SØBORG, Denmark—Consumption of apple pectin, but not whole apples or other apple products, increases the population of Clostridiales species producing butyrate and beta-glucuronidase in the intestines of rats, while depressing populations of Bacteroidetes, according to a new study published in BMC Microbiology.
Researchers fed rats a diet rich in whole apples, apple juice, purée or pomace, or put them on a control diet. They analyzed the microbial content of the rats’ digestive systems to see if eating apples had any impact on the numbers of presumed ‘friendly’ bacteria in the gut.
Principal Component Analysis (PCA) of cecal microbiota profiles obtained by PCR-DGGE targeting bacterial 16S rRNA genes showed an effect of whole apples in a long-term feeding study (14 weeks), while no effects of apple juice, puree or pomace on microbial composition in cecum were observed. Administration of either 0.33 or 3.3 percent apple pectin in the diet resulted in considerable changes in the DGGE profiles. A twofold increase in the activity of beta-glucuronidase was observed in animals fed with pectin (7% in the diet) for four weeks, as compared to control animals (P<0.01). The level of butyrate measured in these pectin-fed animal was more than double of the corresponding level in control animals (P<0.01). Sequencing revealed that DGGE bands, which were suppressed in pectin-fed rats, represented Gram-negative anaerobic rods belonging to the phylum Bacteroidetes, whereas bands that became more prominent represented mainly Gram-positive anaerobic rods belonging to the phylum Firmicutes, and specific species belonging to the Clostridium Cluster XIVa. Quantitative real-time PCR confirmed a lower amount of given Bacteroidetes species in the pectin-fed rats as well as in the apple-fed rats in the four-week study (P<0.05). Additionally, a more than four-fold increase in the amount of Clostridium coccoides (belonging to Cluster XIVa), as well as of genes encoding butyryl-coenzyme A CoA transferase, which is involved in butyrate production, was detected by quantitative PCR in fecal samples from the pectin-fed animals.