Endocrinology
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
Abstract
Dedifferentiation has been implicated in β cell dysfunction and loss in rodent diabetes. However, the pathophysiological significance in humans remains unclear. To elucidate this, we analyzed surgically resected pancreatic tissues of 26 Japanese subjects with diabetes and 11 nondiabetic subjects, who had been overweight during adulthood but had no family history of diabetes. The diabetic subjects were subclassified into 3 disease stage categories, early, advanced, and intermediate. Despite no numerical changes in endocrine cells immunoreactive for chromogranin A (ChgA), diabetic islets showed profound β cell loss, with an increase in α cells without an increase in insulin and glucagon double-positive cells. The proportion of dedifferentiated cells that retain ChgA immunoreactivity without 4 major islet hormones was strikingly increased in diabetic islets and rose substantially during disease progression. The increased dedifferentiated cell ratio was inversely correlated with declining C-peptide index. Moreover, a subset of islet cells converted into exocrine-like cells during disease progression. These results indicate that islet remodeling with dedifferentiation is the underlying cause of β cell failure during the course of diabetes progression in humans.
Authors
Kikuko Amo-Shiinoki, Katsuya Tanabe, Yoshinobu Hoshii, Hiroto Matsui, Risa Harano, Tatsuya Fukuda, Takato Takeuchi, Ryotaro Bouchi, Tokiyo Takagi, Masayuki Hatanaka, Komei Takeda, Shigeru Okuya, Wataru Nishimura, Atsushi Kudo, Shinji Tanaka, Minoru Tanabe, Takumi Akashi, Tetsuya Yamada, Yoshihiro Ogawa, Eiji Ikeda, Hiroaki Nagano, Yukio Tanizawa
Abstract
Insulin-mediated suppression of white adipose tissue (WAT) lipolysis is an important anabolic function that is dysregulated in states of overnutrition. However, the mechanism of short-term high-fat diet (HFD)-induced WAT insulin resistance is poorly understood. Based on our recent studies we hypothesize that a short-term HFD causes WAT insulin resistance through increases in plasma membrane (PM) sn-1,2-diacylglycerols (DAG), which promotes protein kinase C-ε (PKCε) activation to impair insulin signaling by phosphorylating insulin receptor (Insr) Thr1160. To test this hypothesis, we assessed WAT insulin action in 7-day HFD-fed versus regular chow diet-fed rats during a hyperinsulinemic-euglycemic clamp. HFD feeding caused WAT insulin resistance, reflected by reductions in both insulin-mediated WAT glucose uptake and suppression of WAT lipolysis. These changes were specifically associated with increased PM sn-1,2-diacylglycerol (DAG) content, increased PKCε activation and impaired insulin-stimulated InsrY1162 phosphorylation. In order to examine the role of InsrT1160 phosphorylation in mediating lipid-induced WAT insulin resistance, we examined these same parameters in short-term HFD-fed InsrT1150A knockin mice (mouse homolog for human Thr1160). Similar to the rat study HFD feeding induced WAT insulin resistance in WT control mice but failed to induce WAT insulin resistance in InsrT1150A mice. Taken together these data demonstrate that the PM sn-1,2-DAG - PKCε - InsrT1160 phosphorylation pathway plays an important role in mediating lipid-induced WAT insulin resistance and represents a potential therapeutic target to improve insulin sensitivity in WAT.
Authors
Kun Lyu, Dongyan Zhang, Joongyu D. Song, Xiruo Li, Rachel J. Perry, Varman T. Samuel, Gerald I. Shulman
Abstract
Interleukin-10 (IL-10) is a critical cytokine used by immune cells to suppress inflammation. Paradoxically, immune cell-derived IL-10 can drive insulin resistance in obesity by suppressing adipocyte energy expenditure and thermogenesis. However, the source of IL-10 necessary for the suppression of adipocyte thermogenesis is unknown. We show here that CD4+ Foxp3+ regulatory T cells (Tregs) are a significant source of IL-10, and that Treg-derived IL-10 can suppress adipocyte beiging. Unexpectedly, Treg-specific loss of IL-10 resulted in increased insulin sensitivity and reduced obesity in high fat diet (HFD)-fed male mice. Mechanistically, we determined that Treg-specific loss of the transcription factor Blimp-1, a driver of IL-10 expression by Tregs, phenocopied the Treg-specific IL-10-deficient mice. Loss of Blimp-1 expression in Tregs resulted in reduced ST2+, KLRG1+, IL-10-secreting Tregs, particularly in the white adipose tissue. Blimp-1-deficient mice were protected from glucose intolerance, insulin resistance and diet-induced obesity (DIO), through increased white adipose tissue browning. Taken together, our data show that Blimp-1-regulated IL-10 secretion by Tregs represses white adipose tissue beiging to maintain adipose tissue homeostasis.
Authors
Lisa Y. Beppu, Raja Mooli, Xiaoyao Qu, Giovanni J. Marrero, Christopher A. Finley, Allen N. Fooks, Zackary P. Mullen, Adolfo B. Frias Jr., Ian J. Sipula, Bingxian Xie, Katherine E. Helfrich, Simon C. Watkins, Amanda C. Poholek, Sadeesh K. Ramakrishnan, Michael J. Jurczak, Louise M. D'Cruz
Abstract
Subjects with obesity frequently have elevated serum vasopressin levels, noted by the stable analog, copeptin. Vasopressin acts primarily to reabsorb water via urinary concentration. However, fat is also a source of metabolic water, raising the possibility that vasopressin might have a role in fat accumulation. Fructose has also been reported to stimulate vasopressin. Here we tested the hypothesis that fructose induced metabolic syndrome is mediated by vasopressin. Orally administered fructose, glucose or high fructose corn syrup increased vasopressin (copeptin) concentrations and was mediated by fructokinase, an enzyme specific for fructose metabolism. Suppressing vasopressin with hydration both prevented and ameliorated fructose-induced metabolic syndrome. The vasopressin effects were mediated by the Vasopressin 1b receptor, as Vasopressin 1b receptor knockout mice were completely protected while V1a knockout paradoxically showed worse metabolic syndrome. The mechanism is likely mediated in part by de novo expression of V1b in the liver that amplifies fructokinase expression in response to fructose. Thus, our studies document a new role for vasopressin in water conservation via the accumulation of fat as a source of metabolic water. Clinically, it also suggests that increased water intake may be a beneficial way to both prevent or treat metabolic syndrome.
Authors
Ana Andres-Hernando, Thomas J. Jensen, Masanari Kuwabara, David J. Orlicky, Christina Cicerchi, Nanxing Li, Carlos A. Roncal-Jimenez, Gabriela E. Garcia, Takuji Ishimoto, Paul S. Maclean, Petter Bjornstad, Laura Gabriela Sanchez-Lozada, Mehmet Kanbay, Takahiko Nakagawa, Richard Johnson, Miguel Lanaspa
Abstract
Inflammatory damage contributes to β-cell failure in type 1 and 2 diabetes (T1D and T2D). Mitochondria are damaged by inflammatory signaling in β-cells, resulting in impaired bioenergetics and initiation of pro-apoptotic machinery. Hence, the identification of protective responses to inflammation could lead to new therapeutic targets. Here we report that mitophagy serves as a protective response to inflammatory stress in both human and rodent β-cells. Utilizing in vivo mitophagy reporters, we observed that diabetogenic pro-inflammatory cytokines induced mitophagy in response to nitrosative/oxidative mitochondrial damage. Mitophagy-deficient β-cells were sensitized to inflammatory stress, leading to the accumulation of fragmented dysfunctional mitochondria, increased β-cell death, and hyperglycemia. Overexpression of CLEC16A, a T1D gene and mitophagy regulator whose expression in islets is protective against T1D, ameliorated cytokine-induced human β-cell apoptosis. Thus, mitophagy promotes β-cell survival and prevents diabetes by countering inflammatory injury. Targeting this pathway has the potential to prevent β-cell failure in diabetes and may be beneficial in other inflammatory conditions.
Authors
Vaibhav Sidarala, Gemma L. Pearson, Vishal S. Parekh, Benjamin Thompson, Lisa Christen, Morgan A. Gingerich, Jie Zhu, Tracy Stromer, Jianhua Ren, Emma C. Reck, Biaoxin Chai, John A. Corbett, Thomas Mandrup-Poulsen, Leslie S. Satin, Scott A. Soleimanpour
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