Causal Effect of Visceral Adipose Tissue Accumulation on the Human Longevity: A Mendelian Randomization Study

Gilbert's syndrome revisited

Gilbert's syndrome, also known as benign hyperbilirubinaemia, was described more than 100 years ago. It has usually been considered a physiological abnormality characterised by a mild elevation of the systemic level of unconjugated bilirubin, in the absence of any underlying liver or overt haemolytic disease. However, since the re-discovery of the potent antioxidant effects of bilirubin in the late 1980s, as well as multiple intracellular signalling pathways affected by bilirubin, an ever-increasing body of evidence suggests that individuals with Gilbert's syndrome may benefit from the mild hyperbilirubinaemia and are actually protected from the development of a wide variety of "diseases of civilisation" such as cardiovascular diseases, certain cancers, and autoimmune or neurodegenerative diseases. This review analyses the current state of medical knowledge given recent discoveries in this rapidly developing field, as well as their possible clinical significance, and provides a new perspective on this condition.

Association between adiposity and facial aging: results from a Mendelian randomization study

BACKGROUND

Skin, as a sociologically meaningful interface, has psychological implications different from other organs, particularly in the context of the global population aging. Growing evidence suggests that facial aging is associated with an increased risk of adiposity. Existing research, however, were observational, and while they may find some correlations, it is difficult to simply disentangle non-causal or reverse-causal links because these associations may be confounded or fail to accurately reflect true causative linkages.

OBJECTIVES

We conducted a 2-sample Mendelian randomization (MR) study to examine the potential effect of facial aging on the risk of broad obesity and its three major adiposity indicators, including body mass index (BMI), body fat percentage (BF%) and waist circumference (WC).

METHODS

Genetic instruments from IEU OpenGWAS project, one of the largest available genome-wide association studies (GWAS) for facial aging (423,999 samples) were used to investigate the relation to broad obesity (32,858 cases, 65,839 controls). Using the inverse-variance weighted (IVW) technique, single nucleotide polymorphisms (SNPs) associated with adiposity indicators (BMI (461,460 samples), BF% (454,633 samples), and WC (462,166 samples)) were investigated in relationship to facial aging. Further sensitivity analyses were performed, including Mendelian randomization-Egger (MR-Egger), weighted median estimates, and leave-one-out analysis, to evaluate the consistency of the results and related potential issues in MR studies.

RESULTS

We identified strong and significant correlations between adiposity and facial aging in the 17 broad obesity-associated SNPs (IVW estimate of odds ratio OR = 1.020, 95% CI 1.010-1.029, P = 7.303e - 05), 458 BMI-associated SNPs (IVW estimate of odds ratio OR = 1.047, 95% CI 1.0357-1.058, P = 1.154e - 16),for the 395 BF%-associated SNPs (OR = 1.056, 95%CI 1.040-1.072,P = 7.617e - 12), or for the 374 WC-associated SNPs (OR = 1.072, 95% CI 1057-1.087,P = 1.229e - 23). A range of complementary methodologies have been employed to evaluate horizontal pleiotropy and related potential caveats occurring in MR research.

CONCLUSIONS

Using Mendelian randomization as an alternative approach to investigate causality, we found a causal relationship between adiposity and facial aging, which was statistically strong and significant.

Which Factors Influence Healthy Aging? A Lesson from the Longevity Village of Bama in China

A growing aging population is associated with increasing incidences of aging-related diseases and socioeconomic burdens. Hence, research into healthy longevity and aging is urgently needed. Longevity is an important phenomenon in healthy aging. The present review summarizes the characteristics of longevity in the elderly population in Bama, China, where the proportion of centenarians is 5.7-fold greater than the international standard. We examined the impact of genetic and environmental factors on longevity from multiple perspectives. We proposed that the phenomenon of longevity in this region is of high value for future investigations in healthy aging and aging-related disease and may provide guidance for fostering the establishment and maintenance of a healthy aging society.

Functionally Significant Variants in Genes Associated with Abdominal Obesity: A Review

The high prevalence of obesity and of its associated diseases is a major problem worldwide. Genetic predisposition and the influence of environmental factors contribute to the development of obesity. Changes in the structure and functional activity of genes encoding adipocytokines are involved in the predisposition to weight gain and obesity. In this review, variants in genes associated with adipocyte function are examined, as are variants in genes associated with metabolic aberrations and the accompanying disorders in visceral obesity.

Association of Chinese Visceral Adiposity Index and Carotid Atherosclerosis in Steelworkers: A Cross-Sectional Study

The Chinese Visceral Adiposity Index (CVAI) is an indicator of visceral adiposity dysfunction used to evaluate the metabolic health of the Chinese population. Steelworkers are more likely to be obese due to their exposure to special occupational factors, and have a higher prevalence of carotid atherosclerosis (CAS). This study aimed to analyze the special relationship between CVAI and CAS among steelworkers. A total of 4075 subjects from a northern steel company were involved in the cross-sectional study. Four logistic regression models were developed to analyze the correlation between CVAI and CAS. In addition, the restricted cubic spline was applied to fit the dose-response association between CVAI and CAS risk. In the study, the prevalence of CAS was approximately 25.94%. After adjustment for potential confounders, we observed a positive correlation between CVAI and CAS risk. Compared to the first CVAI quartile, the effect value odds ratio (OR) and 95% CI in the second, third, and fourth CVAI quartile were 1.523 (1.159-2.000), 2.708 (2.076-3.533), and 4.101 (3.131-5.372), respectively. Additionally, this positive correlation was stable in all subgroups except for female. Furthermore, we also found a non-linear relationship between CVAI and CAS risk (p nonlinear < 0.05). Notably, CVAI could increase the risk of CAS when higher than 106. In conclusion, our study showed that CVAI might be a reliable indicator to identify high-risk populations of CAS among steelworkers.

Sleep traits, fat accumulation, and glycemic traits in relation to gastroesophageal reflux disease: A Mendelian randomization study

Background

Sleep traits, fat accumulation, and glycemic traits are associated with gastroesophageal reflux disease (GERD) in observational studies. However, whether their associations are causal remains unknown. We performed a Mendelian randomization (MR) study to determine these causal relationships.

Methods

Independent genetic variants associated with insomnia, sleep duration, short sleep duration, body fat percentage, visceral adipose tissue (VAT) mass, type 2 diabetes, fasting glucose, and fasting insulin at the genome-wide significance level were selected as instrumental variables. Summary-level data for GERD were derived from a genome-wide association meta-analysis including 78,707 cases and 288,734 controls of European descent. Inverse variance weighted (IVW) was used for the main analysis, with weighted median and MR-Egger as complements to IVW. Sensitivity analyses were performed using Cochran's Q test, MR-Egger intercept test, and leave-one-out analysis to estimate the stability of the results.

Results

The MR study showed the causal relationships of genetically predicted insomnia (odds ratio [OR] = 1.306, 95% confidence interval [CI] 1.261 to 1.352; p = 2.24 × 10^-51), short sleep duration (OR = 1.304, 95% CI: 1.147 to 1.483, p = 4.83 × 10^-5), body fat percentage (OR = 1.793, 95% CI 1.496 to 2.149; p = 2.68 × 10^-10), and visceral adipose tissue (OR = 2.090, 95% CI 1.963 to 2.225; p = 4.42 × 10^-117) with the risk of GERD. There was little evidence for causal associations between genetically predicted glycemic traits and GERD. In multivariable analyses, genetically predicted VAT accumulation, insomnia, and decreased sleep duration were associated with an increased risk of GERD.

Conclusion

This study suggests the possible roles of insomnia, short sleep, body fat percentage, and visceral adiposity in the development of GERD.

Effect of visceral adipose tissue mass on coronary artery disease and heart failure: A Mendelian randomization study

OBJECTIVES

Obesity is associated with coronary artery disease (CAD) and its risk factors in observational studies. This two-sample Mendelian randomization (MR) study investigated the effect of visceral adipose tissue (VAT) mass on coronary artery disease (CAD), myocardial infarction (MI) and heart failure (HF).

METHODS

Genetic variants (220 SNPs, P < 5 × 10^-8) associated with VAT mass were obtained from a genome-wide association study (GWAS) in the UK Biobank. Genetic associations with CAD outcomes including CAD and myocardial infarction (MI) were obtained from the CARDIoGRAMplusC4D 1000 Genomes-based GWAS (including up to 60,801 cases and 123,504 controls) and data on patients with HF were obtained from the HERMES Consortium (47,309 cases and 930,014 controls). The effects of VAT mass on CAD outcomes and HF were estimated using the inverse variance weighted (IVW) method. Sensitivity analysis and multi-variable MR were used to examine the stability of the IVW results.

RESULTS

Our results showed that genetically predicted higher VAT mass was associated with increased risk of CAD (odds ratio [OR] 1.57, 95% confidence interval [CI], 1.44-1.71; P = 7.62 × 10^-24), MI (OR 1.63, 95% CI: 1.48-1.79; P = 3.76 × 10^-24) and HF (OR 1.71, 95% CI: 1.60-1.83; P = 1.72 × 10^-53). These findings remained significant in the sensitivity analysis and multi-variable MR.

CONCLUSION

This MR study suggests that genetic determinants of VAT mass are causally associated with CAD, MI and HF.