Research on Hexarelin and Its Role in Reducing Cardiac Fibrosis

by Dr. James Ross

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MMP Regulation by Hexarelin

Matrix metalloproteinases (MMPs), particularly MMP-2 and MMP-9, are critical collagen-degrading enzymes that play important roles in the development of cardiac fibrosis. When comparing spontaneous hypertensive rats (SHRs) to Wistar rats, no significant differences in basal MMP-2 and MMP-9 activity were noted. However, following administration of hexarelin, SHRs exhibited a marked increase in MMP-2 and MMP-9 activity, with the most pronounced effect observed on MMP-9.

This effect was dependent on activation of the growth hormone secretagogue receptor (GHS-R), as pharmacological blockade of GHS-R abolished the hexarelin-induced rise in MMP activity. Additionally, transcriptional analysis showed that tissue inhibitor of metalloproteinases-1 (TIMP-1) mRNA, which was markedly elevated in SHRs compared with Wistar controls, was significantly reduced by hexarelin in a GHS-R–dependent manner.

Hexarelin suppressed TIMP-1 mRNA and its inhibition of collagen degrading enzymes

In keeping with the gene expression findings, protein analysis confirmed that collagen types I and III were elevated in SHRs relative to controls. Treatment with hexarelin reduced both collagen I and collagen III levels at the transcript and protein level.

When SHRs were administered (D-Lys3)-GHRP-6, a selective GHS-R blocker, the anti-collagen effects of hexarelin were abolished. This demonstrates that the reduction in collagen by hexarelin is directly mediated through GHS-R signaling pathways.

Interestingly, in normal Wistar rats, hexarelin treatment did not alter collagen I or III expression, suggesting that its modulatory effects are particularly significant in disease conditions marked by fibrosis, such as hypertension.

Hexarelin reduced Collagen I and III in the heart

Overall, hexarelin reduced myocardial fibrosis in hypertensive rats by stimulating collagen degradation through enhanced MMP activity while simultaneously reducing TIMP-1 expression. This dual action shifted the balance toward extracellular matrix breakdown, resulting in decreased levels of collagen I and collagen III in cardiac tissue.

However, when hexarelin was combined with GHRP-6, another growth hormone secretagogue that blocks GHS-R activity, its beneficial effects on collagen reduction were nearly abolished. These findings provide strong evidence that the anti-fibrotic action of hexarelin is dependent on intact GHS-R signaling.