Faculty Bibliography

Introduction: To provide longer-term follow-up of a previously published pilot randomized trial comparing bariatric surgery vs. intensive medical weight management (MWM) in patients with type 2 diabetes (T2DM) and BMI 30-35. Additionally, to assess whether the soluble form of RAGE (receptor for advanced glycation end-products) is an adequate diabetes biomarker that may help determine which patient population would benefit most from surgery. Methods: Originally, 57 patients with T2DM and BMI 30-35 were randomized to surgery (bypass, sleeve or band, based on patient preference; n=29) vs. MWM (n=28). The 6 month results showed that surgery was significantly effective (previously published data). We performed an updated review of this patient cohort to evaluate weight loss and diabetes remission at 2 years. A repeated measures linear model was created to compare the change in HbA1C and BMI between the two groups. The outcomes were also compared to baseline sRAGE status using a repeated measures linear model. Patients who ultimately crossed over from MWM to surgery group (after the initial study) were included. Results: At baseline, mean BMI was 32.6 and mean HbA1c was 7.8. At 2 years the following was noted: The surgery group continued to have significantly higher diabetes remission (50% vs. 0%), lower BMI (28.5 vs. 30.9; p<0.0001) and lower HbA1c (7.0 vs. 7.9; p=0.019) than the MWM group. In the surgical group, those with a higher baseline sRAGE had a lower post-op BMI (p=0.037). Conclusion: At 2 years, bariatric surgery was very effective in patients with T2DM and BMI 30-35. Higher baseline sRAGE predicted success with surgery. However, larger studies will be required to confirm the accuracy of these observations

Introduction: Inflammatory bowel diseases (IBD) are chronic and relapsing, lifelong diseases of the gastrointestinal tract. Environmental factors which have a crucial role in the development of these diseases remain largely unknown. Few studies have described Advanced Glycation End-Products (AGE) as potential contributors of intestinal inflammation, and the role of AGE and their receptor RAGE in the pathophysiology of IBD are not yet fully elucidated. Aims & Methods: The global aim of our study was to address the link between AGE, RAGE, and IBD which might help to better understand the role of nutrition, as a major source for AGE, in the pathophysiology of IBD. Three different models of intestinal and colonic inflammation (indomethacin, dextran sodium sulfate (DSS) and trinitro benzene sulfonic acid (TNBS)) were induced in C57BL/6 wild type (WT) and RAGE null mice. In a second set of experiments, mice were orally administered with the food derived ligand for RAGE, carboxymethyllysine-bovine serum albumin (CML-BSA) or control BSA for 30 days; then, intestinal and colonic inflammation were induced. Severity of inflammation was evaluated using macroscopic, histologic and molecular parameters in the small intestine and colon of mice. Results: Following indomethacin administration, a significant decrease in ulcerations number and area was observed in the duodenum, jejunum and ileum of RAGE null mice compared to WT mice. Consistently, IL1b mRNA levels were significantly decreased in the three intestinal segments. RAGE null mice were protected from DSS- and TNBS-induced colitis, with a significant decrease of clinical and macroscopic parameters. Myeloperoxidase (MPO) activity, reflecting the neutrophil infiltration, was also significantly reduced in the colon of TNBStreated RAGE null mice compared to TNBS- treated WT mice. IL1b and iNOS mRNA expression were significantly decreased in colitic RAGE null mice compared to colitic WT mice. Chronic BSA-CML administration to mice worsened indomethacin-induced enteritis, as evidenced by a significant increase in ulcerations number and area in the duodenum, jejunum and ileum compared to control BSA-treated mice. Consistently, MPO activity and oxidative stress assessed by anion superoxide dosage were significantly increased in the ileum of CML BSAtreated mice compared to control BSA-treated mice. Chronic CML-BSA administration did not induce any effect on colonic inflammation. Conclusion: We demonstrated that RAGE signaling pathway is implicated in intestinal and colonic inflammation in mice. We showed that BSA-CML might be a dietary factor involved in intestinal inflammation. The role of RAGE and AGE in IBD now merits further investigations

Emerging evidence links the receptor for advanced glycation endproducts (RAGEs) to the pathogenesis of tissue damage in chronic metabolic and inflammatory diseases. In human subjects, multiple reports suggest that in the plasma/serum, circulating levels of distinct forms of soluble RAGEs may be biomarkers of the presence or absence, and the extent of chronic disease. These considerations prompt us to consider in this review, what are soluble RAGEs; how are they formed; what might be their natural functions; and may they serve as biomarkers of inflammatory and metabolic disease activity? In this brief review, we seek to address what is known and suggest new areas for scientific investigation to uncover the biology of soluble RAGEs.

Types 1 and 2 diabetes are on the rise worldwide. Although the treatment of hyperglycemia has benefitted from recent advances, aggressive efforts to maintain euglycemia may be fraught with risk, especially in older subjects or in subjects vulnerable to hypoglycemic unawareness. Hence, strategies to prevent and treat the complications of hyperglycemia are essential. In this review, we summarize recent updates on the biology of the receptor for advanced glycation endproducts (RAGE) in the pathogenesis of both micro- and macrovascular complications of diabetes, insights from the study of mouse models of obesity and diabetic complications, and from associative studies in human subjects. The study of the mechanisms and consequences of the interaction of the RAGE cytoplasmic domain with the formin, mDia1, in RAGE signal transduction, will be discussed. Lastly, we review the 'state-of-the-art' on RAGE-directed therapeutics. Tackling RAGE/mDia1 may identify a novel class of therapeutics preventing diabetes and its complications

Background: The risk of developing Alzheimer's disease (AD) is magnified in individuals with metabolic dysfunction, specifically obesity and type 2 diabetes. In cases of insulin deficiency or resistance, elevated and fluctuating levels of blood glucose lead to the production of Advanced Glycation End Products (AGEs) that bind their receptor, RAGE, with pathological consequences. AGE-RAGE ligand binding induces intracellular signaling cascades, in part via the formin signal transduction effector, diaphanous- 1 (mDia1). Activation of this cellular mechanism activates NF-KB activation, upregulates pro-inflammatory molecules, increases RAGE expression, and ignites a positive feedback loop driving chronic inflammation in the periphery. Given that AGEs are increased in the brains of both diabetic and AD patients, here we investigate AGE-RAGE binding and subsequent mDia1 signal transduction as a possible mechanism of neuroinflammation, which contributes to the pathogenesis of AD. Methods: mDia1 and RAGE expression in microglia was evaluated by Immunoflourescent IHC in temporal cortex brain slices of AD and Non-Demented Aged human tissue. CD11b+ microglia were isolated from young (<10 month) and old (>16 month) APP London mice and aged matched controls and subjected to molecular analysis. BV-2 microglial- like cells were stimulated by the prototypic RAGE ligand, Carboxy Methyl Lysine (CML-AGE) (100 mug/mL) for 24 h, harvested, and Ager (RAGE), Drf1 (mDia1), Cd36, and Cd68RNA transcript levels were analyzed by q-RT-PCR. Results: mDia1 and RAGE are highly expressed in human AD and aged brain and colocalize, at least in part, to CD68+ activated microglia. mDia1 is highly expressed in CD11b+ microglia from APP London mice vs. aged matched controls. CML-AGE stimulated BV-2 cells display a 2-fold increased expression of mDia1, RAGE, CD36, and CD68 vs. vehicle treatment. Conclusions: RAGE and mDia1 are highly expressed in AD human brain, supporting their possible role in mediating pathogenesis. Acute stimulation with RAGE ligands upregulates inflammatory and phagocytosis markers in cultured BV-2 cells. Primary isolates of murine CD11b+ microglia demonstrate high levels of expression of mDia. These data suggest that RAGE may exert its pathogenic effects in AD brain, at least in part via mDia1-mediated neuroinflammation, thereby driving the AD phenotype. (Figure presented)

We investigated treatment with a receptor for advanced glycation endproduct (RAGE) blocking antibody on angiogenic response to hind limb ischemia in diabetic mice. Streptozotocin treated C57BL/6 mice received either murine monoclonal anti-RAGE F(ab')2 intraperitoneally (n=10) or saline (n=9) for 9 weeks. Diabetic plus 10 non-diabetic C57BL/6 mice underwent left femoral artery ligation and 5 days later angiogenesis imaging with (99m)Tc-Arg-Gly-Asp (RGD) nanoSPECT/CT. Twenty-four days later, hind limb blood flow was measured with ultrasound, the mice were euthanized, and tissue was taken for immunohistochemistry. The angiogenic imaging signal in ischemic limbs was higher in RAGE-ab treated versus saline treated mice at day 5 (3.1+/-1.4 vs 1.68+/-0.35, p=0.02) and blood flow was higher at day 24 (1.49+/-0.5 vs 0.61+/-0.39, p=0.04). Immunohistochemistry of ischemic muscles showed greater capillary density in the RAGE-ab treated group versus the vehicle-treated group (p<0.001) (NS from non-diabetic mice). In conclusion, treatment with anti-RAGE F(ab')2 in diabetic mice improves neovascularization in the ischemic leg.

SCOPE: Advanced glycation end-products (AGEs) are endogenously produced and are present in food. N(epsilon) -carboxymethyllysine (CML) is an endothelial activator via the receptor for AGEs (RAGEs) and is a major dietary AGE. This work investigated the effects of a CML-enriched diet and RAGE involvement in aortic aging in mice. METHODS AND RESULTS: After 9 months of a control diet or CML-enriched diets (50, 100, or 200 mugCML /g of food), endothelium-dependent relaxation, RAGE, vascular cell adhesion molecule-1, and sirtuin-1 expression, pulse wave velocity and elastin disruption were measured in aortas of wild-type or RAGE(-/-) male C57BL/6 mice. Compared to the control diet, endothelium-dependent relaxation was reduced in the wild-type mice fed the CML-enriched diet (200 mugCML /g) (66.8 +/- 12.26 vs. 94.3 +/- 2.6%, p < 0.01). RAGE and vascular cell adhesion molecule-1 (p < 0.05) expression were increased in the aortic wall. RAGE(-/-) mice were protected against CML-enriched diet-induced endothelial dysfunction. Compared to control diet, the CML-enriched diet (200 mugCML /g) increased the aortic pulse wave velocity (86.6 +/- 41.1 vs. 251.4 +/- 41.1 cm/s, p < 0.05) in wild-type animals. Elastin disruption was found to a greater extent in the CML-fed mice (p < 0.05). RAGE(-/-) mice fed the CML-enriched diet were protected from aortic stiffening. CONCLUSION: Chronic CML ingestion induced endothelial dysfunction, arterial stiffness and aging in a RAGE-dependent manner.

Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron disorder of largely unknown pathogenesis. Recent studies suggest that enhanced oxidative stress and neuroinflammation contribute to the progression of the disease. Mounting evidence implicates the receptor for advanced glycation end-products (RAGE) as a significant contributor to the pathogenesis of certain neurodegenerative diseases and chronic conditions. It is hypothesized that detrimental actions of RAGE are triggered upon binding to its ligands, such as AGEs (advanced glycation end products), S100/calgranulin family members, and High Mobility Group Box-1 (HMGB1) proteins. Here, we examined the expression of RAGE and its ligands in human ALS spinal cord. Tissue samples from age-matched human control and ALS spinal cords were tested for the expression of RAGE, carboxymethyllysine (CML) AGE, S100B, and HMGB1, and intensity of the immunofluorescent and immunoblotting signals was assessed. We found that the expression of both RAGE and its ligands was significantly increased in the spinal cords of ALS patients versus age-matched control subjects. Our study is the first report describing co-expression of both RAGE and its ligands in human ALS spinal cords. These findings suggest that further probing of RAGE as a mechanism of neurodegeneration in human ALS is rational.