Lipids are a group of substances which have a common property of being insoluble in water. This includes cholesterol, triglycerides, cholesteryl esters and phospholipids. The common thing about these is that they are insoluble in water.
This is what makes them important. In order to solubilise them, they are made into lipoproteins and which are then transported from one part of the body to another and that's when many problems occur. During the transport of these proteins, if there is a problem while processing, they may enter into the endothelium and may cause problems.
There are different types of lipids:
. Simple lipids
. Complex lipids
In the body, we have free fatty acids but otherwise, most of the lipids are actually components of lipoprotein (complex lipids and proteins). Depending upon the actual composition of the lipoproteins we further have chylomicrons, very low density lipoproteins, low density lipoproteins and high density lipoproteins.
Lipids play an important role in atherosclerotic (heart) diseases. It is primarily a problem with lipoprotein clearance. If there is a problem in clearing LDL particles then LDL cholesterol goes up and that is the strongest risk factor for the atherosclerotic cardiovascular disease. A study 'Decreased Lipoprotein Clearance is Responsible for Increased Cholesterol in LDL Receptor Knockout Mice with Streptozotocin-induced Diabetes' published in the journal Diabetes in 2008 has shown that streptozotocin-induced diabetic, cholesterol-fed mice developed hyperlipidemia due to a non-LDL receptor defect in the clearance of circulating lipoproteins. If there are high triglyceride- containing particles then pancreatitis occurs. In some way, it also modulates the other LDL particles and that cause heart disease as well.
A study 'Low-density Lipoprotein Clearance in Patients with Chronic Renal Failure' published in Nephrology Dialysis Transplantation has shown that the clearance of LDL seems to be related to the severity of renal (kidney) impairment. A remarkable reduction in LDL catabolism (the breakdown of complex molecules in living organisms to form simpler ones, together with the release of energy) can be observed only in people with advanced renal failure. Thus, lipid imbalance affects not only the heart but it also adversely affects the pancreas and the kidneys.
Cholesterol is a kind of lipid. It is a 27 carbon atom. Cholesterol exists in every single cell of the body. Cholesterol is an integral part of the cell wall. Cholesterol is a precursor of many important hormones such as bile and adrenal hormones.
Cholesterol itself is not bad. The problem lies in the cholesterol containing lipoproteins. If clearance is impeded, these lipoproteins can build up in the form of plaques and cause atherosclerosis. This includes coronary artery disease, cerebrovascular disease and peripheral vascular disease.
Cholesterol and blood glucose levels
Understanding cholesterol has gained importance because one of the side effects of cholesterol lowering medications is elevated blood glucose levels. It is very mild, not clinically significant but nonetheless, it certainly increases a bit.
There seems to be an inverse relation between cholesterol and blood glucose. The genetic data shows that those who are genetically predisposed to have high cholesterol have lesser incidences of Diabetes. On the converse, people who are genetically predisposed to low cholesterol levels have a higher incidence of Diabetes. People with Diabetes are known to have a high cardiovascular risk and one way of reducing the risk is by reducing cholesterol levels.
The make-up of lipoprotein is different in people with Type 1 and Type 2 Diabetes. Yet cholesterol doesn't act differently in Type 1 and Type 2 Diabetes. It is just that people with Type 2 Diabetes may display other cardiovascular risks. Usually, they have hypertension, high triglyceride levels and visceral obesity as a result of which they may have an increased risk of heart disease.
Insulin is an important regulator of lipid metabolism. The main role of insulin is to prevent lipolysis, i.e., the unregulated breakdown of triglycerides to fatty acids. When insulin production is hampered or there is insulin resistance, the free fatty acids increase. This results in an increase in triglyceride levels. This causes low HDL levels. In fact, severe triglyceridaemia is managed by intravenous insulin.
It is important for people with Diabetes to manage their cholesterol levels. In most people with Diabetes, the leading cause of death is cardiovascular disease. If you want to make a real effect on the overall outcomes in people with Diabetes, it is important to reduce the cardiovascular risk and reducing cholesterol levels is probably the most important thing.
Lifestyle changes, diet and exercise can help lower the cholesterol levels. It is best to avoid refined carbohydrates and saturated fats as much as possible. Not all fats are bad. Mono unsaturated and polyunsaturated fats are probably the good fats. A very high carbohydrate diet
is not good either. The most important thing is to make sure to get the right amount of calories to lose weight if you are overweight or to ensure that you don't gain
weight. Regular exercise for at least 150 minutes a week is the goal for people with Diabetes.
Additionally, some people require medication, primarily statins, to lower cholesterol. There is an upcoming class of medication that lowers the cholesterol levels. It also lowers the cardiovascular risk in people with Diabetes. In my opinion, aggressive lipid management is more important than aggressive blood glucose management.
Lipid management is as important as blood glucose management in people with Diabetes as only controlling blood glucose levels is insufficient. Optimal body weight, regular exercise, healthy dietary patterns, lowering and regulating lipids levels and judicious use of medication like statins are the cornerstones of lipid management.
Dr Vinaya Simha (MBBS, MD) is a Consultant in the Division of Endocrinology, and Assistant Professor, Department of Internal Medicine at Mayo Clinic, Rochester, USA. He served as the faculty at University of Texas Southwestern Medical Centre and in Texas Tech University Health Sciences Centre. He is board certified in Internal Medicine, Endocrinology and Clinical Lipidology. His research interests include lipodystrophy and the role of body fat distribution on glucose and lipid homeostasis. Dr Vinaya Simha also has many publications in the field of lipodystrophy and leptin-replacement therapy. He has a keen interest in clinical lipidology and is an investigator in some of the early trials of PCSK9 inhibitors.