Dyslipidemia Is a Risk Factor for Hypothyroidism in Women: A Longitudinal Cohort Study from South Korea

Background: Hypothyroidism is a risk factor for dyslipidemia. We explored whether dyslipidemia is a risk factor for hypothyroidism. Methods: We performed a retrospective analysis of data from a longitudinal cohort study of South Korean adults who underwent medical examination and ≥4 biochemical assessments of thyroid function. The primary outcome was hypothyroidism (thyrotropin [TSH] >4.2 mU/L), and the secondary outcome was severe subclinical hypothyroidism (SCH; TSH ≥10.0 mU/L and normal free thyroxine [fT4] level) or overt hypothyroidism (OH; total triiodothyronine <80 ng/dL and/or fT4 < 0.93 ng/dL and high TSH values). The association of baseline dyslipidemia status with subsequent hypothyroidism was evaluated using Kaplan-Meier curves with the log-rank test and Cox proportional hazards regression models (for the entire population and respective genders). Subgroup analyses according to age (<40 and ≥40 years) and body-mass index (BMI; <23, 23-25, and ≥25 kg/m²) were performed according to gender. Results: We included 1665 participants. During a median follow-up period of 61.0 months, 24.3% (404/1665) individuals developed hypothyroidism. Among these, 36 participants (2.1%) had severe SCH or OH. Excluding patients with a first abnormal TSH level at last follow-up, 44.5% (126/283) of the patients with hypothyroidism had spontaneous TSH normalization. In respective multivariate analyses, dyslipidemia at baseline was independently associated with development of hypothyroidism in women (adjusted hazard ratio [HR] = 2.05 [1.31-3.19], p = 0.002), but not in men (adjusted HR = 1.00 [0.77-1.30], p = 0.991). In women, the presence of dyslipidemia at baseline was associated with development of severe SCH or OH (adjusted HR = 5.33 [1.41-20.12], p = 0.014). In women, respective associations according to age and BMI were as follows: age <40 years, adjusted HR = 2.90 (1.34-6.26, p = 0.007); age ≥40 years, adjusted HR = 1.85 (1.08-3.14, p = 0.023); BMI <23 kg/m², adjusted HR = 1.68 (0.82-3.43, p = 0.151); BMI = 23-25 kg/m², adjusted HR = 2.17 (0.93-5.07, p = 0.071); and BMI ≥25 kg/m², adjusted HR = 2.82 (1.16-6.86, p = 0.022). Conclusions: In Korean adults, dyslipidemia was associated with development of hypothyroidism in women. Our findings require confirmation.

Lipid metabolism in autoimmune rheumatic disease: implications for modern and conventional therapies

Suppressing inflammation has been the primary focus of therapies in autoimmune rheumatic diseases (AIRDs), including rheumatoid arthritis and systemic lupus erythematosus. However, conventional therapies with low target specificity can have effects on cell metabolism that are less predictable. A key example is lipid metabolism; current therapies can improve or exacerbate dyslipidemia. Many conventional drugs also require in vivo metabolism for their conversion into therapeutically beneficial products; however, drug metabolism often involves the additional formation of toxic by-products, and rates of drug metabolism can be heterogeneous between patients. New therapeutic technologies and research have highlighted alternative metabolic pathways that can be more specifically targeted to reduce inflammation but also to prevent undesirable off-target metabolic consequences of conventional antiinflammatory therapies. This Review highlights the role of lipid metabolism in inflammation and in the mechanisms of action of AIRD therapeutics. Opportunities for cotherapies targeting lipid metabolism that could reduce immunometabolic complications and potential increased cardiovascular disease risk in patients with AIRDs are discussed.

Causal relationships between rheumatism and dyslipidemia: A two-sample Mendelian randomization study

BACKGROUND

Dyslipidemia is often observed in rheumatic diseases, such as ankylosing spondylitis (AS), rheumatoid arthritis (RA), and systemic lupus erythematosus (SLE), yet it remains to be detected whether rheumatic diseases have a causal effect on dyslipidemia.

METHODS

Significant (P < 5 × 10^-8) and independent (r² < 0.1) single-nucleotide polymorphisms in genome-wide association studies were selected as instrumental variables to conduct Mendelian randomization (MR) analysis. Inverse variance weighted, weighted median, and MR-Egger regression were adopted for the causal inference. Subsequently, sensitivity analysis was conducted to assess the stability and reliability of MR.

RESULTS

The MR results revealed positive causal relationships of AS with total cholesterol (TC) (β = 0.089, 95% CI = 0.050 to 0.128, P = 6.07 × 10^-6), low-density lipoprotein (LDL) (β = 0.087, 95% CI = 0.047 to 0.127, P = 1.91 × 10^-5), and high-density lipoprotein (HDL) (β = 0.043, 95% CI = 0.001 to 0.074, P = 0.009). There was no causal effect of RA on TC (β = 0.008, 95% CI = 4.86 × 10^-4 to 0.017, P = 0.064), LDL (β = 6.4 × 10^-4, 95% CI = -0.008 to 0.007, P = 0.871), or HDL (β = 0.005, 95% CI = -0.003 to 0.013, P = 0.200). Additionally, SLE had negative causal links for TC (β = -0.025, 95% CI = -0.036 to -0.015, P = 4.42 × 10^-6), LDL (β = -0.015, 95% CI = -0.025 to -0.005, P = 0.003), and HDL (β = -0.013, 95% CI = -0.021 to -0.004, P = 0.004). The results were stable and reliable.

CONCLUSION

This study suggested positive causal effects of AS on TC, LDL, and HDL and negative causal effects of SLE on these cholesterol levels, which could provide much help for the pathogenesis and treatment of rheumatic disease patients with dyslipidemia.

Sex hormones drive changes in lipoprotein metabolism

Women have a reduced cardiovascular disease (CVD) risk compared with men, which could be partially driven by sex hormones influencing lipid levels post puberty. The interrelationship between sex hormones and lipids was explored in pre-pubertal children, young post-pubertal cis-men/women, and transgender individuals on cross-sex-hormone treatment (trans-men/women) using serum metabolomics assessing 149 lipids. High-density lipoproteins (HDL, typically atheroprotective) were significantly increased and very-low- and low-density lipoproteins (typically atherogenic) were significantly decreased in post-pubertal cis-women compared with cis-men. These differences were not observed pre-puberty and were induced appropriately by cross-sex-hormone treatment in transgender individuals, supporting that sex hormones regulate lipid metabolism in vivo. Only atheroprotective apolipoprotein (Apo)A1 expressing lipoproteins (HDL) were differentially expressed between all hormonally unique comparisons. Thus, estradiol drives a typically atheroprotective lipid profile through upregulation of HDL/ApoA1, which could contribute to the sexual dimorphism observed in CVD risk post puberty. Together, this could inform sex-specific therapeutic strategies for CVD management.

High-density lipoprotein functionality in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a heterogeneous disease which is characterized with excessive inflammation and autoantibodies, macrophage and complement activation, and subsequently immunologically mediated tissue damage. In spite of improved treatments of SLE, these patients experience premature atherosclerosis and the rate of mortality among them remains high. Autoantibodies and circulating immune complexes might contribute to the pathogenesis of atherosclerosis by injuring the endothelium, as well as inducing pro-inflammatory and pro-adhesive endothelial cell phenotypes, as well as altering the metabolism of lipoproteins involved in atherogenesis. Hence, high levels of atherogenic lipoproteins (like low-density lipoprotein (LDL) and very low-density lipoprotein (VLDL)) and low levels of high-density lipoprotein (HDL-C) are important risk factors for atherosclerotic cardiovascular complications in SLE patients but these traditional risk factors fail to fully explain the increased risk of cardiovascular disease (CVD) in these patients. The exact mechanism by which inflammation decreases HDL levels is not defined, but decreases in apoA-I production and lecithin cholesterol acyltransferase (LCAT) activity, as well as increased serum amyloid A (SAA), endothelial lipase and secretory phospholipase A2 activity (PLA2) could all contribute. In addition, during inflammation multiple changes in HDL structure occur, leading to alterations in HDL function which may be implicated in the CVD complications of SLE. Therefore, this review will aim to identify the mechanisms implicated in HDL dysfunction which occurs in SLE patients.

Serum Immunoglobulin M Concentration Varies with Triglyceride Levels in an Adult Population: Tianjin Chronic Low-Grade Systemic Inflammation and Health (TCLSIHealth) Cohort Study

Persistent low-grade inflammation is thought to underlie the pathogenesis of many chronic diseases, such as cardiovascular diseases and metabolic syndrome. Autoimmunity is correlated with increased levels of chronic low-grade inflammation, and immunoglobulin M (IgM) is reactive to autoantigens and believed to be important for autoimmunity. Triglyceride (TG) is fatty acid carrier and initiator of oxidative stress, and it has been hypothesized that TG stimulates B cells to secrete IgM. However, few studies have investigated the relationship between TG and IgM in human populations. We designed a cross-sectional and prospective cohort study to evaluate how serum TG levels are related to IgM concentration. Participants were recruited from Tianjin Medical University General Hospital-Health Management Centre. Both a baseline cross-sectional (n = 10,808) and a prospective assessment (n = 2,615) were performed. Analysis of covariance was used in the cross-sectional analysis. After multiple adjustments for confounding factors, serum IgM level in the highest quartile of TG in males was significantly higher than levels in lower quartiles (P <0.05). There was no significant difference between the four quartiles in females (P = 0.91). In follow-up analysis, a multiple linear regression model showed a significant and positive correlation between changes in IgM levels and changes of TG concentration in males (P = 0.04, standard β coefficient = 0.882). This cross-sectional and cohort study is the first to show that serum concentration of IgM varies with TG levels in adult male populations. Further research is needed to explore the mechanism by which TG leads to increased IgM concentration.