Increased urine podocyte-associated messenger RNAs in severe obesity are evidence of podocyte injury.

OBJECTIVE: The aim of this study was to correlate different degrees of excess weight with the expression of podocyte-associated messenger RNAs (mRNAs) in urine. METHODS: The sample comprised 83 patients with overweight or obesity class I, II, or III and 18 healthy controls. The expression of nephrin, podocin, podocalyxin, α-actinin-4, α3ß1integrin, vascular endothelial growth factor, and transforming growth factor-beta (TGF-ß1 ) mRNA in urine was quantified with the real-time polymerase chain reaction. mRNA expression was correlated with body mass index, the metabolic syndrome, albuminuria, and inflammation. RESULTS: Adults with obesity class III had higher levels of serum lipids, glucose, HbA1C, insulin resistance, and C-reactive protein (P < 0.05), with 85% of the subjects meeting criteria for the metabolic syndrome (P < 0.001 vs. other groups). Urinary podocyte-associated mRNAs were higher in adults with obesity class III than in other groups (P < 0.05). Patients with overweight or obesity class I or II also had higher levels of podocyte mRNAs than controls: nephrin (P = 0.021), α-actinin-4 (P = 0.014), α3ß1integrin (P = 0.036), and TGF-ß1 (P = 0.005). Metabolic syndrome, hyperinsulinemia, and C-reactive protein were correlated with podocyturia, but only higher insulin levels were related regardless of obesity. CONCLUSIONS: Severe obesity and hyperinsulinemia were associated with higher urinary expression of podocyte-associated mRNAs, even at normal urinary albumin excretion rates.

Messenger RNA levels of podocyte-associated proteins in subjects with different degrees of glucose tolerance with or without nephropathy.

BACKGROUND: To investigate gene expression of podocyte-specific proteins in urine of diabetes and prediabetes subjects and the association of these proteins with albuminuria. METHODS: Fifteen controls, 19 prediabetes, and 67 diabetes subjects were included. Messenger RNA of nephrin, podocin, podocalyxin, synaptopodin, TRPC6, alpha-actinin-4, and TGF-ß1 were measured using RT-PCR. Podocyte marker expression was correlated with albuminuria, glycemic control, and renal function. The diagnostic performance of the genes used to detect increased albuminuria was assessed using ROC curves and Poisson regressions. RESULTS: Podocyte marker expression was significantly higher in diabetic subjects. Urinary nephrin was correlated with increasing levels of albuminuria; risk of albuminuria increased by 20% for every one-unit increase in the log10 of nephrin mRNA. Nephrinuria was found in 53%, 71%, and 90% of normo-, micro-, and macroalbuminuric diabetes subjects, respectively (p = 0.023). Urinary nephrin, podocalyxin, TRPC6, podocin, and alpha actinin-4 were correlated with glycemic control and albuminuria but not with renal function. CONCLUSIONS: Diabetes subjects had higher urinary mRNA levels of podocyte proteins than nondiabetic subjects, even the normoalbuminuric patients. Nephrinuria was correlated with diabetic nephrophathy stage and predicted pathological albuminuria. Urinary mRNA levels of podocyte markers of prediabetic subjects did not differ from controls.