Effects of high fructose corn syrup on intestinal microbiota structure and obesity in mice

The study examines how high fructose corn syrup (HFCS), a widely used sweetener in foods and beverages, affects obesity-related phenotypes and gut microbiota in mice. Excessive HFCS intake has been linked to obesity, insulin resistance-related conditions including NAFLD, cardiovascular disease, type 2 diabetes, reproductive diseases, and cancer. The gut microbiota regulates host metabolism, immunity, and intestinal barrier function, and dysbiosis is associated with chronic diseases. Given limited research on HFCS-driven changes in gut microbiota composition, the authors used 16S rDNA sequencing to assess how HFCS ingestion alters intestinal microbiota diversity and composition, and correlated these changes with body weight, visceral and epididymal fat, and liver fat percentage to infer mechanisms by which microbiota changes may induce obesity signs.

Prior work links HFCS intake to metabolic disturbances such as NAFLD and diabetes. Gut microbiota plays extensive roles in lipid and carbohydrate metabolism, vitamin production, intestinal integrity, immune regulation, and pathogen defense; dysbiosis contributes to metabolic diseases including NAFLD, cardiovascular disease, obesity, T2DM, and metabolic syndrome. Studies show microbiota influences fat deposition (e.g., germ-free mice gain weight more slowly than conventional mice). Reports on Firmicutes/Bacteroidetes shifts in obesity are mixed, with some showing higher Firmicutes and Bacteroidetes in high-fat diet/obese states, while others show reduced Firmicutes-to-Bacteroidetes ratio and decreased microbial abundance. Lachnospiraceae can degrade dietary carbohydrates to contribute additional calories, potentially promoting obesity. Christensenellaceae abundance has been associated with host BMI, colorectal cancer, inflammatory bowel disease, and visceral fat, with evidence of a negative correlation between Christensenellaceae and visceral fat. Diets high in refined sugars have been associated with decreased Christensenellaceae R-7 group.

- Animals: Sixteen male SPF C57BL/6J mice, 3 weeks old, 18–22 g, from Shanghai SLAC Laboratory Animal Co., Ltd. Ethics approvals obtained (Zhejiang Provincial Ethics Committee for Laboratory Animals No. 78865576; Animal Experimentation License No. 286868667). - Design: After 1 week acclimation, mice were randomized into control (n=8) and HFCS (n=8) groups. Housing: 21 ± 2°C, 50–80% RH, 12-h light/dark, ad libitum food and water. - Diets and intervention: Normal Co60-irradiated feed (18.6% crude protein, 4.8% crude fat, 61% carbohydrate). HFCS (F55; 55% fructose, 45% glucose) administered as 30% (w/v) in drinking water to the HFCS group; controls received pure water. Duration: 16 weeks. - Sample collection: After 16 weeks, mice were anesthetized and dissected. Colons were removed and contents collected into sterile tubes and stored at −80°C for microbiota analyses. Livers were fixed in 4% paraformaldehyde; frozen sections were stained with Oil Red O and examined microscopically. - DNA extraction and sequencing: Genomic DNA from colonic contents was extracted using QIAamp DNA Stool Mini Kit; integrity confirmed by 1% agarose gel. V3+V4 regions of 16S rDNA were amplified with barcoded primers; amplicons were recovered from agarose gels. High-throughput sequencing was performed (platform not specified). Community richness, beta-diversity, taxonomic composition at phylum and genus levels, and differential genera were analyzed. - Bioinformatics and statistics: Beta-diversity clustering used R vegan package (vegdist, hclust). Heat maps of significantly different genera were generated. Phenotypic comparisons (body weight, fat depots, liver fat percentage) used two-sided t-tests; data reported as mean ± SEM. Correlations between selected genera (e.g., Christensenellaceae R-7 group, Tyzzerella, Erysipelatoclostridium, Helicobacter) and obesity indices (body weight, perirenal fat, epididymal fat, liver fat percentage) were assessed (details of correlation test not specified).

- Long-term intake of 30% (w/v) HFCS in drinking water for 16 weeks significantly increased obesity-related phenotypes: body weight (P=0.001), perirenal fat weight (P=0.0009), epididymal fat weight (P=0.007), and liver fat percentage (P<0.0001), with increased Oil Red O-positive lipid droplets in liver. - Colonic microbiota community richness was significantly decreased in HFCS mice versus controls; beta-diversity showed significantly distinct clustering between groups. - Dominant phyla in both groups were Firmicutes, Bacteroidetes, Proteobacteria, Actinobacteria, Tenericutes, and Deferribacteres (>99.29% of community). - At the genus level, top genera included Erysipelotrichaceae_uncultured, Bacteroidales S24-7 group_norank, Allobaculum, Faecalibaculum, Staphylococcus, Lactobacillus, Bacteroides, Lachnospiraceae_uncultured, Turicibacter, and Lachnospiraceae NK4A136. - Among 42 genera differing between groups, Tyzzerella (Lachnospiraceae) increased after HFCS, and conditional pathogens Erysipelatoclostridium and Helicobacter were significantly increased in HFCS mice. - Correlation analyses: Tyzzerella, Erysipelatoclostridium, and Helicobacter positively correlated with body weight, perirenal fat, epididymal fat, and liver fat percentage, whereas Christensenellaceae R-7 group was strongly negatively correlated with these obesity indices.

HFCS consumption led to increased body weight, visceral and epididymal fat, and hepatic lipid accumulation, paralleling prior evidence linking microbiota to fat deposition and metabolic disorders. The study observed HFCS-driven remodeling of the colonic microbiota, including decreased richness and distinct beta-diversity patterns. Literature indicates that specific taxa, such as Lachnospiraceae, can increase energy harvest from dietary carbohydrates, while Christensenellaceae are associated with lower BMI and visceral fat and are reduced by refined sugar diets. The present findings align with these reports: HFCS reduced Christensenellaceae R-7 group and increased genera (Tyzzerella, Erysipelatoclostridium, Helicobacter) that were positively associated with obesity indices. The strong negative correlation between Christensenellaceae R-7 group and body weight and fat measures suggests a potential mechanistic role of this taxon in mediating HFCS-induced obesity. Thus, HFCS may promote obesity by altering gut microbiota composition, particularly by decreasing Christensenellaceae R-7 group and increasing potentially obesogenic or pathogenic taxa, impacting host metabolic status.

This study demonstrates that long-term intake of 30% HFCS in drinking water significantly increases adiposity and hepatic fat in mice and induces marked alterations in colonic microbiota diversity and composition. Notably, Christensenellaceae R-7 group abundance was negatively associated with obesity-related phenotypes, while Tyzzerella, Erysipelatoclostridium, and Helicobacter were positively associated. These findings support the concept that HFCS may induce obesity via microbiota modulation, highlighting Christensenellaceae R-7 group as a potential protective taxon. Future research should elucidate the specific mechanisms linking HFCS, Christensenellaceae R-7 group dynamics, and host metabolic outcomes.

The study identifies that the specific mechanism by which HFCS affects the Christensenellaceae R-7 group and induces obesity remains unclear. Additional mechanistic investigations are needed.