Whey Protein Augments Leucinemia and Post-Exercise p70S6K1 Activity Compared to a Hydrolysed Collagen Blend When in Recovery From Training With Low Carbohydrate Availability

We examined the effects of whey versus collagen protein on skeletal muscle cell signalling responses associated with mitochondrial biogenesis and protein synthesis in recovery from an acute training session completed with low carbohydrate (CHO) availability. In a repeated measures design (after adhering to a 36-h exercise-dietary intervention to standardise pre-exercise muscle glycogen), eight males completed a 75-min non-exhaustive cycling protocol and consumed 22 g of a hydrolysed collagen blend (COLLAGEN) or whey (WHEY) protein 45 min prior to exercise, 22 g during exercise and 22 g immediately post-exercise. Exercise decreased (P0.05) was observed for p53, Parkin and Beclin1 mRNA. Exercise suppressed (P<0.05) p70S6K1 activity in both conditions immediately post-exercise (≈ 25 fmol.min-1.mg-1). Post-exercise feeding increased p70S6K1 activity at 1.5 h post-exercise (P<0.05), the magnitude of which was greater (P <0.05) in WHEY (180 ± 105 fmol.min-1.mg-1) versus COLLAGEN (73 ± 42 fmol.min-1.mg-1). We conclude that protein composition does not modulate markers of mitochondrial biogenesis when in recovery from a training session deliberately completed with low CHO availability. In contrast, whey protein augments post-exercise p70S6K activity compared with hydrolysed collagen, as likely mediated via increased leucine availability

Multiple AMPK activators inhibit L-Carnitine uptake in C2C12 skeletal muscle myotubes

Mutations in the gene that encodes the principal L-Carnitine transporter, OCTN2, can lead to a reduced intracellular L-Carnitine pool and the disease Primary Carnitine Deficiency. L-Carnitine supplementation is used therapeutically to increase intracellular L-Carnitine. As AMPK and insulin regulate fat metabolism and substrate uptake we hypothesised that AMPK activating compounds and insulin would increase L-Carnitine uptake in C2C12myotubes. The cells express all three OCTN transporters at the mRNA level and immunohistochemistry confirmed expression at the protein level. Contrary to our hypothesis, despite significant activation of PKB and 2DG uptake, insulin did not increase L-Carnitine uptake at 100nM. However, L-Carnitine uptake was modestly increased at a dose of 150nM insulin. A range of AMPK activators that increase intracellular calcium content [caffeine (10mM, 5mM, 1mM, 0.5mM), A23187 (10&mu;M)], inhibit mitochondrial function [Sodium Azide (75&mu;M), Rotenone (1&mu;M), Berberine (100&mu;M), DNP (500&mu;M)] or directly activate AMPK [AICAR (250&mu;M)] were assessed for their ability to regulate L-Carnitine uptake. All compounds tested significantly inhibited L-Carnitine uptake. Inhibition by caffeine was not dantrolene (10&mu;M) sensitive. Saturation curve analysis suggested that caffeine did not competitively inhibit L-Carnitine transport. However, the AMPK inhibitor Compound C (10&mu;M) partially rescued the effect of caffeine suggesting that AMPK may play a role in the inhibitory effects of caffeine. However, caffeine likely inhibits L-Carnitine uptake by alternative mechanisms independently of calcium release. PKA activation or direct interference with transporter function may play a role

Protein‐carbohydrate ingestion alters Vps34 cellular localization independent of changes in kinase activity in human skeletal muscle

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this recordData Availability Statement: The data that support the findings of this study are available from the corresponding author upon reasonable request.The Class III PI3Kinase, Vps34, has recently been proposed as a nutrient sensor, essential for activation of the mechanistic target of rapamycin (mTOR) complex 1 (mTORC1). We therefore investigated the effects of increasing nutrient availability through protein‐carbohydrate (PRO‐CHO) feeding on Vps34 kinase activity and cellular localization in human skeletal muscle. Eight young, healthy males (21 ± 0.5 yrs, 77.7 ± 9.9 kg, 25.9 ± 2.7 kg/m2, mean ± SD) ingested a PRO‐CHO beverage containing 20/44/1 g PRO/CHO/FAT respectively, with skeletal muscle biopsies obtained at baseline and 1 h and 3 h post‐feeding. PRO‐CHO feeding did not alter Vps34 kinase activity, but did stimulate Vps34 translocation toward the cell periphery (PRE (mean ± SD) – 0.273 ± 0.040, 1 h – 0.348 ± 0.061, Pearson's Coefficient (r)) where it co‐localized with mTOR (PRE – 0.312 ± 0.040, 1 h – 0.348 ± 0.069, Pearson's Coefficient (r)). These alterations occurred in parallel to an increase in S6K1 kinase activity (941 ± 466% of PRE at 1 h post‐feeding). Subsequent in vitro experiments in C2C12 and human primary myotubes displayed no effect of the Vps34‐specific inhibitor SAR405 on mTORC1 signalling responses to elevated nutrient availability. Therefore, in summary, PRO‐CHO ingestion does not increase Vps34 activity in human skeletal muscle, whilst pharmacological inhibition of Vps34 does not prevent nutrient stimulation of mTORC1 in vitro. However, PRO‐CHO ingestion promotes Vps34 translocation to the cell periphery, enabling Vps34 to associate with mTOR. Therefore, our data suggests that interaction between Vps34 and mTOR, rather than changes in Vps34 activity per se may be involved in PRO‐CHO activation of mTORC1 in human skeletal muscle.University of Birmingha