Cellular mechanisms by which proinsulin C-peptide prevents insulin-induced neointima formation in human saphenous vein

AIMS/HYPOTHESIS: Endothelial cells (ECs) and smooth muscle cells (SMCs) play key roles in the development of intimal hyperplasia in saphenous vein (SV) bypass grafts. In diabetic patients, insulin administration controls hyperglycaemia but cardiovascular complications remain. Insulin is synthesised as a pro-peptide, from which C-peptide is cleaved and released into the circulation with insulin; exogenous insulin lacks C-peptide. Here we investigate modulation of human SV neointima formation and SV-EC and SV-SMC function by insulin and C-peptide. METHODS: Effects of insulin and C-peptide on neointima formation (organ cultures), EC and SMC proliferation (cell counting), EC migration (scratch wound), SMC migration (Boyden chamber) and signalling (immunoblotting) were examined. A real-time RT-PCR array identified insulin-responsive genes, and results were confirmed by real-time RT-PCR. Targeted gene silencing (siRNA) was used to assess functional relevance. RESULTS: Insulin (100 nmol/l) augmented SV neointimal thickening (70% increase, 14 days), SMC proliferation (55% increase, 7 days) and migration (150% increase, 6 h); effects were abrogated by 10 nmol/l C-peptide. C-peptide did not affect insulin-induced Akt or extracellular signal-regulated kinase signalling (15 min), but array data and gene silencing implicated sterol regulatory element binding transcription factor 1 (SREBF1). Insulin (1-100 nmol/l) did not modify EC proliferation or migration, whereas 10 nmol/l C-peptide stimulated EC proliferation by 40% (5 days). CONCLUSIONS/INTERPRETATION: Our data support a causative role for insulin in human SV neointima formation with a novel counter-regulatory effect of proinsulin C-peptide. Thus, C-peptide can limit the detrimental effects of insulin on SMC function. Co-supplementing insulin therapy with C-peptide could improve therapy in insulin-treated patients

Renal versus cerebral saturation trajectories: the perinatal transition in preterm neonates

BACKGROUND: The aim of this study was to develop reference renal saturation (rSrO) curves in premature infants, depict how they differ from cerebral saturation (rScO) curves, and evaluate the effect of blood pressure on these values using near-infrared spectroscopy (NIRS). METHODS: This is a prospective cohort study of 57 inborn infants \u3c12 h and \u3c30 weeks gestation. rScO, rSrO, fractional tissue oxygen extraction (FTOE), and mean arterial blood pressure (MAP) were continuously monitored every 30 s for 96 h. Quantile regression was used to establish nomograms, and mean saturation values were evaluated for different MAP ranges. RESULTS: Median rSrO at the start of monitoring was ~10% higher than rScO. rSrO showed a significant decline over time while rScO peaked at 26 h. FTOE demonstrated a similar but inverse trend to their saturation counterparts. rScO declined as MAP increased, while rSrO2 showed a peak and decline as MAP increased. CONCLUSIONS: We provide rSrO reference curves for the first 4 days of life, which differ in their trajectory from rScO and from what has previously been reported for rSrO in the full-term population. In addition, we observed a peak and decline in renal saturation with increasing MAP, suggesting a renovascular response to blood pressure changes. IMPACT: This article depicts reference renal saturation curves during the perinatal transition in preterm infants. We show how renal saturation compares to cerebral saturation trends over time. We describe a peak and decline in renal saturation with increasing MAP, suggesting a renovascular response to blood pressure changes

Autonomic markers of extubation readiness in premature infants

BACKGROUND: In premature infants, extubation failure is common and difficult to predict. Heart rate variability (HRV) is a marker of autonomic tone. Our aim is to test the hypothesis that autonomic impairment is associated with extubation readiness. METHODS: Retrospective study of 89 infants \u3c28 weeks. HRV metrics 24 h prior to extubation were compared for those with and without extubation success within 72 h. Receiver-operating curve analysis was conducted to determine the predictive ability of each metric, and a predictive model was created. RESULTS: Seventy-three percent were successfully extubated. The success group had significantly lower oxygen requirement, higher sympathetic HRV metrics, and a lower parasympathetic HRV metric. α (measure of autocorrelation, related to sympathetic tone) was the best predictor of success-area under the curve (AUC) of .73 (p = 0.001), and incorporated into a predictive model had an AUC of 0.81 (p \u3c 0.0001)-sensitivity of 81% and specificity of 78%. CONCLUSIONS: Extubation success is associated with HRV. We show an autonomic imbalance with low sympathetic and elevated parasympathetic tone in those who failed. α, a marker of sympathetic tone, was noted to be the best predictor of extubation success especially when incorporated into a clinical model. IMPACT: This article depicts autonomic markers predictive of extubation success. We depict an autonomic imbalance in those who fail extubation with heightened parasympathetic and blunted sympathetic signal. We describe a predictive model for extubation success with a sensitivity of 81% and specificity of 78%

Association of PDGFRB Mutations With Pediatric Myofibroma and Myofibromatosis.

IMPORTANCE: Myofibroma is the most frequent fibrous tumor in children. Multicentric myofibroma (referred to as infantile myofibromatosis) is a life-threatening disease. OBJECTIVE: To determine the frequency, spectrum, and clinical implications of mutations in the PDGFRB receptor tyrosine kinase found in sporadic myofibroma and myofibromatosis. DESIGN, SETTING, AND PARTICIPANTS: In this retrospective study of 69 patients with sporadic myofibroma or myofibromatosis, 85 tumor samples were obtained and analyzed by targeted deep sequencing of PDGFRB. Mutations were confirmed by an alternative method of sequencing and were experimentally characterized to confirm gain of function and sensitivity to the tyrosine kinase inhibitor imatinib. MAIN OUTCOMES AND MEASURES: Frequency of gain-of-function PDGFRB mutations in sporadic myofibroma and myofibromatosis. Sensitivity to imatinib, as assessed experimentally. RESULTS: Of the 69 patients with tumor samples (mean [SD] age, 7.8 [12.7] years), 60 were children (87%; 29 girls [48%]) and 9 were adults (13%; 4 women [44%]). Gain-of-function PDGFRB mutations were found in samples from 25 children, with no mutation found in samples from adults. Mutations were particularly associated with severe multicentric disease (13 of 19 myofibromatosis cases [68%]). Although patients had no familial history, 3 of 25 mutations (12%) were likely to be germline, suggesting de novo heritable alterations. All of the PDGFRB mutations were associated with ligand-independent receptor activation, and all but one were sensitive to imatinib at clinically relevant concentrations. CONCLUSIONS AND RELEVANCE: Gain-of-function mutations of PDGFRB in myofibromas may affect only children and be more frequent in the multicentric form of disease, albeit present in solitary pediatric myofibromas. These alterations may be sensitive to tyrosine kinase inhibitors. The PDGFRB sequencing appears to have a high value for diagnosis, prognosis, and therapy of soft-tissue tumors in children