Quantifying mitochondrial redox and bilirubin content in intact primary hepatocytes of obese mice using fluorescent reporters

Assessing the physiological role of H2O2 requires sensitive techniques to quantify H2O2 and antioxidants in live cells. Here, we present a protocol to assess the mitochondrial redox state and unconjugated bilirubin levels in intact live primary hepatocytes from obese mice. We described steps to quantify H2O2, GSSG/GSH, and bilirubin content in the mitochondrial matrix and the cytosol using the fluorescent reporters roGFP2-ORP1, GRX1-roGFP2, and UnaG, respectively. We detail hepatocyte isolation, plating, and transduction and live-cell imaging using a high-content imaging reader. For complete details on the use and execution of this protocol, please refer to Shum et al.1.

Restoration of lysosomal acidification rescues autophagy and metabolic dysfunction in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease in the world. High levels of free fatty acids in the liver impair hepatic lysosomal acidification and reduce autophagic flux. We investigate whether restoration of lysosomal function in NAFLD recovers autophagic flux, mitochondrial function, and insulin sensitivity. Here, we report the synthesis of novel biodegradable acid-activated acidifying nanoparticles (acNPs) as a lysosome targeting treatment to restore lysosomal acidity and autophagy. The acNPs, composed of fluorinated polyesters, remain inactive at plasma pH, and only become activated in lysosomes after endocytosis. Specifically, they degrade at pH of ~6 characteristic of dysfunctional lysosomes, to further acidify and enhance the function of lysosomes. In established in vivo high fat diet mouse models of NAFLD, re-acidification of lysosomes via acNP treatment restores autophagy and mitochondria function to lean, healthy levels. This restoration, concurrent with reversal of fasting hyperglycemia and hepatic steatosis, indicates the potential use of acNPs as a first-in-kind therapeutic for NAFLD.

NCLX prevents cell death during adrenergic activation of the brown adipose tissue

A sharp increase in mitochondrial Ca2+ marks the activation of brown adipose tissue (BAT) thermogenesis, yet the mechanisms preventing Ca2+ deleterious effects are poorly understood. Here, we show that adrenergic stimulation of BAT activates a PKA-dependent mitochondrial Ca2+ extrusion via the mitochondrial Na+/Ca2+ exchanger, NCLX. Adrenergic stimulation of NCLX-null brown adipocytes (BA) induces a profound mitochondrial Ca2+ overload and impaired uncoupled respiration. Core body temperature, PET imaging of glucose uptake and VO2 measurements confirm a thermogenic defect in NCLX-null mice. We show that Ca2+ overload induced by adrenergic stimulation of NCLX-null BAT, triggers the mitochondrial permeability transition pore (mPTP) opening, leading to a remarkable mitochondrial swelling and cell death. Treatment with mPTP inhibitors rescue mitochondrial function and thermogenesis in NCLX-null BAT, while calcium overload persists. Our findings identify a key pathway through which BA evade apoptosis during adrenergic stimulation of uncoupling. NCLX deletion transforms the adrenergic pathway responsible for thermogenesis activation into a death pathway.

Sex-specific metabolic functions of adipose Lipocalin-2

OBJECTIVE

Lipocalin-2 (LCN2) is a secreted protein involved in innate immunity and has also been associated with several cardiometabolic traits in both mouse and human studies. However, the causal relationship of LCN2 to these traits is unclear, and most studies have examined only males.

METHODS

Using adeno-associated viral vectors we expressed LCN2 in either adipose or liver in a tissue specific manner on the background of a whole-body Lcn2 knockout or wildtype mice. Metabolic phenotypes including body weight, body composition, plasma and liver lipids, glucose homeostasis, insulin resistance, mitochondrial phenotyping, and metabolic cage studies were monitored.

RESULTS

We studied the genetics of LCN2 expression and associated clinical traits in both males and females in a panel of 100 inbred strains of mice (HMDP). The natural variation in Lcn2 expression across the HMDP exhibits high heritability, and genetic mapping suggests that it is regulated in part by Lipin1 gene variation. The correlation analyses revealed striking tissue dependent sex differences in obesity, insulin resistance, hepatic steatosis, and dyslipidemia. To understand the causal relationships, we examined the effects of expression of LCN2 selectively in liver or adipose. On a Lcn2-null background, LCN2 expression in white adipose promoted metabolic disturbances in females but not males. It acted in an autocrine/paracrine manner, resulting in mitochondrial dysfunction and an upregulation of inflammatory and fibrotic genes. On the other hand, on a null background, expression of LCN2 in liver had no discernible impact on the traits examined despite increasing the levels of circulating LCN2 more than adipose LCN2 expression. The mechanisms underlying the sex-specific action of LCN2 are unclear, but our results indicate that adipose LCN2 negatively regulates its receptor, LRP2 (or megalin), and its repressor, ERα, in a female-specific manner and that the effects of LCN2 on metabolic traits are mediated in part by LRP2.

CONCLUSIONS

Following up on our population-based studies, we demonstrate that LCN2 acts in a highly sex- and tissue-specific manner in mice. Our results have important implications for human studies, emphasizing the importance of sex and the tissue source of LCN2.

Mitochondria Bound to Lipid Droplets Have Unique Bioenergetics, Composition, and Dynamics that Support Lipid Droplet Expansion

Mitochondria associate with lipid droplets (LDs) in fat-oxidizing tissues, but the functional role of these peridroplet mitochondria (PDM) is unknown. Microscopic observation of interscapular brown adipose tissue reveals that PDM have unique protein composition and cristae structure and remain adherent to the LD in the tissue homogenate. We developed an approach to isolate PDM based on their adherence to LDs. Comparison of purified PDM to cytoplasmic mitochondria reveals that (1) PDM have increased pyruvate oxidation, electron transport, and ATP synthesis capacities; (2) PDM have reduced β-oxidation capacity and depart from LDs upon activation of brown adipose tissue thermogenesis and β-oxidation; (3) PDM support LD expansion as Perilipin5-induced recruitment of mitochondria to LDs increases ATP synthase-dependent triacylglyceride synthesis; and (4) PDM maintain a distinct protein composition due to uniquely low fusion-fission dynamics. We conclude that PDM represent a segregated mitochondrial population with unique structure and function that supports triacylglyceride synthesis.

Hepatocyte-specific Ptpn6 deletion promotes hepatic lipid accretion, but reduces NAFLD in diet-induced obesity: potential role of PPARγ

Hepatocyte-specific Shp1 knockout mice (Ptpn6(H-KO)) are protected from hepatic insulin resistance evoked by high-fat diet (HFD) feeding for 8 weeks. Unexpectedly, we report herein that Ptpn6(H-KO) mice fed an HFD for up to 16 weeks are still protected from insulin resistance, but are more prone to hepatic steatosis, as compared with their HFD-fed Ptpn6(f/f) counterparts. The livers from HFD-fed Ptpn6(H-KO) mice displayed 1) augmented lipogenesis, marked by increased expression of several hepatic genes involved in fatty acid biosynthesis, 2) elevated postprandial fatty acid uptake, and 3) significantly reduced lipid export with enhanced degradation of apolipoprotein B (ApoB). Despite more extensive hepatic steatosis, the inflammatory profile of the HFD-fed Ptpn6(H-KO) liver was similar (8 weeks) or even improved (16 weeks) as compared to their HFD-fed Ptpn6(f/f) littermates, along with reduced hepatocellular damage as revealed by serum levels of hepatic enzymes. Interestingly, comparative microarray analysis revealed a significant up-regulation of peroxisome proliferator-activated receptor gamma (PPARγ) gene expression, confirmed by quantitative polymerase chain reaction. Elevated PPARγ nuclear activity also was observed and found to be directly regulated by Shp1 in a cell-autonomous manner.

CONCLUSION

These findings highlight a novel role for hepatocyte Shp1 in the regulation of PPARγ and hepatic lipid metabolism. Shp1 deficiency prevents the development of severe hepatic inflammation and hepatocellular damage in steatotic livers, presenting hepatocyte Shp1 as a potential novel mediator of nonalcoholic fatty liver diseases in obesity.

Angiotensin II type 2 receptor promotes adipocyte differentiation and restores adipocyte size in high-fat/high-fructose diet-induced insulin resistance in rats

This study was aimed at establishing whether specific activation of angiotensin II (ANG II) type 2 receptor (AT2R) modulates adipocyte differentiation and function. In primary cultures of subcutaneous (SC) and retroperitoneal (RET) preadipocytes, both AT2R and AT1R were expressed at the mRNA and protein level. Cells were stimulated with ANG II or the AT2R agonist C21/M24, alone or in the presence of the AT1R antagonist losartan or the AT2R antagonist PD123,319. During differentiation, C21/M24 increased PPARγ expression in both RET and SC preadipocytes while the number of small lipid droplets and lipid accumulation solely increased in SC preadipocytes. In mature adipocytes, C21/M24 decreased the mean size of large lipid droplets. Upon abolishment of AT2R expression using AT2R-targeted shRNAs, expressions of AT2R, aP2, and PPARγ remained very low, and cells were unable to differentiate. In Wistar rats fed a 6-wk high-fat/high-fructose (HFHF) diet, a significant shift toward larger adipocytes was observed in RET and SC adipose tissue depots. C21/M24 treatments for 6 wk restored normal adipocyte size distribution in both these tissue depots. Moreover, C21/M24 and losartan decreased hyperinsulinemia and improved insulin sensitivity impaired by HFHF diet. A strong correlation between adipocyte size area and glucose infusion rate during euglycemic-hyperinsulinemic clamp was observed. These results indicate that AT2R is involved in early adipocyte differentiation, while in mature adipocytes and in a model of insulin resistance AT2R activation restores normal adipocyte morphology and improves insulin sensitivity.

The incidence of prostate cancer in patients under the age of 60 from an urban setting

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Background: Although the risk for developing prostate cancer increases with age, few studies have reported the incidence of prostate cancer in men younger than 60 from an urban setting. Methods: All patients diagnosed and treated for prostate cancer at The Cancer Institute of New Jersey at Cooper University Hospital in Camden County, New Jersey from January 1, 2004 to December 31, 2004 were retrospectively identified from our tumor registry. Age comparison at diagnosis was made utilizing the Cooper registry and the National Cancer Database (NCDB), 2001. Results: A total of 141 men (88 Caucasians, 37 African Americans, 14 Hispanic, and 6 unknown) with a median age of 64 years (range, 44–88 years) were diagnosed with prostate cancer in 2004. Staging revealed Stage II (118), Stage III (3), Stage IV (4), Stage unknown (16) cases. Median Gleason score was 6. 74 patients underwent radical prostatectomy, 50 had radiation, 30 received hormone therapy and 2 received chemotherapy. At diagnosis, 19.95% of the men were under 50 and 41.84% were under 60 years of age. Our dataset from these two age groups compared to NJ and US figures are noted below. Conclusions: When comparing the respective data sets from CINJ at Cooper to NJ and US utilizing the NCDB, there are striking differences with a higher incidence of prostate cancer in younger men. These incidences parallel those seen in other urban university teaching hospitals from the Healthcare Utilization Project (2005), where more patients under the age of 60 are being diagnosed with prostate cancer when compared to community centers. Subset analysis shows that our institution had a disproportionately larger number of African American men with prostate cancer which may relate to our culturally directed screening program, accounting for the higher incidence. These data support that hospital characteristics may impact age at diagnosis of prostate cancer, and further investigation is warranted. [Table: see text]

No significant financial relationships to disclose.

Improved survival in patients with locally advanced esophageal cancer utilizing a multidisciplinary approach

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Background: Locally advanced esophageal cancer studies have reported a three year overall survival rate of 32% with a median survival of 16 months. These patients were treated with combined chemotherapy and radiation with surgery, when applicable. We conducted this study to determine whether using an individualized, multidisciplinary approach affected survival outcomes in patients treated for locally advanced esophageal cancer. Methods: All patients treated for locally advanced esophageal cancer were retrospectively identified from our database at The Cancer Institute of New Jersey at Cooper University Hospital. All patients were presented and discussed in a multidisciplinary gastrointestinal tumor board conference. After a consensus was obtained, a treatment plan was established for each patient based on his or her respective clinical characteristics: stage, performance status, medical suitability for surgery and resectabilty. Results: A total of 23 patients (median age: 66 years [range, 55–88 years]) were identified, the histopathologic diagnosis was adenocarcinoma in 13 and squamous cell carcinoma in 10 cases. TNM staging was as follows: 18 (78.3%) stage II or III and 5 (21.7%) stage IV. Initial management included esophagectomy for 9 (39.1%), 6 of which received preoperative chemotherapy (5-FU) and three received postoperative adjuvant chemotherapy, 14 (60.9%) received only combined chemotherapy (average four cycles of 5FU 1000 mg per square meter of body surface + Cisplatin 75 mg per square meter of body surface) and radiation at doses 50–64 Gy. Overall median survival was not reached since only five patients (21.7%) have died. The 1- year and 2-year survival rates were 87% and 74% respectively. Median follow-up for patients who received combination chemotherapy and radiation vs. surgery with preoperative therapy was 29 and 41 months, respectively. Conclusion: This retrospective analysis shows promising outcomes compared to published data supporting the role of an individualized, multidisciplinary approach in the management of each patient with esophageal cancer.

No significant financial relationships to disclose.

Beryllium Sensitization, Chronic Beryllium Disease, and Exposures at a Beryllium Mining and Extraction Facility

In this study, we examine beryllium sensitization, chronic beryllium disease (CBD), and workplace exposures at a beryllium mining (mine) and extraction facility (mill) in Delta, Utah. Historical airborne beryllium data collected between 1970-1999 included general area (GA), breathing zone (BZ), and personal lapel (LP) measurements and calculations of job-specific quarterly daily-weighted averages (DWVAs). We compared GA, BZ, and DWA data to airborne beryllium data from a mixed beryllium products facility and a beryllium ceramics facility located in Elmore, Ohio and Tucson, Arizona, respectively. At the Delta facility, jobs involving beryllium hydrolysis and wet-grinding activities had the highest air concentrations; annual median GA concentrations were less than 0.3 microg/m3 or both areas. Annual median GA sample concentrations ranged from 0.1-0.4 microg/m(-3) at Delta. These levels were generally lower than Elmore (0.1-1.0 microg/m3) and were comparable to the Tucson facility (0.1-0.4 microg/m3). Median BZ concentrations were higher, whereas DWAs were lower at the Delta facility than at the other two facilities. Among the 87 employees at the Delta facility, 75 participated in the medical survey; there were three persons sensitized, one with CBD. The individual with CBD previously worked at the Elmore facility for 10 years. Cumulative CBD incidence rates were significantly lower at the Delta facility: 0.3 percent compared to 2.0 percent for Elmore and 2.5 percent for the Tucson facility. Sensitization and CBD prevalence rates determined from cross-sectional surveys for the Delta facility were lower than but not significantly different from rates at the other two facilities. There was no sensitization or CBD among those who worked only at the mine where the only exposure to beryllium results from working with bertrandite ore. Although these results are derived from a small sample, this study suggests that the form of beryllium may affect the likelihood of developing CBD. Specifically, exposure to beryl and bertrandite ore dusts or to beryllium salts, in the absence of exposure to beryllium oxide particulates appears to pose a lower risk for developing CBD.

Airborne concentrations of ethyl and methyl cyanoacrylate in the workplace

A survey was conducted of persons who manufacture, mix, bottle, and package methyl 2-cyanoacrylate (MCA) and ethyl 2-cyanoacrylate (ECA). Airborne concentrations of these cyanoacrylates also were measured during waste-handling operations. During a 1-week period, 162 personal and area samples were collected. About 90% of the samples were analyzed for ECA (the predominant adhesive being manufactured at the facility). About 50% of the samples were collected during periods of 15 min or less, the remainder for 15 to 240 min. Some 8-hour time-weighted average (TWA) samples also were collected. Samples were collected using Tenax tubes with subsequent analysis by high-performance liquid chromatography. Most samples were collected where highest exposure was likely (e.g., during mixing, bottling, and packaging). Peak concentrations of exposure (duration of 15 min or less), measured during a variety of tasks, ranged from 0.003 to 1.5 ppm. In particular, personal mean short-term airborne concentrations of ECA for the mixing operators ranged from 0.039 ppm to 0.650 ppm, while various 10-min to 1-hour activities were performed, with a TWA concentration of 0.07 ppm. Personal short-term airborne concentrations of ECA for bottling and packaging workers (n = 60) were 0.040 ppm +/- 0.016 ppm (mean +/- standard deviation), with similar 8-hour TWA concentrations due to the continuous nature of bottling and packaging. Other personal samples were not significantly different. The area samples were normally within a factor of 2 of the peak personal sampling results. These data indicate that, when handled at room temperature and relative humidity ranging from 40-69%, both MCA and ECA produce airborne concentrations that are nearly always less than about 0.1 ppm, which is less than the threshold of irritation.