Efecto de la suplementación con calcio y cla sobre el balance energético, su repercusión sobre la adiposidad y mecanismos implicados

Abstract

Some nutrients play a role in the regulation of energy balance and, as a result, may be incorporated in nutritional interventions addressed to prevent, mitigate and/or treat obesity. The aim of the current thesis was to gain insight into the knowledge of the effects of two nutrients, calcium and CLA, on body fat deposition and energy metabolism. The present results demonstrate the potential beneficial effects of dietary calcium supplementation on body weight and adiposity: it contributes to reduced weight gain and fat deposition in mice fed a high-fat diet, and accelerates weight loss in overweight mice under normal-fat diet feeding. Increased Ucp1 protein or transcript levels are not observed in brown adipose tissue, which suggest that the anti-obesity effect of dietary calcium must be mediated by a mechanism different from the induction of adaptive thermogenesis in this tissue. Supplementation of diet with calcium from dairy sources entails an increase in the intake of dietary magnesium and zinc. The higher bioavailability of these minerals increases their urine excretion without negatively affecting their bone accretion. Reduction of adiposity, induced by the use of high doses of CLA or the trans-10, cis12 isomer alone, may be accompanied in mice, the most sensitive species, by adverse effects (hepatic steatosis, hyperinsulinaemia and/or insulin resistance). Our results indicate that the use of moderate doses of CLA mixture (50:50, trans-10, cis-12 y cis-9, trans-11) reduces fat deposition in mice fed a normal- or high-fat diet, without promoting an inflammatory state in adipose tissue or reducing mature adipocyte marker gene expression. Insulin sensitivity is preserved, as is triacylglycerol hepatic content, which remains unaltered, partly due to the balance observed at transcriptional level between oxidative and lipogenesis pathways. The specific, high increase in muscle Scd1 expression, which could be related to the maintenance of energy homeostasis, together with the results that indicate that miRNAs expression may be modulated by CLA treatment, engender novel perspectives in the research of CLA effects and mechanisms of action.