Mechanisms underlying postprandial and obesity-associated plasma ghrelin reductions are incompletely understood. Here, using ghrelin cell-selective insulin receptor-knockout (GhIRKO) mice, we tested the impact of insulin, acting via ghrelin cell-expressed insulin receptors (IRs), to suppress ghrelin secretion. Insulin reduced ghrelin secretion from cultured gastric mucosal cells of control mice but not from those of GhIRKO mice. Acute insulin challenge and insulin infusion during both hyperinsulinemic-hypoglycemic clamps and hyperinsulinemic-euglycemic clamps lowered plasma ghrelin in control mice but not GhIRKO mice. Thus, ghrelin cell-expressed IRs are required for insulin-mediated reductions in plasma ghrelin. Furthermore, interventions that naturally raise insulin (glucose gavage, re-feeding following fasting, and chronic high-fat diet) also lowered plasma ghrelin only in control mice but not GhIRKO mice. Thus, meal- and obesity-associated increases in insulin, acting via ghrelin cell-expressed IRs, represent a major, direct negative modulator of ghrelin secretion in vivo, as opposed to ingested or metabolized macronutrients. Re-fed GhIRKO mice exhibited reduced plasma insulin, highlighting ghrelin’s actions to inhibit insulin release via positive feedback. Moreover, GhIRKO mice required reduced glucose infusion rates during hyperinsulinemic-hypoglycemic clamps, suggesting that suppressed ghrelin release resulting from direct insulin action on ghrelin cells usually limits ghrelin’s full potential to protect against insulin-induced hypoglycemia.
Kripa Shankar, Shota Takemi, Deepali Gupta, Salil Varshney, Bharath K. Mani, Sherri Osborne-Lawrence, Nathan P. Metzger, Corine P. Richard, Eric D. Berglund, Jeffrey M. Zigman
Islet-enriched transcription factors (TFs) exert broad control over cellular processes in pancreatic α and β cells and changes in their expression are associated with developmental state and diabetes. However, the implications of heterogeneity in TF expression across islet cell populations are not well understood. To define this TF heterogeneity and its consequences for cellular function, we profiled >40,000 cells from normal human islets by scRNA-seq and stratified α and β cells based on combinatorial TF expression. Subpopulations of islet cells co-expressing ARX/MAFB (α cells) and MAFA/MAFB (β cells) exhibited greater expression of key genes related to glucose sensing and hormone secretion relative to subpopulations expressing only one or neither TF. Moreover, all subpopulations were identified in native pancreatic tissue from multiple donors. By Patch-seq, MAFA/MAFB co-expressing β cells showed enhanced electrophysiological activity. Thus, these results indicate combinatorial TF expression in islet α and β cells predicts highly functional, mature subpopulations.
Shristi Shrestha, Diane C. Saunders, John T. Walker, Joan Camunas-Soler, Xiao-Qing Dai, Rachana Haliyur, Radhika Aramandla, Greg Poffenberger, Nripesh Prasad, Rita Bottino, Roland Stein, Jean-Philippe Cartailler, Stephen C.J. Parker, Patrick E. MacDonald, Shawn E. Levy, Alvin C. Powers, Marcela Brissova
BACKGROUND The incidence of burn injuries in older patients is dramatically increasing as the population of older people grows. Despite the increased demand for elderly burn care, the mechanisms that mediate increased morbidity and mortality in older trauma patients are unknown. We recently showed that a burn injury invokes white adipose tissue browning that leads to a substantially increased hypermetabolic response associated with poor outcomes. Therefore, the aim of this study was to determine the effect of age on the metabolic adipose response of browning after a burn injury.METHOD One hundred and seventy patients with burn injury admitted to the Ross Tilley Burn Centre were prospectively enrolled and grouped by age as older (≥50 years) and young (≤35 years). Adipose tissue and sera were collected and analyzed for browning markers and metabolic state via histology, gene expression, and resting energy expenditure assays.RESULTS We found that older patients with burn injury lacked the adipose browning response, as they showed significant reductions in uncoupling protein 1 (UCP1) expression. This failure of the browning response was associated with reduced whole-body metabolism and decreased survival in older patients with burn injury. Mechanistically, we found that the adipose of both aged patients after burn trauma and aged mice after a burn showed impairments in macrophage infiltration and IL-6, key immunological regulators of the browning process after a severe trauma.CONCLUSION Targeting pathways that activate the browning response represents a potential therapeutic approach to improve outcomes after burn trauma for elderly patients.FUNDING NIH (R01-GM087285-01), Canadian Institutes of Health Research (grant no. 123336), and Canada Foundation for Innovation Leaders Opportunity Fund (no. 25407).
Abdikarim Abdullahi, Carly M. Knuth, Christopher Auger, Thibacg Sivayoganathan, Alexandra Parousis, Marc G. Jeschke
We identified a microRNA (miRNA) profile characterizing HIV lipodystrophy and explored the downstream mechanistic implications with respect to adipocyte biology and the associated clinical phenotype. miRNA profiles were extracted from small extracellular vesicles (sEV) of HIV-infected individuals with and without lipodystrophic changes and individuals without HIV, among whom we previously showed significant reductions in adipose Dicer expression related to HIV. miR-20a-3p was increased and miR-324-5p and miR-186 reduced in sEV from HIV lipodystrophic individuals. Changes in these miRNAs correlated with adipose Dicer expression and clinical markers of lipodystrophy, including fat redistribution, insulin resistance, and hypertriglyceridemia. Human preadipocytes transfected with mimic miR-20a-3p, anti-miR-324-5p or anti-miR-186 induced consistent changes in Ltbp2, Wisp2, and Nebl expression. Knockdown of Ltbp2 (Latent-transforming growth factor beta-binding protein 2) downregulated markers of adipocyte differentiation (Fabp4, Pparg, C/ebpa, Fasn, adiponectin, Glut4, CD36), and Lamin C, and increased expression of genes involved in inflammation (IL1β, IL6, and Ccl20). Our studies suggest a unique sEV miRNA signature related to dysregulation of Dicer in adipose in HIV. Enhanced miR-20a-3p or depletion of miR-186 and miR-324-5p may downregulate Ltbp2 in HIV leading to dysregulation in adipose differentiation and inflammation, which could contribute to acquired HIV lipodystrophy and associated metabolic and inflammatory perturbations.
Suman Srinivasa, Ruben Garcia-Martin, Martin Torriani, Kathleen V. Fitch, Anna R. Carlson, C. Ronald Kahn, Steven K. Grinspoon
BACKGROUND Roux-en-Y gastric bypass (RYGB) decreases energy intake and is, therefore, an effective treatment of obesity. The behavioral bases of the decreased calorie intake remain to be elucidated. We applied the methodology of microstructural analysis of meal intake to establish the behavioral features of ingestion in an effort to discern the various controls of feeding as a function of RYGB.METHODS The ingestive microstructure of a standardized liquid meal in a cohort of 11 RYGB patients, in 10 patients with obesity, and in 10 healthy-weight adults was prospectively assessed from baseline to 1 year with a custom-designed drinkometer. Statistics were performed on log-transformed ratios of change from baseline so that each participant served as their own control, and proportional increases and decreases were numerically symmetrical. Data-driven (3 seconds) and additional burst pause criteria (1 and 5 seconds) were used.RESULTS At baseline, the mean meal size (909.2 versus 557.6 kCal), burst size (28.8 versus 17.6 mL), and meal duration (433 versus 381 seconds) differed between RYGB patients and healthy-weight controls, whereas suck volume (5.2 versus 4.6 mL) and number of bursts (19.7 versus 20.1) were comparable. At 1 year, the ingestive differences between the RYGB and healthy-weight groups disappeared due to significantly decreased burst size (P = 0.008) and meal duration (P = 0.034) after RYGB. The first-minute intake also decreased after RYGB (P = 0.022).CONCLUSION RYGB induced dynamic changes in ingestive behavior over the first postoperative year. While the eating pattern of controls remained stable, RYGB patients reduced their meal size by decreasing burst size and meal duration, suggesting that increased postingestive sensibility may mediate postbariatric ingestive behavior.TRIAL REGISTRATION NCT03747445; https://clinicaltrials.gov/ct2/show/NCT03747445.FUNDING This work was supported by the University of Zurich, the Swiss National Fund (32003B_182309), and the Olga Mayenfisch Foundation. Bálint File was supported by the Hungarian Brain Research Program Grant (grant no. 2017-1.2.1-NKP-2017-00002).
Daniel Gero, Bálint File, Daniela Alceste, Lukas D. Frick, Michele Serra, Aiman E.M. Ismaeil, Robert E. Steinert, Alan C. Spector, Marco Bueter
Mitochondrial biogenesis and function are controlled by anterograde regulatory pathways involving more than one thousand nuclear-encoded proteins. Transcriptional networks controlling the nuclear-encoded mitochondrial genes remain to be fully elucidated. Here we show that histone demethylase LSD1 knockout from adult mouse liver (LSD1-LKO) reduces the expression of one-third of all nuclear-encoded mitochondrial genes and decreases mitochondrial biogenesis and function. LSD1-modulated histone methylation epigenetically regulates nuclear-encoded mitochondrial genes. Furthermore, LSD1 regulates gene expression and protein methylation of nicotinamide mononucleotide adenylyltransferase 1 (NMNAT1), which controls the final step of NAD+ synthesis and limits NAD+ availability in nucleus. Lsd1 knockout reduces NAD+-dependent SIRT1 and SIRT7 deacetylase activity, leading to hyperacetylation and hypofunctioning of GABPβ and PGC-1α, the major transcriptional factor/cofactor for nuclear-encoded mitochondrial genes. Despite the reduced mitochondrial function in liver, LSD1-LKO mice are protected from diet-induced hepatic steatosis and glucose intolerance, partially due to induction of hepatokine FGF21. Thus, LSD1 orchestrates a core regulatory network involving epigenetic modifications and NAD+ synthesis to control mitochondrial function and hepatokine production.
Yang Cao, Lingyi Tang, Kang Du, Kitt Paraiso, Qiushi Sun, Zhengxia Liu, Xiaolong Ye, Yuan Fang, Fang Yuan, Yu-Han Chen, Yumay Chen, Xiaorong Wang, Clinton Yu, Ira L. Blitz, Ping H. Wang, Lan Huang, Haibo Cheng, Xiang Lu, Ken W.Y Cho, Marcus Seldin, Zhuyuan Fang, Qin Yang
The alpha ketoglutarate-dependent dioxygenase, prolyl-4-hydroxylase 3 (PHD3), is a Hypoxia-Inducible Factor (HIF) target that uses molecular oxygen to hydroxylate peptidyl prolyl residues. While PHD3 has been reported to influence cancer cell metabolism and liver insulin sensitivity, relatively little is known about effects of this highly conserved enzyme in insulin-secreting β-cells in vivo. Here, we show that deletion of PHD3 specifically in β-cells (βPHD3KO) is associated with impaired glucose homeostasis in mice fed high fat diet. In the early stages of dietary fat excess, βPHD3KO islets energetically rewire, leading to defects in the management of pyruvate fate and a shift from glycolysis to increased fatty acid oxidation (FAO). However, under more prolonged metabolic stress, this switch to preferential FAO in βPHD3KO islets is associated with impaired glucose-stimulated ATP/ADP rises, Ca2+ fluxes and insulin secretion. Thus, PHD3 might be a pivotal component of the β-cell glucose metabolism machinery in mice by suppressing the use of fatty acids as a primary fuel source during the early phases of metabolic stress.
Daniela Nasteska, Federica Cuozzo, Katrina Viloria, Elspeth M. Johnson, Alpesh Thakker, Rula Bany Bakar, Rebecca L. Westbrook, Jonathan P. Barlow, Monica Hoang, Jamie W. Joseph, Gareth G. Lavery, Ildem Akerman, James Cantley, Leanne Hodson, Daniel A. Tennant, David J. Hodson
A dynamically regulated microenvironment, which is mediated by crosstalks between adipocytes 2 and neighboring cells, is critical for adipose tissue homeostasis and function. However, information on 3 key molecules and/or signaling pathways regulating the crosstalks remains limited. In this study, we 4 identify adipocyte miR-182-5p as a crucial anti-obesity molecule that stimulates beige fat thermogenesis 5 by promoting the crosstalk between adipocytes and macrophages. miR-182-5p is highly enriched in 6 thermogenic adipocytes and its expression is markedly stimulated by cold exposure in mice. In contrast, 7 miR-182-5p expression is significantly reduced in adipose tissues of obese humans and mice. Knockout 8 of miR-185-5p decreased cold-induced beige fat thermogenesis whereas overexpression of miR-185-5p 9 increased beiging and thermogenesis in mice. Mechanistically, miR-182-5p promotes FGF21 expression 10 and secretion in adipocytes by suppressing Nr1d1 at 5'UTR, which in turn stimulates acetylcholine 11 synthesis and release in macrophages. Increased acetylcholine expression activates the nicotine 12 acetylcholine receptor in adipocytes, which stimulates PKA signaling and consequent thermogenic gene 13 expression. Our study reveals a key role of the miR-182-5p/FGF21/acetylcholine/acetylcholine receptor 14 axis that mediates the crosstalk between adipocytes and macrophages to promote beige fat 15 thermogenesis. Activation of the miR-182-5p-induced signaling pathway in adipose tissue may be an 16 effective approach to ameliorate obesity and associated metabolic diseases.
Wen Meng, Ting Xiao, Xiuci Liang, Jie Wen, Xinyi Peng, Jing Wang, Yi Zou, Jiahao Liu, Christie Bialowas, Hairong Luo, Yacheng Zhang, Bilian Liu, Jingjing Zhang, Fang Hu, Meilian Liu, Lily Q. Dong, Zhiguang Zhou, Feng Liu, Juli Bai
Thyroid hormone receptor beta (THRB) is post-translationally modified by small ubiquitin-like modifier (SUMO). We generated a mouse model with a mutation that disrupts sumoylation at lysine 146 (K146Q) and resulted in desumoylated THRB as the predominant form in tissues. The THRB K146Q mutant mice had normal serum thyroxine (T4), markedly elevated serum thyrotropin (TSH) (81-fold above control), and enlargement of both the pituitary and the thyroid gland. The marked elevation in TSH, despite a normal serum T4, indicated blunted feedback regulation of TSH. The THRB K146Q mutation altered transcription factors (TFs) recruitment to the TSHβ gene promoter, compared to wild-type, in hyperthyroidism and hypothyroidism. Thyroid hormone content (T4, T3 and rT3) in the thyroid gland of the THRB K146Q mice was 10-fold lower (per gram tissue) than control, despite normal TSH bioactivity. Expression of Thyroglobulin and Duox2 genes in the thyroid was reduced and associated with modifications of CREB DNA binding and cofactor interactions in the presence of the desumoylated THRB. Thyroid hormone production, therefore, has both TSH -dependent and -independent components. We conclude that THRB sumoylation at K146 is required for normal TSH feedback regulation and TH synthesis in the thyroid gland, by a TSH-independent pathway.
Sujie Ke, Yan-Yun Liu, Rajendiran Karthikarj, Kurunthanchalam Kannan, Jingjing Jiang, Kiyomi Abe, Anna Milanesi, Gregory A. Brent
BACKGROUND. Wolfram syndrome is a rare endoplasmic reticulum disorder characterized by insulin-dependent diabetes mellitus, optic nerve atrophy, and progressive neurodegeneration. Although there is currently no treatment to delay, halt, or reverse the progression of Wolfram syndrome, preclinical studies in cell and rodent models suggest that therapeutic strategies targeting endoplasmic reticulum calcium homeostasis, including dantrolene sodium, may be beneficial. METHODS. Based on the results from preclinical studies on dantrolene sodium and ongoing longitudinal studies, our group put together the first-ever clinical trial in pediatric and adult patients with Wolfram syndrome. An open-label phase 1b/2a trial design was chosen. The primary objective of the study was to assess the safety and tolerability of dantrolene sodium in adult and pediatric patients with Wolfram syndrome. Secondary objectives were to evaluate the efficacy of dantrolene sodium on residual pancreatic beta-cell functions, visual acuity, quality of life measures related to vision, and neurological functions. RESULTS. The results indicate that dantrolene sodium is well tolerated by patients with Wolfram syndrome. Overall, β-cell functions were not significantly improved by dantrolene, but there was a significant correlation between baseline β-cell functions and the change in β-cell responsiveness (R2, p=0.004) after 6 months of dantrolene therapy. Other outcome measures, including visual acuity and neurological functions, were not improved by dantrolene sodium treatment within 6 months. As previously reported, markers of inflammatory cytokines and oxidative stress, such as IFNγ, IL-1β, TNFα, and isoprostane, were elevated in subjects with Wolfram syndrome. CONCLUSION. This study justifies further investigation into using dantrolene sodium and other small molecules targeting the endoplasmic reticulum for the treatment of Wolfram syndrome. TRIAL REGISTRATION. ClinicalTrials.gov Identifier NCT02829268
Damien Abreu, Stephen I. Stone, Toni S. Pearson, Robert C. Bucelli, Ashley N. Simpson, Stacy Hurst, Cris M. Brown, Kelly Kries, Chinyere Onwumere, Hongjie Gu, James Hoekel, Lawrence Tychsen, Gregory P. Van Stavern, Neil H. White, Bess A. Marshall, Tamara Hershey, Fumihiko Urano
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