Regulation of neuronal energy metabolism by calcium: Role of MCU and Aralar/malate-aspartate shuttle

Serum magnesium and calcium were inversely associated with hemoglobin glycation index and triglyceride-glucose index in adults with coronary artery disease

Little is known about the associations of magnesium (Mg) and calcium (Ca) with hemoglobin glycation index (HGI) and triglyceride-glucose index (TyG) in adults. In this study, we examined the associations of serum Mg and Ca with HGI and TyG in adults with coronary artery disease (CAD). This hospital-based cross-sectional study included 10757 CAD patients with a mean age of 61.6 years. Serum concentrations of Mg and Ca were measured in clinical laboratory. Overall, serum Mg and Ca were inversely associated with HGI and TyG. In multivariable analyses, Mg and Ca were inversely associated with HGI (MgQ4 vs. Q3: -0.601 vs. -0.528; CaQ4 vs. Q1: -0.769 vs. -0.645). In terms of TyG, inverse associations of serum Mg and Ca with TyG were observed. The corresponding TyG values were 9.054 (vs. 9.099) for Mg and 9.068 (vs. 9.171) for Ca in the fourth quartile compared with the first quartile. Moreover, Mg, Ca or Mg/Ca ratio were also inversely associated with HbA1c and FBG. In path analysis, no mediating effects of obesity on "serum Mg (or Ca)- HGI (or TyG)" associations were observed. Generally, our study identified the inverse associations of the serum Mg and Ca levels with HGI and TyG in adults with CAD. Large sample longitudinal study, and particularly randomized controlled trials, are warranted to validate our findings and overcome the limitations of cross-sectional studies.

Responses and correlation among ER stress, Ca2+ homeostasis, and fatty acid metabolism in Penaeus vannamei under ammonia stress

The role of endoplasmic reticulum (ER) stress, Ca2+ homeostasis, and fatty acid metabolism in the environmental adaptation of aquatic animals is significant, but further confirmation of the relationship between these factors is needed. This study aimed to investigate the responses and correlations among ER stress, Ca2+ homeostasis, and fatty acid metabolism in Penaeus vannamei under ammonia stress. A total of 640 P. vannamei weighing 3.0 ± 0.4 g were selected and exposed to different total ammonia concentrations (0 mg/L for the control group and 3.80, 7.60, and 11.40 mg/L for the stress groups). The experiment involved a 96 h ammonia stress period to assess indicators related to ER stress, Ca2+ homeostasis, and fatty acid metabolism. The experimental results revealed that after 12 h, exposure to ammonia induced the ER stress response in the hepatopancreas of the shrimp. The groups exposed to concentrations of 3.8 mg/L and 7.6 mg/L exhibited an increase in ER Ca2+ efflux, a decrease in influx, an elevation in mitochondrial Ca2+ influx, an enhanced energy demand within the organism, and substantial consumption of triglycerides. The 11.3 mg/L group exhibited a significant enhancement in fatty acid metabolism. At 24 h, the ER stress response induced by ammonia in the shrimp exhibited a gradual recovery. In the 7.6 mg/L and 11.3 mg/L groups, the ER Ca2+ influx and efflux exhibited significant enhancements, while the mitochondrial Ca2+ influx decreased and the organism's energy demand increased. Moreover, there was a substantial enhancement in fatty acid metabolism. At 48 h, the ER stress response disappeared in each stress group, ER Ca2+ efflux was reduced, triglycerides were consumed, and the body's energy homeostasis was basically restored. At 96 h, a stress response reoccurred in the ER in each stress group, resulting in increased influx of Ca2+ into the ER, augmented energy demand within the organism, and notable enhancement in fatty acid metabolism. Pearson correlation analysis revealed a significant positive correlation between the NH3-N content in the hepatopancreas and the expression of ER stress-related genes, as well as between ER Ca2+ influx/efflux and energy homeostasis/fatty acid metabolism. The findings indicate that the stress induced by ammonia triggers an ER stress response in P. vannamei, resulting in ER Ca2+ efflux and mitochondrial Ca2+ influx, which, in turn, enhances fatty acid metabolism to generate additional energy for adaptation in stressful environments. This study contributes to a deeper understanding of the environmental adaptability of P. vannamei in the context of Ca2+ homeostasis.

Calcium-Dependent Interaction of Nitric Oxide Synthase with Cytochrome c Oxidase: Implications for Brain Bioenergetics

Targeted nitric oxide production is relevant for maintaining cellular energy production, protecting against oxidative stress, regulating cell death, and promoting neuroprotection. This study aimed to characterize the putative interaction of nitric-oxide synthase with mitochondrial proteins. The primary finding of this study is that cytochrome c oxidase (CCO) subunit IV (CCOIV) is associated directly with NOS in brain mitochondria when calcium ions are present. The matrix side of CCOIV binds to the N-terminus of NOS, supported by the abrogation of the binding by antibodies towards the N-terminus of NOS. Evidence supporting the interaction between CCOIV and NOS was provided by the coimmunoprecipitation of NOS from detergent-solubilized whole rat brain mitochondria with antibodies to CCOIV and the coimmunoprecipitation of CCOIV from crude brain NOS preparations using antibodies to NOS. The CCOIV domain that interacts with NOS was identified using a series of overlapping peptides derived from the primary sequence of CCOIV. As calcium ions not only activate NOS, but also facilitate the docking of NOS to CCOIV, this study points to a dynamic mechanism of controlling the bioenergetics by calcium changes, thereby adapting bioenergetics to cellular demands.

Nonlinear relationship between dietary calcium and magnesium intake and peripheral neuropathy in the general population of the United States

Background

Calcium and magnesium are essential minerals that have significant roles in nerve function and regulation. There may be a correlation between dietary calcium and magnesium intake and peripheral neuropathy. However, this relationship remains unclear and requires further study.

Methods

Data from 7,726 participants in the National Health and Nutrition Examination Survey (NHANES) from 1999 to 2004 were analyzed in this study. The relationship between total dietary calcium and magnesium intake, as well as each quantile, and peripheral neuropathy was analyzed using a multifactor logistic regression model. To illustrate the dose-response relationship between calcium and magnesium intake and peripheral neuropathy, we utilized a restricted cubic spline (RCS) plot.

Results

Our analysis found a positive correlation between dietary intake of calcium and magnesium and peripheral neuropathy (calcium: OR 1.000, 95% CI 1.000-1.000; magnesium: OR 1.001, 95% CI 1.00-1.002). Participants in the first and third quantiles of dietary calcium intake had a significantly higher incidence of peripheral neuropathy than those in the second quantile (OR 1.333, 95% CI 1.034-1.719, OR 1.497, 95% CI 1.155-1.941). Those in the first and third quantiles of dietary magnesium intake also had a significantly higher incidence of peripheral neuropathy than those in the second quantile (OR 1.275, 95% CI 1.064-1.528, OR 1.525, 95% CI 1.231-1.890). The restricted cubic spline analysis revealed a U-shaped nonlinear relationship between dietary intake of calcium and magnesium and peripheral neuropathy.

Conclusion

The study found a U-shaped non-linear relationship between dietary calcium and magnesium intake levels and peripheral neuropathy, indicating that both excessive and insufficient intake of calcium and magnesium can increase the incidence of peripheral neuropathy.

The mitochondrial Ca2+ channel MCU is critical for tumor growth by supporting cell cycle progression and proliferation

Introduction: The mitochondrial uniporter (MCU) Ca²⁺ ion channel represents the primary means for Ca²⁺ uptake by mitochondria. Mitochondrial matrix Ca²⁺ plays critical roles in mitochondrial bioenergetics by impinging upon respiration, energy production and flux of biochemical intermediates through the TCA cycle. Inhibition of MCU in oncogenic cell lines results in an energetic crisis and reduced cell proliferation unless media is supplemented with nucleosides, pyruvate or α-KG. Nevertheless, the roles of MCU-mediated Ca²⁺ influx in cancer cells remain unclear, in part because of a lack of genetic models. Methods: MCU was genetically deleted in transformed murine fibroblasts for study in vitro and in vivo. Tumor formation and growth were studied in murine xenograft models. Proliferation, cell invasion, spheroid formation and cell cycle progression were measured in vitro. The effects of MCU deletion on survival and cell-death were determined by probing for live/death markers. Mitochondrial bioenergetics were studied by measuring mitochondrial matrix Ca²⁺ concentration, membrane potential, global dehydrogenase activity, respiration, ROS production and inactivating-phosphorylation of pyruvate dehydrogenase. The effects of MCU rescue on metabolism were examined by tracing of glucose and glutamine utilization for fueling of mitochondrial respiration. Results: Transformation of primary fibroblasts in vitro was associated with increased MCU expression, enhanced MCU-mediated Ca²⁺ uptake, altered mitochondrial matrix Ca²⁺ concentration responses to agonist stimulation, suppression of inactivating-phosphorylation of pyruvate dehydrogenase and a modest increase of mitochondrial respiration. Genetic MCU deletion inhibited growth of HEK293T cells and transformed fibroblasts in mouse xenograft models, associated with reduced proliferation and delayed cell-cycle progression. MCU deletion inhibited cancer stem cell-like spheroid formation and cell invasion in vitro, both predictors of metastatic potential. Surprisingly, mitochondrial matrix [Ca²⁺], membrane potential, global dehydrogenase activity, respiration and ROS production were unaffected. In contrast, MCU deletion elevated glycolysis and glutaminolysis, strongly sensitized cell proliferation to glucose and glutamine limitation, and altered agonist-induced cytoplasmic Ca²⁺ signals. Conclusion: Our results reveal a dependence of tumorigenesis on MCU, mediated by a reliance on MCU for cell metabolism and Ca²⁺ dynamics necessary for cell-cycle progression and cell proliferation.

Lactate shuttling as an allostatic means of thermoregulation in the brain

Lactate, the redox-balanced end product of glycolysis, travels within and between cells to fulfill an array of physiologic functions. While evidence for the centrality of this lactate shuttling in mammalian metabolism continues to mount, its application to physical bioenergetics remains underexplored. Lactate represents a metabolic "cul-de-sac," as it can only re-enter metabolism by first being converted back to pyruvate by lactate dehydrogenase (LDH). Given the differential distribution of lactate producing/consuming tissues during metabolic stresses (e.g., exercise), we hypothesize that lactate shuttling vis-à-vis the exchange of extracellular lactate between tissues serves a thermoregulatory function, i.e., an allostatic strategy to mitigate the consequences of elevated metabolic heat. To explore this idea, the rates of heat and respiratory oxygen consumption in saponin-permeabilized rat cortical brain samples fed lactate or pyruvate were measured. Heat and respiratory oxygen consumption rates, and calorespirometric ratios were lower during lactate vs. pyruvate-linked respiration. These results support the hypothesis of allostatic thermoregulation in the brain with lactate.

The mitochondrial Ca 2+ channel MCU is critical for tumor growth by supporting cell cycle progression and proliferation

The mitochondrial uniporter (MCU) Ca ²⁺ ion channel represents the primary means for Ca ²⁺ uptake into mitochondria. Here we employed in vitro and in vivo models with MCU genetically eliminated to understand how MCU contributes to tumor formation and progression. Transformation of primary fibroblasts in vitro was associated with increased MCU expression, enhanced mitochondrial Ca ²⁺ uptake, suppression of inactivating-phosphorylation of pyruvate dehydrogenase, a modest increase of basal mitochondrial respiration and a significant increase of acute Ca ²⁺ -dependent stimulation of mitochondrial respiration. Inhibition of mitochondrial Ca ²⁺ uptake by genetic deletion of MCU markedly inhibited growth of HEK293T cells and of transformed fibroblasts in mouse xenograft models. Reduced tumor growth was primarily a result of substantially reduced proliferation and fewer mitotic cells in vivo , and slower cell proliferation in vitro associated with delayed progression through S-phase of the cell cycle. MCU deletion inhibited cancer stem cell-like spheroid formation and cell invasion in vitro , both predictors of metastatic potential. Surprisingly, mitochondrial matrix Ca ²⁺ concentration, membrane potential, global dehydrogenase activity, respiration and ROS production were unchanged by genetic deletion of MCU in transformed cells. In contrast, MCU deletion elevated glycolysis and glutaminolysis, strongly sensitized cell proliferation to glucose and glutamine limitation, and altered agonist-induced cytoplasmic Ca ²⁺ signals. Our results reveal a dependence of tumorigenesis on MCU, mediated by a reliance on mitochondrial Ca ²⁺ uptake for cell metabolism and Ca ²⁺ dynamics necessary for cell-cycle progression and cell proliferation.