GLP-1 analog liraglutide-induced cardiac dysfunction due to energetic starvation in heart failure with non-diabetic dilated cardiomyopathy

Figures

• 

  Fig. 1. Representative image of hearts from J2N-n and J2N-k hamsters. a J2K hamsters, which present dilated cardiomyopathy, were implanted with Alzet 2006 osmotic pumps containing PBS (HF group), low-dose liraglutide (20 µg/kg/day, HF-L group), or high-dose liraglutide (100 µg/kg/day, HF-H group) at 31 weeks of age and sacrificed at 37 weeks of age. The cardiac enlargement at 37 weeks of age is shown for the high-dose liraglutide group. b Heart/body weight indicates severity of heart failure. Increased rate of heart/body weight was observed in HF-H group. *p > 0.05 vs. HF group

• 

  Fig. 2. Fibrosis of cardiac muscles. a Sirius red staining shows more severe fibrosis in the liraglutide groups among all groups (scale bar: 500 µm). Representative images of anterior wall in short axis of the heart are shown. b The rates of fibrosis area/whole area were calculated using the Image J software. Fibrosis was exacerbated by liraglutide administration in a dose-dependent manner. *p < 0.005 (n = 4 in each group) vs. HF group

• 

  Fig. 3. Respiratory gas was analyzed every 2 min in 32-week-old hamsters for 2 days. Average values in light and dark phases are shown in the graph [open bar: light phase, closed bar: dark phase (n = 6 in each group)]. a Energy expenditure and b RQ tended to be upregulated in the compensated period of heart failure. Liraglutide administration emphasized energy expenditure and RQ upregulation in hamsters with heart failure, indicating increased dependency on carbohydrate as an energy substrate during liraglutide administration. c VO2/BW, d CHO consumption, and e FAT consumption in J2N-n hamsters (normal hamsters), J2N-k hamsters with/without administration of high-dose liraglutide. RQ respiratory quotient, VO2 oxygen consumption, CHO carbohydrate, FAT fat

• 

  Fig. 4. a Serum HbA1c and FFA levels in each group. No significant difference was observed among all HF groups, although HbA1c tended to decrease in HF and decrease further in the HF-L and HF-H groups. b The serum FFA concentration was more upregulated in the HF group than that in the N group, but it tended to decrease in the HF-H group despite more severe cardiac dysfunction, although it was not statistically significant. FFA free fatty acid

• 

  Fig. 5. Protein expression and ATP content in the heart muscles of hamsters. a Liraglutide administration further upregulated cleaved caspase-3, an apoptosis marker in J2K hamsters. b Liraglutide also increased LC3 II/I level that indicated increased autophagy, suggesting that substrate starvation for cardiac muscles occurred in the liraglutide groups. c, d Liraglutide increased the levels of the glucose transporter GLUT-4 and fatty acid transporter CD36 in cardiac muscles. e The upregulation of AMPK phosphorylation tended to occur in the HF groups. f, g The ATP content in the cardiac tissues slightly decreased in the HF-H groups in 1 g cardiac muscles; however, as a whole heart, higher ATP content was estimated due to the enlarged cardiac tissue in the HF groups. *p < 0.05 vs. HF + PBS group (n = 6 in each group)

• 

  Fig. 6. An additional 10% glucose administration to the high-dose liraglutide group ameliorated cardiac dilation and fibrosis. a An image representing the cardiac long axis view. b Heart/body weight which indicates severity of heart failure, was clearly decreased in HF-H-G group. c Sirius red staining showed improved cardiac fibrosis by 10% glucose treatment in combination with high-dose liraglutide (n = 4). Representative images of anterior wall in short axis of the heart are shown (scale bar: 500 µm). *p > 0.05 vs. HF + high-dose liraglutide group. HF heart failure, HF-H-G heart failure + 10% glucose

• 

  Fig. 7. Kaplan–Meier survival curve demonstrates 10% glucose administration attenuated mortality in J2N-K hamsters. The earlier lethality in this group than in HF group was not significant for the liraglutide treatment in this experiment. In contrast, 10% glucose addition saved the mortality of HF hamsters administered with PBS, low-dose, or high-dose liraglutide. Log-rank test, *p = 0.025, HF-H-G vs. HF groups; HF: n = 31; HF + high lira: n = 21; HF + low lira: n = 20; HF + high lira + G: n = 22

• 

  Fig. 8. The serum HbA1c and FFA levels in HF-H and HF-H-G groups. The HbA1c level increased by 10% free glucose intake. In contrast, FFA slightly decreased without statistical significance. HF-H: n = 13, HF-H-G: n = 12

• 

  Fig. 9. Respiratory gas was captured every 2 min in 32-week-old hamsters for 2 days. Average values of light and dark phases are shown in the graph [open bar: light phase, closed bar: dark phase (n = 6 in each group)]. a Energy expenditure was similar for administration of high-dose liraglutide with/without 10% glucose; however, b RQ was significantly upregulated in the group with 10% glucose administration. c VO2/BW in hamsters with heart failure treated with liraglutide with/without 10% glucose. Liraglutide administration emphasized RQ upregulation in hamsters with heart failure, indicating increased dependency on (d) carbohydrate as an energy substrate during liraglutide administration and thereby suggesting that glucose was efficiently metabolized as an energy source. e In contrast, fat oxidation reduced with addition of 10% glucose. RQ respiratory quotient, VO2 oxygen consumption, CHO carbohydrate, FAT fat. *p > 0.05 vs. HF-H group

• 

  Fig. 10. Changed protein expression in cardiac muscles by 10% glucose administration for heart failure deteriorated by high-dose liraglutide. a, b GLUT-4 and CD36 were upregulated further. c, d The levels of the apoptotic marker cleaved caspase-3 and autophagy marker LC3 II/I significantly reduced with 10% glucose administration. n = 6 in each group