Relationship between dietary protein intake and the changes in creatinine clearance and glomerular cross-sectional area in patients with IgA nephropathy.
BACKGROUND
Dietary protein intake (PI) induces glomerular hyperfiltration and reduced dietary PI can be effective in preserving kidney function. However, there is limited information regarding the relationship between dietary PI and glomerular histological changes in chronic kidney disease. We investigated the relationship between changes in dietary PI and both the changes in creatinine clearance and glomerular histomorphometry in adult patients with IgA nephropathy (IgAN).


METHODS
A total of 24 consecutive adult patients with biopsy-confirmed IgAN were enrolled and glomerular histomorphometric variables and clinical variables were investigated. The main clinical variables were differences in creatinine clearance (Ccr) (dCcr) and in PI (dPI) which were calculated by subtracting PI and Ccr values in patients on a controlled diet during hospitalization for kidney biopsy from the respective values in patients on daily diets as outpatients. These values of PI were estimated from urinary urea excretion measured by 24-h urine collection. The main renal histomorphometric variable was glomerular tuft area (GTA) (μm(2)).


RESULTS
dCcr positively correlated with dPI (r = 0.726, P < 0.001). GTA correlated positively with dPI (r = 0.556, P = 0.013). Multiple regression analysis showed that dPI was independently associated with both dCcr and GTA. Additionally, GTA positively correlated with dietary PI as outpatients (r = 0.457, P = 0.043).


CONCLUSIONS
Changes in dietary PI were associated with the changes in glomerular filtration rate. Furthermore, histomorphometric findings suggested that a greater dietary PI can affect the glomerular size at the time of the initial diagnostic biopsy for IgAN.
Department of Nephrology, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo, 160-0023, Japan, toshi-wa@tokyo-med.ac.jp.
Toshikazu
T
Wada
Toshiyuki
T
Nakao
Hiroshi
H
Matsumoto
Tomonari
T
Okada
Yume
Y
Nagaoka
Hideaki
H
Iwasawa
Asako
A
Gondo
Ami
A
Niwata
Yoshihiko
Y
Kanno
D000328:Adult; D003404:Creatinine / Q000652:urine; D004044:Dietary Proteins / Q000494:pharmacology*; D005260:Female; D005919:Glomerular Filtration Rate; D005922:Glomerulonephritis, IGA / Q000473:pathology / Q000503:physiopathology* / Q000652:urine; D006801:Humans; D007678:Kidney Glomerulus / Q000187:drug effects* / Q000473:pathology; D008297:Male; D055815:Young Adult
D004044:Dietary Proteins; D003404:Creatinine