Comparison of traditional measurements with macroglycogen and proglycogen analysis of muscle glycogen

Traditionally, there have been two methods for measuring total muscle glycogen (Gly(tot)), either by acid hydrolysis (AC) or by enzymatic hydrolysis (EZ). As well, it has been determined that rodent muscle contains two pools of glycogen, macroglycogen (MG) and proglycogen (PG). This MG/PG determination of Gly(tot) has never been compared with AC or EZ methods, nor has it been determined whether the two pools exist in human skeletal muscle. A detailed comparison of the three methods was performed by using both rodent and human muscle. It was found that repeated analysis of independent portions of muscle generally gave coefficients of variation of <10%. The PG fraction was always in excess of MG, which was 6-10% of Gly(tot) in rodent muscle and in human samples when Gly(tot) was low but increased to similar to 40% when Gly(tot) was high. It was found that AC and EZ Gly(tot) were not statistically different (P < 0.05), nor was there a difference between the MG+PG; Gly(tot) and that determined by AC or EZ. The Gly(tot) from MG+PG extraction had a strong correlation with the values obtained by either AC (r = 1.0) or EZ (r = 0.96). These data suggest that MG+PG do exist in human skeletal muscle and can be measured reliably in biopsy-sized samples. All three methods give an accurate representation of human Gly(tot) and are comparable in their precision.