Saturated fatty acids like palmitate contribute to muscle atrophy in a number of conditions (e.g., type II diabetes) by altering insulin signaling. Akt is a key modulator of protein balance that inhibits the FoxO transcription factors (e.g., FoxO3) which selectively induce the expression of atrophy-inducing genes (atrogenes) in the ubiquitin-proteasome and autophagy-lysosome systems. Conversely, omega-3 polyunsaturated fatty acids have beneficial effects on insulin signaling and may preserve muscle mass. In an earlier report, the omega-3 fatty acid docosahexaenoic acid (DHA) protected myotubes from palmitate-induced atrophy; the mechanisms underlying the alterations in protein metabolism were not identified. This study investigated whether DHA prevents a palmitate-induced increase in proteolysis by restoring Akt/FoxO signaling. Palmitate increased the rate of protein degradation, while cotreatment with DHA prevented the response. Palmitate reduced the activation state of Akt and increased nuclear FoxO3 protein while decreasing its cytosolic level. Palmitate also increased the messenger RNAs (mRNAs) of two FoxO3 atrogene targets, the E3 ubiquitin ligase atrogin-1/MAFbx and the autophagy mediator Bnip3. DHA attenuated the effects of palmitate on Akt activation, FoxO3 localization and atrogene mRNAs. DHA, alone or in combination with palmitate and decreased the ratio of LC3B-II:LC3B-I protein as well as the rate of autophagosome formation, as indicated by reduced LC3B-II protein in the presence of 10 mmol/L methylamine, suggesting an independent effect of DHA on the macroautophagy pathway. These data indicate that palmitate induces myotube atrophy, at least in part, by activating multiple proteolytic systems and that DHA counters the catabolic effects of palmitate by restoring Akt/FoxO signaling.
BACKGROUND: Matrix Gla protein is a vitamin K-dependent inhibitor of vascular calcification. Warfarin use is associated with increased breast arterial calcification, but whether this is reflective of other arteries or occurs in men is unclear. In this study, the prevalence of calcification in peripheral arteries was compared in patients with and without warfarin therapy.
METHODS AND RESULTS: This retrospective matched cohort study assessed 430 patients with radiographs performed during or after warfarin therapy who were identified by a computerized search of medical records. Each patient was matched to a patient without warfarin exposure based on age, sex, and diabetes status. Patients with warfarin exposure <1 month, history of end-stage renal disease, or serum creatinine >2.0 mg/dl were excluded. Radiographs were reviewed visually for arterial calcification. The prevalence of arterial calcification was 44% greater in patients with versus without warfarin use (30.2% versus 20.9%, P=0.0023) but not on radiographs performed before warfarin therapy (26.4% versus 22.4%, n=156) or prior to 5 years of warfarin therapy. The increase was noted only in the ankle and foot, was limited to a medial pattern of calcification, and was similar in men and women.
CONCLUSIONS: Warfarin use is associated with lower extremity arterial calcification in both men and women independent of age, sex, diabetes status, and other patient characteristics. This may have implications for the choice of therapies for long-term anticoagulation.
by
Kento Kitada;
Steffen Daub;
Yahua Zhang;
Janet Klein;
Daisuke Nakano;
Tetyana Pedchenko;
Louise Lantier;
Lauren M. LaRocque;
Adriana Marton;
Patrick Neubert;
Agnes Schroeder;
Natalia Rakova;
Jonathan Jantsch;
Anna E. Dikalova;
Sergey I. Dikalov;
David Harrison;
Dominik N. Mueller;
Akira Nishiyama;
Manfred Rauh;
Raymond C. Harris;
Friedrich C. Luft;
David H. Wassermann;
Jeff Sands;
Jens Titze
Natriuretic regulation of extracellular fluid volume homeostasis includes suppression of the renin-angiotensin-aldosterone system, pressure natriuresis, and reduced renal nerve activity, actions that concomitantly increase urinary Na+ excretion and lead to increased urine volume. The resulting natriuresis-driven diuretic water loss is assumed to control the extracellular volume. Here, we have demonstrated that urine concentration, and therefore regulation of water conservation, is an important control system for urine formation and extracellular volume homeostasis in mice and humans across various levels of salt intake. We observed that the renal concentration mechanism couples natriuresis with correspondent renal water reabsorption, limits natriuretic osmotic diuresis, and results in concurrent extracellular volume conservation and concentration of salt excreted into urine. This water-conserving mechanism of dietary salt excretion relies on urea transporter-driven urea recycling by the kidneys and on urea production by liver and skeletal muscle. The energy-intense nature of hepatic and extrahepatic urea osmolyte production for renal water conservation requires reprioritization of energy and substrate metabolism in liver and skeletal muscle, resulting in hepatic ketogenesis and glucocorticoid-driven muscle catabolism, which are prevented by increasing food intake. This natriuretic-ureotelic, water-conserving principle relies on metabolism-driven extracellular volume control and is regulated by concerted liver, muscle, and renal actions.
Chaperone-mediated autophagy (CMA) is a lysosomal proteolytic pathway in which cytosolic substrate proteins contain specific chaperone recognition sequences required for degradation and are translocated directly across the lysosomal membrane for destruction. CMA proteolytic activity has a reciprocal relationship with macroautophagy: CMA is most active in cells in which macroautophagy is least active. Normal renal proximal tubular cells have low levels of macroautophagy, but high basal levels of CMA activity. CMA activity is regulated by starvation, growth factors, oxidative stress, lipids, aging, and retinoic acid signaling. The physiological consequences of changes in CMA activity depend on the substrate proteins present in a given cell type. In the proximal tubule, increased CMA results from protein or calorie starvation and from oxidative stress. Overactivity of CMA can be associated with tubular lysosomal pathology and certain cancers. Reduced CMA activity contributes to protein accumulation in renal tubular hypertrophy, but may contribute to oxidative tissue damage in diabetes and aging. Although there are more questions than answers about the role of high basal CMA activity, this remarkable feature of tubular protein metabolism appears to influence a variety of chronic diseases.
The thiazide-sensitive sodium chloride cotransporter (NCC) and the epithelial sodium channel (ENaC) are two of the most important determinants of salt balance and thus systemic blood pressure. Abnormalities in either result in profound changes in blood pressure. There is one segment of the nephron where these two sodium transporters are coexpressed, the second part of the distal convoluted tubule. This is a key part of the aldosterone-sensitive distal nephron, the final regulator of salt handling in the kidney. Aldosterone is the key hormonal regulator for both of these proteins. Despite these shared regulators and coexpression in a key nephron segment, associations between these proteins have not been investigated. After confirming apical localization of these proteins, we demonstrated the presence of functional transport proteins and native association by blue native PAGE. Extensive coimmunoprecipitation experiments demonstrated a consistent interaction of NCC with α-And γ-ENaC. Mammalian two-hybrid studies demonstrated direct binding of NCC to ENaC subunits. Fluorescence resonance energy transfer and immunogold EM studies confirmed that these transport proteins are within appropriate proximity for direct binding. Additionally, we demonstrate that there are functional consequences of this interaction, with inhibition of NCC affecting the function of ENaC. This novel finding of an association between ENaC and NCC could alter our understanding of salt transport in the distal tubule.
Pertussis disease, characterized by severe and prolonged coughing episodes, can progress to a critical stage with pulmonary inflammation and death in young infants. However, there are currently no effective treatments for pertussis. We previously studied the role of pertussis toxin (PT), an important Bordetella pertussis virulence factor, in lung transcriptional responses to B. pertussis infection in mouse models. One of the genes most highly upregulated in a PT-dependent manner encodes an epithelial transporter of bicarbonate, chloride, and thiocyanate, named pendrin, that contributes to asthma pathology. In this study, we found that pendrin expression is upregulated at both gene and protein levels in the lungs of B. pertussis-infected mice. Pendrin upregulation is associated with PT production by the bacteria and with interleukin-17A (IL-17A) production by the host. B. pertussis-infected pendrin knockout (KO) mice had higher lung bacterial loads than infected pendrin-expressing mice but had significantly reduced levels of lung inflammatory pathology. However, reduced pathology did not correlate with reduced inflammatory cytokine expression. Infected pendrin KO mice had higher levels of inflammatory cytokines and chemokines than infected pendrin-expressing mice, suggesting that these inflammatory mediators are less active in the airways in the absence of pendrin. In addition, treatment of B. pertussis-infected mice with the carbonic anhydrase inhibitor acetazolamide reduced lung inflammatory pathology without affecting pendrin synthesis or bacterial loads. Together these data suggest that PT contributes to pertussis pathology through the upregulation of pendrin, which promotes conditions favoring inflammatory pathology. Therefore, pendrin may represent a novel therapeutic target for treatment of pertussis disease.
Background:Plasmodium vivax is the most geographically widespread human malaria parasite. Cohort studies in Papua New Guinea have identified a rapid onset of immunity against vivax-malaria in children living in highly endemic areas. Although numerous P. vivax merozoite antigens are targets of naturally acquired antibodies, the role of many of these antibodies in protective immunity is yet unknown.Methodology/Principal Findings:In a cohort of children aged 1-3 years, antibodies to different regions of Merozoite Surface Protein 3α (PvMSP3α) and Merozoite Surface Protein 9 (PvMSP9) were measured and related to prospective risk of P. vivax malaria during 16 months of active follow-up. Overall, there was a low prevalence of antibodies to PvMSP3α and PvMSP9 proteins (9-65%). Antibodies to the PvMSP3α N-terminal, Block I and Block II regions increased significantly with age while antibodies to the PvMSP3α Block I and PvMSP9 N-terminal regions were positively associated with concurrent P. vivax infection. Independent of exposure (defined as the number of genetically distinct blood-stage infection acquired over time ( mol FOB)) and age, antibodies specific to both PvMSP3α Block II (adjusted incidence ratio (aIRR) = 0.59, p = 0.011) and PvMSP9 N-terminus (aIRR = 0.68, p = 0.035) were associated with protection against clinical P. vivax malaria. This protection was most pronounced against high-density infections. For PvMSP3α Block II, the effect was stronger with higher levels of antibodies.Conclusions:These results indicate that PvMSP3α Block II and PvMSP9 N-terminus should be further investigated for their potential as P. vivax vaccine antigens. Controlling for mol FOB assures that the observed associations are not confounded by individual differences in exposure.
Background: Urea, the end product of protein metabolism, has been considered to have negligible toxicity for a long time. Our previous study showed a depression phenotype in urea transporter (UT) B knockout mice, which suggests that abnormal urea metabolism may cause depression. The purpose of this study was to determine if urea accumulation in brain is a key factor causing depression using clinical data and animal models.
Methods: A meta-analysis was used to identify the relationship between depression and chronic diseases. Functional Magnetic Resonance Imaging (fMRI) brain scans and common biochemical indexes were compared between the patients and healthy controls. We used behavioural tests, electrophysiology, and molecular profiling techniques to investigate the functional role and molecular basis in mouse models.
Findings: After performing a meta-analysis, we targeted the relevance between chronic kidney disease (CKD) and depression. In a CKD mouse model and a patient cohort, depression was induced by impairing the medial prefrontal cortex. The enlarged cohort suggested that urea was responsible for depression. In mice, urea was sufficient to induce depression, interrupt long-term potentiation (LTP) and cause loss of synapses in several models. The mTORC1-S6K pathway inhibition was necessary for the effect of urea. Lastly, we identified that the hydrolysate of urea, cyanate, was also involved in this pathophysiology.
Interpretation: These data indicate that urea accumulation in brain is an independent factor causing depression, bypassing the psychosocial stress. Urea or cyanate carbamylates mTOR to inhibit the mTORC1-S6K dependent dendritic protein synthesis, inducing impairment of synaptic plasticity in mPFC and depression-like behaviour. CKD patients may be able to attenuate depression only by strict management of blood urea.
Objectives: Evidence from industrialized populations suggests that urine concentrating ability declines with age. However, lifestyle factors including episodic protein intake and low hypertension may help explain differences between populations. Whether this age-related decline occurs among small-scale populations with active lifestyles and non-Western diets is unknown. We test the universality of age-related urine concentration decline.
Materials and Methods: We used urine specific gravity (Usg) and urine osmolality (Uosm) data from 15,055 U.S. nonpregnant adults without kidney failure aged 18–80 in 2007–2012 participating in the National Health and Nutrition Examination Survey (NHANES). We tested the relationship of age on urine concentration biomarkers with multiple linear regressions using survey commands. We compared results to longitudinal data on Usg from 116 Tsimane’ forager-horticulturalists (266 observations) adults aged 18–83 in 2013–2014 from Lowland Bolivia, and to 38 Hadza hunter-gatherers (156 observations) aged 18–75 in 2010–2015 from Tanzania using random-effects panel linear regressions.
Results: Among U.S. adults, age was significantly negatively associated with Usg (Adjusted beta [B] = −0.0009 g/mL/10 years; SE = 0.0001; p < 0.001) and Uosm (B = −28.1 mOsm/kg/10 yr; SE = 2.4; p < 0.001). In contrast, among Tsimane’ (B = 0.0003 g/mL/10 yr; SE = 0.0002; p = 0.16) and Hadza (B = −0.0004 g/mL/10 yr; SE = 0.0004; p = 0.29) age was not associated with Usg. Older Tsimane’ and Hadza exhibited similar within-individual variability in Usg equivalent to younger adults. Discussion: While U.S. adults exhibited age-related declines in urine concentration, Tsimane’ and Hadza adults did not exhibit the same statistical decline in Usg. Mismatches between evolved physiology and modern environments in lifestyle may affect kidney physiology and disease risk.
We have previously reported the design and expression of chimeric recombinant proteins as an effective platform to deliver malaria vaccines. The erythrocytic and exoerythrocytic protein chimeras described included autologous T helper epitopes genetically linked to defined B cell epitopes. Proof-of-principle studies using vaccine constructs based on the Plasmodium yoelii circumsporozoite protein (CSP) and P. yoelii merozoite surface protein-1 (MSP-1) showed encouraging results when tested individually in this mouse malaria model. To evaluate the potential synergistic or additive effect of combining these chimeric antigens, we constructed a synthetic gene encoding a hybrid protein that combined both polypeptides in a single immunogen. The multistage vaccine was expressed in soluble form in Escherichia coli at high yield. Here we report that the multistage protein induced robust immune responses to individual components, with no evidence of vaccine interference. Passive immunization using purified IgG from rabbits immunized with the hybrid protein conferred more robust protection against the experimental challenge with P. yoelii sporozoites than passive immunization with purified IgG from rabbits immunized with the individual proteins. High antibody titers and high frequencies of CD4(+)- and CD8(+)-specific cytokine-secreting T cells were elicited by vaccination. T cells were multifunctional and able to simultaneously produce interleukin-2 (IL-2), gamma interferon (IFN-γ), and tumor necrosis factor alpha (TNF-α). The mechanism of vaccine-induced protection involved neutralizing antibodies and effector CD4(+) T cells and resulted in the control of hyperparasitemia and protection against malarial anemia. These data support our strategy of using an array of autologous T helper epitopes to maximize the response to multistage malaria vaccines.