Adiponectin is a fat-derived hormone that appears to play a crucial role in protecting against insulin resistance, diabetes, and atherosclerosis. Decreased adiponectin levels are thought to play a central role in the development of type 2 diabetes, obesity, and cardiovascular diseases.
Adiponectin is a 244-amino acid protein secreted mainly by the adipose tissue. It has been proved, that adiponectin is expressed in other tissues including osteoblasts, liver parenchyma cells, myocytes, epithelial cells, and placental tissue. Human adiponectin is encoded by the Adipo Q gene, which is located on chromosome 3. Serum levels of adiponectin decrease with obesity and are positively associated with insulin sensitivity.
Adiponectin exhibits anti-diabetic, anti-inflammatory, and anti-atherogenic effects, and it also functions as an insulin sensitizer. Hence, it is a novel therapeutic target for diabetes and metabolic syndrome. Adiponectin also plays a central role in energy homeostasis through its action in the hypothalamus.
Adiponectin and obesity
People with obesity have decreased levels of adiponectin. On the other hand, adiponectin levels are higher than normal in people who are severely underweight, such as people who have anorexia nervosa or malnutrition. In general, the more body fat someone has, the lower their adiponectin levels are, and vice versa. Weight loss in people with obesity results in increased adiponectin levels.
Adiponectin and insulin resistance
Since adiponectin aids in insulin sensitivity, people who experience insulin resistance typically have low levels of adiponectin. Insulin resistance happens when cells don’t respond to insulin as they should, which results in excess insulin release (hyperinsulinemia).
Insulin resistance can result in prediabetes, type 2 diabetes, and gestational diabetes. While insulin resistance is often associated with obesity, people can have insulin resistance without having obesity. And people who have insulin resistance without obesity usually have low adiponectin levels as well. This suggests that there may be a genetic factor involved with insulin resistance and adiponectin.
Adiponectin and atherosclerosis
Atherosclerosis is a condition that happens when plaque builds up on the inside walls of arteries. Plaque is a sticky substance made of fat, cholesterol, calcium, and other substances. As plaque builds up, arteries become hard and narrow.
Since adiponectin has anti-inflammatory effects that help protect the heart and blood vessels, low levels of adiponectin can contribute to atherosclerosis and other cardiovascular issues, such as myocardial infarctions.
Adiponectin and lipodystrophy
Lipodystrophy is a group of rare syndromes that cause a lack of fat (adipose tissue) in some parts of the body, while having excess amounts of fat in other areas, including on organs like the liver. A person can be born with lipodystrophy or develop it later in life.
Congenital (from birth) and HIV-related lipodystrophies are associated with low levels of adiponectin. This is likely because adiponectin plays a role in how the body stores fat.
Treatment for abnormal adiponectin levels
A natural treatment to improve adiponectin levels is consistent exercise and healthy weight loss.
Medications such as metformin and thiazolidinediones, prescribed to treat type 2 diabetes, result in an increase in adiponectin levels.