Resting energy expenditure in chronic kidney disease: relationship with glomerular filtration rate.

BACKGROUND

The kidneys may account for up to 20% of resting energy expenditure (REE), but there is controversy regarding the relationship between severity of renal impairment and REE. Furthermore, reduction in protein intake is associated with declining glomerular filtration rate (GFR) that contributes to malnutrition. If a selective aversion to protein intake or a global reduction in food intake takes place is not known.

METHODS

To define the relationship between REE and its relationship to GFR, we measured REE with indirect calorimetry, GFR with iothalamate clearance, and body composition with creatinine kinetics and skin-fold measurements in 16 patients with mild to moderate renal failure due to type 2 diabetes mellitus (n = 12) or glomerulonephritides (n = 4).

RESULTS

In univariate analysis, age, weight, height, body mass index, lean body mass, urine urea nitrogen but not hemoglobin or albumin correlated with REE. In multivariate analysis, lean body mass emerged as the strongest predictor of REE followed by GFR. A lower GFR was associated with a lower REE. Also, we found reduced REE, but not a fall in GFR, was associated with a fall in dietary protein intake. This supports the hypothesis that patients with CKD have no selective aversion to protein; reduction in dietary protein intake with progressive CKD is due to global reduction in food intake.

CONCLUSIONS

We conclude that REE falls with declining renal function in patients with CKD. This is likely secondary to combination of reduced energy expenditure of kidneys, adaptation to decreased energy intake or alteration in cellular energy metabolism.