Excretion of urinary epidermal growth factor in non-insulin dependent diabetes mellitus

Retinal blood oxygen saturation and aqueous humour biomarkers in early diabetic retinopathy

PURPOSE

The aim of this study was to assess the relationship between retinal blood oxygen saturation (SO₂ ) and specific aqueous humour (AH) concentrations of proangiogenic biomarkers in diabetic patients with nonproliferative diabetic retinopathy (NPDR) and to compare them with those of matched control subjects.

METHODS

The sample comprised 14 participants with mild-to-moderate NPDR (69.1 ± 6.6 years) and 17 age-matched healthy controls (69.7 ± 6.3 years); all participants were previously scheduled for routine cataract extraction with intraocular lens implantation. Multiplex cytokine analyses of specific biomarkers, including vascular endothelial growth factor A (VEGF-A), angiopoietin2 (Ang2), epidermal growth factor (EGF), hepatocyte growth factor (HGF) and interleukin-8 (IL-8) were performed by BioPlex 200 system. Six non-invasive hyperspectral retinal images were acquired.

RESULTS

Mean SO₂ was significantly higher in both arterioles (94.4 ± 1.9 versus 93.0 ± 1.6) and venules (64.4 ± 5.6 versus 55.9 ± 4.8) of NPDR than in the healthy controls (p < 0.001). AH levels of HGF (p = 0.018), Ang2 (p = 0.005) and IL-8 (p = 0.034) were significantly higher, and EGF (p = 0.030) was significantly lower in NPDR subjects. The study demonstrated a correlation between venular retinal blood oxygen saturation and proangiogenic factors HGF (r = 0.558, p = 0.038), Ang2 (r = 0.556, p = 0.039) and EGF (r = -0.554, p = 0.040), but did not find any correlation for IL-8 (r = 0.330, p = 0.249) even though this biomarker was significantly higher in the diabetic group.

CONCLUSION

To our knowledge, the present study is the first report considering the association between SO₂ and AH concentrations of protein biomarkers in diabetic retinopathy. The biomarkers of interest have been shown to participate in cell death, which may explain higher oxygen saturation in NPDR.

Urinary biomarkers involved in type 2 diabetes: a review

Diabetes mellitus is one of the most challenging health concerns of the 21st century. With at least 30% of the diabetic population remaining undiagnosed, effective and early diagnosis is of critical concern. Development of a diagnostic test, more convenient and reliable than those currently used, would therefore be highly beneficial. Urine as a diagnostic medium allows for non-invasive detection of biomarkers, including some associated with type 2 diabetes and its complications. This review provides a synopsis of those urinary biomarkers that potentially may provide a basis for the development of improved diagnostic tests. Three main pathways for the sourcing of potential makers are identified: kidney damage, oxidative stress and low-grade inflammation including atherosclerosis/vascular damage. This review briefly presents each pathway and some of the most relevant urinary biomarkers that may be used to monitor the development or progression of diabetes and its complications. In particular, biomarkers of renal dysfunction such as transferrin, type IV collagen and N-acetyl-beta-D-glucosaminidase might prove to be more sensitive than urinary albumin, the current gold standard, in the detection of incipient nephropathy and risk assessment of cardiovascular disease. Inflammatory markers including orosomucoid, tumour necrosis factor-alpha, transforming growth factor-beta, vascular endothelial growth factor and monocyte chemoattractant protein-1, as well as oxidative stress markers such as 8-hydroxy-2'deoxyguanosine may also be useful biomarkers for diagnosis or monitoring of diabetic complications, particularly kidney disease. However, the sensitivity of these markers compared with albumin requires further investigation.

Influence of long-term diabetes on renal glycogen metabolism in the rat

BACKGROUND/AIMS

The effects of acute insulin deficiency on the kidney have been investigated in animal models of experimental diabetes; however, the impact of long-term diabetes has not been determined.

METHODS

We measured renal glycogen contents in streptozotocin (STZ)-diabetic rats 3 weeks (n = 12) or 9 months (n = 12) after the induction of diabetes, and in 2 groups of control rats of similar age (n = 16 and n = 12, respectively), in the fed state and after a 24-hour fast.

RESULTS

Diabetic rats had high glucose levels, low insulin but normal glucagon concentrations in portal blood. In the fasting state, kidney glycogen content was very low in both young control and young diabetic rats (54 +/- 15 and 189 +/- 26 microg/g, respectively, mean +/- SD); in contrast, glycogen levels were markedly elevated in rats with long-standing diabetes as compared to old nondiabetic animals (2,628 +/- 1,023 +/- and 1,968 +/- 989 microg/g of diabetic rat, fasting and fed, respectively, p < 0.001 vs. 0 +/- 0 and 4 +/- 6 microg/g of control rats). On electron microscopy, large glycogen clusters were localized to the renal tubules. Kidney phosphorylase activity was higher, and synthase activity lower in diabetic than control rats (p < 0.05 for both), whereas kidney glycogen was strongly related to plasma glucose levels, suggesting that the enzyme changes were secondary to glycogen accumulation itself. Renal hexosephosphates and fructose-2,6-bisphosphate contents were both increased in long-term diabetic rats (p < 0.05), implying enhanced fluxes through both glycolysis and gluconeogenesis.

CONCLUSION

In chronic, untreated diabetes glycogen accumulates in the renal tubules; prolonged hyperglycemia is the sole driving force for this phenomenon.

Growth factors and the kidney in diabetes mellitus

Nephromegaly and mesangial matrix expansion observed in the diabetic kidney are all clues of a role of growth factors in the pathogenesis of these lesions. A growing body of evidence shows that changes in (1) insulin-like growth factor I regulation, and (2) the transforming growth factor beta loop exist in the kidney in the diabetic hypertrophic kidney and in diabetic glomerulosclerosis. However, other growth factors may be involved in some diabetic renal changes. The abnormalities in growth factor content and regulation, the role of growth factors in the diabetic kidney, and the effect of hyperglycemia and advanced glycosylation end products on growth factors in the kidney are reviewed.

Increased content of epidermal growth factor in platelet lysates in non-insulin-dependent diabetes mellitus

We evaluated the content of EGF in platelet lysates obtained from 49 patients with non-insulin-dependent diabetes mellitus (NIDDM)(18 males, 31 females, age 58 +/- 13 years) and from 23 clinically healthy control subjects (11 males, 12 females, age 53 +/- 18 years). Platelets were collected from platelet-rich plasma and lysed. EGF was determined by radioimmunoassay. The immunoreactive EGF content in the platelet lysates in diabetic patients significantly exceeded that of control subjects (44.9 +/- 18.5 pg/mm3platelet vs. 34.2 +/- 7.8 pg/mm3platelet, mean +/- SD p < 0.008). In performing multiple regression analysis with ten clinical parameters, urinary albumin excretion (F = 16.1, r = 0.551, p < 0.001), duration of diabetes (F = 13.0, r = 0.511, p < 0.001) and the presence of diabetic proliferative retinopathy (F = 8.8, p < 0.01) were significantly associated with irEGF content in platelet lysates. These observations suggest that the amount of EGF in platelets may increase with the progression of diabetic complications. The mechanism for the increase of EGF in platelets remains to be clarified.