Erratum to: Ventricular assist device implantation improves skeletal muscle function, oxidative capacity, and growth hormone/insulin-like growth factor-1 axis signaling in patients with advanced heart failure

Background: Skeletal muscle dysfunction in patients with heart failure (HF) has been linked to impaired growth hormone (GH)/insulin-like growth factor (IGF)-1 signaling. We hypothesized that ventricular assist device (VAD) implantation reverses GH/IGF-1 axis dysfunction and improves muscle metabolism in HF. Methods: Blood and rectus abdominis muscle samples were collected during VAD implantation and explantation from patients with HF and controls. Clinical data were obtained from medical records, biomarkers measured by enzyme-linked immunosorbent assay (ELISA), and gene expression analyzed by reverse transcription and real-time polymerase chain reaction (RT-PCR). Grip strength was assessed by dynamometry. Oxidative capacity was measured using oleate oxidation rates. Muscle fiber type and size were assessed by histology. Results: Elevated GH (0.27 ± 0.27 versus 3.6 ± 7.7 ng/ml in HF; p = 0.0002) and lower IGF-1 and insulin-like growth factor binding protein (IGFBP)-3 were found in HF (IGF-1, 144 ± 41 versus 74 ± 45 ng/ml in HF, p < 0.05; and IGFBP-3, 3,880 ± 934 versus 1,935 ± 862 ng/ml in HF, p = 0.05). The GH/IGF-1 ratio, a marker of GH resistance, was elevated in HF (0.002 ± 0.002 versus 0.048 ± 0.1 pre-VAD; p < 0.0039). After VAD support, skeletal muscle expression of IGF-1 and IGFBP-3 increased (10-fold and 5-fold, respectively; p < 0.05) accompanied by enhanced oxidative gene expression (CD36, CPT1, and PGC1α) and increased oxidation rates (+1.37-fold; p < 0.05). Further, VAD implantation increased the oxidative muscle fiber proportion (38 versus 54 %, p = 0.031), fiber cross-sectional area (CSA) (1,005 ± 668 versus 1,240 ± 670 μm2, p < 0.001), and Akt phosphorylation state in skeletal muscle. Finally, hand grip strength increased 26.5 ± 27.5 % at 180 days on-VAD (p < 0.05 versus baseline). Conclusion: Our data demonstrate that VAD implantation corrects GH/IGF-1 signaling, improves muscle structure and function, and enhances oxidative muscle metabolism in patients with advanced HF

Optimal Allocation of Curtailment Levels of PV Power Output in Different Regions in Consideration of Reduction of Aggregated Fluctuations

Due to the high penetration of photovoltaic power generation system (PV) anticipated in the future, the curtailment of PV power output becomes crucial, not only to maintain supply-demand balance but also to preserve an adequate capacity for the frequency control. When the curtailment level (CL) of the aggregated PV power output is determined in a day-ahead unit commitment (UC) scheduling, different CL should be applied to different regions with distinctive weather modes in the power system area so that the fluctuations of aggregated PV power output are minimized. The objective of this study is to optimally allocate the CL to each region based on the short-term forecasting of the weather modes so that the hourly maximum fluctuation of the aggregated PV power output (MFagg) is minimized as long as the aggregated average power output (Avgagg) becomes the same as the scheduled value in UC. Based on the past observations of PV power output, the proposed method employs relations between the regions&#x2019; MF and CL (MF-CL patterns), and relations between the regions&#x2019; Avg and CL (Avg-CL patterns) for several typical weather modes. Thus, a specific MF-CL pattern and Avg-CL pattern are determined for each region based on the short-term forecasting of the weather mode, and the CL optimization is proceeded by using these patterns. The proposed methods are tested by using the time-series of PV power output at 61 observation points in the central region of Japan for one year. As a result, it is demonstrated that merely acknowledging the weather mode of each region enabled the proposed methods to reduce MFagg significantly and these results are practically similar to the method where perfect short-term forecasting of PV power output was utilized in the entire year