Major depression is more prevalent among women than men, and progesterone might be involved in the mechanisms that generate these differences. Progesterone is clinically used for women in several reproductive events, but its antidepressant effect is unclear. Animal studies showed the interference of progesterone on depressive behaviors of rodents, but they are inconclusive, and no study compared different treatment durations. This study investigated the antidepressant effect of low doses of progesterone in male and female rats under acute or chronic administration. Male and female Wistar rats in different phases of the estrous cycle were acutely administered different doses of progesterone (0.0, 0.4. 0.8 and 1.2mg/kg) and tested in the forced swimming test (FST). The lowest dose of progesterone (0.4 mg/kg) was chronically administered during two complete estrous cycles and diestrous II female and male rats were tested in the FST. Progesterone decreased depressive-like behaviors only in chronically treated diestrous II female rats and increased immobility in male rats. This low dose of progesterone did not interfere in the hormonal cycling in female rats. Results also showed that diestrous II female rats had greater immobility than male rats in the FST. The greater immobility of diestrous II female rats shows that rats in this estrous phase present more depressive-like behaviors that may be associated with their lower serum levels of progesterone. We showed that progesterone chronically administered at low doses reverses these depressive-like behaviors and has an antidepressant effect during the diestrous II phase of the estrous cycle.

Consumption of energy-dense/high-fat diets is strongly and positively associated with overweight and obesity, which are associated with increase in the prevalence of certain chronic diseases. We evaluated the effect of hypercaloric/fat or normocaloric diets on some biochemical parameters in rats. Seventy-two rats were divided into four groups that were fed for 16 weeks with diets: normocaloric [9.12% soy oil, normocaloric soy oil (NSO)], hypercaloric olive oil [43.8% olive oil, hypercaloric olive oil (HOO)], hypercaloric saturated fat [43.8% saturated fat, hypercaloric saturated fat (HSF)] and normocaloric saturated fat [43.8% saturated fat, normocaloric saturated fat (NSF)]. HSF rats consumed more calories daily than the others and gained more retroperitoneal fat, although HSF and HOO rats had higher body weight. In liver, glycogen synthesis and concentration were higher in rats HSF and NSF. In plasma, total cholesterol (TC) levels were higher in HSF rats than in the others, and triacylglycerol (TAG) levels were lower in HOO and higher in HSF rats in relation to the others. In liver, TC and TAG were elevated in HSF, NSF and HOO rats. Paraoxonase 1 activity, which is related to high-density lipoprotein cholesterol and has anti-atherogenic role was lower in rats HSF. In HOO rats, glucose tolerance test was altered, but insulin tolerance test was normal. These results suggest that consumption of energy-dense/high-fat diets, both saturated or monounsaturated, causes damaging effects. However, more studies are necessary to understand the mechanisms by which these diets cause the metabolic alterations observed.

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Long-chain polyunsaturated n-3 fatty acids (n-3 LCPUFAs) have hypolipidemic effects and modulate intermediary metabolism to prevent or reverse insulin resistance in a way that is not completely elucidated. Here, effects of these fatty acids on the lipid profile, phosphoenolpyruvate carboxykinase (PEPCK) activity, lipid synthesis from glucose in epididymal adipose tissue (Ep-AT) and liver were investigated. Male rats were fed a high-sucrose diet (SU diet), containing either sunflower oil or a mixture of sunflower and fish oil (SU-FO diet), and the control group was fed a standard diet. After 13 weeks, liver, adipose tissue and blood were harvested and analysed. The dietary n-3 LCPUFAs prevented sucrose-induced increase in adiposity and serum free fat acids, serum and hepatic triacylglycerol and insulin levels. Furthermore, these n-3 LCPUFAs decreased lipid synthesis from glucose and increased PEPCK activity in the Ep-AT of rats fed the SU-FO diet compared to those fed the SU diet, besides reducing lipid synthesis from glucose in hepatic tissue. Thus, the inclusion of n-3 LCPUFAs in the diet may be beneficial for the prevention or attenuation of dyslipidemia and insulin resistance, and for reducing the risk of related chronic diseases.