Ethanol-induced formation of colorectal tumours and precursors in a mouse model of Lynch syndrome

Lynch Syndrome (LS) confers an inherited cancer predisposition, particularly for colorectal cancer, due to germline mutations in one of the DNA mismatch repair (MMR) genes, such as MSH2. MMR is a DNA damage repair pathway involved in the removal of base mismatches and insertion/deletion loops, caused by several endogenous and exogenous factors. Loss of MMR through somatic alteration of the wild-type MMR allele in LS results in defective MMR (dMMR). Lifestyle factors can modify cancer risk for LS and sporadic patients. Ethanol and its metabolite acetaldehyde, are classified as group one carcinogens by the International Agency for Research on Cancer, and are risk factors for sporadic cancers of the upper aerodigestive tract, liver, breast and colorectum. Acetaldehyde is metabolised to acetate by the Aldh family of enzymes, particularly Aldh1b1 in the intestines. Acetaldehyde is very reactive and may cause a range of DNA lesions. However, DNA repair pathways responsible for correcting such lesions remain unknown. It was hypothesized that MMR plays a role in protecting intestinal cells from ethanol/acetaldehyde-induced DNA damage. This study aimed to determine if there is a gene/environment interaction between dMMR and ethanol/acetaldehyde that accelerates colorectal tumour development and progression.A conditional Msh2 knockout (“Msh2-LS”) mouse model with one deleted and one conditional knockout Msh2 allele was used, as it mimics the LS patients’ pattern of MMR gene inactivation. The Msh2-LS model mice were fed either with 20% ethanol in drinking water or normal drinking water. Long-term ethanol consumption led to large intestinal mucosal epithelial hyperproliferation and adenoma formation in 65% (15/23) mice and, in some cases, invasive adenocarcinoma (5/23 mice, 21.7%) within 6 months (mostly in the proximal and mid-colon), compared with 0% (0/23 mice) at 6 months and only one colonic tumour after 15 months in the water-treated mice (p<0.0001). No small intestinal tumours were observed. Additionally, a conditional Aldh1b1 knockout (Aldh1b1flox/flox) Msh2-LS mouse model and a constitutive Aldh1b1 knockout (Aldh1b1-/-) Msh2-LS mouse model were generated, in which the lack of Aldh1b1 enzyme caused increased acetaldehyde levels and acetaldehyde-induced DNA damage. In these Aldh1b1-deficient mice, long-term ethanol consumption led to increased numbers of colorectal adenomas per mouse (4.2, 21 neoplasms in 5 tumour-bearing conditional Aldh1b1fl/fl Msh2-LS mice; and 4.8, 35 neoplasms in 8 tumour-bearing constitutive Aldh1b1-/- Msh2-LS mice) compared with 2.4 (36 neoplasms in 15 tumour-bearing mice) colorectal adenomas per mouse observed in the Msh2-LS mouse model with wild-type Aldh1b1 (p=0.0319 and p=0.0103) , but no colonic tumours were observed in water-treated controls.Precursor lesions were observed as dMMR crypts in the murine colon in all of these mouse models, and their quantification showed increased numbers of dMMR crypt foci in ethanol-treated mice compared with water-treated controls (p=0.0029 in Aldh1b1wt Msh2-LS mice, p=0.0006 in Aldh1b1fl/fl Msh2-LS mice and p<0.0001 in Aldh1b1-/- Msh2-LS mice). A significant increase in DNA damage was detected in the large intestinal epithelium of ethanol-treated mice of all genotypes compared with the respective water-treated controls (p=0.0009 in Aldh1b1wt Msh2-LS mice, p<0.0001 in Aldh1b1fl/fl Msh2-LS mice and in Aldh1b1-/- Msh2-LS mice), along with increased plasma acetaldehyde levels in ethanol-treated mice and acetaldehyde levels were higher in the plasma of Aldh1b1flox/flox Msh2-LS mice and Aldh1b1-/- Msh2-LS mice than in the plasma of Msh2-LS mice.In this study, evidence was provided for a role for Msh2 in protecting the MMR-proficient colonic epithelial cells against ethanol/acetaldehyde-induced DNA damage by activating DNA mismatch repair, triggering cell cycle arrest or cell death by apoptosis. A key role for Aldh1b1 was confirmed for protecting the large intestines from acetaldehyde-induced DNA damage and tumour formation. Long-term ethanol/acetaldehyde exposure was shown to accelerate dMMR-driven intestinal tumour formation and this is proposed to act via promoting proliferation (mucosal epithelial hyperproliferation) and suppressing apoptosis, thus enhancing survival of aberrant dMMR intestinal epithelial cells/crypts relative to MMR-proficient intestinal epithelial cells/crypts, leading to adenoma development (with microsatellite instability) with some progressing to adenocarcinomas. In conclusion, there is strong evidence for a gene/environment interaction between acetaldehyde/dMMR, causing the acceleration of dMMR-driven intestinal tumour formation upon ethanol exposure

The role of ecosystem services in the spatial assessment of land degradation: a transdisciplinary study in the Ethiopian Great Rift Valley

Land degradation is a widespread problem that affects about 1.5 billion people globally. It can be defined as the decline in the productive capacity of the land, and the loss of functionality of ecosystems. Overall, land degradation leads to ecosystem services degradation, because it affects and causes the depletion of several soil functions (e.g. sediment retention, nutrient cycling, carbon stocks, and water retention). Therefore, it is also a constraint in securing food production and it could cause food insecurity. Hence, land degradation represents a considerable problem especially in developing countries, where people strongly rely on the ecosystems and natural resources for their livelihoods. The principal aim of this study was to assess land degradation by integrating different sources of knowledges and data, to derive a synthesis relevant to inform decision-making processes, and to target priority areas for conservation and restoration interventions. In this study, three ecosystem services (ESS) were modelled to infer land degradation in a small area, in the Halaba special woreda, located in the Ethiopian Great Rift Valley. In particular, sediment erosion and retention, nutrient retention and export, and carbon storage and sequestration were modelled. Data from a local soil survey, from global coverage datasets, and from a supervised land use cover classification were used for the ESS modelling. Remote Sensing data were used during the parametrisation phase of the ESS modelling. Local knowledges and perspectives were gathered using an extensive participatory approach that targeted the communities of three kebeles in the study area, and the experts of the Halaba woreda Agricultural Office. 33 focus group discussions and 32 semi-structured interviews were conducted in the summer 2016. The information acquired through the ESS modelling and during the participatory approach was then integrated in a Bayesian Belief Network (BBN), a probabilistic graphical model, to derive a spatial explicit land degradation risk assessment. The results showed that assessing land degradation through the lens of key ecosystem services represents a valid approach. The ESS modelling results showed that the study area is characterised by high soil erosion rates, low carbon storage and sequestration, and low nitrogen retention. Moreover, the ESS modelling also showed that using data from global coverage datasets could affect the reliability of the ESS assessment. Furthermore, the qualitative study, derived from the participatory approach, highlighted the presence of complex linkages between environmental and socio-economic factors, which exacerbate land degradation. The integration of ESS modelling results, participatory approach and literature data in the BBN proved to be an efficient approach to derive a synthesis of the several knowledges acquired during the several steps of this PhD project. Overall, this study demonstrated that a transdisciplinary and interdisciplinary approach is an effective means to address land degradation risks, taking into consideration people needs and priorities. In order to reverse land degradation trends, there is the need to adopt intense restoration and sustainable land management programs. However, there is also the need to couple conservation interventions with development strategies, such as market access and development, land tenure system improvements, off-farm job opportunities generation, and livelihoods diversification. This could foster land conservation and restoration, and could support sustainable economic growth and inclusive development

Stability of heartbeat interval distributions in chronic high altitude hypoxia

Recent studies of nonlinear dynamics of the long-term variability of heart rate have identified nontrivial long-range correlations and scale-invariant power-law characteristics (1/f noise) that were remarkably consistent between individuals and were unrelated to external or environmental stimuli (Meyer et al., 1998a). The present analysis of complex nonstationary heartbeat patterns is based on the sequential application of the wavelet transform for elimination of local polynomial nonstationary behavior and an analytic signal approach by use of the Hilbert transform (Cumulative Variation Amplitude Analysis). The effects of chronic high altitude hypoxia on the distributions and scaling functions of cardiac intervals over 24 hr epochs and 4 hr day/nighttime subepochs were determined from serial heartbeat interval time series of digitized 24 hr ambulatory ECGs recorded in 9 healthy subjects (mean age 34 yrs) at sea level and during a sojourn at high altitude (5,050 m) for 34 days (Ev-K2-CNR Pyramid Laboratory, Sagarmatha National Park, Nepal). The results suggest that there exists a hidden, potentially universal, common structure in the heterogeneous time series. A common scaling function with a stable Gamma distribution defines the probability density of the amplitudes of the fluctuations in the heartbeat interval time series of individual subjects. The appropriately rescaled distributions of normal subjects at sea level demonstrated stable Gamma scaling consistent with a single scaled plot (data collapse). Longitudinal assessment of the rescaled distributions of the 24 hr recordings of individual subjects showed that the stability of the distributions was unaffected by the subject's exposure to a hypobaric (hypoxic) environment. The rescaled distributions of 4 hr subepochs showed similar scaling behavior with a stable Gamma distribution indicating that the common structure was unequivocally applicable to both day and night phases and, furthermore, did not undergo systematic changes in response to high altitude. In contrast, a single function stable over a wide range of time scales was not observed in patients with congestive heart failure or patients after cardiac transplantation. The functional form of the scaling in normal subjects would seem to be attributable to the underlying nonlinear dynamics of cardiac control. The results suggest that the observed Gamma scaling of the distributions in healthy subjects constitutes an intrinsic dynamical property of normal heart function that would not undergo early readjustment or late acclimatization to extrinsic environmental physiological stress, e.g., chronic hypoxi

Is the heart preadapted to hypoxia? Evidence from fractal dynamics of heartbeat interval fluctuations at high altitude (5,050 m)

The dynamics of heartbeat interval time series over large time scales were studied by a modifed random walk analysis introduced recently asDetrended Fluctuation Analysis. In this analysis, the intrinsic fractal long-range power-law correlation properties of beat-to-beat fluctuations generated by the dynamical system (i.e., cardiac rhythm generator), after decomposition from extrinsic uncorrelated sources, can be quantified by the scaling exponent (α) which, in healthy subjects, for time scales of ∼104 beats is ∼1.0. The effects of chronic hypoxia were determined from serial heartbeat interval time series of digitized twenty-four-hour ambulatory ECGs recorded in nine healthy subjects (mean age thirty-four years old) at sea level and during a sojourn at 5,050 m for thirty-four days (Ev-K2-CNR Pyramid Laboratory, Sagarmatha National Park, Nepal). The group averaged α exponent (±SD) was 0.99±0.04 (range 0.93-1.04). Longitudinal assessment of α in individual subjects did not reveal any effect of exposure to chronic high altitude hypoxia. The finding of α∼1 indicating scale-invariant long-range power-law correlations (1/f noise) of heartbeat fluctuations would reflect a genuinely self-similar fractal process that typically generates fluctuations on a wide range of time scales. Lack of a characteristic time scale along with the absence of any effect from exposure to chronic hypoxia on scaling properties suggests that the neuroautonomic cardiac control system is preadapted to hypoxia which helps prevent excessive mode-locking (error tolerance) that would restrict its functional responsiveness (plasticity) to hypoxic or other physiological stimul

Oxygen affinity of blood in altitude Sherpas

Oxygen equilibrium curves on blood within 6 h from sampling have been estimated from polarographic measurements of oxyhemoglobin concentration, in 13 male 14- to 50-yr old Sherpas residing at 3,850 m above sea level (Kumjung, Nepal). In samples with red blood cell counts = 4.7 +/- 0.8 (SD) x 10(6)/mm3, total hemoglobin concentration [Hb] = 17.0 +/- 1.9 g/dl, and hematocrit = 53.3 +/- 5.0, the mean oxygen half-saturation of hemoglobin (P50) (pH = 7.4 and PCO2 = 40 Torr) was 27.3 +/- 1.8 Torr. The P50 of altitude Sherpas was not significantly different from that of acclimatized lowlanders (28.2 +/- 1.3; n = 7), sea-level Caucasian residents (26.5 +/- 1.0; n = 17), and Sherpas at sea level (27.1; n = 3). The 2,3-diphosphoglyceric acid-to-hemoglobin concentration ratio ([2,3-DPG]/[Hb]) in altitude Sherpas was 1.22 +/- 0.03, the same as that of acclimatized Caucasians (1.22 +/- 0.10). The Bohr effect measured for the blood of one altitude Sherpas by the ratio deltalog P50/deltapH was -0.32 and -0.45 at PCO2 levels of 40 and 20 Torr, respectively. These values are not significantly different from those found in Caucasians at sea level where deltalog P50/deltalpH was -0.35 and -0.42, respectively. It is concluded that the P50 in native highlanders is not significantly different from that observed in sea-level dwellers. [2,3-DPG]/[Hb] at altitude, both in natives and in newcomers, is 20% higher than in sea-level residents

Diversity of human skeletal muscle in health and disease: contribution of proteomics

Muscle represents a large fraction of the human body mass. It is an extremely heterogeneous tissue featuring in its contractile structure various proportions of heavy- and light-chain slow type 1 and fast types 2A and 2X myosins, actins, tropomyosins, and troponin complexes as well as metabolic proteins (enzymes and most of the players of the so-called excitation-transcription coupling). Muscle is characterized by wide plasticity, i.e. capacity to adjust size and functional properties in response to endogenous and exogenous influences. Over the last decade, proteomics has become a crucial technique for the assessment of muscle at the molecular level and the investigation of its functional changes. Advantages and shortcomings of recent techniques for muscle proteome analysis are discussed. Data from differential proteomics applied to healthy individuals in normal and unusual environments (hypoxia and cold), in exercise, immobilization, aging and to patients with neuromuscular hereditary disorders (NMDs), inclusion body myositis and insulin resistance are summarized, critically discussed and, when required, compared with homologous data from pertinent animal models. The advantages as well as the limits of proteomics in view of the identification of new biomarkers are evaluate

Muscle Oxygen Delivery in the Forearm and in the Vastus Lateralis Muscles in Response to Resistance Exercise: A Comparison Between Nepalese Porters and Italian Trekkers

Altitude ascending represents an intriguing experimental model reproducing physiological and pathophysiological conditions sharing hypoxemia as the denominator. The aim of the present study was to investigate fractional oxygen extraction and blood dynamics in response to hypobaric hypoxia and to acute resistance exercises, taking into account several factors including different ethnic origin and muscle groups. As part of the “Kanchenjunga Exploration &amp; Physiology” project, six Italian trekkers and six Nepalese porters took part in a high altitude trek in the Himalayas. The measurements were carried out at low (1,450 m) and high altitude (HA; 4,780 m). Near-infrared spectroscopy (NIRS)-derived parameters, i.e., Tot-Hb and tissue saturation index (TSI), were gathered at rest and after bouts of 3-min resistive exercise, both in the quadriceps and in the forearm muscles. TSI decreased with altitude, particularly in forearm muscles (from 66.9 to 57.3%), whereas the decrement was less in the quadriceps (from 62.5 to 57.2%); Nepalese porters were characterized by greater values in thigh TSI than Italian trekkers. Tot-Hb was increased after exercise. At altitude, such increase appeared to be higher in the quadriceps. This effect might be a consequence of the long-term adaptive memory due to the frequent exposures to altitude. Although speculative, we suggest a long-term adaptation of the Nepalese porters due to improved oxygenation of muscles frequently undergoing hypoxic exercise. Muscle structure, individual factors, and altitude exposure time should be taken into account to move on the knowledge of oxygen delivery and utilization at altitude

HUMAN RED-BLOOD-CELL AGING AT 5,050-M ALTITUDE - A ROLE DURING ADAPTATION TO HYPOXIA

To test the hypothesis that the human red blood cell aging process participates actively in the adaptation to hypoxia, we studied some physical and biochemical hematologic variables in 10 volunteers at sea level (SL) and after 1 (1WK) or 5 wk (5WK) of exposure to 5,050-m altitude. The 2,3- diphosphoglycerate-to-hemoglobin ratio (2,3-DPG/Hb) was 0.88 \ub1 0.03 (mol/mol) at SL and increased to 1.08 \ub1 0.03 (P = 0.002) and 1.28 \ub1 0.05 (P < 0.0001) at 1WK and 5WK, respectively. The average red blood cell density (D50), which is inversely proportional to the fraction of young red blood cells and is therefore an index of the red blood cell aging process, was 1.1053 \ub1 0.0007 g/ml at SL and decreased to 1.1046 \ub1 0.0008 g/ml (NS) and 1.1018 \ub1 0.0008 g/ml (P < 0.0001) at 1WK and 5WK, respectively. D50 was correlated with 2,3-DPG/Hb at SL (P = 0.004), only weakly at 5WK (P = 0.1), but not at all at 1WK. The arterial O2 saturation was correlated with the change of 2,3-DPG/Hb in 1WK (P = 0.02) and that of D50 in 5WK (P = 0.04). It is concluded that short-term (1WK) increase of 2,3-DPG/Hb is not associated with the erythropoietic response but is presumably due to respiratory alkalosis. By contrast, after prolonged hypoxia (5WK), erythropoiesis may provide an efficient way for increasing blood 2,3-DPG through an augmented proportion of young red blood cells

Blood O2 affinity and maximal O2 consumption in elite bicycle racers

The PO2 at which hemoglobin is half-saturated with O2 (P50) at 37\ub0C, PCO2 = 42 Torr, measured pH and 2,3-diphosphoglycerate-to-hemoglobin concentration ratio ([2,3-DPG]/[Hb]) values, Hill's coefficient (n) at rest, and maximal O2 consumption (V\u307O2(max)) were determined in 11 world-class professional bicycle racers off-season (control, C), after 3 mo of 3 h daily training (preseason, PrS), and after additional 6 mo of competitions (competitive season, CoS). The results indicate that the P50 observed in trained athletes was the same as that of a comparable group of sedentary subjects (Sed) under the same conditions of pH, PCO2, and [2,3-DPG]/[Hb] and was similar to that obtained after 'normalization' in respect to pH and the [2,3-DPG]/[Hb]; [2,3-DPG]/[Hb] increased as a function of training from 0.72 to 0.95 (P < 0.001); the slope of the central portion of the O2 equilibrium curve (OEC) was nearly unaffected by endurance training as indicated by the n value (n(CoS) = 2.70 \ub1 0.08; n(Sed) = 2.65 \ub1 0.08); and V\u307O2(max) increased in the course of training 7 and 9% (P < 0.001), respectively, when expressed in absolute units or per kilogram body weight. The V\u307O2(max) predicted on the basis of a computer simulation does not increase significantly as a consequence of the measured rise in [2,3-DPG]. Therefore, the observed increase of V\u307O2(max) cannot be explained with adaptive changes of the OEC. The present results differ from previous findings reported in other types of athletes