Does heart have GLUT4?

In the heart, the most abundant glucose transporters are GLUT1 and GLUT4.

Where is GLUT4 located?

GLUT4 expression is highest in adipose tissue and skeletal muscle, but GLUT4 is also found in other organs such as brain, kidney and intestine (Brosius et al., 1992; Rayner et al., 1994; Stöckli and James, 2009) and its possible role as a glucose sensor in these and other organs is worthy of future investigation.

What is the structure of GLUT4?

GLUT4 comprises 509 amino acids with 12 helices traversing through the lipid bilayer, and a large cytoplasmic loop located between transmembrane helices 6 and 7 [18], [19].

What is GLUT4 stimulated by?

Insulin stimulates glucose transport in fat and skeletal muscle cells primarily by inducing the translocation of GLUT4 (glucose transporter isoform 4) to the PM (plasma membrane) from specialized GSVs (GLUT4 storage vesicles).

Does the heart need insulin to uptake glucose?

The main role of insulin in the heart under physiological conditions is obviously the regulation of substrate utilization. Indeed, insulin promotes glucose uptake and its utilization via glycolysis.

Why is GLUT4 important?

GLUT4 is one of the most important downstream sites of the insulin receptor because it sits at the rate-limiting step in the insulin transduction signal pathway. It has been reported that GLUT4 protein and mRNA are reduced in type 2 diabetes (Chen et al., 2003).

How is GLUT4 mobilized?

In cells not stimulated with insulin, GLUT4 is targeted to specialized GLUT4 storage vesicles (GSVs), which sequester it away from the cell surface. Insulin acts within minutes to mobilize these vesicles, translocating GLUT4 to the plasma membrane to enhance glucose uptake.

What type of receptor is GLUT4?

Glucose transporter type 4 (GLUT4), also known as solute carrier family 2, facilitated glucose transporter member 4, is a protein encoded, in humans, by the SLC2A4 gene. GLUT4 is the insulin-regulated glucose transporter found primarily in adipose tissues and striated muscle (skeletal and cardiac).

What are GLUT4 vesicles?

Fat and muscle cells contain a specialized, intracellular organelle known as the GLUT4 storage vesicle (GSV). Insulin stimulation mobilizes GSVs, so that these vesicles fuse at the cell surface and insert GLUT4 glucose transporters into the plasma membrane.

How does glucose enter the heart?

Glucose for the heart is derived either from the bloodstream or from intracellular stores of glycogen (Figure 1). The transport of glucose into the cardiomyocyte occurs along a steep concentration gradient and is regulated by specific transporters.

Does the heart prefer ketones or glucose?

While a normal heart relies on fat and carbohydrates for 60 per cent of its energy, a failing heart is running out of those energy stores, but rather than stop, it increasingly relies on ketones.