Whole body protein anabolism in COPD patients and healthy older adults is not enhanced by adding either carbohydrates or leucine to a serving of protein

Abstract

Background & aims: Carbohydrates (CHO) and leucine (LEU) both have insulinotropic properties, and could therefore enhance the protein anabolic capacity of dietary proteins, which are important nutrients in preventing muscle loss in patients with Chronic Obstructive Pulmonary Disease (COPD). LEU is also known to activate protein anabolic signaling pathways independent of insulin. Based on our previous findings in COPD, we hypothesized that whole body protein anabolism is enhanced to a comparable extent by the separate and combined co-ingestion of CHO and LEU with protein.

Methods: To disentangle the protein anabolic effects of CHO and/or free LEU when co-ingested with a high-quality protein, we studied 10 patients with moderate to very severe COPD and dyspnea (GOLD: II-IV, mMRC dyspnea scale ≥ 2), at risk for muscle loss, and 10 healthy age- and gender-matched controls. On four occasions, in a single-blind randomized crossover design, each subject ingested a drink containing 0.6 g/kg fat-free mass (ffm) hydrolyzed casein protein with, a) no add-ons (protein), b) 0.3 g/kg ffm CHO (protein + CHO), c) 0.095 g/kg ffm leucine (protein + LEU), d) both add-ons (protein + CHO + LEU). Whole body protein breakdown (PB), protein synthesis (PS), and net protein balance (= PS - PB) were measured by IV primed and continuous infusion of L-[ring-²H₅]-phenylalanine and L-[¹³C₉,¹⁵N]-tyrosine. L-[¹⁵N]-phenylalanine was added to the protein drinks to measure splanchnic extraction.

Results: In both groups, whole body PS, PB and net protein balance responses were comparable between the four protein drinks, despite higher postprandial plasma LEU concentrations for the LEU supplemented drinks (P < 0.05), and higher insulin concentrations for the CHO supplemented drinks as compared to the protein only drink (P < 0.05).

Conclusions: Adding CHO and/or LEU to a serving of high-quality protein does not further augment whole body protein anabolism in dyspneic COPD patients at risk for muscle loss or healthy older adults.

Trial registry: ClinicalTrials.gov; No. NCT01734473; URL: www.clinicaltrials.gov.

Keywords: Anabolic response; COPD; Carbohydrate; Coingestion; Leucine.

Figure 1.

Study design. All participants were studied during four experimental test days (≥1 day apart and ≤2 days per week) within a time frame of one month. The responses to four different protein drinks were examined according to a randomized cross-over design. Time points t = −20, −10 and 0 min were used to analyze postabsorptive protein metabolism. Postprandial protein kinetics were measured by using the time points t = 0 −240 min in order to calculate the area under the curve between 0 and 4 h.

Figure 2.

Mean (± SE) postprandial increase over the 4h postprandial period in COPD patients (n=10) and healthy age matched controls (n=11) for plasma PHE concentration (A), and plasma LEU concentration (B). Protein drinks were ingested orally and consisted of 0.6 g/kg ffm hydrolyzed casein protein with, a) no add-ons (protein), b) 0.3 g/kg ffm CHO (protein+CHO), c) 0.095 g/kg ffm leucine (protein+LEU), d) both add-ons (protein+CHO+LEU). Two-factor repeated measures analysis of variance for PHE concentration showed a significant protein drink effect (P=0.0286), but no group effect or group-by-protein drink interactions. For LEU concentration, we observed a group effect (P=0.0200) and protein drink effect (P<0.0001), but no group-by-protein drink interactions. a, b, c Different letters indicate statistical within group differences between protein drinks, at P<0.05. CHO: carbohydrates. COPD: chronic obstructive pulmonary disease. ffm: fat-free mass. LEU: leucine.

Figure 3.

Mean (± SE) postprandial increase over the 4h postprandial period in COPD patients (n=10) and healthy age matched controls (n=11) for plasma glucose concentration (A), and plasma insulin concentration (B). Protein drinks were ingested orally and consisted of 0.6 g/kg ffm hydrolyzed casein protein with, a) no add-ons (protein), b) 0.3 g/kg ffm CHO (protein+CHO), c) 0.095 g/kg ffm leucine (protein+LEU), d) both add-ons (protein+CHO+LEU). Two-factor repeated measures analysis of variance showed a significant protein drink effect for glucose and insulin concentrations (P<0.0001). No group effect or group-by-protein drink interactions were observed. a, b, c Different letters indicate statistical within group differences between protein drinks, at P<0.001 for glucose and P<0.05 for insulin. CHO: carbohydrates. COPD: chronic obstructive pulmonary disease. ffm: fat-free mass. LEU: leucine.

Figure 4.

Mean (± SE) plasma cTTR in healthy controls (n=11) for L-[ring-²H₅]-PHE (A1), L-[¹⁵N]-PHE (B1), L-[U-¹³C₉, ¹⁵N]-TYR (C1), and L-[ring-²H₄]-TYR (D1), before and after intake of 4 different protein drinks. Protein drinks were ingested orally (at time = 0 min) and consisted of 0.6 g/kg ffm hydrolyzed casein protein with, a) no add-ons (protein), b) 0.3 g/kg ffm CHO (protein+CHO), c) 0.095 g/kg ffm leucine (protein+LEU), d) both add-ons (protein+CHO+LEU). Two-factor repeated measures analysis of variance showed a significant time effect for L-[ring-²H₅]-PHE, L-[¹⁵N]-PHE, L-[U-¹³C₉, ¹⁵N]-TYR, L-[ring-²H₄]-TYR (P<0.0001) and time-by-protein drink interaction for L-[ring-²H₅]-PHE, L-[¹⁵N]-PHE, L-[ring-²H₄]-TYR (P<0.0001), L-[U −¹³C₉, ¹⁵N]-TYR (P=0.07). No protein drink effects were observed for any of the measures. Mean (± SE) plasma cTTR in COPD patients (n=10) for L-[ring-²H₅]-PHE (A2), L-[¹⁵N]-PHE (B2), L-[U-¹³C₉, ¹⁵N]-TYR (C2), and L-[ring-²H₄]-TYR (D2), before and after intake of 4 different protein drinks. Protein drinks were ingested orally (at time = 0 min) and consisted of 0.6 g/kg ffm hydrolyzed casein protein with, a) no add-ons (protein), b) 0.3 g/kg ffm CHO (protein+CHO), c) 0.095 g/kg ffm leucine (protein+LEU), d) both add-ons (protein+CHO+LEU). Two-factor repeated measures analysis of variance showed a significant time effect for L-[ring-²H₅]-PHE, L-[¹⁵N]-PHE, L-[U-¹³C₉, ¹⁵N]-TYR, L-[ring-²H₄]-TYR (P<0.0001) and time-by-protein drink interaction for L-[¹⁵N]-PHE (P<0.0001). No protein drink effects were observed for any of the measures. CHO: carbohydrates. COPD: chronic obstructive pulmonary disease. cTTR: stable isotope tracer/tracee ratio corrected for natural abundance. ffm: fat-free mass. LEU: leucine. PHE: phenylalanine. TYR: tyrosine

Figure 4.

Mean (± SE) plasma cTTR in healthy controls (n=11) for L-[ring-²H₅]-PHE (A1), L-[¹⁵N]-PHE (B1), L-[U-¹³C₉, ¹⁵N]-TYR (C1), and L-[ring-²H₄]-TYR (D1), before and after intake of 4 different protein drinks. Protein drinks were ingested orally (at time = 0 min) and consisted of 0.6 g/kg ffm hydrolyzed casein protein with, a) no add-ons (protein), b) 0.3 g/kg ffm CHO (protein+CHO), c) 0.095 g/kg ffm leucine (protein+LEU), d) both add-ons (protein+CHO+LEU). Two-factor repeated measures analysis of variance showed a significant time effect for L-[ring-²H₅]-PHE, L-[¹⁵N]-PHE, L-[U-¹³C₉, ¹⁵N]-TYR, L-[ring-²H₄]-TYR (P<0.0001) and time-by-protein drink interaction for L-[ring-²H₅]-PHE, L-[¹⁵N]-PHE, L-[ring-²H₄]-TYR (P<0.0001), L-[U −¹³C₉, ¹⁵N]-TYR (P=0.07). No protein drink effects were observed for any of the measures. Mean (± SE) plasma cTTR in COPD patients (n=10) for L-[ring-²H₅]-PHE (A2), L-[¹⁵N]-PHE (B2), L-[U-¹³C₉, ¹⁵N]-TYR (C2), and L-[ring-²H₄]-TYR (D2), before and after intake of 4 different protein drinks. Protein drinks were ingested orally (at time = 0 min) and consisted of 0.6 g/kg ffm hydrolyzed casein protein with, a) no add-ons (protein), b) 0.3 g/kg ffm CHO (protein+CHO), c) 0.095 g/kg ffm leucine (protein+LEU), d) both add-ons (protein+CHO+LEU). Two-factor repeated measures analysis of variance showed a significant time effect for L-[ring-²H₅]-PHE, L-[¹⁵N]-PHE, L-[U-¹³C₉, ¹⁵N]-TYR, L-[ring-²H₄]-TYR (P<0.0001) and time-by-protein drink interaction for L-[¹⁵N]-PHE (P<0.0001). No protein drink effects were observed for any of the measures. CHO: carbohydrates. COPD: chronic obstructive pulmonary disease. cTTR: stable isotope tracer/tracee ratio corrected for natural abundance. ffm: fat-free mass. LEU: leucine. PHE: phenylalanine. TYR: tyrosine

Figure 5.

Mean (± SE) postprandial changes over the 4h postprandial in COPD patients (n=10) and healthy age matched controls (n=11) for whole body protein synthesis (A), breakdown (B), and net protein balance (protein synthesis - protein breakdown) (C). Net protein balance showed positive values when PS > PB, and negative values when PB > PS. Protein drinks were ingested orally and consisted of 0.6 g/kg ffm hydrolyzed casein protein with, a) no add-ons (protein), b) 0.3 g/kg ffm CHO (protein+CHO), c) 0.095 g/kg ffm leucine (protein+LEU), d) both add-ons (protein+CHO+LEU). Two-factor repeated measures analysis of variance showed a significant group effect for protein synthesis (P=0.0060) and breakdown (P=0.0448), and a tendency towards a greater net protein gain (P=0.0526). No protein drink effects or group-by-protein drink interactions were observed for any of the measures. CHO: carbohydrates. COPD: chronic obstructive pulmonary disease. ffm: fat-free mass. LEU: leucine.