Blueberry proanthocyanidins and anthocyanins improve metabolic health through a gut microbiota-dependent mechanism in diet-induced obese mice.

Blueberry consumption can prevent obesity-linked metabolic diseases and it has been proposed that its polyphenol content may contribute to these effects. Polyphenols have been shown to favourably impact metabolic health, but the role of specific polyphenol classes, and whether the gut microbiota is linked to these effects remains unclear. We aimed to evaluate the impact of whole blueberry and blueberry polyphenols against the development of obesity and insulin resistance, and to determine the potential role of gut microbes in these effects by using fecal microbiota transplantation (FMT). Seventy C57BL/6 male mice were assigned to one of the following diets for 12 weeks: balanced diet (Chow), high-fat high-sucrose (HFHS) diet, or HFHS supplemented with whole blueberry powder (BB), anthocyanidin (ANT) or proanthocyanidin (PAC)-rich extracts. After 8 weeks, mice were housed in metabolic cages and an oral glucose tolerance test (oGTT) was performed. Sixty germ-free mice fed HFHS diet received FMT from one of the above groups bi-weekly for 8 weeks, followed by an oGTT. PAC-treated mice were leaner than HFHS controls although they had the same energy intake and were more physically active. This observation was reproduced in germ-free mice receiving FMT from PAC-treated mice. PAC and ANT-treated mice showed improved insulin responses during oGTT, and this finding was also reproduced in germ-free mice following FMT. These results show that blueberry PAC and ANT polyphenols can reduce diet-induced body weight and improve insulin sensitivity, and that at least part of these beneficial effects are explained by modulation of the gut microbiota.