| 1. |
- Tattikota, Sudhir G, et al.
(author)
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MiR-184 regulates pancreatic β-cell function according to glucose metabolism.
- 2015
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In: Journal of Biological Chemistry. - 1083-351X. ; 290:33, s. 20284-20294
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Journal article (peer-reviewed)abstract
- In response to fasting or hyperglycemia, the pancreatic β-cell alters its output of secreted insulin; however the pathways governing this adaptive response are not entirely established. While the precise role of microRNAs (miRNAs) is also unclear, a recurring theme emphasizes their function in cellular stress responses. We recently showed that miR-184, an abundant miRNA in the β-cell, regulates compensatory proliferation and secretion during insulin resistance. Consistent with previous studies showing miR-184 suppresses insulin release, expression of this miRNA was increased in islets after fasting, demonstrating an active role in the β-cell as glucose levels lower and the insulin demand ceases. Additionally, miR-184 was negatively regulated upon administration of a sucrose-rich diet in Drosophila demonstrating strong conservation of this pathway through evolution. Furthermore, miR-184 and its target Argonaute2 (Ago2) remained inversely correlated as concentrations of extracellular glucose increased, underlining a functional relationship between this miRNA and its targets. Lastly, restoration of Ago2 in the presence of miR-184 rescued suppression of miR-375-targeted genes suggesting these genes act in a coordinated manner during changes in the metabolic context. Together, these results highlight the adaptive role of miR-184 according to glucose metabolism and suggest the regulatory role of this miRNA in energy homeostasis is highly conserved.
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| 2. |
- Fischer, Katrin, et al.
(author)
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The scaffold protein p62 regulates adaptive thermogenesis through ATF2 nuclear target activation
- 2020
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 11:1
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Journal article (peer-reviewed)abstract
- During beta -adrenergic stimulation of brown adipose tissue (BAT), p38 phosphorylates the activating transcription factor 2 (ATF2) which then translocates to the nucleus to activate the expression of Ucp1 and Pgc-1 alpha. The mechanisms underlying ATF2 target activation are unknown. Here we demonstrate that p62 (Sqstm1) binds to ATF2 to orchestrate activation of the Ucp1 enhancer and Pgc-1 alpha promoter. P62(Delta 69-251) mice show reduced expression of Ucp1 and Pgc-1 alpha with impaired ATF2 genomic binding. Modulation of Ucp1 and Pgc-1 alpha expression through p62 regulation of ATF2 signaling is demonstrated in vitro and in vivo in p62(Delta 69-251) mice, global p62(-/-) and Ucp1-Cre p62(flx/flx) mice. BAT dysfunction resulting from p62 deficiency is manifest after birth and obesity subsequently develops despite normal food intake, intestinal nutrient absorption and locomotor activity. In summary, our data identify p62 as a master regulator of BAT function in that it controls the Ucp1 pathway through regulation of ATF2 genomic binding. Beta-adrenergic stimulation of brown adipose tissue leads to thermogenesis via the activating transcription factor 2 (ATF2) mediated expression of the thermogenic genes Ucp1 and Pgc-1 alpha. Here, the authors show that the scaffold protein p62 regulates brown adipose tissue function through modifying ATF2 genomic binding and subsequent Ucp1 and Pgc-1 alpha induction.
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| 3. |
- Kabra, Uma D, et al.
(author)
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Direct Substrate Delivery into Mitochondrial-Fission Deficient Pancreatic Islets Rescues Insulin Secretion
- 2017
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In: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 66:5, s. 1247-1257
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Journal article (peer-reviewed)abstract
- In pancreatic beta cells, mitochondrial bioenergetics control glucose-stimulated insulin secretion (GSIS). Mitochondrial dynamics are generally associated with quality control, maintaining the functionality of bioenergetics. By acute pharmacological inhibition of mitochondrial fission protein Drp1, we here demonstrate that mitochondrial fission is necessary for GSIS in mouse and human islets. We confirm that genetic silencing of Drp1 increases mitochondrial proton leak in MIN6 cells. However, our comprehensive analysis of pancreatic islet bioenergetics reveals that Drp1 does not control insulin secretion via its effect on proton leak but instead via modulation of glucose-fuelled respiration. Notably, pyruvate fully rescues the impaired insulin secretion of fission-deficient beta cells, demonstrating that defective mitochondrial dynamics solely impact substrate supply upstream of oxidative phosphorylation. The present findings provide novel insights in how mitochondrial dysfunction may cause pancreatic beta cell failure. In addition, the results will stimulate new thinking in the intersecting fields of mitochondrial dynamics and bioenergetics, as treatment of defective dynamics in mitochondrial diseases appears to be possible by improving metabolism upstream of mitochondria.
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| 4. |
- Schriever, Sonja C., et al.
(author)
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Type 2 diabetes risk gene Dusp8 regulates hypothalamic Jnk signaling and insulin sensitivity
- 2020
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In: Journal of Clinical Investigation. - 0021-9738. ; 130:11, s. 6093-6108
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Journal article (peer-reviewed)abstract
- Recent genome-wide association studies (GWAS) identified DUSP8, encoding a dual-specificity phosphatase targeting mitogen-activated protein kinases, as a type 2 diabetes (T2D) risk gene. Here, we reveal that Dusp8 is a gatekeeper in the hypothalamic control of glucose homeostasis in mice and humans. Male, but not female, Dusp8 loss-of-function mice, either with global or corticotropin-releasing hormone neuron–specific deletion, had impaired systemic glucose tolerance and insulin sensitivity when exposed to high-fat diet (HFD). Mechanistically, we found impaired hypothalamic-pituitary-adrenal axis feedback, blunted sympathetic responsiveness, and chronically elevated corticosterone levels driven by hypothalamic hyperactivation of Jnk signaling. Accordingly, global Jnk1 ablation, AAV-mediated Dusp8 overexpression in the mediobasal hypothalamus, or metyrapone-induced chemical adrenalectomy rescued the impaired glucose homeostasis of obese male Dusp8-KO mice, respectively. The sex-specific role of murine Dusp8 in governing hypothalamic Jnk signaling, insulin sensitivity, and systemic glucose tolerance was consistent with functional MRI data in human volunteers that revealed an association of the DUSP8 rs2334499 risk variant with hypothalamic insulin resistance in men. Further, expression of DUSP8 was increased in the infundibular nucleus of T2D humans. In summary, our findings suggest the GWAS-identified gene Dusp8 as a novel hypothalamic factor that plays a functional role in the etiology of T2D.
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| 5. |
- Tschöp, Matthias, et al.
(author)
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Gut hormone-based pharmacology : novel formulations and future possibilities for metabolic disease therapy
- 2023
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In: Diabetologia. - 0012-186X. ; 66:10, s. 1796-1808
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Research review (peer-reviewed)abstract
- Glucagon-like peptide-1 (GLP-1) receptor agonists are established pharmaceutical therapies for the treatment of type 2 diabetes and obesity. They mimic the action of GLP-1 to reduce glucose levels through stimulation of insulin secretion and inhibition of glucagon secretion. They also reduce body weight by inducing satiety through central actions. The GLP-1 receptor agonists used clinically are based on exendin-4 and native GLP-1 and are available as formulations for daily or weekly s.c. or oral administration. GLP-1 receptor agonism is also achieved by inhibitors of dipeptidyl peptidase-4 (DPP-4), which prevent the inactivation of GLP-1 and glucose-dependent insulinotropic polypeptide (GIP), thereby prolonging their raised levels after meal ingestion. Other developments in GLP-1 receptor agonism include the formation of small orally available agonists and compounds with the potential to pharmaceutically stimulate GLP-1 secretion from the gut. In addition, GLP-1/glucagon and GLP-1/GIP dual receptor agonists and GLP-1/GIP/glucagon triple receptor agonists have shown the potential to reduce blood glucose levels and body weight through their effects on islets and peripheral tissues, improving beta cell function and stimulating energy expenditure. This review summarises developments in gut hormone-based therapies and presents the future outlook for their use in type 2 diabetes and obesity. Graphical Abstract: [Figure not available: see fulltext.].
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| 6. |
- Ukkola, Olavi, et al.
(author)
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Role of ghrelin polymorphisms in obesity based on three different studies.
- 2002
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In: Obesity research. - : Wiley. - 1071-7323. ; 10:8, s. 782-91
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Journal article (peer-reviewed)abstract
- OBJECTIVE: Associations between preproghrelin DNA variants and obesity-related phenotypes were studied in 3004 subjects from the Québec Family Study (QFS), the HERITAGE Family Study (HERITAGE), and the Swedish Obese Subjects (SOS) Study. RESEARCH METHODS AND PROCEDURES: Body mass index (BMI), fat mass (FM) from underwater weighing, and abdominal fat from computerized tomography were measured. The ghrelin polymorphisms were identified by polymerase chain reaction. RESULTS: Arg51Gln QFS subjects (n = 6) had lower ghrelin concentrations (p = 0.007) than Arg51Arg subjects (n = 14). White preproghrelin Met72Met subjects in HERITAGE had the lowest BMI (p = 0.020), and those in the QFS cohort had the lowest FM (p < 0.001). Met72 carrier status (Met72+) was associated with lower FM (p = 0.026) and higher insulin-like growth factor-1 levels (p = 0.019) among blacks. Met72Met QFS subjects had less visceral fat (p = 0.002) and a lower fasting respiratory quotient (p = 0.037). HERITAGE Met72+ white subjects also showed lower exercise respiratory quotient (p = 0.030) and higher maximal oxygen uptake (p = 0.023). Furthermore, the prevalence of Met72+ was higher (19.2%; p < 0.05) in SOS subjects whose BMI was < or =25 kg/m(2) than in those with BMI >25 kg/m(2) (14.8%). SOS Met72+ obese women had a lower (11.4%; p = 0.032) prevalence of hypertension than noncarriers (23.9%). DISCUSSION: Arg51Gln mutation was associated with lower plasma ghrelin levels but not with obesity. The preproghrelin Met72 carrier status seems to be protective against fat accumulation and associated metabolic comorbidities.
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| 7. |
- Zhang, Qian, et al.
(author)
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The glucose-dependent insulinotropic polypeptide (GIP) regulates body weight and food intake via CNS-GIPR signaling
- 2021
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In: Cell Metabolism. - : Elsevier BV. - 1550-4131 .- 1932-7420. ; 33:4, s. 833-844
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Journal article (peer-reviewed)abstract
- Uncertainty exists as to whether the glucose-dependent insulinotropic polypeptide receptor (GIPR) should be activated or inhibited for the treatment of obesity. Gipr was recently demonstrated in hypothalamic feeding centers, but the physiological relevance of CNS Gipr remains unknown. Here we show that HFD-fed CNS-Gipr KO mice and humanized (h)GIPR knockin mice with CNS-hGIPR deletion show decreased body weight and improved glucose metabolism. In DIO mice, acute central and peripheral administration of acyl-GIP increases cFos neuronal activity in hypothalamic feeding centers, and this coincides with decreased body weight and food intake and improved glucose handling. Chronic central and peripheral administration of acyl-GIP lowers body weight and food intake in wild-type mice, but shows blunted/absent efficacy in CNS-Gipr KO mice. Also, the superior metabolic effect of GLP-1/GIP co-agonism relative to GLP-1 is extinguished in CNS-Gipr KO mice. Our data hence establish a key role of CNS Gipr for control of energy metabolism.
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