Intracellular C3 protects β-cells from IL-1β-driven cytotoxicity via interaction with Fyn-related kinase

One of the hallmarks of type 1 but also type 2 diabetes is pancreatic islet inflammation, associated with altered pancreatic islet function and structure, if unresolved. IL-1β is a proinflammatory cytokine which detrimentally affects β-cell function. In the course of diabetes, complement components, including the central complement protein C3, are deregulated. Previously, we reported high C3 expression in human pancreatic islets, with upregulation after IL-1β treatment. In the current investigation, using primary human and rodent material and CRISPR/Cas9 gene-edited β-cells deficient in C3, or producing only cytosolic C3 from a noncanonical in-frame start codon, we report a protective effect of C3 against IL-1β-induced β-cell death, that is attributed to the cytosolic fraction of C3. Further investigation revealed that intracellular C3 alleviates IL-1β-induced β-cell death, by interaction with and inhibition of Fyn-related kinase (FRK), which is involved in the response of β-cells to cytokines. Furthermore, these data were supported by increased β-cell death in vivo in a β-cell-specific C3 knockout mouse. Our data indicate that a functional, cytoprotective association exists between FRK and cytosolic C3.

Comparative study of the estimation of exocrine pancreatic function using p-(N-acetyl-L-tyrosyl)- and p-(N-benzoyl-L-tyrosyl)aminobenzoic acid

A comparative study using the oral test with chymotrypsin substrates p-(N-acetyl-L-tyrosyl)- and p-(N-benzoyl-L-tyrosyl) aminobenzoic acid (Ac-Tyr-PAB and Bz-Tyr-PAB) was carried out in 43 adults divided into four groups comprising controls (n = 18), chronic pancreatitis (n = 13), after acute pancreatitis (n = 7), and celiac sprue (n = 4), after separate administration of both derivatives and determination of PABA urinary output in 6 and 8 hours. Both derivatives were diagnostically comparable. The specificity of both derivatives in the investigated group in 6 and 8 hours was 100%, and test sensitivity in patients with chronic pancreatitis, was in 6 hours 90.9% for Ac-Tyr-PAB and 72.7% for Bz-Tyr-PAB, and 8 hours 81.8% for both compounds. Differentiation between the controls and the chronic pancreatitis group was better in Ac-Tyr-PAB, as adjudged by the sensitivity and significance of the Student t-test criterion.