Adipocyte JAK2 mediates growth hormone–induced hepatic insulin resistance

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Abstract

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 Jak2 (JAK2A), an obligate transducer of GH signaling. Similar to whole-body GHI, JAK2A mice had increased adiposity and extreme insulin sensitivity. Loss of adipocyte Jak2 augmented hepatic insulin sensitivity and conferred resistance to diet-induced metabolic stress without overt changes in circulating fatty acids. While GH injections induced hepatic insulin resistance in control mice, the diabetogenic action was absent in JAK2A mice. Adipocyte GH signaling directly impinged on both adipose and hepatic insulin signal transduction. Collectively, our results show that adipose tissue governs the effects of GH on insulin and glucose homeostasis. Further, we show that JAK2 mediates liver insulin sensitivity via an extrahepatic, adipose tissue–dependent mechanism.

Authors

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

Prostatic compensation of the vitamin D axis in African American men

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Abstract

BACKGROUND. African American (AA) men are disproportionately affected by both prostate cancer (PCa) and vitamin D deficiency compared with European American (EA) men. Vitamin D deficiency is linked to increased PCa aggressiveness and mortality. Therefore, it has been hypothesized that vitamin D deficiency may contribute to the PCa disparity between AA and EA men.

METHODS. We studied a cross sectional group of 60 PCa patients (AA, n = 31; EA, n = 29) who underwent radical prostatectomy. Vitamin D metabolites 25-hydroxyvitamin D (25(OH)D) and 1,25-dihydroxyvitamin D (1,25(OH)₂D) were measured in the serum and tissue by uHPLC-MS-MS. Tissue was laser capture microdissected, and gene expression was quantified by microarray. DNA isolated from whole blood was genotyped for West African ancestry markers and vitamin D–related SNPs.

RESULTS. Serum concentrations of 25(OH)D were lower in AAs, but concentrations of 1,25(OH)₂D in the prostate tissue were higher compared with EAs. Expression of the vitamin D receptor was higher in prostate tissue from AAs. Expression of the extracellular receptor of vitamin D binding protein, LRP2, was positively associated with West African ancestry and inversely associated with tissue 25(OH)D concentrations in AAs.

CONCLUSIONS. The relationships between vitamin D binding protein LRP2 and vitamin D metabolites suggest that the prohormone is actively transported into the prostate, followed by intraprostatic conversion to the active hormone, rather than passive diffusion. These findings support the presence of a compensatory response in prostate tissue to vitamin D deficiency in AAs and reveal a previously unknown complexity involving tissue distribution of vitamin D metabolites.

FUNDING. Department of Defense Prostate Cancer Research Program Idea Award for Disparities Research PC121923 (LN and RK) and the NIH 1R01MD007105 (RK).

Authors

Zachary Richards, Ken Batai, Rachael Farhat, Ebony Shah, Andrew Makowski, Peter H. Gann, Rick Kittles, Larisa Nonn

Proproliferative and antiapoptotic action of exogenously introduced YAP in pancreatic β cells

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Abstract

Loss of functional pancreatic β cells is a hallmark of both type 1 and 2 diabetes. Identifying the pathways that promote β cell proliferation and/or block β cell apoptosis is a potential strategy for diabetes therapy. The transcriptional coactivator Yes-associated protein (YAP), a major downstream effector of the Hippo signaling pathway, is a key regulator of organ size and tissue homeostasis by modulating cell proliferation and apoptosis. YAP is not expressed in mature primary human and mouse β cells. We aimed to identify whether reexpression of a constitutively active form of YAP promotes β cell proliferation/survival. Overexpression of YAP remarkably induced β cell proliferation in isolated human islets, while β cell function and functional identity genes were fully preserved. The transcription factor forkhead box M1 (FOXM1) was upregulated upon YAP overexpression and necessary for YAP-dependent β cell proliferation. YAP overexpression protected β cells from apoptosis triggered by multiple diabetic conditions. The small redox proteins thioredoxin-1 and thioredoxin-2 (Trx1/2) were upregulated by YAP; disruption of the Trx system revealed that Trx1/2 was required for the antiapoptotic action of YAP in insulin-producing β cells. Our data show the robust proproliferative and antiapoptotic function of YAP in pancreatic β cells. YAP reconstitution may represent a disease-modifying approach to restore a functional β cell mass in diabetes.

Authors

Ting Yuan, Sahar Rafizadeh, Zahra Azizi, Blaz Lupse, Kanaka Durga Devi Gorrepati, Sushil Awal, Jose Oberholzer, Kathrin Maedler, Amin Ardestani

β Cell–specific increased expression of calpastatin prevents diabetes induced by islet amyloid polypeptide toxicity

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Abstract

The islet in type 2 diabetes (T2D) shares many features of the brain in protein misfolding diseases. There is a deficit of β cells with islet amyloid derived from islet amyloid polypeptide (IAPP), a protein coexpressed with insulin. Small intracellular membrane-permeant oligomers, the most toxic form of IAPP, are more frequent in β cells of patients with T2D and rodents expressing human IAPP. β Cells in T2D, and affected cells in neurodegenerative diseases, share a comparable pattern of molecular pathology, including endoplasmic reticulum stress, mitochondrial dysfunction, attenuation of autophagy, and calpain hyperactivation. While this adverse functional cascade in response to toxic oligomers is well described, the sequence of events and how best to intervene is unknown. We hypothesized that calpain hyperactivation is a proximal event and tested this in vivo by β cell–specific suppression of calpain hyperactivation with calpastatin overexpression in human IAPP transgenic mice. β Cell–specific calpastatin overexpression was remarkably protective against β cell dysfunction and loss and diabetes onset. The critical autophagy/lysosomal pathway for β cell viability was protected with calpain suppression, consistent with findings in models of neurodegenerative diseases. We conclude that suppression of calpain hyperactivation is a potentially beneficial disease-modifying strategy for protein misfolding diseases, including T2D.

Authors

Tatyana Gurlo, Safia Costes, Jonathan D. Hoang, Jacqueline F. Rivera, Alexandra E. Butler, Peter C. Butler

Insulin resistance uncoupled from dyslipidemia due to C-terminal PIK3R1 mutations

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Abstract

Obesity-related insulin resistance is associated with fatty liver, dyslipidemia, and low plasma adiponectin. Insulin resistance due to insulin receptor (INSR) dysfunction is associated with none of these, but when due to dysfunction of the downstream kinase AKT2 phenocopies obesity-related insulin resistance. We report 5 patients with SHORT syndrome and C-terminal mutations in PIK3R1, encoding the p85α/p55α/p50α subunits of PI3K, which act between INSR and AKT in insulin signaling. Four of 5 patients had extreme insulin resistance without dyslipidemia or hepatic steatosis. In 3 of these 4, plasma adiponectin was preserved, as in insulin receptor dysfunction. The fourth patient and her healthy mother had low plasma adiponectin associated with a potentially novel mutation, p.Asp231Ala, in adiponectin itself. Cells studied from one patient with the p.Tyr657X PIK3R1 mutation expressed abundant truncated PIK3R1 products and showed severely reduced insulin-stimulated association of mutant but not WT p85α with IRS1, but normal downstream signaling. In 3T3-L1 preadipocytes, mutant p85α overexpression attenuated insulin-induced AKT phosphorylation and adipocyte differentiation. Thus, PIK3R1 C-terminal mutations impair insulin signaling only in some cellular contexts and produce a subphenotype of insulin resistance resembling INSR dysfunction but unlike AKT2 dysfunction, implicating PI3K in the pathogenesis of key components of the metabolic syndrome.

Authors

Isabel Huang-Doran, Patsy Tomlinson, Felicity Payne, Alexandra Gast, Alison Sleigh, William Bottomley, Julie Harris, Allan Daly, Nuno Rocha, Simon Rudge, Jonathan Clark, Albert Kwok, Stefano Romeo, Emma McCann, Barbara Müksch, Mehul Dattani, Stefano Zucchini, Michael Wakelam, Lazaros C. Foukas, David B. Savage, Rinki Murphy, Stephen O’Rahilly, Inês Barroso, Robert K. Semple

PKA regulatory subunit 1A inactivating mutation induces serotonin signaling in primary pigmented nodular adrenal disease

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Abstract

Primary pigmented nodular adrenocortical disease (PPNAD) is a rare cause of ACTH-independent hypercortisolism. The disease is primarily caused by germline mutations of the protein kinase A (PKA) regulatory subunit 1A (PRKAR1A) gene, which induces constitutive activation of PKA in adrenocortical cells. Hypercortisolism is thought to result from PKA hyperactivity, but PPNAD tissues exhibit features of neuroendocrine differentiation, which may lead to stimulation of steroidogenesis by abnormally expressed neurotransmitters. We hypothesized that serotonin (5-HT) may participate in the pathophysiology of PPNAD-associated hypercortisolism. We show that PPNAD tissues overexpress the 5-HT synthesizing enzyme tryptophan hydroxylase type 2 (Tph2) and the serotonin receptors types 4, 6, and 7, leading to formation of an illicit stimulatory serotonergic loop whose pharmacological inhibition in vitro decreases cortisol production. In the human PPNAD cell line CAR47, the PKA inhibitor H-89 decreases 5-HT₄ and 5-HT₇ receptor expression. Moreover, in the human adrenocortical cell line H295R, inhibition of PRKAR1A expression increases the expression of Tph2 and 5-HT_4/6/7 receptors, an effect that is blocked by H-89. These findings show that the serotonergic process observed in PPNAD tissues results from PKA activation by PRKAR1A mutations. They also suggest that Tph inhibitors may represent efficient treatments of hypercortisolism in patients with PPNAD.

Authors

Zakariae Bram, Estelle Louiset, Bruno Ragazzon, Sylvie Renouf, Julien Wils, Céline Duparc, Isabelle Boutelet, Marthe Rizk-Rabin, Rossella Libé, Jacques Young, Dennis Carson, Marie-Christine Vantyghem, Eva Szarek, Antoine Martinez, Constantine A. Stratakis, Jérôme Bertherat, Hervé Lefebvre

Whole-exome sequencing identifies ADRA2A mutation in atypical familial partial lipodystrophy

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Abstract

Despite identification of causal genes for various lipodystrophy syndromes, the molecular basis of some peculiar lipodystrophies remains obscure. In an African-American pedigree with a novel autosomal dominant, atypical familial partial lipodystrophy (FPLD), we performed linkage analysis for candidate regions and whole-exome sequencing to identify the disease-causing mutation. Affected adults reported marked loss of fat from the extremities, with excess fat in the face and neck at age 13–15 years, and developed metabolic complications later. A heterozygous g.112837956C>T mutation on chromosome 10 (c.202C>T, p.Leu68Phe) affecting a highly conserved residue in adrenoceptor α 2A (ADRA2A) was found in all affected subjects but not in unaffected relatives. ADRA2A is the main presynaptic inhibitory feedback G protein–coupled receptor regulating norepinephrine release. Activation of ADRA2A inhibits cAMP production and reduces lipolysis in adipocytes. As compared with overexpression of a wild-type ADRA2A construct in human embryonic kidney–293 cells and differentiated 3T3-L1 adipocytes, the mutant ADRA2A produced more cAMP and glycerol, which were resistant to the effects of the α2-adrenergic receptor agonist clonidine and the α2-adrenergic receptor antagonist yohimbine, suggesting loss of function. We conclude that heterozygous p.Leu68Phe ADRA2A mutation causes a rare atypical FPLD, most likely by inducing excessive lipolysis in some adipose tissue depots.

Authors

Abhimanyu Garg, Shireesha Sankella, Chao Xing, Anil K. Agarwal

STAT3 accelerates uterine epithelial regeneration in a mouse model of decellularized uterine matrix transplantation

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Abstract

Although a close connection between uterine regeneration and successful pregnancy in both humans and mice has been consistently observed, its molecular basis remains unclear. We here established a mouse model of decellularized uterine matrix (DUM) transplantation. Resected mouse uteri were processed with SDS to make DUMs without any intact cells. DUMs were transplanted into the mouse uteri with artificially induced defects, and all the uterine layers were recovered at the DUM transplantation sites within a month. In the regenerated uteri, normal hormone responsiveness in early pregnancy was observed, suggesting the regeneration of functional uteri. Uterine epithelial cells rapidly migrated and formed a normal uterine epithelial layer within a week, indicating a robust epithelial-regenerating capacity. Stromal and myometrial regeneration occurred following epithelial regeneration. In ovariectomized mice, uterine regeneration of the DUM transplantation was similarly observed, suggesting that ovarian hormones are not essential for this regeneration process. Importantly, the regenerating epithelium around the DUM demonstrated heightened STAT3 phosphorylation and cell proliferation, which was suppressed in uteri of Stat3 conditional knockout mice. These data suggest a key role of STAT3 in the initial step of the uterine regeneration process. The DUM transplantation model is a powerful tool for uterine regeneration research.

Authors

Takehiro Hiraoka, Yasushi Hirota, Tomoko Saito-Fujita, Mitsunori Matsuo, Mahiro Egashira, Leona Matsumoto, Hirofumi Haraguchi, Sudhansu K. Dey, Katsuko S. Furukawa, Tomoyuki Fujii, Yutaka Osuga

Increased apoptosis and browning of TAK1-deficient adipocytes protects against obesity

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Abstract

Obesity is an increasing health problem worldwide, and nonsurgical strategies to treat obesity have remained rather inefficient. We here show that acute loss of TGF-β–activated kinase 1 (TAK1) in adipocytes results in an increased rate of apoptotic adipocyte death and increased numbers of M2 macrophages in white adipose tissue. Mice with adipocyte-specific TAK1 deficiency have reduced adipocyte numbers and are resistant to obesity induced by a high-fat diet or leptin deficiency. In addition, adipocyte-specific TAK1-deficient mice under a high-fat diet showed increased energy expenditure, which was accompanied by enhanced expression of the uncoupling protein UCP1. Interestingly, acute induction of adipocyte-specific TAK1 deficiency in mice already under a high-fat diet was able to stop further weight gain and improved glucose tolerance. Thus, loss of TAK1 in adipocytes reduces the total number of adipocytes, increases browning of white adipose tissue, and may be an attractive strategy to treat obesity, obesity-dependent diabetes, and other associated complications.

Authors

Antonia Sassmann-Schweda, Pratibha Singh, Cong Tang, Astrid Wietelmann, Nina Wettschureck, Stefan Offermanns

Trimeprazine increases IRS2 in human islets and promotes pancreatic β cell growth and function in mice

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Abstract

The capacity of pancreatic β cells to maintain glucose homeostasis during chronic physiologic and immunologic stress is important for cellular and metabolic homeostasis. Insulin receptor substrate 2 (IRS2) is a regulated adapter protein that links the insulin and IGF1 receptors to downstream signaling cascades. Since strategies to maintain or increase IRS2 expression can promote β cell growth, function, and survival, we conducted a screen to find small molecules that can increase IRS2 mRNA in isolated human pancreatic islets. We identified 77 compounds, including 15 that contained a tricyclic core. To establish the efficacy of our approach, one of the tricyclic compounds, trimeprazine tartrate, was investigated in isolated human islets and in mouse models. Trimeprazine is a first-generation antihistamine that acts as a partial agonist against the histamine H1 receptor (H1R) and other GPCRs, some of which are expressed on human islets. Trimeprazine promoted CREB phosphorylation and increased the concentration of IRS2 in islets. IRS2 was required for trimeprazine to increase nuclear Pdx1, islet mass, β cell replication and function, and glucose tolerance in mice. Moreover, trimeprazine synergized with anti-CD3 Abs to reduce the progression of diabetes in NOD mice. Finally, it increased the function of human islet transplants in streptozotocin-induced (STZ-induced) diabetic mice. Thus, trimeprazine, its analogs, or possibly other compounds that increase IRS2 in islets and β cells without adverse systemic effects might provide mechanism-based strategies to prevent the progression of diabetes.

Authors

Alexandra Kuznetsova, Yue Yu, Jennifer Hollister-Lock, Lynn Opare-Addo, Aldo Rozzo, Marianna Sadagurski, Lisa Norquay, Jessica E. Reed, Ilham El Khattabi, Susan Bonner-Weir, Gordon C. Weir, Arun Sharma, Morris F. White