Adiposity Impacts Intrarenal Hemodynamic Function in Adults With Long-standing Type 1 Diabetes With and Without Diabetic Nephropathy: Results From the Canadian Study of Longevity in Type 1 Diabetes

Abstract

OBJECTIVE

Central adiposity is considered to be an important cardiorenal risk factor in the general population and in type 1 diabetes. We sought to determine the relationship between central adiposity and intrarenal hemodynamic function in adults with long-standing type 1 diabetes with and without diabetic nephropathy (DN).

RESEARCH DESIGN AND METHODS

Patients with type 1 diabetes ( n = 66, duration ≥50 years) and age-/sex-matched control subjects ( n = 73) were studied. The cohort was stratified into 44 DN Resistors (estimated glomerular filtration rate [eGFR] >60 mL/min/1.73 m ² and <30 mg/day urine albumin) and 22 patients with DN (eGFR ≤60 mL/min/1.73 m ² or ≥30 mg/day urine albumin). Intrarenal hemodynamic function (glomerular filtration rate for inulin [GFR _INULIN], effective renal plasma flow for p-aminohippuric acid [ERPF _PAH]) was measured. Afferent arteriolar resistance, efferent arteriolar resistance, renal blood flow, renal vascular resistance [RVR], filtration fraction, and glomerular pressure were derived from the Gomez equations. Fat and lean mass were quantified by DXA.

RESULTS

Whereas measures of adiposity did not associate with GFR _INULIN or ERPF _PAH in healthy control subjects, trunk fat mass inversely correlated with GFR _INULIN ( r = −0.46, P < 0.0001) and ERPF _PAH ( r = −0.31, P = 0.01) and positively correlated with RVR ( r = 0.53, P = 0.0003) in type 1 diabetes. In analyses stratified by DN status, greater central adiposity related to lower GFR _INULIN values in DN and DN Resistors, but the relationships between central adiposity and ERPF _PAH and RVR were attenuated and/or reversed in patients with DN compared with DN Resistors.

CONCLUSIONS

The adiposity-intrarenal hemodynamic function relationship may be modified by the presence of type 1 diabetes and DN, requiring further study of the mechanisms by which adiposity influences renal hemodynamic function.