Obesity Paradox in Caucasian Seniors: Results of the PolSenior Study.

OBJECTIVES: To investigate the influence of overweight and obesity on general performance and mortality in seniors. DESIGN: Cross-sectional multidisciplinary study on ageing of the Polish population. SETTING: Community-dwelling individuals aged 65 years or older, selected using three-stage stratified, proportional draw. PARTICIPANTS: 4944 Polish Caucasian seniors, aged 65 years or older recruited between October 2007 and October 2010. MEASUREMENTS: All study subjects underwent measurement of body mass index (BMI), waist circumference (WC), and arm circumference (AC). The physical and cognitive performance was evaluated using the Katz Activities of Daily Living (ADL) score and Mini-Mental State Examination (MMSE), respectively. Morbidity data were obtained from a medical questionnaire. Mortality data were obtained from the Population Register of Poland between October 2015 and October 2018. RESULTS: Increasing age was associated with a decreased prevalence of obesity (all p<0.001). Higher BMI, WC and AC values were associated with higher ADL and MMSE scores (all p<0.001). On multivariate analysis, all three body measurements in women remained independent predictors of the ADL score (BMI p=0.002, WC p=0.005, AC p<0.001) and MMSE score (p<0.001, p=0.003, p<0.001). In men, physical functioning was associated with AC (p=0.003), and cognitive status was associated with AC (p<0.001) and BMI (p=0.013). There was no association between general obesity, abdominal obesity, or AC with several aging-related adverse conditions. Kaplan-Meier survival curves showed that overweight and obesity were associated with the lowest mortality. On multivariate analysis, BMI and AC values remained independent predictors of mortality. In successfully aging individuals, neither BMI, WC, nor AC remained such predictors. CONCLUSIONS: Overweight and obesity in Caucasian seniors are not associated with deterioration of physical and cognitive function or with increased mortality.

SIRT1, miR-132 and miR-212 link human longevity to Alzheimer's Disease.

Alzheimer's Disease (AD) is the most common cause of dementia in the elderly. Centenarians - reaching the age of >100 years while maintaining good cognitive skills - seemingly have unique biological features allowing healthy aging and protection from dementia. Here, we studied the expression of SIRT1 along with miR-132 and miR-212, two microRNAs known to regulate SIRT1, in lymphoblastoid cell lines (LCLs) from 45 healthy donors aged 21 to 105 years and 24 AD patients, and in postmortem olfactory bulb and hippocampus tissues from 14 AD patients and 20 age-matched non-demented individuals. We observed 4.0-fold (P = 0.001) lower expression of SIRT1, and correspondingly higher expression of miR-132 (1.7-fold; P = 0.014) and miR-212 (2.1-fold; P = 0.036), in LCLs from AD patients compared with age-matched healthy controls. Additionally, SIRT1 expression was 2.2-fold (P = 0.001) higher in centenarian LCLs compared with LCLs from individuals aged 56-82 years; while centenarian LCLs miR-132 and miR-212 indicated 7.6-fold and 4.1-fold lower expression, respectively. Correlations of SIRT1, miR-132 and miR-212 expression with cognitive scores were observed for AD patient-derived LCLs and postmortem AD olfactory bulb and hippocampus tissues, suggesting that higher SIRT1 expression, possibly mediated by lower miR-132 and miR-212, may protect aged individuals from dementia and is reflected in their peripheral tissues.

Prevalence of anemia in relation to socio-economic factors in elderly Polish population: the results of PolSenior study.

Anemia is an independent risk factor for functional decline and mortality among older adults. Since mild anemia in older people is often under-diagnosed and ignored, its prevalence needs precise determination and recognition of predisposing factors. None of the previous studies based on the data obtained from the representative elderly population identified the influence of socio-economic factors on the prevalence of anemia. PolSenior was a cross-sectional population-based study performed on the nationally representative sample of Polish seniors. Complete blood count was assessed in 4003 respondents aged 65 years or above (1910 women) divided into six five-year cohorts and a reference group of 622 people aged 55 - 59 years (333 women). Anemia was defined based on the WHO criteria: Hb < 12.0 g/dL in women and Hb < 13.0 g/dL in men. The following socio-economic factors were evaluated through the multiple logistic regression analysis: education level, marital status, place of residence, living arrangements and self-reported poverty. The prevalence of anemia in older persons standardized for the population was 10.8% (17.4% of the study group) and was more frequent in men than in women (20.8% versus 13.6%). The frequency of anemia progressed with age from 5.3% in the youngest to 37.7% in the oldest cohort, and the progression was higher in men. The multiple logistic regression analysis revealed the link between anemia and age in both genders, as well as unmarried status and urban dwelling in men. When age was not taken into account, logistic regression showed the link between anemia and unmarried status, urban place of residence (both genders), and low level of education (women only). Among seniors, those poorly educated, unmarried and city inhabitants require intense screening for anemia.

Components of metabolic syndrome in relation to plasma levels of retinol binding protein 4 (RBP4) in a cohort of people aged 65 years and older.

PURPOSE: Elevated plasma concentration of retinol binding protein 4 (RBP4) has recently emerged as a potential risk factor as a component of developing metabolic syndrome (MS). Therefore, this study aimed to analyse the relationship between components of MS and concentrations of plasma RBP4 in a population of subjects 65 years and older. METHODS: The study sample consisted of 3038 (1591 male) participants of the PolSenior study, aged 65 years and older. Serum lipid profile, concentrations of RBP4, glucose, insulin, C-reactive protein, IL-6, and activity of aminotransferases were measured. Nutritional status (BMI/waist circumference) and treatment with statins and fibrates were evaluated. Glomerular filtration rate (eGFR), de Ritis ratio, and fatty liver index (FLI), as well as HOMA-IR were calculated. RESULTS: Our study revealed a strong relationship between components of MS and RBP4 in both sexes: plasma RBP4 levels were increased in men by at least 3×, and in women by at least 4×. Hypertriglyceridemia was most strongly associated with elevated plasma RBP4 levels. Multivariate, sex-adjusted regression analysis demonstrated that chronic kidney disease [OR 1.86 (95% CI 1.78-1.94)], hypertriglyceridemia [OR 1.52 (1.24-1.87)], hypertension [OR 1.15 (1.12-1.19)], low serum HDL cholesterol [OR 0.94 (0.92-0.97)], and age > 80 years [OR 0.86 (0.81-0.90)] were each independently associated with RBP4 concentration (all p < 0.001). CONCLUSIONS: In Caucasians 65 years and older, RBP4 serum levels are associated with a number of components of MS, independent of sex and kidney function. Hypertriglyceridemia as a component of MS is most significantly related to RBP4 concentration.

SIRT1 and SIRT7 expression in adipose tissues of obese and normal-weight individuals is regulated by microRNAs but not by methylation status.

BACKGROUND/OBJECTIVE: Given their importance in the regulation of metabolism, sirtuins (SIRTs) constitute promising subjects of research on the pathogenesis of obesity and the metabolic syndrome. The aim of this study was to assess whether obesity in humans is associated with changes in the expression of SIRT genes in adipose tissue and whether epigenetic mechanisms, DNA methylation and microRNA (miRNA) interference, mediate in this phenomenon. SUBJECTS/METHODS: The expression of SIRTs and of SIRT1 and SIRT7 mRNA-interacting miRNAs was evaluated by real-time PCR in visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) of 58 obese (body mass index (BMI) >40 kg m-2) and 31 normal-weight (BMI 20-24.9 kg m-2) individuals. The methylation status of SIRTs was studied by the methylation-sensitive digestion/real-time PCR method. RESULTS: SIRT1 mRNA levels were lower in adipose tissues of obese patients than of normal-weight controls (VAT: P=0.0002, SAT: P=0.008). In contrast, expression of SIRT7 was higher in adipose tissues of obese patients than in the control group (VAT: P=0.001, SAT: P=0.008). The mean methylation of the SIRT1 and SIRT7 CpG islands was similar in tissues with high and low expression of these genes, and there was no correlation between the level of expression and the level of methylation. On the other hand, expression of SIRT1 in VAT of obese subjects correlated negatively with the expression of miR-22-3p (P<0.0001, rs=-0.514), miR-34a-5p (P=0.01, rs=-0.326) and miR-181a-3p (P<0.0001, rs=-0.536). In turn, expression of SIRT7 in VAT of slim individuals correlated negatively with the expression of miR-125a-5p (P=0.003, rs=-0.562) and miR-125b-5p (P=0.018, rs=-0.460). CONCLUSIONS: We observed obesity-associated downregulation of SIRT1 and upregulation of SIRT7 mRNA levels that were not associated with the methylation status of their promoters. We found a negative correlation between mRNA levels of SIRT1 in VAT of obese individuals and SIRT7 in VAT of the normal-weight subjects and expression of the relevant miRNAs.

Expression of thyroid hormone receptors is disturbed in human renal clear cell carcinoma.

Human renal clear cell carcinoma (RCCC) accounts for up to 2% of human cancers. To find out if thyroid hormone (T3) and its receptors (TRs) play a role in tumorigenesis of RCCC, the expression of TRs was evaluated on mRNA and protein level. It was found that TRalpha (both alpha1 and alpha2) mRNA amount was significantly decreased in tumors while compared with healthy kidney tissue, and this decrease was deepest in G1 (well differentiated) RCCCs. In contrast, TRalpha1 protein was 1.6x overexpressed in tumors. TRbeta1 mRNA amount was overexpressed in 30% and significantly decreased in 70% of examined tumors. On the protein level, TRbeta1 amount was 1.7x lower in tumors than in healthy controls.

Differential regulation of three thyroid hormone-responsive matrix metalloproteinase genes implicates distinct functions during frog embryogenesis.

Matrix metalloproteinases (MMPs) are a family of Zn(2+)-dependent extracellular proteases capable of degrading various proteinaceous components of the extracellular matrix (ECM). They are expressed in developmental and pathological processes such as postlactation mammary gland involution and tumor metastasis. Relatively few studies have been carried out to investigate the function of MMPs during embryogenesis and postembryonic organ development. Using Xenopus development as a model system, we and others have previously isolated three MMP genes as thyroid hormone response genes. They have distinct temporal and organ-specific regulations during thyroid hormone-dependent metamorphosis. We demonstrate here that three MMPs-stromelysin-3 (ST3), collagenases-3 (Col3), and collagenases-4 (Col4)-also have distinct spatial and temporal expression profiles during embryogenesis. Consistent with earlier suggestions that ST3 is a direct thyroid hormone response gene whereas Col3 and Col4 are not, we show that precocious overexpression of thyroid hormone receptors in the presence of thyroid hormone lead to increased expression of ST3, but not Col3. Furthermore, our whole-mount in situ hybridizations reveal a tight but distinct association of individual MMPs with tissue remodeling in different regions of the animal during embryogenesis. These results suggest that ST3 is likely to play a role in ECM remodeling that facilitate apoptotic tissue remodeling or resorption, whereas Col3 and Col4 appear to participate in connective tissue degradation during development.

Both thyroid hormone and 9-cis retinoic acid receptors are required to efficiently mediate the effects of thyroid hormone on embryonic development and specific gene regulation in Xenopus laevis.

Tissue culture transfection and in vitro biochemical studies have suggested that heterodimers of thyroid hormone receptors (TRs) and 9-cis retinoic acid receptors (RXRs) are the likely in vivo complexes that mediate the biological effects of thyroid hormone, 3,5,3'-triiodothyronine (T3). However, direct in vivo evidence for such a hypothesis has been lacking. We have previously reported a close correlation between the coordinated expression of TR and RXR genes and tissue-dependent temporal regulation of organ transformations during Xenopus laevis metamorphosis. By introducing TRs and RXRs either individually or together into developing Xenopus embryos, we demonstrate here that RXRs are critical for the developmental function of TRs. Precocious expression of TRs and RXRs together but not individually leads to drastic, distinct embryonic abnormalities, depending upon the presence or absence of T3, and these developmental effects require the same receptor domains as those required for transcriptional regulation by TR-RXR heterodimers. More importantly, the overexpressed TR-RXR heterodimers faithfully regulate endogenous T3 response genes that are normally regulated by T3 only during metamorphosis. That is, they repress the genes in the absence of T3 and activate them in the presence of the hormone. On the other hand, the receptors have no effect on a retinoic acid (RA) response gene. Thus, RA- and T3 receptor-mediated teratogenic effects in Xenopus embryos occur through distinct molecular pathways, even though the resulting phenotypes have similarities.

Functional characterization of a mutant thyroid hormone receptor in Xenopus laevis.

Thyroid hormone plays a causative role during frog metamorphosis, and its effect is mediated by thyroid hormone receptors (TRs). To investigate the function of Xenopus TRs, we have recently developed a thyroid hormone dependent in vivo transcription system by introducing TRs and RXRs (9-cis-retinoic acid receptors) into Xenopus oocytes. Interestingly, using this system, we have found that the TRalphaB cloned previously is defective in transcriptional activation compared with TRalphaA. In vitro DNA binding experiments show that TRalphaB.RXR heterodimers have drastically reduced affinity for a thyroid hormone response element. Site-directed mutagenesis shows that two of the seven amino acid residues that differ between TRalphaA and TRalphaB are responsible for the defect in TRalphaB function. These two residues affect the DNA binding by both TR.RXR heterodimers and TR homodimers. In contrast, heterodimer formation with RXRs is not affected as demonstrated by coimmunoprecipitation and dominant-transcriptional inhibition experiments. By cDNA and genomic DNA sequence analysis, we have demonstrated that the residues, which affect TRalphaB function when mutated, are identical between the wild type TRalphaB and TRalphaA. Thus, our experiments have discovered the first amphibian TR mutant. The DNA binding and transcription activation functions of the mutant are discussed in relation to the recently published TR crystal structure.

Thyroid Hormone Receptors: Mechanisms of Transcriptional Regulation and Roles during Frog Development.

Thyroid hormone receptors (TRs) are members of the fast growing superfamily of nuclear hormone receptors. They are dual function transcription factors. In the unliganded form, they repress basal transcription of their target genes. The presence of thyroid hormone leads to not only the relief of this repression but also a strong transcriptional activation above the basal level. Mechanistically, thyroid hormone receptors appear to function as heterodimers with 9-cis-retinoic acid receptors both in the absence and in the presence of thyroid hormone. Recent studies indicate that the heterodimers can interact with thyroid hormone response elements in chromatin independently of thyroid hormone and that the receptors have evolved to function efficiently in a chromatin environment, utilizing chromatin assembly to effectively repress transcription in the absence of thyroid hormone and overcoming the repression by chromatin by inducing chromatin disruption in the presence of the hormone. In addition, a number of TR-interacting proteins have been isolated. How these proteins participate in the regulation of transcription by TRs remains to be elucidated. Independent of the exact mechanisms of action, the developmental expression of thyroid hormone receptor genes during amphibian metamorphosis suggests that both the repression and activation functions of the receptors are important for proper control of the temporal and tissue-specific regulation of metamorphosis. Copyright 1996 S. Karger AG, Basel

Tadpole competence and tissue-specific temporal regulation of amphibian metamorphosis: roles of thyroid hormone and its receptors.

Amphibian metamorphosis is a post-embryonic process that systematically transforms different tissues in a tadpole. Thyroid hormone plays a causative role in this complex process by inducing a cascade of gene regulation. While natural metamorphosis does not occur until endogenous thyroid hormone has been synthesized, tadpoles are competent to respond to exogenous thyroid hormone shortly after hatching. In addition, even though the metamorphic transitions of individual organs are all controlled by thyroid hormone, each occurs at distinct developmental stages. Recent molecular studies suggest that this competence of premetamorphic tadpoles to respond to the hormone and the developmental stage-dependent regulation of tissue-specific transformations are determined in part by the levels of thyroid hormone receptors and the concentrations of cellular free thyroid hormone. In addition, at least two genes, encoding a cytosolic thyroid hormone binding protein and a 5-deiodinase, respectively, are likely to be critical players in regulating cellular free thyroid hormone concentrations. This review discusses how all of these molecular components coordinate to induce amphibian metamorphosis in a correct spatial and temporal manner. These studies provide us with general clues as to how and why tissues become competent to respond to hormonal signals.

Nuclear factor I as a potential regulator during postembryonic organ development.

Nuclear factor I (NFI) family members are transcription factors that are believed to also participate in DNA replication. We have cloned two Xenopus laevis NFIs that are up-regulated by thyroid hormone. They are 84-95% identical to their counterparts in birds and mammals. In contrast, the two Xenopus NFIs are much less homologous to each other, sharing only 58% homology, which largely resides in the DNA binding domain at the amino terminus. However, both NFIs can bind to a consensus NFI binding site and activate the transcription of a promoter bearing the site. Northern blot reveals that both NFI genes are regulated in tissue- and developmental stage-dependent manners. They are first activated, independently of thyroid hormone, to low levels at stages 23/24, around the onset of larval organogenesis. After stage 54, their mRNA levels are dramatically upregulated by endogenous thyroid hormone, and high levels of their expression correlate with organ-specific metamorphosis. Furthermore, gel mobility shift assay indicates that the NFI proteins are present in different organs and that their levels are regulated similarly to the mRNA levels. These results strongly suggest that NFIs play important roles during postembryonic organ development, in contrast to the general belief that NFIs are ubiquitous factors.