Meta-analytic evidence for increased low-grade systemic inflammation and oxidative stress in hypothyroid patients. Can levothyroxine replacement therapy mitigate the burden?

PURPOSE

This series of meta-analyses were aimed to elucidate the impact of hypothyroidism on low-grade systemic inflammation and oxidative stress assessed by C-reactive protein (CRP) and malondialdehyde (MDA) respectively; and to evaluate the effect of levothyroxine replacement therapy (LRT) on those outcomes.

METHODS

PubMed database and the key studies references were searched prior to March 3, 2020. Data on serum or plasma CRP and MDA levels in SHT (subclinical) and/or OHT (overt) hypothyroid patients and controls were extracted to compute overall standardized mean differences (SMD) by the random-effects model.

RESULTS

A total of 93 studies were entered into analyses and ten main meta-analyses were performed. OHT (SMD = 0.72 [0.39; 1.04], k = 35), SHT (SMD = 1.58 [0.78; 2.38], k = 56) and even mild SHT (TSH < 10 mU/L, SMD = 2.19 [0.02; 4.37], k = 13) proved to have a detrimental effect on CRP levels. LRT showed a favorable effect on CRP levels, particularly in OHT (SMD = -0.30 [-0.57; -0.02], k = 17). Increased levels of MDA were also found, especially in OHT (SMD = 2.49 [0.66; 4.31], k = 13). LRT may also improve MDA levels; however future studies would further validate the advantageous effect of LRT in hypothyroidism. Heterogeneity primarily originated from different study designs and geographic locations.

CONCLUSION

Overall, these meta-analyses reveal that screening for hs-CRP and MDA in hypothyroid patients as simple biomarkers of low-grade systemic inflammation and oxidative stress may become a useful tool to identify those at increased risk who may benefit most from early interventions.

Update on Neonatal Isolated Hyperthyrotropinemia: A Systematic Review

The purpose of this paper was to systematically summarize the published literature on neonatal isolated hyperthyrotropinemia (HTT), with a focus on prevalence, L-T4 management, re-evaluation of thyroid function during infancy or childhood, etiology including genetic variation, thyroid imaging tests, and developmental outcome. Electronic and manual searches were conducted for relevant publications, and a total of 46 articles were included in this systematic review. The overall prevalence of neonatal HTT was estimated at 0.06%. The occurrence of abnormal imaging tests was found to be higher in the persistent than in the transient condition. A continuous spectrum of thyroid impairment severity can occur because of genetic factors, environmental factors, or a combination of the two. Excessive or insufficient iodine levels were found in 46% and 16% of infants, respectively. Thirty-five different genetic variants have been found in three genes in 37 patients with neonatal HTT of different ethnic backgrounds extracted from studies with variable design. In general, genetic variants reported in the TSHR gene, the most auspicious candidate gene for HTT, may explain the phenotype of the patients. Many practitioners elect to treat infants with HTT to prevent any possible adverse developmental effects. Most patients with thyroid abnormalities and/or carrying monoallelic or biallelic genetic variants have received L-T4 treatment. For all those neonates on treatment with L-T4, it is essential to ensure follow-up until 2 or 3 years of age and to conduct medically supervised trial-off therapy when warranted. TSH levels were found to be elevated following cessation of therapy in 44% of children. Withdrawal of treatment was judged as unsuccessful, and medication was restarted, in 78% of cases. Finally, data extracted from nine studies showed that none of the 94 included patients proved to have a poor developmental outcome (0/94). Among subjects presenting with normal cognitive performance, 82% of cases have received L-T4 therapy. Until now, the precise neurodevelopmental risks posed by mild disease remain uncertain.

Prenatal stress and later metabolic consequences: Systematic review and meta-analysis in rodents

BACKGROUND

Numerous rodent studies have evaluated the effects of maternal stress (MS) on later in life susceptibility to Metabolic Syndrome (MetS) intermediate phenotypes with varying results. The aim of this study was to quantitatively synthesize the available data on the effects of MS on offspring obesity, estimated indirectly by body mass (BM), body fat (BF) and plasma leptin; systolic blood pressure (SBP); plasma glucose (and insulin) and blood lipid concentrations.

METHODS

Literature was screened and summary estimates of the effect of MS outcomes were calculated by using random-effects models. Data on the effects of exogenous corticosteroid administration (or inhibition of 11β-HSD2) during pregnancy in rodents was analysed separately to characterize the direct phenotypic effects of prenatal corticosteroid excess (PCE).

RESULTS

We conducted 14 separate meta-analyses and synthesized relevant data on outcomes scarcely reported in literature. Both MS and PCE were associated with low birth weight without rapid catch-up growth resulting in decreased body mass later in life. Our analysis also revealed significant and contradictory effects on offspring adiposity. Little evidence was found for effects on glucose metabolism and blood lipids. We identified increased SBP in offspring exposed to PCE; however, there is not enough data to draw any conclusion about effects of MS on SBP.

CONCLUSIONS

Neonatal weight proved to be decreased in offspring prenatally exposed to stress or corticosteroids, but laboratory rodents in the absence of a challenging environment did not show catch-up growth. The available evidence is inconclusive regarding the effect on adiposity revealing clear methodological and knowledge gaps. This meta-analysis also confirmed a significant positive association between PCE and SBP. Nevertheless, additional studies should address the association with MS.

Perinatal taurine exerts a hypotensive effect in male spontaneously hypertensive rats and down-regulates endothelial oxide nitric synthase in the aortic arch

Essential hypertension is considered to be a result of the interaction between genetic and environmental factors, including perinatal factors. Different advantageous perinatal factors proved to have beneficial long-lasting effects against an abnormal genetic background. Taurine is a ubiquitous sulphur-containing amino acid present in foods such as seafood. The antihypertensive effects of taurine have been reported in experimental studies and in human hypertension. We aimed to investigate the effects of perinatal treatment with taurine in spontaneously hypertensive rats (SHR), a known model of genetic hypertension. Female SHR were administered with taurine (3 g/L) during gestation and lactation (SHR-TAU). Untreated SHR and Wistar-Kyoto rats (WKY) were used as controls. Long-lasting effects in offspring were investigated. Addition of taurine to the mother's drinking water reduced blood pressure in adult offspring. No differences were observed in cardiac hypertrophy. Findings on morphometric evaluations suggest that perinatal treatment with taurine would be partially effective in improving structural alterations of the aorta. Modifications in gene expression of Bcl-2 family members and upregulation of endothelial nitric oxide synthase in the aorta of 22-week-old male offspring were found. No differences were observed on relative telomere length in different cardiovascular tissues between SHR and SHR-TAU. Altogether results suggest that taurine programming, albeit sex specific, is associated with gene expression changes which ultimately may lead to improvement of aortic remodelling and enhanced endothelial function because of augmented nitric oxide (NO) production.

The Association between High Fat Diet around Gestation and Metabolic Syndrome-related Phenotypes in Rats: A Systematic Review and Meta-Analysis

Numerous rodent studies have evaluated the effects of a maternal high-fat diet (HFD) on later in life susceptibility to Metabolic Syndrome (MetS) with varying results. Our aim was to quantitatively synthesize the available data on effects of maternal HFD around gestation on offspring's body mass, body fat, plasma leptin, glucose, insulin, lipids and systolic blood pressure (SBP). Literature was screened and summary estimates of the effect of maternal HFD on outcomes were calculated by using fixed- or random-effects models. 362 effect sizes from 68 studies together with relevant moderators were collected. We found that maternal HFD is statistically associated with higher body fat, body weight, leptin, glucose, insulin and triglycerides levels, together with increased SBP in offspring later in life. Our analysis also revealed non-significant overall effect on offspring's HDL-cholesterol. A main source of variation among studies emerged from rat strain and lard-based diet type. Strain and sex -specific effects on particular data subsets were detected. Recommendations are suggested for future research in the field of developmental programming of the MetS. Despite significant heterogeneity, our meta-analysis confirms that maternal HFD had long-term metabolic effects in offspring.

Common variants in SOCS7 gene predict obesity, disturbances in lipid metabolism and insulin resistance

BACKGROUND AND AIMS

Specific Suppressor of Cytokine Signaling (SOCS) members, such as SOCS7, may play a role in the development of insulin resistance (IR) owing to their ability to inhibit insulin signaling pathways. The objective was to explore the association between common variants and related haplotypes in SOCS7 gene and metabolic traits related to obesity, lipid metabolism and IR.

METHODS AND RESULTS

780 unrelated men were included in a cross-sectional study. We selected three tagged SNPs that capture 100% of SNPs with minor allele frequency ≥ 0.10. Analyses were done separately for each SNP and followed up by haplotype analysis. rs8074124C was associated with both obesity (p = 0.005) and abdominal obesity (p = 0.002) and allele C carriers showed, in comparison with TT carriers, lower BMI (p = 0.001) and waist circumference (p = 0.001). rs8074124CC- carriers showed lower fasting insulin (p = 0.017) and HOMA-IR (p = 0.018) than allele T carriers. rs12051836C was associated with hypertriglyceridemia (p = 0.009) and hypertriglyceridemic waist (p = 0.006). rs12051836CC- carriers showed lower fasting insulin (p = 0.043) and HOMA-IR (p = 0.042). Haplotype-based association analysis (rs8074124 and rs12051836 in that order) showed associations with lipid and obesity -related phenotypes, consistent with single locus analysis. Haplotype analysis also revealed association between haplotype CT and both decreased HDL-C (p = 0.026) and HDL-C (p = 0.014) as a continuous variable.

CONCLUSIONS

We found, for the first time, significant associations between SOCS7 common variants and related haplotypes and obesity, IR and lipid metabolism disorders.

Association between β2-adrenoceptor (ADRB2) haplotypes and insulin resistance in PCOS

OBJECTIVE

The aim of this study was to explore β2-adrenoceptor (ADRB2) haplotype associations with phenotypes and quantitative traits related to insulin resistance (IR) and the metabolic syndrome (MS) in a polycystic ovary syndrome (PCOS) population. A secondary purpose was to assess the association between ADRB2 haplotype and PCOS.

DESIGN

Genetic polymorphism analysis. Cross-sectional case-control association study.

SETTING

Medical University Hospital and research laboratory.

PATIENTS

One hundred and sixty-five unrelated women with PCOS and 116 unrelated women without PCOS (control sample).

MEASUREMENTS

Clinical and biochemical measurements, and ADRB2 genotyping in PCOS patients and control subjects.

METHODS

ADRB2 haplotypes (comprising rs1042711, rs1801704, rs1042713 and rs1042714 in that order), genotyping and statistical analysis to evaluate associations with continuous variables and traits related to IR and MS in a PCOS population. Associations between ADRB2 haplotypes and PCOS were also assessed.

RESULTS

We observed an age-adjusted association between ADRB2 haplotype CCGG and lower insulin (P = 0·018) and HOMA (P = 0·008) in the PCOS sample. Interestingly, the expected differences in surrogate measures of IR between cases and controls were not significant in CCGG/CCGG carriers. In the case-control study, genotype CCGG/CCGG was associated with a 14% decrease in PCOS risk (P = 0·043), taking into account confounding variables.

CONCLUSIONS

Haplotype I (CCGG) has a protective role for IR and MS in PCOS.

The rs1801278 G>A polymorphism of IRS-1 is associated with metabolic syndrome in healthy nondiabetic men. Modulation by cigarette smoking status

AIMS

To explore associations between IRS-1 rs1801278 G>A polymorphism and metabolic syndrome (MS).

METHODS

rs1801278 G>A was genotyped in 610 healthy Argentinian men.

RESULTS

GA carriers had lower risk of MS (OR=0.52, P=0.045), particularly among smokers (OR=0.10, P=0.006).

CONCLUSIONS

rs1801278 GA carriers had lower risk of MS, especially among smokers.

Association of the TGrI29 microsatellite in thyroglobulin gene with autoimmune thyroiditis in a Argentinian population: a case-control study

Autoimmune thyroid disease (AITD) is a multifactorial disorder that involves a putative association with thyroid autoantigen-specific and immune regulatory genes, as well as environmental factors. The thyroglobulin gene is the main identified thyroid autoantigen-specific gene associated to autoimmune thyroiditis. The aim of this work was to test for evidence of allelic association between autoimmune thyroiditis (AT) and thyroglobulin polymorphism markers in Argentinian patients. We studied six polymorphisms distributed throughout all the thyroglobulin gene: four microsatellites (Tgms1, Tgms2, TGrI29, and TGrI30), one insertion/deletion polymorphism (IndelTG-IVS18), and one exonic single nucleotide polymorphism (c.7589G>A) in 100 AT patients and 100 healthy control subjects. No differences in allele and genotype frequencies distribution were observed between autoimmune thyroiditis cases and controls for Tgms1, Tgms2, TGrI30, IndelTG-IVS18, and c.7589G>A. However, when we analyzed autoimmune thyroiditis patients with the TGrI29 microsatellite we found a significant association between the 197-bp allele and autoimmune thyroiditis (33.50% vs. 19.00% in control group) (P = 0.001). In addition, a significant major prevalence of the 197/201-bp genotype has been also seen in autoimmune thyroiditis subjects (59% vs. 24% in control group, P < 0.0001). In conclusion, our work showed the association between the thyroglobulin gene and autoimmune thyroiditis in Argentinian population and supports the described evidence of thyroglobulin as a thyroid-specific gene linked to AITD.

A functional nonsynonymous toll-like receptor 4 gene polymorphism is associated with metabolic syndrome, surrogates of insulin resistance, and syndromes of lipid accumulation

Toll-like receptor 4 (TLR4) plays a key role in the activation of innate immune responses. Loss-of-function mutations in TLR4 prevent diet-induced obesity and insulin resistance (IR). We conducted a population cross-sectional study to evaluate whether Asp299Gly (rs4986790) TLR4 gene polymorphism is associated with metabolic syndrome (MS), surrogates of IR, and syndromes of lipid accumulation (SLAs) in Argentinean healthy male subjects. rs4986790 was genotyped in 621 healthy unrelated male blood donors. National Cholesterol Education Program/Adult Treatment Panel III-MS (NCEP/ATP III-MS); SLAs such as enlarged waist elevated triglyceride syndrome (EWET), hypertriglyceridemic waist (HW), and overweight-lipid syndrome (OLS); and surrogates of IR were assessed. The prevalence of MS, OLS, and EWET was significantly higher among Asp299Asp carriers (P < .05). These findings were confirmed using 32 000 bootstrap samples. Surrogate markers of IR were also significantly higher in Asp299Asp carriers (P < .05). Most findings were especially strengthened among individuals with C-reactive protein below the 95th percentile and/or total cholesterol to high-density lipoprotein cholesterol ratio >or=5. This is the first report to find, in Argentinean healthy male blood donors, associations between the Asp299Asp genotype of rs4986790 TLR4 gene polymorphism and high risk for NCEP/ATP III-MS, SLAs, and surrogates of IR. These findings are consistent with previous functional and observational studies showing that Asp299 allele, in comparison with Gly299, is associated with increased TLR4 activation, higher levels of inflammatory cytokines, acute-phase reactants and soluble adhesion molecules, and higher risk of atherosclerosis.

Pro12Ala polymorphism of the peroxisome proliferatoractivated receptor-gamma gene is associated with metabolic syndrome and surrogate measures of insulin resistance in healthy men: interaction with smoking status

BACKGROUND

The Pro12Ala polymorphism (rs1801282), a nonsynonymous substitution of peroxisome proliferator-activated receptor-gamma (PPARG), has been robustly associated with type 2 diabetes. However, its role in metabolic syndrome (MetS) remains poorly understood. The associations among rs1801282, MetS and surrogate measures of insulin resistance (IR) were investigated in the present study.

METHODS AND RESULTS

A cross-sectional population-based survey of 572 unrelated healthy male Argentinian blood donors with normal findings on medical examination and not taking any medication was conducted. MetS was assessed using the National Cholesterol Education Program/Adult Treatment Panel III (NCEP/ATP III) criteria, and the HOMA-IR, and QUICKI were calculated. Genotyping of rs1801282 was performed using RFLP-PCR. The prevalence of MetS was 26.2%. The Pro/Ala genotype (and the Ala12 allele) was associated with a high risk for MetS (odds ratio (OR) 1.67 [95% confidence interval (CI) 1.03-2.72], P=0.0394). This was highlighted among nonsmokers (OR 2.20 [95%CI 1.25-3.88], P=0.0059). ANCOVA confirmed an interaction between smoking status and this association (P=0.031). Ala12 carriers had a higher waist circumference than noncarriers (P=0.0065). Among nonsmokers, surrogates of IR, such as HOMA-IR, were significantly higher in Ala12 carriers than in noncarriers (P<0.05).

CONCLUSIONS

Healthy men, in particular nonsmokers, carrying the Ala12 allele of PPARG rs1801282 polymorphism, have a high risk for MetS and IR.