Dynamic contrast-enhanced MRI of brown and beige adipose tissues.

PURPOSE: The vascular blood flow in brown adipose tissue (BAT) is important for handling triglyceride clearance, increased blood flow and oxygenation. We used dynamic contrast-enhanced (DCE)-MRI and fat fraction (FF) imaging for investigating vascular perfusion kinetics in brown and beige adipose tissues with cold exposure or treatment with ß3-adrenergic agonist. METHODS: FF imaging and DCE-MRI using gadolinium-diethylenetriaminepentaacetic acid were performed in interscapular BAT (iBAT) and beige tissues using male Wister rats (n = 38). Imaging was performed at thermoneutral condition and with either cold exposure, treatment with pharmacological agent CL-316,243, or saline. DCE-MRI and FF data were co-registered to enhance the understanding of metabolic activity. RESULTS: Uptake of contrast agent in activated iBAT and beige tissues were significantly (P < .05) higher than nonactivated iBAT. The Ktrans and kep increased significantly in iBAT and beige tissues after treatment with either cold exposure or ß3-adrenergic agonist. The FF decreased in activated iBAT and beige tissues. The Ktrans and FF from iBAT and beige tissues were inversely correlated (r = 0.97; r = 0.94). Significant increase in vascular endothelial growth factor expression and Ktrans in activated iBAT and beige tissues were in agreement with the increased vasculature and vascular perfusion kinetics. The iBAT and beige tissues were validated by measuring molecular markers. CONCLUSION: Increased Ktrans and decreased FF in iBAT and beige tissues were in agreement with the vascular perfusion kinetics facilitating the clearance of free fatty acids. The methodology can be extended for the screening of browning agents.

A 12-week aerobic exercise intervention results in improved metabolic function and lower adipose tissue and ectopic fat in high-fat diet fed rats.

Investigations of long-term exercise interventions in humans to reverse obesity is expensive and is hampered by poor compliance and confounders. In the present study, we investigated intrahepatic and muscle fat, visceral and subcutaneous fat pads, plasma metabolic profile and skeletal muscle inflammatory markers in response to 12-week aerobic exercise in an obese rodent model. Six-week-old male Wistar rats (n=20) were randomized to chow-fed control (Control, n=5), sedentary high-fat diet (HFD, n=5), chow-fed exercise (Exercise, n=5) and HFD-fed exercise (HFD+Exercise, n=5) groups. The exercise groups were subjected to 12 weeks of motorized treadmill running at a speed of 18 m/min for 30 min/day. Differences in post-intervention measures were assessed by analysis of covariance (ANCOVA), adjusted for baseline bodyweight and pre-intervention measures, where available. Post-hoc analyses were performed with Bonferroni correction. Plasma metabolic profile was worsened and fat pads, ectopic fat in muscle and liver and inflammatory markers in skeletal muscle were elevated in sedentary HFD-fed animals relative to chow-fed controls. HFD+Exercise animals had significantly lower leptin (P=0.0004), triglycerides (P=0.007), homeostatic model assessment of insulin resistance (HOMA-IR; P=0.065), intramyocellular lipids (IMCLs; P=0.003), intrahepatic lipids (IHLs; P<0.0001), body fat% (P=0.001), subcutaneous adipose tissue (SAT; P<0.0001), visceral adipose (P<0.0001) and total fat mass (P<0.0001), relative to sedentary HFD-fed animals, despite only modestly lower bodyweight. Messenger RNA (mRNA) expression of inflammatory markers Interleukin 6 (IL6) and Tumor necrosis factor α (TNFα) were also reduced with aerobic exercise in skeletal muscle. Our results suggest that 12 weeks of aerobic exercise training is effective in improving metabolic health, fat depots, ectopic fat and inflammation even against a high-fat dietary background.

Inhibiting Glycine Decarboxylase Suppresses Pyruvate-to-Lactate Metabolism in Lung Cancer Cells.

Glycine decarboxylase (GLDC) gene is frequently upregulated in various types of cancer including lung, prostate and brain. It catabolizes glycine to yield 5,10-methylenetetrahydrofolate, an important substrate in one-carbon metabolism for nucleotide synthesis. In this study, we used exon splicing modulating steric hindrance antisense oligonucleotide (shAON) to suppress GLDC expression and investigated its effect on pyruvate metabolism via hyperpolarized carbon-13 magnetic resonance spectroscopy (MRS). The MRS technique allows us to study in vivo metabolic flux in tumor tissues with/without GLDC-shAON intervention. Here, we show that GLDC-shAON treatment is able to suppress lung cancer cell growth and tumorigenesis, both in vitro and in vivo. The carbon-13 MRS results indicated that the conversion of pyruvate into lactate in GLDC-shAON-treated tumor tissues was significantly reduced, when compared with the control groups. This observation corroborated with the reduced activity of lactate dehydrogenase and pyruvate dehydrogenase in GLDC-shAON-treated lung cancer cells and tumor tissues. Glycolysis stress test showed that extracellular acidification rate was significantly suppressed after GLDC-shAON treatment. Besides lung cancer, the antitumor effect of GLDC-shAON was also observed in brain, liver, cervical, and prostate cancer cell lines. Furthermore, it enhanced the treatment efficacy of cisplatin in lung cancer cells. Taken together, our findings illustrate that pyruvate metabolism decreases upon GLDC inhibition, thereby starving cancer cells from critical metabolic fuels.

TDP-43-mediated neuron loss in vivo requires RNA-binding activity.

Alteration and/or mutations of the ribonucleoprotein TDP-43 have been firmly linked to human neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). The relative impacts of TDP-43 alteration, mutation, or inherent protein function on neural integrity, however, remain less clear--a situation confounded by conflicting reports based on transient and/or random-insertion transgenic expression. We therefore performed a stringent comparative investigation of impacts of these TDP-43 modifications on neural integrity in vivo. To achieve this, we systematically screened ALS/FTLD-associated and synthetic TDP-43 isoforms via same-site gene insertion and neural expression in Drosophila; followed by transposon-based motor neuron-specific transgenesis in a chick vertebrate system. Using this bi-systemic approach we uncovered a requirement of inherent TDP-43 RNA-binding function--but not ALS/FTLD-linked mutation, mislocalization, or truncation--for TDP-43-mediated neurotoxicity in vivo.

Genetic profile of patients with epilepsy on first-line antiepileptic drugs and potential directions for personalized treatment.

BACKGROUND: The first-line antiepileptic drugs, although affordable and effective in the control of seizures, are associated with adverse drug effects, and there is large interindividual variability in the appropriate dose at which patients respond favorably. This variability may partly be explained by functional consequences of genetic polymorphisms in the drug-metabolizing enzymes, such as the CYP450 family, microsomal epoxide hydrolase and UDP-glucuronosyltransferases, drug transporters, mainly ATP-binding cassette transporters, and drug targets, including sodium channels. The purpose of this study was to determine the allele and genotype frequencies of such genetic variants in patients with epilepsy from North India administered first-line antiepileptic drugs, such as phenobarbitone, phenytoin, carbamazepine and valproic acid, and compare them with worldwide epilepsy populations. MATERIALS & METHODS: SNP screening of 19 functional variants from 12 genes in 392 patients with epilepsy was carried out, and the patients were classified with respect to the metabolizing rate of their drug-metabolizing enzymes, efflux rate of drug transporters and sensitivity of drug targets. RESULTS: A total of 16 SNPs were found to be polymorphic, and the allelic frequencies for these SNPs were in conformance with Hardy-Weinberg equilibrium. Among all the polymorphisms studied, functional variants from genes encoding CYP2C19, EPHX1, ABCB1 and SCN1A were highly polymorphic in North Indian epilepsy patients, and might account for differential drug response to first-line antiepileptic drugs. CONCLUSION: Interethnic differences were elucidated for several polymorphisms that might be responsible for differential serum drug levels and optimal dose requirement for efficacious treatment.