Relationships between the proportion of dietary fiber intake and LPS biosynthesis pathway of human gut microbiota

Abstract

Dietary fiber in diet is primarily metabolized by human gut bacteria. Lipopolysaccharide (LPS) is an outer membrane component of the bacteria, which may regulate inflammation in the host human body. This study was designed to investigate how the biosynthesis of LPS in the gut microbiota varies with the balance of nutrients in the diet, especially to examine the relationship between the proportion of dietary fiber intake and LPS biosynthesis of gut microbiota. This study was conducted on 927 disease-free participants who gave informed consent in writing or on the web. The proportion of dietary fiber intake was calculated as the relative proportion of dietary fiber intake to the sum of protein, fat, carbohydrate, and dietary fiber intake (energy equivalent) in diet based on the Food Frequency Questionnaire. The biosynthesis of LPS was predicted by meta-16S rRNA gene analysis and PICRUSt2 as the relative proportion of LPS biosynthetic pathways present in the gut microbiota. The proportion of the LPS biosynthetic pathway was higher in obese than in normal-weight participants. Furthermore, the proportion of the LPS biosynthetic pathway was shown to be significantly associated with the proportion of dietary fiber intake, although not with that of protein, fat, or carbohydrate intake. However, in the participants by body mass index (BMI) category (lean, normal-weight, obese), a significant decrease in the proportion of LPS biosynthesis pathway due to the proportion of dietary fiber intake was detected only in the normal-weight group. These results suggest that the proportion of dietary fiber intake is associated with the biosynthesis of LPS of the gut microbiota, and also suggest the possibility that the effect of dietary fiber intake on the LPS depends on the host human's BMI.