Förändringar i den muskulära proteinsyntesen vid övervikt

[King Grub]

Objective:

To investigate the sequential changes of protein synthesis in skeletal muscle during establishment of obesity, considering muscle typology.

Experimental Design:

Adult Wistar rats were fed with a standard diet during 16 weeks (C; n=14), or with a high-fat, high-sucrose diet during 16 (HF16; n=14) or 24 weeks (HF24; n=15). Body composition was measured using a dual-energy-x-ray absorptiometry scanner. The fractional synthesis rates (FSR) of muscle protein fractions were calculated in tibialis anterior (TA) and soleus muscles by incorporation of 1-13C-Valine in muscle protein. Muscle lipid and mitochondria contents were determined using histochemical analysis.

Results:

Obesity occurred in an initial phase, from 1 to 16 weeks, with an increase in weight (P<0.05), fat mass (P<0.001), muscle mass (P<0.001), and FSR in TA (actin: 5.3±0.2 vs 8.8±0.5 %/d, C vs HF16, P<0.001) compared to standard diet. The second phase, from 16 to 24 weeks, was associated with a weight stabilization, a decrease in muscle mass (P<0.05) and a decrease in FSR in TA (mitochondrial: 5.6±0.2 vs 4.2±0.4 %/d, HF16 vs HF24, P<0.01) compared to HF16 group. Muscle lipid content was increased in TA in the second phase of obesity development (P<0.001).

Conclusion:

Muscle mass, lipid infiltration and muscle protein synthesis were differently affected, depending on the stage of obesity development and muscle typology. Chronic lipid infiltration in glycolytic muscle is concomitant with a reduction of muscle protein synthesis, suggesting that muscle lipid infiltration in response to high-fat diet is deleterious for the incorporation of amino acid in skeletal muscle proteins.

J Physiol. 2012 Jul 16. Time-course changes of muscle protein synthesis associated with obesity-induced lipotoxicity.

http://jp.physoc.org/content/early/2....full.pdf+html

[C.E.J.]

Sköj!