With a constantly growing elderly population, incidences of neurodegenerative diseases are also rising and are expected to further increase over the next years, while costing health systems across the world trillions of dollars. Therefore, biomarkers to detect manifestations of brain aging early and interventions to slow down its pace are of great interest. In the last years, the importance of the neurotrophins brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) in the context of cognitive function and the aging brain has increased, besides the already well-established amyloid-beta (Aβ) and tau plaques. Due to their wide range of beneficial health effects as well as their antioxidant and anti-inflammatory properties, a class of secondary plant-metabolites, the so-called polyphenols, gained increasing attention. In this review, we discuss the roles of BDNF, Aβ, NGF, and tau proteins as biomarkers of brain aging and the effect of dietary polyphenol interventions on these biomarkers, assessed via blood analysis, magnetic resonance imaging (MRI), and positron emission tomography (PET).

Contrary to carbohydrate and fat metabolism, the influence of a single exercise dose on protein metabolism has not been adequately explored yet. We assessed the effects of different exercise intensities and durations on blood protein changes and their association with carbohydrate (CHO) and fat metabolism in six eligible trained subjects. Subjects performed maximal incremental (IE₁₀₀: at 100%VO_2max) and submaximal continuous exercise (CE) at 75%VO_2max for 30 min (CE₇₅) and at 50%VO_2max for 90 min (CE₅₀). Blood samples were collected at rest (R), end of exercise (EE), and 1 h after recovery to assess blood urea nitrogen (BUN), plasma amino acids (AA), glucose, lactate, FFA, and glycerol. In IE₁₀₀ blood lactate, CHO-oxidation (g/min), energy expenditure (kcal/min), and RER were significantly increased during rest (p < 0.05). CE₅₀ induced significantly higher BUN, FFA, glycerol, and fat oxidation (g/min) (p < 0.05). At recovery, the mean sum of the free AA pool (µmol/L) reduced by 8% (p < 0.03) during CE₅₀. Values for CE₇₅ were between IE₁₀₀ and CE₅₀. Beside lipolysis, also proteolysis (BUN) was an important source of fuel for low-to-moderate intensity CE₅₀. An increased uptake of AA from the plasma bed during CE₅₀ suggests the importance for oxidation and synthesis of other metabolic sources such as gluconeogenesis necessary for recovery. Therefore, one needs to be cautious of protein diet following prolonged cycle exercise training.

Ageing is a process characterised by chronic low-grade inflammation and oxidative stress which could lead to increased prevalence of both physical and mental age-related chronic conditions. A healthy balanced diet, rich in fruit and vegetables as well as omega-3 polyunsaturated fatty acids (n3 PUFA), could reduce oxidative stress and improve markers of low-grade inflammation. Nonetheless, considering that a large part of the population struggles to meet current guidelines on fruit and vegetable and n3 PUFA recommendations, fruit and vegetable concentrate supplements and mixed omega fatty acid supplements could be an effective strategy to bridge the gap between actual and recommended intakes. In this randomised, controlled, open-labelled, parallel-grouped clinical trial, 112 participants will be allocated to one of four arms (n = 28 on each arm): an encapsulated juice powder concentrate, a plant-based omega fatty acid supplement, both or a control group. We aim to investigate whether long-term separate or combined ingestion of the two can affect biomarkers of cardiovascular health, low-grade inflammation and indicators of ageing, including cognitive function, in middle-aged and elderly people. We will additionally explore the effect of the different supplementations on plasma levels of vitamins, carotenoids and fatty acids. Intervention will last 2 years and participants will be assessed at baseline and at follow-up visits at 6, 12, 18 and 24 months. This study will provide evidence whether long-term, plant-based dietary supplementation can support cardiovascular health, anti-inflammatory processes, immunity and nutritional status in ageing. Trial registration This trial was registered at ClinicalTrials.gov (NCT04763291) on February 21, 2021.