It is actually one of the main causes of hyperlipidemia, and this factor is ignored by too many people!

At present, atherosclerotic cardiovascular disease (ASCVD) has become the leading cause of death among Chinese residents, and dyslipidemia is the most important pathogenic risk factor in the development of ASCVD. Hyperlipidemia can promote the formation of atherosclerosis and induce cardiovascular disease. It is reported that the prevalence and mortality of hyperlipidemia and its complications have risen rapidly in recent years, accounting for more than half of the global deaths. The "Guidelines for Blood Lipid Management in China (2023)" pointed out that the total prevalence of dyslipidemia in adults aged ≥18 years in my country is as high as 35.6%, which is equivalent to nearly 4 out of 10 people suffering from dyslipidemia. At the same time, the incidence of hyperlipidemia is showing a trend of younger age, and more than 20% of children and adolescents in my country have dyslipidemia. In short, hyperlipidemia seriously affects the health of residents and needs to be taken seriously by everyone.

1. Air pollution is an important factor that causes dyslipidemia

Blood lipid levels are affected by many factors, including genetic factors, diet, lifestyle, and economic level. In particular, diet and lifestyle are well known. However, among the many factors that affect blood lipids, there is an important factor that is often overlooked - air pollution.

We know that the four most common test indicators in blood lipid tests include triglycerides (TG), total cholesterol (TC), "good cholesterol" and "bad cholesterol". "Good cholesterol" is actually called high-density lipoprotein cholesterol (HDL-C). Most studies have shown that it helps the body excrete more bad cholesterol, reduce the risk of cardiovascular and cerebrovascular diseases, and protect our cardiovascular and cerebrovascular systems. "Bad cholesterol" is actually called low-density lipoprotein cholesterol (LDL-C), which can cause lipid deposition in blood vessels, narrowing of blood vessels, insufficient blood flow, and atherosclerosis. If you are not careful, coronary heart disease, myocardial infarction, cerebral thrombosis and other diseases will follow. A large number of studies have shown that high levels of LDL-C, TG and TC are risk factors for cardiovascular disease, and high levels of HDL-C are protective factors for cardiovascular disease.

More and more research evidence shows that air pollutants are significantly correlated with increases in TG, TC, and LDL-C or decreases in HDL-C. Dyslipidemia may be one of the important intermediate links in the process of air pollution leading to cardiovascular disease. Air pollution affects lipid metabolism, leading to dyslipidemia, and ultimately increases the incidence of cardiovascular and cerebrovascular diseases, diabetes, etc., posing a serious threat to human life safety.

So, how does air pollution affect blood lipid levels?

First, air pollutants can cause lipid metabolism disorders and disrupt normal blood lipid levels.

Oxidative stress and inflammation play an important role in the potential molecular mechanism of air pollution affecting blood lipids. Air pollutants such as PM10, PM2.5, and PM0.1 can enter the blood and tissues through the respiratory barrier, digestive tract, etc., causing oxidative stress and systemic inflammatory response in the human body, affecting the whole body through cytokines and chemokines, affecting the mitochondrial function in cells, thereby reducing fat decomposition and energy consumption in the human body, leading to lipid metabolism disorders. Taking PM2.5 as an example, the study found that for every 10μg/m3 increase in PM2.5 concentration, triglycerides (TG) increased by 2.23%, total cholesterol (TC) increased by 0.92%, "bad cholesterol" low-density lipoprotein cholesterol (LDL-C) increased by 3.04%, and "good cholesterol" high-density lipoprotein cholesterol (HDL-C) decreased by 2.03%.

Secondly, PM2.5 exposure can also cause dysfunction of "good cholesterol".

Air pollutants not only affect blood lipid levels, but also cause lipoprotein dysfunction. Studies from China and the United States have found that air pollutants affect the ability of high-density lipoprotein to promote cholesterol efflux. A study in the United States found that on the fifth day of exposure to high levels of PM2.5, for every 10μg/m3 increase in PM2.5 concentration, cholesterol efflux decreased by 1.93%.

In addition, air pollution can induce endocrine disorders and increase the risk of insulin resistance.

Air pollution can affect the body's hormone secretion, causing metabolic changes. Insulin is the only hormone in the body that can lower blood sugar. In fact, insulin can also reduce the secretion of very low-density lipoprotein in the liver and promote the absorption of "bad cholesterol" low-density lipoprotein cholesterol. Studies have shown that in the early stages of air pollution, PM2.5 can lead to increased insulin levels in the body; long-term exposure to air pollution may lead to insulin resistance, that is, the body is insensitive to insulin or has decreased responsiveness, further aggravating the abnormality of low-density lipoprotein cholesterol in the body. In addition, air pollution stimulates the activation of the hypothalamic-pituitary (HPA) axis and the autonomic nervous system, leading to increased secretion of glucocorticoids, norepinephrine and adrenaline in healthy adults, increased risk of insulin resistance, and lipid metabolism disorders, ultimately leading to dyslipidemia.

2. The main hazards of dyslipidemia caused by air pollution

Air pollution-induced increases in triglycerides, total cholesterol, low-density lipoprotein cholesterol and decreases in high-density lipoprotein cholesterol all promote the formation of atherosclerosis and lead to cardiovascular and cerebrovascular diseases. A study of Chinese patients with cardiovascular disease found that long-term exposure to air pollution was associated with a higher prevalence of cardiovascular disease, with the strongest association with hyperbetalipoproteinemia, indicating that blood lipids play an important role in air pollution and cardiovascular disease.

The American Heart Association states that exposure to PM2.5 for hours to weeks can lead to cardiovascular events. Studies have shown that every 10 μg/m3 increase in short-term PM2.5 exposure is associated with a 1.1% increase in in-hospital mortality from stroke.

In addition, air pollution is associated with a variety of metabolic disorders, such as fatty liver, diabetes and obesity, all of which are related to dyslipidemia.

III. Key protected groups and protective measures

Therefore, for people with hyperlipidemia, in addition to actively improving their lifestyles by taking medication as directed, controlling their diet, quitting smoking, managing their weight, and increasing exercise, they also need to pay close attention to the adverse effects of air pollution on blood lipids and strengthen relevant protection. There are significant differences in the susceptibility of different groups to air pollution. According to my country's "Guidelines for Health Protection of People in Air Pollution (Haze)", the following groups are more susceptible to air pollution and should pay more attention to protection:

1. Children, the elderly, pregnant women and other sensitive groups;

2. Patients with cardiopulmonary diseases, such as coronary heart disease, heart failure, asthma or chronic obstructive pulmonary disease;

3. People who work outdoors for a long time, such as traffic police, sanitation workers, construction workers, etc.

For individuals, especially those in the above-mentioned sensitive groups with hyperlipidemia, they need to pay more attention to the impact of air pollution on the body and take good protection. Pay attention to the air quality forecast of the meteorological and environmental departments, and arrange travel according to the air quality forecast. In bad weather, you should reduce or even avoid going out and outdoor sports. If you must go out in severely polluted weather, if your physical condition allows, it is recommended to wear a protective mask with a breathing valve. Close doors and windows in time in severe air pollution weather. Use air purifiers indoors reasonably, avoid smoking, and minimize air pollution related to kitchen fumes. In addition, you should also pay attention to scientific diet and rest, strengthen physical exercise, and enhance the body's immunity. Maintain a normal mentality and relax. Advocate green living and reduce pollutant emissions to minimize the health risks brought by air pollution.

References

1. Joint Expert Committee on the Revision of the Chinese Lipid Management Guidelines. Chinese Lipid Management Guidelines (2023). Chinese Journal of Circulation. 2023, 38(3): 237-271

2.Zhang Y, Shi J, Ma Y, Yu N, Zheng P, Chen Z, Wang T, Jia G. Association between Air Pollution and Lipid Profiles. Toxics. 2023;11(11):894.

3.Ossoli A, Cetti F, Gomaraschi M. Air Pollution: Another Threat to HDL Function. Int J Mol Sci. 2022;24(1):317.

4.GBD 2019 Risk Factors Collaborators. Global burden of 87 risk factors in 204 countries and territories, 1990–2019: A systematic analysis for the Global Burden of Disease Study 2019. Lancet 2020, 396, 1223–1249

5.Shah, ASV; Lee, KK; McAllister, DA; Hunter, A.; Nair, H.; Whiteley, W.; Langrish, JP; Newby, DE; Mills, NL Short term exposure to air pollution and stroke: Systematic review and meta-analysis. BMJ 2015, 350, h1295.

6. Arias-Pérez, RD; Taborda, NA; Gómez, DM; Narvaez, JF; Porras, J.; Hernandez, JC Inflammatory effects of particulate matter air pollution. Environ. Sci. Pollut. Res. 2020, 27, 42390–42404.

7.Della Guardia, L.; Shin, AC White and brown adipose tissue functionality is impaired by fine particulate matter (PM2.5) exposure. J. Mol. Med. 2022, 100, 665–676.

8. Wang, L.; Chen, G.; Pan, Y.; Xia, J.; Chen, L.; Zhang, X.; Silang, Y.; Chen, J.; Xu, H.; Zeng, C.; et al.

9.Mathew, AV; Yu, J.; Guo, Y.; Byun, J.; Chen, YE; 565–570.

10.Sundaram, M.; Yao, Z. Recent progress in understanding protein and lipid factors affecting hepatic VLDL assembly and secretion. Nutr. Metab. 2010, 7, 35. [CrossRef]

11. Mihailescu, DV; Vora, A.; Mazzone, T. Lipid Effects of Endocrine Medications. Curr. Atheroscler. Rep. 2011, 13, 88–94. [CrossRef]

de Castro, G.; Zanotto, TM; Boico, VF; Quaresma, PGF; Lima, RPA; et al. Short-term exposure to air pollution (PM(2.5)) induces hypothalamic inflammation, and long-term leads to leptin resistance and obesity via Tlr4/Ikbke in mice. Sci. Rep. 2020, 10, 10160.

13.Chen, Z.; Salam, MT; Toledo-Corral, C.; Watanabe, RM; Xiang, AH; Buchanan, TA; Habre, R.; Bastain, TM; Lurmann, F.;Wilson, JP; 39, 547–554.

14.Yang, BY; Guo, Y.; Markevych, I.; Qian, Z.; Bloom, MS; Heinrich, J.; Dharmage, SC; Rolling, CA; Jordan, SS; Komppula, M.;

15. General Office of the National Health Commission. Notice on Issuing the Health Protection Guidelines for People in Air Pollution (Haze). National Health Commission Disease Control Letter [2019] No. 874.