Role of the circulating milieu in age-related arterial dysfunction: a novel ex vivo approach.

The circulating milieu, bioactive molecules in the bloodstream, is altered with aging and interfaces constantly with the vasculature. This anatomic juxtaposition suggests that circulating factors may actively modulate arterial function. Here, we developed a novel, translational experimental model that allows for direct interrogation of the influence of the circulating milieu on age-related arterial dysfunction (aortic stiffening and endothelial dysfunction). To do so, we exposed young and old mouse arteries to serum from young and old mice and young and midlife/older (ML/O) adult humans. We found that old mouse and ML/O adult human, but not young, serum stiffened young mouse aortic rings, assessed via elastic modulus (mouse and human serum, P = 0.003 vs. young serum control), and impaired carotid artery endothelial function, assessed by endothelium-dependent dilation (EDD) (mouse serum, P < 0.001; human serum, P = 0.006 vs. young serum control). Furthermore, young mouse and human, but not old, serum reduced aortic elastic modulus (mouse serum, P = 0.009; human serum, P < 0.001 vs. old/MLO serum control) and improved EDD (mouse and human serum, P = 0.015 vs. old/MLO serum control) in old arteries. In human serum-exposed arteries, in vivo arterial function assessed in the human donors correlated with circulating milieu-modulated arterial function in young mouse arteries (aortic stiffness, r = 0.634, P = 0.005; endothelial function, r = 0.609, P = 0.004) and old mouse arteries (aortic stiffness, r = 0.664, P = 0.001; endothelial function, r = 0.637, P = 0.003). This study establishes novel experimental approaches for directly assessing the effects of the circulating milieu on arterial function and implicates changes in the circulating milieu as a mechanism of in vivo arterial aging.NEW & NOTEWORTHY Changes in the circulating milieu with advancing age may be a mechanism underlying age-related arterial dysfunction. Ex vivo exposure of young mouse arteries to the circulating milieu from old mice or midlife/older adults impairs arterial function whereas exposure of old mouse arteries to the circulating milieu from young mice or young adults improves arterial function. These findings establish that the circulating milieu directly influences arterial function with aging.

Proteomic Profiles of Human Arterioles Isolated From Fresh Adipose Tissue or Following Overnight Storage.

Arterioles are key determinants of the total peripheral vascular resistance, which, in turn, is a key determinant of arterial blood pressure. However, the amount of protein available from one isolated human arteriole may be less than 5 µg, making proteomic analysis challenging. In addition, obtaining human arterioles requires manual dissection of unfrozen clinical specimens. This limits its feasibility, especially for powerful multicenter clinical studies in which clinical specimens need to be shipped overnight to a research laboratory for arteriole isolation. We performed a study to address low-input, test overnight tissue storage and develop a reference human arteriolar proteomic profile. In tandem mass tag proteomics, use of a booster channel consisting of human induced pluripotent stem cell-derived endothelial and vascular smooth muscle cells (1:5 ratio) increased the number of proteins detected in a human arteriole segment with a false discovery rate of <0.01 from 1051 to more than 3000. The correlation coefficient of proteomic profile was similar between replicate arterioles isolated freshly, following cold storage, or before and after the cold storage (1-way analysis of variance; P = .60). We built a human arteriolar proteomic profile consisting of 3832 proteins based on the analysis of 12 arteriole samples from 3 subjects. Of 1945 blood pressure-relevant proteins that we curated, 476 (12.5%) were detected in the arteriolar proteome, which was a significant overrepresentation (χ2 test; P < .05). These findings demonstrate that proteomic analysis is feasible with arterioles isolated from human adipose tissue following cold overnight storage and provide a reference human arteriolar proteome profile highly valuable for studies of arteriole-related traits.

17ß-Estradiol promotes sex-specific dysfunction in isolated human arterioles.

Despite data showing that estrogen is vasculoprotective in large conduit arteries, hormone therapy (HT) during menopause has not proven to mitigate cardiovascular disease (CVD) risk. Estrogen exposure through prolonged oral contraceptive use and gender-affirming therapy can also increase cis- and trans-females' risk for future CVD, respectively. The microvasculature is a unique vascular bed that when dysfunctional can independently predict future adverse cardiac events; however, studies on the influence of estrogen on human microvessels are limited. Here, we show that isolated human arterioles from females across the life span maintain nitric oxide (NO)-mediated dilation to flow, whereas chronic (16-20 h) exposure to exogenous (100 nM) 17ß-estradiol promotes microvascular endothelial dysfunction in vessels from adult females of <40 and ≥40 yr of age. The damaging effect of estrogen was more dramatic in arterioles from biological males, as they exhibited both endothelial and smooth muscle dysfunction. Furthermore, females of <40 yr have greater endothelial expression of estrogen receptor-ß (ER-ß) and G protein-coupled estrogen receptor (GPER) compared with females of ≥40 yr and males. Estrogen receptor-α (ER-α), the prominent receptor associated with protective effects of estrogen, was identified within the adventitia as opposed to the endothelium across all groups. To our knowledge, this is the first study to report the detrimental effects of estrogen on the human microvasculature and highlights differences in estrogen receptor expression.NEW & NOTEWORTHY Microvascular dysfunction is an independent predictor of adverse cardiac events; however, the effect of estrogen on the human microcirculation represents a critical knowledge gap. To our knowledge, this is the first study to report sex-specific detrimental effects of chronic estrogen on human microvascular reactivity. These findings may offer insight into the increased CVD risk associated with estrogen use in both cis- and trans-females.

Onset of the COVID-19 pandemic reduced active time in patients with implanted cardiac devices.

BACKGROUND: Physical inactivity and sedentary behavior are modifiable risk factors for chronic disease and all-cause mortality that may have been negatively impacted by the COVID-19 shutdowns. METHODS: Accelerometry data was retrospectively collected from 332 permanent pacemaker (PPM) and 244 implantable cardiac defibrillation (ICD) patients for 6 time points: March 15-May 15, 2020 (pandemic period), January 1-March 14, 2020, October 1-December 31, 2019, March 15-May 15, 2019, January 1-March 14, 2019, and October 1-December 31, 2018. Paired t-tests, with Bonferroni correction, were used to compare time periods. RESULTS: Activity significantly decreased during the pandemic period compared to one year prior by an average of 0.53 ± 1.18h/day (P < 0.001) for PPM patients and 0.51 ± 1.2h/day (P < 0.001) for ICD patients. Stratification of subjects by active time (< 2 versus ≥ 2h/day) showed patients with < 2h, particularly those with ICDs, had modestly greater activity reductions with the pandemic onset. Logistical regression analyses suggest a trend toward a greater reduction in active time at the onset of the pandemic and an increased risk of hospital or emergency department (ED) admission for PPM patients, but not ICD patients. CONCLUSION: The onset of the pandemic in the United States was associated with a significant drop in PPM and ICD patient active hours that was modestly more pronounced in less active patients and cannot be explained by one year of aging or seasonal variation. If sustained, these populations may experience excess cardiovascular morbidity.

Structural studies of human fission protein FIS1 reveal a dynamic region important for GTPase DRP1 recruitment and mitochondrial fission.

Fission protein 1 (FIS1) and dynamin-related protein 1 (DRP1) were initially described as being evolutionarily conserved for mitochondrial fission, yet in humans the role of FIS1 in this process is unclear and disputed by many. In budding yeast where Fis1p helps to recruit the DRP1 ortholog from the cytoplasm to mitochondria for fission, an N-terminal "arm" of Fis1p is required for function. The yeast Fis1p arm interacts intramolecularly with a conserved tetratricopeptide repeat core and governs in vitro interactions with yeast DRP1. In human FIS1, NMR and X-ray structures show different arm conformations, but its importance for human DRP1 recruitment is unknown. Here, we use molecular dynamics simulations and comparisons to experimental NMR chemical shifts to show the human FIS1 arm can adopt an intramolecular conformation akin to that observed with yeast Fis1p. This finding is further supported through intrinsic tryptophan fluorescence and NMR experiments on human FIS1 with and without the arm. Using NMR, we observed the human FIS1 arm is also sensitive to environmental changes. We reveal the importance of these findings in cellular studies where removal of the FIS1 arm reduces DRP1 recruitment and mitochondrial fission similar to the yeast system. Moreover, we determined that expression of mitophagy adapter TBC1D15 can partially rescue arm-less FIS1 in a manner reminiscent of expression of the adapter Mdv1p in yeast. These findings point to conserved features of FIS1 important for its activity in mitochondrial morphology. More generally, other tetratricopeptide repeat-containing proteins are flanked by disordered arms/tails, suggesting possible common regulatory mechanisms.

Broad-acting therapeutic effects of miR-29b-chitosan on hypertension and diabetic complications.

MicroRNA miR-29 promotes endothelial function in human arterioles in part by targeting LYPLA1 and increasing nitric oxide production. In addition, miR-29 is a master inhibitor of extracellular matrix gene expression, which may attenuate fibrosis but could also weaken tissue structure. The goal of this study was to test whether miR-29 could be developed as an effective, broad-acting, and safe therapeutic. Substantial accumulation of miR-29b and effective knockdown of Lypla1 in several mouse tissues were achieved using a chitosan-packaged, chemically modified miR-29b mimic (miR-29b-CH-NP) injected systemically at 200 µg/kg body weight. miR-29b-CH-NP, injected once every 3 days, significantly attenuated angiotensin II-induced hypertension. In db/db mice, miR-29b-CH-NP treatment for 12 weeks decreased cardiac and renal fibrosis and urinary albuminuria. In uninephrectomized db/db mice, miR-29b-CH-NP treatment for 20 weeks significantly improved myocardial performance index and attenuated proteinuria. miR-29b-CH-NP did not worsen abdominal aortic aneurysm in ApoE knockout mice treated with angiotensin II. miR-29b-CH-NP caused aortic root fibrotic cap thinning in ApoE knockout mice fed a high-cholesterol and high-fat diet but did not worsen the necrotic zone or mortality. In conclusion, systemic delivery of low-dose miR-29b-CH-NP is an effective therapeutic for several forms of cardiovascular and renal disease in mice.

Acute effects of singing on cardiovascular biomarkers.

Background: Singing is a physical activity involving components of the vagal nerves manifested as changes in cardiac autonomic regulation. Aims: The aim of this pilot study is to investigate the acute effects of singing on biomarkers of cardiovascular health. Methods: Adult subjects were recruited from cardiology clinics to participate in a single 90-min study visit. Vascular function was measured at the fingertips with peripheral arterial tonometry (PAT) before and after singing to a 14-min video led by a voice expert. Heart rate variability (HRV) was measured with a chest strap sensor at baseline, during, and after singing. PAT measurements were expressed as reactive hyperemia index (RHI) and Framingham reactive hyperemia index (fRHI). Measures of HRV included root mean square of successive RR interval differences (RMSSD) and standard deviation of NN (or RR) intervals (SDNN). Results: Sixty subjects completed the study (68% female, mean age 61 ±13 years, mean BMI 32 ± 8). There was a significant increase in fRHI (1.88 ± 0.14 to 2.10 ± 0.14, p = 0.02) after singing with no significant change in the RHI (1.99 ± 0.10 to 2.12 ± 0.09, p = 0.22). There was a reduction in HRV during singing (compared to baseline) (RMSSD: 42.0 ± 5 to 32.6 ± 4, p = 0.004 and SDNN: 54 ± 4 to 33.5 ± 3, p = 0.009). HRV measures trended back toward baseline after singing. Conclusions: A short duration of singing improved vascular function acutely. Improvements were more substantial in subjects with abnormal baseline endothelial function. HRV patterns were similar to that of light-intensity exercise. Future studies should confirm favorable vascular adaptation to more sustained singing interventions. Clinical trial registration: ClinicalTrials.gov, identifer: NCT03805529.

Novel <i>DNM1L</i> variants impair mitochondrial dynamics through divergent mechanisms.

Imbalances in mitochondrial and peroxisomal dynamics are associated with a spectrum of human neurological disorders. Mitochondrial and peroxisomal fission both involve dynamin-related protein 1 (DRP1) oligomerisation and membrane constriction, although the precise biophysical mechanisms by which distinct DRP1 variants affect the assembly and activity of different DRP1 domains remains largely unexplored. We analysed four unreported de novo heterozygous variants in the dynamin-1-like gene <i>DNM1L</i>, affecting different highly conserved DRP1 domains, leading to developmental delay, seizures, hypotonia, and/or rare cardiac complications in infancy. Single-nucleotide DRP1 stalk domain variants were found to correlate with more severe clinical phenotypes, with in vitro recombinant human DRP1 mutants demonstrating greater impairments in protein oligomerisation, DRP1-peroxisomal recruitment, and both mitochondrial and peroxisomal hyperfusion compared to GTPase or GTPase-effector domain variants. Importantly, we identified a novel mechanism of pathogenesis, where a p.Arg710Gly variant uncouples DRP1 assembly from assembly-stimulated GTP hydrolysis, providing mechanistic insight into how assembly-state information is transmitted to the GTPase domain. Together, these data reveal that discrete, pathological <i>DNM1L</i> variants impair mitochondrial network maintenance by divergent mechanisms.

Abnormal hearing patterns are not associated with endothelium-dependent vasodilation and carotid intima-media thickness: The Framingham Heart Study.

INTRODUCTION: Prior data suggest associations between hearing loss, cardiovascular (CV) risk factors, and CV disease. Whether specific hearing loss patterns, including a strial pattern associated with inner ear vascular disease, are associated with systemic endothelial dysfunction and carotid intima-media thickness (IMT) remains unclear. METHODS: We evaluated participants without prevalent CVD in the Framingham Offspring Study who underwent formal audiogram testing and brachial and carotid artery ultrasounds. Audiograms were categorized as normal or as belonging to one of four abnormal patterns: cochlear-conductive, low-sloping, sensorineural, or strial. Endothelial function as measured by brachial artery flow-mediated dilation (FMDmm and FMD%). Internal and common intima-media thicknesses (icIMT and ccIMT, respectively) were compared between audiogram patterns. RESULTS: We studied 1672 participants (mean age 59 years, 57.6% women). The prevalence of each hearing pattern was as follows: 43.7% normal; 20.3% cochlear-conductive; 20.3% sensorineural; 7.7% low-sloping; and 8.0% strial. Strial pattern hearing loss was nearly twice as prevalent (p = 0.001) in those in the highest quartile of ccIMT and nearly 50% higher in those in the highest icIMT quartile (p = 0.04). There were no statistically significant differences between the prevalence of the strial pattern comparing the lowest quartiles of FMDmm and FMD% with the upper three quartiles. Age- and sex-adjusted linear regression models did not show significant associations between the vascular measures and hearing patterns. CONCLUSION: Abnormal hearing patterns were not significantly associated with impaired brachial FMD and increased carotid IMT after adjusting for age and sex effects, which may reflect age and sex-related distributional differences based on hearing loss pattern.

Dietary Sodium Restriction Results in Tissue-Specific Changes in DNA Methylation in Humans.

[Figure: see text].

Mitochondrial Fission Protein 1: Emerging Roles in Organellar Form and Function in Health and Disease.

Mitochondrial fission protein 1 (Fis1) was identified in yeast as being essential for mitochondrial division or fission and subsequently determined to mediate human mitochondrial and peroxisomal fission. Yet, its exact functions in humans, especially in regard to mitochondrial fission, remains an enigma as genetic deletion of Fis1 elongates mitochondria in some cell types, but not others. Fis1 has also been identified as an important component of apoptotic and mitophagic pathways suggesting the protein may have multiple, essential roles. This review presents current perspectives on the emerging functions of Fis1 and their implications in human health and diseases, with an emphasis on Fis1's role in both endocrine and neurological disorders.

The impact of standing desks on cardiometabolic and vascular health.

Sedentary behavior is associated with cardiovascular disease (CVD) and mortality, independent of physical activity. The biological mechanisms underlying these associations are largely unknown. We hypothesized that obese subjects with sedentary desk jobs, when assigned a sit-stand desk, will reduce daily sedentary time, and show improvement in arterial flow-mediated dilation (FMD), an early indicator of CVD. Overweight and obese subjects without known CVD were recruited at our institution and given an adjustable sit-stand desk at work. Activities were quantified with an accelerometer for 7 days at baseline and during the intervention. FMD of the brachial and superficial femoral arteries, fasting lipids, insulin and glucose labs, and anthropometrics were measured at baseline, and 12 and 24 weeks. Repeated one-way ANOVA tests were used to compare measurements over time. Fifteen participants were enrolled (93% female, mean age 40 ± 5 years, mean body mass index [BMI] 33 ± 5). Mean daily sedentary time at work decreased by 90 minutes from baseline (385 ± 49 minutes) to 12 weeks (297 ± 80 minutes, p = 0.002) and 24 weeks (295 ± 127 minutes, p = 0.015). Femoral FMD increased from baseline (4.9 ± 1.7%) to 12 weeks (6.4 ± 2.3%, p = 0.043) and further to 24 weeks (8.1 ± 3.2%, p = 0.009). Significant improvement in fasting triglycerides and insulin resistance occurred. There was no change in brachial FMD, exercise activity, step counts, weight, or BMI. A significant reduction in sedentary time during working hours was identified with utilization of a sit-stand desk and sustained over 24 weeks. Improvements in FMD, triglycerides, and insulin resistance provide insight into mechanisms of adverse health risks associated with sedentary behavior.

Lactobacillus plantarum 299v probiotic supplementation in men with stable coronary artery disease suppresses systemic inflammation.

Recent trials demonstrate that systemic anti-inflammatory therapy reduces cardiovascular events in coronary artery disease (CAD) patients. We recently demonstrated Lactobacillus plantarum 299v (Lp299v) supplementation improved vascular endothelial function in men with stable CAD. Whether this favorable effect is in part due to anti-inflammatory action remains unknown. Testing this hypothesis, we exposed plasma obtained before and after Lp299v supplementation from these subjects to a healthy donor's PBMCs and measured differences in the PBMC transciptome, performed gene ontological analyses, and compared Lp299v-induced transcriptome changes with changes in vascular function. Daily alcohol users (DAUs) (n = 4) had a significantly different response to Lp299v and were separated from the main analyses. Non-DAUs- (n = 15) showed improved brachial flow-mediated dilation (FMD) and reduced circulating IL-8, IL-12, and leptin. 997 genes were significantly changed. I.I.com decreased (1.01 ± 0.74 vs. 0.22 ± 0.51; P < 0.0001), indicating strong anti-inflammatory effects. Pathway analyses revealed downregulation of IL-1ß, interferon-stimulated pathways, and toll-like receptor signaling, and an increase in regulator T-cell (Treg) activity. Reductions in GBP1, JAK2, and TRAIL expression correlated with improved FMD. In non-DAU men with stable CAD, post-Lp299v supplementation plasma induced anti-inflammatory transcriptome changes in human PBMCs that could benefit CAD patients. Future studies should delineate changes in circulating metabolites responsible for these effects.

Pacemaker detected active minutes are superior to pedometer-based step counts in measuring the response to physical activity counseling in sedentary older adults.

BACKGROUND: In patients with permanent pacemakers (PPM), physical activity (PA) can be monitored using embedded accelerometers to measure pacemaker detected active hours (PDAH), a strong predictor of mortality. We examined the impact of a PA Counseling (PAC) intervention on increasing activity as measured by PDAH and daily step counts. METHODS: Thirteen patients (average age 80 ± 6 years, 84.6% women) with implanted Medtronic PPMs with a ≤ 2 PDAH daily average were included in this study. Patients were randomized to Usual Care (UC, N = 6) or a Physical Activity Counseling Intervention (PACI, N = 7) groups. Step count and PDAH data were obtained at baseline, following a 12-week intervention, then 12 weeks after intervention completion. Data were analyzed using independent t-tests, Pearson's r, chi-square, and general linear models for repeated measures. RESULTS: PDAH significantly differed by time point for all subject combined (P = 0.01) but not by study group. Subjects with baseline gait speeds of > 0.8 m/sec were responsible for the increases in PDAH observed. Step counts did not differ over time in the entire cohort or by study group. Step count and PDAH significantly correlated at baseline (r = 0.60, P = 0.03). This correlation disappeared by week 12. CONCLUSION(S): PDAH can be used to monitor PA and PA interventions and may be superior to hip-worn pedometers in detecting activity. A significant increase in PA, regardless of treatment group, suggests that patient awareness of the ability to monitor PA through a PPM increases PA in these patients, particularly in patients with gait speeds of < 0.8 m/sec. TRIAL REGISTRATION: ClincalTrials.gov NCT03052829. Date of Registration: 2/14/2017.

Circulating levels of mitochondrial uncoupling protein 2, but not prohibitin, are lower in humans with type 2 diabetes and correlate with brachial artery flow-mediated dilation.

BACKGROUND: Excessive reactive oxygen species from endothelial mitochondria in type 2 diabetes individuals (T2DM) may occur through multiple related mechanisms, including production of mitochondrial reactive oxygen species (mtROS), inner mitochondrial membrane (Δψm) hyperpolarization, changes in mitochondrial mass and membrane composition, and fission of the mitochondrial networks. Inner mitochondrial membrane proteins uncoupling protein-2 (UCP2) and prohibitin (PHB) can favorably impact mtROS and mitochondrial membrane potential (Δψm). Circulating levels of UCP2 and PHB could potentially serve as biomarker surrogates for vascular health in patients with and without T2DM. METHODS: Plasma samples and data from a total of 107 individuals with (N = 52) and without T2DM (N = 55) were included in this study. Brachial artery flow mediated dilation (FMD) was measured by ultrasound. ELISA was performed to measure serum concentrations of PHB1 and UCP2. Mitochondrial membrane potential was measured from isolated leukocytes using JC-1 dye. RESULTS: Serum UCP2 levels were significantly lower in T2DM subjects compared to control subjects (3.01 ± 0.34 vs. 4.11 ± 0.41 ng/mL, P = 0.04). There were no significant differences in levels of serum PHB. UCP2 levels significantly and positively correlated with FMDmm (r = 0.30, P = 0.03) in T2DM subjects only and remained significant after multivariable adjustment. Within T2DM subjects, serum PHB levels were significantly and negatively correlated with UCP2 levels (ρ = - 0.35, P = 0.03). CONCLUSION: Circulating UCP2 levels are lower in T2DM patients and correlate with endothelium-dependent vasodilation in conduit vessels. UCP2 could be biomarker surrogate for overall vascular health in patients with T2DM and merits additional investigation.

Lactobacillus plantarum 299v Supplementation Improves Vascular Endothelial Function and Reduces Inflammatory Biomarkers in Men With Stable Coronary Artery Disease.

RATIONALE: A strong association has emerged between the gut microbiome and atherosclerotic disease. Our recent data suggest Lactobacillus plantarum 299v (Lp299v) supplementation reduces infarct size in male rats. Limited human data are available on the impact of Lp299v on the vasculature. OBJECTIVE: To determine whether oral Lp299v supplementation improves vascular endothelial function and reduces systemic inflammation in humans with stable coronary artery disease (CAD). METHODS AND RESULTS: Twenty men with stable CAD consumed a drink containing Lp299v (20 billion CFU) once daily for 6 weeks. After a 4-week washout, subjects were given an option of additionally participating in a 10-day study of oral liquid vancomycin (250 mg QID). Vascular endothelial function was measured by brachial artery flow-mediated dilation. Before and after Lp299v, plasma short-chain fatty acids, trimethylamine oxide, and adipokine levels were measured. Additional plasma samples underwent unbiased metabolomic analyses using liquid chromatography/mass spectroscopy. 16S rRNA sequencing was used to determine changes of the stool microbiome. Arterioles from patients with CAD were obtained, and endothelium-dependent vasodilation was measured by video microscopy after intraluminal incubation with plasma from Lp299v study subjects. Lp299v supplementation improved brachial flow-mediated dilation ( P=0.008) without significant changes in plasma cholesterol profiles, fasting glucose, or body mass index. Vancomycin did not impact flow-mediated dilation. Lp299v supplementation decreased circulating levels of IL (interleukin)-8 ( P=0.01), IL-12 ( P=0.02), and leptin ( P=0.0007) but did not significantly change plasma trimethylamine oxide concentrations ( P=0.27). Plasma propionate ( P=0.004) increased, whereas acetate levels decreased ( P=0.03). Post-Lp299v plasma improved endothelium-dependent vasodilation in resistance arteries from patients with CAD ( P=0.02).16S rRNA analysis showed the Lactobacillus genus was enriched in postprobiotic stool samples without other changes. CONCLUSIONS: Lp299v improved vascular endothelial function and decreased systemic inflammation in men with CAD, independent of changes in traditional risk factors and trimethylamine oxide. Circulating gut-derived metabolites likely account for these improvements and merit further study. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov . Unique identifier: NCT01952834.

Tissue-specific effects of targeted mutation of Mir29b1 in rats.

BACKGROUND: miR-29 is a master regulator of extracellular matrix genes, but conflicting data on its anti-fibrotic effect have been reported. miR-29 improves nitric oxide (NO) production in arterioles by targeting Lypla1. Mir29b1 targeted mutation exacerbates hypertension in a model derived from the Dahl salt-sensitive rat. We examined the effect of Mir29b1 mutation on tissue fibrosis and NO levels with a focus on kidney regions. METHODS: Mir29b1 targeted mutant rats on the genetic background of SS-Chr13BN rats were studied. Masson trichrome staining, molecular and biochemical assays, metabolic cage studies, and bioinformatic analysis of human genomic data were performed. FINDINGS: The abundance of miR-29b and the co-transcribed miR-29a was substantially lower in mutant rats. Tissue fibrosis was significantly increased in the renal outer medulla, but not in the renal cortex, heart or liver in mutant rats on a 0.4% NaCl diet. Lypla1 protein abundance was significantly higher and NO levels lower in the renal outer medulla, but not in the renal cortex. After 14 days of a 4% NaCl diet, 24 h urine volume and urinary sodium excretion was significantly lower in mutant rats, and tissue fibrosis became higher in the heart. NO levels were lower in the renal outer medulla and heart, but not in the renal cortex. Human miR-29 genes are located in proximity with blood pressure-associated single nucleotide polymorphisms. INTERPRETATION: The renal outer medulla might be particularly susceptible to the injurious effects of a miR-29 insufficiency, which might contribute to the development of hypertension in Mir29b1 mutant rats.

Mitochondrial regulation of diabetic vascular disease: an emerging opportunity.

Diabetes-related vascular complication rates remain unacceptably high despite guideline-based medical therapies that are significantly more effective in individuals without diabetes. This critical gap represents an opportunity for researchers and clinicians to collaborate on targeting mechanisms and pathways that specifically contribute to vascular pathology in patients with diabetes mellitus. Dysfunctional mitochondria producing excessive mitochondrial reactive oxygen species (mtROS) play a proximal cell-signaling role in the development of vascular endothelial dysfunction in the setting of diabetes. Targeting the mechanisms of production of mtROS or mtROS themselves represents an attractive method to reduce the prevalence and severity of diabetic vascular disease. This review focuses on the role of mitochondria in the development of diabetic vascular disease and current developments in methods to improve mitochondrial health to improve vascular outcomes in patients with DM.