Manlio Vinciguerra

MicroRNA-29 in Aortic Dilation: Implications for Aneurysm Formation

Rationale: Aging represents a major risk factor for coronary artery disease and aortic aneurysm formation. MicroRNAs (miRs) have emerged as key regulators of biological processes, but their role in age-associated vascular pathologies is unknown. Objective: We aim to identify miRs in the vasculature that are regulated by age and play a role in age-induced vascular pathologies. Methods and Results: Expression profiling of aortic tissue of young versus old mice identified several age-associated miRs. Among the significantly regulated miRs, the increased expression of miR-29 family members was associated with a profound downregulation of numerous extracellular matrix (ECM) components in aortas of aged mice, suggesting that this miR family contributes to ECM loss, thereby sensitizing the aorta for aneurysm formation. Indeed, miR-29 expression was significantly induced in 2 experimental models for aortic dilation: angiotensin II-treated aged mice and genetically induced aneurysms in Fibulin-4R/R mice. More importantly, miR-29b levels were profoundly increased in biopsies of human thoracic aneurysms, obtained from patients with either bicuspid (n=79) or tricuspid aortic valves (n=30). Finally, LNA-modified antisense oligonucleotide-mediated silencing of miR-29 induced ECM expression and inhibited angiotensin II-induced dilation of the aorta in mice. Conclusion: In conclusion, miR-29-mediated downregulation of ECM proteins may sensitize the aorta to the formation of aneurysms in advanced age. Inhibition of miR-29 in vivo abrogates aortic dilation in mice, suggesting that miR-29 may represent a novel molecular target to augment matrix synthesis and maintain vascular wall structural integrity.

Interventions to Slow Aging in Humans: Are We Ready?

The workshop entitled ‘Interventions to Slow Aging in Humans: Are We Ready?’ was held in Erice, Italy, on October 8–13, 2013, to bring together leading experts in the biology and genetics of aging and obtain a consensus related to the discovery and development of safe interventions to slow aging and increase healthy lifespan in humans. There was consensus that there is sufficient evidence that aging interventions will delay and prevent disease onset for many chronic conditions of adult and old age. Essential pathways have been identified, and behavioral, dietary, and pharmacologic approaches have emerged. Although many gene targets and drugs were discussed and there was not complete consensus about all interventions, the participants selected a subset of the most promising strategies that could be tested in humans for their effects on healthspan. These were: (i) dietary interventions mimicking chronic dietary restriction (periodic fasting mimicking diets, protein restriction, etc.); (ii) drugs that inhibit the growth hormone/IGF‐I axis; (iii) drugs that inhibit the mTOR–S6K pathway; or (iv) drugs that activate AMPK or specific sirtuins. These choices were based in part on consistent evidence for the pro‐longevity effects and ability of these interventions to prevent or delay multiple age‐related diseases and improve healthspan in simple model organisms and rodents and their potential to be safe and effective in extending human healthspan. The authors of this manuscript were speakers and discussants invited to the workshop. The following summary highlights the major points addressed and the conclusions of the meeting.

MicroRNA-29 in aortic dilation: implications for aneurysm formation [Molecular Medicine]

Rationale: Aging represents a major risk factor for coronary artery disease and aortic aneurysm formation. MicroRNAs (miRs) have emerged as key regulators of biological processes, but their role in age-associated vascular pathologies is unknown. Objective: We aim to identify miRs in the vasculature that are regulated by age and play a role in age-induced vascular pathologies. Methods and Results: Expression profiling of aortic tissue of young versus old mice identified several age-associated miRs. Among the significantly regulated miRs, the increased expression of miR-29 family members was associated with a profound downregulation of numerous extracellular matrix (ECM) components in aortas of aged mice, suggesting that this miR family contributes to ECM loss, thereby sensitizing the aorta for aneurysm formation. Indeed, miR-29 expression was significantly induced in 2 experimental models for aortic dilation: angiotensin II-treated aged mice and genetically induced aneurysms in Fibulin-4R/R mice. More importantly, miR-29b levels were profoundly increased in biopsies of human thoracic aneurysms, obtained from patients with either bicuspid (n=79) or tricuspid aortic valves (n=30). Finally, LNA-modified antisense oligonucleotide-mediated silencing of miR-29 induced ECM expression and inhibited angiotensin II-induced dilation of the aorta in mice. Conclusion: In conclusion, miR-29-mediated downregulation of ECM proteins may sensitize the aorta to the formation of aneurysms in advanced age. Inhibition of miR-29 in vivo abrogates aortic dilation in mice, suggesting that miR-29 may represent a novel molecular target to augment matrix synthesis and maintain vascular wall structural integrity.

Dietary phytoestrogens activate AMP-activated protein kinase with improvement in lipid and glucose metabolism

OBJECTIVE— Emerging evidence suggests that dietary phytoestrogens can have beneficial effects on obesity and diabetes, although their mode of action is not known. Here, we investigate the mechanisms mediating the action of dietary phytoestrogens on lipid and glucose metabolism in rodents. RESEARCH DESIGN AND METHODS— Male CD-1 mice were fed from conception to adulthood with either a high soy–containing diet or a soy-free diet. Serum levels of circulating isoflavones, ghrelin, leptin, free fatty acids, triglycerides, and cholesterol were quantified. Tissue samples were analyzed by quantitative RT-PCR and Western blotting to investigate changes of gene expression and phosphorylation state of key metabolic proteins. Glucose and insulin tolerance tests and euglycemic-hyperinsulinemic clamp were used to assess changes in insulin sensitivity and glucose uptake. In addition, insulin secretion was determined by in situ pancreas perfusion. RESULTS— In peripheral tissues of soy-fed mice, especially in white adipose tissue, phosphorylation of AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase was increased, and expression of genes implicated in peroxisomal fatty acid oxidation and mitochondrial biogenesis was upregulated. Soy-fed mice also showed reduced serum insulin levels and pancreatic insulin content and improved insulin sensitivity due to increased glucose uptake into skeletal muscle. Thus, mice fed with a soy-rich diet have improved adipose and glucose metabolism. CONCLUSIONS— Dietary soy could prove useful to prevent obesity and associated disorders. Activation of the AMPK pathway by dietary soy is likely involved and may mediate the beneficial effects of dietary soy in peripheral tissues.

A Periodic Diet that Mimics Fasting Promotes Multi-System Regeneration, Enhanced Cognitive Performance, and Healthspan

Prolonged fasting (PF) promotes stress resistance, but its effects on longevity are poorly understood. We show that alternating PF and nutrient-rich medium extended yeast lifespan independently of established pro-longevity genes. In mice, 4 days of a diet that mimics fasting (FMD), developed to minimize the burden of PF, decreased the size of multiple organs/systems, an effect followed upon re-feeding by an elevated number of progenitor and stem cells and regeneration. Bi-monthly FMD cycles started at middle age extended longevity, lowered visceral fat, reduced cancer incidence and skin lesions, rejuvenated the immune system, and retarded bone mineral density loss. In old mice, FMD cycles promoted hippocampal neurogenesis, lowered IGF-1 levels and PKA activity, elevated NeuroD1, and improved cognitive performance. In a pilot clinical trial, three FMD cycles decreased risk factors/biomarkers for aging, diabetes, cardiovascular disease, and cancer without major adverse effects, providing support for the use of FMDs to promote healthspan.

Fibroblast growth factor 21 protects against cardiac hypertrophy in mice

Fibroblast growth factor 21 is an endocrine factor, secreted mainly by the liver, that exerts metabolic actions that favour glucose metabolism. Its role in the heart is unknown. Here we show that Fgf21(-/-) mice exhibit an increased relative heart weight and develop enhanced signs of dilatation and cardiac dysfunction in response to isoproterenol infusion, indicating eccentric hypertrophy development. In addition, Fgf21(-/-) mice exhibit enhanced induction of cardiac hypertrophy markers and pro-inflammatory pathways and show greater repression of fatty acid oxidation. Most of these alterations are already present in Fgf21(-/-) neonates, and treatment with fibroblast growth factor 21 reverses them in vivo and in cultured cardiomyocytes. Moreover, fibroblast growth factor 21 is expressed in the heart and is released by cardiomyocytes. Fibroblast growth factor 21 released by cardiomyocytes protects cardiac cells against hypertrophic insults. Therefore, the heart appears to be a target of systemic, and possibly locally generated, fibroblast growth factor 21, which exerts a protective action against cardiac hypertrophy.

Unsaturated fatty acids inhibit the expression of tumor suppressor phosphatase and tensin homolog (PTEN) via microRNA-21 up-regulation in hepatocytes†‡

Phosphatase and tensin homolog (PTEN) is a regulator of phosphoinositide 3‐kinase signaling and an important tumor suppressor mutated/deleted in human cancers. PTEN deletion in the liver leads to insulin resistance, steatosis, inflammation, and cancer. We recently demonstrated that unsaturated fatty acids trigger steatosis by down‐regulating PTEN expression in hepatocytes via activation of a mammalian target of rapamycin (mTOR)/nuclear factor kappa B (NF‐κB) complex, but the molecular mechanisms implicated in this process are still unknown. Here, we investigated potential genetic and epigenetic mechanisms activated by fatty acids leading to PTEN down‐regulation. Our results indicate that unsaturated fatty acids down‐regulate PTEN messenger RNA expression in hepatocytes through mechanisms unrelated to methylation of the PTEN promoter, histone deacetylase activities, or repression of the PTEN promoter activity. In contrast, unsaturated fatty acids up‐regulate the expression of microRNA‐21, which binds to PTEN messenger RNA 3′‐untranslated region and induces its degradation. The promoter activity of microRNA‐21 was increased by mTOR/NF‐κB activation. Consistent with these data, microRNA‐21 expression was increased in the livers of rats fed high‐fat diets and in human liver biopsies of obese patients having diminished PTEN expression and steatosis. Conclusion: Unsaturated fatty acids inhibit PTEN expression in hepatocytes by up‐regulating microRNA‐21 synthesis via an mTOR/NF‐κB–dependent mechanism. Aberrant up‐regulation of microRNA‐21 expression by excessive circulating levels of fatty acids exemplify a novel regulatory mechanism by which fatty acids affect PTEN expression and trigger liver disorders. (HEPATOLOGY 2009.)

Chronic mTOR inhibition by rapamycin induces muscle insulin resistance despite weight loss in rats

BACKGROUND AND PURPOSE mTOR inhibitors are currently used as immunosuppressants in transplanted patients and as promising anti‐cancer agents. However, new‐onset diabetes is a frequent complication occurring in patients treated with mTOR inhibitors such as rapamycin (Sirolimus). Here, we investigated the mechanisms associated with the diabetogenic effects of chronic Sirolimus administration in rats and in in vitro cell cultures.

Regulation of Muscle Atrophy in Aging and Disease

Muscle aging is characterized by a decline in functional performance and restriction of adaptability, due to progressive loss of muscle tissue coupled with a decrease in strength and force output. Together with selective activation ofapoptotic pathways, a hallmark of age-related muscle loss or sarcopenia is the progressive incapacity of regeneration machinery to replace damaged muscle. These characteristics are shared by pathologies involving muscle wasting, such as muscular dystrophies or amyotrophic lateral sclerosis, cancer and AIDS, all characterized by alterations in metabolic and physiological parameters, progressive weakness in specific muscle groups. Modulation ofextracellular agonists, receptors, protein kinases, intermediate molecules, transcription factors and tissue-specific gene expression collectively compromise the functionality of skeletal muscle tissue, leading to muscle degeneration and persistent protein degradation through activation ofproteolytic systems, such as calpain, ubiquitin-proteasome and caspase. Additional decrements in muscle growth factors compromise skeletal muscle growth, differentiation, survival and regeneration. A better understanding of the mechanisms underlying the pathogenesis of muscle atrophy and wasting associated with different diseases has been the objective of numerous studies and represents an important first step for the development of therapeutic approaches. Among these, insulin-like growth factor-1 (IGF-1) has emerged as a growth factor with a remarkably wide range of actions and a tremendous potential as a therapeutic in attenuating the atrophy and frailty associated with muscle aging and diseases. In this chapter we provide an overview of current concepts in muscle atrophy, focusing specifically on the molecular basis of IGF-1 action and survey current gene and cell therapeutic approaches to rescue muscle atrophy in aging and disease.

A phytoestrogen-rich diet increases energy expenditure and decreases adiposity in mice

Background Obesity is an increasingly prevalent health problem, and natural effective therapeutic approaches are required to prevent its occurrence. Phytoestrogens are plant-derived compounds with estrogenic activities; they can bind to both estrogen receptors α and β and mimic the action of estrogens on target organs. Objectives The purpose of this study was to examine the influence of soy-derived phytoestrogens on energy balance and metabolism. Methods Male outbred mice (CD-1) were allowed ad libitum access to either a high soy-containing diet or a soy-free diet from conception to adulthood. We measured circulating serum isoflavone levels using reverse-phase solid-phase extraction for subsequent liquid chromatography electrospray tandem mass spectrometry analysis. Adult animals were analyzed for body composition by dual-energy X-ray absorptiometry, locomotor activity by running-wheel experiments, respiratory exchange rate by indirect calorimetry, and food intake using metabolic cages. Quantitative reverse transcriptase-polymerase chain reaction was performed to determine the expression of hypothalamic neuropeptide genes. Results We found that adult mice fed a soy-rich diet had reduced body weight, adiposity, and resistance to cold. This lean phenotype was associated with an increase in lipid oxidation due to a preferential use of lipids as fuel source and an increase in locomotor activity. The modulation of energy balance was associated with a central effect of phytoestrogens on the expression of hypothalamic neuropeptides, including agouti-related protein. Conclusion The data suggest that dietary soy could have beneficial effects on obesity, but they also emphasize the importance of monitoring the phytoestrogen content of diets as a parameter of variability in animal experiments.