Small G proteins in insulin action: Rab and Rho families at the crossroads of signal transduction and GLUT4 vesicle traffic

Insulin stimulates glucose uptake into muscle and adipose tissues through glucose transporter 4 (GLUT4). GLUT4 cycles between the intracellular compartments and the plasma membrane. GLUT4 traffic-regulating insulin signals are largely within the insulin receptor-insulin receptor substrate-phosphatidylinositol 3-kinase (IR-IRS-PI3K) axis. In muscle cells, insulin signal bifurcates downstream of the PI3K into one arm leading to the activation of the Ser/Thr kinases Akt and atypical protein kinase C, and another leading to the activation of Rho family protein Rac1 leading to actin remodelling. Activated Akt inactivates AS160, a GTPase-activating protein for Rab family small G proteins. Here we review the roles of Rab and Rho proteins, particularly Rab substrates of AS160 and Rac1, in insulin-stimulated GLUT4 traffic. We discuss: (1) how distinct steps in GLUT4 traffic may be regulated by discrete Rab proteins, and (2) the importance of Rac1 activation in insulin-induced actin remodelling in muscle cells, a key element for the net gain in surface GLUT4.     

Extracapsular extension on multiparametric magnetic resonance imaging better predicts pT3 disease at radical prostatectomy compared to perineural invasion on biopsy

IntroductionRisk assessment for non-organ-confined prostate cancer (PCa) is important in the surgical planning for radical prostatectomy (RP). Perineural invasion (PNI) on prostate biopsy has been associated with adverse pathological outcomes at prostatectomy. Similarly, the identification of suspected extracapsular extension (ECE) on multiparametric magnetic resonance imaging (mpMRI) has been shown to predict non-organ-confined disease. However, no prior study has compared these factors in predicting adverse pathology at prostatectomy. We evaluated mpMRI ECE and prostate biopsy PNI on multivariable analysis to determine their ability to predict pathological stage at time of RP.MethodsWe retrospectively investigated the prostatectomy database at our institution to identify men who underwent prostate biopsy with pre-biopsy mpMRI and subsequent RP from 2013–2017. Multivariable regression analysis was performed to compare the association of mpMRI ECE (mECE) and PNI on prostate biopsy on the likelihood of finding pT3 disease on pathology post-prostatectomy.ResultsOf a total 454 RP between 2013 and 2017, 191 patients met our inclusion criteria. Stage pT2 and pT3+ were found in 120 (62.8%) and 71 (37.2%) patients, respectively. Patients with mECE had 4.84 cumulative odds of worse pathological stage on RP (p=0.045) compared to PNI on biopsy, which showed cumulative odds of 2.25 (p=0.048). When controlling only for those patients without PNI, mECE was still found to be a significant predictor of pT3 disease at RP (p=0.030); however, in patients without mECE, PNI was not significant (p=0.062).ConclusionsWhile mECE and biopsy PNI were both associated with worse pathological stage on RP, mECE had significantly higher cumulative odds compared to PNI. The significant predictive ability of mECE adds further clinical value to the use of mpMRI in PCa management. While validation in a larger cohort is required, these factors have important clinical implications with regards to early diagnosis of advanced disease and surgical planning.     

Central nervous system lymphoma and Epstein-Barr virus in immunocompetent patients in Thailand

A series of 11 apparently immunocompetent patients with primary non-Hodgkin's lymphoma of the central nervous system (NHL-CNS) together with six patients with systemic lymphoma involving the spinal cord and/or brain were studied for immunophenotyping and the presence of Epstein-Barr virus (EBV). Immunohistochemistry and polymerase chain reaction (PCR) were performed on paraffin-embedded tissues. Nine of 11 primary NHL-CNS and all six secondary CNS lesions were of B cell origin. The EBV sequences were detected in six primary tumors and four systemic lesions by PCR while the immuno-histochemical marker for the EBV-latent membrane protein was positive in five primary lesions and three secondary neoplasms. Our results suggest that the association of EBV and NHL-CNS is not only restricted to patients with immunosuppression but that it includes a broad spectrum of conditions in which this relationship occurs in patients without immunodeficiency. The mortality rate is high particularly in patients with EBV-associated NHL-CNS.     

New concepts in the management of ischaemic lower extremities

Experience with a new operative procedure namely arterialization of popliteal vein (APV) on 182 cases with 80% success for ischaemic lower extremity due to chronic nonspecific arterial occlusive diseases (ChNAOD) not responding to conservative methods of management currently in vogue is described. Success of this new operation saves the limbs from amputation which was done when conservative methods failed. The main purpose of this article is to write about etiology-clinical features--laboratory--and angiographic findings of this ChNAOD and APV operation. Accidental discovery of gastrocnemious muscle circulation responsible for success of APV operation is mentioned.     

Fas expression in lung metastasis from osteosarcoma patients

The authors' animal studies have shown that the metastatic potential of osteosarcoma (OS) cells correlates inversely with Fas expression-that is, Fas-negative cells metastasize but Fas-positive cells do not. One reason for this in the context of OS lung metastases may be that Fas-positive cells are eliminated by engagement with the Fas ligand (FasL) constitutively expressed on the surface of pneumocytes, whereas Fas-negative tumor cells are not. The purpose of this study was to determine the status of Fas expression in OS lung metastases from patients. Specifically, archived paraffin-embedded specimens of lung metastases from 38 patients with OS were analyzed by immunohistochemistry. Lung nodules from 23 of the 38 patients (60%) were Fas negative, those from 12 patients (32%) were weakly positive, and that from only 1 patient (3%) was strongly positive. Findings in the samples from the remaining two patients (5%) could not be interpreted because of extensive necrosis. Most patients with the weakly positive tumors and the single patient with the strongly positive tumor received chemotherapy prior to lung resection. There was a significant correlation between Fas expression and the administration of preoperative salvage chemotherapy (P = 0.0013). These data indicate that loss of Fas may be one mechanism by which OS cells evade host resistance in the lung. Chemotherapy may induce regression by upregulating Fas.     

Gallbladder management during laparoscopic Roux-en-Y gastric bypass surgery: routine preoperative screening for gallstones and postoperative prophylactic medical treatment are not necessary

In the bariatric surgery literature, the optimum approach to the gallbladder is controversial. Recommendations range from concomitant cholecystectomy to selective screening and postoperative medical prophylaxis. At our institution, we have taken a highly selective approach where patients are not routinely screened for gallstones, nor are they medically treated postoperatively with bile salts. We have reviewed our experience with this approach. From January 2003 to January 2005, 407 laparoscopic Roux en Y gastric bypasses were performed at UCLA and postoperative outcomes were collected into a prospective database. Exclusion criteria included previous cholecystectomy, a follow-up period less than 6 months, or incomplete records. One hundred ninety-nine patients were included in the study. With a mean follow up period of 17.8 months, 12 (6%) patients required cholecystectomy for gallstone-induced pathology. Laparoscopic removal was performed in 11 (92%) patients. Indications for surgery included acute cholecystitis in five (2.5%) patients, gallstone pancreatitis in two (1%) patients, and biliary colic alone in another five (2.5%) patients. The incidence of symptomatic gallstones requiring cholecystectomy after laparoscopic Roux en Y gastric bypass is low. These results are similar to those from institutions where routine preoperative screening and prophylactic postoperative medical therapy is used. Routine preoperative screening or medical prophylaxis may not be necessary.     

Preoperative parameters, including percent positive biopsy, in predicting seminal vesicle involvement in patients with prostate cancer

PURPOSE: Complete dissection of the SVs during RP can contribute to increased morbidity including erectile dysfunction and incontinence. Therefore we evaluated the clinical parameters associated with a positive SV finding on final pathology and identified those patients with a minimal risk of SV involvement for potential SV sparing surgery. MATERIALS AND METHODS: We retrospectively reviewed our RP database from 1991 to 1999 to evaluate the incidence and clinical correlates of SV invasion. Variables studied included preoperative total serum PSA, percent positive biopsy cores, DRE and biopsy Gleason score. Statistical analysis included univariate, multivariate regression analysis and ROC curves. RESULTS: Of our 1,056 patients 79 (7.4%) had SV involvement. Of the 356 patients with less than 17% positive biopsies, only 2 (0.5%) had SV involvement on final pathology. Preoperative PSA, biopsy Gleason score and percent positive biopsies were all highly predictive of SV invasion on multivariate analysis. Percent positive biopsy was found to be the single best predictor of seminal vesicle invasion (p <0.0001). CONCLUSIONS: In our series percent positive biopsy was the single best predictor of SV invasion at the time of RP. An analysis of preoperative parameters including percent positive biopsy, biopsy Gleason score and preoperative PSA may define a subset of patients in which prospective studies could be used to determine the value and safety of SV sparing surgery.     

Toxicity and immunogenicity of Neisseria meningitidis lipopolysaccharide incorporated into liposomes.

To obtain nontoxic and highly immunogenic lipopolysaccharide (LPS) for immunization, we incorporated Neisseria meningitidis LPS into liposomes. Native LPS and its salts were incorporated by the method of dehydration-rehydration of vesicles or prolonged cosonication. The most complete incorporation of LPS into liposomes and a decrease in toxicity were achieved by the method of dehydration-rehydration of vesicles. Three forms of LPS (H+ form, Mg2+ salt, and triethanolamine salt) showed different solubilities in water, the acidic form of LPS, with the most pronounced hydrophobic properties, being capable of practically complete association with liposomal membranes. An evaluation of the activity of liposomal LPS in vitro (by the Limulus amoebocyte test) and in vivo (by monitoring the pyrogenic reaction in rabbits) revealed a decrease in endotoxin activity of up to 1,000-fold. In addition, the pyrogenic activity of liposomal LPS was comparable to that of a meningococcal polysaccharide vaccine. Liposomes had a pronounced adjuvant effect on the immune response to LPS. Thus, the level of anti-LPS plaque-forming cells in the spleens of mice immunized with liposomal LPS was 1 order of magnitude higher and could be observed for a longer time (until day 21, i.e., the term of observation) than in mice immunized with free LPS. The same regularity was revealed in a study done with an enzyme-linked immunosorbent assay. This study also established that antibodies induced by immunization belonged to the immunoglobulin M and G classes, which are capable of prolonged circulation. Moreover, liposomal LPS induced a pronounced immune response in CBA/N mice (defective in B lymphocytes of the LyB-5+ subpopulation). The latter results indicate that the immunogenic action of liposomal LPS occurs at an early age.