Elevated norepinephrine may be an etiological factor in a wide range of diseases: Age-related macular degeneration, systemic lupus erythematosus, atrial fibrillation, metabolic syndrome

Ocular findings in metabolic syndrome: a review

Metabolic syndrome (MetS) has emerged as a worldwide health hazard of the modern lifestyle, representing a cluster of metabolic abnormalities and a risk factor for cardiovascular disease. Eye diseases, such as diabetic retinopathy, central retinal artery occlusion, cataract, age-related macular degeneration, glaucoma, and dry eye syndrome have been linked with many of MetS components. Their relationship with MetS itself is, however, a recent topic of investigation. This review aims to gather published evidence supporting associations between ocular findings and MetS and to explore the related physiopathological processes that congregate in this syndrome and lead to these diseases. Despite compiling interesting and compelling evidence, it raises awareness to the need of further studies in this field to keep solidifying these associations and unveiling the pathological processes that support them. It ultimately targets MetS patients as a population of individuals who are at increased risk of developing age-related eye diseases and vision loss.

Serious infection may systemically increase noradrenergic signaling and produce psychological effects

Serious infection elicits inflammatory processes that act through a range of molecular pathways, including cytokine signaling. It is not established however that noradrenaline (NA), a widely distributed neurotransmitter in the brain that is also a principal output molecule of the sympathetic nervous system, can produce psychological effects associated with infection. This paper puts forth the hypothesis that through neural-immune crosstalk, serious infection increases noradrenergic signaling, both in the central nervous system and in peripheral organs. In this manner, elevated noradrenergic transmission may help produce basic symptoms of infection such as fever, fatigue, aches and pains (including headache), nausea, and loss of appetite. NA may also promote cognitive impairment, major depression, unipolar mania, and even epileptic seizures in some cases. The paper focuses on three major types of infection: influenza (viral), tuberculosis (bacterial), malaria (parasitic), while also summarizing the potential relationship between NA and human immunodeficiency virus (HIV) infection. Four lines of evidence are used to test association between NA and influenza, tuberculosis, and malaria: direct measures of NA and its metabolites; and incidence of hypertension, bipolar mania, and epileptic seizures, since the latter three conditions may be associated with elevated NA. In addition, heart rate variability data are examined with respect to a number of infectious diseases, since those data provide information on sympathetic nervous system activity. While the data do not unequivocally support elevated noradrenergic signaling promoting psychological symptomatology with infection, many studies are consistent with this view.

Neurodining: Common dietary factors may be substrates in novel biosynthetic pathways for monoaminergic neurotransmitters

It is not established that there are multiple endogenous mechanisms for synthesizing each of the three major monoamine neurotransmitters: serotonin, norepinephrine, and dopamine. Having multiple biosynthetic pathways for each of these important signaling molecules would provide greater assurance that they are available in sufficient quantities for their various physiological roles in the body. This paper puts forth the hypothesis that a number of common dietary factors-including sucrose and glucose, fats, plant components, and even ethanol-are substrates in novel biosynthetic pathways for the monoamines. A major aspect of this hypothesis is that in a range of multicellular organisms, D-glucose in particular may participate in novel biosynthetic pathways for the monoamines, where this sugar has already been linked with synthesis of the neurotransmitters acetylcholine, glutamate, and GABA through the tricarboxylic acid cycle. Another major aspect of the hypothesis is that phenol or polyphenol molecules, found in various plants, may combine with particular fats or even ethanol to form dopamine, which can then be converted to norepinephrine through the already established step involving the enzyme dopamine beta-hydroxylase. If such a biosynthetic pathway exists for converting ethanol to dopamine in humans, it could be a major factor in substance abuse, including early onset alcoholism. Further, if the above biosynthetic pathways exist in a range of organisms, they may be associated with appetitive processes regulating consumption of particular dietary factors, such as fruits and vegetables, to maintain internal "set points" of, for example, elevated noradrenergic signaling. In this scenario, exposure to psychological stress, which could eventually deplete neurotransmitters such as norepinephrine, may result in craving for sucrose, fats, or alcohol to help replenish the depleted cellular levels of this signaling molecule. An alternative to the overall biosynthetic hypothesis put forth here is that animal cells do not possess these pathways, but the animal microbiome harbors bacteria that do carry out these reactions and helps supply the body with monoamines and other signaling molecules.

Phenome-Wide Association Studies Uncover a Novel Association of Increased Atrial Fibrillation in Male Patients With Systemic Lupus Erythematosus

OBJECTIVE

Phenome-wide association studies (PheWAS) scan across billing codes in the electronic health record (EHR) and re-purpose clinical EHR data for research. In this study, we examined whether PheWAS could function as an EHR-based discovery tool for systemic lupus erythematosus (SLE) and identified novel clinical associations in male versus female patients with SLE.

METHODS

We used a de-identified version of the Vanderbilt University Medical Center EHR, which includes more than 2.8 million subjects. We performed EHR-based PheWAS to compare SLE patients with age-, sex-, and race-matched control subjects and to compare male SLE patients with female SLE patients, controlling for multiple testing using a false discovery rate (FDR) P value of 0.05.

RESULTS

We identified 1,097 patients with SLE and 5,735 matched control subjects. In a comparison of patients with SLE and matched controls, SLE patients were shown to be more likely to have International Classification of Diseases, Ninth Revision codes related to the SLE disease criteria. In the PheWAS of male versus female SLE patients, with adjustment for age and race, male patients were shown to be more likely to have atrial fibrillation (odds ratio 4.50, false discovery rate P = 3.23 × 10^-3 ). Chart review confirmed atrial fibrillation, with the majority of patients developing atrial fibrillation after the SLE diagnosis and having multiple risk factors for atrial fibrillation. After adjustment for age, sex, race, and coronary artery disease, SLE disease status was shown to be significantly associated with atrial fibrillation (P = 0.002).

CONCLUSION

Using PheWAS to compare male and female patients with SLE, we identified a novel association of an increased incidence of atrial fibrillation in male patients. SLE disease status was shown to be independently associated with atrial fibrillation, even after adjustment for age, sex, race, and coronary artery disease. These results demonstrate the utility of PheWAS as an EHR-based discovery tool for SLE.

α2A -Adrenergic receptor polymorphisms and mRNA expression levels are associated with delay discounting in cocaine users

Cocaine users characteristically display preferences for smaller immediate rewards over larger delayed rewards, and this delay discounting (DD) has been proposed as an endophenotype of cocaine addiction. Recent evidence suggests that the norepinephrine system and more specifically the α_2A -adrenergic receptor (ADRA2A) are impacted by chronic cocaine use while also being potentially involved in the neural mechanisms underlying DD. Hence, we investigated the effects of ADRA2A polymorphisms and ADRA2A mRNA expression levels on DD of cocaine users and stimulant-naïve controls. Two hundred and twenty-three participants (129 cocaine users and 94 stimulant-naïve healthy controls) completed a computerized DD paradigm and were genotyped for three single nucleotide polymorphisms (SNPs; rs1800544, rs521674 and rs602618) in the ADRA2A gene, while their peripheral ADRA2A mRNA expression was quantified in whole blood samples. The three SNPs were in near-perfect linkage disequilibrium. Accordingly, significant group*genotype interactions were found for all three ADRA2A variants revealing steeper DD in cocaine users (but not in controls) carrying the G-allele of SNP rs1800544, the T-allele of rs521674 and the C-allele of rs602618. Similarly, high ADRA2A mRNA expression levels were significantly associated with a reduced tendency to choose smaller more immediate rewards (over larger delayed rewards) in cocaine users but not in controls. As the relationship between DD and cocaine use was moderated by ADRA2A SNPs and by peripheral ADRA2A gene expression, we propose that the norepinephrine system is involved in DD deficits observed in cocaine using individuals. Consequently, pharmacological compounds targeting ADRA2As might be considered for the symptom-specific treatment of delay aversion in stimulant addiction.

Metabolic syndrome and eye diseases

Metabolic syndrome is becoming a worldwide medical and public health challenge as it has been seen increasing in prevalence over the years. Age-related eye diseases, the leading cause of blindness globally and visual impairment in developed countries, are also on the rise due to aging of the population. Many of the individual components of the metabolic syndrome have been shown to be associated with these eye diseases. However, the association of metabolic syndrome with eye diseases is not clear. In this review, we reviewed the evidence for associations between metabolic syndrome and certain ocular diseases in populations. We also reviewed the association of individual metabolic syndrome components with ocular diseases due to a paucity of research in this area. Besides, we also summarised the current understanding of etiological mechanisms of how metabolic syndrome or the individual components lead to these ocular diseases. With increasing evidence of such associations, it may be important to identify patients who are at risk of developing metabolic syndrome as prompt treatment and intervention may potentially decrease the risk of developing certain ocular diseases.

The central nervous norepinephrine network links a diminished sense of emotional well-being to an increased body weight

OBJECTIVES

The neurobiological mechanisms linking obesity to emotional distress remain largely undiscovered.

METHODS

In this pilot study, we combined positron emission tomography, using the norepinephrine transporter (NET) tracer [(11)C]-O-methylreboxetine, with functional connectivity magnetic resonance imaging, the Beck depression inventory (BDI), and the impact of weight on quality of life-Lite questionnaire (IWQOL-Lite), to investigate the role of norepinephrine in the severity of depression (BDI), as well as in the loss of emotional well-being with body weight (IWQOL-Lite).

RESULTS

In a small group of lean-to-morbidly obese individuals (n=20), we show that an increased body mass index (BMI) is related to a lowered NET availability within the hypothalamus, known as the brain's homeostatic control site. The hypothalamus displayed a strengthened connectivity in relation to the individual hypothalamic NET availability to the anterior insula/frontal operculum, as well as the medial orbitofrontal cortex, assumed to host the primary and secondary gustatory cortex, respectively (n=19). The resting-state activity in these two regions was correlated positively to the BMI and IWQOL-Lite scores, but not to the BDI, suggesting that the higher the resting-state activity in these regions, and hence the higher the BMI, the stronger the negative impact of the body weight on the individual's emotional well-being was.

CONCLUSIONS

This pilot study suggests that the loss in emotional well-being with weight is embedded within the central norepinephrine network.

Noradrenaline transmission reducing drugs may protect against a broad range of diseases

1 A growing body of evidence suggests that the signalling molecule, noradrenaline (NA), plays a pathophysiological role in a broad range of psychiatric, neurological and peripheral disorders. Both preclinical and clinical data suggest that elevated NA signalling may be involved in the aetiology of major diseases such as depression, Alzheimer's disease and diabetes mellitus. 2 The molecular pathways by which NA may cause the manifestation of disease remain poorly understood, although they may include G protein-coupled receptor modulation of the Ras/MAP kinase, Stat3 and PI3K pathways, among others. In both individual animals and humans, NA tone may be elevated largely due to genetics, but also because of the exposure to marked psychological stress or trauma, or other environmental factors. 3 As NA is involved in the 'fight or flight' response by the sympathetic nervous system, this transmitter may be elevated in a large number of organisms due to evolutionary selection of enhancing responses to immediate environmental dangers. Likewise, acetylcholine signalling by the parasympathetic ('rest and digest') nervous system may be relatively diminished. This putative autonomic imbalance may result in diminished engagement in homeostatic processes, resulting in the emergence and progression of a number of diseases throughout the body. 4 In this scenario, a large number of individuals may benefit from chronic use of pharmacological agents - such as clonidine, guanfacine, propranolol or prazosin - that diminish NA signalling throughout the body. If so, NA transmission lowering drugs may protect against a wide range of diseases.

Mild cold-stress depresses immune responses: Implications for cancer models involving laboratory mice

Physiologically accurate mouse models of cancer are critical in the pre-clinical development of novel cancer therapies. However, current standardized animal-housing temperatures elicit chronic cold-associated stress in mice, which is further increased in the presence of tumor. This cold-stress significantly impacts experimental outcomes. Data from our lab and others suggest standard housing fundamentally alters murine physiology, and this can produce altered immune baselines in tumor and other disease models. Researchers may thus underestimate the efficacy of therapies that are benefitted by immune responses. A potential mediator, norepinephrine, also underlies stress pathways common in mice and humans. Therefore, research into mechanisms connecting cold-stress and norepinephrine signaling with immune depression in mice could highlight new combination therapies for humans to simultaneously target stress while stimulating anti-tumor immunity.