Non‐invasive imaging of functional pancreatic islet beta‐cell mass in people with type 1 diabetes mellitus

Aims: To investigate whether manganese-enhancedmagnetic resonance imagingcan assess functional pancreatic beta-cellmass in people with type 1 diabetes mellitus.Methods: In a prospective case–controlstudy, 20 people with type 1 diabetesmellitus (10 with low (≥50 pmol/L) and 10 with very low (concentrations) and 15 healthy volunteers underwent manganese-enhancedmagnetic resonance imaging of the pancreas following an oral glucose load. Scan-rescanreproducibility was performed in 10 participants.Results: Mean pancreatic manganese uptake was 31 ± 6 mL/100 g of tissue/minin healthy volunteers (median 32 [interquartile range 23–36]years, 6 women),falling to 23 ± 4 and 13 ± 5 mL/100 g of tissue/min (p ≤ 0.002 for both) in peoplewith type1 diabetes mellitus (52 [44–61]years, 6 women) and low or very lowplasma C-peptideconcentrations respectively. Pancreatic manganese uptakecorrelated strongly with plasma C-peptideconcentrations in people with type1diabetes mellitus (r = 0.73, p < 0.001) but not in healthy volunteers (r = −0.054,p = 0.880). There were no statistically significant correlations between manganeseuptake and age, body-massindex, or glycated haemoglobin. There was strongintra-observer(mean difference: 0.31 (limits of agreement −1.42 to 2.05) mL/100 gof tissue/min; intra-classcorrelation, ICC = 0.99), inter-observer(−1.23 (−5.74 to3.27) mL/100 g of tissue/min; ICC = 0.85) and scan-rescan(−0.72 (−2.9 to 1.6)mL/100 g of tissue/min; ICC = 0.96) agreement for pancreatic manganese uptake.Conclusions: Manganese-enhancedmagnetic resonance imaging provides a potentialreproducible non-invasivemeasure of functional beta-cellmass in people with type1 diabetes mellitus. This holds major promise for investigating type 1 diabetes, monitoringdisease progression and assessing novel immunomodulatory interventions.