Mitochondria and aging in the vascular system

Impaired response to exercise intervention in the vasculature in metabolic syndrome

Physical activity decreases risk for diabetes and cardiovascular disease morbidity and mortality; however, the specific impact of exercise on the diabetic vasculature is unexamined. We hypothesized that an acute, moderate exercise intervention in diabetic and hypertensive rats would induce mitochondrial biogenesis and mitochondrial antioxidant defence to improve vascular resilience. SHHF/Mcc-fa(cp) lean (hypertensive) and obese (hypertensive, insulin resistant), as well as Sprague Dawley (SD) control rats were run on a treadmill for 8 days. In aortic lysates from SD rats, we observed a significant increase in subunit proteins from oxidative phosphorylation (OxPhos) complexes I-III, with no changes in the lean or obese SHHF rats. Exercise also increased the expression of mitochondrial antioxidant defence uncoupling protein 3 (UCP3) (p < 0.05) in SHHF lean rats, whereas no changes were observed in the SD or SHHF obese rats with exercise. We evaluated upstream signalling pathways for mitochondrial biogenesis, and only peroxisome proliferators-activated receptor gamma coactivator 1α (PGC-1α) significantly decreased in SHHF lean rats (p < 0.05) with exercise. In these experiments, we demonstrate absent mitochondrial induction with exercise exposure in models of chronic vascular disease. These findings suggest that chronic vascular stress results in decreased sensitivity of vasculature to the adaptive mitochondrial responses normally induced by exercise.

Nandrolone attenuates aortic adaptation to exercise in rats

AIMS

In this study, we investigated the interaction between exercise-induced mitochondrial adaptation of large vessels and the effects of chronic anabolic androgenic steroids (AASs).

METHODS AND RESULTS

Four groups of Sprague-Dawley rats were studied: (i) sedentary, (ii) sedentary + nandrolone-treated, (iii) aerobic exercise trained, and (iv) trained + nandrolone-treated. Aerobic training increased the levels of aortic endothelial nitric oxide synthase (eNOS) and heme oxygenase-1 (HO-1) in accordance with improved acetylcholine-induced vascular relaxation. These beneficial effects were associated with induction of mitochondrial complexes I and V, increased mitochondrial DNA copy number, and greater expression of transcription factors involved in mitochondrial biogenesis/fusion. We also observed enhanced mitochondrial autophagy pathway activity, including increased conversion of LC3-I to LC3-II and greater expression of beclin1 and autophagy-related protein-7 (ATG7). The levels of thiobarbituric acid-reactive substances and protein carbonyls remained unchanged, whereas significant increases in catalase and mitochondrial manganese superoxide dismutase (MnSOD) levels were observed in the aortas of trained animals, when compared with sedentary controls. Nandrolone increased oxidative stress biomarkers and inhibited exercise-induced increases of eNOS, HO-1, catalase, and MnSOD expression. In addition, it also attenuated elevated peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) and mitofusin-2 expression, and further up-regulated LC3II conversion, beclin1, ATG7, and dynamin-related protein-1 expression.

CONCLUSION

These results demonstrate that nandrolone attenuates aortic adaptations to exercise by regulating mitochondrial dynamic remodelling, including down-regulation of mitochondrial biogenesis and intensive autophagy.

Mitochondrial dysfunction and oxidative stress activate inflammasomes: impact on the aging process and age-related diseases

Oxidative stress and low-grade inflammation are the hallmarks of the aging process and are even more enhanced in many age-related degenerative diseases. Mitochondrial dysfunction and oxidative stress can provoke and potentiate inflammatory responses, but the mechanism has remained elusive. Recent studies indicate that oxidative stress can induce the assembly of multiprotein inflammatory complexes called the inflammasomes. Nod-like receptor protein 3 (NLRP3) is the major immune sensor for cellular stress signals, e.g., reactive oxygen species, ceramides, and cathepsin B. NLRP3 activation triggers the caspase-1-mediated maturation of the precursors of IL-1β and IL-18 cytokines. During aging, the autophagic clearance of mitochondria declines and dysfunctional mitochondria provoke chronic oxidative stress, which disturbs the cellular redox balance. Moreover, increased NF-κB signaling observed during aging could potentiate the expression of NLRP3 and cytokine proforms enhancing the priming of NLRP3 inflammasomes. Recent studies have demonstrated that NLRP3 activation is associated with several age-related diseases, e.g., the metabolic syndrome. We will review here the emerging field of inflammasomes in the appearance of the proinflammatory phenotype during the aging process and in age-related diseases.

Differential modulation of nitric oxide synthases in aging: therapeutic opportunities

Vascular aging is the term that describes the structural and functional disturbances of the vasculature with advancing aging. The molecular mechanisms of aging-associated endothelial dysfunction are complex, but reduced nitric oxide (NO) bioavailability and altered vascular expression and activity of NO synthase (NOS) enzymes have been implicated as major players. Impaired vascular relaxation in aging has been attributed to reduced endothelial NOS (eNOS)-derived NO, while increased inducible NOS (iNOS) expression seems to account for nitrosative stress and disrupted vascular homeostasis. Although eNOS is considered the main source of NO in the vascular endothelium, neuronal NOS (nNOS) also contributes to endothelial cells-derived NO, a mechanism that is reduced in aging. Pharmacological modulation of NO generation and expression/activity of NOS isoforms may represent a therapeutic alternative to prevent the progression of cardiovascular diseases. Accordingly, this review will focus on drugs that modulate NO bioavailability, such as nitrite anions and NO-releasing non-steroidal anti-inflammatory drugs, hormones (dehydroepiandrosterone and estrogen), statins, resveratrol, and folic acid, since they may be useful to treat/to prevent aging-associated vascular dysfunction. The impact of these therapies on life quality in elderly and longevity will be discussed.

Curcumin and vitamin E modulate hepatic antioxidant gene expression in PTU-induced hypothyroid rats

In the present study, regulatory role of vitamin E and curcumin on antioxidant gene (AOG) expression in hypothyroid rat liver is reported. Adult male rats were rendered hypothyroid by administration of 0.05 % 6-propyl-thiouracil in their drinking water, while vitamin E (200 mg/kg body weight) and curcumin (30 mg/kg body weight) were supplemented orally for 30 days. Expression of antioxidant genes (Cu/Zn-superoxide dismutase; SOD1, Mn superoxide dismutase; SOD2, catalase; CAT, glutathione peroxidase; GPx1 and glutathione reductase; GR) was evaluated using RT-PCR and Western blot analyses. The activities of antioxidant enzymes were measured in mitochondrial fraction (MF) and post-mitochondrial fraction (PMF) of rat liver. In addition measurement of glutathione redox status was also carried out in both the fractions. The enhanced transcripts of CAT, GPx1 and GR in hypothyroid rat liver were alleviated by administration of vitamin E and curcumin. Elevated levels of translated product of all AOGs in hypothyroid group were remained unchanged after antioxidant administration. However, enhanced SOD1, GPx1 and decreased GR activities in PMF were normalized by vitamin E and curcumin. Similarly the increased SOD2, GPx1 and decreased CAT activities in MF were also normalized by vitamin E and curcumin supplementation. Administration of vitamin E and curcumin enhanced mitochondrial GSH level; whereas the enhanced GSH level in PMF of hypothyroid rats was alleviated by vitamin E. Thus it can be concluded that besides the antioxidant role of vitamin E and curcumin, they also regulate hepatic antioxidant gene expression in hypothyroid rats.

Is There a Link between Mitochondrial Reserve Respiratory Capacity and Aging?

Oxidative phosphorylation is an indispensable resource of ATP in tissues with high requirement of energy. If the ATP demand is not met, studies suggest that this will lead to senescence and cell death in the affected tissue. The term reserve respiratory capacity or spare respiratory capacity is used to describe the amount of extra ATP that can be produced by oxidative phosphorylation in case of a sudden increase in energy demand. Depletion of the reserve respiratory capacity has been related to a range of pathologies affecting high energy requiring tissues. During aging of an organism, and as a result of mitochondrial dysfunctions, the efficiency of oxidative phosphorylation declines. Based on examples from the energy requiring tissues such as brain, heart, and skeletal muscle, we propose that the age-related decline of oxidative phosphorylation decreases the reserve respiratory capacity of the affected tissue, sensitizes the cells to surges in ATP demand, and increases the risk of resulting pathologies.

Mechanisms involved in the aging-induced vascular dysfunction

Vascular aging is a key process determining health status of aged population. Aging is an independent cardiovascular risk factor associated to an impairment of endothelial function, which is a very early and important event leading to cardiovascular disease. Vascular aging, formerly being considered an immutable and inexorable risk factor, is now viewed as a target process for intervention in order to achieve a healthier old age. A further knowledge of the mechanisms underlying the age-related vascular dysfunction is required to design an adequate therapeutic strategy to prevent or restore this impairment of vascular functionality. Among the proposed mechanisms that contribute to age-dependent endothelial dysfunction, this review is focused on the following aspects occurring into the vascular wall: (1) the reduction of nitric oxide (NO) bioavailability, caused by diminished NO synthesis and/or by augmented NO scavenging due to oxidative stress, leading to peroxynitrite formation (ONOO(-)); (2) the possible sources involved in the enhancement of oxidative stress; (3) the increased activity of vasoconstrictor factors; and (4) the development of a low-grade pro-inflammatory environment. Synergisms and interactions between all these pathways are also analyzed. Finally, a brief summary of some cellular mechanisms related to endothelial cell senescence (including telomere and telomerase, stress-induced senescence, as well as sirtuins) are implemented, as they are likely involved in the age-dependent endothelial dysfunction, as well as in the lower vascular repairing capacity observed in the elderly. Prevention or reversion of those mechanisms leading to endothelial dysfunction through life style modifications or pharmacological interventions could markedly improve cardiovascular health in older people.

Thymoquinone improves aging-related endothelial dysfunction in the rat mesenteric artery

Aging-related endothelial dysfunction is characterized by blunted nitric oxide (NO)- and endothelium-derived hyperpolarizing factor (EDHF)-mediated relaxations in arteries, which may be due, at least in part, to increased oxidative stress. Endothelial dysfunction will promote the initiation and development of major cardiovascular diseases such as atherosclerosis and hypertension. Thymoquinone (TQ) is the most active constituent of the volatile oil of Nigella sativa seeds with well-documented antioxidative properties and vasodilator effects. This study determined whether TQ improves the endothelial function in middle-aged rats. Control young rats (16 weeks) received solvent (ethanol, 3% v/v), and middle-aged rats (46 weeks) either solvent or TQ (10 mg/kg/day) in the drinking water. Mesenteric artery reactivity was determined in organ chambers, vascular oxidative stress by dihydroethidine and MitoSOX staining, and expression of target proteins by immunohistochemical staining. Aging-related blunted NO- and EDHF-mediated responses were associated with downregulation of endothelial NO synthase (eNOS) and calcium-activated potassium channels (SK(Ca) and IK(Ca)) expression. Endothelial dysfunction was also associated with oxidative stress and an upregulation of angiotensin II and AT1 receptor expressions. Intake of TQ for 14 days restored NO- and EDHF-mediated relaxations, normalized oxidative stress, the expression level of eNOS, SK(Ca), IK(Ca), and the components of the angiotensin system in the mesenteric artery of middle-aged rats. Thus, TQ improves endothelial function in aging, at least in part, through inhibition of oxidative stress and normalization of the angiotensin system. TQ may represent a novel therapeutic approach for aging-associated vascular diseases.

Mitochondria and Oxidative Stress in the Cardiorenal Metabolic Syndrome

Mitochondria play a fundamental role in the maintenance of normal structure, function, and survival of tissues. There is considerable evidence for mitochondrial dysfunction in association with metabolic diseases including insulin resistance, obesity, diabetes, and the cardiorenal metabolic syndrome. The phenomenon of reactive oxygen species (ROS)-induced ROS release through interactions between cytosolic and mitochondrial oxidative stress contributes to a vicious cycle of enhanced oxidative stress and mitochondrial dysfunction. Activation of the cytosolic and mitochondrial NADPH oxidase system, impairment of the mitochondrial electron transport, activation of p66shc pathway-targeting mitochondria, endoplasmic reticular stress, and activation of the mammalian target of the rapamycin-S6 kinase pathway underlie dysregulation of mitochondrial dynamics and promote mitochondrial oxidative stress. These processes are further modulated by acetyltransferases including sirtuin 1 and sirtuin 3, the former regulating nuclear acetylation and the latter regulating mitochondrial acetylation. The regulation of mitochondrial functions by microRNAs forms an additional layer of molecular control of mitochondrial oxidative stress. Alcohol further exacerbates mitochondrial oxidative stress induced by overnutrition and promotes the development of metabolic diseases.

Inflammation and type 2 diabetes

Low-grade inflammation is a common feature in subjects with type 2 diabetes (T2D). Heart disease, the metabolic syndrome and T2D all have in common the increased concentration of circulatory cytokines as a result of inflammation. Inflammatory cytokines are produced by different cell types and secreted into the circulation, where they regulate different tissues through their local, central and peripheral actions. This review focuses on C-reactive protein (CRP), a well-established marker of the development of inflammation, on tumour necrosis factor (TNF)-α, an inflammatory marker strongly associated with diabetes, and on adiponectin, a cytokine produced by adipose tissue and associated with insulin sensitivity. While it is clear from the literature that these cytokines play a major role in the development of T2D or, in the case of adiponectin, its prevention, the best strategy for favourably altering the inflammatory response is still a matter of debate.

Association of the sirtuin and mitochondrial uncoupling protein genes with carotid plaque

Objective

Sirtuins (SIRTs) and mitochondrial uncoupling proteins (UCPs) have been implicated in cardiovascular diseases through the control of reactive oxygen species production. This study sought to investigate the association between genetic variants in the SIRT and UCP genes and carotid plaque.

Methods

In a group of 1018 stroke-free subjects from the Northern Manhattan Study with high-definition carotid ultrasonography and genotyping, we investigated the associations of 85 single nucleotide polymorphisms (SNPs) in the 11 SIRT and UCP genes with the presence and number of carotid plaques, and evaluated interactions of SNPs with sex, smoking, diabetes and hypertension as well as interactions between SNPs significantly associated with carotid plaque.

Results

Overall, 60% of subjects had carotid plaques. After adjustment for demographic and vascular risk factors, T-carriers of the SIRT6 SNP rs107251 had an increased risk for carotid plaque (odds ratio, OR = 1.71, 95% CI = 1.23–2.37, Bonferroni-corrected p = 0.03) and for a number of plaques (rate ratio, RR = 1.31, 1.18–1.45, Bonferroni-corrected p = 1.4×10⁻⁵), whereas T-carriers of the UCP5 SNP rs5977238 had an decreased risk for carotid plaque (OR = 0.49, 95% CI = 0.32–0.74, Bonferroni-corrected p = 0.02) and plaque number (RR = 0.64, 95% CI = 0.52–0.78, Bonferroni-corrected p = 4.9×10⁻⁴). Some interactions with a nominal p≤0.01 were found between sex and SNPs in the UCP1 and UCP3 gene; between smoking, diabetes, hypertension and SNPs in UCP5 and SIRT5; and between SNPs in the UCP5 gene and the UCP1, SIRT1, SIRT3, SIRT5, and SIRT6 genes in association with plaque phenotypes.

Conclusion

We observed significant associations between genetic variants in the SIRT6 and UCP5 genes and atherosclerotic plaque. We also found potential effect modifications by sex, smoking and vascular risk factors of the SIRT/UCP genes in the associations with atherosclerotic plaque. Further studies are needed to validate our observations.

Characterization of age-related gene expression profiling in bone marrow and epididymal adipocytes

Background

While an increase in bone marrow adiposity is associated with age-related bone disease, the function of bone marrow adipocytes has not been studied. The aim of this study was to characterize and compare the age-related gene expression profiles in bone marrow adipocytes and epididymal adipocytes.

Results

A total of 3918 (13.7%) genes were differentially expressed in bone marrow adipocytes compared to epididymal adipocytes. Bone marrow adipocytes revealed a distinct gene profile with low expression of adipocyte-specific genes peroxisome proliferator-activated receptor gamma (PPARγ), fatty acid binding protein 4 (FABP4), perilipin (Plin1), adipsin (CFD) and high expression of genes associated with early adipocyte differentiation (CCAAT/enhancer binding protein beta (C/EBPβ), regulator of G-protein signaling 2 (RGS2). In addition, a number of genes including secreted frizzled related protein 4 (SFRP4), tumor necrosis factor α (TNFα), transforming growth factor beta 1(TGFβ1), G-protein coupled receptor 109A (GPR109A) and interleukin 6 (IL-6), that could affect adipose-derived signaling to bone are markedly increased in bone marrow adipocytes. Age had a substantial effect on genes associated with mitochondria function and inflammation in bone marrow adipocytes. Twenty seven genes were significantly changed with age in both adipocyte depots. Among these genes, IL6 and GPR109A were significantly reduced with age in both adipocyte depots.

Conclusions

Overall, gene profiling reveals a unique phenotype for primary bone marrow adipocytes characterized by low adipose-specific gene expression and high expression of inflammatory response genes. Bone marrow and epididymal adipocytes share a common pathway in response to aging in mice, but age has a greater impact on global gene expression in epididymal than in bone marrow adipocytes. Genes that are differentially expressed at greater levels in the bone marrow are highly regulated with age.

The importance of mitochondrial DNA in aging and cancer

Mitochondrial dysfunction has been implicated in premature aging, age-related diseases, and tumor initiation and progression. Alterations of the mitochondrial genome accumulate both in aging tissue and tumors. This paper describes our contemporary view of mechanisms by which alterations of the mitochondrial genome contributes to the development of age- and tumor-related pathological conditions. The mechanisms described encompass altered production of mitochondrial ROS, altered regulation of the nuclear epigenome, affected initiation of apoptosis, and a limiting effect on the production of ribonucleotides and deoxyribonucleotides.