Scanning electron microscopic analysis of skin resolution as an aid in identifying trauma in forensic investigations.

The forensic investigator is frequently confronted with cases that present with wounds and blunt force trauma. Presently, the forensic investigator depends upon previous experience and further investigative deduction of the crime scene to analyze these injuries. Although not readily apparent to the naked eye, many skin tissue injuries can be visualized with scanning electron microscopy (SEM). This study was designed to establish skin trauma resolution using SEM in various skin preparations. Tissue trauma was induced on leather, preserved skin, fresh skin, and living skin using dies of varying thread size. Calibrated pressure forces in pounds per square inch (psi) were applied and impressions made using vinyl polysiloxane. Positive replicas of the tissues were prepared for SEM using isocyanate resin. After sputter coating the cast with 35 nm of gold-palladium, electron micrographs were generated using a Jeol JSM-5310LV scanning electron microscope. To establish resolution, thread widths of 52, 104, and 208 threads per inch (tpi) and trauma forces of 150, 200, and 250 psi were used to produce the impressions. Microgrooves that were identified on the die threads were analyzed. The optimum pressure for resolution studies was 150 psi using the 52 tpi die on the leather sample (4.67 +/- 0.88 microm, p = 0.046 and 0.025, respectively, by ANOVA). The resolution was compared to that of leather using preserved, fresh, and living skin. The resolution in preserved and fresh skin was less than for leather (9.00 +/- 1.73 and 10.5 +/- 4.5 versus 4.67 +/- 0.88 microm, p = 0.09 and p = 0.20, respectively). Living skin resolution was 3 microm at 52 tpi and 100 psi. Various implements of blunt force trauma were also examined using the leather sample. Time after trauma resolution was examined at 0 (3 microm), 5 (6 microm), 10 (8 microm), and 20 (9 microm) min in living tissue. A comparison between the microgrooves on the die replicas and the tissue trauma impressions revealed striking agreement for both linearity and resolution. Analysis of the microgrooves suggests that discrete morphological characteristics are seen in skin tissue traumas. This method could expand the tools available for the forensic investigation of blunt force trauma.

Pioglitazone attenuates basal and postprandial insulin concentrations and blood pressure in the spontaneously hypertensive rat.

Subjects with hypertension are hyperinsulinemic and resistant to insulin-stimulated glucose uptake. A similar paradigm is found in the spontaneously hypertensive rat (SHR). These findings suggest the possibility that insulin resistance and hyperinsulinemia may play an important role in blood pressure regulation. Pioglitazone, a thiazolidinedione derivative, sensitizes target tissues to insulin and decreases hyperglycemia and hyperinsulinemia in various insulin-resistant animals. The purpose of this study was to assess the influence of pioglitazone administration on pre- and postprandial glucose and insulin concentrations and determine whether changes in beta-cell secretion resulted in any change in blood pressure measurements. Twelve SHR were fed custom diets ad libitum, six with and six without pioglitazone (20 mg/kg chow). Fasting and postprandial glucose levels were unaltered by pioglitazone treatment. Fasting insulin concentrations were similar at week 1, but were significantly lower (P < .01) in the pioglitazone group at weeks 3 (1.89 +/- 0.3 v7.94 +/- 1.5 ng/mL) and 4 (4.5 +/- 1.4 v9.1 +/- 0.7 ng/mL), compared with the control group. Pioglitazone also significantly (P < .01) lowered postprandial insulin concentrations after an oral glucose challenge. Systolic, mean, and diastolic blood pressures were significantly lower (P < .01), 177 +/- 3 v190 +/- 4.7 mm Hg, 162 +/- 2.1 v175 +/- 5.9 mm Hg, and 156 +/-2.1 v168 +/- 6.2 mm Hg, respectively, in the animals receiving pioglitazone versus the control group. Heart rate, body weight, serum cholesterol, and triglyceride levels were comparable between the two groups. In conclusion, pioglitazone significantly decreased fasting and postprandial insulin concentrations and effectively lowered blood pressure in the SHR.

The impact of ethanol and Marinol/marijuana usage on HIV+/AIDS patients undergoing azidothymidine, azidothymidine/dideoxycytidine, or dideoxyinosine therapy.

Therapeutic observations suggest that azidothymidine (AZT)-resistant HIV+/AIDS patients are frequently offered AZT/dideoxycytidine (DDC) or dideoxyinosine (DDI) therapy. The latter therapies have been associated with the development of acute pancreatitis. During the initial portion of this study, when patients reported limiting ethanol consumption, an increase in CD4+, a decrease in amylase, and a decrease in lipase was observed in patients on DDI monotherapy. Marinol/marijuana usage was associated with depressed CD4+ counts and elevated amylase levels within the DDI subgroup. The purpose of this study was to follow these patients over 1 year and compare clinical indicators of pancreatitis and HIV progression. After 1 year, the remaining 56 patients were reexamined in the follow-up portion for clinical indicators of HIV disease progression and pancreatoxic/hepatotoxic effects. Those in the AZT group, who remained on this therapy throughout the year, had significantly increased amylase values from 55.3 to 69.3 IU/liter (p < 0.05). In the AZT/DDC group, those who remained on combination therapy throughout the year, 4 of the 5 clinical indicators of disease progression changed. Amylase, ALT, and AST all increased significantly from 55.2 to 77.8 IU/liter (p < 0.01), from 38.0 to 92.3 IU/liter (p < 0.05), and from 55.2 to 97.0 IU/liter (p < 0.05), respectively. Lipase levels decreased significantly (106.0 to 74.6 IU/liter, p < 0.05). The most remarkable changes occurred in the AZT/DDC group (who reduced ethanol consumption), wherein clinical indicators of pancreatitis and liver dysfunction declined, including amylase (65.0 to 20.0 IU/liter, p < 0.05), ALT (350.0 to 100.0 IU/liter, p < 0.01), and AST (240.0 to 95.0 IU/liter, p < 0.01). No significant changes were noted in the DDI or AZT groups. Marinol/marijuana use was associated with declining health status in both the AZT and AZT/DDC groups. In contrast, all clinical indicators of pancreatitis improved in the DDI patients who utilized Marinol/marijuana, including amylase (-34%), lipase (-30.8%), ALT (-21.4%), and AST (-20.1%). This paired follow-up study suggests that HIV+/AIDS patients on antiretroviral therapies should restrict their ethanol consumption. In HIV+/AIDS patients with the lowest CD4+ counts (those on DDI monotherapy), utilization of Marinol/marijuana does not seem to have a deleterious impact.

Polyunsaturated fats enhance peripheral glucose utilization in rats.

Carbohydrate intolerance is positively correlated with saturated fat consumption. In contrast, individuals consuming diets comprised of polyunsaturated fatty acids (PUFA) have a lower incidence of diabetes mellitus (DM). To test the hypothesis that dietary fats may influence insulin sensitivity, insulin-stimulated glucose utilization was estimated in vivo in rats consuming diets enriched with saturated fatty acids (SFA) (cocoa butter), monounsaturated fatty acid (MUFA) (olive oil), or PUFA derived from corn or fish sources. Each test meal provided (as percentage of calories) 45% carbohydrate, 39% fat, and 16% protein. The meals were consumed over an 8-week period. Metabolic clearance rate (MCR) for glucose was significantly higher (p less than 0.01; 5.69 +/- 0.46 and 5.18 +/- 0.29 ml/kg/min) for diets containing fish and corn oil sources, respectively, when compared to olive oil (4.34 +/- 0.32 ml/kg/min) and cocoa butter (4.61 +/- 0.11 ml/kg/min). Although the MCR between the fish and corn oil diets were not significantly different, the steady state plasma insulin concentration was lower during the fish oil meal (75 +/- 20 microU/ml) when compared to the corn meal (112 +/- 13 microU/ml). Fasting plasma insulin concentrations were significantly lower (p less than 0.01) following the PUFA diets compared to the other two diets. Fasting plasma glucose levels, despite being lower in the fish meal, were insignificantly different among the four test meals. Lastly, body weights were comparable among the four groups tested. These results suggest that diets enriched with PUFA enhance peripheral glucose utilization significantly more than diets comprised of MUFA or SFA sources.(ABSTRACT TRUNCATED AT 250 WORDS)

A morphological and immunohistochemical investigation of endocrine pancreata from obese ob+/ob+ mice.

There is a marked difference in insulin secretion between the ob+/ob+ obese mouse and its non-obese littermate. Numerous peptides have been implicated in the modification of postprandial insulin secretion. In this study, the morphological and immunohistochemical studies of the genetically obese mouse (ob+/ob+) pancreata were compared with control littermates. Additionally, the distribution of gastric inhibitory polypeptide, somatostatin, glucagon, and insulin immunoreactive cells was also quantitated. Hyperglycemia and hyperinsulinemia were verified in the obese mice. The control animals had some islets and ductules with mononuclear infiltrations of a possible immune character. The obese individuals had a marked increase in both number and size of the islets of Langerhans compared with lean controls. The insulin immunocytochemical reaction in the obese pancreatic beta-cells was weaker than that of controls, as was the aldehyde-fuchsin reaction. The glucagon, gastric inhibitory polypeptide, and somatostatin containing cells were intermingled with the beta-cells. In contrast, the control animals showed a peripheral localization of these cell types. The morphometric analysis of the obese pancreas showed a decreased proportion of non-beta cells within the islets but not in total pancreatic volume in comparison with controls. The obese mouse also had cavities filled with eosin-stained material among numerous beta-cells. No complete epithelial lining distinguished these formations from the surrounding islet cells. The content of the cavities was not stained by any of the immunocytochemical reactions applied. In conclusion, the pancreatic islets of the ob+/ob+ mouse show marked differences in both morphological and immunocytochemical characteristics if compared with control littermates. These differences in architecture may be related to the eventual development of diabetes mellitus in the ob+/ob+ mouse.

Gastric inhibitory polypeptide mechanisms of augmenting insulin secretion.

The cellular mechanisms whereby gastric inhibitory polypeptide (GIP) augments glucose-dependent insulin secretion remains poorly defined. Since glucose-dependent insulin secretion is modulated by membrane associated phospholipase A2 (PLA2) and intracellular lipoxygenase (LPX) and cyclooxygenase (CO) we hypothesize that GIP's augmentation of insulin secretion involves these enzyme systems. Neonatal rat pancreatic islet cell cultures were preincubated with 5.6mM glucose for 60 minutes. The cultures were then stimulated for 60 minutes with 16mM glucose alone or with GIP with or without the addition of PLA2, LPX, and CO inhibitors. Insulin secretion significantly increased (P less than 0.05) when the glucose concentration was raised from 5.6 to 16mM glucose and this was further augmented by the addition of GIP (P less than 0.05). PLA2 inhibitors significantly (P less than 0.025) decreased 16mM glucose insulin secretion but this was restored by the simultaneous addition of GIP. LPX inhibitors significantly (P less than 0.01) decreased glucose-dependent insulin secretion and this decrease persisted despite the addition of GIP. Simultaneous treatment of islet cell cultures with GIP and CO inhibitors yielded insulin responses that were indistinguishable from CO inhibition alone. These studies suggest that GIP exerts its influence in part by modulating membrane associated PLA2 activity. Furthermore, the formation of intracellular LPX products appears to be a pivotal step in the insulinotrophic action of GIP.

Dissimilar fatty acid composition of standard rat chow.

The lower incidence of coronary heart disease in populations consuming polyunsaturated fatty acids has spurred interest in the possible cardioprotective nature of these fatty acids. Furthermore, the source of dietary fats may modify the natural history of some chronic inflammatory disorders such as rheumatoid arthritis and systemic lupus erythematosus. Some studies examining these issues have involved animals fed a standard chow diet to which the desired fatty acids were added. Our observation that two lots of standard rat chow varied considerably in fatty acid composition, prompted us to analyze two additional standard rat chow lots for fatty acid composition. Each lot was extracted and fatty acid chain length determined by gas chromatography with the percentage of total fatty acids determined by integration. A wide variation in the total saturated (27.4-42.1%), monounsaturated (8.3-30.9%), omega 6 (17.2-44.2%), and omega 3 (3.8-11.2%) fatty acids was observed. By one-way analysis of variance, significant differences (p less than 0.025) between the various lots were observed for total saturated, monounsaturated, and omega 6 fatty acid groups. These findings suggest that fatty acid composition of standard rat chow is not similar. If the baseline fatty acid composition is critical to the experimental design, custom chow diets should be used.

Sensitivity, specificity, and cost-effectiveness of the sensitive thyrotropin assay in the diagnosis of thyroid disease in ambulatory patients.

The sensitivity and specificity of two sensitive thyrotropin assays were compared with those of other standard thyroid function tests in 544 ambulatory subjects who were clinically euthyroid, thyrotoxic, or hypothyroid. Both sensitive thyrotropin assays had the highest sensitivity and specificity (95%/89% and 92%/95%), following by estimated free thyroxine (T4) level (82% and 94%), calculated free T4 index (78% and 93%), and free triiodothyronine index (86% and 88%). Sensitivity of the two thyrotropin assay kits in the diagnosis of thyrotoxicosis was 86% and 95%, and that in the diagnosis of hypothyroidism was 92% and 94%. Other tests were nearly as sensitive in the diagnosis of thyrotoxicosis but not hypothyroidism. A cost analysis of a testing strategy that used either total T4, free T4 index, or sensitive thyrotropin assay alone as the first-line thyroid test disclosed that to establish the patient's thyroid metabolic status would have cost $11,093, $14,536, and $24,902, respectively, using each test first. We suggest that, at current prices, routine use of the thyrotropin assay as a first-line test in ambulatory patients is not as cost-effective as the free T4 index.

Comparison of once-daily captopril or enalapril in mild essential hypertension.

The purpose of this study was to assess the effect of a daily low dose of the angiotensin-converting enzyme (ACE) inhibitors, captopril or enalapril, in mild essential hypertension. Nine men with seated diastolic blood pressure between 95 and 104 mm Hg on placebo participated in the study. After one month of placebo, captopril 25 mg was administered; blood pressure, heart rate, ACE activity and plasma renin activity were measured hourly for 4 hours. Each patient then received captopril 50 mg once daily for 8 weeks and similar measurements were made 24 hours post-dose every 2 weeks. After another month of placebo, the identical protocol was repeated after enalapril 5 mg. Although blood pressure and ACE activity decreased significantly (P less than 0.05) within 2-4 hours of the acute doses of each inhibitor, neither captopril or enalapril produced significant reductions 24 hours after the small daily dose. Thus, neither ACE inhibitor alone was adequate to control blood pressure in mild hypertension when given once daily during 8 weeks of treatment.

The postprandial response of gastric inhibitory polypeptide to various dietary fats in man.

Gastric Inhibitory Polypeptide (GIP) is secreted in response to oral glucose, amino acid, and fats. In the presence of hyperglycemia, GIP augments nutrient stimulated insulin secretion. Studies looking at the effect of fat on GIP release, however, have focused primarily on corn oil, a polyunsaturated fat. To determine if other fats give similar GIP results to those with corn oil, nine normal subjects underwent four tolerance tests with fats derived from saturated (cocoa butter), monounsaturated (olive oil), or polyunsaturated (corn oil and fish oil) sources. Fifty grams of each triglyceride rich fat were ingested and serum cholesterol, triglyceride, glucose, insulin, and GIP levels were determined over a 180-minute period. Serum cholesterol, triglyceride, glucose, and insulin levels were similar following each fat tolerance test. GIP concentrations, however, were significantly lower (P less than 0.01) with the fish oil, when compared to the other fats studied. Similar GIP responses were observed with olive oil and corn oil, but both were higher than with the cocoa butter. These findings suggest that the source of fatty acids affect GIP secretion. The reason for these differences in serum GIP responses is uncertain, but is not readily explained by changes in serum glucose, insulin, or triglyceride concentrations. Since GIP augments nutrient stimulated insulin release 1-3 hours postprandially, the source of dietary fat consumed as part of a mixed meal could ultimately influence pancreatic beta cell insulin secretion.

Effect of source of dietary fats on serum glucose, insulin, and gastric inhibitory polypeptide responses to mixed test meals in subjects with non-insulin dependent diabetes mellitus.

We recently demonstrated that normal subjects given mixed test meals of varying fatty acid composition showed significantly greater serum insulin responses to meals enriched with polyunsaturated fat as compared to those in which the fat content was derived from saturated fatty acids. To determine if a similar phenomenon occurs in subjects with non-insulin dependent diabetes mellitus (NIDDM), serum glucose, insulin, C-peptide, and gastric inhibitory polypeptide (GIP) responses to three mixed test meals of varying fatty acid composition were assessed in twelve subjects with NIDDM. Baseline means (+/- SEM) fasting serum glucose concentration was 205 +/- 15 mg/dl and mean glycosylated hemoglobin was 8.5 +/- 0.5%. Fatty acids in the test meals were either saturated fats, or polyunsaturated fats derived from vegetables or fish. Each test meal provided 40% of the subjects' calculated daily caloric requirement and contained approximately 45% carbohydrate, 40% fat, and 15% protein. No appreciable differences in serum glucose, insulin, and C-peptide responses occurred during the three mixed test meals. Although GIP values were higher in the saturated fat and the vegetable meals when compared to the fish meal, the differences did not reach statistical significance. The inability of NIDDM subjects to evoke a greater insulin response to polyunsaturated fatty acids than to saturated fatty acids suggests another pathogenetic factor contributing to their glucose intolerance.(ABSTRACT TRUNCATED AT 250 WORDS)

Polyunsaturated fatty acids augment insulin secretion.

Carbohydrate intolerance is positively correlated with animal fat consumption and is more common in beef eating populations. In contrast, individuals consuming diets comprised of polyunsaturated fats have a lower incidence of diabetes mellitus. To test the hypothesis that dietary fats may influence carbohydrate metabolism, serum glucose, insulin, and gastric inhibitory polypeptide (GIP) responses to three mixed test meals of varying fatty acid composition were assessed in 12 normal subjects. Fatty acids in the meals were either saturated fats or polyunsaturated fats derived from vegetables or fish. Each test meal provided 40% of a subject's calculated daily caloric requirement and contained approximately 45% carbohydrate, 40% fat, and 15% protein. Serum insulin responses were 62% higher (p less than 0.01) after the fish and 39% higher (p less than 0.01) after the vegetable meals compared to the saturated fat meal. No significant differences in insulin responses were observed between the vegetable and fish meals. Serum glucose concentration was slightly higher (p less than 0.02) during the fish meal than with the vegetable or saturated fat meals. The GIP levels were comparable following the fish and vegetable meals and were 25% lower than those observed with the saturated fat meal. These findings suggest that diets enriched with polyunsaturated fatty acids augment insulin secretion significantly more than a diet comprised primarily of saturated fatty acids. The mechanism for this increased insulin secretion is unknown but did not appear to be mediated through differences in serum glucose values or through the insulin-otrophic effects of GIP.(ABSTRACT TRUNCATED AT 250 WORDS)

GIP increases insulin receptor affinity and cellular sensitivity in adipocytes.

Glucose ingestion has been previously shown to rapidly increase both the affinity of the insulin receptor and the cellular sensitivity of target tissues for insulin. We now demonstrate that gastric inhibitory polypeptide (GIP), a gastrointestinal hormone released by glucose ingestion, can mimic these effects in vitro. Incubation of rat adipocytes with GIP (10-100 ng/ml) resulted in both a displacement to the left of the insulin binding isotherm (i.e., increased receptor affinity) and potentiated insulin-mediated glucose uptake at insulin concentrations less than 1 ng/ml (i.e., increased cellular insulin sensitivity). Cholecystokinin, another gastrointestinal hormone, did not alter the insulin receptor binding characteristics or glucose uptake of the adipocytes in vitro. We suggest that GIP, a known potentiator of glucose-stimulated insulin secretion, may also modulate the effects of insulin by directly altering target tissue sensitivity to insulin.

Increased gastric inhibitory polypeptide is not reduced in patients with noninsulin-dependent diabetes mellitus treated with intense insulin therapy.

Serum glucose and gastric inhibitory polypeptide (GIP) responses during mixed test meals and primed continuous infusion of insulin using the insulin clamp technique were studied in nine patients with noninsulin-dependent diabetes mellitus (NIDDM) before and after vigorous insulin treatment. Fasting serum glucose concentrations fell an average of 167 mg/dl (P less than 0.001), and there was a 67% reduction (P less than 0.001) in the postprandial glucose response. Mean hemoglobin A1c declined and paralleled the fall in serum glucose concentrations (9.2 +/- 0.5% to 5.9% +/- 0.3%; P less than 0.01). This improvement in glycemic control, however, was not associated with any appreciable change in GIP secretion. Basal and meal-stimulated serum GIP levels were not reduced after intense insulin therapy. Furthermore, hyperinsulinemia at physiological (100 microU/ml) and superphysiological (1000 microU/ml) levels failed to reduce GIP secretion before and after insulin therapy. Before insulin therapy, seven patients had elevated basal GIP levels and five had increased GIP levels after meals compared to values in nondiabetic subjects. Insulin administration did not alter these elevated GIP levels. These findings suggest that the increased meal-stimulated GIP secretion in some patients with NIDDM is not due to a failure of insulin feedback on GIP secretion.

Gastric inhibitory polypeptide responses to nutrients in Caucasians and American Indians with obesity and noninsulin-dependent diabetes mellitus.

Serum gastric inhibitory polypeptide (GIP), insulin, and glucose responses to either a 75-g oral glucose challenge or a 500-cal liquid test meal were determined in 141 Caucasians and American Indians. The Caucasians were normal weight, averaging 101 +/- 3% (+/-SEM) ideal BW (IBW), or were obese (168 +/- 21% IBW) and had normal glucose tolerance (n = 77), impaired glucose tolerance (IGT; n = 12), or noninsulin-dependent diabetes mellitus (NIDDM; n = 19). The American Indians were all obese (144 +/- 6% IBW) and had either normal glucose tolerance (n = 22) or NIDDM (n = 11). In all study subjects, including obese individuals with and without glucose intolerance, diabetic patients both thin and obese, and lean subjects with impaired glucose tolerance, fasting serum insulin and GIP, and incremental glucose, insulin, and GIP were greater than they were in normal lean subjects, especially during the first hour of the tests. Obese subjects and diabetic patients exceeded lean normal subjects by up to 620% for glucose, up to 640% for insulin, and up to 360% for GIP during the first hour after glucose ingestion or the test meal. Exceptions were two groups with the most severe diabetes in whom incremental insulin values after oral glucose were only 70% (thin Caucasians) and 110% (obese Indians) that of lean normal subjects. The smallest differences in GIP responses occurred between lean normal subjects and obese nondiabetic Caucasians tested with either a meal or oral glucose, whereas American Indians consistently had the greatest insulin and GIP responses to the tests. High fasting GIP and exaggerated GIP increments in response to nutrients could be attributed to neither obesity nor diabetes alone nor to the type of nutrient used to stimulate its release, but, instead, may be genetic or dietary in origin or may be due to other as yet unidentified factors. High basal GIP and exaggerated nutrient-stimulated GIP release were associated with hyperinsulinemia, except in the most severe diabetic patients. These observations suggest that exaggerated GIP release, along with a greater rise in serum glucose in response to nutrients, may play a role in the pathogenesis of the hyperinsulinemia of obesity and early NIDDM.

Effect of source of dietary carbohydrate on plasma glucose, insulin, and gastric inhibitory polypeptide responses to test meals in subjects with noninsulin-dependent diabetes mellitus.

Previous reports have documented the fact that plasma glucose and insulin responses can vary in response to the ingestion of different carbohydrate-rich foods. This has led to the creation of a "glycemic index," a classification of dietary carbohydrates on the basis of the relative rise in plasma glucose after the administration of the food in question as compared to a standard glucose challenge. In order to test the clinical utility of these observations, we evaluated plasma glucose, insulin, and gastric inhibitory polypeptide responses to four major sources of carbohydrate (potato, rice, spaghetti, lentil) as part of a conventional mixed meal in patients with noninsulin-dependent diabetes mellitus. Each test meal provided 40% of the subjects' calculated caloric requirement and contained 15% of total calories as protein, 40% as fat, and 45% as carbohydrate. The test carbohydrate represented 66% of total carbohydrate. The results indicated that plasma glucose concentrations after meals containing equal amounts of carbohydrate as rice, spaghetti, or lentil were similar and somewhat lower than meals containing potato. The plasma insulin responses to the four carbohydrate foods paralleled the glucose responses. Changes in gastric inhibitory polypeptide levels did not account for the effect of potato. These results are totally disparate from what would have been predicted by previously published values for the "glycemic index" of the four foods studied, and suggest that a "glycemic index" based on isolated challenges would have minimal clinical utility in efforts aimed at reducing postprandial hyperglycemia in patients with noninsulin-dependent diabetes mellitus.

Augmented gastric inhibitory polypeptide and insulin responses to a meal after an increase in carbohydrate (sucrose) intake.

The gastric inhibitory polypeptide (GIP) response to certain stimuli may be exaggerated in patients with obesity and noninsulin-dependent diabetes mellitus. To explore the effects of increased caloric intake and dietary composition on GIP secretion, 20 normal lean volunteers underwent a 4-week ambulatory study. A baseline week (usual diet) was followed by 3 weeks in which the usual diet was supplemented with 45 g fat (diet A), 100 g carbohydrate in the form of sucrose (diet B), or 50 g protein (diet C) for 1 week each. Almost equal numbers of subjects followed sequence ABC, BCA, or CAB in this cross-over study. At the end of the baseline week and each study week, serum glucose, insulin, and GIP were measured in response to a 500-cal liquid test meal. Daily intake of carbohydrate, protein, or fat, as monitored by food records, increased significantly (P less than 0.01) during the appropriate dietary periods, whereas body weight changed slightly, but not significantly, during the 3 study periods. No changes occurred in the total integrated serum glucose concentrations, whereas integrated insulin concentrations changed significantly (P less than 0.05), being 32.5 +/- 3.1 (+/- SEM), 37.2 +/- 4.0, and 30.3 +/- 3.1 microU/ml min-1 during periods A, B, and C, respectively. Insulin secretion was greatest during period B, the carbohydrate week, when insulin concentrations 15-60 min after the test meal were significantly greater (P less than 0.05 to P less than 0.01) than after the baseline period. Total integrated incremental serum GIP concentrations were also significantly different (P less than 0.01) during the 3 study periods, being 1.93 +/- 0.13, 2.53 +/- 0.24, and 1.90 +/- 0.11 ng/ml min-1 during A, B, and C, respectively. Serum GIP was highest during period B (carbohydrate), when average concentrations were significantly higher (P less than 0.01) 15-60 min after the meal compared to those during the baseline study. Similar changes did not occur with the other diets. Thus, GIP and insulin secretion were substantially altered by an acute increase in sucrose intake. The exaggerated GIP response to a meal in some patients with obesity may possibly be the result of adaptation of intestinal GIP cells to diet, particularly one rich in sucrose.

Effects of gastric inhibitory polypeptide on leucine- and arginine-stimulated insulin release.

Insulin release stimulated by single amino acids, with and without gastric inhibitory polypeptide (GIP), was studied in vivo in anesthetized rats and in vitro in collagenase-digested isolated rat pancreatic islets. Insulin release in vivo during a 15-min intravenous infusion of leucine (0.97 mM) or arginine (0.97 mM) with GIP (17 ng/min) was greater than with infusion of either amino acid or GIP alone. Serum immunoreactive GIP was in the physiological range, and serum glucose showed no significant change in these studies. In contrast, insulin release did not occur with valine infused alone or with GIP. Insulin release in vitro by isolated islets was greater during a 45-min incubation period with leucine (5-20 mM) or arginine (20 mM) plus GIP (10 ng to 10 micrograms/ml) than with either amino acid alone. This effect that occurred in the absence of glucose could not be demonstrated with low concentrations of leucine (1.5 mM) or with 20 mM valine. In vitro insulin release during paired perfusion studies of isolated islets was greater with leucine (20 mM) plus GIP (50 ng/min) than with leucine alone, and augmentation of insulin release by GIP was demonstrable in both the early and late phases of insulin release. From these results it is concluded that insulin release is greater, both in vivo and in vitro, after leucine or arginine plus GIP than with either amino acid or GIP alone. This effect appears to be specific for the insulinotropic amino acids tested, does not appear to be glucose dependent, and can be demonstrated in both the early and late phases of insulin release.

Dietary chromium - forms and availabilities.

The chromium naturally occurring in plants eluted from Sephadex G-25 at approximately 2600 D. Total chromium was quantitated with flameless atomic absorption spectrophotometry. A plant ligand tagged with radioactive chromium both in vivo and in vitro migrated on Sephadex G-25 identically to the naturally occurring chromium compound. The molecular weight of the radioactively tagged chromium compound was 2600 daltons on Sephadex G-25. Similar complexes isolated from plant species were found attached to an organic ligand. The ligand appears to have 2 components, differing in composition by an amine group. This extremely stable (KD = 9 X 10(-5)anionic complex does not contain peptide or deoxyribose units. When alfalfa was exposed to either Cr(III) or Cr(VI), only Cr(III) was isolated in this organic chromium compound. The alfalfa bioreduction system can be saturated, as evidenced by Cr(VI) isolation of ionic in those plant extracts incubated with high levels of Cr(VI) in vitro. The gastrointestinal chromium physiology studies show that the radioactively labelled plant chromium compounds remained intact through the gastrointestinal tract up to the large intestine. Some degradation products were identified in the rat cecum. Approximately 30% of the plant chromium available to the rat was absorbed across the gastrointestinal tract.