Metabolic syndrome is a disorder that is seen frequently in patients with chronic kidney disease. Insulin resistance is sometimes used as a synonym for metabolic syndrome. Insulin resistance occurs when the effect of insulin on the target tissue is reduced. There are two types of insulin resistance: hepatic insulin resistance and peripheral insulin resistance. Hepatic insulin resistance is the impairment of glucose synthesis in the hepatic (liver) system. Peripheral insulin resistance is a reduced response to insulin in the adipose or skeletal muscle tissue.
As insulin resistance progresses, there is an increase in insulin by the pancreas. This is a compensatory mechanism. This results in too much insulin being produced in order to maintain the glucose levels in the blood. After some time, the pancreas will slow down producing insulin and as a result, glucose will become elevated (hyperglycemia). As a result, the person will develop Type 2 diabetes. The main cause of insulin resistance in chronic kidney disease is thought to be from the tissues that are insensitive to insulin.
Incidences of Chronic Kidney Disease and Insulin Resistance
Chronic kidney disease is prevalent among American adults. There are 30 million people living in America with chronic kidney disease. According to the World Health Organization, 10% of people worldwide have kidney disease. Millions die worldwide because of inadequate health care. At least 50% of the people with severely impaired renal function are not aware that they have chronic kidney disease. The Centers for Disease Control stated that “According to the 2010 Global Burden of Disease study, chronic kidney disease was ranked 27th in the list of causes of total number of deaths worldwide in 1990, but rose to 18th in 2010. This degree of movement up the list was second only to that for HIV and AIDS”. Over 2 million people worldwide need dialysis to stay alive. More than 80% of people who received dialysis lived in affluent neighborhoods. Treatment for dialysis is a huge financial burden for the people who need it. In many countries, the people cannot afford dialysis, and it is estimated that 2 million people die from not receiving dialysis. In America, treatment of chronic kidney disease will exceed $50 billion per year. Treatment for chronic kidney failure consumes 7% Medicare budget.
Insulin resistance is becoming increasingly prevalent. In order to be diagnosed with insulin resistance or metabolic syndrome, a person needs to have 3 out of 5 disorders. These five disorders are:
- Abdominal obesity
- Low HDL cholesterol
- High triglyceride levels
- Hyperglycemia or elevated sugar
Eighty million people in the United States have metabolic syndrome. The lowest prevalence is in African American men, and the highest prevalence is in Hispanic women. Metabolic syndrome has been associated with cardiovascular disease and diabetes. However, of the five disorders that are known to be characteristics of insulin resistance, impaired fasting glucose and waist circumference is the most important in predicting diabetes.
Insulin resistance is also becoming prevalent in pediatrics because of the obesity epidemics. Children are also developing insulin resistance because of the diets that are high in sugar. The World Health Organization has identified insulin resistance as a powerful predictor of future cardiovascular events and the development of diabetes. Thirty million people in the United States have diabetes. Only 23 million have been diagnosed. Metabolic syndrome greatly increases a person’s risk of developing cardiovascular disease.
Causes of Insulin Resistance in Chronic Kidney Disease
Insulin resistance occurs in people with chronic kidney disease, and it happens early in the disease. In these patients, insulin resistance gets worse as the kidney function declines. In normal kidney functions, 25-80% of the circulating insulin is removed by the kidneys. When you have decreased kidney function, insulin sensitivity is impaired, and the insulin can’t get to the tissues. Even though metabolic syndrome or insulin resistance has been shown to be a factor in chronic kidney disease, the mechanisms of how the beta cell function in the pancreas is impacted is poorly understood. Beta cells (B cells) produce insulin and are the most abundant of the islet cells in the pancreas.
There are many reasons why people with kidney disease develop metabolic syndrome. Some of the reasons are :
- Unhealthy lifestyles and smoking
- Metabolic acidosis
- Inflammation (chronic)
- Vitamin D deficiency
- Uremic toxicity
- Abdominal fat accumulation
Inflammation is thought to be the root cause of insulin resistance Inflammatory cytokines has been proven to contribute to insulin resistance..
Implications of Insulin Resistance and Chronic Kidney Disease
Insulin resistance or metabolic syndrome is associated with premature deaths from cardiovascular disease. There have been some studies that showed that insulin resistance is a risk factor for cardiovascular death in end-stage renal disease. The relationship between insulin resistance and chronic kidney disease can probably be made through oxidative stress, endothelial dysfunction, renin-aldosterone system, and systemic inflammation. Hypertension, elevated cholesterol, and obesity are related to metabolic syndrome or syndrome x.
Treatment for Insulin Resistance and Metabolic Syndrome
The primary treatment for insulin resistance is lifestyle changes. The suggested treatments are :
- Reduction of carbohydrates in the diet
- Increased physical activity
- Stop smoking
The morbidity and mortality rates are increased in metabolic syndrome when the people are physically inactive or they smoke. Aerobic exercise has a beneficial effect on insulin resistance. A study was done that included people diagnosed with insulin resistance. After three months of aerobic exercise for 30 minutes a day, 3 times a week, the subjects all had decreased insulin levels and their blood pressure was decreased.
A low carb diet or a keto diet has been shown to be effective against insulin resistance. However, most low carb diets are high in potassium and potassium is limited in people with chronic kidney disease. Metformin, which is an anti-diabetic agent has been used successfully in people with insulin resistance. Metformin works in the body by helping to sensitize insulin. Vitamin D deficiency is also related to insulin resistance.
Insulin resistance is common in chronic kidney disease because of kidney dysfunction. Disorders associated with chronic kidney diseases such as vitamin d deficiency, acidosis, uremic toxicity, and inflammation are all related to insulin resistance. With lifestyle modifications, insulin resistance can be controlled, and people with chronic kidney disease can have a better quality of life.