Influence of glycemic control on the development of diabetic cardiovascular and kidney disease

The changes of serum sKlotho and NGAL levels and their correlation in type 2 diabetes mellitus patients with different stages of urinary albumin

OBJECTIVE

To investigate the changes of serum anti-aging protein Klotho and neutrophil gelatinase-associated lipocalin (NGAL) levels and their correlation in type 2 diabetes mellitus (T2DM) patients at different stages of diabetic kidney disease (DKD) determined by urinary albuminuria.

METHODS

462 cases with T2DM were divided into three groups: normoalbuminuric [N-UAlb; urinary albumin to creatinine ratio (UACR) < 30 mg/g, n=180], microalbuminuric [M-UAlb; UACR 30-300 mg/g, n = 158], macroalbuminuric [L-UAlb; UACR > 300 mg/g, n = 124]. The levels of serum soluble-Klotho (sKlotho), NGAL, 8-isoprostane prostaglandin F2α (8-iso-PGF2α), monocyte chemotactic protein-1 (MCP-1), tumor necrosis factor-α (TNF-α), transforming growth factor-β1 (TGF-β1) were determined by enzyme-linked immunosorbent assay (ELISA) in all cases and 160 control subjects.

RESULTS

Compared with control, serum sKlotho levels were significantly decreased (P < 0.001), and serum NGAL levels increased significantly (P < 0.001) in T2DM patients. Furthermore, serum sKlotho and NGAL levels were significantly negatively correlated (P < 0.001). Serum sKlotho levels negatively correlated with UACR, TG, CHO, LDL, 8-Iso-PGF2α, MCP-1, TNF-α, TGF-β1 (P < 0.001), but positively correlated with LDL (P < 0.001). Serum NGAL levels positively correlated with UACR, 8-Iso-PGF2α, MCP-1, TNF-α, TGF-β1 (P < 0.001). In addition, serum NGAL levels and LDL were significantly positively correlated (P = 0.005), and HDL was significantly negatively correlated (P < 0.001).

CONCLUSION

Serum Klotho and NGAL levels may become new biomarkers of the early diagnosis of DKD in T2DM. Klotho may participate in the development of DKD pathological mechanism such as oxidative stress related to inflammation, renal fibrosis, lipid metabolic disorders, modulating the pathological process of diabetic kidney tissue. NGAL may play a part in these mechanisms.

The renal transcriptome of db/db mice identifies putative urinary biomarker proteins in patients with type 2 diabetes: a pilot study

We sought to identify novel urinary biomarkers of kidney function in type 2 diabetes. We screened the renal transcriptome of db/db and db/m mice for differentially expressed mRNA transcripts that encode secreted proteins with human orthologs. Whether elevated urine levels of the orthologous proteins correlated with diminished glomerular filtration rate was tested in a cross-sectional study of n = 56 patients with type 2 diabetes. We identified 36 putative biomarker genes in db/db kidneys: 31 upregulated and 5 downregulated. Urinary protein levels of six selected candidates (endothelin-1, lipocalin-2, transforming growth factor-β, growth and differentiation factor-15, interleukin-6, and macrophage chemoattractant protein-1) were elevated in type 2 diabetic patients with subnormal glomerular filtration rate (i.e., <90 ml·min(-1)·1.73 m(-2)), independent of microalbuminuria, age, sex, race, and use of angiotensin-converting enzyme inhibitors and angiotensin receptor antagonists. In contrast, urinary levels of fibroblast growth factor were not increased. A composite variable of urine albumin and any of the six candidate markers was associated with subnormal estimated glomerular filtration rate more closely than albumin alone. In addition, urinary endothelin-1, growth and differentiation factor-15, and interleukin-6 were associated with a marker of proximal tubule damage, N-acetyl-β-d-glucosaminidase activity. These results suggest that gene expression profiling in diabetic mouse kidney can complement existing proteomic-based approaches for renal biomarker discovery in humans.

Therapeutic management of diabetic kidney disease

During the past 10 years, a global pandemic of end-stage renal disease (ESRD) attributed to diabetes mellitus has changed the therapeutic strategies based on landmark trials that have shown that diabetic micro- and macrovascular complications might be preventable. However, the remaining risk of the progression of diabetic kidney disease to ESRD is still high, despite newly introduced anti-diabetic, antihypertensive and dyslipidemic drugs in the 21st century. Here, we show the importance of targeting remission and regression of microalbuminuria in type 2 diabetic patients. To achieve the remission and regression of microalbuminuria, physicians have revised the management strategy of diabetic patients and have to act immediately. Early detection of microalbuminuria with continuous screening, the use of renin-angiotensin system blockades, and targets for HbA1c of <7.35% and systolic blood pressure of <130 mmHg are closely associated with the remission and regression of microalbuminuria, resulting in protection against the progression of diabetic kidney disease, as well as cardiovascular events. Our concept of the natural history of diabetic kidney disease has to be modified by our results and others. Reducing microalbuminuria is therefore considered to be an important therapeutic target and could be a pivotal biomarker of therapeutic success in diabetic patients. (J Diabetes Invest, doi:10.1111/j.2040-1124.2011.00112.x, 2011).