Insulin is anabolic anticatabolic hormone
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The role of insulin in glucose homeostasis is represented by the direct effect of insulin on skeletal muscle, liver, and white adipocytes.
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Insulin induces synthesizing glycogen from glucose and converting excess glucose into fatty acids and precursor triglycerides (TAGs).
A. Role of Insulin in the Regulation of Liver Function
The liver is the primary organ of insulin action. A- Insulin upregulates glucose-utilizing activity:
- Accelerated hepatic glucose utilization
- Glycolysis
- Glycogenesis
- B- Insulin downregulates glucose production by
- Suppressing net glucose production
- Gluconeogenesis
- Glycogenolysis.
B. Role of Insulin in the Regulation of Muscle Function
- Approximately 70% of the whole-body glucose uptake is used by skeletal muscle.
- Patients with type 2 diabetes are associated with poor muscle strength and function.
- In skeletal muscle, a representative insulin-acting tissue, insulin promotes glucose utilization and storage by increasing glucose transport and net glycogen synthesis.
C. Role of Insulin in the Regulation of Fat
In white adipocyte tissue, insulin inhibits lipolysis and increases glucose transport and adipogenesis.
D- Role of Insulin in the Regulation of Endothelium and Vasculature
- Increases nitric oxide (NO) bioavailability
- Decreases oxidative stress mediated by elevated reactive oxygen species (ROS) production,
- Prevents the expression of pro-inflammatory and pro-thrombotic factors.
- Thus, insulin dysfunction predisposes to increased susceptibility to atherosclerosis, coronary heart disease, and hypertension.
E. Insulin effects on the Brain
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Increases glucose uptake in the spinal cord tissues and some brain regions, such as the choroid plexus, the pineal gland, and the pituitary.
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Controls neuronal plasticity, memory processing, and cognition
F. Insulin effects on the Bone
- Promotes bone development
- Increases bone mineralization
- Increases osteoblast proliferation, collagen synthesis, and alkaline phosphatase production rate.
- Inhibits the activities of osteoclasts