Erwin Tafeit

Body fat distribution of overweight females with a history of weight cycling

Weight cycling may cause a redistribution of body fat to the upper body fat compartments. We investigated the distribution of subcutaneous adipose tissue (SAT) in 30 overweight women with a history of weight-cycling and age-matched controls (167 normal weight and 97 overweight subjects). Measurements of SAT were performed using an optical device, the Lipometer. The SAT topography describes the thicknesses of SAT layers at 15 anatomically well-defined body sites from neck to calf. The overweight women with a history of weight cycling had significantly thicker SAT layers on the upper body compared to the overweight controls, but even thinner SAT layers on their legs than the normal weight women. An android fat pattern was attributed to overweight females and, even more pronounced, to the weight cyclers. The majority of normal weight women showed a gynoid fat pattern. Using stepwise discriminant analysis, 89.0% of all weight cyclers and overweight controls could be classified correctly into the two groups. These findings show the importance of normal weight maintenance as a health-promoting factor.

Artificial neural networks in laboratory medicine and medical outcome prediction.

Abstract Since the early nineties the number of scientific papers reporting on artificial neural network (ANN) applications in medicine has been quickly increasing. In the present paper, we describe in some detail the architecture of network types used most frequently in ANN applications in the broad field of laboratory medicine and clinical chemistry, present a technique-structured review about the recent ANN applications in the field, and give information about the improvements of available ANN software packages. ANN applications are divided into two main classes: supervised and unsupervised methods. Most of the described supervised applications belong to the fields of medical diagnosis (n=7) and outcome prediction (n=9). Laboratory and clinical data are presented to multilayer feed-forward ANNs which are trained by the back propagation algorithm. Results are often better than those of traditional techniques such as linear discriminant analysis, classification and regression trees (CART), Cox regression analysis, logistic regression, clinical judgement or expert systems. Unsupervised ANN applications provide the ability of reducing the dimensionality of a dataset. Low-dimensional plots can be generated and visually understood and compared. Results are very similar to that of cluster analysis and factor analysis. The ability of Kohonens self-organizing maps to generate 2D maps of molecule surface properties was successfully applied in drug design.

Measurement of subcutaneous adipose tissue topography (SAT-Top) by means of a new optical device, LIPOMETER, and the evaluation of standard factor coefficients in healthy subjects.

The quantification of obesity in respect to subcutaneous adipose tissue and fat distribution is a matter of interest. We recently reported on a new optical device, LIPOMETER, and its ability to measure the thickness of subcutaneous adipose tissue and its advantages compared with other methods. To describe the subcutaneous adipose tissue distribution of the human body in a precise, reproducible, and comparable manner, 15 well‐defined body sites distributed from neck to calf on the right body side were used. This set of sites defines subcutaneous adipose tissue topography (SAT‐Top). To visualize SAT‐Top for subjects or groups, special SAT‐Top plots were used. Subcutaneous adipose tissue distribution can be recognized easily with these techniques. SAT‐Top of 590 healthy men and women was measured. Factor analysis was used to extract the essential information from these 590*15 intercorrelated single measurements and to provide standard factor coefficients for later applications. As an example of how to use the results of factor analysis, the strong SAT‐Top deviation of women with clinically proven type‐2 diabetes mellitus (NIDDM) from healthy controls is described. Am. J. Hum. Biol. 12:231–239, 2000.

Estimating percentage total body fat and determining subcutaneous adipose tissue distribution with a new noninvasive optical device LIPOMETER

A newly developed optical device was applied to measure the subcutaneous adipose tissue (SAT) thickness of 20 healthy women and 18 healthy men at specified body sites. These measurements were used to derive equations to estimate percentage total body fat (TBF%). Total body electrical conductivity (TOBEC) was employed as a reference method; caliper techniques and measurements of absorbances of infrared light in fat versus lean tissue were also compared. The LIPOMETER results show good agreement with TOBEC data (r = 0.96). The technique allows the precise determination of the distribution of SAT thickness at specified body sites. The method also permits the construction of profiles of SAT thicknesses, e.g., the profiles are significantly different between women and men. Based on the normal profiles of healthy subjects, patients with proven type‐2 diabetes mellitus were also evaluated. The patients showed significantly different profiles. By linear discriminant analysis, classification functions were extracted with good predictive accuracy classification of subjects according to the presence or absence of type‐2 diabetes mellitus. The data suggest that measurement of SAT thickness might aid in the diagnosis and/or classification of metabolic disorders. Am. J. Hum. Biol. 12:221–230, 2000.

Effects of weight loss on leptin, sex hormones, and measures of adiposity in obese children.

Adipose tissue influences steroid conversion by paracrine and autocrine mechanisms. Leptin is secreted by adipocytes and influenced by sex hormones and adiposity. Short-term weight loss in the treatment of childhood obesity reduces leptin and adipose tissue. We therefore asked, Do alterations in sex hormones occur owing to weight loss? and can these alterations be explained by changes in fat mass or sc fat and are alterations in sex hormones directly related to the fall in leptin? Twenty obese boys and 40 obese girls were studied before and after 3 wk of low-calorie diet and physical activity. The weight loss program significantly lowered fat mass, abdominal fat distribution, sc fat (all p<0.0001), leptin, insulin, and estradiol (all p<0.0001) but not testosterone. Changes in leptin were related to changes in body mass and to changes in fat mass in boys. In girls, changes in leptin were related to changes in sc fatness and also to changes in insulin. In boys, the reduction in sc fat was positively correlated to changes in testosterone (r=0.54; p<0.01) and inversely related to the fall in estradiol (r=−0.41; p<0.05). In girls, changes in testosterone (r=0.33; p<0.05) and in estradiol (r=0.40; p<0.001) were related to changes in insulin. Stepwise regression showed that initial leptin was the best determinant for the fall in leptin (adjusted R2=0.87; p<0.0001). The results show that alterations in sex hormones are related to changes in certain fat depots in boys where as in girls changes in insulin might participate in changes in sex hormones. A greater fall in leptin owing to short-term weight loss is not associated with greater alterations in sex hormones and initial leptin is the best determinant to explain the variability in changes in leptin. The possibility of sex differences in changes in sex hormones secondary to the reduction in fatness warrants further study.

Insights into epiploic appendagitis

Epiploic appendagitis is a rare cause of abdominal pain. Diagnosis of epiploic appendagitis, although infrequent, is easily made with CT or ultrasonography in experienced hands. As reported in the literature, most patients with primary epiploic appendagitis are treated conservatively without surgery, with or without anti-inflammatory drugs. A small number of patients are treated with antibiotics and some patients require surgical intervention to ensure therapeutic success. Symptoms of primary epiploic appendagitis usually resolve with or without treatment within a few days. A correct diagnosis of epiploic appendagitis with imaging procedures enables conservative and successful outpatient management of the condition and avoids unnecessary surgical intervention and associated additional health-care costs. Gastroenterologists and all medical personnel should be aware of this rare disease, which mimics many other intra-abdominal acute and subacute conditions, such as diverticulitis, cholecystitis and appendicitis. This article reviews epiploic appendagitis and includes discussion of clinical findings, pathophysiology, diagnosis and therapeutic possibilities.

NADH stimulates endogenous dopamine biosynthesis by enhancing the recycling of tetrahydrobiopterin in rat phaeochromocytoma cells

Treatment of Parkinson patients with L-DOPA (3,4-dihydroxy-L-phenylalanine) leads to endproduct inhibition of tyrosine hydroxylase, the key enzyme in dopamine biosynthesis and the enzyme needing tetrahydrobiopterin and iron as cofactors. To overcome this problem an alternative treatment was investigated which attempted to stimulate endogenous dopamine biosynthesis. Incubation of rat PC 12 cells with NADH (beta-nicotinamide adeninedinucleotide) leads to increased dopamine production. We investigated the possibility that this increase of dopamine biosynthesis was due to stimulation of quinonoid dihydropteridine reductase, the enzyme which recycles the inactive dihydrobiopterin to the active tetrahydrobiopterin. The experiments showed that whereas NADH is able to increase dopamine production in PC 12 cells (rat phaeochromocytoma cells, clone PC 12) up to three-fold, no influence is exerted by NADH on pteridine metabolism; neither are tetrahydrobiopterin concentrations nor the de novo-biosynthesis of pteridines from guanosine triphosphate altered by NADH. Further no influence of NADH on protein de novo synthesis of quinonoid dihydropteridine reductase was observed. However, NADH was able to directly increase the catalytic activity of this enzyme. Our results suggest that the stimulation of dopamine biosynthesis by NADH is due to more rapid regeneration of quinonoid dihydrobiopterin to tetrahydrobiopterin.

Evaluation of Risk Profiles by Subcutaneous Adipose Tissue Topography in Obese Juveniles

Objective: To compare subcutaneous adipose tissue topography (SAT‐top) in obese juveniles with age‐matched normal‐weight controls.

ROC and CART analysis of subcutaneous adipose tissue topography (SAT-Top) in type-2 diabetic women and healthy females

Women suffering from type‐2 diabetes mellitus (NIDDM) show a more android fat pattern than healthy females, but to date no exact determination of their fat distribution differences exists. Measurements at 15 specified body sites with an optical device, the LIPOMETER, provide a subcutaneous adipose tissue topography (SAT‐Top) of the individual. SAT‐Top of 20 female NIDDM patients and 122 healthy controls was measured. ROC curve analysis was applied to evaluate the discriminative power of each body site and to provide cutoff values. Then a classification tree by the CART algorithm was established, showing SAT‐Top differences between the two groups. Best discriminating results were achieved by the neck site (ROC area index = 0.76, sensitivity = 61.3%, specificity = 77.8%), the four sites of the thigh (area indices from 0.71 to 0.76), and a linear combination of all body sites stemming from a previous factor analysis, which provides condensed information of the extremities SAT‐Top (area index = 0.80, sensitivity = 80.4%, specificity = 64.6%). The results could be improved by a summary measure of “android fat pattern” (area index = 0.89, sensitivity = 73.6%, specificity =88.3%) and a proportional measure of SAT‐distribution, the relative neck (area index = 0.84, sensitivity = 83.0%, specificity = 70.5%). Overall, 136 (95.8%) of the 142 subjects were correctly classified by the classification tree (sensitivity = 75%, specificity = 99.2%). Both methods show the expected increased upper trunk obesity and decreased lower body obesity of NIDDM women compared with healthy females. Am. J. Hum. Biol. 12:388–394, 2000.

Differences of subcutaneous adipose tissue topography between type-2 diabetic men and healthy controls

Men with noninsulin-dependent diabetes mellitus (type 2 DM) provide a different subcutaneous body fat distribution and a concentration of fatness on the upper trunk compared with healthy subjects. However, subcutaneous fat distribution is always measured in an inaccurate and/or very simplified way (e.g., by caliper), and to date, there exists no study reporting on the exact and complete subcutaneous adipose tissue distribution of type 2 DM men. A new optical device, the LIPOMETER, enables the nonivasive, quick, and safe determination of the thickness of subcutaneous adipose tissue layers at any given site of the human body. The specification of 15 evenly distributed body sites allows the precise measurement of subcutaneous body fat distribution, so-called subcutaneous adipose tissue topography (SAT-Top). SAT-Tops of 21 men with clinically proven type 2 DM (mean age of 57.5 ± 6.7 years) and 111 healthy controls of similar age (mean age 59.0 ± 5.4 years) were measured. In this paper, we describe the precise SAT-Top differences of these two groups and we present the multidimensional SAT-Top information condensed in a two-dimensional factor value plot. In type 2 DM men, especially in the upper trunk, SAT-Top is significantly increased (up to +50.7% at the neck) compared with their healthy controls. One hundred eleven of the 132 individuals (84.1%) are correctly classified (healthy or type 2 DM) by their subcutaneous fat pattern by stepwise discriminant analysis.