Increasing carbohydrates or nitrogenous compounds by cecal infusion leads to an opposite influence on colonic microbiota and host metabolism in a pig model
Bibliographic record
Abstract
Gut microbes, particularly those in the hindgut, play an important role in fermenting undigested nutrients (carbohydrates and proteins) and in regulating host metabolism via the gut-host metabolic axis. However, the effects of variations in the ratio of carbohydrates to proteins on host metabolism remain largely unknown. In this study, we investigated the response of large intestinal microbiota and host metabolism to changes in nutrient substrate availability by infusing corn starch or casein hydrolysate via cecal cannulas. Twenty-four growing pigs with cecal cannulas were randomly divided into three groups ( n = 8): a control group infused with saline; a starch group infused with corn starch; and a casein group infused with casein hydrolysate (50 g/d) dissolved in saline. The infusion was performed daily for 19 d. Compared with the control, starch infusion significantly increased the relative abundances of Bifidobacterium , Bacteroidales S24-7 group and Megasphaera ( P < 0.05), while decreasing Anaerovibrio , Campylobacter and Veillonella ( P < 0.05). Conversely, casein hydrolysate infusion significantly increased Streptococcus , Desulfovibrio and Mogibacterium ( P < 0.05), while decreasing Coprococcus and Ruminococcus at the genus level ( P < 0.05). Starch infusion increased short-chain fatty acid (SCFA) concentrations ( P = 0.001), whereas casein hydrolysate infusion reduced them ( P = 0.001); these effects were observed in both colonic digesta and liver. Additionally, serum metabolomics and liver gene expression analysis revealed that host metabolic states were significantly altered in different ways following starch and casein hydrolysate infusion ( P < 0.05). Starch infusion enhanced host energy metabolism, gluconeogenesis and lipid metabolism by increasing concentrations of tricarboxylic acid (TCA) cycle-related metabolites (e.g., succinic acid, oxaloacetic acid, L-malic acid) and fatty acid (FA) synthesis (e.g., D-glyceric acid, stearic acid and palmitic acid) ( P < 0.05), alongside upregulation of FA synthase ( FAS ), stearoyl-CoA desaturase ( SCD ), acetyl-CoA carboxylase ( ACC ), phosphoenolpyruvate carboxykinase 1 ( PCK1 ) and pyruvate kinase ( PK ) gene expression ( P < 0.05). In contrast, casein hydrolysate infusion enhanced glycolysis and reduced FA synthesis by increasing glucose-6-phosphate, L-lactic acid, glycerol, glycolic acid, etc. ( P < 0.05), in parallel with upregulation of acyl-CoA oxidase 1 ( ACOX-1 ), peroxisome proliferator-activated receptors α ( PPAR-α ), carnitine palmitoyltransferase-1α ( CPT-1α ) and PK gene expressions in the liver ( P < 0.05). Correlation result demonstrated a strong association between altered gut microbiota and several serum metabolites ( P < 0.05). In summary, these results indicate that increasing carbohydrate or nitrogenous compound levels in the large intestine can distinctly alter microbiota composition, thereby influencing host metabolism. These findings provide novel insights into the crosstalk between the large intestinal microbiome and host metabolism.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".