Metabolism alteration in follicular niche: The nexus among intermediary metabolism,mitochondrial function,and classic polycystic ovary syndrome

Classic polycystic ovary syndrome (PCOS) is a high-risk phenotype accompanied by increased risks of reproductive and metabolic abnormalities; however, the local metabolism characteristics of the ovaries and their effects on germ cell development are unclear. The present study used targeted metabolomics to detect alterations in the intermediate metabolites of follicular fluid from classic PCOS patients, and the results indicated that hyperandrogenism but not obesity induced the changed intermediate metabolites in classic PCOS patients. Regarding the direct contact, we identified mitochondrial function, redox potential, and oxidative stress in cumulus cells which were necessary to support oocyte growth before fertilization, and suggested dysfunction of mitochondria, imbalanced redox potential, and increased oxidative stress in cumulus cells of classic PCOS patients. Follicular fluid intermediary metabolic profiles provide signatures of classic PCOS ovary local metabolism and establish a close link with mitochondria dysfunction of cumulus cells, highlighting the role of metabolic signal and mitochondrial cross talk involved in the pathogenesis of classic PCOS.     

Direct anabolic metabolism of three-carbon propionate to a six-carbon metabolite occurs in vivo across tissues and species

Anabolic metabolism of carbon in mammals is mediated via the one- and two-carbon carriers S-adenosyl methionine and acetyl-coenzyme A. In contrast, anabolic metabolism of three-carbon units via propionate has not been shown to extensively occur. Mammals are primarily thought to oxidize the three-carbon short chain fatty acid propionate by shunting propionyl-CoA to succinyl-CoA for entry into the TCA cycle. Here, we found that this may not be absolute as, in mammals, one nonoxidative fate of propionyl-CoA is to condense to two three-carbon units into a six-carbon trans-2-methyl-2-pentenoyl-CoA (2M2PE-CoA). We confirmed this reaction pathway using purified protein extracts provided limited substrates and verified the product via LC-MS using a synthetic standard. In whole-body in vivo stable isotope tracing following infusion of ¹³C-labeled valine at steady state, 2M2PE-CoA was found to form via propionyl-CoA in multiple murine tissues, including heart, kidney, and to a lesser degree, in brown adipose tissue, liver, and tibialis anterior muscle. Using ex vivo isotope tracing, we found that 2M2PE-CoA also formed in human myocardial tissue incubated with propionate to a limited extent. While the complete enzymology of this pathway remains to be elucidated, these results confirm the in vivo existence of at least one anabolic three- to six-carbon reaction conserved in humans and mice that utilizes propionate.     

Light-dependence of the metabolic balance of a highly productive Philippine seagrass community

Seagrass meadows are important primary producers in SE-Asia coastal areas that are increasingly threatened by human activities resulting in a deterioration of the underwater light environment. The resilience of seagrass meadows to decreasing light availability should be approached in an integrative manner, because they shelter complex communities of primary and secondary producers. The aim of this study was to measure the in situ metabolism of a seagrass community under different levels of light availability following changes in the water column dissolved oxygen (DO) and dissolved inorganic carbon (DIC), the sediment redox potential and seagrass production. Net community production (NCP) and respiration were measured along two diel cycles to produce a balance of NCP under different light treatments. On a daily basis, at full irradiance, the community metabolism presented a net production which was close to zero, with values of −7.75 to 16.6 mmol O₂ m⁻² day⁻¹ for DO, and −56.8 to 22.7 mmol C m⁻² day⁻¹ for DIC in the first and second incubation runs, respectively. Compensation irradiance for the NCP was thus found to be close to 80% of the present light availability. Shading resulted in a general decrease in the sediment redox potential, while the initial redox potential had not recovered 6 days after exposure to full sunlight. This community appears to be in a fragile equilibrium with the environment, and any minor decrease in the water transparency would lead to a shift from an autotrophic to a heterotrophic system.     

Phenotypic flexibility in the energetic strategy of the greater white-toothed shrew,Crocidura russula

The balance between energetic acquisition and expenditure depends on the amount of energy allocated to biological functions such as thermoregulation, growth, reproduction and behavior. Ambient temperature has a profound effect on this balance, with species inhabiting colder climates often needing to invest more energy in thermoregulation to maintain body temperature. This leads to local behavioral and physiological adaptations that increase energetic efficiency. In this study, we investigated the role of activity, behavior and thermogenic capacity in the ability of the greater white-toothed shrew, Crocidura russula, to cope with seasonal changes. Individuals were captured in the Sintra-Cascais Natural Park, a Mediterranean region, and separated into three experimental groups: a control group, acclimated to a 12L:12D photoperiod and temperature of 18–20 °C; a winter group, acclimatized to natural winter fluctuations of light and temperature; and a summer group, acclimatized to natural summer fluctuations of light and temperature. No differences were found in resting metabolic rate and nonshivering thermogenesis between the three groups. However, winter shrews significantly reduced their activity, particularly at night, compared to the control and summer groups. Differences in torpor use were also found between groups, with winter shrews entering torpor more frequently and during shorter periods of time than summer and control shrews. Our results indicate C. russula from Sintra relies on the flexibility of energy saving mechanisms, namely daily activity level and torpor use, to cope with seasonal changes in a Mediterranean climate, rather than mechanisms involving body heat production.     

ZRT/IRT-like Protein 14 (ZIP14) Promotes the Cellular Assimilation of Iron from Transferrin

ZIP14 is a transmembrane metal ion transporter that is abundantly expressed in the liver, heart, and pancreas. Previous studies of HEK 293 cells and the hepatocyte cell lines AML12 and HepG2 established that ZIP14 mediates the uptake of non-transferrin-bound iron, a form of iron that appears in the plasma during pathologic iron overload. In this study we investigated the role of ZIP14 in the cellular assimilation of iron from transferrin, the circulating plasma protein that normally delivers iron to cells by receptor-mediated endocytosis. We also determined the subcellular localization of ZIP14 in HepG2 cells. We found that overexpression of ZIP14 in HEK 293T cells increased the assimilation of iron from transferrin without increasing levels of transferrin receptor 1 or the uptake of transferrin. To allow for highly specific and sensitive detection of endogenous ZIP14 in HepG2 cells, we used a targeted knock-in approach to generate a cell line expressing a FLAG-tagged ZIP14 allele. Confocal microscopic analysis of these cells detected ZIP14 at the plasma membrane and in endosomes containing internalized transferrin. HepG2 cells in which endogenous ZIP14 was suppressed by siRNA assimilated 50% less iron from transferrin compared with controls. The uptake of transferrin, however, was unaffected. We also found that ZIP14 can mediate the transport of iron at pH 6.5, the pH at which iron dissociates from transferrin within the endosome. These results suggest that endosomal ZIP14 participates in the cellular assimilation of iron from transferrin, thus identifying a potentially new role for ZIP14 in iron metabolism.     

Structural Enzymology of Cellvibrio japonicus Agd31B Protein Reveals α-Transglucosylase Activity in Glycoside Hydrolase Family 31

The metabolism of the storage polysaccharides glycogen and starch is of vital importance to organisms from all domains of life. In bacteria, utilization of these α-glucans requires the concerted action of a variety of enzymes, including glycoside hydrolases, glycoside phosphorylases, and transglycosylases. In particular, transglycosylases from glycoside hydrolase family 13 (GH13) and GH77 play well established roles in α-glucan side chain (de)branching, regulation of oligo- and polysaccharide chain length, and formation of cyclic dextrans. Here, we present the biochemical and tertiary structural characterization of a new type of bacterial 1,4-α-glucan 4-α-glucosyltransferase from GH31. Distinct from 1,4-α-glucan 6-α-glucosyltransferases (EC 2.4.1.24) and 4-α-glucanotransferases (EC 2.4.1.25), this enzyme strictly transferred one glucosyl residue from α(1→4)-glucans in disproportionation reactions. Substrate hydrolysis was undetectable for a series of malto-oligosaccharides except maltose for which transglycosylation nonetheless dominated across a range of substrate concentrations. Crystallographic analysis of the enzyme in free, acarbose-complexed, and trapped 5-fluoro-β-glucosyl-enzyme intermediate forms revealed extended substrate interactions across one negative and up to three positive subsites, thus providing structural rationalization for the unique, single monosaccharide transferase activity of the enzyme.     

The Effect of Leaf Age on Gas Exchange and Malate Accumulation in C3-CAM Plant Marrubium Frivaldszkyanum (Lamiaceae)

For the first time the expression of C₃ and CAM in the leaves of different age of Marrubium frivaldszkyanum Boiss, is reported. With increasing leaf age a typical C₃ photosynthesis pattern and high transpiration rate were found. In older leaves a shift to CAM occurred and the 24-h transpiration water loss decreased. A correlation was established between leaf area and accumulation of malate. Water loss at early stages of leaf expansion may be connected with the shift to CAM and the water economy of the whole plant.     

Increased demand for NAD+ relative to ATP drives aerobic glycolysis

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