Peptidoglycan fragments decrease food intake and body weight gain in rats

Area of Science:

• Microbiology
• Immunology
• Physiology

Background:

• Bacterial infections often lead to appetite loss and weight reduction.
• Peptidoglycan (PG) is a major component of bacterial cell walls.
• The role of PG fragments in regulating appetite is not fully understood.

Purpose of the Study:

• To investigate the effects of purified soluble peptidoglycan (PG) fragments on appetite and body weight gain in rats.
• To determine the dose-dependency and structural requirements for PG-induced appetite suppression.

Main Methods:

• Rats received intraperitoneal injections of purified soluble PG fragments, with endotoxin removed.
• Food consumption and body weight gain were measured post-injection.
• Different molecular weights and structural modifications of PG fragments were tested, including muramyl dipeptide (MDP).

Main Results:

• Injections of both macromolecular and low-molecular-weight PG fragments dose-dependently reduced food intake and body weight gain in rats.
• Muramyl dipeptide (MDP) also suppressed appetite, but was less potent than macromolecular PG.
• Inactive PG fragments included muramidase-derived monomers and peptide cross-linked dimers.
• Appetite suppression was observed in both Lewis and F344 rat strains.
• Oral administration of PG fragments did not elicit a hypophagic response.

Conclusions:

• Soluble peptidoglycan fragments are potent appetite and weight gain suppressants in rats.
• Macromolecular PG is more potent than low-molecular-weight fragments, but O-acetylation and glycosidic linkage are not required for activity.
• PG fragments may contribute to appetite loss experienced during bacterial infections.