Erlingur Johannsson

Cellular and subcellular expression of monocarboxylate transporters in the pigment epithelium and retina of the rat

The cellular and subcellular expression of the monocarboxylate transporters MCT1, MCT2 and MCT4 [corresponding to MCT3 of Price N. T. et al. (1998) Biochem. J. 329, 321-328] were investigated in the pigment epithelium and outer retina of rats. Immunofluorescence and postembedding immunogold analyses revealed strong MCT1 labelling in the apical membrane of the pigment epithelial and no detectable signal in the basolateral membrane. In contrast, antibodies to the glucose transporter GLUT1 produced intense labelling in both membranes. Neither MCT1 nor GLUT1 was enriched in intracellular compartments. The monocarboxylate transporter MCT4 was very weakly expressed in the retinal pigment epithelium of adult animals, but occurred at higher concentrations at this site in 14-day-old rats. However, even at the latter stage, the immunolabelling of MCT4 was weak compared to that of MCT1. In the neural retina, the data were consistent with a predominant glial localization of MCT1. Specifically, immunogold particles signalling MCT1 occurred in Müller cell microvilli and in the velate processes between the photoreceptors. No labelling was obtained with antibodies to MCT2. Taken together with previous biochemical analyses, the present findings indicate that MCT1 is involved in the outward transport of lactate through the retinal pigment epithelial cells, and in the transfer of lactate between Müller cells and photoreceptors.

Tracking of overweight from early childhood to adolescence in cohorts born 1988 and 1994: overweight in a high birth weight population

Objective:To investigate the prevalence and tracking of overweight and obesity in childhood cohorts born 1988 and 1994 in a population of high birth weight.Subjects:Icelandic cohorts born in 1988 and 1994.Materials and methods:Out of 1328, 9- and 15-year-old children from 18 randomly selected schools all over Iceland, 934 participated (71%). Height and mass were measured by the investigators. Also, height and mass at birth, and at age 2.5, 6, 9, and 12 years, were collected from maternity wards and school health registers.Results:The prevalence of overweight children ranged from 10.1% for 2.5-year-olds to 18.7% for 9-year-olds. No difference was observed between the two cohorts or sex. The prevalence of obesity in the 1994 cohort (4.3%) was significantly higher (P=0.01) at age 6 years, compared to the 1988 cohort (1.1%). The children who were overweight at age 2.5 years were more likely to be overweight at age 6 (OR=12.2) and 9 years (OR=4.9), but not significantly at age 12 or 15 years, compared with normal weight 2.5-year-olds. Overweight children at age 6 or 9 years were much more likely (OR 10.4 and OR 18.6, respectively) to be overweight at age 15 years compared to their normal weight peers. Of overweight 6-year-olds, 51% were overweight at 15 years, and were about one-third of all overweight children at that age. The children that weighed above the 85th percentile at birth were more likely than the other children to be overweight at the age of 6 years (OR=1.8), 9 years (OR=2.1), and 15 (OR=2.0) years.Conclusion:The results show high prevalence of overweight and obesity even before the start of compulsory schooling. Approximately, 51% of overweight 6-year-olds were still overweight after puberty. Therefore, preschool overweight prevention, along with prevention at school age, seems to be of uttermost importance.

Electrical stimulation induces fiber type-specific translocation of GLUT-4 to T tubules in skeletal muscle

Insulin and contraction independently stimulate glucose transport in skeletal muscle. Whereas insulin activates glucose transport more in muscles composed of type I and IIa fibers, electrical stimulation increases glucose transport at least as much in type IIb fiber-enriched muscles despite the fact that the latter fiber type contains less GLUT-4 glucose transporters. The aim of the present study was to test the hypothesis that a greater GLUT-4 translocation to the cell surface may underlie the higher contraction-stimulated glucose transport in type IIb myofibers. Leg muscles from rats were stimulated in situ at 100 Hz (200 ms) each 2 s via the sciatic nerve over a period of 20 min while the contralateral leg was kept at rest. Muscle 2-[3H]deoxy-D-glucose uptake (2-DG) was measured in separated red gastrocnemius (RG, type I and IIa fibers) and white gastrocnemius (WG, type IIb fibers) muscles. Resting 2-DG uptake was greater in RG than WG. Electrical stimulation increased 2-DG uptake over resting values similarly in WG and RG. Fractions enriched with either plasma membranes, transverse (T) tubules, triads, or GLUT-4-enriched intracellular membranes were isolated from RG and WG using a recently developed subcellular fractionation procedure. Electrical stimulation similarly increased GLUT-4 protein content in plasma membranes of RG and WG, whereas it stimulated GLUT-4 translocation more (approximately 50%) in T tubules of WG than in RG. GLUT-4 content was not changed in triads of both muscle types. The increments in cell surface GLUT-4 protein levels were paralleled by significant reductions in the amount of the transporter in the intracellular membrane fractions of both muscle types (by 60% in RG and 56% in WG). It is concluded that electrically induced contraction stimulates GLUT-4 translocation more in T tubules of WG than RG. The physiological implications of this finding for glucose uptake by contracting RG and WG muscles is discussed.Insulin and contraction independently stimulate glucose transport in skeletal muscle. Whereas insulin activates glucose transport more in muscles composed of type I and IIa fibers, electrical stimulation increases glucose transport at least as much in type IIb fiber-enriched muscles despite the fact that the latter fiber type contains less GLUT-4 glucose transporters. The aim of the present study was to test the hypothesis that a greater GLUT-4 translocation to the cell surface may underlie the higher contraction-stimulated glucose transport in type IIb myofibers. Leg muscles from rats were stimulated in situ at 100 Hz (200 ms) each 2 s via the sciatic nerve over a period of 20 min while the contralateral leg was kept at rest. Muscle 2-[3H]deoxy-d-glucose uptake (2-DG) was measured in separated red gastrocnemius (RG, type I and IIa fibers) and white gastrocnemius (WG, type IIb fibers) muscles. Resting 2-DG uptake was greater in RG than WG. Electrical stimulation increased 2-DG uptake over resting values similarly in WG and RG. Fractions enriched with either plasma membranes, transverse (T) tubules, triads, or GLUT-4-enriched intracellular membranes were isolated from RG and WG using a recently developed subcellular fractionation procedure. Electrical stimulation similarly increased GLUT-4 protein content in plasma membranes of RG and WG, whereas it stimulated GLUT-4 translocation more (∼50%) in T tubules of WG than in RG. GLUT-4 content was not changed in triads of both muscle types. The increments in cell surface GLUT-4 protein levels were paralleled by significant reductions in the amount of the transporter in the intracellular membrane fractions of both muscle types (by 60% in RG and 56% in WG). It is concluded that electrically induced contraction stimulates GLUT-4 translocation more in T tubules of WG than RG. The physiological implications of this finding for glucose uptake by contracting RG and WG muscles is discussed.

Limited effects of a 2-year school-based physical activity intervention on body composition and cardiorespiratory fitness in 7-year-old children

The aim of this study was to assess the effects of a 2-year cluster-randomized physical activity and dietary intervention program among 7-year-old (at baseline) elementary school participants on body composition and objectively measured cardiorespiratory fitness. Three pairs of schools were selected and matched, then randomly selected as either an intervention (n = 151) or control school (n = 170). None of the effect sizes of body composition were statistically significant. Children in the intervention group increased their fitness by an average of 0.37 z score units more than the controls (95% CI:-0.27 to 1.01, P = 0.18), representing an improvement of 0.286 W/kg. Boys had higher fitness (mean(diff) = 0.35 z scores, 95% CI: 0.13-0.58, P = 0.001) than girls, independent of study group, fitness z score at baseline and body mass index. Post hoc analysis showed that the intervention school with the highest fitness z score change was significantly different from two of the lowest control schools (mean(diff) = 0.83 z scores, 95% CI: 0.44-1.21, P < 0.0001 and mean(diff) = 0.70 z scores, 95% CI: 0.29-1.10, P = 0.01), but it was also significantly different from the lowest intervention school (mean(diff) = 0.59 z scores, 95% CI: 0.19-0.99, P = 0.05). The results of this intervention are inconclusive as regards to the effects on fitness, but the intervention did not have any statistically significant effect on body composition.

Effects of a 6-month multimodal training intervention on retention of functional fitness in older adults: A randomized-controlled cross-over design

BackgroundOlder adults have the highest rates of disability, functional dependence and use of healthcare resources. Training interventions for older individuals are of special interest where regular physical activity (PA) has many health benefits. The main purpose of this study was to assess the immediate and long-term effects of a 6-month multimodal training intervention (MTI) on functional fitness in old adults.MethodsFor this study, 117 participants, 71 to 90 years old, were randomized in immediate intervention group and a control group (delayed intervention group). The intervention consisted of daily endurance and twice-a-week strength training. The method was based on a randomized-controlled cross-over design. Short Physical Performance Battery (SPPB), 8 foot up-and-go test, strength performance, six min walking test (6 MW), physical activity, BMI and quality of life were obtained at baseline, after a 6-month intervention- and control phase, again after 6-month crossover- and delayed intervention phase, and after anadditional 6-month follow-up.ResultsAfter 6 months of MTI, the intervention group improved in physical performance compared with the control group via Short Physical Performance Battery (SPPB) score (mean diff = 0.6, 95 % CI: 0.1, 1.0) and 8-foot up-and-go test (mean diff = −1.0 s, 95 % CI: -1.5, -0.6), and in endurance performance via 6-minute walking test (6 MW) (mean diff = 44.2 meters, 95 % CI: 17.1, 71.2). In strength performance via knee extension the intervention group improved while control group declined (mean diff = 55.0 Newton, 95 % CI: 28.4, 81.7), and also in PA (mean diff = 125.9 cpm, 95 % CI: 96.0, 155.8). Long-term effects of MTI on the particpants was assesed by estimating the mean difference in the variables measured between time-point 1 and 4: SPPB (1.1 points, 95 % CI: 0.8, 1.4); 8-foot up-and-go (−0.9 s, 95 % CI: -1.2, -0.6); 6 MW (18.7 m, 95 % CI: 6.5, 31.0); knee extension (4.2 Newton, 95 % CI: -10.0, 18.3); hand grip (6.7 Newton, 95 % CI: -4.4, 17.8); PA (−4.0 cpm, 95 % CI: -33.9, 26.0); BMI (−0.6 kg/m2, 95 % CI: -0.9, -0.3) and Icelandic quality of life (0.3 points, 95 % CI: -0.7, 1.4).ConclusionsOur results suggest that regular MTI can improve and prevent decline in functional fitness in older individuals, influence their lifestyle and positively affect their ability to stay independent, thus reducing the need for institutional care.Trial registrationThis study was approved by the National Bioethics Committee in Iceland, VSNb20080300114/03-1

Differences in Physical Activity among Youth with and without Intellectual Disability.

INTRODUCTION Very little is known about physical activity (PA) and PA patterns measured with objective methods among children with intellectual disability (ID). PURPOSE This study aimed to investigate PA and PA patterns among Icelandic school children with mild-to-severe ID. METHODS A sample of 91 children with ID and a randomly selected age- and sex-matched group of 93 typically developed individuals (TDI) took part in the study. Basic anthropometric measurements were attained, and PA was assessed with ActiGraph accelerometers for 7-10 consecutive days. A questionnaire was used to collect data on PA behavior. RESULTS Although children with ID were 40% less physically active and spent 9% more time sedentary than their TDI peers, there was interaction between group and sex (P < 0.05). TDI boys were more active and less sedentary than TDI girls (P < 0.05), but no sex differences were found among children with ID on any PA variable. In addition, there was no difference between workday PA and weekend PA among children with ID. Only 16% of children with ID walked or biked to school, whereas the proportion was 74% among TDI children (P < 0.001). Similarly, a lower fraction (33%) of children with ID took part in 2 h·wk or more in sports compared with TDI children (76%, P < 0.001). No children with ID met the recommendation of 60 min of daily moderate-to-vigorous PA, whereas 40% of the TDI children met the recommendation. CONCLUSIONS PA of children with ID is considerably lower than that among their TDI peers, and there seem to be no sex differences in PA and PA patterns among children with ID. The fact that no children with ID met the recommended daily MVPA calls for special PA measures in this group.

Effects of a school-based intervention on adherence of 7-9-year-olds to food-based dietary guidelines and intake of nutrients.

OBJECTIVE To assess the effects of a school-based intervention on the diets of 7-9-year-olds. DESIGN Dietary intake of children in second and fourth grades was assessed with 3d weighed dietary records in autumn 2006 and autumn 2008, before and after a school-based intervention that started in the middle of second grade, and compared with control schools with no intervention. The diet was evaluated by comparison with food-based dietary guidelines (FBDG) and reference values for nutrient intake. The intervention aimed at several determinants of intake: knowledge, awareness, preferences/taste, self-efficacy and parental influence. Nutrition education material was developed for the intervention and implemented in collaboration with teachers. The main focus of the intervention was on fruit and vegetable intake as the childrens intake was far from meeting the FBDG on fruit and vegetables at baseline. SETTING Elementary schools in Reykjavik, Iceland. SUBJECTS Complete dietary records were available for 106 children both at baseline and follow-up. RESULTS Total fruit and vegetable intake increased by 47 % in the intervention schools (mean: 61.3 (sd 126.4) g/d) and decreased by 27 % in the control schools (mean: 46.5 (sd 105.3) g/d; P < 0.001). The majority of the children in the intervention schools did still not meet the FBDG on fruits and vegetables at follow-up. Fibre intake increased significantly in the intervention schools, as well as that of potassium, magnesium, beta-carotene and vitamin C (borderline). CONCLUSIONS The school-based intervention in 7-9-year-olds was effective in increasing fruit and vegetable intake, by 47 % increase from baseline, which was mirrored in nutrient intake.

Association between aerobic fitness, body composition, and physical activity in 9- and 15-year-olds

Abstract The aim of this study was to examine the interrelationship between aerobic fitness, body composition, and physical activity in 9- and 15-year-olds. The 270 participants were randomly selected from 18 primary and secondary schools in Iceland. Aerobic fitness was assessed by a graded exercise test on a bicycle ergometer. Body composition was estimated via: logarithm of sum of four skinfolds (loge skinfolds), waist adjusted for height, and body mass index (BMI). Physical activity was measured with Actigraph activity monitors using total activity each day as the physical activity variable. Aerobic fitness was chosen as the primary outcome variable, body composition as the secondary variable, and physical activity as the tertiary variable. All the full models explained a similar proportion of fitness variance for both age groups (45–65%). Among the 15-year-olds, loge skinfolds explained a significantly larger proportion of the fitness variance (54%) than waist adjusted for height (29%) and BMI (15%), but all the body composition variables explained a similar proportion of the fitness variance (35–42%) among the 9-year-olds. Physical activity explained a smaller proportion (0%) of the unadjusted variance in fitness for the 9-year-olds than for the 15-year-olds (19%). This group difference became non-significant (0% vs. 4%) when adjusting for loge skinfolds but remained significant when controlling for waist adjusted for height (0% vs. 15%) and BMI (0% vs. 18%). Gender differences in aerobic fitness after puberty can largely be explained by gender differences in loge skinfolds and physical activity. In conclusion, the interrelationship between fitness, body composition, physical activity, and gender is not the same among 9- and 15-year-olds.

Result of school-based intervention on cardiovascular risk factors

Abstract Objective. To assess the effectiveness of a two-year school-based intervention, consisting of integrated and replicable physical activity and nutritional education on weight, fat percentage, cardiovascular risk factors, and blood pressure. Design and setting. Six elementary schools in Reykjavik were randomly assigned to be either intervention (n = 3) or control (n = 3) schools. Seven-year-old children in the second grade in these schools were invited to participate (n = 321); 268 (83%) underwent some or all of the measurements. These 286 children were followed up for two years. Intervention. Children in intervention schools participated in an integrated and replicable physical activity programme, increasing to approximately 60 minutes of physical activity during school in the second year of intervention. Furthermore, they received special information about nutrition, and parents, teachers, and school food service staff were all involved in the intervention. Subjects. 321seven-year-old schoolchildren. Main outcome measures. Blood pressure, obesity, percentage of body fat, lipid profile, fasting insulin. Results. Children in the intervention group had a 2.3 mmHg increase in systolic blood pressure (SBP) and a 2.9 mmHg increase in diastolic blood pressure (DBP) over the two-year intervention period, while children in the control group increased SBP by 6.7 mmHg and DPB by 8.4 mmHg. These changes were not statistically significant. Furthermore there were no significant changes in percentage body fat, lipid profile, or fasting insulin between the intervention and control schools. Conclusion. A two-year school-based intervention with increased physical activity and healthy diet did not have a significant effect on common cardiovascular risk factors.

Association of BMI and fasting insulin with cardiovascular disease risk factors in seven-year-old Icelandic children

Objective. To look at overweight and common cardiovascular disease (CVD) risk factors, and associations with body mass index (BMI) and fasting insulin in seven-year-old schoolchildren in Reykjavik, Iceland. Study design. Cross-sectional study of seven-year-old schoolchildren. Setting. Six elementary schools in Reykjavik. Subjects. All children attending second grade in these six schools were invited to participate. Main outcome measures. Overweight, fasting serum insulin, CVD risk factors. Results. Some 14% of the participating children were classified as overweight. Overweight children had higher fasting insulin, higher fasting glucose, and higher systolic and diastolic blood pressure. Furthermore, they had significantly lower total cholesterol (TC), lower high-density lipoprotein (HDL), and lower low-density lipoprotein (LDL) but a similar TC/LDL ratio to normal-weight children. The factors that were strongly associated with BMI were serum fasting insulin, systolic blood pressure (SBP), HDL and fasting glucose, while the sum of four skinfolds, triglycerides, glucose, and LDL were highly associated with fasting insulin. Conclusion. Overweight children are likelier to have unfavourable levels of common CVD risk factors included in metabolic syndrome, but surprisingly had lower LDL and TC. Skinfold thickness, higher triglyceride and glucose levels, and being female were associated with increased serum insulin.