Serum proprotein convertase subtilisin/Kexin type 9 and vascular disease in type 2 diabetic patients.

BACKGROUND: Proprotein Convertase Subtilisin/Kexin type 9 (PCSK9) levels have been suggested as novel atherosclerotic biomarker. PCSK9 plays important roles in the pathogenesis of atherosclerosis by regulating the degradation of low-density lipoprotein receptor as well as different inflammatory pathways. Considering the important prognostic role of arterial stiffness in cardiovascular disease (CVD), the aim of the study is to investigate the correlation between PCSK9 levels and arterial stiffness in a cohort of diabetic patients, without previous CV events. METHODS: This cross-sectional analysis enrolled 401 Caucasian patients with type II diabetes mellitus (T2DM). PCSK9 levels were measured by ELISA test, arterial stiffness was estimated by measuring carotid-femoral pulse wave velocity (PWV). RESULTS: Patients were divided in three tertiles according to increasing value of PCSK9. From the I to the III tertiles, there was a significant increase in high sensitivity C-reactive protein (hs-CRP), fibrinogen and white blood cells (WBC) and a reduction in estimated glomerular filtration rate (e-GFR). Patients with higher levels of PCSK9 presented increased systolic, diastolic blood pressure, pulse pressure and PWV. PWV was significantly and directly correlated with PCSK9, fibrinogen, age, BMI and PP, and indirectly correlated with diet, lifestyle and e-GFR. Serum PCSK9 was the major predictor of PWV, justifying a 16.9% of its variation. CONCLUSION: Our study demonstrates a close association between circulating PCSK9 levels and PWV in T2DM subjects without previous CV events even after adjusting for well-known CV risk factor and pharmacological medications. Serum PCSK9 could be a useful biomarker for CV risk stratification in diabetic subjects.

Taurine prevents apoptosis induced by high ambient glucose in human tubule renal cells.

BACKGROUND: Hyperglycemia selectively triggers apoptosis in tubule and endothelial cells. Taurine, a conditionally essential amino acid, is abundant in several tubule segments, but its role has not been defined fully. It can serve as an osmolyte or as an endogenous antioxidant. Taurine metabolism is altered in diabetes mellitus, with extracellular and intracellular pools reduced. It is still unknown whether taurine can play a role as a protective agent in apoptosis induced by high glucose in tubular cells. METHODS: Apoptosis (by annexin V binding and the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling method), cellular reactive oxygen species (ROS) formation (by fluorescent probe 2'-7' dichlorofluorescin diacetate and FACScan flow cytometry), and Bcl-2 and Bax proteins (by immunostaining) were studied in a human proximal tubular cell line (HK-2) grown in a medium with physiologic (5.5 mM) or high (30 mM) glucose concentrations for 48 hours. In separate experiments, taurine (3-24 mM) was added to the media. RESULTS: The exposure of human tubule cells to 30 mM glucose for 48 hours resulted in a significant increase in apoptosis compared with 5.5 mM glucose (35 +/- 8% vs. 6 +/- 3%, p < 0.001). Thirty mM mannitol failed to induce the effects of high glucose. High glucose-mediated apoptosis was associated with a decrease in the expression of Bcl-2 (-87%) and a twofold increase in the expression of Bax protein. Taurine had a dose-dependent effect in preventing high-glucose-induced apoptosis (-78%, p < 0.001 at 24 mM). Moreover, with taurine, intracellular ROS decreased by 34% (p < 0.05), and changes in intracellular ROS formation induced by taurine at 24 hours predicted the variations in the apoptotic index at 48 hours (r = 0.87, p < 0.02). Other antioxidants, such as glutathione and N-acetylcysteine, also attenuated the high glucose-induced apoptosis. CONCLUSION: These results demonstrate that taurine attenuates hyperglycemia-induced apoptosis in human tubular cells via an inhibition of oxidative stress. Taurine might act as an endogenous antioxidant in tubule cells and could exert a beneficial effect in preventing tubulointerstitial injury in diabetic nephropathy.

Oxidative stress mediates apoptotic changes induced by hyperglycemia in human tubular kidney cells.

Reactive oxygen species (ROS) are important mediators for several biologic responses, including apoptosis. The present study evaluated the time course of changes in intracellular ROS production and apoptosis-related proteins, as well as apoptotic changes in human tubular proximal cells (HK-2 cells) exposed to hyperglycemia. Apoptosis (annexin V binding), ROS formation (fluorescence probe dichlorofluorescin diacetate and FACScan flow cytometry), and X chromosome-linked protein (XIAP; Western blot) were studied in HK-2 cells grown in a medium containing normal (NG) or high glucose (HG) concentrations (5.5 or 30 mM, respectively) for 18 to 48 h. HG promoted an increase (65% at 18 h and 73% at 24 h; P < 0.05 versus NG) in intracellular ROS generation. At 18 h, the NF-kB binding activity (evaluated by electrophoretic mobility-shift assay) was suppressed by HG. At the same time, the expression of NF-kB-induced antiapoptotic XIAP was reduced in HG-treated cells. Apoptotic changes were observed at 48 h (34 +/- 7% in HG versus 10 +/- 3% in NG; P < 0.001). Changes in ROS production at 24 h predicted changes in the apoptotic index at 48 h (r = 0.96, P < 0.0001). These results suggest that hyperglycemia induces apoptotic changes in human tubular cells via an increase in oxidative stress and that a downregulation of antiapoptotic protein XIAP is a component of this response.