Changes in Gut Bacteriome Composition on Low-Carbohydrate Diet in Children with Type 1 Diabetes

Objectives: Low-carbohydrate diet (LCD) is a controversial but popular dietary choice for many children and adolescents with type 1 diabetes (CwD). In a cross-over trial with LCD (clinicaltrials.gov NCT05078658), we assessed whether even a short period of tightly controlled LCD is able to change the gut bacteriome in CwD. Methods: Twenty CwD (aged 15.1±3.0 years) were recruited into an intervention trial with a 5-week period of LCD (95±3 g carbs daily) followed by 5 weeks of regular carbohydrate diet (RCD) (193±18 g carbs daily) with the order randomized. The diets did not differ in energy intake (8360 vs. 8392 kJ, P=0.08). The fecal samples were collected regularly before, after and throughout the interventions (median number of samples collected per subject was 12, IQR 10-15). The fecal bacteriome was assessed using massively parallel sequencing of the variable regions V3-V4 of 16S rDNA. Mixed effects regression models were built where responses were principal components of the bacteriome community, alpha diversity indices and individual taxa. The predictors were the type of the diet, time since start of the diet and randomized order of the diets. Results: We observed shifts in the bacteriome community composition on the LCD which were apparent at all taxonomic levels (P for various principal components ranging from 5×10-4 to 0.015); their magnitude was however moderate. Of individual taxa, Bifidobacterium sp. and its higher taxonomic categories were negatively associated with LCD; the overall effects observed on the community composition were however broader than could be explained by changes in this single taxon. The alpha diversity decreased with time regardless of the intervention sequence, but did not associate with LCD. Conclusions: Even a short period of LCD is associated with subtle yet significant changes in the stool bacteriome community composition mainly in the Bifidobacterium sp. The observed changes may help us understand the possible effects of LCD on T1D. Disclosure V.Neuman: None. O.Cinek: None. L.Hlináková: None. L.Plachy: None. L.Petruzelkova: None. B.Obermannova: None. S.Pruhova: None. S.Kolouskova: None. J.Havlik: None. Z.Sumnik: None. Funding Czech Ministry of Health (AZVNU21-01-00085)