Effect of citrulline on muscle functions during moderate dietary restriction in healthy adult rats.

Low calorie diets are designed to reduce body weight and fat mass, but they also lead to a detrimental loss of lean body mass, which is an important problem for overweight people trying to lose weight. In this context, a specific dietary intervention that preserves muscle mass in people following a slimming regime would be of great benefit. Leucine (LEU) and Citrulline (CIT) are known to stimulate muscle protein synthesis (MPS) in post-prandial and post-absorptive state, respectively. This makes them interesting bioactive components to test in the context of dietary restriction. We tested the concept of combining LEU and CIT in adult female rats. We postulated that the sequential administration of LEU (mixed in chow) and CIT (given in drinking water before a rest period) could be beneficial for preservation of muscle function during food restriction. Sixty female rats (22 weeks old) were randomized into six groups: one group fed ad libitum with a standard diet (C) and five food-restricted groups (60 % of spontaneous intake for 2 weeks) receiving a standard diet (R group), a CIT-supplemented diet (0.2 or 1 g/kg/day, CIT0.2 group and CIT1 group, respectively), a LEU-supplemented diet (1.0 g/kg/day) or a CIT + LEU-supplemented diet (CIT + LEU 1.0 g/kg/day each). At the end of the experiment, body composition, muscle contractile properties and muscle protein synthesis (MPS) rate were studied in the tibialis anterior muscle. Dietary restriction tended to decrease MPS (R: 2.5 ± 0.2 vs. C: 3.4 ± 0.4 %/day, p = 0.06) and decrease muscle strength (R: 3,045 ± 663 vs. C: 5,650 ± 661 A.U., p = 0.03). Only CIT administration (1 g/kg) was able to restore MPS (CIT1: 3.4 ± 0.3 vs. R: 2.5 ± 0.2 %/day, p = 0.05) and increase muscle maximum tetanic force (CIT1: 441 ± 15 vs. R: 392 ± 22 g, p = 0.05) and muscle strength (CIT1: 4,259 ± 478 vs. R: 3,045 ± 663 A.U., p = 0.05). LEU had no effect and CIT + LEU supplementation had few effects, limited to adipose mass and fatigue force. The results of this study highlight the ability of CIT alone to preserve muscle function during dietary restriction. Surprisingly, LEU antagonized some effects of CIT. The mechanisms involved in this antagonistic effect warrant further study.

Prevalence and genotyping of tick-borne encephalitis virus in questing Ixodes ricinus ticks in a new endemic area in western Switzerland.

Tick-borne encephalitis virus (TBEV) is the causative agent of tick-borne encephalitis (TBE) and causes neurological disease in humans in Eurasia. TBEV is transmitted by ticks of the genus Ixodes. Currently 10,000-12,000 clinical cases are reported annually in approximately 30 TBE endemic countries. Since 1990 the epidemiology of TBE is characterized by a global increase of clinical cases and an expansion of risk areas. Similar trends are also observed in Switzerland but few studies confirmed the emergence of new TBE foci by detecting viral RNA in field-collected ticks. In this study, free-living Ixodes ricinus (L.) ticks from one nonendemic and three new TBE endemic regions located in the Western part of Switzerland were screened during four consecutive years (2007-2010) for the presence of TBEV. A total of 9,868 I. ricinus ticks (6,665 nymphs and 3,203 adults) were examined in pools for TBEV by real-time reverse transcription polymerase chain reaction. Our results confirmed the presence of viral RNA in 0.1% (6/6120) of questing ticks collected in one new endemic region. Among TBE endemic sites, the minimal infection rate per 100 ticks tested ranged from 0.21 (1/477) to 0.95 (1/105). Four positive samples were sequenced and phylogenetic analysis of the NS5 gene showed that all TBEV nucleotide sequences belonged to the European subtype and were split into two distinct lineages originating probably independently from two distinct foci located North-East and East of the study region.

Microclimate and the zoonotic cycle of tick-borne encephalitis virus in Switzerland.

The focal distribution of tick-borne encephalitis virus (TBEV; Flaviviridae, Flavivirus) appears to depend mainly on cofeeding transmission between infected Ixodes ricinus L. nymphs and uninfected larvae. To better understand the role of cofeeding ticks in the transmission of TBEV, we investigated tick infestation of rodents and the influence of microclimate on the seasonality of questing I. ricinus ticks. A 3-yr study was carried out at four sites, including two confirmed TBEV foci. Free-living ticks and rodents were collected monthly, and microclimatic data were recorded. A decrease in questing nymph density was observed in 2007, associated with low relative humidity and high temperatures in spring. One site, Thun, did not show this decrease, probably because of microclimatic conditions in spring that favored the questing nymph population. During the same year, the proportion of rodents carrying cofeeding ticks was lower at sites where the questing nymph density decreased, although the proportion of infested hosts was similar among years. TBEV was detected in 0.1% of questing ticks, and in 8.6 and 50.0% of larval ticks feeding on two rodents. TBEV was detected at all but one site, where the proportion of hosts with cofeeding ticks was the lowest. The proportion of hosts with cofeeding ticks seemed to be one of the factors that distinguished a TBEV focus from a non-TBEV focus. The enzootic cycle of TBEV might be disrupted when dry and hot springs occur during consecutive years.