Preferential loss of visceral fat following aerobic exercise, measured by magnetic resonance imaging

The aim of this study was to use whole-body magnetic resonance imaging (MRI) together with biochemical and anthropometric measurements to study the influence of regular moderate exercise with no dietary intervention on adipose tissue distribution in nonobese healthy women. We found significant decreases in both total (28.86+/-2.24 vs. 27.00+/-2.27 liters, P < 0.05) and regional fat depots (visceral fat: 1.68+/-0.21 vs. 1.26+/-0.18 liters, P < 0.01) using whole-body MRI despite no significant change in body weight, body mass index, or the waist-to-hip ratio. Interestingly, no changes in body fat content were found using anthropometry or impedance. There was a significant increase in high density lipoprotein cholesterol (1.58+/-0.06 vs. 1.66+/-0.08 mmol/L P < 0.02) following exercise although there were no changes in other blood lipids such as triglycerides. In summary, moderate aerobic exercise over a period of 6 mon resulted in a preferential loss in visceral fat in nonobese healthy women, and this may help to explain some of the health benefits associated with regular and moderate physical activity.

The relevance of the glycaemic index to our understanding of dietary carbohydrates

AIMS

To review the evidence for the importance of glycaemic index of dietary carbohydrate in disease prevention and control.

METHODS

A critical appraisal of the literature published in English between and cited on Medline between January 1966 and October 1999.

RESULTS

Using basic, intervention and epidemiological studies from experienced teams, evidence that the glycaemic index of diet may influence outcome in terms of cardiovascular risk, risk of metabolic syndrome diseases and pregnancy was found.

CONCLUSIONS

Consideration of glycaemic indices in making dietary recommendations may be expected to produce additional health benefit.

Role of mechanical power estimates in the O2 cost of walking in children with cerebral palsy

It has been established in able-bodied children that traditional biomechanical descriptors of gait such as stride length or stride frequency do not fully account for the differences seen in the energy cost of locomotion noted with age. Hence, measures of total body mechanical power output have been adopted to explain these differences.

PURPOSE

The aim of this study was to estimate the ability of this mechanical power calculation to explain the variability in the metabolic energy cost of treadmill walking in children with spastic cerebral palsy (CP).

METHODS

Thirteen subjects volunteered for the study. One group consisted of eight (6 male, 2 female) children with CP (age 12.2 +/- 2.7 yr). The second group consisted of five (4 male, 1 female) able-bodied controls (age 13.4 +/- 2.8 yr). The treadmill walking protocol consisted of one 4-min stage at 0% grade, 3 km x h(-1). Infrared markers were placed on 12 anatomical landmarks and data were collected using the OPTOTRAK motion analysis system over a 5-s time period during the last 30 s of the 4-min stage. On-line oxygen consumption VO2 measurements were obtained throughout using the Beckman Horizon Metabolic Cart.

RESULTS

Relative VO2 (mL x kg(-1) x min(-1)) was significantly (P < 0.05) different between the two groups (CP: 16.6 +/- 6.5 vs control: 10.2 +/- 1.2). Simple linear regression analysis demonstrated that mechanical power measurements, incorporating transfers of energy between and within adjacent body segments, accounted for 87.2% of the total variability noted in VO2 for the children with CP, compared with only 2.4% in the able-bodied subjects.

CONCLUSIONS

The results indicate that mechanical power differences explain the majority of the variability noted in VO2 in children with CP at a submaximal walking speed.

Glycaemic index as a determinant of serum HDL-cholesterol concentration

BACKGROUND

Diet influences the prevalence of coronary heart disease (CHD). Insulin sensitivity and concentrations of HDL cholesterol, two metabolic predictors of CHD, are also influenced by diet. Dietary carbohydrates with a high glycaemic index cause a high postprandial glucose and insulin response, and are associated with decreased insulin sensitivity and an increased risk of CHD. This study examined whether the glycaemic index of dietary carbohydrates is a determinant of serum HDL-cholesterol concentrations.

METHOD

Dietary, anthropometric, and biochemical data from the 1986-87 Survey of British Adults (n=2200) were reanalysed by a multiple regression model, which examined the relation between serum total cholesterol, HDL-cholesterol, and calculated LDL-cholesterol concentrations and various dietary characteristics, including the type of carbohydrate, the glycaemic index, and fat intake.

FINDINGS

Among the 1420 participants with complete data, there was a significant negative relation between serum HDL-cholesterol concentration and the glycaemic index of the diet for both men (regression coefficient -0.00724 [95% CI -0.0101 to -0.00434], p=0.02) and women (-0.01326 [-0.0162 to -0.0102], p<0.0001). No other significant relation was found with total cholesterol or LDL-cholesterol concentration or with any other dietary carbohydrate or fat constituent.

INTERPRETATION

In a cross-sectional study of middle-aged adults, the glycaemic index of the diet was the only dietary variable significantly related to serum HDL-cholesterol concentration. Thus, the glycaemic index of the diet is a stronger predictor than dietary fat intake of serum HDL-cholesterol concentration.

Effect of large bowel fermentation on insulin, glucose, free fatty acids, and glucagon-like peptide 1 (7-36) amide in patients with coronary heart disease

Insulin resistance syndrome has recently been described as a unifying hypothesis to explain the relationship between the many risk factors of coronary heart disease. Carbohydrate that is malabsorbed and fermented in the colon has been demonstrated to decrease insulin response to a glucose load and improve other risk factors associated with coronary heart disease, although the mechanism remains unclear. The object of the present study was to investigate whether this observation could be explained by the production of fermentation products induced by malabsorbed carbohydrate in the colon, or by stimulating the incretin glucagon-like peptide 1 (7-36) amide that is released from the large bowel. We used lactulose as a model for resistant starch carbohydrate. Ten insulin-resistant male volunteers, who had undergone previous coronary artery bypass grafting, volunteered to take part in the study and underwent 6 d of lactulose loading (15 g/d for 2 d and 30 g/d for 4 d). There was no significant change in insulin, glucose, free fatty acids, or glucagon-like peptide 1 (7-36) amide response to an oral glucose tolerance test following the lactulose despite a significant rise in breath hydrogen. Large bowel fermentation stimulated by lactulose appears to have no significant effect on insulin, glucose, free fatty acids, and glucagon-like peptide 1 (7-36) response in patients with coronary heart disease.

Magnetic resonance imaging of total body fat

In this study we assessed different magnetic resonance imaging (MRI) scanning regimes and examined some of the assumptions commonly made for measuring body fat content by MRI. Whole body MRI was used to quantify and study different body fat depots in 67 women. The whole body MRI results showed that there was a significant variation in the percentage of total internal, as well as visceral, adipose tissue across a range of adiposity, which could not be predicted from total body fat and/or subcutaneous fat. Furthermore, variation in the amount of total, subcutaneous, and visceral adipose tissue was not related to standard anthropometric measurements such as skinfold measurements, body mass index, and waist-to-hip ratio. Finally, we show for the first time subjects with a percent body fat close to the theoretical maximum (68%). This study demonstrates that the large variation in individual internal fat content cannot be predicted from either indirect methods or direct imaging techniques, such as MRI or computed tomography, on the basis of a single-slice sampling strategy.

Insulin sensitivity in women at risk of coronary heart disease and the effect of a low glycemic diet

The risk of coronary heart disease (CHD) is influenced by family history, insulin sensitivity (IS), and diet. Adiposity affects CHD and IS. The cellular mechanism of IS is thought to involve the adipocyte cytokine tumor necrosis factor-alpha (TNF-alpha). Insulin-stimulated glucose uptake in isolated subcutaneous and omental adipocytes obtained during elective surgery was measured in 61 premenopausal women, 24 with a parental history (PH) of CHD. In vivo IS was measured using the short insulin tolerance test (SITT) in 28 women, 16 with PH-CHD, before and 3 weeks after randomization to a low glycemic index (LGI) or high glycemic index (HGI) diet. In vitro adipocyte IS and TNF-alpha production was measured following dietary modification. On the habitual diet, in vitro insulin-stimulated glucose uptake in adipocytes as a percentage increase over basal was less in women with PH-CHD than in those without it (presented as the median with 95% confidence limits: subcutaneous, 28% (17% to 39%) v 96% (70% to 120%), P < .01); omental, 40% (28% to 52%) v 113% (83% to 143%), P < .01). In vivo IS in 16 PH-CHD subjects and 12 controls before dietary randomization was similar, and increased in both groups consuming a LGI versus HGI diet (PH-CHD, 0.31 (0.26 to 0.37) v 0.14 (0.10 to 0.24) mmol/L/min, P < .01; controls, 0.31 (0.1 to 0.53) v 0.15 (0.06 to 0.23) mmol/L/min, P < .05). Adipocyte IS was greater in PH-CHD women on a LGI versus HGI diet (subcutaneous, 50% (20% to 98%) v 13% (1% to 29%); omental, 97% (47% to 184%) v 29% (4% to 84%), P < .05). Adipocyte TNF-alpha production was higher in women with versus without PH-CHD (subcutaneous, 0.3 (0.18 to 0.42) v 0.93 (0.39 to 1.30) ng/mL/min; visceral, 0.22 (0.15 to 1.30) v 0.64 (0.24 to 1.1) ng/mL/min, P < .04, respectively), but was uninfluenced by the dietary glycemic index. We conclude that in vitro adipocyte IS is reduced and adipocyte TNF-alpha production is increased in premenopausal women with PH-CHD. A LGI diet improves both adipocyte IS in women with PH-CHD and in vivo IS in women with and without PH-CHD.

Hyaluronan is a prerequisite for ductal branching morphogenesis

Hyaluronan, a macromolecular carbohydrate polymer of the extracellular matrix is prominent early in embryogenesis, coinciding with rapid tissue growth. CD44, the predominant receptor for hyaluronan on vertebrate cells, is a variably expressed transmembrane glycoprotein. Mouse anterior prostate glands obtained at various postnatal time points were examined for the expression of hyaluronan and CD44. Reverse transcriptase polymerase chain reaction analysis was used to map the temporal regulation of specific CD44 variant isoforms. In each age group, hyaluronan was localized exclusively in the stromal matrix. Hyaluronan was greatly reduced in the later ages and was entirely absent around the developmentally quiescent proximal regions of the ducts. Early in prostate development, CD44 was prominent in the mesenchyme. However, in the later phases, CD44 expression became associated with membranes of epithelial cells. The role of hyaluronan-CD44 interactions in ductal branching morphogenesis was studied by serum-free organ culture of mouse anterior prostate. In the presence of optimal levels of testosterone, the organs underwent ductal branching morphogenesis. Treatment with either neutralizing anti-CD44 antibodies, hyaluronan hexasaccharides or the enzyme hyaluronidase inhibited androgen-stimulated ductal branching morphogenesis. These results are suggestive of the significant role played by hyaluronan-CD44 interactions in mediating androgen-induced prostatic growth and morphogenesis.

Changes in adipose tissue composition in malnourished patients before and after liver transplantation: a carbon-13 magnetic resonance spectroscopy and gas-liquid chromatography study

We investigated adipose tissue fatty acid composition in 22 moderately to severely malnourished patients with cirrhosis and in 22 healthy volunteers by in vivo carbon-13 magnetic resonance spectroscopy (MRS). Gas-liquid chromatography (GLC) of adipose tissue samples was also performed in 11 of the patients and in 4 volunteers. In vivo 13C magnetic resonance spectra were obtained from the subcutaneous adipose tissue before and after eight weeks following orthotopic liver transplantation (OLT). Adipose tissue biopsy samples were obtained for GLC analysis at the time of transplantation in the patients and at inguinal hernia repair in the 4 volunteers. No significant differences were found in the subcutaneous adipose tissue total-saturated, -polyunsaturated or -monounsaturated fatty acid composition between patients and healthy volunteers by in vivo 13C MRS. GLC analysis of adipose tissue samples confirmed that total levels of saturated, poly-, and monounsaturated fatty acids remained the same but revealed significant differences in levels of individual fatty acids, particularly n-3 fatty acids (total n-3, cirrhotics: .84% +/- .07% vs. controls: 1.36% +/- .13%, P < .01). Eight weeks following transplantation, recipients showed a considerable increase in body mass (pretransplantation: 59.3 +/- 3.2 vs. posttransplantation: 63.2 +/- 3 kg, P < .01). 13C MRS revealed a significant increase in saturated fatty acids (pretransplantation: 21.6 +/- 2.8 vs. posttransplantation: 25.5% +/- 1.2%, P < .05) and a significant decrease in unsaturated fatty acids. The application of noninvasive MRS techniques may be important to identify the differential uptake of fats, examining both specific fatty acids and different body fat compartments. In the future, this may be useful in optimizing the dietary management of severely malnourished patients with chronic liver disease before liver transplantation.

Cocontraction and phasic activity during GAIT in children with cerebral palsy

Simultaneous activity of agonist and antagonistic muscles during a task is known as cocontraction. The primary aim of the present study was to use a cocontraction index (CI) to quantify differences in EMG activity between a group of CP and control children at two different walking speeds. The secondary aim was to compare the amount of time the muscles were activated ("on" thresholds) between the groups. Seventeen subjects volunteered for the study. One group consisted of 9 (7M, 2F) children with CP (age 12.7 +/- 2.8 years, mean +/- SD). The second group consisted of 8 able-bodied controls (7M, 1F). The discontinuous submaximal treadmill walking protocol had two 4min stages at 0% gradient. Speeds selected were 3 km.h-1 and 90% of the pre-determined fastest walking speed (FWS). Two sites of CI were measured from the EMGs of tibialis anterior and soleus (leg) and vastus lateralis and hamstrings (thigh). Significantly (p < 0.05) higher CI values were noted for the CP subjects compared to the controls, irrespective of speed or cocontraction site and there was a significant (p < 0.05) increase in CI values with increased walking speed for both CP and control subjects. Phasic analyses for 5% max EMG and 10% max EMG "on" thresholds demonstrated significant (p < 0.05) main effects for group (CP subjects had a longer time period of muscle activation than controls) and speed (muscles were active longer at 90% FWS than 3 km.h-1). The precise mechanisms by which cocontraction contributes toward abnormal gait and wasted mechanical energy require further research incorporating both electromyographic and kinematic analysis.

Role of cocontraction in the O2 cost of walking in children with cerebral palsy

A major movement related limitation for children with spastic cerebral palsy (CP) is the compromised gait pattern, which may explain their excessive energy cost of locomotion. The aims of this study were to determine differences in the O2 cost of locomotion between children with CP (7 males, 2 females; 12.7 +/- 2.8 yr) and able-bodied controls (7 male, 1 female; 13.6 +/- 2.1 yr) and to assess the contribution that cocontraction of agonist and antagonist muscles had upon the elevated O2 cost seen in children with CP versus able-bodied controls. The treadmill submaximal walking protocol consisted of 2 x 4 min intermittent stages at 3 km.h-1 and 90% of the predetermined fastest walking speed (FWS) at 0% grade. Electromyographic data were collected during the final minute of each bout from vastus lateralis and hamstrings (thigh) and tibialis anterior and soleus (lower leg). Significant (P < 0.05) differences were noted at 3 km.h-1 for mass-relative VO2. (CP: 16.6 +/- 6.5 vs control: 10.2 +/- 1.2 ml.kg-1.min-1), % VO2max (CP: 53.5 +/- 26.0 vs

CONTROL

22.5 +/- 4.93) and heart rate (CP: 143 +/- 41 vs

CONTROL

91 +/- 14 beats.min-1). Thigh and lower leg muscle cocontraction accounted for 51.4% and 42.8%, respectively, of the variability in VO2 for the subjects with CP at 3 km.h-1. These results suggest that cocontraction is a major factor responsible for the higher energy cost of walking seen in children with CP.

The effect of low-glycemic carbohydrate on insulin and glucose response in vivo and in vitro in patients with coronary heart disease

The insulin resistance syndrome has recently been implicated in the etiology of coronary heart disease, with a possible metabolic defect at the level of the adipocyte. We report the effects of a low- versus high-glycemic-index (LGI and HGI, respectively) diet on insulin and glucose response as assessed by oral glucose tolerance test (OGTT) and insulin-stimulated glucose uptake in isolated adipocytes in a group of 32 patients with advanced coronary heart disease. The area under the insulin curve following OGTT was significantly reduced after 4 weeks in the LGI group (P < .03), but not in the HGI group. Insulin-stimulated glucose uptake in isolated adipocytes harvested from a presternal fat biopsy was significantly greater following the LGI diet (P < .05). This study demonstrates that simple short-term dietary measures can improve insulin sensitivity in patients with coronary heart disease.

Development of a rapid and efficient magnetic resonance imaging technique for analysis of body fat distribution

Fast scan magnetic resonance imaging techniques for adipose tissue (AT) quantification were compared to a conventional T1-weighted spin-echo (SE) sequence (TR = 500 ms, TE = 20 ms), imaging a mid-abdominal slice. A rapid T1-weighted SE sequence (TR = 36 ms, TE = 14 ms) was optimal, with minimal distortion (field, motion, flow artefact). Tissue contrast was higher and visceral AT was clearly differentiated. Quantification of all AT compartments (total, subcutaneous, internal, visceral) showed close agreement with the T1-weighted SE sequence and reproducibility was high (coefficient of variation < 4.7%). For AT quantification in a whole subject, this fast technique allows each image to be acquired serially at the magnet isocenter, as the subject is moved through the scanner (serial isocenter scanning, SIS). This method provides minimal image distortion and allows rapid coverage of the whole body.

An in vivo 13C magnetic resonance spectroscopic study of the relationship between diet and adipose tissue composition

13C magnetic resonance spectroscopy (MRS) is a noninvasive technique used in the study of lipids. We applied 13C MRS to assess the effects of long-term dietary variation on adipose tissue composition in humans. In vivo 13C MRS was used to analyze the fatty acid composition of adipose tissue in 88 healthy volunteers with significantly different diets (38 vegans, 11 vegetarians, and 39 omnivores) assessed by analysis of dietary records. Results were compared with the serum lipid profile. 13C MRS revealed clear differences in the adipose tissue composition of vegans, which contained more unsaturated (P < 0.01) and fewer saturated fatty acids (P < 0.01) compared with omnivores and vegetarians. The vegan subjects had a significantly lower intake of saturated fatty acids and higher intake of polyunsaturated fatty acids than either the omnivore or the vegetarian groups (P < 0.01). These findings were associated with significantly lower levels of serum total cholesterol and low density lipoprotein-cholesterol in the vegan group compared with the omnivores. Our results demonstrate the use of 13C MRS for the noninvasive study of adipose tissue composition and its application to the study of the interaction between long-term dietary and metabolic risk factors in humans.

Outpatient quality assurance monitor: constipation/encopresis

Quality Assurance (QA) programs assure that patients are getting the appropriate care, information, and support needed to produce better health outcomes. In this article, the authors describe monitoring nursing process by documentation of care in patients with constipation/encopresis. Longitudinal follow up to monitor patient outcomes completed the QA program. The process portion of the monitor was very successful, but the results of the outcome monitor were disappointing.