Parasutterella excrementihominis is associated with attenuated metabolic improvements during obesity therapy in humans.

Parasutterella excrementihominis abundance was significantly reduced during the weight reduction phase of an obesity therapy program.

• Study enrolled n=215 human subjects in an interdisciplinary non-surgical obesity therapy program
• The program consisted of an initial weight-reduction phase (weeks 1-12) followed by a weight-maintenance phase (weeks 13-26)
• P. excrementihominis was quantified by qPCR
• The reduction in abundance was statistically significant during weeks 1-12

Baseline P. excrementihominis abundance did not predict success of weight reduction but was inversely associated with C-reactive protein improvements.

• Baseline abundance levels were not predictive of the degree of weight loss achieved during the intervention
• Higher baseline levels of P. excrementihominis were associated with attenuated improvements in C-reactive protein (CRP), an inflammatory marker
• This suggests the bacterium influences inflammatory rather than weight outcomes at baseline

The decrease in P. excrementihominis abundance during the weight reduction phase was positively correlated with improvements in insulin sensitivity throughout the overall obesity intervention.

• Greater reductions in P. excrementihominis during weeks 1-12 were associated with greater improvements in insulin sensitivity
• This association was observed across the full 26-week intervention period
• The finding suggests a mechanistic link between this bacterium and insulin resistance in obese humans

Re-increase of P. excrementihominis abundance during the weight maintenance phase was significantly associated with weight regain.

• During the weight-maintenance phase (weeks 13-26), P. excrementihominis levels re-increased in some subjects
• This re-increase was significantly associated with weight regain during the maintenance phase
• The finding highlights a potential role of this bacterial species in metabolic adaptation and weight maintenance after initial weight loss

Parasutterella species had previously been found to be increased in human obesity and type 2 diabetes and linked to abnormalities in triglyceride metabolism and L-cysteine homeostasis.

• Prior findings came from the cross-sectional FoCus cohort
• Parasutterella species were elevated in subjects with obesity and type 2 diabetes
• Associations were identified with abnormal triglyceride metabolism
• L-cysteine homeostasis disruption was also linked to Parasutterella, noted as important for beta-cell function