Krishnamurthy P Gudehithlu1, Peter D Hart2,3,4, Jane Vernik2,3, Periannan Sethupathi5, George Dunea2,5,4, Jose A L Arruda2,5,4, Ashok K Singh2,5,4. 1. Division of Nephrology, John H. Stroger, Jr. Hospital of Cook County (JSH), 1900 West Polk Street, Suite 643, Chicago, IL, 60612, USA. kgudehithlu@cookcountyhhs.org. 2. Division of Nephrology, John H. Stroger, Jr. Hospital of Cook County (JSH), 1900 West Polk Street, Suite 643, Chicago, IL, 60612, USA. 3. Department of Internal Medicine, Rush University Medical College, Chicago, IL, USA. 4. The Hektoen Institute of Medicine, Chicago, IL, USA. 5. Section of Nephrology, University of Illinois at Chicago, Chicago, IL, USA.
Abstract
BACKGROUND: To protect the kidney effectively with medication in type 2 diabetics, it is crucial to identify such at-risk patients early for treatment. We investigated whether peptiduria precedes proteinuria (the earliest urinary marker in our model), and thereby serve as an early predictor of diabetic nephropathy. METHODS: A longitudinal study was performed in a rat model of diabetic nephropathy. Peptides, defined as degradation products of proteins of < 13 kD size, were quantified by a previously validated method using a combination of Lowry and Biorad protein assays. Peptides in urine were also confirmed by chromatographically separating low molecular weight fractions from urine and quantifying albumin fragments in these fractions by enzyme immunoassay. Also, the mechanism of peptiduria was addressed by measuring acid phosphatase, a marker of lysosomal activity, in urine and on kidney sections (histochemically). RESULTS: In rats with diabetic nephropathy, proteinuria occurred after 12 weeks of diabetes, while peptiduria occurred as early as 2 weeks after diabetes. Peptiduria was confirmed by showing that the chromatographically separated low molecular weight fractions of urine containing albumin fragments is in proportion to the level of peptiduria. The time course of peptiduria paralleled the increase in urinary acid phosphatase suggesting that the mechanism of early peptiduria could be due to upregulation of lysosomal enzyme activity in the tubules. CONCLUSIONS: Our results showing that peptiduria precedes proteinuria in diabetic nephropathy provide a compelling rationale to perform a prospective human clinical trial to investigate whether peptiduria can serve as an early predictor of diabetic nephropathy.
BACKGROUND: To protect the kidney effectively with medication in type 2 diabetics, it is crucial to identify such at-risk patients early for treatment. We investigated whether peptiduria precedes proteinuria (the earliest urinary marker in our model), and thereby serve as an early predictor of diabetic nephropathy. METHODS: A longitudinal study was performed in a rat model of diabetic nephropathy. Peptides, defined as degradation products of proteins of < 13 kD size, were quantified by a previously validated method using a combination of Lowry and Biorad protein assays. Peptides in urine were also confirmed by chromatographically separating low molecular weight fractions from urine and quantifying albumin fragments in these fractions by enzyme immunoassay. Also, the mechanism of peptiduria was addressed by measuring acid phosphatase, a marker of lysosomal activity, in urine and on kidney sections (histochemically). RESULTS: In rats with diabetic nephropathy, proteinuria occurred after 12 weeks of diabetes, while peptiduria occurred as early as 2 weeks after diabetes. Peptiduria was confirmed by showing that the chromatographically separated low molecular weight fractions of urine containing albumin fragments is in proportion to the level of peptiduria. The time course of peptiduria paralleled the increase in urinary acid phosphatase suggesting that the mechanism of early peptiduria could be due to upregulation of lysosomal enzyme activity in the tubules. CONCLUSIONS: Our results showing that peptiduria precedes proteinuria in diabetic nephropathy provide a compelling rationale to perform a prospective human clinical trial to investigate whether peptiduria can serve as an early predictor of diabetic nephropathy.
Authors: Hee-Sung Ahn; Jong Ho Kim; Hwangkyo Jeong; Jiyoung Yu; Jeonghun Yeom; Sang Heon Song; Sang Soo Kim; In Joo Kim; Kyunggon Kim Journal: Int J Mol Sci Date: 2020-06-14 Impact factor: 5.923