Can you increase your metabolic rate – even when resting – by eating a high-fat diet? Likewise, will exercise kick you into fat-burning mode?
PPARδ is a key player in how and when your muscles burn fat for fuel. Genetic variants in the PPARD gene impact how well your muscles utilize fatty acids. These variants also impact how much of a fat-burning benefit you get from exercise.[ref]
PPARδ: Fat burning and exercise response
PPARδ (PPAR-delta) is part of the PPAR family of receptors. These receptors are found in the nucleus of the cell, surrounding certain areas of the DNA. PPARδ is activated by fatty acids, and then it causes other genes to be transcribed into their proteins.
Essentially, PPARδ is a sensor for cellular metabolism, switching on the genes needed for burning fat instead of glucose.
PPARδ is found in many different tissue types, but it is most important in the liver, skeletal muscles, and heart muscles.
In the skeletal muscles, PPARδ is important in using fatty acids for fuel and how muscles respond to exercise.[ref]
In the liver, PPARδ increases the use of fat for fuel, and it is thus protective against fatty liver disease.[ref]
Increased levels of PPARδ are linked to less fat in the heart muscles and better uptake of glucose and fatty acids in the skeletal muscles. Increased levels of PPAR-delta can also lead to decreased cholesterol absorption in the intestines.[ref]
There are a number of different long-chain fatty acids that can bind to and activate PPARδ, produced in the body, or from foods. Common fatty acids from foods include polyunsaturated fats such as arachidonic acid and linoleic acid.[ref]
PPARδ in weight loss and exercise training:
There are different goals for exercising and training – and PPAR-delta influences how easily you can reach those goals.
Some people work out to lose weight; others train to increase muscle mass. For some, exercise gives greater cardiovascular health benefits; for others, it can raise (or lower) cholesterol levels.
PPARδ acts as an energy manager for endurance exercise – switching the muscles to burning fat and preserving some glucose. Animal studies show that stimulating PPAR-delta using drugs that bind to it can extend running time significantly. Research shows that it does this by using fatty acids for fuel and sparing glucose to be used as needed.[ref]
The PPARD gene codes for PPARδ. Genetic variants in the PPARD gene influence how exercise impacts weight loss, strength gains, cholesterol levels, and cardiovascular health benefits – often in opposite ways.
It is not as simple as “this is a good genetic variant” for PPARD. There are trade-offs, and your view of the variants may depend on your goals.
PPAR-delta and Muscle Fiber Type:
There are two main categories for muscle fiber type: type 1 (slow) and type 2 (fast-twitch). Type I muscle fibers are used more in endurance athletes (long-distance runners), and type 2, or fast-twitch muscle fibers, are important for a burst of speed such as in sprinting or powerlifting.
In animal studies, activating PPARδ causes a switch to forming more type 1, slow-twitch muscle fibers.[ref]
PPAR-delta is anti-inflammatory:
In general, increasing PPARδ can tamp down an overactive inflammatory response.
In a cell culture of heart tissue, increasing PPARδ caused a decrease in the production of the inflammatory cytokine TNF-alpha. In cells created without the PPAR-delta gene, the addition of a bacterial inflammatory molecule causes exaggerated TNF-alpha production (not good).[ref]
Your muscles accumulate tissue damage when you work out – or just through everyday life. Activating PPAR-delta, in turn, activates FOXA2, which tamps down the inflammatory response to tissue damage. Studies are now looking at drugs that activate PPAR-delta as a way of combating muscular pain disorders.[ref]
Can you influence PPAR-delta with fat intake?
Research from the 90s shows that a high-fat diet may increase overall metabolism in the muscles through increasing mitochondrial fatty acid oxidation.
Quick science refresher: Your mitochondria (the powerhouse of the cell :-) turn fat or sugar into energy in the form of ATP. Cells have hundreds to thousands of mitochondria, processing fuel and turning it into energy. More mitochondria, therefore, increases using up fat or sugar and causes an increase in energy.
Studies in rats show that increasing long-chain fatty acids increases mitochondrial fatty acid oxidation in the skeletal muscles. This is thought to be due to the increase in PPAR-delta.[ref]
Medium-chain fatty acids may not be the way to go, though. Animal studies also show that coconut oil, high in medium-chain fatty acids, inhibits PPARδ.[ref]
PPARD in cancer:
The PPARδ agonist known as GW-501 has been shown in cell studies and animal studies to promote tumorigenesis. Activating the PPAR-delta receptor in breast cancer cells also increases the spread of cancer. On the other hand, some studies show that PPAR-delta is downregulated in prostate cancer. Additionally, the topical application of a PPAR-delta agonist has been shown to delay chemical-induced skin cancer.[ref]
PPARδ in the brain:
In addition to its role in fatty acid metabolism in muscles, PPARδ is found abundantly in the brain, where it is neuroprotective.[ref]
People with Huntington’s disease, a progressive, genetic neurodegenerative disease, have low levels of PPARδ in the neurons. Animal studies show that specifically targeting neurons with certain PPARδ activators can reverse some of the neurodegenerative effects of Huntington’s.[ref][ref]
In animal models of depression, low brain levels of PPARδ are linked with chronic mild stress and learned helplessness. Increasing the brain PPARδ prevented depression-like behaviors.[ref]
PPARD Genotype Report:
Lifehacks for increasing PPARδ:
A great way to boost PPARD in muscles is through exercise. Research shows that hard workouts boost PPARD for hours, increasing the usage of fat for fuel.[ref]
As you can see from the PPARD genetic variants above, we don’t all get the same ‘bang for your buck’ with exercise. But… don’t let this be an excuse for you.
Exercise is good for (almost) everyone. So whether or not you get as much cardiovascular benefit from exercise as others do – you will still get some benefit. It may be that you just need to work out a little more often – or a little longer – than other people to get the same benefits.
Like a lot of cellular processes, PPARδ is under circadian control. The body’s core molecular clock relies on increased levels of certain molecules (CLOCK, BMAL1) during the day, and then at night, a couple of other molecules (CRY and PER) rule the dark.
A recent study showed that CRY1 and CRY2 (circadian clock molecules that are activated at night) repress some of the target genes turned on by PPARδ.[ref]
Thus, if you are looking for exercise benefits due to boosting PPARδ, working out during the day may be better than working out later in the evening or at night.
In cell studies, 24 hours of fasting caused a significant up-regulation of PPAR-delta.[ref]
Other websites suggest that you can increase PPARδ by sun exposure, but reading the referenced studies paints a different picture. UVB radiation that causes damage to skin cells does eventually increase PPAR-delta in those cells. This increase is thought to counteract the inflammatory process that is going on in wound healing due to the damage from overexposure to UVB.[ref] Getting some sunshine each day is great – but you don’t want too much sun, causing skin damage to raise the PPARδ.
Supplements and Peptides that affect PPAR-delta:
Related Articles and Topics:
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The ACTN3 gene codes for actinin alpha-3, a protein found in muscles. Some people don’t produce this protein, which changes the composition of their muscles.
Sore Muscles Every Time You Work Out?
Do you end up getting sore after pretty much every workout at the gym? It could be that a deficiency caused by the AMPD1 genetic variant is the cause.
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Fasting is often promoted as a way to lose weight and get healthy. There are some solid, science-based benefits to fasting. But is it right for you? Your genes may hold the answers.
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