Skeletal muscle magnesium content in identical twins, discordant for type 2 diabetes

BACKGROUND: Low magnesium (Mg) status has been implied as a factor in the development of type 2 diabetes mellitus (DM) and its complications. We therefore studied Mg-status in identical twins, discordant for type 2 DM and in matched controls. Through correlation analysis, possible associations between Mg-status and glucose uptake were evaluated.

METHODS: Plasma Mg concentration was measured in 12 monozygote twin pairs, discordant for type 2 DM and in 12 matched controls. Muscle Mg content was measured in 10 persons from each group. An oral glucose tolerance test and a euglycaemic, hyperinsulinaemic clamp were utilized.

RESULTS: Neither muscle Mg content nor plasma Mg concentration differed among groups. Plasma Mg concentration decreased during the euglycaemic, hyperinsulinaemic clamp. In the control group, muscle Mg content correlated positively with insulin stimulated glucose disposal rate (r=0.77, p<0.01) and negatively with two hour plasma glucose concentration during an oral glucose tolerance test (OGTT) (r=- 0.64, p<0.05). In the control group, the two hour plasma glucose concentration during an oral glucose tolerance test correlated with the decrease in plasma Mg concentration (r=- 0.80, p<0.002) and with the change in muscle Mg content (r=0.90, p<0.0005) induced by the clamp. None of these associations were found in the two twin groups.

CONCLUSIONS: Normal plasma Mg concentration and muscle Mg content were found in persons with type 2 DM and in persons, who were heavily predisposed to the development of type 2 DM, indicating a normal whole-body Mg content. However, the missing associations between measures of glucose disposal and changes in both plasma Mg concentration and muscle Mg content in the two twin groups indicates, that physiological mechanisms, which partly regulates insulin sensitivity and Mg status in healthy individuals are either exhausted or fully utilized in both type 2 DM and in genetically identical twins without DM.