Physical inactivity differentially alters dietary oleate and palmitate trafficking.
OBJECTIVE
Obesity and diabetes are characterized by the incapacity to use fat as fuel. We hypothesized that this reduced fat oxidation is secondary to a sedentary lifestyle.


METHODS
We investigated the effect of a 2-month bed rest on the dietary oleate and palmitate trafficking in lean women (control group, n = 8) and the effect of concomitant resistance/aerobic exercise training as a countermeasure (exercise group, n = 8). Trafficking of stable isotope-labeled dietary fats was combined with muscle gene expression and magnetic resonance imaging-derived muscle fat content analyses.


RESULTS
In the control group, bed rest increased the cumulative [1-(13)C]oleate and [d(31)]palmitate appearance in triglycerides (37%, P = 0.009, and 34%, P = 0.016, respectively) and nonesterified fatty acids (NEFAs) (37%, P = 0.038, and 38%, P = 0.002) and decreased muscle lipoprotein lipase (P = 0.043) and fatty acid translocase CD36 (P = 0.043) mRNA expressions. Plasma NEFA-to-triglyceride ratios for [1-(13)C]oleate and [d(31)]palmitate remained unchanged, suggesting that the same proportion of tracers enters the peripheral tissues after bed rest. Bed rest did not affect [1-(13)C]oleate oxidation but decreased [d(31)]palmitate oxidation by -8.2 +/- 4.9% (P < 0.0001). Despite a decreased spontaneous energy intake and a reduction of 1.9 +/- 0.3 kg (P = 0.001) in fat mass, exercise training did not mitigate these alterations but partially maintained fat-free mass, insulin sensitivity, and total lipid oxidation in fasting and fed states. In both groups, muscle fat content increased by 2.7% after bed rest and negatively correlated with the reduction in [d(31)]palmitate oxidation (r(2) = 0.48, P = 0.003).


CONCLUSIONS
While saturated and monounsaturated fats have similar plasma trafficking and clearance, physical inactivity affects the partitioning of saturated fats toward storage, likely leading to an accumulation of palmitate in muscle fat.
Bergouignan
Audrey
A
Department of Ecology, Physiology, and Ethology, Hubert Curien Pluridisciplinary Institute, Louis Pasteur University, UMR7178 Centre National de Recherche Scientifique (CNRS), Strasbourg, France.
Trudel
Guy
G
Simon
Chantal
C
Chopard
Angèle
A
Schoeller
Dale A
DA
Momken
Iman
I
Votruba
Susanne B
SB
Desage
Michel
M
Burdge
Graham C
GC
Gauquelin-Koch
Guillemette
G
Normand
Sylvie
S
Blanc
Stéphane
S
D000328:Adult; D001510:Bed Rest; D001692:Biological Transport / Q000502:physiology; D001823:Body Composition; D002247:Carbon Isotopes / Q000378:metabolism; D015444:Exercise / Q000502:physiology*; D005230:Fatty Acids, Nonesterified / Q000378:metabolism; D005260:Female; D005947:Glucose / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000378:metabolism; D007333:Insulin Resistance; D009132:Muscles / Q000378:metabolism; D019301:Oleic Acid / Q000378:metabolism*; D010084:Oxidation-Reduction; D010168:Palmitates / Q000378:metabolism*; D014280:Triglycerides / Q000378:metabolism
D002247:Carbon Isotopes; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D010168:Palmitates; D014280:Triglycerides; D019301:Oleic Acid; D005947:Glucose