APOL1 Kidney-Risk Variants Induce Mitochondrial Fission

Introduction

APOL1 G1 and G2 nephropathy-risk variants cause mitochondrial dysfunction and contribute to kidney disease. Analyses were performed to determine the genetic regulation of APOL1 and elucidate potential mechanisms in APOL1-nephropathy.

Methods

A global gene expression analysis was performed in human primary renal tubule cell lines derived from 50 African American individuals. Follow-up gene knock out, cell-based rescue, and microscopy experiments were performed.

Results

APOL1 genotypes did not alter APOL1 expression levels in the global gene expression analysis. Expression quantitative trait locus (eQTL) analysis in polyinosinic-polycytidylic acid (poly IC)–stimulated renal tubule cells revealed that single nucleotide polymorphism (SNP) rs513349 adjacent to BAK1 was a trans eQTL for APOL1 and a cis eQTL for BAK1; APOL1 and BAK1 were co-expressed in cells. BAK1 knockout in a human podocyte cell line resulted in diminished APOL1 protein, supporting a pivotal effect for BAK1 on APOL1 expression. Because BAK1 is involved in mitochondrial dynamics, mitochondrial morphology was examined in primary renal tubule cells and HEK293 Tet-on cells of various APOL1 genotypes. Mitochondria in APOL1 wild-type (G0G0) tubule cells maintained elongated morphology when stimulated by low-dose poly IC, whereas those with G1G1, G2G2, and G1G2 genotypes appeared to fragment. HEK293 Tet-on cells overexpressing APOL1 G0, G1, and G2 were created; G0 cells appeared to promote mitochondrial fusion, whereas G1 and G2 induced mitochondrial fission. The mitochondrial dynamic regulator Mdivi-1 significantly preserved cell viability and mitochondrial cristae structure and reversed mitochondrial fission induced by overexpression of G1 and G2.

Conclusion

Results suggest the mitochondrial fusion/fission pathway may be a therapeutic target in APOL1-nephropathy.

A Low Iron Diet Protects from Steatohepatitis in a Mouse Model

High tissue iron levels are a risk factor for multiple chronic diseases including type 2 diabetes mellitus (T2DM) and non-alcoholic fatty liver disease (NAFLD). To investigate causal relationships and underlying mechanisms, we used an established NAFLD model-mice fed a high fat diet with supplemental fructose in the water ("fast food", FF). Iron did not affect excess hepatic triglyceride accumulation in the mice on FF, and FF did not affect iron accumulation compared to normal chow. Mice on low iron are protected from worsening of markers for non-alcoholic steatohepatitis (NASH), including serum transaminases and fibrotic gene transcript levels. These occurred prior to the onset of significant insulin resistance or changes in adipokines. Transcriptome sequencing revealed the major effects of iron to be on signaling by the transforming growth factor beta (TGF-β) pathway, a known mechanistic factor in NASH. High iron increased fibrotic gene expression in vitro, demonstrating that the effect of dietary iron on NASH is direct. Conclusion: A lower tissue iron level prevents accelerated progression of NAFLD to NASH, suggesting a possible therapeutic strategy in humans with the disease.

Endometrium and endometriosis tissue mitochondrial energy metabolism in a nonhuman primate model

BACKGROUND

Endometriosis is the growth of uterine lining (endometrium) outside of the uterus. In other chronic inflammatory diseases, mitochondrial dysfunction is suspected of playing a role in disease pathogenesis. However, little is known about endometriosis mitochondrial function or its effects on tissue metabolism. The objectives of this study were to analyze mitochondrial function in nonhuman primate (NHP) endometrium and endometriosis tissue and to identify the metabolic features of these tissues that may contribute to disease.

METHODS

Mitochondrial function in endometriosis tissue and endometrium was measured using mitochondrial respirometry analysis to determine if changes in oxidative phosphorylation exist in endometrium and endometriosis tissue compared to control endometrium from clinically healthy NHPs. Targeted metabolomics and multidimensional statistical analysis were applied to quantify key metabolites in energy and amino acid biosynthesis pathways.

RESULTS

Mitochondrial respirometry assays showed endometrium from NHPs with endometriosis had reduced complex II-mediated oxygen consumption rates (OCR) across all energy states (basal, p = 0.01; state 3, p = 0.02; state 3u, p = 0.04; state 4o, p = 0.008) and endometriosis tissue had reduced state 3, complex I-mediated OCR (p = 0.02) and respiratory control rates (p = 0.01) compared to normal endometrium. Targeted metabolomics performed on tissue revealed carnitine (p = 0.001), creatine phosphate (p = 0.01), NADH (p = 0.0001), FAD (p = 0.001), tryptophan (p = 0.0009), and malic acid (p = 0.005) were decreased in endometriosis tissue compared to normal endometrium samples. FAD (p = 0.004), tryptophan (p = 0.0004) and malic acid (p = 0.03) were significantly decreased in endometrium from NHPs with endometriosis compared to normal endometrium. Significant metabolites identified in endometriosis and endometrium samples from animals with endometriosis were part of amino acid biosynthesis or energy metabolism pathways.

CONCLUSIONS

Here, endometrial mitochondrial energy production and metabolism were decreased in endometrium and endometriosis tissue. Decreased mitochondrial energy production may be due to oxidative stress-induced damage to mitochondrial DNA or membranes, a shift in cell metabolism, or decreased energy substrate; however, the exact cause remains unknown. Additional research is needed to determine the implications of reduced mitochondrial energy production and metabolism on endometriosis and endometrium.

Mitochondria-targeted Probes for Imaging Protein Sulfenylation

Mitochondrial reactive oxygen species (ROS) are essential regulators of cellular signaling, metabolism and epigenetics underlying the pathophysiology of numerous diseases. Despite the critical function of redox regulation in mitochondria, currently there are limited methods available to monitor protein oxidation in this key subcellular organelle. Here, we describe compounds for imaging sulfenylated proteins in mitochondria: DCP-NEt₂-Coumarin (DCP-NEt₂C) and rhodamine-based DCP-Rho1. Side-by-side comparison studies are presented on the reactivity of DCP-NEt₂C and DCP-Rho1 with a model protein sulfenic acid (AhpC-SOH) and mitochondrial localization to identify optimized experimental conditions for labeling and visualization of protein sulfenylation that would be independent of mitochondria membrane potential and would not impact mitochondrial function. These probes are applied to image mitochondrial protein sulfenylation under conditions of serum starvation and in a cell culture model of lung cancer exposed to ionizing radiation and silver nanoparticles, agents serving dual functions as environmental stressors and cancer therapeutics.

Regulators of mitochondrial quality control differ in subcutaneous fat of metabolically healthy and unhealthy obese monkeys

OBJECTIVE

Obesity exists with and without accompanying cardiometabolic disease, termed metabolically unhealthy obesity (MUO) and healthy obesity (MHO), respectively. Underlying differences in the ability of subcutaneous (SQ) fat to respond to nutrient excess are emerging as a key pathway. This study aimed to document the first spontaneous animal model of MHO and MUO and differences in SQ adipose tissue.

METHODS

Vervet monkeys (Chlorocebus aethiops; N = 171) were screened for metabolic syndrome. A subset of MHO and MUO monkeys (n = 6/group) had SQ fat biopsies collected for histological evaluations and examination of key mitochondrial proteins.

RESULTS

Obesity was seen in 20% of monkeys, and within this population, 31% were healthy, which mirrors human prevalence estimates. MUO monkeys had more than 60% lower adiponectin concentrations despite similar fat cell size, uncoupling protein 3, and activated macrophage abundance. However, alternatively activated/anti-inflammatory macrophages were 70% lower. Deficiencies of 50% or more in mitochondrial quality control regulators and selected mitochondrial fission and fusion markers were observed in the SQ fat of MUO monkeys despite comparable mitochondrial content.

CONCLUSIONS

A novel and translatable spontaneously obese animal model of MHO and MUO, occurring independently of dietary factors, was characterized. Differences in mitochondrial quality and inflammatory cell populations of subcutaneous fat may underpin divergent metabolic health.

Blood cell respirometry is associated with skeletal and cardiac muscle bioenergetics: Implications for a minimally invasive biomarker of mitochondrial health

Blood based bioenergetic profiling strategies are emerging as potential reporters of systemic mitochondrial function; however, the extent to which these measures reflect the bioenergetic capacity of other tissues is not known. The premise of this work is that highly metabolically active tissues, such as skeletal and cardiac muscle, are susceptible to differences in systemic bioenergetic capacity. Therefore, we tested whether the respiratory capacity of blood cells, monocytes and platelets, are related to contemporaneous respirometric assessments of skeletal and cardiac muscle mitochondria. 18 female vervet/African green monkeys (Chlorocebus aethiops sabaeus) of varying age and metabolic status were examined for this study. Monocyte and platelet maximal capacity correlated with maximal oxidative phosphorylation capacity of permeabilized skeletal muscle (R=0.75, 95% confidence interval [CI]: 0.38-0.97; R=0.51, 95%CI: 0.05-0.81; respectively), isolated skeletal muscle mitochondrial respiratory control ratio (RCR; R=0.70, 95%CI: 0.35-0.89; R=0.64, 95%CI: 0.23-0.98; respectively), and isolated cardiac muscle mitochondrial RCR (R=0.55, 95%CI: 0.22-0.86; R=0.58, 95%CI: 0.22-0.85; respectively). These results suggest that blood based bioenergetic profiling may be used to report on the bioenergetic capacity of muscle tissues. Blood cell respirometry represents an attractive alternative to tissue based assessments of mitochondrial function in human studies based on ease of access and the minimal participant burden required by these measures.

APOL1 Renal-Risk Variants Induce Mitochondrial Dysfunction

APOL1 G1 and G2 variants facilitate kidney disease in blacks. To elucidate the pathways whereby these variants contribute to disease pathogenesis, we established HEK293 cell lines stably expressing doxycycline-inducible (Tet-on) reference APOL1 G0 or the G1 and G2 renal-risk variants, and used Illumina human HT-12 v4 arrays and Affymetrix HTA 2.0 arrays to generate global gene expression data with doxycycline induction. Significantly altered pathways identified through bioinformatics analyses involved mitochondrial function; results from immunoblotting, immunofluorescence, and functional assays validated these findings. Overexpression of APOL1 by doxycycline induction in HEK293 Tet-on G1 and G2 cells led to impaired mitochondrial function, with markedly reduced maximum respiration rate, reserve respiration capacity, and mitochondrial membrane potential. Impaired mitochondrial function occurred before intracellular potassium depletion or reduced cell viability occurred. Analysis of global gene expression profiles in nondiseased primary proximal tubule cells from black patients revealed that the nicotinate phosphoribosyltransferase gene, responsible for NAD biosynthesis, was among the top downregulated transcripts in cells with two APOL1 renal-risk variants compared with those without renal-risk variants; nicotinate phosphoribosyltransferase also displayed gene expression patterns linked to mitochondrial dysfunction in HEK293 Tet-on APOL1 cell pathway analyses. These results suggest a pivotal role for mitochondrial dysfunction in APOL1-associated kidney disease.

Local intra-uterine Ang-(1-7) infusion attenuates PGE2 and 6-keto PGF1α in decidualized uterus of pseudopregnant rats

BACKGROUND

Cyclooxygenase (COX)-derived prostanoids (PGE_2, PGI₂) are important contributors to the process of decidualization. Previous studies showed the presence of Ang-(1-7) in the primary and secondary decidualized zones of the implantation site at early pregnancy. Decreased concentrations of Ang-(1-7) were found in the decidualized uterus compared to the non-decidualized uterus of pseudopregnant rats, suggesting that low levels of Ang-(1-7) are required for successful decidualization at early pregnancy.

METHODS

To understand the role of Ang-(1-7) in prostaglandin production in a decidualized uterus, induced by a bolus injection of sesame oil, Ang-(1-7) (24 μg/kg/h) or vehicle was then infused directly into the decidualized uterine horn using an osmotic minipump. The right horns were not injected or infused and served as non-decidualized uterine horns in both groups of animals.

RESULTS

Decidualization increased PGE₂ concentration in the uterus (0.53 ± 0.05 vs. 12.0 ± 3.2 pmol/mg protein, p < 0.001, non-decidualized vs. decidualized horns); Ang-(1-7) infusion attenuated the increase of PGE₂ (12.0 ± 3.2 vs. 5.1 ± 1.3 pmol/mg protein, p < 0.01 control vs. Ang-(1-7) treated decidualized horns). The stable metabolite of PGI₂ (6-keto PGF_1α) was increased with decidualization (0.79 ± 0.17 vs. 3.5 ± 0.82 pmol/mg protein, p < 0.001, non-decidualized vs. decidualized horns). Ang-(1-7) infusion attenuated the increase in 6-keto PGF_1α in the decidualized horn (3.5 ± 0.82 vs 1.8 ± 0.37 pmol/mg protein, p < 0.05 control vs. Ang-(1-7) treated decidualized horns). The circulating levels of 6-keto-PGF_1a and TXB₂ were decreased by Ang-(1-7) infusion, while no difference was observed in circulating PGE₂. Although the global assessment of cleaved caspase 3 immunostaining, a marker of apoptosis, was unchanged within the Ang-(1-7) decidualized horn, there were localized decreases in cleaved caspase 3 staining in the luminal region in the decidualized uterus of Ang-(1-7)-treated rats.

CONCLUSIONS

These studies show that increased local uterine Ang-(1-7) alters the uterine prostaglandin environment, possibly leading to disruptions of early events of decidualization.

Skeletal Muscle Mitochondrial Content, Oxidative Capacity, and Mfn2 Expression Are Reduced in Older Patients With Heart Failure and Preserved Ejection Fraction and Are Related to Exercise Intolerance

OBJECTIVES

The aim of this study was to examine skeletal muscle mitochondria content, oxidative capacity, and the expression of key mitochondrial dynamics proteins in patients with heart failure with preserved ejection fraction (HFpEF), as well as to determine potential relationships with measures of exercise performance.

BACKGROUND

Multiple lines of evidence indicate that severely reduced peak exercise oxygen uptake (peak VO2) in older patients with HFpEF is related to abnormal skeletal muscle oxygen utilization. Mitochondria are key regulators of skeletal muscle metabolism; however, little is known about how these organelles are affected in HFpEF.

METHODS

Both vastus lateralis skeletal muscle citrate synthase activity and the expression of porin and regulators of mitochondrial fusion were examined in older patients with HFpEF (n = 20) and healthy, age-matched control subjects (n = 17).

RESULTS

Compared with age-matched healthy control subjects, mitochondrial content assessed by porin expression was 46% lower (p = 0.01), citrate synthase activity was 29% lower (p = 0.01), and Mfn2 (mitofusin 2) expression was 54% lower (p <0.001) in patients with HFpEF. Expression of porin was significantly positively correlated with both peak VO2 and 6-min walk distance (r = 0.48, p = 0.003 and r = 0.33, p = 0.05, respectively). Expression of Mfn2 was also significantly positively correlated with both peak VO2 and 6-min walk distance (r = 0.40, p = 0.02 and r = 0.37, p = 0.03 respectively).

CONCLUSIONS

These findings suggest that skeletal muscle oxidative capacity, mitochondrial content, and mitochondrial fusion are abnormal in older patients with HFpEF and might contribute to their severe exercise intolerance.

Relationships between mitochondrial content and bioenergetics with obesity, body composition and fat distribution in healthy older adults

Background

Mitochondrial function declines with age; however, the relationship between adiposity and mitochondrial function among older adults is unclear. This study examined relationships between skeletal muscle mitochondrial content and electron transport chain complex 2 driven respiration with whole body and thigh composition, body fat distribution, and insulin sensitivity in older adults.

Methods

25 healthy, sedentary, weight-stable men (N = 13) and women (N = 12) >65 years of age, with a BMI range of 18-35 kg/m², participated in this study. Vastus lateralis biopsies were analyzed for citrate synthase (CS) activity and succinate mediated respiration of isolated mitochondria. Whole body and thigh composition were measured by DXA and CT. HOMA-IR was calculated using fasting glucose and insulin as an estimate of insulin sensitivity.

Results

Similar to reports in middle-aged adults, skeletal muscle CS activity was negatively correlated with BMI (R = −0.43) in our cohort of older adults. Higher total and thigh adiposity were correlated with lower CS activity independent of BMI (R = −0.50 and −0.71 respectively). Maximal complex 2 driven mitochondrial respiration was negatively correlated with lower body adiposity in males (R = −0.66). In this cohort of non-diabetic older adults, both HOMA-IR and insulin were positively correlated with CS activity when controlling for BMI (R = 0.57 and 0.66 respectively).

Conclusions

Adiposity and body composition are correlated with skeletal muscle mitochondrial content and electron transport chain function in healthy, sedentary, community dwelling, older adults. Specific relationships of mitochondrial bioenergetics with gender and insulin sensitivity are also apparent.

Trial registration

ClinicalTrials.gov identifier NCT01049698

Electronic supplementary material

The online version of this article (doi:10.1186/s40608-015-0070-4) contains supplementary material, which is available to authorized users.

Blood-cell bioenergetics are associated with physical function and inflammation in overweight/obese older adults

BACKGROUND

Physical function and strength decline with age and lead to limited mobility and independence in older adults. Alterations in mitochondrial function are thought to underlie numerous age-related changes, including declining physical ability. Recent studies suggest that systemic changes in bioenergetic capacity may be reported by analyzing mitochondrial function in circulating cells. The objective of this study was to determine whether the bioenergetic capacity of peripheral blood mononuclear cells (PBMCs) is related to differences in physical function among older, overweight/obese, adults. To address this, we tested the hypothesis that greater PBMC respirometric capacity would be associated with better physical function, muscular strength, leg lean mass, and muscle quality. Furthermore, we tested whether the respirometric capacity of PBMCs is related to cellular composition and inflammatory status reported by interleukin-6 (IL-6).

METHODS

Fasted PBMC respiration (pmol/min/500,000 cells), expanded short physical performance battery (Ex-SPPB), peak knee extensor (KE) strength (Nm), grip strength (kg), leg lean mass (kg, via dual energy X-ray absorptiometry [DXA]), muscle quality (Nm/kg), and plasma IL-6 (pg/mL) were analyzed in 15 well-functioning, community-dwelling, sedentary overweight/obese older men (n=9) and women (n=6) aged 65 to 78 (mean 68.3 ± 3.5 years). Pearson and partial correlations were calculated to determine associations between PBMC respiration and these variables.

RESULTS

Higher maximal respiration of PBMCs was associated with better Ex-SPPB (r=0.58, p=0.02), greater KE strength (r=0.60, p=0.02), greater grip strength (r=0.52, p=0.05) and lower IL-6 (r=-0.58, p=0.04). Higher spare respiratory capacity was associated with better Ex-SPPB (r=0.59, p=0.02), greater KE strength (r=0.60, p=0.02), greater grip strength (r=0.54, p=0.04), greater leg muscle quality (r=0.56, p=0.04), and lower IL-6 (r=-0.55, p=0.05). Monocyte and lymphocyte counts were not related to PBMC respiratory capacity.

CONCLUSIONS

Our results indicate that respirometric profiles of readily obtainable blood cells are associated with physical function and strength. Future studies should be undertaken in order to determine whether blood-based bioenergetic profiling can provide an objective index of systemic mitochondrial health.

Energy metabolism in a matched model of radiation resistance for head and neck squamous cell cancer

While radiation therapy is commonly used for treating cancer, radiation resistance can limit long-term control of the disease. In this study, we investigated the reprogramming of the energy metabolism in radiosensitive and radioresistant head and neck squamous cell carcinomas (HNSCC) using a preclinical matched model of radiation resistance. Our investigation found that radioresistant rSCC-61 cells: 1. They display increased glucose uptake and decreased fatty acid uptake; 2. They deviate from the classical Warburg effect by diverting the glycolytic flux into the pentose phosphate pathway; 3. They are more dependent on glucose than glutamine metabolism to support growth; 4. They have decreased mitochondrial oxidative phosphorylation; 5. They have enhanced fatty acid biosynthesis by increasing the expression of fatty acid synthase; and 6. They utilize endogenous fatty acids to meet the energy demands for proliferation. Inhibition of fatty acid synthase with orlistat or FASN siRNA resulted in increased cytotoxicity and sensitivity to radiation in rSCC-61 cells. These results demonstrate the potential of combination therapy using radiation and orlistat or other inhibitors of lipid and energy metabolism for treating radiation resistance in HNSCC.

Preparation and respirometric assessment of mitochondria isolated from skeletal muscle tissue obtained by percutaneous needle biopsy

Respirometric profiling of isolated mitochondria is commonly used to investigate electron transport chain function. We describe a method for obtaining samples of human Vastus lateralis, isolating mitochondria from minimal amounts of skeletal muscle tissue, and plate based respirometric profiling using an extracellular flux (XF) analyzer. Comparison of respirometric profiles obtained using 1.0, 2.5 and 5.0 μg of mitochondria indicate that 1.0 μg is sufficient to measure respiration and that 5.0 μg provides most consistent results based on comparison of standard errors. Western blot analysis of isolated mitochondria for mitochondrial marker COX IV and non-mitochondrial tissue marker GAPDH indicate that there is limited non-mitochondrial contamination using this protocol. The ability to study mitochondrial respirometry in as little as 20 mg of muscle tissue allows users to utilize individual biopsies for multiple study endpoints in clinical research projects.

Sequential actions of SIRT1-RELB-SIRT3 coordinate nuclear-mitochondrial communication during immunometabolic adaptation to acute inflammation and sepsis

We reported that NAD(+)-dependent SIRT1, RELB, and SIRT6 nuclear proteins in monocytes regulate a switch from the glycolysis-dependent acute inflammatory response to fatty acid oxidation-dependent sepsis adaptation. We also found that disrupting SIRT1 activity during adaptation restores immunometabolic homeostasis and rescues septic mice from death. Here, we show that nuclear SIRT1 guides RELB to differentially induce SIRT3 expression and also increases mitochondrial biogenesis, which alters bioenergetics during sepsis adaptation. We constructed this concept using TLR4-stimulated THP1 human promonocytes, a model that mimics the initiation and adaptation stages of sepsis. Following increased expression, mitochondrial SIRT3 deacetylase activates the rate-limiting tricarboxylic acid cycle (TCA) isocitrate dehydrogenase 2 and superoxide dismutase 2, concomitant with increases in citrate synthase activity. Mitochondrial oxygen consumption rate increases early and decreases during adaptation, parallel with modifications to membrane depolarization, ATP generation, and production of mitochondrial superoxide and whole cell hydrogen peroxide. Evidence of SIRT1-RELB induction of mitochondrial biogenesis included increases in mitochondrial mass, mitochondrial-to-nuclear DNA ratios, and both nuclear and mitochondrial encoded proteins. We confirmed the SIRT-RELB-SIRT3 adaptation link to mitochondrial bioenergetics in both TLR4-stimulated normal and sepsis-adapted human blood monocytes and mouse splenocytes. We also found that SIRT1 inhibition ex vivo reversed the sepsis-induced changes in bioenergetics.

Examination of bioenergetic function in the inner mitochondrial membrane peptidase 2-like (Immp2l) mutant mice

Inner mitochondrial membrane peptidase 2-like (IMMP2L) protein is a mitochondrial inner membrane peptidase that cleaves the signal peptide sequences of cytochrome c1 (CYC1) and mitochondrial glycerol phosphate dehydrogenase (GPD2). Immp2l mutant mice show infertility and early signs of aging. It is unclear whether mitochondrial respiratory deficiency underlies this phenotype. Here we show that the intermediate forms of GPD2 and CYC1 have normal expression levels and enzymatic function in Immp2l mutants. Mitochondrial respiration is not diminished in isolated mitochondria and cells from mutant mice. Our data suggest that respiratory deficiency is not the cause of the observed Immp2l mutant phenotypes.

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Expression of IMMP2L substrates CYC1 and GPD2 is not affected in Immp2l mutant mice.

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Mitochondria of mutant mice have normal complex III and GPD2 activities.

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Mitochondrial respiration of mutant mice is not diminished.

Respirometric Profiling of Muscle Mitochondria and Blood Cells Are Associated With Differences in Gait Speed Among Community-Dwelling Older Adults

BACKGROUND

Gait speed provides an integrated measure of physical ability that is predictive of morbidity, disability, and mortality in older adults. Energy demands associated with walking suggest that mitochondrial bioenergetics may play a role in gait speed. Here, we examined the relationship between gait speed and skeletal muscle mitochondrial bioenergetics, and further evaluated whether blood-based bioenergetic profiling might have similar associations with gait speed.

METHODS

Participants in this study were comprised of two subsets (n = 17 per subset) and were overweight/obese (body mass index, 30.9 ± 2.37), well-functioning, community-dwelling older adults (69.1 ± 3.69 years) without major comorbidity. Gait speeds were calculated from a fast-paced 400 m walk test. Respiratory control ratios were measured from mitochondria isolated from leg skeletal muscle biopsies from one subset. Maximal respiration and spare respiratory capacity were measured from peripheral blood mononuclear cells from the other subset.

RESULTS

Individual differences in gait speed correlated directly with respiratory control ratio of mitochondria isolated from skeletal muscle (r = .536, p = .027) and with both maximal respiration and spare respiratory capacity of peripheral blood mononuclear cells (r = .585 and p = .014; r = .609 and p = .009, respectively).

CONCLUSIONS

The bioenergetic profile of mitochondria isolated from skeletal muscle is associated with gait speed in older adults. Blood-based bioenergetic profiling is also associated with gait speed and may provide an alternative measure of mitochondrial function.

Utero-placental expression of angiotensin-(1-7) and ACE2 in the pregnant guinea-pig

BACKGROUND

In humans, trophoblast invasion, vascular remodeling and placental development are critical to determine the fate of pregnancy. Since guinea-pigs (GP) and humans share common pregnancy features including extensive trophoblast invasion, transformation of the uterine spiral arteries and a haemomonochorial placenta, the GP animal model was deemed suitable to extend our knowledge on the spatio-temporal immunoreactive expression of the vasodilator arpeptide of the renin-angiotensin system, angiotensin-(1-7) [Ang-(1-7)] and its main generating enzyme, angiotensin converting enzyme 2 (ACE2).

METHODS

Utero-placental units were collected in days 15, 20, 40 and 60 of a 64-67 day long pregnancy in 25 Pirbright GP. Ang-(1-7) and ACE2 expression in utero-placental units were evaluated by immunohistochemistry.

RESULTS

Ang-(1-7) and ACE2 were detected in the endothelium and syncytiotrophoblast of the labyrinthine placenta, interlobium, subplacenta, giant cells, syncytial sprouts, syncytial streamers, and myometrium throughout pregnancy. In late pregnancy, perivascular or intramural trophoblasts in spiral and mesometrial arteries expressed both factors. Immunoreactive Ang-(1-7) and ACE2 were present in decidua and in the vascular smooth muscle of spiral, myometrial and mesometrial arteries, which also express kallikrein (Kal), the bradykinin receptor 2 (B2R), vascular endothelial growth factor (VEGF) and its type 2 receptor (KDR), but no endothelial nitric oxide synthase (eNOS). In addition, the signal of Ang-(1-7) and ACE2 was especially remarkable in giant cells, which also show Kal, B2R. eNOS, VEGF and KDR.

CONCLUSIONS

The spatio-temporal expression of Ang-(1-7) and ACE2 in GP, similar to that of humans, supports a relevant evolutionary conserved function of Ang-(1-7) and ACE2 in decidualization, trophoblast invasion, vascular remodeling and placental flow regulation, as well as the validity of the GP model to understand the local adaptations of pregnancy. It also integrates Ang-(1-7) to the utero-placental vasodilatory network. However, its antiangiogenic effect may counterbalance the proangiogenic activity of some of the other vasodilator components.

Decidualized pseudopregnant rat uterus shows marked reduction in Ang II and Ang-(1-7) levels

Previous studies showed that angiotensin (Ang) II and Ang-(1-7) concentrations were reduced in the implantation site at day 7 of pregnancy in Sprague-Dawley rats as compared to the site immediately adjacent to it, which does not have the embryo attached, clearly showing the importance of the blastocyst in the regulation of renin-angiotensin system (RAS).

OBJECTIVE

The objective of this study was to evaluate the regulation of the RAS in the decidualized uterus in the pseudopregnant rat, a model without the presence of a conceptus.

METHODS

Ovariectomized, adult female rats were sensitized for the decidual cell reaction with steroid treatments; decidualization was induced by oil-injection of the right horn; the left horn served as a control. The uterine content of Ang I, Ang II, and Ang-(1-7) was examined in the decidualized and non-decidualized uteri.

RESULTS

Both Ang-(1-7) and Ang II and ACE and ACE2 mRNA were significantly reduced in the decidualized horn as compared to the non-decidualized horn. Immunocytochemical characterization of Ang II, Ang-(1-7), ACE and ACE2 demonstrated that Ang-(1-7), Ang II, and ACE2 polarize to the anti-mesometrial pole with decidualization.

CONCLUSION

The decidualization process elicits marked reduction in uterine Ang II and Ang-(1-7) content as compared to the non-decidualized horn. The differential immunocytochemical expression of Ang II and Ang-(1-7) with ACE2, but not ACE in the anti-mesometrial pole of the decidualized horn may favor the formation and action of Ang-(1-7) in the anti-mesometrial pole, an area which plays a role in triggering the decidualization process.

Angiotensin-converting enzyme 2 deficiency is associated with impaired gestational weight gain and fetal growth restriction

Angiotensin-converting enzyme 2 (ACE2) is a key enzyme of the renin-angiotensin system that influences the relative expression of angiotensin II (Ang II) and Ang-(1-7). Although ACE2 expression increases in normal pregnancy, the impact of ACE2 deficiency in pregnancy has not been elucidated. We determined the influence of ACE2 deficiency on circulating and tissue renin-angiotensin system components, fetal and maternal growth characteristics, and maternal hemodynamics (mean blood pressure and cardiac output) at day 18 of gestation. Gestational body weight gain was lower in the ACE2 knockout (KO) versus C57BL/6 (wild-type) mice (30.3±4.7 versus 38.2±1.0 g; P<0.001). Fetal weight (0.94±0.1 versus 1.24±0.01 g; P<0.01) and length (19.6±0.2 versus 22.2±0.2 mm; P<0.001) were less in KO. Mean blood pressure was significantly reduced in C57BL/6 with pregnancy; it was elevated (P<0.05) in the KO virgin and pregnant mice, and this was associated with an increased cardiac output in both C57BL/6 and KO pregnant mice (P<0.05). Plasma Ang-(1-7) was reduced in pregnant KO mice (P<0.05). Placenta Ang II levels were higher in KO mice (52.9±6.0 versus 22.0±3.3 fmol/mg of protein; P<0.001). Renal Ang II levels were greater in KO virgin mice (30.0±1.7 versus 23.7±1.1 fmol/mg of protein; P<0.001). There was no change in the Ang-(1-7) levels in the KO placenta and virgin kidney. These results suggest that ACE2 deficiency and associated elevated placenta Ang II levels impact pregnancy by impairing gestational weight gain and restricting fetal growth.

Dysfunctional HDL containing L159R ApoA-I leads to exacerbation of atherosclerosis in hyperlipidemic mice

The mutation L159R apoA-I or apoA-I(L159R) (FIN) is a single amino acid substitution within the sixth helical repeat of apoA-I. It is associated with a dominant negative phenotype, displaying hypoalphaproteinemia and an increased risk for atherosclerosis in humans. Mice lacking both mouse apoA-I and LDL receptor (LDL(-/-), apoA-I(-/-)) (double knockout or DKO) were crossed>9 generations with mice transgenic for human FIN to obtain L159R apoA-I, LDLr(-/-), ApoA-I(-/-) (FIN-DKO) mice. A similar cross was also performed with human wild-type (WT) apoA-I (WT-DKO). In addition, FIN-DKO and WT-DKO were crossed to obtain WT/FIN-DKO mice. To determine the effects of the apoA-I mutations on atherosclerosis, groups of each genotype were fed either chow or an atherogenic diet for 12weeks. Interestingly, the production of dysfunctional HDL-like particles occurred in DKO and FIN-DKO mice. These particles were distinct with respect to size, and their enrichment in apoE and cholesterol esters. Two-dimensional gel electrophoresis indicated that particles found in the plasma of FIN-DKO mice migrated as large α(3)-HDL. Atherosclerosis analysis showed that FIN-DKO mice developed the greatest extent of aortic cholesterol accumulation compared to all other genotypes, including DKO mice which lack any apoA-I. Taken together these data suggest that the presence of large apoE enriched HDL particles containing apoA-I L159R lack the normal cholesterol efflux promoting properties of HDL, rendering them dysfunctional and pro-atherogenic. In conclusion, large HDL-like particles containing apoE and apoA-I(L159R) contribute rather than protect against atherosclerosis, possibly through defective efflux properties and their potential for aggregation at their site of interaction in the aorta. This article is part of a Special Issue entitled Advances in High Density Lipoprotein Formation and Metabolism: A Tribute to John F. Oram (1945-2010).

Ratio determination of plasma wild-type and L159R apoA-I using mass spectrometry: tools for studying apoA-IFin

In this report, methods are described to isolate milligram quantities of a mutant apolipoprotein A-I (apoA-I) protein for use in structure-function studies. Expression of the L159R apoA-I mutation in humans reduces the concentration of plasma wild-type apoA-I, thus displaying a dominant negative phenotype in vivo. Earlier attempts to express and isolate this mutant protein resulted in extensive degradation and protein misfolding. Using an Escherichia coli expression system used predominantly for the isolation of soluble apoA-I mutant proteins, we describe the expression and purification of L159R apoA-I (apoA-I(Fin)) from inclusion bodies. In addition, we describe a mass spectrometric method for measuring the L159R-to-wild-type apoA-I ratio in a 1 microl plasma sample. These new methods will facilitate further studies into the mechanism behind the dominant negative phenotype associated with the expression of the L159R apoA-I protein in humans.

Apolipoprotein A-I helix 6 negatively charged residues attenuate lecithin-cholesterol acyltransferase (LCAT) reactivity

Apolipoprotein A-I (apoA-I), the major protein in high density lipoprotein (HDL) regulates cholesterol homeostasis and is protective against atherosclerosis. An examination of the amino acid sequence of apoA-I among 21 species shows a high conservation of positively and negatively charged residues within helix 6, a domain responsible for regulating the rate of cholesterol esterification in plasma. These observations prompted an investigation to determine if charged residues in helix 6 maintain a structural conformation for protein-protein interaction with lecithin-cholesterol acyltransferase (LCAT) the enzyme for which apoA-I acts as a cofactor. Three apoA-I mutants were engineered; the first, (3)/(4) no negative apoA-I, eliminated 3 of the 4 negatively charged residues in helix 6, no negative apoA-I (NN apoA-I) eliminated all four negative charges, while all negative (AN apoA-I) doubled the negative charge. Reconstituted phospholipid-containing HDL (rHDL) of two discrete sizes and compositions were prepared and tested. Results showed that LCAT activation was largely influenced by both rHDL particle size and the net negative charge on helix 6. The 80 A diameter rHDL showed a 12-fold lower LCAT catalytic efficiency when compared to 96 A diameter rHDL, apparently resulting from an increased protein-protein interaction, at the expense of lipid-protein association on the 80 A rHDL. When mutant apoproteins were compared bound to the two different sized rHDL, a strong inverse correlation (r = 0.85) was found between LCAT catalytic efficiency and apoA-I helix 6 net negative charge. These results support the concept that highly conserved negatively charged residues in apoA-I helix 6 interact directly and attenuate LCAT activation, independent of the overall particle charge.