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Effects of dietary fat on gut microbiota and faecal metabolites, and their relationship with cardiometabolic risk factors: a 6-month randomised controlled-feeding trial.

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PubMed ID: 30782617

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Wan Y, Wang F, Yuan J, Li J, Jiang D, Zhang J, Li H, Wang R, Tang J, Huang T, Zheng J, Sinclair AJ, Mann J, Li D

Gut. Feb 2019

COMMENT: In most developping countries, the rates of obesity and other cardiometabolic disorders suchs as type 2 diabetes and cardiovascular diseases have increased rapidly in parallel with a transition from a lower-fat diet to a lower carbohydrate and relatively high-fat diet. Studies in murine models suggest that a high-fat diet unbalances the gut microbiota and impairs the gut barrier, resulting in cardiometabolic diseases. This work presents the effects of different proportions of dietary fat intake on gut microbiota, faecal metabolomics and plasma inflammatory factors in healthy young adults. 

OBJECTIVE:

To investigate whether diets differing in fat content alter the gut microbiota and faecal metabolomic profiles, and to determine their relationship with cardiometabolic risk factors in healthy adults whose diet is in a transition from a traditional low-fat diet to a diet high in fat and reduced in carbohydrate.

MAIN RESULTS:

(...) whereas the community diversity estimated by the Shannon index was significantly increased in the lower-fat diet group relative to the higher-fat diet group.

Compared with the lower-fat diet, the higher-fat diet significantly increased the abundance of Bacteroidetes and decreased the abundance of the Firmicutes (...). At genus level, the lower-fat diet resulted in a significant increase in relative abundance of Blautia (p=0.007) and Faecalibacterium (p=0.04) after the intervention; while the higher-fat diet led to a reduction in Faecalibacterium (p=0.04) and an increase in Alistipes (p=0.04) and Bacteroides (p<0.001) (...). Compared with lower-fat diet, the higher-fat diet led to a significant decrease in Blautia and Faecalibacterium abundance, while there was a significant increase in the abundance of Alistipes and Bacteroides.

Individual metabolite analysis identified four significantly changed faecal metabolites, including three amino acid metabolites (p-cresol, indole and 3-indolepro- pionic acid) and one SCFA (butyric acid), in the lower-fat group after FDR correction (...). Among these four metabolites, two were decreased (p-cresol and indole) and two were increased (3-indolepropionic acid and butyric acid). While in the higher-fat group, eight faecal metabolites including long-chain saturated fatty acids, SCFAs and amino acid metabolites were found to be significantly changed. Among them, three were decreased (butyric acid, valeric acid and ethyl- methylacetic acid) and five were increased (indole, palmitic acid, stearic acid, arachidonic acid and indoleacetic acid). 

Plasma concentration of hs-CRP was significantly increased during the higher-fat diet intervention, compared with the moderate-fat (p for higher-fat vs moderate-fat <0.001) and lower-fat (p for higher-fat vs lower-fat <0.001) diet groups. Likewise, compared with the lower-fat diet, plasma concentration of the inflammatory mediators TXB2 was increased on the higher-fat diet (p for higher-fat vs lower-fat=0.02). Additionally, LTB4 and PGE2 were significantly decreased in the lower-fat diet group, when compared with moderate-fat diet group (p for lower-fat vs moderate-fat=0.006, 0.003, respectively) and higher-fat diet group (p for lower-fat vs higher-fat=0.02, <0.001, respectively). 

CONCLUSION:

In summary, compared with a lower-fat diet, long-term consumption of a higher-fat diet appears to be undesirable owing to changes in gut microbiota, faecal metabolomic profiles and proinflammatory factors for healthy young adults whose diet is in transition from the traditionally consumed lower fat, higher carbohydrate diet to one characterised by an appreciably higher fat content. These findings might also have relevance in developed countries in which fat intake is already high. 

Contributor

Raquel Ruiz-Arroyo