Prognostic Value of Sarcopenia and Albumin in the Surgical Management of Localized Renal Cell Carcinoma

INTRODUCTION

A universally accepted model for preoperative surgical risk stratification in localized RCC patients undergoing nephrectomy is currently lacking. Both the evaluation of body composition and nutritional status has demonstrated prognostic value for patients with cancer. This study aims to investigate the potential associations between sarcopenia and hypoalbuminemia and survival outcomes in patients with localized kidney cancer treated with partial or radical nephrectomy.

MATERIALS AND METHODS

We retrospectively analyzed 473 patients with localized RCC managed with radical and partial nephrectomy. Skeletal muscle index (SMI) was measured from preoperative CT and MRI. Sarcopenic criteria were created using BMI- and sex-stratified thresholds. Relationships between sarcopenia and hypoalbuminemia (Albumin <3.5 g/dL) with overall (OS), recurrence-free (RFS), and cancer-specific survival (CSS) were determined using multivariable and Kaplan-Meier analysis.

RESULTS

Of the 473 patients, 42.5% were sarcopenic and 24.5% had hypoalbuminemia. Sarcopenia was significantly associated with shorter OS (HR=1.51, 95% CI 1.07-2.13), however, was nonsignificant in the RFS (HR = 1.33, 95% CI 0.88-2.03) and CSS (HR=1.66, 95% CI 0.96-2.87) models. Hypoalbuminemia predicted shorter OS (HR=1.76, 95% CI 1.22-2.55), RFS (HR=1.86, 95% CI 1.19-2.89), and CSS (HR=1.82, 95% CI 1.03-3.22). Patients were then stratified into low, medium, and high-risk groups based on the severity of sarcopenia and hypoalbuminemia. Risk groups demonstrated an increasing association with shorter OS (all p<0.05). Reduced RFS was observed in the medium risk-hypoalbuminemia (HR=2.18, 95% CI 1.16-4.09) and high-risk groups (HR=2.42, 95% CI 1.34-4.39). Shorter CSS was observed in the medium risk-hypoalbuminemia (HR=2.31, 95% CI 1.00-5.30) and high-risk groups (HR=2.98, 95% CI 1.34-6.61).

CONCLUSION

Localized RCC patients with combined preoperative sarcopenia and hypoalbuminemia displayed a two to a three-fold reduction in OS, RFS, and CSS after nephrectomy. These data have implications for guiding prognostication and treatment election in localized RCC patients undergoing extirpative surgery.

Regulation of mitochondrial fragmentation in microvascular endothelial cells isolated from the SU5416/hypoxia model of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a morbid disease characterized by progressive right ventricle (RV) failure due to elevated pulmonary artery pressures (PAP). In PAH, histologically complex vaso-occlusive lesions in the pulmonary vasculature contribute to elevated PAP. However, the mechanisms underlying dysfunction of the microvascular endothelial cells (MVECs) that comprise a significant portion of these lesions are not well understood. We recently showed that MVECs isolated from the Sugen/hypoxia (SuHx) rat experimental model of PAH (SuHx-MVECs) exhibit increases in migration/proliferation, mitochondrial reactive oxygen species (ROS; mtROS) production, intracellular calcium levels ([Ca2+]i), and mitochondrial fragmentation. Furthermore, quenching mtROS with the targeted antioxidant MitoQ attenuated basal [Ca2+]i, migration and proliferation; however, whether increased mtROS-induced [Ca2+]i entry affected mitochondrial morphology was not clear. In this study, we sought to better understand the relationship between increased ROS, [Ca2+]i, and mitochondrial morphology in SuHx-MVECs. We measured changes in mitochondrial morphology at baseline and following inhibition of mtROS, with the targeted antioxidant MitoQ, or transient receptor potential vanilloid-4 (TRPV4) channels, which we previously showed were responsible for mtROS-induced increases in [Ca2+]i in SuHx-MVECs. Quenching mtROS or inhibiting TRPV4 attenuated fragmentation in SuHx-MVECs. Conversely, inducing mtROS production in MVECs from normoxic rats (N-MVECs) increased fragmentation. Ca2+ entry induced by the TRPV4 agonist GSK1017920A was significantly increased in SuHx-MVECs and was attenuated with MitoQ treatment, indicating that mtROS contributes to increased TRPV4 activity in SuHx-MVECs. Basal and maximal respiration were depressed in SuHx-MVECs, and inhibiting mtROS, but not TRPV4, improved respiration in these cells. Collectively, our data show that, in SuHx-MVECs, mtROS production promotes TRPV4-mediated increases in [Ca2+]i, mitochondrial fission, and decreased mitochondrial respiration. These results suggest an important role for mtROS in driving MVEC dysfunction in PAH.

CD36 mediates H2O2-induced calcium influx in lung microvascular endothelial cells

Elevated levels of reactive oxygen species and intracellular Ca²⁺ play a key role in endothelial barrier dysfunction in acute lung injury. We previously showed that H₂O₂-induced increases in intracellular calcium concentrations ([Ca²⁺]_i) in lung microvascular endothelial cells (LMVECs) involve the membrane Ca²⁺ channel, transient receptor potential vanilloid-4 (TRPV4) and that inhibiting this channel attenuated H₂O₂-induced barrier disruption in vitro. We also showed that phosphorylation of TRPV4 by the Src family kinase, Fyn, contributes to H₂O₂-induced Ca²⁺ influx in LMVEC. In endothelial cells, Fyn is tethered to the cell membrane by CD36, a fatty acid transporter. In this study, we assessed the effect of genetic loss or pharmacological inhibition of CD36 on Ca²⁺ responses to H₂O₂ H₂O₂-induced Ca²⁺ influx was attenuated in LMVEC isolated from mice lacking CD36 (CD36^-/-). TRPV4 expression and function was unchanged in LMVEC isolated from wild-type (WT) and CD36^-/- mice, as well as mice with deficiency for Fyn (Fyn^-/-). TRPV4 immunoprecipitated with Fyn, but this interaction was decreased in CD36^-/- LMVEC. The amount of phosphorylated TRPV4 was decreased in LMVEC from CD36^-/- mice compared with WT controls. Loss of CD36 altered subcellular localization of Fyn, while inhibition of CD36 fatty acid transport with succinimidyl oleate did not attenuate H₂O₂-induced Ca²⁺ influx. Lastly, we found that CD36^-/- mice were protected from ischemia-reperfusion injury in vivo. In conclusion, our data suggest that CD36 plays an important role in H₂O₂-mediated lung injury and that the mechanism may involve CD36-dependent scaffolding of Fyn to the cell membrane to facilitate TRPV4 phosphorylation.