Desaturation of skeletal muscle structural and depot lipids in obese individuals during a very-low-calorie diet intervention.
OBJECTIVE
This study investigated whether a very-lowcalorie dietary intervention (VLCD) may influence composition of skeletal muscle cell membrane phospholipid and composition and concentration of intramyocellular triglyceride (IMTG) in obese subjects. The working hypothesis proposed that a VLCD would decrease saturated fatty acids (FAs) and increase long-chain polyunsaturated FAs (LCPUFAs) in muscular structural lipids, as such changes have been associated with improved insulin sensitivity.


METHODS
Skeletal muscle biopsies (vastus lateralis) were obtained from 13 obese subjects (nine women) before and after 8 weeks on VLCD (approximately 600 to 800 kcal/d). FA composition in muscle cell membrane phospholipid and concentration and FA composition of IMTG were determined by gas-liquid chromatography.


RESULTS
Baseline BMI was 36.0 +/- 3.4 kg/m2. Weight loss was 9.3 +/- 1.1 kg (8.8 +/- 1.1%; p < 0.0001); loss of adipose tissue was 5.9 +/- 0.9 kg (p < 0.0001). Insulin resistance (by homeostasis model assessment) decreased (-44 +/- 7%; p < 0.001). Muscle cell membrane phospholipid saturated FAs decreased (-3.2 +/- 1.3%; p < 0.05), whereas monounsaturated FAs (4.3 +/- 1.7%; p < 0.05), LCPUFAs (11 +/- 6%; p < 0.05), and the ratio of LCPUFAs to saturated FAs (12 +/- 5%; p < 0.05) increased. IMTG decreased, but not significantly (-5%). IMTG-saturated FAs decreased (-3.3 +/- 1.5%; p < 0.05), whereas LCPUFAn-3 (29 +/- 9%; p < 0.01), LCPUFAn-6 (33 +/- 9%; p < 0.01), and the ratio of LCPUFAs to saturated FAs (34 +/- 8%; p < 0.001) increased. Plasma total cholesterol (-15 +/- 6%; p < 0.05), low-density lipoprotein-cholesterol (-16 +/- 5%; p < 0.01), high-density lipoprotein-cholesterol (-8 +/- 2%; p < 0.01), and plasma triglyceride (-19 +/- 12%; p = 0.10) all decreased during the VLCD.


CONCLUSIONS
Desaturation of both muscle cell membrane phospholipid and IMTG was significant but modest during a VLCD in obese subjects. Further research must delineate whether such changes in skeletal muscle structural and depot lipid composition themselves are enough to promote the observed improvements in insulin action.
Haugaard
Steen B
SB
Department of Endocrinology and Internal Medicine, Hvidovre University Hospital, University of Copenhagen, Hvidovre, Copenhagen, Denmark. sbhau@dadlnet.dk
Vaag
Allan
A
Høy
Carl-Erik
CE
Madsbad
Sten
S
D001706:Biopsy; D031204:Caloric Restriction; D002784:Cholesterol / Q000097:blood; D005227:Fatty Acids / Q000032:analysis* / Q000378:metabolism; D005260:Female; D006801:Humans; D007333:Insulin Resistance; D050356:Lipid Metabolism; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000737:chemistry* / Q000378:metabolism; D009765:Obesity / Q000178:diet therapy / Q000378:metabolism*; D010743:Phospholipids / Q000737:chemistry*; D014280:Triglycerides / Q000032:analysis / Q000378:metabolism
D005227:Fatty Acids; D010743:Phospholipids; D014280:Triglycerides; D002784:Cholesterol