Changes in myoﬁlament proteins, but not Ca 2 (cid:1) regulation, are associated with a high-fat diet-induced improvement in contractile function in heart failure

Changes in myoﬁlament proteins, but not Ca 2 (cid:1) regulation, are associated with a high-fat diet-induced improvement in contractile function in heart failure. Am J Physiol Heart Circ Physiol 301: H1438–H1446, 2011. Pathological conditions such as diabetes, insulin resistance, and obesity are characterized by elevated plasma and myocardial lipid levels and have been reported to exacerbate the progression of heart failure (HF). Alterations in cardiomyocyte Ca 2 (cid:1) regulatory properties and myoﬁlament proteins have also been implicated in contractile dysfunction in HF. However, our prior studies reported that high saturated fat (SAT) feeding improves in vivo myocardial contractile function, thereby exerting a cardioprotective effect in HF. Therefore, we hypothesized that SAT feeding improves contractile function by altering Ca 2 (cid:1) regulatory properties and myoﬁlament protein expression in HF. Male Wistar rats underwent coronary artery ligation (HF) or sham surgery (SH) and were fed normal chow (SHNC and HFNC groups) or a SAT diet (SHSAT and HFSAT groups) for 8 wk. Contractile properties were measured in vivo [echocardiography and left ventricular (LV) cannulation] and in isolated LV cardiomyocytes. In vivo measures of contractility (peak LV (cid:1) dP/d t and (cid:2) dP/d t ) were depressed in the HFNC versus SHNC group but improved in the HFSAT group. Isolated cardiomyocytes from both HF groups were hypertrophied and had decreased percent cell shortening and a prolonged time to half-decay of the Ca 2 (cid:1) transient versus the SH group; however, SAT feeding reduced in vivo myocyte hypertrophy in the HFSAT group only. The peak velocity of cell shortening was reduced in the HFNC group but not the HFSAT group and was positively correlated with in vivo contractile function (peak LV (cid:1) dP/d t ). The HFNC group demonstrated a myosin heavy chain (MHC) isoform switch from fast MHC- (cid:3) to slow MHC- (cid:4) , which was prevented in the HFSAT group. Alterations in Ca 2 (cid:1) transients, L-type Ca 2 (cid:1) currents, and protein expression of sarco(endo)plasmic reticulum Ca 2 (cid:1) -ATPase and phosphorylated phospholamban could not account for the changes in the in vivo contractile properties. In conclusion, the cardioprotective effects associated with SAT feeding in HF may occur at the level of the isolated cardiomyocyte, speciﬁcally involving changes in myoﬁlament function but not sarcoplasmic reticulum Ca 2 (cid:1) regulatory properties. by incubations with the appropriate secondary antibodies. were incubated with chemiluminescence reagents (Thermo Scientiﬁc) and exposed to ﬁlms. Densitometry of bands was determined using ImageJ (NIH). A standardizing sample was run on each gel to allow for normalizing densitometry across individual gels. Ca Myoﬁlament protein phosphorylation and expression. LV tissue ( n (cid:5) 6) was harvested, and myoﬁlament proteins were puriﬁed using a previously described protocol (20). Ten micrograms of protein were loaded onto a 4–12% XT Bis-Tris gel (Bio-Rad), followed by Pro-Q Diamond Phosphoprotein Gel staining (Invitrogen) per the manufac- turer’s protocol. The same gel was then stained with Coomassie blue for total protein expression. Densitometry of bands was performed using ImageJ (NIH). The degree of protein phosphorylation was quantiﬁed as Pro-Q density/Coomassie blue density. Statistics. All statistical analyses were performed using SigmaStat software. Differences were determined using two-way ANOVA fol- lowed by Bonferroni post hoc analysis for multiple pairwise compar-isons unless otherwise noted. Signiﬁcance was established at P (cid:8) 0.05. Data are expressed as means (cid:9) SE.