A protease-containing kiwifruit alters postprandial plasma and brain bioamine concentrations in a growing pig model for adult humans

Objective: In vitro digestion and fermentation studies show kiwifruit (KF) modulates bioamines but whether this translates to central neurochemical changes in vivo remains unclear. This study investigated the temporal effects of a dietary protease found in green KF (actinidin) on plasma and brain neurotransmitters and related compound concentrations, including γ-aminobutyric acid (GABA) and serotonin, which play key roles in central neurotransmission, using a porcine model.Methods: Entire male pigs (n = 48) were fed either two green KF (actinidin-containing, Actinidia deliciosa cv. Hayward) or two gold KF (actinidin-free control, Actinidia chinensis cv. Hort16A) with soda bread, equivalent to a habitual serving of KF. Pigs were euthanised at 20 min, 1, 2, and 5 h postprandially (n = 6/treatment/time). Jugular plasma and brain tissues (brain stem, striatum, hippocampus, and prefrontal cortex) were analysed via liquid chromatography-mass spectrometry. Data were analysed using polynomial regression models to assess treatment, time, and interaction effects (P < 0.05).Results: Plasma histidine increased more after green than gold KF. Most bioamine concentrations in all brain regions increased over time (P < 0.05), peaking two hours postprandially with green KF, while gold KF decreased metabolite concentrations initially before increasing. GABA concentrations increased in all brain regions with green KF over time but decreased with gold KF. Green KF also led to sustained serotonin levels in the hippocampus, while gold KF caused an initial increase followed by a decrease after two hours.Discussion: Brain bioamines increased more after protease containing green KF than gold KF, suggesting actinidin may contribute to central bioaminergic modulation in vivo and influence neurotransmission-related pathways.