Liver X receptors (LXRs) are transcription factors essential for cholesterol homeostasis and lipogenesis. LXRα has been implicated in regulating hepatic triglyceride (TG) accumulation upon both influx of adipose-derived fatty acids (FAs) during fasting and stimulation of de novo FA synthesis by chemical agonism of LXR. However, whether or not a convergent mechanism is employed to drive deposition of FAs from these 2 different sources in TGs is undetermined. Here, we report that the G0/G1 Switch Gene 2 (G0S2), a selective inhibitor of intracellular TG hydrolysis/lipolysis, is a direct target gene of LXRα. Transcriptional activation is conferred by LXRα binding to a direct repeat 4 (DR4) motif in the G0S2 promoter. While LXRα–/– mice exhibited decreased hepatic G0S2 expression, adenoviral expression of G0S2 was sufficient to restore fasting-induced TG storage and glycogen depletion in the liver of these mice. In response to LXR agonist T0901317, G0S2 ablation prevented hepatic steatosis and hypertriglyceridemia without affecting the beneficial effects on HDL. Thus, the LXRα-G0S2 axis plays a distinct role in regulating hepatic TG during both fasting and pharmacological activation of LXR.
Bradlee L. Heckmann, Xiaodong Zhang, Alicia M. Saarinen, Gabriele Schoiswohl, Erin E. Kershaw, Rudolf Zechner, Jun Liu
Visceral fat is considered the genuine and harmful white adipose tissue (WAT) that is associated to development of metabolic disorders, cardiovascular disease, and cancer. Here, we present a new concept to turn the harmful visceral fat into a beneficial energy consumption depot, which is beneficial for improvement of metabolic dysfunctions in obese mice. We show that low temperature–dependent browning of visceral fat caused decreased adipose weight, total body weight, and body mass index, despite increased food intake. In high-fat diet–fed mice, low temperature exposure improved browning of visceral fat, global metabolism via nonshivering thermogenesis, insulin sensitivity, and hepatic steatosis. Genome-wide expression profiling showed upregulation of WAT browning–related genes including
Xiaoyan Yang, Wenhai Sui, Meng Zhang, Mei Dong, Sharon Lim, Takahiro Seki, Ziheng Guo, Carina Fischer, Huixia Lu, Cheng Zhang, Jianmin Yang, Meng Zhang, Yangang Wang, Caixia Cao, Yanyan Gao, Xingguo Zhao, Meili Sun, Yuping Sun, Rujie Zhuang, Nilesh J. Samani, Yun Zhang, Yihai Cao
Fructose has been implicated in the pathogenesis of obesity and type 2 diabetes. In contrast to glucose, CNS delivery of fructose in rodents promotes feeding behavior. However, because circulating plasma fructose levels are exceedingly low, it remains unclear to what extent fructose crosses the blood-brain barrier to exert CNS effects. To determine whether fructose can be endogenously generated from glucose via the polyol pathway (glucose → sorbitol → fructose) in human brain, 8 healthy subjects (4 women/4 men; age, 28.8 ± 6.2 years; BMI, 23.4 ± 2.6; HbA1C, 4.9% ± 0.2%) underwent 1H magnetic resonance spectroscopy scanning to measure intracerebral glucose and fructose levels during a 4-hour hyperglycemic clamp (plasma glucose, 220 mg/dl). Using mixed-effects regression model analysis, intracerebral glucose rose significantly over time and differed from baseline at 20 to 230 minutes. Intracerebral fructose levels also rose over time, differing from baseline at 30 to 230 minutes. The changes in intracerebral fructose were related to changes in intracerebral glucose but not to plasma fructose levels. Our findings suggest that the polyol pathway contributes to endogenous CNS production of fructose and that the effects of fructose in the CNS may extend beyond its direct dietary consumption.
Janice J. Hwang, Lihong Jiang, Muhammad Hamza, Feng Dai, Renata Belfort-DeAguiar, Gary Cline, Douglas L. Rothman, Graeme Mason, Robert S. Sherwin
Tregs can adopt a catabolic metabolic program with increased capacity for fatty acid oxidation–fueled oxidative phosphorylation (OXPHOS). It is unclear why this form of metabolism is favored in Tregs and, more specifically, whether this program represents an adaptation to the environment and developmental cues or is “hardwired” by Foxp3. Here we show, using metabolic analysis and an unbiased mass spectroscopy–based proteomics approach, that Foxp3 is both necessary and sufficient to program Treg-increased respiratory capacity and Tregs’ increased ability to utilize fatty acids to fuel oxidative phosphorylation. Foxp3 drives upregulation of components of all the electron transport complexes, increasing their activity and ATP generation by oxidative phosphorylation. Increased fatty acid β-oxidation also results in selective protection of Foxp3+ cells from fatty acid–induced cell death. This observation may provide novel targets for modulating Treg function or selection therapeutically.
Duncan Howie, Stephen Paul Cobbold, Elizabeth Adams, Annemieke Ten Bokum, Andra Stefania Necula, Wei Zhang, Honglei Huang, David J. Roberts, Benjamin Thomas, Svenja S. Hester, David J. Vaux, Alexander G. Betz, Herman Waldmann
Heterozygous germline gain-of-function mutations of G-protein subunit α11 (Gα11), a signaling partner for the calcium-sensing receptor (CaSR), result in autosomal dominant hypocalcemia type 2 (ADH2). ADH2 may cause symptomatic hypocalcemia with low circulating parathyroid hormone (PTH) concentrations. Effective therapies for ADH2 are currently not available, and a mouse model for ADH2 would help in assessment of potential therapies. We hypothesized that a previously reported dark skin mouse mutant (
Caroline M. Gorvin, Fadil M. Hannan, Sarah A. Howles, Valerie N. Babinsky, Sian E. Piret, Angela Rogers, Andrew J. Freidin, Michelle Stewart, Anju Paudyal, Tertius A. Hough, M. Andrew Nesbit, Sara Wells, Tonia L. Vincent, Stephen D.M. Brown, Roger D. Cox, Rajesh V. Thakker
The heme oxygenase-1 (
Hagir B. Suliman, Jeffrey E. Keenan, Claude A. Piantadosi
Canavan disease (CD) is a debilitating and lethal leukodystrophy caused by mutations in the aspartoacylase (
Dominic J. Gessler, Danning Li, Hongxia Xu, Qin Su, Julio Sanmiguel, Serafettin Tuncer, Constance Moore, Jean King, Reuben Matalon, Guangping Gao
For nearly 100 years, growth hormone (GH) has been known to affect insulin sensitivity and risk of diabetes. However, the tissue governing the effects of GH signaling on insulin and glucose homeostasis remains unknown. Excess GH reduces fat mass and insulin sensitivity. Conversely, GH insensitivity (GHI) is associated with increased adiposity, augmented insulin sensitivity, and protection from diabetes. Here, we induce adipocyte-specific GHI through conditional deletion of
Kevin C. Corbit, João Paulo G. Camporez, Jennifer L. Tran, Camella G. Wilson, Dylan A. Lowe, Sarah M. Nordstrom, Kirthana Ganeshan, Rachel J. Perry, Gerald I. Shulman, Michael J. Jurczak, Ethan J. Weiss
A role for oxidative stress in the brain has been suggested in the pathogenesis of diet-induced obesity (DIO), although the underlying neural regions and mechanisms remain incompletely defined. We tested the hypothesis that NADPH oxidase–dependent oxidative stress in the paraventricular nucleus (PVN), a hypothalamic energy homeostasis center, contributes to the development of DIO. Cre/LoxP technology was coupled with selective PVN adenoviral microinjection to ablate
Heinrich E. Lob, Jiunn Song, Chansol Hurr, Alvin Chung, Colin N. Young, Allyn L. Mark, Robin L. Davisson
Clinical trials revealed limited response duration of glioblastomas to VEGF-neutralizing antibody bevacizumab. Thriving in the devascularized microenvironment occurring after antiangiogenic therapy requires tumor cell adaptation to decreased glucose, with 50% less glucose identified in bevacizumab-treated xenografts. Compared with bevacizumab-responsive xenograft cells, resistant cells exhibited increased glucose uptake, glycolysis, 13C NMR pyruvate to lactate conversion, and survival in low glucose. Glucose transporter 3 (GLUT3) was upregulated in bevacizumab-resistant versus sensitive xenografts and patient specimens in a HIF-1α–dependent manner. Resistant versus sensitive cell mitochondria in oxidative phosphorylation–selective conditions produced less ATP. Despite unchanged mitochondrial numbers, normoxic resistant cells had lower mitochondrial membrane potential than sensitive cells, confirming poorer mitochondrial health, but avoided the mitochondrial dysfunction of hypoxic sensitive cells. Thin-layer chromatography revealed increased triglycerides in bevacizumab-resistant versus sensitive xenografts, a change driven by mitochondrial stress. A glycogen synthase kinase-3β inhibitor suppressing GLUT3 transcription caused greater cell death in bevacizumab-resistant than -responsive cells. Overexpressing GLUT3 in tumor cells recapitulated bevacizumab-resistant cell features: survival and proliferation in low glucose, increased glycolysis, impaired oxidative phosphorylation, and rapid in vivo proliferation only slowed by bevacizumab to that of untreated bevacizumab-responsive tumors. Targeting GLUT3 or the increased glycolysis reliance in resistant tumors could unlock the potential of antiangiogenic treatments.
Ruby Kuang, Arman Jahangiri, Smita Mascharak, Alan Nguyen, Ankush Chandra, Patrick M. Flanigan, Garima Yagnik, Jeffrey R. Wagner, Michael De Lay, Diego Carrera, Brandyn A. Castro, Josie Hayes, Maxim Sidorov, Jose Luiz Izquierdo Garcia, Pia Eriksson, Sabrina Ronen, Joanna Phillips, Annette Molinaro, Suneil Koliwad, Manish K. Aghi
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