A new role for the brain in metabolic control

Visceral adipose tissue glucose uptake is linked to prognosis in multiple myeloma patients: An exploratory study

BACKGROUND & AIMS

The use of computerized tomography to opportunistically assess body composition has highlighted abnormalities such as low muscle mass and high adiposity may be hidden conditions in cancer patients. However, the role of skeletal muscle (SM), subcutaneous (SAT) and visceral (VAT) adipose tissue glucose uptake measured by ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET)-CT on patient prognostication is unclear.

METHODS

Patients with multiple myeloma (MM) with satisfactory image frame for assessing body composition and for semi-quantification of SM, SAT and VAT glucose uptakes were included. Plasmatic pro-inflammatory cytokine and adipokine levels were measured.

RESULTS

High VAT mean standardized uptake value (SUV) at baseline was associated with shorter event-free survival (EFS) (hazard ratio [HR]: 7.89; 95% confidence interval [CI], 1.58-39.30; P = 0.012) and overall survival (OS) (HR, 15.24; 95% CI, 2.69-86.30; P = 0.002) among patients with newly diagnosed MM, even after adjustment for covariates. The highest tertile of VAT SUV was significantly correlated with worse MM-EFS (HR for the highest vs the lowest tertile 3.71; 95% CI, 1.22-10.56; P_trend = 0.035) and mortality (HR, 4.41; 95% CI, 1.28-12.77; P_trend = 0.019). Notably, patients with higher VAT SUV presented with lower VAT area, VAT index, higher SAT SUV, and higher number of individuals with visceral obesity (all P < 0.01). Additionally, we found a negative correlation between VAT mean SUV with leptin (R² = 0.20, P = 0.003); no correlations were detected between VAT mean SUV and resistin, tumor necrosis factor (TNF) or interleukin (IL)-6.

CONCLUSIONS

Functional VAT activity estimated by ¹⁸F-FDG PET-CT is a relevant prognostic factor in MM patients, specifically, a higher VAT SUV might be an early biomarker of cancer cachexia in these patients.

Spinal cord injury causes insulin resistance associated with PI3K signaling pathway in hypothalamus

Spinal cord injury (SCI) is an independent risk factor for type 2 diabetes, and may induce insulin resistance that leads to this disease. Studies have shown that greater phosphoinositide 3-kinase (PI3K) activation in the hypothalamus leads to activation of the anti-inflammatory pathway, and the anti-inflammatory reflex may protect against insulin resistance and type 2 diabetes. However, the importance of this phenomenon in type 2 diabetes pathogenesis after SCI remains elusive. In the present study, the expression of c-Fos in the hypothalamus of rats with SCI was elevated, and the hypothalamus injury was observer following SCI. Then we showed that SCI could induce increased levels of blood glucose and glucose tolerance in rats. Also, we found that SCI could damage the liver, adipocyte and pancreas, and led to lipid position in liver. Western blots were used to detect the level of PI3K and p-Akt in the hypothalamus, and the results showed a significant downregulation of PI3K and p-Akt after SCI. Furthermore, to verify the activity of the PI3K signaling pathway, immunofluorescence was used to examine the expression of neurons positive for p-S6 (a marker of PI3K activation) after SCI. The results showed that the expression of p-S6-positive neurons decreased after SCI. In addition, the effect of SCI on peripheral inflammation was also investigated. Following SCI, the serum levels of tumor necrosis factor-α, interleukin (IL)-1β, and IL-6 increased. Collectively, our results suggest abnormality in glucose metabolism after SCI, and demonstrate that SCI may impair activation of the PI3K signaling pathway in the hypothalamus. The reduced activity of the PI3K signaling pathway in the hypothalamus may lead to peripheral inflammation, which might be the mechanism underlying the development of insulin resistance and type 2 diabetes following SCI.

Gastrointestinal hormones and the gut connectome

PURPOSE OF REVIEW

Provision of adequate nutrients by the gut is essential for survival and essential behaviors are linked to the proper ingestion and digestion of food. Recently, a new neural connection has been reported between sensory cells of the gut epithelium and the nervous system that mediates signals from the gut to the brain.

RECENT FINDINGS

This review describes how the gut senses its environment, relays those signals to the brain, and how the brain influences the gut.

SUMMARY

This gut-brain connection provides a pathway for how the body handles food.

Neural regulation of immunity: molecular mechanisms and clinical translation

Studies bridging neuroscience and immunology have identified neural pathways that regulate immunity and inflammation. Recent research using methodological advances in molecular genetics has improved our understanding of the neural control of immunity. Here we outline mechanistic insights, focusing on translational relevance and conceptual developments. We also summarize findings from recent clinical studies of bioelectronic neuromodulation in inflammatory and autoimmune diseases.

Neuroendocrinological and Epigenetic Mechanisms Subserving Autonomic Imbalance and HPA Dysfunction in the Metabolic Syndrome

Impact of environmental stress upon pathophysiology of the metabolic syndrome (MetS) has been substantiated by epidemiological, psychophysiological, and endocrinological studies. This review discusses recent advances in the understanding of causative roles of nutritional factors, sympathomedullo-adrenal (SMA) and hypothalamic-pituitary adrenocortical (HPA) axes, and adipose tissue chronic low-grade inflammation processes in MetS. Disturbances in the neuroendocrine systems for leptin, melanocortin, and neuropeptide Y (NPY)/agouti-related protein systems have been found resulting directly in MetS-like conditions. The review identifies candidate risk genes from factors shown critical for the functioning of each of these neuroendocrine signaling cascades. In its meta-analytic part, recent studies in epigenetic modification (histone methylation, acetylation, phosphorylation, ubiquitination) and posttranscriptional gene regulation by microRNAs are evaluated. Several studies suggest modification mechanisms of early life stress (ELS) and diet-induced obesity (DIO) programming in the hypothalamic regions with populations of POMC-expressing neurons. Epigenetic modifications were found in cortisol (here HSD11B1 expression), melanocortin, leptin, NPY, and adiponectin genes. With respect to adiposity genes, epigenetic modifications were documented for fat mass gene cluster APOA1/C3/A4/A5, and the lipolysis gene LIPE. With regard to inflammatory, immune and subcellular metabolism, PPARG, NKBF1, TNFA, TCF7C2, and those genes expressing cytochrome P450 family enzymes involved in steroidogenesis and in hepatic lipoproteins were documented for epigenetic modifications.

Radiologic evidence that hypothalamic gliosis is associated with obesity and insulin resistance in humans

OBJECTIVE

To use quantitative magnetic resonance imaging (MRI) to test whether mediobasal hypothalamic (MBH) gliosis is associated with obesity and insulin resistance in humans.

METHODS

Sixty-seven participants underwent a fasting blood draw and MRI. Cases with radiologic evidence of MBH gliosis (N = 22) were identified as the upper tertile of left MBH T2 relaxation time and were compared to controls (N = 23) from the lowest tertile. In a separate postmortem study, brain slices (N = 10) through the MBH were imaged by MRI and stained for glial fibrillary acidic protein (GFAP).

RESULTS

In all participants, longer T2 relaxation time in the left MBH was associated with higher BMI (P = 0.01). Compared with controls, cases had longer T2 relaxation times in the right MBH (P < 0.05), as well as higher BMI (P < 0.05), fasting insulin concentrations (P < 0.01), and HOMA-IR values (P < 0.01), adjusted for sex and age. Elevations in insulin and HOMA-IR were also independent of BMI. In the postmortem study, GFAP staining intensity was positively associated with MBH T2 relaxation time (P < 0.05), validating an MRI-based method for the detection of MBH gliosis in humans.

CONCLUSIONS

These findings link hypothalamic gliosis to insulin resistance in humans and suggest that the link is independent of the level of adiposity.