Over-expression of miR-34c leads to early-life visceral fat accumulation and insulin resistance.

Overweight children and adolescents are at high risk for adult and late life obesity. This report investigates some underlying mechanisms contributing to obesity during early life in an animal model. We generated a strain of transgenic mice, cU2, overexpressing human microRNA 34c, a microRNA functionally implicated in adipogenesis. Male and female cU2 mice exhibit significant weight gain, accompanied by marked increase in abdominal fat mass and metabolic abnormalities, including reduction of both glucose clearance rate and insulin sensitivity, as early as two months of age. Adipogenesis derailment at this early age is suggested by decreased expression of adiponectin, the fat mass and obesity-associated gene, and the adiponectin receptor R1, coupled with a reduction of the brown fat biomarker PAT2 and the adipogenesis inhibitor SIRT1. Notably, adiponectin is an important adipokine and an essential regulator of glucose and fatty acid homeostasis. cU2 mice may provide a crucial animal model for investigating the role of miR-34c in early onset insulin resistance and visceral fat mass increase, contributing to accelerated body weight gain and metabolic disorders. Intervention in this dysregulation may open a new preventive strategy to control early-life weight gain and abnormal insulin resistance, and thus prevalent adult and late life obesity.

1H-MRS Quantitation of Age-Dependent Taurine Changes in Mouse Brain.

PURPOSE: A mouse model of Alzheimer's disease demonstrates reduced beta-amyloid levels in the whole brain, associated with a gain of hippocampal memory, after drinking taurine-enriched water; this suggests that a taurine supplement could be a promising treatment for cognitive deficit. The objective of this study is to establish a methodology for quantifying taurine in the whole brain, taking advantage of the rapid development of non-invasive imaging techniques such as magnetic resonance imaging and magnetic resonance spectroscopy (MRS). PROCEDURES: Single-voxel proton MRS was used to obtain quantifiable taurine peaks at 3.25 and 3.43 ppm. Quantitative MRS results were obtained in C57BL/6 mice of various age groups: 4, 11, 18, and 27 months old. RESULTS: Compared with the 4-month-old group, taurine levels dropped significantly only at 27 months of age (p = 0.03). However, a significant decrease of N-acetyl-aspartate (NAA) in the brain was observed at both 18 and 27 months (p = 0.03 and p = 0.02). In addition, MRS-measured taurine level is highly correlated with hippocampal volume (r = 0.95). CONCLUSIONS: These results suggest that decreased taurine levels in the brain could be used as biomarkers for hippocampal changes and are fully translatable into putative cognitive loss in both animal models and human studies without the ex vivo approach.

MicroRNAs as predictive biomarkers for myocardial injury in aged mice following myocardial infarction.

The occurrence of myocardial infarction (MI) increases appreciably with age. In the Framingham Heart Study, the incidence of MI more than doubles for men and increases more than five-fold in women (ages 55-64 years compared to 85-94 years). MicroRNAs (miRNAs) quantitatively regulate their target's expression post-transcriptionally by either silencing action through binding at the 3'UTR domains or degrading the messages at their coding regions. In either case, these regulations affect the cardiac transcriptional output and cardiac function. Among the known cardiac associated miRNA, miRNA-1, miRNA-133a, and miRNA-34a have been shown to induce adverse structural remodeling to impair cardiac contractile function. In the present study, an in vivo model of MI in young (3 month) and old (22 month) mice is used to investigate the possible role whereby these three miRNAs exert negative effects on heart function following MI. Herein we demonstrate that in older mouse heart, all three microRNAs show increased levels of expression, while miRNA-1 shows a further increase in old mouse heart following MI, which corresponds to left ventricular (LV) wall thinning. These structural changes in cardiac tissue may causes downstream LV dilation and subsequent LV dysfunction. Results presented here suggest that significantly elevated levels of miRNA-1 in post-MI old heart could be predictive of cardiac injury in older mice as the high risk biomarker for MI in older individuals.

Maternally induced intraclutch cannibalism: an adaptive response to predation risk?

Theory on condition-dependent risk-taking indicates that when prey are in poor condition, their anti-predator responses should be weak. However, variation in responses resulting from differences in condition is generally considered an incidental by-product of organisms living in a heterogeneous environment. Using Leptinotarsa decemlineata beetles and stinkbug (Podisus maculiventris) predators, we hypothesised that in response to predation risk, parents improve larval nutritional condition and expression of anti-predator responses by promoting intraclutch cannibalism. We showed that mothers experiencing predation risk increase production of unviable trophic eggs, which assures provisioning of an egg meal to the newly hatched offspring. Next, we experimentally demonstrated that egg cannibalism reduces L. decemlineata vulnerability to predation by improving larval nutritional condition and expression of anti-predator responses. Intraclutch cannibalism in herbivorous insects might be a ubiquitous strategy, aimed to overcome the dual challenge of feeding on protein-limited diets while living under constant predation threat.

Mucin-Inspired Thermoresponsive Synthetic Hydrogels Induce Stasis in Human Pluripotent Stem Cells and Human Embryos.

Human pluripotent stem cells (hPSCs; both embryonic and induced pluripotent) rapidly proliferate in adherent culture to maintain their undifferentiated state. However, for mammals exhibiting delayed gestation (diapause), mucin-coated embryos can remain dormant for days or months in utero, with their constituent PSCs remaining pluripotent under these conditions. Here we report cellular stasis for both hPSC colonies and preimplantation embryos immersed in a wholly synthetic thermoresponsive gel comprising poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate) [PGMA55-PHPMA135] diblock copolymer worms. This hydroxyl-rich mucin-mimicking nonadherent 3D gel maintained PSC viability and pluripotency in the quiescent G0 state without passaging for at least 14 days. Similarly, gel-coated human embryos remain in a state of suspended animation (diapause) for up to 8 days. The discovery of a cryptic cell arrest mechanism for both hPSCs and embryos suggests an important connection between the cellular mechanisms that evoke embryonic diapause and pluripotency. Moreover, such synthetic worm gels offer considerable utility for the short-term (weeks) storage of either pluripotent stem cells or human embryos without cryopreservation.

Loss of protein targeting to glycogen sensitizes human hepatocellular carcinoma cells towards glucose deprivation mediated oxidative stress and cell death.

Protein targeting to glycogen (PTG) is a ubiquitously expressed scaffolding protein that critically regulates glycogen levels in many tissues, including the liver, muscle and brain. However, its importance in transformed cells has yet to be explored in detail. Since recent studies have demonstrated an important role for glycogen metabolism in cancer cells, we decided to assess the effect of PTG levels on the ability of human hepatocellular carcinoma (HepG2) cells to respond to metabolic stress. Although PTG expression did not significantly affect the proliferation of HepG2 cells under normal culture conditions, we determined that PTG plays an important role during glucose deprivation. Overexpression of PTG protected cells from cell death in the absence of glucose, whereas knocking down PTG further promoted cytotoxicity, as measured by the release of lactate dehydrogenase (LDH) into the media. Additionally, we demonstrated that PTG attenuates glucose deprivation induced haeme oxygenase-1 (HO-1) expression, suggesting that PTG protects against glucose deprivation-induced oxidative stress. Indeed, treating cells with the antioxidant N-acetyl cysteine (NAC) rescued cells from cytotoxicity caused by glucose deprivation. Finally, we showed that loss of PTG resulted in enhanced autophagy. In control cells, glucose deprivation suppressed autophagy as determined by the increase in the levels of p62, an autophagy substrate. However, in knockdown cells, this suppression was relieved. Blockade of autophagy also attenuated cytotoxicity from glucose deprivation in PTG knockdown cells. Taken together, our findings identify a novel role for PTG in protecting hepatocellular carcinoma cells from metabolic stress, in part by regulating oxidative stress and autophagy.

NRMT1 knockout mice exhibit phenotypes associated with impaired DNA repair and premature aging.

Though defective genome maintenance and DNA repair have long been known to promote phenotypes of premature aging, the role protein methylation plays in these processes is only now emerging. We have recently identified the first N-terminal methyltransferase, NRMT1, which regulates protein-DNA interactions and is necessary for both accurate mitotic division and nucleotide excision repair. To demonstrate if complete loss of NRMT1 subsequently resulted in developmental or aging phenotypes, we constructed the first NRMT1 knockout (Nrmt1(-/-)) mouse. The majority of these mice die shortly after birth. However, the ones that survive, exhibit decreased body size, female-specific infertility, kyphosis, decreased mitochondrial function, and early-onset liver degeneration; phenotypes characteristic of other mouse models deficient in DNA repair. The livers from Nrmt1(-/-) mice produce less reactive oxygen species (ROS) than wild type controls, and Nrmt1(-/-) mouse embryonic fibroblasts show a decreased capacity for handling oxidative damage. This indicates that decreased mitochondrial function may benefit Nrmt1(-/-) mice and protect them from excess internal ROS and subsequent DNA damage. These studies position the NRMT1 knockout mouse as a useful new system for studying the effects of genomic instability and defective DNA damage repair on organismal and tissue-specific aging.

Heme oxygenase-1 modulates microRNA expression in cultured astroglia: implications for chronic brain disorders.

BACKGROUND: Over-expression of the heme-degrading enzyme, heme oxygenase-1 (HO-1) promotes iron deposition, mitochondrial damage, and autophagy in astrocytes and enhances the vulnerability of nearby neuronal constituents to oxidative injury. These neuropathological features and aberrant brain microRNA (miRNA) expression patterns have been implicated in the etiopathogeneses of various neurodevelopmental and aging-related neurodegenerative disorders. OBJECTIVE: To correlate glial HO-1 overexpression with altered miRNA patterns, which have been linked to the aforementioned "core" neuropathological features. METHODS: miRNA microchip assays were performed on HMOX1- and sham-transfected primary rat astroglia and affected miRNAs were further validated by qPCR. The roles of the heme degradation products, carbon monoxide (CO), iron (Fe) and bilirubin on miRNA expression were assessed and salient mRNA targets of the impacted miRNAs were ascertained. RESULTS: In HMOX1-transfected astrocytes, rno-miR-140*, rno-miR-17, and rno-miR-16 were significantly up-regulated, and rno-miR-297, rno-miR-206, rno-miR-187, rno-miR-181a, rno-miR-138 and rno-miR-29c were down-regulated, compared to sham-transfected controls. CO and Fe were implicated in the HMOX1 effects, whereas bilirubin was inert or counteracted the HMOX1-related changes. mRNA levels of Ngfr, Vglut1, Mapk3, Tnf-α, and Sirt1, known targets of the down-regulated miRNAs and abnormal in various human brain disorders, were significantly increased in the HMOX-1-transfected astrocytes. CONCLUSIONS: In chronic CNS disorders, altered expression of salient miRNAs and their mRNA targets may contribute to the neural damage accruing from the over-expression of glial HO-1.

Increased microRNA-34c abundance in Alzheimer's disease circulating blood plasma.

Circulating microRNAs, present either in the cellular component, peripheral blood mononuclear cells (PBMC), or in cell-free plasma, have emerged as biomarkers for age-dependent systemic, disease-associated changes in many organs. Previously, we have shown that microRNA (miR)-34a is increased in circulating PBMC of Alzheimer's disease (AD) patients. In the present study, we show that this microRNA's sister, miR-34c, exhibits even greater increase in both cellular and plasma components of AD circulating blood samples, compared to normal age-matched controls. Statistical analysis shows the accuracy of levels of miR-34c assayed by receiver operating characteristic (ROC) analysis: the area under the curve is 0.99 (p < 0.0001) and the 95% confidence level extends from 0.97 to 1. Pearson correlation between miR-34c levels and mild and moderate AD, as defined by the mini-mental state examination (MMSE), shows an r-value of -0.7, suggesting a relatively strong inverse relationship between the two parameters. These data show that plasma levels of microRNA 34c are much more prominent in AD than those of its sister, miR-34a, or than its own level in PBMC. Transfection studies show that miR-34c, as does its sister miR-34a, represses the expression of several selected genes involved in cell survival and oxidative defense pathways, such as Bcl2, SIRT1, and others, in cultured cells. Taken together, our results indicate that increased levels of miR-34c in both PBMC and plasma may reflect changes in circulating blood samples in AD patients, compared to age-matched normal controls.

Chitosan dressing promotes healing in third degree burns in mice: gene expression analysis shows biphasic effects for rapid tissue regeneration and decreased fibrotic signaling.

Burns are a significant health challenge and healing can result in scar formation. Chitosan, a derivative of chitin, has been used to promote wound healing. In this study we used gene expression profiling in a mouse model of full thickness cutaneous burn to assess the benefits of treating with a chitosan lactate dressing. Three days after wounding mice treated with chitosan showed increased expression of genes associated with formation of granulation tissue. At a later time point, seven days after wounding, genes that initially showed increased expression were now down-regulated, and there was increased expression of genes involved in remodeling suggesting that the chitosan treatment results in accelerated healing. Quantitative RT-PCR showed modulated mRNA levels for TGFß1 by the chitosan dressing. TGFß1 initially promotes healing but extended activity can result in scarring. Importantly we found that expression was elevated at day three, but decreased at day seven suggesting that chitosan treatment will not result in scar formation, and may even be beneficial in preventing scar formation. Additionally, the biphasic regulation of expression of TGFß1 could be a powerful biomarker for future studies of the wound-healing potential of chitosan based and other treatments for burn wounds.

Full-length 3'-untranslated region reporter construction with recombineering.

Complexity in higher animals derives in part from various modalities of protein-coding gene expression regulation, including microRNA repression by binding to 3'-untranslated regions (UTRs) of specific genes. Reporter constructs containing candidate microRNA target sites are a popular approach of functional studies, and full-length 3'-UTR sequences are preferred because they contain all regulatory elements and preserve higher order structure as much as possible. However, this approach is often handicapped by the extreme length of the 3'-UTR. Here, we present a rapid and accurate cloning procedure to generate full-length 3'-UTR reporter constructs by recombinogenic engineering (recombineering) in vivo cloning. The approach includes making retrieval constructs by sequence- and ligation-independent cloning (SLIC) and retrieving the full-length 3'-UTR in one exon to the retrieval construct from a bacterial artificial chromosome (BAC) by recombineering to generate the final full-length 3'-UTR reporter construct for the gene of interest. This method is successfully implemented with mouse full-length 3'-UTRs of Igf1 (6.5 kb), Igf1r (7.5 kb), and Sp1 (5.5 kb). Expansion of this method is adaptable to retrieve 3'-UTRs encoded in more than one exon by removing the introns from the BAC first with recombineering. This method will advance functional studies of regulation of gene expression at the post-transcriptional level through microRNA suppression.

Circulatory miR34a as an RNAbased, noninvasive biomarker for brain aging.

MicroRNAs in blood samples have been identified as an important class of biomarkers, which can reflect physiological changes from cancer to brain dysfunction. In this report we identify concordant increases in levels of expression of miR-34a in brain and two components of mouse blood samples, peripheral blood mononuclear cells (PBMCs) and plasma, from 2 day old neonates through young adulthood and mid-life to old age at 25 months. Levels of this microRNA's prime target, silent information regulator 1 (SIRT1), in brain and the two blood-derived specimens decrease with age inversely to miR-34a, starting as early as 4 months old, when appreciable tissue aging has not yet begun. Our results suggest that: 1. Increased miR-34a and the reciprocal decrease of its target, SIRT1, in blood specimens are the accessible biomarkers for age-dependent changes in brain; and 2. these changes are predictors of impending decline in brain function, as early as in young adult mice.

Post-transcriptional regulation of IGF1R by key microRNAs in long-lived mutant mice.

Long-lived mutant mice, both Ames dwarf and growth hormone receptor gene-disrupted or knockout strains, exhibit heightened cognitive robustness and altered IGF1 signaling in the brain. Here, we report, in both these long-lived mice, that three up-regulated lead microRNAs, miR-470, miR-669b, and miR-681, are involved in posttranscriptional regulation of genes pertinent to growth hormone/IGF1 signaling. All three are most prominently localized in the hippocampus and correspond to reduced expression of key IGF1 signaling genes: IGF1, IGF1R, and PI3 kinase. The decline in these genes' expression translates into decreased phosphorylation of downstream molecules AKT and FoxO3a. Cultures transfected with either miR-470, miR-669b, or miR-681 show repressed endogenous expression of all three genes of the IGF1 signaling axis, most significantly IGF1R, while other similarly up-regulated microRNAs, including let-7g and miR-509, do not induce the same levels of repression. Transduction study in IGF1-responsive cell cultures shows significantly reduced IGF1R expression, and AKT to some extent, most notably by miR-681. This is accompanied by decreased levels of downstream phosphorylated forms of AKT and FoxO3a upon IGF1 stimulation. Suppression of IGF1R by the three microRNAs is further validated by IGF1R 3'UTR reporter assays. Taken together, our results suggest that miR-470, miR-669b, and miR-681 are all functionally able to suppress IGF1R and AKT, two upstream genes controlling FoxO3a phosphorylation status. Their up-regulation in growth hormone signaling-deficient mutant mouse brain suggests reduced IGF1 signaling at the posttranscriptional level, for numerous gains of neuronal function in these long-lived mice.

Gain of survival signaling by down-regulation of three key miRNAs in brain of calorie-restricted mice.

The decline in cognitive robustness with aging can be attributed to complex genetic pathways involving many cellular dysfunctions, cumulative over time, precipitating in frailty and loss of wellness in the elderly brain. The size and health of the neuronal cell population determines cognitive robustness in mammals. A transgenic mouse model over-expressing Bcl-2 has been shown to rescue neurons from naturally occurring cell death (NOCD). Here we show that in the brain of calorie-restricted (CR) mice, there is an age-dependent decreased expression of microRNAs mmu-miR-181a-1*, mmu-miR-30e and mmu-miR-34a, with a corresponding gain in Bcl-2 expression, and decreases in pro-apoptosis genes such as Bax and cleavage of Caspases. Functional characterization shows that these miRNAs repress Bcl-2 expression by the 3'UTR reporter assays, accompanied by loss of this gene's endogenous expression, and a gain in pro-apoptosome-specific proteins. Over-expression of these miRNAs increases the rate of apoptosis, accompanied by a decline in Bcl-2 expression in miRNA-transfected mouse and human cell lines. We report here that down-regulation of miR-34a, -30e, and -181a permits their shared target gene expression (Bcl-2) to remain at a high level without post-transcriptional repression, accompanied by concomitant low levels of Bax expression and Caspase cleaving; this chain event may be a part of the underlying mechanism contributing to the gain in neuronal survival in long-lived CR-fed mice.

Increased expression of miR-34a and miR-93 in rat liver during aging, and their impact on the expression of Mgst1 and Sirt1.

Age-dependent loss of oxidative defense is well recognized in rodent models, although the control mechanism is still obscure; a few studies have shown how microRNAs, a non-coding RNA species, regulate the expression of their target genes at the post-transcriptional level. In the current study, miR-34a and miR-93 are observed to increase in middle- and old-age rat liver, compared to young rats; the up-regulation of these two miRNAs is determined by qPCR through a grind-and-find approach, and histochemical in situ hybridization. Three commonly used miRNA target prediction programs suggest four candidate targets of miR-34a and miR-93: Sp1, Nrf2 (Nfe2l2), Sirt1 and Mgst1; their expression is found to be reduced inversely to the up-regulation of the two miRNAs by Western blotting of protein extracts, as well as immunofluorescence staining of intact liver tissues. Furthermore, the suppression of the four proteins by miR-34a/miR-93 is examined in HEK 293 cells by transfection and co-transfection; miR-34a represses all four proteins' expression, whereas miR-93 affects only Sp1, Sirt1 and Mgst1. Taken together, our study suggests a model of post-transcriptional repression, not only of genes involved in oxidative stress regulation and oxidative stress defense proteins, such as Sirt1 and Mgst1, but also of upstream transcription factors (TFs) regulating their activation, since Sp1 is the TF for both Sirt1 and Mgst1, and Nrf2 is the TF of Mgst1. Thus, up-regulation of both miR-34a and miR-93 constitutes an inescapable repression of two vital oxidative defense genes, by targeting not only the targets, but also transcription factors controlling their activation, a double dampening regulation at the post-transcriptional level.

Up-regulation of key microRNAs, and inverse down-regulation of their predicted oxidative phosphorylation target genes, during aging in mouse brain.

Although significant advances have been made in the study of the molecular mechanisms controlling brain aging, post-transcriptional gene regulation in normal brain aging has yet to be explored. Our lab recently reported that predominant microRNA up-regulation is observed in liver during aging, with key microRNAs predicted to target detoxification genes. Here we examine the role of microRNA regulation in brain during the normal aging process. MicroRNA microarrays and global proteomic profiling were used to compare the brain tissues of 10-, 18-, 24-, and 33-month-old mice. Our results suggest that: (1) like liver, during aging the brain exhibits predominant microRNA up-regulation, and this trend starts in mid-life; (2) of the 70 up-regulated microRNAs, 27 are predicted to target 10 genes of mitochondrial complexes III, IV, and F0F1-ATPase, which exhibit inversely correlated expression; (3) mice of extreme longevity (33-month old) exhibit fewer microRNA expression changes from 10-month-old levels than do old adult mice (24-month old). We found unique de-regulated microRNAs shared between aging brain and aging liver, as well as brain- vs. liver-specific microRNAs during normal aging.

Prosaposin in the secretome of marrow stroma-derived neural progenitor cells protects neural cells from apoptotic death.

Functionally, adult stem cells not only participate in replication and differentiation to various cell lineages, but also may be involved in rescuing cells from apoptosis. Identifying functional factors secreted by stem cells, as well as their target cells, may advance our understanding of stem cells' multifaceted physiologic functions. Here, we report that mouse bone marrow stromal cell-derived neuroprogenitor cells (mMSC-NPC) provide a protective function by secreting a key factor, prosaposin (PSAP), capable of rescuing mature neurons from apoptotic death. This factor is identified as the lead protein in the secretome of mMSC-NPC cultures by tandem mass spectroscopic profiling, and further validated by western blotting and immunocytochemistry. The secretome of MSC-NPC reduces toxin-induced cell death in cultures of rat pheochromocytoma neuronal cells, human ReNcell CX neurons, and rat cortical primary neurons; removal of PSAP by immunodepletion annuls this protective effect. This neuronal protection against toxin treatment was validated further by the recombinant PSAP peptide. Interestingly, the secretome of neuronal culture does not possess such a self-protective action. We suggest that upon injury, a subgroup of MSCs differentiates into neural/neuronal progenitor cells, and remains in this intermediate stem cell-like stage, defending injured neighboring mature neurons from apoptosis by secreting PSAP.

MicroRNA regulation in Ames dwarf mouse liver may contribute to delayed aging.

The Ames dwarf mouse is well known for its remarkable propensity to delay the onset of aging. Although significant advances have been made demonstrating that this aging phenotype results primarily from an endocrine imbalance, the post-transcriptional regulation of gene expression and its impact on longevity remains to be explored. Towards this end, we present the first comprehensive study by microRNA (miRNA) microarray screening to identify dwarf-specific lead miRNAs, and investigate their roles as pivotal molecular regulators directing the long-lived phenotype. Mapping the signature miRNAs to the inversely expressed putative target genes, followed by in situ immunohistochemical staining and in vitro correlation assays, reveals that dwarf mice post-transcriptionally regulate key proteins of intermediate metabolism, most importantly the biosynthetic pathway involving ornithine decarboxylase and spermidine synthase. Functional assays using 3'-untranslated region reporter constructs in co-transfection experiments confirm that miRNA-27a indeed suppresses the expression of both of these proteins, marking them as probable targets of this miRNA in vivo. Moreover, the putative repressed action of this miRNA on ornithine decarboxylase is identified in dwarf mouse liver as early as 2 months of age. Taken together, our results show that among the altered aspects of intermediate metabolism detected in the dwarf mouse liver--glutathione metabolism, the urea cycle and polyamine biosynthesis--miRNA-27a is a key post-transcriptional control. Furthermore, compared to its normal siblings, the dwarf mouse exhibits a head start in regulating these pathways to control their normality, which may ultimately contribute to its extended health-span and longevity.

MicroRNA group disorganization in aging.

Among non-coding RNAs, microRNAs may be one of the best known subgroups, due to their unique function of negatively controlling gene expression, by either degrading target messages or binding to their 3'-untranslated region to inhibit translation. Thus gene expression can be repressed through post-transcriptional regulation, implemented as a 'dimmer switch', in contrast to the all-or-none mode of suppression. Work from our laboratory and others shows that during aging, dysregulated expression of microRNAs generally occurs in groups, suggesting that their actions may be functionally coordinated as a 'pack' by common transcriptional regulators; the accumulation of these 'pack' disorganizations may be the underlying culprit contributing to the pathoetiology of many age-dependent disease states. The fact that many microRNAs are coordinated in their expression, due to either the close proximity of their genomic locations or sharing the same transcriptional regulation, suggests that future strategies for correcting age-dependent microRNA disorganization may need to involve a system biology, rather than a reductionist, approach. Therefore, understanding age-dependent changes of microRNA expression in 'packs' may open an entirely new frontier, i.e. how particular groups of non-coding RNAs, functioning together, contribute to mechanisms regulating aging and longevity.

A GSTM3 polymorphism associated with an etiopathogenetic mechanism in Alzheimer disease.

Brain-specific glutathione S-transferase Mu 3 (GSTM3) colocalizes with amyloid-beta plaques in Alzheimer's disease (AD). A functional polymorphism rs7483 in GSTM3 may contribute to the decrease in GSTM3 expression in AD. The association of the rs7483 SNP with late-onset AD and mild cognitive impairment (MCI) was evaluated and the impact of a SNP background on gene expression was analyzed in blood mononuclear cells (BMC). The allelic association of the GSTM3 allele with AD was significant in women and in APOEvarepsilon4-negative stratum. A significant association was also found in both MCI and AD subjects with AD family history. GSTM3 transcript levels in BMC were lower in AD than in normal elderly controls, and the presence of the risk allele was associated with further mRNA reduction. Diminished GSTM3 mRNA levels correlated with decreased minichromosome maintenance deficient 3 (MCM3) mRNA levels in a diagnostic and SNP-dependent fashion. Reduced antioxidant defense and genome maintenance associated with the GSTM3 polymorphism suggest a common hub of regulatory networks which, when impaired, may lead to AD.