Differential contribution of alpha and beta cell dysfunction to impaired fasting glucose and impaired glucose tolerance

AIMS/HYPOTHESIS

People with isolated impaired fasting glucose (IFG) have normal beta cell function. We hypothesised that an increased glucose threshold for beta cell secretion explains IFG.

METHODS

We used graded glucose infusion to examine the relationship of insulin secretion rate (ISR) and glucagon secretion rate (GSR) with rising glucose. We studied 39 non-diabetic individuals (53 ± 2 years, BMI 30 ± 1 kg/m2), categorised by fasting glucose and glucose tolerance status. After an overnight fast, a variable insulin infusion was used to maintain glucose at ~4.44 mmol/l (07:00 to 08:30 hours). At 09:00 hours, graded glucose infusion commenced at 1 mg kg-1 min-1 and doubled every 60 min until 13:00 hours. GSR and ISR were calculated by nonparametric deconvolution from concentrations of glucagon and C-peptide, respectively.

RESULTS

The relationship of ISR with glucose was linear and the threshold for insulin secretion in isolated IFG did not differ from that in people with normal fasting glucose and normal glucose tolerance. GSR exhibited a single-exponential relationship with glucose that could be characterised by G50, the change in glucose necessary to suppress GSR by 50%. G50 was increased in IFG compared with normal fasting glucose regardless of the presence of impaired or normal glucose tolerance.

CONCLUSIONS/INTERPRETATION

These data show that, in non-diabetic humans, alpha cell dysfunction contributes to the pathogenesis of IFG independently of defects in insulin secretion. We also describe a new index that quantifies the suppression of glucagon secretion by glucose.

Presentation and outcomes of adrenal ganglioneuromas: A cohort study and a systematic review of literature

OBJECTIVE

To describe the presentation and outcomes of patients with adrenal ganglioneuromas (AGNs).

DESIGN

Single-centre retrospective cohort study (1 January 1995 to 31 December 2019) and systematic review of literature (1 January 1980 to 19 November 2019).

PATIENTS

Diagnosed with histologically confirmed AGN.

MEASUREMENTS

Baseline clinical, imaging and biochemical characteristics, recurrence rates and mortality. Subgroup analysis was performed on tumours with histologic elements of ganglioneuroma and pheochromocytoma (ie composite tumours).

RESULTS

The cohort study included 45 patients with AGN, 20 (44%) of which had composite tumours. Compared to pure AGN, patients with composite tumour were older (median age, 62.5 vs. 35 years, p < .001), had smaller tumours (median size, 3.9 vs. 5.7 cm, p = .016) and were discovered incidentally less frequently (65% vs. 84%, p = .009). No recurrences or ganglioneuroma-specific mortality occurred during follow-up (range, 0-266 months). The systematic review included 14 additional studies and 421 patients. The mean age of diagnosis was 39 years, and 47% were women. AGNs were discovered incidentally in 72% of patients, were predominantly unilateral (99%) and had a mean diameter of 5.8 cm and an unenhanced computed tomography (CT) attenuation of -118 to 49 Hounsfield units (HU). On imaging, 69% of AGNs were homogenous, 41% demonstrated calcifications, and 40% were lobulated.

CONCLUSIONS

AGNs are rare benign tumours that present with variable imaging features including large size, unenhanced CT attenuation >20 HU, calcifications and lobulated shape. Imaging characteristics can assist in establishing a diagnosis and avoiding an unnecessary adrenalectomy. The association of pheochromocytomas with AGNs is frequent. Diagnosis should include biochemical testing.

Hemodynamic instability during percutaneous ablation of extra-adrenal metastases of pheochromocytoma and paragangliomas: a case series

Background

Surgical manipulation of pheochromocytomas and paragangliomas (PPGLs) may induce large hemodynamic oscillations due to catecholamine release. Little is known regarding hemodynamic instability during percutaneous ablation of PPGLs. We examined intraprocedural hemodynamic variability and postoperative complications related to percutaneous ablation of extra-adrenal metastases of PPGL.

Methods

From institutional PPGL registry we identified patients undergoing ablation of extra-adrenal PPGL metastases from January 1, 2000, through December 31, 2016. We reviewed medical records for clinical characteristics and hospital outcomes. Tumors were categorized as functional or nonfunctional based on preprocedural fractionated catecholamine and metanephrine profiles.

Results

Twenty-one patients (14 female [67%]) underwent 38 ablations. Twenty-four ablations were performed in patients with functional metastatic lesions, and 14 were in nonfunctional lesions. Intraprocedural use of potent vasodilators for hypertension was higher for patients with functional tumors (P = 0.02); use of vasopressors for hypotension was similar for functional and nonfunctional tumors (P = 0.74). Mean (±SD) intraprocedural blood pressure range (maximum–minimum blood pressure) during 38 procedures was greater for functional than nonfunctional tumors [systolic: 106 (±48) vs 64 (±30) mm Hg, P = 0.005; diastolic: 58 (±22) vs 35 (±14) mm Hg, P = 0.002; mean arterial: 84 (±43) vs 47 (±29) mm Hg, P = 0.007]. Complications included 5 unplanned intensive care unit admissions (3 for precautionary monitoring, 1 for recalcitrant hypotension, and 1 for hypertensive crisis), 1 case of postoperative bleeding, and 1 death.

Conclusions

Substantial hemodynamic instability may develop during ablation of functional and nonfunctional PPGL metastases. When anesthesia is provided for ablation of metastatic PPGLs in radiology suites, preparation for hemodynamic management should match standards used for surgical resection.

Clinical, Biochemical, and Radiological Characteristics of a Single-Center Retrospective Cohort of 705 Large Adrenal Tumors

OBJECTIVE

To characterize large adrenal tumors (≥4 cm in diameter) and to identify features associated with malignancy.

PATIENTS AND METHODS

We investigated the clinical, biochemical, and imaging characteristics in a large retrospective single-center cohort of patients with adrenal tumors of 4 cm or more in diameter during the period of January 1, 2000, through December 31, 2014.

RESULTS

Of 4085 patients with adrenal tumors, 705 (17%) had adrenal masses measuring 4 cm or more in diameter; of these, 373 (53%) were women, with a median age of 59 years (range, 18-91 years) and median tumor size of 5.2 cm (range, 4.0-24.4 cm). Underlying diagnoses were adrenocortical adenomas (n=216 [31%]), pheochromocytomas (n=158 [22%]), other benign adrenal tumors (n=116 [16%]), adrenocortical carcinomas (n=88 [13%]), and other malignant tumors (n=127 [18%]). Compared with benign tumors, malignant tumors were less frequently diagnosed incidentally (45.5% vs 86.7%), were larger (7 cm [range, 4-24.4 cm] vs 5 cm [range, 4-20 cm]), and had higher unenhanced computed tomographic (CT) attenuation (34.5 Hounsfield units [HU] [range, 14.1-75.5 HU] vs 11.5 HU [range, -110 to 71.3 HU]; P<.001). On multivariate analysis, older age at diagnosis, male sex, nonincidental mode of discovery, larger tumor size, and higher unenhanced CT attenuation were all found to be statistically significant predictors of malignancy.

CONCLUSION

The prevalence of malignancy in patients with adrenal tumors of 4 cm or more in diameter was 31%. Older age, male sex, nonincidental mode of discovery, larger tumor size, and higher unenhanced CT attenuation were associated with an increased risk for malignancy. Clinical context should guide management in patients with adrenal tumors of 4 cm or more in diameter.

Abstract A09: Diet-induced obesity promotes breast cancer progression by LPA-signaling-mediated functional changes of mitochondria and angiogenesis

Despite insight that obesity greatly increases cancer risk including breast cancer (BC) is supported by epidemiological studies, the direct link and mechanisms by which obesity increases BC risk remain largely unknown. Nutritional obesity is associated with a prediabetic state characterized by alteration in glucose homeostasis. The increased glucose level may aid cancer cells in generating metabolic advantage. Obesity is also accompanied by an autotaxin (ATX) mediated synthesis of bioactive signaling phospholipid or lysophosphatidic acid (LPA). ATX and plasma LPA are up-regulated in diet-induced obese (DIO) mice. We have shown that LPA stimulated angiogenesis via turning off CD36 antiangiogenic switch in endothelial cells (ECs) via protein kinase PKD-1 pathway. We hypothesize that obesity-derived LPA is a key bona fide tumor promoter by modifying mitochondrial bioenergetic metabolism and stimulating BC angiogenesis in response to high glucose. Using Seahorse Bioscience Extracellular Flux Analyzer, we discovered that LPA enhanced mitochondrial respiration of human breast adenocarcinoma cell MDA-MB231 transduced with wild type PKD-1 (PKD-WT) under high glucose conditions. LPA exposure significantly changed oxygen consumption rate (OCR), ATP linked OCAR but not extracellular acidification rate (ECAR) in cells exposed to high glucose. However, the change of OCR was attenuated by a selective PKD inhibitor CID755673. Furthermore, when exposed to conditional medium from human microvascular endothelial cells (HMVECs), MDA-MB231 overexpressing PKD-WT showed lower levels of basal OCR, ATP linked OCAR and ECAR compared with control medium. Obesity-derived LPA also inhibited CD36 expression in tumor-associated ECs and promoted BC cell growth, which was partially abolished by ATX inhibitor. Intriguingly, CID755673 inhibited clonogenic survival of MDA-MB231. To determine in vivo mechanisms of obesity-derived LPA, we established a syngeneic BC model by subcutaneously implanting E0771 adenocarcinoma in female C57BL/6J mice. DIO greatly promoted BC development in mice, demonstrated by huge tumors in DIO but not in control mice. DIO mice also showed increase in LPA receptor 1 in tumor endothelium, with robust angiogenesis and extensive bleeding inside tumor. Additionally, a high level of PD-1 expression was found in CD8 T cells inside the tumor in obese mice, implicating diet-induced obesity leads to T cell dysfunction. Our data suggests that LPA is a key player in BC angiogenesis and development but it is not the only mediator responsible for obesity-induced tumor progression. LPA-stimulated tumor progression may be associated with alternation of bioenergetic function via PKD signaling under high glucose conditions. DIO-enhanced LPA signaling may contribute to EC CD36 downregulation and dysregulated mitochondrial functions, leading to proangiogenic responses in tumor microenvironment. DIO-stimulated LPA signaling could modulate switch between mitochondrial oxidative phosphorylation and aerobic glycolysis in both BC and tumor endothelium. Targeting LPA-PKD-metabolic signaling axis may provide a novel therapeutic strategy.

Citation Format: Ye Yuan, Jacob D. Kohlenberg, Yiliang Chen, Steve Komas, Gang Xin, Gloria Yuan, Weiguo Cui, Shiyong Wu, Bin Ren. Diet-induced obesity promotes breast cancer progression by LPA-signaling-mediated functional changes of mitochondria and angiogenesis. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr A09. doi:10.1158/1538-7445.CHTME14-A09

Abstract 229: Protein Kinase D-1 Regulates CD36 Transcription and Arteriogenic Differentiation of Endothelial Cells

CD36 is a microvascular endothelial cell (MVEC) receptor mediating angiostatic activity of TSP-1 and related proteins. We previously reported that lysophosphatidic acid (LPA), a biologically active lipid signaling mediator, inhibited MVEC CD36 transcription via PKD-1 signaling. Moreover, CD36 transcriptional repression abolished endothelial cell responses to TSP-1 in vitro and in vivo . We now show with luciferase transfection assays that LPA exposure significantly suppressed CD36 promoter activity in MVEC. Co-exposure to class II HDAC inhibitors SAHA or TSA reversed the inhibition of promoter activity and restored transcription. HDAC7 knockdown by shRNA also attenuated LPA-suppressed CD36 promoter activity and mRNA levels. Mechanistically, FoxO1 was found to directly interact with putative FoxO1 binding sites (FHRE) in proximal promoter in vitro by avidin-biotin-conjugated DNA-binding assay, and in vivo by chromatin IP assay. Furthermore, FHRE mutations significantly attenuated the promoter activity. Western blots and immunofluorescence microscopy showed increased nuclear accumulation of PKD-1, FoxO1 and HADC7 after MVEC were exposed to LPA. Co-IP of nuclear extracts showed a physical interaction of HDAC7 with FoxO1 that was attenuated with PKD-1 knockdown. These data demonstrate that HDAC7 modulation by LPA receptor/PKD-1 signaling pathway represses FoxO1-mediated CD36 transcriptional activity. Additionally, angiogenic transcription profiling of endothelial cells revealed significantly increased mRNA expression of 17 angiogenic genes in response to LPA, including ephrin B2 expression that was confirmed by Western Blots. Transduction of constitutively active PKD-1 (PKD-CA) into EC also increased ephrin B2 expression. Functionally, PKD-CA overexpression promoted branching morphogenesis of arterial endothelial cells in a three-dimensional spheroid assay. The data indicate that PKD-1 is a potent angiogenic and arteriogenic kinase in EC by down-regulating CD36 transcription and promoting arteriogenesis. PKD-1-FoxO1-CD36 signaling axis may have potential as an important target in cardiovascular ischemia and malignant tumors.