Membrane Composition and Raf[CRD]-Membrane Attachment Are Driving Forces for K-Ras4B Dimer Stability.

Ras proteins are membrane-anchored GTPases that regulate key cellular signaling networks. It has been recently shown that different anionic lipid types can affect the properties of Ras in terms of dimerization/clustering on the cell membrane. To understand the effects of anionic lipids on key spatiotemporal properties of dimeric K-Ras4B, we perform all-atom molecular dynamics simulations of the dimer K-Ras4B in the presence and absence of Raf[RBD/CRD] effectors on two model anionic lipid membranes: one containing 78% mol DOPC, 20% mol DOPS, and 2% mol PIP2 and another one with enhanced concentration of anionic lipids containing 50% mol DOPC, 40% mol DOPS, and 10% mol PIP2. Analysis of our results unveils the orientational space of dimeric K-Ras4B and shows that the stability of the dimer is enhanced on the membrane containing a high concentration of anionic lipids in the absence of Raf effectors. This enhanced stability is also observed in the presence of Raf[RBD/CRD] effectors although it is not influenced by the concentration of anionic lipids in the membrane, but rather on the ability of Raf[CRD] to anchor to the membrane. We generate dominant K-Ras4B conformations by Markov state modeling and yield the population of states according to the K-Ras4B orientation on the membrane. For the membrane containing anionic lipids, we observe correlations between the diffusion of K-Ras4B and PIP2 and anchoring of anionic lipids to the Raf[CRD] domain. We conclude that the presence of effectors with the Raf[CRD] domain anchoring on the membrane as well as the membrane composition both influence the conformational stability of the K-Ras4B dimer, enabling the preservation of crucial interface interactions.

Improving the prediction of persistent and recurrent differentiated thyroid cancer using the American Thyroid Association 2015 risk stratification system.

PURPOSE: The 2015 American Thyroid Association risk stratification system (ATA RSS) is used in patients with differentiated thyroid carcinoma (DTC) to assess their risk of persistent/recurrent disease. Our aims were to validate the 2015 ATA RSS in a registry of DTC patients and to examine whether the addition of factors not included in it, such as pre-radioactive iodine therapy stimulated thyroglobulin (pre-RAI sTg), gender, and age could increase its predictive ability. METHODS: We studied 403 patients with DTC, treated at a tertiary center from 1990 to 2018 and subjected to total thyroidectomy. All patients had received RAI therapy, except those with low-risk papillary microcarcinoma. RESULTS: Of our patients, 81.9% were women and 91.1% had papillary thyroid carcinoma. After a median follow-up of 5.0 years, 53 cases of persistent and 21 cases of recurrent disease were recorded. The proportion of variance explained (PVE) regarding the outcome (presence or absence of recurrent/persistent disease) using the 2015 ATA RSS alone was 18.3% (persistence) and 16.9% (recurrence), increasing to 74.4% and 52.0%, respectively, when pre-RAI sTg was added to the logistic regression model. Gender and age were not associated with the disease outcome. In ROC analysis, pre-RAI sTg had a high predictive value for persistent (AUC 0.983, 95% CI 0.962-1.000) and recurrent disease (AUC 0.856, 95% CI 0.715-0.997). The optimal cut-offs and sensitivity, specificity, and positive and negative predictive value for pre-RAI sTg were the following: for persistence 12.75 ng/ml, 100%, 90.5%, 64%, and 100%, and for recurrence 8.05 ng/ml, 77.8%, 85.5%, 36.8%, and 97%. CONCLUSIONS: The 2015 ATA RSS displayed moderate performance in predicting recurrent/persistent disease in patients with DTC, which improved with the inclusion of pre-RAI sTg values; pre-RAI sTg was an independent predictor of the disease outcome, with high negative prognostic value.

Low-risk papillary thyroid carcinoma patients who underwent near-total thyroidectomy without prophylactic central compartment lymph node dissection and were ablated with low-dose 50mCi RAI had excellent 10-year prognosis.

BACKGROUND: The current trend in the management of low risk differentiated thyroid carcinoma is to follow less aggressive strategies. OBJECTIVE: To assess the long-term morbidity and mortality outcomes of low-risk papillary thyroid carcinoma (PTC) patients undergoing minimal intervention. DESIGN: We retrospectively analyzed 137 patients with low-risk PTC (stage I: n=77; stage II: n=60). Of these patients, 107 (Group 1) had macro-PTC and underwent near-total thyroidectomy and received postoperatively 50mCi RAI. The remaining 30 patients (Group 2) had micro-PTC (<1cm) and were treated only by means of near-total thyroidectomy. RESULTS: The median follow-up for Group 1 patients was 10 years (range: 3-30). At 1-year evaluation, 8 patients of Group 1 had indeterminate or incomplete biochemical response, of whom 4 had also incomplete structural response to initial therapy. Only 1 of 4 patients with structural incomplete response underwent cervical lymph node dissection and then received an additional dose of 100mCi RAI. The remaining 7 patients received only an additional dose of 100mCi RAI. These patients have been continuously followed till the present time with no recurrences or deaths (median follow-up: 17.5 years; 3-30 years). At 15 years, 2 patients of Group 1 experienced biochemical recurrence and they received 100mCi RAI. Three patients of Group 2 experienced recurrence, with 2 receiving 50mCi RAI and 1 undergoing cervical lymph node dissection with 50mCi RAI. CONCLUSIONS: Patients with low-risk macro-PTC treated by means of near-total thyroidectomy without PCCLND and receiving postoperatively a low dose of 50mCi RAI have excellent long-term prognosis.

The role of ghrelin, neuropeptide Y and leptin peptides in weight gain after deep brain stimulation for Parkinson's disease.

BACKGROUND: The exact mechanism of weight gain (WG) after deep brain stimulation (DBS) of the subthalamic nucleus (STN) in patients with idiopathic Parkinson's disease remains unknown. OBJECTIVES: To investigate a possible involvement of ghrelin, neuropeptide Y (NPY) and leptin in WG after DBS. METHODS: Twenty-three Parkinson patients were submitted for body composition measurements and blood sampling 3 days before, and 3 and 6 months after STN DBS. Peripheral concentrations of ghrelin, NPY, and leptin were determined, as well as the L-dopa equivalent daily dose. Patients were clinically evaluated using the Unified Parkinson's Disease Rating Scale. RESULTS: Three months after surgery, a significant WG was observed (3.09 ± 5.00 kg; p = 0.007) with no further increase at 6 months. Three months postoperatively, NPY circulating levels increased significantly (p = 0.05), while the increase of ghrelin levels reached statistical significance at 6 months (p = 0.001). WG was significantly associated with changes of ghrelin and leptin levels at 3 and 6 months, respectively. CONCLUSIONS: STN DBS seems to temporarily dysregulate the hypothalamic secretion of NPY and ghrelin. The variation of weight may be attributed to an increased production of ghrelin and leptin. A possible neuroprotective role of DBS, exerted through the increase of ghrelin levels, should be further studied.

Measurement of salivary resistin, visfatin and adiponectin levels.

Hormonal determination in saliva offers several advantages. Peptides enter the salivary glands either by active transport mechanisms or are expressed and secreted by the salivary glands themselves. The collection of saliva is a noninvasive, easily repeatable and less stressful technique than blood withdrawal. The purpose of the present study was to introduce a method for measuring salivary resistin, visfatin and adiponectin levels and to evaluate their associations with serum levels. Resistin, visfatin and adiponectin levels were measured in serum and saliva of 50 healthy adult volunteers (17 male and 33 female) using commercial enzyme immunoassay kits for serum with minor modifications. The present study documented the determination of resistin and adiponectin levels in saliva and the significant correlation of salivary levels with serum levels (r=0.441, p<0.01 and r=0.347, p<0.05, respectively). Moreover, the identification of visfatin in saliva was achieved, but no significant correlation with serum visfatin levels was observed. To our knowledge, this is the first study to report the determination of resistin and visfatin in saliva and the significant correlation of salivary resistin with serum levels, while it confirmed the significant association between salivary and serum adiponectin. The introduction of salivary determinations of adipokines could contribute to the elucidation of the physiology and the role of the specific adipokines in various clinical conditions (obesity, insulin resistance, inflammation, reproduction, energy imbalance and stress response).