Continuous versus discontinuous drinking of an ethanol liquid diet in peripubertal rats: effect on 24-h variation of lymph node and splenic mitogenic responses and lymphocyte subset populations.

Excessive alcohol consumption continues to be a major public health problem, particularly in the adolescent and young adult populations. Generally, such a behavior tends to be confined to the weekends, to attain frequently binge drinking. This study in peripubertal male rats compares the effect of the discontinuous feeding of a liquid diet containing a moderate amount of ethanol (6.2% wt/vol) to that of continuous ethanol administration or a control diet, taking as end points the 24-h variations of plasma prolactin levels and mitogenic responses and lymphocyte subset populations in submaxillary lymph nodes and spleen. Animals received the ethanol liquid diet starting on day 35 of life, the diet being similar to that given to controls except for that maltose was isocalorically replaced by ethanol. Ethanol provided 36% of the total caloric content. Every week, the discontinuous ethanol group received the ethanol diet for 3 days and the control liquid diet for the remaining 4 days. After 4 weeks, rats were killed at six time intervals, beginning at 0900 h. A significant decrease of splenic cells' response to concanavalin A, and of lymph node and splenic cells' response to lipopolysaccharide was found in rats under the discontinuous ethanol regime, when compared with control- or ethanol-chronic rats. Under discontinuous ethanol feeding, mean values of lymph node and splenic CD8(+) and CD4(+)-CD8(+) cells decreased, whereas those of lymph node and splenic T cells, and splenic B cells, augmented. In rats chronically fed with ethanol, splenic mean levels of CD8(+) and CD4(+)-CD8(+) cells augmented. Both modalities of ethanol administration disrupted the 24 h variation in immune function seen in controls. Mean plasma prolactin levels increased by 3.6-fold and 8.5-fold in rats chronically or discontinuously fed with alcohol, respectively. The immune parameters examined in an additional group of rats fed regular chow and water ad libitum did not differ significantly from control liquid diet. The results support the view that the discontinuous drinking of a moderate amount of ethanol can be more harmful for the immune system than a continuous ethanol intake, presumably by inducing a greater stress as indicated by the augmented plasma prolactin levels observed.

Melatonin effect on plasma adiponectin, leptin, insulin, glucose, triglycerides and cholesterol in normal and high fat-fed rats.

Melatonin effect on body weight progression, mean levels and 24-hr pattern of circulating adiponectin, leptin, insulin, glucose, triglycerides and cholesterol were examined in rats fed a normal or a high-fat diet. In experiment 1, rats fed a normal diet were divided into two groups: receiving melatonin (25 µg/mL drinking water) or vehicle for 9 wk. In experiment 2, animals were divided into three groups: two fed with a high-fat diet (35% fat) and melatonin (25 µg/mL) or vehicle in drinking water for 11 wk, while a third group was given a normal diet (4% fat). At the end of experiments, groups of eight rats were killed at six different time intervals throughout a 24-hr period. Melatonin administration for 9 wk decreased body weight gain from the 3rd wk on without affecting food intake. A significant reduction in circulating insulin, glucose and triglyceride mean levels and disrupted daily patterns of plasma adiponectin, leptin and insulin were observed after melatonin. In high fat-fed rats, melatonin attenuated body weight increase, hyperglycemia and hyperinsulinemia, as well as the increase in mean plasma adiponectin, leptin, triglycerides and cholesterol levels. The high-fat diet disrupted normal 24-hr patterns of circulating adiponectin, insulin and cholesterol, the effects on insulin and cholesterol being counteracted by melatonin. Nocturnal plasma melatonin concentration in control and obese rats receiving melatonin for 11 wk attained values 21-24-fold greater than controls. The results indicate that melatonin counteracts some of the disrupting effects of diet-induced obesity in rats.

Effect of cadmium on 24-hour pattern in expression of redox enzyme and clock genes in rat medial basal hypothalamus.

The effect of cadmium (Cd) in the brain has been attributed to an increase in reactive oxygen species in cells, particularly when high amounts of the metal are given. In this study we examined the effect of a low dose of Cd (7.5 microg/day) on 24-h changes in expression of redox pathway enzyme and circadian genes in rat medial basal hypothalamus (MBH). Rats receiving CdCl(2) (5 ppm in drinking water) or tap water for 1 month were killed at six different time intervals throughout a 24 h cycle. MBH mRNA levels were measured by real-time PCR analysis. In CdCl(2) treated rats a disruption of 24-h pattern of hypothalamic gene expression of nitric oxide synthase (NOS)-1 and -2, heme oxygenase (HO)-1 and -2, Mn- superoxide dismutase (SOD), catalase, glutathione peroxidase and glutathione reductase was detectable. Mean levels of MBH mRNA for HO-2, Mn-SOD and catalase augmented after Cd intake, whereas those of NOS-2 decreased. After CdCl(2) intake rats the 24-h pattern of clock gene expression in MBH seen in controls was significantly suppressed (Bmal1) or changed in phase (Per1, Per2, Cry2) while in the case of Clock significant 24-h variations were induced. The results are compatible with the view that a low amount of Cd given in tap water brought about significant changes in circadian expression of redox enzyme and clock genes in rat MBH.

Effect of a high-fat diet on 24-hour pattern of circulating adipocytokines in rats.

We have shown a significant disruption of 24-h pattern of plasma pituitary, adrenal, and gonadal hormones in high-fat-fed rats. Our objective was to assess the effect of a high-fat diet (35% fat) on mean levels and 24-h pattern of several adipocytokines in rats. A normal diet-fed rats (4% fat) were used as controls. When body weight of high-fat-fed rats attained values about 25% higher than controls (after 66 days of treatment), the animals were killed at six different time intervals throughout a 24-h cycle. Plasma concentrations of insulin, adiponectin, interleukin (IL)-1, leptin, ghrelin, plasminogen activator inhibitor-1 (PAI-1), and monocyte chemoattractant protein-1 (MCP-1) were measured in a multianalyte profiling by using the Luminex-100 system. Tumor necrosis factor alpha (TNFalpha) and IL-6 were measured by enzyme-linked immunosorbent assay. A significant hyperglycemia developed in high-fat-fed rats, together with a significant increase in plasma insulin. Mean levels of plasma adiponectin, IL-1, IL-6, TNFalpha, and leptin augmented, and ghrelin decreased, in high-fat-fed rats. The normal daily pattern of plasma insulin, adiponectin, IL-1, IL-6, TNFalpha, leptin, ghrelin, and MCP-1 became disrupted in high-fat-fed rats. The results indicate that a high-fat diet may bring about signs of insulin resistance and mild inflammation in rats, together with the disruption in daily variations of circulating insulin and ghrelin, and of several adipocytokines including leptin, adiponectin, IL-1, IL-6, TNFalpha, and MCP-1.

Immune response after experimental allergic encephalomyelitis in rats subjected to calorie restriction.

Male Lewis rats (6 weeks-old) were submitted to a calorie restriction equivalent to 33% or 66% of food restriction. Fifteen days later, groups of 7 animals were injected with complete Freund's adjuvant plus spinal cord homogenate (SCH) to induce experimental allergic encephalomyelitis (EAE) or with complete Freund's adjuvant alone. EAE was defined solely on clinical grounds. Rats were assessed daily for clinical signs of EAE and were killed on day 15 after immunization. Both diet and SCH injection diminished body weight significantly. In contrast to rats receiving a normal diet or a 33% calorie-restricted diet, rats subjected to severe calorie restriction did not exhibit clinical signs of EAE. Concomitantly with the lack of disease manifestation, 66% of calorie-restricted rats injected with SCH showed significantly less splenic and lymph node mitogenic response to concanavalin A (Con A) and a higher splenic response to lipopolysaccharide. Fewer splenic, lymph node and thymic CD4+ cells, greater numbers of splenic and lymph node CD8+ and CD4+- CD8+ cells, and fewer splenic T, B and T-B cells, and lymph node and thymic B and T-B cells were observed. There was impaired interferon (IFN)-gamma production occurred in the three examined tissues. The results are compatible with the view that the acute phase of EAE can be curtailed by severe calorie restriction, presumably through impaired IFN-gamma production.