Jerome L Knittle

Weight Reduction in Young Obese Children. I. Effects on Adipose Tissue Cellularity and Metabolism

Summary: A 10-year longitudinal study was conducted on 26 prepubescent youngsters who had undergone successful weight reduction. Their ages ranged from 2 to 10 years when the study began. In all subjects, weight reduction proceeded only by a decrease in adipose cell size (from 0.62 ± 0.02 to 0.46 ± 0.02 μg lipid per cell) and resulted in a corresponding 33% decrease (from 177 ± 6 to 144 ± 5%) in percent ideal body weights. Cell numbers did not change appreciably during the period of weight loss (29.4 ± 2.6 versus 28.7 ± 2.3 × 109 total adipocytes). Three years after the start of the study, 14 of 20 youngsters had maintained their reduced percent ideal body weights, including eight who remained below 130% ideal body weight. Ten years later, only four remained below 130% ideal body weight. AH four children had total adipose cell numbers below 20 × 109 total adipocytes at the start of the weight reduction program, a value below the lower limit for adult normal weight subjects. Thirteen other children have maintained or decreased their initial percent ideal weights. The remaining nine youngsters have further increased their percent ideal body weights. In vitro metabolic studies of the patients adipocytes revealed a >50% depression of epinephrine-stimulated lipolysis pre- and immediately postweight reduction; this decrease persisted for the entire period of study, irrespective of the maintenance of a normal percent ideal body weight. At the same time, normal 150% increases in the in vitro production of 14CO2 from [1-14C]glucose in the presence of insulin occurred.Speculation: Maintaining weight reduction long term is generally unsuccessful except in a small minority of very young obese children. Therefore, if the prevalence of obesity and its associated diseases are to be decreased, very early identification of at-risk youngsters is important. Specific enzymatic and metabolic alterations in these children, e.g., depression of in vitro epinephrine-stimulated lipolysis, appear to be useful for early identification of susceptible individuals. In addition, this study indicates that factors such as genetics and gestation may lay the groundwork for the future development of increased adiposity.

Adipose Tissue Cellularity and Metabolism in Newly Diagnosed Juvenile Diabetics

Adipose tissue cell number and size were determined in ten juvenile diabetics, ages one to seventeen, four of whom had a history of significant obesity antedating development of symptomatic glucosuria. Studies were performed at the time of diagnosis (before administration of insulin) and two to twenty-five months after institution of therapy. Results were compared with those found in a group of thirtyfour children of normal weight with no blood sugar abnormalities. An increase in adipose cell number was documented while adipose cell size was significantly decreased in the diabetics in both study periods. Weight gain after insulin treatment was due primarily to an increase in total body fat, which was reflected by increased cell size. However, the cells were still significantly smaller than normal. Cell number was not increased by the insulin treatment. In vitro studies of glycerol release revealed blunting of epinephrine-stimulated lipolysis, compatible with diminished adenylcyclase or cyclic AMP activity. However, the effects of in vitro insulin upon glycerol release and upon conversion of glucose l-C-14 to 14-CO2 did not differ from results in normal controls. Baseline values of glycerol release were related to the presence of acidosis, while hormonal responses were unchanged after therapy. Thus, adipose tissue hypercellularity is present at the time of diagnosis of insulin-requiring diabetes mellitus in children and is not accompanied by adipose tissue peripheral “insulin resistance” as measured by two different parameters. A possible role for growth hormone in the development of this hypercellularity, which is also present in childhood obesity, is presented.

Effect of Emulsions of Medium and Long Chain Triglyceride on Human Adipose Tissue Prostaglandin Production in Vitro

Preliminary in vitro studies have been performed to assess the effect of experimental lipid emulsions of varying fatty acid composition on human adipose tissue metabolism. Subcutaneous human adipose tissue was obtained during elective surgery and placed in tissue culture. Physical mixtures of long chain triglyceride (LCT) and/or medium chain triglyceride (MCT) were added to the tissue culture medium so that the final concentration was 400 mg/dl. After a 3-day incubation period the tissue was harvested, placed in buffer and used to determine in vitro production of the prostaglandins prostacyclin I2 (measured as its stable endproduct 6-keto PGF1 alpha), thromboxane A2 (measured as TXB2), and prostaglandin E2. Measurements of the fatty acid profile found in the neutral- and phospholipid fraction of the adipose tissue and fat cell size were also made. The results demonstrate that samples incubated in 100% MCT had the most significant increase in prostaglandin production whereas those incubated in 100% LCT had the most significant decrease in activity of the three prostaglandins assayed, when compared to controls. The addition of LCT to MCT caused a dose-related decrease in adipose tissue prostaglandin production. There were no significant changes in the profile of fatty acids found in the neutral- or phospholipid fraction of adipose tissue. The results indicate that the relative level of MCT/LCT incubated with human adipose tissue has a significant effect on prostaglandin production.

Circulating Factors Affect 6-Phosphofructokinase Activity in Human Adipose Tissue

6-Phosphofructokinase activity was lower in adipose tissue of obese, insulin-resistant subjects studied at stable body weight than in nonobese controls. This difference was absent during weight loss due to an increase in 6-phosphofructokinase activity in the obese subjects; the change suggested possible regulation by circulating factors. In an initial test of this hypothesis, blood serum collected from obese subjects at stable weight and incubated with adipose tissue in vitro produced lower 6-phosphofructokinase activity than did sera from nonobese controls.

241 ADIPOSE TISSUE DEVELOPMENT IN OFFSPRING OF DIABETIC MOTHERS

Macrosomia and increased adiposity are well-recognized sequelae in newborn infants of diabetic mothers. However, the long-term consequences of such alterations remain controversial. In order to prospectively evaluate these factors, 23 infants of gestaional diabetic mothers, IGDMs,(mean birthweight 3.6kg.), 8 infants of Class B and C insulin-dependent diabetic mothers, IDMS, (mean birthweight 3.2kg.) and 11 control infants (mean birth-weight 3.1kg.) have been studied sequentially over the past 9-10 years. Increased numbers of adipose tissue cells were found in the IGDMs as early as age one (mean 6.2 × 109 total adipocytes) and have persisted to date with mean values of 19.8 × 109 adipocytes, 52% greater than normal, at age 6.8 years and 28.4 × 109 at age 9.4 years. Concomitantly, obesity (greater than 130% ideal body weight for height and age) was found in only 3 infants at age one but in 19 IGDMs by ages 6-9. In the IDM group at age one, no infants were obese, but by age 7, six had become obese having a mean of 18.6 × 109 total adipocytes. Adipose cell size was increased above 0.50 ug lipid/cell in both IGDMs and IDMs by age 6. Normal weight children were born only to mothers of normal weight prior to pregnancy. In vitro studies of adipocyte metabolism revealed blunting of epinephrine-stimulated lipolysis beginning as early as age one month and persisting to date in all obese children. The data indicate the importance of in utero factors in the development of childhood obesity.

868 EFFECT OF DIET ON FAT CELL NUMBER, SIZE AND ENZYMES IN OBESE PEDIATRIC PATIENTS

Cell size, cell number and several lipogenic enzymes were measured from adipose tissue from 4 subjects (11-15 yrs, and >200% of ideal body wt) who were undergoing wt reduction. Subjects were placed on a 2600 cal diet (A) and 2 hypocaloric diets (880 cal), one high in fat (B), the other high in carbohydrate (C). Adipose tissue was obtained by needle aspiration from the buttock at the end of each dietary period. Fat cell number remained constant whereas fat cell size significantly decreased (p<.05) during wt reduction. Citrate cleavage enzyme (CCE) and phosphofructokinase (PFK) activities both increased during the reducing diets. Malic enzyme (ME) and α-glycerophosphate dehydrogenase (αGPD) were highest on diet C. Two-way analysis of variance and Scheffé testing indicate that CCE, PFK, and αGPD were highest on diet C (p<.05). Malic enzyme remained the same on diet B, but increased on diet C (p<.01). These data demonstrate that adipose tissue enzymes respond to diet with some activities increasing as cell size decreases.

GENETIC FACTORS IN THE DETERMINATION OF HUMAN ADIPOSE TISSUE MASS

The determinants of human adipose tissue mass are not yet elucidated. In order to characterize the role of genetic factors, total fat cell number was measured in 12 sets of identical and 6 sets of fraternal twins, ages 1 to 16, and one set of 10 year old identical female triplets. 8 of 10 sets of normal weight identical twins were concordant for total adipose cell number, current weight and height and birthweight while the other two sets of identical twins had significantly dissimilar birthweights and total cell numbers. In these latter children, cell number was lower in the twin with the smaller birthweight. In addition, the triplets were identical for all the parameters measured. Three seta of identical obese twins with similar birthweights all displayed significant and concordant adipose tissue hypercellularity for age. Differences in the degree of their adiposity were reflected primarily by alterations in fat cell size. The 6 sets of fraternal pairs had both similar and disparate fat cell numbers independent of their current weights and birthweights.The data indicate an important genetic component in the development of the adipose tissue depot in man with in utero factors modulating the final outcome.

High pyridoxine diet in the rate: Implications for clinical megavitamin therapy

Megavitamin therapy has found increased clinical application. Although the toxicity of fat soluble vitamins is well established, little has been learned of the actions and fate of massive doses of the water soluble vitamins. Current interest in the use of vitamin B6 in the treatment of homocystinuria due to cystathionine synthase deficiency prompted us to explore its mode of action and metabolic side effects in the rat. Large amounts of pyridoxine in the diet had no effect on appetite but resulted in a 20% increase in body weight and 40% in liver weight of pair-fed controls. The fat/protein ratio and the percentage of each in liver was unchanged despite the increased liver weight. The weights of brain, pancreas and kidney were unaffected. There appeared to be an increase in peritoneal fat, however, the epiyimal fat pads were significantly smaller in the high-pyridoxine group becuase of smaller cell size. Concentrations of free amino acids were unchanged as were the activities of cystathionine synthase and cystathionase. Incorporation of 35S from both methionine and cystine into the proteins of various organs were also unchanged. In the rats on high-pyridoxine diets there was greater incorporation of 35S from cystine into reduced glutathione and less into oxidized glutathione. Since the amounts of pyridoxine consumed by the experimental group was of the order of magnitude as that currently used in the treatment of homocystinuria, further studies are needed before it can be assumed that massive doses of water soluble vitamins can be used with impunity.