If you are diagnosed with diabetes, you must already be aware that controlling your blood glucose levels is important. It is also important to check your cholesterol levels on the regular basis and seek timely treatments in case the test shows abnormal results in order to prevent complications such as diabetic retinopathy.

You need to monitor your blood sugar levels on a regular basis to be able to detect any rise in the levels at the earliest before any serious complications arise.

It is known that keeping the blood sugar levels in control is the key to avoiding the risk of developing diabetic complications like neuralgias, nephropathy, retinopathy, macular edema, and cataracts.

An increase in the levels of cholesterol and other lipids like triglycerides can raise your risk of diabetic retinopathy through various mechanisms. Keep reading to learn why it is important to manage your cholesterol levels for preventing diabetic retinopathy.

What is cholesterol?

Cholesterol is a form of blood lipids (blood fats) that has the ability to form a layer or a membrane for the cells in the body. These fats are carried through the bloodstream by proteins known as lipoproteins. It is actually these lipoproteins that are measured during a cholesterol test.

The lipoproteins commonly tested include:

LDL (Low-Density Lipoprotein)

It is also referred to as bad cholesterol, as it is this type of cholesterol that has a tendency to build up in the blood vessels, form plaques, and block them thus interrupting the flow of blood to the vital organs.

However, it should be noted that though LDL is often referred to as bad cholesterol, it is required by the body for performing certain functions. Hence, HDL is usually considered healthy as long as its levels are within the normal limits.

HDL (High-Density Lipoprotein)

HDL is usually referred to as good cholesterol, as it can help to clear the excess LDL from the blood.

Total cholesterol

It provides the levels of all the different forms of blood lipids added together. An abnormally high level of total cholesterol could be considered detrimental for the health of patients, especially those diagnosed with diabetes, as it can put them at a higher risk of life-threatening diseases like heart attacks and stroke.

However, the values of total cholesterol should always be correlated to that of the HDL and LDL values to get a good idea of the composition of different forms of lipids and assess their impact on your risk of complications.

Total Cholesterol to HDL Ratio

This ratio is obtained by dividing the value of the total cholesterol by the value of the HDL. It provides an indicator for assessing cardiac health and is considered more reliable than the total cholesterol and LDL values.

Triglycerides

Triglycerides refer to another form of blood lipids that are also measured during a cholesterol test.

How are diabetes and high cholesterol related?

Patients, who have both diabetes, as well as high cholesterol, have a much higher risk of stroke and heart attacks compared to those who have either of these. 

According to the American Heart Association (AHA), diabetes can cause a decline in the levels of HDL cholesterol and raise the levels of LDL cholesterol and triglycerides. These changes could raise your risk of cardiac diseases like heart attacks, and stroke.

Moreover, the specific complications linked to diabetes such as renal dysfunctions, cataracts, diabetic retinopathy, and macular edema tend to occur more commonly in diabetic patients who have abnormal cholesterol levels. This indicates the need to monitor your cholesterol levels on a regular basis just the way you monitor your blood glucose levels to be able to avoid the complications of diabetes.

How does high cholesterol contribute to the risk of diabetic complications?

High cholesterol levels could result in serious harm to the heart and blood vessels. As discussed earlier, cholesterol is a form of fat, which, when in excess, can build up in the arteries. Over a period of time, these plaques harden forming a stiff plaque.

The plaques can cause damage to the arteries, making their walls hard and stiff. The hardening or stiffening of the walls of the arteries caused due to the deposition of cholesterol plaques is called atherosclerosis.

Due to the stiffening, the blood vessels lose their ability to contract and relax while carrying blood. This can hamper the smooth flow of blood to the vital organs.

Moreover, the loss of contractile activity of the muscles in the walls of the blood vessels can also prevent them from regulating the blood flow to the tissues depending on the specific needs at different times and in different situations.

Above all, the cholesterol plaques can make the inner diameter of the blood vessels narrower thus inhibiting the blood flow through them. This may result in the reduced blood supply to the vital organs such as the heart and brain triggering the development of heart attacks and stroke, respectively.

It may also hamper the blood flow into the eyes due to which the tissues of the eyes such as the retina may not receive an adequate supply of oxygen and other nutrients. The damage to the tiny blood vessels that supply blood to the macular region or the retina could also result in abnormal changes in these tissues. This could increase the risk of diabetic retinopathy, cataracts, and macular edema. We have covered what causes macular edema and how to prevent diabetic retinopathy here in detail.

These risks and complications linked to high cholesterol are compounded further due to the increase in blood sugar levels in patients with uncontrolled diabetes. It can accelerate the pathogenesis of atherosclerosis due to which diabetic patients are put at risk of these diseases within a shorter period than in those who have healthy blood sugar levels.

Hence, it is important for diabetic patients to be aware of how their cholesterol levels can influence their risk of serious complications and seek appropriate measures to avoid them.

Various mechanisms have been implicated to be responsible for triggering diabetic complications due to high cholesterol levels.

Let us move further to learn how exactly high cholesterol levels affect the pathogenesis of diabetic complications through various mechanisms. 

The mechanisms involved in the development of diabetic complications

Metabolic abnormalities

Diabetes and lipid dysfunctions are known to trigger metabolic abnormalities that can have a cascading effect on the health of a person.

The metabolic abnormalities, which are known to accompany diabetes, include the disturbances in the production as well as clearance of the plasma lipoproteins. It may also result in postprandial lipemia.

The development of dyslipidemia could also be a harbinger for the high risk of developing diabetic complications like retinopathy in the future. 

This pattern is more common in patients with type 2 diabetes. The pathophysiological alterations in diabetes can lead to various forms of dyslipidemia, which, in turn, can cause damage to the small blood vessels in the eyes due to which your risk of retinopathy may increase by several folds.

Defects in insulin action

According to one research study published in The Journal of Lipid Research, blood glucose, cholesterol, and insulin can interact with each other and are also influenced by the activities of each other.

Defects in the action of insulin and the resulting hyperglycemia in patients with diabetes may become worse at a faster rate if they also have abnormal lipid levels due to the changes in plasma lipoproteins caused due to the high blood sugar levels.

Moreover, the insulin-resistant and obesity-related metabolic disarray that is found to be at the root of type 2 diabetes could itself lead to severe lipid abnormalities that are exclusive of hyperglycemia.

The mechanisms involved in the pathogenesis of type 1 diabetes also provide a clear understanding of the link between diabetes, lipid/lipoprotein metabolism, and insulin deficiency. Patients with poorly controlled type 1 diabetes can develop ketoacidosis and hypertriglyceridemia both of which can reduce the HDL level significantly.

The replacement of insulin hormone in these patients could help to correct these abnormalities and reduce the risk of diabetic retinopathy that is associated with uncontrolled diabetes, especially in patients with high cholesterol.

Blocks the blood flow

An increased cholesterol level is likely to trigger faster damage to the delicate tissues of the eyes such as the retina and macula. The cholesterol plaques could block the blood vessels in these regions due to which the retina would be deprived of an adequate supply of oxygen and healing nutrients. This could speed up the degenerative processes occurring in the retina putting you at a higher risk of diabetic retinopathy.

Similarly, the damage to the blood vessels in the macular region may lead to the oozing of the fluid due to which you may develop macular edema. This indicates the role of abnormal lipids levels in worsening your risk of diabetic complications.

Diabetic dyslipidemia

The healthcare experts at the American Heart Association (AHA) have stated that diabetes can raise the risk of a condition called diabetic dyslipidemia.

Diabetic dyslipidemia is linked to a lower level of HDL cholesterol and increased levels of LDL cholesterol and triglycerides.

This suggests that a strong association between diabetes and cholesterol works in both ways.

It is not just the increased cholesterol level that can raise the risk of diabetic complications, but having a high blood sugar level can also create disturbances in the metabolism of fats and increase the risk of lipid dysfunctions.

This is another reason why diabetic patients need to watch their cholesterol levels regularly.

The increased blood sugar levels caused due to diabetes and the resulting changes in the secretion of insulin and metabolic processes can lead to disruptions in the breakdown of fats due to which you may develop diabetic dyslipidemia.

Diabetic dyslipidemia, in turn, could put you at risk of stroke and heart attack. Monitoring your cholesterol levels would allow you to seek timely medical intervention to restore healthy lipid levels and protect you against these complications.

Role of liver apoproteins

Liver apoproteins and lipid-metabolizing proteins have been found to play a role in triggering the development of diabetic retinopathy in patients with abnormal lipid levels.

A number of studies have demonstrated that the production of ApoB (Apolipoprotein B), which is a major protein component of VLDL (very low-density lipoprotein) and LDL in the liver, is increased in patients with type 2 diabetes.

ApoB is a large protein, the production of which is regulated differently than the synthesis of most other proteins in the body. The production of ApoB is also not altered remarkably by the dietary changes in patients with diabetes.

Instead, a large amount of the newly synthesized form of this protein gets degraded during and immediately after its translation.

The degradation could be avoided when lipid is combined with a protein via the action of another protein called microsomal triglyceride transfer protein. However, this protein is often defective in patients with insulin deficiency and insulin resistance. 

Insulin has the ability to regulate the production of several other proteins that can affect the levels of lipoproteins in the blood. This suggests that the underlying mechanisms that worsen the risk of diabetes can also play a role in the development of abnormalities in the lipid levels.

Hence it is important to assess your cholesterol levels regularly to ensure any change in the lipid level is detected early to allow you to adopt appropriate measures to prevent the serious complications of dyslipidemia.

Conclusion

Diabetes and the increased cholesterol levels can occur together through different mechanisms. There are several ways through which diabetes can cause a rise in cholesterol levels, especially HDL cholesterol.

This, in turn, can worsen your risk of diabetic retinopathy by causing damage or the blood vessel in the eyes.

Similarly, high cholesterol levels can influence insulin production and other metabolic processes occurring in the body thus hampering your glycemic control.

This is why; it is important to monitor your blood cholesterol levels just the way you monitor your blood sugar levels to be able to detect the abnormalities arising out of the same.

Early detection of high cholesterol levels would help you begin proper treatments to restore the levels within the healthy range. It will also allow you to adopt appropriate dietary and lifestyle habits to control the levels and minimize their influence on your risk of developing diabetic complications.