Caloric restriction reverses left ventricular hypertrophy through the regulation of cardiac iron homeostasis in impaired leptin signaling mice

Abstract

Leptin-deficient and leptin-resistant mice manifest obesity, insulin resistance, and left ventricular hypertrophy (LVH); however, LVH's mechanisms are not fully understood. Cardiac iron dysregulation has been recently implicated in cardiomyopathy. Here we investigated the protective effects of caloric restriction on cardiac remodeling in impaired leptin signaling obese mice. RNA-seq analysis was performed to assess the differential gene expressions in the heart of wild-type and ob/ob mice. In particular, to investigate the roles of caloric restriction on iron homeostasis-related gene expressions, 10-week-old ob/ob and db/db mice were assigned to ad libitum or calorie-restricted diets for 12 weeks. Male ob/ob mice exhibited LVH, cardiac inflammation, and oxidative stress. Using RNA-seq analysis, we identified that an iron uptake-associated gene, transferrin receptor, was upregulated in obese ob/ob mice with LVH. Caloric restriction attenuated myocyte hypertrophy, cardiac inflammation, fibrosis, and oxidative stress in ob/ob and db/db mice. Furthermore, we found that caloric restriction reversed iron homeostasis-related lipocalin 2, divalent metal transporter 1, transferrin receptor, ferritin, ferroportin, and hepcidin expressions in the heart of ob/ob and db/db mice. These findings demonstrate that the cardioprotective effects of caloric restriction result from the cellular regulation of iron homeostasis, thereby decreasing oxidative stress, inflammation, and cardiac remodeling. We suggest that decreasing iron-mediated oxidative stress and inflammation offers new therapeutic approaches for obesityinduced cardiomyopathy.Disruption of leptin signaling leads to obesity-induced cardiac remodeling 1,2 , and this progression of cardiac hypertrophy to heart failure is a major contributor to morbidity and mortality in obese patients 3 . Although the pathophysiology of cardiac remodeling in obesity is complex, leptin-deficient (ob/ob) and leptin-resistant (db/ db) signaling serve an important role in obesity-associated left ventricular hypertrophy (LVH) 1,2,4 . The cardiomyopathy that stems from disruption of leptin signaling is due to several factors including insulin resistance, myocardial steatosis, inflammation, oxidative stress, and direct effects of deficiencies in leptin or leptin receptors 1,5,6 . However, the precise role of leptin on obesity-induced cardiomyopathy is not completely understood.Effect of CR on cardiac iron uptake in ob/ob and db/db mice. Due to our observation of elevated cardiac ferrous iron levels in ob/ob mice (Fig. 2f), we examined regulation of iron uptake-related genes via qRT-PCR. LCN2, DMT1, Tfrc, and L-ferritin mRNA levels were significantly lower in ob/ob+CR mice relative to ob/ob and db/db mice fed ad libitum (Figs. S6 and S8). Although the level of 24p3R mRNA in the hearts of ob/ob mice was significantly reduced by CR, we did not observe the same pattern in db/db mice (Figs. S6b and S8b). In addition, CR did not cause the change of iron uptake-related genes in WT and db/m mice ( Figs. S...

The Role of SHIP1 on Apoptosis and Autophagy in the Adipose Tissue of Obese Mice

“…Our previous studies demonstrated that CR attenuates body weight in DIO and ob/ob mice [ 16 , 17 ]. Compared with DIO and ob/ob mice, calorie-restricted DIO and ob/ob mice exhibited fewer SHIP1-positive CD11b, a macrophage marker ( Figure 5 A and Figure 6 A).…”

“…The sequencing library was constructed using Illumina’s TruSeq RNA Prep kit (illumina Inc., San Diego, CA, USA), and data generation was performed using the NextSeq 500 platform (illumina Inc.) following the manufacturer’s protocol. RNA-seq analysis was performed as previously described [ 17 ].…”

“…Total RNA from epididymal adipose tissue ( n = 4–6 per group) was prepared using a previously reported method [ 17 ]. PCR primers used for this study are presented in Table S2 .…”

Adipokines and Inflammation: Focus on Cardiovascular Diseases

“…Studies carried out in leptin-deficient/resistant murine animal models have shown that leptin participates in the regulation of cardiac metabolism, contraction, hypertrophy, and apoptosis, with some contradictory results but overall indicating that the deregulation of leptin signalling may have important implications in heart physiology [ 45 ]. In this line, leptin-deficient ob/ob and leptin-resistant db/db mice suffer from impaired cardiac function due to cardiac hypertrophy, inflammation, oxidative stress, and iron overload, an effect that is reverted by calorie restriction through the restoring of iron levels [ 46 ].…”

tRNA-Derived Small RNAs and Their Potential Roles in Cardiac Hypertrophy

“…Moreover, there is also an interesting link between calorie restriction and aging retardation as well as cardiac functional improvement. A number of studies suggest that caloric restriction can prevent or reduce cardiac hypertrophy, improve cardiac function, and even retard aging (Yu, 1994;Cruzen and Colman, 2009;Dolinsky et al, 2010;de Lucia et al, 2018;An et al, 2020). Although the mechanisms are still unclear, there is evidence showed that aging and caloric restriction can modulate specific 5' tRNA halves (Dhahbi et al, 2013).…”