Fructose Alters Adiponectin, Haptoglobin and Angiotensinogen Gene Expression in 3T3-L1 Adipocytes

Fructose- or sucrose-rich diets can cause insulin resistance and increase the risk of cardiovascular disease. Adipokines are correlated with the development of these diseases in obesity. We hypothesize that fructose and sucrose induce insulin resistance via effects on adipokine gene expression in adipocytes. This study analyzed the effect of fructose or glucose on adiponectin, haptoglobin, and angiotensinogen gene expression in 3T3-L1 adipocytes. Ten days after differentiation, the cells were pretreated with serum- and glucose-free medium. Twenty-four hours later, fructose or glucose (0, 5, 10, or 20 mmol) was added into the medium, and the cells were collected after a further 24 hours. Adiponectin, haptoglobin, and angiotensinogen gene expression were determined. Adiponectin gene expression increased when 10 or 20 mmol glucose was added compared with that observed for the non–hexose-treated cells. A similar effect occurred when 5 mmol fructose was added. Glucose (10 mmol) and fructose (20 mmol) stimulated haptoglobin gene expression in 3T3-L1 adipocytes compared with 0 mmol, with glucose producing a more pronounced effect. Although 20 mmol fructose caused an increase in angiotensinogen gene expression, glucose did not. In conclusion, in this study of 2 hexoses revealed an increase in adiponectin gene expression, suggesting that the effect of a glucose-rich diet on the development of insulin resistance is not related to the effect of these hexoses on adipocyte adiponectin gene expression. However, insulin resistance and cardiovascular disease promoted by fructose-rich diets could be partially related to the effect of fructose on adiponectin and angiotensinogen gene expression.

Lipid Metabolism of Monosodium Glutamate Obese Rats after Partial Removal of Adipose Tissue

We analyzed the effects of partial fat pad removal on retroperitoneal and epididymal fat depots and carcass metabolism of control (C) and MSG-obese (M) rats. Three-month-old C and M male Wistar rats were submitted to either partial surgical excision of epididymal and retroperitoneal fat tissue (lipectomy, L) or sham surgery (S) and studied after 7 or 30 days. Retroperitoneal and epididymal tissue re-growth after lipectomy was not observed, as indicated by the low pads weight of the L groups. The lipolysis rate was stimulated in LC7 and LM7, probably due to surgical stress and low insulin levels. In LM7, but not in LC7, in vivo lipogenesis rate increased in retroperitoneal and epididymal fat tissue, as did the diet-derived lipid accumulation in epididymal fat tissue. Although these local increases were no longer present in LM30, this group showed a large increase in the percentage of small area adipocytes in both pads as well as increased carcass lipogenesis rate. The present data showed that the partial removal of fat depots affected the metabolism of control and MSG-obese rats differently. In the obese animals only, it stimulated both local and carcass lipogenesis rate as well as adipocyte differentiation, i.e. responses likely to favor excised tissue re-growth and/or compensatory growth of non-excised depots.