Description:
<jats:sec><jats:title>Background and aim</jats:title><jats:p>Inadequacies of micronutrients with antioxidant‐properties are common among older adults and have been associated with higher risk of frailty, adverse functional outcome and impaired muscle health. However, a causal relationship is less well known. The aim was to determine in old mice the impact of reduced dietary intake of vitamins A/E/B6/B12/Folate, selenium and zinc on muscle mass, oxidative capacity, strength and physical activity (PA) over time.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>21‐months‐old mice were fed either AIN‐93M or a diet low in micronutrients with antioxidant‐properties (=LOWOX: 50% of mouse recommended daily intake of vitamin A/E/B6/B12/folate/selenium/zinc) for 4 months. Muscle mass, grip strength, PA, and general oxidative status (liver malondialdehyde (MDA)) were assessed and m. <jats:italic>tibialis anterior</jats:italic> (TA) was used to determine <jats:italic>ex vivo</jats:italic> muscle protein synthesis (MPS via SUnSET method) and breakdown (MPB via 3‐methylhistine release). Moreover, muscle fatigue was measured on m. <jats:italic>extensor digitorum longus</jats:italic> (<jats:italic>EDL)</jats:italic> during an <jats:italic>ex‐vivo</jats:italic> moderate exercise‐protocol. Effects on oxidative capacity (succinate dehydrogenase (SDH) activity), muscle fiber type, number and cross‐sectional area (FCSA) were assessed on m.p<jats:italic>lantaris (PL</jats:italic>) using histochemistry.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>From 2 months on the diet, bodyweight of LOWOX‐mice was lower compared to control‐mice (P<0.0001) without difference in food intake, and mainly due to lower fat mass (P<0.0001). After 4 months, oxidative status of LOWOX‐mice was lower, demonstrated by decreased vitamin E plasma levels (P<0.05) and increased liver MDA levels (P=0.018). PA was significantly lower in LOWOX‐mice (P<0.001). Muscle mass was not affected, although <jats:italic>PL</jats:italic>‐FCSA was decreased (~16%; P=0.028) while SDH‐activity and muscle fiber type distribution remained unaffected. The <jats:italic>ex vivo</jats:italic> anabolic response to amino acid enriched buffer was totally blunted in LOWOX‐mice (P=0.039) with an increase of MPB (P=0.036). In LOWOX‐mice, <jats:italic>EDL‐</jats:italic>force production was decreased at lower stimulation frequencies (P=0.038) and fatigue resistance was diminished (P=0.023).</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>Reduced dietary intake of vitamins A/E/B6/B12/Folate/selenium/zinc has major impact on muscle health as shown by decreased force production and PA, without effects on muscle mass. Moreover, muscle protein turnover was affected. The reduced FCSA in combination with lack of effect on SDH‐activity suggests that such dietary reductions cause muscle fiber atrophy and reduced muscle oxidative capacity resulting in reduced muscle fatigue resistance.</jats:p></jats:sec>