Seymour R. Levin

Differential regulation of gastrin and somatostatin secretion from isolated perfused rat stomachs

In order to examine the relationships between gut somatostatinlike immunoreactivity and gastrin, we studied the regulation of their secretion from isolated perfused extrinsically denervated rat gut preparations by bombesin nonapeptide and carbamyl choline. Carbamyl choline inhibited somatostatinlike immunoreactivity and stimulated gastrin secretion in a dose-dependent fashion with maximum responses at 10−6 M. These effects of carbamyl choline were abolished by atropine but not by hexamethonium. Conversely, bombesin nonapeptide stimulated both somatostatinlike immunoreactivity and gastrin secretion in doses as low as 10−10 M for somatostatinlike immunoreactivity and 10−9 M for gastrin. Neither atropine nor hexamethonium influenced bombesin-stimulated gastrin release but both agents abolished bombesin-stimulated somatostatinlike immunoreactivity secretion. The combination of carbamyl choline and bombesin affected somatostatinlike immunoreactivity and gastrin secretion in an identical fashion as carbamyl choline alone. These results suggest that somatostatinlike immunoreactivity and gastrin secretion from the gut are differentially regulated. Carbamyl choline stimulates gastrin release and inhibits somatostatin release by activation of muscarinic cholinergic receptors. Bombesin stimulates somatostatin release by activation of neural pathways involving both nicotinic and muscarinic cholinergic receptors. However, stimulation of gastrin release by bombesin does not involve cholinergic neural pathways and may reflect a direct action on gastrin cells.

A randomized clinical trial comparing the efficacy of mandibular implant-supported overdentures and conventional dentures in diabetic patients. Part I: Methodology and clinical outcomes.

STATEMENT OF PROBLEM Scientific evidence is lacking to support the general application of implant-supported mandibular overdentures. PURPOSE This randomized clinical trial was undertaken to compare the efficacy of conventional mandibular and implant-supported overdentures in diabetic edentulous patients with clinically acceptable metabolic control. METHOD A total of 102 diabetic patients, treated with or without insulin, were randomized to receive a new maxillary denture and either a conventional or an implant-supported removable mandibular overdenture. Treatment was completed for 89 patients, 37 with the conventional and 52 with implant-supported dentures. Detailed examinations, tests, and questionnaires were given before and at 6- and 24-months after treatment completion. Comparisons between the two treatment groups were made for treatment failures based on prespecifed criteria and the type and amount of maintenance care provided. RESULTS The insulin and noninsulin treated groups were collapsed because of the lack of significant differences at entry. The conventional denture and implant-supported overdenture groups were similar in terms of general demographics, medical status, quality of their original dentures and denture support, several functional measures, and patient satisfaction. Treatment was judged to be successful in 56.9% of patients with conventional dentures and 72.1% with overdentures. This difference in success rate was not statistically significant (p > 0.05). Patients with treatment failures in both groups required excessive maintenance care. Those with conventional dentures needed frequent denture base adjustments and relines, whereas those with overdentures required frequent clip replacements and repairs. Although significant improvements were seen with both treatment modalities, a higher percentage of patients with implant-supported overdentures than those with conventional dentures reported improvements in chewing comfort and moderate-to-complete overall satisfaction.

Effects of Chromium and Yeast Supplements on Carbohydrate and Lipid Metabolism in Diabetic Men

Diabetes mellitus has been shown to develop as a consequence of chromium (Cr) deficiency in experimental animals and in humans sustained by prolonged total parenteral nutrition. Prior limited trials in humans had indicated that Cr supplements, in either inorganic or organic form, may improve carbohydrate utilization. We report here a clinical double-blind, random crossover trial of inorganic Cr trichloride, a brewers yeast that contained Cr as glucose tolerance factor (GTF), a brewers yeast extract without GTF, and a placebo. Forty-three outpatient diabetic men received three of these supplements for 4 mo each. Subgroups included 21 ketosis-prone men; 7 ketosis-resistant, nonobese men; and 15 ketosis-resistant obese men. Chromium levels were followed pre- and posttreatment in hair, red blood cells, plasma, and urine. Response of carbohydrate metabolism to treatment was assessed in terms of change in insulin requirements, fasting plasma glucose, plasma cholesterol, and triglycerides, as well as change in plasma glucose, glucagon, and insulin or C-peptide levels in response to a standard meal. In some men, these parameters were also measured after i.v. tolbutamide. Both the inorganic and organic oral Cr supplements increased measurable body pools of Cr in hair and red blood cells by about 25%. However, fasting plasma glucose and lipids and the glucose response to either the standard meal or to tolbutamide were not significantly altered by any of the treatments. Despite this lack of effect on carbohydrate levels, the ketosis-resistant subgroups demonstrated a significant increase in postprandial insulin after treatment with the brewers yeast that contained GTF.

Randomized clinical trial comparing the efficacy of mandibular implant-supported overdentures and conventional dentures in diabetic patients. Part III: Comparisons of patient satisfaction

STATEMENT OF PROBLEM There is insufficient evidence to indicate the functional superiority of mandibular implant-supported overdentures to justify their use in edentulous patients. PURPOSE This study compared the benefits perceived by patients who received a new maxillary denture and a mandibular conventional denture (CD) and an implant-supported overdenture (IOD). METHOD New maxillary and mandibular dentures were delivered to 89 diabetic denture wearers with clinically acceptable metabolic control who treated their diabetes either with insulin (IT) or without insulin (NIT). Of the 89 patients, 37 received maxillary and mandibular CDs and 52 received a maxillary CD and an IOD. Two questionnaires with categorical responses were used; the first contained 13 questions to ascertain a patients absolute assessments of original dentures at entry and study dentures at 6- and 24-months after treatment completion; the second questionnaire had 11 questions that assessed the relative change perceived by patients with study dentures. Of the 78 patients who completed the posttreatment (PT) assessments at 6 months, 68 patients provided longitudinal data for questionnaire I and cross-sectional data for questionnaire II. In addition, 46 patients (18 CD and 28 IOD) also provided PT assessments at 24 months. RESULTS Both mean scores and percentage distributions of longitudinal data for questionnaire I showed perceptual improvements with both types of study dentures. Improvements were higher in the IOD than in the CD group. Mean scores failed to show any significant differences between the 2 treatment groups. The only significant difference was found in the change in percentage distributions for perceptual chewing ability in favor of the IOD group. Even this advantage was lost at 24 months. With the comparative questionnaire, a higher percentage of patients in the IOD group than in the CD group perceived improvements with study dentures from their original dentures in chewing ability, chewing comfort, and denture security. However, mean differences were statistically significant in favor of the IOD group only for chewing ability and less difficulty to chew hard foods. CONCLUSION The mandibular implant-supported overdenture offers same advantage in terms of perceived chewing function over the conventional denture.

Adenosine Triphosphatases of Rat Pancreatic Islets: COMPARISON WITH THOSE OF RAT KIDNEY

Electrolyte fluxes are fundamental to normal endocrine pancreatic function. Adenosine triphosphatases (ATPases) are enzyme systems believed to modulate electrolyte movements across membranes in a number of cell types. This study was undertaken to measure cation-dependent ATPases of rat pancreatic islets. In addition, we compared effects of substances which influence endocrine pancreatic function upon ATPases in homogenates of islets and kidney, the latter being a tissue which would not be expected to have a stimulus-secretion response to substances which activate islets. Both tissues were generally similar with respect to apparent Michaelis constant (ATP) of Na(+)K(+)ATPase, Mg(++)ATPase, and Ca(++)ATPase. In islets and kidney, Na(+)K(+)ATPase specific activity was increased when the Na:K ratio was lowered from 250:1 (175:0.7 mM) to 5:1 (100:20 mM). Inhibition of Na(+)K(+)ATPase at either Na:K ratio by ouabain, an activator of secretion, and enhancement of the high-ratio Na(+)K(+)ATPase by diphenylhydantoin, an islet secretory inhibitor, were also common to both tissues. Because both inhibition and enhancement of Na(+)K(+)ATPase could be studied at the high Na:K ratio, we examined the effect of regulators of secretion upon the activity of this enzyme. Like ouabain, substances which induce or support islet secretion, glucose 16 mM or 3.3 mM, arginine 14.2 mM (with 3.3 mM glucose), or Ca(++) 1 mM, inhibited high-ratio islet Na(+)K(+)ATPase. Like diphenylhydantoin, the inhibitors of insulin secretion, diazoxide 0.22 mM, or NH(4)Cl 16 mM, enhanced this islet ATPase. Neither valine, which is non-secretogenic, nor arginine without glucose, which is a weak secretagogue, had any effect upon islet Na(+)K(+)ATPase. We examined the effect of these substances upon other cation-dependent islet ATPases. Ca(++) inhibited Mg(++)ATPase, and glucose inhibited Ca(++)ATPase. Leucine, 22.9 mM, which induces insulin secretion in the absence of glucose, suppressed islet Ca(++)ATPase and had no effect upon high-ratio Na(+)K(+)ATPase. In contrast to the observations in the islets, most substances which influence islet function had no effect on kidney ATPases, or effects which were different from those seen in islets. Except for ouabain, none of these substances influenced the three kidney ATPases in a manner similar to that seen with islets. These findings support the hypothesis that cation-dependent ATPases are involved in specificity of islet response to substances which influence endocrine pancreatic activity.

Response to Intensive Therapy Steps and to Glipizide Dose in Combination With Insulin in Type 2 Diabetes: VA feasibility study on glycemic control and complications (VA CSDM)

OBJECTIVE The feasibility study for the VA Cooperative Study on Glycemic Control and Complications in Type 2 Diabetes (VA CSDM) prospectively studied 153 insulin-requiring type 2 diabetes patients, randomized between an intensively treated arm and a standard treatment arm during a mean follow-up of 27 months. The glycemic response to each of the progressive, sequential phases of insulin treatment was assessed, along with the incidence of hypoglycemic reactions and the relative efficacy of different doses of glipizide in combination with fixed doses of insulin. RESEARCH DESIGN AND METHODS Five medical centers participated; half of the patients were assigned to the intensive treatment arm aiming for normal HbA1c levels. Age of patients was 60 ± 6 years, duration of diabetes 8 ± 3 years, and BMI 30.7 ± 4 kg/m2. A fourstep management technique was used, with patients moving to the next step if the operational goals were not met: Phase I, evening intermediate or long-acting insulin; phase II, added daytime glipizide; phase III, two injections of insulin alone; and phase IV multiple daily insulin injections. Home glucose monitoring measurements were done twice daily and at 3:00 A.M. once a week. Hypoglycemic reactions and home glucose monitoring results were recorded and counted in each of the treatment phases. RESULTS Baseline HbA1c was 9.3 ± 1.8%, and fasting plus serum glucose was 11.4 ± 3.3 mmol/1. Fasting serum glucose fell to near normal in phase I, and remained so in the other treatment phases. An HbA1c separation of 2.1% between the arms was maintained during the course of the study, while the intensive arm kept HbA1c levels below 7.3% (P = 0.001). Most of the decrease in HbA1c occurred with one injection of insulin alone (phase I, − 1.4%) or adding daytime glipizide (phase II, −1.9% compared with baseline). HbA1c did not decrease further after substituting two injections of insulin alone, with twice the insulin dose. Multiple daily injections resulted in an additional HbA1c fall (−2.4% compared with baseline). However, two-thirds of the patients were still on one or two injections a day at the end of the study Changes in home glucose monitoring levels paralleled those of the HbA1c, as did the increments in number of reported hypoglycemic reactions, virtually all either “mild” or “moderate” in character. For the combination of glipizide and insulin (phase II), the only significant effect was obtained with daily doses up to 10 mg a day; there were no significant additional benefits with up to fourfold higher daily doses, and HbA1c levels had an upward trend with doses >20 mg/day. CONCLUSIONS A simple regime of a single injection of insulin, alone or with glipizide, seemed sufficient to obtain clinically acceptable levels of HbA1c for most obese, insulin-requiring type 2 diabetes patients. Further decrease of HbA1c demanded multiple daily injections at the expense of doubling the insulin dose and the rate of hypoglycemic events. In combination therapy, doses of glipizide >20 mg/day offered no additional benefit.

Nephropathy in non-insulin-dependent diabetes mellitus.

End-stage renal disease develops in about 5 percent of patients with non-insulin-dependent diabetes mellitus (NIDDM). The large majority of diabetic patients have this form of the disease. Thus, end-stage renal disease is an important clinical problem in patients with NIDDM. Moreover, hypertension and its macrovascular sequelae are significant problems in patients with NIDDM and may be linked with renal disease. A review of the problem of nephropathy in NIDDM is attempted, pointing out, where data are available, the clinical and pathophysiologic differences from its presentation in insulin-dependent diabetes. The need for further studies of the impact of renal disease in this maturity onset form of diabetes is emphasized.

Glycemic Control and Complications in Type II Diabetes: Design of a feasibility trial

OBJECTIVE To determine, after 1 yr of follow-up in type II diabetes patients, whether a statistically and clinically significant difference can be achieved in HbA1c between a standard therapy group and an intensively treated group, while maintaining HbA1c levels in both groups within ranges acceptable in regular community practice. Secondary objectives include assessment of patient adherence to protocol, side effects, and accuracy of data collection. RESEARCH DESIGN AND METHODS This is a prospective, randomized, controlled VA CS conducted with 151 patients at five VAMCs. Patients are males, age 40–69 yr, treated at entry with a maximum dose of sulfonylurea or with insulin, exhibiting an HbA1c level > 3 SDs above the normal mean (5.05 + 3 × 0.50 = > 6.55%). Standard control is achieved with insulin and intensive control with a step-up regimen including insulin alone or insulin/glipizide combinations. Education and management of cardiovascular risk factors are handled similarly in both groups. Primary macrovascular end points are nonfatal myocardial infarction, congestive heart failure, stroke, amputation, and cardiovascular death. Primary microvascular end points are appearance and progression of retinopathy, documented by centrally read seven-field-stereo fundus photographs. Other measured indicators include resting and ambulatory ECGs, ventricular function (MUGA scan), serum lipid and apolipoprotein levels, plasma fibrinogen, nonsymptomatic peripheral vasculopathy, neuroautonomic status by heart-beat variation on Valsalva maneuver, and microalbuminuria. CONCLUSIONS This study may be the basis for a long-term trial, involving 1400 patients, to assess the long-term effects of metabolic control on macro- and microvascular end points.

Insulinotropic Effects of Vanadate

Vanadium compounds are known to affect multiple membrane and cytosolic phosphoenzymes from various tissues; the most characterized effect is the inhibition of Na+-K+-ATPase. Since we previously reported that immunoreactive insulin (IRI) secretagogues tend to inhibit rat islet cationdependent ATPases, we examined the effects of sodium vanadate on rat IRI secretion from incubated and perifused rat islets. In the presence of 2.4 mM Ca2+, vanadate (10−3 M) induced biphasic IRI secretion with a background glucose of 100 mg/dl. In the absence of extracellular Ca2+, IRI released from incubated islets by vanadate at 100 and 300 mg/dl glucose was doubled and tripled, respectively. Furthermore, this stimulatory effect was completely abolished by known inhibitors of IRI release such as somatostatin, epinephrine, and diphenylhydantoin. Although we found the expected dose-dependent inhibition by vanadate of islet membrane Na+-K+- ATPase activity, the mechanism of action of vanadate on IRI secretion remains unknown. Vanadate probably interacts in a complex fashion with different islet phosphoenzymes and may prove to be a useful probe to further unravel the mechanisms leading to insulin secretion.

In vivo time-resolved autofluorescence measurements to test for glycation of human skin.

We present an evaluation of time-resolved fluorescence measurements on human skin for screening type 2 diabetes. In vivo human skin is excited with a pulse diode at 375 nm and pulse width of 700 ps. Fluorescence decays are recorded at four different emission wavelengths: 442, 460, 478, and 496 nm. Experiments are performed at various locations, including the palms, arms, legs, and cheeks of a healthy Caucasian subject to test single-subject variability. The fluorescence decays obtained are modeled using a three-exponential decay. The variations in the lifetimes and amplitudes from one location to another are minimal, except on the cheek. We compare the fluorescent decays of 38 diabetic subjects and 37 nondiabetic subjects, with different skin complexions and of ages ranging from 6 to 85 yr. The average lifetimes for nondiabetic subjects were 0.5, 2.6, and 9.2 ns with fractional amplitudes of 0.78, 0.18, and 0.03, respectively. The effects of average hemoglobin A1c (HbA1c) from the previous 4 yr and diabetes duration are evaluated. While no significant differences between the fluorescence lifetimes of nondiabetic and diabetic subjects are observed, two of the fractional amplitudes are statistically different. Additionally, none of the six fluorescence parameters correlated with diabetes duration or HbA1c. One of the lifetimes as well as two of the fractional amplitudes differ between diabetic subjects with foot ulcers and nondiabetic subjects.