AIM: To determine whether adiponectin detected in urine is present in its native form and if adiponectin receptors (AdipoR) present and functional in proximal tubular (HK-2) cells. BACKGROUND: Adiponectin is a protein with anti-inflammatory, anti-atherogenic and insulin-sensitizing properties. It has previously been detected antigenically in the urine in several forms of renal disease. METHODS: We compared the isoform distribution of urinary adiponectin in patients with proteinuric and non-proteinuric renal disease with that of matched controls using chromatography and enzyme-linked immunosorbent assay. We examined whether AdipoR were present in HK-2 cells by real-time reverse transcription polymerase chain reaction. Their functionality was investigated by determining the effect of recombinant adiponectin on adenosine monophosphate-activated protein kinase phosphorylation using western blotting, and on the secretion of monocyte chemotactic protein-1 and C3 using enzyme-linked immunosorbent assays. RESULTS: Adiponectin in the urine is physiologically intact and largely present as the low molecular weight isoform. Subjects with urinary protein >150 mg/L excreted significantly more adiponectin and its high and low molecular weight isoforms than those with <150 mg/L. mRNA for AdipoR were present in HK-2 cells, with levels of mRNA for AdipoR1 being 20 times greater than those for AdipoR2. Ligation of AdipoR on proximal tubular cells increased phosphorylation of adenosine monophosphate-activated protein kinase, and downregulated the secretion of the inflammatory cytokine monocyte chemotactic protein-1, but not of C3. CONCLUSION: Physiologically relevant isoforms of adiponectin are present in the urine of normal subjects and those with proteinuria. In addition, functional receptors for adiponectin are present in HK-2 cells. Abnormal levels of adiponectin in the urine may therefore activate these receptors, potentially resulting in anti-inflammatory activity.
AIM: To determine whether adiponectin detected in urine is present in its native form and if adiponectin receptors (AdipoR) present and functional in proximal tubular (HK-2) cells. BACKGROUND:Adiponectin is a protein with anti-inflammatory, anti-atherogenic and insulin-sensitizing properties. It has previously been detected antigenically in the urine in several forms of renal disease. METHODS: We compared the isoform distribution of urinary adiponectin in patients with proteinuric and non-proteinuric renal disease with that of matched controls using chromatography and enzyme-linked immunosorbent assay. We examined whether AdipoR were present in HK-2 cells by real-time reverse transcription polymerase chain reaction. Their functionality was investigated by determining the effect of recombinant adiponectin on adenosine monophosphate-activated protein kinase phosphorylation using western blotting, and on the secretion of monocyte chemotactic protein-1 and C3 using enzyme-linked immunosorbent assays. RESULTS:Adiponectin in the urine is physiologically intact and largely present as the low molecular weight isoform. Subjects with urinary protein >150 mg/L excreted significantly more adiponectin and its high and low molecular weight isoforms than those with <150 mg/L. mRNA for AdipoR were present in HK-2 cells, with levels of mRNA for AdipoR1 being 20 times greater than those for AdipoR2. Ligation of AdipoR on proximal tubular cells increased phosphorylation of adenosine monophosphate-activated protein kinase, and downregulated the secretion of the inflammatory cytokine monocyte chemotactic protein-1, but not of C3. CONCLUSION: Physiologically relevant isoforms of adiponectin are present in the urine of normal subjects and those with proteinuria. In addition, functional receptors for adiponectin are present in HK-2 cells. Abnormal levels of adiponectin in the urine may therefore activate these receptors, potentially resulting in anti-inflammatory activity.
Authors: Seung Seok Han; Eunjin Bae; Shin Young Ahn; Sejoong Kim; Jung Hwan Park; Sung Joon Shin; Sang Ho Lee; Bum Soon Choi; Ho Jun Chin; Chun Soo Lim; Suhnggwon Kim; Dong Ki Kim Journal: BMC Nephrol Date: 2015-08-01 Impact factor: 2.388