Endocrinology
Abstract
Bariatric surgery is the most effective method for weight loss in morbid obesity. There is significant individual variability in the weight loss outcomes, yet factors leading to postoperative weight loss or weight regain remain elusive. Alterations in the µ-opioid receptor (MOR) and dopamine D2 receptor (D2R) systems are associated with obesity and appetite control, and the magnitude of initial brain receptor system perturbation may predict long-term surgical weight loss outcomes. We tested this hypothesis by studying 19 morbidly obese women (mean BMI 40) scheduled to undergo bariatric surgery. We measured their preoperative MOR and D2R availabilities using positron emission tomography (PET) with [11C]carfentanil and [11C]raclopride, respectively, and then assessed their weight development association with regional MOR and D2R availabilities at 24-month follow-up. MOR availability in the amygdala consistently predicted weight development throughout the follow-up period, but no associations were found for D2R. This is the first study to demonstrate that neuroreceptor markers prior to bariatric surgery are associated with the postoperative weight loss. Postoperative weight regain may derive from dysfunction in the opioid system, and weight loss outcomes after bariatric surgery may be partially predicted based on preoperative brain receptor availability opening up new potential for treatment possibilities.
Authors
Henry K. Karlsson, Lauri Tuominen, Semi Helin, Paulina Salminen, Pirjo Nuutila, Lauri Nummenmaa
Abstract
Perilipin 2 (PLIN2) is the lipid droplet (LD) protein in β cells that increases under nutritional stress. Down-regulation of PLIN2 is often sufficient to reduce LD accumulation. To determine whether PLIN2 positively or negatively affects β cell function under nutritional stress, PLIN2 was down-regulated in mouse β cells, INS1 cells, and human islet cells. β cell specific deletion of PLIN2 in mice on a high fat diet reduced glucose-stimulated insulin secretion (GSIS) in vivo and in vitro. Down-regulation of PLIN2 in INS1 cells blunted GSIS after 24 h incubation with 0.2 mM palmitic acids. Down-regulation of PLIN2 in human pseudoislets cultured at 5.6 mM glucose impaired both phases of GSIS, indicating that PLIN2 is critical for GSIS. Down-regulation of PLIN2 decreased specific OXPHOS proteins in all three models and reduced oxygen consumption rates in INS1 cells and mouse islets. Moreover, we found that PLIN2 deficient INS1 cells increased the distribution of a fluorescent oleic acid analog to mitochondria and showed signs of mitochondrial stress as indicated by susceptibility to fragmentation and alterations of acyl-carnitines and glucose metabolites. Collectively, PLIN2 in β cells have an important role in preserving insulin secretion, β cell metabolism, and mitochondrial function under nutritional stress.
Authors
Akansha Mishra, Siming Liu, Joseph Promes, Mikako Harata, William I. Sivitz, Brian D. Fink, Gourav Bhardwaj, Brian T. O'Neill, Chen Kang, Rajan Sah, Stefan Strack, Samuel B. Stephens, Timothy H. King, Laura Jackson, Andrew S. Greenberg, Frederick Anokye-Danso, Rexford S. Ahima, James A. Ankrum, Yumi Imai
Abstract
Both innate and adaptive immune cells are critical players in autoimmune destruction of insulin-producing β-cells in type 1 diabetes. However, the early pathogenic events triggering the recruitment and activation of innate immune cells in islets remain obscure. Here we show that circulating fatty acid binding protein 4 (FABP4) level is significantly elevated in type1 diabetes patients and their first-degree relatives, and positively correlates with the titers of several islet autoantibodies. In non-obese diabetic (NOD) mice, increased FABP4 expression in islet macrophages starts from the neonatal period, well before the occurrence of overt diabetes. Furthermore, the spontaneous development of autoimmune diabetes in NOD mice is markedly reduced by pharmacological inhibition or genetic ablation of FABP4, or adoptive transfer of FABP4-deficient bone marrow cells. Mechanistically, FABP4 activates innate immune responses in islets by enhancing the infiltration and polarization of macrophages to pro-inflammatory M1 subtype, thus creating an inflammatory milieu required for activation of diabetogenic CD8+ T cells and shift of CD4+ helper T cells towards the Th1 subtypes. These findings demonstrate FABP4 as an early mediator for β-cell autoimmunity by facilitating crosstalk between innate and adaptive immune cells, suggesting that pharmacological inhibition of FABP4 may represent a promising therapeutic strategy for autoimmune diabetes.
Authors
Yang Xiao, Lingling Shu, Xiaoping Wu, Yang Liu, Lai Yee Cheong, Boya Liao, Xiaoyu Xiao, Ruby L.C. Hoo, Zhiguang Zhou, Aimin Xu
Abstract
Osteoclasts are specialized cells of the hematopoietic lineage that are responsible for bone resorption and play a critical role in musculoskeletal disease. JAK2 is a key mediator of cytokine and growth factor signaling; however, its role in osteoclasts in vivo has yet to be investigated. To elucidate the role of JAK2 in osteoclasts, we generated an osteoclast-specific JAK2–KO (Oc-JAK2–KO) mouse using the Cre/Lox-P system. Oc-JAK2–KO mice demonstrated marked postnatal growth restriction; however, this was not associated with significant changes in bone density, microarchitecture, or strength, indicating that the observed phenotype was not due to alterations in canonical osteoclast function. Interestingly, Oc-JAK2–KO mice had reduced osteoclast-specific expression of IGF1, suggesting a role for osteoclast-derived IGF1 in determination of body size. To directly assess the role of osteoclast-derived IGF1, we generated an osteoclast-specific IGF1–KO mouse, which showed a similar growth-restricted phenotype. Lastly, overexpression of circulating IGF1 by human transgene rescued the growth defects in Oc-JAK2–KO mice, in keeping with a causal role of IGF1 in these models. Together, our data show a potentially novel role for Oc-JAK2 and IGF1 in the determination of body size, which is independent of osteoclast resorptive function.
Authors
David W. Dodington, Jenalyn L. Yumol, Jiaqi Yang, Evan Pollock-Tahiri, Tharini Sivasubramaniyam, Sandra M. Sacco, Stephanie A. Schroer, Yujin E. Li, Helen Le, Wendy E. Ward, Minna Woo
Abstract
Secretory protein misfolding has been linked to ER stress and cell death. We expressed a TGrdw transgene encoding TG-G(2298)R, a misfolded mutant thyroglobulin reported to be linked to thyroid cell death. When the TGrdw transgene was expressed at low-level in thyrocytes of TGcog/cog mice that experience severe ER stress, we observed increased thyrocyte cell death and increased expression of CIDE-A (Cell death-inducing DFFA-like effector-A, a protein of lipid droplets) in whole thyroid gland. Here we demonstrate that acute ER stress in cultured PCCL3 thyrocytes increases Cidea mRNA levels, maintained at least in part by increased mRNA stability, while being negatively regulated by ATF6 — with similar observations other cell types. CIDE-A protein is sensitive to proteasomal degradation yet is stabilized by ER stress, and elevated expression levels accompany increased cell death. Unlike acute ER stress, PCCL3 cells adapted and surviving chronic ER stress maintain a disproportionately lower relative mRNA level of Cidea compared to that of other, classical ER stress markers, as well as a blunted Cidea mRNA response to a new, unrelated acute ER stress challenge. We suggest that CIDE-A is a novel marker linked to a non-canonical ER stress-response program, with implications for cell death and survival.
Authors
Yoshiaki Morishita, Aaron P. Kellogg, Dennis Larkin, Wei Chen, Suryakiran Vadrevu, Leslie S. Satin, Ming Liu, Peter Arvan
Abstract
Recent advances in proteomic technologies have made high throughput profiling of low abundance proteins in large epidemiological cohorts increasingly feasible. We investigated whether aptamer-based proteomic profiling could identify biomarkers associated with future development of type 2 diabetes (T2DM) beyond known risk factors. We identified dozens of markers with highly significant associations with future T2DM across two large longitudinal cohorts (n=2,839) followed for up to 16 years. We leveraged proteomic, metabolomic, genetic and clinical data from humans to nominate one specific candidate to test for potential causal relationships in model systems. Our studies identified functional effects of aminoacylase 1 (ACY1), a top protein association with future T2DM risk, on amino acid metabolism and insulin homeostasis in vitro and in vivo. Further, a loss-of-function variant associated with circulating levels of the biomarker WAP, Kazal, immunoglobulin, Kunitz and NTR domain-containing protein 2 (WFIKKN2) was in turn associated with fasting glucose, hemoglobin A1c and HOMA-IR measurements in humans. In addition to identifying novel disease markers and potential pathways in T2DM, we provide publicly available data to be leveraged for new insights about gene function and disease pathogenesis in the context of human metabolism.
Authors
Debby Ngo, Mark D. Benson, Jonathan Z. Long, Zsu-Zsu Chen, Ruiqi Wang, Anjali K. Nath, Michelle J. Keyes, Dongxiao Shen, Sumita Sinha, Eric Kuhn, Jordan E. Morningstar, Xu Shi, Bennet D. Peterson, Christopher Chan, Daniel H. Katz, Usman A. Tahir, Laurie A. Farrell, Olle Melander, Jonathan D. Mosley, Steven A. Carr, Ramachandran S. Vasan, Martin G. Larson, J. Gustav Smith, Thomas J. Wang, Qiong Yang, Robert E. Gerszten
Abstract
BACKGROUND. Type 1 diabetes (T1D) is a risk factor for dementia and structural brain changes. It remains to be determined whether transient insulin deprivation that frequently occurs in insulin treated T1D individual alters brain function. METHODS. We therefore, performed functional and structural magnetic resonance imaging, magnetic resonance spectroscopy, and neuropsychological testing at baseline and following 5.4 ± 0.6 hours of insulin deprivation in 14 T1D and compared to 14 age-, sex-, and body mass index–matched, nondiabetic (ND) participants with no interventions. RESULTS. Insulin deprivation in T1D increased blood glucose, and β-hydroxybutyrate, while reducing bicarbonate levels. T1D participants showed lower baseline brain N-acetyl aspartate and myo-inositol levels but higher cortical fractional anisotropy, suggesting unhealthy neurons and brain microstructure. Although cognitive functions did not differ between T1D and ND at baseline, significant changes in fine motor speed as well as attention and short-term memory occurred following insulin deprivation in T1D participants. Insulin deprivation also reduced brain adenosine triphosphate levels and altered phosphocreatine/ adenosine triphosphate ratio. Baseline differences in functional connectivity in brain regions between T1D and ND were noted and on insulin deprivation further alterations in functional connectivity between regions especially cortical and hippocampus-caudate regions were observed. These alterations in functional connectivity correlated to brain metabolites and to changes in cognition. CONCLUSIONS. Transient insulin deprivation thus, caused alterations in executive aspects of cognitive function concurrent with functional connectivity between memory regions and the sensory cortex. These findings have important clinical implications as many patients with T1D inadvertently have periods of transient insulin deprivation. TRIAL REGISTRATION NUMBER. NCT03392441
Authors
Ana L. Creo, Tiffany M. Cortes, Hang Joon Jo, Andrea R.S. Huebner, Surendra Dasari, Jan-Mendelt Tillema, Aida N. Lteif, Katherine A. Klaus, Gregory N. Ruegsegger, Yogish C. Kudva, Ronald C. Petersen, John D. Port, K. Sreekumaran Nair
Abstract
Glucagon-like peptide-1 (GLP-1) is an incretin hormone that potentiates glucose-stimulated insulin secretion. GLP-1 is classically produced by gut L cells; however, under certain circumstances α cells can express the prohormone convertase required for proglucagon processing to GLP-1, prohormone convertase 1/3 (PC1/3), and can produce GLP-1. However, the mechanisms through which this occurs are poorly defined. Understanding the mechanisms by which α cell PC1/3 expression can be activated may reveal new targets for diabetes treatment. Here, we demonstrate that the GLP-1 receptor (GLP-1R) agonist, liraglutide, increased α cell GLP-1 expression in a β cell GLP-1R–dependent manner. We demonstrate that this effect of liraglutide was translationally relevant in human islets through application of a new scRNA-seq technology, DART-Seq. We found that the effect of liraglutide to increase α cell PC1/3 mRNA expression occurred in a subcluster of α cells and was associated with increased expression of other β cell–like genes, which we confirmed by IHC. Finally, we found that the effect of liraglutide to increase bihormonal insulin+ glucagon+ cells was mediated by the β cell GLP-1R in mice. Together, our data validate a high-sensitivity method for scRNA-seq in human islets and identify a potentially novel GLP-1–mediated pathway regulating human α cell function.
Authors
Mridusmita Saikia, Marlena M. Holter, Leanne R. Donahue, Isaac S. Lee, Qiaonan C. Zheng, Journey L. Wise, Jenna E. Todero, Daryl J. Phuong, Darline Garibay, Reilly Coch, Kyle W. Sloop, Adolfo Garcia-Ocana, Charles G. Danko, Bethany P. Cummings
Abstract
Hindered by a limited understanding of the mechanisms responsible for diabetic gastroenteropathy (DGE), management is symptomatic. We investigated the duodenal mucosal expression of protein-coding genes and microRNAs (miRNA) in DGE and related them to clinical features. The diabetic phenotype, gastric emptying, mRNA, and miRNA expression and ultrastructure of duodenal mucosal biopsies were compared in 39 DGE patients and 21 controls. Among 3175 differentially expressed genes (FDR < 0.05), several mitochondrial DNA–encoded (mtDNA-encoded) genes (12 of 13 protein coding genes involved in oxidative phosphorylation [OXPHOS], both rRNAs and 9 of 22 transfer RNAs) were downregulated; conversely, nuclear DNA–encoded (nDNA-encoded) mitochondrial genes (OXPHOS) were upregulated in DGE. The promoters of differentially expressed genes were enriched in motifs for transcription factors (e.g., NRF1), which regulate mitochondrial biogenesis. Seventeen of 30 differentially expressed miRNAs targeted differentially expressed mitochondrial genes. Mitochondrial density was reduced and correlated with expression of 9 mtDNA OXPHOS genes. Uncovered by principal component (PC) analysis of 70 OXPHOS genes, PC1 was associated with neuropathy (P = 0.01) and delayed gastric emptying (P < 0.05). In DGE, mtDNA- and nDNA-encoded mitochondrial genes are reduced and increased — associated with reduced mitochondrial density, neuropathy, and delayed gastric emptying — and correlated with cognate miRNAs. These findings suggest that mitochondrial disturbances may contribute to delayed gastric emptying in DGE.
Authors
Susrutha Puthanmadhom Narayanan, Daniel O’Brien, Mayank Sharma, Karl Miller, Peter Adams, João F. Passos, Alfonso Eirin, Tamas Ordog, Adil E. Bharucha
Abstract
Somatostatin (SS) inhibits glucagon-like peptide-1 (GLP-1) secretion in a paracrine manner. We hypothesized that blocking somatostatin subtype receptor 2 (SSTR2) and 5 (SSTR5) would improve glycaemia by enhancing GLP-1 secretion. In the perfused mouse small intestine the selective SSTR5 antagonist (SSTR5a) stimulated glucose-induced GLP-1 secretion to a larger degree than the SSTR2 antagonist (SSTR2a). In parallel, mice lacking the SSTR5R showed increased glucose-induced GLP-1 secretion. Both antagonists improved glycaemia in vivo in a GLP-1 receptor (GLP-1R) dependent manner, as the glycaemic improvements were absent in mice with impaired GLP-1R signalling and in mice treated with a GLP-1R specific antagonist. SSTR5a had no direct effect on insulin secretion in the perfused pancreas whereas SSTR2a increased insulin secretion in a GLP-1R independent manner. Adding a dipeptidyl peptidase 4 inhibitor (DPP-4i) in vivo resulted in additive effects on glycaemia, however, when glucose was administered intraperitoneally the antagonists was incapable of lowering blood glucose. Oral administration of SSTR5a, but not SSTR2a lowered blood glucose in diet induced obese mice. In summary, we demonstrate that selective SSTR antagonists can improve glucose control primarily through the intestinal GLP-1 system in mice.
Authors
Sara L. Jepsen, Nicolai J. Wewer Albrechtsen, Johanne Agerlin Windeløv, Katrine D. Galsgaard, Jenna Elizabeth Hunt, Thomas B. Farb, Hannelouise Kissow, Jens Pedersen, Carolyn F. Deacon, Rainer E. Martin, Jens J. Holst
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