Publications

Neuronal microtubules impact lifespan.
Apple E, Chen L
Aging (Albany NY). 2019 Sep 6;11(17):6616-6617. doi: 10.18632/aging.102224. Epub 2019 Sep 6.


A Non-canonical Role of YAP/TEAD Is Required for Activation of Estrogen-Regulated Enhancers in Breast Cancer.
Zhu C, Li L, Zhang Z1 Bi M, Wang H, Su W, Hernandez K, Liu P, Chen J, Chen M, Huang TH, Chen L*, Liu Z*
Molecular Cell. 2019 Aug 22;75(4):791-806.e8. doi: 10.1016/j.molcel.2019.06.010. Epub 2019 Jul 11. *co-corresponding authors

Abstract:

YAP/TEAD are nuclear effectors of the Hippo pathway, regulating organ size and tumorigenesis largely through promoter-associated function. However, their function as enhancer regulators remains poorly understood. Through an in vivo proximity-dependent labeling (BioID) technique, we identified YAP1 and TEAD4 protein as co-regulators of ERα on enhancers. The binding of YAP1/TEAD4 to ERα-bound enhancers is augmented upon E2 stimulation and is required for the induction of E2/ERα target genes and E2-induced oncogenic cell growth. Furthermore, their enhancer binding is a prerequisite for enhancer activation marked by eRNA transcription and for the recruitment of the enhancer activation machinery component MED1. The binding of TEAD4 on active ERE-containing enhancers is independent of its DNA-binding behavior, and instead, occurs through protein-tethering trans-binding. Our data reveal a non-canonical function of YAP1 and TEAD4 as ERα cofactors in regulating cancer growth, highlighting the potential of YAP/TEAD as possible actionable drug targets for ERα+ breast cancer.


Cell-autonomous and non-autonomous roles of daf-16 in muscle function and mitochondrial capacity in aging C. elegans.
Wang H#, Webster P#, Chen L, Fisher AL
Aging (Albany NY). 2019 Apr 24;11(8):2295-2311. doi: 10.18632/aging.101914.

Abstract:

Sarcopenia, defined as the loss of skeletal muscle mass and strength, contributes to disability and health-related conditions with aging. In vitro studies indicate that age-related mitochondrial dysfunction could play a central role in the development and progression of sarcopenia, but because of limitations in the methods employed, how aging affects muscle mitochondrial function in vivo is not fully understood. We use muscle-targeted fluorescent proteins and the ratiometric ATP reporter, ATeam, to examine changes in muscle mitochondrial mass and morphology, and intracellular ATP levels in C. elegans. We find that the preserved muscle function in aging daf-2 mutants is associated with higher muscle mitochondrial mass, preserved mitochondrial morphology, and higher levels of intracellular ATP. These phenotypes require the daf-16/FOXO transcription factor. Via the tissue-specific rescue of daf-16, we find that daf-16 activity in either muscle or neurons is sufficient to enhance muscle mitochondrial mass, whereas daf-16 activity in the muscle is required for the enhanced muscle function and mobility of the daf-2 mutants. Finally, we show through the use of drugs known to enhance mitochondrial activity that augmenting mitochondrial function leads to improved mobility during aging. These results suggest an important role for mitochondrial function in muscle aging.


Hyperadrenocorticism of calorie restriction contributes to its anti-inflammatory action in mice.
Allen BD, Liao CY, Shu J, Muglia LJ, Majzoub JA, Diaz V, Nelson JF
Aging Cell. 2019 Jun;18(3):e12944. doi: 10.1111/acel.12944. Epub 2019 Apr 1.

Abstract:

Calorie restriction (CR), which lengthens lifespan in many species, is associated with moderate hyperadrenocorticism and attenuated inflammation. Given the anti-inflammatory action of glucocorticoids, we tested the hypothesis that the hyperadrenocorticism of CR contributes to its attenuated inflammatory response. We used a corticotropin-releasing-hormone knockout (CRHKO) mouse, which is glucocorticoid insufficient. There were four controls groups: CRHKO mice and wild-type (WT) littermates fed either ad libitum (AL) or CR (60% of AL food intake), and three experimental groups: (a) AL-fed CRHKO mice given corticosterone (CORT) in their drinking water titrated to match the integrated 24-hr plasma CORT levels of AL-fed WT mice, (b) CR-fed CRHKO mice given CORT to match the 24-hr CORT levels of AL-fed WT mice, and (c) CR-fed CHRKO mice given CORT to match the 24-hr CORT levels of CR-fed WT mice. Inflammation was measured volumetrically as footpad edema induced by carrageenan injection. As previously observed, CR attenuated footpad edema in WT mice. This attenuation was significantly blocked in CORT-deficient CR-fed CRHKO mice. Replacement of CORT in CR-fed CRHKO mice to the elevated levels observed in CR-fed WT mice, but not to the levels observed in AL-fed WT mice, restored the anti-inflammatory effect of CR. These results indicate that the hyperadrenocorticism of CR contributes to the anti-inflammatory action of CR, which may in turn contribute to its life-extending actions.


Hepatic posttranscriptional network comprised of CCR4-NOT deadenylase and FGF21 maintains systemic metabolic homeostasis
Morita M, Siddiqui N, Katsumura S, Rouya C, Larsson O, Nagashima T, Hekmatnejad B, Takahashi A, Kiyonari H, Zang M, St-Arnaud R, Oike Y, Giguère V, Topisirovic I, Okada-Hatakeyama M, Yamamoto T, Sonenberg N
PNAS. 2019 Apr 16;116(16):7973-7981. doi: 10.1073/pnas.1816023116. Epub 2019 Mar 29.

Abstract

Whole-body metabolic homeostasis is tightly controlled by hormone-like factors with systemic or paracrine effects that are derived from nonendocrine organs, including adipose tissue (adipokines) and liver (hepatokines). Fibroblast growth factor 21 (FGF21) is a hormone-like protein, which is emerging as a major regulator of whole-body metabolism and has therapeutic potential for treating metabolic syndrome. However, the mechanisms that control FGF21 levels are not fully understood. Herein, we demonstrate that FGF21 production in the liver is regulated via a posttranscriptional network consisting of the CCR4-NOT deadenylase complex and RNA-binding protein tristetraprolin (TTP). In response to nutrient uptake, CCR4-NOT cooperates with TTP to degrade AU-rich mRNAs that encode pivotal metabolic regulators, including FGF21. Disruption of CCR4-NOT activity in the liver, by deletion of the catalytic subunit CNOT6L, increases serum FGF21 levels, which ameliorates diet-induced metabolic disorders and enhances energy expenditure without disrupting bone homeostasis. Taken together, our study describes a hepatic CCR4-NOT/FGF21 axis as a hitherto unrecognized systemic regulator of metabolism and suggests that hepatic CCR4-NOT may serve as a target for devising therapeutic strategies in metabolic syndrome and related morbidities.


Age-related changes in the marmoset gut microbiome
Reveles KR, Patel S, Forney L, Ross CN
American Journal of Primatology. 2019 Feb;81(2):e22960. doi: 10.1002/ajp.22960. Epub 2019 Feb 25.

Abstract

The gut microbiome is known to play a significant role in human health but its role in aging remains unclear. The objective of this study was to compare the gut microbiome composition between young adult and geriatric non-human primates (marmosets) as a model of human health and disease. Stool samples were collected from geriatric (8+ years) and young adult males (2-5 years). Stool 16S ribosomal RNA V4 sequences were amplified and sequenced on the Illumina MiSeq platform. Sequences were clustered into operational taxonomic units and classified via Mothur’s Bayesian classifier referenced against the Greengenes database. A total of 10 young adult and 10 geriatric marmosets were included. Geriatric marmosets had a lower mean Shannon diversity compared with young marmosets (3.15 vs. 3.46; p = 0.0191). Geriatric marmosets had a significantly higher mean abundance of Proteobacteria (0.22 vs. 0.09; p = 0.0233) and lower abundance of Firmicutes (0.15 vs. 0.19; p = 0.0032) compared with young marmosets. Geriatric marmosets had a significantly higher abundance of Succinivibrionaceae (0.16 vs. 0.01; p = 0.0191) and lower abundance of Porphyromonadaceae (0.07 vs. 0.11; p = 0.0494). In summary, geriatric marmosets had significantly altered microbiome diversity and composition compared with young adult marmosets. Further studies are needed to test microbiome-targeted therapies to improve healthspan and lifespan.


Rapamycin and Alzheimer’s disease: Time for a clinical trial?
Kaeberlein M, Galvan V
Science Translational Medicine. 2019 Jan 23;11(476). pii: eaar4289. doi: 10.1126/scitranslmed.aar4289.
PMID: 30674654

Abstract:

The drug rapamycin has beneficial effects in a number of animal models of neurodegeneration and aging including mouse models of Alzheimer’s disease. Despite its compelling preclinical record, no clinical trials have tested rapamycin or other mTOR inhibitors in patients with Alzheimer’s disease. We argue that such clinical trials should be undertaken.


Microtubule regulators act in the nervous system to modulate fat metabolism and longevity through DAF‐16 in C. elegans.
Aiping Xu, Zhao Zhang, Su‐Hyuk Ko, Alfred L. Fisher, Zhijie Liu, Lizhen Chen
Aging Cell. 14 January 2019. doi: 10.1111/acel.12884. [Epub ahead of print].

Abstract:

Microtubule (MT) regulation is involved in both neuronal function and the maintenance of neuronal structure, and MT dysregulation appears to be a general downstream indicator and effector of age‐related neurodegeneration. But the role of MTs in natural aging is largely unknown. Here, we demonstrate a role of MT regulators in regulating longevity. We find that loss of EFA‐6, a modulator of MT dynamics, can delay both neuronal aging and extend the lifespan of C. elegans. Through the use of genetic mutants affecting other MT‐regulating genes in C. elegans, we find that loss of MT stabilizing genes (including ptrn‐1 and ptl‐1) shortens lifespan, while loss of MT destabilizing gene hdac‐6 extends lifespan. Via the use of tissue‐specific transgenes, we further show that these MT regulators can act in the nervous system to modulate lifespan. Through RNA‐seq analyses, we found that genes involved in lipid metabolism were differentially expressed in MT regulator mutants, and via the use of Nile Red and Oil Red O staining, we show that the MT regulator mutants have altered fat storage. We further find that the increased fat storage and extended lifespan of the long‐lived MT regulator mutants are dependent on the DAF‐16/FOXO transcription factor. Our results suggest that neuronal MT status might affect organismal aging through DAF‐16‐regulated changes in fat metabolism, and therefore, MT‐based therapies might represent a novel intervention to promote healthy aging.


Effects of intravenous AICAR (5-aminoimidazole-4-carboximide riboside) administration on insulin signaling and resistance in premature baboons, Papio sp.
Blanco CL, Gastaldelli A, Anzueto DG, Winter LA, Seidner SR, McCurnin DC, Liang H, Javors MA, DeFronzo RA, Musi N
PLoS one. 2018 Dec 12;13(12):e0208757. doi: 10.1371/journal.pone.0208757. eCollection 2018.

Abstract:

Premature baboons exhibit peripheral insulin resistance and impaired insulin signaling. 5′ AMP-activated protein kinase (AMPK) activation improves insulin sensitivity by enhancing glucose uptake (via increased glucose transporter type 4 [GLUT4] translocation and activation of the extracellular signal-regulated kinase [ERK]/ atypical protein kinase C [aPKC] pathway), and increasing fatty acid oxidation (via inhibition of acetyl-CoA carboxylase 1 [ACC]), while downregulating gluconeogenesis (via induction of small heterodimer partner [SHP] and subsequent downregulation of the gluconeogenic enzymes: phosphoenolpyruvate carboxykinase [PEPCK], glucose 6-phosphatase [G6PASE], fructose- 1,6-bisphosphatase 1 [FBP1], and forkhead box protein 1 [FOXO1]). The purpose of this study was to investigate whether pharmacologic activation of AMPK with AICAR (5-aminoimidazole-4-carboximide riboside) administration improves peripheral insulin sensitivity in preterm baboons. 11 baboons were delivered prematurely at 125±2 days (67%) gestation. 5 animals were randomized to receive 5 days of continuous AICAR infusion at a dose of 0.5 mg·g-1·day-1. 6 animals were in the placebo group. Euglycemic hyperinsulinemic clamps were performed at 5±2 and 14±2 days of life. Key molecules potentially altered by AICAR (AMPK, GLUT4, ACC, PEPCK, G6PASE, FBP1, and FOXO1), and the insulin signaling molecules: insulin receptor (INSR), insulin receptor substrate 1 (IRS-1), protein kinase B (AKT), and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) were measured using RT-PCR and western blotting. AICAR infusion did not improve whole body insulin-stimulated glucose disposal in preterm baboons (12.8±2.4 vs 12.4±2.0 mg/(kg·min), p = 0.8, placebo vs AICAR). One animal developed complications during treatment. In skeletal muscle, AICAR infusion did not increase phosphorylation of ACC, AKT, or AMPK whereas it increased mRNA expression of ACACA (ACC), AKT, and PPARGC1A (PGC1α). In the liver, INSR, IRS1, G6PC3, AKT, PCK1, FOXO1, and FBP1 were unchanged, whereas PPARGC1A mRNA expression increased after AICAR infusion. This study provides evidence that AICAR does not improve insulin sensitivity in premature euglycemic baboons, and may have adverse effects.


Lipidomics reveals a systemic energy deficient state that precedes neurotoxicity in neonatal monkeys after sevoflurane exposure.
Wang C, Liu F, Frisch-Daiello JL, Martin S, Patterson TA, Gu Q, Liu S, Paule MG, Hanig JP, Slikker W Jr, Crawford PA, Wang C, Han X
Analytica Chimica Acta. 2018 Dec 11;1037:87-96. doi: 10.1016/j.aca.2017.11.052. Epub 2017 Nov 30.

Abstract:

Although numerous studies have raised public concerns regarding the safety of anesthetics including sevoflurane in children, the biochemical mechanisms leading to anesthetics-induced neurotoxicity remain elusive. Moreover, potential biomarker(s) for early detection of general anesthetics-induced brain injury are urgent for public health. We employed an enabling technology of shotgun lipidomics and analyzed nearly 20 classes and subclasses of lipids present in the blood serum of postnatal day (PND) 5 or 6 rhesus monkeys temporally collected after exposure to sevoflurane at a clinically relevant concentration or room-air as control. Lipidomics analysis revealed numerous significant anesthetic-induced changes of serum lipids and their metabolites as well as short chain acylcarnitines in the brain and cerebrospinal fluid after anesthetic exposure. These include decreased carnitine and acylcarnitines, unchanged triacylglycerol mass but accumulation of 16:0 and 18:1 fatty acyl chains in the triacylglycerol pool, losses of polyunsaturated fatty acids in both non-esterified fatty acid and phospholipid pools, and increased 4-hydroxynonenal content as early as 2 h after sevoflurane exposure. Importantly, the amounts of short chain acylcarnitines in the brain and cerebrospinal fluid were also significantly reduced after anesthetic exposure. We propose that this serum lipidomic profile can serve as indicative of neuronal damage. Our results reveal that sevoflurane exposure induces an energy deficient state in the brain evidenced by reduced free and acyl carnitine contents, as well as the presence of a pro-inflammatory state in the exposed animals, providing deep insights into the underlying mechanisms responsible for anesthetic-induced neurotoxicity.


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