Relationship between plasma cyclo (His-Pro), a neuropeptide common to processed protein-rich food, and C-peptide/insulin molar ratio in obese women.

Cyclo (His-Pro) (CHP) is a gut-brain peptide whose plasma levels in humans are increased after glucose ingestion and preferentially altered by oral glucose ingestion compared to intravenous administration in rats, suggesting a role in the enteroinsular response to nutrient ingestion. We were interested in examining levels of CHP in women of differing weights and comparing these levels to various parameters of insulin secretion. Plasma from 26 fasting, nondiabetic women ranging from 21 to 70 years of age and weighing 43 to 114 kg was assayed for CHP. Insulin and C-peptide levels were measured in 17 of the 26. Fasting CHP levels were elevated in obese compared to nonobese women (2075+/-144 vs. 905+/-187 pg/ml; p < 0.001) and were related by regression analysis to weight (r = 0.668, p < 0.001) and body mass index (r = 0.636, p = 0.001). The fasting C peptide/insulin molar ratio, which may be used as an estimate of hepatic insulin clearance (HIC), was inversely related to CHP levels (r = -0.568, p = 0.017). We conclude CHP levels are increased in obese women and inversely related to their C-peptide/insulin molar ratio. The elevation of CHP in those with a decrease in this estimate of HIC (obese) is interesting as the greater insulin response seen in normal persons after oral glucose compared to intravenous glucose has been postulated to be due to a decrease in HIC by some gut factor. The presence of such a factor in excess in the obese might explain part of their hyperinsulinemia.

Insulinoma masquerading as factitious hypoglycemia.

A 36-year-old woman without significant medical history complained of "spells" of diplopia, fatigue, and dizziness. On formal fasting, her glucose dropped to 40 mg/dL, with simultaneous insulin levels of 15 microU/mL (normal <6 microU/mL) and C-peptide of 2.5 ng/ml (normal <2 ng/mL). An isolated plasma sulfonylurea screen done during the fast was positive for tolbutamide, suggesting the diagnosis of factitious hypoglycemia, but further workup revealed multiple pancreatic masses resulting in an eventual diagnosis of multiple insulinomas that was confirmed surgically. We discuss the approach to hypoglycemia caused by insulin excess and distinguishing clinical and biochemical features.

Projecting physician supply at a state level: physicians in Louisiana in 2001 and 2006.

BACKGROUND: Many studies predicting physician supply are based on national statistics, which may not be applicable at the state level. METHODS: To facilitate meaningful planning of future physician supply in our state, we developed a conservative, population-based projection of the total number of generalist and specialist physicians who will practice in Louisiana per 100,000 population in 2001 and 2006. RESULTS: Our projections, which err toward our goal of overestimating physician supply, indicate that the total physician number per 100,000 population in Louisiana will rise from the current level of 139 to 162, then to 186, in 2001 and 2006, respectively. The number of primary care physicians will rise from 52 to 59, then to 67, and specialists from 87 to 103, then to 119, in 2001 and 2006, respectively. These numbers are well within the range of need reported in several widely published demand scenarios used for comparison. CONCLUSION: In planning future policies on physician supply, states should develop their own projections rather than simply extrapolating national data to their individual situations.

The Neuropeptide Cyclo(His-Pro) Levels are Increased in Diabetic Ketoacidosis and Fall with Treatment in Parallel with Levels of Glucagon.

The importance of insulin deficiency and glucagon excess is recognized as critical in the pathogenesis of diabetic ketoacidosis (DKA). The finding of elevated levels of another gut peptide in DKA with potential relevant physiological effects might renew discussion of the pathogenesis of this disorder. Cyclo(His-Pro) is a gut-brain peptide found in gut of rat and man. In pancreas it is localized to alpha cells. A stereospecific hepatic bonding site has been found. We have shown that cyclo(His-Pro) augments the insulin response to oral glucose in rat by decreasing hepatic insulin clearance. In view of cyclo(His-Pro)'s location in alpha cells, the hepatic binding site and action described, we wondered if levels of cyclo(His-Pro) might be elevated in a hyperglucagonemic state such as DKA and whether these levels might correlate with those of glucagon and other commonly followed parameters in DKA. Plasma was collected from 7 nondiabetic controls and 9 patients in DKA before and after 4, 8, 12, and 24 h of therapy and assayed for glucose, HCO3, anion gap, glucagon and cyclo(His-Pro). Cyclo(His-Pro) levels were higher in DKA patients before therapy than controls (15.6 ± 3.2 vs. 8.0 ± 0.2 pmol/ml; p =0.023) as were glucagon levels (201 ± 4 vs. 56 ± 5ng/L; p = 0.006). Cyclo(His-Pro) levels fell significantly with treatment (15.6 ± 3.2 vs 8.1 ± 1.1; p = 0.024) and in parallel with those of glucagon. We conclude that cyclo(His-Pro) levels are increased in patients with DKA before therapy and fall in parallel with those of glucagon. This represents the first report of altered levels of this peptide in a disease state.

Outcomes analysis of teaching on a medical service with trainees of diverse medical experience.

BACKGROUND: Rotations in medical subspecialties often involve trainees with diverse levels of medical knowledge and experience. We conducted a study to determine whether teaching on such a clinical service could be delivered effectively to all members of the group despite their disparate backgrounds. METHODS: The Section of Endocrinology offers a 4-week rotation that is taken jointly by third- and fourth-year medical students, interns, residents and endocrinology fellows. Over the past 4 years enrollees were required to complete both a pre and postcourse test of written, multiple choice examination in general endocrinology. The mean and SEM percentage of correct answers were compared. RESULTS: It was found that the scores on the prerotation test were correlated with the level of experience; students scored the lowest and fellows the highest. There was a significant overlap; however, between groups, students' results, for example, were not statistically different from those of the interns but were lower than those of the residents and very different from fellows (p value < 0.0001). CONCLUSIONS: Rotations of trainees with mixed ability clearly lead to objective improvements in all groups except fellows. Students and interns appear to gain the greatest increment. Residents also improve. It is concluded that all levels of trainees (below the level of fellow) can increase their fund of knowledge by taking a subspeciality rotation even though the group may be of mixed levels of ability.

The bioactive peptide cyclo(His-Pro) may be absorbed following ingestion of nutritional supplements that contain it.

OBJECTIVE: Food contains a number of peptides with potential bioactivity. We previously found ng/mliter to mcg/mliter quantities of cyclo(His-Pro)-like immunoreactivity in a number of foods and nutritional supplements. A number of activities have been attributed to cyclo(His-Pro) (CHP), including appetite inhibition and inhibition of insulin secretion in vitro. We wondered whether the cyclo(His-Pro)-like immunoreactivity present in nutritional supplements might be absorbed and, if so, whether parameters of insulin secretion would be altered. METHODS: After performing a pilot study which suggested some common nutritional supplements contain CHP, a follow-up study was done to confirm and expand the findings of the pilot study. Eight fasting volunteers ingested approximately 250 mL of a CHP-containing supplement one day, and then an equienergetic CHP-free supplement the next. RESULTS: Blood drawn for CHP, insulin, glucose, and C-peptide a number of times on both days revealed that when volunteers ingested CHP-containing supplements, CHP levels at 120 minutes were significantly higher than baseline (7.69 +/- 0.50 pmol/mL vs. 9.18 +/- 0.48 pmol/mL; p = 0.011 in the CHP group and 7.90 +/- 0.85 pmol/mL vs. 7.22 +/- 0.73 pmol/mL, p > 0.3 in the CHP-free group) and significantly higher than levels achieved when they drank CHP-free supplements. Levels of glucose, insulin, and C-peptide were not different in the two groups. CONCLUSION: CHP in nutritional supplements may be absorbed when ingested orally and does not grossly affect glucose or parameters of insulin secretion.

The effect of DHEA given chronically to Zucker rats.

Dehydroepiandrosterone (DHEA) has been reported to exert antiglucocorticoid activity. When administered to obese, hypercorticosteronemic Zucker rats, it causes a diminution of food intake and a reduction in their rate of weight gain. This experiment was conducted to evaluate whether this biologic effect could be ascribed to chronic adrenal insufficiency. Obese and lean Zucker rats were treated with DHEA as a food supplement for 28 days. Upon sacrifice, organ weights and serum chemistries were measured, along with neurotransmitter levels in regions of the hypothalamus. Results showed that although the obese animals gained weight more slowly, had lower insulin levels, and ate less, their serum glucose, corticosterone, and ACTH levels were not different from control. Hypothalamic neurotransmitters in the obese rat were unaffected by chronic DHEA treatment. We concluded that, although DHEA clearly affects Zucker weight gain, it does not induce chronic adrenal insufficiency.

Identification of cyclo(His-Pro)-like immunoreactivity in human follicular fluid: correlation with steroid and peptide hormones.

OBJECTIVE: The purpose of this study was to evaluate human follicular fluid (FF) for the presence of cyclo(His-Pro)-like immunoreactivity (CHP-LI). After verifying its presence, we quantitated the levels and investigated correlations with other follicular parameters, including hormone levels. METHODS: Follicular fluid was collected from female volunteers undergoing controlled ovarian hyperstimulation. Fluid was collected by follicular puncture, either transvaginally (in vitro fertilization) or laparoscopically (gamete intrafallopian transfer) at the time of oocyte retrieval (N = 137). Follicular size was determined ultrasonographically. Assays for steroid and peptide hormones were determined with commercially available radioimmunoassay kits. CHP-LI was measured using a previously reported assay; parallel dilution curves and column chromatography aided in immunoidentity. RESULTS: The mean FF CHP-LI concentration (13.10 +/- 1.83 nmol/L, N = 137) was greater than the corresponding serum values (9.42 +/- 2.45 nmol/L; N = 21) (P < .05). Large follicles (20 mm or greater; 14.45 +/- 1.74 nmol/L) contained significantly more CHP-LI than either medium follicles (16-19 mm; 11.51 +/- 1.88 nmol/L) or small follicles (15 mm or smaller; 10.83 +/- 2.12 nmol/L) (P < .05). Positive correlations were found between FF CHP-LI values and corresponding FF progesterone and prolactin concentrations (r = 0.67 and 0.62, respectively; P < .05). CONCLUSION: Mean CHP-LI levels in the FF are greater than those in the corresponding serum. We suggest that the neuropeptide may be originating from either peptidase cleavage of precursor peptides or from granulosa cell production.

Relationship between serum cyclo(His-Pro) concentrations and the nutritional status of HIV-infected patients.

Cyclo(His-Pro) (CHP) is a gut-neuropeptide that influences both appetite and carbohydrate metabolism. This study was undertaken to determine whether concentrations of CHP correlated with various clinical markers of nutritional status and progression of HIV infection. Serum concentrations of CHP were analyzed in a clinical sample of 100 HIV-positive patients whose HIV clinical status ranged from asymptomatic to advanced disease with weight loss. We found a relationship between CHP concentrations and serum albumin and hemoglobin levels, markers of chronic nutrition and disease. However, no correlation was seen between CHP and cortisol concentrations, a marker of acute stress. To analyze the relationship of HIV clinical stage and CHP, patients were divided into three subgroups: asymptomatic, mildly symptomatic, and clear-cut AIDS. CHP concentrations were significantly correlated with HIV clinical stage. These data lead to the hypothesis that CHP is a marker of disease progression and that it potentially plays a role in modulating the nutrition of HIV-infected patients.

The relationship of serum DHEA-S and cortisol levels to measures of immune function in human immunodeficiency virus-related illness.

Human immunodeficiency virus (HIV) is a major cause of immunoincompetence. Whether the virus, itself, accounts for all the deficiency remains in question. Steroids can also influence immune function; glucocorticoids cause immunoincompetence while dehydroepiandrosterone (DHEA) enhances immune function. Changes in the levels of such hormones during the course of HIV illness might result in significant changes in immune competence. The purpose of this study is to investigate whether dehydroepiandrosterone-sulphate (DHEA-S) or cortisol levels correlate with absolute CD4 lymphocyte levels. Plasma for cortisol and DHEA-S was drawn from 98 adults with HIV. Of these, 67 had simultaneous CD4 levels. Cortisol levels were 12.4 +/- 4.6 micrograms/dl, DHEA-S 262 +/- 142 micrograms/dl, and CD4 levels were 308 +/- 217/mm3 (mean +/- SD). Correlational analysis revealed a significant relationship between DHEA-S and CD4 levels (r = 0.30; p = 0.01) but not between CD4 levels and cortisol (r = 0.11; p = 0.36) or cortisol/DHEA-S ratios (r = 0.17; p = 0.16). When analyzed by clinical subgroups, significant differences were also found with a decrease in DHEA-S levels seen in persons with more advanced illness. The data exhibit a positive relationship between the immune status of patients with HIV-related illness and DHEA, leading to the hypothesis that DHEA deficiency may worsen immune status.

Food contains the bioactive peptide, cyclo(His-Pro).

Cyclo(His-Pro) (CHP) is a cyclic dipeptide with numerous biological activities. As small di- and tripeptides may be absorbed intact when ingested orally, we were interested in examining several common foods for the presence of cyclo(His-Pro)-like immunoreactivity (CHP-LI). In all foods tested, CHP-LI was found at levels 5-1500 times those previously found in human plasma. This CHP-LI was identical to authentic CHP by immunoidentity and chromatographic behavior. We conclude that 1) CHP-LI is readily detectable in several common food sources; 2) this CHP-LI is indistinguishable from authentic CHP; and 3) it is likely the CHP-LI in foods is absorbed in quantities sufficient to cause elevations of CHP-LI in plasma to biologically significant levels.

Increased cerebrospinal fluid cyclo(His-Pro) content in schizophrenia.

Cyclo(His-Pro) (CHP) is a peptide endogenous to human brain and cerebrospinal fluid (CSF). In animal studies administration of exogenous CHP augments dopaminergic neurotransmission. To explore the role of this peptide in schizophrenia, a disease characterized by a hyperdopaminergic state, we have measured CSF CHP levels in control, never-medicated schizophrenics and medicated schizophrenics. Our data show a 53% increase in CSF levels of CHP in never-medicated schizophrenics (p = 0.015), and a 25% increase in medicated schizophrenics when compared to controls. We speculate that CHP may contribute to the expression of hyperdopaminergic symptoms in schizophrenia.

Could dietary proteins serve as cyclo(His-Pro) precursors?

Cyclic dipeptides or diketopiperazines are readily generated during in vitro hydrolysis of proteins and polypeptides. This led us to examine whether cyclo(His-Pro) (CHP), a diketopiperazine containing histidine and proline, could be formed in vivo from dietary proteins. The data presented here show that at least in rat, neither urinary nor plasma concentration of CHP is elevated by consumption of a diet rich in proteins. Several dietary supplements derived from casein and/or soy protein hydrolysates, however, contain high levels of CHP-LI. Oral intake of one such supplement led to a sharp increase in the plasma level of CHP-LI.

The neuropeptide histidyl proline diketopiperazine throughout human pregnancy: an inverse correlation with amniotic fluid prolactin.

Histidyl proline diketopiperazine values have been established in human amniotic fluid (n = 81) and maternal serum (n = 36) throughout gestation (10 to 42 weeks). Newborn cord serum (n = 10) and first-voided fetal urine (n = 10) levels were also documented. These measurements reveal increasing amniotic fluid levels with term gestation values (15,551 pg/ml) nearly thirteen-fold higher than maternal serum concentrations (1150 pg/ml). Corresponding fetal urine and cord serum concentrations were 16,781 and 2160 pg/ml, respectively. The amniotic fluid values are not influenced by fetal sex or maternal labor, nor do they correlate with amniotic fluid alpha-fetoprotein levels. However, there is a significant inverse correlation (r = -0.628; p less than 0.0001) between amniotic fluid prolactin and histidyl proline diketopiperazine after midgestation. The hypothesis that histidyl proline diketopiperazine may be a regulatory peptide for decidual prolactin production was tested by culturing term decidua in the presence of varying concentrations of histidyl proline diketopiperazine, but no inhibitory effect was observed. Decidual cultures did not produce measurable amounts of histidyl proline diketopiperazine. It is suggested that amniotic fluid histidyl proline diketopiperazine is derived from fetal urine.

Isolation of cyclo(His-Pro)-like immunoreactivity from human urine and demonstration of its immunologic, pharmacologic, and physico-chemical identity with the synthetic peptide.

Measurements of cyclo(His-Pro) levels in human urine were carried out by specific radioimmunoassay. Cyclo(His-Pro)-like immunoreactivity in Human urine was found to be immunologically, pharmacologically, and physico-chemically identical to that of synthetic cyclo(His-Pro). The concentration of urinary cyclo(His-Pro) in 24-h collection was 1133.8 +/- 122.5 nmol/L, with a range of 606 to 1865 nmol/L. The daily excretion rate of cyclo(His-Pro) was 1812 +/- 248 nmol cyclo(His-Pro)/g creatinine, or 1814 +/- 199 nmol cyclo(His-Pro/day.

Acute alterations of cyclo(His-Pro) levels after oral ingestion of glucose.

We analyzed the response of plasma cyclo(His-Pro) (CHP) (N = 14), insulin (N = 8), and glucose (N = 8) to oral ingestion of 75 grams of glucose in normal volunteers. Mean Fasting CHP levels prior to glucose were 614 +/- 112 pg/ml (+/-SE). After glucose ingestion there occurred an acute rise of plasma CHP within 15 minutes (12/14) followed by a fall in plasma concentrations to below baseline values (11 of 14). The mean of highest levels within the first 15 minutes after glucose ingestion was 1035 +/- 300 pg/ml (+/-SE), significantly above baseline (p = 0.002). The mean of lowest values below baseline was 490 +/- 94 pg/ml (+/-SE), p less than 0.001. We conclude that levels of CHP are acutely and reversibly altered by the ingestion of glucose. The possible significance of these perturbations in CHP concentrations is discussed.

Change in circulating cyclo(His-Pro) concentrations in rats after ingestion of oral glucose compared to intravenous glucose and controls.

Changes in circulating cyclo(His-Pro) (CHP) levels after ingestion of 0.5 g/kg of glucose (oral) were measured in 32 Sprague Dawley rats at varying time points between 0 (before glucose) and 60 minutes. Each rat provided one time point. CHP levels displayed a biphasic response rising from 933 +/- 56 pg/ml to 1083 +/- 287 pg/ml (p greater than 0.05), followed by a fall to 543 +/- 46 pg/ml (p = 0.002) and then a recovery to near baseline values. To further investigate this response, a separate group of rats were sampled sequentially after 3 g/kg oral glucose (n = 7), 0.6 g/kg I.V. glucose (n = 6) or controls given saline only (n = 14). CHP levels were significantly elevated in the oral glucose group at 5 (p = 0.048) and 12 (p = 0.02) minutes compared to controls, while the i.v. glucose group was not statistically different from controls. Comparison of the mean of the highest incremental response to baseline values in each group revealed a greater excursion in CHP levels after oral (p = 0.027) glucose than after I.V. (p = 0.08) glucose. These data suggest CHP is acutely and reversibly elevated after glucose ingestion in rats and that the response is greater after oral glucose than after i.v. glucose.

Identification and characterization of cyclo(His-Pro)-like immunoreactivity in amniotic fluid.

Amniotic fluid (AF) from 25 term pregnancies was analyzed for cyclo(His-Pro)-like immunoreactivity (CHP-LI). CHP-LI was detected in all AF samples and was indistinguishable from synthetic CHP by immunoidentity, by gel chromatography on Sephadex G-25, and by high pressure liquid chromatography. The mean concentration of CHP-LI in AF was 13,622 +/- 1288 pg/ml (+/- SE) and concentrations were not altered by maternal labor. Plasma concentrations of CHP-LI were similar in 4 pregnant and 4 control subjects [2260 +/- 432 pg/ml vs. 2162 +/- 419 pg/ml (+/- SE), respectively]. We conclude that 1) CHP-LI is readily detected in AF from term pregnancies and is indistinguishable from synthetic CHP, and 2) concentrations of CHP-LI in human AF are significantly higher than concentrations of maternal plasma CHP-LI, suggesting CHP AF originates by mechanisms other than diffusion from maternal plasma.