dos Santos, T. G. | bioRxiv Science

bioRxiv2022

Adiponectin Promotes Glucose-Sensitive Insulin Secretion and Prevents β-Cell Damage by Obesity

Obesity significantly decreases life expectancy and increases the incidence of age-related dysfunctions, including {beta}-cell dysregulation leading to inadequate insulin secretion. Here, we show that diluted plasma from obese human donors acutely impairs {beta}-cell integrity and insulin secretion relative to plasma from lean subjects. Similar results were observed with diluted sera from obese rats fed ad libitum, when compared to sera from lean, calorically-restricted, animals. The damaging effects of obese circulating factors on {beta}-cells occurs in the absence of nutrient overload, and mechanistically involves mitochondrial dysfunction, limiting glucose-supported oxidative phosphorylation and ATP production. We demonstrate that increased levels of adiponectin, as found in lean plasma, are the protective characteristic preserving {beta}-cell function; indeed, sera from adiponectin knockout mice limits {beta}-cell metabolic fluxes relative to controls. Furthermore, oxidative phosphorylation and glucose-sensitive insulin secretion, which are completely abrogated in the absence of this hormone, are restored by the presence of adiponectin alone, surprisingly even in the absence of other serological components, for both the insulin-secreting INS1 cell line and primary islets. The addition of adiponectin to cells treated with plasma from obese donors completely restored {beta}-cell functional integrity, indicating the lack of this hormone was causative of the dysfunction. Overall, our results demonstrate that low circulating adiponectin is a key damaging element for {beta}-cells, and suggest strong therapeutic potential for the modulation of the adiponectin signaling pathway in the prevention of age-related {beta}-cell dysfunction. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=154 SRC="FIGDIR/small/501128v3_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@1df5041org.highwire.dtl.DTLVardef@e066borg.highwire.dtl.DTLVardef@c79132org.highwire.dtl.DTLVardef@d89d1_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract: Incubation of -cells with sera or plasma from obese rats and humans hampers mitochondrial oxidative phosphorylation and glucose-stimulated insulin secretion (GSIS) relative to sera and plasma from lean rats and humans. Adiponectin, found at elevated levels in lean subjects, supports -cell function on its own, in the absence of sera, and also reverses the effects of obese plasma. Prepared using Biorender.com. C_FIG

biochemistry↗

bioRxiv2020

What and When Local Predictors Drive Tadpole Diversity in Subtropical Temporary Ponds?

We evaluated seasonal variation in taxonomic, functional and phylogenetic diversity and redundancy of tadpoles in 401 points of 10 ponds in southern Brazil. We predicted i) congruent patterns between all components of diversity and environmental descriptors; ii) stronger effects of environment in the diversity components in seasons when the water level in ponds is low; iii) diversity components to be influenced by distinct sets of environmental factors in different periods. Predictions were tested using Linear Mixed Models. We observed positive influence of water depth on taxonomic, functional and phylogenetic diversity, as well as on functional redundancy during periods when the water level in ponds is high. Phylogenetic redundancy was not explained by any of the selected environmental variables. When the water level in ponds is low none of the environmental descriptors affects any of the diversity components. Environmental filtering seems to strongly influence tadpole community structure in temporary ponds, at least in periods when water depth gradients create a variety of micro-habitats allowing diverse sets of species to settle and co-occur. These species sets are then filtered according to their swimming and foraging abilities along the depth gradient, where intermediate depths should contain the greatest tadpole diversity.

ecology↗