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Loss-of-function mutations in the histone demethylases KDM5A, KDM5B, or KDM5C are found in intellectual disability (ID) and autism spectrum disorders (ASD) patients. Here, we use the model organism Drosophila melanogaster to delineate how KDM5 contributes to ID and ASD. We show that reducing KDM5 causes intestinal barrier dysfunction and changes in social behavior that correlates with compositional changes in the gut microbiota. Therapeutic alteration of the dysbiotic microbiota through antibiotic administration or feeding with a probiotic Lactobacillus strain partially rescues the behavioral, lifespan, and cellular phenotypes observed in kdm5-deficient flies. Mechanistically, KDM5 was found to transcriptionally regulate component genes of the immune deficiency (IMD) signaling pathway and subsequent maintenance of host-commensal bacteria homeostasis in a demethylase-dependent manner. Together, our study uses a genetic approach to dissect the role of KDM5 in the gut-microbiome-brain axis and suggests that modifying the gut microbiome may provide therapeutic benefits for ID and ASD patients.

Excessive macroautophagy/autophagy leads to pancreatic β-cell failure that contributes to the development of diabetes. Our previous study proved that the occurrence of deleterious hyperactive autophagy attributes to glucolipotoxicity-induced NR3C1 activation. Here, we explored the potential protective effects of (-)-epigallocatechin 3-gallate (EGCG) on β-cell-specific NR3C1 overexpression mice in vivo and NR3C1-enhanced β cells in vitro. We showed that EGCG protects pancreatic β cells against NR3C1 enhancement-induced failure through inhibiting excessive autophagy. RNA demethylase FTO (FTO alpha-ketoglutarate dependent dioxygenase) caused diminished m6A modifications on mRNAs of three pro-oxidant genes (Tlr4, Rela, Src) and, hence, oxidative stress occurs; by contrast, EGCG promotes FTO degradation by the ubiquitin-proteasome system in NR3C1-enhanced β cells, which alleviates oxidative stress, and thereby prevents excessive autophagy. Moreover, FTO overexpression abolishes the beneficial effects of EGCG on β cells against NR3C1 enhancement-induced damage. Collectively, our results demonstrate that EGCG protects pancreatic β cells against NR3C1 enhancement-induced excessive autophagy through suppressing FTO-stimulated oxidative stress, which provides novel insights into the mechanisms for the anti-diabetic effect of EGCG. Abbreviation 3-MA: 3-methyladenine; AAV: adeno-associated virus; Ad: adenovirus; ALD: aldosterone; AUC: area under curve; βNR3C1 mice: pancreatic β-cell-specific NR3C1 overexpression mice; Ctrl: control; CHX: cycloheximide; DEX: dexamethasone; DHE: dihydroethidium; EGCG: (-)-epigallocatechin 3-gallate; FTO: FTO alpha-ketoglutarate dependent dioxygenase; GSIS: glucose-stimulated insulin secretion; HFD: high-fat diet; HG: high glucose; i.p.: intraperitoneal; IOD: immunofluorescence optical density; KSIS: potassium-stimulated insulin secretion; m6A: N6-methyladenosine; MeRIP-seq: methylated RNA immunoprecipitation sequencing; NO: nitric oxide; NR3C1/GR: nuclear receptor subfamily 3, group C, member 1; NR3C1-Enhc.: NR3C1-enhancement; NAC: N-acetylcysteine; NC: negative control; PBS: phosphate-buffered saline; PI: propidium iodide; OCR: oxygen consumption rate; Palm.: palmitate; RELA: v-rel reticuloendotheliosis viral oncogene homolog A (avian); RNA-seq: RNA sequencing; O2.-: superoxide anion; SRC: Rous sarcoma oncogene; ROS: reactive oxygen species; T2D: type 2 diabetes; TEM: transmission electron microscopy; TLR4: toll-like receptor 4; TUNEL: terminal dUTP nick-end labeling; UTR: untranslated region; WT: wild-type. [ABSTRACT FROM AUTHOR]

Pancreatic β-cell dysfunction caused by obesity can be associated with alterations in the levels of miRNAs. However, the role of miRNAs in such processes remains elusive. Here, we show that pancreatic islet miR-27a-5p, which is markedly increased in obese mice and impairs insulin secretion, is mainly delivered by visceral adipocyte–derived extracellular vesicles (EVs). Depleting miR-27a-5p significantly improved insulin secretion and glucose intolerance in db / db mice. Supporting the function of EV miR-27a-5p as a key pathogenic factor, intravenous injection of miR-27a-5p–containing EVs showed their distribution in mouse pancreatic islets. Tracing the injected adeno-associated virus (AAV)-miR-27a-5p (AAV-miR-27a) or AAV-FABP4-miR-27a-5p (AAV-FABP4-miR-27a) in visceral fat resulted in upregulating miR-27a-5p in EVs and serum and elicited mouse pancreatic β-cell dysfunction. Mechanistically, miR-27a-5p directly targeted L-type Ca2+ channel subtype CaV1.2 (Cacna1c) and reduced insulin secretion in β-cells. Overexpressing mouse CaV1.2 largely abolished the insulin secretion injury induced by miR-27a-5p. These findings reveal a causative role of EV miR-27a-5p in visceral adipocyte–mediated pancreatic β-cell dysfunction in obesity-associated type 2 diabetes mellitus. Article Highlights: miR-27a-5p expression in the islets is increased in obesity-associated diabetes mouse models. miR-27a-5p overexpression in β-cells impairs β-cell function in vitro and in vivo. Visceral adipocyte–derived extracellular vesicles and their cargo miR-27a-5p lead to β-cell insulin secretion injury and glucose intolerance by targeting L-type Ca2+ channel subtype CaV1.2. Blockage of visceral adipocyte extracellular vesicle miR-27a-5p expression improves β-cell insulin secretion and glucose tolerance in db / db mice. [ABSTRACT FROM AUTHOR]

Maturation of postnatal β-cells is regulated in a cell-autonomous manner, and metabolically stressed β-cells regress to an immature state, ensuring defective β-cell function and the onset of type 2 diabetes. The molecular mechanisms connecting the nutritional transition to β-cell maturation remain largely unknown. Here, we report a mature form of miRNA (miR-203)/ZBTB20/MAFA regulatory axis that mediates the β-cell maturation process. We show that the level of the mature form of miRNA (miR-203) in β-cells changes during the nutritional transition and that miR-203 inhibits β-cell maturation at the neonatal stage and under high-fat diet conditions. Using single-cell RNA sequencing, we demonstrated that miR-203 elevation promoted the transition of immature β-cells into CgBHi endocrine cells while suppressing gene expressions associated with β-cell maturation in a ZBTB20/MAFA-dependent manner. ZBTB20 is an authentic target of miR-203 and transcriptionally upregulates MAFA expression. Manipulating the miR-203/ZBTB20/MAFA axis may therefore offer a novel strategy for boosting functional β-cell numbers to alleviate diabetes. Article Highlights: Nutritional transition from a high-fat diet to carbohydrate-rich diet inhibits expression of the mature form of miRNA (miR-203). Failure to inhibit miR-203 during high-fat diet feeding causes β-cell immaturity and loss of identity. Ablation of miR-203 in β-cells prevents high-fat diet–induced β-cell dysfunction. The miR-203-ZBTB20-MAFA axis mediates β-cell immaturity and is conserved in humans. [ABSTRACT FROM AUTHOR]

Aim: To assess the expression and function of miR‐483‐5p in diabetic β cells. Methods: The expression of miR‐483‐5p was evaluated in the pancreatic islets of obesity mouse models by quantitative reverse transcription polymerase chain reaction. Dual‐luciferase activity, and western blotting assays, were utilized for miR‐483‐5p target gene verification. Mice with β cell‐specific miR‐483‐5p downregulation were studied under metabolic stress (i.e. a high‐fat diet) condition. Lineage tracing was used to determine β‐cell fate. Results: miR‐483‐5p increased in the islets of obese mouse models. Expression levels of miR‐483‐5p were significantly upregulated with the treatment of high glucose and palmitate, in both MIN6 cells and mouse islets. Overexpression of miR‐483‐5p in β cells results in impaired insulin secretion and β‐cell identity. Cell lineage‐specific analyses revealed that miR‐483‐5p overexpression deactivated β‐cell identity genes (insulin, Pdx1 and MafA) and derepressed β‐cell dedifferentiation (Ngn3) genes. miR‐483‐5p downregulation in β cells of high‐fat diet‐fed mice alleviated diabetes and improved glucose intolerance by enhancing insulin secretory capacity. These detrimental effects of miR‐483‐5p relied on its seed sequence recognition and repressed expression of its target genes Pdx1 and MafA, two crucial markers of β‐cell maturation. Conclusions: These findings indicate that the miR‐483‐5p–mediated reduction of mRNAs specifies β‐cell identity as a contributor to β‐cell dysfunction via the loss of cellular differentiation. [ABSTRACT FROM AUTHOR]

Chronic inflammation promotes pancreatic β-cell decompensation to insulin resistance because of local accumulation of supraphysiologic interleukin 1β (IL-1β) levels. However, the underlying molecular mechanisms remain elusive. We show that miR-503-5p is exclusively upregulated in islets from humans with type 2 diabetes and diabetic rodents because of its promoter hypomethylation and increased local IL-1β levels. β-Cell–specific miR-503 transgenic mice display mild or severe diabetes in a time- and expression-dependent manner. By contrast, deletion of the miR-503 cluster protects mice from high-fat diet–induced insulin resistance and glucose intolerance. Mechanistically, miR-503-5p represses c-Jun N-terminal kinase–interacting protein 2 (JIP2) translation to activate mitogen-activated protein kinase signaling cascades, thus inhibiting glucose-stimulated insulin secretion (GSIS) and compensatory β-cell proliferation. In addition, β-cell miR-503-5p is packaged in nanovesicles to dampen insulin signaling transduction in liver and adipose tissues by targeting insulin receptors. Notably, specifically blocking the miR-503 cluster in β-cells effectively remits aging-associated diabetes through recovery of GSIS capacity and insulin sensitivity. Our findings demonstrate that β-cell miR-503-5p is required for the development of insulin resistance and β-cell decompensation, providing a potential therapeutic target against diabetes. Article Highlights: Promoter hypomethylation during natural aging permits miR-503-5p overexpression in islets under inflammation conditions, conserving from rodents to humans. Impaired β-cells release nanovesicular miR-503-5p to accumulate in liver and adipose tissue, leading to their insulin resistance via the miR-503-5p/insulin receptor/phosphorylated AKT axis. Accumulated miR-503-5p in β-cells impairs glucose-stimulated insulin secretion via the JIP2-coordinated mitogen-activated protein kinase signaling cascades. Specific blockage of β-cell miR-503-5p improves β-cell function and glucose tolerance in aging mice. [ABSTRACT FROM AUTHOR]

Background and Purpose: Dopamine agonists targeting D2 receptor have been used for decades in treating pituitary adenomas. There has been little clear evidence implicating the canonical G protein signalling as the mechanism by which D2 receptor suppresses the growth of pituitary tumours. We hypothesize that β-arrestin2-dependent signalling is the molecular mechanism dictating D2 receptor inhibitory effects on pituitary tumour growth.Experimental Approach: The involvement of G protein and β-arrestin2 in bromocriptine-mediated growth suppression in rat MMQ and GH3 tumour cells was assessed. The anti-growth effect of a β-arrestin2-biased agonist, UNC9994, was tested in cultured cells, tumour-bearing nude mice and primary cultured human pituitary adenomas. The effect of G protein signalling on tumour growth was also analysed by using a G protein-biased agonist, MLS1547, and a Gβγ inhibitor, gallein, in vitro.Key Results: β-arrestin2 signalling but not G protein pathways mediated the suppressive effect of bromocriptine on pituitary tumour growth. UNC9994 inhibited pituitary tumour cell growth in vitro and in vivo. The suppressive function of UNC9994 was obtained by inducing intracellular reactive oxygen species generation through downregulating mitochondrial complex I subunit NDUFA1. The effects of Gαi/o signalling and Gβγ signalling via D2 receptor on pituitary tumour growth were cell-type-dependent.Conclusion and Implications: Given the very low expression of Gαi/o proteins in pituitary tumours and the complexity of the responses of pituitary tumours to G protein signalling pathways, our study reveals D2 receptor β-arrestin2-biased ligand may be a more promising choice to treat pituitary tumours with improved therapeutic selectivity. [ABSTRACT FROM AUTHOR]

The accumulation of mitochondria in thermogenic adipose tissue (i.e., brown and beige fat) increases energy expenditure, which can aid in alleviating obesity and metabolic disorders. However, recent studies have shown that knocking out key proteins required to maintain mitochondrial function inhibits the energy expenditure in thermogenic fat, and yet the knockout mice are unexpectedly protected from developing obesity or metabolic disorders when fed a high-fat diet (HFD). In the present study, non-biased sequencing-based screening revealed the importance of YY1 in the transcription of electron transport chain genes and the enhancement of mitochondrial function in thermogenic adipose tissue. Specifically, adipocyte YY1 null (YAKO) mice showed lower energy expenditure and were intolerant to cold stress. Interestingly, YAKO mice showed alleviation of HFD-induced metabolic disorders, which can be attributed to a suppression of adipose tissue inflammation. Metabolomic analysis revealed that blocking YY1 directed glucose metabolism toward lactate, enhanced the uptake of glutamine, and promoted the production of anti-inflammatory spermidine. Conversely, blocking spermidine production in YAKO mice reversed their resistance to HFD-induced disorders. Thus, although blocking adipocyte YY1 impairs the thermogenesis, it promotes spermidine production and alleviates adipose tissue inflammation, therefore leads to an uncoupling of adipose tissue energy expenditure from HFD-induced metabolic disorders., (© 2024 by the American Diabetes Association.)