Effect of fenofibrate on the need for laser treatment for diabetic retinopathy (FIELD study): a randomised controlled trial.

BACKGROUND: Laser treatment for diabetic retinopathy is often associated with visual field reduction and other ocular side-effects. Our aim was to assess whether long-term lipid-lowering therapy with fenofibrate could reduce the progression of retinopathy and the need for laser treatment in patients with type 2 diabetes mellitus. METHODS: The Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) study was a multinational randomised trial of 9795 patients aged 50-75 years with type 2 diabetes mellitus. Eligible patients were randomly assigned to receive fenofibrate 200 mg/day (n=4895) or matching placebo (n=4900). At each clinic visit, information concerning laser treatment for diabetic retinopathy-a prespecified tertiary endpoint of the main study-was gathered. Adjudication by ophthalmologists masked to treatment allocation defined instances of laser treatment for macular oedema, proliferative retinopathy, or other eye conditions. In a substudy of 1012 patients, standardised retinal photography was done and photographs graded with Early Treatment Diabetic Retinopathy Study (ETDRS) criteria to determine the cumulative incidence of diabetic retinopathy and its component lesions. Analyses were by intention to treat. This study is registered as an International Standard Randomised Controlled Trial, number ISRCTN64783481. FINDINGS: Laser treatment was needed more frequently in participants with poorer glycaemic or blood pressure control than in those with good control of these factors, and in those with a greater burden of clinical microvascular disease, but the need for such treatment was not affected by plasma lipid concentrations. The requirement for first laser treatment for all retinopathy was significantly lower in the fenofibrate group than in the placebo group (164 [3.4%] patients on fenofibrate vs 238 [4.9%] on placebo; hazard ratio [HR] 0.69, 95% CI 0.56-0.84; p=0.0002; absolute risk reduction 1.5% [0.7-2.3]). In the ophthalmology substudy, the primary endpoint of 2-step progression of retinopathy grade did not differ significantly between the two groups overall (46 [9.6%] patients on fenofibrate vs 57 [12.3%] on placebo; p=0.19) or in the subset of patients without pre-existing retinopathy (43 [11.4%] vs 43 [11.7%]; p=0.87). By contrast, in patients with pre-existing retinopathy, significantly fewer patients on fenofibrate had a 2-step progression than did those on placebo (three [3.1%] patients vs 14 [14.6%]; p=0.004). An exploratory composite endpoint of 2-step progression of retinopathy grade, macular oedema, or laser treatments was significantly lower in the fenofibrate group than in the placebo group (HR 0.66, 95% CI 0.47-0.94; p=0.022). INTERPRETATION: Treatment with fenofibrate in individuals with type 2 diabetes mellitus reduces the need for laser treatment for diabetic retinopathy, although the mechanism of this effect does not seem to be related to plasma concentrations of lipids.

Microvascular complications in cystic fibrosis-related diabetes mellitus: a case report.

CONTEXT, The prevalence of cystic fibrosis-related diabetes mellitus is increasing and is associated with increased survival from cystic fibrosis. CASE REPORT, This study describes a case of the premature onset of disabling and widespread microvascular complications resulting from cystic fibrosis-related diabetes mellitus. Previously asymptomatic retinopathy was diagnosed on recognition of diabetic nephropathy. CONCLUSIONS, The treatment of pulmonary exacerbations has become more complex due to the nephrotoxic potential of intravenous aminoglycoside drugs which are frequently used to control chronic Pseudomonas infection in cystic fibrosis.

Analysis of functional cooperativity between individual transcription-stimulating elements in the proximal region of the rat prolactin gene.

The proximal region of the rat PRL gene contains at least five transcription-stimulating elements that are located within a 170-basepair region up-stream of the TATA box. These cis-acting elements include four binding sites for the pituitary-specific transcription factor Pit-1 as well as another site for an unidentified factor. In this study interactions between different DNA elements have been examined through the construction of PRL-luciferase fusion genes containing mutations that disrupt various combinations of the individual DNA elements. In general, the disruption of multiple factor-binding sites had a much more than additive effect on expression of the luciferase constructs. Interestingly, comparison of the effects of disrupting pairs of binding sites demonstrated substantial differences in the effects of different combinations of mutations, suggesting that cooperative interactions may reflect specific interactions. Mutations that disrupted all five cis-elements of the PRL proximal region essentially abolished transcription from the proximal promoter. This finding suggests that there are no other DNA elements within the proximal 200 basepairs of the PRL gene that can independently stimulate transcription. Although there is strong functional cooperativity between different cis-elements in the PRL gene, DNase footprint studies failed to detect cooperative binding between different Pit-1 elements. Overall, the findings demonstrate that the normal transcription of the PRL gene involves strong cooperative interactions between individual DNA elements in the proximal region.

Culture requirements for optimal expression of 1 alpha,25-dihydroxyvitamin D3-enhanced thyrotropin secretion.

An effect of the hormone, 1 alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3] on hormone secretion by normal rat pituitary cells was investigated in vitro. Based on previous findings using GH4C1 cells, dispersed anterior pituitary cell cultures were prepared and maintained in serum-free conditions for up to 6 d. Under these circumstances, there was no effect of 1,25(OH)2D3 to alter medium or cell-associated levels of thyrotropin (TSH), prolactin (PRL), or growth hormone (GH). Cultures maintained under these conditions had lower medium and cell-associated hormone levels and lesser responses to agonists than cultures maintained in serum-supplemented medium. In the presence of 10% charcoal-treated fetal bovine serum, treatment with 10(-8) M 1,25(OH)2D3 for 24 h selectively increased TRH (10(-10) to 10(-7) M)-induced TSH secretion (P less than 0.001), with maximal enhancement observed at 10(-9) M TSH-releasing hormone (TRH). Enhancement of TSH secretion by 1,25(OH)2D3 was detected after 15 min exposure to TRH. There was no effect on agonist-induced PRL or GH secretion or on cell-associated hormone levels. The effect was evident after 24 h treatment with 1,25(OH)2D3, and decreased thereafter. Several other steroid hormones had no effect on 10(-9) M TRH-induced TSH secretion. These data contrast with the effect of 1,25(OH)2D3 in GH cells. They suggest that 1,25(OH)2D3 may act selectively in the normal pituitary to modulate TSH secretion.

Clustered point mutation analysis of the rat prolactin promoter.

To identify DNA regions important for basal and hormone-stimulated transcription of the rat PRL gene, a series of clustered point mutations were prepared within the immediate 5' flanking region. DNA fragments representing the wild-type and 19 different linker-scanner mutations of the PRL gene were each linked to a luciferase marker gene, and the DNA constructs were transferred into GH3 pituitary tumor cells by electroporation. Luciferase activity was determined 24 h after transfection in extracts from control cells or cells treated with 0.5 mM chlorophenylthio-cAMP, 100 nM TRH, or 100 nM phorbol myristate acetate. The individual clustered point mutations covered a region from just up-stream of the TATA box (position -30) to a position 193 basepairs up-stream from the start of transcription. Five regions in which mutations produced substantial decreases in both basal and cAMP-, TRH-, or phorbol ester-stimulated expression of the marker gene were detected. Three of these regions (positions -41 to -58, -113 to -124, and -149 to -156) correspond to previously identified binding sites for the pituitary-specific, homeobox protein, Pit-1/GHF-1. The fourth and fifth regions do not correspond to Pit-1/GHF-1-binding sites and presumably represent sites for an unidentified factor. Within these regions, sequences with some similarity to a consensus cAMP response element and an AP-2-binding site have been detected. These data confirm the importance of Pit-1/GHF-1 as a key factor in PRL gene transcription. In addition, the results suggest that additional transcription factors are probably required for efficient expression of the PRL gene.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of tri-iodothyronine, cortisol and transcriptional inhibitors on vitamin D3-enhanced thyrotrophin secretion by rat pituitary cells in vitro.

The hormone 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) has been shown to selectively enhance agonist-induced TSH release in the rat thyrotroph in vitro. The interaction of 1,25-(OH)2D3 with tri-iodo-thyronine (T3) and cortisol was studied in primary cultures of dispersed anterior pituitary cells. TRH (1 nmol/l)-induced TSH release over 1 h was enhanced by 70% (P less than 0.01) following exposure to 10 nmol 1,25-(OH)2D3/l for 24 h. Pretreatment with T3 (1 pmol/l-1 mumol/l) for 24 h caused a dose-dependent inhibition of TRH-induced TSH release. Net TRH-induced TSH release was inhibited by 85% at T3 concentrations of 3 nmol/l or greater. Co-incubation with 1,25-(OH)2D3 resulted in enhanced TRH-induced TSH release at all T3 concentrations tested (P less than 0.001). The increment of TRH-induced TSH release resulting from 1,25-(OH)2D3 pretreatment was equivalent in the presence or absence of maximal inhibitory T3 concentrations. At 1 nmol T3/l, there was a two- to threefold relative increase in 1,25-(OH)2D3-enhanced TRH-induced TSH release. Incubation with cortisol (100 pmol/l-100 nmol/l) had no effect on basal or TRH-induced TSH release, nor did it alter 1,25-(OH)2D3-enhanced TRH-induced TSH release when added 24 h before, or at the time of addition of 1,25-(OH)2D3. Actinomycin D and alpha-amanitin abolished 1,25-(OH)2D3-enhanced TSH secretion. These data demonstrate that the action of 1,25-(OH)2D3 in the thyrotroph required new RNA transcription, and was not affected by cortisol. In the presence of T3, the response of the thyrotroph to TRH induced by 1,25-(OH)2D3 was increased. We have shown that 1,25-(OH)2D3 has significant effects on the action of TRH and T3 in vitro. These findings support the proposal that 1,25-(OH)2D3 may modulate TSH secretion in vivo.

Vitamin D-enhanced thyrotrophin release from rat pituitary cells: effects of Ca2+, dihydropyridines and ionomycin.

Vitamin D may regulate pituitary function, as there are selective effects of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) on gene expression in clonal pituitary tumour cells, and on TRH-induced TSH release in normal rat pituitary cells in vitro. The role of Ca2+ in 1,25-(OH)2D3-enhanced TSH release from primary rat pituitary cell cultures was investigated. Pretreatment with 10 nmol 1,25-(OH)2D3/l for 24 h augmented KCl (3-60 mmol/l)-induced TSH release over 1 h at all KCl concentrations greater than 7.5 mmol/l (P less than 0.001), with a 76% enhancement of TSH release induced by 30 mmol KCl/l (P less than 0.001). The Ca2+ channel antagonist nifedipine (10 nmol/l-10 mumol/l) caused a concentration-dependent inhibition of KCl (60 mmol/l)-induced TSH secretion. Pretreatment with 1,25-(OH)2D3 enhanced KCl-induced release at all concentrations of nifedipine (P less than 0.001). The Ca2+ selective divalent cation ionophore ionomycin (1 nmol/l-1 mumol/l), and the Ca2+ channel agonist BAY K 8644 (10 nmol/l-1 mumol/l) increased prolactin secretion but did not increase TSH release, and 1,25-(OH)2D3 had no effect. At an extracellular Ca2+ concentration of less than 500 nmol/l, TRH-induced TSH release was observed only after treatment with 1,25-(OH)2D3 (P less than 0.01). As the extracellular Ca2+ concentration was increased, greater increments of TRH-induced TSH release were observed following pretreatment with 1,25-(OH)2D3 (P less than 0.01). However, the effect of 1,25-(OH)2D3 in the thyrotroph was independent of the pretreatment extracellular Ca2+ concentration. We have shown that 1,25-(OH)2D3 acts selectively on the thyrotroph to enhance in-vitro responsiveness to TRH and KCl. These data suggest that the action of 1,25-(OH)2D3 in the thyrotroph is to enhance intracellular signal transduction. They further support a permissive or regulatory role of vitamin D in the normal pituitary gland.

Treatment of non-toxic multinodular goiter with radioactive iodine.

Fourteen patients with large non-toxic multinodular goiters were treated with 20 to 100 mCi (740 to 3,700 MBq) of radioactive iodine (iodine-131). In seven, the goiter had recurred after a partial thyroidectomy and four of these had had two operations. Eight had symptoms of respiratory obstruction, two had dysphagia, and the others sought treatment for cosmetic reasons. After administration of iodine-131, there was a significant decrease in goiter size in 11 of the 14 patients, and all those with obstructive symptoms showed improvement. No significant local side effects occurred, but hypothyroidism and Graves' disease each occurred once during follow-up from one to 13 years. Radioactive iodine in doses of 20 to 100 mCi is an effective, safe therapeutic alternative in patients with large non-toxic multinodular goiter, particularly when there is recurrence following surgery or when there are contraindications to surgery.

1,25-Dihydroxyvitamin D3 enhances thyrotropin releasing hormone induced thyrotropin secretion in normal pituitary cells.

The findings of specific binding of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] in normal rat pituitary tissue and selective effects of 1,25-(OH)2D3 on gene expression in clonal pituitary tumour cells have suggested that vitamin D may regulate pituitary function. Therefore, the in vitro effect of 1,25-(OH)2D3 on normal pituitary cells was investigated. Primary anterior pituitary cell cultures prepared from female rats were maintained in experimental medium +/- 10(-8) M 1,25-(OH)2D3 for up to 24 h and then incubated with fresh experimental medium containing TRH (10(-10)-10(-8) M) or vehicle for 1 h. Pretreatment with 1,25-(OH)2D3 for 24 h led to increased TSH release at all TRH concentrations tested (P less than 0.0001), a decrease in the half-maximal stimulatory dose of TRH for TSH release from 2 X 10(-9) M to 0.4 X 10(-9) M, a 22% increase in maximal TSH release (P less than 0.01), and an 81% increase in TSH release at 10(-9) M TRH (P less than 0.001). 1 X 10(-9) M 1,25-(OH)2D3 increased TRH (10(-9) M)-induced TSH release by 20% (P less than 0.05) but 10(-7) M and 10(-6) M 25-hydroxyvitamin D3 (25-OH D3) had no effect. The effect of 1,25-(OH)2D3 on TRH (10(-9) M)-induced TSH release was evident within 8 h and was maximal by 16 h. There was no effect on basal TSH release, TSH accumulation in the medium in the preceding 24 h nor on cell-associated TSH. 1,25-(OH)2D3 pretreatment had no effect on TRH-induced PRL secretion, PRL accumulation in the medium nor on cell-associated PRL. We have shown that 1,25-(OH)2D3 acts selectively on the thyrotroph to enhance in vitro responsiveness to physiologically relevant concentrations of TRH. These findings are consistent with the reported autoradiographic localization of [3H]-1,25-(OH)2D3 in the thyrotroph and support a permissive or regulatory role of vitamin D in the normal pituitary gland.

Rapid improvement in visual field defects following bromocriptine treatment of patients with non-functioning pituitary adenomas.

The role of bromocriptine in the treatment of non-functioning pituitary tumours is not yet defined. Patients with these tumours who present with visual field defects usually undergo immediate surgery. Three consecutive patients are reported: each had rapid improvement in their visual field defects following bromocriptine 7.5 mg/d before surgery. Histological and immunohistochemical examination confirmed that their tumours were non-functioning chromophobe adenomas. Their responses indicate that bromocriptine may have a role in the management of some patients with non-functioning pituitary tumours.