31P NMR investigation of free intracellular magnesium, pH and energy balance in striated muscle of patients with kidney disease: relation to insulin resistance.

BACKGROUND

High prevalence (48%) of insulin resistance (IR) in patients with mild to moderate kidney function reduction, and the potential pathogenetic role of magnesium (Mg) deficiency in IR prompted us to study skeletal muscle free Mg (fMg) concentration in patients with impaired kidney function.

METHODS

fMg concentration, intracellular pH (pHi) and parameters of energy balance were determined employing 31P NMR spectroscopy in the calf muscle of the dominant leg of 18 healthy controls (C) and 22 patients (P) with decreased kidney function. 10 patients suffered from insulin resistance (IR).

RESULTS

No difference in fMg concentration in skeletal muscle was observed (C: 0.929 +/- 0.075; P: 0.948 +/- 0.062 mmol/l; x +/- SEM). In patients a slight shift of pHi towards acidic values was found (C: 7.036 +/- 0.0.004; P: 7.013 +/- 0.004; p < 0.004), which was even more expressed in IR patients (7.008 +/- 0.005). Serum creatinine levels and creatinine clearance correlated with pHi in the patient's group. Adenosintriphosphate (ATP) to inorganic phosphate (Pi) ratio in skeletal muscle was lower, phosphocreatine (Pcr)/ATP ratio was higher, while that of Pcr/Pi showed only a trend towards an increase in the patient's group.

CONCLUSION

In patients with reduction of kidney function IR does not associate with a change in skeletal muscle free magnesium concentration, or deficiency in macroergic phosphate levels. Shift in intracellular pH towards acidic values may participate in IR. Decreased activity of Na+/H+ antiporter is suggested. (Fig. 5, Tab. 2, Ref. 22.)