Neural correlates of eating behaviour in obesity and after obesity surgery

Background: Obesity is a serious, worldwide health concern. The urgent need to find an effective, safe and long-term treatment for this multifaceted chronic disease, requires a full and comprehensive understanding of its pathology. Indeed, eating behaviour is essential in understanding obesity development and consequently; is a key in optimising treatment. Functional magnetic resonance imaging (fMRI) has been recently utilized to understand the neural correlates of eating behaviour in obesity, specifically the reward system within the brain. Objectives: This thesis aimed to investigate the neural correlates of eating behaviour in obesity by examining the effect of: (i) obesity surgery, (ii) body mass index (BMI), and (iii) insulin resistance on food cue reactivity and other eating behaviour measures. Methods: Neural correlates of eating behaviour were examined by performing: (i) a comprehensive systemic review of functional magnetic resonance imaging (fMRI) studies after Roux-en Y gastric bypass (RYGB), vertical sleeve gastrectomy (VSG) and adjusted gastric band (AGB) surgeries; (ii) secondary analysis of three datasets to examine BMI and insulin resistance value as markers of food cue reactivity in three cohorts predominately consisting patients with obesity. Results: Findings from fMRI studies systematic review suggested the following: (i) after obesity surgery, specifically RYGB surgery, high-energy food cue reactivity sometimes decreased or else did not change in striatal, limbic and insula, regions implicated in reward processing. (ii) Although little evidence is available from VSG and AGB surgeries suggesting changes in food cue reactivity in brain regions involved in reward processing, a potential effect of VSG surgery on food cue reactivity in the dorsolateral prefrontal cortex. (iii) Some consistent evidence for a potential role for satiety gut hormones glucagon-like-peptide 1 (GLP-1) and peptide tyrosine tyrosine (PYY) in reduced food cue reactivity after RYGB surgery. Findings from secondary analysis of three datasets examining the effect of BMI on food cue reactivity revealed that contrary to expectations, no difference between groups in food cue 8 reactivity to high-energy food pictures in all cohorts. However, in participants with severe obesity compared to participant with non-severe obesity, lower food cue reactivity to low- energy food pictures in one cohort. Findings from secondary analysis of three datasets examining the effect of insulin resistance on food cue reactivity revealed that in participants with higher insulin resistance compared to participants with lower insulin resistance, higher food cue reactivity to high-energy vs. low- energy food pictures. However, these findings were only seen in one cohort and were not reproducible in the other two cohorts. Conclusion: In fMRI studies after obesity surgery, large methodological variation across studies, often with small numbers, with variable results of changes in food cue reactivity after obesity surgery, limits conclusions. Obesity surgeries, specifically RYGB and VSG, alter food cue reactivity in regions involved in reward processing and cognitive control. Heterogeneity in participants across the three cohorts limited findings replicability; however, findings suggest BMI as a potential marker for altered brain responses in regions implicated in reward processing in obesity. Moreover, altered food cue reactivity in obesity is not consistently seen as heightened reactivity for high energy food, it might be manifested as lower reactivity to low energy food. Finally, limited evidence for insulin resistance as a marker for food cue reactivity and other eating behaviour measures in obesity.Open Acces

The role of vitamin d and calcium supplementation in the pathogenesis of type 2 diabetes mellitus

Mounting evidence suggests a crucial role for vitamin D in the pathogenesis of type 2 diabetes mellitus (T2DM). Our objectives were to examine the correlation between serum calcidiol and diabetes outcomes, and determine whether vitamin 03 and calcium supplementation would attenuate the severity of T2DM. Eleven non-white, post-menopausal women with T2DM (age, 61 ± 11 y) were supplemented for 3 y with either placebo or 1800 IU 03 + 720 mg calcium (CaD)/day. The relative change over 3 y in serum calcidiol significantly inversely correlated with the relative change in body weight, BMI, body fat (%), hip circumference, serum TC/HDL-C and serum PTH, whereas it positively correlated with serum calcium. Retrospective analysis showed differences between the CaD vs. placebo in hip circumference, serum calcidiol, serum PTH and systolic blood pressure. We conclude that modest improvements in vitamin D status may mitigate the decrement in T2DM-related sequelae in non-white, post-menopausal women

Reading Additions in Children and Young Adults with Low Vision – Effects on Reading Performance

Reading is one of the most important activities in most people’s life. For children, reading is a window to knowledge, good educational achievement and better job opportunities in the future. Thus reading fluency is a very important factor in the child’s education. Children and young adults with low vision usually use a close working distance to gain relative distance magnification. Unlike adults, they have active accommodation. Many studies, however, have shown that children and young adults with low vision have reduced accommodation response compared to the norms of their age. Reading additions (high plus lenses) can correct for this reduction in accommodation and may be an optimum method of prescribing magnification in younger adults with low vision. There have been no studies to verify the best method of prescribing reading additions in young adults with low vision and few studies of their effect on reading performance. This is the first study to compare different methods to determine reading additions and their effect on reading performance in young adults with low vision. The aims of the present study are 1) to investigate if three different methods to determine reading additions would lead to significantly different dioptric powers 2) to determine which method (if any) would lead to better reading performance. Reading performance was assessed by measuring the maximum reading speed, critical print size (CPS), print size threshold and the area under the reading speed curve. This was an experimental study involving thirty participants with low vision aged between 8 to 35 years. Participants were recruited from the Low Vision Clinic at the School of Optometry, University of Waterloo, Canadian National Institute for the Blind (CNIB) and the Vision Institute of Canada. All participants underwent a routine clinical examination including distance visual acuity, near visual acuity, Pelli-Robson contrast sensitivity, unilateral cover test, static retinoscopy, subjective refraction and measurement of the habitual reading distance. A questionnaire was used to determine their usage of any low vision aids, their perceived difficulty with reading and time spent reading. Reading additions were determined by 1) an objective method using Nott dynamic retinoscopy 2) an age-based formula 3) a subjective method based on the participant’s response to lenses. Reading tasks and dynamic retinoscopy were conducted at a fixed working distance of 12.5cm. Reading performance was assessed using MNREAD-style reading charts with each of the reading additions and without a reading addition, in a random order. Sentences were arranged in way that no sentence was repeated by the same participant. Participants were timed with a stop watch in order to calculate the reading speed in correct words per minute (CWPM). Reading speeds were plotted against print size to calculate the maximum reading speed, the critical print size, MNREAD threshold and the area under the reading speed curve. The participant’s mean age was 16 (± 6) years. There were equal number of males and females. The mean distance visual acuity of the tested eye ranged from 0.357 to 1.184 logMAR with a mean of 0.797 ± 0.220 logMAR. The near visual acuity ranged between 0.301 to 1.301 logMAR with a mean of 0.80 ± 0.26 logMAR. There were six participants who already had a reading addition. Maximum reading speed ranged between 52 to 257 wpm (165 ± 61 wpm). Critical print size ranged between 0.325 to 1.403 logMAR (0.965 ± 0.279 logMAR). Repeated measures ANOVA on the whole group showed that there was a significant difference between the reading additions (p=0.001). The retinoscopy reading addition power was significantly lower than the age add (p=0.002) and the subjective add (p=0.038). Repeated measures ANOVA did not show any improvement of any of the reading measures with the reading additions compared to without the reading addition. A re-analysis was undertaken excluding participants who had normal accommodation at 12.5cm. The results of repeated measures ANOVA showed that there was no significant difference in the dioptric powers obtained by the three methods, although, all reading addition power were significantly greater than zero (t-test <0.0005). There was a significant difference in the area under the reading speed curve (p=0.035), which was greater with the subjective addition than with no reading addition (p=0.048). The MNREAD threshold significantly improved with the age addition compared to no addition (p=0.012). There was a large variability between the participants in their response to a reading addition. Analysis of individual data showed that some participants showed a clear improvement in reading performance with a reading addition. Other participants did not demonstrate any obvious improvement in reading performance with reading additions. Of those participants who showed an improvement, all but one participant had abnormal accommodation. However, not all participants who did not show an improvement had normal accommodation. Univariate analysis and forward step-wise linear regression analysis were used to investigate if any improvement in reading performance and the habitual reading performance without a reading addition could be predicted by factors that were measured in the study. These factors included distance visual acuity, near visual acuity, contrast sensitivity, lag of accommodation, age, time spent on reading each day, perceived difficulty of reading regular print and whether or not the participant received training for the usage of his/her low vision aids. Improvement in reading performance could not be predicted by any of these factors. Habitual reading performance without a reading addition was correlated with some factors. Univariate analysis showed that critical print size was associated with MNREAD threshold (r=0.904. p<0.0005), distance visual acuity (r=0.681, p<0.0005) and contrast sensitivity (r=-0.428, p=0.018) and MNREAD threshold without an addition was associated with the contrast sensitivity (r=-0.431, p=0.017,) and distance visual acuity (r=0.728, p<0.0005). Difficulty of reading correlated with near visual acuity (Spearman correlation coefficient=0.620, p=0.0009), MNREAD threshold (Spearman correlation coefficient=0.450, p=0.02) and maximum reading speed (Spearman correlation coefficient=-0.472, p=0.014). Time spent on reading each day correlated with the area under the reading speed curve (Spearman correlation coefficient=0.659, p=0.0024). The multiple regression analysis showed that MNREAD threshold was best predicted by distance visual acuity (R=0.728, p <0.0005), critical print size could be predicted by distance visual acuity (R=0.681, p <0.0005) and age (R=0.748, p=0.022) and the power of the subjective addition could be predicted by age (R=0.583, p=0.001) and near visual acuity (R=0.680, p=0.028). There was evidence that a reading addition improved reading performance as measured by the area under the curve and MNREAD (reading acuity) thresholds, but this was not predicted by any visual factor, except that all those who gained improvement had poor accommodation. Therefore, it is recommended that an eye care practitioner should demonstrate a reading addition in a low vision assessment of children and young adults, particularly with patients who have reduced accommodation

Development of an Arabic Continuous Text Near Acuity Chart

Purpose: Near visual acuity is an essential measurement during an oculo-visual assessment. Continuous text near visual acuity charts measure reading acuity and other aspects of reading performance. Arabic is ranked as the fourth spoken language globally. Yet, there are no standardized continuous text near visual acuity charts in Arabic. The aims of this study are to create and compose a large pool of standardized sentences, to validate these sentences in children and adults and choose a final set with equal readability to use in the development of a standardized Arabic continuous text reading chart, and then to design and validate the first standardized Arabic continuous text near visual acuity chart, the Balsam Alabdulkader-Leat (BAL) chart. Methods: Initially, 90 Arabic pairs of sentences were created for use in constructing a chart with similar layout to the Colenbrander chart. They were created following accepted criteria for creating sentences for near visual acuity charts. They had the same grade level of difficulty and physical length. Fifty-three Arabic-speaking adults and sixteen children were recruited to validate the sentences. Reading speed in correct words per minute (CWPM) and standard length words per minute (SLWPM) were measured and errors were counted. Elimination criteria based on reading speed and errors made in each sentence pair were applied to exclude sentence pairs with more outlying characteristics, and to select the final group of sentence pairs. The final sub-set of validated sentences was used in the construction of three versions of the BAL chart. Eighty-six bilingual adults with normal vision aged 15 to 59 years were recruited to validate the charts. Reading acuity and reading speed in standard words per minute were measured for the three versions of the BAL chart and three English charts (MNREAD, Colenbrander, and Radner charts). The Arabic version of the IReST chart was used to test the validity of the BAL chart in measuring reading speed. ANOVA was used to compare reading acuity and reading speed in standard words per minute. Bland-Altman plots were used to analyze agreement between the charts. Normal visual acuity (0.00 logMAR) was calibrated for the BAL chart with linear regression between the reading acuity of the BAL chart against reading acuity measured with the MNREAD and the Radner charts. Results: Forty-five sentence pairs were selected according to the elimination criteria. For adults, the average reading speed for the final sentences was 166 CWPM and 187 SLWPM and the average number of errors per sentence pair was 0.21. Childrens’ average reading speed for the final group of sentences was 61 CWPM and 64 SLWPM. Their average error rate was 1.71. The Cronbach’s alpha for the final set of sentence pairs in CWPM and SLWPM was 0.986 for adults and 0.996 for children, showing that the final sentences had very good internal consistency. Three versions of the BAL chart were created. Each chart had fifteen print size levels. Average reading acuity for BAL1, BAL2 and BAL3 was 0.62, 064 and 0.65 log-point print respectively (equivalent to -0.08, -0.06 and -0.05 logMAR respectively). These differences in reading acuity among the BAL charts were statistically significantly different (repeated measures ANOVA, p < 0.05), but not considered clinically significant. Average reading acuity for the Colenbrander, MNREAD and Radner charts was -0.05, -0.13 and -0.03 logMAR respectively. The coefficient of agreement for reading acuity between the BAL charts was 0.054 (between BAL1 and BAL2), 0.061 (between BAL2 and BAL3) and 0.059 (between BAL1 and BAL3). Linear regression between the average reading acuity for the BAL chart and the MNREAD and Radner charts showed that 0.7 log-point size is equivalent to 0.00 logMAR. The new BAL chart was labelled accordingly. Mean SLWPM for the BAL charts was 201, 195 and 195 SLWPM respectively and for the Colenbrander, MNREAD and Radner charts was 146, 171 and 146 respectively. The coefficients of agreement for log-SLWPM between BAL1 and BAL2, BAL2 and BAL3 and BAL1 and BAL3 were 0.063, 0.064 and 0.057 log SLWPM respectively. Conclusions: The reliability analysis showed that the final 45 sentence pairs are highly comparable. They were used in constructing three versions of the BAL chart. The BAL chart showed high inter-chart agreement and can be recommended for accurate near performance measures in Arabic for both research and clinical settings

Effects of bariatric surgery and dietary interventions for obesity on brain neurotransmitter systems and metabolism: A systematic review of positron emission tomography (PET) and single-photon emission computed tomography (SPECT) studies

This systematic review collates studies of dietary or bariatric surgery interventions for obesity using positron emission tomography and single-photon emission computed tomography. Of 604 publications identified, 22 met inclusion criteria. Twelve studies assessed bariatric surgery (seven gastric bypass, five gastric bypass/sleeve gastrectomy), and ten dietary interventions (six low-calorie diet, three very low-calorie diet, one prolonged fasting). Thirteen studies examined neurotransmitter systems (six used tracers for dopamine DRD2/3 receptors: two each for 11C-raclopride, 18F-fallypride, 123I-IBZM; one for dopamine transporter, 123I-FP-CIT; one used tracer for serotonin 5-HT2A receptor, 18F-altanserin; two used tracers for serotonin transporter, 11C-DASB or 123I-FP-CIT; two used tracer for μ-opioid receptor, 11C-carfentanil; one used tracer for noradrenaline transporter, 11C-MRB); seven studies assessed glucose uptake using 18F-fluorodeoxyglucose; four studies assessed regional cerebral blood flow using 15O-H2O (one study also used arterial spin labeling); and two studies measured fatty acid uptake using 18F-FTHA and one using 11C-palmitate. The review summarizes findings and correlations with clinical outcomes, eating behavior, and mechanistic mediators. The small number of studies using each tracer and intervention, lack of dietary intervention control groups in any surgical studies, heterogeneity in time since intervention and degree of weight loss, and small sample sizes hindered the drawing of robust conclusions across studies

Effect of obesity surgery on taste

Obesity surgery is a highly efficacious treatment for obesity and its comorbidities. The underlying mechanisms of weight loss after obesity surgery are not yet fully understood. Changes to taste function could be a contributing factor. However, the pattern of change in different taste domains and among obesity surgery operations is not consistent in the literature. A systematic search was performed to identify all articles investigating gustation in human studies following bariatric procedures. A total of 3323 articles were identified after database searches, searching references and deduplication, and 17 articles were included. These articles provided evidence of changes in the sensory and reward domains of taste following obesity procedures. No study investigated the effect of obesity surgery on the physiological domain of taste. Taste detection sensitivity for sweetness increases shortly after Roux-en-Y gastric bypass. Additionally, patients have a reduced appetitive reward value to sweet stimuli. For the subgroup of patients who experience changes in their food preferences after Roux-en-Y gastric bypass or vertical sleeve gastrectomy, changes in taste function may be underlying mechanisms for changing food preferences which may lead to weight loss and its maintenance. However, data are heterogeneous; the potential effect dilutes over time and varies significantly between different procedures

Global, regional, and national cancer incidence, mortality, years of life lost, years lived with disability, and disability-Adjusted life-years for 29 cancer groups, 1990 to 2017 : A systematic analysis for the global burden of disease study

Importance: Cancer and other noncommunicable diseases (NCDs) are now widely recognized as a threat to global development. The latest United Nations high-level meeting on NCDs reaffirmed this observation and also highlighted the slow progress in meeting the 2011 Political Declaration on the Prevention and Control of Noncommunicable Diseases and the third Sustainable Development Goal. Lack of situational analyses, priority setting, and budgeting have been identified as major obstacles in achieving these goals. All of these have in common that they require information on the local cancer epidemiology. The Global Burden of Disease (GBD) study is uniquely poised to provide these crucial data. Objective: To describe cancer burden for 29 cancer groups in 195 countries from 1990 through 2017 to provide data needed for cancer control planning. Evidence Review: We used the GBD study estimation methods to describe cancer incidence, mortality, years lived with disability, years of life lost, and disability-Adjusted life-years (DALYs). Results are presented at the national level as well as by Socio-demographic Index (SDI), a composite indicator of income, educational attainment, and total fertility rate. We also analyzed the influence of the epidemiological vs the demographic transition on cancer incidence. Findings: In 2017, there were 24.5 million incident cancer cases worldwide (16.8 million without nonmelanoma skin cancer [NMSC]) and 9.6 million cancer deaths. The majority of cancer DALYs came from years of life lost (97%), and only 3% came from years lived with disability. The odds of developing cancer were the lowest in the low SDI quintile (1 in 7) and the highest in the high SDI quintile (1 in 2) for both sexes. In 2017, the most common incident cancers in men were NMSC (4.3 million incident cases); tracheal, bronchus, and lung (TBL) cancer (1.5 million incident cases); and prostate cancer (1.3 million incident cases). The most common causes of cancer deaths and DALYs for men were TBL cancer (1.3 million deaths and 28.4 million DALYs), liver cancer (572000 deaths and 15.2 million DALYs), and stomach cancer (542000 deaths and 12.2 million DALYs). For women in 2017, the most common incident cancers were NMSC (3.3 million incident cases), breast cancer (1.9 million incident cases), and colorectal cancer (819000 incident cases). The leading causes of cancer deaths and DALYs for women were breast cancer (601000 deaths and 17.4 million DALYs), TBL cancer (596000 deaths and 12.6 million DALYs), and colorectal cancer (414000 deaths and 8.3 million DALYs). Conclusions and Relevance: The national epidemiological profiles of cancer burden in the GBD study show large heterogeneities, which are a reflection of different exposures to risk factors, economic settings, lifestyles, and access to care and screening. The GBD study can be used by policy makers and other stakeholders to develop and improve national and local cancer control in order to achieve the global targets and improve equity in cancer care. © 2019 American Medical Association. All rights reserved.Peer reviewe

Toward developing a standardized Arabic continuous text reading chart

Purpose: Near visual acuity is an essential measurement during an oculo-visual assessment. Short duration continuous text reading charts measure reading acuity and other aspects of reading performance. There is no standardized version of such chart in Arabic. The aim of this study is to create sentences of equal readability to use in the development of a standardized Arabic continuous text reading chart. Methods: Initially, 109 Arabic pairs of sentences were created for use in constructing a chart with similar layout to the Colenbrander chart. They were created to have the same grade level of difficulty and physical length. Fifty-three adults and sixteen children were recruited to validate the sentences. Reading speed in correct words per minute (CWPM) and standard length words per minute (SLWPM) was measured and errors were counted. Criteria based on reading speed and errors made in each sentence pair were used to exclude sentence pairs with more outlying characteristics, and to select the final group of sentence pairs. Results: Forty-five sentence pairs were selected according to the elimination criteria. For adults, the average reading speed for the final sentences was 166 CWPM and 187 SLWPM and the average number of errors per sentence pair was 0.21. Childrens’ average reading speed for the final group of sentences was 61 CWPM and 72 SLWPM. Their average error rate was 1.71. Conclusions: The reliability analysis showed that the final 45 sentence pairs are highly comparable. They will be used in constructing an Arabic short duration continuous text reading chart

Reading in children with low vision

There have been numerous and extensive studies into the visual requirements for reading in adults with low vision. There are far fewer studies involving children with low vision. This article compares the studies on children which do exist with the findings in adults. Acuity reserve (magnification), contrast reserve and visual field requirements are considered. We also review the literature which compares the efficacy of large print with optical magnification for children. From the few studies that exist, there are indications that the requirements for children are not the same as for adults. Therefore, we suggest that one cannot directly apply the results from adults to children and that there is a gap in the literature (and therefore our understanding) of the visual requirements for reading in children