David E. Laaksonen

Sedentary lifestyle, poor cardiorespiratory fitness, and the metabolic syndrome

PURPOSE The cross-sectional associations of leisure-time physical activity (LTPA) and cardiorespiratory fitness with the metabolic syndrome (MS) were investigated in a population-based sample of 1069 middle-aged men without diabetes, cardiovascular disease, or cancer. METHODS LTPA was assessed using a detailed quantitative questionnaire. Maximal oxygen uptake VO(2max) and core and related features of the MS were determined. A modified World Health Organization definition of the MS and factor analysis were used. RESULTS Men who engaged in at least moderate-intensity (>or=4.5 metabolic equivalents) LTPA <1.0 h.wk-1 were 60% more likely to have the MS than those engaging in >or= 3.0 h.wk-1 even after adjustment for confounders. Low-intensity (<4.5 metabolic equivalents) LTPA was not associated with the metabolic syndrome. Men with a VO(2max) <29.1 mL x kg-1 x min-1 were almost seven times more likely to have the MS than those with a VO(2max) >or=35.5 mL.kg-1.min-1 even after adjusting for confounders. In first-order factor analysis using a promax rotation, the principal factor explained 20% of total variance and had heavy loadings for VO(2max) (-0.57) and at least moderate-intensity LTPA (-0.44), and moderate or heavy loadings for the main components of the MS. The second-order factor analysis generated a principal factor that was strongly loaded on by the main components of the MS and VO(2max) (-0.50) but not LTPA. CONCLUSION A sedentary lifestyle and especially poor cardiorespiratory fitness are not only associated with the MS but could also be considered features of the MS. Measurement of VO(2max) in sedentary men with risk factors may provide an efficient means for targeting individuals who would benefit from interventions to prevent the MS and its consequences.

Back and hip extensor fatigability in chronic low back pain patients and controls

OBJECTIVE To compare the lumbar paraspinal and gluteus maximus muscle fatigability between chronic low back pain patients and healthy controls by using electromyographic (EMG) spectral analysis during a maximal isometric endurance task. DESIGN A cross-sectional comparative study between chronic low back pain patients and healthy control subjects. SETTING Physical medicine and rehabilitation clinic in Finland. SUBJECTS Twenty women with nonspecific chronic low back pain (longer than 3 months) and 15 healthy controls. INTERVENTION Subjects performed maximal voluntary isometric back extensions (MVC) at 30 degrees forward flexion in a specially designed measurement unit. A 50% MVC load was used in isometric endurance test. OUTCOME MEASURES Low back pain intensity was assessed by using the visual analogue scale and functional disability by the Oswestry disability index. Time to endurance was measured. Bipolar surface EMG recordings were made over the lumbar paraspinal muscles (L3-L4, L5-S1) and over the gluteus maximus muscles. Average EMG (aEMG%), and initial spectral median frequency (MFinit) and change over time (MFslope) were computed. RESULTS Pain intensity and functional disability were higher and MVC and time to endurance were lower in the chronic low back pain group (p < .05). Similar muscle activity levels (aEMG%) and MFinit indicated similar muscle loading in both groups at the beginning of the endurance test. EMG spectral decreases (MFslope) indicated that lumbar paraspinal muscle fatigability was similar in both groups. In the chronic low back pain group, the gluteus maximus fatigued faster than in the control group (greater MFslope, p < .05). However, the shorter endurance time indicated greater fatigability in the chronic low back pain group in general (p < .05). CONCLUSIONS The chronic low back pain patients were weaker and fatigued faster than the healthy controls. The EMG fatigue analysis results suggest that the gluteus maximus muscles are more fatigable in chronic low back pain patients than in healthy control subjects during a sustained back extension endurance test.

Dietary fatty acids and cardiovascular disease: an epidemiological approach.

The quality of dietary fat in relation to cardiovascular disease forms the basis of the diet-heart hypothesis. Current recommendations on dietary fat now emphasise quality rather than quantity. The focus of this review is to summarise the results from prospective cohort studies on dietary fat and cardiovascular disease outcomes. Relatively few prospective cohort studies have found an association between dietary fat quality and cardiovascular disease, partly because of limitations in estimating dietary intake. Saturated and trans fatty acids have increased cardiovascular risk in several studies. Both n-6 and n-3 polyunsaturated fatty acids have been associated with lower cardiovascular risk. Within the n-6 series, linoleic acid seems to decrease cardiovascular risk. Within the n-3 series the long-chain fatty acids (eicosapentaenoic and docosahexaenoic acids) are associated with decreased risk for especially fatal coronary outcomes, whereas the role of alpha-linolenic acid is less clear. Dietary fat quality also influences the activity of enzymes involved in the desaturation of fatty acids in the body. Serum desaturase indices have been consistently associated with adverse cardiovascular outcomes. Data from metabolic and clinical studies reinforce findings from observational studies supporting recommendations to replace saturated and trans fat with unsaturated fat in the prevention of cardiovascular disease.

Metabolic Syndrome and the Risk of Stroke in Middle-Aged Men

Background and Purpose— The metabolic syndrome, a clustering of disturbed glucose and insulin metabolism, obesity and abdominal fat distribution, dyslipidemia, and hypertension is associated with cardiovascular diseases. The aim of this study was to examine the relationship of metabolic syndrome, as defined by National Cholesterol Education Program (NCEP) and World Health Organization (WHO) criteria, with the risk for stroke. Methods— Population-based cohort study with an average follow-up of 14.3 years from eastern Finland. A total of 1131 men with no history of cardiovascular disease and diabetes at baseline participated. Sixty-five strokes occurred, of which 47 were ischemic strokes. Results— Men with the metabolic syndrome as defined by the NCEP criteria had a 2.05-fold (95% CI, 1.03 to 4.11; P=0.042) risk for all strokes and 2.41-fold (95% CI, 1.12 to 5.32; P=0.025) risk for ischemic stroke, after adjusting for socioeconomic status, smoking, alcohol, and family history of coronary heart disease. Additional adjustment for ischemic changes during exercise test, serum low-density lipoprotein cholesterol, plasma fibrinogen, energy intake for saturated fats, energy expenditure of leisure time physical activity, and white blood cell count, the results remained significant. The risk ratios among men with metabolic syndrome as defined by the WHO criteria were 1.82 (95% CI, 1.01 to 3.26; P=0.046) for all strokes and 2.16 (95% CI, 1.11 to 4.19; P=0.022) for ischemic stroke. After further adjustment, the respective risks were 2.08 (95% CI, 1.12 to 3.87; P=0.020) and 2.47 (95% CI, 1.21 to 5.07; P=0.013). Conclusion— The risk of any stroke is increased in men with metabolic syndrome, in the absence of stroke, diabetes and cardiovascular disease at baseline. Prevention of the metabolic syndrome presents a great challenge for clinicians with respect to stroke.

Viscosity of Oat Bran-Enriched Beverages Influences Gastrointestinal Hormonal Responses in Healthy Humans

Viscous fibers, including beta-glucan in oat bran, favorably affect satiety as well as postprandial carbohydrate and lipid metabolism. However, effects of fiber viscosity on modulation of satiety-related gut hormone responses are largely unknown. We examined the effects of modified oat bran, with or without its natural viscosity, on sensations of appetite and satiety-related gastrointestinal (GI) hormone responses to establish the relevance of viscosity of beta-glucan in oat bran. Twenty healthy, normal-weight participants (16 female, 4 male, aged 22.6 +/- 0.7 y) ingested 2 isocaloric (1250 kJ) 300-mL oat bran beverages with low or high viscosity (carbohydrates, 57.9 g; protein, 7.8 g; fat, 3.3 g; fiber, 10.2 g) after a 12-h fast in randomized order. Viscosity of the low-viscosity oat bran beverage was reduced by beta-glucanase treatment. Blood samples were drawn before and 15, 30, 45, 60, 90, 120, and 180 min after beverage consumption. The oat bran beverage with low viscosity induced a greater postprandial increase in satiety (P = 0.048) and plasma glucose (P < 0.001), insulin (P = 0.008), cholecystokinin (P = 0.035), glucagon-like peptide 1 (P = 0.037), and peptide YY (P = 0.051) and a greater decrease in postprandial ghrelin (P = 0.009) than the beverage with high-viscosity oat bran. Gastric emptying as measured by paracetamol absorption was also faster (P = 0.034) after low-viscosity oat bran beverage consumption. In conclusion, viscosity differences in oat beta-glucan in a liquid meal with identical chemical composition strongly influenced not only glucose and insulin responses, but also short-term gut hormone responses, implying the importance of food structure in the modulation of postprandial satiety-related physiology.

Serum fatty acid composition predicts development of impaired fasting glycaemia and diabetes in middle-aged men.

Aims Dietary fatty acid intake is reflected in serum fatty acid composition. Studies prospectively investigating serum fatty acids and development of impaired fasting glycaemia (IFG) or diabetes mellitus (DM) are largely lacking. We assessed the association of serum fatty acid composition with development of IFG or DM.

Age, sex, and body mass index as determinants of back and hip extensor fatigue in the isometric Sørensen back endurance test

OBJECTIVE To study the ability of a widely used isometric back endurance test to measure lumbar back erector muscle fatigue and to assess the influence of age, sex, and body mass index (BMI) on back and hip extensor muscle fatigability (EMG spectral indices). DESIGN Cross-sectional study of men and women without back problems. SETTING Occupational health center and rehabilitation clinic in Finland. SUBJECTS Experiment 1 consisted of 233 consecutive occupational health center customers (133 women, 100 men) without back problems. Experiment 2 consisted of 20 healthy women. INTERVENTION Subjects performed the isometric Sørensen back endurance test up to 240sec in experiment 1 and to the limit of endurance in experiment 2. OUTCOME MEASURES Raw surface EMG was recorded bilaterally over the belly of lumbar erector spinae muscles at L1-L2 and L4-L5 levels in experiment 1, and bilaterally over the medial paraspinal muscles at L1-L2, L3-L4, and L5-S1 levels and over the major hip extensor muscles (gluteus maximus and biceps femoris) in experiment 2. In both experiments, time to endurance was recorded (in experiment 1 up to 240sec). The EMG spectral median frequency (MF) decrease over time was used for the assessment of back and hip extensor fatigability. RESULTS In experiment 1, the rate of change in paraspinal MF was greater in men than in women, indicating greater paraspinal fatigability in men. Multiple regression analysis indicated that the rate of MF decrease (fatigue) during the test was dependent on age and BMI in both sexes and that the effects of age and BMI were more pronounced in women than in men. Correlation analysis revealed that the rate of paraspinal muscle MF decrease was associated with endurance time and BMI in women and with endurance time and age in men. In experiment 2, the paraspinal muscles, as well as the hip extensor muscles, biceps femoris, and gluteus maximus, showed clear decreases in MF during the isometric endurance test in women. MF decrease was highly related to endurance time and BMI in women. CONCLUSIONS Lumbar paraspinal muscle fatigability during the Sørensen test is influenced by subject characteristics. Further, the hip extensor muscles also significantly fatigue, indicating load sharing between back and hip extensor muscles during the test. According to these results, the validity of this widely used back endurance test in specifically measuring lumbar paraspinal muscle endurance is questionable, as is the direct comparison of test results between women and men.

Aerobic exercise and the lipid profile in type 1 diabetic men: a randomized controlled trial

PURPOSE Despite the potential importance of favorable changes in the lipid profile produced by aerobic exercise, training-induced lipid profile changes in atherosclerosis-prone type 1 diabetes mellitus (DM) have not heretofore been adequately addressed. METHODS We assessed the effect of a 12- to 16-wk aerobic exercise program on cardiorespiratory fitness and the lipid profile in young men with type 1 DM. Generally active men aged 20-40 yr with type 1 DM (N = 56) were randomized into training (N = 28) and control (untrained, N = 28) groups after baseline measurements. Training consisted of 30-60 min moderate-intensity running 3-5 times a week for 12-16 wk. RESULTS For the 42 men finishing the study, peak oxygen consumption (VO2 peak) increased significantly only in the trained group. Total and low-density lipoprotein (LDL) cholesterol and apolipoprotein (apo) B decreased and the high-density lipoprotein (HDL)/apo A-I ratio increased in the trained group. HDL and apo A-I increased in both groups. The exercise program brought about improvements in the HDL/LDL and apo A-I/apo B ratios and apo B and triglyceride levels when comparing the relative (%) changes in the trained versus control group. In the trained group, men with HDL/LDL ratios below the group median at baseline showed even more favorable changes in their lipid profile than those with higher initial HDL/LDL ratios. Body mass index, percent body fat and hemoglobin A1c did not change during the training period in either group. CONCLUSIONS Endurance training improved the lipid profile in already physically active type 1 diabetic men, independently of effects on body composition or glycemic control. The most favorable changes were in patients with low baseline HDL/LDL ratios, likely the group with the greatest benefit to be gained by such changes.

Epidemiology and treatment of the metabolic syndrome.

Recent definitions of the metabolic syndrome from the World Health Organization (WHO) and National Cholesterol Education Program (NCEP) have given us a clearer picture of the prevalence of the metabolic syndrome and the risks it poses for cardiovascular disease and type 2 diabetes. Solid epidemiological and trial evidence support lifestyle changes as the main modifiable risk factors, including abdominal obesity, sedentary lifestyle and a diet rich in saturated fat and low in fiber content, in the treatment of individual components of the metabolic syndrome. Physical activity may prevent the metabolic syndrome as defined by the WHO and NCEP, but the evidence for lifestyle changes using these definitions is still sparse. No trials on the treatment of the metabolic syndrome to prevent diabetes have been published. However, both the Finnish Diabetes Prevention Study and the Diabetes Prevention Program found that moderate lifestyle interventions in persons with impaired glucose tolerance, a condition related to the metabolic syndrome, decreased the incidence of type 2 diabetes by 58%. Some drugs may also prevent diabetes. Further research on lifestyle modifications in the prevention and treatment of the metabolic syndrome, and on how best to promote lifestyle changes, is needed. In the meantime, efforts to curb obesity and overweight, increase physical activity and improve compliance with current dietary recommendations should continue.

A Psyllium Fiber-Enriched Meal Strongly Attenuates Postprandial Gastrointestinal Peptide Release in Healthy Young Adults

Dietary fiber (DF) and protein are essential constituents of a healthy diet and are well known for their high satiety impact. However, little is known about their influence on postprandial gastrointestinal (GI) peptide release. Our aim in this single-blind, randomized, cross-over study was to investigate the effects of DF and/or protein enrichments on satiety-related metabolic and hormonal responses. Sixteen healthy, nonobese volunteers participated in the study and ingested 1 of 5 isoenergetic test meals in a randomized order on separate days. The test meals were as follows: 1) low in protein (2.8 g) and fiber (7.6 g); 2) low in protein (2.6 g) and high in soluble fiber (psyllium, 23.0 g); 3) high in protein (soy, 19.7 g) and low in fiber (6.2 g); 4) high in protein (18.4 g) and fiber (23.0 g); and 5) white wheat bread. Serum insulin and plasma glucose, ghrelin, glucagon-like peptide 1 (GLP-1), and peptide YY (PYY) concentrations were determined for 2 h following the meals. In addition, hunger and satiety ratings were collected. Postprandial glucose, insulin, ghrelin, GLP-1, and PYY responses all differed among the meals (P <or= 0.05). Fiber-enriched meals decreased glucose, insulin, ghrelin, and PYY responses; in addition, PYY secretion was prolonged compared with the other meals. The postprandial GLP-1 concentration was significantly suppressed after a fiber- and protein-rich meal, in contrast to the initial increases following the other meals. However, postprandial ratings of appetite were mostly similar after the test meals. In conclusion, solid meals enriched with psyllium fiber strongly modified postprandial signals arising from the GI tract.