Effects of GIP on regional blood flow during normoglycemia and hyperglycemia in anesthetized rats

Abstract

The incretin hormone glucose‐dependent insulinotropic polypeptide (GIP) potentiates glucose‐stimulated insulin secretion, and affects β‐cell turnover. This study aimed at evaluating if some of the beneficial effects of GIP on glucose homeostasis can be explained by modulation of islet blood flow. Anesthetized Sprague–Dawley rats were infused intravenously with different doses of GIP (10, 20, or 60 ng/kg*min) for 30 min. Subsequent organ blood flow measurements were performed with microspheres. In separate animals, islets were perfused ex vivo with GIP (10−6–10−12 mol/L) during normo‐ and hyperglycemia and arteriolar responsiveness was recorded. The highest dose of GIP potentiated insulin secretion during hyperglycemia, but had no effect in normoglycemic rats. The highest GIP concentration decreased blood perfusion of whole pancreas, pancreatic islets, duodenum, colon, liver and kidneys. The decrease in blood flow was unaffected by ganglion blockade or adenosine receptor inhibition. In contrast to this, in single perfused islets GIP induced a dose‐dependent arteriolar dilation. Thus, high doses of GIP exert a direct dilatory effect on islet arterioles in isolated islets, but induce a generalized vasoconstriction in splanchnic organs, including the whole pancreas and islets, in vivo. The latter effect is unlikely to be mediated by adenosine, the autonomic nervous system, or endothelial mediators.

Renal effects of GLP-1 receptor agonists and tirzepatide in individuals with type 2 diabetes: seeds of a promising future

“…Conversely, despite being detected in several tissues (i.e., heart, adipose tissue), no GIPR expression was found in human kidneys [ 62 ]. In Sprague-Dawley rats, intravenous infusion of supraphysiologic doses of GIP induced vasoconstriction of splanchnic organs, including the kidney, with unclear mechanisms [ 63 ]. The engagement of GIPR in perirenal and intrarenal adipose tissue might produce anti-inflammatory effects reducing kidney damage [ 64 ].…”