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Biomedical subjects

J B Redmon

Publications and source records attributed to J B Redmon.

At least 19 recordsLinked to original sources

Chronic treatment with phentermine combined with fenfluramine lowers plasma serotonin.

As expected on the basis of published research in both humans and animals, treatment with phentermine/fenfluramine lowers plasma 5-hydroxytryptamine [corrected], whereas treatment with phentermine had no significant effect. In light of these findings, future research should focus on mechanisms other than increased plasma 5-hydroxytryptamine [corrected] to explain how fenfluramine increases the risk of primary pulmonary hypertension and valvular heart disease.

Administration, Oral↗

A survey of oncologists regarding sperm cryopreservation and assisted reproductive techniques for male cancer patients.

BACKGROUND: The authors surveyed the current knowledge, opinions, and clinical practices of oncologists regarding pretherapy cryopreservation of semen from male cancer patients since the introduction of intracytoplasmic sperm injection (ICSI). METHODS: A survey was sent to all members of the American Society of Clinical Oncology in Minnesota. RESULTS: Forty-six of 165 oncologists (28%) responded. Factors considered important in how strongly to recommend cryopreservation were patient age at the time of diagnosis (94%), type of treatment (83%), type of cancer (65%), urgency to initiate treatment (63%), and preexisting infertility (57%). Oncologists perceived patients to be significantly more concerned about cryopreservation than they were themselves during pretherapy counseling (P = 0.0005). Oncologists estimated that 27% of their patients chose to cryopreserve sperm. However, only 26% of the oncologists knew about ICSI. The cancers perceived to warrant cryopreservation the most were lymphomas, leukemias, and testicular carcinomas. The treatment modalities perceived to warrant cryopreservation the most were distributed among various chemotherapy and radiation regimens. A majority of respondents to the survey knew where patients could go to cryopreserve sperm (89%), but less than half of the respondents gave accurate information about the cost. CONCLUSIONS: Most of the oncologists surveyed were unaware of recent advances in reproductive technology in which only a few sperm are needed for successful in vitro fertilization with ICSI. This lack of awareness may be contributing to underutilization of sperm cryopreservation by male cancer patients. Currently, all male cancer patients of reproductive age who will have treatment that may affect testicular function and who may desire children in the future should cryopreserve sperm before the initiation of therapy.

Cryopreservation↗

Autoimmune hypoglycemia.

Autoimmune hypoglycemia is a rare but fascinating syndrome of hypoglycemia caused by the interaction of endogenous antibodies with insulin or the insulin receptor. Awareness of autoimmune hypoglycemia is important because the syndrome may produce severe neuroglycopenic symptoms and may be confused with the presence of an insulinoma. A correct diagnosis is important to avoid unnecessary surgical intervention in patients who are best treated with conservative support, watchful waiting, or in some cases, immunosuppressive therapy.

Antibodies↗

Pharmacologic induction of weight loss to treat type 2 diabetes.

OBJECTIVE: Most individuals with type 2 diabetes are overweight, and weight loss for them is an important therapeutic objective. However, usual weight-loss strategies have generally not produced sustained weight loss. Pharmacologic agents to assist weight loss might be useful, but no long-term data on their effectiveness and safety in patients with type 2 diabetes are available. We therefore initiated a 2-year placebo-controlled trial of the weight-loss medications fenfluramine and phentermine in type 2 diabetic subjects. RESEARCH DESIGN AND METHODS: A total of 44 overweight (> 120% ideal body weight) subjects with type 2 diabetes were enrolled in a randomized, placebo-controlled, double-blind trial of fenfluramine and phentermine. All subjects received intensive nutrition counseling, an exercise prescription, and instruction in behavior modification. Subjects were randomly assigned to 20 mg fenfluramine three times a day and 37.5 mg phentermine daily (n = 23) or dual placebos (n = 21). Diabetes medications were adjusted as necessary to achieve glycemic goals. Changes in weight, glycemia, lipemia, and blood pressure were assessed every 2 months, as were adverse events. In September 1997, when fenfluramine was withdrawn from the U.S. market, fenfluramine was stopped in all subjects. Thus the length of drug treatment varied, but 16 subjects (8 in each group) reached 12 months of treatment. Only data obtained before the withdrawal of fenfluramine are included in this report. RESULTS: A study termination, diabetes medications had been reduced in 1 subject in the placebo group (5%) and 11 subjects in the drug treatment group (52%) (P = 0.005). Drug treatment resulted in significant reductions in body weight, BMI, and HbA1c at all time points through 6 months. Changes in weight at 6 months were -2.7 +/- 1.4 kg (mean +/- SEM) with placebo treatment and -9.6 +/- 1.5 kg with drug treatment (P = 0.003). Even though more subjects in the drug treatment group required reductions in diabetes medications, at 6 months, changes in HbA1c were -0.3 +/- 0.2% with placebo treatment and -1.6 +/- 0.3% with drug treatment (P = 0.002). Fasting plasma glucose and triglycerides were significantly reduced at some time points with drug treatment. No serious adverse events attributable to study medications were observed. CONCLUSIONS: Premature study termination decreased the power of our study at later time points. However, our data suggest that weight loss medications are an effective treatment for type 2 diabetes during active weight loss. Whether the benefit persists after weight loss has stopped remains to be determined.

Appetite Depressants↗

Hypoglycemia after pancreas transplantation.

OBJECTIVE: Hypoglycemia is a serious complication of therapy for diabetes. Chronic hypoglycemia and the attendant decrease in quality of life have been rationales for advocating pancreas transplantation as an alternative treatment. However, reports have appeared that suggest that as high as 30-50% of pancreas transplant recipients have occasional symptoms of mild hypoglycemia. Therefore, we studied glucose and hormone levels in transplant recipients and healthy control subjects. RESEARCH DESIGN AND METHODS: We studied glucose and hormone levels in transplant recipients reporting frequent symptoms of hypoglycemia (n = 10), transplant recipients without symptoms of hypoglycemia (n = 9), and healthy control subjects (n = 8) after a mixed meal and during a subsequent 24-h modified fast. All transplant recipients were insulin-independent; were receiving prednisone, cyclosporine, and azothioprine; and had functioning grafts with systemic venous drainage. RESULTS: No significant differences were observed in the fasting glucose, insulin, C-peptide, or glucagon levels when comparing the symptomatic with the asymptomatic groups of patients who had undergone successful pancreas transplantation. Similarly, no significant differences were found in the immediate postprandial period after a mixed meal. However, during the subsequent 24-h fast, glucose levels fell lower in the symptomatic than in the asymptomatic group of patients receiving a transplanted pancreas (71+/-2 vs. 81+/-2 mg/dl, P < 0.002). During the fast, no significant differences were found in insulin, C-peptide, or glucagon levels when comparing asymptomatic to symptomatic groups. Of 10 symptomatic recipients of pancreas transplantation, 5 reported symptoms of hypoglycemia during the study. In four of these five subjects, the onset of symptoms corresponded to nadirs in serum glucose, which occurred at values 2 SD or more below the mean glucose observed for the control and the asymptomatic pancreas recipient groups. The serum glucose levels at the time of symptoms in these four subjects were 55, 66, 51, and 57 mg/dl. In each of these four subjects, symptoms abated and the glucose levels rose spontaneously without intervention. One of these four subjects had elevated insulin binding activity in his serum consistent with endogenous insulin antibodies. This individual had a serum glucose value of 55 mg/dl at the conclusion of the 24-h fast without symptoms. CONCLUSIONS: Among a group of pancreas transplant recipients reporting frequent symptoms of hypoglycemia, some individuals demonstrated transient, symptomatic postprandial hypoglycernia. With the exception of one recipient with insulin antibodies, no evidence was found for hypoglycemia during fasting. Although postprandial hypoglycemia may occur in some pancreas transplant recipients, it does not appear to be a highly significant clinical problem.

Activities of Daily Living↗

Effects of tacrolimus (FK506) on human insulin gene expression, insulin mRNA levels, and insulin secretion in HIT-T15 cells.

FK506 (tacrolimus) is an immunosuppressive drug which interrupts Ca2+-calmodulin-calcineurin signaling pathways in T lymphocytes, thereby blocking antigen activation of T cell early activation genes. Regulation of insulin gene expression in the beta cell may also involve Ca2+-signaling pathways and FK506 has been associated with insulin-requiring diabetes mellitus during clinical use. The purpose of this study was to characterize the effects of FK506 on human insulin gene transcription, insulin mRNA levels, and insulin secretion using as a model the HIT-T15 beta cell line. FK506 had no acute effect on insulin secretion in the HIT cell, but caused a reversible time- and dose-dependent (10(-9)-10(-6) M) decrease in HIT cell insulin secretion. Decreased insulin secretion in the presence of FK506 was also accompanied by a dose-dependent decrease in HIT cell insulin content, insulin mRNA levels, and expression of a human insulin promoter-chloramphenicol acetyl transferase (CAT) reporter gene. FK506 decreased HIT cell expression of the human insulin promoter-CAT reporter gene by 40% in the presence of both low (0.4 mM) at high (20 mM) glucose concentrations. Western blot analysis of HIT cell proteins gave evidence for the presence of calcineurin in the HIT cell. These findings suggest that FK506 may have direct effects to reversibly inhibit insulin gene transcription, leading to a decline in insulin mRNA levels, insulin synthesis, and ultimately insulin secretion.

Blotting, Northern↗

Glucose, insulin, and glucagon levels during exercise in pancreas transplant recipients.

OBJECTIVE: To determine whether pancreas transplant recipients maintain normal blood glucose levels during physical exercise. RESEARCH DESIGN AND METHODS: We measured serum glucose, insulin, C-peptide, and plasma glucagon levels in six pancreas transplant recipients and six healthy control subjects matched for age, sex, body size, and level of conditioning during 1 h of bicycle exercise at a workload set to achieve 40% of each individual's previously determined peak oxygen consumption (VO2). RESULTS: Serum glucose values were not different between control subjects and transplant recipients before the start of exercise (5.0 +/- 0.1 and 4.9 +/-0.1 mmol/l, respectively). Serum glucose levels fell slightly but significantly in both recipients and control subjects during exercise. There were no significant differences in glucose levels between the two groups at any time point during exercise, although mean nadir glucose during exercise was slightly lower in transplant recipients compared with control subjects (4.4 +/- 0.1 vs. 4.8 +/- 0.1 mmol/l, P = 0.04). In control subjects, insulin and C-peptide levels fell significantly within 15-30 min of exercise and glucagon levels rose significantly after 60 min of exercise. In transplant recipients, there was a trend for insulin and C-peptide levels to fall and glucagon levels to rise during exercise, although these changes were delayed and were not statistically significant. CONCLUSIONS: No significant abnormalities in blood glucose were detected in pancreas transplant recipients during bicycle exercise at 40% of peak VO2 for 1 h. Compared with levels in control subjects, subtle alterations in insulin and glucagon levels may occur in transplant recipients during exercise. However, these alterations do not appear to result in either hyperglycemia or hypoglycemia during light exercise for up to 1 h.

Adult↗

Regulation of human insulin gene transcription by glucose, epinephrine, and somatostatin.

We observed in the HIT cell, a clonal insulin-secreting cell line, that epinephrine and somatostatin lower insulin mRNA levels and intracellular insulin content in addition to the well-recognized effect of these hormones to inhibit insulin secretion. To determine whether these inhibitory hormones might regulate insulin synthesis at the level of insulin gene transcription, we studied HIT cell expression of a human insulin-chloramphenicol acetyl transferase (CAT) reporter gene in the presence of glucose, epinephrine, and somatostatin. HIT cell expression of this human insulin-CAT reporter gene was responsive to glucose in a concentration-dependent manner, increasing threefold as the glucose concentration increased from 0.4 to 11 mM. Epinephrine significantly inhibited insulin-CAT reporter gene expression (61 +/- 5% of control), an effect mediated specifically by the human insulin gene promoter/enhancer sequence. Somatostatin significantly inhibited expression of the human insulin-CAT reporter gene (65 +/- 4% of control) and, to a lesser extent, expression of a control reporter gene, pRSVCAT (78 +/- 4% of control). Thus, somatostatin may inhibit insulin gene transcription by insulin gene-specific effects as well as more general effects on gene expression. Both epinephrine and somatostatin inhibited expression of the human insulin-CAT reporter gene in a concentration-dependent manner that paralleled inhibition of insulin secretion. These studies indicate that epinephrine and somatostatin lower HIT cell insulin mRNA levels in part by inhibiting insulin gene transcription. Thus, hormonal inhibition of insulin secretion may be coupled with inhibition of insulin synthesis, thereby allowing the beta-cell to match insulin supply to secretory demand.

Animals↗

Effects of glucose, galactose, and lactose ingestion on the plasma glucose and insulin response in persons with non-insulin-dependent diabetes mellitus.

Galactose usually is ingested as lactose, which is composed of equimolar amounts of glucose and galactose. The contribution of galactose to the increase in glucose and insulin levels following ingestion of equimolar amounts of galactose and glucose, or lactose, has not been reported in people with non-insulin-dependent diabetes mellitus (NIDDM). Therefore, we studied the effects of galactose ingestion alone, as well as with glucose either independently or in the form of lactose, in subjects with untreated NIDDM. Eight male subjects with untreated NIDDM ingested 25 g glucose, 25 g galactose with or without 25 g glucose, or 50 g lactose as a breakfast meal in random sequence. They also received 50 g glucose on two occasions as a reference. Water only was given as a control meal. Plasma galactose, glucose, glucagon, alpha-amino nitrogen (AAN), nonesterified fatty acids (NEFA), and serum insulin and C-peptide concentrations were determined over a 5-hour period. The integrated area responses were quantified over the 5-hour period using the water control as a baseline. Following ingestion of 25 g galactose, the maximal increase in plasma galactose concentration was 1 mmol/L. The mean maximal increases in plasma galactose concentration following ingestion of 25 g galactose + 25 g glucose or following 50-g lactose meals were similar and were only 12% of that following ingestion of galactose alone (P < .05). The mean galactose area response over the water control for the 25-g galactose meal was 0.95 +/- 0.31 mmol.h/L.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

Chronic exposure of HIT cells to high glucose concentrations paradoxically decreases insulin gene transcription and alters binding of insulin gene regulatory protein.

Chronically culturing HIT-T15 cells in media containing high glucose concentrations leads to decreased insulin mRNA levels, insulin content, and insulin secretion. These changes can be prevented by culturing the cells in media containing lower glucose levels (Robertson, R. P., H.-J. Zhang, K. L. Pyzdrowski, and T. F. Walseth. 1992. J. Clin. Invest. 90:320-325). The mechanism of this seemingly paradoxical phenomenon was examined by transiently transfecting HIT cells with a chloramphenicol acetyl transferase (CAT) reporter gene controlled by the 5'-regulatory domain of the human insulin gene (INSCAT). Early passages of HIT cells readily expressed INSCAT, whereas late passages of cells chronically cultured in 11.1 mM glucose expressed only 28.7 +/- 2.3% (mean +/- SEM) of the CAT activity expressed in early passages. In contrast, late passages of HIT cells chronically cultured in 0.8 mM glucose retained the ability to express the INSCAT reporter gene to 69.6 +/- 10.0% of the CAT activity observed in early passages. The decrease in INSCAT expression in late passages of cells serially cultured in 11.1 mM glucose was associated with the inability to form a specific nuclear protein-DNA complex with the CT motifs of the human insulin promoter. Formation of this specific protein-DNA complex was preserved in late passages of HIT cells when serially cultured in 0.8 mM glucose. Mutations of the CT motifs caused markedly diminished CAT activity in all passages examined. These data indicate that chronic exposure of the beta cell to high glucose concentrations can paradoxically decrease insulin gene transcription, in part, by altering the ability of a regulatory protein (GSTF) to interact with the insulin gene promoter. This provides a potential mechanism for glucotoxic effects on the beta cell at the level of the insulin gene.

Animals↗

No effect of deferoxamine therapy on glucose homeostasis and insulin secretion in individuals with NIDDM and elevated serum ferritin.

Deferoxamine has been proposed as a potentially important therapy for individuals with NIDDM and mild elevations in serum ferritin. Previously, iron chelation therapy with intravenous deferoxamine over a 5-13-wk period has been reported to normalize serum ferritin and markedly improve glycemic control. To confirm these results and to study potential beneficial effects of deferoxamine on insulin secretion, 9 individuals with NIDDM and elevated serum ferritin levels were treated twice weekly with deferoxamine infusion, following a previously described protocol. Although 8 of 9 subjects achieved normal or near-normal serum ferritin values after deferoxamine therapy, we found little evidence that it produced beneficial effects on glycemic control. Fasting glucose levels pre- and post-deferoxamine therapy were unchanged (11.6 +/- 1.2 and 11.3 +/- 1.5 mM, respectively, P = 0.80). GHb levels declined slightly after deferoxamine therapy (9.3 +/- 0.7 vs. 8.8 +/- 0.7%, P < 0.05); however, this effect was small and was not associated with elimination of or even substantial reduction in insulin or oral hypoglycemic therapy. Deferoxamine therapy did not significantly alter fasting insulin or C-peptide levels, nor stimulated insulin or C-peptide responses to intravenous arginine or glucose. During follow-up studies 1.5-8 mo after deferoxamine therapy, serum ferritin levels again were elevated in 5 of 8 subjects who showed an initial response. Thus, although deferoxamine therapy reduced serum ferritin levels in our subjects, we were unable to confirm a previous report that this effect was associated with any meaningful improvement in glycemic control or insulin secretion.

Arginine↗

[Hyperinsulinemia as a consequence of systemic venous drainage in patients with pancreas transplantation].

To evaluate the metabolic consequences of pancreatic transplantation with systemic venous drainage on beta cell function, we examined insulin and C-peptide responses to arginine and secretin in type I diabetic recipients of pancreas transplantation (n = 16), and normal controls (n = 28). Basal insulin levels were 24 +/- 3 microU/l in pancreas recipients, and 7 +/- 1 microU/l in controls (p less than 0.001). Stimulated insulin levels following arginine (MANOVA, p less than 0.001), and secretin (MANOVA, p less than 0.001) were 1.5 to 3 fold elevated compared to controls. In contrast, integrated C-peptide responses following stimulation with arginine or secretin did not differ significantly between the two groups. We conclude that recipients of pancreas allografts with systemic venous drainage have elevated basal and stimulated insulin levels and that these alterations are primarily due to alterations of first pass hepatic insulin clearance although insulin resistance secondary to immunosuppressive therapy (including prednisone) may also play a contributing role. To avoid hyperinsulinemia and its possible long term adverse consequences, transplantation of pancreas allografts in sites with portal rather than systemic venous drainage may be preferable.

Adult↗

Somatostatin and epinephrine decrease insulin messenger ribonucleic acid in HIT cells through a pertussis toxin-sensitive mechanism.

The sites of action for somatostatin and epinephrine to inhibit insulin secretion have been reported to be exclusively in the exocytotic pathway. We used HIT cells, a clonal line of beta-cells, to examine whether these hormones might have as yet undescribed, nonexocytotic effects on insulin messenger RNA levels. We observed that both somatostatin and epinephrine not only inhibit insulin secretion (53 +/- 2% and 50 +/- 2% of control, respectively) but also decrease insulin mRNA levels (54 +/- 5% and 66 +/- 5% of control, respectively) and insulin content in HIT cells (61 +/- 2% and 51 +/- 1% of control, respectively). The latter two effects are discernible by 24 h, maximal by 48 h, and are prevented by preincubation of HIT cells with pertussis toxin. These new observations suggest that somatostatin and epinephrine negatively modulate insulin availability through a guanine nucleotide binding protein-mediated step in insulin synthesis before the exocytotic pathway. This general mechanism may allow these two hormones to serve as more long-term regulators of insulin availability in distinction to their shorter term and more readily reversible inhibitory effects on the exocytotic pathway.

Animals↗

Failure of insulin to antagonize cAMP-mediated glycogenolysis in rat ventricular cardiomyocytes.

Isolated rat ventricular cardiomyocytes were used to study the effects of insulin on glycogen metabolism in cells treated with various agents that activate adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase. Incubation of myocytes with isoproterenol produced a rapid concentration-dependent increase in cAMP concentration, cAMP-dependent protein kinase activity, and phosphorylase activity and a simultaneous decrease in the glycogen synthase activity ratio. Various cAMP analogues also produced a concentration-dependent increase in phosphorylase activity and a decline in the glycogen synthase activity ratio. Incubation of cells with insulin produced no change in basal phosphorylase activity but produced a rapid 40% increase in the glycogen synthase activity ratio. Inclusion of insulin in cell incubations containing increasing concentrations of isoproterenol did not modify the increases in cAMP concentration, protein kinase activity, or phosphorylase activity. Insulin also did not antagonize the ability of any of the cAMP analogues tested to activate phosphorylase, irrespective of the suitability of the particular cAMP analogue as a substrate for cAMP phosphodiesterases. The failure of insulin to antagonize the glycogenolytic effects of isoproterenol or cAMP analogues was paralleled by its failure to activate low-Km phosphodiesterase activity, but the cAMP analogue, 8-parachlorophenylthio-cAMP produced a small reproducible activation of the low-Km enzyme. In contrast to hepatocytes and adipocytes, where some effects of insulin appear to be due to activation of the phosphodiesterase and hydrolysis of cAMP, the effects in cardiomyocytes appear to be independent of an insulin-sensitive phosphodiesterase or of the effects on other components of the cAMP cascade.

3',5'-Cyclic-AMP Phosphodiesterases↗

Glucagon, catecholamine and pancreatic polypeptide secretion in type I diabetic recipients of pancreas allografts.

Successful pancreas transplantation in type I diabetic patients restores normal fasting glucose levels and biphasic insulin responses to glucose. However, virtually no data from pancreas recipients are available relative to other islet hormonal responses or hormonal counterregulation of hypoglycemia. Consequently, glucose, glucagon, catecholamine, and pancreatic polypeptide responses to insulin-induced hypoglycemia and to stimulation with arginine and secretin were examined in 38 diabetic pancreas recipients, 54 type I diabetic nonrecipients, and 26 nondiabetic normal control subjects. Glucose recovery after insulin-induced hypoglycemia in pancreas recipients was significantly improved. Basal glucagon levels were significantly higher in recipients compared with nonrecipients and normal subjects. Glucagon responses to insulin-induced hypoglycemia were significantly greater in the pancreas recipients compared with nonrecipients and similar to that observed in control subjects. Glucagon responses to intravenous arginine were significantly greater in pancreas recipients than that observed in both the nonrecipients and normal subjects. No differences were observed in epinephrine responses during insulin-induced hypoglycemia. No differences in pancreatic polypeptide responses to hypoglycemia were observed when comparing the recipient and nonrecipient groups, both of which were less than that observed in the control subjects. Our data demonstrate significant improvement in glucose recovery after hypoglycemia which was associated with improved glucagon secretion in type I diabetic recipients of pancreas transplantation.

Arginine↗

Systemic venous drainage of pancreas allografts as independent cause of hyperinsulinemia in type I diabetic recipients.

To evaluate the metabolic consequences of pancreas transplantation with systemic venous drainage on beta-cell function, we examined insulin and C-peptide responses to glucose and arginine in type I (insulin-dependent) diabetic pancreas recipients (n = 30), nondiabetic kidney recipients (n = 8), and nondiabetic control subjects (n = 28). Basal insulin levels were 66 +/- 5 pM in control subjects, 204 +/- 18 pM in pancreas recipients (P less than 0.0001 vs. control), and 77 +/- 17 pM in kidney recipients. Acute insulin responses to glucose were 416 +/- 44 pM in control subjects, 763 +/- 91 pM in pancreas recipients (P less than 0.01 vs. control), and 589 +/- 113 pM in kidney recipients (NS vs. control). Basal and stimulated insulin levels in two pancreas recipients with portal venous drainage were normal. Integrated acute C-peptide responses were not statistically different (25.3 +/- 4.3 nM/min in pancreas recipients, 34.2 +/- 5.5 nM/min in kidney recipients, and 23.7 +/- 2.1 nM/min in control subjects). Similar insulin and C-peptide results were obtained with arginine stimulation, and both basal and glucose-stimulated insulin-C-peptide ratios in pancreas recipients were significantly greater than in control subjects. We conclude that recipients of pancreas allografts with systemic venous drainage have elevated basal and stimulated insulin levels and that these alterations are primarily due to alterations of first-pass hepatic insulin clearance, although insulin resistance secondary to immunosuppressive therapy (including prednisone) probably plays a contributing role. To avoid hyperinsulinemia and its possible long-term adverse consequences, transplantation of pancreas allografts into sites with portal rather than systemic venous drainage should be considered.

Adult↗