PPAR agonists are
drug
A drug is any chemical substance that causes a change in an organism's physiology or psychology when consumed. Drugs are typically distinguished from food and substances that provide nutritional support. Consumption of drugs can be via insuffla ...
s which act upon the
peroxisome proliferator-activated receptor
In the field of molecular biology, the peroxisome proliferator-activated receptors (PPARs) are a group of nuclear receptor proteins that function as transcription factors regulating the expression of genes. PPARs play essential roles in the regu ...
. They are used for the treatment of symptoms of the
metabolic syndrome
Metabolic syndrome is a clustering of at least three of the following five medical conditions: abdominal obesity, high blood pressure, high blood sugar, high serum triglycerides, and low serum high-density lipoprotein (HDL).
Metabolic syndrome ...
, mainly for lowering
triglyceride
A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids (from ''tri-'' and ''glyceride'').
Triglycerides are the main constituents of body fat in humans and other vertebrates, as w ...
s and
blood sugar
Glycaemia, also known as blood sugar level, blood sugar concentration, or blood glucose level is the measure of glucose concentrated in the blood of humans or other animals. Approximately 4 grams of glucose, a simple sugar, is present in the blo ...
.
Classification
PPAR-alpha and PPAR-gamma are the molecular targets of a number of marketed drugs. The main classes of PPAR agonists are:
PPAR-alpha agonists
An endogenous compound, 7(S)-Hydroxydocosahexaenoic Acid (7(S)-HDHA), which is a
Docosanoid
In biochemistry, docosanoids are signaling molecules made by the metabolism of twenty-two-carbon fatty acids (EFAs), especially the omega-3 fatty acid, Docosahexaenoic acid (DHA) (i.e. 4''Z'',7''Z'',10''Z'',13''Z'',16''Z'',19''Z''-docosahexaenoic a ...
derivative of the omega-3 fatty acid DHA was isolated as an endogenous high affinity ligand for PPAR-alpha in the rat and mouse brain. The 7(S) enantiomer bound with micromolar affity to PPAR alpha with 10 fold higher affinity compared to the (R) enantiomer and could trigger dendritic activation.
PPARα (alpha) is the main target of
fibrate
In pharmacology, the fibrates are a class of amphipathic carboxylic acids and esters. They are derivatives of fibric acid (phenoxyisobutyric acid). They are used for a range of metabolic disorders, mainly hypercholesterolemia (high cholesterol), ...
drugs
A drug is any chemical substance that causes a change in an organism's physiology or psychology when consumed. Drugs are typically distinguished from food and substances that provide nutritional support. Consumption of drugs can be via inhalat ...
, a class of amphipathic carboxylic acids (
clofibrate
Clofibrate (trade name Atromid-S) is a lipid-lowering agent used for controlling the high cholesterol and triacylglyceride level in the blood. It belongs to the class of fibrates. It increases lipoprotein lipase activity to promote the conversion ...
,
gemfibrozil,
ciprofibrate
Ciprofibrate is a fibrate that was developed as a lipid-lowering agent Lipid-lowering agents, also sometimes referred to as hypolipidemic agents, cholesterol-lowering drugs, or antihyperlipidemic agents are a diverse group of pharmaceuticals that ...
,
bezafibrate
Bezafibrate (marketed as Bezalip and various other brand names) is a fibrate drug used as a lipid-lowering agent to treat hyperlipidaemia. It helps to lower LDL cholesterol and triglyceride in the blood, and increase HDL.
It was patented in 197 ...
, and
fenofibrate
Fenofibrate (sold under the brand names ''Tricor'', ''Fenobrat'' etc.), is an oral medication of the fibrate class used to treat abnormal blood lipid levels. It is less commonly used compared than statins because it treats a different type of c ...
). They were originally indicated for
cholesterol
Cholesterol is any of a class of certain organic molecules called lipids. It is a sterol (or modified steroid), a type of lipid. Cholesterol is biosynthesized by all animal cells and is an essential structural component of animal cell mem ...
disorders and more recently for disorders that feature high triglycerides.
PPAR-gamma agonists
PPARγ (gamma) is the main target of the drug class of
thiazolidinedione
The thiazolidinediones , abbreviated as TZD, also known as glitazones after the prototypical drug ciglitazone, are a class of heterocyclic compounds consisting of a five-membered C3NS ring. The term usually refers to a family of drugs used i ...
s (TZDs), used in
diabetes mellitus
Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ap ...
and other diseases that feature
insulin resistance
Insulin resistance (IR) is a pathological condition in which cell (biology), cells fail to respond normally to the hormone insulin.
Insulin is a hormone that facilitates the transport of glucose from blood into cells, thereby reducing blood gluco ...
. It is also mildly activated by certain
NSAID
Non-steroidal anti-inflammatory drugs (NSAID) are members of a therapeutic drug class which reduces pain, decreases inflammation, decreases fever, and prevents blood clots. Side effects depend on the specific drug, its dose and duration of ...
s (such as
ibuprofen
Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) that is used for treating pain, fever, and inflammation. This includes painful menstrual periods, migraines, and rheumatoid arthritis. It may also be used to close a patent ductus arte ...
) and
indole
Indole is an aromatic heterocyclic organic compound with the formula C8 H7 N. It has a bicyclic structure, consisting of a six-membered benzene ring fused to a five-membered pyrrole ring. Indole is widely distributed in the natural environmen ...
s, as well as from a number of natural compounds. Known inhibitors include the experimental agent GW-9662.
They are also used in treating hyperlipidaemia in
atherosclerosis
Atherosclerosis is a pattern of the disease arteriosclerosis in which the wall of the artery develops abnormalities, called lesions. These lesions may lead to narrowing due to the buildup of atheroma, atheromatous plaque. At onset there are usu ...
. Here they act by increasing the expression of
ABCA1, which transports extra-hepatic cholesterol into HDL. Increased uptake and excretion from the liver therefore follows.
Animal studies have shown their possible role in amelioration of pulmonary inflammation, especially in asthma.
PPAR-delta agonists
PPARδ (delta) is the main target of a research chemical named
GW501516
GW501516 (also known as GW-501,516, GW1516, GSK-516, Cardarine, and on the black market as Endurobol) is a PPARδ receptor agonist that was invented in a collaboration between Ligand Pharmaceuticals and GlaxoSmithKline in the 1990s. It entere ...
. It has been shown that agonism of PPARδ changes the body's fuel preference from glucose to lipids.
Dual and pan PPAR agonists
A fourth class of dual PPAR agonists, so-called ''glitazars'', which bind to both the α and γ PPAR isoforms, are currently under active investigation for treatment of a larger subset of the symptoms of the metabolic syndrome.
These include the experimental compounds
aleglitazar,
muraglitazar
Muraglitazar (proposed tradename Pargluva) is a dual peroxisome proliferator-activated receptor agonist with affinity to PPARα and PPARγ.
The drug had completed phase III clinical trials, however in May, 2006 Bristol-Myers Squibb announced t ...
and
tesaglitazar
Tesaglitazar (also known as AZ 242) is a dual peroxisome proliferator-activated receptor agonist with affinity to PPARα and PPARγ, proposed for the management of type 2 diabetes.
The drug had completed several phase III clinical trials, howe ...
. In June 2013,
saroglitazar
Saroglitazar (INN, trade name Lipaglyn) is a drug for the treatment of type 2 diabetes mellitus and dyslipidemia. It is approved for use in India by the Drug Controller General of India. Saroglitazar is indicated for the treatment of diabetic dysl ...
was the first glitazar to be approved for clinical use.
In addition, there is continuing research and development of new dual α/δ and γ/δ PPAR agonists for additional
therapeutic
A therapy or medical treatment (often abbreviated tx, Tx, or Tx) is the attempted remediation of a health problem, usually following a medical diagnosis.
As a rule, each therapy has indications and contraindications. There are many different ...
indications, as well as "pan" agonists acting on all three isoforms.
Research
A relatively recent avenue of drug research in treating depression and drug addiction is through
PPARα
Peroxisome proliferator-activated receptor alpha (PPAR-α), also known as NR1C1 (nuclear receptor subfamily 1, group C, member 1), is a nuclear receptor protein functioning as a transcription factor that in humans is encoded by the ''PPARA'' gen ...
and
PPARγ
Peroxisome proliferator- activated receptor gamma (PPAR-γ or PPARG), also known as the glitazone reverse insulin resistance
receptor, or NR1C3 (nuclear receptor subfamily 1, group C, member 3) is a type II nuclear receptor functioning as a tran ...
activation. Both
TLR4
Toll-like receptor 4 is a protein that in humans is encoded by the ''TLR4'' gene. TLR4 is a transmembrane protein, member of the toll-like receptor family, which belongs to the pattern recognition receptor (PRR) family. Its activation leads to an ...
-mediated and
NF-κB
Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) is a protein complex that controls transcription of DNA, cytokine production and cell survival. NF-κB is found in almost all animal cell types and is involved in cellular ...
-mediated signalling pathways have been implicated in the development of addiction to several drugs such as opioids and cocaine, and therefore are appealing targets for pharmacotherapy. Despite a breadth of preclinical research showing potential in animal models in the treatment of drug addictions including alcohol, nicotine, cocaine, opioids and methamphetamine, the human evidence is limited with the amount of trials looking at using PPAR agonists for humans still being low; and so far (as of 2020) not being particularly promising. There are several suggested hypotheses for the poor translation from animal to human research evidence such as the potency and selectivity of PPAR ligands, sex-related variability, and species differences in the distribution and signaling of PPAR.
References
{{PPAR modulators
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Transcription factors