Abstract:
It is well established that diabetes is of critical importance in the world as the number of
people affected increases globally. Although a great deal is known about the pancreas
and its function, there are still unanswered basic questions about normal pancreatic
physiology/function. Presently, pancreatic endocrine function is assessed using
biochemical tests of insulin release or serum glucose. Knowing the functional efficiency
of the pancreas would certainly be beneficial in the development of novel therapies aimed
at maintaining or increasing endocrine function particularly during progressive
pathologies. Here we present an application of functional MRI to the rodent pancreas
using manganese (Mn) enhanced imaging (MEMRI) in response to glucose stimulation.
To image rodent pancreas is extremely difficult for many reasons including organ size,
tissue density, location, and motion. To overcome these constraints, a novel application
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of Magnetization Prepared RApid Gradient Echo (MP-RAGE) was applied to achieve
significant T1 weighted contrast in response to glucose stimulation.
A pre- and post glucose activation in rodent pancreas indicated a signal increment or
decrement depending on the dynamic of the stimulant. A simultaneous injection of
stimulant with Mn has shown an overall increase of 20% to 26%, signal enhancement.
Uptake of Mn was confirmed via atomic absorption and insulin release via ELISA.
In addition, the research also focused to aid islet transplantation by developing a
method to make pre-transplant functional assessments of isolated human islets as they
were subjected to both physiological and mechanical stress during isolation. As
proposed, the islets labeled with a contrast agent (manganese) would alter their molecular
magnetic properties such as longitudinal (T1) and transverse (T2) relaxation time, and
there as a result there would be a change in their signal intensity. This change in signal
intensity has been exploited to distinguish between adjacent soft tissues, to delineate
pathologic tissues, and, in principle, to characterize tissue viability. μMRI of isolated
islets revealed a significant change in T1 and diffusion coefficient between the controls
versus stimulated islet where no changes was observed in transverse relaxation.
