Description of the condition

Hypercholesterolaemia is a metabolic derangement characterised by elevated levels of serum cholesterol in the blood. In 2008 the estimated global prevalence of hypercholesterolaemia amongst adults was 39%, with the highest rates in Europe (54%) and the lowest in Africa (23%). It is also noted that the prevalence rate of hypercholesterolaemia increases in accordance with the income level of the country, with the highest rates in high income countries (WHO 2011). Hypercholesterolaemia is estimated to attribute to 2.6 million deaths annually (4.5% of total annual deaths) and accounts for 29.7 million disability adjusted life years (DALYs) (2% of total DALYs) (WHO 2009).

There is currently no world‐wide standard definition of hypercholesterolaemia and definitions can vary from country to country. The American Heart Association guidelines outlined by the National Cholesterol Education Program (NCEP) expert panel on detection, evaluation and treatment of high blood cholesterol in adults, defines hypercholesterolaemia as a total serum cholesterol level greater than or equal to 6.20 mmol/L (240 mg/dL) (NCEP 2002).

Cholesterol is transported in the blood in the form of lipoprotein particles which are categorised according to increasing density. The two main lipoproteins found within the bloodstream are low density lipoprotein (LDL) and high density lipoprotein (HDL). LDL makes up approximately 60% to 70% of total serum cholesterol (NCEP 2002) and serves to transport cholesterol to peripheral tissues (outside of the liver and intestine) and regulates de novo cholesterol synthesis within these tissues (Berg 2002). The remaining 20% to 30% of serum cholesterol is mostly made up of HDL (NCEP 2002) which binds and esterifies cholesterol released from peripheral tissues and transfers them to tissues that utilise cholesterol for steroid hormone synthesis or returns it back to the liver in the process called reverse cholesterol transport (Berg 2002). Excess LDL‐cholesterol in the blood stream is oxidated to become oxidised LDL which is then taken up by macrophages to form foam cells. These foam cells become trapped in arterial walls, forming a fatty streak which consequently gets overlaid by a layer of scar tissue, forming a fibrous plaque (Berg 2002). Unstable plaques are prone to rupture and luminal thrombosis formation which is responsible for acute coronary syndromes such as myocardial infarction, unstable angina and coronary death. Approximately 16% of cardiovascular deaths can be attributed to hypercholesterolaemia (WHO 2009).  

Past studies have shown that there is a direct relationship between total serum cholesterol levels and occurrence of coronary events. Any LDL‐cholesterol level greater than 100 mg/dL appears to be atherogenic (conducive to the formation of plaques on arterial wall), with higher levels of LDL‐cholesterol corresponding to greater risks of coronary heart disease (NCEP 2002). This relationship can be shown most prominently in genetic forms of hypercholesterolaemia, such as familial hypercholesterolaemia, where advanced coronary atherosclerosis (large amounts of deposits of plaques containing cholesterol on coronary arterial walls) and premature chronic heart disease still occur despite the absence of other risk factors (Brown 1986). A LDL‐cholesterol and total serum cholesterol concentration reduction of 0.6 mmol/L is associated with a 50% reduction in risk of ischaemic heart disease in men aged 40, and a 20% reduction in men aged 70 and over. Although there is little reduction in risk in the first two years, a full reduction in ischaemic heart disease risk can be achieved within five years with similar reduction rates in women (Law 1994).

Unlike familial hypercholesterolaemia, which is caused by a genetic defect on chromosome 19, and secondary hypercholesterolaemia where other diseases such as liver dysfunction, nephrotic syndrome or endocrine disorders cause elevated levels of cholesterol, the exact mechanisms of 'primary' hypercholesterolaemia remain unclear. It has been suggested that several different causes can result in primary hypercholesterolaemia, including age and the suppression of LDL‐receptor activity due to the large consumption of cholesterol and saturated fatty acids (Vega 1991).

Description of the intervention

Current first line treatment for hypercholesterolaemia is statin therapy which involves a class of drugs that competitively inhibits HMG‐CoA reductase, the rate limiting enzyme of cholesterol synthesis. Reduced cholesterol synthesis results in up‐regulation of LDL‐receptor synthesis which increases LDL‐clearance from plasma into hepatocytes (Maron 2000). Statins are generally well tolerated with mild adverse effects that include myalgia, insomnia, gastrointestinal disturbances and rash. Major adverse effects of statin therapy include angio‐oedema (a vascular reaction characterised by dilatation and increased permeability of capillaries causing localised oedema in skin or mucosal tissue) and myositis (inflammation of voluntary muscles), however occurrences of these are rare (Rang 2007). Commonly used statin drugs include simvastatin, pravastatin, atorvastatin and lovastatin.

Acupuncture is an ancient therapeutic needling therapy originating in China many centuries ago. The first documented evidence for acupuncture can be found in the yellow emperor's classic of internal medicine dating from 100 B.C. which contains a compilation of centuries of traditions and texts. Although the precise anatomical locations of acupoints were established later, the concept of Qi and channels through which Qi flows was well established (White 2004).

In Traditional Chinese Medicine philosophy, all phenomena seen in the universe are composed of Qi. Although it is commonly translated as 'vital energy', it is more accurately described as a state between matter and energy where it can be seen as energy that is about to materialise or matter on the verge of transforming into energy. Unlike Western thinking, matter and energy were seen as a continuous state. In a physical aspect, Qi is associated with movement, activation, tension and engineering while from a psychological perspective, Qi is associated with desire, resolution, motivation and awareness of possibilities. Within the body Qi has five main functions: protection, movement, warming the body, transformation and stability (Kaptchuck 2000).

Within the body there is a system of channels whose primary function is to distribute and circulate Qi, termed Meridian channels. Each channel has a number of fixed acupoints, which when stimulated either by needling or other methods, change the flow of Qi along the channel which then affects and alters the body systems, producing a therapeutic effect (Birch 1999). Although multiple studies have been conducted to verify the physical existence of the Meridian channels, there has been little conclusive evidence to date of their existence.

Although acupuncture in its most traditional sense is defined as puncturing body acupoints with needles, it is often combined with moxibustion and other forms of stimulation. Other common forms of acupuncture include electroacupuncture which involves stimulating acupuncture points using electricity and acupressure which involves applying external pressure to the acupoints. For the purposes of this review acupuncture will be defined in a broad sense to include body needling, electroacupuncture and acupressure.

How the intervention might work

Although the exact mechanism of action by which acupuncture can reduce serum cholesterol levels is unknown, it is likely that it works by a combination of different pathways. Animal studies have shown that electroacupuncture at ST40 alters the expression of certain genes such as LXRα and CYP7α1 which are involved in cholesterol metabolism in the liver (Li 2007).  Acupuncture also affects enzymatic pathways within in the body by up‐regulating of acyl‐coenzyme A oxidase 1 and 2 responsible for lipid oxidation, down‐regulating of stearoyl‐coenzyme A desaturase 1 responsible for catalysing the biosynthesis of monosaturated fatty acids (Kang 2007), and increasing β‐endorphin levels which stimulate lipolysis (Cabioğlu 2005). Acupuncture may also reduce cholesterol levels by acting on the neuroendocrine pathways such as increasing serotonin levels in the central nervous system (Wenhe 1981) and preserving satiation (Shiraishi 1995), leading to appetite suppression.

Why it is important to do this review

We are unaware of a systematic review on acupuncture for primary hypercholesterolaemia. Studies in obese participants have shown that acupuncture is an effective treatment for reducing total cholesterol (TC), LDL‐ and triglyceride (TG) serum levels (Cabioğlu 2005). Acupuncture is widely used by the general public and officially recognised by governments within Asia. Since its introduction into Western society in the 19^th century, acupuncture has been slowly gaining popularity amongst the public as a ‘natural’ alternative to Western medicine. In Australia it has been estimated that approximately 9.2% of the population use acupuncture (Xue 2008). However, scepticism remains about the true therapeutic effects and mechanisms of action of acupuncture therapy especially in the West. Given that hypercholesterolaemia is a risk factor for causing cardiovascular events, there is a need for a systematic and evidence‐based evaluation of the efficacy of acupuncture therapy in the treatment of this condition.