Changes in renal glucose transporters in an animal model of metabolic syndrome.

Considering the similarity between structural, hemodynamic, and functional changes of obesity-related renal disease and diabetic nephropathy, we hypothesized that renal glucose transporter changes occur in obesity as in diabetes. The aim of the work was to evaluate GLUT1 and GLUT2 in kidneys of an animal model of metabolic syndrome. Neonate spontaneously hypertensive rats (SHR), n=15/group, were treated with monosodium glutamate (5 mg/g) (MetS) for 9 days and compared with saline-treated Wistar-Kyoto (C) and SHR (H) rats. Lee index, systolic arterial pressure (SAP), glycemia, insulin resistance, triglycerides, and HDL cholesterol were evaluated at 3 and 6 months. Medullar GLUT1 and cortical GLUT2 were analyzed by Western blot. MetS vs. C and H rats had the highest Lee index (p<0.001) and insulin resistance (3-months C: 4.3±0.7, H: 3.9±0.9, MetS: 2.7±0.6; 6-months C: 4.2±0.6, H: 3.8±0.5, MetS: 2.4±0.6% · min⁻¹, p<0.001), similar glycemia, and the lowest HDL-cholesterol at 6-months (p<0.001). In the MetS and H rats, SAP was higher vs. C at 3-months (p<0.001) and 6-months (C: 151±15, H: 190±11, MetS: 185±13 mm Hg, p<0.001) of age. GLUT1 was Ì´ 13× lower (p<0.001) at 3-months, reestablishing its content at 6-months in MetS group, while GLUT2 was 2× higher (p<0.001) in this group at 6-months of age. Renal GLUT1 and GLUT2 are modulated in kidney of rats with metabolic syndrome, where obesity, insulin resistance and hypertension coexist, despite normoglycemia. Like in diabetes, cortical GLUT2 overexpression may contribute to the development of kidney disease.

Progressive cardiovascular autonomic dysfunction in rats with evolving metabolic syndrome.

Metabolic syndrome is linked to increased cardiovascular mortality, which may be partially attributed to cardiac sympatho-vagal imbalance. However, autonomic changes were not evaluated during the metabolic syndrome development in a monosodium glutamate-induced animal model. We evaluate temporal changes in cardiovascular autonomic modulation in an animal model of metabolic syndrome. Eighteen neonate male spontaneously hypertensive rats (SHR) were treated with monosodium glutamate (MetS), and compared with Wistar-Kyoto (C) and saline-treated SHR (H). Lee index, insulin resistance and autonomic control (spectral analysis) were evaluated at 3 (3-mo), 6 (6-mo) and 9 (9-mo) months of age (compared by two-way ANOVA, p<0.05). Weight of visceral fat, Lee index and arterial pressure were higher in the MetS vs. C and H groups (p<0.001) at all ages. Heart rate variability (HRV) was decreased in the MetS and H groups at 3-mo and 9-mo vs. C. The LF component of HRV was reduced in the MetS group at 3-mo vs. C (p=0.032), and higher vs. C and H at 9-mo (p<0.001, all comparisons). H and MetS rats had a higher LF/HF index vs. C at 9-mo (p=0.001, all comparisons). The VLF component of systolic arterial pressure variability of the MetS was higher earlier (6-mo) than that of the H group. A reduction of 70%, 98% and 54% in αLF index of H and MetS rats vs. C, was observed at 3, 6 and 9 months, respectively. Metabolic syndrome and hypertension in rats evolve with progressive autonomic dysfunction (worst at 9 months), with specific derangements occurring very early.

Exercise-stimulated GLUT4 expression is similar in normotensive and hypertensive rats.

The effects of exercise training on systolic blood pressure (BP), insulin sensitivity, and plasma membrane GLUT4 protein content in spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats were compared. 16 SHR and 16 WKY male rats, aged 6 months, were randomized into sedentary and trained (treadmill running, 5 days/week, 60 min/day for 10 weeks) groups (n=8/group). At baseline, SHR had lower insulin sensitivity than WKY rats, however, there were no differences between WKY and SHR GLUT4 expression. The 10-week training reduced BP by ∼19% in SHR, improved insulin sensitivity by ∼24% in SHR, but not in WKY, and increased GLUT4 expression in both animal models. Compared to the sedentary group, there was an increase of GLUT4 in WKY rats by ∼25% in the heart, by ∼23% in the gastrocnemius, and by ∼15% in the fat tissue. Trained SHR presented an increase in GLUT4 of ∼21%, ∼20%, and ∼14%, in the same tissues, respectively. There were no differences between SHR and WKY rats in post-training GLUT4 expression. We conclude that training determined BP and insulin resistance reduction in SHR, and increased GLUT4 expression in both normotensive and hypertensive rats. However, considering the similar rise in GLUT4-induced training in SHR and WKY, it is possible that GLUT4 levels in plasma membrane fraction do not have a pivotal role in the exercise-induced improvement of insulin sensitivity in SHR.