Dietary quercetin enhances flight endurance and insecticide tolerance in honey bees

Quercetin is a common and abundant flavonoid in pollen and honey. Previous research has revealed that consumption of certain flavonoids affects CYP450 gene expression and influences detoxification of pesticides of honey bees. Quercetin has also been found to affect energy production in cells, in vitro and to  increase energy expenditure in mice and exercise performance in humans. However, there is very little known about the effects of dietary quercetin in honey bees. In this research, we designed a “flight treadmill” for bees to examine the flight performance of quercetin-treated foragers. The foragers from a quercetin-treated colony (for 6 weeks) exhibited higher frequencies of wing flapping than the foragers from the control colony. This finding suggests that quercetin-treated foragers are capable of flying faster. A biochemical assay showed that the ATP concentrations in flight muscles of quercetin-treated foragers (≈ 37.5 pmol ATP / mg protein) were about four times higher than in the foragers from a control colony, which indicates that the quercetin-treated foragers may have a higher metabolic rate. In addition, when the synthetic pyrethroid insecticide bifenthrin or cyfluthrin was added to a sugar syrup diet, the foragers that consumed quercetin simultaneously possessed a higher tolerance to the toxicity and could fly longer before paralysis set in than foragers treated with pyrethroids alone. Interestingly, the rescue effect of quercetin did not occur with a neonicotinoid, imidacloprid. In sum, quercetin enhances flying performance as well as tolerance of foragers to the pyrethroid insecticides; this ubiquitous dietary constituent thus appears to play a central role in regulating honey bee health.