Horace J. Spencer

Endoplasmic Reticulum Stress Markers Are Associated with Obesity in Nondiabetic Subjects

OBJECTIVE Adipocyte and hepatocyte endoplasmic reticulum (ER) stress response is activated in dietary and genetic models of obesity in mice. We hypothesized that ER stress was also activated and associated with reduced insulin sensitivity (SI) in human obesity. RESEARCH DESIGN AND METHODS We recruited 78 healthy, nondiabetic individuals over a spectrum of body mass index (BMI) who underwent oral and iv glucose tolerance tests, and fasting sc adipose and muscle biopsies. We tested expression of 18 genes and levels of total and phosphorylated eukaryotic initiation factor 2alpha, c-jun, and c-Jun N-terminal kinase 1 in adipose tissue. We compared gene expression in stromal vascular and adipocyte fractions in paired samples from 22 individuals, and tested clustering on gene and protein markers. RESULTS Adipocyte expression of most markers of ER stress, including chaperones downstream of activating transcription factor 6, were significantly correlated with BMI and percent fat (r>0.5; P<0.00001). Phosphorylation of eukaryotic initiation factor 2alpha but not of c-Jun N-terminal kinase 1 or c-jun was increased with obesity. ER stress response (as elsewhere) was also increased with obesity in a second set of 86 individuals, and in the combined sample (n=161). The increase was only partially attributable to the stromal vascular fraction and macrophage infiltration. ER stress markers were only modestly correlated with S(I). Clustering algorithms supported ER stress activation with high BMI but not low SI. CONCLUSIONS Multiple markers of ER stress are activated in human adipose with obesity, particularly for protective chaperones downstream of activating transcription factor 6alpha.

Thrombospondin-1 Is an Adipokine Associated With Obesity, Adipose Inflammation, and Insulin Resistance

OBJECTIVE—We examined the relationship between the expression of thrombospondin (TSP)1, an antiangiogenic factor and regulator of transforming growth factor-β activity, obesity, adipose inflammation, and insulin resistance. RESEARCH DESIGN AND METHODS—TSP1 gene expression was quantified in subcutaneous adipose tissue (SAT) of 86 nondiabetic subjects covering a wide range of BMI and insulin sensitivity, from visceral adipose (VAT) and SAT from 14 surgical patients and from 38 subjects with impaired glucose tolerance randomized to receive either pioglitazone or metformin for 10 weeks. An adipocyte culture system was also used to assess the effects of pioglitazone and coculture with macrophages on TSP1 gene expression. RESULTS—TSP1 mRNA was significantly associated with obesity (BMI) and insulin resistance (low insulin sensitivity index). Relatively strong positive associations were seen with markers of inflammation, including CD68, macrophage chemoattractant protein-1, and plasminogen activator inhibitor (PAI)-1 mRNA (r ≥ 0.46, P = 0.001 for each), that remained significant after controlling for BMI and Si. However, TSP1 mRNA was preferentially expressed in adipocyte fraction, whereas inflammatory markers predominated in stromal vascular fraction. Coculture of adipocytes and macrophages augmented TSP1 gene expression and secretion from both cell types. Pioglitazone (not metformin) treatment resulted in a 54% decrease (P < 0.04) in adipose TSP gene expression, as did in vitro pioglitazone treatment of adipocytes. CONCLUSIONS—TSP1 is a true adipokine that is highly expressed in obese, insulin-resistant subjects; is highly correlated with adipose inflammation; and is decreased by pioglitazone. TSP1 is an important link between adipocytes and macrophage-driven adipose tissue inflammation and may mediate the elevation of PAI-1 that promotes a prothrombotic state.

Methylation Profiling of Archived Non–Small Cell Lung Cancer: A Promising Prognostic System

Purpose: Enhanced prognostication power is becoming more desirable in clinical oncology. In this study, we explored the prognostic potential of multigene hypermethylation profiling in non–small-cell lung cancer. Experimental Design: We evaluated a panel of eight genes (p16, APC, ATM, hMLH1, MGMT, DAPK, ECAD, and RASSF1A) using methylation-specific PCR in 105 archived specimens of non–small-cell lung cancer representing all stages of the illness. We analyzed the effect of gene methylation status on outcome individually in a cumulative manner and in a combinatorial approach using recursive partitioning to identify methylation profiles, which affect overall survival. Results: In this data set, tumors harboring promoter hypermethylation at two or more genes exhibit similar survival trends to others in the cohort. Using recursive partitioning, three genes (APC, ATM, and RASSF1A) emerged as determinants of prognostic groups. This designation retained its statistical significance even when disease stage and age were entered into a multivariate analysis. Using this approach, patients whose tumors were hypermethylated at APC and those hypermethylated at only ATM (not also at APC or RASSF1A) enjoyed substantially longer 1- and 2-year survival than patients in the remaining groups. In 32 adjacent histologically normal lung tissue specimens, we detected similar methylation abnormalities. Conclusion: Assessment of promoter hypermethylation aberrations may facilitate prognostic profiling of lung tumors, but validation in independent data sets is needed to verify these profiles. This system uses material that is abundantly available with linked outcome data and can be used to generate reliable epigenetic determinants.

Lipin expression is attenuated in adipose tissue of insulin-resistant human subjects and increases with peroxisome proliferator-activated receptor γ activation

Lipin-α and -β are the alternatively spliced gene products of the Lpin1 gene, whose product lipin is required for adipocyte differentiation. Lipin deficiency causes lipodystrophy, fatty liver, and insulin resistance in mice, whereas adipose tissue lipin overexpression results in increased adiposity but improved insulin sensitivity. To assess lipin expression and its relation to insulin resistance in humans, we examined lipin-α and -β mRNA levels in subjects with normal or impaired glucose tolerance. We found higher expression levels of both lipin isoforms in lean, insulin-sensitive subjects. When compared with normal glucose-tolerant subjects, individuals with impaired glucose tolerance were more insulin resistant, demonstrated higher levels of intramyocellular lipids (IMCLs), and expressed ∼50% lower levels of lipin-α and -β. In addition, there was a strong inverse correlation between adipose tissue lipin expression and muscle IMCLs but no evidence for an increase in muscle lipid oxidation. After treatment of the impaired glucose-tolerant subjects with insulin sensitizers for 10 weeks, pioglitazone (but not metformin) resulted in a 60% increase in the insulin sensitivity index (Si) and a 32% decrease in IMCLs (both P < 0.01), along with an increase in lipin-β (but not lipin-α) expression by 200% (P < 0.005). Lipin expression in skeletal muscle, however, was not related to obesity or insulin resistance. Hence, high adipose tissue lipin expression is found in insulin-sensitive subjects, and lipin-β expression increases following treatment with pioglitazone. These results suggest that increased adipogenesis and/or lipogenesis in subcutaneous fat, mediated by the LPIN1 gene, may prevent lipotoxicity in muscle, leading to improved insulin sensitivity.

Long-term results of the treatment of aortic graft infection by in situ replacement with femoral popliteal vein grafts

OBJECTIVE Graft excision and neo-aortoiliac system (NAIS) reconstruction with large caliber, femoral popliteal vein (FPV) grafts have been reported as successful treatment of aortic graft infection (AGI) in several small series with limited follow-up. The goal of this study was to evaluate long-term outcomes in large cohort of consecutive patients treated with NAIS for AGI. METHODS From 1990 to 2006, 187 patients (age: 63 +/- 10 years) with AGI were treated with in situ reconstructions using 336 FPV grafts. Data from a prospectively maintained data base were analyzed. RESULTS NAIS reconstruction was performed for 144 infected aortofemoral bypasses, 21 infected aortic-iliac grafts, and 22 infected axillofemoral bypasses that had been placed to treat AGI. Polymicrobial cultures were present in 37% while 17% showed no growth. There were 55% gram positive, 32% gram negative, 13% anaerobic, and 18% fungal infections. The mean Society for Vascular Surgery run-off resistance score was 4.5 +/- 2.3. Concomitant infrainguinal bypass was necessary in 27 (14%) patients (32 limbs). Major amputations were performed in 14 (7.4%) patients. Out of 14 amputations, five patients had irreversible ischemia and in four, there was no conduit available. Graft disruption from reinfection occurred in 10 patients (5%). While 30-day mortality was 10%, procedure-related mortality was 14%. Independent risk factors for perioperative death on multivariate analysis were: preoperative sepsis (odds ratio [OR] 3.5) ASA class 4 (OR 2.9), Candida species (OR 3.4), Candida glabrata (OR 7.6), Klebsiella pneumoniae (OR 3.5), and Bacteroides fragilis (OR 4.1). Perioperative factors included use of platelets (OR 2.4), blood loss >3.0 liters (OR 9.5). Cumulative primary patency at 72 months was 81%; secondary/assisted primary patency was 91%. Limb salvage at 72 months was 89%. Five-year survival was 52%. CONCLUSIONS These results compare favorably with other methods of treating AGI, especially in patients with multilevel occlusive disease. Principle advantages include acceptable perioperative mortality, low amputation rate, superior durability with excellent long-term patency, and freedom from secondary interventions and recurrent infections.

Development of Oxidative Stress in the Peritubular Capillary Microenvironment Mediates Sepsis-Induced Renal Microcirculatory Failure and Acute Kidney Injury

Acute kidney injury is a frequent and serious complication of sepsis. To better understand the development of sepsis-induced acute kidney injury, we performed the first time-dependent studies to document changes in renal hemodynamics and oxidant generation in the peritubular microenvironment using the murine cecal ligation and puncture (CLP) model of sepsis. CLP caused an increase in renal capillary permeability at 2 hours, followed by decreases in mean arterial pressure, renal blood flow (RBF), and renal capillary perfusion at 4 hours, which were sustained through 18 hours. The decline in hemodynamic parameters was associated with hypoxia and oxidant generation in the peritubular microenvironment and a decrease in glomerular filtration rate. The role of oxidants was assessed using the superoxide dismutase mimetic/peroxynitrite scavenger MnTMPyP [Mn(III)tetrakis(1-methyl-4-pyridyl)porphyrin]. At 10 mg/kg administered 6 hours after CLP, MnTMPyP did not alter blood pressure, but blocked superoxide and peroxynitrite generation, reversed the decline in RBF, capillary perfusion, and glomerular filtration rate, preserved tubular architecture, and increased 48-hour survival. However, MnTMPyP administered at CLP did not prevent capillary permeability or the decrease in RBF and capillary perfusion, which suggests that these early events are not mediated by oxidants. These data demonstrate that renal hemodynamic changes occur early after sepsis and that targeting the later oxidant generation can break the cycle of injury and enable the microcirculation and renal function to recover.

Muscle protein synthesis in cancer patients can be stimulated with a specially formulated medical food

OBJECTIVE Maintenance of muscle mass is crucial to improving outcome and quality of life in cancer patients. Stimulating muscle protein synthesis is the metabolic basis for maintaining muscle mass, but in cancer patients normal dietary intake has minimal effects on muscle protein synthesis. Adding leucine to high protein supplements stimulates muscle protein synthesis in healthy older subjects. The objective was to determine if a specially formulated medical food, high in leucine and protein, stimulates muscle protein synthesis acutely in individuals with cancer to a greater extent than a conventional medical food. DESIGN A randomized, controlled, double-blind, parallel-group design was used in 25 patients with radiographic evidence of cancer. Patients were studied before their cancer treatment was started or 4 weeks after their treatment was completed or halted. The fractional rate of muscle protein synthesis (FSR) was measured using the tracer incorporation technique with L-[ring-(13)C(6)]-phenylalanine. The experimental group (n = 13) received a medical food containing 40 g protein, based on casein and whey protein and enriched with 10% free leucine and other specific components, while the control group (n = 12) was given a conventionally used medical food based on casein protein alone (24 g). Blood and muscle samples were collected in the basal state and 5h hours after ingestion of the medical foods. RESULTS The cancer patients were in an inflammatory state, as reflected by high levels of C-reactive protein (CRP), IL-1 β and TNF-α, but were not insulin resistant (HOMA). After ingestion of the experimental medical food, plasma leucine increased to about 400 μM as compared to the peak value of 200 μM, after the control medical food (p < 0.001). Ingestion of the experimental medical food increased muscle protein FSR from 0.073 (SD: 0.023) to 0.097 (SD: 0.033) %/h (p = 0.0269). In contrast, ingestion of the control medical food did not increase muscle FSR; 0.073 (SD: 0.022) and 0.065 (SD: 0.028) %/h. CONCLUSIONS In cancer patients, conventional nutritional supplementation is ineffective in stimulating muscle protein synthesis. This anabolic resistance can be overcome with a specially formulated nutritional supplement.

Quantity of dietary protein intake, but not pattern of intake, affects net protein balance primarily through differences in protein synthesis in older adults

To examine whole body protein turnover and muscle protein fractional synthesis rate (MPS) following ingestions of protein in mixed meals at two doses of protein and two intake patterns, 20 healthy older adult subjects (52-75 yr) participated in one of four groups in a randomized clinical trial: a level of protein intake of 0.8 g (1RDA) or 1.5 g·kg(-1)·day(-1) (∼2RDA) with uneven (U: 15/20/65%) or even distribution (E: 33/33/33%) patterns of intake for breakfast, lunch, and dinner over the day (1RDA-U, 1RDA-E, 2RDA-U, or 2RDA-E). Subjects were studied with primed continuous infusions of L-[(2)H5]phenylalanine and L-[(2)H2]tyrosine on day 4 following 3 days of diet habituation. Whole body protein kinetics [protein synthesis (PS), breakdown, and net balance (NB)] were expressed as changes from the fasted to the fed states. Positive NB was achieved at both protein levels, but NB was greater in 2RDA vs. 1RDA (94.8 ± 6.0 vs. 58.9 ± 4.9 g protein/750 min; P = 0.0001), without effects of distribution on NB. The greater NB was due to the higher PS with 2RDA vs. 1RDA (15.4 ± 4.8 vs. -18.0 ± 8.4 g protein/750 min; P = 0.0018). Consistent with PS, MPS was greater with 2RDA vs. 1RDA, regardless of distribution patterns. In conclusion, whole body net protein balance was greater with protein intake above recommended dietary allowance (0.8 g protein·kg(-1)·day(-1)) in the context of mixed meals, without demonstrated effects of protein intake pattern, primarily through higher rates of protein synthesis at whole body and muscle levels.

Impact of sarA on Daptomycin Susceptibility of Staphylococcus aureus Biofilms In Vivo

ABSTRACT We used a murine model of catheter-associated biofilm formation to determine whether the mutation of the staphylococcal accessory regulator (sarA) has an impact on the susceptibility of established Staphylococcus aureus biofilms to treatment with daptomycin in vivo. The experiments were done with two clinical isolates, one of which (UAMS-1) was obtained from the bone of a patient suffering from osteomyelitis, while the other (UAMS-1625) is an isolate of the USA300 clonal lineage of community-acquired methicillin (meticillin)-resistant S. aureus. UAMS-1625 had a reduced capacity to form a biofilm in vivo compared to that of UAMS-1 (P = 0.0015), but in both cases the mutation of sarA limited biofilm formation compared to that of the corresponding parent strain (P ≤ 0.001). The mutation of sarA did not affect the daptomycin MIC for either strain, but it did result in increased susceptibility in vivo in the context of an established biofilm. Specifically, daptomycin treatment resulted in the clearance of detectable bacteria from <10% of the catheters colonized with the parent strains, while treatment with an equivalent daptomycin concentration resulted in the clearance of 46.4% of the catheters colonized with the UAMS-1 sarA mutant and 69.1% of the catheters colonized with the UAMS-1625 sarA mutant. In the absence of daptomycin treatment, mice with catheters colonized with the UAMS-1625 parent strain also developed skin lesions in the region adjacent to the implanted catheter. No such lesions were observed in any other experimental group, including untreated mice containing catheters colonized with the UAMS-1625 sarA mutant.

Impact of Extracellular Nuclease Production on the Biofilm Phenotype of Staphylococcus aureus under In Vitro and In Vivo Conditions

ABSTRACT Recent studies suggest that extracellular DNA promotes biofilm formation in Staphylococcus aureus and, conversely, that extracellular nucleases limit the ability to form a biofilm. S. aureus produces at least two extracellular nucleases, and in the study described in this report, we examined the impact of each of these nucleases on biofilm formation under both in vitro and in vivo conditions. Our results demonstrate that both nucleases impact biofilm formation in the clinical isolate UAMS-1. Under certain in vitro conditions, this impact is negative, with mutation of either or both of the nuclease genes (nuc1 and nuc2) resulting in an enhanced capacity to form a biofilm. However, this effect was not apparent in vivo in a murine model of catheter-associated biofilm formation. Rather, mutation of either or both nuclease genes appeared to limit biofilm formation to a degree that could be correlated with increased susceptibility to daptomycin.