Uremic solutes and risk of end-stage renal disease in type 2 diabetes: metabolomic study

Abstract

Here we studied plasma metabolomic profiles as determinants of progression to end-stage renal disease (ESRD) in patients with type 2 diabetes (T2D). This nested case-control study evaluated 40 cases who progressed to ESRD during 8-12 years of follow-up and 40 controls who remained alive without ESRD from the Joslin Kidney Study cohort. Controls were matched with cases for baseline clinical characteristics, although controls had slightly higher eGFR and lower levels of urinary albumin excretion than cases. Plasma metabolites at baseline were measured by mass spectrometry-based global metabolomic profiling. Of the named metabolites in the library, 262 were detected in at least 80% of the study patients. The metabolomic platform recognized 78 metabolites previously reported to be elevated in ESRD (uremic solutes). Sixteen were already elevated in the baseline plasma of our cases years before ESRD developed. Other uremic solutes were either not different or not commonly detectable. Essential amino acids and their derivatives were significantly depleted in the cases, whereas certain amino acid-derived acylcarnitines were increased. All findings remained statistically significant after adjustment for differences between study groups in albumin excretion rate, eGFR, or HbA1c. Uremic solute differences were confirmed by quantitative measurements. Thus, abnormal plasma concentrations of putative uremic solutes and essential amino acids either contribute to progression to ESRD or are a manifestation of an early stage(s) of the disease process that leads to ESRD in T2D.

Figure 1

Stability of the common metabolites within individual in subjects with type 2 diabetes in plasma samples taken 1-2 years apart. Footnote: Spearman rank correlation coefficients ( r ) are presented per individual measurements. Blue line and number represents median value per a specific class.

Figure 2

Multivariate analysis (volcano plot) of all common metabolites measured on the Metabolon platform and their association with progression to ESRD are demonstrated as a fold difference (x axis) and significance adjusted for multiple comparisons and presented as q values (y axis). Uremic solutes comprise metabolites of interests in Figure 2A, amino acids are metabolites of interests in Figure 2B. Uremic solutes are not displayed in Figure 2B. Common and stable metabolites of interest are represented as red circles (), common, but not stable over time as red empty circles (), all other common as grey circles (). Blue circles represent essential amino acids ().

Figure 2

Multivariate analysis (volcano plot) of all common metabolites measured on the Metabolon platform and their association with progression to ESRD are demonstrated as a fold difference (x axis) and significance adjusted for multiple comparisons and presented as q values (y axis). Uremic solutes comprise metabolites of interests in Figure 2A, amino acids are metabolites of interests in Figure 2B. Uremic solutes are not displayed in Figure 2B. Common and stable metabolites of interest are represented as red circles (), common, but not stable over time as red empty circles (), all other common as grey circles (). Blue circles represent essential amino acids ().

Figure 3

Logistic regression analysis of the effect of the plasma concentration of metabolites identified as uremic solutes on the risk of progression to ESRD in patients with T2D. Footnote: Data are odds ratios and 95% confidence intervals (OR, 95% CI) estimated for an effect of one standard deviation change of the metabolite. Abbreviations: ESRD – end stage renal disease, T2D – type 2 diabetes, HbA1c – hemoglobin A1c, AER – albumin excretion rate, eGFR – estimated glomerular filtration rate.

Figure 4

Logistic regression analysis of the effect of the plasma concentration of proteogenic amino acids and amino acid derivatives on the risk of progression to ESRD in subjects with T2D. Footnote: Data are odds ratios and 95% confidence intervals (OR, 95% CI) estimated for an effect of one standard deviation change of the metabolite. * Metabolite was not stable over time but is shown for its biological relevance. Abbreviations: ESRD – end stage renal disease, T2D – type 2 diabetes,HbA1c – hemoglobin A1c, AER – albumin excretion rate, eGFR – estimated glomerular filtration rate, OR – odds ratio.

Figure 5

Hierarchical cluster analysis (Ward's method) of the metabolites significantly associated with progression to ESRD. Separate clusters are marked in different colors. Distance scale is shown. Footnote: C1-C6 represent respective clusters.