The islet in type 2 diabetes (T2D) is characterized by amyloid deposits derived from islet amyloid polypeptide (IAPP), a protein co-expressed with insulin by β-cells. In common with amyloidogenic proteins implicated in neurodegeneration, human IAPP (hIAPP) forms membrane permeant toxic oligomers implicated in misfolded protein stress. Here, we establish that hIAPP misfolded protein stress activates HIF1α/PFKFB3 signaling, this increases glycolysis disengaged from oxidative phosphorylation with mitochondrial fragmentation and perinuclear clustering, considered a protective posture against increased cytosolic Ca 2+ characteristic of toxic oligomer stress. In contrast to tissues with the capacity to regenerate, β-cells in adult humans are minimally replicative, and therefore fail to execute the second pro-regenerative phase of the HIF1α/PFKFB3 injury pathway. Instead, β-cells in T2D remain trapped in the pro-survival first phase of the HIF1α injury repair response with metabolism and the mitochondrial network adapted to slow the rate of cell attrition at the expense of β-cell function.

Circadian disruption and obesity synergize to predispose to development of type 2 diabetes mellitus (T2DM), signifying that therapeutic targeting of both circadian and metabolic dysfunctions should be considered as a potential treatment approach. To address this hypothesis, we studied rats concomitantly exposed to circadian disruption and diet-induced obesity (CDO), a rat model recently shown to recapitulate phenotypical aspects of obese T2DM (eg, circadian disruption, obesity, insulin resistance, and islet failure). CDO rats were subsequently treated daily (for 12 wk) by timed oral gavage with vehicle, melatonin (a known chronobiotic), metformin, or combination treatment of both therapeutics. Melatonin treatment alone improved circadian activity rhythms, attenuated induction of β-cell failure, and enhanced glucose tolerance. Metformin alone did not modify circadian activity but enhanced insulin sensitivity and glucose tolerance. Importantly, the combination of melatonin and metformin had synergistic actions to modify progression of metabolic dysfunction in CDO rats through improved adiposity, circadian activity, insulin sensitivity, and islet cell failure. This study suggests that management of both circadian and metabolic dysfunctions should be considered as a potential preventative and therapeutic option for treatment of obesity and T2DM.

Cell replication is a fundamental attribute of growth and repair in multicellular organisms. Pancreatic beta-cells in adults rarely enter cell cycle, hindering the capacity for regeneration in diabetes. Efforts to drive beta-cells into cell cycle have so far largely focused on regulatory molecules such as cyclins and cyclin-dependent kinases (CDKs). Investigations in cancer biology have uncovered that adaptive changes in metabolism, the mitochondrial network, and cellular Ca are critical for permitting cells to progress through the cell cycle. Here, we investigated these parameters in the replication-competent beta-cell line INS 832/13. Cell cycle synchronization of this line permitted evaluation of cell metabolism, mitochondrial network, and cellular Ca compartmentalization at key cell cycle stages. The mitochondrial network is interconnected and filamentous at G1/S but fragments during the S and G2/M phases, presumably to permit sorting to daughter cells. Pyruvate anaplerosis peaks at G1/S, consistent with generation of biomass for daughter cells, whereas mitochondrial Ca and respiration increase during S and G2/M, consistent with increased energy requirements for DNA and lipid synthesis. This synchronization approach may be of value to investigators performing live cell imaging of Ca or mitochondrial dynamics commonly undertaken in INS cell lines because without synchrony widely disparate data from cell to cell would be expected depending on position within cell cycle. Our findings also offer insight into why replicating beta-cells are relatively nonfunctional secreting insulin in response to glucose. They also provide guidance on metabolic requirements of beta-cells for the transition through the cell cycle that may complement the efforts currently restricted to manipulating cell cycle to drive beta-cells through cell cycle.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Background Spontaneous Coronary Artery Dissection (SCAD) is a rare cause of myocardial infarction and sudden cardiac death that is mostly seen in younger patients without significant cardiac risk factors. The mechanism by which SCAD causes an acute coronary event is related to the compromise of the coronary artery lumen as a result of hematoma within the vessel wall. In comparison to their non-pregnant counterparts, when SCAD is associated with pregnancy, it has been associated with an increased risk of life-threatening arrhythmias, cardiogenic shock, and death. The underlying mechanism behind SCAD is not yet fully understood, and despite the condition’s high mortality rate, it remains underdiagnosed. Case Presentation Our case features a 38-year-old woman at 29 weeks of gestation presenting with chest pain that persisted despite initial management. Coronary angiography revealed a Type 2a spontaneous dissection of the left anterior descending artery. Given the risks of percutaneous coronary intervention in SCAD management and overall clinical stability, the patient was treated with conservative management. Conclusion SCADs are a rare cause of acute coronary syndrome that can be found in patients without any prior cardiac risk factors. It is important to have a high index of suspicion when diagnosing SCADs given, they can cause life-threatening arrhythmias, cardiogenic shock, and death. This case highlights considerations that must be taken into account when treating P-SCAD, as opposed to SCAD in the postpartum period.