Advanced glycation end products (AGEs) are a heterogeneous group of compounds that form continuously in the body. Their rate of endogenous formation is markedly increased in diabetes mellitus, a condition in which AGEs play a major pathological role. It is also known, however, that AGEs form during the cooking of foods, primarily as the result of the application of heat. This review focuses on the generation of AGEs during the cooking of food, the gastrointestinal absorption of these compounds, and their biological effects in vitro and in vivo. We also present preliminary evidence of a direct association between dietary AGE intake and markers of systemic inflammation such as C-reactive protein in a large group of healthy subjects. Together with previous evidence from diabetics and renal failure patients, these data suggest that dietary AGEs may play an important role in the causation of chronic diseases associated with underlying inflammation.

Dietary advanced glycosylation end products (AGEs) have been linked to insulin resistance in db/db(؉؉) mice. To test whether dietary AGEs play a role in the progression of insulin resistance in normal mice fed high-fat diets, normal C57/BL6 mice were randomly assigned to high-fat diets (35% g fat), either high (HAGE-HF group; 995.4 units/mg AGE) or low (by 2.4-fold LAGE-HF group; 329.6 units/mg AGE) in AGE content for 6 months. Age-matched C57/BL6 and db/db (؉؉) mice fed regular diet (5% g fat, 117.4 units/mg AGE) served as controls. After 6 months, 75% of HAGE-HF mice were diabetic and exhibited higher body weight (P < 0.001), fasting glucose (P < 0.001), insulin (P < 0.001), and serum AGEs (P < 0.01) than control mice, while none of the LAGE-HF mice were diabetic despite a similar rise in body weight and plasma lipids. The HAGE-HF group displayed markedly impaired glucose and insulin responses during glucose tolerance tests and euglycemic and hyperglycemic clamps and altered pancreatic islet structure and function compared with those of LAGE-HF mice, in which findings resembled those of control mice. The HAGE-HF group had more visceral fat (by two-and fourfold) and more AGE-modified fat (by two-and fivefold) than LAGE-HF and control mice, respectively. In the HAGE-HF group, plasma 8-isoprostane was higher (P < 0.01) and adiponectin lower (P < 0.001) than control mice, while in the LAGE-HF group, these were more modestly affected (P < 0.05). These results demonstrate that the development of insulin resistance and type 2 diabetes during prolonged high-fat feeding are linked to the excess AGEs/advanced lipoxidation end products inherent in fatty diets. Diabetes 54: 2314 -2319, 2005

Patients with end-stage renal disease (ESRD) undergoing hemodialysis are known to suffer cognitive deficits and stroke of unknown etiology. It has been suspected that the treatment itself may contribute to the syndrome by unknown mechanisms, which we investigated in this study. Endstage renal disease patients on hemodialysis (n = 19) or peritoneal dialysis (PD, n = 5) were compared with 14 healthy controls. Subjects participated in magnetic resonance imaging (MRI) measurements of cerebral atrophy, cerebral blood flow (CBF) arterial spin labeled-MRI (ASL-MRI), quantitative Doppler blood flow through the internal carotid artery, and cerebral oxymetry. The Doppler and oxymetry procedures were also performed at the beginning and end of a single hemodialysis session. End-stage renal disease patients on hemodialysis showed significant cerebral atrophy, associated with longer hemodialysis duration and cognitive deficits, including focal bilateral lesions in the caudate nucleus and midbrain. Cerebral oxygenation was extremely low before dialysis (rSO 2 41613, compared with 7062 in controls, P < 0.02) and improved only slightly after dialysis. Carotid blood flow was also very low at the start of dialysis (115628 mL/sec, versus 193656 in controls, P < 0.005) but normalized at the end of the session (181 mL/sec). The PD patients showed intermediate values, between the hemodialysis and controls. Notably, duration of hemodialysis treatment predicted global gray-matter volume (r = À0.74), change of blood flow during dialysis (r = À0.65), and baseline rSO 2 (r = À0.65). The findings suggest that ESRD patients on hemodialysis suffer low CBF during the interdialytic cycle. Coupled with low cerebral oxygenation levels and atherosclerosis, this may contribute significantly to the etiology of the observed cerebral atrophy, cognitive deficits, and high stroke prevalence.

Small GTPases of the Rho family are well known intracellular signaling proteins that act as molecular switches to control actin cytoskeleton organization in many cell types including smooth muscle (1-4). Recent studies indicate that RhoA-dependent signaling pathway controls vascular smooth muscle cell functions such as contraction, migration, and proliferation (5-6). In VSMCs, 1 the contractile effect of RhoA results from the activation of Rho-dependent kinase (ROK-␣), which phosphorylates the regulatory subunit of myosin light chain phosphatase (MBS) and thereby inhibits the phosphatase activity (7-8), thus allowing an increase in the level of phosphorylated myosin light chain and contraction at a constant intracellular calcium level [Ca 2ϩ ] i (9). This phenomenon is defined as Ca 2ϩ sensitization (10). ROK-␣ and another isoform Rho kinase, ROCK1, are serine/ threonine protein kinases that contain an amino-terminal catalytic kinase domain, a central coiled-coil domain in which Rho/GTP binds, and a carboxyl-terminal pleckstrin homology (PH) domain that is split by a cysteine-rich region (11-12). Insulin receptor substrate proteins (IRS) also contain an amino-terminal PH domain and phosphotyrosine binding domain domain. The PH domain is required for efficient phosphorylation of IRS-1 by the insulin receptor (13-15). In addition, IRS-1 also interacts with 14-3-3 proteins, a process apparently dependent on serine phosphorylation of IRS-1 (16).Recent studies from our laboratory (17) have shown that insulin rapidly stimulates myosin-associated phosphatase (MBP) activity by causing a site-specific decrease in MBS T695 phosphorylation by inactivating thrombin-stimulated Rho and one of its downstream effectors, Rho kinase. Furthermore, inhibition of PI3-kinase, nitric-oxide synthase (NOS), and cGMP signaling pathways abolished insulin-stimulated MBP activation suggesting the involvement of these signaling pathways in MBP activation (18). Thus, insulin stimulates MBP in VSMCs by activating the NO/cGMP signaling pathway that also inactivates Rho/Rho kinase (17). The effects of insulin on MBP activation and vasorelaxation were severely impaired in VSMCs isolated from diabetic Goto-Kakizaki rats and spontaneous hypertensive rats (SHR) due to defective IRS-1/PI3-kinase signaling as well as up-regulation of Rho kinase activity (18,19). These observations prompted us to explore in detail potential interactions between Rho signaling and insulin signaling pathways.In the present study, VSMCs were infected with an activated RhoA V14 , dominant negative RhoA N19 , and cGK I␣. We examined the effects of insulin and thrombin on ROK-␣/IRS-1 association, IRS-1 tyrosine phosphorylation, IRS-1/p85 PI3-kinase association, and PI3-kinase activation and its impact on MBS T695 site-specific phosphorylation and MBP activation. * This work was supported by a American Heart Association Established Investigator grant, medical education funds from Winthrop University Hospital, and by Deutsche Forschungsgemeinschaft Grant SFB355. The costs of ...

Our laboratory has demonstrated that insulin rapidly stimulates myosin-bound phosphatase (MBP) activity in vascular smooth muscle cells (VSMCs). In this study, we examined whether diabetes is accompanied by alterations in MBP activation and elucidated the components of the signaling pathway that mediate the effects of diabetes. VSMCs isolated from Goto-Kakizaki (GK) diabetic rats (a model for type 2 diabetes) exhibited marked impairment in MBP activation by insulin that was accompanied by failure of insulin to decrease the phosphorylation of a regulatory myosin-bound subunit (

BACKGROUNDThe appropriate dose of aspirin to lower the risk of death, myocardial infarction, and stroke and to minimize major bleeding in patients with established atherosclerotic cardiovascular disease is a subject of controversy. METHODSUsing an open-label, pragmatic design, we randomly assigned patients with established atherosclerotic cardiovascular disease to a strategy of 81 mg or 325 mg of aspirin per day. The primary effectiveness outcome was a composite of death from any cause, hospitalization for myocardial infarction, or hospitalization for stroke, assessed in a time-to-event analysis. The primary safety outcome was hospitalization for major bleeding, also assessed in a time-to-event analysis. RESULTSA total of 15,076 patients were followed for a median of 26.2 months (interquartile range [IQR], 19.0 to 34.9). Before randomization, 13,537 (96.0% of those with available information on previous aspirin use) were already taking aspirin, and 85.3% of these patients were previously taking 81 mg of daily aspirin. Death, hospitalization for myocardial infarction, or hospitalization for stroke occurred in 590 patients (estimated percentage, 7.28%) in the 81-mg group and 569 patients (estimated percentage, 7.51%) in the 325-mg group (hazard ratio, 1.02; 95% confidence interval [CI], 0.91 to 1.14). Hospitalization for major bleeding occurred in 53 patients (estimated percentage, 0.63%) in the 81-mg group and 44 patients (estimated percentage, 0.60%) in the 325-mg group (hazard ratio, 1.18; 95% CI, 0.79 to 1.77). Patients assigned to 325 mg had a higher incidence of dose switching than those assigned to 81 mg (41.6% vs. 7.1%) and fewer median days of exposure to the assigned dose (434 days [IQR, 139 to 737] vs. 650 days [IQR, 415 to 922]). CONCLUSIONSIn this pragmatic trial involving patients with established cardiovascular disease, there was substantial dose switching to 81 mg of daily aspirin and no significant differences in cardiovascular events or major bleeding between patients assigned to 81 mg and those assigned to 325 mg of aspirin daily. (Funded by the Patient-Centered Outcomes Research Institute; ADAPTABLE ClinicalTrials.gov number, NCT02697916.

Our laboratory has recently demonstrated that insulin induces relaxation of vascular smooth muscle cells (VSMCs) by activating myosin-bound phosphatase (MBP) and by inhibiting Rho kinase (Begum N, Duddy N, Sandu OA, Reinzie J, and Ragolia L. Mol Endocrinol 14: 1365-1376, 2000). In this study, we tested the hypothesis that insulin via the nitric oxide (NO)/cGMP pathway may inactivate Rho, resulting in a decrease in phosphorylation of the myosin-bound subunit (MBS(Thr695)) of MBP and in its activation. Treatment of confluent serum-starved VSMCs with insulin prevented thrombin-induced increases in membrane-associated RhoA, Rho kinase activation, and site-specific phosphorylation of MBS(Thr695) of MBP and caused MBP activation. Preexposure to N(G)-monomethyl-L-arginine, a NO synthase inhibitor, and R-p-8-(4-chlorophenylthio)cGMP, a cGMP antagonist, attenuated insulin's inhibitory effect on Rho translocation and restored thrombin-mediated Rho kinase activation and site-specific MBS(Thr695) phosphorylation, resulting in MBP inactivation. In contrast, 8-bromo-cGMP, a cGMP agonist, mimicked insulin's inhibitory effects by abolishing thrombin-mediated Rho signaling and promoted dephosphorylation of MBS(Thr695). Furthermore, expression of a dominant-negative RhoA decreased basal as well as thrombin-induced MBS(Thr695) phosphorylation and caused insulin activation of MBP. Collectively, these results indicate that insulin inhibits Rho signaling by decreasing RhoA translocation via the NO/cGMP signaling pathway to cause MBP activation via site-specific dephosphorylation of its regulatory subunit MBS.

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