Copper-deficient diet-induced cardiomyopathy is characterized by global decreases in circulating and cardiac copper concentrations. Cu
+ comprises 95% of total copper and localizes intracellularly, whereas Cu
2+ comprises 5% of total copper and localizes extracellularly
[83]. In contrast to copper deficiency-induced cardiomyopathy, increases in circulating copper concentrations and 2–3-fold increases in extracellular myocardial Cu
2+ levels, but decreases in intracellular myocardial Cu
+ levels, were reported in humans and rodents with DM cardiomyopathy. The reduced myocardial copper content and elevated systemic and total cardiac copper content in DM cardiomyopathy reflect defective uptake of copper by myocardiocytes
[84][85][86][87]. Glycosylation of proteins to form advanced glycation end-products (AGEs) is a deleterious consequence of hyperglycemia in diabetes and metabolic syndrome
[88]. In hearts of rats with DM, increased extracellular Cu
2+ increases gene expression of
Tgfβ,
Smad4, and collagens, which results in collagen deposition and increases the formation of AGEs of collagens. These events cause vascular injury and increase susceptibility to IHD
[89]. Elevated extracellular Cu
2+ in DM cardiomyopathy is likely loosely bound to extracellular matrix components, such as collagens
[84][85]. Interestingly, in rodents and humans with DM cardiomyopathy, Cu
2+-selective chelators, including trientine and triethylenetetramine (TETA) dihydrochloride, prevent excessive cardiac collagen deposition, improve cardiac structure and function, and restore antioxidant defense by promoting copper excretion
[84][90][91][92][93][94]. Zhang et al. reported that the expression of the
Ctr1 gene was downregulated in hearts of rats with DM, which is consistent with impaired cardiac copper uptake in DM
[92]. Although TETA decreases the expression of cardiac
Ctr1 in rats, it increases CTR2 localization to the plasma membrane and, thus, concomitantly normalizes the reduced cardiac Cu
+ levels in DM. In addition, TETA increases localization of ATP7A to the TGN and peri-nuclear region and corrects the defects in copper delivery to the secretory pathway and, thus, improves the utilization of copper by cuproenzymes, including ATOX1 and SOD1
[92]. These data suggest that TETA normalizes cardiac copper homeostasis and restores cardiac function in DM by restoring expression and localizations of copper transporters and copper-binding proteins. In addition, TETA restores mRNA and protein expression of copper chaperones, including COX11, COX17, CCS, and SOD1 and, thus, restores copper availability and trafficking, and improves cardiac functions in hearts of rats with DM
[91]. Although the highly selective Cu
2+ chelator trientine efficiently treats DM cardiomyopathy, long-term clinical studies are necessary to determine whether the improvement of cardiac function by trientine is associated with long-term benefits for mortality. Similarly, additional studies investigating the effects of trientine for treatment of other cardiomyopathies, such as IHD, are also warranted.