No independent or combined effects of vitamin D and conjugated linoleic acids on muscle protein synthesis in older adults: a randomized, double-blind, placebo-controlled clinical trial.
Am J Clin Nutr
; 112(5): 1382-1389, 2020 11 11.
Article
in En
| MEDLINE
| ID: mdl-32860399
ABSTRACT
BACKGROUND:
Aging is associated with skeletal muscle anabolic resistance (i.e., reduced muscle protein synthesis during anabolic conditions such as hyperaminoacidemia). The results from studies conducted in cell culture systems and animals suggest that both vitamin D and conjugated linoleic acids (CLAs) stimulate muscle protein synthesis.OBJECTIVES:
To conduct a randomized, double-blind, placebo-controlled clinical trial to determine the independent and combined effects of dietary vitamin D and CLA supplementation on myofibrillar protein synthesis rates in sedentary older adults.METHODS:
Thirty-two sedentary, older adults were randomized to receive either 1) 2000 IU vitamin D-3 (Vit D) per day; 2) 4000 mg CLA per day; 3) both Vit D (2000 IU/d) and CLA (4000 mg/d); or 4) placebo for 8 wk. Myofibrillar protein synthesis rates were evaluated by using intravenous [ring-2H5]phenylalanine infusion in conjunction with muscle biopsies during basal, postabsorptive conditions and during combined amino acid and insulin infusion before and after the supplementation period.RESULTS:
Before the intervention, basal myofibrillar protein synthesis rates were not different among groups (Placebo 0.033 ± 0.003; Vit D 0.034 ± 0.002; CLA 0.029 ± 0.005; Vit D + CLA 0.038 ± 0.005 %·h-1), and hyperinsulinemia-hyperaminoacidemia increased myofibrillar protein synthesis rates by â¼35%. Compared with placebo, neither Vit D nor CLA nor combined Vit D + CLA supplementation affected the basal myofibrillar protein synthesis rates (placebo 0.040 ± 0.004%/h; Vit D 0.044 ± 0.006%/h; CLA 0.039 ± 0.006%/h; Vit D + CLA 0.040 ± 0.007%/h) or the hyperinsulinemia-hyperaminoacidemia-induced increase in myofibrillar protein synthesis (percentage increase from basal before and after theinterventions:
placebo, 30 ± 11 and 36 ± 11; Vit D, 38 ± 8 and 34 ± 10; CLA, 50 ± 14 and 51 ± 16; Vit D + CLA, 29 ± 15 and 35 ± 8).CONCLUSIONS:
Vitamin D and/or CLA supplementation, at the doses provided in our study, does not have muscle anabolic effects in sedentary older adults.The study was registered at clinicaltrials.gov (NCT03115775).Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Vitamin D
/
Vitamins
/
Gene Expression Regulation
/
Linoleic Acids, Conjugated
/
Muscle Proteins
Type of study:
Clinical_trials
Limits:
Aged
/
Female
/
Humans
/
Male
Language:
En
Journal:
Am J Clin Nutr
Year:
2020
Document type:
Article