Insulin-like growth factor binding proteins (IGFBPs) in serum and urine and IGFBP-2 protease activity in patients with insulin-dependent diabetes mellitus.

Diabetes mellitus and glucose dysregulation have significant effects on the circulating level of insulin-like growth factor-I (IGF-I) and IGF binding proteins (IGFBPs). In the present study, serum and urine IGFBP (IGFBP-1, -2, and -3) and serum IGF-I and -II levels were measured by radioimmunoassay (RIA) in 27 patients with type 1 diabetes aged 9 to 48 years compared with 9 healthy subjects aged 10 to 28 years. The patients were divided into 3 groups according to the amount of albumin excreted in 24 hours. The macroalbuminuria group (>500 mg/24 h) had elevated serum IGFBP-1 and -2 and decreased IGF-I levels (P < .01 v normal controls). Serum IGFBP-3 and IGF-II were not different among the patient groups and controls (P > .05). The mean urinary IGFBP-1 was decreased in all 3 patient groups compared with the controls (P < .05). Urinary IGFBP-2 and IGFBP-3 were increased in patients with macroalbuminuria. Immunoblot analysis showed increased low-molecular-weight fragments of urinary IGFBP-2 in the poorly controlled diabetics, and direct evidence for increased urinary IGFBP-2 proteolytic activity could be demonstrated in both the microalbuminuric and macroalbuminuric groups. Low-molecular-weight fragments of urinary IGFBP-3 were also increased in both the microalbuminuric and macroalbuminuric groups. In conclusion, alterations of IGFBPs in urine and serum are related to metabolic control in diabetic patients, and there is an increase of urinary IGFBP-2 protease activity in poorly controlled diabetics. The changes in serum IGFBP concentrations (eg, increases in IGFBP-1 and IGFBP-2) may lead to alterations in the availability of IGF-I to peripheral tissues.

Calcium absorption, bone mass accumulation, and kinetics increase during early pubertal development in girls.

To evaluate the changes in calcium and bone mineral metabolism associated with early pubertal development, we performed longitudinal measurements of calcium absorption, calcium kinetics, bone mineral content, and hormonal markers related to puberty in a multiethnic group of girls beginning when they were 7 or 8 yr old. Girls were Tanner stage 1 (breast) at the start of the study. They were placed on a 1200 mg/day dietary calcium intake and studied at approximately 6-month intervals until they reached Tanner stage 2 (breast). Results at that time point (PUB) were compared to values obtained approximately 1 yr earlier (LatePRE) and those 1 yr before that (EarlyPRE). We found an increase in calcium absorption comparing PUB to LatePRE (n = 34; 36.6 +/- 8.7% vs. 30.7 +/- 9.9%; P = 0.002). Using whole body, dual energy, x-ray absorptiometry scanning, we found an increase in calcium gain during the LatePRE to PUB period compared with that during the EarlyPRE to LatePRE period (135 +/- 53 vs. 110 +/- 45 mg/day; P = 0.04). Calcium kinetic studies showed a significant increase in the bone calcium deposition rate (Vo+) during the PUB compared to the LatePRE period. Hormonal and biochemical markers of bone development were also significantly increased at PUB compared to LatePRE. Hormonal activity, as evidenced by the unstimulated LH level, was significantly correlated with calcium gain between the LatePRE and PUB studies and the bone calcium deposition rate in the PUB study. These data demonstrate, using multiple independent methods, an increase in calcium utilization associated with the earliest physical signs of puberty.

Ethnic differences in androgens, IGF-I and body fat in healthy prepubertal girls.

OBJECTIVE: To examine ethnic differences in adrenal androgen production, IGF-I, and IGFBP-1 and -3 in relation to bone age, insulin, and body composition in healthy prepubertal girls. METHODS: Serum levels of DHEA-S, androstenedione, IGF-I, and IGFBP-1 and -3 were examined in relation to bone age, insulin, and body composition (determined by dual-energy X-ray absorptiometry) in 47 (19 Caucasian, 9 African-American, 19 Mexican-American) healthy prepubertal girls aged 7.5-9.0 years. RESULTS: Age, weight, height, bone age, androstenedione, insulin, glucose:insulin ratios, and IGFBP-3 levels were not statistically different among groups. Mexican-American girls had higher % body fat than African-Americans or Caucasians (P < 0.001). DHEA-S levels in African-Americans were twofold higher than in Caucasians (P = 0.024), although their % body fat was not significantly different (16.1% and 19.4%, respectively; P = 0.138). DHEA-S levels in Mexican-American girls were intermediate. Bone age and weight were significant covariates for DHEA-S levels. Plasma IGF-I levels were also higher in African-American than in Caucasian or Mexican-American girls (P = 0.009). Covariance analysis showed that IGF-I levels were influenced mainly by ethnicity (P = 0.009) and were independent of bone age. Despite similar insulin levels among groups, IGFBP-1 levels were higher in Caucasians than in Mexican-Americans or African-Americans (P < 0.001). CONCLUSIONS: In healthy prepubertal girls, DHEA-S concentrations are higher in African-Americans than in Caucasians or Mexican-Americans, even before any clinical evidence of adrenarche. Furthermore, IGF-I concentrations are higher in African-American girls than in Caucasian or Mexican-American girls which may contribute to the higher DHEA-S levels observed. Conversely, higher DHEA-S and IGF-I levels in African-American girls may be indicative of an influence not only of gonadal but also of adrenal androgens on the GH/IGF-I axis.

Characterization of two novel homozygous missense mutations involving codon 6 and 259 of type II 3beta-hydroxysteroid dehydrogenase (3betaHSD) gene causing, respectively, nonsalt-wasting and salt-wasting 3betaHSD deficiency disorder.

We identified two homozygous missense mutations in the human type II 3beta-hydroxysteroid dehydrogenase (3/betaHSD) gene, the first in codon 6 of exon II [CTT (Leu) to TTT (Phe)] in a male infant with hyperpigmented scrotum and hypospadias, raised as a male and no apparent salt-wasting since neonatal age, and the second in codon 259 of exon IV [ACG (Thr) to ATG (Met)] in a male pseudohermaphrodite with labial scrotal folds, microphallus, chordee, and fourth degree hypospadias, raised as a female and with salt-wasting disorder since neonatal age. In vitro transient expression of mutant type II 3betaHSD complementary DNAs of L6F, T259M, as well as T259R for comparison was examined by a site-directed mutagenesis and transfection of construct into COS-1 and COS-7 cells. Northern blot analysis revealed expression of similar amounts of type II 3betaHSD messenger ribonucleic acid from the COS-1 cells transfected by L6F, T259M, T259R, and wild-type (WT) complementary DNAs. Western immunoblot analysis revealed a similar amount of L6F mutant protein compared to WT enzyme from COS-1 cells, but neither L6F from COS-7 cells nor T259M or T259R mutant protein in COS-1 or COS-7 cells was detectable. Enzyme activity in intact COS-1 cells using 1 micromol/L pregnenolone as substrate in the medium after 6 h revealed relative conversion rates of pregnenolone to progesterone of 46% by WT enzyme, 22% by L6F enzyme, and 8% by T259M enzyme and less than 4% activity by T259R enzyme. Using 1 micromol/L dehydroepiandrosterone as substrate, the relative conversion rate of dehydroepiandrosterone to androstenedione after 6 was 89% by WT enzyme, 35% by L6F enzyme, 5.1% by T259M enzyme and no activity by T259R enzyme. However, the L6F mutant 3betaHSD activity, despite its demonstration in the intact cells, was not detected in homogenates of COS-1 cells or in immunoblots of COS-7 cells, suggestive of the relatively unstable nature of this protein in vitro, possibly attributable to the decreased 3betaHSD activity. In the case of T259M and T259R mutations, consistently undetectable proteins in both COS cells despite detectable messenger ribonucleic acids indicate severely labile proteins resulting in either no or very little enzyme activity, and these data further substantiate the deleterious effect of a structural change in this predicted putative steroid-binding domain of the gene. In conclusion, the findings of the in vitro study of mutant type II 3betaHSD enzyme activities correlated with a less severe clinical phenotype of nonsalt-wasting and a lesser degree of genital ambiguity in the patient with homozygous L6F mutation compared to a more severe clinical phenotype of salt-wasting and severe degree of genital ambiguity in the patient with homozygous T259M mutation in the gene.

Serum concentrations of insulin, insulin-like growth factor-I and insulin-like growth factor binding proteins are different between white and African American girls.

OBJECTIVES: To determine whether serum insulin-like growth factor (IGF)-I and IGF binding protein (IGFBP) concentrations are different between African American and white girls. STUDY DESIGN: Serum glucose and hormone concentrations were measured in blood samples collected after a 12-hour fast from 79 white and 57 African American healthy girls between 9 and 17 years of age. Tanner stages of pubic hair development were evaluated by physical examination, and body composition by dual energy x-ray absorptiometry. RESULTS: The African American girls were older and sexually more mature and had higher fat mass, higher serum insulin and free IGF-I concentrations, higher serum free IGF-I to total IGF-I ratio, but lower serum IGFBP-1 concentrations than the white girls. After controlling for sexual maturation and fat mass, the serum concentrations of total IGF-I, bound IGF-I, and IGFBP-3 in the white girls became significantly higher than those in the African American girls. The higher concentrations of total IGF-I in the white girls were due to a proportional increase in the concentrations of bound IGF-I that coincided with a similar increase in serum IGFBP-3 concentrations. CONCLUSIONS: Higher serum insulin concentrations in the African American girls are associated with lower serum IGFBP-1 concentrations and increased bioavailability of free IGF-I, which may contribute to their accelerated growth compared with their white counterparts.

Evaluation of a real-time blood glucose monitor in children with diabetic ketoacidosis.

Use of a real-time bedside glucose monitor was analyzed during the course of management of diabetic ketoacidosis (DKA) in children. Simultaneous determinations of blood glucose were obtained, using three methods: bedside glucose meter (One Touch II), laboratory glucose analyzer (YSI 2300 STAT), and a real-time bedside glucose monitor (VIA 1-01G Blood Chemistry monitor). Study patients included seventeen patients < 18 years of age admitted to a Pediatric Intensive Care Unit, with blood samples obtained during treatment of DKA by continuous insulin infusion. Four patients did not complete the study. Three experienced temporary technical problems with the monitor, and four required repeat IV placement. Duration of monitor use ranged between 6 and 47 h (mean 24 +/- 4 h). Blood glucose values ranged between 2.6 and 22.5 mmol/l. Overall correlation of blood glucose values were as follows: 0.965, 0.965, 0.973, VIA 1-01G vs. One Touch II, VIA 1-01G vs. YSI 2300 STAT, and One Touch II vs. YSI 2300 STAT, respectively (all P-values < 0.0001). This real-time bedside glucose monitor is accurate at glucose values < 13.8 mmol/l, and reliable for rapid, repetitive analyses. Results indicate that blood glucose values obtained using this real-time monitor are comparable to those using standard methods of measurement, and that this device is clinically applicable for use in management of children with DKA.

Vitamin D receptor gene Fok1 polymorphism predicts calcium absorption and bone mineral density in children.

The vitamin D receptor (VDR) gene has been implicated as one of the major genetic components of osteoporosis. We evaluated the relationship between markers of mineral status and restriction fragment length polymorphisms of the VDR gene in 72 healthy children age 7-12 years. Using stable isotope techniques and dual-energy X-ray absorptiometry, we measured dietary calcium absorption, bone calcium deposition rates, and total body bone mineral density (BMD). The Fok1 polymorphism at the VDR translation initiation site was significantly associated with BMD (p = 0.02) and calcium absorption (p = 0.04). Children who were FF homozygotes had a mean calcium absorption that was 41.5% greater than those who were ff homozygotes and 17% greater absorption than Ff heterozygotes. BMD was 8.2% greater in the FF genotype than the ff genotype and 4.8% higher than the Ff genotype. These results suggest a substantial relationship between the VDR gene and bone metabolism at one or more levels, including dietary absorption of calcium and BMD in growing children.

Combination growth hormone and estrogen increase bone mineralization in girls with Turner syndrome.

Turner syndrome is characterized by osteopenia and impaired skeletal growth. Neither feature is normalized by current modes of hormone therapy. The purpose of this study was to determine whether GH would increase protein anabolism and provide additional benefit to a regimen of estrogen replacement on calcium metabolism in girls and women with Turner syndrome. Using stable isotopes of calcium and leucine, we determined calcium absorption, urinary calcium loss, calcium retention, deposition into bone, leucine rate of appearance from protein, leucine incorporation into protein, and leucine oxidation in seven girls (10-17 y of age) and four adult females (16-34 y of age) with Turner syndrome, before and after 3 mo of GH treatment. All adults were treated with estrogen (ethinyl estradiol, 50 micrograms/d) and progesterone before and throughout the study. Three girls received no estrogen, and four girls were treated with low-dose estrogen (ethinyl estradiol, 5 micrograms/d) in combination with GH. The addition of estrogen to GH treatment resulted in a significant increase in calcium absorption and deposition in girls. GH did not affect calcium kinetics in adults already receiving estrogen/progesterone replacement therapy, nor did GH alone affect calcium kinetics in girls, and neither GH nor estrogen affected protein metabolism. These data suggest that the addition of low-dose estrogen to a regimen of GH improves bone deposition and calcium metabolism in girls with Turner syndrome and that estrogen is facultative for GH effects on bone.

Calcium absorption and kinetics are similar in 7- and 8-year-old Mexican-American and Caucasian girls despite hormonal differences.

To assess the possibility of ethnic differences in mineral metabolism in prepubertal children, we compared measures of calcium metabolism in 7- and 8-y-old Mexican-American (MA) and non-Hispanic Caucasian (CAU) girls (n = 38) living in southeastern Texas. We found similar fractional calcium absorption, urinary calcium excretion, calcium kinetic values and total-body bone mineral content in the MA and CAU girls. In contrast, parathyroid hormone (PTH) concentrations were greater in MA girls (4.01 +/- 0.47 vs. 1. 96 +/- 0.50 pmol/L, P = 0.005) than in CAU girls. Serum 25-hydroxyvitamin D concentrations were lower in MA girls (68.9 +/- 7.7 vs. 109.4 +/- 8.4 nmol/L, P = 0.001) than in CAU girls, but 1, 25-dihydroxyvitamin D concentrations did not differ between groups. Seasonal variability was seen for 25-hydroxyvitamin D concentrations in girls of both ethnic groups, but values in all of the girls were >30 nmol/L (12 ng/mL). We conclude the following: 1) greater PTH levels in MA girls than CAU girls are present without evidence of vitamin D deficiency; and 2) differences in 25-hydroxyvitamin D and PTH concentrations between MA and CAU girls do not have a large effect on calcium absorption, excretion or bone calcium kinetics. These data do not provide evidence for adjusting dietary recommendations for mineral or vitamin D intake by MA girls.

Participants' evaluation of a weight-loss program.

OBJECTIVE: The purpose of this study was to evaluate participants' perceptions of the weight-loss intervention used in a hypertension prevention clinical trial. DESIGN: A total of 308 overweight and moderately obese subjects participated in the weight-management intervention. After the 18-month program, 281 participants completed a questionnaire designed to evaluate their perceptions of the program's effectiveness. SUBJECTS/SETTING: Adult participants (224 men and 84 women) in the weight-loss modality of the Trials of Hypertension Prevention Phase I, surveyed in 1991. STATISTICAL ANALYSES PERFORMED: chi 2 Analyses were used to test for statistical significance of group differences. RESULTS: Intervention components that were most useful are presented. Older participants (older than 50 years) were most likely to attend sessions and women were most likely to identify stress and frustration because of disappointing results. Successful participants were more likely to incorporate exercise into their daily activities, exercise regularly, and use self-monitoring strategies. Few participants found group exercise to be useful. CONCLUSION: These findings suggest that interventionists in weight-loss programs need to find flexible and creative ways to maintain contact with participants, continue to develop better methods of self-monitoring, obtain the skills needed to recognize frustration and provide timely support, continue to couple the message of diet and exercise, and emphasize helping participants develop their problem-solving skills. This may require training outside the traditional field of dietetics.

Telephone charges and payments in a diabetes clinic.

OBJECTIVES: To determine reimbursement rates after initiation of charges for certain telephone calls in a pediatric diabetes care center. DESIGN: A review of charges and payments data during 1996. RESULTS: Four hundred seventy-two telephone calls initiated by patients and parents were billed during the study period. These calls regarded treatment of hypoglycemia, hyperglycemia, ketonuria, sick day treatment, and insulin dose changes. Insured patients were charged for 384 telephone calls and indigent patients were charged for 88 telephone calls. Telephone calls from insured patients generated charges of $9215 and payments of $3074. Insurance payments were $1677 (18% of charges), and patient payments were $1396 (15% of charges). Telephone calls from uninsured patients covered by Texas Medicaid or Chronically Ill and Disabled Children funding generated charges of $2193 and no payments. CONCLUSIONS: Telephone charges were reimbursed by all payors at an overall rate of 27%.

Developmental changes in the relationship between IGF-I and body composition during puberty.

To examine the hypothesis that anthropometric measures and physical fitness influence circulating insulin-like growth factor-I (IGF-I) during puberty, we measured IGF-I, free IGF-I, IGFBP-1, and IGFBP-3 concentrations in 156 healthy girls (9-16 years old) characterized by aerobic capacity (VO2max), fat-free mass (FFM), percent fat mass and pubertal development. IGF-I, free IGF-I and IGFBP-3 increased with pubertal development while IGFBP-1 declined. Percent fat mass correlated inversely with IGFBP-1 (r = -0.57) and directly with insulin (r = 0.50), while VO2max correlated inversely with percent fat mass (r = -0.63), body mass index (BMI, r = -0.57), and FFM (r = -0.40). When subdivided by Tanner stage, IGF-I correlated directly with weight, height, BMI, and FFM in pre-pubertal girls, but these relationships all diminished or disappeared completely by late puberty. Inverse correlations between IGF-I and percent fat mass, and direct correlations between IGF-I and VO2max as observed previously in adults, were not seen until late puberty. These data suggest that in pre-pubertal and early pubertal girls, IGF-I concentrations in blood reflect overall somatic size. This relationship between IGF-I and body size diminishes with sexual maturation, while correlations between IGF-I and both fitness and fatness emerge.

The secretion of insulin-like growth factor I, prolactin and insulin-like growth factor binding protein 1 by the decidua as predictors of human fetal growth.

To determine if in vitro secretion of the decidual peptides insulin-like growth factor I (IGF-I), prolactin or insulin-like growth factor binding protein 1 (IGFBP-1) correlates with infant birthweight in uncomplicated, term human pregnancies, decidua from 45 pregnancies with normally distributed birthweights was cultured in defined medium for 24 h. IGF-I, prolactin and IGFBP-1 concentrations in the culture medium were measured by radioimmunoassay. Neither infant birthweight nor a normalized measure of infant birthweight (birthweight z-score) correlated with the quantity of IGF-I, prolactin or IGFBP-1 secreted by the decidua from that pregnancy. There were no differences in any of the peptide hormones assayed when the pregnancies were grouped by infant sex. IGF-I and prolactin secretion by individual decidual samples correlated positively. IGF-I and IGFBP-1 secretion also correlated positively in individual samples. A previously identified correlation between decidual IGF-I secretion and infant birthweight among a group of normal and growth restricted (IUGR) pregnancies was not confirmed in the current study. These data indicate that the decrease in decidual IGF-I and prolactin secretion seen in IUGR pregnancies is not the hormone profile of the low birthweight end of a normal population, but a distinct endocrine profile.

Insulin does not stimulate protein synthesis acutely in prepubertal children with insulin-dependent diabetes mellitus.

Insulin treatment in adult type I diabetic patients decreases protein loss primarily by inhibiting protein breakdown without stimulating protein synthesis. In young growing rodents, insulin treatment has been reported to stimulate protein synthesis. We examined whether insulin stimulates protein synthesis in normally growing prepubertal children with insulin-dependent diabetes mellitus. Five prepubertal children with insulin-dependent diabetes mellitus (aged 8.6-11.25 yr) were studied in the postabsorptive state on two occasions: once during insulin deprivation (I-; blood glucose, 325 +/- 67.8 mg/dL; mean +/- SD) and once during insulin administration for 4 h (I+; blood glucose, 96 +/- 23.6 mg/dL). Leucine kinetics were measured using a 4-h primed continuous infusion of L-[1-13C]leucine. Serum insulin concentrations were lower (I- vs. I+, 0.6 +/- 0.3 vs. 7.5 +/- 4.3 microU/mL; mean +/- SD; P = 0.02), whereas serum beta-hydroxy-butyrate (I- vs. I+, 3.4 +/- 0.5 vs. 0.9 +/- 0.5 mg/dL; P < 0.001) and free fatty acid concentrations (I- vs. I+, 2.9 +/- 0.4 vs. 0.9 +/- 0.4 mEq/L; P < 0.001) were higher in the insulin-deprived state than during insulin administration. Leucine Ra, an index of protein breakdown (I- vs. I+, 200.5 +/- 23.4 vs. 167 +/- 17 mumol/kg.h; P = 0.008), and leucine oxidation (I- vs. I+, 56.5 +/- 20.7 vs. 29.6 +/- 9.3 mumol/kg.h; P = 0.03) were reduced by insulin treatment. Nonoxidative leucine disposal, an index of protein synthesis, was not affected by insulin treatment (I- vs. I+, 144 +/- 20.8 vs. 137.5 +/- 13.5 mumol/kg.h; P = 0.4). We conclude that the acute decline in net protein loss during insulin treatment in growing prepubertal children, like that in adults, is due primarily to an inhibition of protein breakdown without stimulation of protein synthesis.

Maternal insulin sensitivity and cord blood peptides: relationships to neonatal size at birth.

OBJECTIVE: To examine the relationship of multiple maternal and cord blood correlates of newborn size to determine the relative strength of the insulin-like growth factor-I association. METHODS: Thirty-seven venous cord blood specimens were obtained at the time of delivery. Ponderal index and birth weight percentile were calculated at birth. Neonatal length estimates were performed with a measuring board. All mothers were nonsmokers and had normal glucose tolerance. There was a wide range of maternal prepregnancy body mass indexes (BMI) (19.6-43.4). Neonates had a wide range of ponderal indexes (2.12-2.75) and birth weight percentiles (7-99th percentile). Univariate correlation coefficients were calculated to determine simple relationships. Stepwise linear regression analyses were performed to determine the relative contribution of potential explanatory variables to both ponderal index and birth weight percentile. Potentially explanatory independent variables included maternal prepregnancy BMI, weight gain in pregnancy, and maternal insulin sensitivity at 32 weeks' gestation. Maternal insulin sensitivity was estimated using the minimal model technique. Neonatal variables included sex, cord blood albumin, insulin, insulin-like growth factor-I, insulin-like growth factor-binding protein-1, and insulin-like growth factor-binding protein-3. RESULTS: Significant positive univariate correlations were identified between cord blood insulin-like growth factor-I and insulin-like growth factor-binding protein-3 with neonatal ponderal index and birth weight percentile. Maternal insulin sensitivity demonstrated a negative correlation with birth weight percentile (r = -.35, P < .05). Cord blood insulin correlated positively with birth weight percentile (r = .32, P < .05). There were no significant associations of cord blood insulin-like growth factor-binding protein-1 or albumin with either index of newborn size. Stepwise logistic regression analysis demonstrated an independent association of insulin-like growth factor-I with ponderal index (r2 = .41, P < .001). Both insulin-like growth factor-I and male sex were associated independently with birth weight percentile (r2 = .38, P < .001). No additional independent variables contributed to the prediction of ponderal index or birth weight percentile. CONCLUSION: These data support a unique relationship between cord blood insulin-like growth factor-I and newborn size under normal growth conditions. This is manifest by the strength and independence of the association between insulin-like growth factor-I and neonatal birth weight percentile ponderal index.

The efficiency of dietary protein utilization is increased during puberty.

We investigated whether the efficiency of dietary protein utilization for growth increases during the pubertal growth spurt in both nondiabetic and diabetic subjects. We measured leucine oxidation and retention (intake minus oxidation) in orally fed nondiabetic (n = 9) and diabetic (n = 9) human subjects, aged 7-17 yr. Eight subjects were Tanner stage I, and 10 were Tanner stages III-V; groups were not matched for gender. After 3 days of consuming a diet containing approximately 1 g/kg. day protein, subjects drank a commercial liquid nutrition formula, containing L-[1(-13)C]leucine, every 30 min for a total of 6 h to provide 1 g protein/kg. day. Isotopic enrichment of CO2 was used to calculate the fractional leucine oxidation rate and, together with alpha-ketoisocaproate isotopic enrichment, to calculate total leucine oxidation. Leucine oxidation rates decreased with puberty in both nondiabetic subjects (36.0 +/- 10.4 vs. 23.9 +/- 4.2 mumol/kg fat-free mass (FFM).h, prepubertal and pubertal, respectively; P < 0.05) and diabetic (33.6 +/- 4.9% vs. 27.3 +/- 3.4 mumol/kg FFM.h, prepubertal and pubertal, respectively; P < 0.1) subjects. Leucine retention increased with puberty in both nondiabetic (0.27 +/- 3.2 vs. 15.7 +/- 5.3 mumol/kg FFM.h, prepubertal and pubertal, respectively; P < 0.001) and diabetic (1.9 +/- 4.9 vs. 13.2 +/- 4.4 mumol/kg FFM.h, prepubertal and pubertal subjects, respectively; P < 0.05) subjects. The data suggest that the pubertal growth spurt is associated with a marked increase in the efficiency of dietary protein utilization for growth.

Hepatic insulin gene expression as treatment for type 1 diabetes mellitus in rats.

Type 1 diabetes mellitus is caused by a lack of insulin that results from the autoimmune destruction of the pancreatic beta-cells. Severe diabetes, if not controlled by periodic insulin injections, can lead to ketoacidosis and death. We have previously shown that sustained low level production of insulin in the liver of diabetic rats prevented their death from complications of diabetes. To test the hypothesis that there is a window of serum insulin concentrations that can prevent ketoacidosis without significant risk of hypoglycemia secondary to hyperinsulinemia, rats were infused with various doses of a recombinant retrovirus encoding an engineered rat preproinsulin-1 gene. The gene was engineered to allow processing into mature insulin by the protease furin. At the lower doses tested, fatal ketoacidosis was prevented, but the rats exhibited nonfasting hyperglycemia. At intermediate doses, which resulted in serum insulin concentrations of 1.6 mg/ml, the rats achieved near-normoglycemia and no serum ketones. These rats did not exhibit hypoglycemia even during a 24-h fast. At high virus doses, the animals achieved nonfasting normoglycemia but exhibited hypoglycemia during the fast. In conclusion, we have defined a therapeutic window of hepatic insulin expression that provides protection against ketoacidosis without significant risk of hypoglycemia. This window of sustained hepatic insulin expression might permit its development into a novel treatment modality for the prevention of ketoacidosis in patients with severe insulin-dependent diabetes mellitus.

Correction of obesity and diabetes in genetically obese mice by leptin gene therapy.

The ob/ob mouse is genetically deficient in leptin and exhibits both an obese and a mild non-insulin-dependent diabetic phenotype. To test the hypothesis that correction of the obese phenotype by leptin gene therapy will lead to the spontaneous correction of the diabetic phenotype, the ob/ob mouse was treated with a recombinant adenovirus expressing the mouse leptin cDNA. Treatment resulted in dramatic reductions in both food intake and body weight, as well as the normalization of serum insulin levels and glucose tolerance. The subsequent diminishment in serum leptin levels resulted in the rapid resumption of food intake and a gradual gain of body weight, which correlated with the gradual return of hyperinsulinemia and insulin resistance. These results not only demonstrated that the obese and diabetic phenotypes in the adult ob/ob mice are corrected by leptin gene treatment but also provide confirming evidence that body weight control may be critical in the long-term management of non-insulin-dependent diabetes mellitus in obese patients.