AAV GCG-EGFP, a new tool to identify glucagon-secreting α-cells

Restoring glutamate receptor signaling in pancreatic alpha cells rescues glucagon responses in type 1 diabetes

Glucagon secretion from pancreatic alpha cells is crucial to prevent hypoglycemia. People with type 1 diabetes lose this glucoregulatory mechanism and are susceptible to dangerous hypoglycemia for reasons still unclear. Here we determine that alpha cells in living pancreas slices from donors with type 1 diabetes do not mount an adequate glucagon response and cannot activate the positive autocrine feedback mediated by AMPA/kainate glutamate receptors. This feedback is required to elicit full glucagon responses in the healthy state. Reactivating residual AMPA/kainate receptor function with positive allosteric modulators restores glucagon secretion in human slices from donors with type 1 diabetes as well as glucose counterregulation in non-obese diabetic mice. Our study thus identifies a defect in autocrine signaling that contributes to alpha cell failure. The use of positive allosteric modulators of AMPA/kainate receptors overcomes this deficiency and prevents hypoglycemia, an effect that could be used to improve the management of diabetes.

Gene Delivery of Manf to Beta-Cells of the Pancreatic Islets Protects NOD Mice from Type 1 Diabetes Development

In type 1 diabetes, dysfunctional glucose regulation occurs due to the death of insulin-producing beta-cells in the pancreatic islets. Initiation of this process is caused by the inheritance of an adaptive immune system that is predisposed to responding to beta-cell antigens, most notably to insulin itself, coupled with unknown environmental insults priming the autoimmune reaction. While autoimmunity is a primary driver in beta-cell death, there is growing evidence that cellular stress participates in the loss of beta-cells. In the beta-cell fragility model, partial loss of islet mass requires compensatory upregulation of insulin production in the remaining islets, driving a cellular stress capable of triggering apoptosis in the remaining cells. The Glis3-Manf axis has been identified as being pivotal to the relative fragility or robustness of stressed islets, potentially operating in both type 1 and type 2 diabetes. Here, we have used an AAV-based gene delivery system to enhance the expression of the anti-apoptotic protein Manf in the beta-cells of NOD mice. Gene delivery substantially lowered the rate of diabetes development in treated mice. Manf-treated mice demonstrated minimal insulitis and superior preservation of insulin production. Our results demonstrating the therapeutic potential of Manf delivery to enhance beta-cell robustness and avert clinical diabetes.

Integrin αEβ7 is involved in the intestinal barrier injury of sepsis

Background: IL-9-producing CD4(+) T (Th9) cell was related to acute intestinal barrier injury in sepsis. Integrin αEβ7 was an important lymphocyte homing receptor on the surface of intestinal Th9 cells. However, the roles of αEβ7 in the intestinal injury caused by Th9 cells were not clear in sepsis.

Methods: To investigate the roles of αEβ7 in the intestinal injury caused by Th9 cells in sepsis model, the Th9 cells percentages, αEβ7, E-cadherin, IL-9, and D-lactate levels in both serum and intestinal tissue were measured. The intestinal histopathology, epithelium apoptosis, and mucosal permeability measurement were also performed. The survival rate of septic rats was recorded daily for 14 days.

Results: Rats were assigned to four cohorts: control cohort, sepsis cohort, sepsis+αEβ7i (αEβ7 inhibition) cohort, and sepsis+αEβ7e (αEβ7 overexpression) cohort. The Th9 cells percentages, αEβ7, IL-9, and D-lactate levels of the sepsis cohort were significantly higher than those of the control cohort. The levels of these variables were also elevated progressively in the sepsis+αEβ7i cohort, sepsis cohort, and sepsis+αEβ7e cohort. The E-cadherin levels were decreased progressively in the control cohort, sepsis+αEβ7i cohort, sepsis cohort, and sepsis+αEβ7e cohort. Moreover, αEβ7 overexpression could decrease the 14-day survival rate. The findings of histopathology staining, apoptosis detection, and intestinal permeability test also confirmed that the barrier injury was deteriorated or relieved by elevating or decreasing the αEβ7 expression levels, respectively.

Conclusions: Integrin αEβ7 was closely associated with the intestinal barrier injury caused by Th9 lymphocytes in sepsis.

Interleukin-9 promotes intestinal barrier injury of sepsis: a translational research

Background

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection. Intestinal mucosal barrier injury is one of the important manifestations of sepsis. Interleukin-9 (IL-9) and IL-9-producing CD4(+) T cells were emerging pro-inflammatory mediators with development of intestinal injury. However, it is unclear whether IL-9 is related to the intestinal barrier injury of sepsis.

Methods

To investigate the roles of IL-9-producing CD4(+) T cells and IL-9 in the process of barrier injury in sepsis, serum IL-9-producing CD4(+) T cell percentages, IL-9, and D-lactate levels were measured in septic patients and controls. The markers of barrier function in serum and intestinal tissue were also collected in septic rats. Moreover, the barrier injury degree and survival rate of septic rats were also investigated after increasing or interfering with IL-9 expression.

Results

The serum IL-9-producing CD4(+) T cell percentages, IL-9, and D-lactate levels were significantly higher in septic patients or rats than those in controls. IL-9-producing CD4(+) T cells and IL-9 levels were positively correlated with D-lactate levels and had a high predictive value of 28-day mortality in septic patients. The non-survivors had significantly higher serum T cell percentages, IL-9, and D-lactate levels compared with survivors. In septic rats, IL-9 increased the expression levels of D-lactate, whereas that decreased the expression levels of zonula occludens 1. Moreover, the barrier injury was aggravated or alleviated by increasing or interfering with IL-9 expression, respectively. Survival rate analysis also showed that IL-9 decreased the 14-day survival rate of septic rats.

Conclusion

IL-9 is closely related to intestinal mucosal barrier injury and mortality in sepsis. IL-9 blockade has the potential to improve the barrier injury in sepsis.

Trial registration

The study was registered at ClinicalTrials.gov (ID: NCT03791866, Date: December 2018).

AAV8 Ins1-Cre can produce efficient β-cell recombination but requires consideration of off-target effects

In vivo genetic manipulation is used to study the impact of gene deletion or re-expression on β-cell function and organism physiology. Cre-LoxP is a system wherein LoxP sites flanking a gene are recognized by Cre recombinase. Cre transgenic mice are the most prevalent technology used to deliver Cre but many models have caveats of off-target recombination, impaired β-cell function, and high cost of animal production. Inducible estrogen receptor conjugated Cre models face leaky recombination and confounding effects of tamoxifen. As an alternative, we characterize an adeno associated virus (AAV) with a rat insulin 1 promoter driving Cre recombinase (AAV8 Ins1-Cre) that is economical and rapid to implement, and has limited caveats. Intraperitoneal AAV8 Ins1-Cre produced efficient β-cell recombination, alongside some hepatic, exocrine pancreas, α-cell, δ-cell, and hypothalamic recombination. Delivery of lower doses via the pancreatic duct retained good rates of β-cell recombination and limited rates of off-target recombination. Unlike inducible Cre in transgenic mice, AAV8 Ins1-Cre required no tamoxifen and premature recombination was avoided. We demonstrate the utility of this technology by inducing hyperglycemia in inducible insulin knockout mice (Ins1^−/−;Ins2^f/f). AAV-mediated expression of Cre in β-cells provides an effective alternative to transgenic approaches for inducible knockout studies.