Association between intramuscular fat in the arm following arm training and INSIG2

Insulin-induced gene 2 (INSIG2) single-nucleotide polymorphism (SNP rs7566605) is linked to lipid metabolism, and this study assessed its potential influence on fat in the upper arm following arm training. Twenty healthy sedentary volunteers (22.0 ± 1.1 years, body mass index 25.4 ± 4.0 kg/m(2) ; mean ± standard deviation) carried out a 12-week two-arm elbow extensor training (10 maximal extensions with 1 min recovery between bouts) five times per day, five times per week. For 17 volunteers, upper arm muscle and adipose tissue [subcutaneous (SCAT) and intramuscular (IMAT)] volumes were evaluated by magnetic resonance imaging before, immediately after, and 12 months after training and variables were related to the subjects' INSIG2 SNP rs7566605 genotype. Muscle volume and SCAT for the upper arm, as the decrease in IMAT during training were not related to INSIG2 SNP rs7566605: GG: %IMAT 1.0 ± 0.9%; GC/CC: %IMAT 0.6 ± 0.5% (P > 0.05). However, in the year following the training, accumulation of upper arm IMAT was twice as large in participants homozygous for the G allele (GG: Δ%IMAT +2.5 ± 0.8%; GC/CC: Δ%IMAT +1.1 ± 0.7%; P < 0.01). This study suggests that the G allele in the INSIG2 SNP rs7566605 is more relevant for changes in IMAT following training than for the amount of subcutaneous fat.