Browsing by Author "Pattar, Guruprasad R."

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    A Nutrient Network Regulating Cellular Cholesterol and Glucose Metabolism
    (2014) Pattar, Guruprasad R.; Elmendorf, Jeffrey S.; Considine, Robert V.; Deeg, Mark A.; Herring, B. Paul; Kempson, Stephen A.
    Insulin resistance, a hallmark of type 2 diabetes (T2D), is associated with accompanying derangements such as hyperinsulinemia that promote the progression of insulin resistance, yet a mechanism(s) is imperfectly understood. Data have demonstrated that hyperinsulinemia promotes insulin resistance as evidenced by diminished ability of insulin to mobilize glucose transporter GLUT4 to the plasma membrane (PM). We found that loss of PM phosphatidylinositol 4,5-bisphosphate (PIP2)-regulated filamentous actin (F-actin) structure contributes to hyperinsulinemia-induced insulin resistance. We tested if increased glucose flux through hexosamine biosynthesis pathway (HBP) causes dysregulation of PM components necessary for GLUT4 translocation. Increased HBP activity was detected in 3T3-L1 adipocytes cultured in hyperinsulinemia (5 nM Ins; 12 h) and also 2 mM glucosamine (GlcN), a distal HBP activator, inducing losses of PM PIP2 and F-actin. In accordance with HBP flux directly weakening PIP2/F-actin structure, inhibition of the rate-limiting HBP enzyme (glutamine:fructose-6-phosphate amidotransferase) restored F-actin and insulin responsiveness. Furthermore, less invasive challenges with glucose led to PIP2/F-actin dysregulation. New findings support a negative correlation between PM cholesterol accrual, PIP2/F-actin structure and GLUT4 regulation. These data stemmed from parallel study aimed at understanding the antidiabetic mechanism of the nutrient chromium (Cr3+). We found that chromium picolinate (CrPic) enhanced insulin-stimulated GLUT4 trafficking via reduction in PM cholesterol. In line with glucose/cholesterol toxicity findings, we demonstrated that therapeutic effects of CrPic occurred solely in adipocytes with increased HBP activity and a concomitant elevation in PM cholesterol. Mechanistically, data are consistent with a role of AMP-activated protein kinase (AMPK) in CrPic action. These data show that CrPic increases AMPK activity and perhaps suppresses cholesterol synthesis via distal phosphorylation and inactivation of 3-hydroxy-3-methylglutaryl CoA reductase (HMGR), a rate-limiting enzyme in cholesterol synthesis. Continued study of the consequence of increased HBP activity revealed alterations in cholesterogenic transcription factors – Sp1, SREBP-1, and NFY – with Sp1 showing a significant increase in O-linked glycosylation. Consistent with Sp1 modification eliciting maximal transcriptional activation of SREBP-1, Hmgr mRNA was significantly enhanced. In conclusion, these data are consistent with a central role of PM cholesterol in glucose transport and suggest perturbations in this lipid have a contributory role in developing insulin resistance.
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    Posterior sub-Tenon capsule anesthesia for photocoagulation treatment of diabetic retinopathy performed in an inner-city county hospital clinic setting
    (Office of the Vice Chancellor for Research, 2015-04-17) Wise, Ryan J.; Pattar, Guruprasad R.; Xie, Jun; Phan, Anh-Danh T.
    Proliferative diabetic retinopathy (PDR) is a blinding eye disease demanding prompt therapy. However, treatment with panretinal photocoagulation (PRP) can be painful thereby limiting its extent. In addition, compliance to diabetic eye visits remains poor particularly in inner cities. Therefore, it is imperative to optimize treatment during clinic visits. The purpose of this study is to present the effect of sub-Tenon (Sub-T) capsule lidocaine anesthesia on PRP treatment extent for PDR performed during the eye clinic visit. This is an IRB-approved retrospective review of initial 12 eyes (9 subjects) with PDR undergoing PRP treatment involving Sub-T anesthesia in the eye clinic. Sub-T capsule lidocaine anesthesia was delivered and PRP was immediately performed. Primary end point was extent of treatment (number of PRP laser spots) delivered. Comparison was made to PRP in prior sessions without Sub-T anesthesia. All subjects had active PDR and sometimes vitreous hemorrhage (VH) at time of treatment. Decision was made to offer Sub-T anesthesia due to intolerable pain from prior PRP treatments in all subjects. We observed all subjects were able to tolerate a significantly greater extent of PRP with Sub-T anesthesia even with presence of VH, oftentimes undergoing thousands of laser spots and capable to complete treatment in same clinic visit. By comparison, prior PRP treatments (without Sub-T anesthesia) were much less extensive sometimes involving only a few laser spots. We conclude that Sub-T anesthesia allows a tier of pain control for those not able to tolerate traditional PRP without anesthesia performed in the eye clinic. This new information suggests that certain patients undergoing PRP can be offered Sub-T anesthesia, and it will be important to define algorithm for selection of such individuals.