Modulation of Systemic Metabolism by MMP-2: From MMP-2 Deficiency in Mice to MMP-2 Deficiency in Patients

Matrix metalloproteinase-2 (MMP-2) is a 72-kDa zinc-and calcium-dependent endopeptidase with intracellular and extracellular functions ranging from the modulation of extracellular matrix remodeling to cell growth and migration, angiogenesis, inflammation, and metabolism. An upregulation of MMP-2 activity has the potential to deregulate lipid metabolism through the cleavage of numerous metabolic mediators including plasma lipoproteins and cell surface receptors of lipoproteins. Paradoxically, MMP-2 deficiency induces inflammation and deregulates metabolism. Humans and mice with a deficiency in MMP-2 activity share a complex metabolic and inflammatory syndrome including cardiac dysfunction associated with congenital heart defects (in humans) and metabolic disorder (mice), arthritis, loss of bone mass, lipodystrophy, and delayed growth. The etiology of the inflammatory and metabolic syndrome in MMP-2 deficiency is unknown and there is currently no cure for MMP-2 deficiency in patients. Recent research suggests that the pathophysiology of MMP-2 deficiency in mice and humans is influenced by a heart-centric endocrine mechanism signaled by a cardiac-specific secreted phospholipase A2 (cardiac sPLA2), which is released from cardiomyocytes in response to monocyte chemoattractant protein-3, a proinflammatory cytokine normally cleaved and inactivated by MMP-2. This review summarizes many important proteolytic functions of MMP-2 and recapitulates recent reports linking the heart to systemic metabolic control through the MMP-2/cardiac sPLA2 axis. The authors suggest that MMP-2 deficiency should, perhaps, be viewed and treated as an endocrine condition of excess sPLA2, a concept with particular importance for the therapeutic treatment of MMP-2-deficient patients. The possible existence of tissue-specific MMP/cytokine/PLA2 signaling systems is discussed. (C) 2016 American Physiological Society.