Acute metabolic and cardiovascular effects of mirabegron in healthy individuals

AIMS

To quantify acute energy expenditure, supraclavicular skin temperature and cardiovascular responses to four doses of the β3-adrenoceptor agonist, mirabegron.

MATERIALS AND METHODS

A total of 17 individuals (11 men, six women) participated in this ascending-dose study, receiving single 50-, 100-, 150- and 200-mg doses of mirabegron on four separate days with 3 to 14 days wash-out between each dose. All variables were measured each visit from baseline to 180 minutes post mirabegron treatment. To determine brown adipose tissue (BAT) thermogenic efficacy at each dose, energy expenditure and supraclavicular skin temperature were compared from baseline to 180 minutes post mirabegron treatment. To examine safety, changes in cardiovascular variables at 100, 150 and 200 mg were compared with the standard clinical dose of 50 mg.

RESULTS

Energy expenditure significantly increased after the 100- (35.6 ± 5.4 kJ/h) and 200-mg (35.6 ± 13.1 kJ/h) doses (P ≤ 0.05), and trended towards an increase after 150 mg (24.1 ± 13.6 kJ/h). Supraclavicular skin temperature increased after 50- (0.22 ± 0.1°C), 100- (0.30 ± 0.1°C) and 150-mg mirabegron doses (0.29 ± 0.1°C; P ≤ 0.05). The change in systolic blood pressure was greater after 150- (7.1 ± 1.3 mm Hg) and 200-mg doses (9.3 ± 1.9 mm Hg) than after the 50-mg dose (2.2 ± 1.3 mm Hg; P ≤ 0.05). The change in heart rate was greater after 200 mg (9.0 ± 2.2 bpm) compared with 50 mg (2.9 ± 1.4 bpm; P ≤ 0.05).

CONCLUSIONS

A 100-mg dose of mirabegron increases energy expenditure and supraclavicular skin temperature in a β3-adrenoceptor-specific manner, without the off-target elevations in blood pressure or heart rate observed at higher doses.

Correction to: Pioglitazone reduces cold-induced brown fat glucose uptake despite induction of browning in cultured human adipocytes: a randomised, controlled trial in humans

The baseline insulin data given in Table 1 for the placebo group were incorrectly reported as 51 ± 10 pmol/l instead of 48 ± 10 pmol/l. This mistake also impacts on data reported in Table 4.

Pioglitazone reduces cold-induced brown fat glucose uptake despite induction of browning in cultured human adipocytes: a randomised, controlled trial in humans

AIMS/HYPOTHESIS

Increasing brown adipose tissue (BAT) activity is a possible therapeutic strategy to increase energy expenditure and glucose and lipid clearance to ameliorate obesity and associated comorbidities. The thiazolidinedione (TZD) class of glucose-lowering drugs increase BAT browning in preclinical experimental models but whether these actions extend to humans in vivo is unknown. The aim of this study was to determine the effect of pioglitazone treatment on adipocyte browning and adaptive thermogenesis in humans.

METHODS

We first examined whether pioglitazone treatment of cultured human primary subacromioclavicular-derived adipocytes induced browning. Then, in a blinded, placebo-controlled, parallel trial, conducted within the Baker Institute clinical research laboratories, 14 lean male participants who were free of cardiometabolic disease were randomised to receive either placebo (lactose; n = 7, age 22 ± 1 years) or pioglitazone (45 mg/day, n = 7, age 21 ± 1 years) for 28 days. Participants were allocated to treatments by Alfred Hospital staff independent from the study via electronic generation of a random number sequence. Researchers conducting trials and analysing data were blind to treatment allocation. The change in cold-stimulated BAT activity, assessed before and after the intervention by [¹⁸F]fluorodeoxyglucose uptake via positron emission tomography/computed tomography in upper thoracic and cervical adipose tissue, was the primary outcome measure. Energy expenditure, cardiovascular responses, core temperature, blood metabolites and hormones were measured in response to acute cold exposure along with body composition before and after the intervention.

RESULTS

Pioglitazone significantly increased in vitro browning and adipogenesis of adipocytes. In the clinical trial, cold-induced BAT maximum standardised uptake value was significantly reduced after pioglitazone compared with placebo (-57 ± 6% vs -12 ± 18%, respectively; p < 0.05). BAT total glucose uptake followed a similar but non-significant trend (-50 ± 10% vs -6 ± 24%, respectively; p = 0.097). Pioglitazone increased total and lean body mass compared with placebo (p < 0.05). No other changes between groups were detected.

CONCLUSIONS/INTERPRETATION

The disparity in the actions of pioglitazone on BAT between preclinical experimental models and our in vivo human trial highlight the imperative to conduct human proof-of-concept studies as early as possible in BAT research programmes aimed at therapeutic development. Our clinical trial findings suggest that reduced BAT activity may contribute to weight gain associated with pioglitazone and other TZDs.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02236962 FUNDING: This work was supported by the Diabetes Australia Research Program and OIS scheme from the Victorian State Government.

Incidence of chronic kidney disease among people with diabetes: a systematic review of observational studies

AIMS

The aim was to systematically review published articles that reported the incidence of chronic kidney disease among people with diabetes.

METHODS

A systematic literature search was performed using MEDLINE, Embase and CINAHL databases. The titles and abstracts of all publications identified by the search were reviewed and 10 047 studies were retrieved.

RESULTS

A total of 71 studies from 30 different countries with sample sizes ranging from 505 to 211 132 met the inclusion criteria. The annual incidence of microalbuminuria and albuminuria ranged from 1.3% to 3.8% for Type 1 diabetes. For Type 2 diabetes and studies combining both diabetes types, the range was from 3.8% to 12.7%, with four of six studies reporting annual rates between 7.4% and 8.6%. In studies reporting the incidence of eGFR < 60 ml/min/1.73 m² using the Modification of Diet on Renal Disease (MDRD) equation, apart from one study which reported an annual incidence of 8.9%, the annual incidence ranged from 1.9% to 4.3%. The annual incidence of end-stage renal disease ranged from 0.04% to 1.8%.

CONCLUSIONS

The annual incidence of microalbuminuria and albuminuria is ~ 2-3% in Type 1 diabetes, and ~ 8% in Type 2 diabetes or mixed diabetes type. The incidence of developing eGFR < 60 ml/min/1.73 m² is ~ 2-4% per year. Despite the wide variation in methods and study design, within a particular category of kidney disease, there was only modest variation in incidence rates. These findings may be useful in clinical settings to help understand the risk of developing kidney disease among those with diabetes.

A pilot study to examine the tolerability and device preference in type 1 diabetes of insulin aspart administered by InsuJet compared with subcutaneous injection

BACKGROUND

Jet injectors allow needle-free insulin delivery. The study objective was to compare the tolerability and device preference of subcutaneous insulin aspart delivery by jet injector (InsuJet™; European Pharma Group, Schiphol-Rijk, The Netherlands) with pen injection in an open-label, randomized, crossover pilot study.

SUBJECTS AND METHODS

Ten participants with type 1 diabetes underwent two meal tolerance tests 1 week apart. Plasma glucose and serum insulin levels were sampled from 10 min preceding to 240 min after insulin aspart administration by InsuJet or FlexPen(®) (Novo Nordisk Pharmaceuticals Pty. Ltd., Baulkham Hills, NSW, Australia). Insulin dose was calculated using participants' insulin-to-carbohydrate ratios. Immediately after insulin administration, participants drank 500 mL of Ensure(®) (Abbott Australasia Pty. Ltd., Botany, NSW, Australia) (providing 2,240 kJ of energy, 18.6 g of protein, 96 g of carbohydrate, and 3 g of fat).

RESULTS

In this small pilot study, the devices were similar in glucose excursion (median [quartile 1, quartile 3], InsuJet vs. FlexPen, 9.4 [4.8, 12.8] vs. 8.1 [5.4, 10.6] mmol/L; P=0.43), in the area under the glucose concentration-time curve for 0-240 min corrected for baseline glucose level (InsuJet vs. FlexPen, 1,230 [623, 2,012] vs. 1,175 [91, 1,774] mmol · min/L; P=0.4), and in insulin absorption over the 240-min period. Devices were similar for participant preference and relative injection pain.

CONCLUSIONS

Subcutaneous jet injection of aspart insulin was well tolerated.

The association between cystatin C and incident type 2 diabetes is related to central adiposity

BACKGROUND

Cystatin C has recently been shown to be associated with incident type 2 diabetes. This study aims to validate this association and to study the impact of baseline adiposity.

METHODS

We investigated the 3-year diabetes incidence in 2849 participants from the French Data of an Epidemiological Study on the Insulin Resistance syndrome study, without overt kidney disease. Odds ratios (ORs) associated with cystatin C were adjusted for classical diabetes risk factors and interactions between cystatin C and these risk factors were studied.

RESULTS

Baseline serum cystatin C was significantly associated with incident diabetes on univariate analysis (OR/1 SD of log cystatin C: 1.74; 95% confidence interval [CI] 1.33-2.28; P=0.0001) and after adjustment for age and gender (OR 1.55; 95% CI 1.15-2.10; P=0.0039). This association was independent of serum creatinine-derived measures of baseline renal function and independent of fasting plasma glucose and HbA1c. When body mass index (BMI), waist circumference or baseline insulin resistance index were used as covariates, there was an interaction with cystatin C level. Cystatin C was associated only with incident diabetes for people with BMI, waist circumference or insulin resistance index≥median value with OR (95% CIs), respectively: 1.35 (0.98-1.84, P=0.0625); 1.39 (1.01-1.91, P=0.0441) and 1.41 (1.02-1.94, P=0.0398).

CONCLUSIONS

Cystatin C was associated with 3-year incident diabetes but only in people with central adiposity or insulin resistance. This should be considered in further studies assessing the clinical relevance of its prognostic value.

Epidemiology of diabetic kidney disease

The increasing prevalence of diabetes has led to DKD becoming the leading cause of ESRD in many regions. The economic cost of DKD will grow to prohibitive amounts unless strategies to prevent its onset or progression are urgently implemented. In type 1 and type 2 diabetes, the presence of microalbuminuria and macroalbuminuria confers increased risk of developing ESRD and of death. Comparison of recent studies with earlier historical studies shows that the incidence of ESRD and death has decreased in DKD. Increased risk of albuminuria has been identified in certain non-European ethnic groups. However, the initial concept of progression of DKD as an albuminuric phenotype involving development of microalbuminuria, macroalbuminuria, and then ESRD has had to be modified. Albumin excretion frequently regresses, and GFR can decline without abnormality in albumin excretion. There is emerging evidence that changes in renal function occurring early in the course of diabetes predict future outcomes. The major challenges are to prevent DKD onset, to detect it early, and to improve DKD outcomes globally.

The GIANT study, a cluster-randomised controlled trial of efficacy of education of doctors about type 2 diabetes mellitus management guidelines in primary care practice

OBJECTIVES

Primary aim: does general practitioner (GP) education on type 2 diabetes treatment improve HbA1c? Secondary aim: cardiovascular risk factors, hypoglycaemia, treatment intensification, health service utilisation, treatment barriers.

METHODS

99 Asia-Pacific GPs were cluster-randomised to be educated on regional diabetes management guidelines (intervention) or continue standard care (control). The intervention employed meetings, reminders, medical record summary sheets and patient result cards. Each GP recruited four type 2 diabetic patients, assessed at baseline, 6 and 12 months. The primary outcome was mean change in HbA1c from 0 to 6 months in patients with baseline HbA1c≥6.5%.

RESULTS

361 patients (93%) completed 6 month follow-up. The primary HbA1c outcome was -0.11% (95% CI -0.27, 0.05) with intervention and -0.22% (95% CI -0.39, -0.05) in the control group (p=0.340). The groups did not differ in control of other glycaemic indices, blood pressure or lipids after 6 or 12 months. In those with HbA1c≥9.0%, approximately 50% received intensified treatment by 6 months, and 30% in the final 6 months. GPs identified treatment costs and patient reluctance to use insulin as management barriers.

CONCLUSIONS/INTERPRETATION

A structured GP education programme did not improve HbA1c in patients with type 2 diabetes.

Sulodexide fails to demonstrate renoprotection in overt type 2 diabetic nephropathy

Sulodexide, a mixture of naturally occurring glycosaminoglycan polysaccharide components, has been reported to reduce albuminuria in patients with diabetes, but it is unknown whether it is renoprotective. This study reports the results from the randomized, double-blind, placebo-controlled, sulodexide macroalbuminuria (Sun-MACRO) trial, which evaluated the renoprotective effects of sulodexide in patients with type 2 diabetes, renal impairment, and significant proteinuria (>900 mg/d) already receiving maximal therapy with angiotensin II receptor blockers. The primary end point was a composite of a doubling of baseline serum creatinine, development of ESRD, or serum creatinine ≥6.0 mg/dl. We planned to enroll 2240 patients over approximately 24 months but terminated the study after enrolling 1248 patients. After 1029 person-years of follow-up, we did not detect any significant differences between sulodexide and placebo; the primary composite end point occurred in 26 and 30 patients in the sulodexide and placebo groups, respectively. Side effect profiles were similar for both groups. In conclusion, these data do not suggest a renoprotective benefit of sulodexide in patients with type 2 diabetes, renal impairment, and macroalbuminuria.

Pyridorin in type 2 diabetic nephropathy

Pyridoxamine dihydrochloride (Pyridorin, NephroGenex) inhibits formation of advanced glycation end products and scavenges reactive oxygen species and toxic carbonyls, but whether these actions translate into renoprotective effects is unknown. In this double-blind, randomized, placebo-controlled trial, we randomly assigned 317 patients with proteinuric type 2 diabetic nephropathy to twice-daily placebo; Pyridorin, 150 mg twice daily; or Pyridorin, 300 mg twice daily, for 52 weeks. At baseline, the mean age ± SD was 63.9±9.5 years, and the mean duration of diabetes was 17.6±8.5 years; the mean serum creatinine level was 2.2±0.6 mg/dl, and the mean protein-to-creatinine ratio was 2973±1932 mg/g. Regarding the primary end point, a statistically significant change in serum creatinine from baseline to 52 weeks was not evident in either Pyridorin group compared with placebo. However, analysis of covariance suggested that the magnitude of the treatment effect differed by baseline renal function. Among patients in the lowest tertile of baseline serum creatinine concentration, treatment with Pyridorin associated with a lower average change in serum creatinine concentration at 52 weeks (0.28, 0.07, and 0.14 mg/dl for placebo, Pyridorin 150 mg, and Pyridorin 300 mg, respectively; P=0.05 for either Pyridorin dose versus placebo); there was no evidence of a significant treatment effect in the middle or upper tertiles. In conclusion, this trial failed to detect an effect of Pyridorin on the progression of serum creatinine at 1 year, although it suggests that patients with less renal impairment might benefit.

Sulodexide for kidney protection in type 2 diabetes patients with microalbuminuria: a randomized controlled trial

BACKGROUND

Sulodexide, a heterogenous group of sulfated glycosaminoglycans, includes low-molecular-weight heparin (~80% ± 8%), high-molecular-weight heparin (~5% ± 3%), and dermatan (~20% ± 8%), with a mean molecular weight of ~9 kDa. The drug is absorbed orally and has no anticoagulant effect in the doses used. Small preliminary studies consistently showed sulodexide to be associated with decreased albuminuria in patients with diabetes.

STUDY DESIGN

We conducted a multicenter placebo-controlled double-blinded study to determine the effect of sulodexide on urine albumin excretion in patients with type 2 diabetic nephropathy.

SETTING & PARTICIPANTS

Patients with type 2 diabetes and urine albumin-creatinine ratios (ACRs) of 35-200 mg/g in men and 45-200 mg/g in women were enrolled. Serum creatinine level was <1.5 mg/dL. Blood pressure goal was 130/80 mm Hg. A maximum US Food and Drug Administration-approved dose of an angiotensin-converting enzyme inhibitor or angiotensin receptor blocker for a minimum of 4 months before randomization was required.

INTERVENTION

The study drug was sulodexide, 200 mg/d.

OUTCOME & MEASUREMENTS

The primary end point was normoalbuminuria (ACR <20 mg/g and a decrease >25%) or 50% decrease in baseline ACR.

RESULTS

In 1,056 randomly assigned patients with a mean baseline ACR of 107.8 ± 83.7 mg/g, comparing the sulodexide versus placebo groups, the primary end point was achieved in 16.5% versus 18.4%; normoalbuminuria, in 7.9% versus 6.1%; and a 50% decrease in albuminuria, in 15.4% versus 17.6%. The relative probability of any given change in albuminuria was identical in both groups.

LIMITATIONS

We were unable to determine whether the administered sulodexide was absorbed from the gastrointestinal tract.

CONCLUSION

Sulodexide failed to decrease urine albumin excretion in patients with type 2 diabetic nephropathy and microalbuminuria.

Proteinuria in type 2 diabetic patients with renal impairment: the changing face of diabetic nephropathy

Type 2 diabetic nephropathy (type 2 DN) patients traditionally develop significant proteinuria prior to the development of renal impairment. However, this clinical paradigm, based on observations prior to the widespread usage of angiotensin-converting enzyme inhibitors (ACEi) or angiotensin receptor blockers (ARB), has recently been questioned. 2,303 patients enrolled in the Sulodexide Overt Nephropathy Study (OVERT) were analyzed. Prior therapy with ACEi and/or ARB at the time of screening was recorded in 951 patients. 22% of patients had significant renal impairment with a PCR at screening of <500 mg/g. Therapy with ACEi and/or ARB at the time of screening was recorded in 94%, where prior medication data was available. In patients with type 2 DN and advanced renal impairment, levels of proteinuria below that which traditionally defines overt diabetic nephropathy, are found in more than one fifth of patients. We suggest that the high prevalence of ACEi and ARB usage in patients with type 2 DN may be effecting the traditional clinical paradigm of type 2 DN.

Rationale for and study design of the sulodexide trials in Type 2 diabetic, hypertensive patients with microalbuminuria or overt nephropathy

BACKGROUND

Patients with Type 2 diabetes and albuminuria are at high risk to progress to end-stage renal disease (ESRD). Although angiotensin receptor blockers confer renoprotection, many diabetic patients still develop overt nephropathy and reach ESRD. Glycosaminoglycans belong to the same family as heparin and heparinoids. Pilot studies with sulodexide, a glycosaminoglycan, have shown that sulodexide can reduce urinary albumin excretion rates in diabetic patients. No hard renal end-point data are available.

METHODS

Two multicentre, double-masked, randomized placebo controlled trials were designed to study the renoprotective potential of sulodexide. The Sulodexide Microalbuminuria Trial examined the efficacy of sulodexide given over 26 weeks in 1000 patients with Type 2 diabetes, hypertension and microalbuminuria. The Sulodexide Overt Nephropathy Trial examined the efficacy of sulodexide in 2240 patients with Type 2 diabetes, hypertension and proteinuria > or = 900 mg/24 h.

RESULTS

The primary outcome of The Sulodexide Microalbuminuria Trial was (i) conversion to normoalbuminuria and at least a 25% decrease in the urinary albumin creatinine ratio (UACR), or (ii) at least a 50% reduction in UACR. The primary outcome of The Sulodexide Overt Nephropathy Trial was time to a composite end point of doubling of serum creatinine or ESRD.

CONCLUSIONS

The sulodexide nephropathy programme will document whether therapy with sulodexide confers renal protection in Type 2 diabetes and nephropathy.

Modulation by progestogens of the effects of oestrogen on hepatic endocrine function in postmenopausal women

OBJECTIVE

Oral but not transdermal oestrogen administration reduces IGF-I, and increases GH binding protein (GHBP) reflecting effects on hepatic endocrine function in postmenopausal women. As progestogens attenuate the effects of oestrogen on circulating lipid levels according to their androgenic properties, we have investigated the impact of progestogen types on the hepatic endocrine effects of oestrogen.

DESIGN

Four progestogens differing in androgenicity were co-administered in a monthly cyclical regimen in random order to postmenopausal women receiving either oral (n = 9, premarin 1.25 mg) or transdermal (n = 10, Estraderm 100 microg patches twice weekly). The four progestogens were cyproterone acetate (CA 5 mg, antiandrogenic), dydrogesterone (20 mg, neutral), medroxyprogesterone acetate (MPA 10 mg, mildly androgenic), norethisterone (2.5 mg, androgenic).

PATIENTS

Nineteen postmenopausal women (age 57 +/- 3 years, mean +/- SE) were studied.

MEASUREMENTS

The effects of oestrogen alone and the combined effects with each progestogen type on IGF-I, GHBP, SHBG, cholesterol, triglycerides and lipoprotein(a) were investigated.

RESULTS

Mean IGF-I fell while GHBP and SHBG levels increased with oral (P < 0.01) but not transdermal oestrogen administration. When the combined effects were examined, progestogens did not affect IGF-I, GHBP and SHBG during oral oestrogen treatment, while they significantly increased (P < 0.01) mean IGF-I levels during transdermal therapy. Among the progestogen types, only norethisterone prevented the fall in IGF-I induced by oral oestrogen. During transdermal therapy, MPA and norethisterone but not CA or dydrogesterone significantly increased (P < 0.005) IGF-I. The rise in GHBP induced by oral oestrogens tended to be lower during co-administration of MPA and norethisterone. The increase in SHBG induced by oral oestrogen was attenuated (P < 0.05) by norethisterone which was the only progestogen that lowered SHBG (P < 0.05) during transdermal oestrogen treatment. Mean IGF-I was higher (P < 0.001), GHBP and SHBG lower during co-administration of androgenic progestogens (MPA and norethisterone).

CONCLUSIONS

Oestrogen effects on IGF-I, GHBP and SHBG are dependent on the route of administration with progestogens having variable effects. Among the progestogen types, norethisterone, the most androgenic, had the greatest effect, particularly on IGF-I. Progestogens modulate the effects of oestrogen on hepatic endocrine function in relation to their intrinsic androgenic properties. The modulatory effects of progestogens on IGF-I during oestrogen therapy may have long-term implications for lean body mass.

The role of Ink4a/Arf in ErbB2 mammary gland tumorigenesis

Most human tumors display inactivation of the p53 and the p16(INK4)/pRb pathway. The Ink4a/alternative reading frame (ARF) locus encodes the p16(INK4a) and p14(ARF) (murine p19(ARF)) proteins. p16(INK4a) is deleted in 40-60% of breast cancer cell lines, and p16(INK4a) inactivation by DNA methylation occurs in < or =30% of human breast cancers. In mice genetically heterozygous for p16(INK4a) or Ink4a/Arf, predisposition to specific tumor types is enhanced. Ink4a/Arf(+/-) mice have increased E micro -Myc-induced lymphomagenesis and epidermal growth factor receptor-induced gliomagenesis. ErbB2 (epidermal growth factor receptor-related protein B2) is frequently overexpressed in human breast cancer and is sufficient for mammary tumorigenesis in vivo. We determined the role of heterozygosity at the Ink4a/Arf locus in ErbB2-induced mammary tumorigenesis. Compared with mouse mammary tumor virus-ErbB2 Ink4a/Arf(+/-) mice, mouse mammary tumor virus-ErbB2 Ink4a/Arf(wt) mammary tumors showed increased p16(INK4a), reduced Ki-67 expression, and reduced cyclin D1 protein but increased mammary tumor apoptosis with no significant change in the risk of developing mammary tumors. These studies demonstrate the contribution of Ink4a/Arf heterozygosity to tumor progression is tissue specific in vivo. In view of the important role of Ink4a/Arf in response to chemotherapy, these transgenic mice may provide a useful model for testing breast tumor therapies.

Endophilin-1: a multifunctional protein

Endophilin-1, a cytoplasmic Src homology 3 (SH3) domain-containing protein, localises in brain presynaptic nerve termini. Endophilin dimerises through its N-terminus, and participates at multiple stages in clathrin-coated endocytosis, from early membrane invagination to synaptic vesicle uncoating. Both its C-terminal SH3 domain and N-terminus are required for endocytosis. Through its SH3 domain, endophilin bound to proline-rich domains (PRDs) in other endocytic proteins, including synaptojanin and dynamin. The N-terminal region possesses unique functions affecting lipid membrane curvature, through lysophosphatidic acid acyl transferase (LPAAT) activity and direct binding and tubulating activity. In addition to synaptic vesicle formation, endophilin-1 complexes with signalling molecules, including cell surface receptors, metalloprotease disintegrins and germinal centre kinase-like kinase (GLK). Therefore, endophilin-1 may serve to couple vesicle biogenesis with intracellular signalling cascades.

Direct acetylation of the estrogen receptor alpha hinge region by p300 regulates transactivation and hormone sensitivity

Regulation of nuclear receptor gene expression involves dynamic and coordinated interactions with histone acetyl transferase (HAT) and deacetylase complexes. The estrogen receptor (ERalpha) contains two transactivation domains regulating ligand-independent and -dependent gene transcription (AF-1 and AF-2 (activation functions 1 and 2)). ERalpha-regulated gene expression involves interactions with cointegrators (e.g. p300/CBP, P/CAF) that have the capacity to modify core histone acetyl groups. Here we show that the ERalpha is acetylated in vivo. p300, but not P/CAF, selectively and directly acetylated the ERalpha at lysine residues within the ERalpha hinge/ligand binding domain. Substitution of these residues with charged or polar residues dramatically enhanced ERalpha hormone sensitivity without affecting induction by MAPK signaling, suggesting that direct ERalpha acetylation normally suppresses ligand sensitivity. These ERalpha lysine residues also regulated transcriptional activation by histone deacetylase inhibitors and p300. The conservation of the ERalpha acetylation motif in a phylogenetic subset of nuclear receptors suggests that direct acetylation of nuclear receptors may contribute to additional signaling pathways involved in metabolism and development.

Cyclin D1 binds the androgen receptor and regulates hormone-dependent signaling in a p300/CBP-associated factor (P/CAF)-dependent manner

The androgen receptor (AR) is a ligand-regulated member of the nuclear receptor superfamily. The cyclin D1 gene product, which encodes the regulatory subunit of holoenzymes that phosphorylate the retinoblastoma protein (pRB), promotes cellular proliferation and inhibits cellular differentiation in several different cell types. Herein the cyclin D1 gene product inhibited ligand-induced AR- enhancer function through a pRB-independent mechanism requiring the cyclin D1 carboxyl terminus. The histone acetyltransferase activity of P/CAF (p300/CBP associated factor) rescued cyclin D1-mediated AR trans-repression. Cyclin D1 and the AR both bound to similar domains of P/CAF, and cyclin D1 displaced binding of the AR to P/CAF in vitro. These studies suggest cyclin D1 binding to the AR may repress ligand-dependent AR activity by directly competing for P/CAF binding.

p300 and p300/cAMP-response element-binding protein-associated factor acetylate the androgen receptor at sites governing hormone-dependent transactivation

The androgen receptor (AR) is a sequence-specific DNA-binding protein that plays a key role in prostate cancer cellular proliferation by dihydrotestosterone and the induction of secondary sexual characteristics. In this study we demonstrate that the AR can be modified by acetylation in vitro and in vivo. p300 and p300/cAMP-response element-binding protein acetylated the AR at a highly conserved lysine-rich motif carboxyl-terminal to the zinc finger DNA-binding domain. [(14)C]acetate-labeling experiments demonstrated that AR acetylation by p300 in cultured cells requires the same residues identified in vitro. Point mutation of the AR acetylation site (K632A/K633A) abrogated dihydrotestosterone-dependent transactivation of the AR in cultured cells. Mutation of the p300 CH3 region or the p300/cAMP-response element-binding protein histone acetylase domain reduced ligand-dependent AR function. The identification of the AR as a direct target of histone acetyltransferase co-activators has important implications for targeting inhibitors of AR function.

The application of a lentiviral vector for gene transfer in fetal human hepatocytes

BACKGROUND

The applications of traditional retroviral vectors are limited because proviral integrations into the host genome require DNA synthesis. Lentiviruses are considered to be advantageous because of their ability to infect non-dividing cells.

METHODS

To demonstrate the potential of lentiviral vectors, we used a human immunodeficiency virus (HIV)-1 virus encoding the green fluorescence protein (GFP) to infect fetal human hepatocytes. GFP-expressing cells were transplanted into the liver of Balb/C SCID mice via intrasplenic injection.

RESULTS

Primary fetal hepatocytes incorporated the GFP reporter with high (30-40%) efficiency. A cell line derived from human fetal liver (HFL) exhibited similar transduction efficiency to the lentiviral vector. To demonstrate the relationship between lentiviral gene transfer and cell proliferation, cells were subjected to gamma-irradiation, which attenuated the replication of primary fetal hepatocytes. However, lentiviral gene transfer was unaffected by this decrease in cell proliferation. GFP expression in transduced cells was preserved during multiple passages in cell culture. When GFP-expressing cells were transplanted into the liver of Balb/C SCID mice via intrasplenic injection, GFP expression was observed throughout the 3 week duration of the study.

CONCLUSION

These studies establish that human hepatocytes are amenable to lentiviral gene transfer with sustained transgene expression. Incorporation of lentiviral vectors will be helpful in testing strategies for hepatic gene therapy.

Sustained mammary gland-directed, ponasterone A-inducible expression in transgenic mice

The ability to regulate temporal- and spatial-specific expression of target genes in transgenic mice will facilitate analysis of gene function and enable the generation of murine models of human diseases. The genetic analysis of mammary gland tumorigenesis requires the development of mammary gland-specific transgenics, which are tightly regulated throughout the adult mammary epithelium. Analysis of genes implicated in mammary gland tumorigenesis has been hampered by mosaic transgene expression and the findings that homozygous deletion of several candidate genes (cyclin D1, Stat5A, prolactin receptor) abrogates normal mammary gland development. We describe the development of transgenic mouse lines in which sustained transgene expression was inducibly regulated, both specifically and homogeneously, in the adult mammary gland epithelium. Transgenes encoding RXRalpha and a chimeric ecdysone receptor under control of a modified MMTV-LTR, which targets mammary gland expression, were used. These transgenic 'receptor' lines were crossed with transgenic 'enhancer' lines in which the ecdysone/RXR binding site induced ligand-dependent expression of transgenic beta-galactosidase. Pharmacokinetic analysis of a highly bioactive ligand (ponasterone A), identified through screening ecdysteroids from local plants, demonstrated sustained release and transgene expression in vivo. This transgenic model with both tightly regulated and homogeneous transgene expression, which was sustained in vivo using ligands readily extracted from local flora, has broad practical applicability for genetic analysis of mammary gland disease.

Cell-cycle dysregulation and the molecular mechanisms of prostate cancer

Prostate cancer is the most common cause of non-cutaneous cancer in men and although frequently latent is the second commonest cause of death. Screening for the disease was historically based on symptoms of urethral obstruction, clinical examination of the prostate gland and serum measurements of prostate specific antigen. As prostate cancer growth in the early stages is enhanced by androgens, the mainstay of therapy has been androgen ablation by pharmaco-therapeutic or surgical means. The subsequent development of androgen therapy resistant prostate cancer in many patients, for whom therapeutic options remain limited, has led researchers to focus attention on understanding the molecular genetics of prostate cancer. The array of genetic abnormalities observed in prostate tumors, which include changes in components of the cell cycle, suggest the disease is quite heterogeneous and may require further sub-classification based on genetic markers. Such analyses may lead to identification of relevant new prognostic and therapeutic indicators. The advent of transgenic mouse models of prostate cancer may provide a critical tool for the implementation of rational genetic based therapeutics and alternate drug design.

Activation of the cyclin D1 gene by the E1A-associated protein p300 through AP-1 inhibits cellular apoptosis

The adenovirus E1A protein interferes with regulators of apoptosis and growth by physically interacting with cell cycle regulatory proteins including the retinoblastoma tumor suppressor protein and the coactivator proteins p300/CBP (where CBP is the CREB-binding protein). The p300/CBP proteins occupy a pivotal role in regulating mitogenic signaling and apoptosis. The mechanisms by which cell cycle control genes are directly regulated by p300 remain to be determined. The cyclin D1 gene, which is overexpressed in many different tumor types, encodes a regulatory subunit of a holoenzyme that phosphorylates and inactivates PRB. In the present study E1A12S inhibited the cyclin D1 promoter via the amino-terminal p300/CBP binding domain in human choriocarcinoma JEG-3 cells. p300 induced cyclin D1 protein abundance, and p300, but not CBP, induced the cyclin D1 promoter. cyclin D1 or p300 overexpression inhibited apoptosis in JEG-3 cells. The CH3 region of p300, which was required for induction of cyclin D1, was also required for the inhibition of apoptosis. p300 activated the cyclin D1 promoter through an activator protein-1 (AP-1) site at -954 and was identified within a DNA-bound complex with c-Jun at the AP-1 site. Apoptosis rates of embryonic fibroblasts derived from mice homozygously deleted of the cyclin D1 gene (cyclin D1(-/-)) were increased compared with wild type control on several distinct matrices. p300 inhibited apoptosis in cyclin D1(+/+) fibroblasts but increased apoptosis in cyclin D1(-/-) cells. The anti-apoptotic function of cyclin D1, demonstrated by sub-G(1) analysis and annexin V staining, may contribute to its cellular transforming and cooperative oncogenic properties.

Activator protein-2 mediates transcriptional activation of the CYP11A1 gene by interaction with Sp1 rather than binding to DNA

The ovine P45 side chain cleavage (CYP11A1) enzyme gene, which catalyzes the initial enzymatic step in steroid hormone biosynthesis is transcriptionally regulated in cultured steroidogenic human trophoblastic JEG-3 cells. The ovine CYP11A1 promoter contains two GC-rich footprinted regions referred to as ovine footprints 5 (OF5) and OF3, which are well conserved among the CYP11A1 promoters of different species. These GC-rich sequences resemble activator protein-2 (AP-2)/Sp1 binding sites and were previously implicated in basal and cAMP-regulated activity of the bovine and ovine CYP11A1 promoters. In the current studies, AP-2 induced the ovine CYP11A1 promoter 4.5-fold in JEG-3 cells with full induction requiring the previously defined cAMP-responsive elements. Point mutation of OF3 abolished induction by AP-2, and OF3 was sufficient for induction by AP-2 when linked to a heterologous promoter. AP-2 induction of the CYP11A1 promoter required the basic region (N165-N278) and the carboxy terminus of AP-2 (N413-N437). In the course of investigating the mechanisms by which OF5 and OF3 regulated CYP11A1 transcription, we found that OF5 and OF3 bound Sp1 and Sp3 in JEG-3 cells. AP-2 did not bind OF5 or OF3 directly but rather formed a multiprotein complex with Sp1 in JEG-3 cells. AP-2 associated directly with Sp1 in vitro requiring the AP-2 basic region and the Sp1 carboxy terminus. AP-2 induced Sp1/Sp3 activity independently of AP-2 binding to DNA using a GAL4 paradigm. The Sp1 and Sp3 transactivation domains were linked to the DNA-binding domain of GAL4, and their activity was assessed using a luciferase reporter gene containing only the GAL4 DNA-binding sites linked to the minimal TATA site. AP-2 induced Sp1/ Sp3-GAL4 activity 3- to 4-fold, requiring both the amino and extreme carboxy terminus of AP-2. We conclude that AP-2 can bind to and stimulate Sp1 activity and induces the ovine CYP11A1 promoter through conserved Sp1/Sp3-binding sites in JEG-3 cells. The induction of Sp1 activity by AP-2 may contribute to the induction of other genes that bind Sp1.

Clinical and functional effects of mutations in the DAX-1 gene in patients with adrenal hypoplasia congenita

Adrenal hypoplasia congenita (AHC) is an X-linked disorder caused by mutations in a gene referred to as DAX-1. AHC is characterized by adrenal insufficiency and failure to undergo puberty because of hypogonadotropic hypogonadism. The DAX-1 protein is structurally related to orphan nuclear receptors, although it lacks the characteristic zinc finger DNA-binding domain that is highly conserved in other members of this family. In this report, we describe the clinical features and genetic alterations in six families with AHC. These patients reveal the variable clinical presentation of adrenal insufficiency in AHC and underscore the importance of considering this diagnosis. Nonsense mutations that introduce a stop codon were found in three cases (W171X, W171X, Y399X). Frameshift mutations (405delT, 501delA, and 702delC), each of which resulted in a premature stop codon at amino acid 263, were found in the other three families. Three of these mutations (Y399X, 405delT, 702delC) are novel. Using transient gene expression assays to assess DAX-1 function, these mutations were shown to eliminate the ability of DAX-1 to repress the transcription of genes that are stimulated by a related nuclear receptor, steroidogenic factor-1. These studies reveal the variable clinical presentation of DAX-1 mutations and emphasize the value of genetic testing in boys with primary adrenal insufficiency and suspected X-linked AHC.

A highly sensitive growth hormone (GH) enzyme-linked immunosorbent assay uncovers increased contribution of a tonic mode of GH secretion in adults with organic GH deficiency

The limited sensitivity of conventional GH assays has impeded a better understanding of the pathophysiology of GH secretion. In normal subjects, interpulse GH levels often fall below assay sensitivity, making it unclear whether secretion stops or is maintained at a tonic level below assay detectability. In patients with severe organic GH deficiency (GHD), GH levels are mostly undetectable. Using an ultrasensitive GH enzyme-linked immunosorbent assay to measure 24-h integrated GH concentrations, we recently provided evidence that these patients secrete low, but measurable, amounts of GH. In this report, we apply the same assay to characterize and compare 24-h GH profiles obtained by 20-min sampling in 10 subjects with organic GHD and 10 normal subjects matched for age, sex, and body mass index. With deconvolution analysis, which provides estimates of GH secretion and half-life, our aim was to determine 1) whether normal GH secretion is exclusively pulsatile, 2) how GH is secreted in subjects with organic GHD, and 3) the attributes of GH secretion that determine circulating insulin-like growth factor I (IGF-I) levels. All samples, including nadirs, from GHD subjects were well within the assay detection limit (1 ng/L). Peak 24-h GH levels in GHD subjects were lower and did not overlap those in the normal subjects. Nadir GH concentrations were significantly lower in GHD subjects (14 +/- 5 vs. 43 +/- 9 ng/L; P = 0.008), but the range overlapped that of normal subjects. Endogenous GH half-life did not differ significantly between the two groups. Normal subjects secreted GH in a mixed pulsatile and tonic mode, with pulsatile secretion accounting for 93 +/- 2% of the total production. Total daily GH production in GHD was approximately 5% of the production in matched normal subjects. This difference resulted from a greater reduction in the pulsatile (by 96%) than in the tonic (by 47%) component, so that the fractional daily contribution by tonic GH release in GHD subjects was markedly greater. There was a significant relationship between pulsatile GH secretion and serum IGF-I levels for the two groups combined. In summary, 1) peak, but not nadir, GH levels were completely segregated between GHD and normal subjects; and 2) although normal subjects secrete GH in a tonic and pulsatile mode, both modes are reduced in organic GHD, with a proportionately greater reduction in pulsatile secretion. We conclude that 1) nadir GH levels are not sufficiently discriminatory to be useful for the diagnosis of GH deficiency; 2) normal GH profiles arise from a mixed pattern of tonic and pulsatile secretion, whereas reduced GH secretion in organic GHD arises primarily from a marked diminution in the amount of pulsatile GH release; and 3) pulsatile GH release is a significant regulator of the IGF-I level in normal and GHD subjects.

Evaluation and application of a highly sensitive assay for serum growth hormone (GH) in the study of adult GH deficiency

Previous work from our laboratory addressing the diagnosis of GH deficiency in adults showed that RIA measurement of the 24-h integrated GH concentration (IGHC) was unable to discriminate between hypopituitary and age-, sex-, and body mass index-matched normal subjects because of the occurrence of undetectable levels (< 200 ng/L) within both groups. In contrast, full separation was achieved using stimulation by the insulin tolerance test (ITT). The data showed no significant relationship between IGHC and insulin-like growth factor-I (IGF-I) within either group. To determine whether limited sensitivity obscured diagnostic and physiological information, we assessed and modified a commercially available enzyme-linked immunosorbent assay (Elegance GH ELISA, Bioclone Australia) to achieve a high sensitivity (1 ng/L) and applied it to the study of IGHC and the relationship to IGF-I in a study group of 30 normal and 19 subjects with severe organic hypopituitarism. Using this assay, the IGHCs from all subjects were detectable and correlated significantly with detectable values obtained by RIA (n = 24; r = 0.80; P = 0.0001). Mean IGHC in normal subjects was significantly higher than that in hypopituitary subjects (852 +/- 131 vs. 97 +/- 28 ng/L), but the IGHCs from the two groups were not completely separate. Twenty-six percent of hypopituitary subjects had IGHC values within the normal range (111-3454 ng/L). IGHC decreased with age in normal subjects. Age stratification improved the separation, but an overlap remained in the young (< 50 yr old) and old (> 50 yr old) groups. Measurement of 12-h nocturnal IGHC levels improved the separation between hypopituitary and normal subjects in the young subjects only. IGHC was significantly related to IGF-I in hypopituitary (r = 0.59; P = 0.0084) and normal subjects (r = 0.55; P = 0.0017) and in the combined groups (r = 0.64; P = 0.0001). The data show that a sensitive ELISA reliably quantifies IGHC in normal and hypopituitary subjects. IGHCs in hypopituitary patients are lower, but not clearly separated from values in normal counterparts despite their having unequivocally impaired GH responses to ITT. We conclude that 1) IGHC in normal subjects can be reliably defined by sensitive ELISAs; 2) the diagnostic utility of the IGHC does not match the reliability or simplicity of an ITT, and 3) GH is a significant regulator of IGF-I in both normal and reduced states of GH secretion.