Allium species and their organosulfur-derived compounds could prevent obesity and metabolic dysfunction, as they exhibit immunomodulatory and antimicrobial properties. Here, we report the anti-obesogenic potential and dose-dependent effects (0.1 or 1 mg/kg/day) of propyl propane thiosulfinate (PTS) in a murine model of diet-induced obesity. The obesogenic diet increased body weight gain and adipocyte size, and boosted inflammatory marker (Cd11c) expression in the adipose tissue. Conversely, PTS prevented these effects in a dose-dependent manner. Moreover, the higher dose of PTS improved glucose and hepatic homeostasis, modulated lipid metabolism, and raised markers of the thermogenic capacity of brown adipose tissue. In the colon, the obesogenic diet reduced IL-22 levels and increased gut barrier function markers (Cldn3, Muc2, Reg3g, DefaA); however, the highest PTS dose normalized all of these markers to the levels of mice fed a standard diet. Gut microbiota analyses revealed no differences in diversity indexes and only minor taxonomic changes, such as an increase in butyrate producers, Intestimonas and Alistipes, and a decrease in Bifidobacterium in mice receiving the highest PTS dose. In summary, our study provides preclinical evidence for the protective effects of PTS against obesity, which if confirmed in humans, might provide a novel plant-based dietary product to counteract this condition.

Excess energy intake contributes to adiposity in obesity. We investigated whether the human intestinal bacterium Phascolarctobacterium faecium could prevent obesity via enteroendocrine pathways in a mouse model of diet-induced obesity (DIO). Daily administration of P. faecium (2 × 10⁹ cells/mouse) reduced food intake through the early overproduction of the satiety hormone peptide YY (PYY) compared to untreated DIO mice. Moreover, P. faecium increased the intestinal levels of branched-chain amino acids, which, in turn, stimulated PYY secretion in neuroendocrine cell cultures and also modified gut microbiota composition. A pair-feeding study demonstrated that the anorexigenic effect of P. faecium contributes to its effects in attenuating body weight gain in DIO mice, but that other mechanisms are also involved in its metabolic benefits. Specifically, P. faecium accelerated gut transit and serum lipid clearance, thereby limiting adiposity independently of food intake. This study identifies the mode of action of a human intestinal bacterium recently linked to obesity protection, providing valuable insights into host-microbe interactions governing body weight.

Background/Objectives: The prevalence of the commensal gut bacterium species, Phascolarctobacterium faecium, has been associated with normal weight in humans. Preclinical evidence suggests that the strain P. faecium DSM 32890 exerts beneficial effects on metabolic and immune function in diet-induced obesity. Herein, we aimed to evaluate the safety and tolerability of this strain in a preclinical study and a pilot interventional trial in humans. Methods: A repeated-dose oral toxicity study of 28 days was performed in Wistar rats (male and female), during which adverse signs and clinical outcomes were assessed, along with histological, hematologic, biochemical, and immune markers. Subsequently, a pilot human intervention trial was conducted, including 20 participants (11 overweight and 9 normal weight) who received P. faecium DSM 32890 daily for 15 days. Body composition, dietary intake, physical activity, clinical data, perceived health, gastrointestinal symptoms, and blood analyses were assessed to determine tolerability and identify potential adverse effects. Results: In rats, the administration of the bacterium did not cause behavioral, physiological, histologic, immune, or biochemical alterations. In humans, there was no evidence of adverse effects on general health, hematological and biochemical profiles, bowel habits, or gastrointestinal symptoms. Overweight participants experienced reductions in flatulence and nausea after the intervention. Conclusions: The consumption of P. faecium DSM 32890 did not raise safety concerns and was well tolerated in rats and humans. The findings represent a step forward in the path toward future, longer-term studies to explore the potential efficacy.