plays a significant role in how the gut microbiome evolves with age, even within a genetically diverse background. Importantly, this is the first study to show that the mitochondrial-haplotype of a host impacts the age-related changes in the microbiome.

Decoding aging clocks: New insights from metabolomics

Chronological age is a crucial risk factor for diseases and disabilities among older adults. However, individuals of the same chronological age often exhibit divergent biological aging states, resulting in distinct individual risk profiles. Chronological age estimators based on omics data and machine learning techniques, known as aging clocks, provide a valuable framework for interpreting molecular-level biological aging. Metabolomics is an intriguing and rapidly growing field of study, involving the comprehensive profiling of small molecules within the body and providing the ultimate genome-environment interaction readout. Consequently, leveraging metabolomics to characterize biological aging holds immense potential. The aim of this review was to provide an overview of metabolomics approaches, highlighting the establishment and interpretation of metabolomic aging clocks while emphasizing their strengths, limitations, and applications, and to discuss their underlying biological significance, which has the potential to drive innovation in longevity research and development.

Unveiling the Potential Prebiotic Effects of Edible Mushroom Pleurotus djamor During In Vitro Colonic Fermentation

The ability of edible mushrooms to modulate the intestinal microbiota is a topic of interest. This study shows that digested Pleurotus djamor powder (MUS) exhibits prebiotic effects during an in vitro colonic fermentation. Phenolic compounds, including epicatechin (3.03 ± 1.54 mg/L), gallic acid (2.71 ± 1.54 mg/L), and quercetin 3-glucoside (2.40 ± 1.54 mg/L), were found in P. djamor. MUS significantly increased the relative abundance of Lactobacillus spp./Enterococcus spp. (1.12% - 4.83%), Bifidobacterium spp. (0.59% - 1.85%), Ruminococcus albus/R. flavefaciens (0.37% - 1.88%), and reduced Clostridium histolyticum (2.89% - 1.22%) during 48 of colonic fermentation. MUS enhanced lactic acid and short-chain fatty acid production and decreased pH levels. The 1H NMR analysis revealed the presence of essential amino acids, branched-chain amino acids, and other compounds that benefit human health. The results indicate the prebiotic effects of P. djamor on human intestinal microbiota.

Temporal changes in the mouse gut bacteriota influenced by host sex, diet, and exercise

The gut microbiota plays an important role in host physiology. However, the effects of host sex, lifestyle, and temporal influences on the bacterial community within the gut remain ill-defined. To address this gap, we evaluated 56 male and female mice over a 10-wk study to assess the effects of sex, diet, and exercise on gut community dynamics. Mice were randomly assigned to high-fat or control diet feeding and had free access to running wheels or remained sedentary throughout the study period. The fecal bacterial community was characterized by rRNA operon profiling via nanopore sequencing. Differential abundance testing indicated that ∼200 bacterial taxa were significantly influenced by sex, diet, or exercise (4.2% of total community), which also changed over time (82 taxa, 1.7% of total community). Phylogenetic analysis of taxa closely related to Dysosmobacter welbionis, and several members of the family Muribaculaceae were examined more closely and demonstrated distinct species/strain level subclustering by host sex, diet, and exercise. Collectively, these data suggest that sex and lifestyle can alter the gut bacteriota at the species/strain level that may play a role in host health. These results also highlight the need for improved characterization methods to survey microbial communities at finer taxonomic resolution.NEW & NOTEWORTHY This study demonstrates that host sex, diet, and exercise can each modulate gut bacterial community structure, which may have consequences to host physiology. Our analysis shows selection of novel strains and genera for some members of the Oscillospiraceae and Muribaculaceae by host sex, diet, and activity status. Overall, these findings provide a framework for detecting the next generation of beneficial bacteria targeting obesity and associated metabolic diseases in a sex-specific manner.

Age, sex, and mitochondrial-haplotype influence gut microbiome composition and metabolites in a genetically diverse rat model

We evaluated the impact of sex and mitochondrial-haplotype on the age-related changes in the fecal gut microbiome of the genetically heterogeneous rodent model, the OKC-HETB/W rat. Alpha-diversity, measuring richness and evenness of gut microbiome composition, did not change with age or mitochondrial-haplotype. However, beta-diversity, a measure of microbial differences among samples, was significantly modulated by age in male and female rats in both mitochondrial-haplotypes. The age-related changes in the microbiome differed markedly between male and female rats. Five microbial species changed significantly with age in male rats compared to nine microbial species in female rats. Only three of these microbes changed with age in both male and female rats. The mitochondrial-haplotype of the rats also affected how aging altered the microbiome. Interestingly, most of the microbial species that changed significantly with age were mitochondrial-haplotype and sex specific, i.e., changing in one sex and not the other. We also discovered that sex and mitochondrial-haplotype significantly affected the age-related variations in content of fecal short-chain fatty acids and plasma metabolites that influence or are regulated by the microbiome, e.g., tryptophan derived metabolites and bile acids. This study demonstrates that the host's sex plays a significant role in how the gut microbiome evolves with age, even within a genetically diverse background. Importantly, this is the first study to show that the mitochondrial-haplotype of a host impacts the age-related changes in the microbiome and supports previous studies suggesting a bidirectional interaction between the gut microbiome and host mitochondria.

Comparative characterization of the infant gut microbiome and their maternal lineage by a multi-omics approach

The human gut microbiome establishes and matures during infancy, and dysregulation at this stage may lead to pathologies later in life. We conducted a multi-omics study comprising three generations of family members to investigate the early development of the gut microbiota. Fecal samples from 200 individuals, including infants (0-12 months old; 55% females, 45% males) and their respective mothers and grandmothers, were analyzed using two independent metabolomics platforms and metagenomics. For metabolomics, gas chromatography and capillary electrophoresis coupled to mass spectrometry were applied. For metagenomics, both 16S rRNA gene and shotgun sequencing were performed. Here we show that infants greatly vary from their elders in fecal microbiota populations, function, and metabolome. Infants have a less diverse microbiota than adults and present differences in several metabolite classes, such as short- and branched-chain fatty acids, which are associated with shifts in bacterial populations. These findings provide innovative biochemical insights into the shaping of the gut microbiome within the same generational line that could be beneficial in improving childhood health outcomes.

Changes in Plasma, Urine, and Fecal Metabolome after 16 Weeks of Consuming Dairy With Different Food Matrixes - A Randomized Controlled Trial

SCOPE

Understanding the mode-of-action by which fermented dairy consumption influences health is of interest. The aim of this study is to elucidate the impact of the chemical-physical properties of the dairy matrix and postbiotic effects on the metabolomics response to fermented dairy consumption.

METHODS AND RESULTS

Hundred males (Body Mass Index (BMI) 28.0-45.0 kg m-2, waist circumference ≥ 102 cm) are included in the study. During a 16-week intervention, the study subjects are instructed to consume 400 g per day of either 1) milk, 2) yogurt, 3) heat-treated yogurt, or 4) chemically acidified milk as part of their habitual diet. Nuclear Magnetic Resonance (NMR)-based metabolomics is conducted on plasma, urine, and fecal samples collected before and after the intervention. Both consumption of acidified milk and heat-treated yogurt resulted in changes in the fecal metabolome including decreases in the level of amino acids (leucine, valine, and threonine), and the branched-chain fatty acid (BCFA) isobutyrate that indicated an altered protein putrefaction, and proteolytic metabolism in the gut. In the plasma metabolome, an increased citrate is found for yogurt consumption. No difference in the urine metabolome is found.

CONCLUSIONS

Our metabolomics analyses indicate that consumption of heat-treated yogurt and acidified milk exerted similar effects on the metabolic activity in the gut as yogurt consumption.

Genetic hypogonadal mouse model reveals niche-specific influence of reproductive axis and sex on intestinal microbial communities

BACKGROUND

The gut microbiome has been linked to many diseases with sex bias including autoimmune, metabolic, neurological, and reproductive disorders. While numerous studies report sex differences in fecal microbial communities, the role of the reproductive axis in this differentiation is unclear and it is unknown how sex differentiation affects microbial diversity in specific regions of the small and large intestine.

METHODS

We used a genetic hypogonadal mouse model that does not produce sex steroids or go through puberty to investigate how sex and the reproductive axis impact bacterial diversity within the intestine. Using 16S rRNA gene sequencing, we analyzed alpha and beta diversity and taxonomic composition of fecal and intestinal communities from the lumen and mucosa of the duodenum, ileum, and cecum from adult female (n = 20) and male (n = 20) wild-type mice and female (n = 17) and male (n = 20) hypogonadal mice.

RESULTS

Both sex and reproductive axis inactivation altered bacterial composition in an intestinal section and niche-specific manner. Hypogonadism was significantly associated with bacteria from the Bacteroidaceae, Eggerthellaceae, Muribaculaceae, and Rikenellaceae families, which have genes for bile acid metabolism and mucin degradation. Microbial balances between males and females and between hypogonadal and wild-type mice were also intestinal section-specific. In addition, we identified 3 bacterial genera (Escherichia Shigella, Lachnoclostridium, and Eggerthellaceae genus) with higher abundance in wild-type female mice throughout the intestinal tract compared to both wild-type male and hypogonadal female mice, indicating that activation of the reproductive axis leads to female-specific differentiation of the gut microbiome. Our results also implicated factors independent of the reproductive axis (i.e., sex chromosomes) in shaping sex differences in intestinal communities. Additionally, our detailed profile of intestinal communities showed that fecal samples do not reflect bacterial diversity in the small intestine.

CONCLUSIONS

Our results indicate that sex differences in the gut microbiome are intestinal niche-specific and that sampling feces or the large intestine may miss significant sex effects in the small intestine. These results strongly support the need to consider both sex and reproductive status when studying the gut microbiome and while developing microbial-based therapies.

Changes in fecal metabolic and lipidomic features by anti-TNF treatment and prediction of clinical remission in patients with ulcerative colitis

Background

Therapeutic targets for ulcerative colitis (UC) and prediction models of antitumor necrosis factor (TNF) therapy outcomes have not been fully reported.

Objective

Investigate the characteristic metabolite and lipid profiles of fecal samples of UC patients before and after adalimumab treatment and develop a prediction model of clinical remission following adalimumab treatment.

Design

Prospective, observational, multicenter study was conducted on moderate-to-severe UC patients (n = 116).

Methods

Fecal samples were collected from UC patients at 8 and 56 weeks of adalimumab treatment and from healthy controls (HC, n = 37). Clinical remission was assessed using the Mayo score. Metabolomic and lipidomic analyses were performed using gas chromatography mass spectrometry and nano electrospray ionization mass spectrometry, respectively. Orthogonal partial least squares discriminant analysis was performed to establish a remission prediction model.

Results

Fecal metabolites in UC patients markedly differed from those in HC at baseline and were changed similarly to those in HC during treatment; however, lipid profiles did not show these patterns. After treatment, the fecal characteristics of remitters (RM) were closer to those of HC than to those of non-remitters (NRM). At 8 and 56 weeks, amino acid levels in RM were lower than those in NRM and similar to those in HC. After 56 weeks, levels of 3-hydroxybutyrate, lysine, and phenethylamine decreased, and dodecanoate level increased in RM similarly to those in HC. The prediction model of long-term remission in male patients based on lipid biomarkers showed a higher performance than clinical markers.

Conclusion

Fecal metabolites in UC patients markedly differ from those in HC, and the levels in RM are changed similarly to those in HC after anti-TNF therapy. Moreover, 3-hydroxybutyrate, lysine, phenethylamine, and dodecanoate are suggested as potential therapeutic targets for UC. A prediction model of long-term remission based on lipid biomarkers may help implement personalized treatment.

Associations of disordered eating with the intestinal microbiota and short-chain fatty acids among young adults with type 1 diabetes

BACKGROUND AND AIMS

Disordered eating (DE) in type 1 diabetes (T1D) includes insulin restriction for weight loss with serious complications. Gut microbiota-derived short chain fatty acids (SCFA) may benefit host metabolism but are reduced in T1D. We evaluated the hypothesis that DE and insulin restriction were associated with reduced SCFA-producing gut microbes, SCFA, and intestinal microbial diversity in adults with T1D.

METHODS AND RESULTS

We collected stool samples at four timepoints in a hypothesis-generating gut microbiome pilot study ancillary to a weight management pilot in young adults with T1D. 16S ribosomal RNA gene sequencing measured the normalized abundance of SCFA-producing intestinal microbes. Gas-chromatography mass-spectrometry measured SCFA (total, acetate, butyrate, and propionate). The Diabetes Eating Problem Survey-Revised (DEPS-R) assessed DE and insulin restriction. Covariate-adjusted and Bonferroni-corrected generalized estimating equations modeled the associations. COVID-19 interrupted data collection, so models were repeated restricted to pre-COVID-19 data. Data were available for 45 participants at 109 visits, which included 42 participants at 65 visits pre-COVID-19. Participants reported restricting insulin "At least sometimes" at 53.3% of visits. Pre-COVID-19, each 5-point DEPS-R increase was associated with a -0.34 (95% CI -0.56, -0.13, p = 0.07) lower normalized abundance of genus Anaerostipes; and the normalized abundance of Lachnospira genus was -0.94 (95% CI -1.5, -0.42), p = 0.02 lower when insulin restriction was reported "At least sometimes" compared to "Rarely or Never".

CONCLUSION

DE and insulin restriction were associated with a reduced abundance of SCFA-producing gut microbes pre-COVID-19. Additional studies are needed to confirm these associations to inform microbiota-based therapies in T1D.

Strategizing the human microbiome for small molecules: Approaches and perspectives

Studies of the human microbiome are providing a deeper understanding of its significance to human health, and increasing evidence links the microbiota with several diseases. Nevertheless, the exact mechanisms involved in human-microbe interactions are mostly undefined. The genomic potential of the human microbiome to biosynthesize distinct molecules outmatches its known chemical space, and small-molecule discovery in this context remains in its infancy. The profiling of microbiome-derived small molecules and their contextualization through cause-effect mechanistic studies may provide a better understanding of host-microbe interactions, guide new therapeutic interventions, and modulate microbiome-based therapies. This review describes the advances, approaches, and allied challenges in mining new microbial scaffolds from the human microbiome using genomic, microbe cultivation, and chemical analytic platforms. In the future, the complete biological characterization of a single microbe-derived molecule that has a specific therapeutic application could resolve the current limitations of microbiota-modulating therapies.

Sex, puberty, and the gut microbiome

In brief

Sex differences in the gut microbiome may impact multiple aspects of human health and disease. In this study, we review the evidence for microbial sex differences in puberty and adulthood and discuss potential mechanisms driving differentiation of the sex-specific gut microbiome.

Abstract

In humans, the gut microbiome is strongly implicated in numerous sex-specific physiological processes and diseases. Given this, it is important to understand how sex differentiation of the gut microbiome occurs and how these differences contribute to host health and disease. While it is commonly believed that the gut microbiome stabilizes after 3 years of age, our review of the literature found considerable evidence that the gut microbiome continues to mature during and after puberty in a sex-dependent manner. We also review the intriguing, though sparse, literature on potential mechanisms by which host sex may influence the gut microbiome, and vice versa, via sex steroids, bile acids, and the immune system. We conclude that the evidence for the existence of a sex-specific gut microbiome is strong but that there is a dearth of research on how host-microbe interactions lead to this differentiation. Finally, we discuss the types of future studies needed to understand the processes driving the maturation of sex-specific microbial communities and the interplay between gut microbiota, host sex, and human health.

Fermentation Supernatant of Elderly Feces with Inulin and Partially Hydrolyzed Guar Gum Maintains the Barrier of Inflammation-Induced Caco-2/HT29-MTX-E12 Co-Cultured Cells

Intestinal barrier function declines with aging. We evaluated the effect of dietary fibers and indigestible oligosaccharides on intestinal barrier function by altering the microbiota of the elderly. The feces were anaerobically cultured with indigestible dextrin, inulin, partially hydrolyzed guar gum (PHGG), lactulose, raffinose, or alginate, and the fermented supernatant was added to inflammation-induced Caco-2/HT29-MTX-E12 co-cultured cells. Our data showed that inulin- and PHGG-derived supernatants exerted a protective effect on the intestinal barrier. The protective effect was significantly positively correlated with total short-chain fatty acids (SCFAs) and butyric acid production in the supernatant and negatively correlated with the claudin-2 (CLDN2) gene expression in the cultured cells. Furthermore, we showed that the CLDN2 levels are regulated by butyric acid. Thus, inulin and PHGG can change the intestinal environment of the elderly and maintain the intestinal barrier by accelerating the production of SCFAs and modifying the expression levels of barrier function-related genes.

Lower plasma concentrations of short-chain fatty acids (SCFAs) in patients with ADHD

Short-chain fatty acids (SCFAs), produced during bacterial fermentation, have been shown to be mediators in the microbiota-gut-brain axis. This axis has been proposed to influence psychiatric symptoms seen in attention deficit hyperactivity disorder (ADHD). However, there is no report of plasma SCFA concentrations in ADHD. The aim of this study was to explore the plasma concentrations of SCFAs in children and adults with ADHD and the possible factors that could influence those levels. We collected data on age group, sex, serum vitamin D levels, delivery mode, body mass index, diet, medication and blood samples from 233 ADHD patients and 36 family-related healthy controls. The concentrations of SCFAs and the intermediary metabolite succinic acid, were measured using liquid chromatography-mass spectrometry. Adults with ADHD had lower plasma concentrations of formic, acetic, propionic and succinic acid than their healthy family members. When adjusting for SCFA-influential factors among those with ADHD, children had lower concentrations of formic, propionic and isovaleric acid than adults, and those who had more antibiotic medications during the last 2 years had lower concentrations of formic, propionic and succinic acid. When adjusting for antibiotic medication, we found that among children, those currently on stimulant medication had lower acetic and propionic acid levels, and adults with ADHD had lower formic and propionic acid concentrations than adult healthy family members. In all, our findings show lower-than-normal plasma concentrations of SCFAs in ADHD explained in-part by antibiotic medication, age and stimulant medication. Whether or not this is of clinical significance is yet to be explored.

Untargeted Metabolomics Pilot Study Using UHPLC-qTOF MS Profile in Sows' Urine Reveals Metabolites of Bladder Inflammation

Urinary tract infections (UTI) of sows (characterized by ascending infections of the urinary bladder (cyst), ureters, and renal pelvis), are major health issues with a significant economic impact to the swine industry. The current detection of UTI incidents lacks sensitivity; thus, UTIs remain largely under-diagnosed. The value of metabolomics in unraveling the mechanisms of sow UTI has not yet been established. This study aims to investigate the urine metabolome of sows for UTI biomarkers. Urine samples were collected from 58 culled sows from a farrow-to-finish herd in Greece. Urine metabolomic profiles in 31 healthy controls and in 27 inflammatory ones were evaluated. UHPLC-qTOF MS/MS was applied for the analysis with a combination of multivariate and univariate statistical analysis. Eighteen potential markers were found. The changes in several urine metabolites classes (nucleosides, indoles, isoflavones, and dipeptides), as well as amino-acids allowed for an adequate discrimination between the study groups. Identified metabolites were involved in purine metabolism; phenylalanine; tyrosine and tryptophan biosynthesis; and phenylalanine metabolism. Through ROC analysis it was shown that the 18 identified metabolite biomarkers exhibited good predictive accuracy. In summary, our study provided new information on the potential targets for predicting early and accurate diagnosis of UTI. Further, this information also sheds light on how it could be applied in live animals.

Distinctive Role of the Systemic Inflammatory Profile in Non-Small-Cell Lung Cancer Younger and Elderly Patients Treated with a PD-1 Immune Checkpoint Blockade: A Real-World Retrospective Multi-Institutional Analysis

An immune checkpoint blockade with mAbs to PD-1 and PD-L1 is an expanding therapeutic option for mNSCLC patients. This treatment strategy is based on the use of mAbs able to restore the anti-tumor activity of intratumoral T cells inhibited by PD-1 binding to PD-L1/2 on tumor and inflammatory cells. It has been speculated that a chronic status of systemic inflammation as well as the immunosenescence physiologically occurring in elderly patients may affect the efficacy of the treatment and the occurrence of irAEs. We performed a multi-institutional retrospective study aimed at evaluating the effects of these mAbs (nivolumab or atezolizumab) in 117 mNSCLC patients younger (90 cases) and older (27 cases) than 75 years in correlation with multiple inflammatory parameters (NLR, CRP, ESR, LDH and PCT). No differences were observed when the cohorts were compared in terms of the frequency of PFS, OS, inflammatory markers and immune-related adverse events (irAEs). Similarly, the occurrence of irAEs was strictly correlated with a prolonged OS survival in both groups. On the contrary, a negative correlation between the high baseline levels of inflammatory markers and OS could be demonstrated in the younger cohort only. Overall, PD-1/PD-L1-blocking mAbs were equally effective in young and elderly mNSCLC patients; however, the detrimental influence of a systemic inflammation at the baseline was only observed in young patients, suggesting different aging-related inflammation immunoregulative effects.

Human Fecal Metabolome Reflects Differences in Body Mass Index, Physical Fitness, and Blood Lipoproteins in Healthy Older Adults

This study investigated how body mass index (BMI), physical fitness, and blood plasma lipoprotein levels are related to the fecal metabolome in older adults. The fecal metabolome data were acquired using proton nuclear magnetic resonance spectroscopy and gas chromatography-mass spectrometry on 163 healthy older adults (65-80 years old, 80 females and 83 males). Overweight and obese subjects (BMI ≥ 27) showed higher levels of fecal amino acids (AAs) (valine, alanine, and phenylalanine) compared to normal-weight subjects (BMI ≤ 23.5). Adults classified in the high-fitness group displayed slightly lower concentrations of fecal short-chain fatty acids, propionic acid, and AAs (methionine, leucine, glutamic acid, and threonine) compared to the low-fitness group. Subjects with lower levels of cholesterol in low-density lipoprotein particles (LDLchol, ≤2.6 mmol/L) displayed higher fecal levels of valine, glutamic acid, phenylalanine, and lactic acid, while subjects with a higher level of cholesterol in high-density lipoprotein particles (HDLchol, ≥2.1 mmol/L) showed lower fecal concentration of isovaleric acid. The results from this study suggest that the human fecal metabolome, which primarily represents undigested food waste and metabolites produced by the gut microbiome, carries important information about human health and should be closely integrated to other omics data for a better understanding of the role of the gut microbiome and diet on human health and metabolism.