Cardiac effect of short-term experimental weight gain and loss in dogs

A pooled analysis of nine studies in one institution to assess effects of whole heart irradiation in rat models

PURPOSE

Over the years, animal models of local heart irradiation have provided insight into mechanisms of and treatments for radiation-induced heart disease in human populations. However, it is not completely clear which manifestations of radiation injury are most commonly seen after whole heart irradiation, and whether certain biological factors impact experimental results. Combining 9 homogeneous studies in rat models of whole heart irradiation from one laboratory, we sought to identify experimental and/or biological factors that impact heart outcomes. We evaluated the usefulness of including (1) heart rate and (2) bodyweight as covariates when analyzing biological parameters, and (3) we determined which echocardiography, histological, and immunohistochemistry parameters are most susceptible to radiation effects. Finally, (4) as an educational example, we illustrate a hypothetical sample size calculation for a study design commonly used in evaluating radiation modifiers, using the pooled estimates from the 9 rat studies only for context. The results may assist investigators in the design and analyses of pre-clinical studies of whole heart irradiation.

MATERIALS AND METHODS

We made use of data from 9 rat studies from our labs, 8 published elsewhere in 2008-2017, and one unpublished study. Echocardiography, histological, and immunohistochemical parameters were collected from these studies. Using mixed effects analysis of covariance models, we estimated slopes for heart rate and bodyweight and estimated the radiation effect on each of the parameters.

RESULTS

Bodyweight was related to most echocardiography parameters, and heart rate had an effect on echocardiography parameters related to the diameter of the left ventricle. For some parameters, there was evidence that heart rate and bodyweight relationships with the parameter depended on whether the rats were irradiated. Radiation effects were found in systolic measures of echocardiography parameters related to the diameter of the left ventricle, with ejection fraction and fractional shortening, with atrial wall thickness, and with histological measures of capillary density, collagen deposition, and mast cells infiltration in the heart.

CONCLUSION

Accounting for bodyweight, as well as heart rate, in analyses of echocardiography parameters should reduce variability in estimated radiation effects. Several echocardiography and histological parameters were particularly susceptible to whole heart irradiation, showing robust effects compared to sham-irradiation. Lastly, we provide an example approach for a sample size calculation that will contribute to a rigorous study design and reproducibility in experiments studying radiation modifiers.

Impact of maternal height, weight at presentation and gestational weight gain on cardiac adaptation in pregnancy

OBJECTIVE

To compare longitudinal maternal hemodynamic changes throughout gestation between different groups stratified according to weight at presentation and assess the relative influence of height, weight at presentation and gestational weight gain on cardiac adaptation.

METHODS

This was a prospective, longitudinal study assessing maternal hemodynamics using bioreactance technology at 11 + 0 to 13 + 6, 19 + 0 to 24 + 0, 30 + 0 to 34 + 0 and 35 + 0 to 37 + 0 weeks' gestation. Women were divided into three groups according to maternal weight at presentation at the first visit at 11 + 0 to 13 + 6 weeks: Group 1, < 60.0 kg (n = 421); Group 2, 60.0-79.7 kg (n = 904); Group 3, > 79.7 kg (n = 427). A multilevel linear mixed-effects model was used to compare the repeated measures of hemodynamic variables, correcting for demographics, medical and obstetric history, pregnancy complications, maternal weight and time of evaluation. The linear mixed-effects model was then repeated using maternal height, weight at presentation and gestational weight gain Z-scores, and the standardized coefficients were used to evaluate the relative impact of each of these demographic parameters on longitudinal changes of maternal hemodynamics.

RESULTS

Compared with Group 1, women in Group 3 demonstrated higher cardiac output (CO), heart rate (HR) and mean arterial pressure (MAP) throughout pregnancy. Groups 2 and 3 had higher stroke volume (SV) than Group 1 at the first visit, but their SV plateaued between the first and second visits and demonstrated an earlier significant decrease from the second visit to the third visit when compared with Group 1. Compared with Groups 1 and 2, there was a higher prevalence of pre-eclampsia, gestational hypertension and gestational diabetes in Group 3. Maternal height was the most important contributor to CO, peripheral vascular resistance (PVR), SV and HR, while weight at presentation was the most important contributor to MAP. Gestational weight gain was the second most important characteristic influencing the longitudinal changes of PVR and SV.

CONCLUSIONS

Women with greater weight at presentation have a pathological hemodynamic profile, with higher CO, HR and MAP compared to women with lower weight at presentation. Height is the main determinant of CO, SV, HR and PVR, weight is the main determinant of MAP, and gestational weight gain is the second most important determinant of SV and PVR. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Mitigation of late cardiovascular effects of oxygen ion radiation by γ-tocotrienol in a mouse model

PURPOSE

While there is concern about degenerative tissue effects of exposure to space radiation during deep-space missions, there are no pharmacological countermeasures against these adverse effects. γ-Tocotrienol (GT3) is a natural form of vitamin E that has anti-oxidant properties, modifies cholesterol metabolism, and has anti-inflammatory and endothelial cell protective properties. The purpose of this study was to test whether GT3 could mitigate cardiovascular effects of oxygen ion (¹⁶O) irradiation in a mouse model.

MATERIALS AND METHODS

Male C57BL/6 J mice were exposed to whole-body ¹⁶O (600 MeV/n) irradiation (0.26-0.33 Gy/min) at doses of 0 or 0.25 Gy at 6 months of age and were followed up to 9 months after irradiation. Animals were administered GT3 (50 mg/kg/day s.c.) or vehicle, on Monday - Friday starting on day 3 after irradiation for a total of 16 administrations. Ultrasonography was used to measure in vivo cardiac function and blood flow parameters. Cardiac tissue remodeling and inflammatory infiltration were assessed with histology and immunoblot analysis at 2 weeks, 3 and 9 months after radiation.

RESULTS

GT3 mitigated the effects of ¹⁶O radiation on cardiac function, the expression of a collagen type III peptide, and markers of mast cells, T-cells and monocytes/macrophages in the left ventricle.

CONCLUSIONS

GT3 may be a potential countermeasure against late degenerative tissue effects of high-linear energy transfer radiation in the heart.

Effect of a Weight Loss Program on Biochemical and Immunological Profile, Serum Leptin Levels, and Cardiovascular Parameters in Obese Dogs

This study aimed to investigate the effects of a weight loss program (WLP) on biochemical and immunological profile, and cardiovascular parameters in a cohort of dogs with naturally occurring obesity. Eleven obese dogs [body condition scoring (BCS), ≥7/9] were enrolled into the study and underwent clinical and cardiovascular examination, and blood testing before (T0) and after 6 months (T1) of WLP. Eleven normal weight (BCS, 4/5) healthy dogs were used as a control (CTR) group. Compared to the CTR group, at T0 obese dogs expressed higher serum leptin concentrations (p < 0.0005) that significantly decreased after weight loss (p < 0.005) but remained higher than the CTR group. Furthermore, obese dogs showed considerably lower levels (p < 0.0005) of regulatory T cell (Treg) compared to the CTR group, but they did not change after weight loss at T1. In obese dogs, tumor necrosis factor (TNF)-α and interleukin (IL)-6 concentrations were substantially reduced at T1 (p < 0.0001 and p < 0.005). Regarding the cardiovascular parameters, only one obese dog was hypertensive at T0, and systolic blood pressure values showed no significant differences at the end of the WLP. The ratio of interventricular septal thickness in diastole to left ventricle internal diameter in diastole (IVSd/LVIDd) was significantly greater in obese dogs at T0 than in the CTR group (p < 0.005). It decreased after weight loss (p < 0.05). In obese dogs, troponin I level significantly reduced with weight loss (p < 0.05), while endothelin-1 level did not differ statistically. The results suggest that the immune dysregulation in the presence of high leptin levels and reduced number of Treg could affect obese dogs as well as humans. Based on our findings, we may speculate that a more complete immune-regulation restore could be obtained by a greater reduction in fat mass and a longer-term WLP. Finally, left ventricular remodeling may occur in some obese dogs. However, in canine species, further studies are needed to investigate the impact of obesity and related WLP on cardiovascular system.

Pet obesity management: beyond nutrition

Excess weight has been associated with many clinical and subclinical conditions that put a pet's health at risk. Successful weight management programs extend beyond standard nutritional management and incorporate an understanding of human-animal interaction. Understanding the processes and dynamics of human-animal relationships can be a useful tool for practitioners in developing successful treatment plans for their clients. Obesity is a nutritional disorder requiring lifelong management; however, when veterinarians go beyond standard treatment to include an understanding of human-animal interaction, it is also one of the few conditions in veterinary medicine that is completely preventable and curable.