Development and characterization of an experimental model of diet-induced metabolic syndrome in rabbit

Abstract

Metabolic syndrome (MetS) has become one of the main concerns for public health because of its link to cardiovascular disease. Murine models have been used to study the effect of MetS on the cardiovascular system, but they have limitations for studying cardiac electrophysiology. In contrast, the rabbit cardiac electrophysiology is similar to human, but a detailed characterization of the different components of MetS in this animal is still needed. Our objective was to develop and characterize a diet-induced experimental model of MetS that allows the study of cardiovascular remodeling and arrhythmogenesis. Male NZW rabbits were assigned to control (n = 15) or MetS group (n = 16), fed during 28 weeks with high-fat, high-sucrose diet. We measured weight, morphological characteristics, blood pressure, glycaemia, standard plasma biochemistry and the metabolomic profile at weeks 14 and 28. Liver histological changes were evaluated using hematoxylin-eosin staining. A mixed model ANOVA or unpaired t-test were used for statistical analysis (P<0.05). Weight, abdominal contour, body mass index, systolic, diastolic and mean arterial pressure increased in the MetS group at weeks 14 and 28. Glucose, triglycerides, LDL, GOT-AST, GOT/GPT, bilirubin and bile acid increased, whereas HDL decreased in the MetS group at weeks 14 and 28. We found a 40% increase in hepatocyte area and lipid vacuoles infiltration in the liver from MetS rabbits. Metabolomic analysis revealed differences in metabolites related to fatty acids, energetic metabolism and microbiota, compounds linked with cardiovascular disease. Administration of high-fat and high-sucrose diet during 28 weeks induced obesity, glucose intolerance, hypertension, non-alcoholic hepatic steatosis and metabolic alterations, thus reproducing the main clinical manifestations of the metabolic syndrome in humans. This experimental model should provide a valuable tool for studies into the mechanisms of cardiovascular problems related to MetS, with special relevance in the study of cardiovascular remodeling, arrhythmias and SCD.

Fig 1. Weight evolution during the experimental period.

Weekly weight measurement is displayed in panel (A), while comparison of weight increase at weeks 14 and 28 are shown in panel (B). Control (n = 12), MetS (n = 13), An = acclimation week, *p<0.05 vs. control, error bars display SEM.

Fig 2. Energy intake in the experimental groups.

Panel (A) illustrates the evolution of weekly intake during the 28 weeks of the experimental period. In panel (B), mean caloric intake is displayed. The relative intake in percentage of kcal from high-fat chow and the drinking solution can be observed in panel (C). Control (n = 6), MetS (n = 8), *p<0.05 vs. control, error bars display SEM.

Fig 3. Blood glucose regulation.

Blood glucose measurements were taken after fasting before diet and at 14 and 28 weeks of high-fat, high-sucrose administration (A). The results of the IVGTT at weeks 14 and 28 are shown in panel (C) and the quantification of the area under the curve (AUC) is depicted in panel (B). Control (n = 12), MetS (n = 13), *p<0.05 vs. control, ^$p<0.05 vs basal, error bars display SEM.

Fig 4. Modifications in blood pressure.

Panels (A) and (B) show systolic and diastolic blood pressure measurements at week 14 and 28 in both experimental groups. Mean arterial pressure (MAP) is presented in panel (C). Control (n = 10), MetS (n = 11), *p<0.05 vs. control, error bars display SEM.

Fig 5. Lipid profile.

Plasma measurements of total cholesterol (A), HDL (B), LDL (C) and tryglicerides (D) at weeks 14 and 28. Control (n = 11), MetS (n = 13), *p<0.05 vs. control, error bars display SEM.

Fig 6. Liver damage markers at week 14 and 28.

Plasma measurements of transaminases (GOT-AST, GPT-ALT and GOT/GPT ratio) are depicted in panels (A-C). Other liver function markers such as gamma-glutamyl transferase (GGT), bile acid and bilirubin are shown in panels (D-F). Control (n = 11), MetS (n = 13), *p<0.05 vs. control, error bars display SEM.

Fig 7. Liver histological study.

Representative microphotographs (central veins area) after hematoxylin-eosin staining are shown in panel (A) for control (left) and MetS (right). Quantification of hepatocyte area and lipid vacuole/hepatocyte ratio is displayed in panels (B) and (C), respectively. Control (N = 3, n = 15), MetS (N = 2, n = 10), *p<0.05 vs. control, error bars display SEM.