Hyperfiltration may lead to renal function loss and onset or progression of nephropathy in some patients with type 2 diabetes,
a new study has found.
European researchers performed a longitudinal cohort study to examine hyperfiltration (defined as a glomerular filtration
rate [GFR] ≥120 mL/min/1.73 m2) and its relation to
GFR decreases and nephropathy in patients with type 2 diabetes and
normo- or microalbuminuria. Six hundred
patients from two randomized trials examining the effect of
angiotensin-converting enzyme inhibitors on nephropathy in hypertensive
patients with type 2 diabetes and normo- or microalbuminuria
(albuminuria <200 µg/min) were included. Predefined
study end points were rate of GFR decline over time and time to
persistent micro- or macroalbuminuria (≥20 µg/min
and <200 µg/min or ≥200 µg/min, respectively). The study results were published online July 6 by Diabetes Care.
Patients were followed for a median of 4.0 years (range, 1.7 to
8.1 years). Ninety study patients (15%) had hyperfiltration
at baseline. Of the 47 with persistent hyperfiltration, 11
(23.4%) developed micro- or macroalbuminuria compared with 53 of
502 patients (10.6%) who had ameliorated hyperfiltration
(defined as a GFR reduction of 10%) at six months or who never developed
hyperfiltration (hazard ratio, 2.16; 95% CI, 1.13 to 4.14).
Over the study period, GFR decreased by 3.37 mL/min/1.73 m2
per year. Change in GFR from baseline to six months was the best
predictor of subsequent slope; a large change during this
period indicated a higher likelihood of a slower slope later.
Patients with persistent hyperfiltration tended to have faster
GFR decline than those with ameliorated hyperfiltration or
those who never developed hyperfiltration (4.19 vs. 3.23 mL/min/1.73
m2; P=0.09). Hyperfiltration amelioration
did not appear to be related to baseline characteristics or
angiotensin-converting enzyme
inhibitor treatment but was significantly associated with
improved blood pressure and improved metabolic control, amelioration
of glucose disposal rate and slower long-term decline of GFR
during follow-up.
The authors acknowledged that the post hoc observational nature
of the study limited their findings and that their results
are hypothesis-generating. However, they concluded that
persistent hyperfiltration may be an independent risk factor for faster
renal loss and nephropathy in patients with type 2 diabetes and
hypertension who have normo- or microalbuminuria, and that
ameliorating hyperfiltration may be renoprotective in such
patients. "Prospective ad hoc studies are needed to unravel the
mechanisms underlying persistent hyperfiltration despite
optimized metabolic and [blood pressure] control and to assess whether
and to what extent glomerular hyperfiltration can be a specific
treatment target for novel interventions aimed to limit renal
function loss in this population," they wrote.
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