Abstract
Kale (Brassica oleracea var. acephala) is a vegetable common in most cultures but is less studied as a functional food compared to other cruciferous vegetables, such as broccoli. We investigated the effect of supplementing a high-fat diet (HFD) with kale (HFKV) in C57BL/6J mice. We particularly explored its role in metabolic parameters, gut bacterial composition and diversity using 16S rRNA sequencing, systematically compared changes under each phylum and predicted the functional potential of the altered bacterial community using PICRUSt2. Like other cruciferous vegetables, kale attenuated HFD-induced inflammation. In addition, kale modulated HFD-induced changes in cecal microbiota composition. The HFD lowered bacterial diversity, increased the Firmicutes: Bacteroidetes (F/B) ratio and altered composition. Specifically, it lowered Actinobacteria and Bacteroidetes (Bacteroidia, Rikenellaceae and Prevotellaceae) but increased Firmicutes (mainly class Bacilli). Kale supplementation lowered the F/B ratio, increased both alpha and beta diversity and reduced class Bacilli and Erysipelotrichi but had no effect on Clostridia. Within Actinobacteria, HFKV particularly increased Coriobacteriales/Coriobacteriaceae about four-fold compared to the HFD (p < 0.05). Among Bacteroidia, HFKV increased the species Bacteroides thetaiotaomicron by over two-fold (p = 0.05) compared to the HFD. This species produces plant polysaccharide digesting enzymes. Compared to the HFD, kale supplementation enhanced several bacterial metabolic functions, including glycan degradation, thiamine metabolism and xenobiotic metabolism. Our findings provide evidence that kale is a functional food that modulates the microbiota and changes in inflammation phenotype.
Highlights
Diet has increasingly become a key strategy for preventing disease and improving health conditions
We report that supplementing the high-fat diet (HFD) with kale increases bacterial diversity and impacts the community structure of the microbiota and its metabolic function, with the most abundant changes attributed to the abundance of bacteria within the family Coriobacteriaceae and the species B. thetaiotaomicron and their metabolic functions
Calorie intake was not different among the three groups but the HFD induced significantly higher body weight, insulin resistance and inflammation compared to the low-fat diet (LFD)
Summary
Diet has increasingly become a key strategy for preventing disease and improving health conditions. In this context, cruciferous vegetables (genus Brassica) have been investigated for several years. Cabbage, cauliflower and brussels sprouts are the most popular brassica crops. Broccoli has been the most widely studied and widely reviewed cruciferous vegetable. Acephala), traditionally a less recognized member of the genus Brassica, has gained popularity in the United States in recent years. It has become an important crop in the southern US as a result of its suitability to year-round growing conditions [1]. Similar to other cruciferous vegetables, phytochemicals in kale include sulfur-containing indolic glucosinolates and aliphatic glucosinolates, polyphenols like the flavonoid glycosides of quercetin, kaempferol and isorhamnetin and carotenoid groups [3,4,5,6]
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