Influence of Macitentan on the Vascular Tone and Recruitment of Finger Capillaries Under Hypobaric Hypoxia in High Altitude.

Betge, Stefan, Stefan Drinda, Thomas Neumann, Laura Bäz, Alexander Pfeil, Christian Schulze, Ralf Mrowka, Christian Jung, and Marcus Franz. Influence of macitentan on the vascular tone and recruitment of finger capillaries under hypobaric hypoxia in high altitude. High Alt Med Biol. 21:336-345, 2020. Introduction: Acute normobaric (NH) and hypobaric hypoxia (HH) has effects on the vascular tone of larger arteries and may have effects on the microcirculation. These effects may be noninvasively detectable by automated devices. A part of these effects may be mediated by endothelin (ET) and should be influenced by macitentan (MAC), a dual endothelin receptor antagonist (ERA). Methods: We used photoplethysmographic sensors, fingertip volume sensors, nailfold capillaroscopy, and laser Doppler probes at rest and after a 5-minute forearm ischemia in healthy study subjects under NH, under HH, and under HH plus a single dose of MAC. Results: NH at simulated 4000 m led to increased heart rates (HR) and pulse wave velocities (PWV) and reduced augmentation index (AIX). The values for the AIX showed a high SD and differed between the used devices. At simulated 5500 m, only baseline mean value (BMV; EndoPAT) showed a further change, indicating less filled capillaries of the fingertips. HH (2978 m) increased HR, blood pressure values, and PWV. Focusing on the microcirculation of the fingertips, HH reduced the BMV and the nailfold capillary density and the postischemic capillary recruitment. MAC had no effect on the BMV, but antagonized the effects of HH on the nailfold capillaries and led to a strongly increased postischemic diameter of the arterial limbs. Concordantly, the postischemic blood flow velocity increment, measured through ultrasound Doppler, was increased at ALT+MAC. Conclusions: The BMV may be a parameter for changes of the microcirculation of the finger tips. A single dose of MAC blocked hypoxia-induced capillary rarefaction and enhanced postischemic hyperemia of the fingertips. These results indicate the importance of ET-1 for the regulation of the microcirculation under hypoxia. The German Registry of Clinical Studies (DRKS) ID: 00005459.

Effects of Periodic Fasting on Fatty Liver Index-A Prospective Observational Study.

This prospective observational trial investigated effects and safety of periodic fasting in subjects with and without type 2 diabetes mellitus (T2DM). The primary end point was set as the change of fatty liver index (FLI) as a surrogate parameter of non-alcoholic fatty liver disease (NAFLD). Six-hundred and ninety-seven subjects (38 with T2DM) were enrolled. A baseline FLI ≥ 60 (the threshold for fatty liver) was found in 264 subjects (37.9%). The mean duration of fasting was 8.5 ± 4.0 days (range 6-38). FLI decreased significantly (-14.02 ± 11.67; p < 0.0001), with a larger effect in individuals with T2DM (-19.15 ± 11.0; p < 0.0001; p = 0.002 compared to non-diabetic subjects). Body mass index (BMI) decreased by -1.51 ± 0.82 kg/m2, and 49.9% of the subjects lost ≥5% body weight. After fasting, nearly half of the 264 subjects with FLI ≥ 60 (highest risk category) shifted to a lower category. The improvement of FLI correlated with the number of fasting days (r = -0.20, p < 0.0001) and with the magnitude of BMI reduction (r = 0.14, p = 0.0001). Periodic fasting with concomitant weight reduction leads to significant rapid improvement of FLI in subjects with and without T2DM.

Mesencephalic Astrocyte-Derived Neurotrophic Factor Is Upregulated with Therapeutic Fasting in Humans and Diet Fat Withdrawal in Obese Mice.

Dietary restriction induces beneficial metabolic changes and prevents age-related deterioration. Mesencephalic astrocyte-derived neurotrophic factor (MANF) shows protective effects on cells in various models of degenerative diseases. Here we studied whether circulating concentrations of MANF are associated with fasting-induced positive effects. We quantified the levels of circulating MANF from 40 human subjects before and after therapeutic fasting. As measured by an enzyme-linked immunosorbent assay (ELISA), the mean concentration of plasma MANF increased after an average fasting of 15 days. Plasma MANF levels correlated inversely with adiponectin, a hormone that regulates metabolism, thus suggesting that MANF levels are related to metabolic homeostasis. To study the effects of dietary intervention on MANF concentrations in mice, we developed an ELISA for mouse MANF and verified its specificity using MANF knock-out (KO) tissue. A switch from high-fat to normal diet increased MANF levels and downregulated the expression of unfolded protein response (UPR) genes in the liver, indicating decreased endoplasmic reticulum (ER) stress. Liver MANF and serum adiponectin concentrations correlated inversely in mice. Our findings demonstrate that MANF expression and secretion increases with dietary intervention. The MANF correlation to adiponectin and its possible involvement in metabolic regulation and overall health warrants further studies.

Safety, health improvement and well-being during a 4 to 21-day fasting period in an observational study including 1422 subjects.

Only few studies document longer periods of fasting in large cohorts including non-obese participants. The aim of this study was to document prospectively the safety and any changes in basic health and well-being indicators during Buchinger periodic fasting within a specialised clinic. In a one-year observational study 1422 subjects participated in a fasting program consisting of fasting periods of between 4 and 21 days. Subjects were grouped in fasting period lengths of 5, 10, 15 and 20±2 days. The participants fasted according to the Buchinger guidelines with a daily caloric intake of 200-250 kcal accompanied by a moderate-intensity lifestyle program. Clinical parameters as well as adverse effects and well-being were documented daily. Blood examinations before and at the end of the fasting period complemented the pre-post analysis using mixed-effects linear models. Significant reductions in weight, abdominal circumference and blood pressure were observed in the whole group (each p<0.001). A beneficial modulating effect of fasting on blood lipids, glucoregulation and further general health-related blood parameters was shown. In all groups, fasting led to a decrease in blood glucose levels to low norm range and to an increase in ketone bodies levels (each p<0.001), documenting the metabolic switch. An increase in physical and emotional well-being (each p<0.001) and an absence of hunger feeling in 93.2% of the subjects supported the feasibility of prolonged fasting. Among the 404 subjects with pre-existing health-complaints, 341 (84.4%) reported an improvement. Adverse effects were reported in less than 1% of the participants. The results from 1422 subjects showed for the first time that Buchinger periodic fasting lasting from 4 to 21 days is safe and well tolerated. It led to enhancement of emotional and physical well-being and improvements in relevant cardiovascular and general risk factors, as well as subjective health complaints.

AGE-RAGE Interaction Does Not Explain the Clinical Improvements after Therapeutic Fasting in Osteoarthritis.

BACKGROUND: Therapeutic fasting improves joint pain in patients with osteoarthritis (OA), but the underlying mechanisms are unknown. Interactions of advanced glycation end products (AGEs) and their receptors (RAGE) play a role in OA pathogenesis. This study aimed to investigate whether the benefits of fasting in OA can be explained by changes in AGEs or RAGE. PATIENTS AND METHODS: 37 patients with OA underwent fasting for 8 days. Serum levels of an AGE (N-ε-(carboxymethyl)-lysine; CML) and the soluble RAGE (sRAGE) as well as clinical outcome parameters such pain characteristics (measured by visual analogue scale; VAS), joint function (determined by the Western Ontario and McMaster Universities Arthritis Index; WOMAC), and quality of life (via the 36-Item Short-Form Health Survey (SF-36) questionnaire) were assessed. The variables were measured at baseline, the end of fasting, and at follow-up at 4 weeks. RESULTS: The CML levels did not significantly change from baseline to the end of intervention (Δ = -25.6 ± 92.2 ng/ml; p = 0.10). In contrast, the sRAGE levels (Δ = -182.7 ± 171.4 ng/ml; p < 0.0001) and the sRAGE/CML ratio (Δ = -0.4 ± 0.6; p < 0.001) significantly decreased, but they returned to baseline levels 4 weeks after the end of fasting. The scores for pain, WOMAC, and the physical subscale of the SF-36 significantly improved during fasting. There was no correlation between the clinical outcomes and changes in serum levels of CML, sRAGE, or the sRAGE/CML ratio. CONCLUSIONS: Fasting resulted in a significant but non-sustained reduction of sRAGE levels and the sRAGE/CML ratio in OA, while the CML levels did not change. Improvement in clinical endpoints of OA does not correlate with changes in CML or sRAGE.

Retinal vessel regulation at high altitudes1.

PURPOSE: To measure static and dynamic changes of retinal vessels in response to normobaric hypoxia (NH, study A) and hypobaric hypoxia (HH, study B). METHODS: Study A included 10 healthy individuals exposed to a simulated altitude of 5500 meters in a NH chamber; study B included 17 individuals studied after ascent to 3000-meter altitude. Retinal vessel diameter, response to flicker light, retinal oxygen saturation and retinal venous pressure were measured at baseline, under the corresponding hypoxia condition. The effects of macitentan, an endothelin receptor antagonist, were examined in study B. RESULTS: The mean age of participants was 34.6±9.3 years in study A and 36.7±10.8 years in study B. Retinal arterial and venous diameter increased, arterial and venous response to flicker light decreased, while retinal oxygen saturation remained stable under both experimental conditions. Retinal venous pressure increased in six individuals after ascent to 3000 meters and normalized after macitentan treatment. The occurrence of acute mountain sickness (AMS) correlated only with the decrease of arterial constriction after ascent to 3000 meters. CONCLUSIONS: Retinal arterial and venous vessels react to NH and HH with a diameter increase and an impaired response to flicker light. Macitentan was capable to normalize the increased retinal venous pressure observed at high altitudes.

Identification of the receptor for advanced glycation end products in synovial tissue of patients with rheumatoid arthritis.

OBJECTIVES: Generation of advanced glycation end products (AGE) is an inevitable process in vivo and can be accelerated under pathologic conditions such as oxidative stress, e.g. in rheumatoid arthritis (RA). This process is mediated by the AGE-specific receptor (RAGE). In this study we analysed the presence of RAGE in RA and osteoarthritic (OA) synovial tissue using immunohistology. METHODS: Frozen synovial tissue samples from 11 RA patients and 12 OA patients were treated with goat anti-RAGE immunoglobulin G (IgG) and rabbit antigoat IgG. Immunostaining was visualised with streptavidin horse radish peroxidase (chromogen amino-ethyl-carbazole). Cell differentiation was performed with antibodies against CD68, CD45RO, and CD20. RESULTS: In 9/11 RA and 8/12 OA synovial specimens, RAGE was detected in synovial lining, sublining, and stroma. In RA, many T cells (CD45RO(+)) and some macrophages (CD68(+)) showed positive immunostaining for RAGE, whereas B cells were mostly negative. We found no difference in staining patterns between the RA and OA samples. CONCLUSIONS: We detected RAGE in RA and OA synovial tissue. The presence of RAGE on macrophages, T cells, and some B cells suggests its role in the pathogenesis of inflammatory joint disease.