In mice, the scavenger receptor class B type I (SR-BI) is essential for the delivery of high-density lipoprotein (HDL) cholesterol to the liver and steroidogenic organs. Paradoxically, elevated HDL cholesterol levels are associated with increased atherosclerosis in SR-BI–knockout mice. It is unclear what role SR-BI plays in human metabolism.

There is unequivocal evidence of an inverse association between plasma high-density lipoprotein (HDL) cholesterol concentrations and the risk of cardiovascular disease, a finding that has led to the hypothesis that HDL protects from atherosclerosis. This review details the experimental evidence for this "HDL hypothesis". In vitro studies suggest that HDL has a wide range of anti-atherogenic properties but validation of these functions in humans is absent to date. A significant number of animal studies and clinical trials support an atheroprotective role for HDL; however, most of these findings were obtained in the context of marked changes in other plasma lipids. Finally, genetic studies in humans have not provided convincing evidence that HDL genes modulate cardiovascular risk. Thus, despite a wealth of information on this intriguing lipoprotein, future research remains essential to prove the HDL hypothesis correct.

This study used the Global Burden of Disease data (2010–2021) to analyze the rates and trends of point prevalence, annual incidence, and years lived with disability (YLDs) for metabolic dysfunction-associated steatotic liver disease (MASLD) in 204 countries. Total numbers and age-standardized rates per 100,000 population for MASLD prevalence, annual incidence, and YLDs were compared across regions and countries by age, sex, and sociodemographic index (SDI). Smoothing spline models were used to evaluate the relationship between the burden of MASLD and SDI. Estimates were reported with uncertainty intervals (UI). Globally, in 2021, the age-standardized rates per 100,000 population of point prevalence of MASLD were 15,018.1 cases (95% UI 13,756.5–16,361.4), annual incidence rates were 608.5 cases (598.8–617.7), and YLDs were 0.5 (0.3–0.8) years. MASLD point prevalence was higher in men than women (15,731.4 vs. 14,310.6 cases per 100,000 population). Prevalence peaked at ages 45–49 for men and 50–54 for women. Kuwait (32,312.2 cases per 100,000 people; 95% UI: 29,947.1–34,839.0), Egypt (31,668.8 cases per 100,000 people; 95% UI: 29,272.5–34,224.7), and Qatar (31,327.5 cases per 100,000 people; 95% UI: 29,078.5–33,790.9) had the highest prevalence rates in 2021. The largest increases in age-standardized point prevalence estimates from 2010 to 2021 were in China (16.9%, 95% UI 14.7%–18.9%), Sudan (13.3%, 95% UI 9.8%–16.7%) and India (13.2%, 95% UI 12.0%–14.4%). MASLD incidence varied with SDI, peaking at moderate SDI levels. MASLD is a global health concern, with the highest prevalence reported in Kuwait, Egypt, and Qatar. Raising awareness about risk factors and prevention is essential in every country, especially in China, Sudan and India, where disease incidence and prevalence are rapidly increasing. This research provides a comprehensive analysis of the global burden of MASLD, highlighting its rising prevalence and incidence, particularly in countries with varying sociodemographic indices. The findings are significant for both clinicians and policymakers, as they offer critical insights into the regional disparities in MASLD burden, which can inform targeted prevention and intervention strategies. However, the study’s reliance on modeling and available data suggests cautious interpretation, and further research is needed to validate these findings in clinical and real-world settings.

Background— Prospective epidemiological studies have shown that low plasma levels of HDL cholesterol (HDL-C) are associated with an increased risk for cardiovascular disease (CVD). Despite nearly 40 years of research, however, it is unclear whether this also holds true for individuals with severely reduced levels of HDL-C due to mutations in the lecithin:cholesterol acyltransferase ( LCAT ) gene. Better insight into CVD risk in these individuals may provide clues toward the potential of LCAT as a pharmaceutical target to raise HDL-C levels. Methods and Results— Lipids, lipoproteins, high-sensitivity C-reactive protein (CRP), and carotid artery intima-media thickness (IMT) were assessed in 47 heterozygotes for LCAT gene mutations and 58 family controls. Compared with controls, heterozygotes presented with a mean 36% decrease in HDL-C levels ( P <0.0001), a 23% increase in triglyceride levels ( P <0.0001), and a 2.1-fold increase in CRP levels ( P <0.0001). Mean carotid IMT was significantly increased in heterozygotes compared with family controls (0.623±0.13 versus 0.591±0.08 mm). After adjustment for age, gender, and alcohol use, this difference proved statistically significant ( P <0.0015). Conclusions— The data show that heterozygosity for LCAT gene defects is associated with low HDL-C levels and elevated concentration of triglycerides and CRP in plasma. This phenotype underlies increased IMT in carriers versus controls, which suggests that LCAT protects against atherosclerosis. This in turn indicates that targeting LCAT to raise HDL-C may reduce CVD risk.

The prevalence and severity of metabolic dysfunction–associated steatotic liver disease (MASLD) are increasing. Physicians who treat patients with MASLD may acknowledge the strong coincidence with cardiometabolic disease, including atherosclerotic cardiovascular disease (asCVD). This raises questions on co-occurrence, causality, and the need for screening and multidisciplinary care for MASLD in patients with asCVD, and vice versa. Here, we review the interrelations of MASLD and heart disease and formulate answers to these matters. Epidemiological studies scoring proxies for atherosclerosis and actual cardiovascular events indicate increased atherosclerosis in patients with MASLD, yet no increased risk of asCVD mortality. MASLD and asCVD share common drivers: obesity, insulin resistance and type 2 diabetes mellitus (T2DM), smoking, hypertension, and sleep apnea syndrome. In addition, Mendelian randomization studies support that MASLD may cause atherosclerosis through mixed hyperlipidemia, while such evidence is lacking for liver-derived procoagulant factors. In the more advanced fibrotic stages, MASLD may contribute to heart failure with preserved ejection fraction by reduced filling of the right ventricle, which may induce fatigue upon exertion, often mentioned by patients with MASLD. Some evidence points to an association between MASLD and cardiac arrhythmias. Regarding treatment and given the strong co-occurrence of MASLD and asCVD, pharmacotherapy in development for advanced stages of MASLD would ideally also reduce cardiovascular events, as has been demonstrated for T2DM treatments. Given the common drivers, potential causal factors and especially given the increased rate of cardiovascular events, comprehensive cardiometabolic risk management is warranted in patients with MASLD, preferably in a multidisciplinary approach.