Renal hyperfiltration in type 2 diabetes: effect of age-related decline in glomerular filtration rate

Abstract

Aims/hypothesis: We sought to characterise the effect of the age-related decline of GFR on hyperfiltration in type 2 diabetes and to identify clinical characteristics associated with hyperfiltration. Materials and methods: GFR was measured in 662 type 2 diabetic patients by plasma disappearance of 99 m-technetium-diethylene-triaminepenta-acetic acid. The prevalence of hyperfiltration was calculated using both an age-unadjusted GFR threshold of >130 ml min −1 1.73 m −2 and an age-adjusted threshold incorporating a decline of 1 ml min −1 year −1 after the age of 40. The hyperfiltering patients were compared with type 2 diabetic subjects who had a GFR between 90 and 130 ml min −1 1.73 m −2 and were matched for age, sex and disease duration to allow for identification of modifiable factors associated with hyperfiltration. Results: The prevalence of hyperfiltration was 7.4% when age-unadjusted and 16.6% when age-adjusted definitions were used. The age-unadjusted vs -adjusted prevalence rates for hyperfiltration were 50 vs 50%, 12.9 vs 23.4% and 0.3 vs 9.0% for patients aged <40 years, 40 to 65 years and >65 years, respectively. Both the age-unadjusted and -adjusted hyperfiltration groups had lower mean diastolic blood pressure and lower serum creatinine levels than the control groups. Although the ageunadjusted hyperfiltration group had larger kidneys compared to the control group, this difference was no longer significant when the age-adjusted definition was used. There were no differences in HbA 1 c, mean arterial pressure, antihypertensive use, insulin therapy, dyslipidaemia, frequency of macro-or microvascular complications, BMI, urinary sodium, urea and albumin excretion between the groups. Conclusions/interpretation: Hyperfiltration was still more common among younger patients with type 2 diabetes even after adjusting for the expected age-related decline in GFR. Hyperfiltration was associated with a lower mean diastolic blood pressure independent of age.

Factors affecting the progression of diabetic nephropathy and its complications: A single-center experience in Saudi Arabia

“…The presence of persistent proteinuria was a strong risk factor for subsequent loss of GFR, as shown by our findings that 75.6% of our patients had proteinuria and 16.5% reached ESRD, re-emphasizing earlier reports that established the importance of sustained increases in urine albumin excretion in the pathogenesis and diagnosis of diabetic kidney disease 13–1620. This is considerably higher than the reported rate in diabetic Pima Indians, with 15% progressing to ESRD at approximately 20 years of diabetes 26.…”

Estimating glomerular filtration rate in diabetes: a comparison of cystatin-C- and creatinine-based methods

“…The reference value iGFR was obtained by measuring the plasma disappearance of 99m Tc-diethylene-triamine-pentaacetic acid employing the Brochner-Mortensen correction [3]. Urinary albumin and serum electrolytes were measured as described previously [3].…”

“…Urinary albumin and serum electrolytes were measured as described previously [3]. Creatinine was measured on an automatic analyser (Hitachi 911; Roche Diagnostics, Mannheim, Germany), which produces creatinine values that fall within less than ±15% of the reference MDRD method.…”

The clinical significance of hyperfiltration in diabetes

“…In older patients with type 2 diabetes, hyperfiltration can be masked by this age-related decline in GFR. We documented the prevalence of hyperfiltration with and without adjustment for age in patients with type 2 diabetes in a clinic-based cross-sectional study of 662 patients with type 2 diabetes [28]. The overall prevalence of hyperfiltration was 7.4% without age correction and 16.6% after adjustment for age (Fig.…”

“…The age-unadjusted threshold for hyperfiltration was defined arbitrarily as a BrochnerMortensen corrected GFR of >130 ml min −1 1.73 m −2 . To account for the age-related decline in GFR, hyperfiltration was defined as GFR >130 ml min −1 1.73 m −2 minus 1 ml min −1 1.73 m −2 per year after the age of 40 [28]. Studies in hypertensive non-diabetic participants, using creatinine clearance as an index of GFR, have suggested that elevated GFR may be an indicator of early target organ damage [37,38].…”