Sex Difference in Capillary Reperfusion After Transient Middle Cerebral Artery Occlusion in Diabetic Mice.

BACKGROUND: Type 2 diabetes (DM2) exacerbates stroke injury, reduces efficacy of endovascular therapy, and worsens long-term functional outcome. Sex differences exist in stroke incidence, response to therapy, poststroke microvascular dysfunction, and functional recovery. In this study, we tested the hypotheses that poor outcome after stroke in the setting of DM2 is linked to impaired microvascular tissue reperfusion and that male and female DM2 mice exhibit different microvascular reperfusion response after transient middle cerebral artery occlusion (MCAO). METHODS: Transient MCAO was induced for 60 minutes using an intraluminal filament in young adult DM2 and nondiabetic control male and female mice. Capillary flux in deep cortical layers was assessed using optical coherence tomography-based optical microangiography (OMAG), and associated regional brain infarct size was evaluated by hematoxylin and eosin staining. RESULTS: Compared to baseline, MCAO reduced absolute capillary red blood cell flux by 84% at 24 hours post-MCAO in male DM2 (P<0.001) but not male control mice. When normalized to pre-MCAO baseline, red blood cell flux 24 hours after stroke was 64% lower in male DM2 mice than male nondiabetic controls (P<0.01). In females, MCAO decreased capillary flux by 48% at 24 hours post-MCAO compared with baseline in DM2 (P<0.05) but not in control mice. Red blood cell flux of female DM2 mice did not differ from that of nondiabetic controls either before or 24 hours after MCAO. Furthermore, normalized capillary flux 24 hours after MCAO failed to differ between female DM2 mice and nondiabetic controls. Concomitantly, male but not female DM2 mice experienced 25% larger infarct in caudate-putamen versus respective nondiabetic controls (P<0.05). CONCLUSIONS: DM2 impairs capillary perfusion and exacerbates ischemic deep brain injury in male but not female young adult mice. Premenopausal females appear to be protected against DM2-related capillary dysfunction and brain injury.

GPR39 Knockout Worsens Microcirculatory Response to Experimental Stroke in a Sex-Dependent Manner.

No current treatments target microvascular reperfusion after stroke, which can contribute to poor outcomes even after successful clot retrieval. The G protein-coupled receptor GPR39 is expressed in brain peri-capillary pericytes, and has been implicated in microvascular regulation, but its role in stroke is unknown. We tested the hypothesis that GPR39 plays a protective role after stroke, in part due to preservation of microvascular perfusion. We generated GPR39 knockout (KO) mice and tested whether GPR39 gene deletion worsens capillary blood flow and exacerbates brain injury and functional deficit after focal cerebral ischemia. Stroke was induced in male and female GPR39 KO and WT littermates by 60-min middle cerebral artery occlusion (MCAO). Microvascular perfusion was assessed via capillary red blood cell (RBC) flux in deep cortical layers in vivo using optical microangiography (OMAG). Brain injury was assessed by measuring infarct size by 2,3,5-triphenyltetrazolium chloride staining at 24 h or brain atrophy at 3 weeks after ischemia. Pole and cylinder behavior tests were conducted to assess neurological function deficit at 1 and 3 weeks post-stroke. Male but not female GPR39 KO mice exhibited larger infarcts and lower capillary RBC flux than WT controls after stroke. Male GPR39 KO mice also exhibited worse neurologic deficit at 1 week post-stroke, though functional deficit disappeared in both groups by 3 weeks. GPR39 deletion worsens brain injury, microvascular perfusion, and neurological function after experimental stroke. Results indicate that GPR39 plays a sex-dependent role in re-establishing microvascular flow and limiting ischemic brain damage after stroke.

Soluble Epoxide Hydrolase Blockade after Stroke Onset Protects Normal but Not Diabetic Mice.

Soluble epoxide hydrolase (sEH) is abundant in the brain, is upregulated in type 2 diabetes mellitus (DM2), and is possible mediator of ischemic injury via the breakdown of neuroprotective epoxyeicosatrienoic acids (EETs). Prophylactic, pre-ischemic sEH blockade with 4-[[trans-4-[[(tricyclo[3.3.1.13,7]dec-1-ylamino)carbonyl]amino]cyclohexyl]oxy]-benzoic acid (tAUCB) reduces stroke-induced infarct in normal and diabetic mice, with larger neuroprotection in DM2. The present study tested whether benefit occurs in normal and DM2 mice if tAUCB is administered after stroke onset. We performed 60 min middle cerebral artery occlusion in young adult male C57BL mice divided into four groups: normal or DM2, with t-AUCB 2 mg/kg or vehicle 30 min before reperfusion. Endpoints were (1) cerebral blood flow (CBF) by laser Doppler, and (2) brain infarct at 24 h. In nondiabetic mice, t-AUCB reduced infarct size by 30% compared to vehicle-treated mice in the cortex (31.4 ± 4 vs. 43.8 ± 3 (SEM)%, respectively) and 26% in the whole hemisphere (26.3 ± 3 vs. 35.2 ± 2%, both p < 0.05). In contrast, in DM2 mice, tAUCB failed to ameliorate either cortical or hemispheric injury. No differences were seen in CBF. We conclude that tAUCB administered after ischemic stroke onset exerts brain protection in nondiabetic but not DM2 mice, that the neuroprotection appears independent of changes in gross CBF, and that DM2-induced hyperglycemia abolishes t-AUCB-mediated neuroprotection after stroke onset.

Mechanism of protection by soluble epoxide hydrolase inhibition in type 2 diabetic stroke.

Inhibition of soluble epoxide hydrolase (sEH) is a potential target of therapy for ischemic injury. sEH metabolizes neuroprotective epoxyeicosatrienoic acids (EETs). We recently demonstrated that sEH inhibition reduces infarct size after middle cerebral artery occlusion (MCAO) in type 1 diabetic mice. We hypothesized that inhibition of sEH would protect against ischemic injury in type 2 diabetic mice. Type 2 diabetes was produced by combined high-fat diet, nicotinamide and streptozotocin in male mice. Diabetic and control mice were treated with vehicle or the sEH inhibitor t-AUCB then subjected to 60-min MCAO. Compared to chow-fed mice, high fat diet-fed mice exhibited an upregulation of sEH mRNA and protein in brain, but no differences in brain EETs levels were observed between groups. Type 2 diabetic mice had increased blood glucose levels at baseline and throughout ischemia, decreased laser-Doppler perfusion of the MCA territory after reperfusion, and sustained larger cortical infarcts compared to control mice. t-AUCB decreased fasting glucose levels at baseline and throughout ischemia, improved cortical perfusion after MCAO and significantly reduced infarct size in diabetic mice. We conclude that sEH inhibition, as a preventative treatment, improves glycemic status, post-ischemic reperfusion in the ischemic territory, and stroke outcome in type 2 diabetic mice.

Role of soluble epoxide hydrolase in exacerbation of stroke by streptozotocin-induced type 1 diabetes mellitus.

Hyperglycemia worsens stroke, yet rigorous glycemic control does not improve neurologic outcome. An alternative is to target downstream molecular mediator(s) triggered by hyperglycemia but independent of prevailing glycemia. Soluble epoxide hydrolase (sEH) is a potential mediator of injury via its metabolism of neuroprotective epoxyeicosatrienoic acids (EETs). We tested whether hyperglycemia exacerbates cerebral injury by upregulating sEH and decreasing brain EET levels. Type 1 diabetes mellitus was modeled by streptozotocin (STZ; 50 mg/kg per day intraperitoneally, 5 days) in male mice. At 4 weeks, STZ-treated and control mice underwent 45-minute middle cerebral artery occlusion (MCAO) with or without sEH blockade by trans-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid (t-AUCB; 1 mg/kg intraperitoneally daily for 6 days before MCAO). The STZ-treated mice had increased sEH mRNA expression in cerebral vessels and decreased EET concentrations in brain. There was no difference in cortical perfusion between groups. The STZ-treated mice sustained larger brain infarct than controls. Pretreatment with t-AUCB eliminated the difference in infarct size and EETs concentration between STZ-treated mice and controls, without altering glycemia. We conclude that type 1 diabetes mellitus upregulates sEH mRNA and decreases concentrations of neuroprotective EETs within the brain, leading to worse stroke outcome. The data indicate that sEH antagonism may be beneficial in the setting of hyperglycemic stroke.

Dichloroacetate stabilizes the intraoperative acid-base balance during liver transplantation.

Lactic acidosis occurs during orthotopic liver transplantation (OLT), especially during the anhepatic and early postreperfusion phases. Dichloroacetate (DCA) inhibits pyruvate dehydrogenase kinase-1, indirectly activating mitochondrial pyruvate dehydrogenase. This, in turn, markedly reduces systemic lactate production and, to a lesser extent, increases hepatic lactate uptake. The result is moderation of lactic acidosis in many clinical conditions. This study evaluated the efficacy of DCA in controlling lactic acidosis during OLT and improving perioperative outcome from OLT. After informed consent, 250 patients for OLT received either intraoperative DCA or placebo. DCA (40 mg/kg intravenously) or placebo was administered after anesthesia induction and repeated 4 hours later. Intraoperative measures were arterial blood gases, lactate, and Na+ and utilization of blood products, CaCl2, and NaHCO3. Outcome measures were time to tracheal extubation, intensive care unit length of stay, hospital length of stay, requirement for postoperative plasma transfusion, retransplantation, and perioperative mortality. DCA reduced the arterial lactic acid concentration by an average of 44% (1.8 mmol L(-1), P < 0.001), stabilized the acid-base balance, and reduced NaHCO(3) administration by 80% (P < 0.001). Postoperatively, DCA-treated patients required 50% less postoperative plasma transfusion (2 versus 4 units, respectively, P = 0.016), but the incidence of transfusion was similar in both groups (62% versus 60%, P = 0.381). DCA did not alter time to extubation, intensive care unit length of stay, or hospital length of stay. In conclusion, DCA attenuated lactic acidosis during OLT, stabilizing the intraoperative acid-base balance and decreasing NaHCO3 use. DCA decreased postoperative plasma transfusion requirement but otherwise had no measurable effect on perioperative outcome parameters.

Managing intergenerational differences in academic anesthesiology.

PURPOSE OF REVIEW: Common definitions for workplace generations are the silent generation (born 1925-1945), the baby boomer generation (1946-1962), generation X (1963-1981), and generation Y (1982-2000). Distinct motivational and value perceptions stereotype generations. This review defines the characteristics of workplace generations today and provides insight into how differences influence the workplace environment. RECENT FINDINGS: Senior faculty members are mostly boomers, whereas residents and junior faculty members tend to belong to generation X. Medical students and incoming interns are from generation Y. When compared with boomers, generation X is more savvy with technology, more independent, less loyal to the institution, and seeks balance between work and lifestyle. The 80-h resident working week restriction has reinforced differences between older and younger physicians. Generation Y exhibits traits that are similar to those of generation X. Their increased interest in anesthesiology may reflect, in part, their assumption that it affords better control of lifestyle. SUMMARY: Understanding, improved communication strategies, mentorship, and flexibility in methods employed to achieve common goals are most likely to capture the interest and cooperation of members of generation X and possibly Y. Future studies should test effects of particular interventions on outcome in terms of recruitment and performance milestones.

Volume replacement therapy during major orthopedic surgery using Voluven (hydroxyethyl starch 130/0.4) or hetastarch.

BACKGROUND: The purpose of this study was to test the equivalence of efficacy and compare the safety of the 6% hydroxyethyl starches (HES) Voluven (HES 130/0.4; Fresenius Kabi, Bad Homburg, Germany) and hetastarch (HES 670/0.75 in saline) for intravascular volume replacement therapy during major orthopedic surgery. METHODS: In a prospective, controlled, randomized, double-blind, multicenter trial of patients undergoing major orthopedic surgery, 49 patients were treated with HES 130/0.4 and 51 patients were treated with hetastarch. Infusion of colloids was guided by central venous and arterial blood pressures. The primary efficacy endpoint was the volume of colloid solution infused; the primary safety endpoints were calculated total erythrocyte loss, the nadir factor VIII activity, and the nadir von Willebrand factor concentration within 2 h of completion of surgery. RESULTS: The total volume of colloid solution required for intraoperative volume replacement did not differ between HES 130/0.4 and hetastarch (1,613+/-778 [SD] ml for HES 130/0.4 and 1,584+/-958 ml for hetastarch). The nadir factor VIII activity within 2 h of the end of surgery was lower for hetastarch than for HES 130/0.4 (P=0.0499); for those who received greater than 1,000 ml colloid, the nadir factor VIII activity and von Willebrand factor concentration within 2 h of end of surgery were lower for hetastarch than for HES 130/0.4 (P=0.0487 and P=0.008, respectively). CONCLUSION: Voluven (HES 130/0.4) and hetastarch are equally efficacious plasma volume substitutes; however, HES 130/0.4 has a lesser effect on coagulation.

Effect of short-term drinking water exposure to dichloroacetate on its pharmacokinetics and oral bioavailability in human volunteers: a stable isotope study.

Dichloroacetic acid (DCAA) is a by-product of drinking water disinfection, is a known rodent hepatocarcinogen, and is also used therapeutically to treat a variety of metabolic disorders in humans. We measured DCAA bioavailability in 16 human volunteers (eight men, eight women) after simultaneous administration of oral and iv DCAA doses. Volunteers consumed DCAA-free bottled water for 2 weeks to wash out background effects of DCAA. Subsequently, each subject consumed (12)C-DCAA (2 mg/kg) dissolved in 500 ml water over a period of 3 min. Five minutes after the start of the (12)C-DCAA consumption, (13)C-labeled DCAA (0.3 mg/kg) was administered iv over 20 s and plasma (12)C/(13)C-DCAA concentrations measured at predetermined time points over 4 h. Volunteers subsequently consumed for 14 consecutive days DCAA 0.02 microg/kg/day dissolved in 500 ml water to simulate a low-level chronic DCAA intake. Afterward, the (12)C/(13)C-DCAA administrations were repeated. Study end points were calculation of AUC(0-->infinity), apparent volume of distribution (V(ss)), total body clearance (Cl(b)), plasma elimination half-life (t((1/2),beta)), oral absorption rate (K(a)), and oral bioavailability. Oral bioavailability was estimated from dose-adjusted AUC ratios and by using a compartmental pharmacokinetic model after simultaneous fitting of oral and iv DCAA concentration-time profiles. DCAA bioavailability had large interindividual variation, ranging from 27 to 100%. In the absence of prior DCAA intake, there were no significant differences (p > 0.05) in any pharmacokinetic parameters between male and female volunteers, although there was a trend that women absorbed DCAA more rapidly (increased K(a)), and cleared DCAA more slowly (decreased Cl(b)), than men. Only women were affected by previous 14-day DCAA exposure, which increased the AUC(0-->infinity) for both oral and iv DCAA doses (p < 0.04 and p < 0.014, respectively) with a corresponding decrease in the Cl(b).

Mechanism of dichloroacetate-induced hypolactatemia in humans with or without cirrhosis.

Dichloroacetate (DCA) has been used as an experimental treatment for lactic acidosis because it lowers plasma lactic acid concentration. Three potential mechanisms could underlie the hypolactatemic action of DCA, but the dominant mechanism in vivo remains unclear. This study tested whether DCA-induced hypolactatemia occurs via decreased lactate production, increased lactate clearance, or decreased rate of glycolysis in healthy humans and in patients with end-stage cirrhosis. Cirrhosis is associated with decreased hepatic pyruvate dehydrogenase (PDH) content. Six healthy volunteers and 7 cirrhotic patients received a primed, constant infusion of 1-13C-pyruvate and 15N-alanine for 5 hours. DCA (35 mg/kg intravenously) was administered at 2 hours. Plasma isotopic enrichment was measured by gas chromatography/mass spectrometry (GC/MS), and exhaled CO2 enrichment by isotope ratio mass spectrometry. Pyruvate and alanine production rates (Ra) were determined by isotope dilution, and pyruvate oxidation calculated as 13CO2 production from 13C-pyruvate. Ra lactate was calculated as the difference between Ra pyruvate and its disposal by oxidation to CO2 and conversion to alanine. Baseline plasma lactate kinetics in cirrhotic patients did not differ from controls. DCA decreased lactate concentration in both groups by approximately 53%. DCA decreased glycolysis (Ra pyruvate) by 24%, increased the fraction of pyruvate oxidized to CO2 by 26%, and decreased pyruvate transamination to alanine by 25%. DCA also inhibited lactate production by 85%, but decreased plasma lactate clearance by 60% in both groups. DCA reduces plasma lactic acid concentration by inhibiting production, via stimulating pyruvate oxidation and inhibiting glycolysis, rather than increasing clearance. In addition, end-stage cirrhosis does not alter either the mechanism or the magnitude of the metabolic response to DCA.