Norman Kretchmer

Risk Factors for Diabetes and Cardiovascular Disease in Young Australian Aborigines: A 5-year follow-up study

OBJECTIVE To test the hypothesis that hyperinsulinemia and glucose intolerance are present at an early age in australian aborigines and can be used to predict the eventual development of NIDDM. RESEARCH DESIGN AND METHODS Baseline anthropometric, pubertal stage, and blood pressure data were collected for 100 Australian aboriginal children and adolescents in 1989. Plasma concentrations of glucose, insulin, C-peptide, triglycerides, and LDL, HDL, and total cholesterol were measured before and during an oral glucose tolerance test. All measurements were repeated in 74 individuals from the original study population in 1994. Results were compared among hyperinsulinemic and normoinsulinemic subjects, and subjects with normal or abnormal glucose tolerance. RESULTS The percentage of subjects who were overweight increased from 2.7% at baseline to 17.6% 5 years later. At a mean age of 18.5 years, 8.1% of the population had impaired glucose tolerance (IGT), 2.7% had diabetes, and 21.6% had elevated cholesterol concentrations in plasma. Dyslipidemia was particularly prevalent among male subjects in the population: 34.4% had elevated plasma cholesterol and 21.9% had elevated LDL cholesterol values. Of the eight subjects who had diabetes or IGT in 1994, four were classified as hyperinsulinemic in 1989 and four were not. CONCLUSIONS The major finding of this study is the high prevalence of risk factors for NIDDM and cardiovascular disease in this population of aboriginal children and adolescents. Abnormalities of carbohydrate and lipid metabolism were well established by late in the second decade of life. Although many subjects had high insulin levels and there was evidence of insulin resistance in the population, hyperinsulinemia did not predict the development of abnormal glucose tolerance 5 years later.

Intestinal absorption of fructose in the rat

The objective of this study was to investigate the mechanisms involved in intestinal absorption of fructose. The results indicate that adult rats readily absorbed 0.4 g of fructose, an amount equivalent to 1.4-1.6 g fructose/kg body wt. Acute malabsorption of fructose occurred with doses greater than 0.6 g (2.1-2.4 g/kg body wt). Continued exposure to dietary fructose resulted in a decrease in the evidence of colonic fermentation. Glucose or galactose administered with fructose enhanced the absorption of fructose. The greatest absorption was observed when equal amounts of fructose and glucose were given simultaneously. If glucose was ingested as a polymer (starch or dextrin), the stimulatory effect was dependent on the digestibility of the polymer. Sucrose given with the fructose and glucose diminished the absorption of fructose. Acarbazone, a specific inhibitor of alpha-glucosidases, including sucrase, also inhibited the facilitating effect of glucose and galactose in absorption of fructose. These results give evidence for joint absorption of the two monosaccharides, fructose and glucose.

Unusual high-density lipoprotein subclass distribution during late pregnancy

Plasma lipoprotein distribution during late pregnancy is unusual since high-density lipoprotein (HDL) levels are increased in the presence of hypertriglyceridemia; the latter is usually associated with decreases in HDL levels. To determine whether there is a relationship between late-pregnancy lipid levels and specific HDL subclasses, HDL size distribution was determined by nondenaturing gradient gel electrophoresis (GGE) in a group of 36 women at 35 to 36 weeks of gestation and again at 6 weeks postpartum, and in a group of 10 nonpregnant women. At 35 to 36 weeks of gestation, plasma triglyceride (TG) and cholesterol concentrations were significantly increased over postpartum levels (218 +/- 62 v 112 +/- 69 mg/dL and 234 +/- 48 v 197 +/- 36 mg/dL, respectively). During late pregnancy, apolipoprotein A-I (apo A-I) and HDL cholesterol concentrations were also increased relative to postpartum levels (211 +/- 42 v 168 +/- 20 mg/dL and 63 +/- 13 v 53 +/- 11 mg/dL, respectively). GGE analysis indicated that at 35 to 36 weeks of gestation, 86% of the subjects had a substantial increase of the most buoyant and largest of the HDL species, HDL2b; postpartum and nonpregnant HDL subclass distribution was characterized by the predominance of HDL3a, which are smaller, more dense HDL. The shift in the HDL subclass distribution during late pregnancy was associated with significant positive correlations between HDL2b and apo A-I (r = .50, P < .05) and HDL cholesterol (r = .60, P < .001). There were significant elevations in the concentrations of cholesteryl ester transfer protein (CETP) and estrogen during late pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of Prolonged Nursing on the Activity of Intestinal Lactase in Rats

Abstract Litters of 10-day-old rats and their mothers were placed in specially designed cages which enabled the pups to continue to suckle, not to have access to water, solid foods, or feces, and to ensure that their sole dietary carbohydrate was lactose. The animals were killed at intervals and intestinal β-galactosidases, α-glucosidases, and cellular proliferation were measured. Although the specific activity of intestinal lactase followed the usual decline observed during development, the enzyme was maintained at a significantly higher activity than that of control rats. These animals were also able to hydrolyze lactose more readily as demonstrated by their having a significantly higher concentration of glucose in blood after ingestion of lactose. When segments of intestine were incubated with lactose, glucose plus galactose, sucrose, mannitol, or saline, the decline in the activity of lactase was much less in the presence of lactose than in any of the other media. Thus, the substrate had a stabilizing or protective effect on the enzyme. The developmental pattern of the intestinal a-glucosidases and the acid β-galactosidases, and the normal morphological maturation of the intestine were not altered by prolonged nursing and elimination of carbohydrates other than lactose.

Development of ornithine metabolism in the mouse intestine.

ABSTRACT: Circulating arginine available for synthesis of protein is produced in the kidney of the adult mammal by the action of the last two enzymes of the urea cycle, argininosuccinate synthase and argininosuccinate lyase. In a previous publication, we reported the presence of a complete biosynthetic pathway for arginine in the intestine of the neonatal mouse at a time when no other endogenous sources of arginine were available. Our present study was aimed at the determination of the source of ornithine used by the intestine of the neonatal mouse for the synthesis of arginine. We established the developmental profile of the two intestinal mitochondrial enzymes, pyrroline 5-carbox-ylate synthase and ornithine aminotransferase, responsible for the conversion of glutamate to ornithine. Both enzymatic activities were found to be significantly elevated throughout the suckling period with a peak of activity during the 2nd wk of life. Glutamate dehydrogenase activity in the intestine did not appear to be developmentally regulated during the suckling and weaning periods; therefore, this enzyme was used as a convenient marker to quantify mitochondrial preparations. Ornithine decarboxylase activity was undetectable in the intestine of the mouse during the suckling period and was detected briefly at weaning, indicating that ornithine synthesized in the intestinal mitochondria is probably not diverted actively into the polyamine pathway and is available for synthesis of arginine by the enzymes of the urea cycle.

Maternal Obesity and Body Composition of the Neonate

Obese women generally deliver heavier infants, but the body composition of these infants is unknown. The principal objective of this study was to determine if neonates of obese women have more adipose tissue. At 35-36 weeks of gestation, a fasting blood sample was collected from 37 pregnant women. Shortly after birth, the body fat of the neonates was measured with an infant total-body electrical conductivity (TOBEC) instrument using a prediction equation derived from 10 miniature pigs. At 6 weeks post partum, the infant body fat was measured a second time, and the body fat of each mother was measured using an adult TOBEC instrument. We found no differences between the obese (n = 16) and lean subjects (n = 21) in the concentrations of glycerol, beta-hydroxybutyrate, triglyceride, total cholesterol, high-density lipoprotein cholesterol, or glucose in the blood. However, the insulin concentration was elevated in the obese women (199 +/- 57 pmol/l) as compared with the lean women (128 +/- 68 pmol/l, p < 0.01). At birth, maternal adiposity (% body fat) was significantly associated with infant adiposity (r = 0.37, p < 0.05). However, by 6 weeks post partum the association no longer existed. Multiple regression analysis showed that maternal adiposity, fasting glucose level, and gestational age are independently associated at birth with infant adiposity.

Renal trehalase: function and development.

1. Following injection of trehalose into the bloodstream, no trehalose was found in urine of rabbits until the concentration of trehalose in blood exceeded 0.6 mg/ml. 2. Absence of trehalose in urine of the rabbit when the concentration of the sugar in blood is elevated supports the hypothesis that renal trehalase functions as a digestive enzyme in kidney. 3. The rat does not possess renal trehalase, and excretion of trehalose was in direct relation to the concentration of trehalose in blood. 4. There are differences in expression of the disaccharidases in kidney and intestine although they share many structural and enzymatic characteristics.

Development of glutaminase along the villus-crypt axis in the jejunum of rat.

The activity of glutaminase (E.C. 3.5.1.2), the entry enzyme for oxidation of glutamine, was measured in enterocytes isolated along the villus-crypt axis from rat jejunum. Specific activity of glutaminase was 5.05 +/- 0.24 mumol glutamate/mg protein/h in villus cells (fully differentiated cells) and 4.16 +/- 0.30 in the deep crypt (undifferentiated cells). Activity of glutaminase was significantly (p less than 0.05) increased in cells isolated from the villus-crypt junction (differentiating cells) compared to the activity of the enzyme in both the villus and crypt at 6.21 +/- 0.45. A similar pattern of activity of glutaminase was observed when the cells of the villus-crypt gradient were separated by sequential horizontal sectioning with a cryostat. Oxidation of L-[U-14C]glutamine to 14CO2 was also significantly (p less than 0.01) higher in cells isolated from the villus-crypt junction compared to both villus or deep crypt cells. The quantity of glutaminase protein was determined by a dot immunobinding assay using an antibody to purified glutaminase. Immunoreactive glutaminase protein relative to total cellular protein was 6.06 +/- 0.40 cpm/microgram homogenate protein in the villus cells, 3.01 +/- 0.24 (p less than 0.05) at the villus-crypt junction, and 4.49 +/- 0.57 (p less than 0.05) in the deep crypt. Thus, the highest activity of glutaminase present in the villus-crypt junction is the result of an increase in activity of the enzyme rather than an increase in the enzyme protein.

Participation of pancreatic enzymes in the degradation of intestinal sucrase-isomaltase.

The pancreatic ducts of the rats were bypassed with a catheter placed within the common bile duct to prevent the entry of pancreatic enzymes into the duodenum without interrupting bile flow. For 8 days, the animals were fed a diet (peptones, sucrose, coconut oil, vitamins, and minerals) that could be digested without pancreatic enzymes. Control animals were sham operated and pair-fed with the same diet. Relative rates of synthesis and degradation were estimated by pulse labeling and double labeling, respectively, for sucrase and for total protein, in intestinal mucosa and along the gradient of cells collected from the tip of the villus to the bottom of the crypt. The rate of degradation of sucrase was 1.7 times greater than that of total protein in controls, whereas in animals with the pancreatic bypass it was equal to that of total protein. This decrease in rate of degradation produced a proportional increase of activity of sucrase in experimental animals. The hydrolytic effect of pancreatic enzymes on sucrase was apparent along the entire length of the villus but not in the crypt. These data support the hypothesis that pancreatic proteases release sucrase-isomaltase from the brush border membrane, resulting in the observed increase of the rate of degradation. Electrophoretic separation of immunoprecipitated sucrase-isomaltase showed that the intact pro-sucrase-isomaltase observed in operated animals is split into two subunits (sucrase and isomaltase) by action of pancreatic proteases in control animals.

Relationships between glucose metabolism and thermogenesis with and without prior exercise in obese women with non—insulin-dependent diabetes mellitus

The rate of insulin-stimulated glucose disposal is reduced in individuals with insulin resistance, and is associated with a blunted or absent increase in energy expenditure in response to a glucose load. The magnitude of the effect of glucose on energy expenditure (EGEE) may be a function of opposing changes in the rate of glucose disposal (Rd) and hepatic glucose production (HGP). In this study, six women with non-insulin-dependent diabetes mellitus (NIDDM) were studied on a metabolic ward in each of three conditions. On days 1 and 2, they did no exercise (NX) or else performed low-intensity exercise ([LO] 3,118 kJ [745 kcal]) at 50% maximal oxygen consumption [V0(2)max]) or high-intensity exercise ([HI] 3,114 kJ [744 kcal] at 75% V0(2)max). On day 3, infusion of 6,6(2)H-glucose in the basal state was immediately followed by infusion of glucose, 6,6(2)H-glucose, and insulin at fixed rates. Indirect calorimetry was performed during the last 30 minutes of each infusion. EGEE was not different among the three conditions (mean +/- SEM: NX -0.18 +/- 0.11, LO -0.08 +/- 0.05, and HI -0.08 +/- 0.07 kJ/min) and was inversely related to steady-state plasma glucose concentration, a direct measure of insulin resistance (r = -.89, P < .05). EGEE was positively correlated with glucose Rd (r = .94, P < .001) and negatively correlated with HGP (r = -.91, P < .05). The data indicate that the glucose effect on energy expenditure was slightly positive in the more insulin-sensitive individuals, but negative in the more insulin-resistant subjects. The EGEE appears to be determined by the relative balance between energy required to store glucose and energy saved by suppression of glucose production.