Results from a Phase 1 Study Assessing the Pharmacokinetics of the Aldosterone Synthase Inhibitor Baxdrostat in Participants with Varying Degrees of Renal Function

Baxdrostat is a selective small-molecule aldosterone synthase inhibitor in development for treatment of hypertension and chronic kidney disease. This phase 1, open-label, parallel-group study assessed the safety and pharmacokinetics (PK) of baxdrostat in participants with varying degrees of renal function. Participants were enrolled into control (estimated glomerular filtration rate [eGFR] ≥60 mL/min), moderate to severe renal impairment (eGFR 15-59 mL/min), or kidney failure (eGFR <15 mL/min) groups and received a single 10-mg baxdrostat dose followed by 7 days of inpatient PK blood and urine sampling. Safety was assessed by adverse events, clinical laboratory evaluations, vital signs, physical examinations, and electrocardiograms (ECGs). Thirty-2 participants completed the study. There were no deaths and only 1 mild drug-related adverse event (diarrhea). No clinically meaningful changes in laboratory values, vital signs, physical examinations, or ECGs occurred. Plasma concentration-time curves of baxdrostat were similar among all groups. Urine PK parameters were similar (approximately 12% excreted) in the moderate to severe renal impairment and control groups. Inadequate urine production in the kidney failure group resulted in minimal urinary baxdrostat excretion. Renal impairment had no significant impact on systemic exposure or clearance of baxdrostat, suggesting that dose adjustment due to PK differences in patients with kidney disease is unnecessary.

Bexagliflozin as an adjunct to metformin for the treatment of type 2 diabetes in adults: A 24-week, randomized, double-blind, placebo-controlled trial

AIM

To evaluate the relative safety and effectiveness of bexagliflozin as an adjunct to metformin for the treatment of type 2 diabetes mellitus.

METHODS

In total, 317 participants were randomized to receive bexagliflozin or placebo plus metformin. The primary endpoint was the change in glycated haemoglobin (HbA1c) from baseline to week 24, with secondary endpoints for systolic blood pressure (SBP), fasting plasma glucose and weight loss. An open label arm enrolled participants with HbA1c >10.5% and was analysed separately.

RESULTS

The mean change in HbA1c was -1.09% (95% CI -1.24%, -0.94%) in the bexagliflozin arm and -0.56% (-0.71%, -0.41%) in the placebo arm, a difference of -0.53% (-0.74%, -0.32%; p < .0001). Excluding observations after rescue medication, the intergroup difference was -0.70% (-0.92, -0.48; p < .0001). The open label group change in HbA1c was -2.82% (-3.23%, -2.41%). Placebo-adjusted changes from baseline SBP, fasting plasma glucose and body mass were -7.07 mmHg (-9.83, -4.32; p < .0001), -1.35 mmol/L (-1.83, -0.86; p < .0001) and -2.51 kg (-3.45, -1.57; p < .0001). Adverse events affected 42.4% and 47.2% of subjects in the bexagliflozin and placebo arms, respectively; fewer subjects in the bexagliflozin arm experienced serious adverse events.

CONCLUSIONS

Bexagliflozin produced clinically meaningful improvement in glycaemic control, estimated glomerular filtration rate and SBP when added to metformin in a population of adults with diabetes.

Phase 2 Trial of Baxdrostat for Treatment-Resistant Hypertension

BACKGROUND

Aldosterone synthase controls the synthesis of aldosterone and has been a pharmacologic target for the treatment of hypertension for several decades. Selective inhibition of aldosterone synthase is essential but difficult to achieve because cortisol synthesis is catalyzed by another enzyme that shares 93% sequence similarity with aldosterone synthase. In preclinical and phase 1 studies, baxdrostat had 100:1 selectivity for enzyme inhibition, and baxdrostat at several dose levels reduced plasma aldosterone levels but not cortisol levels.

METHODS

In this multicenter, placebo-controlled trial, we randomly assigned patients who had treatment-resistant hypertension, with blood pressure of 130/80 mm Hg or higher, and who were receiving stable doses of at least three antihypertensive agents, including a diuretic, to receive baxdrostat (0.5 mg, 1 mg, or 2 mg) once daily for 12 weeks or placebo. The primary end point was the change in systolic blood pressure from baseline to week 12 in each baxdrostat group as compared with the placebo group.

RESULTS

A total of 248 patients completed the trial. Dose-dependent changes in systolic blood pressure of -20.3 mm Hg, -17.5 mm Hg, -12.1 mm Hg, and -9.4 mm Hg were observed in the 2-mg, 1-mg, 0.5-mg, and placebo groups, respectively. The difference in the change in systolic blood pressure between the 2-mg group and the placebo group was -11.0 mm Hg (95% confidence interval [CI], -16.4 to -5.5; P<0.001), and the difference in this change between the 1-mg group and the placebo group was -8.1 mm Hg (95% CI, -13.5 to -2.8; P = 0.003). No deaths occurred during the trial, no serious adverse events were attributed by the investigators to baxdrostat, and there were no instances of adrenocortical insufficiency. Baxdrostat-related increases in the potassium level to 6.0 mmol per liter or greater occurred in 2 patients, but these increases did not recur after withdrawal and reinitiation of the drug.

CONCLUSIONS

Patients with treatment-resistant hypertension who received baxdrostat had dose-related reductions in blood pressure. (Funded by CinCor Pharma; BrigHTN ClinicalTrials.gov number, NCT04519658.).

A 96-week, double-blind, randomized controlled trial comparing bexagliflozin to glimepiride as an adjunct to metformin for the treatment of type 2 diabetes in adults

AIM

To compare the effects of bexagliflozin tablets 20 mg, with those of optimally titrated glimepiride when used to treat adults with type 2 diabetes mellitus (T2DM) inadequately controlled by metformin.

METHODS

Adults with type 2 diabetes (n = 426) taking metformin, and with a glycated haemoglobin (HbA1c) level between 53 and 91 mmol/mol [7.0% and 10.5%], were randomized to receive bexagliflozin tablets 20 mg or titrated glimepiride. The primary endpoint was the intergroup difference in the change from baseline to Week 60 in percent HbA1c. Secondary endpoints included changes from baseline in body mass and systolic blood pressure (SBP), and proportion of subjects experiencing severe or documented symptomatic hypoglycaemia.

RESULTS

The intergroup difference in percent HbA1c (bexagliflozin minus glimepiride) from baseline to Week 60 was -0.55 mmol/mol (95% confidence interval [CI] -2.30, 1.20)-[-0.05% (-0.21, 0.11)], establishing noninferiority of bexagliflozin to glimepiride by the prespecified margin of 3.83 mmol/mol [0.35%]. Prespecified tests gave, in order, a difference in body mass of -4.31 kg (95% CI -5.10, -3.52; P < 0.0001), a difference in SBP of -6.53 mm Hg (95% CI -10.56, -2.51; P = 0.0008), and an odds ratio of 0.12 (95% CI 0.05, 0.28; P < 0.0001) for severe or documented symptomatic hypoglycaemia. At the follow-up visit the mean difference in estimated glomerular filtration rate (eGFR) between arms was 6.05 mL min^-1 per 1.73 m² (95% CI, 3.24, 8.87; P < 0.0001).

CONCLUSIONS

Bexagliflozin was noninferior to glimepiride in lowering HbA1c, was superior to glimepiride for decreases in body mass and SBP, and was associated with significantly fewer hypoglycaemic events than glimepiride. A favourable effect on eGFR was observed.

Efficacy of Tocilizumab in Patients Hospitalized with Covid-19

BACKGROUND

The efficacy of interleukin-6 receptor blockade in hospitalized patients with coronavirus disease 2019 (Covid-19) who are not receiving mechanical ventilation is unclear.

METHODS

We performed a randomized, double-blind, placebo-controlled trial involving patients with confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, hyperinflammatory states, and at least two of the following signs: fever (body temperature >38°C), pulmonary infiltrates, or the need for supplemental oxygen in order to maintain an oxygen saturation greater than 92%. Patients were randomly assigned in a 2:1 ratio to receive standard care plus a single dose of either tocilizumab (8 mg per kilogram of body weight) or placebo. The primary outcome was intubation or death, assessed in a time-to-event analysis. The secondary efficacy outcomes were clinical worsening and discontinuation of supplemental oxygen among patients who had been receiving it at baseline, both assessed in time-to-event analyses.

RESULTS

We enrolled 243 patients; 141 (58%) were men, and 102 (42%) were women. The median age was 59.8 years (range, 21.7 to 85.4), and 45% of the patients were Hispanic or Latino. The hazard ratio for intubation or death in the tocilizumab group as compared with the placebo group was 0.83 (95% confidence interval [CI], 0.38 to 1.81; P = 0.64), and the hazard ratio for disease worsening was 1.11 (95% CI, 0.59 to 2.10; P = 0.73). At 14 days, 18.0% of the patients in the tocilizumab group and 14.9% of the patients in the placebo group had had worsening of disease. The median time to discontinuation of supplemental oxygen was 5.0 days (95% CI, 3.8 to 7.6) in the tocilizumab group and 4.9 days (95% CI, 3.8 to 7.8) in the placebo group (P = 0.69). At 14 days, 24.6% of the patients in the tocilizumab group and 21.2% of the patients in the placebo group were still receiving supplemental oxygen. Patients who received tocilizumab had fewer serious infections than patients who received placebo.

CONCLUSIONS

Tocilizumab was not effective for preventing intubation or death in moderately ill hospitalized patients with Covid-19. Some benefit or harm cannot be ruled out, however, because the confidence intervals for efficacy comparisons were wide. (Funded by Genentech; ClinicalTrials.gov number, NCT04356937.).

A 12-week, randomized, double-blind, placebo-controlled, four-arm dose-finding phase 2 study evaluating bexagliflozin as monotherapy for adults with type 2 diabetes

AIM

To compare the safety and efficacy of bexagliflozin administered as monotherapy at three dosage strengths over a 12-week period to patients with type 2 diabetes who were either naïve to pharmacotherapy or were previously prescribed one oral hypoglycaemic agent and underwent a 6-week period of medication abstinence.

METHODS

Adults with type 2 diabetes (n = 292) having an HbA1c of between 7.0% and 8.5% were randomized to receive one of three dosage strengths of bexagliflozin (5, 10 or 20 mg) or placebo. The primary endpoint was the change from baseline to week 12 in the %HbA1c. Secondary endpoints included the changes from baseline in fasting plasma glucose (FPG), systolic blood pressure and diastolic blood pressure, body mass and fraction of patients achieving an HbA1c of <7%.

RESULTS

The mixed model repeated measure estimates of the placebo-adjusted change in %HbA1c from baseline to week 12 for the 5, 10 and 20 mg groups were -0.55% (95% CI: -0.76%, -0.34%, P < 0.0001), -0.68% (95% CI: -0.89%, -0.47%, P < 0.0001) and -0.80% (95% CI: -1.01%, -0.59%, P < 0.0001), respectively. Significant and dose-dependent placebo-adjusted mean reductions from baseline to week 12 in FPG and body mass were observed. The fraction of subjects achieving an HbA1c of <7% was significantly greater in the 20 mg bexagliflozin group. The incidence of adverse events was similar for participants in all active arms (42.3%) compared with the rate measured in those receiving placebo (40.3%).

CONCLUSIONS

Bexagliflozin confers substantial and dose-dependent benefits on subjects with type 2 diabetes and has an acceptable safety profile. Further evaluation of bexagliflozin for the control of type 2 diabetes in adults is warranted.

A 24-week, randomized, double-blind, active-controlled clinical trial comparing bexagliflozin with sitagliptin as an adjunct to metformin for the treatment of type 2 diabetes in adults

AIM

To compare the relative safety and effectiveness of bexagliflozin and sitagliptin as adjuncts to metformin for the treatment of adults with type 2 diabetes.

METHODS

Participants (n = 386) were randomized to receive bexagliflozin (20 mg) or sitagliptin (100 mg) in addition to their existing doses of metformin. The primary endpoint was the non-inferiority of bexagliflozin to sitagliptin for change in HbA1c from baseline to week 24. Changes from baseline to week 24 in fasting plasma glucose (FPG), body mass (in subjects with baseline body mass index ≥25 kg m^-2 ) and systolic blood pressure (SBP) were secondary endpoints.

RESULTS

The mean change from baseline to week 24 in HbA1c was -0.74 (95% CI -0.86%, -0.62%) in the bexagliflozin arm and -0.82% (95% CI -0.93%, -0.71%) in the sitagliptin arm, establishing non-inferiority. The changes from baseline FPG, body mass and SBP were -1.82 mmol L^-1 , -3.35 kg and -4.23 mmHg in the bexagliflozin arm and -1.45 mmol L^-1 , -0.81 kg and -1.90 mmHg in the sitagliptin arm, respectively. These differences were significant for the first two measures (one-sided P = 0.0123, P < 0.0001 and P = 0.0276, respectively.) Adverse events were experienced by 47.1% of subjects in the bexagliflozin arm and 56.0% of subjects taking sitagliptin. Serious adverse events affected 3.7% of subjects in the bexagliflozin arm and 2.1% of subjects in the sitagliptin arm.

CONCLUSIONS

Bexagliflozin was non-inferior to sitagliptin and provided benefits over sitagliptin in FPG and body mass. Adverse event incidences in the two arms were similar.

Metabolism and disposition of the SGLT2 inhibitor bexagliflozin in rats, monkeys and humans

Bexagliflozin is a C-aryl glucoside inhibitor of human sodium-glucose linked transporter 2 (SGLT2) that undergoes oxidation and glucuronidation to form six principal metabolites in humans.In vitro metabolism by human liver microsomes and recombinant enzymes is primarily mediated by CYP3A4 and UGT1A9. Three major oxidation products and three major glucuronides have been identified in vivo. Metabolism by rats is mostly by oxidation whereas metabolism by monkeys and humans is mostly by glucuronidation. Metabolism by monkeys closely resembles metabolism by humans and all metabolites found in humans are also found in monkeys. A greater diversity of metabolites has been identified among human in vivo specimens than among in vitro reaction products.Following oral dosing of humans with ¹⁴C-bexagliflozin, the 3'-O-glucuronide contributed 32% of the parent AUC and all other metabolites contributed <10%. Of the 91.6% of input radioactivity recovered, 51.1% was in faeces, predominantly as bexagliflozin, and 40.5% was in urine, largely as the 3'-O-glucuronide. Unidentified metabolites contributed 0.27% of the input radiolabel.A quantitative accounting for the metabolism and disposition of bexagliflozin in vivo has been developed.

Safety and dosing of bevacizumab (avastin) for the treatment of recurrent respiratory papillomatosis

OBJECTIVES

Increasing evidence supports the use of laryngeal injections of the antiangiogenic agent bevacizumab (Avastin) for the adjuvant treatment of recurrent respiratory papillomatosis (RRP). A recent prospective open-label investigation, approved by the US Food and Drug Administration, employing 12.5 mg of sublesional bevacizumab demonstrated single-site efficacy without complications; however, the safety of multiple-site injections and higher dosing has not yet been reported. The primary objective of this study was to report on the safety of increased doses of bevacizumab for the treatment of RRP.

METHODS

Two cohorts of adult patients were evaluated. In the first group, a prospective analysis was performed on patients with a diagnosis of laryngeal RRP after t heir participation in th e initial clinical trial with a single-site lowerdose (7.5 to 12.5 mg). They received higher doses of sublesional laryngeal bevacizumab (15 to 50 mg total) with detailed physiologic, hematologic, and serum chemistry measurements performed before and after each bevacizumab injection. A second cohort of patients received sublesional laryngeal injections of bevacizumab (15 to 88 mg total) without physiologic measurements and underwent a retrospective analysis of reported complications.

RESULTS

One hundred consecutive laryngeal injection sessions (office, 87; operating room, 13) with bevacizumab were performed in 43 patients, with a mean dose of 30 mg total per treatment (range, 15 to 88 mg). Sixty-three of the 100 sessions were accompanied by KTP laser photoangiolysis of the papilloma prior to bevacizumab injections. Eighteen patients (cohort 1) underwent detailed physiologic assessment, and no dysfunction was observed. There were no local or systemic complications of bevacizumab administration. The second group of 25 patients (cohort 2) also reported no significant local or systemic complications. Neither patient group was observed to have a local wound problem in the larynx.

CONCLUSIONS

This investigation provides evidence that higher doses of bevacizumab are relatively safe in adult patients with laryngeal RRP. Further refinements in pharmacologic concentration and drug delivery will determine the optimal treatment regimens in the future.

Local injection of bevacizumab (Avastin) and angiolytic KTP laser treatment of recurrent respiratory papillomatosis of the vocal folds: a prospective study

OBJECTIVES

Photoangiolytic laser treatment of recurrent respiratory papillomatosis (RRP) is effective, but does not reliably prevent recurrence. Therefore, sublesional injections of the antiangiogenic agent bevacizumab (Avastin) were given to assess the adjunctive effect on disease recurrence. Since bevacizumab is a new therapeutic modality for RRP, there were also primary safety objectives to determine whether there was a pegative impact on the voice and whether there were local or systemic complications.

METHODS

A prospective open-label investigation was conducted in 20 adult patients with bilateral vocal fold RRP. The patients underwent planned 532-nm pulsed KTP laser photoangiolysis of bilateral glottal disease 4 times with an approximately 6-week interval between procedures. At each planned laser procedure, the vocal fold that on initial presentation had a greater volume of disease also underwent 4 serial sublesional bevacizumab injections (7.5 to 12.5 mg in 0.3 to 0.5 mL). A sham injection with saline solution was administered to the other vocal fold as a control. Disease resolution was compared between subjects' vocal folds, and objective measures of vocal function (acoustic, aerodynamic), as well as patients' self-assessments of vocal function (Voice-Related Quality of Life survey), were obtained.

RESULTS

All 20 patients completed the study, and there were no local or systemic complications. After 4 injections, 3 of the 20 patients had no discernible disease in either vocal fold. Of the remaining 17 subjects, 16 had less disease in the bevacizumab-treated vocal fold despite starting with more disease. Only 1 of the 17 had more disease in the bevacizumab-treated vocal fold after 4 injections. Moreover, 7 of the 20 patients (35%) did not require a laser procedure in the vocal fold that had received 4 bevacizumab injections, as compared with 3 of the 20 vocal folds (15%) that were treated with laser alone. All of the vocal function measures displayed statistically significant posttreatment improvements, except for average fundamental frequency in the 3 female patients, in whom it fell below the normal range.

CONCLUSIONS

This prospective investigation provided evidence that bevacizumab injections enhanced KTP laser treatment of glottal papillomatosis without systemic or local complications. Coupling the antiangiogenesis agent bevacizumab with KTP laser photoangiolysis is conceptually synergistic and scientifically promising since the mechanisms of action are complementary.

Extracellular matrix mineralization and osteoblast gene expression by human adipose tissue-derived stromal cells

Human adipose tissue represents an abundant reservoir of stromal cells with potential utility for tissue engineering. The current study demonstrates the ability of human adipose tissue-derived stromal cells to display some of the hallmarks of osteoblast differentiation in vitro. Following treatment with ascorbate, beta-glycerophosphate, dexamethasone, and 1,25 dihydroxy vitamin D(3), adipose tissue-derived stromal cells mineralize their extracellular matrix based on detection of calcium phosphate deposits using Alizarin Red and von Kossa histochemical stains. Fourier transform infrared analysis demonstrates the apatitic nature of these crystals. Mineralization is accompanied by increased expression or activity of the osteoblast-associated proteins osteocalcin and alkaline phosphatase. These and other osteoblast-associated gene markers are detected based on polymerase chain reaction. In contrast, the adipocyte gene markers--leptin, lipoprotein lipase, and peroxisome proliferator activated receptor gamma2--are reduced under mineralization conditions, consistent with the reciprocal relationship postulated to exist between adipocytes and osteoblasts. The current work supports the presence of a multipotent stromal cell population within human extramedullary adipose tissue. These findings have potential implications for human bone tissue bioengineering.

Extracellular matrix mineralization and osteoblast gene expression by human adipose tissue-derived stromal cells

Human adipose tissue represents an abundant reservoir of stromal cells with potential utility for tissue engineering. The current study demonstrates the ability of human adipose tissue-derived stromal cells to display some of the hallmarks of osteoblast differentiation in vitro. Following treatment with ascorbate, beta-glycerophosphate, dexamethasone, and 1,25 dihydroxy vitamin D(3), adipose tissue-derived stromal cells mineralize their extracellular matrix based on detection of calcium phosphate deposits using Alizarin Red and von Kossa histochemical stains. Fourier transform infrared analysis demonstrates the apatitic nature of these crystals. Mineralization is accompanied by increased expression or activity of the osteoblast-associated proteins osteocalcin and alkaline phosphatase. These and other osteoblast-associated gene markers are detected based on polymerase chain reaction. In contrast, the adipocyte gene markers--leptin, lipoprotein lipase, and peroxisome proliferator activated receptor gamma2--are reduced under mineralization conditions, consistent with the reciprocal relationship postulated to exist between adipocytes and osteoblasts. The current work supports the presence of a multipotent stromal cell population within human extramedullary adipose tissue. These findings have potential implications for human bone tissue bioengineering.

Trans-10, cis-12, but not cis-9, trans-11, conjugated linoleic acid attenuates lipogenesis in primary cultures of stromal vascular cells from human adipose tissue

We have previously shown that both a commercially available mixture of conjugated linoleic acid (CLA) isomers and the trans-10, cis-12 isomer of CLA reduced the triglyceride (TG) content and induced apoptosis in differentiating cultures of murine 3T3-L1 preadipocytes. However, the influence of CLA isomers on differentiating human (pre)adipocytes is unknown. Therefore, we conducted a series of studies using primary cultures of stromal vascular cells isolated from human adipose tissue to determine: 1) the influence of seeding density and thiazolidinedione (TZD) concentration on TG content; 2) the chronic dose response of cis-9, trans-11 CLA vs. trans-10, cis-12 CLA on TG content; 3) whether chronic linoleic acid supplementation could rescue the TG content of CLA-treated cultures; and 4) whether trans-10, cis-12-mediated reduction in cellular TG was due to decreased lipogenesis and/or increased lipolysis. In expt. 1, the TG content [micromol/(L x 10(6) cells)] increased as both seeding density and TZD concentration increased. For example, cultures seeded at 4 x 10(4) cells/cm(2) and supplemented with 10 micromol/L BRL 49653 had 10-fold more TG than similarly seeded cultures without BRL 49653. In expt. 2, TG content decreased as the level of trans-10, cis-12 CLA increased from 1 to 10 micromol/L, whereas the TG content increased with increasing concentrations of either linoleic acid or cis-9, trans-11 CLA. In expt. 3, linoleic acid supplementation restored the TG content of cultures treated with trans-10, cis-12 CLA compared with cultures treated with CLA alone, suggesting that attenuation of TG content by CLA is reversible. In expt. 4, glucose incorporation into total lipid decreased with increasing levels of trans-10, cis-12 CLA, whereas neither CLA isomer acutely affected lipolysis. These data suggest that the reported antiobesity actions of a supplement containing a crude mixture of CLA isomers given to humans may be due to inhibition of lipogenesis by the trans-10, cis-12 isomer.

Thiazolidinediones and glucocorticoids synergistically induce differentiation of human adipose tissue stromal cells: biochemical, cellular, and molecular analysis

While adipocyte differentiation has been studied extensively in murine cultures, the lack of a readily available preadipocyte model has hindered equivalent studies in man. We describe methods for the isolation and culture of primary human stromal cells from surgical adipose tissue specimens. In vitro, the stromal cells rapidly differentiate in response to a combination of adipogenic agents. Among these, glucocorticoids and thiazolidinediones act together to induce the formation of lipid vacuoles within the cells. These morphologic changes accompany the increased expression of 2 characteristic adipocyte proteins, the cytoplasmic enzyme glycerol phosphate dehydrogenase (GPDH) and the secreted cytokine leptin. Likewise, stromal cell differentiation results in elevated mRNA levels for the fatty acid binding protein aP2 and the adipogenic regulatory transcription factors CCAAT/enhancer binding protein alpha (C/EBPalpha) and peroxisome proliferator-activated receptor gamma (PPARgamma) in addition to leptin. The in vitro differentiated stromal cells exhibit a lipolytic response to beta-adrenergic agonists, comparable to that reported with primary human adipocytes. These studies demonstrate the validity of human adipose tissue-derived stromal cells as a reliable in vitro model for investigations of adipocyte metabolism in humans.

Adipogenic potential of human adipose derived stromal cells from multiple donors is heterogeneous

The current study was done to assess if heterogeneity existed in the degree of adipogenesis in stromal cells (preadipocytes) from multiple donors. In addition to conventional lipid-based methods, we have employed a novel signal amplification technology, known as branched DNA, to monitor expression of an adipocyte specific gene product aP2. The fatty acid binding protein aP2 increases during adipocyte differentiation and is induced by thiazolidinediones and other peroxisome proliferator activated receptor gamma ligands. The current work examined the adipogenic induction of aP2 mRNA levels in human adipose tissue stromal cells derived from 12 patients (mean age +/- SEM, 38.9 +/- 3.1) with mild to moderate obesity (mean body mass index +/- SEM, 27.8 +/- 2.4). Based on branched DNA technology, a rapid and sensitive measure of specific RNAs, the relative aP2 level in adipocytes increased by 679 +/- 93-fold (mean +/- SEM, n=12) compared to preadipocytes. Normalization of the aP2 mRNA levels to the housekeeping gene, glyceraldehyde phosphate dehydrogenase, did not significantly alter the fold induction in a subset of 4 patients (803.6 +/- 197.5 vs 1118.5 +/- 308.1). Independent adipocyte differentiation markers were compared between adipocytes and preadipocytes in parallel studies. Leptin secretion increased by up to three-orders of magnitude while measurements of neutral lipid accumulation by Oil Red O and Nile Red staining increased by 8.5-fold and 8.3-fold, respectively. These results indicate that preadipocytes isolated from multiple donors displayed varying degrees of differentiation in response to an optimal adipogenic stimulus in vitro. This work also demonstrates that branched DNA measurement of aP2 is a rapid and sensitive measure of adipogenesis in human stromal cells. The linear range of this assay extends up to three-orders of magnitude and correlates directly with independent measures of cellular differentiation.

Role of intracellular calcium in human adipocyte differentiation

Intracellular calcium ([Ca(2+)](i)) modulates adipocyte lipid metabolism and inhibits the early stages of murine adipogenesis. Consequently, we evaluated effects of increasing [Ca(2+)](i) in early and late stages of human adipocyte differentiation. Increasing [Ca(2+)](i) with either thapsigargin or A23187 at 0-1 h of differentiation markedly suppressed differentiation, with a 40-70% decrease in triglyceride accumulation and glycerol-3 phosphate dehydrogenase (GPDH) activity (P < 0.005). However, a 1-h pulse of either agent at 47-48 h only modestly inhibited differentiation. Sustained, mild stimulation of Ca(2+) influx with either agouti protein or 10 mM KCl-induced depolarization during 0-48 h of differentiation inhibited triglyceride accumulation and GPDH activity by 20-70% (P < 0.05) and markedly suppressed peroxisome proliferator-activated receptor gamma (PPARgamma) expression. These effects were reversed by Ca(2+) channel antagonism. In contrast, Ca(2+) pulses late in differentiation (71-72 h or 48-72 h) markedly increased these markers of differentiation. Thus increasing [Ca(2+)](i) appears to exert a biphasic regulatory role in human adipocyte differentiation, inhibiting the early stages while promoting the late stage of differentiation and lipid filling.

Human adipocyte proteomics--a complementary way of looking at fat

As little as 100 years ago, and for some of the world’s population even today, starvation was and is a predominant component of our nutritional state. Adipose evolved as an efficient energy storage depot to sustain life during such prolonged periods of fasting. However, adipose has been largely overlooked in the study of the process of controlling energy balance. Interest in adipose has increased in parallel with adiposity in modern affluent western society. In the last decade, it has become apparent that adipose is an active player in the management of energy storage, transfer and utilisation, rather than just a passive storage facility. Genomics has facilitated the renaissance of a new understanding of the repertoire of genes expressed in adipose and has supported its regulatory role in energy metabolism. However, significant differences exist between rodent and human adipose biology which have led to some unexpected failures in clinical trials. Recently, leptin showed great promise in rodents as an anti-obesity therapeutic, but has not readily translated to human therapy. We propose that the study of human adipose will greatly facilitate the understanding of human adipose pathologies and metabolic imbalances. Genomics approaches will continue to yield novel genes expressed in adipose; however, it will become increasingly important to study the expression of the proteome to relate these genes to function. We have chosen to focus this review on the secreted proteome of human adipose, as this most directly reflects the endocrine role of this tissue in metabolism.

Differential regulation of peroxisome proliferator activated receptor gamma1 (PPARgamma1) and PPARgamma2 messenger RNA expression in the early stages of adipogenesis

Adipocyte differentiation is driven by the expression and activation of three transcription factor families: the differentially expressed CAAT/enhancer binding proteins (C/EBPs) alpha, beta, and delta; the helix-loop-helix adipocyte differentiation and determination factor-1; and peroxisome proliferator activated receptor gamma (PPARgamma), expressed as two isoforms, PPARgamma1 and the adipocyte-specific PPARgamma2. Overexpression of PPARgamma can induce adipocyte differentiation; therefore, we analyzed the expression of the two PPARgamma isoforms during early stages of differentiation to determine whether one was preferentially induced as an early determining event. Surprisingly, in the first 24 h, a 3-6-fold increase of PPARgamma2 mRNA was observed, whereas PPARgamma1 mRNA remained unchanged. PPARgamma1 was induced 1 day later. Overexpression of C/EBPbeta has also been shown to induce adipocyte differentiation. A C/EBP site was identified only in the human PPARgamma2 promoter. Its deletion blunted the response of PPARgamma2 promoter to cotransfected C/EBPbeta or methylisobutylxanthine treatment. We hypothesize that PPARgamma2 initiates adipocyte differentiation.

Dual DNA binding specificity of ADD1/SREBP1 controlled by a single amino acid in the basic helix-loop-helix domain

Adipocyte determination- and differentiation-dependent factor 1 (ADD1), a member of the basic helix-loop-helix (bHLH) family of transcription factors, has been associated with both adipocyte differentiation and cholesterol homeostasis (in which case it has been termed SREBP1). Using PCR-amplified binding analysis, we demonstrate that ADD1/SREBP1 has dual DNA sequence specificity, binding to both an E-box motif (ATCACGTGA) and a non-E-box sequence previously shown to be important in cholesterol metabolism, sterol regulatory element 1 (SRE-1; ATCACCCCAC). The ADD1/SREBP1 consensus E-box site is similar to a regulatory sequence designated the carbohydrate response element, defined by its ability to regulate transcription in response to carbohydrate in genes involved in fatty acid and triglyceride metabolism in liver and fat. When expressed in fibroblasts, ADD1/SREBP1 activates transcription through both the carbohydrate response E-box element and SRE-1. Substitution of an atypical tyrosine in the basic region of ADD1/SREBP1 to an arginine found in most bHLH protein causes a restriction to only E-box binding. Conversely, substitution of a tyrosine for the equivalent arginine in another bHLH protein, upstream stimulatory factor, allows this factor to acquire a dual binding specificity similar to that of ADD1/SREBP1. Promoter activation by ADD1/SREBP1 through the carbohydrate response element E box is not sensitive to the tyrosine-to-arginine mutation, while activation through SRE-1 is completely suppressed. These data illustrate that ADD1/SREBP1 has dual DNA sequence specificity controlled by a single amino acid residue; this dual specificity may provide a novel mechanism to coordinate different pathways of lipid metabolism.

Vasodilation of rat retinal microvessels induced by monobutyrin. Dysregulation in diabetes

1-Butyryl-glycerol (monobutyrin) is a simple lipid product of adipocytes with angiogenic activity. Recent studies have shown that the biosynthesis of this compound is tightly linked to lipolysis, a process associated with changes in blood flow. We now present data indicating that monobutyrin is an effective vasodilator of rodent blood vessels using a fluorescent retinal angiogram assay. The vasodilatory activity of monobutyrin is potent (ED50 = 3.3 x 10(-7) M), dose dependent, and stereospecific. Because diabetes represents a catabolic, lipolytic state with numerous vascular complications, we examined the action and regulation of monobutyrin in insulin-deficient diabetic rats. Serum levels of monobutyrin in streptozotocin-induced diabetic rats were greatly elevated compared to normal animals. At the same time, the retinal vessels of the diabetic animals develop a resistance to the vasodilatory activity of monobutyrin. These results demonstrate a role for monobutyrin in the control of vascular tone and suggest a possible involvement in the pathology of diabetes.

Identification of base and backbone contacts used for DNA sequence recognition and high-affinity binding by LAC9, a transcription activator containing a C6 zinc finger

The LAC9 protein of Kluyveromyces lactis is a transcriptional regulator of genes in the lactose-galactose regulon. To regulate transcription, LAC9 must bind to 17-bp upstream activator sequences (UASs) located in front of each target gene. LAC9 is homologous to the GAL4 protein of Saccharomyces cerevisiae, and the two proteins must bind DNA in a very similar manner. In this paper we show that high-affinity, sequence-specific binding by LAC9 dimers is mediated primarily by 3 bp at each end of the UAS: [Formula: see text]. In addition, at least one half of the UAS must have a GC or CG base pair at position 1 for high-affinity binding; LAC9 binds preferentially to the half containing the GC base pair. Bases at positions 2, 3, and 4 in each half of the UAS make little if any contribution to binding. The center base pair is not essential for high-affinity LAC9 binding when DNA-binding activity measured in vitro. However, the center base pair must play an essential role in vivo, since all natural UASs have 17, not 16, bp. Hydroxyl radical footprinting shows that a LAC9 dimer binds an unusually broad region on one face of the DNA helix. Because of the data, we suggest that LAC9 contacts positions 6, 7, and 8, both plus and minus, of the UAS, which are separated by more than one turn of the DNA helix, and twists part way around the DNA, thus protecting the broad region of the minor groove between the major-groove contacts.

The transcription factor LAC9 from Kluyveromyces lactis-like GAL4 from Saccharomyces cerevisiae forms a Zn(II)2Cys6 binuclear cluster

The DNA binding domain of the transcription factor LAC9 contains 6 cysteine residues with spacing in the primary peptide sequence identical to that found in the DNA binding domain of the GAL4 transcription factor. In GAL4, the CysX2CysX6CysX6CysX2CysX6Cys motif has been shown to form a Zn(II)2Cys6 binuclear cluster (Pan, T. and Coleman, J. E. (1990) Proc. Natl. Acad. Sci. U. S. A. 87, 2077-2081), representing a new structure for a Zn(II)-containing transcription factor which differs from the "zinc finger" motif first described for TFIIIA. LAC9 has been shown to bind two Zn(II) ions (Halvorsen, Y. C., Nandabalan, K., and Dickson, R. D. (1990) J. Biol. Chem. 265, 13283-13289). The similarity of the amino acid sequence and the Cys spacing within the DNA binding domain suggest that LAC9 should also be capable of forming the Zn(II)2Cys6 cluster found in GAL4. A fragment of LAC9 consisting of 144 amino acid residues spanning the DNA binding domain has been prepared with 113Cd(II) substituted for the two native Zn(II) ions. 113Cd NMR of this fragment (denoted LAC9(85-228*] has been carried out in an attempt to test the hypothesis that LAC9, like GAL4, forms a binuclear cluster. The chemical shifts of the two bound 113Cd(II) ions, 705 and 692 ppm respectively, are consistent with ligation of each 113Cd(II) ion to 4 sulfur atoms. The best model for such ligation is that two of the cysteine S- form bridges between the two Cd(II) ions. Formation of a Zn(II)-Cd(II) hybrid form of LAC9(85-228*) has also been observed. We conclude that LAC9 contains a Zn(II)2Cys6 binuclear cluster as previously reported for GAL4.