Shai Gavi

Influence of Age on the Association of Retinol-binding Protein 4 With Metabolic Syndrome

Objective: The relationships of retinol‐binding protein 4 (RBP4) with insulin sensitivity and body fat distribution have been investigated in a few recent studies with conflicting results. This may have been due to differences in ages of the subjects in the different studies. The aim of this study was to investigate whether the association of RBP4 and insulin sensitivity and percent trunk fat are influenced by age.

Trafficking of β2-adrenergic receptors: insulin and β-agonists regulate internalization by distinct cytoskeletal pathways

Insulin and β-adrenergic agonists stimulate a rapid phosphorylation and sequestration of the β2-adrenergic receptors (β2ARs). Although the expectation was that a common pathway would be involved in the trafficking of the β2AR in response to either hormone, studies reported herein show the existence of unique cytoskeletal requirements for internalization/recycling of G-protein-coupled receptors, such as the β2AR. Treatment of human epidermoid carcinoma A431 cells with nocodazole, which binds tubulin monomer in vivo and catalyzes the depolymerization of microtubules, effectively blocks β-adrenergic agonist-induced, but not insulin-induced, sequestration of β2ARs. Treatment with latrunculin-A, an agent that sequesters actin monomer and leads to loss of actin filaments, had no effect on the ability of β-adrenergic agonists to stimulate internalization of β2ARs, but blocked the ability of insulin to stimulate counterregulation of β2ARs via internalization. Although nocodazole had no effect on insulin-stimulated sequestration of β2ARs, the recycling of the internalized receptors to the cell membrane was sensitive to depolymerization of microtubules by this agent. Latrunculin-A, by contrast, blocks the recycling of β2ARs internalized in response to β-agonist, while attenuating recycling of receptors internalized in response to insulin stimulation. These data show the existence of unique cytoskeletal requirements for G-protein-coupled-receptor trafficking in response to agonist compared with a counterregulatory hormone, and for sequestration versus recycling of the receptors to the cell membrane.

Plasma Retinol-Binding Protein-4 Concentrations Are Elevated in Human Subjects With Impaired Glucose Tolerance and Type 2 Diabetes Response to Cho et al.

In their recent study, Cho et al. (1) demonstrated higher levels of retinol-binding protein-4 (RBP4) in in-dividuals with impaired glucose tolerance and type 2 diabetes. Additionally, higher waist circumferences increased with plasma RBP4 quartiles. This was also demonstrated by Graham et al. (2). Cho et al. suggested that visceral fat may be more important than total body fat in determining circulating RBP4 levels. In our study (3), we investigated whether visceral …

Test Results Follow-Up: A Systematic Review

To the Editors:—We applaud the work by Callen et al.,1 as it highlights a tremendous patient safety issue. As hospitalists, one of our greatest concerns has been the potential neglect in the ambulatory setting of the incidental radiological findings identified in hospitalized patients. The fact that these findings are not the center of attention during the hospital stay makes these findings less likely to be addressed in the medical chart, discussed with the patient, or communicated to the next provider to assure appropriate follow-up.