Hormone Sensitive Lipase (HSL) is an enzyme found inside cells that plays a role in how the body uses and stores fat. HSL is involved in fat metabolism, especially in adipose tissue, the body’s primary site for fat storage. The enzyme helps manage the body’s energy reserves by breaking down stored fats.
How It Breaks Down Stored Fat
HSL’s primary function involves breaking down stored fats through a process called lipolysis. In fat cells, fat is stored as triglycerides. HSL acts on these triglycerides, breaking them down.
While HSL can break down triglycerides, it has a higher affinity for diglycerides, which are triglycerides that have already lost one fatty acid. The enzyme primarily cleaves a fatty acid from a diglyceride, leaving behind a monoglyceride and a free fatty acid. This action releases free fatty acids and glycerol into the bloodstream, making these components available for other tissues to use as energy.
Hormonal Control of Its Activity
The activity of HSL is controlled by various hormones, which is why it is called “hormone-sensitive.” This regulation ensures fat is mobilized when the body needs energy and stored when energy is abundant. Insulin, a hormone released after meals, inhibits HSL activity. When insulin levels are high, it signals fat cells to reduce the breakdown of stored fat, promoting energy storage.
In contrast, hormones like glucagon, adrenaline (epinephrine), and noradrenaline (norepinephrine) activate HSL. Glucagon is released when blood glucose levels are low, such as during fasting, signaling the need for alternative energy sources. Adrenaline and noradrenaline, often released during stress or exercise, also stimulate HSL activity. These hormones activate HSL, allowing it to begin breaking down stored fat.
Supplying Energy for the Body
The breakdown of stored fat by HSL supplies energy to the body, particularly when glucose is less available. The free fatty acids released from fat cells can be transported through the bloodstream to various tissues, including muscles and the liver, where they are used as fuel. For example, during fasting or prolonged exercise, when carbohydrate stores are depleted, fatty acids become a primary energy source.
Glycerol, the other product of triglyceride breakdown, is transported to the liver. The liver can then convert glycerol into glucose, providing an additional source of energy, especially for tissues like the brain that rely heavily on glucose. This mobilization of energy reserves by HSL is important for maintaining overall energy balance and supporting bodily functions during increased energy demand.
Its Role in Health and Disease
Dysregulation of HSL activity can impact various health conditions, especially metabolic disorders. Altered HSL function, either too much or too little activity, can contribute to imbalances in fat metabolism. For instance, elevated plasma free fatty acids, often linked to high HSL activity, are associated with insulin resistance, obesity, and type 2 diabetes.
In conditions like type 2 diabetes, impaired HSL activity or its regulation can lead to issues with both fat and glucose metabolism. Research indicates that inhibition of HSL may help improve insulin sensitivity and blood glucose control in individuals with type 2 diabetes by reducing the excess release of free fatty acids. Understanding HSL’s role in these conditions may aid in developing strategies for managing metabolic health.