The prevalence of malnutrition among individuals with chronic kidney disease (CKD) is 30% to 40%, and the presence of protein-energy wasting malnutrition is a key predictor of increased risk for morbidity and mortality in that patient population. Results of previous studies have identified several nutritional factors, including serum albumin levels, creatinine levels, body mass index (BMI), and subjective global assessment (SGA) scores, as independent predictors of CKD mortality and treatment failure.
Among patients with autosomal dominant polycystic kidney disease (ADPKD), even in early stages of the disease, nutritional status may deteriorate due to external compression of the gastrointestinal tract from enlarged kidneys or liver. However, conventional anthropometric parameters, such as body weight and BMI, are ineffective in ADPKD settings.
Jinwoo Lee, MD, and colleagues in South Korea conducted a study to examine the association between good nutritional status and preservation of kidney function in a population of patients with ADPKD. Results were reported in the Journal of Renal Nutrition.
The prospective, observational study enrolled ambulatory patients with ADPKD at nine tertiary medical centers in Korea from May 2019 to December 2021. Exclusion criteria were age less than 18 years, known end-stage kidney disease at time of enrollment, diagnosis of atypical ADPKD, and use of tolvaptan.
The primary outcome of interest was a decline in estimated glomerular filtration rate (eGFR) of >3 mL/min/1.73 m2, based on nutritional status assessed by SGA score. Secondary outcomes included a decline in eGFR of >1 mL/min/1.73 m2, an increase in urine protein-creatinine ratio (UPCR) >0, and an increase in UPCR >0.3, based on SGA score after the 1-year follow-up.
The odds ratio for the primary outcome was calculated using a logistic regression model. In addition, due to differences in several variables, including Mayo classification, serum hemoglobin, serum creatinine, and UPCR between groups stratified according to SGA score, the researchers matched propensity scores.
The final analysis included 236 typical patients with ADPKD with 1-year follow-up data on kidney function and urine proteinuria. Mean age was 45.0 years and 49.6% were female. Approximately 36% had Mayo class 1C ADPKD, 82% had a history of hypertension, and 4% had a history of diabetes. Participants were stratified according to SGA score: SGA 3-5, n=12; SGA 6, n=37; and SGA 7, n=187.
Overall, mean eGFR at baseline was 81.9 mL/min/1.73 m2, and CKD stage 1 was the most common stage (42.8%). The three groups were similar in the proportion of use of angiotensin-converting enzyme inhibitor/angiotensin II receptor antagonist (ACEi/ARB). Of the baseline variables, there were significant trends only in Mayo classification, hemoglobin levels, basal renal function, UPCR, height-adjusted total kidney volume, height-adjusted total liver volume, and height-adjusted total kidney-liver volume (htTKLV).
At 1 year following enrollment, 38.6% of the 236 participants with available follow-up data (n=91) had a decrease of >3 mL/min/ 1.73 m2 in eGFR. The rates of a 1-year eGFR decline >3 mL/min/1.73 m2 were 53.1% in the SGA 3-6 group and 34.8% in the SGA 7 group (P=.029). The rates of a 1-year increase in UPCR >0.3 were 8.2% in the SGA 3-6 group and 2.7% in the SGA 7 group (P=.172).
In univariable logistic regression models, htTKLV and SGA 3-6 (vs SGA 7) were significant factors related to 1-year eGFR decline of >3 mL/min/1.73 m2. In a subsequent multivariable regression model that included all independent variables as adjusting variables, the risk of a 1-year decline in eGFR of >3 mL/min/1.73 m2 was higher in the SGA 3-6 group than in the SGA 7 group, irrespective of the adjustment.
In most subgroups, the preservation of kidney function in the SGA 7 group remained consistent. There was a significant benefit in patients with any of these criteria: age 60 or more years, male, BMI lower than 28, PKD1 mutation, history of hypertension, absence of diabetes mellitus, and eGFR <60 mL/min/1.73 m2. In contrast to other subgroups, among patients with a BMI greater than 28, there were no beneficial effects regarding preservation of kidney function associated with a well-nourished status (SGA 7).
The 1-year decline in eGFR of >3 mL/min/ 1.73 m2 remained higher in the SGA 3-6 group regardless of proteinuria matching propensity scores.
In results of analysis of covariance, there was a significant association between larger abdominal muscle mass area (AMMA) and better preserved 1-year kidney function. The association remained significant after adjustment for factors such as sex, Mayo classification, history of hypertension, serum hemoglobin, serum albumin, baseline eGFR, baseline UPCR, use of ACEi/ARB, and htTKLV. As AMMA increased, the 1-year follow-up eGFR significantly increased. However, while there was a decreasing proteinuria trend based on AMMA, the trend did not reach statistical significance. In contrast to SGA and AMMA, as abdominal fat mass area increased, the 1-year follow-up eGFR significantly decreased.
In citing limitations to the study, the researchers included the prospective, observational cohort design that could not completely determine the causality between good nutritional status and preserved kidney function; the possibility of selection bias and residual confounding factors; the lack of various biochemical and setting parameters other than eGFR and UPCR in the 1-year follow-up data; and the inability to accurately reflect the trend or trajectory of change in renal function.
In conclusion, the authors said, “Good nutritional status is associated with better-preserved kidney function in nonobese typical ADPKD patients not taking tolvaptan, and these beneficial effects on preserving renal function were reinforced when accompanied by more muscle mass and less fat mass. Future randomized clinical trials should determine the causality between them, and the present results can serve as a foundation for these.”
Source: Journal of Renal Nutrition
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