Alterations of the immunosuppressive IL4I1 enzyme activity induced by naturally occurring SNP/mutations.

The immunosuppressive phenylalanine oxidase interleukin 4-induced gene 1 (IL4I1), primarily produced by antigen-presenting cells, inhibits T-cell proliferation and promotes the generation of Foxp3(+) regulatory T cells in vitro. Highly expressed by tumour-associated macrophages from human cancers, IL4I1 has a potential role in immune evasion from the anti-tumour immune response. We have reviewed single-nucleotide polymorphisms (SNPs) and mutations described for the exon 4 of the IL4I1 isoform 1, which is expressed in lymphoid tissue. Two of them were expressed in an exogenous system to analyse their effect on the enzymatic activity. The N92D SNP leads to a hyperactive enzyme, while the R102G mutation is hypomorphic. Moreover, we show that IL4I1 activity is not only directed against phenylalanine, as initially described, but also at a lower level against arginine. These data pave the way to more extensive analyses of the mutational state of IL4I1 in pathological conditions such as cancer, where its participation in immune system dysfunctions may have therapeutic implications.

Dietary triglycerides act on mesolimbic structures to regulate the rewarding and motivational aspects of feeding.

Circulating triglycerides (TGs) normally increase after a meal but are altered in pathophysiological conditions, such as obesity. Although TG metabolism in the brain remains poorly understood, several brain structures express enzymes that process TG-enriched particles, including mesolimbic structures. For this reason, and because consumption of high-fat diet alters dopamine signaling, we tested the hypothesis that TG might directly target mesolimbic reward circuits to control reward-seeking behaviors. We found that the delivery of small amounts of TG to the brain through the carotid artery rapidly reduced both spontaneous and amphetamine-induced locomotion, abolished preference for palatable food and reduced the motivation to engage in food-seeking behavior. Conversely, targeted disruption of the TG-hydrolyzing enzyme lipoprotein lipase specifically in the nucleus accumbens increased palatable food preference and food-seeking behavior. Finally, prolonged TG perfusion resulted in a return to normal palatable food preference despite continued locomotor suppression, suggesting that adaptive mechanisms occur. These findings reveal new mechanisms by which dietary fat may alter mesolimbic circuit function and reward seeking.

External noise synchronizes forced oscillators.

Periodic pulsatile perturbation of nonlinear oscillators generates phase-locking, quasiperiodic, and chaotic responses. This work shows that the application of external noise to ensembles of such forced systems can synchronize oscillations, even in regimes where neither the noise nor the periodic forcing, when applied alone, would lead to such a phenomenon.

Effects of autonomic blockers on linear and nonlinear indexes of blood pressure and heart rate in SHR.

Recent results in normotensive Wistar-Kyoto (WKY) rats show that nonlinear method may be more specific to quantify sympathetic and parasympathetic activities than the low (LF) and high frequencies (HF) spectral powers of blood pressure (BP) and R-R interval (RR). The present study extends this conclusion to spontaneously hypertensive rats (SHR). Blood pressure was recorded for 30 min before and after intravenous injection of saline, hexamethonium, atropine, atenolol, or prazosin. Mean level, standard deviation (SD), spectral LF and HF components, and three nonlinear indexes (percentage of recurrence, percentage of determinism, and length index of the recurrence plot method) were used to analyze the BP and RR signals. In conscious SHR, sympathetic but not parasympathetic blockade reduced BP level and LF-BP, and increased nonlinear indexes of BP. RR increased after beta-sympathetic and ganglionic blockade, decreased after parasympathetic blockade, and remained unchanged after alpha(1)-sympathetic blockade. SD-RR decreased after ganglionic and alpha(1) blockade, whereas HF-RR increased after beta-sympathetic blockade. The effects on nonlinear indexes of RR are clear and consistent: only alpha(1)-blockade increased the indexes. Our nonlinear indexes may be useful to investigate cardiovascular functions in normotension and hypertension.

[Normal and abnormal daily variability of urinary excretion of albumin]. / Variabilité journalière normale et anormale de l'excrétion urinaire d'albumine.

Urinary albumin excretion (UAE) is very variable from day to day. We analyzed day-to-day UAE in 207 elderly (60-75 years) inpatients (134 with and 73 without diabetes mellitus) attending the department of internal medicine of the Angers University hospital. Twenty-four-hour urine was collected 3 times during a 5-10 day hospitalization period. One-hundred-fifty-one patients (73%) displayed normoalbuminuria (UAE < 30 mg/24 h in 2 or 3 measures) while 56 patients (27%) had microalbuminuria (UAE within 30-300 mg/24 h in 2 or 3 measures). As the raw data of UAE was not normally distributed, we transformed UAE into the variable z = log(log(k+ UAE)) where k is an integer. We found that z has a gaussian distribution for k = 2. Mean value and coefficient of variation of z in the 3 measurements were used to define the level and the temporal intra-individual variability of UAE. Expressed in term of z, the day-to-day intra-individual variability of UAE showed a potent change (from large variability to small variability) at the particular level z = 1.25, corresponding to UAE = 30.8 mg/24 h, which is precisely the level currently used to define microalbuminuria in diabetic subjects.

Normal and abnormal day-to-day variability of urinary albumin excretion in control and diabetic subjects.

Urinary albumin excretion (UAE) is very variable from day to day. This variability, more or less potent, might by itself have a patho-physiological significance. We analyzed day-to-day UAE in 207 elderly (60-75 years) inpatients (134 with and 73 without diabetes mellitus) attending the department of internal medicine of the Angers University hospital. Twenty-four-hour urine was collected 3 times during a 5-10 day hospitalization period. One-hundred-fifty-one patients (73%) displayed normoalbuminuria (UAE<30 mg/24 h in 2 or 3 measures) while 56 patients (27%) had microalbuminuria (UAE within 30-300 mg/24 h in 2 or 3 measures). As the raw data of UAE was not normally distributed, we transformed UAE into the variable z=log (log (k + UAE)) where k is an integer and looked for a k value for which z might be normally distributed. We found that z was actually normally distributed for k=2. Mean value and coefficient of variation of z in the 3 measurements were used to define the level and the temporal intra-individual variability of UAE. Expressed in term of z, the day-to-day intra-individual variability of UAE showed a potent change (from large variability to small variability) at the particular level z=1.25, corresponding to UAE=30.8 mg/24 h. This value is precisely the level currently used to define microalbuminuria in diabetic subjects. It is remarkable that the day-to-day variability of UAE collapses when UAE crosses the level which has been used to define microalbuminuria.

Quantification of sympathetic and parasympathetic tones by nonlinear indexes in normotensive rats.

Because the use of spectral powers of blood pressure (BP) and R-R interval (RR) in the low (LF) and high frequencies (HF) to quantify sympathetic and parasympathetic activities is still under debate, we questioned whether nonlinear methods may give better results. The BP signal was recorded for 30 min before and after intravenous injection of hexamethonium (20 mg/kg), atropine (0.5 mg/kg), atenolol (1 mg/kg), and prazosin (1 mg/kg) in conscious, normotensive Wistar-Kyoto rats. Three nonlinear indexes [percentage of recurrence, percentage of determinism, and length index (Lmax)] extracted from the recurrence plot method were used to analyze the BP signal. Sympathetic but not parasympathetic blockade reduced BP level and its LF component. RR increased and decreased after beta- and alpha-blockades, respectively. Hexamethonium increased HF, and atropine reduced LF, of RR. Sympathetic blockade and, in particular, alpha-sympathetic blockade increased nonlinear indexes of BP. In contrast, parasympathetic blockade by atropine increased nonlinear indexes of RR. These results suggest that, compared with spectral indexes, nonlinear indexes may be more specific markers of sympathetic and parasympathetic tones.

Use of nonlinear methods to assess effects of clonidine on blood pressure in spontaneously hypertensive rats.

In spontaneously hypertensive rats (SHR), chronic infusion of clonidine failed to decrease blood pressure and blood pressure variability. We used nonlinear methods to get a deeper insight on the effects of clonidine on blood pressure dynamics. For 24 h and 4 wk, clonidine (0.1 mg . kg-1 . day-1 sc) was infused by minipumps in the conscious SHRs, and, for comparison, a vehicle was infused in SHRs and in Wistar-Kyoto rats. Blood pressure was recorded for 30 min before and after treatments. We used the Lyapunov exponent, approximated by the inverse of the lmax index derived from the recurrence plot method, to characterize nonlinear dynamics. Before treatment, lmax index of blood pressure was lower (P < 0.01) in the SHRs than in the Wistar-Kyoto rats. Clonidine significantly increased lmax (P < 0.01) to the level observed in normotensive rats, at 24 h and up to 4 wk after infusion. We conclude that clonidine has a significant chronic effect on blood pressure dynamics, as evidenced by nonlinear methods. Our study also suggests that the mechanisms governing blood pressure variations are nonlinear.

Relationship between diabetic autonomic dysfunction and heart rate variability assessed by recurrence plot.

Beat-to-beat heart rate (HR) and blood pressure were measured by the Finapres system in 44 healthy and 64 diabetic subjects in the at-rest condition. Autonomic control in diabetic subjects was assessed by the Ewing test. HR variability was explored by both linear and nonlinear methods. Linear methods used HR standard deviation and power spectrum. The percentage of the spectrum in the low frequencies was used to assess the sympathetic tone of the autonomic control. The nonlinear method used the "recurrence plot." This method explored long parallel subsequences in the HR time series. These sequences characterize the dependence of the HR dynamics on initial values. The HR standard deviation was reduced in the diabetic subjects compared with the healthy subjects (2.80 +/- 1.17 vs. 3.64 +/- 1.45 beats/min; P < 0.001). In the diabetic subjects, the HR standard deviation and the percentage of the spectrum in the low frequencies showed no correlations with the Ewing score (P > 0.10). In contrast, the longest length index was very strongly correlated to the Ewing score (r = -0.60; P < 0.0001). The results suggest that nonlinear methods might be powerful to explore the autonomic dysfunction in diabetic subjects.

[Evaluation of the degree of diabetic dysautonomy with the analysis of heart rate measured at rest with the FINAPRES system]. / Evaluation du degré de dysautonomie diabétique par l'analyse de la fréquence cardiaque mesurée au repos par le système FINAPRES.

In this work, we developped the ERK (Eckmann, Ruelle and Khamporst) method of recurrent plots to analyse Heart Rate Variability (HRV), measured by the FINAPRES system in diabetic subjects. Our aim was to search some indices that might characterize the degree of dysautonomy detected in diabetic subjects, using the Ewing tests. The idea was to analyze the recurrences of the HR to previously observed values. When a value of HR, xi measured at the j-th beat come back to an already observed value, we compare the distances between the following measures (xi + 1 to xj + 1), (xj + 2 to xj + 2)... If the distances are under a given criteria during k beats, xi is deterministic of order k. Let n1 be the number of recurrent points and nk the number of k-order deterministic points, with k = 2, 3, 4... We defined the index of determinism nk + 1/nk and the Shannon entropy of the Nk = nk-nk + 1. These indices will be correlated to the total score of the 5 Ewing tests, which represent the standard measure to evaluate the diabetic dysautonomy. Blood pressure (BP) and HR were measured during about 30 minutes using the FINAPRES system in 44 healthy subjects and 60 non-hypertensive diabetic subjects. In the diabetic subjects, the age, the body weight and systolic and diastolic BP were 56 +/- 13 years (mean +/- standard-deviation), 79 +/- 14 kg, 80 +/- 10 mmHg and 137 +/- 20 mmHg. HR was weakly correlated to age (r = 0.29; p = 0.02) and the Ewing score (r = 0.31; p = 0.01). Its standard-deviation is also weakly correlated to age (r = 0.32; p = 0.01) and to the Ewing score (r = 0.34; p = 0.01). Using the ERK method, we obtained indices which are much more correlated to the Ewing score. In particular, the ratio n2/n1 and Shannon entropy were correlated to the Ewing score with r = 0.51 and r = 0.53, respectively (p < 0.0001 in both cases). These indices are also correlated to age (r = 0.40; p = 0.003) in both cases. The ERK method give some indices which are easy to obtain (measurement of HR during a rest period) and easy to interpret. These indices are strongly linked to the dysautonomy score which required a good cooperation of the patient and a great vigilance during its execution. This method could be applied to BP to explore BP regulation in hypertensive subjects.

Use of runs test to assess cardiovascular autonomic function in diabetic subjects.

OBJECTIVE: We suggest a simple, noninvasive method to assess the autonomic function in diabetic subjects. The method requires only a monitoring of heart rate (HR) with subjects in the sitting position. RESEARCH DESIGN AND METHODS: Sixty diabetic subjects, 44 men and 16 women, between 20-80 years of age, were recruited, chronologically, for this study. Subjects treated for high blood pressure were not included. Their autonomic function was assessed by the total score of five classical cardiovascular function tests. In the same subjects and in 44 healthy subjects, blood pressure and HR were determined from beat to beat by the Finapres system with subjects in the sitting position. We examined the randomness of the HR changes by calculating the zeta statistic of the runs test on 1,000 successive HR readings (the zeta value is low if the HR changes are random). When the HR changes are random, we consider that the autonomic control of HR is impaired. RESULTS: The zeta values of HR changes were significantly lower in diabetic subjects compared with normal subjects (2.98 +/- 0.97 vs. 3.54 +/- 0.97, P < 0.004). In diabetic subjects, the zeta value was closely correlated to the total score of disautonomy (r = -0.66, P < 0.0001, after correction for age effect) and to the office systolic blood pressure (r = -0.43, P < 0.001). CONCLUSIONS: The zeta value of HR changes might be a marker of the autonomic function in diabetic subjects.

[Is placebo necessary in a clinical trial on ambulatory blood pressure?]. / Le placebo est-il nécessaire dans un essai clinique sur la pression artérielle ambulatoire?

Placebo has only a slight effect on ambulatory blood pressure (ABP). Some authors have suggested that the use of a placebo is not necessary in a study on the drugs effect on ABP. We demonstrate that even if placebo effect is small, the use of a placebo group is still necessary. Effects of one daily dose of 50 mg atenolol + 20 mg slow-released nifedipine (AN) were investigated. Patients with office DBP 90-110 mmHg received, in a double-blind protocol, either AN (group AN, n = 31) or a placebo (group P, n = 26). Ambulatory BP (ABP) and HR were measured (Spacelabs or Diasys systems) for 24 h before and one month after treatment. The 2 groups were comparable before treatment. After 1 month under treatment, ABP was significantly lower in the AN group, compared to the P group, and this over the whole day (p = 0.03 to p < 0.0001). The effect was the most important between 10-17 h (p < 0.0001). HR was significantly lower in the AN group during daytime (6-22 h), but not during the night (22-6 h). Over the whole group, placebo effect was not significant. However, ABP did decrease under placebo in subjects with high initial pressure. As a result, an analysis without data from the placebo group led to an overestimation of the effects of the drug.