Steven A. Goldman

Glucose Control and Vascular Complications in Veterans with Type 2 Diabetes

BACKGROUND The effects of intensive glucose control on cardiovascular events in patients with long-standing type 2 diabetes mellitus remain uncertain. METHODS We randomly assigned 1791 military veterans (mean age, 60.4 years) who had a suboptimal response to therapy for type 2 diabetes to receive either intensive or standard glucose control. Other cardiovascular risk factors were treated uniformly. The mean number of years since the diagnosis of diabetes was 11.5, and 40% of the patients had already had a cardiovascular event. The goal in the intensive-therapy group was an absolute reduction of 1.5 percentage points in the glycated hemoglobin level, as compared with the standard-therapy group. The primary outcome was the time from randomization to the first occurrence of a major cardiovascular event, a composite of myocardial infarction, stroke, death from cardiovascular causes, congestive heart failure, surgery for vascular disease, inoperable coronary disease, and amputation for ischemic gangrene. RESULTS The median follow-up was 5.6 years. Median glycated hemoglobin levels were 8.4% in the standard-therapy group and 6.9% in the intensive-therapy group. The primary outcome occurred in 264 patients in the standard-therapy group and 235 patients in the intensive-therapy group (hazard ratio in the intensive-therapy group, 0.88; 95% confidence interval [CI], 0.74 to 1.05; P=0.14). There was no significant difference between the two groups in any component of the primary outcome or in the rate of death from any cause (hazard ratio, 1.07; 95% CI, 0.81 to 1.42; P=0.62). No differences between the two groups were observed for microvascular complications. The rates of adverse events, predominantly hypoglycemia, were 17.6% in the standard-therapy group and 24.1% in the intensive-therapy group. CONCLUSIONS Intensive glucose control in patients with poorly controlled type 2 diabetes had no significant effect on the rates of major cardiovascular events, death, or microvascular complications with the exception of progression of albuminuria (P = 0.01) [added]. (ClinicalTrials.gov number, NCT00032487.)

Inflammation, Pravastatin, and the Risk of Coronary Events After Myocardial Infarction in Patients With Average Cholesterol Levels

BACKGROUND We studied whether inflammation after myocardial infarction (MI) is a risk factor for recurrent coronary events and whether randomized treatment with pravastatin reduces that risk. METHODS AND RESULTS A nested case-control design was used to compare C-reactive protein (CRP) and serum amyloid A (SAA) levels in prerandomization blood samples from 391 participants in the Cholesterol and Recurrent Events (CARE) trial who subsequently developed recurrent nonfatal MI or a fatal coronary event (cases) and from an equal number of age- and sex-matched participants who remained free of these events during follow-up (control subjects). Overall, CRP and SAA were higher among cases than control subjects (for CRP P=0.05; for SAA P=0.006) such that those with levels in the highest quintile had a relative risk (RR) of recurrent events 75% higher than those with levels in the lowest quintile (for CRP RR= 1.77, P=0.02; for SAA RR= 1.74, P=0.02). The study group with the highest risk was that with consistent evidence of inflammation (elevation of both CRP and SAA) who were randomly assigned to placebo (RR=2.81, P=0.007); this risk estimate was greater than the product of the individual risks associated with inflammation or placebo assignment alone. In stratified analyses, the association between inflammation and risk was significant among those randomized to placebo (RR=2.11, P=0.048) but was attenuated and nonsignificant among those randomized to pravastatin (RR=1.29, P=0.5). CONCLUSIONS Evidence of inflammation after MI is associated with increased risk of recurrent coronary events. Therapy with pravastatin may decrease this risk, an observation consistent with a nonlipid effect of this agent.

A Paravascular Pathway Facilitates CSF Flow Through the Brain Parenchyma and the Clearance of Interstitial Solutes, Including Amyloid β

Cerebrospinal fluid flows through channels around brain blood vessels that are bounded by astrocytic endfeet, mediated by water transport through aquaporin-4. A New Footing for Waste Clearance in the Brain Where are the lymph vessels of the brain? The lymphatic system’s complex network of vessels extends throughout most of the body, transporting excess fluid and waste products from the interstitial spaces between cells to the blood. Such vessels are notably absent from the brain, however, leading to long-standing questions about how interstitial fluid in this organ is cleared of waste. Now, Iliff et al. describe an anatomically distinct clearing system in the brain that serves a lymphatic-like function. The researchers first investigated the fate of tracer molecules introduced into the cerebrospinal fluid (CSF) in mice. Produced in ventricular cavities deep within the brain, the CSF fills the subarachnoid space—a gap between two of the membranes that encase the brain and spinal cord. Whereas tracers infused into the ventricle remained near that site, those injected into the subarachnoid space rapidly entered the brain itself. By visualizing fluorescent tracers through a cranial window in live mice, the authors found that CSF enters the brain in specific channels that are defined by features of small blood vessels in the brain. Such vessels are almost entirely ensheathed by astrocytic endfeet (terminal enlargements of long processes that project from astrocytes). The CSF tracers readily flow inward to the brain matter in a compartment between the outside of vessels—in this case small arteries entering the brain—and the astrocytic endfeet. At later time points, the tracer exits the brain in similar channels surrounding veins, having apparently circulated through the brain interstitium. Such CSF flux—and the clearance of tracers injected into the brain itself—were markedly reduced in mice lacking aquaporin-4, a water channel localized to astrocytic endfeet, indicating that these channels mediate this flux. These findings may have relevance for understanding or treating neurodegenerative diseases that involve the mis-accumulation of soluble proteins, such as amyloid β in Alzheimer’s disease. Indeed, Iliff et al. found that normal clearance of amyloid β (previously injected into the brain) requires aquaporin-4. Because it lacks a lymphatic circulation, the brain must clear extracellular proteins by an alternative mechanism. The cerebrospinal fluid (CSF) functions as a sink for brain extracellular solutes, but it is not clear how solutes from the brain interstitium move from the parenchyma to the CSF. We demonstrate that a substantial portion of subarachnoid CSF cycles through the brain interstitial space. On the basis of in vivo two-photon imaging of small fluorescent tracers, we showed that CSF enters the parenchyma along paravascular spaces that surround penetrating arteries and that brain interstitial fluid is cleared along paravenous drainage pathways. Animals lacking the water channel aquaporin-4 (AQP4) in astrocytes exhibit slowed CSF influx through this system and a ~70% reduction in interstitial solute clearance, suggesting that the bulk fluid flow between these anatomical influx and efflux routes is supported by astrocytic water transport. Fluorescent-tagged amyloid β, a peptide thought to be pathogenic in Alzheimer’s disease, was transported along this route, and deletion of the Aqp4 gene suppressed the clearance of soluble amyloid β, suggesting that this pathway may remove amyloid β from the central nervous system. Clearance through paravenous flow may also regulate extracellular levels of proteins involved with neurodegenerative conditions, its impairment perhaps contributing to the mis-accumulation of soluble proteins.

Effect of Captopril on Mortality and Morbidity in Patients with Left Ventricular Dysfunction after Myocardial Infarction

BACKGROUND Left ventricular dilatation and dysfunction after myocardial infarction are major predictors of death. In experimental and clinical studies, longterm therapy with the angiotensin-converting--enzyme inhibitor captopril attenuated ventricular dilatation and remodeling. We investigated whether captopril could reduce morbidity and mortality in patients with left ventricular dysfunction after a myocardial infarction. METHODS Within 3 to 16 days after myocardial infarction, 2231 patients with ejection fractions of 40 percent or less but without overt heart failure or symptoms of myocardial ischemia were randomly assigned to receive doubleblind treatment with either placebo (1116 patients) or captopril (1115 patients) and were followed for an average of 42 months. RESULTS Mortality from all causes was significantly reduced in the captopril group (228 deaths, or 20 percent) as compared with the placebo group (275 deaths, or 25 percent); the reduction in risk was 19 percent (95 percent confidence interval, 3 to 32 percent; P = 0.019). In addition, the incidence of both fatal and nonfatal major cardiovascular events was consistently reduced in the captopril group. The reduction in risk was 21 percent (95 percent confidence interval, 5 to 35 percent; P = 0.014) for death from cardiovascular causes, 37 percent (95 percent confidence interval, 20 to 50 percent; P less than 0.001) for the development of severe heart failure, 22 percent (95 percent confidence interval, 4 to 37 percent; P = 0.019) for congestive heart failure requiring hospitalization, and 25 percent (95 percent confidence interval, 5 to 40 percent; P = 0.015) for recurrent myocardial infarction. CONCLUSIONS In patients with asymptomatic left ventricular dysfunction after myocardial infarction, long-term administration of captopril was associated with an improvement in survival and reduced morbidity and mortality due to major cardiovascular events. These benefits were observed in patients who received thrombolytic therapy, aspirin, or beta-blockers, as well as those who did not, suggesting that treatment with captopril leads to additional improvement in outcome among selected survivors of myocardial infarction.

New roles for astrocytes: Redefining the functional architecture of the brain

Astrocytes have traditionally been considered ancillary, satellite cells of the nervous system. However, work over the past decade has revealed that they interact with the vasculature to form a gliovascular network that might organize not only the structural architecture of the brain but also its communication pathways, activation, thresholds and plasticity. The net effect is that astroglia demarcate gray matter regions, both cortical and subcortical, into functional compartments whose internal activation thresholds and external outputs are regulated by single glial cells. The array of these astrocyte-delimited microdomains along the capillary microvasculature allows the formation of higher-order gliovascular units, which serve to match local neural activity and blood flow while regulating neuronal firing thresholds through coordinative glial signaling. By these means, astrocytes might establish the functional as well as the structural architecture of the adult brain.

Quantitative two-dimensional echocardiographic measurements are major predictors of adverse cardiovascular events after acute myocardial infarction. The protective effects of captopril.

BACKGROUND Left ventricular enlargement after myocardial infarction increases the likelihood of an adverse outcome. In an echocardiographic substudy of the Survival and Ventricular Enlargement (SAVE) Trial, we assessed whether captopril would attenuate progressive left ventricular enlargement in patients with left ventricular dysfunction after acute myocardial infarction and, if so, whether this would be associated with improved clinical outcome. METHODS AND RESULTS Two-dimensional transthoracic echocardiograms were obtained in 512 patients at a mean of 11.1 +/- 3.2 days after infarction and were repeated at 1 year in 420 survivors. Left ventricular size was assessed as left ventricular cavity areas at end diastole and end systole and left ventricular function as percent change in cavity area from end diastole to end systole. Patients were randomly assigned to placebo or captopril, and the incidence of adverse cardiovascular events consisting of cardiovascular death, heart failure requiring either hospitalization or open-label angiotensin-converting enzyme inhibitor therapy, and recurrent infarction were determined over a follow-up period averaging 3.0 +/- 0.6 years. Irrespective of treatment assignment, baseline left ventricular systolic area and percent change in area were strong predictors of cardiovascular mortality and adverse cardiovascular events. At 1 year, left ventricular end-diastolic and end-systolic areas were larger in the placebo than in the captopril group (P = .038, P = .015, respectively), and percent change in cavity area was greater in the captopril group (P = .005). One hundred eleven of the 420 1-year survivors with 1-year echo measurements (26.4%) experienced a major adverse cardiovascular event, and these patients had more than a threefold greater increase in left ventricular cavity areas than those with an uncomplicated course. Sixty-nine patients with adverse cardiovascular events were in the placebo group compared with 42 patients in the captopril-treated group (a risk reduction of 35%, P = .010). CONCLUSIONS Two-dimensional echocardiography provides important and independent prognostic information in patients after infarction. Left ventricular enlargement and function after infarction are associated with the development of adverse cardiac events. Attenuation of ventricular enlargement with captopril in these patients was associated with a reduction in adverse events. This study demonstrates the linkage between attenuation of left ventricular enlargement by captopril after infarction and improved clinical outcome.

Functional engraftment of human ES cell–derived dopaminergic neurons enriched by coculture with telomerase-immortalized midbrain astrocytes

To direct human embryonic stem (HES) cells to a dopaminergic neuronal fate, we cocultured HES cells that were exposed to both sonic hedgehog and fibroblast growth factor 8 with telomerase-immortalized human fetal midbrain astrocytes. These astrocytes substantially potentiated dopaminergic neurogenesis by both WA09 and WA01 HES cells, biasing them to the A9 nigrostriatal phenotype. When transplanted into the neostriata of 6-hydroxydopamine–lesioned parkinsonian rats, the dopaminergic implants yielded a significant, substantial and long-lasting restitution of motor function. However, although rich in donor-derived tyrosine hydroxylase–expressing neurons, the grafts exhibited expanding cores of undifferentiated mitotic neuroepithelial cells, which can be tumorigenic. These results show the utility of recreating the cellular environment of the developing human midbrain while driving dopaminergic neurogenesis from HES cells, and they demonstrate the potential of the resultant cells to mediate substantial functional recovery in a model of Parkinson disease. Yet these data also mandate caution in the clinical application of HES cell–derived grafts, given their potential for phenotypic instability and undifferentiated expansion.

Astrocyte-mediated potentiation of inhibitory synaptic transmission

We investigated the role of astrocytes in activity-dependent modulation of inhibitory synaptic transmission in hippocampal slices. Repetitive firing of an interneuron decreased the probability of synaptic failures in spike-evoked inhibitory postsynaptic currents (unitary IPSCs) in CA1 pyramidal neurons. The GABAB-receptor antagonist CGP55845A abolished this effect. Direct stimulation of astrocytes, or application of the GABAB-receptor agonist baclofen, potentiated miniature inhibitory postsynaptic currents (mIPSCs) in pyramidal neurons. These effects were blocked by inhibition of astrocytic calcium signaling with the calcium chelator BAPTA or by antagonists of the ionotropic glutamate receptors. These observations suggest that interneuronal firing elicits a GABAB-receptor-mediated elevation of calcium in surrounding astrocytes, which in turn potentiates inhibitory transmission. Astrocytes may therefore be a necessary intermediary in activity-dependent modulation of inhibitory synapses in the hippocampus.

Identification and Isolation of multipotential neural progenitor cells from the subcortical white matter of the adult human brain

The subcortical white matter of the adult human brain harbors a pool of glial progenitor cells. These cells can be isolated by fluorescence-activated cell sorting (FACS) after either transfection with green fluorescent protein (GFP) under the control of the CNP2 promoter, or A2B5-targeted immunotagging. Although these cells give rise largely to oligodendrocytes, in low-density culture we observed that some also generated neurons. We thus asked whether these nominally glial progenitors might include multipotential progenitor cells capable of neurogenesis. We found that adult human white-matter progenitor cells (WMPCs) could be passaged as neurospheres in vitro and that these cells generated functionally competent neurons and glia both in vitro and after xenograft to the fetal rat brain. WMPCs were able to produce neurons after their initial isolation and did not require in vitro expansion or reprogramming to do so. These experiments indicate that an abundant pool of mitotically competent neurogenic progenitor cells resides in the adult human white matter.

Coordinated Interaction of Neurogenesis and Angiogenesis in the Adult Songbird Brain

Neurogenesis proceeds throughout life in the higher vocal center (HVC) of the adult songbird neostriatum. Testosterone induces neuronal addition and endothelial division in HVC. We asked if testosterone-induced angiogenesis might contribute importantly to HVC neuronal recruitment. Testosterone upregulated both VEGF and its endothelial receptor, VEGF-R2/Quek1/KDR, in HVC. This yielded a burst in local HVC angiogenesis. FACS-isolated HVC endothelial cells produced BDNF in a testosterone-dependent manner. In vivo, HVC BDNF rose by the third week after testosterone, lagging by over a week the rise in VEGF and VEGF-R2. In situ hybridization revealed that much of this induced BDNF mRNA was endothelial. In vivo, both angiogenesis and neuronal addition to HVC were substantially diminished by inhibition of VEGF-R2 tyrosine kinase. These findings suggest a causal interaction between testosterone-induced angiogenesis and neurogenesis in the adult forebrain.