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

Abstract

The human fecal metabolome is increasingly studied to explore the impact of diet and lifestyle on health and the gut microbiome. However, systematic differences and confounding factors related to age, sex, and diet remain largely unknown. In this study, absolute concentrations of fecal metabolites from 205 healthy Danes (105 males and 100 females, 49 ± 31 years old) were quantified using 1 H NMR spectroscopy and the newly developed SigMa software. The largest systemic variation was found to be highly related to age. Fecal concentrations of short-chain fatty acids (SCFA) were higher in the 18 years old group, while amino acids (AA) were higher in the elderly. Sex-related metabolic differences were weak but significant and mainly related to changes in SCFA. The concentrations of butyric, valeric, propionic, and isovaleric acids were found to be higher in males compared to females. Sex differences were associated with a stronger, possibly masking, effect from differential intake of macronutrients. Dietary fat intake decreased levels of SCFA and AA of both sexes, while carbohydrate intake showed weak correlations with valeric and isovaleric acids in females. This study highlights some possible demographic confounders linked to diet, disease, lifestyle, and microbiota that have to be taken into account when analyzing fecal metabolome data.

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

“…This discrepancy may be because the study by Barton et al was performed as a long-term fitness intervention, while the present study only included baseline fitness levels of free-living community-dwelling older adults who have not (yet) been under specific physical training. Moreover, the older subjects in this study showed significantly lower concentrations of SCFAs than younger, 18-years-old, subjects did, as previously reported [26]. However, the increased concentrations of SCFAs in LF subjects may also be explained by the altered regulation of glucose transport, fatty acid oxidation, and steroid biosynthesis in LF subjects compared to HF subjects [36,37], and this increase has also been related to different rates of glucose homeostasis and lipid metabolism between HF and LF subjects [38].…”

“…It has been shown that LF subjects were eating more protein than the HF subjects [14]. Although this difference in protein consumption does not influence the fecal AA levels, it weakly affects the isovaleric acid and propionic acid levels [26]. In feces, AAs derive from the endogenous metabolism of the gut microbiome [39], and the effect of fitness on changing fecal AA levels is elusive [40].…”

“…The human fecal metabolome was investigated by employing two analytical platforms, namely 1 H NMR spectroscopy and GC-MS. Absolute concentrations of 36 human fecal metabolites and the relative concentrations of 76 unknown spin systems were quantified from 1 H NMR spectra, as described previously [16]. The mean absolute concentrations of the 36 human fecal metabolites are reported in Cui et al [26]. These fecal metabolites covered five SCFAs, 13 AAs, five organic acids (OAs), two sugars, namely glucose and galactose, one nucleobase (uracil), and 11 other common metabolites, including ethanol, trimethylamine, methanol, carnitine, glycerol, guanidinoacetic acid, betaine, xanthine, acetone, and formic acid (Table S1, Cui et al, 2021).…”

“…The mean absolute concentrations of the 36 human fecal metabolites are reported in Cui et al [26]. These fecal metabolites covered five SCFAs, 13 AAs, five organic acids (OAs), two sugars, namely glucose and galactose, one nucleobase (uracil), and 11 other common metabolites, including ethanol, trimethylamine, methanol, carnitine, glycerol, guanidinoacetic acid, betaine, xanthine, acetone, and formic acid (Table S1, Cui et al, 2021). SCFAs and AAs were found to have the highest concentration in fecal metabolites in all subjects, regardless of sex, age, and fitness.…”

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

“…At the same time, the gut microbiome also plays a pivotal role in shaping systemic immune responses and is known to influence the efficacy of immune checkpoint inhibitors [35,36]. Despite the knowledge of the influence of sex, age and diet on the gut microbiome, little is known to what extent these parameters can affect the response to immunotherapy [37,38].…”