The effects of high-fat diet, branched-chainamino acids and exercise on female C57BL/6 mouse Achilles tendon biomechanical properties

Objectives

The goals of this study were: 1) to determine if high-fat diet (HFD) feeding in female mice would negatively impact biomechanical and histologic consequences on the Achilles tendon and quadriceps muscle; and 2) to investigate whether exercise and branched-chain amino acid (BCAA) supplementation would affect these parameters or attenuate any negative consequences resulting from HFD consumption.

Methods

We examined the effects of 16 weeks of 60% HFD feeding, voluntary exercise (free choice wheel running) and BCAA administration in female C57BL/6 mice. The Achilles tendons and quadriceps muscles were removed at the end of the experiment and assessed histologically and biomechanically.

Results

HFD feeding significantly decreased the Achilles tendon modulus without histological alterations. BCAA administration significantly decreased the stiffness of Achilles tendons in the exercised normal diet mice. Exercise partially ameliorated both the weight gain and glucose levels in the HFD-fed mice, led to a significant decrease in the maximum load of the Achilles tendon, and an increase in the average fibril diameter of the quadriceps femoris muscle. There were significant correlations between body weight and several biomechanical properties, demonstrating the importance of controlling obesity for maintaining healthy tendon properties.

Conclusions

In summary, this study showed a significant impact of obesity and body weight on tendon biomechanical properties with limited effects of exercise and BCAAs.

Cite this article: Bone Joint Res 2013;2:186–92.

A comparison of condom use perceptions and behaviours between circumcised and intact men attending sexually transmitted disease clinics in the United States

This investigation compared circumcised and intact (uncircumcised) men attending sexually transmitted infection (STI) clinics on condom perceptions and frequencies of use. Men ( N = 316) were recruited from public clinics in two US states. Circumcision status was self-reported through the aid of diagrams. Intact men were less likely to report unprotected vaginal sex ( P < 0.001), infrequent condom use ( P = 0.02) or lack of confidence to use condoms ( P = 0.049). The bivariate association between circumcision status and unprotected sex was moderated by age ( P < 0.001), recent STD acquisition ( P < 0.001) and by confidence level for condom use ( P < 0.001). The bivariate association between circumcision status and infrequent condom use was also moderated by age ( P = 0.002), recent STI acquisition ( P = 0.02) and confidence level ( P = 0.01). Multivariate findings supported the conclusion that intact men may use condoms more frequently and that confidence predicts use, suggesting that intervention programmes should focus on building men's confidence to use condoms, especially for circumcised men.

Genetics of novelty seeking, amphetamine self-administration and reinstatement using inbred rats

Previous research using outbred rats indicates that individual differences in activity in a novel environment predict sensitivity to the reinforcing effect of psychostimulant drugs. The current study examined if the link between responses related to novelty and amphetamine self-administration is heritable. Twelve inbred rat strains were assessed for locomotor activity in a novel environment, preference for a novel environment, and intravenous amphetamine self-administration (acquisition, extinction and amphetamine-induced reinstatement). Strain differences were observed in activity in a novel environment, novelty preference and amphetamine self-administration, indicating a genetic influence for each of these behaviors. While there was no relation between activity in an inescapable novel environment and amphetamine self-administration, strain-dependent differences in novelty preference were positively correlated with the amount of amphetamine self-administered. There was also a positive correlation between the dose-dependent rate of amphetamine self-administration and magnitude of reinstatement. These results show that the activity in an inescapable novel environment and the preference for a novel environment are different genetically, and thus likely to reflect different behavioral constructs. Moreover, these results implicate a genetic influence on the relation between novelty seeking and stimulant self-administration, as well as on the relation between stimulant reward and reinstatement.