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K C Copeland

Publications and source records attributed to K C Copeland.

At least 37 records · Page 2Linked to original sources
PubMed1997

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.

Animals↗
PubMed1996

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.

Adenoviridae↗
PubMed1996

Spectrophometric assay for measuring branched-chain amino acid concentrations: application for measuring the sensitivity of protein metabolism to insulin.

Plasma amino acid concentrations fall during insulin infusion. Amino acid concentrations can be maintained using an infusion of amino acids if their plasma concentration can be determined within a few minutes. We developed a spectrophometric assay which determines the total concentration of all three branched-chain amino acids in plasma within 1 min. The enzyme leucine dehydrogenase oxidatively deaminates leucine, isoleucine, and valine, with stoichiometric reduction of NAD that is measured using a spectrophotometer. The assay was developed in both a kinetic and end-point format. For the kinetic assay the buffer conditions were formulated to obtain equivalent rates with all three amino acids so that it could be used in samples containing unknown mixtures. For the end-point assay additional enzyme was added so that an end-point could be reached within 1 min. The application of the kinetic assay for "clamping" the branched-chain amino acids during hyperinsulinemic euglycemic clamps in humans is demonstrated.

Amino Acid Oxidoreductases↗
PubMed1996

Gastrointestinal symptoms and diabetes mellitus in children and adolescents.

Because it may be difficult to evaluate gastrointestinal diseases in children with insulin-dependent diabetes mellitus (IDDM), this report highlights several clinical features unique to diabetes and emphasizes the relationship between gastrointestinal pathology and glycemic control. Two children with IDDM are described whose hyperglycemia, ketosis, and abdominal pain were the presenting features of H. pylori-positive duodenal ulcer disease and acute appendicitis, respectively. A third nondiabetic child developed persistent postprandial hyperglycemia as the initial manifestation of dumping syndrome. These patients illustrate the relationship between glycemic control and gastrointestinal pathology in children with diabetes and the effects of gastrointestinal dysfunction on glucose regulation in nondiabetic children. In children with IDDM, gastrointestinal pathology can be confused with ketoacidosis and complicate diabetes control and management. Early recognition and treatment of the underlying gastrointestinal disease often improves glycemic control. Furthermore, severe gastrointestinal dysfunction in nondiabetic children may deleteriously influence glycemic regulation and may be confused with childhood diabetes.

Adolescent↗
PubMed1996

Phenotypic correction of dwarfism by constitutive expression of growth hormone.

GH is normally secreted in a pulsatile fashion. When GH is deficient, dwarfism is the result in both rodents and humans. An adenoviral vector containing the rat GH complementary DNA was used to induce constitutive GH expression in hepatocytes of GH-deficient lit/lit mice. Elevated serum GH increased circulating insulin-like growth factor I concentrations, corrected the growth deficiency, and normalized body composition. The results indicate that correction of the dwarf phenotype can be achieved by constitutive expression of GH at an ectopic site by gene transfer.

Adenoviruses, Human↗
PubMed1996

Genomic sequence of the DAX1 gene: an orphan nuclear receptor responsible for X-linked adrenal hypoplasia congenita and hypogonadotropic hypogonadism.

The gene responsible for X-linked adrenal hypoplasia congenita, DAX1, encodes a member of the nuclear hormone receptor superfamily. We sequenced 8851 bp that contained the DAX1 genomic region. The DAX gene was composed of two exons and one 3.4-kilobase intron. Putative TATA and GC boxes and a putative steroidogenic factor 1 response element were present in the 5'-flanking region. Two potentially polymorphic short tandem repeats were identified. The first exon encoded two putative novel zinc finger motifs within a putative DNA binding domain and part of the ligand binding domain, and the second exon encoded the remainder of the ligand binding domain. Although the putative DNA binding domain of DAX1 does not contain substantial sequence similarity to other nuclear hormone receptor superfamily members, the putative ligand binding domain had remarkable similarity to other family members. Single-strand conformational polymorphism analysis permitted identification of three new mutations in DAX1. In conclusion, single-strand conformational polymorphism analysis facilitates identification of mutations in the DAX1 gene, and the short tandem repeats may permit linkage analysis in families in which mutations are not yet identified. We speculate that DAX1 may be the most primitive member of the nuclear hormone receptor superfamily identified in mammals.

Adrenal Insufficiency↗
PubMed1995

Diagnosis of X-linked adrenal hypoplasia congenita by mutation analysis of the DAX1 gene.

OBJECTIVE: To develop a rapid diagnostic approach to individuals with the X-linked cytomegalic form of adrenal hypoplasia congenita (AHC) and hypogonadotropic hypogonadism (HH) due to mutations in DAX1, a new member of the nuclear hormone receptor gene superfamily. DESIGN: Molecular genetic diagnostic investigations of individuals with AHC and their relatives included polymerase chain reaction amplification of DAX1 for identification of intragenic mutations and fluorescence in situ hybridization with a cosmid containing the DAX1 gene for evaluation of larger deletions. PARTICIPANTS: Families that had males affected with AHC were evaluated for mutations involving the DAX1 gene. RESULTS: DAX1 mutations were identified in four families that had males affected with AHC. Two apparently independent pedigrees had an identical frame-shift mutation due to a single base pair deletion, and a third had a larger deletion involving the entire DAX1 locus. The fourth family was evaluated by fluorescence in situ hybridization for prenatal diagnosis, and both the DAX1 locus and the contiguous glycerol kinase region were deleted. CONCLUSIONS: Molecular genetic and molecular cytogenetic techniques represent rapid and complementary approaches to the diagnosis of mutations in the DAX1 gene responsible for AHC and the associated HH. Specific diagnosis of the cause of adrenal insufficiency in these boys permits anticipatory management of the HH and prenatal counseling for parents of the affected child and other members of their families.

Adrenal Insufficiency↗
PubMed1994

The influence of endurance training on insulin-like growth factor-1 in older individuals.

Previous cross-sectional studies have suggested that lower levels of insulin-like growth factor-1 (IGF-1) in older persons are related in part to diminished physical exercise. However, it is unknown whether the introduction of long-term exercise in previously inactive older individuals increases IGF-1, and whether the response is different between older men and women. Thus, we examined the effects of 8 weeks of endurance training on changes in IGF-1, IGF-1 binding protein-1 (IGFBP-1), IGFBP-3, and maximal aerobic power (VO2max) in 18 older individuals (aged 66.1 +/- 1.4 years, 10 men and eight women). Individuals were also characterized for changes in body composition, estimated energy intake, and fasting plasma levels of glucose, insulin, and glucagon before and after an exercise training program. Endurance training increased VO2max similarly in men (14%, P < .01) and women (14%, P < .01), but women showed a smaller increase in IGF-1 (8%, NS) than men (19%, P < .01). The correlation between changes in VO2max and IGF-1 was significant in men (r = .79, P < .02), but not in women (r = .22, NS). Although no mean group change in IGFBP-1 or IGFBP-3 was noted, the individual changes between IGF-1 and IGFBP-3 showed a tendency to be related in men (r = .48, P = .15), but not in women (-.21, NS). Exercise training decreased plasma glucose (P < .05) in men, but not in women.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

Acute growth hormone effects on amino acid and lipid metabolism.

The anabolic actions of GH are well known, although specific tissue responses and the mechanism of nitrogen conservation are less well understood. This study was designed to examine the acute metabolic effects of GH on whole body and regional protein metabolism, using an experimental protocol which controlled for confounding perturbations in other hormones by a simultaneous infusion of somatostatin. Control subjects received replacement doses of insulin, glucagon, and GH for the entire 7-h study period, whereas GH subjects received an identical protocol, except for an increased dose of GH sufficient to increase serum concentrations into the high-physiological range (12-20 ng/mL) for the final 3.5 h of the study (P < 0.001). Thirteen young, healthy male subjects were studied in the postabsorptive period; five served as control subjects and eight as treatment (GH) subjects. Each received continuous iv infusions of somatostatin, L-[13-C]leucine, and L-[2H5]phenylalanine throughout the study. Femoral arterial and venous sampling allowed for simultaneous measurements across the leg and in the whole body. C-Peptide levels were suppressed throughout the infusion; insulin, glucagon, insulin-like growth factor I, cortisol, epinephrine, norepinephrine, and glucose concentrations were not different between groups. Glycerol concentrations increased 3-fold in GH subjects during the final 3.5-h period (P = 0.04). Concentrations of several amino acids declined through the study, but no differences were observed between treatment groups. Leucine oxidation was reduced in GH compared to control subjects (P = 0.04). No changes in CO2 production or whole body leucine or phenylalanine flux were observed, whereas nonoxidative disposal of leucine was marginally higher in GH compared to control subjects (P = 0.07). By contrast, rates of appearance and disappearance of both leucine and phenylalanine across the leg all were relatively lower in GH compared to control subjects; leucine balance across the leg was reduced by GH (P = 0.03), whereas phenylalanine balance was not influenced by GH. Our data thus demonstrate an acute stimulatory effect of GH on lipolysis, a decrease in leucine oxidation, and no stimulation of muscle protein synthesis in spite of enhanced protein synthesis in nonmuscle tissue.

Adult↗
PubMed1994

Recombinant human insulin-like growth factor-I increases forearm blood flow.

Several recent reports have described systemic effects associated with insulin-like growth factor-I (IGF-I) infusions in humans, including dizziness, syncope, unconsciousness, bradycardia, and asystole. Eleven healthy volunteers (10 males and 1 female) underwent brachial arterial and deep forearm venous catheterizations to evaluate the effects of an intraarterial infusion of IGF-I on blood flow. Saline was infused into the brachial artery for 1 h, followed by infusions of recombinant human IGF-I (1.25, then 10 micrograms/kg BW.h) over 2 subsequent 90-min periods. Blood flow across the forearm was determined from dye dilution curves after an infusion of indocyanine green dye (20 mg/h) into the proximal arterial port. The rate of saline infusion had no effect on forearm blood flow. Likewise, the low dose arterial IGF-I infusion had no effect on blood flow, even though deep venous IGF-I concentrations increased slightly (127 +/- 37 to 172 +/- 19 ng/mL; P = NS). The 10 micrograms/kg.h infusion rate increased deep venous IGF-I concentrations approximately 4-fold above control values (477 +/- 80 vs. 150 +/- 27 ng/mL, respectively; P < 0.0001), whereas IGF-I concentrations in the peripheral circulation were increased approximately 2-fold (299 +/- 50 ng/mL) above control values (P < 0.0001). Arteriovenous glucose differences, peripheral glucose concentrations, and binding protein-3 concentrations were not influenced by either dose of IGF-I. The 10 micrograms/kg.h dose of IGF-I was associated with a 68% increase in forearm blood flow (71 +/- 8 vs. 42 +/- 6 mL/min, respectively; P < 0.0004). These data suggest that an intravascular infusion of IGF-I results in significant alterations in regional blood flow, which may be related to the observed physiological effects or side-effects associated with its use.

Adult↗
PubMed1993

Detection of a novel arginine vasopressin defect by dideoxy fingerprinting.

Autosomal dominant neurohypophyseal diabetes insipidus is a familial form of diabetes insipidus. This disorder is associated with variable levels of arginine vasopressin (AVP) and diabetes insipidus of varying severity, which responds to exogenous AVP. To determine the molecular basis of autosomal dominant neurohypophyseal diabetes insipidus, the AVP genes of members of a large kindred were analyzed. A new method, called dideoxy fingerprinting, was used to detect an AVP mutation that was characterized by DNA sequencing. The novel defect found changes the last codon of the AVP signal peptide from alanine to threonine, which should perturb cleavage of mature AVP from its precursor protein and inhibit its secretion or action.

Arginine Vasopressin↗
PubMed1993

Discordant metabolic actions of insulin in extreme lipodystrophy of childhood.

Congenital lipodystrophy includes a group of disorders characterized by total or partial absence of adipose tissue and insulin resistance. In this study we investigated the nature of insulin resistance in an 11-yr-old girl with one form of congenital lipodystrophy. We examined in vivo insulin and glycemic responses to feeding and iv glucose and in vitro amino acid and thymidine incorporation responses of skin fibroblasts to insulin exposure. In addition, we used stable isotope infusions of glucose, glycerol, and amino acids to investigate the in vivo metabolic actions of insulin on carbohydrate, fat, and protein. At 5 yr of age, she first demonstrated clinical glucose intolerance. Her basal insulin levels were normal (129 and 114 pmol/L), but increased markedly (peak values, 1304 and 5045 pmol/L) after iv glucose and a mixed meal. Insulin antibodies were undetectable, and specific [125I]insulin binding to her skin fibroblasts was normal. Both [3H]aminoisobutyric acid transport and [3H]thymidine incorporation by her fibroblasts were similar to responses obtained using control cells. At 11 5/12 yr of age, while receiving an infusion of stable isotopes, infusions of insulin at doses of 0.1 and 0.3 U/kg BW.h were ineffective in reducing her blood glucose despite elevating her serum insulin level to approximately 2500 pmol/L. Resting metabolic rate, respiratory quotient, VCO2, carbohydrate and lipid oxidation rates, glucose production rate, glycerol appearance rate, and plasma glycerol concentrations were unperturbed by the insulin infusions. By contrast, the insulin infusions reduced plasma leucine concentrations (124.2 to 86.1 to 66.7 mumol/L) and 13CO2 production rates (0.034 to 0.017 to 0.011 mumol/kg/min; baseline, 0.1, and 0.3 U insulin/kg.h, respectively). The leucine appearance rate declined (1.96 to 1.72 mumol/kg.min) in response to the 0.1 U/kg.h dose, but did not decline further in response to the 0.3 U/kg.h dose. The leucine oxidation rate also declined (0.87 to 0.39 to 0.25 mumol/kg.min), and there was a dose-related reduction in most plasma amino acid concentrations. Finally, nonoxidative leucine disposal increased progressively (1.09, 1.34, and 1.48 mumol/kg.min), suggestive of an insulin-induced increase in protein synthesis. These data indicate profound metabolic resistance to the carbohydrate and lipid actions of insulin, with preservation of protein anabolism. These observations suggest that in this patient, the biological effects of insulin on carbohydrate, lipid, and protein are distinct metabolic actions, regulated independently.

Amino Acids↗
PubMed1992

Secretion of prolactin and insulin-like growth factor I by decidual explant cultures from pregnancies complicated by intrauterine growth retardation.

OBJECTIVES: Prolactin and insulin-like growth factor I secretion elsewhere in the uterus have been shown to decrease when tissue-specific growth is limited. We investigated their secretion by decidual explant cultures from pregnancies complicated by fetal intrauterine growth retardation. STUDY DESIGN: Explant cultures from 13 pregnancies complicated by intrauterine growth retardation and 12 control pregnancies were established in minimal essential medium and media was harvested after 24 hours of culture. Prolactin and insulin-like growth factor I concentrations were determined by radioimmunoassay. Total protein in the media was also measured. Data were analyzed by analyses of variance and linear regression. RESULTS: Decidual prolactin secretion in the pregnancies with intrauterine growth retardation was reduced to 109 +/- 31 ng/100 mg tissue per 24 hours compared with 254 +/- 51 ng in the controls (p = 0.01). Insulin-like growth factor I secretion was reduced to 1.9 +/- 0.6 ng/100 mg tissue per 24 hours from 7.1 +/- 0.9 ng/100 mg in the controls (p < 0.0001). Total protein secretion did not differ between the two groups. Decidual prolactin and insulin-like growth factor I secretion had a highly significant positive correlation (r = 0.71, p = 0.0001). CONCLUSIONS: Our data show that two protein hormones secreted by the maternal decidua are dramatically reduced in intrauterine growth retardation and warrant further investigation into their roles in the intrauterine environment.

Analysis of Variance↗
PubMed1992

Heated dorsal hand vein sampling for metabolic studies: a reappraisal.

The purpose of the current study was to determine the accuracy of a given heated dorsal hand vein (HDHV) measurement in predicting a simultaneous arterial measurement and to validate this technique for use in stable isotope studies. Twenty catheterizations of the femoral artery, femoral vein, and a dorsal hand vein were performed in 13 healthy male subjects. Simultaneous blood samples were obtained from all three sites during primed continuous infusions of L-[1-13C]leucine (Leu) and L-[ring-2H5]phenylalanine (Phe) in the postabsorptive state, with or without intravenous glucose infusion. Relationships were examined by linear regression analysis, with 95% prediction intervals for femoral arterial values determined using the HDHV-derived values as independent variable. Glucose concentrations and isotopic enrichments of ketoisocaproate (KIC), Leu, and Phe were similar in HDHV- and arterial-derived blood, with slopes between 0.9414 and 1.0008, intercepts not different from zero, and r2 values of 0.7613 or greater (P < 0.05). Intercepts for KIC, Leu, and Phe concentrations all were different from zero (P < 0.05), and slopes ranged between 0.7560 and 0.8625. For each analysis the HDHV sample correlated better with the femoral arterial sample than with the femoral venous sample. These data support the use of HDHV sampling as a surrogate for direct arterial sampling but document significant limitations in the technique.

Adult↗