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Type 2 diabetes mellitus (T2DM) is a metabolic disease characterized by reduced insulin sensitivity and dysfunction of β-cells. Although the increasing prevalence of diabetes worldwide is largely attributed to genetic predisposition or lifestyle factors (insufficient physical activity), and caloric intake. Environmental factors, exposure to xenobiotics and heavy metals have also been reported to be causative factors of T2DM. At this juncture, we, through our work unveil a plausible link between Pb2+ exposure and diabetes mellitus, and delineated a comprehensive understanding of the potential mechanisms of Pb2+-induced β-cells dysfunction. In our in vivo observations, we found that Pb2+ exposure strongly reduced glucose-stimulated insulin secretion and diminished functional pancreatic β-cell mass. Mechanistically, we found that Pb2+ downregulates intracellular cAMP level via hyper-activating Ca2+/calmodulin-dependent 3′,5′-cyclic nucleotide phosphodiesterase 1C and thereby reduces glucose-stimulated insulin secretion. Further, we report that Pb2+ inhibited mitochondrial adenosine triphosphate production and also identified Pb2+ as a negative regulator of β-cell proliferation via Ca2+/calmodulin-dependent protein kinase kinases-pAMPK-pRaptor axis. Together, our findings strongly reinforce Pb2+ to hijack the physiological role of calcium ions, by mimicking Ca2+ within pancreatic β-cell and thereby stands as a diabetogenic xenobiotic. Graphical Abstract [ABSTRACT FROM AUTHOR]

Dysregulated hepatic de novo lipogenesis contributes to the pathogenesis of nonalcoholic fatty liver disease in both humans and rodents. Clinical evidence suggests fatty liver to have a positive correlation with serum lead (Pb2+) levels. However, an exact mechanism of Pb2+‐induced fatty liver progression is still unknown. Here, we show that exposure to Pb2+ regulates ChREBP‐dependent hepatic lipogenesis. Presence of Pb2+ ions within the hepatocytes reduces transcript and protein levels of sorcin, a cytosolic adaptor partner of ChREBP. Adenovirus‐mediated overexpression of sorcin in Pb2+ exposed hepatocytes and an in vivo mouse model ameliorates liver steatosis and hepatotoxicity. Hereby, we present Pb2+ exposure to be a lethal disruptor of lipid metabolism in hepatocytes and highlight sorcin as a novel therapeutic target against Pb2+‐induced hepatic dyslipidemia. [ABSTRACT FROM AUTHOR]

The anti‐diabetic drug and peroxisome proliferator‐activated receptor‐gamma (PPARγ) agonist, rosiglitazone, alters astrocyte activation; however, its mechanism remains less‐known. We hypothesized participation of epidermal growth factor receptor (EGFR), known to control astrocyte reactivity. We first detected that rosiglitazone promoted glial fibrillary acidic protein (GFAP) expression in primary astrocytes as well as the mouse cerebral cortex, associated with increased EGFR activation. Screening for EGFR ligands revealed a rosiglitazone‐mediated increase of heparin‐binding epidermal growth factor (HB‐EGF) in astrocytes, resulting in HB‐EGF release into culture medium and mouse cerebrospinal fluid too. Treatment with HB‐EGF‐siRNA and EGFR inhibitors showed that the rosiglitazone‐induced HB‐EGF and p‐EFGR were interdependent, which participated in GFAP increase. Interestingly, we observed that rosiglitazone could induce cellular and secreted‐HB‐EGF in neurons also, contributing toward the activated EGFR‐induced GFAP in astrocytes. Probing whether these effects of rosiglitazone were PPARγ‐linked, revealed potential PPARγ‐responsive elements within HB‐EGF gene. Moreover, gel‐shift, site‐directed mutagenesis, chromatin‐immunoprecipitation and luciferase‐reporter assays demonstrated a PPARγ‐dependent HB‐EGF transactivation. Subsequently, we examined effects of rosiglitazone in a high‐fat diet‐fed diabetes mouse model, and supporting observations in the normal cortical cells, identified a rosiglitazone‐induced GFAP, astrocyte and neuronal HB‐EGF and secreted‐HB‐EGF in the cerebral cortex of diabetic mice. Moreover, assessing relevance of increased HB‐EGF and GFAP revealed an anti‐apoptotic role of rosiglitazone in the cerebral cortex, supported by a GFAP‐siRNA as well as HB‐EGF‐siRNA‐mediated increase in cleaved‐caspase 3 and 9 levels in the rosiglitazone‐treated astrocyte–neuron coculture. Overall, our study indicates that rosiglitazone may protect the brain, via a PPARγ‐dependent HB‐EGF/EGFR signaling and increased GFAP. [ABSTRACT FROM AUTHOR]

The astrocyte marker, glial fibrillary acidic protein ( GFAP), has essential functions in the brain, but may trigger astroglial scarring when expressed in excess. Docosahexaenoic acid ( DHA) is an n-3 fatty acid that is protective during brain development. However, the effect of DHA on GFAP levels of developing brain remains unexplored. Here, we detected that treating developing rats with DHA-enriched fish-oil caused dose-dependent GFAP augmentation. We investigated the mechanism promoting GFAP, hypothesizing the participation of fatty acid-binding protein-7 ( FABP7), known to bind DHA. We identified that DHA stimulated FABP7 expression in astrocytes, and FABP7-silencing suppressed DHA-induced GFAP, indicating FABP7-mediated GFAP increase. Further investigation proved FABP7 expression to be phosphatidylinositide 3-kinases ( PI3K)/ AKT and nuclear receptor peroxisome proliferator-activated receptor-gamma ( PPARγ)-dependent. We found that PI3K/ AKT activated PPARγ that triggered FABP7 expression via PPARγ-responsive elements within its gene. Towards identifying FABP7-downstream pathways, we considered our previous report that demonstrated cyclin-dependent kinase-5 ( CDK5)- PPARγ-protein-protein complex to suppress GFAP. We found that the DHA-induced FABP7 underwent protein-protein interaction with PPARγ, which impeded CDK5- PPARγ formation. Hence, it appeared that enhanced FABP7- PPARγ in lieu of CDK5- PPARγ resulted in increased GFAP. PI3K/AKT not only stimulated formation of FABP7- PPARγ protein-protein complex, but also up-regulated a FABP7-independent MAP-kinase-phosphatase-3 pathway that inactivated CDK5 and hence attenuated CDK5- PPARγ. Overall, our data reveal that via the proximal PI3K/ AKT, DHA induces FABP7- PPARγ, through genomic and non-genomic mechanisms, and MAP-kinase-phosphatase-3 that converged at attenuated CDK5- PPARγ and therefore, enhanced GFAP. Accordingly, our study demonstrates a DHA-mediated astroglial hyperactivation, pointing toward a probable injurious role of DHA in brain development. [ABSTRACT FROM AUTHOR]

In Saccharomyces cerevisiae MPS1 is one of the major protein kinase that governs the spindle checkpoint pathway. The S. cerevisiae structural homolog of opportunistic pathogen Candida albicans CaMPS1, is indispensable for the cell viability. The essentiality of Mps1 was confirmed by Homozygote Trisome test. To determine its biological function in this pathogen conditional mutant was generated through regulatable MET3 promoter. Examination of heterozygous and conditional (+Met/Cys) mps1 mutants revealed a mitosis specific arrest phenotype, where mutants showed large buds with undivided nuclei. Flowcytometry analysis revealed abnormal ploidy levels in mps1mutant. In presence of anti-microtubule drug Nocodazole, mps1 mutant showed a dramatic loss of viability suggesting a role of Mps1 in Spindle Assembly Checkpoint (SAC) activation. These mutants were also defective in microtubule organization. Moreover, heterozygous mutant showed defective in-vitro yeast to hyphae morphological transition. Growth defect in heterozygous mutant suggest haploinsufficiency of this gene. qRT PCR analysis showed around 3 fold upregulation of MPS1 in presence of serum. This expression of MPS1 is dependent on Efg1and is independent of other hyphal regulators like Ras1 and Tpk2. Furthermore, mps1 mutants were also sensitive to oxidative stress. Heterozygous mps1 mutant did not undergo morphological transition and showed 5-Fold reduction in colony forming units in response to macrophage. Thus, the vital checkpoint kinase, Mps1 besides cell division also has a role in morphogenesis and oxidative stress tolerance, in this pathogenic fungus. [ABSTRACT FROM AUTHOR]

In Saccharomyces cerevisiae MPS1 is one of the major protein kinase that governs the spindle checkpoint pathway. The S. cerevisiae structural homolog of opportunistic pathogen Candida albicans CaMPS1, is indispensable for the cell viability. The essentiality of Mps1 was confirmed by Homozygote Trisome test. To determine its biological function in this pathogen conditional mutant was generated through regulatable MET3 promoter. Examination of heterozygous and conditional (+Met/Cys) mps1 mutants revealed a mitosis specific arrest phenotype, where mutants showed large buds with undivided nuclei. Flowcytometry analysis revealed abnormal ploidy levels in mps1mutant. In presence of anti-microtubule drug Nocodazole, mps1 mutant showed a dramatic loss of viability suggesting a role of Mps1 in Spindle Assembly Checkpoint (SAC) activation. These mutants were also defective in microtubule organization. Moreover, heterozygous mutant showed defective in-vitro yeast to hyphae morphological transition. Growth defect in heterozygous mutant suggest haploinsufficiency of this gene. qRT PCR analysis showed around 3 fold upregulation of MPS1 in presence of serum. This expression of MPS1 is dependent on Efg1and is independent of other hyphal regulators like Ras1 and Tpk2. Furthermore, mps1 mutants were also sensitive to oxidative stress. Heterozygous mps1 mutant did not undergo morphological transition and showed 5-Fold reduction in colony forming units in response to macrophage. Thus, the vital checkpoint kinase, Mps1 besides cell division also has a role in morphogenesis and oxidative stress tolerance, in this pathogenic fungus. [ABSTRACT FROM AUTHOR]

Type 2 diabetes mellitus (T2DM) is a metabolic disease characterized by reduced insulin sensitivity and dysfunction of β-cells. Although the increasing prevalence of diabetes worldwide is largely attributed to genetic predisposition or lifestyle factors (insufficient physical activity), and caloric intake. Environmental factors, exposure to xenobiotics and heavy metals have also been reported to be causative factors of T2DM. At this juncture, we, through our work unveil a plausible link between Pb 2+ exposure and diabetes mellitus, and delineated a comprehensive understanding of the potential mechanisms of Pb 2+ -induced β-cells dysfunction. In our in vivo observations, we found that Pb 2+ exposure strongly reduced glucose-stimulated insulin secretion and diminished functional pancreatic β-cell mass. Mechanistically, we found that Pb 2+ downregulates intracellular cAMP level via hyper-activating Ca 2+ /calmodulin-dependent 3',5'-cyclic nucleotide phosphodiesterase 1C and thereby reduces glucose-stimulated insulin secretion. Further, we report that Pb 2+ inhibited mitochondrial adenosine triphosphate production and also identified Pb 2+ as a negative regulator of β-cell proliferation via Ca 2+ /calmodulin-dependent protein kinase kinases-pAMPK-pRaptor axis. Together, our findings strongly reinforce Pb 2+ to hijack the physiological role of calcium ions, by mimicking Ca 2+ within pancreatic β-cell and thereby stands as a diabetogenic xenobiotic., (© The Author(s) 2022. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)