Dietary Acid Load is Associated With Serum Bicarbonate but not Insulin Sensitivity in Chronic Kidney Disease.
OBJECTIVE
In chronic kidney disease (CKD), dietary acid may promote metabolic acidosis and insulin resistance, which in turn may contribute to adverse clinical health outcomes. We examined associations between dietary acid load, serum bicarbonate, and insulin sensitivity in CKD.


METHODS
In a cross-sectional study, we collected 3-day prospective food diaries to quantify dietary acid load as net endogenous acid production (NEAP, the nonvolatile acid load produced by the diet's acid balance) and potential renal acid load (PRAL). We measured urine net acid excretion (NAE) in 24-hour urine samples. Insulin sensitivity was measured by hyperinsulinemic euglycemic clamp.


METHODS
Forty-two patients with CKD Stages 3 to 5 attending nephrology clinics in the Pacific Northwest and 21 control subjects (estimated glomerular filtration rate [eGFR] ≥ 60 mL/minute/1.73 m(2)).


METHODS
Serum bicarbonate and insulin sensitivity (SIclamp).


RESULTS
Mean age was 60.8 ± 13.6 years, and 54% of participants were men. Mean eGFR and serum bicarbonate concentrations were 34.4 ± 13.1 mL/minute/1.73 m(2) and 24.1 ± 2.9 mEq/L for participants with CKD and 88.6 ± 14.5 mL/minute/1.73 m(2) and 26.3 ± 1.8 mEq/L for control subjects, respectively. Mean NEAP, PRAL, and NAE were 58.2 ± 24.3, 9.7 ± 18.4, and 32.1 ± 19.8 mEq/day, respectively. Considering all participants, dietary acid load was significantly, inversely associated with serum bicarbonate, adjusting for age, gender, race, eGFR, body mass index, and diuretic use: -1.2 mEq/L per standard deviation (SD) NEAP (95% confidence interval [CI] -1.8 to -0.6, P < .0001); -0.9 mEq/L bicarbonate per SD PRAL (95% CI -1.5 to -0.4, P = .0005); -0.7 mEq/L bicarbonate per SD NAE (95% CI -1.2 to -0.1, P = .01). These associations were similar in participants with and without CKD. However, neither NEAP and PRAL nor NAE was significantly associated with SIclamp. Serum bicarbonate was also not significantly associated with SIclamp.


CONCLUSIONS
In CKD, dietary acid load is associated with serum bicarbonate, suggesting that acidosis may be improved by dietary changes, but not with insulin sensitivity.
University of Vermont College of Medicine, Burlington, Vermont; Kidney Research Institute, University of Washington, Seattle, Washington.
Halil O
HO
Ikizler
Kidney Research Institute, University of Washington, Seattle, Washington.
Leila
L
Zelnick
Kidney Research Institute, University of Washington, Seattle, Washington.
John
J
Ruzinski
Kidney Research Institute, University of Washington, Seattle, Washington.
Laura
L
Curtin
Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, VA Puget Sound Health Care System and University of Washington, Seattle, Washington.
Kristina M
KM
Utzschneider
Kidney Research Institute, University of Washington, Seattle, Washington; Division of Nephrology, Department of Medicine, University of Washington, Seattle, Washington; Department of Epidemiology, University of Washington, Seattle, Washington.
Bryan
B
Kestenbaum
Kidney Research Institute, University of Washington, Seattle, Washington; Division of Nephrology, Department of Medicine, University of Washington, Seattle, Washington.
Jonathan
J
Himmelfarb
Kidney Research Institute, University of Washington, Seattle, Washington; Division of Nephrology, Department of Medicine, University of Washington, Seattle, Washington; Department of Epidemiology, University of Washington, Seattle, Washington. Electronic address: deboer@u.washington.edu.
Ian H
IH
de Boer
D000138:Acidosis / Q000097:blood*; D000368:Aged; D001639:Bicarbonates / Q000097:blood*; D001786:Blood Glucose / Q000378:metabolism; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D004032:Diet / Q000009:adverse effects*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D006946:Hyperinsulinism / Q000097:blood; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged; D051436:Renal Insufficiency, Chronic / Q000097:blood*
D001639:Bicarbonates; D001786:Blood Glucose