A simple deep breathing test reveals altered cerebral autoregulation in type 2 diabetic patients

AIMS/HYPOTHESIS

Patients with diabetes mellitus have an increased risk of stroke and other cerebrovascular complications. The purpose of this study was to evaluate the autoregulation of cerebral blood flow in diabetic patients using a simple method that could easily be applied to the clinical routine screening of diabetic patients.

METHODS

We studied ten patients with type 2 diabetes mellitus and 11 healthy volunteer control participants. Continuous and non-invasive measurements of blood pressure and cerebral blood flow velocity were performed during deep breathing at 0.1 Hz (six breaths per minute). Cerebral autoregulation was assessed from the phase shift angle between breathing-induced 0.1 Hz oscillations in mean blood pressure and cerebral blood flow velocity.

RESULTS

The controls and patients all showed positive phase shift angles between breathing-induced 0.1 Hz blood pressure and cerebral blood flow velocity oscillations. However, the phase shift angle was significantly reduced (p < 0.05) in the patients (48 +/- 9 degrees ) compared with the controls (80 +/- 12 degrees ). The gain between 0.1 Hz oscillations in blood pressure and cerebral blood flow velocity did not differ significantly between the patients and controls.

CONCLUSIONS/INTERPRETATION

The reduced phase shift angle between oscillations in mean blood pressure and cerebral blood flow velocity during deep breathing suggests altered cerebral autoregulation in patients with diabetes and might contribute to an increased risk of cerebrovascular disorders.

Efficacy and safety of pregabalin in treatment refractory patients with various neuropathic pain entities in clinical routine

AIMS

Conventional approaches to the management of neuropathic pain (NeP) often yield unsatisfactory results. We aimed to investigate pregabalin, a gamma-aminobutyric acid (GABA)-analogue, in a wide range of pregabalin naive patients with treatment refractory NeP.

METHODS

Investigator-initiated, 4-week, open, prospective multicentre study in tertiary care. Pregabalin was prescribed at physicians' discretion based on patients' individual responses and tolerability, with or without concomitant analgesics. Consecutive patients were requested to fill in questionnaires at baseline and after 14 and 28 days with numerical pain rating scales (0, none; 10, worst possible), sleep rating scales, parts of the Brief Pain Inventory, Pain Experience Scale, Short Questionnaire on Current Burden and the SF-12 health-related quality of life scale.

RESULTS

In 55 patients, the mean pregabalin dose was 142 +/- 26 mg at day 1 and 348 +/- 161 mg at day 28. The mean pain score decreased from 6.5 +/- 1.7 to 5.5 +/- 1.9 at day 14 and to 4.9 +/- 1.8 at day 28 (-24.6%, p < 0.0001). Significant and rapid improvements were noted in the sleep interference score (p < 0.00001), Short Questionnaire on Current Burden (p < 0.01) and SF-12 (somatic score p < 0.001; psychological score p < 0.01). Pregabalin was well tolerated, and only three patients (5%) discontinued treatment prematurely.

CONCLUSIONS

Our findings suggest that pregabalin is an effective and well-tolerated drug in difficult-to-treat NeP patients under daily clinical practice conditions. A flexible dosing approach appears appropriate to ensure patient compliance and treatment success.

Flexible neural probes with micro-fluidic channels for stable interface with the nervous system

A flexible neural probe with micro-fluidic channels has been developed. The probe is sufficiently flexible to enable minimally invasive recording. The fluidic channel integrated on the probe is capable of injecting chemicals into neural tissues. In addition, it permits a stable interface with the nervous system. We focus on issues concerning: 1) stable recording with electrodes placed in fluidic channels, 2) improved mechanical stiffness by filling channels with a solid that dissolves in neural tissues, and 3) the probe's application to a nerve regeneration electrode.

The adenosine A1 receptor antagonist SLV320 reduces myocardial fibrosis in rats with 5/6 nephrectomy without affecting blood pressure

BACKGROUND AND PURPOSE

Myocardial fibrosis is an unwanted effect associated with chronic renal failure. The adenosine system is involved in cardiac and renal function. Therefore, we investigated the novel selective adenosine A(1) receptor antagonist SLV320 focusing on its potential in preventing cardiomyopathy in rats with 5/6 nephrectomy.

EXPERIMENTAL APPROACH

Male Sprague-Dawley rats were allocated to 4 groups of 12 rats each: 5/6 nephrectomy (5/6 NX), 5/6 NX plus SLV320 (10 mg kg(-1) d(-1) mixed with food), sham and sham plus SLV320. Study duration was 12 weeks, blood pressure was assessed repeatedly. At study end kidney function was assessed, blood samples and hearts were taken for histology/immunohistochemistry. Pharmacological properties of SLV320 were assessed using receptor binding and enzyme assays and in vivo.

KEY RESULTS

SLV320 is a selective and potent adenosine A(1) antagonist in vitro (Ki=1 nM) with a selectivity factor of at least 200 versus other adenosine receptor subtypes. Functional A(1) antagonism was demonstrated in vivo. In rats with 5/6 NX SLV320 significantly decreased albuminuria by about 50%, but did not alter glomerular filtration rate (GFR). SLV320 normalized cardiac collagen I+III contents in 5/6 NX rats. SLV320 prevented nephrectomy-dependent rise in plasma levels of creatinine kinase (CK), ALT and AST. Blood pressure did not differ between study groups.

CONCLUSION

SLV320 suppresses cardiac fibrosis and attenuates albuminuria without affecting blood pressure in rats with 5/6 nephrectomy, indicating that selective A(1) receptor antagonists may be beneficial in uraemic cardiomyopathy.

Duloxetin: Eine neue Behandlungsoption für Schmerzen im Rahmen der diabetischen Polyneuropathie

Diabetics develop numerous chronic associated diseases, among them sensory polyneuropathy. Diabetic polyneuropathy (DPN) often causes pain of various kinds, degree and duration. There are many pharmacological approaches: antidepressants are also important. Duloxetine is a recently approved dual action serotonin and noradrenaline re-uptake inhibitor that in its analgesic efficacy is comparable to established drugs. Duloxetine, in a dosage of 60 mg x 1 or x 2 daily, significantly reduces, from the first week of administration, the pain of DPN, when compared with a placebo. The most commonly observed side effects have been nausea, sleepiness, constipation and fatigue. On average duloxetine has not shown any clinically relevant increase in blood pressure, pulse rate and weight. It thus offers a new option as part of the treatment of pain caused by DPN. The various drugs should be considered individually in any treatment algorithm, also taking into account their side effects. Psychotherapeutic methods serve to support the overcoming of pain.

Altered cerebral regulation in type 2 diabetic patients with cardiac autonomic neuropathy

AIMS/HYPOTHESIS

Assessment of cerebral regulation in diabetic patients is often problematic because of the presence of cardiac autonomic neuropathy. We evaluated the technique of oscillatory neck suction at 0.1 Hz to quantify cerebral regulation in diabetic patients and healthy control subjects.

SUBJECTS AND METHODS

In nine type 2 diabetic patients with cardiac autonomic neuropathy and 11 age-matched controls, we measured blood pressure and cerebral blood flow velocity responses to application of 0.1 Hz neck suction. We determined spectral powers and calculated the transfer function gain and phase shift between 0.1 Hz blood pressure and cerebral blood flow velocity oscillations as parameters of cerebral regulation.

RESULTS

In the patients and control subjects, neck suction did not significantly influence mean values of the RR interval, blood pressure and cerebral blood flow velocity. The powers of 0.1 Hz blood pressure and cerebral blood flow velocity oscillations increased in the control subjects, but remained stable in the patients. Transfer function gain remained stable in both groups. Phase shift decreased in the patients, but remained stable in control subjects.

CONCLUSIONS/INTERPRETATION

The absence of an increase in the power of 0.1 Hz blood pressure and cerebral blood flow velocity oscillations confirmed autonomic neuropathy in the diabetic patients. Gain analysis did not show altered cerebral regulation. The decrease in phase shift in the patients indicates a more passive transmission of neck suction-induced blood pressure fluctuations onto the cerebrovascular circulation, i.e. altered cerebral regulation, in the patients, and is therefore suited to identifying subtle impairment of cerebral regulation in these patients.

Selective contribution of diabetes and other cardiovascular risk factors to cardiac autonomic dysfunction in the general population

Both cardiac autonomic dysfunction adn cardiovascular risk factors are related to and excess risk of mortality. We sought to determine whether the major cardiovascular risk factors are associated with diminished heart rate variability (HRV), prolonged QTc interval, or increased QT dispersion (QTD). Male (n = 1030) and female (n = 957) subjects, aged 55-74 years, who participated in the population-based MONICA Augsburg survey 1989/90 were assessed for the presence of cardiovascular risk factors such as diabetes, hypertension, obesity, dyslipidemia, smoking, and low physical activity. Lowest quartiles for time domain indexes of HRV (SD of R-R intervals [SDNN], max-min difference), QTc > 440 ms, and QTD > 60 ms determined from 12-lead resting ECG were used as cutpoints. In men, after adjustment for age and alcohol consumption, significant independent determinants for the lowest quartiles of SDNN were diabetes, obesity, and smoking. Independent contributors to prolonged QTc were hypertension, obesity, smoking, and low physical activity, whereas for increased QTD it was only hypertension. In women, diabetes was the only contributor to low SDNN, and hypertension was the only determinant of prolonged QTc. In conclusion, diabetes is the primary determinant of reduced HRV in the general population, while hypertension is the primary contributor to prolonged QTc in both sexes. However, obesity and smoking contribute to autonomic dysfunction in men but not women. Thus, a selectivity and sex-related differences exist among the various cardiovascular risk factors as to their influence on autonomic dysfunction.

Interferometric Coupling of the Keck Telescopes with Single-Mode Fibers

Here we report successful interferometric coupling of two large telescopes with single-mode fibers. Interference fringes were obtained in the 2- to 2.3-micrometer wavelength range on the star 107 Herculis by using the two Keck 10-meter telescopes, each feeding their common interferometric focus with 300 meters of single-mode fibers. This experiment demonstrates the potential of fibers for future kilometric arrays of telescopes and is the first step toward the 'OHANA (Optical Hawaiian Array for Nanoradian Astronomy) interferometer at the Mauna Kea observatory in Hawaii. It opens the way to sensitive optical imagers with resolutions below 1 milli-arc second. Our experimental setup can be directly extended to large telescopes separated by many hundreds of meters.

Type 2 diabetes as an inflammatory cardiovascular disorder

Type 2 diabetes carries a 2-6-fold increased risk of cardiovascular disease (CVD) and death. Indeed, the risk of major cardiovascular events in Type 2 diabetic patients without history of coronary heart disease (CHD) is equivalent to that observed in non-diabetic subjects with CHD. However, atherosclerosis may also precede the development of diabetes, suggesting that both disorders share common genetic and environmental antecedent factors ("common soil" hypothesis). One such a possible ancestor is insulin resistance which constitutes both a major feature of Type 2 diabetes and an independent risk factor for CHD. It is well documented that inflammatory processes play an important role in the causation of atherosclerotic CVD. Inflammatory mediators play a paramount role in the initiation, progression, and rupture of atherosclerotic plaques. Thus, markers of inflammation and endothelial dysfunction may provide additional information about a patient's risk of developing CVD and may become new targets for treatment. On the other hand, evidence has emerged suggesting that inflammation is also involved in the development of Type 2 diabetes. Prospective studies have demonstrated that increased levels of pro-inflammatory markers such as CRP or reduced levels of anti-inflammatory markers such as adiponectin predict the development of Type 2 diabetes. Thus, there is accumulating evidence suggesting that inflammation is the bridging link between atherosclerosis and the metabolic syndrome. Interventions by lifestyle modification or agents with anti-inflammatory properties may reduce the risk of both conditions. Drugs exerting anti-inflammatory and vascular effects have future potential to be used within an array of interventions aimed at reducing the enormous cardiovascular burden associated with Type 2 diabetes.

Effective treatment of symptomatic diabetic polyneuropathy by high-frequency external muscle stimulation

AIMS/HYPOTHESIS

Diabetic distal symmetrical sensory polyneuropathy (DSP) affects 20-30% of diabetic patients. Transcutaneous electrical nerve stimulation (TENS) and electrical spinal cord stimulation have been proposed as physical therapies. We performed a controlled, randomised pilot trial to compare the effects of high-frequency external muscle stimulation (HF) with those of TENS in patients with symptomatic DSP.

METHODS

Patients with type 2 diabetes and DSP (n=41) were randomised to receive treatment with TENS or HF using strata for non-painful (n=20) and painful sensory symptoms (n=21). Both lower extremities were treated for 30 min daily for three consecutive days. The patients' degree of symptoms and pain were graded daily on a scale of one to ten, before, during and 2 days after treatment termination. Responders were defined by the alleviation of one or more symptoms by at least three points.

RESULTS

The two treatment groups were similar in terms of baseline characteristics, such as age, duration of diabetes, neurological symptoms scores and neurological disability scores. The responder rate was significantly higher (p<0.05) in the HF group (80%, 16 out of 20) than in the TENS group (33%, seven out of 21). Subgroup analysis revealed that HF was more effective than TENS in relieving the symptoms of non-painful neuropathy (HF: 100%, seven out of seven; TENS: 44%, four out of nine; p<0.05) and painful neuropathy (HF: 69%, nine out of 13; TENS: 25%, three out of 12; p<0.05). The responders did not differ in terms of the reduction in mean symptom intensity during the trial.

CONCLUSIONS/INTERPRETATION

This pilot study shows, for the first time, that HF can ameliorate the discomfort and pain associated with DSP, and suggests that HF is more effective than TENS. External muscle stimulation offers a new therapeutic option for DSP.

Parylene flexible neural probes integrated with microfluidic channels

The fluidic channel in the flexible probe has three functions: (i) to inject chemicals into the tissues, (ii) to measure the neural activities from the tissues, and (iii) to improve the mechanical stiffness of the probe by filling the channel with a solid material. A 10-microm-thick microfluidic channel was embedded into the probe by using sacrificial photoresist patterns. Polyethylene glycol (PEG), which is solid at room temperature and dissolves when in contact with water, was used to fill the channel and increase the stiffness of the probe before insertion into the tissue. The impedance of the electrode inside the fluidic channel was around 100 kOmega at 1 kHz when the channel was filled with saline solution. We were able to insert the probe into a rat's brain and measure the neural signals with the electrode.

Urinary 8-epi-PGF2α and its endogenous β-oxidation products (2,3-dinor and 2,3-dinor-5,6-dihydro) as biomarkers of total body oxidative stress

Although measurements of plasma F2-isoprostanes are established markers of oxidative stress, their quantification only reflects acute non-enzymatic lipid peroxidation. In this study, a new approach is described for the rapid isolation and measurement of urinary 8-epi-PGF2alpha and its endogenous beta-oxidation metabolites (2,3-dinor-8-epi-PGF2alpha and 2,3-dinor-5,6-dihydro-PGF2alpha) for use as index of total body oxidative stress. Isoprostanes were partitioned with ethyl acetate and subsequently purified by chromatography on an aminopropyl (NH2) and silica (Si) cartridge. Final analysis of F2-isoprostanes as trimethylsilyl-ester/pentafluorobenzyl ester derivatives was carried out by stable isotope dilution mass spectrometry. Overall recovery of F2-isoprostanes was 80+/-4%. Inter- and intra-assay coefficients of variation were 5% and 7%, respectively. In a group of healthy humans, the mean excretion rates expressed as nmol/mmol creatinine for 2,3-dinor-8-epi-PGF2alpha, 2,3-dinor-5,6-dihydro-8-epi-PGF2alpha, and 8-epi-PGF2alpha were 5.43+/-1.93, 2.16+/-0.71, and 0.36+/-0.16, respectively. Correlations were obtained between 8-epi-PGF2alpha and 2,3-dinor-8-epi-PGF2alpha or 2,3-dinor-5,6-dihydro-8-epi-PGF2alpha (r=0.998 and r=0.937, respectively). A strong relationship was also seen between 2,3-dinor-8-epi-PGF2 and 2,3-dinor-5,6-dihydro-8-epi-PGF2alpha (r=0.949). The new technique allows for high sample throughput and avoids the need for HPLC and/or other expensive equipment required for the initial sample preparation. Simultaneous analysis of urinary 8-epi-PGF2alpha and its metabolites should provide unique tool in clinical trials exploring the role of oxidant injury in human disease.

Treatment of symptomatic diabetic polyneuropathy with the antioxidant alpha-lipoic acid: a meta-analysis

AIMS

To determine the efficacy and safety of 600 mg of alpha-lipoic acid given intravenously over 3 weeks in diabetic patients with symptomatic polyneuropathy.

METHODS

We searched the database of VIATRIS GmbH, Frankfurt, Germany, for clinical trials of alpha-lipoic acid according to the following prerequisites: randomized, double-masked, placebo-controlled, parallel-group trial using alpha-lipoic acid infusions of 600 mg i.v. per day for 3 weeks, except for weekends, in diabetic patients with positive sensory symptoms of polyneuropathy which were scored by the Total Symptom Score (TSS) in the feet on a daily basis. Four trials (ALADIN I, ALADIN III, SYDNEY, NATHAN II) comprised n=1258 patients (alpha-lipoic acid n=716; placebo n=542) met these eligibility criteria and were included in a meta-analysis based on the intention-to-treat principle. Primary analysis involved a comparison of the differences in TSS from baseline to the end of i.v. Treatment between the groups treated with alpha-lipoic acid or placebo. Secondary analyses included daily changes in TSS, responder rates (> or =50% improvement in TSS), individual TSS components, Neuropathy Impairment Score (NIS), NIS of the lower limbs (NIS-LL), individual NIS-LL components, and the rates of adverse events.

RESULTS

After 3 weeks the relative difference in favour of alpha-lipoic acid vs. placebo was 24.1% (13.5, 33.4) (geometric mean with 95% confidence interval) for TSS and 16.0% (5.7, 25.2) for NIS-LL. The responder rates were 52.7% in patients treated with alpha-lipoic acid and 36.9% in those on placebo (P<0.05). On a daily basis there was a continuous increase in the magnitude of TSS improvement in favour of alpha-lipoic acid vs. placebo which was noted first after 8 days of treatment. Among the individual components of the TSS, pain, burning, and numbness decreased in favour of alpha-lipoic acid compared with placebo, while among the NIS-LL components pin-prick and touch-pressure sensation as well as ankle reflexes were improved in favour of alpha-lipoic acid after 3 weeks. The rates of adverse events did not differ between the groups.

CONCLUSIONS

The results of this meta-analysis provide evidence that treatment with alpha-lipoic acid (600 mg/day i.v.) over 3 weeks is safe and significantly improves both positive neuropathic symptoms and neuropathic deficits to a clinically meaningful degree in diabetic patients with symptomatic polyneuropathy.

IRAS Splice Variants

The human I(1)-imidazoline receptor candidate gene, iras, has previously been cloned and mapped to locus 3p21.1-9 (also known as Nischarin; accession No. AC006208). By comparison to a database of expressed sequence tags (ESTs), three alternatively spliced transcripts have been deduced. A map of 21 exons was constructed for the medium-length transcript (IRAS-M) containing 5,232 base pairs (bp) and encoding 1,504 amino acids (aas). Introns 13B and 13C are inserted into the two alternative transcripts, forming IRAS-S and IRAS-L mRNA (short and long isoforms). Northern blots confirmed the existence of these mRNA isoforms. In most brain regions the order of mRNA abundance was IRAS-M > IRAS-L > IRAS-S mRNA. Although aas 1 through 510 are theoretically identical, truncated proteins could be derived from IRAS-S (2,678 bp transcript yields 515 aas) and IRAS-L (9,457 bp transcript yields 583 aas). Because exon-16 of the iras gene has been proposed to encode the functional domains of imidazoline and a-5 integrin binding, only IRAS-M is expected to possess I(1) receptor properties. Subtype-selective cDNA expression constructs were therefore generated and used to transfect CHO cells. High-affinity I(1) binding was endowed by IRAS-M and IRAS-L, but not by IRAS-S transfection.

Neospora caninum in sheep: a herd case report

Neospora caninum was detected by means of PCR in the brain of 4 out of 20 aborted fetuses in a flock of 117 sheep exhibiting a persistent abortion problem, and N. caninum tissue cysts were furthermore found in encephalitic lesions in one of the PCR-positive fetuses. Toxoplasma gondii was detected as aborting agent in another 3 out of 20 fetuses. Antibodies to N. caninum (by indirect fluorescence antibody test (IFAT)) were found in 10.3% of 117 ewes and antibodies for T. gondii were found in 97.4% of 117 ewes. Other organisms associated with abortion were Chlamydia psittaci in three fetuses and Pasteurella multocida in one fetus. This is the first report of N. caninum associated abortion in naturally infected sheep.