Role of Intermittent Fasting in Improving High Density Lipoprotein Cholesterol

INTRODUCTION:

Overall lipid profile is important in cardiovascular diseases but particularly serum HDL levels have long been recognized as an independent inverse prognostic marker of CVD, when the Framigham study, in 1980s showed that HDL below 40-60mg/dl is of prognostic relevance. A rise of 1mg/dl in HDL levels is considered to reduce coronary artery disease (CAD) risk to 2-3%. Even patients with elevated total cholesterol (TC) and LDL, presenting a high HDL are seen to be protected from atherosclerosis. Multiple human population studies have shown the concentration of HDL cholesterol as an independent, inverse predictor of the risk of having a cardiovascular event. Additionally, HDL has several well-documented functions with the potential to protect against cardiovascular diseases. These include an ability to promote the efflux of cholesterol from macrophages in the artery wall, inhibit the oxidative modification of LDL, inhibit vascular inflammation, inhibit thrombosis, promote endothelial repair, promote angiogenesis, anti-oxidant, enhance endothelial function, improve diabetic control, and inhibit hematopoietic stem cell proliferation. HDL also exerts direct cardio protective effect, which are mediated with its interactions with the myocardium.

Various studies have emphasised the high incidence of CVD within the South Asian countries. The increased risk of cardiovascular events in South Asians at a younger age might be due to unknown factors affecting plaque rupture, the interaction between prothrombotic factors and atherosclerosis, or may be due to any undiscovered risk factors. Urbanisation and westernisation is characterised by a distinct increase in the intake of energy dense foods, a decrease in physical activity, and a heightened level of psychosocial stress, all of which promote the development of hyperglycaemia, hypertension, and dyslipidaemia. Most common dyslipidaemia in South Asians is low HDL-C and high triglycerides. High triglyceride and low HDL-C levels are metabolically interlinked. This metabolic phenotype is also associated with increased levels of small LDL particles despite relatively normal levels of LDL-C among South Asians. This clinical syndrome is accompanied by insulin resistance, a condition frequently referred to as atherogenic dyslipidemia, which is a common metabolic derangement among Asian. South Asians not only have lower HDL levels but also have a higher concentration of small, less-protective HDL particles. One proposed mechanism is presence of dysfunctional HDL particles. Another potential explanation for the apparent blunted cardioprotection of HDL in South Asians might be related to HDL particle size. Small particles might be less efficient in reverse cholesterol transport. In general, HDL particle size tends to be lower in patients with CHD and those with low HDL-C levels . Alarmingly, an estimated 60-80% of Pakistani population has been reported to have low HDL. There are a number of non-pharmacological and pharmacological recommendations for management of low HDL. Non-pharmacological (functional food) strategies are reported to increase HDL levels around 10-15% and which include regular exercise , body weight reduction in obese individuals , cessation of cigarette smoking in smokers and dietary modifications like decrease intake of saturated trans-fatty acids with increase intake of omega-3 polyunsaturated fatty acids . There are also a number of pharmacological agents being considered as therapeutic options but the tolerability and safety issues limit their use in addition to limited success in improving HDL. IF may be a dietary method to aid in the improvement of the lipid profile in healthy, obese and dyslipidemia men and women, reducing total cholesterol, LDL, triglycerides and increasing HDL levels. However, the majority of studies that analyze the IF impacts on the lipid profile and body weight loss are observational and lack detailed information about diet. Randomized clinical trials with larger sample size are needed to evaluate the IF effects mainly in population with dyslipidemia.

HYPOTHESIS:

Intermittent fasting is capable of improving dyslipidemia and particularly enhancement of serum, HDL which can increase the cardioprotection in high risk general population.