Rhonda C. Bell

How many steps/day are enough? For older adults and special populations

Older adults and special populations (living with disability and/or chronic illness that may limit mobility and/or physical endurance) can benefit from practicing a more physically active lifestyle, typically by increasing ambulatory activity. Step counting devices (accelerometers and pedometers) offer an opportunity to monitor daily ambulatory activity; however, an appropriate translation of public health guidelines in terms of steps/day is unknown. Therefore this review was conducted to translate public health recommendations in terms of steps/day. Normative data indicates that 1) healthy older adults average 2,000-9,000 steps/day, and 2) special populations average 1,200-8,800 steps/day. Pedometer-based interventions in older adults and special populations elicit a weighted increase of approximately 775 steps/day (or an effect size of 0.26) and 2,215 steps/day (or an effect size of 0.67), respectively. There is no evidence to inform a moderate intensity cadence (i.e., steps/minute) in older adults at this time. However, using the adult cadence of 100 steps/minute to demark the lower end of an absolutely-defined moderate intensity (i.e., 3 METs), and multiplying this by 30 minutes produces a reasonable heuristic (i.e., guiding) value of 3,000 steps. However, this cadence may be unattainable in some frail/diseased populations. Regardless, to truly translate public health guidelines, these steps should be taken over and above activities performed in the course of daily living, be of at least moderate intensity accumulated in minimally 10 minute bouts, and add up to at least 150 minutes over the week. Considering a daily background of 5,000 steps/day (which may actually be too high for some older adults and/or special populations), a computed translation approximates 8,000 steps on days that include a target of achieving 30 minutes of moderate-to-vigorous physical activity (MVPA), and approximately 7,100 steps/day if averaged over a week. Measured directly and including these background activities, the evidence suggests that 30 minutes of daily MVPA accumulated in addition to habitual daily activities in healthy older adults is equivalent to taking approximately 7,000-10,000 steps/day. Those living with disability and/or chronic illness (that limits mobility and or/physical endurance) display lower levels of background daily activity, and this will affect whole-day estimates of recommended physical activity.

Controlled outcome evaluation of the First Step Program: a daily physical activity intervention for individuals with type II diabetes

OBJECTIVE: To conduct a randomised trial of a physical activity (PA) intervention, The First Step Program (FSP) for adults with type II diabetes.DESIGN: A 16-week intervention study and 24-week follow-up assessment.PARTICIPANTS: A total of 47 overweight/obese, sedentary individuals (age=52.7±5.2 y; BMI=33.3±5.6 kg/m2) recruited through a diabetes education centre.MEASUREMENTS: Primary outcome: daily PA assessed by pedometer (steps/day). Secondary outcomes: anthropometric measures (weight, BMI, waist girth, hip girth); indicators of cardiovascular health (resting heart rate and blood pressure); glycemic control (fasting glucose, insulin, HbA1c, glucose concentration 120 min postglucose load); plasma lipid status (total cholesterol, HDL cholesterol, LDL cholesterol, and triglycerides).RESULTS: Relative to the CONTROL group, FSP participants increased their PA >3000 steps/day (approximately 30 min/day) during the intervention (P<0.0001). Waist and hip girth decreased (approximately 2–3 cm), but did not differ significantly between groups. Significant changes did not emerge for any of the other variables.CONCLUSIONS: The FSP is a practical intervention that elicits an immediate and profound change in walking behaviour. Such change is an important ‘first step’ towards increasing the volume and/or intensity of PA necessary to improve long-term health outcomes in this largely sedentary and overweight or obese population. Relapse by 24 weeks indicates that other strategies such as booster sessions are needed to maintain lifestyle change. Further research must determine realistic and responsive health outcomes for this population that are achievable through practical, real-world programming.

Supplementation of the Diet with High-Viscosity Beta-Glucan Results in Enrichment for Lactobacilli in the Rat Cecum

ABSTRACT BBn (BioBreeding) rats were fed casein-based diets supplemented with barley flour, oatmeal flour, cellulose, or barley β-glucans of high [HV] or low viscosity [LV] in order to measure the prebiotic effects of these different sources of dietary fiber. The dietary impact on the composition of the cecal microbiota was determined by the generation of denaturing gradient gel electrophoresis (DGGE) profiles of PCR-amplified 16S rRNA gene sequences. The DGGE profiles produced from the cecal microbiota of rats within each dietary group were similar, but consensus profiles generated from pooled bacterial DNAs showed differences between rat groups. Animals fed HV glucans (HV-fed rats) had DGGE consensus profiles that were 30% dissimilar from those of the other rat groups. A 16S rRNA gene fragment that was more conspicuous in the profiles of HV-fed animals than in those of cellulose-fed rats had sequence identity with Lactobacillus acidophilus. Measurements of L. acidophilus rRNA abundance (DNA-RNA hybridization), the preparation of cloned 16S rRNA gene libraries, and the enumeration of Lactobacillus cells (fluorescent in situ hybridization) showed that lactobacilli formed a greater proportion of the cecal microbiota in HV-fed rats. In vitro experiments confirmed that some lactobacilli utilize oligosaccharides (degree of polymerization, 3 or 4) present in β-glucan hydrolysates. The results of this study have relevance to the use of purified β-glucan products as dietary supplements for human consumption.

Time course of high-fat diet-induced reductions in adipose tissue mitochondrial proteins: potential mechanisms and the relationship to glucose intolerance

Increasing evidence suggests that reduced adipose tissue mitochondrial content is associated with the pathogenesis of type 2 diabetes. These investigations have utilized severely insulin-resistant rodent models. Thus, it is difficult to ascertain the potential mechanisms that initiate these changes and whether reductions in adipose mitochondria are an initiating event in the development of impaired glucose homeostasis. Thus, we sought to determine the time course of high-fat diet-induced reductions of mitochondrial content in epididymal adipose tissue in relation to changes in purported mediators of mitochondrial biogenesis and the development of impaired glucose homeostasis. Male Wistar rats were fed a high-fat diet ( approximately 59% of kcals from fat) for 2, 4, or 6 wk. Six weeks of high-fat feeding resulted in reductions in CORE I, COX IV, cytochrome c, HSP60, relative mtDNA copy number, and PGC-1alpha expression. These changes were not associated with decreases in eNOS and AMPK or increases in markers of oxidative stress. Interestingly, ex vivo treatment of adipose tissue cultures with palmitate led to decreases in PGC-1alpha expression and COX IV and CORE I protein content as observed in vivo. Thus, the high-fat diet-induced reductions in adipose tissue mitochondrial proteins may be mediated by increases in plasma fatty acids. Importantly, reductions in adipose tissue mitochondrial content occurred after the development of impaired glucose homeostasis. Thus, reductions in adipose tissue mitochondrial proteins are most likely not a causal event in the development of impaired glucose homeostasis.

Pedometer-determined ambulatory activity in individuals with type 2 diabetes

This cross-sectional study presents the first normative data on pedometer-determined ambulatory activity, defined as steps/day, in 160 (98 males, 62 females; age=52.4 +/- 5.3 years; BMI=32.3 +/- 5.7) free-living individuals with type 2 diabetes. Participants took 6662 +/- 3077 steps per day, less than that reported in nondiabetic samples and more than that reported for samples living with more restrictive chronic conditions including claudication, joint replacement, chronic obstructive lung disease, and chronic heart failure. Steps/day and BMI were inversely and significantly correlated (r=-0.27, P<0.01). Further, there was a significant difference between BMI categories (from normal weight to obesity class III) with regard to steps/day (F=2.96, P<0.05). The difference was most apparent between the highest obesity classes (II and III) and normal weight categories. This data is useful for sample comparison purposes. In addition the standard deviation or variance estimates can be used to calculate samples sizes for intervention efforts. Objective quantification of ambulatory activity via simple and inexpensive pedometers permits researchers and practitioners to easily screen for level of activity along a continuum. This study opens the door for future research and clinical applications including identifying threshold values related to important health outcomes and evaluating incremental change due to various interventions in this population.

A modified high-fat diet induces insulin resistance in rat skeletal muscle but not adipocytes.

We hypothesized that variation in dietary fatty acid composition in rats fed a high-fat diet had tissue-specific effects on glucose uptake sufficient to maintain normal glucose tolerance. Rats were fed one of three diets for 3 wk. The isocaloric high-fat-mixed oil (HF-mixed) diet and the high-fat-safflower oil (HF-saff) diet both provided 60% kcal fat, but fat composition differed [HF-mixed = saturated, polyunsaturated (n-3 and n-6), and monounsaturated fatty acids; HF-saff = polyunsaturated fatty acids (mainly n-6)]. The control diet was high carbohydrate (HCHO, 10% kcal fat). Insulin-stimulated 3-O-methylglucose uptake into perfused hindlimb muscles was reduced in rats fed HF-saff and HF-mixed diets compared with those fed HCHO diet (P < 0.02). Basal uptake increased in HF-saff- and HF-mixed-fed rats vs. HCHO-fed rats (P < 0.04). In adipocytes, HF-saff feeding decreased 2-deoxyglucose uptake vs. HF-mixed feeding and HCHO feeding (P < 0.05), but 2-deoxyglucose uptake in HF-mixed-fed rats did not differ from that in HCHO-fed rats (P > 0.05). Glucose tolerance was significantly reduced in HF-saff-fed rats but was unaffected by the HF-mixed diet. Therefore, in skeletal muscle of rats, 1) feeding a diet high in fat induces a reduction in insulin-stimulated glucose uptake but 2) provides an increase in basal glucose uptake. In contrast, 3) in adipocytes, insulin-stimulated glucose transport is reduced only when the high-fat diet is high in n-6 polyunsaturated fatty acids but not when fat comes from these mixed sources. Glucose intolerance becomes evident when insulin resistance is seen in multiple tissues.

Preliminary outcome evaluation of the First Step Program: a daily physical activity intervention for individuals with type 2 diabetes

The First Step Program uses simple and inexpensive pedometers to incrementally increase walking behaviors in sedentary individuals with type 2 diabetes. The pilot sample consisted of nine individuals (six women, three men; group mean age 53+/-6; group mean body mass index=32.9+/-3.4kg/m(2)). A timed self-paced walk while wearing the pedometer allowed for the conversion of changes in pedometer steps per day to time in minutes per day. There was an immediate and dramatic increase in walking behavior (an average of 34.3min of walking a day) that was sustained even 2 months post-intervention and after withdrawal of contact (an average of 22.6min of walking a day). Improvements in other outcomes (systolic blood pressure and waist girth) support a valid change in behavior. Although preliminary, these results warrant further investigation of such approaches.

The Alberta Pregnancy Outcomes and Nutrition (APrON) cohort study: rationale and methods

The Alberta Pregnancy Outcomes and Nutrition (APrON) study is an ongoing prospective cohort study that recruits pregnant women early in pregnancy and, as of 2012, is following up their infants to 3 years of age. It has currently enrolled approximately 5000 Canadians (2000 pregnant women, their offspring and many of their partners). The primary aims of the APrON study were to determine the relationships between maternal nutrient intake and status, before, during and after gestation, and (1) maternal mood; (2) birth and obstetric outcomes; and (3) infant neurodevelopment. We have collected comprehensive maternal nutrition, anthropometric, biological and mental health data at multiple points in the pregnancy and the post-partum period, as well as obstetrical, birth, health and neurodevelopmental outcomes of these pregnancies. The study continues to follow the infants through to 36 months of age. The current report describes the study design and methods, and findings of some pilot work. The APrON study is a significant resource with opportunities for collaboration.

Maternal nutrient restriction during pregnancy differentially alters the unfolded protein response in adipose and renal tissue of obese juvenile offspring

Maternal diet during pregnancy can program an offsprings risk of disease in later life. Obesity adversely alters renal and adipose tissue function, resulting in chronic kidney disease and insulin resistance, respectively, the latter associated with dysregulation of the unfolded protein response (UPR). In view of the current obesity epidemic, we explored the combined effects of in utero early‐ to midgestational nutrient restriction and postnatal obesity on the UPR in ovine juvenile offspring. Nutrient restriction was coincident with fetal kidney development but prior to exponential adipose tissue deposition. Nutrient restricted (NR) and normal diet (control) offspring were exposed to an obesogenic environment throughout adolescence, resulting in similar degrees of juvenile obesity. NR offspring showed enhanced adipose tissue dysregulation characterized by activation of the UPR, perturbed insulin signaling, and marked inflammation, as demonstrated by increased abundance of crownlike structures and proinflammatory genes. Conversely, in renal tissue NR offspring had marked attenuation of cellular stress and inflammation evident as reduced activation of the UPR, down‐regulation of proinflammatory genes, and less histological damage. In conclusion, obesity‐related activation of the UPR can be determined by the in utero nutritional environment, demonstrating organ‐specific effects dependent on the developmental phase targeted within the fetus.— Sharkey, D., Gardner, D. S., Fainberg, H. P., Sebert, S., Bos, P., Wilson, V., Bell, R., Symonds, M. E., Budge, H. Maternal nutrient restriction during pregnancy differentially alters the unfolded protein re‐sponse in adipose and renal tissue of obese juvenile offspring. FASEBJ. 23, 1314–1324 (2009)

β-Glucan extracts inhibit the in vitro intestinal uptake of long-chain fatty acids and cholesterol and down-regulate genes involved in lipogenesis and lipid transport in rats

BACKGROUND Dietary fiber reduces the intestinal absorption of nutrients and the blood concentrations of cholesterol and triglycerides. AIM We wished to test the hypothesis that high-viscosity (HV) and low-viscosity preparations of barley and oat beta-glucan modify the expression of selected genes of lipid-binding proteins in the intestinal mucosa and reduce the intestinal in vitro uptake of lipids. METHODS Five different beta-glucan extracts were separately added to test solutions at concentrations of 0.1-0.5% (wt/wt), and the in vitro intestinal uptake of lipids into the intestine of rats was assessed. An intestinal cell line was used to determine the effect of beta-glucan extracts on the expression of intestinal genes involved in lipid metabolism and fatty acid transport. RESULTS All extracts reduced the uptake of 18:2 when the effective resistance of the unstirred water layer was high. When the unstirred layer resistance was low, the HV oat beta-glucan extract reduced jejunal 18:2 uptake, while most extracts reduced ileal 18:2 uptake. Ileal 18:0 uptake was reduced by the HV barley extract, while both jejunal and ileal cholesterol uptakes were reduced by the medium-purity HV barley extract. The inhibitory effect of HV barley beta-glucan on 18:0 and 18:2 uptake was more pronounced at higher fatty acid concentrations. The expression of genes involved in fatty acid synthesis and cholesterol metabolism was down-regulated with the HV beta-glucan extracts. beta-Glucan extracts also reduced intestinal fatty-acid-binding protein and fatty acid transport protein 4 mRNA. CONCLUSIONS The reduced intestinal fatty acid uptake observed with beta-glucan is associated with inhibition of genes regulating intestinal uptake and synthesis of lipids. The inhibitory effect of beta-glucan on intestinal lipid uptake raises the possibility of their selective use to reduce their intestinal absorption.