Biomarkers of age effect on renal function in Down syndrome

Frailty and biological age. Which best describes our aging and longevity?

Frailty and Biological Age are two closely related concepts; however, frailty is a multisystem geriatric syndrome that applies to elderly subjects, whereas biological age is a gerontologic way to describe the rate of aging of each individual, which can be used from the beginning of the aging process, in adulthood. If frailty reaches less consensus on the definition, it is a term much more widely used than this of biological age, which shows a clearer definition but is scarcely employed in social and medical fields. In this review, we suggest that this Biological Age is the best to describe how we are aging and determine our longevity, and several examples support our proposal.

Evaluation of biochemical and hematological parameters in adults with Down syndrome

Down syndrome (DS) is the most common worldwide cause of intellectual disability of genetic origin and the most common chromosomal disorder affecting live-born infants. In addition to intellectual disability, individuals with DS have other comorbidities and complex medical conditions. The increase in the life expectancy of patients with DS requires expanding the knowledge about their clinical characteristics and related laboratory parameters. Several studies exploring laboratory tests in DS patients exist, but their focus is limited to specific areas of metabolism. Therefore, our main goal was to describe the biochemical and hematological findings in a DS cohort and to compare the values to those of a control population. A total of 248 DS individuals and 84 control subjects were enrolled. DS individuals had a higher frequency of several clinical conditions compared to control individuals and presented with significant differences with respect to the controls in both biochemical and hematological parameters. We found age- and sex-related differences in several of the parameters. A good understanding of the differences in our cohort might be of aid in the clinical follow-up of adults with DS, especially considering that the lifespan of DS individuals may reach 60 years of age in developed countries.

Oxidative stress, thyroid dysfunction & Down syndrome

Down syndrome (DS) is one of the most common chromosomal disorders, occurring in one out of 700-1000 live births, and the most common cause of mental retardation. Thyroid dysfunction is the most typical endocrine abnormality in patients with DS. It is well known that thyroid dysfunction is highly prevalent in children and adults with DS and that both hypothyroidism and hyperthyroidism are more common in patients with DS than in the general population. Increasing evidence has shown that DS individuals are under unusual increased oxidative stress, which may be involved in the higher prevalence and severity of a number of pathologies associated with the syndrome, as well as the accelerated ageing observed in these individuals. The gene for Cu/Zn superoxide dismutase (SOD1) is coded on chromosome 21 and it is overexpressed (~50%) resulting in an increase of reactive oxygen species (ROS) due to overproduction of hydrogen peroxide (H₂O₂). ROS leads to oxidative damage of DNA, proteins and lipids, therefore, oxidative stress may play an important role in the pathogenesis of DS.

Proteinuria and clinical outcome in CHD patients

INTRODUCTION

CHD patients, especially those with associated hypoxaemia, usually have some level of renal function impairment, even though they are relatively young. The aim of the study was to evaluate those clinical and analytical factors that may contribute to microalbuminuria and determine the association of 24-hour proteinuria with thrombotic events and mortality.

METHODS

A total of 251 CHD patients were studied and demographic characteristics, blood test, and 24-hour urinalysis were analysed.

RESULTS

Of the patients, 221 were non-hypoxaemic, and 30 were hypoxaemic (oxygen saturation of 84.3±5.9%). Of the non-hypoxaemic patients, 30 (13.6%), and of the hypoxaemic patients 9 (30%), showed proteinuria (>0.15 g/24 hours) (p=0.028). Hypoxaemic CHD patients also showed higher haematocrit (%) (50.7 (34.6; 72.1) versus 42.8 (34.6; 48.9), p<0.001), serum creatinine (mg/dl) (1.07±0.2 versus 0.96±1.9, p=0.004), microalbuminuria (mg/dl/24 hours) (1.2 (0.0; 261.5) versus 0.5 (0.0; 4.37), p<0.001), proteinuria (gr/24 hours) (1.0 (0.4; 3.1) versus 0.08 (0.04; 0.52), p=0.043), and N-terminal pro-B-type natriuretic peptide (pg/ml) (417.8 (35.7; 8534.0) versus 44.9 (0.0; 670.5), p<0.001) concentrations than non-hypoxaemic CHD patients. During a median follow-up of 26.0 (16.9; 57.7) months, five patients died - one patient had 24-hour proteinuria and four patients did not (p=0.581) - and three patients had some type of thrombosis - two patients had 24-hour proteinuria and one patient did not (p=0.014). Kaplan-Meier survival analysis showed no significant difference between CHD patients with and without 24-hour proteinuria (p=0.631).

CONCLUSION

CHD patients with proteinuria have significantly more thrombosis and more hypoxaemia than those patients without proteinuria.

Prevalence of lower urinary tract symptoms in individuals with Down syndrome

OBJECTIVES

Down syndrome (DS), which is caused by the trisomy of chromosome 21, is the most frequent of all genetic syndromes. The current study aims to estimate the prevalence of lower urinary tract symptoms (LUTS) in individuals with DS buy using the Dysfunctional Voiding Symptom Score (DVSS) and correlate with functional constipation, age, and gender, as well as determine the most sensitive and specific factors associated with LUTS.

METHODS

LUTS was assessed in individuals with DS using a cross-sectional study through the application of a validated and adapted version of the DVSS for the Brazilian population. The presence of functional constipation was evaluated according to the Rome III criteria.

RESULTS

Of the 114 individuals assessed, 84 were included in the study (median age 16 ± 5.0 years, 66.7% female). The prevalence of LUTS was 27.3%. The symptoms were more frequent in males (OR 3.0, 95% CI 1.1-8.3, p = 0.03) and in individuals younger than 10 years of age (OR 5.2, 95% CI 1.8-14, p = 0.001). Functional constipation was observed in 50% of subjects. It was detected in 95.65% of the individuals with LUTS and 32.78% without LUTS (OR 45.1, 95% CI 5.66-301, p = 0.001). The symptom listed in question 8 ("push to pee") was the most specific indicator. When present, this symptom indicated a higher probability of LUTS (LR+ = 6.3), while the symptom listed in question 4 ("push for bowel movements to come out") showed high sensitivity and, when absent, indicated a lower probability of LUTS (LR- = 0.1).

CONCLUSIONS

LUTS was more prevalent in young males with DS and appeared to improve with age. Functional constipation was strongly associated with LUTS. These findings will contribute to raising the awareness of professionals involved in the follow-up of individuals with DS regarding the clinical manifestations and the need for a standardized investigation of LUTS.

α-Tocopherol supplementation reduces biomarkers of oxidative stress in children with Down syndrome: a randomized controlled trial

BACKGROUND

Down syndrome (DS) is the most common human chromosomal abnormality. It is characterized by mental retardation and several metabolic disturbances, including elevated oxidative stress, which may be causally linked. Treatment with dietary antioxidants has been suggested as a potential method to alleviate the oxidative damage and retardation of DS patients, but prior supplementation work has been equivocal.

AIM

To evaluate the effects of supplementation with antioxidants α-tocopherol and α-lipoic acid (ALA) on oxidative stress biomarkers in DS children.

METHODS

Ninety-three DS children aged 7-15 years from both sexes were randomly allocated to three groups: α-tocopherol (400 IU/day), ALA (100 mg/day) and placebo. The intervention period was 4 months. A healthy control group consisted 26 non-DS siblings. Serum thiobarbituric acid reactive substances (TBARS) and urinary 8-hydroxy-2'-deoxyguanosine (8OHdG) were used as biomarkers of oxidative stress.

RESULTS

DS children had greater levels of baseline oxidative stress than their siblings. Moreover, males had greater levels of 8OHdG than females (P<0.001) but there was no significant association between age and biomarkers of oxidative stress. Serum levels of TBARS did not change significantly over time, or relative to placebo. Although urinary 8OHdG concentrations decreased significantly in both α-tocopherol and ALA, groups compared with the baseline levels (P<0.001), mean final levels of urinary 8OHdG concentrations differed significantly only between α-tocopherol and placebo groups (P<0.01).

CONCLUSIONS

α-Tocopherol supplementation of the diets of DS children may attenuate oxidative stress at the DNA level.

Memory decline in Down syndrome and its relationship to iPF2alpha, a urinary marker of oxidative stress

BACKGROUND

Lipid peroxidation may be a marker of free-radical-mediated injury associated with Alzheimer's disease (AD). We aimed to investigate whether changes in lipid peroxidation is associated with cognitive decline in individuals with Down syndrome over a 4-year period.

METHODS

Thirty-two adults with DS participated in a longitudinal study with urinary isoprostane 8,12-iso-iPF2alpha (iPF2alpha) assays at baseline and four years follow-up. Informants rated their functional ability and memory function and the adults with DS attempted assessments of language skills and memory. Twenty-six individuals completed assessments of memory (Modified Memory Object Task, MOMT), adaptive behavior (ABAS), and receptive vocabulary (British Picture vocabulary, BPVS) at both time-points.

RESULTS

Overall change in iPF2alpha level was negatively correlated with change in the MOMT score (Spearman's Rho =  -0.576, p = 0.006), i.e., increased lipid peroxidation was correlated with worse memory functioning over time. An increase of ≥ 0.02 ng/mg creatinine iPF2α had good sensitivity (85.7%), positive predictive value (75%,), specificity (85.7%) and negative predictive value (92.3%) for memory decline.

CONCLUSION

Change in iPF2alpha over time may have potential as a biomarker for memory decline in Down syndrome and potentially also help to track progression of MCI to AD in the general population.

Chronic kidney disease in older people with intellectual disability: results of the HA-ID study

With increasing longevity and cardiovascular events, chronic kidney disease may also become a significant problem in older people with intellectual disability (ID). We studied prevalence and associations of chronic kidney disease as part of the Healthy Ageing and Intellectual Disability (HA-ID) study, a large Dutch cross-sectional study among people with ID aged 50 years and over, using creatinine and cystatin-C measurement in plasma. Glomerular filtration rate (GFR) was calculated using the Modification of Diet in Renal Disease (MDRD) and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations. Equations based on creatinine (as the MDRD equation) may underestimate kidney dysfunction in people with sarcopenia, because low muscle mass leads to a low creatinine production. Therefore, also prevalence of chronic kidney disease was studied in the sarcopenic group, using different GFR equations. Prevalence of chronic kidney disease, among 635 participants, was 15.3%, which equals prevalence in the general Dutch population. In the group of participants with sarcopenia (n=82), the CKD-EPI equation based on creatinine and cystatin-C gave a higher prevalence of chronic kidney disease than did the MDRD equation, but confidence intervals were very wide. Chronic kidney disease was associated with higher age, Down syndrome, obesity, hypercholesterolemia and hypothyroid disease. GFR should be measured in all older people with ID and polypharmacy, and in older people with ID and Down syndrome as part of the regular health checks. Moreover, if sarcopenia is present and information on GFR is required, this should not be measured based on creatinine only, but additional measures, such as cystatin-C, should be taken into account.