Decreased expression of the GLP-1 receptor after segmental artery injury in mice

Abstract

The glucagon-like peptide-1 receptor (GLP-1R) is expressed in the renal vasculature and known to be decreased under hypertensive conditions in rats and humans. However, little is known about the regulation in other types of renal pathology involving vascular changes. This study investigates the expression of the GLP-1R in renal vasculature after glomerular injury in the nephrotoxic nephritis mouse model, high cholesterol, and atherosclerosis in the Ldlr-/- mouse on western diet, and ex vivo injury in an organ culture model. The immunohistochemical signal of the GLP-1R was significantly decreased in arteries from mice with nephrotoxic nephritis after 42 days compared to 7 days and saline control (p<0.05). Histological evaluation of kidneys from Ldlr-/- mice on western diet showed a decreased GLP-1R specific immunohistochemical signal (p<0.05). The dilatory response to liraglutide was decreased in western diet fed Ldlr-/- mice compared to C57Bl/6J controls (p<0.05). Organ culture significantly decreased the immunohistochemical signal of the GLP-1R (p<0.05) and the expression of Glp-1r mRNA (p<0.005) compared to fresh. Organ cultured vessels showed vascular smooth muscle cell remodelling as Acta2 expression was decreased (p<0.005) and Ednrb was increased (p<0.05). In conclusion, nephrotoxic nephritis and hypercholesterolemia led to decreased GLP-1R specific immunohistochemical signal. Ex vivo vascular injury in the organ culture model lead to a decrease in expression of GLP-R expression and contractile VSMC specific markers and increase in expression of dedifferentiation markers suggestive of an inverse relationship between phenotypic swich of the VSMC and the expression of the GLP-1R however, the causal relationship remains elusive.

Activation of the renal GLP‐1R leads to expression of Ren1 in the renal vascular tree

“…The present study was limited to healthy mice and mice with nephrotoxic serum nephritis independent of the pathophysiological consequences of diabetic nephropathy, that includes hyperglycemia and hypoinsulinemia, conditions that are known to affect renal vascular injury 43 . Studies in the hypercholesterolemic and prediabetic Ldlr −/− mouse on western diet and the NTN mouse model of chronic kidney disease showed a decrease in GLP‐1R expression in the renal vasculature in both models 44 . This suggests that the renal vascular GLP‐1 system is affected by prediabetes and atherosclerosis as well as direct chronic kidney damage.…”

“…Ldlr −/− mouse on western diet and the NTN mouse model of chronic kidney disease showed a decrease in GLP-1R expression in the renal vasculature in both models. 44 This suggests that the renal vascular GLP-1 system is affected by prediabetes and atherosclerosis as well as direct chronic kidney damage. In humans, diabetic nephropathy occurs predominantly in T2DM patients and is coincident with cardiovascular disease including atherosclerosis and hypertension.…”

Reagents and models for detecting endogenous GLP1R and GIPR

“…GLP1R/GIPR antisera, fluorescent agonists/antagonists and mouse models validated according to known cell localizations, enzyme self-labels, pharmacology, Glp1r/Gipr expression in enriched fractions, Glp1r − / − tissue, Glp1r − / − cells or GLP1R/GIPR-transfected cells. Reagent Name Source Reported cross-reactivity Validation GLP1R antibody [39] Mab 3F52 Iowa DSHB Human, primate GL1PR_BHK cells (and wild-type cells) GLP1R antibody [50] Mab 7F38 Iowa DSHB Human, Mouse, Rabbit, Rat Glp1r −/− mice GLP1R antagonistic antibody [ 27 , 48 ] Glp1R0017, GLP1R-APC University of Cambridge, Duke University Mouse Glp1r −/− mice, pharmacology, antibody co-localization GLP1R antibody [53] ab218532 Abcam Mouse, Rat Glp1r −/− mice GLP1R antibody * [18] MAB2814 RnD Systems Human SNAP_hGLP1R-U2OS (and wild-type cells) GLP1R agonist [ 57 , 58 , 60 , 61 ] E4 K12 -Fl, E4 ×12 -VT750, EP12-TR, EP12-BTMR, EP12-BTMR-X, EP40-BF, EP40-TR Harvard University Mouse, human GLP1R_HEK293 cells, MIN6, insulin reporter/staining, pharmacology GLP1R agonist [59] E4 x12 -Cy7 Memorial Sloan Kettering Cancer Center Mouse, human GLP1R_HEK293, insulin reporter, pharmacology GLP1R agonist [97] Ex4-Cy3, Ex4-Cy5 Novo Nordisk Mouse Glp1r −/− mice GLP1R agonist [ 65 , …”

“…Only reagents shown to stain/label primary tissues are included. Reagent Name Tissues stained or labeled GLP1R antibody [39] Mab 3F52 Pancreas, kidney, lung, heart, GI tract GLP1R antibody [50] Mab 7F38 Pancreas, kidney, lung, brain (non-fluorescent) GLP1R antagonistic antibody [ 27 , 48 ] Glp1R0017, GLP1R-APC Pancreas GLP1R antibody [53] ab218532 Pancreas, kidney, brain GLP1R agonist [97] Ex4-Cy3, Ex4-Cy5 Pancreas GLP1R agonist [ 65 , 66 ] Liraglutide 594 , Liraglutide 750 , Semaglutide VT750 Pancreas, brain GLP1R antagonist [ 22 , 29 , 66 ] LUXendin492, LUXendin551, LUXendin555, LUXendin615, LUXendin645, LUXendin651, LUXendin762, exendin(9-39) 594 Pancreas, brain …”

“…Mab 3F52 has been shown to stain primate and human islets, kidney, sinoatrial node, GI tract and thyroid [ 21 , 39 ]. One of the newest antibodies, Abcam ab218532, shows clear membrane-localized labeling using fluorescent and non-fluorescent immunohistochemistry of pancreatic islets, and was shown to stain wild-type but not Glp1r −/− tissue [53] . A final antibody, Novus 19400002 was shown to detect human GLP1R in hGLP1R_BHK cells using western blot, but was unable to detect GLP1R in Brunner's gland or pancreas, questioning its sensitivity [21] .…”