Lactotripeptides are two naturally occurring milk

peptides Peptides are short chains of amino acids linked by peptide bonds. A polypeptide is a longer, continuous, unbranched peptide chain. Polypeptides that have a molecular mass of 10,000 Dalton (unit), Da or more are called proteins. Chains of fewer t ...

Isoleucine Isoleucine (symbol Ile or I) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH form under biological conditions), an α-carboxylic acid group (which is in the depro ...

- Proline-Proline (IPP) and

Valine Valine (symbol Val or V) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α- amino group (which is in the protonated −NH3+ form under biological conditions), an α- carboxylic acid group (which is in the deproton ...

-Proline-Proline (VPP). These lactotripeptides are derived from casein, which is a milk protein also found in dairy products. Although most normal dairy products contain lactotripeptides, they are inactive within the original milk proteins. Dairy peptides can be effectively released through enzymatic predigestion – a process by which milk protein is enzymatically broken down into smaller pieces. Some clinical studies have suggested that these lactotripeptides help promote healthy blood pressure levels as part of a healthy diet and lifestyle. However, other clinical trials have seen no effects from these compounds.

Proposed mechanism

Dairy peptides are proposed to inhibit the activity of the angiotensin-converting

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

( ACE). ACE is part of the

renin–angiotensin system The renin–angiotensin system (RAS), or renin–angiotensin–aldosterone system (RAAS), is a hormone system that regulates blood pressure, fluid, and electrolyte balance, and systemic vascular resistance. When renal blood flow is reduced, ...

– a natural mechanism that helps regulate blood pressure in the body. In certain individuals, the renin–angiotensin system can become overactive, often due to stress, an unhealthy diet, and/or unhealthy lifestyle. Under such conditions, ACE becomes overactive and converts more angiotensin I into angiotensin II. Angiotensin II causes blood vessels to constrict, and so increases blood pressure, which has potential to lead to hypertension. But, when ACE activity is inhibited, the formation of angiotensin II is reduced. This then helps the blood vessels to relax and expand back to a normal healthy state, so blood pressure is lowered.

Clinical trials

Several human trials aimed to evaluate the effect of lactotripeptides on blood pressure. Some trials show a blood pressure-lowering effect of lactotripeptides in people with mild to moderate hypertension, however others see no effect from these peptides. A recent systematic review of the literature found no confirmed ACE-inhibitor effects in humans, as well as no conclusive evidence for lactotripeptides as a successful intervention; the meta-analysis cited heterogeneity in methodology and lack of inclusion of recent larger studies by prior meta-analyses to account for the variance between studies.

References

{{reflist Tripeptides Antihypertensive agents