Efeito de duas dietas com diferentes teores de lipídios saturados associadas à bebida enriquecida com frutose introduzidas em fase precoce da vida de ratos

Abstract

Hypercaloric and hyperlipidic diets (HC/HL), added with highly palatable sugary drinks, are used to induce experimental obesity, simulating its close association with increased obesity worldwide. Obtaining these models contributes to the understanding of the mechanisms involved in this disease. However, the results in the literature are quite contradictory and difficult to compare, especially due to the different saturated lipid contents, which vary around 45 to 60% of the total caloric value, which confers different protocols used in the studies. On the other hand, the ingestion of sugary drinks seems to have a greater consensus regarding their participation in obesity. OBJECTIVE: To establish a model of obesity, with causes and characteristics similar to human obesity, by means of HC/HL diet added to a solution of fructose introduced in the early stages of life. METHODS: Twentyseven male Wistar rats (21 days of age, 43±2g) were divided into 3 groups (n=9/group): Control (C): received diet AIN93/G + water; hypercaloric/hyperlipidic containing 45% lipids + 10% fructose solution (HC/HL1); hypercaloric/hyperlipidic containing 60% lipids + 10% fructose solution (HC/HL2). Diets were given for 70 uninterrupted days. Body mass (MC) and food (FI) and water intake (WI) were determined 3x /wk. At the end of the experiment, the animals were anesthetized by inhalation with excess CO2, weighed and measured in terms of body length (naso-anal) and euthanized by means of exsanguination through a guillotine-specific decapitation for this purpose. Confirmation of obesity was performed through energy efficiency (EE), Lee's index (IL) and adiposity index (AI) calculated by the sum of adipose tissue: epididimal + retroperitoneal + omental + perirenal. Morphological analysis of subcutaneous inguinal adipose tissue was performed in histological sections stained in HE, and the area of adipocytes analyzed with the support of ImageJ software. The soleus, gastrocnemius, tibialis anterior, EDL and quadriceps muscles were excised and weighed. Blood samples (8mL) were collected for the determination of the serum concentration of cytokines and hormones, as well as biochemical parameters through commercial kits. Clinical parameters were obtained using the HOMA2-IR, HOMA-β and QUICKI indices. Data were submitted to analysis of variance (ANOVA-One-way) or Kruskal Wallis and, when differences were observed, post-hoc of Tukey or Dunn's, respectively. Statistical analyzes were performed in software (SPSS® 21), and the results were expressed as mean ± SD (p<0.05). RESULTS: MC was higher in HC/HL1 when compared to HC/HL2, both higher than C (p<0.001). FI was higher in HC/HL1 than in HC/HL2 (p=0.02), with no difference in C. Regarding WI, there was no difference between HC/HL1 and HC/HL2, but both were greater than C (p=0.02). EE (p<0.001) and AI (p<0.001) were higher in HC/HL1 and HC/HL2 when compared to C. IL was higher in HC/HL1 compared to C (p=0.02), and without difference compared to HC/HL2. The relative liver mass was higher in HC/HL1 and HC/HL2 compared to C (p<0.001). The relative masses of the heart (p=0.003) and the kidneys (p=0.016) were lower in HC/HL1 compared to the other groups. The relative mass of the soleus (p=0.01), gastrocnemius (p <0.001), anterior tibial (p<0.001), EDL (p<0.001) and quadriceps (p<0.001) muscles were lower in HC/HL1 and HC/HL2 compared to C. The relative masses of the retroperitoneal (p<0.001), perirenal (p<0.001), omental (p=0.004), epididimal (p=0.002) and subcutaneous inguinal (p<0.001) adipose tissues were higher in HC/HL1 and HC/HL2 compared to C. The area of adipocytes was higher in HC/HL1 (3828.0±1047.0) compared to C (1516.0±591.8) and HC/HL2 (2644.0±552.1 (p<0.001), and HC/HL2 was higher than C. Serum triglyceride levels, VLDL-c and HDL-c were higher in HC / HL1 and HC/HL2 compared to C (p<0.001) ; HC/HL1 presented higher values (p=0.007) of cholesterol when compared to the other groups. Non-HDL cholesterol was lower in HC/HL1 and HC/HL2 compared to C (p=0.004). HC/HL1 had a higher concentration of leptin (2563.0±1444 pg/mL, p=0.001) and insulin (950.0±346.0 pg/mL (p=0.001) compared to C (leptin=337.4±168.9 pg/mL and insulin=535.6±277.2 pg/mL) and HC/HL2 (leptin=1263.0±937.6 pg/mL and insulin=332.0±264.5 pg/mL. HC/HL1 group showed no difference in HOMA2-IR (4.5±1.9) and HOMA-β (121.1±39.6) when compared to group C (2,7±1,9; 89,3±53,1), however, showed higher values when compared to HC/HL2 (HOMA2-IR 1.8±1.1, p=0.018) and (HOMA-β=36.4±24.4, p=0, 0007). QUICKI was higher in HC/HL2 (0.35±0.08, p=0.011) compared to HC/HL1 (0.28±0.02), however, both were not different in relation to C (0.30±0.03). CONCLUSION: HC/HL1 diet added to the solution with 10% fructose promoted similar characteristics to human obesity, since the animals presented increase of the Lee Index, subcutaneous and visceral hyperadiposity, hyperleptinemia, hyperinsulinemia and clinical signs of insulin sensitivity to β-cells). Although there was no change in the Lee Index, the animals belonging to HC/HL2 showed lower subcutaneous and visceral hyperadiposity, and clinical signs of impaired βcell function. Taken together, the results of the present study allow us to conclude that a diet containing 45% lipids associated with 10% fructose solution was efficient in inducing an obesity model with characteristics similar to human obesity.