The cerebral glucose-fatty acid cycle: evolutionary roots, regulation, and (patho)physiological importance

Metabolic changes with the occurrence of atherosclerotic plaques and the effects of statins

Atherosclerosis is a common cardiovascular disease caused by the abnormal expression of multiple factors and genes influenced by both environmental and genetic factors. The primary manifestation of atherosclerosis is plaque formation, which occurs when inflammatory cells consume excess lipids, affecting their retention and modification within the arterial intima. This triggers endothelial cell (EC) activation, immune cell infiltration, vascular smooth muscle cell (VSMC) proliferation and migration, foam cell formation, lipid streaks, and fibrous plaque development. These processes can lead to vascular wall sclerosis, lumen stenosis, and thrombosis. Immune cells, ECs, and VSMCs in atherosclerotic plaques undergo significant metabolic changes and inflammatory responses. The interaction of cytokines and chemokines secreted by these cells leads to the onset, progression, and regression of atherosclerosis. The regulation of cell- or cytokine-based immune responses is a novel therapeutic approach for atherosclerosis. Statins are currently the primary pharmacological agents utilised for managing unstable plaques owing to their ability to enhance endothelial function, regulate VSMC proliferation and apoptosis by reducing cholesterol levels, and mitigate the expression and activity of inflammatory cytokines. In this review, we provide an overview of the metabolic changes associated with atherosclerosis, describe the effects of inflammatory responses on atherosclerotic plaques, and discuss the mechanisms through which statins contribute to plaque stabilisation. Additionally, we examine the role of statins in combination with other drugs in the management of atherosclerosis.

Metabolism of vascular smooth muscle cells in vascular diseases

Vascular smooth muscle cells (VSMCs) are the fundamental component of the medial layer of arteries and are essential for arterial physiology and pathology. It is becoming increasingly clear that VSMCs can alter their metabolism to fulfill the bioenergetic and biosynthetic requirements. During vascular injury, VSMCs switch from a quiescent "contractile" phenotype to a highly migratory and proliferative "synthetic" phenotype. Recent studies have found that the phenotype switching of VSMCs is driven by a metabolic switch. Metabolic pathways, including aerobic glycolysis, fatty acid oxidation, and amino acid metabolism, have distinct, indispensable roles in normal and dysfunctional vasculature. VSMCs metabolism is also related to the metabolism of endothelial cells. In the present review, we present a brief overview of VSMCs metabolism and how it regulates the progression of several vascular diseases, including atherosclerosis, systemic hypertension, diabetes, pulmonary hypertension, vascular calcification, and aneurysms, and the effect of the risk factors for vascular disease (aging, cigarette smoking, and excessive alcohol drinking) on VSMC metabolism to clarify the role of VSMCs metabolism in the key pathological process.

Metabolomic analysis of survival in carbohydrate pre-fed pigs subjected to shock and polytrauma

Hemorrhagic shock, a result of extensive blood loss, is a dominant factor in battlefield morbidity and mortality. Early rodent studies in hemorrhagic shock reported carbohydrate feeding prior to the induction of hemorrhagic shock decreased mortality. When repeated in our laboratory with a porcine model, carbohydrate pre-feed resulted in a 60% increase in death rate following hemorrhagic shock with trauma when compared to fasted animals (15/32 or 47% vs. 9/32 or 28%). In an attempt to explain the unexpected death rate for pre-fed animals, we further investigated the metabolic profiles of pre-fed non-survivors (n = 15) across 4 compartments (liver, muscle, serum, and urine) at specific time intervals (pre-shock, shock, and resuscitation) and compared them to pre-fed survivors (n = 17). As hypothesized, pre-fed pigs that died as a result of hemorrhage and trauma showed differences in their metabolic and physiologic profiles at all time intervals and in all compartments when compared to pre-fed survivors. Our data suggest that, although all animals were subjected to the same shock and trauma protocol, non-survivors exhibited altered carbohydrate processing as early as the pre-shock sampling point. This was evident in (for example) the higher levels of ATP and markers of greater anabolic activity in the muscle at the pre-shock time point. Based on the metabolic findings, we propose two mechanisms that connect pre-fed status to a higher death rate: (1) animals that die are more susceptible to opening of the mitochondrial permeability transition pore, a major factor in ischemia/reperfusion injury; and (2) loss of fasting-associated survival mechanisms in pre-fed animals.

Mitochondrial Gene Expression Profiles Are Associated with Maternal Psychosocial Stress in Pregnancy and Infant Temperament

Background

Gene-environment interactions mediate through the placenta and shape the fetal brain development. Between the environmental determinants of the fetal brain, maternal psychosocial stress in pregnancy has been shown to negatively influence the infant temperament development. This in turn may have adverse consequences on the infant neurodevelopment extending throughout the entire life-span. However little is known about the underlying biological mechanisms of the effects of maternal psychosocial stress in pregnancy on infant temperament. Environmental stressors such as maternal psychosocial stress in pregnancy activate the stress response cascade that in turn drives the increase in the cellular energy demand of vital organs with high metabolic rates such as, in pregnancy, the placenta. Key players of the stress response cascade are the mitochondria.

Results

Here, we tested the expression of all 13 protein-coding genes encoded by the mitochondria in 108 placenta samples from the Stress in Pregnancy birth cohort, a study that aims at determining the influence of in utero exposure to maternal psychosocial stress in pregnancy on infant temperament. We showed that the expression of the protein-coding mitochondrial-encoded gene MT-ND2 was positively associated with indices of maternal psychosocial stress in pregnancy including Prenatal Perceived Stress (β = 0.259; p-regression = 0.004; r²-regression = 0.120), State Anxiety (β = 0.218; p-regression = 0.003; r²-regression = 0.153), Trait Anxiety (β = 0.262; p-regression = 0.003; r²-regression = 0.129) and Pregnancy Anxiety Total (β = 0.208; p-regression = 0.010; r²-regression = 0.103). In the meantime MT-ND2 was negatively associated with the infant temperament indices of Activity Level (β = -0.257; p-regression = 0.008; r²-regression = 0.165) and Smile and Laughter (β = -0.286; p-regression = 0.036; r²-regression = 0.082). Additionally, MT-ND6 was associated with the maternal psychosocial stress in pregnancy index of Prenatal Perceived Stress (β = -0.231; p-regression = 0.004; r²-regression = 0.120), while MT-CO2 was associated with the maternal psychosocial stress in pregnancy indices of State Anxiety (β = 0.206; p-regression = 0.003; r²-regression = 0.153) and Trait Anxiety (β = 0.205; p-regression = 0.003; r²-regression = 0.129).

Conclusions

Our data support the role of mitochondria in responding to maternal psychosocial stress in pregnancy, as assessed in placenta, while also suggesting an important role for the mitochondria in the infant temperament development.

Sugarcoated isolation: evidence that social avoidance is linked to higher basal glucose levels and higher consumption of glucose

Objective: The human brain adjusts its level of effort in coping with various life stressors as a partial function of perceived access to social resources. We examined whether people who avoid social ties maintain a higher fasting basal level of glucose in their bloodstream and consume more sugar-rich food, reflecting strategies to draw more on personal resources when threatened. Methods: In Study 1 (N = 60), we obtained fasting blood glucose and adult attachment orientations data. In Study 2 (N = 285), we collected measures of fasting blood glucose and adult attachment orientations from older adults of mixed gender, using a measure of attachment style different from Study 1. In Study 3 (N = 108), we examined the link between trait-like attachment avoidance, manipulation of an asocial state, and consumption of sugar-rich food. In Study 4 (N = 115), we examined whether manipulating the social network will moderate the effect of attachment avoidance on consumption of sugar-rich food. Results: In Study 1, fasting blood glucose levels corresponded with higher attachment avoidance scores after statistically adjusting for time of assessment and interpersonal anxiety. For Study 2, fasting blood glucose continued to correspond with higher adult attachment avoidance even after statistically adjusting for interpersonal anxiety, stress indices, age, gender, social support and body mass. In Study 3, people high in attachment avoidance consume more sugar-rich food, especially when reminded of asocial tendencies. Study 4 indicated that after facing a stressful task in the presence of others, avoidant people gather more sugar-rich food than more socially oriented people. Conclusion: Results are consistent with the suggestion that socially avoidant individuals upwardly adjust their basal glucose levels and consume more glucose-rich food with the expectation of increased personal effort because of limited access to social resources. Further investigation of this link is warranted.

A four-compartment metabolomics analysis of the liver, muscle, serum, and urine response to polytrauma with hemorrhagic shock following carbohydrate prefeed

Objective

Hemorrhagic shock accompanied by injury represents a major physiologic stress. Fasted animals are often used to study hemorrhagic shock (with injury). A fasted state is not guaranteed in the general human population. The objective of this study was to determine if fed animals would exhibit a different metabolic profile in response to hemorrhagic shock with trauma when compared to fasted animals.

Methods

Proton (1H) NMR spectroscopy was used to determine concentrations of metabolites from four different compartments (liver, muscle, serum, urine) taken at defined time points throughout shock/injury and resuscitation. PLS-DA was performed and VIP lists established for baseline, shock and resuscitation (10 metabolites for each compartment at each time interval) on metabolomics data from surviving animals.

Results

Fed status prior to the occurrence of hemorrhagic shock with injury alters the metabolic course of this trauma and potentially affects mortality. The death rate for CPF animals is higher than FS animals (47 vs 28%). The majority of deaths occur post-resuscitation suggesting reperfusion injury. The metabolomics response to shock reflects priorities evident at baseline. FS animals raise the baseline degree of proteolysis to provide additional amino acids for energy production while CPF animals rely on both glucose and, to a lesser extent, amino acids. During early resuscitation levels of metabolites associated with energy production drop, suggesting diminished demand.

Conclusions

Feeding status prior to the occurrence of hemorrhagic shock with injury alters the metabolic course of this trauma and potentially affects mortality. The response to shock reflects metabolic priorities at baseline.

Loneliness, social integration and consumption of sugar-containing beverages: testing the social baseline theory

OBJECTIVE

Social Baseline Theory (SBT) proposes that close relationships aid in metabolic resource management and that individuals without significant relationships may experience more demands on their own neural metabolic resources on a daily basis when solving problems, remaining vigilant against potential threats and regulating emotional responses. This study tests a hypothesised consequence derived from SBT: relative social isolation leads to increased levels of sugar intake.

METHODS

Based on cross-sectional, self-reported data from the Norwegian Mother and Child Cohort Study (N = 90 084), information on social integration and the consumption of both sugar-sweetened and artificially sweetened sodas and juices was obtained from a large number of women in early pregnancy. Multiple regression analyses were conducted to assess whether loneliness, marital status, relationship satisfaction, advice from others than partner, and cohesion at work is associated with consumption of sodas and juices.

RESULTS

Perceived loneliness was associated with elevated intake of all sugary beverages, while relationship satisfaction was negatively associated with all sugary beverages. Being married or cohabitating, having supportive friends, and having a sense of togetherness at work were associated with lower intake of two out of three sugar-containing beverages. These associations were significant, even after controlling for factors such as body mass index, weight related self-image, depression, physical activity, educational level, age and income. In comparison, a statistically significant relationship emerged between relationship satisfaction and artificially sweetened cola. No other predictor variables were significantly associated with any type of artificially sweetened beverage.

CONCLUSIONS

This study indicates that loneliness and social integration influence the level of consumption of sugary beverages. The results support the hypothesis derived from the Social Baseline Theory that relative social isolation leads to increased levels of sugar intake.

Vascular and metabolic dysfunction in Alzheimer's disease: a review

Alzheimer's disease (AD) is thought to start years or decades prior to clinical diagnosis. Overt pathology such as protein misfolding and plaque formation occur at later stages, and factors other than amyloid misfolding contribute to the initiation of the disease. Vascular and metabolic dysfunctions are excellent candidates, as they are well-known features of AD that precede pathology or clinical dementia. While the general notion that vascular and metabolic dysfunctions contribute to the etiology of AD is becoming accepted, recent research suggests novel mechanisms by which these/such processes could possibly contribute to AD pathogenesis. Vascular dysfunction includes reduced cerebrovascular flow and cerebral amyloid angiopathy. Indeed, there appears to be an interaction between amyloid β (Aβ) and vascular pathology, where Aβ production and vascular pathology both contribute to and are affected by oxidative stress. One major player in the vascular pathology is NAD(P)H oxidase, which generates vasoactive superoxide. Metabolic dysfunction has only recently regained popularity in relation to its potential role in AD. The role of metabolic dysfunction in AD is supported by the increased epidemiological risk of AD associated with several metabolic diseases such as diabetes, dyslipidemia and hypertension, in which there is elevated oxidative damage and insulin resistance. Metabolic dysfunction is further implicated in AD as pharmacological inhibition of metabolism exacerbates pathology, and several metabolic enzymes of the glycolytic, tricarboxylic acid cycle (TCA) and oxidative phosphorylation pathways are damaged in AD. Recent studies have highlighted the role of insulin resistance, in contributing to AD. Thus, vascular and metabolic dysfunctions are key components in the AD pathology throughout the course of disease. The common denominator between vascular and metabolic dysfunction emerging from this review appears to be oxidative stress and Aβ. This review also provides a framework for evaluation of current and future therapeutics for AD.

Brain fuel metabolism, aging, and Alzheimer's disease

Lower brain glucose metabolism is present before the onset of clinically measurable cognitive decline in two groups of people at risk of Alzheimer's disease--carriers of apolipoprotein E4, and in those with a maternal family history of AD. Supported by emerging evidence from in vitro and animal studies, these reports suggest that brain hypometabolism may precede and therefore contribute to the neuropathologic cascade leading to cognitive decline in AD. The reason brain hypometabolism develops is unclear but may include defects in brain glucose transport, disrupted glycolysis, and/or impaired mitochondrial function. Methodologic issues presently preclude knowing with certainty whether or not aging in the absence of cognitive impairment is necessarily associated with lower brain glucose metabolism. Nevertheless, aging appears to increase the risk of deteriorating systemic control of glucose utilization, which, in turn, may increase the risk of declining brain glucose uptake, at least in some brain regions. A contributing role of deteriorating glucose availability to or metabolism by the brain in AD does not exclude the opposite effect, i.e., that neurodegenerative processes in AD further decrease brain glucose metabolism because of reduced synaptic functionality and hence reduced energy needs, thereby completing a vicious cycle. Strategies to reduce the risk of AD by breaking this cycle should aim to (1) improve insulin sensitivity by improving systemic glucose utilization, or (2) bypass deteriorating brain glucose metabolism using approaches that safely induce mild, sustainable ketonemia.

Mitochondrial dysfunction in schizophrenia: evidence for compromised brain metabolism and oxidative stress

The etiology and pathophysiology of schizophrenia remain unknown. A parallel transcriptomics, proteomics and metabolomics approach was employed on human brain tissue to explore the molecular disease signatures. Almost half the altered proteins identified by proteomics were associated with mitochondrial function and oxidative stress responses. This was mirrored by transcriptional and metabolite perturbations. Cluster analysis of transcriptional alterations showed that genes related to energy metabolism and oxidative stress differentiated almost 90% of schizophrenia patients from controls, while confounding drug effects could be ruled out. We propose that oxidative stress and the ensuing cellular adaptations are linked to the schizophrenia disease process and hope that this new disease concept may advance the approach to treatment, diagnosis and disease prevention of schizophrenia and related syndromes.