Lifestyle Factors and Development and Natural Course of Gastroenteropancreatic Neuroendocrine Tumors: A Review of the Literature.

INTRODUCTION: The rarity of neuroendocrine tumors (NETs) and their heterogeneous presentation complicate the identification of risk factors for their development and natural course. Several tumor-specific prognostic factors have been identified, but less attention has been given to lifestyle factors as risk and prognostic factors. This review aimed to identify studies on smoking, alcohol use, physical activity, diet, body mass index (BMI), and diabetes and their association with the development and course of gastroenteropancreatic (GEP-) NETs. METHODS: The literature was systematically searched for articles on lifestyle factors and NETs available via PubMed and Embase. Study quality was assessed using the Newcastle-Ottawa scale. RESULTS: A total of 25 eligible studies out of 3,021 screened articles were included. Most studies reported on smoking and alcohol, reporting conflicting results. Diet seems to have an influence on NET development, but few studies were published. Articles reporting on BMI were not unanimous on the effect on GEP-NETs. Diabetes was reported as a risk factor for NETs, while a protective effect was observed with metformin use. CONCLUSION: Different tissues, i.e., the pancreas and small intestine, may respond differently to exposure to alcohol and smoking. Evidence for diet so far is too limited to draw conclusions. Diabetes seems to be an important risk factor for the development of pancreatic NETs with a protective role in disease progression, while BMI is not unequivocally associated with the development and prognosis of NETs. Hence, our findings suggest that lifestyle factors play an important role in NET development as a disease course. Future research should consider lifestyle as an influence on disease progression and treatment response.

Mineralocorticoid receptor status in the human brain after dexamethasone treatment: a single case study.

Background: Synthetic glucocorticoids like dexamethasone can cause severe neuropsychiatric effects. They preferentially bind to the glucocorticoid receptor (GR) over the mineralocorticoid receptor (MR). High dosages result in strong GR activation but likely also result in lower MR activation based on GR-mediated negative feedback on cortisol levels. Therefore, reduced MR activity may contribute to dexamethasone-induced neuropsychiatric symptoms. Objective: In this single case study, we evaluate whether dexamethasone leads to reduced MR activation in the human brain. Brain tissue of an 8-year-old brain tumor patient was used, who suffered chronically from dexamethasone-induced neuropsychiatric symptoms and deceased only hours after a high dose of dexamethasone. Main outcome measures: The efficacy of dexamethasone to induce MR activity was determined in HEK293T cells using a reporter construct. Subcellular localization of GR and MR was assessed in paraffin-embedded hippocampal tissue from the patient and two controls. In hippocampal tissue from the patient and eight controls, mRNA of MR/GR target genes was measured. Results: In vitro, dexamethasone stimulated MR with low efficacy and low potency. Immunofluorescence showed the presence of both GR and MR in the hippocampal cell nuclei after dexamethasone exposure. The putative MR target gene JDP2 was consistently expressed at relatively low levels in the dexamethasone-treated brain samples. Gene expression showed substantial variation in MR/GR target gene expression in two different hippocampus tissue blocks from the same patient. Conclusions: Dexamethasone may induce MR nuclear translocation in the human brain. Conclusions on in vivo effects on gene expression in the brain await the availability of more tissue of dexamethasone-treated patients.

How Metabolic State May Regulate Fear: Presence of Metabolic Receptors in the Fear Circuitry.

Metabolic status impacts on the emotional brain to induce behavior that maintains energy balance. While hunger suppresses the fear circuitry to promote explorative food-seeking behavior, satiety or obesity may increase fear to prevent unnecessary risk-taking. Here we aimed to unravel which metabolic factors, that transfer information about the acute and the chronic metabolic status, are of primary importance to regulate fear, and to identify their sites of action within fear-related brain regions. We performed a de novo analysis of central and peripheral metabolic factors that can penetrate the blood-brain barrier using genome-wide expression data across the mouse brain from the Allen Brain Atlas (ABA). The central fear circuitry, as defined by subnuclei of the amygdala, the afferent hippocampus, the medial prefrontal cortex and the efferent periaqueductal gray, was enriched with metabolic receptors. Some of their corresponding ligands were known to modulate fear (e.g., estrogen and thyroid hormones) while others had not been associated with fear before (e.g., glucagon, ACTH). Additionally, several of these enriched metabolic receptors were coexpressed with well-described fear-modulating genes (Crh, Crhr1, or Crhr2). Co-expression analysis of monoamine markers and metabolic receptors suggested that monoaminergic nuclei have differential sensitivity to metabolic alterations. Serotonergic neurons expressed a large number of metabolic receptors (e.g., estrogen receptors, fatty acid receptors), suggesting a wide responsivity to metabolic changes. The noradrenergic system seemed to be specifically sensitive to hypocretin/orexin modulation. Taken together, we identified a number of novel metabolic factors (glucagon, ACTH) that have the potential to modulate the fear response. We additionally propose novel cerebral targets for metabolic factors (e.g., thyroid hormones) that modulate fear, but of which the sites of action are (largely) unknown.