Chronically Elevated Exogenous Glucose Elicits Antipodal Effects on the Proteome Signature of Differentiating Human iPSC-Derived Pancreatic Progenitors

The past decade revealed that cell identity changes, such as dedifferentiation or transdifferentiation, accompany the insulin-producing β-cell decay in most diabetes conditions. Mapping and controlling the mechanisms governing these processes is, thus, extremely valuable for managing the disease progression. Extracellular glucose is known to influence cell identity by impacting the redox balance. Here, we use global proteomics and pathway analysis to map the response of differentiating human pancreatic progenitors to chronically increased in vitro glucose levels. We show that exogenous high glucose levels impact different protein subsets in a concentration-dependent manner. In contrast, regardless of concentration, glucose elicits an antipodal effect on the proteome landscape, inducing both beneficial and detrimental changes in regard to achieving the desired islet cell fingerprint. Furthermore, we identified that only a subgroup of these effects and pathways are regulated by changes in redox balance. Our study highlights a complex effect of exogenous glucose on differentiating pancreas progenitors characterized by a distinct proteome signature.

PCC 7338 Culture in the Presence of Exogenous Glucose

Synechocystis strains are cyanobacteria that can produce useful biomaterials for biofuel and pharmaceutical resources. In this study, the effects of exogenous glucose (5-mM) on cell growth, photosynthetic pigments, metabolites, and lipids in Synechocystis sp. PCC 7338 (referred to as Synechocystis 7338) were investigated. Exogenous glucose increased cell growth on days 9 and 18. The highest production (mg/L) of chlorophyll a (34.66), phycocyanin (84.94), allophycocyanin (34.28), and phycoerythrin (6.90) was observed on day 18 in Synechocystis 7338 culture under 5-mM glucose. Alterations in metabolic and lipidomic profiles under 5-mM glucose were investigated using gas chromatography-mass spectrometry (MS) and nanoelectrospray ionization-MS. The highest production (relative intensity/L) of aspartic acid, glutamic acid, glycerol-3-phosphate, linolenic acid, monogalactosyldiacylglycerol (MGDG) 16:0/18:1, MGDG 16:0/20:2, MGDG 18:1/18:2, neophytadiene, oleic acid, phosphatidylglycerol (PG) 16:0/16:0, and PG 16:0/17:2 was achieved on day 9. The highest production of pyroglutamic acid and sucrose was observed on day 18. We suggest that the addition of exogenous glucose to Synechocystis 7338 culture could be an efficient strategy for improving growth of cells and production of photosynthetic pigments, metabolites, and intact lipid species for industrial applications.

[Effects of exogenous glucose on growth and root nitrogen metabolism in Malus baccata]

To examine the effects of external glucose on growth, root architecture and nitrogen metabolism of Malus baccata seedlings in low carbon soil condition, Malus baccata seedlings were grown in sandy soil with the concentration of soil organic matter being 0.65%. The experiment consisted of three treatments: Control, with 2 g·kg^-1 glucose that equal to the ambient microbial biomass carbon (MBC), and with 10 g·kg^-1 glucose that was five times higher than the ambient MBC. The plant height, biomass, total root length and superficial area of the five times MBC group were 12.3%, 26.4%, 23.2% and 14.6% higher than that of the control, respectively. Root diameter, root volume and average diameter exhibited no significant difference under glucose treatments. The root activity was significantly increased under equal and five times MBC-glucose treatments, and reached its peak at 3 d and 15 d, about 119.1% and 75.7% higher than the control, respectively. Exogenous glucose addition significantly enhanced the concentrations of NO₃^-, NO₂^- and NH₄⁺ in roots. The activities of nitrate reductase, glutamine synthetase, glutamate dehydrogenase, glutamate synthase, glutamic-oxalacetic transaminase and glutamic-pyruvic transaminase were substantially increased in the roots, especially under five times MBC treatment. Five times higher than the ambient MBC of external carbon source promoted biomass accumulation, root growth, morphogenesis and N absorption of plants in low carbon sandy soil.