Table 2.

Differences in the mRNA levels of GS, GP, G_M and PTG in SOL and TA muscles of young and old rats maintained on different diets.

mRNA	Fold of change (1/2−ΔΔCt)
	Soleus			Tibialis
	AL	ALF	CR	AL	ALF	CR
MGS	−1.31	−1.74	−2.30**	+1.01	+1.37	+1.34
MGP	−1.05	−2.12*	−2.01	+1.10	−1.00	−1.01
BGP	+1.16	−1.74	−1.09	+1.68	+1.26	−1.10
GM	−1.04	−2.47**	−1.96*	+1.44	−1.21	+1.30
PTG	−1.85	−2.72	+4.04*	−1.91	−1.23	+1.62

The relative mRNA levels of muscle GS (MGS), muscle GP (MGP), brain GP (BGP), G_M and PTG were analyzed in muscles from at least 5 rats per group by RT-PCR. The Ct values for the reference probe (18S rRNA gene) were subtracted from each probe Ct (ΔCt). To determine changes in gene expression, the ΔCt values of 6-mo rats were subtracted from the ΔCt values of 24-mo rats for each muscle type and dietary condition. Data are expressed as mean values of 2^−ΔΔCt for upregulated genes and l/2^−ΔΔCt for downregulated ones. The former are shown by + and the latter by −. Age influenced the mRNA levels of: MGS (F 20.4, p < 0.0001), MGP (F12.5 p < 0.005), G_M (F 19.0, p< 0.001) in SOL. Diet influenced the mRNA levels of: MGS (F 4.82, p < 0.05) and G_M (F 13.8, p < 0.0001) in SOL The interaction of diet and age was also significative for MGP (F 3.92, p<0.05), G_M (F 4.37, p<0.05) and PTG (F 8.80, p < 0.001) in SOL and PTG (F 4.38, p < 0.05) in TA. The significance of the differences between 24-mo and 6-mo in the equivalent diet and muscle is *p < 0.05 and **p<0.01.