Gut microbiota and heart disease: Understanding the links

The gut microbiota is a massive community of microorganisms that live in our gastrointestinal tract, where they help our body fight off infections, produce chemicals that feed our cells and influence our physiology and metabolism^1-2.

In recent years, multiple studies have reported on the link between gut microbiota and heart disease, a link that involves a wide range of factors. For example, intestinal-derived chemicals such as lipopolysaccharides³, indoxyl sulfate⁴, and para-cresyl sulfate⁵have shown to have important metabolic roles in conditions like atherosclerosis and cardio-renal dysfunction.

Gut Microbiota and health

The human gut is home for more than 100 trillion bacteria from hundreds of different species, as well as for other microorganisms like viruses and fungi⁶. In recent decades, research has identified multiple important roles for the human gut microbiota, such as:

• Improving host nutrition and energy productivity⁷
• Maintenance of epithelial homeostasis⁸
• Interaction with drug metabolism and toxicity⁹
• Influencing immune function¹⁰
• Protecting our body from invading pathogens¹¹

The gut microbiota are also important producers of chemicals like uremic toxins, bile acids, trimethylamine-N-oxide (TMAO), short-chain fatty acids (SCFA), lipopolysaccharides (LPS), nitric oxide, vitamin K, vitamin B complex, gut hormones, and neurotransmitters^12-20. These chemicals have different and important roles in our body metabolism and influence multiple functions in our body during health and disease.

Studies have identified associations between gut dysbiosis and metabolic disorders (like obesity or diabetes) and cardiovascular disease, including condition like atherosclerosis, dyslipidemia, hypertension, and heart failure^21-25. Gut microbiota influences this condition through direct and indirect pathways. Direct pathways involve the chemicals produced by these microbes, called metabolites, whereas indirect pathways involve the influence gut microbes have on the immune system^21,10.

Focus on: Gut Microbiota and Heart Disease

Heart disease, also known as Cardiovascular Disease (CVD) is the number 1 cause of death worldwide, killing nearly 18 million people each year, according to the World Health Organization. In Australia, more than 41,000 people die each year from heart-related conditions.

Heart disease includes a large number of conditions, such as coronary heart disease, cerebrovascular disease, rheumatic heart disease, angina, heart arrhythmias, heart attack, heart failure, and many others. For a complete let, head to this governmental site. Among these conditions heart attacks and strokes are the most common, representing 4 our 5 deaths due to CVD.

Studies have found links with the composition of the gut microbiota and many of these conditions, including:

• Atherosclerosis
  This condition occurs when blood vessels become narrow, due to the accumulation of plaque, a substance mostly made up of fat and cholesterol. When too much of this plaque accumulated in the veins and arteries, blood cannot flow freely, affecting the delivery of oxygen to vital organs. When this happens in the arteries leading to the heart, conditions like heart attacks or heart failure can occur.

Multiple risk factors are associated with atherosclerosis, including unhealthy diets rich in fats and sugar, smoking, lack of physical activity and certain conditions, like diabetes, high blood pressure, and obesity/overweight, among others.

In recent years, studies have recognised a role for the composition of the gut microbiota in the development of atherosclerosis. One study, for example, found that people with asymptomatic atherosclerotic plaques have an increased abundance of gut bacteria of the Porphyromonadaceae, Bacteroidaceae, Micrococcacaea, and Streptococcacaea families²⁶. Asymptomatic atherosclerotic plaques are a mild form of atherosclerosis that does not have noticeable symptoms, as blood flow is not significantly affected. In contrast, people with symptomatic atherosclerotic plaques contained an increased abundance of pathogenic gut bacteria, including members of the Helicobacteracaea, Neisseriaceae, and Thiotrichacaea families.

Gut dysbiosis, where there is an alteration of the normal composition of a person’s gut microbiota has also been associated with the development of atherosclerosis²⁷. Here, gut microbiota has been shown to activate inflammatory pathways that alter the way our body process fats in adipocytes (fat cells), macrophages (immune cells) and vascular cells²⁷.

• Hypertension
  This is the most common risk factor associated with cardiovascular disease and the main cause of disability and death in developed countries. Hypertension occurs when a person has a blood pressure reading of more than 140/90 mmHg. Worldwide, it is estimated to affect as many as 13 billion people²⁸. In Australia, 1 in 3 adults over the age of 18 has hypertension. Multiple factors are associated with high blood pressure, including lack of exercise, smoking, being overweight, following a diet high in salt, your genetic background, high alcohol consumption and conditions like diabetes.

Recently, the composition of the gut microbiota has also been linked to the development of hypertension. One study, for example, found that people who suffer from hypertension have a lower diversity of their gut microbiota, and different composition, with an overrepresentation of bacteria from the genus Prevotella, compared to people with no hypertension^29-30. Short-chain fatty acids (SCFAs), which are chemicals produced by some gut bacteria, have also been associated with hypertension. Some of these chemicals, for example, have been shown to interact with specific proteins in our body that can lead to hypertension^31-32.

• Heart Failure
  This condition occurs when the heart is not able to pump blood normally, due to damage to structure and function of the heart. Some common symptoms of heart failure include shortness of breath, loss of appetite, tiredness, weight gain, swollen legs, ankles, belly or feet, dizziness and coughing. In many forms of heart disease, like coronary heart disease, heart attack, or high blood pressure, heart failure represents the final stage of the disease, leading to a heart attack and death. Current studies have found significant evidence for the role of gut microbiota in the development and progression of heart failure. For example, one study found that patients suffering from heart failure have been found to host higher levels of pathogenic bacteria, such as Campylobacter, Shigella, Salmonella and Yersinia enterocolitica, compared to healthy people. Also, bacterial species from the Candida, Campylobacter and Shigella genera were positively correlated with the severity of heart failure^33-34. Heart failure has also been associated with increased levels of Escherichia coli, Klebsiella penumoniae, and Streptococcus viridans, according to another study³⁵.

Another study found a link between gut bacteria and the effectiveness of drugs used to treat heart failure. For example, the drug digoxin could be inactivated by the but bacteria Eggerthella lenta³⁶. Likewise, the composition of a person’s gut microbiota can lead to specific metabolic profiles that can affect how heart failure drugs function³⁷. Hence, it important to understand the gut bacterial composition of each patient to identify potential interactions between drugs and bacteria.

Beyond atherosclerosis, hypertension and heart failure, studies have also identified links between the gut microbiota and conditions like stroke, transient ischemic attack, and variations the levels of fats in the blood^38-39.

The Modern Functional Medicine approach

At the Australian Centre for Functional Medicine, we have an in-depth understanding of the different factors that affect heart disease. We take a comprehensive approach to the diagnosis and treatment of patients at high risk of developing heart disease. Our diagnostic approach involves multiple testing, including blood and urine tests, used for the identification of biological markers associated with disease. Stool testing is also used to assess the health of a patient’s gut microbiota, as this is an important factor influencing heart disease.

Our proposed treatments depend on the type and severity of each patient’s condition and are based on the results obtained from our comprehensive testing. Typical treatments may involve a combination of standard medical approaches, with botanicals and probiotics, as well proposed changes in lifestyle factors such as diet and exercise levels. Ultimately, we seek to optimise the composition of your gut microbiota, in parallel with other factors affecting the health of your heart.

BECOME A PATIENT TODAY and reduce the risk of developing heart disease

BECOME A PATIENT

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