PROJECT SUMMARY
The success of preventive and supportive approaches in type 2 diabetes mellitus (T2D) depends on the
spontaneous recovery of ß-cell function. A central component of ß-cell function, glucose metabolism, is
impaired in T2D. Its causes, and how this impairment might lead to functional failure of ß-cells, remain
unknown. Until delineated, targeting of the dysfunctional pathways and addressing the cause of the ab-
normality are unlikely and therapies remain supportive rather than disease-modifying. The overall objec-
tive is to identify components of human ß-cell metabolism that are critical for insulin secretion in healthy
individuals and fail to support physiological secretion in T2D, and to identify components mediating ß-cell
compensation. We have identified a novel intramitochondrial metabolic activation phenomenon as such a
component, and intend to determine its mechanism and role. The central hypothesis of the project is that
in T2D ß-cells a metabolic rearrangement impairs the response of ß-cells to glucose by limiting the acti-
vation of succinate dehydrogenase (SDH), and triggers an upregulation of amplification pathways, alter-
ing the physiological dynamics of insulin secretion in T2D. Using human organ donor islets and micro-
scale bioenergetic and cell physiology assaying together with genetic (CRISPR) and pharmacological
modulation of metabolism, 1) The mechanism of bioenergetic activation of normal human ß-cells during
glucose-stimulated insulin secretion (GSIS) will be identified. We hypothesize that the activation of SDH
is required for GSIS, and this is conveyed by metabolic coupling factor pathways through regulating ma-
trix oxaloacetate, malonate or the flux control by SDH. 2) The mechanism of T2D ß-cell compensation
and its effects in the context of impaired bioenergetic activation will be determined. Here, our hypothesis
is that T2D ß-cells compensate for the loss of bioenergetic control by upregulating amplification path-
ways, and this alters characteristics of secretion. 3) The beta-cell-specific gene expression pattern re-
quired for the bioenergetic activation and compensation will be determined. Our hypothesis is that the
mitochondrial activation mechanism is a network-level phenomenon, requiring a particular gene expres-
sion pattern. Harnessing cell-to-cell and individual-to-individual heterogeneity, mitochondrial function and
nuclear gene expression will be correlated on the single-cell level. The proposed research represents a
substantial departure from the status quo by recognizing a novel mitochondrial regulation mechanism as
the controlling entity of glucose metabolism and insulin secretion. Furthermore, it departs from the tradi-
tional dichotomy of triggering and amplification pathways controlling GSIS by determining how these
pathways converge in bioenergetic regulation. This work will be significant because combining the identi-
fication of abnormalities in T2D ß-cell energy metabolism with knowledge of related compensatory mech-
anisms, will allow targeting of these pathways to support ß-cell function.
