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

Abstract

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.

Keywords: T regulatory cells; canine obesity; hyperlipidemia; left ventricle remodeling; leptin.

Figure 1

Morphometric equations in enrolled dogs. (A) LBM, lean body mass; (B) FM, fat mass; (C) BFP, body fat percentage. Obese dogs at T0, white column; obese dogs at T1, gray column. Statistics: Wilcoxon matched-pairs signed-rank test was used for T0 and T1 comparation in obese dogs. NS means not significant difference.

Figure 2

Biochemical parameters in enrolled dogs. (A) TG, Triglycerides; (B) T-Chol, total cholesterol; (C) Insulin; (D) Urea; (E) Creatinine; (F) Alpha 2-globulins. Control (CTR) group, dashed column; obese dogs at T0, white column; obese dogs at T1, gray column. Statistics: Wilcoxon matched-pairs signed-rank test was used for T0 and T1 comparation in obese dogs, while Mann-Whitney test was performed for the comparation between T0 obese dogs and CTR subjects. NS means not significant difference.

Figure 3

Cardiovascular biomarkers in enrolled dogs. (A) ET-1, endothelin-1; (B) cTnI, cardiac troponin I. Control (CTR) group, dashed column; obese dogs at T0, white column; obese dogs at T1, gray column. Statistics: Wilcoxon matched-pairs signed-rank test was used for T0 and T1 comparation in obese dogs, while Mann–Whitney test was performed for the comparation between T0 obese dogs and CTR subjects. NS means not significant difference.

Figure 4

Echocardiographic parameters in enrolled dogs. (A) IVSd, interventricular septum at end diastole; (B) LVFWd, left ventricle free wall at end diastole. Obese dogs at T0, white column; obese dogs at T1, gray column. Statistics: Wilcoxon matched-pairs signed-rank test was used for T0 and T1 comparation in obese dogs. NS means not significant difference.

Figure 5

Echocardiographic parameters in enrolled dogs. (A) IVSd/LVIDd, ratio of interventricular septal thickness to left ventricular internal dimension at end diastole; (B) LFVFWd/LVIDd, ratio of left ventricular free wall thickness to left ventricular internal dimension at end diastole; (C) indexed IVSd, indexed interventricular septum thickness at end diastole; (D) ESVI, end-systolic volume index. Control (CTR) group, dashed column; obese dogs at T0, white column; obese dogs at T1, gray column. Statistics: Wilcoxon matched-pairs signed-rank test was used for T0 and T1 comparation in obese dogs, while Mann–Whitney test was performed for the comparation between T0 obese dogs and CTR subjects. NS means not significant difference.

Figure 6

Echocardiographic parameters in enrolled dogs. (A) FS, fractional shortening; (B) EF (A–L), ejection fraction calculated with area-length method; (C) A wave, A wave peak velocity; (D) E/A, ratio of peak early to peak late left ventricular inflow velocities. Control (CTR) group, dashed column; obese dogs at T0, white column; obese dogs at T1, gray column. Statistics: Wilcoxon matched-pairs signed-rank test was used for T0 and T1 comparation in obese dogs, while Mann–Whitney test was performed for the comparation between T0 obese dogs and CTR subjects. NS means not significant difference.

Figure 7

The number of Leucocytes, neutrophils and T cell subsets in enrolled dogs. The figure reports the evaluation on the number of (A) leukocytes, (B) neutrophils, (C) total lymphocytes, (D) CD3⁺, (E) CD4⁺, and (F) CD8⁺ T cell subsets in obese dogs, at T0 and T1, and control (CTR) subjects. Referred values in “n × 10⁹ U/L” indicate results obtained in CTR group (dashed column), in obese dogs at T0 (white column) and T1 (gray column), as indicated. Statistics: Wilcoxon matched pairs signed-rank test was used for T0 and T1 comparation in obese dogs, while Mann-Whitney test was performed for the comparation between T0 obese dogs and CTR subjects. NS means not significant difference.

Figure 8

The asset of T cell subsets and the serum level of leptin in enrolled dogs. (A–C) Percentage of total CD3⁺, CD4⁺, and CD8⁺ T lymphocytes in obese dogs, at T0 and T1, and control (CTR) subjects. (D) CD4⁺ CD8⁺ ratio. (E,F) Number (as n × 10⁹ U/L) and percentage of Treg cells (indicated as CD4⁺ CD25^high FoxP3⁺ T cells), in obese, at T0 and T1, and CTR subjects. Referred values indicate results obtained in CTR group (dashed column), in obese dogs at T0 (white column) and T1 (gray column), as indicated. (G) Serum leptin level in obese dogs, at T0 (white column) and T1 (gray column), and CTR (dashed column) subjects. Statistics: Wilcoxon matched-pairs signed-rank test was used for T0 and T1 comparation in obese dogs, while Mann-Whitney test was performed for the comparation between T0 obese and CTR subjects. NS means not significant difference.

Figure 9

B cells, interleukin (IL)-6, and tumor necrosis factor (TNF)-α in enrolled dogs. (A) Evaluation of B cell percentage in obese dogs, at T0 (white column) and T1 (gray column) and control (CTR) (dashed column) subjects, as indicated. (B,C) Amplitude of IL-6 and TNF-a production, respectively, in obese dogs at T0 (white column) and T1 (gray column). Values are in pg/ml. Statistics: Wilcoxon matched-pairs signed-rank test was used for T0 and T1 comparation in obese dogs, while Mann–Whitney test was performed for the comparation between T0 obese and CTR group subjects. NS means not significant difference.