Effect of cafeteria diet feeding on soleus intramyocellular lipid of Wistar rats

Background: The presence of lipid besides muscle fibres facilitates the energy supply for exercise, but it is also indicative of insulin resistance in the untrained. Muscle lipid is associated with increased dietary energy: hyperlipidic diets induce an increase in intramyocellular lipid deposition in skeletal muscle. Methods: In the present study we analyzed the changes in soleus (a red-fibre muscle) intracellular muscle content under a hyperlipidic (cafeteria) diet in Wistar rats. We also analyzed in parallel the mitochondrial content a relative index of energy output capability. Results: Cafeteria diet-fed rats contained more lipid and mitochondria per unit of muscle section area than controls. Conclusions: The correlation found in the increases of muscle lipid and mitochondria hit at this increase as an adaptation of muscle to oxidize excess energy substrates under conditions of excess energy availability, probably contributing to adaptive thermogenesis

Comparative effects of oleoyl-estrone and a specific b3-adrenergic agonist (CL316, 243) on the expression of genes involved in energy metabolism of rat white adipose tissue

Background: The combination of oleoyl-estrone (OE) and a selective b3-adrenergic agonist (B3A; CL316,243) treatment in rats results in a profound and rapid wasting of body reserves (lipid). Methods: In the present study we investigated the effect of OE (oral gavage) and/or B3A (subcutaneous constant infusion) administration for 10 days to overweight male rats, compared with controls, on three distinct white adipose tissue (WAT) sites: subcutaneous inguinal, retroperitoneal and epididymal. Tissue weight, DNA (and, from these values cellularity), cAMP content and the expression of several key energy handling metabolism and control genes were analyzed and computed in relation to the whole site mass. Results: Both OE and B3A significantly decreased WAT mass, with no loss of DNA (cell numbers). OE decreased and B3A increased cAMP. Gene expression patterns were markedly different for OE and B3A. OE tended to decrease expression of most genes studied, with no changes (versus controls) of lipolytic but decrease of lipogenic enzyme genes. The effects of B3A were widely different, with a generalized increase in the expression of most genes, including the adrenergic receptors, and, especially the uncoupling protein UCP1. Discussion: OE and B3A, elicit widely different responses in WAT gene expression, end producing similar effects, such as shrinking of WAT, loss of fat, maintenance of cell numbers. OE acted essentially on the balance of lipolysislipogenesis and the blocking of the uptake of substrates; its decrease of synthesis favouring lipolysis. B3A induced a shotgun increase in the expression of most regulatory systems in the adipocyte, an effect that in the end favoured again the loss of lipid; this barely selective increase probably produces inefficiency, which coupled with the increase in UCP1 expression may help WAT to waste energy through thermogenesis. Conclusions: There were considerable differences in the responses of the three WAT sites. OE in general lowered gene expression and stealthily induced a substrate imbalance. B3A increasing the expression of most genes enhanced energy waste through inefficiency rather than through specific pathway activation. There was not a synergistic effect between OE and B3A in WAT, but their combined action increased WAT energy waste

Effect of cafeteria diet feeding on soleus intramyocellular lipid of Wistar rats

Background: The presence of lipid besides muscle fibres facilitates the energy supply for exercise, but it is also indicative of insulin resistance in the untrained. Muscle lipid is associated with increased dietary energy: hyperlipidic diets induce an increase in intramyocellular lipid deposition in skeletal muscle. Methods: In the present study we analyzed the changes in soleus (a red-fibre muscle) intracellular muscle content under a hyperlipidic (cafeteria) diet in Wistar rats. We also analyzed in parallel the mitochondrial content a relative index of energy output capability. Results: Cafeteria diet-fed rats contained more lipid and mitochondria per unit of muscle section area than controls. Conclusions: The correlation found in the increases of muscle lipid and mitochondria hit at this increase as an adaptation of muscle to oxidize excess energy substrates under conditions of excess energy availability, probably contributing to adaptive thermogenesis