Pancreatic magnetic resonance imaging after manganese injection distinguishes type 2 diabetic and normoglycemic patients

Abstract

A non-invasive method to image the mass and/or function of human pancreatic islets is needed to monitor the progression of diabetes, and the effect of therapeutic interventions. As yet, no method is available for this purpose, which could be applied to in situ human islets. Animal and in vitro studies have documented that manganese infusion could improve the magnetic resonance imaging (MRI) of the endocrine pancreas. Here, we have tested whether a similar approach could discriminate diabetic and non-diabetic patients. In vitro, human isolated islets readily incorporated manganese. In vivo, 243 manganese-enhanced magnetic resonance imaging (MEMRI) examinations were reviewed, including 41 examinations which were run on 24 patients with type 2 diabetes and 202 examinations which were run on 119 normoglycemic patients. The results show that MEMRI discriminates type 2 diabetics from non-diabetic patients, based on the signal enhancement of pancreas.

Figure 1. Manganese is uptaken by human islets. T1-weighted magnetic resonance images of pellets of human islets from non-diabetic multi-organ donors before (A) and after a 30 min exposure to MnCl₂ (B). C) Manganese significantly enhanced the MRI signal to noise ratio (16.0 ± 1.3 vs. 41.6 ± 0.7, p = 0.0003). Data are mean + SEM signal-to-noise ratio.

Figure 2. The MRI signal enhancement of pancreas is enhanced by manganese. T1-weighted magnetic resonance imaging showing the pancreas (area limited by the dashed line) before (A, C) and 20 min after Mn-DPDP infusion (B, D) of a normoglycemic (A, B) and a type 2 diabetic patient (C, D). In both patients, the MRI signal of pancreas was enhanced by the manganese infusion. E) This enhancement was significantly higher in normoglycemic than in type 2 diabetic patients. Data are mean + SEM signal enhancement, expressed as % of the signal evaluated prior to the manganese infusion.

Figure 3. The MEMRI enhancement of pancreas correlated with the BMI of diabetic patients. The pancreas enhancement due to Mn²⁺ was inversely correlated with the BMI (A), but not the age of the diabetic patients (B), as assessed by Pearson’s correlation.

Figure 4. The MEMRI signal of liver (A), muscle (B) and spleen (C) does not differentiate normoglycemic patients from diabetic patients. The signal enhancement of liver (A), muscle (B) and spleen (C) was not statistically different between normoglycemic and type 2 diabetic patients. Data are mean + SEM signal enhancement, expressed as % of the signal evaluated prior to the manganese infusion.