Co-ingestion of carbohydrate and whey protein isolates enhance PGC-1α mRNA expression: a randomised, single blind, cross over study

Abstract

Background: Whey protein isolates (WPI) supplementation is known to improve resistance training adaptations. However, limited information is available on the effects of WPI plus carbohydrate (CHO) supplementation on endurance training adaptations.

Method: Six endurance trained male cyclists and triathletes (age 29 ± 4 years, weight 74 ± 2 kg, VO2 max 63 ± 3 ml oxygen. kg-1. Min-1, height 183 ± 5 cm; mean ± SEM) were randomly assigned to one of two dietary interventions in a single blind cross over design; CHO or CHO + WPI. Each dietary intervention was followed for 16 days which included the last 2 days having increased CHO content, representing a CHO loading phase. The dietary interventions were iso-caloric and carbohydrate content matched. On completion of the dietary intervention, participants performed an exercise bout, consisting of cycling for 60 min at 70% VO2 max, followed by time trial to exhaustion at 90% VO2 max and recovered in the laboratory for 6 hours. Blood samples and muscle biopsies were taken at various time points at rest and through the exercise trial and recovery.

Results: Compared to CHO, CHO + WPI increased plasma insulin during recovery at 180 mins (P < 0.05) and peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) mRNA expression at the end of 6 hours of recovery (P < 0.05). Muscle glycogen did not differ between the two trials.

Conclusion: This study showed co-ingestion of CHO + WPI may have beneficial effects on recovery and adaptations to endurance exercise via, increased insulin response and up regulation of PGC-1α mRNA expression.

Figure 1

Plasma glucose concentration for carbohydrate (CHO) and carbohydrate and whey protein isolates (CHO + WPI) trials. The exercise trial day consisted of 60 min cycling at 70% VO_2 max, with blood samples taken at rest and every 20 min (rest, 20, 40, 60). This was followed by time to fatigue at 90% VO_2 max and blood was taken on completion of this effort (0). The 6 h recovery consisted of blood taken regularly for the first h (10, 20, 30, 40, 60) and every 60 min after that (120, 180, 240, 300, 360). Both CHO and CHO + WPI trials were significantly increased on completion of cycling at 90% VO_2max and remained elevated compared to rest until 40 min during recovery in the CHO + WPI trial (# P < 0.05). Whilst the CHO group remained elevated compared to rest until 60 min during recovery (* P < 0.05). Values are means ± SEM (n = 6).

Figure 2

Plasma insulin concentration for carbohydrate (CHO) and carbohydrate and whey protein isolates (CHO + WPI) trials. The exercise trial day consisted of 60 min cycling at 70% VO_2 max, with blood samples taken at rest and every 20 min (rest, 20, 40, 60). This was followed by time to fatigue at 90% VO_2 max and blood was taken on completion of this effort (0). The 6 h recovery consisted of blood taken regularly for the first h (10, 20, 30, 40, 60) and every 60 min after that (120, 180, 240, 300, 360). Both trials, CHO (* P < 0.05) and CHO + WPI (# P < 0.05), were significantly elevated compared to rest, with CHO + WPI significantly higher than CHO at 180 min (^ P < 0.05) during the recovery period, before returning to resting levels at 240 min. Values are means ± SEM (n = 6).

Figure 3

Muscle glycogen concentration following the 16 day dietary intervention and exercise trial day, which consisted of a resting (rest) muscle biopsy, another following 60 min cycling at 70% VO_{2 max} (70%)_, time to fatigue at 90% VO_{2 max} (90%) and at the end of 6 h recovery (6 h recovery). Carbohydrate (CHO) and carbohydrate and whey protein isolates (CHO + WPI) trial were similar at rest. All time points following exercise were lower than rest in both trials (# P < 0.05). CHO + WPI trial was increased from 90% VO_2 max to end of 6 h recovery (* P < 0.05). Values are means ± SEM (n = 6).

Figure 4

Glycogen synthase mRNA expression for the carbohydrate (CHO) and carbohydrate and whey protein isolates (CHO + WPI) trials. No differences were observed. Values are means ± SEM (n = 6).

Figure 5

AMPK-α2 mRNA expression for carbohydrate (CHO) and carbohydrate and whey protein isolates (CHO + WPI) trials. CHO group is significantly different from rest to 90% and rest to end recovery (* P < 0.05). Values are mean ± SEM (n = 6).

Figure 6

PGC-1α mRNA expression for carbohydrate (CHO) and carbohydrate and whey protein isolate trials (CHO + WPI) following 16 day dietary intervention and exercise trial. Muscle biopsies were taken at rest, another following 60 min cycling at 70% VO_2 max (70%)_, time to fatigue at 90% VO_2 max (90%) and at the end of 6 h recovery (6 h recovery). CHO + WPI trial was significantly lower at rest, following cycling at 70% and 90% VO_2 max, compared to 6 h recovery (# P < 0.05). After 6 h of recovery the CHO + WPI trial was significantly increased compared to CHO trial (^P < 0.05). Values are mean ± SEM (n = 6).