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Objective. The retinol-binding protein 4 (RBP4) has been linked to the insulin resistance state in obesity and type 2 diabetes in animal studies. Data in humans are controversial and their relationship with organ damage in diabetic patients is lacking. We studied the association of plasma RBP4 with organ complications in type 2 diabetic patients.Setting. Sant Joan University Hospital, Reus, Spain.Subjects. 165 nonsmoker type 2 diabetic subjects according to American Diabetes Association criteria, aged 36-79 years, without proteinuria or severely decreased glomerular filtration rates (MDRD-GFR <30 mL min )1 1.73 m )2 ), were included in the study.Main outcome measure. Plasma RBP4 concentrations were the primary outcome variable. Statistics were performed in relation to clinical and subclinical arteriosclerosis, renal function parameters and biochemical data.Results. Plasma RBP4 concentrations were positively correlated with serum creatinine levels (r = 0.322, P < 0.001) and inversely correlated with MDRD-GFR (r = )0.468, P = 0.009). Patients with moderately renal dysfunction (MDRD-GFR <60 mL min )11.73 m )2 ) had higher plasma RBP4 concentrations than those with normal to mildly decreased GFR (55.3 ± 24.6 vs. 40.8 ± 15.4, P < 0.001). Patients in the top quartile of RBP4 concentrations had an increased adjusted odds ratio for moderately renal dysfunction compared with lower quartiles (4.68; 95% CI: 1.52-14.36, P = 0.007). The presence of microalbuminuria was not associated with RBP4. Plasma RBP4 concentrations were higher in those subjects with previous clinical arteriosclerosis than in event-free subjects (48.8 ± 24.2 vs. 40.6 ± 13.9, P = 0.045). The presence of retinopathy or polyneuropathy did not differ across RBP4 quartiles.Conclusions. Plasma RBP4 concentration might be a biomarker of nephropathy and cardiovascular disease in type 2 diabetic subjects.

Objective-Activation of Janus kinase/signal transducers and activators of transcription (STAT) pathway by hyperglycemia and dislypidemia contributes to the progression of diabetic complications, including atherosclerosis. Suppressor of cytokine signaling (SOCS) proteins negatively regulate Janus kinase/STAT and have emerged as promising target for anti-inflammatory therapies. We investigated whether a cell-permeable lipopeptide corresponding to the kinase inhibitory region of SOCS1 could reduce atherosclerosis in diabetic mice and identified the mechanisms involved. Approach and Results-Streptozotocin-induced diabetic apolipoprotein E-deficient mice (aged 8 and 22 weeks) were given intraperitoneal injections of vehicle, SOCS1-derived peptide, or control mutant peptide for 6 to 10 weeks. SOCS1 therapy suppressed STAT1/STAT3 activation in atherosclerotic plaques of diabetic mice and significantly reduced lesion size at both early and advanced stages of lesion development compared with vehicle group. Plaque characterization demonstrated that SOCS1 peptide decreased the accumulation of lipids, macrophages, and T lymphocytes, whereas increasing collagen and smooth muscle cell content. This atheroprotective effect was accompanied by systemic (reduced proinflammatory Ly6C high monocytes and splenic cytokine expression) and local (reduced aortic expression of chemokines and cytokines) mechanisms, without impact on metabolic parameters. In vitro, SOCS1 peptide dose dependently inhibited STAT1/ STAT3 activation and target gene expression in vascular smooth muscle cells and macrophages and also suppressed cytokine-induced cell migration and adhesion processes. Conclusions-SOCS1-based targeting

Heat shock proteins (HSPs) are induced by cellular stress and function as molecular chaperones that regulate protein folding. Diabetes impairs the function/expression of many HSPs, including HSP70 and HSP90, key regulators of pathological mechanisms involved in diabetes complications. Therefore, we investigated whether pharmacological HSP90 inhibition ameliorates diabetes-associated renal damage and atheroprogression in a mouse model of combined hyperglycemia and hyperlipidemia (streptozotocin-induced diabetic apolipoprotein E-deficient mouse). Treatment of diabetic mice with 17-dimethylaminoethylamino-17-demethoxygeldanamycin (DMAG, 2 and 4 mg/kg, 10 weeks) improved renal function, as evidenced by dose-dependent decreases in albuminuria, renal lesions (mesangial expansion, leukocyte infiltration, and fibrosis), and expression of proinflammatory and profibrotic genes. Furthermore, DMAG significantly reduced atherosclerotic lesions and induced a more stable plaque phenotype, characterized by lower content of lipids, leukocytes, and inflammatory markers, and increased collagen and smooth muscle cell content. Mechanistically, the renoprotective and antiatherosclerotic effects of DMAG are mediated by the induction of protective HSP70 along with inactivation of nuclear factor-kB (NF-kB) and signal transducers and activators of transcription (STAT) and target gene expression, both in diabetic mice and in cultured cells under hyperglycemic and proinflammatory conditions. In conclusion, HSP90 inhibition by DMAG restrains the progression of renal and vascular damage in experimental diabetes, with potential implications for the prevention of diabetes complications.

Interactive relationships between metabolism, inflammation, oxidative stress, and autophagy in the vascular system play a key role in the pathogenesis of diabetic cardiovascular disease. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is a stress-sensitive guarantor of cellular homeostasis, which cytoprotective contributions extend beyond the antioxidant defense. We investigated the beneficial effects and underlying mechanisms of the Nrf2 inducer tert-butyl hydroquinone (tBHQ) on diabetes-driven atherosclerosis. In the experimental model of streptozotocin-induced diabetes in apolipoprotein E-deficient mice, treatment with tBHQ increased Nrf2 activity in macrophages and vascular smooth muscle cells within atherosclerotic lesions. Moreover, tBHQ significantly decreased the size, extension and lipid content of atheroma plaques, and attenuated inflammation by reducing lesional macrophages (total number and M1/M2 phenotype balance), foam cell size and chemokine expression. Atheroprotection was accompanied by both systemic and local antioxidant effects, characterized by lower levels of superoxide anion and oxidative DNA marker 8-hydroxy-2′-deoxyguanosine, reduced expression of NADPH oxidase subunits, and increased antioxidant capacity. Interestingly, tBHQ treatment upregulated the gene and protein expression of autophagy-related molecules and also enhanced autophagic flux in diabetic mouse aorta. In vitro, Nrf2 activation by tBHQ suppressed cytokine-induced expression of pro-inflammatory and oxidative stress genes, altered macrophage phenotypes, and promoted autophagic activity. Our results reinforce pharmacological Nrf2 activation as a promising atheroprotective approach in diabetes, according to the plethora of cytoprotective mechanisms involved in the resolution of inflammation and oxidative stress, and restoring autophagy.

No abstract

Atherosclerosis is a chronic inflammatory disease of the arterial wall. NF-κB is a major regulator of inflammation that controls the expression of many genes involved in atherogenesis. Activated NF-κB was detected in human atherosclerotic plaques, and modulation of NF-κB inflammatory activity limits disease progression in mice. Herein, we investigate the anti-inflammatory and atheroprotective effects of a cell-permeable peptide containing the NF-κB nuclear localization sequence (NLS). In vascular smooth muscle cells and macrophages, NLS peptide specifically blocked the importin α-mediated nuclear import of NF-κB and prevented lipopolysaccharide-induced pro-inflammatory gene expression, cell migration, and oxidative stress. In experimental atherosclerosis (apolipoprotein E-knockout mice fed a high-fat diet), i.p., 0.13 μmol/day NLS peptide administration for 5 weeks attenuated NF-κB activation in atherosclerotic plaques. NLS peptide significantly inhibited lesion development at both early (age 10 weeks) and advanced (age 28 weeks) stages of atherosclerosis in mice, without affecting serum lipid levels. Plaques from NLS-treated mice contained fewer macrophages of pro-inflammatory M1 subtype than those from respective untreated controls. By contrast, the relative smooth muscle cell and collagen content was increased, indicating a more stable plaque phenotype. NLS peptide also attenuated pro-inflammatory gene expression and oxidative stress in aortic lesions. Our study demonstrates that targeting NF-κB nuclear translocation hampers inflammation and atherosclerosis development and identifies cell-permeable NLS peptide as a potential anti-atherosclerotic agent.

Diabetes is the main cause of CKD and ESRD worldwide. Chronic activation of Janus kinase and signal transducer and activator of transcription (STAT) signaling contributes to diabetic nephropathy by inducing genes involved in leukocyte infiltration, cell proliferation, and extracellular matrix accumulation. This study examined whether a cell-permeable peptide mimicking the kinase-inhibitory region of suppressor of cytokine signaling-1 (SOCS1) regulatory protein protects against nephropathy by suppressing STAT-mediated cell responses to diabetic conditions. In a mouse model combining hyperglycemia and hypercholesterolemia (streptozotocin diabetic, apoE-deficient mice), renal STAT activation status correlated with the severity of nephropathy. Notably, compared with administration of vehicle or mutant inactive peptide, administration of the SOCS1 peptidomimetic at either early or advanced stages of diabetes ameliorated STAT activity and resulted in reduced serum creatinine level, albuminuria, and renal histologic changes (mesangial expansion, tubular injury, and fibrosis) over time. Mice treated with the SOCS1 peptidomimetic also exhibited reduced kidney leukocyte recruitment (T lymphocytes and classic M1 proinflammatory macrophages) and decreased expression levels of proinflammatory and profibrotic markers that were independent of glycemic and lipid changes. In vitro, internalized peptide suppressed STAT activation and target gene expression induced by inflammatory and hyperglycemic conditions, reduced migration and proliferation in mesangial and tubuloepithelial cells, and altered the expression of cytokine-induced macrophage polarization markers. In conclusion, our study identifies SOCS1 mimicking as a feasible therapeutic strategy to halt the onset and progression of renal inflammation and fibrosis in diabetic kidney disease.