Islet Adaptations in Fetal Sheep Persist Following Chronic Exposure to High Norepinephrine

Complications in pregnancy elevate fetal norepinephrine (NE) concentrations. Previous studies in NE-infused sheep fetuses revealed that sustained exposure to high NE resulted in lower expression of α2-adrenergic receptors in islets and increased insulin secretion responsiveness after acutely terminating the NE infusion. In this study, we determined if the compensatory increase in insulin secretion following chronic elevation of NE is independent of hyperglycemia in sheep fetuses and whether it is persistent in conjunction with islet desensitization to NE. Following an initial assessment of glucose-stimulated insulin secretion (GSIS) at 129±1 days of gestation, fetuses were continuously infused for seven days with NE and maintained at euglycemia with a maternal insulin infusion. Fetal GSIS studies were again performed on days 8 and 12. Adrenergic sensitivity was determined in pancreatic islets collected at day 12. NE infusion increased (P\u3c0.01) fetal plasma NE concentrations and lowered (P\u3c0.01) basal insulin concentrations compared to vehicle-infused controls. GSIS was 1.8-fold greater (P\u3c0.05) in NE-infused fetuses compared to controls at both one and five days after discontinuing the infusion. Glucose-potentiated arginine-induced insulin secretion was also enhanced (P\u3c0.01) in NE-infused fetuses. Maximum GSIS in islets isolated from NE-infused fetuses was 1.6-fold greater (P\u3c0.05) than controls, but islet insulin content and intracellular calcium signaling were not different between treatments. The half-maximal inhibitory concentration for NE was 2.6-fold greater (P\u3c0.05) in NE-infused islets compared to controls. These findings show that chronic NE exposure and not hyperglycemia produce persistent adaptations in pancreatic islets that augment β-cell responsiveness in part through decreased adrenergic sensitivity

Intrauterine growth-restricted sheep fetuses exhibit smaller hindlimb muscle fibers and lower proportions of insulin-sensitive Type I fibers near term

Intrauterine growthrestricted sheep fetuses exhibit smaller hindlimb muscle fibers and lower proportions of insulin-sensitive Type I fibers near term. Am J Physiol Regul Integr Comp Physiol 310: R1020–R1029, 2016. First published April 6, 2016; doi:10.1152/ajpregu.00528.2015.—Intrauterine growth restriction (IUGR) reduces muscle mass and insulin sensitivity in offspring. Insulin sensitivity varies among muscle fiber types, with Type I fibers being most sensitive. Differences in fibertype ratios are associated with insulin resistance in adults, and thus we hypothesized that near-term IUGR sheep fetuses exhibit reduced size and proportions of Type I fibers. Placental insufficiency-induced IUGR fetuses were 54% smaller (P \u3c 0.05) than controls and exhibited hypoxemia and hypoglycemia, which contributed to 6.9- fold greater (P \u3c 0.05) plasma norepinephrine and 53% lower (P \u3c 0.05) plasma insulin concentrations. IUGR semitendinosus muscles contained less (P \u3c 0.05) myosin heavy chain-I protein (MyHC-I) and proportionally fewer (P \u3c 0.05) Type I and Type I/IIa fibers than controls, but MyHC-II protein concentrations, Type II fibers, and Type IIx fibers were not different. IUGR biceps femoris muscles exhibited similar albeit less dramatic differences in fiber type proportions. Type I and IIa fibers are more responsive to adrenergic and insulin regulation than Type IIx and may be more profoundly impaired by the high catecholamines and low insulin in our IUGR fetuses, leading to their proportional reduction. In both muscles, fibers of each type were uniformly smaller (P \u3c 0.05) in IUGR fetuses than controls, which indicates that fiber hypertrophy is not dependent on type but rather on other factors such as myoblast differentiation or protein synthesis. Together, our findings show that IUGR fetal muscles develop smaller fibers and have proportionally fewer Type I fibers, which is indicative of developmental adaptations that may help explain the link between IUGR and adulthood insulin resistanc

Adrenal Demedullation and Oxygen Supplementation Independently Increase Glucose-Stimulated Insulin Concentrations in Fetal Sheep With Intrauterine Growth Restriction

In pregnancies complicated by placental insufficiency and intrauterine growth restriction (IUGR), fetal glucose and oxygen concentrations are reduced, whereas plasma norepinephrine and epinephrine concentrations are elevated throughout the final third of gestation. Here we study the effects of chronic hypoxemia and hypercatecholaminemia on β-cell function in fetal sheep with placental insufficiency-induced IUGR that is produced by maternal hyperthermia. IUGR and control fetuses underwent a sham (intact) or bilateral adrenal demedullation (AD) surgical procedure at 0.65 gestation. As expected, AD-IUGR fetuses had lower norepinephrine concentrations than intact-IUGR fetuses despite being hypoxemic and hypoglycemic. Placental insufficiency reduced fetal weights, but the severity of IUGR was less with AD. Although 2 basal plasma insulin concentrations were lower in intact-IUGR and AD-IUGR fetuses compared with intact-controls, glucose-stimulated insulin concentrations were greater in AD-IUGR fetuses compared with intact-IUGR fetuses. Interestingly, AD-controls had lower glucose- and arginine-stimulated insulin concentrations than intact-controls, but AD-IUGR and AD-control insulin responses were not different. To investigate chronic hypoxemia in the IUGR fetus, arterial oxygen tension was increased to normal levels by increasing the maternal inspired oxygen fraction. Oxygenation of IUGR fetuses enhanced glucose-stimulated insulin concentrations 3.3-fold in intact-IUGR and 1.7-fold in AD-IUGR fetuses but did not lower norepinephrine and epinephrine concentrations. Together these findings show that chronic hypoxemia and hypercatecholaminemia have distinct but complementary roles in the suppression of β-cell responsiveness in IUGR fetuses. Placental insufficiency restricts the supply of oxygen and nutrients to the fetus and causes intrauterine growth restriction (IUGR) (1, 2). The resulting fetal hypoxemia and hypoglycemia provoke endocrine responses that lower plasma insulin concentrations (3,–5). High norepinephrine and epinephrine concentrations are a hallmark of both human and animal IUGR fetuses (6,–11). These high concentrations of catecholamines inhibit insulin secretion from pancreatic β-cells and may contribute to very low insulin concentrations in the IUGR fetus (12, 13). In addition, chronic elevation of norepinephrine has been shown to slow fetal growth and induce asymmetric growth of fetal tissues (14, 15)

Improved Hemodynamic Recovery and 72-Hour Survival Following Low-Volume Resuscitation with a PEGylated Carboxyhemoglobin in a Rat Model of Severe Hemorrhagic Shock

INTRODUCTION: Hemorrhage is a leading cause of death from potentially survivable civilian and military trauma. As projected conflicts move from settings of tactical and logistical supremacy to hyper-dynamic tactical zones against peer and near-peer adversaries, protracted medical evacuation times are expected. Treatment at the point-of-injury is critical. Although crystalloids like Lactated Ringer\u27s (LR) are ubiquitous, whole blood (WB) is the preferred resuscitation fluid following hemorrhage; however, logistical constraints limit the availability of WB in prehospital settings. Hemoglobin-based oxygen carriers (HBOCs) offer both hemodynamic support and oxygen-carrying capacity while avoiding logistical constraints of WB. We hypothesized that low-volume resuscitation of severe hemorrhagic shock with an HBOC (PEGylated carboxyhemoglobin, [PC]) would improve hemodynamic recovery and 72-hour survival; comparable to WB and superior to LR. MATERIALS AND METHODS: A total of 21 anesthetized male Sprague-Dawley rats underwent severe hemorrhagic shock followed by randomly assigned low-volume resuscitation with LR, WB, or PC, and then recovered from anesthesia for up to 72-hour observation. Mean arterial pressure (MAP) was recorded continuously under anesthesia, and arterial blood gases were measured at baseline (BL), 60 minutes post-hemorrhage (HS1h), and 24 hours post-resuscitation (PR24h). Survival was presented on a Kaplan-Meier plot and significance determined with a log-rank test. Cardiovascular and blood gas data were assessed with one-way analysis of variance and post hoc analysis where appropriate. RESULTS: All measured cardiovascular and blood chemistry parameters were equivalent between groups at BL and HS1h. BL MAP values were 90 ± 3, 86 ± 1, and 89 ± 2 mmHg for LR, PC, and WB, respectively. Immediately following resuscitation, MAP values were 57 ± 4, 74 ± 5, and 62 ± 3 mmHg, with PC equivalent to WB and higher than LR (P \u3c 0.05). WB and LR were both lower than BL (P \u3c 0.0001), whereas PC was not (P = 0.13). The PC group\u27s survival to 72 hours was 57%, which was not different from WB (43%) and higher than LR (14%; P \u3c 0.05). CONCLUSIONS: A single bolus infusion of PC produced superior survival and MAP response compared to LR, which is the standard fluid resuscitant carried by combat medics. PC was not different from WB in terms of survival and MAP, which is encouraging because its reduced logistical constraints make it viable for field deployment. These promising findings warrant further development and investigation of PC as a low-volume, early treatment for hemorrhagic shock in scenarios where blood products may not be available

Intrauterine growth-restricted sheep fetuses exhibit smaller hindlimb muscle fibers and lower proportions of insulin-sensitive Type I fibers near term

Intrauterine growthrestricted sheep fetuses exhibit smaller hindlimb muscle fibers and lower proportions of insulin-sensitive Type I fibers near term. Am J Physiol Regul Integr Comp Physiol 310: R1020–R1029, 2016. First published April 6, 2016; doi:10.1152/ajpregu.00528.2015.—Intrauterine growth restriction (IUGR) reduces muscle mass and insulin sensitivity in offspring. Insulin sensitivity varies among muscle fiber types, with Type I fibers being most sensitive. Differences in fibertype ratios are associated with insulin resistance in adults, and thus we hypothesized that near-term IUGR sheep fetuses exhibit reduced size and proportions of Type I fibers. Placental insufficiency-induced IUGR fetuses were 54% smaller (P \u3c 0.05) than controls and exhibited hypoxemia and hypoglycemia, which contributed to 6.9- fold greater (P \u3c 0.05) plasma norepinephrine and 53% lower (P \u3c 0.05) plasma insulin concentrations. IUGR semitendinosus muscles contained less (P \u3c 0.05) myosin heavy chain-I protein (MyHC-I) and proportionally fewer (P \u3c 0.05) Type I and Type I/IIa fibers than controls, but MyHC-II protein concentrations, Type II fibers, and Type IIx fibers were not different. IUGR biceps femoris muscles exhibited similar albeit less dramatic differences in fiber type proportions. Type I and IIa fibers are more responsive to adrenergic and insulin regulation than Type IIx and may be more profoundly impaired by the high catecholamines and low insulin in our IUGR fetuses, leading to their proportional reduction. In both muscles, fibers of each type were uniformly smaller (P \u3c 0.05) in IUGR fetuses than controls, which indicates that fiber hypertrophy is not dependent on type but rather on other factors such as myoblast differentiation or protein synthesis. Together, our findings show that IUGR fetal muscles develop smaller fibers and have proportionally fewer Type I fibers, which is indicative of developmental adaptations that may help explain the link between IUGR and adulthood insulin resistanc

Fetal Adrenal Demedullation Lowers Circulating Norepinephrine and Attenuates Growth Restriction but not Reduction of Endocrine Cell Mass in an Ovine Model of Intrauterine Growth Restriction

Placental insufficiency is associated with fetal hypoglycemia, hypoxemia, and elevated plasma norepinephrine (NE) that become increasingly pronounced throughout the third trimester and contribute to intrauterine growth restriction (IUGR). This study evaluated the effect of fetal adrenal demedullation (AD) on growth and pancreatic endocrine cell mass. Placental insufficiency-induced IUGR was created by exposing pregnant ewes to elevated ambient temperatures during mid-gestation. Treatment groups consisted of control and IUGR fetuses with either surgical sham or AD at 98 days gestational age (dGA; term = 147 dGA), a time-point that precedes IUGR. Samples were collected at 134 dGA. IUGR-sham fetuses were hypoxemic, hypoglycemic, and hypoinsulinemic, and values were similar in IUGR-AD fetuses. Plasma NE concentrations were ~5-fold greater in IUGR-sham compared to control-sham, control-AD, and IUGR-AD fetuses. IUGR-sham and IUGR-AD fetuses weighed less than controls. Compared to IUGR-sham fetuses, IUGR-AD fetuses weighed more and asymmetrical organ growth was absent. Pancreatic β-cell mass and α-cell mass were lower in both IUGR-sham and IUGR-AD fetuses compared to controls, however, pancreatic endocrine cell mass relative to fetal mass was lower in IUGR-AD fetuses. These findings indicate that NE, independently of hypoxemia, hypoglycemia and hypoinsulinemia, influence growth and asymmetry of growth but not pancreatic endocrine cell mass in IUGR fetuses

Adrenal Demedullation and Oxygen Supplementation Independently Increase Glucose-Stimulated Insulin Concentrations in Fetal Sheep With Intrauterine Growth Restriction

In pregnancies complicated by placental insufficiency and intrauterine growth restriction (IUGR), fetal glucose and oxygen concentrations are reduced, whereas plasma norepinephrine and epinephrine concentrations are elevated throughout the final third of gestation. Here we study the effects of chronic hypoxemia and hypercatecholaminemia on β-cell function in fetal sheep with placental insufficiency-induced IUGR that is produced by maternal hyperthermia. IUGR and control fetuses underwent a sham (intact) or bilateral adrenal demedullation (AD) surgical procedure at 0.65 gestation. As expected, AD-IUGR fetuses had lower norepinephrine concentrations than intact-IUGR fetuses despite being hypoxemic and hypoglycemic. Placental insufficiency reduced fetal weights, but the severity of IUGR was less with AD. Although 2 basal plasma insulin concentrations were lower in intact-IUGR and AD-IUGR fetuses compared with intact-controls, glucose-stimulated insulin concentrations were greater in AD-IUGR fetuses compared with intact-IUGR fetuses. Interestingly, AD-controls had lower glucose- and arginine-stimulated insulin concentrations than intact-controls, but AD-IUGR and AD-control insulin responses were not different. To investigate chronic hypoxemia in the IUGR fetus, arterial oxygen tension was increased to normal levels by increasing the maternal inspired oxygen fraction. Oxygenation of IUGR fetuses enhanced glucose-stimulated insulin concentrations 3.3-fold in intact-IUGR and 1.7-fold in AD-IUGR fetuses but did not lower norepinephrine and epinephrine concentrations. Together these findings show that chronic hypoxemia and hypercatecholaminemia have distinct but complementary roles in the suppression of β-cell responsiveness in IUGR fetuses. Placental insufficiency restricts the supply of oxygen and nutrients to the fetus and causes intrauterine growth restriction (IUGR) (1, 2). The resulting fetal hypoxemia and hypoglycemia provoke endocrine responses that lower plasma insulin concentrations (3,–5). High norepinephrine and epinephrine concentrations are a hallmark of both human and animal IUGR fetuses (6,–11). These high concentrations of catecholamines inhibit insulin secretion from pancreatic β-cells and may contribute to very low insulin concentrations in the IUGR fetus (12, 13). In addition, chronic elevation of norepinephrine has been shown to slow fetal growth and induce asymmetric growth of fetal tissues (14, 15)

Prehospital whole blood resuscitation prevents coagulopathy and improves acid-base status at hospital arrival in a nonhuman primate hemorrhagic shock model.

BACKGROUND: Hemorrhage remains the primary cause of preventable death in civilian and military trauma. The Committee on Tactical Combat Casualty Care recommends prehospital (PH) resuscitation with whole blood (WB). However, 6% hetastarch in lactated electrolyte (HEX) and crystalloids are more commonly available and used for PH resuscitation in military and civilian environments, respectively. The mechanistic benefits of PH WB resuscitation have not been well studied and remain to be elucidated. STUDY DESIGN AND METHODS: The aim of this study was to evaluate the differences in simulated PH WB and HEX resuscitation, specifically with regards to coagulation, physiologic, and metabolic outcomes to better elucidate the mechanistic benefits of WB. In a randomized study, the physiologic, coagulation, and metabolic responses to simulated PH WB (n = 12) or HEX (n = 12) were evaluated in a nonhuman primate model of severe polytraumatic hemorrhagic shock. RESULTS: Notable findings included 1) equivalence of shock reversal between simulated PH WB and HEX treatment groups as determined by hemodynamics and base deficit and 2) prevention of coagulopathy at simulated hospital arrival with initial WB resuscitation as determined by viscoelastic and plasmatic coagulation assays. CONCLUSION: The major benefit of WB, as compared to HEX, in simulated PH resuscitation appears to be prevention of coagulopathy at hospital arrival. Both fluids effectively reversed shock in this model, implying that efficacious provision preload (cardiac output support and hence oxygen delivery) and coagulation proteins (prevention of coagulopathy) are mechanisms underlying WB\u27s effectiveness in early resuscitation of hemorrhagic shock

Islet adaptations in fetal sheep persist following chronic exposure to high norepinephrine.

Complications in pregnancy elevate fetal norepinephrine (NE) concentrations. Previous studies in NE-infused sheep fetuses revealed that sustained exposure to high NE resulted in lower expression of α2-adrenergic receptors in islets and increased insulin secretion responsiveness after acutely terminating the NE infusion. In this study, we determined if the compensatory increase in insulin secretion after chronic elevation of NE is independent of hyperglycemia in sheep fetuses and whether it is persistent in conjunction with islet desensitization to NE. After an initial assessment of glucose-stimulated insulin secretion (GSIS) at 129 ± 1 days of gestation, fetuses were continuously infused for seven days with NE and maintained at euglycemia with a maternal insulin infusion. Fetal GSIS studies were performed again on days 8 and 12. Adrenergic sensitivity was determined in pancreatic islets collected at day 12. NE infusion increased (P < 0.01) fetal plasma NE concentrations and lowered (P < 0.01) basal insulin concentrations compared to vehicle-infused controls. GSIS was 1.8-fold greater (P < 0.05) in NE-infused fetuses compared to controls at both one and five days after discontinuing the infusion. Glucose-potentiated arginine-induced insulin secretion was also enhanced (P < 0.01) in NE-infused fetuses. Maximum GSIS in islets isolated from NE-infused fetuses was 1.6-fold greater (P < 0.05) than controls, but islet insulin content and intracellular calcium signaling were not different between treatments. The half-maximal inhibitory concentration for NE was 2.6-fold greater (P < 0.05) in NE-infused islets compared to controls. These findings show that chronic NE exposure and not hyperglycemia produce persistent adaptations in pancreatic islets that augment β-cell responsiveness in part through decreased adrenergic sensitivity.National Institute of Health [R01DK084842]; National Natural Science Foundation of China (NSFC) [31602021]; Chongqing Science and Technology Commission, Chongqing, China [CSTC2014JCYJA80036]; Southwest University [20140090]; [T32HL7249]12 month embargo; accepted preprint published online 25 November 2016This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Whole blood mitigates the acute coagulopathy of trauma and avoids the coagulopathy of crystalloid resuscitation.

INTRODUCTION: The contributions of type and timing of fluid resuscitation to coagulopathy in trauma remain controversial. As part of a multifunctional resuscitation fluid research effort, we sought to further characterize the coagulation responses to resuscitation, specifically as compared to whole blood. We hypothesized that early whole blood administration mitigates the acute coagulopathy of trauma by avoiding the coagulopathy of CR resuscitation. METHODS: Anesthetized rhesus macaques underwent polytraumatic, hemorrhagic shock, then a crossover study design resuscitation (n = 6 each) with either whole blood first (WB-1st) followed by crystalloid (CR); or CR-1st followed by WB. Resuscitation strategies were the following: WB-1st received 50% shed blood in 30minutes, followed by twice the shed blood volume (SBV) of CR over 30minutes and one times the SBV CR over 60minutes, where CR-1st received twice the SBV of CR over 30minutes, followed by 50% of shed blood in 30minutes, and one times the SBV CR over 60minutes. Blood samples were collected at baseline, end-of-shock, end-of-first and end-of-second resuscitation stages, and end-of-resuscitation for assessment (thromboelastometry, platelet aggregation, and plasmatic coagulation factors). Statistical analyses were conducted using two-way analysis of variance ANOVA with Bonferroni correction and t-tests; significance was at p \u3c 0.05. RESULTS: Survival, blood loss, hemodynamics, and shock duration were equivalent between the groups. Compared to baseline, parameters measured at first and second resuscitation stage time points directly following CR infusion revealed abnormalities in thromboelastometry (clot formation time, α angle, and maximum clot firmness), platelet aggregation response (to collagen, arachidonic acid, and adenosine diphosphate), and plasmatic coagulation (prothrombin time, anti-thrombin 3, and fibrinogen), while whole blood infusion resulted in stabilization or correction of these parameters following its administration. CONCLUSIONS: These data suggest that in the setting of trauma and hemorrhagic shock, the coagulation alterations begin before intervention/resuscitation; however, these are significantly aggravated by CR resuscitation and could perhaps be best termed acute coagulopathy of resuscitation. STUDY TYPE: Translational animal model