Frederico Toledo Campo Dall’Orto et al. Flávia Bittar Brito Arantes Remo H. M. Furtado Pedro G. M. de Barros e Silva
Insulin resistance (IR) is a complex metabolic abnormality associated with genetic and environmental factors, which begins with low glucose metabolism in tissues, particularly in muscle, liver, and adipocytes, with consequent stimulation of pancreatic beta cells to increase insulin production and release.– Accumulation of lipids in a variety of tissues, including muscle, liver, and pancreas, contributes to this process in a phenomenon known as “lipotoxicity.” As IR increases, it stimulates hyperinsulinemia, and this negative cycle perpetuates a metabolic disorder that is a main cause of cardiovascular diseases. In addition, insulin also acts on lipid metabolism, increasing lipid synthesis in liver and adipose cells, in addition to turning off the release of triglycerides (TG) and fatty acids in adipose and muscle tissues.
Several tests are used to identify IR, such as the oral glucose tolerance test, insulin dosage, and the hyperinsulinemic-euglycemic clamp (HIEC), which is considered the gold standard. However, HIEC is complex and time-consuming, which limits its widespread use in clinical practice. Currently, the most widely used test to assess IR is the homeostasis model assessment of insulin resistance (HOMA-IR), which has several limitations including lack of standardization (e.g., variations in laboratory, patients using antidiabetic drugs, low body mass index), calculation based on fasting parameters (which may not be representative of the entire day), and assumptions about IR that are not totally true (e.g., the assumption that IR is proportional to insulin levels and is similar in the liver and peripheral tissues, without considering variation in beta cell function)., Recently, a new marker of IR has been designed, which is the triglyceride-glucose (TyG) index that predicts the risk of IR, diabetes, and cardiovascular disease. The TyG index is calculated by multiplying the TG value by the serum glucose level, in mg/dl, and dividing the result by 2. The TyG index is a non-invasive, low-cost marker for cardiovascular risk stratification. Since IR can be related to the development of more extensive coronary disease, this marker could also be useful to this evaluation.
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