Function (Oxford, England)最新文献

Kidneys are central in maintaining acid-base homeostasis by recovering filtered bicarbonate (HCO3-) in the proximal tubule and by secreting H+ in the collecting duct. Here, we demonstrate a critical role of the exchange protein directly activated by cAMP (Epac) signaling, and particularly the Epac2, in governing renal adaptation to dietary acid load. RNAseq analysis of the renal cortical area revealed that Epac1&2 deficiency was associated with changes in gene profile seen in acidosis. Renal expression of Epac2 but not Epac1 was enhanced by acid load. Epac2-/- mice developed a pronounced metabolic acidosis due to the inability to acidify urine in response to dietary acid load. Deletion of Epac2 and Epac1 exerted additive inhibitory actions on expression of the Na+/H+ exchanger (NHE-3, Slc9a3) in the proximal tubule. Using super-resolution STED microscopy, we detected NHE-3 redistribution to the base of the brush border, which led to the impaired recovery after acidification in freshly isolated split-opened proximal tubules from Epac1&2-/- mice. Deletion of Epac2 but not Epac1 diminished H+ secretion in freshly isolated split-opened collecting ducts, compromised apical translocation of V-ATPase, and reduced anion exchanger 1 (AE1, Slc4a1) expression in the A-type intercalated cells, and caused lower levels of titratable acids in urine, whereas ammoniagenesis was not compromised. Overall, we demonstrate a previously unrecognized role of Epac signaling in renal adaptation to dietary acidification. While both Epac1 and Epac2 isoforms control NHE-3-dependent H+ secretion in the proximal tubule, only Epac2 is essential to augment H+ transport in the collecting duct to acidify urine.

Our bone health as an adult is defined by patterns of development in early life, with perturbed growth during fetal and neonatal periods predisposing individuals to poor bone health in adulthood. Studies have identified poor maternal diet during pregnancy as a critical factor in shaping offspring bone development, with significant impacts on adult bone structure and health. However, the association between a father's diet and the bone health of his offspring remains poorly defined. To address this knowledge gap, we fed male C57BL/6 mice either a control normal protein diet (NPD; 18% protein) or an isocaloric low-protein diet (LPD; 9% protein) for a minimum of 8 wk. Using these males, we generated offspring through artificial insemination, in combination with vasectomized male mating. Using this approach, we derived offspring from either NPD or LPD sperm but in the presence of NPD or LPD seminal plasma. Using micro-computed tomography and synchrotron X-ray diffraction, we observed significant changes in offspring femur morphology and hydroxyapatite crystallographic parameters from just 3 wk of age in offspring derived from LPD sperm or seminal plasma. We also observed that differential femur morphology and hydroxyapatite crystallographic parameters were maintained into adulthood and into a second generation. Analysis of paternal sperm identified a down regulation of 26 osteogenic genes associated with extracellular matrix levels and maintenance, transcription and growth factors, and bone ossification. These observations indicate that poor paternal diet at the time of conception affects offspring bone development and morphology in an age and generation specific manner.

The extent of walking impairment varies among individuals with peripheral artery disease (PAD), which may reflect differences in the adaptability of lower extremity muscles to ischemia-reperfusion injury characteristic of the disease. Analyses of gastrocnemius muscle biopsies from 113 individuals with PAD [mean ankle-brachial index (ABI) = 0.65 ± 0.13, 38 (33.6%) women, 76 (67.2%) Black] showed a wide range of myofiber type distributions (9.6%-82.6% type 1 myofibers). The abundance of oxidative type 1 myofibers negatively correlated with ABI (r = -0.22, P = 0.02), a measure of PAD severity. The abundance of type 1 myofibers also negatively correlated to 2a/x myofiber abundance (r = -0.76, P < 0.001). Eighty % of participants had NCAM+ myofibers, a potential indicator of myofiber denervation. Overall, 3.2% of total myofibers were NCAM+. Of 113 muscle biopsies, 86 (76.1%) contained type 1 myofibers with regions lacking intermyofibrillar mitochondria (IMFM-), which may represent formation of target myofibers. In type 1 myofiber IMFM- areas, 77.8% contained 2x myosin heavy chain and/or the autophagy marker LC3. Electron microscopy within one muscle with IMFM- myofibers confirmed sarcomere disruption in IMFM- regions. These analyses support the possibility of type 2 myofibers transitioning to type 1 in PAD and suggest IMFM- target fibers may represent visualization of this process for the first time. Because type 1 myofibers are more resistant to oxidative damage, results suggest the possibility that a higher proportion of type 1 myofibers in PAD with increasing disease severity may be a compensatory mechanism to maintain muscle.

Sexual dimorphism profoundly influences physiology, disease susceptibility, and therapeutic responses, yet its effects on kidney mitochondrial function remain unclear. We hypothesized that sex differences in kidney mitochondrial function would parallel those in other organs, with females exhibiting greater oxidative capacity and lower oxidative stress. To test this, we measured oxidative phosphorylation (OXPHOS) kinetics and hydrogen peroxide (H2O2) emission in cortical and outer medullary (OM) mitochondria isolated from young male and female Dahl salt-sensitive (SS) rats maintained on a low-salt diet. Unexpectedly, male cortical mitochondria showed significantly higher O2 consumption during ATP synthesis (OXPHOS) than females when fueled by either complex I- or complex II-linked substrates. Cortical H2O2 emission was also greater in males, under both forward and reverse electron transport fueled by succinate. This was accompanied by increased Complex IV protein abundance without changes in mitochondrial DNA copy number or dynamics markers. In the OM, both mitochondrial respiration and H2O2 emission exceeded cortical levels, but showed no sex differences. Analysis of kidney transporter protein abundance revealed a sex-specific "downstream shift" in nephron transport, with males exhibiting greater proximal tubule (PT) sodium reabsorption potential and reduced distal transport capacity. Elevated cortical OXPHOS activity in males likely supports these higher PT energy demands. Thus, sex differences in renal mitochondrial function diverge from other organs, reflecting kidney-specific energetic priorities that override systemic maternal inheritance and sex hormone influences. Enhanced cortical H2O2 emission in males may underlie their heightened susceptibility to kidney injury and salt sensitivity.

Chronic pain is a multifactorial condition often accompanied by comorbidities such as anxiety, depression, and cardiovascular dysfunction. Traditional injury-based models have provided valuable mechanistic insights but are limited in their ability to capture the spontaneous, polygenic, and systemic nature of human chronic pain. Inherited pain models, such as consomic rat strains, transgenic mice, and recombinant inbred panels, offer a unique advantage towards bridging this translational gap: they enable the study of pain-related mechanisms in the absence of experimental injury, reducing confounding effects and better reflecting clinical complexity. These models serve as powerful platforms to investigate neuroimmune signaling, oxidative stress, and epigenetic regulation, and to explore how these pathways interact with sex, stress, and systemic comorbidities. Importantly, while referred to as "inherited pain models," these systems are not designed to model pain transmission across generations, but rather to uncover genetically driven susceptibility to pain and its mechanistic basis. Many of the mechanisms identified in these models overlap with findings from human genome-wide association studies, reinforcing their translational relevance. Beyond mechanistic discovery, inherited pain models can be used for the identification of biomarkers, the study of gene-environment interactions, and the development of mechanism-based therapies. Integration with multi-omics technologies and patient-derived systems further enhance their utility. This review highlights how these models are reshaping the field by enabling biologically informed approaches to diagnosis, prevention, and treatment, thus laying the foundations for a more precise and proactive era in pain medicine.

Randomization is a key component to scientific inquiry as it facilitates unbiased estimation of treatment effects via balancing of measured and unmeasured prognostic variables across treatment groups. Recent reports have noted that randomization is lacking in animal studies, threatening internal validity. Animal studies often involve rodents (mice or rats) sent in small batches to laboratories or bred on site in litters. Randomizing half of each batch to treatment and half to control (simple randomization) is a viable strategy to implementing randomization in animal studies, however experimenters may be concerned about chance imbalances, given the smaller sample sizes utilized in animal studies, in key prognostic variables, eg, baseline weight. Constrained randomization, wherein key prognostic factors are balanced within each batch, may offer benefits over simple randomization, especially if it were sequential, ie, could take balance of previous batches into account when randomly assigning treatment in current batch. Adjusting for prognostic variables in a statistical model is a way to address imbalances, independent of choice of randomization scheme. In simulations designed to mimic realistic scenarios, all methods of randomization tested led to unbiased treatment effect estimation, with model adjustment reducing standard errors and improving statistical power in all scenarios. Treatment effects in unadjusted and adjusted models were nearly an order of magnitude closer to each other in sequentially constrained randomization compared to simple randomization, yielding more robust findings.

Venous diseases commonly involve venous wall and/or valve dysfunction. Chronic venous dilation, a characteristic of varicose veins, can progress to the point where venous valve (VV) leaflets are pulled sufficiently apart that they no longer prevent back flow. Incompetent VVs increase the load on more distal valves by increasing the standing column of proximal blood. We tested VV function by isolating single valves from cervical veins of the mouse and measuring back leak and the adverse pressure gradient required for closure. Valve identification was facilitated by genetically forced expression of GFP in VV endothelium. A causal relationship was found between the relative diameter of the vein and VV closure, with a striking effect of venous tone: ∼60% of mature VVs in the cervical vein were incapable of closing if the vessel lost spontaneous tone and, in another ∼20% of veins, VVs closed only when venous tone exceeded some threshold value. Our results have important implications for the causes and possible treatment of VV incompetence in pathological states such as venous varicosity and chronic venous insufficiency. Moreover, they suggest an underappreciated mechanism whereby loss of venous tone can initiate a feed-forward cycle of events that make valve closure increasingly difficult, thereby elevating local venous pressure and exacerbating the loss of tone. This detrimental cycle may potentially be interrupted by appropriate pharmacological therapy to enhance venous tone and thereby restore VV competence.

Highly K+-selective potassium channels are essential for electrical signaling. The high selectivity of most K+ channels, with relative K+: Na+ permeabilities being as high as 100-1000:1 arises from the conserved so-called K+ channel selectivity filter (SF). Structural and computational studies have shown how the SF forms multiple sites that coordinate K+, by mimicking the water dipoles that coordinate K+ ions in solution, and thermodynamically favoring the binding of K+ over Na+. Selective conduction of K+ ions then results from a "knock-on" mechanism, whereby entering ions destabilize the next ion in the file. This review highlights key biophysical and biochemical research that provides insights to the atomic details of these processes. It then discusses how mutations that alter K+ selectivity and permeation in different K+ channels underlie multiple simple and complex diseases, illustrating how selectivity and permeation are central to physiology and to pathophysiology and important for physiologists to be aware of.

Metabolic dysfunction-associated steatotic liver disease and alcohol-associated liver disease frequently co-occur, manifesting as MetALD. Understanding the hepatocyte-specific effects of alcohol and metabolic stressors is critical to uncovering mechanisms of synergistic injury. This study evaluated the individual and combined effects of ethanol, sugars, and saturated/monounsaturated fats on hepatocyte lipid metabolism, oxidative stress, and mitochondrial function using a 3D human HepaRG spheroid model. HepaRG spheroids were treated with ethanol (50 mm), sugar (glucose and fructose), and fatty acids alone or in combination for 10 d. The combination of ethanol (E) and metabolic (sugar and fat, SF) stressors (ESF) synergistically increased triglyceride content and lipid droplet accumulation. ESF increased gene expression of lipid handling targets including perilipins 1 and 2, fatty acid binding protein 1, and hepatic lipase compared to controls. ESF also induced the highest rate of ROS production compared to E and SF and dysregulated antioxidant gene expression. E and SF additively impaired ATP content and ATP production linked mitochondrial respiration. Ethanol and metabolic stressors synergize to dysregulate hepatocyte lipid homeostasis and oxidative stress while additively impairing mitochondrial bioenergetics. Gene expression results suggest that lipid accumulation may be driven by altered expression of triglyceride storage and lipid handling markers rather than de novo lipogenesis. These findings highlight the importance of metabolic contributions in alcohol-induced hepatocellular dysfunction and establish HepaRG spheroids as a robust model to elucidate hepatocyte-specific responses in MetALD.