Prevalence, glucose control and relative survival of people with Type 2 diabetes in the UK from 1991 to 2013.

AIMS: To characterize the prevalence of Type 2 diabetes between 1991 and 2013 in the UK and to determine whether corresponding glucose control and survival had changed in the diabetic population during this period. METHODS: For this retrospective cohort study, people diagnosed with Type 2 diabetes between 1991 and 2013 were identified from the Clinical Practice Research Datalink (CPRD) and the annual point prevalence calculated. Mean HbA1c by year was estimated. The Cox proportional hazards model was used to calculate the risk of all-cause mortality by year for incident cases of Type 2 diabetes treated with glucose-lowering therapy. RESULTS: Crude prevalence of diagnosed Type 2 diabetes increased from 1.32% [95% confidence interval (95% CI) 1.30% to 1.34%] in 1991 to 4.54% (4.52% to 4.56%) in 2013. Mean HbA1c for people with diagnosed Type 2 diabetes was 71 mmol/mol (8.6%) in 1991, 59 mmol/mol (7.5%) in 2003 and 58 mmol/mol (7.5%) in 2013. For diagnosed Type 2 diabetes treated with glucose-lowering therapy, when compared with 1991, the hazard ratio for all-cause mortality was 0.33 (0.27-0.41) in 2013. CONCLUSION: The prevalence of diagnosed Type 2 diabetes trebled in the UK between 1991 and 2013. Improved survival in people with diagnosed Type 2 diabetes is likely to account, at least in part, for the increase in prevalence observed.

The incidence of type 2 diabetes in the United Kingdom from 1991 to 2010.

AIMS: To characterize the incidence of type 2 diabetes in the UK over the previous 20 years; and determine if there has been an increase in people aged 40 years or less at diagnosis. METHODS: For this retrospective cohort study, patients newly diagnosed with type 2 diabetes between 1991 and 2010 were identified from the UK Clinical Practice Research Datalink (CPRD). Patient data were grouped into 5-year intervals by year of diagnosis and age at diagnosis. A standardized incidence ratio (SIR) was determined (1991-1995 = 100). The percentage of newly diagnosed patients for each age group and aged ≤40 years was calculated for each 5-year calendar period. The incidence rate by age and 5-year calendar period was also determined. RESULTS: In 2010, the crude incidence rate of type 2 diabetes was 515 per 100,000 population. The overall SIR increased to 158 (95% CI 157-160, p < 0.001), 237 (235-238, p < 0.001) and 275 (273-276, p < 0.001) for 1996-2000, 2001-2005 and 2006-2010, respectively. For those ≤40, the respective values were 217 (209-226, p < 0.001), 327 (320-335, p < 0.001) and 598 (589-608, p < 0.001). An increase in incidence occurred with increasing 5-year calendar period. The incidence of type 2 diabetes was higher for males after the age of 40 and higher for females aged ≤40. The percentage of patients aged ≤40 years at diagnosis increased with each increasing 5-year calendar period (5.9, 8.4, 8.5 and 12.4%, respectively). CONCLUSIONS: There was a significant increase in the incidence of diagnosed type 2 diabetes between 1991 and 2010 and the proportion of people diagnosed at a relatively early age has increased markedly.

Prolonged space flight-induced alterations in the structure and function of human skeletal muscle fibres.

The primary goal of this study was to determine the effects of prolonged space flight (180 days) on the structure and function of slow and fast fibres in human skeletal muscle. Biopsies were obtained from the gastrocnemius and soleus muscles of nine International Space Station crew members 45 days pre- and on landing day (R+0) post-flight. The main findings were that prolonged weightlessness produced substantial loss of fibre mass, force and power with the hierarchy of the effects being soleus type I > soleus type II > gastrocnemius type I > gastrocnemius type II. Structurally, the quantitatively most important adaptation was fibre atrophy, which averaged 20% in the soleus type I fibres (98 to 79 µm diameter). Atrophy was the main contributor to the loss of peak force (P(0)), which for the soleus type I fibre declined 35% from 0.86 to 0.56 mN. The percentage decrease in fibre diameter was correlated with the initial pre-flight fibre size (r = 0.87), inversely with the amount of treadmill running (r = 0.68), and was associated with an increase in thin filament density (r = 0.92). The latter correlated with reduced maximal velocity (V(0)) (r = 0.51), and is likely to have contributed to the 21 and 18% decline in V(0) in the soleus and gastrocnemius type I fibres. Peak power was depressed in all fibre types with the greatest loss (55%) in the soleus. An obvious conclusion is that the exercise countermeasures employed were incapable of providing the high intensity needed to adequately protect fibre and muscle mass, and that the crew's ability to perform strenuous exercise might be seriously compromised. Our results highlight the need to study new exercise programmes on the ISS that employ high resistance and contractions over a wide range of motion to mimic the range occurring in Earth's 1 g environment.

Dispensing patterns and financial costs of glucose-lowering therapies in the UK from 2000 to 2008.

INTRODUCTION: A variety of influences determine prescribing behaviour. The purpose of this study was to characterize the pattern of dispensing for glucose-lowering and monitoring in the UK from 2000 to 2008, inclusively. METHODS: Open source data were used from the four UK prescription pricing agencies. Historical patterns of dispensing change were analysed in England, thus data are for England unless otherwise stated. Costs were adjusted for price inflation and reported in UK pound at 2008 prices. RESULTS: The total cost in the UK in 2008 was 702 239 000 UK pounds: 22 897 000 pounds (3.2%) for Northern Ireland, 37 681 000 pounds (5.3%) for Wales, 57 146 000 pounds (8.1%) for Scotland and 590 514 000 pounds (83.4%) for England. As a per cent of the overall primary care drug budget for each region, this represented 6.9% overall and then 5.8, 6.5, 5.9 and 7.1%, respectively. In England, diabetes-related dispensing costs increased from 290m to 591m UK pounds. All glucose-lowering drug classes increased in volume, except the alpha-glucoside inhibitors and the prandial glucose regulators. Insulin costs increased from 128m to 286m UK pounds. Insulin glargine metrics increased year-on-year, whereas neutral protamine Hagedorn (NPH) declined. Analogue insulin increased (2.6 million to 33.9 million prescription items), whereas human insulin declined (21.0 million to 10.3 million). DISCUSSION: The costs of dispensing for diabetes increased markedly between 2000 and 2008 to represent an annual cost to the NHS of 708m UK pounds, or 7% of budget. Costs increased at a higher rate than volume. Changes in prescribing appeared to reflect commercial factors more than clinical evidence. Diabetes dispensing patterns need to be better controlled and costs contained.

The changing prevalence of diagnosed diabetes and its associated vascular complications in a large region of the UK.

AIMS: To characterize the prevalence of diabetes in a large health district in 2004 and compare it with a previous estimate made in 1996. METHODS: The study population comprised the resident population of Cardiff and the Vale of Glamorgan. Routine record linkage was used to identify patients from various sources of hospital and mortality data. Patients with diabetes were identified according to biochemistry test results, coding on routine data or attendance at a diabetes-related clinic. Diabetes-related complications were ascribed according to coding on routine data. RESULTS: It was possible to identify 17 088 people with diabetes alive on 1 January 2005. Of these patients, 9064 (53.0%) were male and 8024 (47.0%) were female. Mean age (+/- sd) was 59.6 +/- 18.9 years for males and 61.2 +/- 20.4 years for females. The crude prevalence of diabetes in 2005 was 3.9% (3.4% adjusted) compared with 2.5% in 1996 (2.3% adjusted). With the exception of females aged > or = 75 years, the prevalence of diabetes increased in all age- and sex-specific subgroups. Within the 2005 cohort, over two-thirds has no recorded complications compared with approximately one half of the 1996 cohort. The prevalence of individual complications decreased, with the exception of renal complications. CONCLUSIONS: The prevalence of identified diabetes appears to have increased substantially over a relatively short period of 9 years to 2004. The increase in prevalence was 46%, with an increase in numbers of patients with diabetes of 53%. A number of factors are likely to have contributed to this, including an increase in case ascertainment.

Estimated costs of acute hospital care for people with diabetes in the United Kingdom: a routine record linkage study in a large region.

AIMS: Diabetes represents a notable burden to health payers. The purpose of this study was to estimate acute hospital care costs of treating people with diabetes with reference to the costs of treating those without. METHODS: This was a retrospective study. Data from routine hospital practice were available from a large health region (439 000 people), with an estimated prevalence of diabetes of 3.4%. Common records were identified using probabilistic record linkage. Cost estimates were attributed to admissions using healthcare resource group software. Outpatient costs were attributed using published values. Data described are for 2004, and prices in pounds sterling for 2005. Standardised cost ratios were estimated to compare the costs observed in the diabetes population with those expected from the non-diabetic reference population. RESULTS: The total annual cost of admissions was pound28 944 811 per 100 000 people, of which pound3 650 869 per 100 000 (12.6%) was diabetes related. The standardised cost rate of inpatient treatment was 2.9. The total cost of outpatient attendances was pound6 589 971 per 100 000, of which pound711 431 per 100 000 (10.8%) was diabetes related. The standardised cost ratio for outpatient care was 4.1. The total cost of hospital care for patients with diabetes was pound11 206 986 per 100 000, or 12.3% of acute hospital expenditure. The combined standardised cost ratio was 3.1. Costs of care for inpatient treatment increased from 8.7% of revenue in 1994 to 12.3% in 2004. CONCLUSIONS: The costs of acute hospital care for treating people with diabetes increased markedly over a decade, and now exceed 12% of revenue.

Allelic variants at insulin-receptor and insulin gene loci and susceptibility to NIDDM in Welsh population.

A cohort of 132 well-documented White Welsh non-insulin-dependent diabetic (NIDDM) subjects were genotyped for 5 restriction-fragment-length polymorphisms (RFLPs) at the insulin-receptor gene (IRG) locus and a polymorphic locus 5' to the insulin gene. There was no significant difference in RFLP frequencies between the NIDDM subjects and a group of 87 matched White control subjects. Paired haplotype analysis of the IRG RFLPs suggested a difference between NIDDM and control groups for the endonuclease combinations Bgl II-Rsa I and Bgl II-Xba I. Analysis of implied haplotypes defined by the endonucleases Bgl II, Rsa I, and Xba I revealed one haplotype to be more prevalent in the NIDDM group; whereas, another haplotype was associated with the control group (P less than 0.02). Subset analysis within the NIDDM cohort compared the metabolic response of NIDDM subjects with the differing IRG haplotypes to a standard meal tolerance test. Both groups showed equivalent basal and postprandial glucose excursions, but one group revealed a significantly exaggerated plasma insulin response compared with the other (P less than 0.05). This may reflect the influence of genetic variation at the IRG locus on insulin sensitivity in patients with NIDDM.

Relationship between absorption of radiolabeled soluble insulin, subcutaneous blood flow, and anthropometry.

OBJECTIVE: To evaluate the interrelationships between the rate of absorption of soluble insulin, SCBF, and anthropometry in normal subjects. RESEARCH DESIGN AND METHODS: In 12 normal men (age range 23-30 yr, BMI 18.2-41.3 kg/m2), simultaneous assessment of the absorption of 125I-labeled soluble insulin and SCBF (99mTc clearance) was performed, on separate study days, for the anterior abdominal wall, anterior midthigh, and the upper arm sites. Each site was examined in a randomized order on two separate occasions. Absorption of 125I-soluble insulin was determined by external monitoring of residual radioactivity levels at the injection site for 6 h postinjection. Residual radioactivity level-time curves, including the characteristic early phase of slow absorption of soluble insulin (the lag phase), were described using two- and three-parameter biexponential models. Anthropometric measurements included BMI, ultrasonic measurement of the subcutaneous adipose tissue layer, and caliper skin fold thickness at the anterior abdominal wall, biceps, triceps, anterior midthigh, and subscapular sites. RESULTS: A highly significant positive relationship was observed between the rate of absorption of 125I-soluble insulin and SCBF (rS = 0.44-0.52; P < 0.01-0.001). The duration of the lag phase was inversely correlated with SCBF (rS = 0.34 - 0.51; P < 0.01-0.001). Inverse relationships also were observed for the subjects' degree of adiposity with the rate of soluble insulin absorption (rS = -0.43(-)-0.71; P < 0.001) and SCBF (rS = -0.27(-)-0.62; P < 0.05-0.001). Significantly shorter lag phase was observed for the abdominal site compared with thigh and arm injection sites (P < 0.05-0.01). CONCLUSIONS: The rate of absorption of soluble insulin, including during the lag phase, is positively correlated with SCBF. Increasing adiposity prolongs the duration of the early lag phase and reduces the rate of absorption of soluble insulin and SCBF.

The epidemiology and cost of inpatient care for peripheral vascular disease, infection, neuropathy, and ulceration in diabetes.

OBJECTIVE: To describe the epidemiology and costs of the acute care of peripheral vascular disease, infection, neuropathy, and ulceration in a U.K. population with special consideration of those patients with diabetes. RESEARCH DESIGN AND METHODS: Routine data describing inpatient care for a 4-year period were analyzed (financial years 1991/1992 to 1994/1995). These data had undergone record-linkage to draw together records from the same patients, and records of patients with diabetes were flagged. Cost estimates were determined by attributing a diagnosis-related group cost-weight to each record. RESULTS: A total of 4,245 admissions (1.2% of all admissions) had a primary diagnosis of peripheral vascular disease, infection, neuropathy, or ulceration, and 7,379 (2.1%) admissions had these categories recorded in any one of six diagnostic fields. These figures were generated by 3,159 and 4,751 patients, respectively. This represented a range of crude annual incidence of admission of between 1.9 and 2.9 per 1,000 people. Patients with diabetes accounted for 625 (15.4%) of primary admissions, a crude annual incidence of admission of 18.8 per 1,000. The age-standardized relative risk of admission for patients with diabetes to the nondiabetic population was 7.61 for men and 6.85 for women. The length of stay for patients with diabetes was almost twice that of the nondiabetic population (15.5 vs. 8.7 days). The relative risk of hospital mortality (diabetes vs. non-diabetes) was 2.83. Surgical procedures were carried out on 857 patients, 272 (31.2%) with diabetes. This represented an age-standardized relative risk of 31.19. The estimated cost of admissions for primary diagnoses in these categories over 4 years was 6,128,211 pounds ($9,743,855). Patients with diabetes accounted for 1,236,623 pounds ($1,966,230), an excess of 87% attributable to the diabetic state. CONCLUSIONS: Diabetes is confirmed as a significant risk factor for peripheral vascular disease, infection, neuropathy, and ulceration. The severity of these disorders in terms of increased risk of hospital mortality, length of stay, and risk of surgical procedure is also demonstrated for those patients with diabetes.

Relationship between diabetes and mortality: a population study using record linkage.

OBJECTIVE: To determine patterns and causes of mortality for patients with diabetes in a district health authority RESEARCH DESIGN AND METHODS: The study used cross-sectional record linkage, combining an electronic death register with a diabetic patient register constructed from a variety of routine health data sources collected from 1991 to 1997. The study was conducted in Cardiff and the Vale of Glamorgan, Wales, U.K., and included all diabetic deaths between 1993 and 1996. RESULTS: Of 1,694 deaths in patients with known diabetes, only 674 (39.8%) had diabetes recorded as an immediate or antecedent cause of death. Mortality rates were 41.8 per 1,000 for the diabetic population and 10.1 per 1,000 for the nondiabetic population. The standard mean ratio for the diabetic population was 1.24 (95% CI 1.12-1.35), with the risk of mortality relative to the nondiabetic population decreasing with age. Males with diabetes lost an average of 7.0 years from the year of diagnosis, and females with diabetes lost an average of 7.5 years. The most common cause of death was cardiovascular disease, which accounted for 49.1% of deaths in the diabetic population. CONCLUSIONS: Diabetes is recorded as a cause of death on a minority of death certificates for patients with diabetes. Using death certificates in isolation, therefore, is a poor method of estimating diabetic mortality, but results can be improved with the use of record linkage techniques. Patients with diabetes have an excess risk of mortality compared with the nondiabetic population. Life-years lost for patients with diabetes is strongly related to age at diagnosis and is a means of expressing mortality without relying on accurate prevalence data.

Comparison of subcutaneous soluble human insulin and insulin analogues (AspB9, GluB27; AspB10; AspB28) on meal-related plasma glucose excursions in type I diabetic subjects.

OBJECTIVE: To compare postprandial glucose excursions and plasma free insulin-analogue levels after subcutaneous injection of three novel human insulin analogues (AspB10; AspB9, GluB27; and AspB28) with those after injection of soluble human insulin (Actrapid HM U-100). RESEARCH DESIGN AND METHODS: Six male subjects with insulin-dependent diabetes, at least 1 wk apart and after an overnight fast and basal insulin infusion, received 72 nmol (approximately 12 U) s.c. of soluble human insulin 30 min before, or 72 nmol of each of the three analogues immediately before, a standard 500-kcal meal. RESULTS: Mean basal glucoses were similar on the 4 study days. Compared to human insulin (6.3 +/- 0.8 mM), mean +/- SE peak incremental glucose rises were similar after analogues AspB10 (5.4 +/- 0.8 mM) and AspB9, GluB27 (5.4 +/- 0.7 mM) and significantly lower after analogue AspB28 (3.6 +/- 1.2 mM, P less than 0.02). Relative to soluble human insulin (100% +/- SE21), incremental areas under the glucose curve between 0 and 240 min were 79% +/- 34 (AspB10, NS), 70% +/- 29 (AspB9, GluB27, NS), and 43% +/- 23 (AspB28, P less than 0.02). Basal plasma free insulin levels were similar on the 4 study days. Plasma free insulin-analogue levels rose rapidly to peak 30 min after injection at 308 +/- 44 pM (AspB10); 1231 +/- 190 pM (AspB9, GluB27) and 414 +/- 42 pM (AspB28) and were significantly higher than corresponding (i.e., 30 min postmeal) plasma free insulin levels of 157 +/- 15 pM (P less than 0.02 in each case). CONCLUSIONS: Plasma profiles of the insulin analogues were more physiological than that of human insulin after subcutaneous injection. All three analogues given immediately before the meal are at least as effective as soluble human insulin given 30 min earlier. These analogues are promising potential candidates for short-acting insulins of the future.

Early-morning hyperglycemia in IDDM. Acute effects of cholinergic blockade.

Growth hormone (GH) hypersecretion in insulin-dependent diabetes mellitus (IDDM) subjects has been shown to be causally related to early-morning hyperglycemia. We studied the effect of nocturnal GH suppression on acute glycemic control in six IDDM patients during a constant overnight insulin infusion (0.075 mU.kg-1.min-1). In control experiments (infusion of insulin alone), plasma glucose increased from 5.6 +/- 0.6 mM at 2400 to 11.1 +/- 1.3 mM at 0900 (P = .0024). When in addition the cholinergic muscarinic antagonist pirenzepine was given (100 mg at 2200 and again at 2400), plasma glucose increased from 5.6 +/- 0.3 mM at 2400 to 8.4 +/- 1.4 mM at 0900 (P greater than .05). The nocturnal surges of GH that were demonstrated in all patients during the control nights were suppressed during the treatment nights. There were no significant changes in insulin, cortisol, or epinephrine concentrations. Mean glucagon and norepinephrine concentrations. Mean glucagon and norepinephrine concentrations were reduced from 127 +/- 2.7 ng/L and 8.7 +/- 0.5 nM to 101 +/- 1.9 ng/L (P less than .001) and 3.5 +/- 0.2 nM (P less than .001) on control and treatment nights, respectively. Neither glucagon nor norepinephrine concentrations changed significantly between 2400 and 0900 on either control or treatment nights. We conclude that nocturnal GH suppression by pirenzepine during a constant low-rate insulin infusion is associated with an attenuation of the early-morning plasma glucose rise.

Thyrotropin regulates thyrotroph responsiveness to dopamine in vitro.

The effect of conditioned vs. fresh culture medium on the dopaminergic inhibition of TSH and PRL secretion by primary cultures of male rat anterior pituitary cells has been studied. In the presence of conditioned medium (that had been in contact with the cells over the 3-day culture period) 10(-6) M dopamine (DA) inhibited PRL secretion by 50% and TSH secretion by 30%. After 4 h of incubation with fresh medium 10(-6) M DA still inhibited PRL secretion by 50% but increased TSH release by 20%. TSH release was rapid and could be prevented by 10(-6) M prazosin, an alpha 1 adrenoreceptor antagonist. Fresh medium did not alter TRH induced TSH release. In parallel cultures and under identical conditions fresh medium reduced [3H]dihydroergocryptine (DHE) binding to DA receptors from 2.5 +/- 0.4 fmol/10(5) cells to 0.95 +/- 0.3 fmol/10(5) cells (means +/- SEM, n = 5, P less than 0.001). The effect of fresh medium was dose dependent against the dopaminergic inhibition of TSH secretion and against DA receptor binding. If 1 mU TSH was included, in fresh medium, the dopaminergic inhibition of TSH secretion remained unchanged and [3H]DHE binding to DA receptors did not fall. The rank order of potency of thyroid stimulators was bovine TSH (21 U/mg) greater than semipurified bovine TSH (Thytropar, 1.4 U/mg) greater than endogenous rat TSH (0.03 U/mg expressed as NIADDK-rat TSH-RP2) greater than Graves' immunoglobulin G (0.01 U/mg) when either DA or bromocriptine was used as the dopaminergic agonist. When anterior pituitary cells from hypothyroid rats were examined, the effects of culture medium on the dopaminergic inhibition of TSH and on DA receptor binding were approximately twice those observed in normal cells, but the inclusion of 1 mU TSH in the fresh medium completely prevented the loss of DA function and binding. PRL, human CG, ACTH, insulin, glucagon, and heat-inactivated TSH were unable to prevent the effect of medium replacement on dopaminergic inhibition of TSH and DA receptor binding. The data suggest a mechanism whereby TSH may control its own secretion via DA.

Alpha 1-adrenoreceptors and alpha 1-adrenoreceptor-mediated thyrotropin release in cultures of euthyroid and hypothyroid rat anterior pituitary cells.

TSH responses to adrenergic agonists have been measured in 3-day monolayer cultures of euthyroid and hypothyroid male rat anterior pituitary (AP) cells. Responses were qualitatively similar in that (-)epinephrine and (-)norepinephrine had the same ED50 in each culture (ED50 = approximately 6 and 16 nM, respectively) and demonstrated the same alpha 1-adrenergic specificity. Hypothyroid cultures secreted approximately twice as much TSH per cell as euthyroid cultures over the 2-h experimental period. (-)Epinephrine produced a 95 +/- 8% (mean +/- SE) release of TSH relative to basal secretion in euthyroid cultures and only 62 +/- 7% release in the hypothyroid cultures (P less than 0.01). The comparable figures for (-)norepinephrine were 62 +/- 7% and 38 +/- 5%, respectively (P less than 0.05). In absolute terms, adrenergic agonists released the same amount of TSH from euthyroid and hypothyroid cultures. In contrast, TRH (and the Ca+2 channel ionophore A23187) released twice as much TSH from the hypothyroid cells as in the euthyroid cultures. Epinephrine-induced TSH release was significantly impaired (P less than 0.001) when either euthyroid or hypothyroid cells were cultured without thyroid hormones. In contrast, TRH-induced TSH release was enhanced (P less than 0.001) in the euthyroid cultures. [3H]Dihydroergocryptine [( 3H]DHE) was used to quantify alpha 1-adrenoreceptors on the same cell preparations as those used to derive the functional data (see above). Prazosin (1 microM) was used to define nonspecific binding of [3H]DHE. Specific binding to euthyroid cells had a Kd of 5.8 +/- 4 nM and a maximum binding capacity of 2.2 +/- 0.4 fmol/10(5) cells (n = 5). In parallel cultures of hypothyroid cells, the Kd (6.2 +/- 5 nM) was not significantly different, whereas the maximum binding capacity (1.4 +/- 0.3 fmol/10(5) cells) was significantly reduced (P less than 0.05). Adrenergic compounds showed a rank order of potency of prazosin greater than (-)epinephrine greater than or equal to (-)norepinephrine greater than or equal to yohimbine greater than clonidine against the binding of 5 nM [3H]DHE to euthyroid and hypothyroid cells. The amount of [3H]DHE binding per cell that each adrenergic compound was able to displace at saturating concentrations was less in hypothyroid cells than in euthyroid cells. There was no change in the ED50 values of these compounds in the same experiments.(ABSTRACT TRUNCATED AT 400 WORDS)

The effects of thyroid hormone deprivation in vivo and in vitro on growth hormone (GH) responses to human pancreatic (tumor) GH-releasing factor (1-40) by dispersed rat anterior pituitary cells.

Anterior pituitary cells from euthyroid and hypothyroid male rats have been cultured as monolayers for 3 days with or without 5 nM T3 and stimulated with either human pancreatic GH-releasing factor 1-40 (hpGRF), TRH, or the Ca2+ channel ionophore A23187. Basal GH secretion was reduced in the hypothyroid cultures (P less than 0.001) and basal TSH secretion increased (P less than 0.001). Culture with T3 increased GH secretion and intracellular GH content in euthyroid and hypothyroid cultures but suppressed TSH secretion with no effect on intracellular TSH content in either euthyroid or hypothyroid cultures. hpGRF released more GH from euthyroid [3.52 +/- 0.2 (SE) micrograms/6 h X 10(5) cells] than hypothyroid cultures of (0.17 +/- 0.01 micrograms/6 h X 10(5) cells, P less than 0.001) without a change in ED50 (approximately 0.02 nM). The reduction in hpGRF-induced GH release remained significant when corrected for the reduced intracellular GH content in the hypothyroid cultures. hpGRF-induced GH release also declined relative to A23187-induced GH release in hypothyroid cultures. Culture with 5 nM T3 doubled maximum hpGRF-induced GH release in euthyroid cultures and increased maximum release 10-fold in hypothyroid cultures without altering the ED50 of hpGRF action. In contrast, T3 suppressed TRH-induced TSH release in euthyroid cultures but was without effect on TRH-induced TSH release in the hypothyroid cultures. T3 did not effect the ED50 of TRH action (2-5 nM). In summary, hypothyroid rat anterior pituitary cells in culture have a reduced maximal GH response to hpGRF, but the same ED50. hpGRF activity can be partially restored by physiological concentrations of T3 in vitro.

Dopamine receptors on intact anterior pituitary cells in culture: functional association with the inhibition of prolactin and thyrotropin.

Dopamine (DA) and the dopaminergic agonists bromocriptine and apomorphine inhibit the secretion of TSH as well as that of PRL by rat anterior pituitary (AP) cells in monolayer culture. The order of potency of the drugs is the same for the inhibition of both hormones: bromocriptine ED50 = 0.006 nM against PRL and 0.017 nM against TSH; apomorphine ED50 = 2.9 and 4.8 nM, respectively, and DA, ED50 = 30 and 370 nM, respectively. The dopaminergic antagonists domperidone (DOM) and metoclopramide prevent the inhibition of TSH and PRL by 10(-6) M DA (IC50 = 0.012 and 0.32 nM for metoclopramide against PRL and TSH, respectively; similarly, IC50 = 0.01 and 0.61 nM for DOM). The action of butaclamol is shown to be stereospecific, in that the (+) isomer is 1000-fold more potent in reversing the inhibition of both TSH and PRL by 10(-6) M DA than the (-) isomer [IC50 = 1.1 and 7200 nM for the (+) and (-) isomers against PRL; similarly, 6.3 and 2600 nM against TSH]. The use of radioligand-binding techniques with tritiated DOM ([3H]DOM) and dihydroergocriptine ([3H]DHE) has demonstrated a high affinity dopaminergic binding site upon rat AP cells under the same conditions as the cell cultures used in the hormone secretion studies. Both ligands have been shown to label a site with high affinity (Kd = 1-2 nM) and low capacity (2-3 fmol/10(5) cells). At this site, dopaminergic agonists and antagonists compete with both radioligands and display a rank order of potency which is the same as that shown against TSH and PRL secretion and which is typically dopaminergic. For [3H]DHE: bromocriptine Ki (0.04 nM) greater than metoclopramide = DOM (0.07 nM) greater than (+)butaclamol (0.7 nM) greater than apomorphine (20 nM) greater than DA (700 nM) greater than (-)butaclamol (2000 nM). Similar data were derived using [3H]DOM. The high affinity site is saturable, has rapid association and dissociation rates, as determined for both radioligands used, and is temperature dependent. In contrast, both radioligands bind to a second binding site on the cells that is of lower affinity (Kd = 244 nM for [3H]DOM and 678 nM for [3H]DHE) and larger capacity (100 fmol/10(5) cells for both ligands). This second site is neither stereospecific nor, using the methodology presented here, does it discriminate between other dopaminergic compounds. It is thus not considered to represent specific DA receptor binding. It is concluded that the dopaminergic stimulus causing the inhibition of TSH and PRL secretion from rat AP cells in culture is mediated via a high affinity DA receptor present upon lactotrophs and thyrotrophs and that this receptor has similar characteristics on the two cell types.

Alpha 1-adrenoreceptors on intact rat anterior pituitary cells: correlation with adrenergic stimulation of thyrotropin secretion.

An in vitro study of the alpha-adrenergic control of TSH secretion was carried out on rat anterior pituitary cells in monolayer culture. The ability of adrenergic agonists and antagonists to alter TSH release from the cells was determined. With the use of parallel cell cultures under the same conditions, alpha-adrenergic binding sites were measured and characterized with [3H]dihydroergocryptine (DHE) as the radioligand. Epinephrine (E) and norepinephrine (NE) released TSH over a 2-h period in a dose-dependent and stereospecific manner (ED50 = 1 and 700 nM for the (-) and (+/-) stereoisomers of E; 7 and 600 nM for the active and inactive stereoisomers of NE respectively). Maximum release was 3- to 4-fold greater than basal secretion for both isomers of E but less (2- to 3-fold) for the isomers of NE. Phenylephrine, an alpha 1-agonist, elicited a 2- to 3-fold increase in TSH secretion (ED50 = 13 nM). Clonidine, an alpha 2-agonist, produced only slight stimulation at concentrations greater than 10(-6) M, and isoproterenol was ineffective. Prazosin, an alpha 2-antagonist (IC50 = 0.12 nM), was 500-fold more effective than yohimbine, an alpha 2-antagonist (IC50 = 60 nM), in reversing the TSH stimulation induced by 10(-7) M E. With [3H]DHE and prazosin as competing ligands, alpha-adrenergic receptors could be quantified independently of dopamine receptors present upon the same mixed cell preparations. The kinetics of specific radioligand binding to the cells were rapid (k1 = 1.75 X 10(-7) M-1 min-1, k2 = 0.131 min-1), equilibrium being reached within 15 min at 22 C. Adsorption isotherms and Scatchard analysis revealed a single population of binding sites with high affinity (kd = 7.2 nM) and low capacity (3 fmol/10(5) cells). Competition by adrenergic agonists for [3H]DHE binding was stereospecific. The rank order of potency against binding was identical with that determined functionally against TSH secretion (Ki for prazosin, 0.7 nM greater than thymoxamine, 2.7 nM greater than (-) E, 7 nM greater than phentolamine, 8 nM greater than (-) NE, 11.5 nM greater than phenylephrine, 100 nM greater than yohimbine, 300 nM greater than clonidine, 4500 nM greater than (+/-) E, 5000 nM greater than (+/-) NE, 7000 nM greater than isoproterenol, 3 X 10(5) nM), and typical of binding to an alpha 1-adrenoreceptor. It is concluded that TSH can be specifically released from rat anterior pituitary cells in monolayer culture by the direct effects of adrenergic agonists and that the stimulation is mediated via a single high affinity population of alpha 1-adrenergic receptors.

Interactions among epinephrine, thyrotropin (TSH)-releasing hormone, dopamine, and somatostatin in the control of TSH secretion in vitro.

Epinephrine and TRH independently release TSH from rat anterior pituitary cells in primary monolayer culture (ED50, 11 and 5 nM, respectively; maximum responses, 80% and 110%, respectively). The effects of these compounds together are additive, even at concentrations at which each is maximally effective alone. Dopamine inhibited basal and epinephrine-stimulated TSH secretion by 25 +/- 5% (+/-SE; ED50, 50 +/- 9 nM in each case). Somatostatin was effective against epinephrine-stimulated, but not basal, TSH secretion (80 +/- 4% inhibition; ED50, 1 +/- 3 nM). The data show that epinephrine is a potential regulator of TSH secretion by its own action and via its interactions with TRH, dopamine, and somatostatin.

Hypothyroid pituitary cells in culture: an analysis of thyrotropin and prolactin responses to dopamine (DA) and DA receptor binding.

Monolayer cultures were prepared from the anterior pituitary (AP) lobes of normal male rats and male rats made hypothyroid by treatment with aminotriazole. After 3 days in culture, the cells from hypothyroid animals showed significantly greater TSH and PRL secretory activity and significantly less GH secretory activity than did parallel euthyroid cultures. The responses of euthyroid and hypothyroid cultures to dopaminergic agonists and antagonists were examined. Bromocriptine, apomorphine, and dopamine (DA) inhibited euthyroid TSH secretion by approximately 30%, whereas each drug inhibited hypothyroid TSH secretion by approximately 60% (P less than 0.01 for each drug). In contrast, the three agonists were less effective in inhibiting PRL secretion from hypothyroid cells (P less than 0.05 for each drug). The rank order of potency [bromocriptine greater than (+)butaclamol greater than apomorphine greater than DA greater than (-)butaclamol] shown against secretion was the same for TSH and PRL in both euthyroid and hypothyroid cell cultures and is typical of a DA receptor-mediated process. The binding of [3H]dihydroergocryptine (DHE) to DA receptors on euthyroid and hypothyroid cells was examined under the same conditions in which the secretory responses were determined. One micromolar concentration of (+)butaclamol was used to define nonspecific binding. Specific binding was saturable and stereospecific in each case. The rank order of potency of dopaminergic agonists and antagonists in competing for [3H] DHE binding was the same as that demonstrated against the secretion of TSH and PRL. Each compound displaced significantly more [3H]DHE from hypothyroid cells than from euthyroid cells (P less than 0.05 for each drug). Construction of adsorption isotherms for [3H]DHE binding to DA receptors on euthyroid and hypothyroid cells and subsequent Scatchard analysis revealed a 3- to 4-fold increase in receptor number without a significant change in affinity. Immunohistochemistry on AP lobes before and after dispersion revealed an increase in thyrotrophs and thyroidectomy cells in hypothyroid rats relative to those in control animals. In euthyroid animals thyrotrophs were 10.1% of the total AP cell population, in hypothyroid animals they plus the thyroidectomy cells were 36.3% of the total AP cells. Therefore, the increased number of DA receptors per lobe could be accounted for by increased numbers of thyrotrophs. The mechanism of the altered sensitivity to DA induced by hypothyroidism in lactotrophs and thyrotrophs remains to be clarified.

Early morning hyperglycemia in insulin-dependent diabetes: acute and sustained effects of cholinergic blockade.

Nocturnal release of GH has been shown to be related to the early morning rise in plasma glucose (PG) seen in insulin-dependent diabetes mellitus (IDDM). We have studied the effects of suppression of nocturnal GH release during a single night (acute study) and after nightly suppression for 1 week (chronic study). Changes in plasma glucose and counter-regulatory hormone concentrations were monitored in six IDDM patients during a constant overnight insulin infusion alone, after addition of the anticholinergic agent pirenzepine to cause acute GH suppression, and again on the seventh night of such treatment. In control experiments (infusion of insulin alone; 0.075 mU/kg.min) PG increased from (mean +/- SEM) 5.6 +/- 0.6 mmol/L at 2400 h to 11.1 +/- 1.3 mmol/L at 0900 h (P = 0.0024). Addition of pirenzepine (100 mg at 2200 h and again at 2400 h) in the acute study resulted in a PG change from 5.6 +/- 0.3 mmol/L at 2400 h to 8.4 +/- 1.4 mmol/L at 0900 h (P = 0.17). After pirenzepine administration at the same dose for 7 nights, PG increased from 4.7 +/- 0.6 mmol/L at 2400 h to 6.8 +/- 1.2 mmol/L at 0900 h (P = 0.11). Increases in PG during the study period were significantly less after chronic treatment than after acute treatment compared with changes on control nights. The nocturnal release of GH, which was demonstrated in all patients during the control nights, was suppressed in all patients during the acute study and in four of six patients during the chronic studies. We conclude that initial reduction of the early morning rise of PG in IDDM is associated with acute suppression of nocturnal GH release, and that the more significant sustained effect of anticholinergic GH suppression on the rise of PG may be associated with additional indirect effects on insulin clearance.