Astrocytes as Key Regulators of Brain Energy Metabolism: New Therapeutic Perspectives

Astrocytes play key roles in the regulation of brain energy metabolism, which has a major impact on brain functions, including memory, neuroprotection, resistance to oxidative stress and homeostatic tone. Energy demands of the brain are very large, as they continuously account for 20–25% of the whole body’s energy consumption. Energy supply of the brain is tightly linked to neuronal activity, providing the origin of the signals detected by the widely used functional brain imaging techniques such as functional magnetic resonance imaging and positron emission tomography. In particular, neuroenergetic coupling is regulated by astrocytes through glutamate uptake that triggers astrocytic aerobic glycolysis and leads to glucose uptake and lactate release, a mechanism known as the Astrocyte Neuron Lactate Shuttle. Other neurotransmitters such as noradrenaline and Vasoactive Intestinal Peptide mobilize glycogen, the reserve for glucose exclusively localized in astrocytes, also resulting in lactate release. Lactate is then transferred to neurons where it is used, after conversion to pyruvate, as a rapid energy substrate, and also as a signal that modulates neuronal excitability, homeostasis, and the expression of survival and plasticity genes. Importantly, glycolysis in astrocytes and more generally cerebral glucose metabolism progressively deteriorate in aging and age-associated neurodegenerative diseases such as Alzheimer’s disease. This decreased glycolysis actually represents a common feature of several neurological pathologies. Here, we review the critical role of astrocytes in the regulation of brain energy metabolism, and how dysregulation of astrocyte-mediated metabolic pathways is involved in brain hypometabolism. Further, we summarize recent efforts at preclinical and clinical stages to target brain hypometabolism for the development of new therapeutic interventions in age-related neurodegenerative diseases.

Mitochondrial, exosomal miR137-COX6A2 and gamma synchrony as biomarkers of parvalbumin interneurons, psychopathology, and neurocognition in schizophrenia

Early detection and intervention in schizophrenia requires mechanism-based biomarkers that capture neural circuitry dysfunction, allowing better patient stratification, monitoring of disease progression and treatment. In prefrontal cortex and blood of redox dysregulated mice (Gclm-KO ± GBR), oxidative stress induces miR-137 upregulation, leading to decreased COX6A2 and mitophagy markers (NIX, Fundc1, and LC3B) and to accumulation of damaged mitochondria, further exacerbating oxidative stress and parvalbumin interneurons (PVI) impairment. MitoQ, a mitochondria-targeted antioxidant, rescued all these processes. Translating to early psychosis patients (EPP), blood exosomal miR-137 increases and COX6A2 decreases, combined with mitophagy markers alterations, suggest that observations made centrally and peripherally in animal model were reflected in patients' blood. Higher exosomal miR-137 and lower COX6A2 levels were associated with a reduction of ASSR gamma oscillations in EEG. As ASSR requires proper PVI-related networks, alterations in miR-137/COX6A2 plasma exosome levels may represent a proxy marker of PVI cortical microcircuit impairment. EPP can be stratified in two subgroups: (a) a patients' group with mitochondrial dysfunction "Psy-D", having high miR-137 and low COX6A2 levels in exosomes, and (b) a "Psy-ND" subgroup with no/low mitochondrial impairment, including patients having miR-137 and COX6A2 levels in the range of controls. Psy-D patients exhibited more impaired ASSR responses in association with worse psychopathological status, neurocognitive performance, and global and social functioning, suggesting that impairment of PVI mitochondria leads to more severe disease profiles. This stratification would allow, with high selectivity and specificity, the selection of patients for treatments targeting brain mitochondria dysregulation and capture the clinical and functional efficacy of future clinical trials.

Behavioral Intervention Components Associated With Cost-effectiveness: A Comparison of Six Domains

Background

To help implement behavior change interventions (BCIs) it is important to be able to characterize their key components and determine their effectiveness.

Purpose

This study assessed and compared the components of BCIs in terms of intervention functions identified using the Behaviour Change Wheel Framework (BCW) and in terms of their specific behavior change techniques (BCTs) identified using the BCT TaxonomyV1, across six behavioral domains and the association of these with cost-effectiveness.

Methods

BCIs in 251 studies targeting smoking, diet, exercise, sexual health, alcohol and multiple health behaviors, were specified in terms of their intervention functions and their BCTs, grouped into 16 categories. Associations with cost-effectiveness measured in terms of incremental cost-effectiveness ratio (ICER) upper and lower estimates were determined using regression analysis.

Results

The most prevalent functions were increasing knowledge through education (72.1%) and imparting skills through training (74.9%). The most prevalent BCT groupings were shaping knowledge (86.5%), changing behavioral antecedents (53.0%), supporting self-regulation (47.7%), and providing social support (44.6%). Intervention functions associated with better cost-effectiveness were those based on training (β_low = −15044.3; p = .002), persuasion (β_low = −19384.9; p = .001; β_upp = −25947.6; p < .001) and restriction (β_upp = −32286.1; p = .019), and with lower cost-effectiveness were those based on environmental restructuring (β = 15023.9_low; p = .033). BCT groupings associated with better cost-effectiveness were goals and planning (β_low = −8537.3; p = .019 and β_upp = −12416.9; p = .037) and comparison of behavior (β_low = −13561.9, p = .047 and β_upp = −30650.2; p = .006). Those associated with lower cost-effectiveness were natural consequences (β_low = 7729.4; p = .033) and reward and threat (β_low = 20106.7; p = .004).

Conclusions

BCIs that focused on training, persuasion and restriction may be more cost-effective, as may those that encourage goal setting and comparison of behaviors with others.

Bluetongue dynamics in French wildlife: exploring the driving forces

Bluetongue (BT) was monitored in wildlife in France during two consecutive years corresponding to contrasting incidence rates in livestock: in 2008 at the peak of domestic outbreaks and in 2009 when very few outbreaks were observed. The disease status of 2 798 ruminants comprising 837 red deer (Cervus elaphus) was explored using ELISA test on serum and real-time RT-PCR test on blood or spleen. A large proportion of red deer were seropositive and positive to RT-PCR in 2008, but also in 2009 (seroprevalence: 47.1% and 24.3%), suggesting that red deer could maintain infection when domestic incidence was negligible. By contrast, low seroprevalence (<3%) and few RT-PCR positive results were observed in other wild ruminant species, which rather appeared thus as dead-end hosts. The risk factors of bluetongue circulation during the periods of high (2008) and low (2009) domestic incidence were explored in red deer using logistic mixed models. In this species, prevalence has been mainly influenced by the initial peak of BT in livestock, but also by environmental factor such as elevation and edge density between forest and pastures. Surprisingly, cattle density has a negative influence on prevalence in red deer, possibly due to the protective effect of cattle regarding midges' bites and/or to still unexplained factors dealing with the host/midge interface. To our knowledge, this study is the first attempt at measuring the effect of landscape and wildlife/domestic interface on BT prevalence in wildlife in Europe.

Mediation analysis of the association between use of NRT for smoking reduction and attempts to stop smoking

OBJECTIVES

Use of nicotine replacement therapy (NRT) for smoking reduction (SR) is linked to higher quit attempt rates than SR without NRT. This study aimed to assess the possible mediating roles of confidence in ability to quit, enjoyment of smoking and motivation to quit in this association.

DESIGN

Cross-sectional survey.

MAIN OUTCOME MEASURES

Smokers were asked if they were currently attempting SR, and if they were, whether they were using NRT. Motivation to stop, enjoyment of smoking, confidence in ability to stop, and previous quit attempts, were also assessed.

RESULTS

There was no evidence that confidence in ability to quit or enjoyment of smoking mediated the association between the use of NRT for SR and attempts to quit. Only motivation to stop partially mediated between the use of NRT for SR and attempts to stop (indirect effect: odds ratio 1.08, p < 0.001).

CONCLUSION

Although this study is limited by its cross-sectional design, the findings point towards the possibility that the use of NRT to aid SR may promote attempts to stop through increasing motivation to quit but not by increasing confidence or by reducing enjoyment of smoking. Longitudinal studies are required to draw firmer conclusions about the possible mediating effects of motivation to quit.

Use of nicotine replacement therapy for smoking reduction and during enforced temporary abstinence: a national survey of English smokers

AIMS

To assess the prevalence of nicotine replacement therapy (NRT) use for smoking reduction (SR) and temporary abstinence (TA), the association between the two and the strength of the association between NRT use for SR or TA and socio-demographic characteristics, cigarette consumption and past quit attempts.

DESIGN

Cross-sectional monthly surveys.

SETTING

England.

PARTICIPANTS

A total of 11, 414 smokers.

MEASUREMENTS

Participants were asked (i) whether they were reducing the amount they smoked: if so, whether they used NRT; and (ii) whether they used NRT for TA. Demographic characteristics, daily cigarette consumption and whether a quit attempt had been made in the past 12 months were also assessed.

FINDINGS

Of the participants, 56% were attempting SR, 14% were using NRT for SR and 14% were using NRT for TA. Use of NRT for SR and TA were highly correlated. The nicotine patch was the most commonly used form of NRT. The use of NRT for SR, compared with unassisted SR, was more common among older smokers, while the use of NRT for TA was more common among women. Cigarette consumption was higher in those using NRT for SR than those attempting SR without NRT. The use of NRT for SR and TA was associated positively with past quit attempts.

CONCLUSIONS

Nicotine replacement therapy use for smoking reduction and temporary abstinence is common in England. The use of NRT for SR and TA does not appear to be associated with lower cigarette consumption relative to SR or TA without NRT, but is associated with a higher rate of past quit attempts.

The case of the combative CFO

Minute Publishing Chairman and CEO Neil Harcum has a right to be proud of his new national newspaper, America Today. It has won three Pulitzer Prizes and attracted one million readers in just three years of publication. But, as CFO Peter Rawson points out, it's also losing $100 million a year and has broken Minute's 20-year string of earnings gains. In the process, the company has been split between two warring factions: one is backing Harcum and favors continuing the paper. The other agrees with Rawson that the project must be stopped. The board of directors has been assembled to decide the newspaper's fate. In his speech to the board, Rawson says it's time to cut Minute's losses and put an end to America Today. And Wall Street agrees. Several brokerage houses have taken Minute off their buy lists, and rating agencies are about to down-grade the company's debt. "America Today is not a good investment," Rawson argues. "Certainly, it isn't in keeping with our commitment to deliver maximum value to our shareholders." But Harcum thinks Rawson is way out of line. "We cannot allow our bean-counters to set policy," he claims. Harcum sees the newspaper as a product of the future that has created its own market. It's only a matter of time before America Today attracts enough advertising to put it in the black. He has a successful track record, and he doesn't want the board to lose faith in him now.(ABSTRACT TRUNCATED AT 250 WORDS)

Postural changes in cardiac volumes in men in relation to adult age

Cardiac volumes by equilibrium gated cardiac blood pool scans and heart rate were measured in the supine and sitting positions in 64 male volunteer subjects (age 25-80 yrs) who had been rigorously screened to exclude cardiovascular disease. After the upright position was assumed, the average cardiac output of all subjects was unchanged but heart rate increased and stroke volume decreased due to a decrease in end diastolic volume. Neither the supine or sitting cardiac output nor the average postural change in cardiac output, cardiac volumes or heart rate was age-related. While the average cardiac output among the subjects was unaltered with a change in posture, in some individuals it increased slightly while in others it decreased. The postural change in cardiac output among the individuals correlated by linear regression analysis with a change in heart rate only in younger subjects and with a change in stroke volume in all age groups, but the slope of this relationship was greater in older than in younger subjects. The postural change in stroke volume was strongly correlated with a change in end diastolic volume and this relationship did not vary with age. Thus, although the average postural change in cardiac output among healthy subjects is not age-related, a given change in cardiac output with posture in an older individual depends more on a change in stroke volume and less on a heart rate change than in a younger one. This result, like the response to vigorous upright exercise previously demonstrated to occur with aging, indicates a greater reliance in the elderly on the Frank-Starling mechanism than on heart rate for a given change in cardiac output in response to perturbations from the basal supine state.