Proinsulin C-peptide reduces diabetes-induced glomerular hyperfiltration via efferent arteriole dilation and inhibition of tubular sodium reabsorption.
C-peptide reduces diabetes-induced glomerular hyperfiltration in diabetic patients and experimental animal models. However, the mechanisms mediating the beneficial effect of C-peptide remain unclear. We investigated whether altered renal afferent-efferent arteriole tonus or alterations in tubular Na+ transport (T(Na)) in response to C-peptide administration mediate the reduction of diabetes-induced glomerular hyperfiltration. Glomerular filtration rate, filtration fraction, total and cortical renal blood flow, total kidney O2 consumption (QO2), T(Na), fractional Na+ and Li+ excretions, and tubular free-flow and stop-flow pressures were measured in anesthetized adult male normoglycemic and streptozotocin-diabetic Sprague-Dawley rats. The specific effect of C-peptide on transport-dependent QO2 was investigated in vitro in freshly isolated proximal tubular cells. C-peptide reduced glomerular filtration rate (-24%), stop-flow pressure (-8%), and filtration fraction (-17%) exclusively in diabetic rats without altering renal blood flow. Diabetic rats had higher baseline T(Na) (+40%), which was reduced by C-peptide. Similarly, C-peptide increased fractional Na+ (+80%) and Li+ (+47%) excretions only in the diabetic rats. None of these parameters was affected by vehicle treatments in either group. Baseline QO2 was 37% higher in proximal tubular cells from diabetic rats than controls and was normalized by C-peptide. C-peptide had no effect on ouabain-pretreated diabetic cells from diabetic rats. C-peptide reduced diabetes-induced hyperfiltration via a net dilation of the efferent arteriole and inhibition of tubular Na+ reabsorption, both potent regulators of the glomerular net filtration pressure. These findings provide new mechanistic insight into the beneficial effects of C-peptide on diabetic kidney function.
Nordquist
Lina
L
Division of Integrative Physiology, Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden.
Brown
Russell
R
Fasching
Angelica
A
Persson
Patrik
P
Palm
Fredrik
F
D000818:Animals; D001160:Arterioles / Q000187:drug effects; D002096:C-Peptide / Q000494:pharmacology*; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism* / Q000503:physiopathology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005919:Glomerular Filtration Rate / Q000187:drug effects*; D007684:Kidney Tubules / Q000187:drug effects / Q000378:metabolism*; D008094:Lithium / Q000378:metabolism; D008297:Male; D009129:Muscle Tonus / Q000187:drug effects; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D010101:Oxygen Consumption / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D012079:Renal Circulation / Q000187:drug effects; D012964:Sodium / Q000378:metabolism*; D014664:Vasodilation / Q000187:drug effects*
D002096:C-Peptide; D004791:Enzyme Inhibitors; D010042:Ouabain; D008094:Lithium; D012964:Sodium; D019331:NG-Nitroarginine Methyl Ester