Freitas EDS, Kras KA, Roust LR, De Filippis EA, Kimball SR, Buras M, Katsanos CS. Lower muscle protein synthesis in humans with obesity concurrent with lower expression of muscle IGF1 splice variants.
Obesity (Silver Spring) 2023;
31:2689-2698. [PMID:
37840435 PMCID:
PMC10650963 DOI:
10.1002/oby.23896]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 08/02/2023] [Accepted: 08/07/2023] [Indexed: 10/17/2023]
Abstract
OBJECTIVE
This study tested the hypothesis that expression of insulin-like growth factor 1 (IGF-1) protein and mRNA splice variants is lower in skeletal muscle of humans with obesity who have a lower mixed-muscle protein fractional synthesis rate (MMP-FSR) when compared with individuals without obesity.
METHODS
The study included nine participants with obesity (OB, mean [SD], BMI = 35 [3] kg/m2 , MMP-FSR = 0.06%/h [0.02%/h]) and nine participants without obesity (W-OB, BMI = 24 [3] kg/m2 , MMP-FSR = 0.08%/h [0.02%/h]; for both BMI and MMP-FSR p < 0.05). MMP-FSR and mitochondrial protein FSR were measured following an overnight fast.
RESULTS
Along with lower MMP-FSR, OB participants displayed lower mitochondrial protein FSR (p = 0.03) compared with W-OB participants. Expression of IGF-1 (p = 0.04) and IGF-1 receptor (p < 0.01) proteins was lower in muscle of OB participants. In addition, OB participants had lower (p < 0.05) mRNA expression of IGF1 variants Eb and Ec. This study demonstrates that lower protein synthesis in muscle of humans with obesity occurs concurrently with lower expression of muscle IGF-1 and IGF-1 receptor proteins, as well as lower mRNA expression of the IGF1 splice variants.
CONCLUSIONS
These findings indicate that lower protein synthesis observed in muscle of humans with obesity may result from diminished muscle IGF1 gene expression.
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