Evidence demonstrates that sympathetic nervous system (SNS) activation causes osteopenia via b 2 -adrenoceptor (b2-AR) signaling. Here we show that female mice with chronic sympathetic hyperactivity owing to double knockout of adrenoceptors that negatively regulate norepinephrine release, a 2A -AR and a 2C -AR (a 2A /a 2C -ARKO), present an unexpected and generalized phenotype of high bone mass with decreased bone resorption and increased formation. In a 2A /a 2C -ARKO versus wild-type (WT) mice, micro-computed tomographic (mCT) analysis showed increased, better connected, and more plate-shaped trabeculae in the femur and vertebra and increased cortical thickness in the vertebra, whereas biomechanical analysis showed increased tibial and femoral strength. Tibial mRNA expression of tartrate-resistant acid phosphatase (TRACP) and receptor activator of NF-kB (RANK), which are osteoclast-related factors, was lower in knockout (KO) mice. Plasma leptin and brain mRNA levels of cocaine amphetamine-regulated transcript (CART), which are factors that centrally affect bone turnover, and serum levels of estradiol were similar between mice strains. Tibial b 2 -AR mRNA expression also was similar in KO and WT littermates, whereas a 2A -, a 2B -and a 2C -AR mRNAs were detected in the tibia of WT mice and in osteoblast-like MC3T3-E1 cells. By immunohistochemistry, we detected a 2A -, a 2B -, a 2C -and b 2 -ARs in osteoblasts, osteoclasts, and chondrocytes of 18.5-day-old mouse fetuses and 35-day-old mice. Finally, we showed that isolated osteoclasts in culture are responsive to the selective a 2 -AR agonist clonidine and to the nonspecific a-AR antagonist phentolamine. These findings suggest that b 2 -AR is not the single adrenoceptor involved in bone turnover regulation and show that a 2 -AR signaling also may mediate the SNS actions in the skeleton. ß

objective: This study aimed to examine and compare the effects of continuous or intermittent exercises on adiposity and fatty liver in rats fed with high-fat diet. Methods and Procedures: Wistar rats were divided according to diet composition-chow diet (C) or high-fat diet (H)-and kinds of exercise-sedentary (S), continuous (CE), or intermittent (IE) exercises. The CE group swam 90 min/ day, and the IE group swam 3 × 30 min/day (at 4-h intervals between sessions); both groups exercised 5 days/week during 8 weeks. Body weight and food intake were recorded daily. Lipogenesis rate in vivo was determined by the incorporation of 3 H 2 O into saponified lipids in retroperitoneal (RET), epididymal (EPI), and visceral (VIS) white adipose tissues, brown adipose tissue (BAT), liver (L), and gastrocnemius muscle (GAST) using the gravimetric method. Total cholesterol, high-density lipoprotein (HDL)-cholesterol, and triacylglycerol (TG) were analyzed. Results: The major finding of this study is that IE was more efficient than CE in reducing the adverse effects of high-fat diet and sedentarism. There was an improvement in the lipid profile and a reduction in food intake, body weight gain, visceral and central adiposity, and fatty liver, contributing to the control of obesity and other comorbidities, including nonalcoholic fat liver diseases. Discussion: Earlier studies have discussed the effects of diet consumption on adiposity and their relation to chronic diseases and obesity. This study discusses the effects of high-fat diet consumption and the different kinds of exercise on weight gain, adiposity, fatty liver, and lipid profile in rats. The results may depend on the exercise, time of each session, age, gender, and experimental period.

During the past decade, a number of reports indicated that the mammalian pineal gland is magnetosensitive in terms of spatial orientation. This indication is based on observations that artificial alterations of the direction of the earth's magnetic field (MF) markedly decreased the gland's capability to synthesize melatonin. These findings, however, seem paradoxical since animals as well as humans experience such alterations whenever they turn their heads. Therefore, the potential of the pineal for sensing magnetic fields was re-investigated. During the dark phase, rats were exposed to repeatedly inverted MFs, generated by two identical pairs of Helmholz coils; one pair connected to a power supply automatically, the other pair manually using an integrated potentiometer. Only the pineals of animals exposed to the automatically activated field responded with a reduced activity of the rate-limiting enzyme serotonin-N-acetyltransferase, lower melatonin levels and increases in serotonin and 5-hydroxyindole acetic acid. Hence, MF exposure itself did not affect the pineal. Rather, induced eddy currents in the animals, resulting from rapid On/Off transients of the artificially applied MF, are most likely the explanation.

The purpose of this study was to investigate the influence of resistance training on the activity of matrix metalloproteinase (MMP)-2 and bone biomechanical properties in ovariectomized and intact rats. Forty-eight female rats were divided into two distinct groups, ovariectomized (OVX) and intact (Int), which were subdivided into three similar subgroups: sedentary, acute exercise and chronic exercise. Rats performed a resistance training for 12 weeks in which animals climbed a vertical ladder of 1.1 m with weights attached to their tails. Sessions were performed with an interval of 3, 4-9 and 8-12 days scaled dynamic movements of climbing. Biomechanical and physical analyses were performed using a universal testing machine, and MMP-2 activity analysis by zymography. Bone density (BD), mineral density (MD), maximum load and fracture load was reduced in sedentary and acute exercise OVX groups compared with the sedentary intact group (P<0.05); in contrast, chronically trained groups (OVX and Int) showed a significant increase in BD, MD and fracture load compared with all the other groups. MMP-2 activity in chronically trained groups also showed a significant increase, while the sedentary OVX group showed a decrease in MMP-2 activity compared with the intact sedentary group (P<0.05). Our results suggest that the resistance training proposed in our work was efficient in reverting the deleterious effects of ovariectomy on bone tissue, and also produced modeling effects in intact rats. On the other hand, ovariectomy reduced the activity of MMP-2 and produced deleterious effects on bone tissue, mimicking menopause intrinsically.

No abstract