Measurement of magnesium absorption and retention in type 2 diabetic patients with the use of stable isotopes.

BACKGROUND: Magnesium deficiency has been associated with type 2 diabetes and may reduce insulin sensitivity and impair glucose tolerance. The etiology of magnesium depletion in diabetes is unclear. Animal studies suggest that diabetes may impair magnesium absorption; however, there are no published data on magnesium absorption in humans with diabetes. OBJECTIVE: Magnesium absorption from a test meal and the excretion and retention of magnesium were compared between patients with type 2 diabetes and healthy control subjects. DESIGN: A meal labeled with 10 mg (26)Mg isotopic label was administered, and stool and urine samples were collected for 10 and 6 d, respectively. Apparent absorption was calculated as the difference between the oral dose of (26)Mg isotopic label and the total amount of the isotopic label excreted in the feces. Magnesium retention was calculated from the apparent absorption and urinary excretion of (26)Mg isotopic label in the 6 d after administration. RESULTS: Mean (+/- SD) values for fractional magnesium absorption in the diabetic patients and the control subjects were 59.3 +/- 7.0% and 57.6 +/- 8.5%, respectively (NS). Mean (+/- SD) urinary magnesium excretion values in the diabetic patients and the control subjects were 11.2 +/- 2.6% and 11.7 +/- 3.8%, respectively (NS); retention values were 54.2 +/- 7.1% and 51.4 +/- 6.1%, respectively (NS). CONCLUSION: Dietary magnesium absorption and retention are not impaired in patients with reasonably well-controlled type 2 diabetes.

Low plasma magnesium in type 2 diabetes.

QUESTIONS UNDER STUDY/PRINCIPLES: Magnesium depletion has a negative impact on glucose homeostasis and insulin sensitivity in type 2 diabetic patients. Low plasma magnesium concentration is a highly specific indicator of poor magnesium status. In the USA and some European countries, plasma magnesium concentrations have been found to be decreased in diabetics. The aim of this study was to compare plasma magnesium concentrations of type 2 diabetics and healthy controls in Switzerland. METHODS: Plasma magnesium concentrations were determined in 109 type 2 diabetics and 156 age- and sex-matched healthy controls. RESULTS: Mean (+/- SD) plasma magnesium concentrations of the diabetics and controls were 0.77 +/- 0.08 and 0.83 +/- 0.07 mmol/L, respectively (p <0.001). Plasma magnesium concentrations were below the normal reference range in 37.6% of the diabetic patients and 10.9% of the control subjects (p <0.001). Plasma magnesium was not correlated with glycemic control as measured by HbA1c. CONCLUSIONS: Lower plasma magnesium concentrations and poor magnesium status are common in type 2 diabetics in Zurich, Switzerland.