Background

Excess adipose tissue and sarcopenia presents a multifaceted clinical challenge that promotes morbidity and mortality in the obese, elderly population. Unfortunately, the mortality risks of muscle loss may outweigh the potential benefits of weight loss in the elderly. We have previously demonstrated the effectiveness of whey protein and essential amino acids towards the preservation of lean tissue, even under the conditions of strict bedrest in the elderly.

Methods

In the context of caloric restriction-based weight loss, we hypothesized that a similar formulation given as a meal replacement (EAAMR) would foster the retention of lean tissue through an increase in the skeletal muscle fractional synthesis rate (FSR). We also proposed that EAAMR would promote the preferential loss of adipose tissue through the increased energy cost of skeletal muscle FSR. We recruited and randomized 12 elderly individuals to an 8 week, caloric restriction diet utilizing equivalent caloric meal replacements (800 kcal/day): 1) EAAMR or a 2) competitive meal replacement (CMR) in conjunction with 400 kcal of solid food that totaled 1200 kcal/day designed to induce 7% weight loss. Combined with weekly measurements of total body weight and body composition, we also measured the acute change in the skeletal muscle FSR to EAAMR and CMR.

Results

By design, both groups lost ~7% of total body weight. While EAAMR did not promote a significant preservation of lean tissue, the reduction in adipose tissue was greater in EAAMR compared to CMR. Interestingly, these results corresponded to an increase in the acute skeletal muscle protein FSR.

Conclusion

The provision of EAAMR during caloric restriction-induced weight loss promotes the preferential reduction of adipose tissue and the modest loss of lean tissue in the elderly population.

Increases in plasma lipids, tissue triglycerides and decreases in mitochondrial function have been linked to insulin resistance and aging. In animals, peroxisome proliferator-activated receptor-α (PPARα) agonists decrease plasma lipids, intramyocellular fat (IMCL) and liver fat (LFAT) and improve mitochondrial β- oxidative function and insulin sensitivity, but the effects in elderly were not known. Insulin sensitivity was assessed with a 2-hour oral glucose tolerance test, magnetic resonance spectroscopy was used to asses IMCL, LFAT and plasma lipids were measured before and after 6, 11 and 61 days of PPAR-α agonist (fenofibrate) administration in 19 elderly (age 70±1 years) volunteers. Volunteers were stratified into healthy (N=7) and insulin resistant (N=12) groups. The baseline insulin sensitivity index (8.1±1.2 vs. 3.8±0.5, healthy vs. insulin resistant; P<0.001) was significantly higher in the healthy group. Fenofibrate treatment induced significant reductions in plasma triglycerides (P<0.001) and total cholesterol (P<0.001) in both groups. Nonetheless, neither fasted free fatty acids, glucose, insulin, nor insulin sensitivity improved in either group (Day 1 vs. day 61, 8.1±1.2 vs. 8.1±0.9, healthy; and 3.8±0.5 vs. 4.2±0.05, insulin resistant). Furthermore, there was no change in IMCL or LFAT. These results indicate that whereas fenofibrate significantly lowers plasma lipids it does not affect insulin sensitivity nor intracellular lipids in elderly.

Insulin resistance in the acute burn period has been well described, however, it is unknown if alterations in glucose metabolism persist beyond discharge from the acute injury. To measure the duration of insulin resistance following recovery from the acute burn injury, we performed a prospective cross-sectional study with a standard two hour oral glucose tolerance test in 46 severely burned children at 6, 9 or 12 months following initial injury. Glucose uptake and insulin secretion were assessed following the glucose load. Results were compared to those previously published in healthy children. At 6 months post-burn, the 2 hour glucose concentration was significantly (P<0.001) greater than controls, and the area under the curve (AUC) of glucose was significantly higher compared to 12 months and to healthy children (P=0.027 and P<0.001, respectively). The 9 month AUC glucose was higher than controls (P<0.01). The 6 month 2 hour insulin in was significantly higher than controls, as was the AUC of insulin in all time points post-burn. The AUC of C-peptide was significantly greater at 6 months post-injury compared to 9 and 12 months (P<0.01 for both). Increased 2 hour and AUC glucose and insulin indicate that glucose metabolism is still altered at 6 and 9 months post-injury, and coincides with previously documented defects in bone and muscle metabolism at these time points. Insulin breakdown is also still increased in this population. Further study of this population is warranted to determine if specific treatment is needed.

Background

Mitochondrial proteins and genes are damaged after burn injury in animals but have not previously been assessed in human burn patients.

Methods

The rates of maximal muscle mitochondrial oxidative capacity(ATP production) and uncoupled oxidation(heat production) for both palmitate and pyruvate were measured in muscle biopsies from 40 children sustaining burns >40% body surface area and from 13 healthy children controls.

Results

Maximal mitochondrial oxidation of pyruvate and palmitate were reduced in burn patients compared to controls (4.0±0.2:1.9±0.1 µmolO2/citrate synthase activity/mg protein/min pyruvate; Control:Burn;P<0.001 and 3.0±0.1:0.9±0.03 µmolO2/citrate synthase activity/mg protein/min palmatyl CoA; Control:Burn;P=0.003). Uncoupled oxidation was the same between groups.

Conclusions

The maximal coupled mitochondrial oxidative capacity is severely impaired after burn injury, although there are no alterations in the rate of uncoupled oxidative capacity. It may be that the ratio of these indicates that a larger portion of energy production in trauma patients is wasted through uncoupling, rather than used for healing.

Purpose

This study was performed to determine if there is an age-related specificity in the response of muscle protein metabolism to severe burn injury during acute hospitalization. This is a retrospective analysis of previously published data. Methods: Nineteen adult and 58 pediatric burn-injured patients (age 43.3 ± 14.3 vs. 7.2 ± 5.3 years, adult vs. children) participated in stable isotope [ring-2H5]phenylalanine (Phe) infusion studies. Femoral arterial and venous blood samples and muscle biopsy samples were collected throughout the study. Data are presented as means ± standard deviation (SD). A p value less than 0.05 was considered statistically significant.

Results

Muscle net protein balance (NB) was higher in children (adult vs. children, -43 ± 61 vs. 8 ± 68 nmol Phe/min/100 ml leg volume, p < 0.05). Muscle protein fractional synthesis rate (FSR) was higher in children (adult vs. children, 0.11 ± 0.05 vs. 0.16 ± 0.10 %/h, p < 0.05). Leg muscle protein breakdown was not different between the groups (adult vs. children, 179 ± 115 vs. 184 ± 124 nmol Phe/ min/100 ml leg volume, p < 0.05; synthesis rate was 134 ± 96 and 192 ± 128 nmol Phe/min/100 ml leg volume in adults and children, respectively (p = 0.07). Age significantly correlated with muscle protein NB (p = 0.01) and FSR (p = 0.02); but not with breakdown (p = 0.67) and synthesis (p = 0.07) rates measured by using a three-pool model.

Conclusion

In burn injury, the muscle protein breakdown may be affected to the same extent in adults and children, whereas synthesis may have age-related specificities, resulting in a better but still low NB in children.

Context

Solid organ transplant recipients have elevated cancer risk due to immunosuppression and oncogenic viral infections. Since most prior research has concerned kidney recipients, large studies that include recipients of differing organs can inform cancer etiology.

Objective

Describe the overall pattern of cancer among solid organ transplant recipients.

Design

Cohort study using linked data from the U.S. Scientific Registry of Transplant Recipients (1987–2008) and 13 state/regional cancer registries.

Participants and Setting

Solid organ transplant recipients in the U.S.

Main Outcome Measure

Standardized incidence ratios (SIRs) and excess absolute risks (EARs) assessing relative and absolute cancer risk in transplant recipients compared to the general population.

Results

Registry linkages yielded data on 175,732 solid organ transplants (58.4% kidney, 21.6% liver, 10.0% heart, 4.0% lung). Overall cancer risk was elevated (N=10,656 cases, incidence 1374.7 per 100,000 person-years; SIR 2.10, 95%CI 2.06–2.14; EAR 719.3, 95%CI 693.3–745.6, per 100,000 person-years). Risk was increased (p<0.001) for 32 different malignancies, some related to known infections (e.g., anal cancer, Kaposi sarcoma) and others unrelated (e.g., melanoma, thyroid and lip cancers). The most common malignancies with elevated risk were non-Hodgkin lymphoma (N=1504, incidence 194.0; SIR 7.54, 95%CI 7.17–7.93; EAR 168.3, 95%CI 158.6–178.4) and cancers of the lung (N=1344, incidence 173.4; SIR 1.97, 95%CI 1.86–2.08; EAR 85.3, 95%CI 76.2–94.8), liver (N=930, incidence 120.0; SIR 11.56, 95%CI 10.83–12.33; EAR 109.6, 95%CI 102.0–117.6), and kidney (N=752, incidence 97.0; SIR 4.65, 95%CI 4.32–4.99; EAR 76.1, 95%CI 69.3–83.3). Lung cancer risk was most elevated in lung recipients (SIR 6.13, 95%CI 5.18–7.21) but also increased among other recipients (SIR 1.46, 95%CI 1.34–1.59 for kidney; 1.95, 1.74–2.19 for liver; 2.67, 2.40–2.95 for heart). Liver cancer was elevated only among liver recipients (SIR 43.83, 95%CI 40.90–46.91), who manifested exceptional risk in the first 6 months (SIR 508.97, 95%CI 474.16–545.66) and continuing two-fold excess for 10–15 years (SIR 2.22, 95%CI 1.57–3.04). Among kidney recipients, kidney cancer was elevated (SIR 6.66, 95%CI 6.12–7.23) and bimodal in onset. Kidney cancer was also increased in liver and heart recipients (SIR 1.80, 95%CI 1.40–2.29, and 2.90, 2.32–3.59, respectively).

Conclusions

Recipients of a kidney, liver, heart, or lung transplant have an increased risk for diverse infection-related and unrelated cancers, compared with the general population.

Ingestion of sufficient dietary protein is a fundamental prerequisite for muscle protein synthesis and maintenance of muscle mass and function. The elderly are often at increased risk for protein-energy malnutrition, sarcopenia and a diminished quality of life. This study sought to compare changes in muscle protein synthesis and anabolic efficiency in response to a single moderate (113 g; 220 kcal; 30 g protein) or large serving (340 g; 660 kcal; 90 g protein) of 90% lean beef. Venous blood and vastus lateralis muscle biopsy samples were obtained during a primed, constant infusion (0.08 μmol/kg/min) of L-[ring-13C6] phenylalanine in healthy young (n=17; 34±3yrs) and elderly (n=17; 68±2yrs) individuals. Mixed muscle fractional synthesis rate (FSR) was calculated during a 3 h post-absorptive period and for 5 h following meal ingestion. Data were analysed using a two-way repeated measures ANOVA with Tukey's pair-wise comparisons. A 113 g serving of lean beef increased muscle protein synthesis by approximately 50% in both young and older volunteers. Despite a 3-fold increase in protein and energy content, there was no further increase in protein synthesis following ingestion of 340 g of lean beef in either age group. Ingestion of more than 30 g of protein in a single meal does not further enhance the stimulation of muscle protein synthesis in young and elderly.

Muscle mass declines with aging. Amino acids alone stimulate muscle protein synthesis in the elderly. However, mixed nutritional supplementation failed to improve muscle mass. We hypothesized that the failure of nutritional supplements is due to altered responsiveness of muscle protein anabolism to increased amino acid availability associated with endogenous hyperinsulinemia.

We measured muscle protein synthesis and breakdown, and amino acid transport in healthy young (30 ± 3 yr) and elderly (72 ± 1 yr) volunteers in the basal postabsorptive state and during the administration of an amino acid-glucose mixture, using l-[ring-2H5]phenylalanine infusion, femoral artery and vein catheterization, and muscle biopsies. Basal muscle amino acid turnover was similar in young and elderly subjects. The mixture increased phenylalanine leg delivery and transport into the muscle in both groups. Phenylalanine net balance increased in both groups (young, −27 ± 8 to 64 ± 17; elderly, −16 ± 4 to 29 ± 7 nmol/(min·100 mL); P < 0.0001, basal vs. mixture), but the increase was significantly blunted in the elderly (P = 0.030 vs. young). Muscle protein synthesis increased in the young, but remained unchanged in the elderly [young, 61 ± 17 to 133 ± 30 (P = 0.005); elderly, 62 ± 9 to 70 ± 14 nmol/(min·100 mL) (P = NS)]. In both groups, protein breakdown decreased (P = 0.012) and leg glucose uptake increased (P = 0.0258) with the mixture.

We conclude that the response of muscle protein anabolism to hyperaminoacidemia with endogenous hyperinsulinemia is impaired in healthy elderly due to the unresponsiveness of protein synthesis.

Background

Nutritional supplementation may be used to treat muscle loss with aging (sarcopenia). However, if physical activity does not increase, the elderly tend to compensate for the increased energy delivered by the supplements with reduced food intake, which results in a calorie substitution rather than supplementation. Thus, an effective supplement should stimulate muscle anabolism more efficiently than food or common protein supplements. We have shown that balanced amino acids stimulate muscle protein anabolism in the elderly, but it is unknown whether all amino acids are necessary to achieve this effect.

Objective

We assessed whether nonessential amino acids are required in a nutritional supplement to stimulate muscle protein anabolism in the elderly.

Design

We compared the response of muscle protein metabolism to either 18 g essential amino acids (EAA group: n = 6, age 69 ± 2 y; x̄ ± SD) or 40 g balanced amino acids (18 g essential amino acids + 22 g nonessential amino acids, BAA group; n = 8, age 71 ± 2 y) given orally in small boluses every 10 min for 3 h to healthy elderly volunteers. Muscle protein metabolism was measured in the basal state and during amino acid administration via l-[ring-2H5]phenylalanine infusion, femoral arterial and venous catheterization, and muscle biopsies.

Results

Phenylalanine net balance (in nmol · min−1 · 100 mL leg volume−1) increased from the basal state (P < 0.01), with no differences between groups (BAA: from −16 ± 5 to 16 ± 4; EAA: from −18 ± 5 to 14 ± 13) because of an increase (P < 0.01) in muscle protein synthesis and no change in breakdown.

Conclusion

Essential amino acids are primarily responsible for the amino acid–induced stimulation of muscle protein anabolism in the elderly.

Intravitreally injected AAV2 transduced inner retinal cells in a restricted region at the macaque fovea. Because macaque and human eyes are similar, the results suggest a need to improve transduction methods in gene therapy for the human inner retina.

Purpose.

Adeno-associated virus serotype 2 (AAV2) has been shown to be effective in transducing inner retinal neurons after intravitreal injection in several species. However, results in nonprimates may not be predictive of transduction in the human inner retina, because of differences in eye size and the specialized morphology of the high-acuity human fovea. This was a study of inner retina transduction in the macaque, a primate with ocular characteristics most similar to that of humans.

Methods.

In vivo imaging and histology were used to examine GFP expression in the macaque inner retina after intravitreal injection of AAV vectors containing five distinct promoters.

Results.

AAV2 produced pronounced GFP expression in inner retinal cells of the fovea, no expression in the central retina beyond the fovea, and variable expression in the peripheral retina. AAV2 vector incorporating the neuronal promoter human connexin 36 (hCx36) transduced ganglion cells within a dense annulus around the fovea center, whereas AAV2 containing the ubiquitous promoter hybrid cytomegalovirus (CMV) enhancer/chicken-β-actin (CBA) transduced both Müller and ganglion cells in a dense circular disc centered on the fovea. With three shorter promoters—human synapsin (hSYN) and the shortened CBA and hCx36 promoters (smCBA and hCx36sh)—AAV2 produced visible transduction, as seen in fundus images, only when the retina was altered by ganglion cell loss or enzymatic vitreolysis.

Conclusions.

The results in the macaque suggest that intravitreal injection of AAV2 would produce high levels of gene expression at the human fovea, important in retinal gene therapy, but not in the central retina beyond the fovea.

Context

Sarcopenia is associated with loss of strength and function, eventually leading to loss of independence. Some studies suggest that basal muscle protein turnover is reduced with aging, but other studies do not confirm this finding.

Objective

To determine if aging per se affects basal muscle protein turnover in men.

Design and Setting

Cross-sectional study conducted from June 1997 to July 2000 in a general US community.

Participants

Twenty-six young (mean [SE] age, 28 [2] years) and 22 older (mean [SE] age, 70 [1] years) men, who were healthy and independent based on activities of daily living, physical examinations, and screening tests. Subjects were excluded if they had cardiac, pulmonary, liver, or kidney disease; any impairment in activities of daily living; or steroid use.

Main Outcome Measures

We measured basal muscle protein and amino acid kinetics, based on stable isotope techniques with femoral arteriovenous catheterization and muscle biopsies. Three models (arteriovenous balance, three-pool, and fractional synthesis rate) were used to estimate the metabolic parameters.

Results

Mean (SE) total leg volume was 9.60 (0.32) L in older men vs 10.83 (0.43) L in younger men, which suggests muscle loss in the older men. Net muscle protein balance was similar in both groups (older men, −19 [2] nmol/min per 100 mL of leg volume vs younger men, −21 [2] nmol/min per 100 mL of leg volume; P=.51). Small differences were found in mean (SE) muscle protein synthesis in comparisons of older vs younger men: arteriovenous balance, 48 (5) nmol/min per 100 mL of leg volume vs 32 (3) nmol/min per 100 mL of leg volume; P=.004; three-pool, 58 (5) nmol/min per 100 mL of leg volume vs 43 (4) nmol/min per 100 mL of leg volume; P=.04; and fractional synthesis rate, 0.0601 (0.0046) %/h vs 0.0578 (0.0047) %/h; P=.73. Small differences were also found in mean (SE) muscle protein breakdown: arteriovenous balance, 66 (5) nmol/min per 100 mL of leg volume in older vs 53 (4) nmol/min per 100 mL of leg volume in younger men, P=.045; and three-pool, 76 (6) nmol/min per 100 mL of leg volume vs 64 (5) nmol/min per 100 mL of leg volume, P=.14.

Conclusion

Differences in basal muscle protein turnover between older and younger men do not appear to explain muscle loss that occurs with age.

Spaceflight represents a unique physiological challenge to humans, altering hormonal profiles and tissue insulin sensitivity. Among these hormonal alterations, hypercortisolemia and insulin insensitivity are thought to negatively affect muscle mass and function with spaceflight. As insulin sensitivity influences the accumulation of muscle triglycerides, we examined this relationship during hypercortisolemia and inactivity. Six young healthy volunteers were confined to bed rest for 28 days. To mimic the stress response observed during spaceflight, hypercortisolemia (20–24mg/dL) was induced and maintained by oral ingestion of hydrocortisone. On days 1 and 28 of bed rest, insulin sensitivity across the leg was assessed with a local (femoral arterial insulin infusion) 2 stage hyperinsulinemic-euglycemic clamp (stage 1: 35 µU/min/ml leg; stage 2: 70 µU/min/ml leg). Intramuscular lipid was measured with magnetic resonance spectroscopy. Following bed rest, there was a decrease in insulin sensitivity, as assessed by glucose uptake during hyperinsulinemia (from 9.1±1.3 (mean ± SEM) mg/kg.leg/min to 5.2±0.7 mg/kg.leg/min (P=0.015)). Intramuscular triglyceride increased from 0.077±0.011 to 0.136±0.018 (signal area of fat/signal area of standard; P=0.009). Intramuscular lipid content correlated with the glucose uptake at day 28, (R= −0.85; P=0.035). These data demonstrate that muscular inactivity and hypercortisolemia are associated with an increase in intramuscular triglyceride and skeletal muscle insulin resistance in previously healthy subjects.

Purpose

The ability to resolve single retinal cells in rodents in vivo has applications in rodent models of the visual system and retinal disease. We have characterized the performance of a fluorescence adaptive optics scanning laser ophthalmoscope (fAOSLO) that provides cellular and subcellular imaging of rat retina in vivo.

Methods

Green fluorescent protein (eGFP) was expressed in retinal ganglion cells of normal Sprague Dawley rats via intravitreal injections of adeno-associated viral vectors. Simultaneous reflectance and fluorescence retinal images were acquired using the fAOSLO. fAOSLO resolution was characterized by comparing in vivo images with subsequent imaging of retinal sections from the same eyes using confocal microscopy.

Results

Retinal capillaries and eGFP-labeled ganglion cell bodies, dendrites, and axons were clearly resolved in vivo with adaptive optics (AO). AO correction reduced the total root mean square wavefront error, on average, from 0.30 μm to 0.05 μm (1.7-mm pupil). The full width at half maximum (FWHM) of the average in vivo line-spread function (LSF) was ∼1.84 μm, approximately 82% greater than the FWHM of the diffraction-limited LSF.

Conclusions

With perfect aberration compensation, the in vivo resolution in the rat eye could be ∼2× greater than that in the human eye due to its large numerical aperture (∼0.43). While the fAOSLO corrects a substantial fraction of the rat eye's aberrations, direct measurements of retinal image quality reveal some blur beyond that expected from diffraction. Nonetheless, subcellular features can be resolved, offering promise for using AO to investigate the rodent eye in vivo with high resolution.

Objective

Hypertriglyceridemia is a risk factor for coronary heart disease. The aim of this study was to determine the effect of AA supplementation on plasma, liver and muscle lipid concentrations and insulin sensitivity in elderly.

Methods

Twelve impaired glucose tolerant elderly (67.0 ± 5.6 (SD) years, 7 females, 5 males) ingested 11 g of essential AA + arginine twice a day for 16 weeks, after a 7 week control run in. Diet and activity were not otherwise modified. Plasma lipid concentrations and oral glucose tolerance were measured every 4th week, and tissue lipid concentrations (magnetic resonance spectroscopy) every 8th week.

Results

No changes in plasma lipids were observed during the control run-in. AA supplementation lowered plasma triglyceride (TG) (P < 0.001), total cholesterol (P = 0.048) and very low density lipoprotein (VLDL)-cholesterol (P < 0.001) concentrations. Plasma TG dropped ~20% from the initial value of 1.45 ± 0.18 (SE) mmol/l (128 ± 16 mg/dl), with greatest decrease in the subjects starting out with highest concentrations (r = −0.83). Similarly, liver fat content (liver TG/intralipid standard) decreased ~50% from the initial value of 0.34 ± 0.06 (P = 0.021; n = 9), with greatest decrease in the subjects that initially had highest values (r = −0.86). Intramuscular fat content and insulin sensitivity did not change.

Conclusion

Diet supplementation with AA lowers plasma TG, total cholesterol and VLDL-cholesterol concentrations, and liver lipid content in impaired glucose tolerant elderly. AA supplementation may have a potential role in treatment of hypertriglyceridemia or hepatic steatosis.

A reduced response of older skeletal muscle to anabolic stimuli may contribute to the development of sarcopenia. We hypothesized that muscle proteins are resistant to the anabolic action of insulin in the elderly. We examined the effects of hyperinsulinemia on muscle protein metabolism in young (25±2 year) and older (68±1 year) healthy subjects using stable isotope tracer techniques. Leg blood flow was higher in the young at baseline and increased during hyperinsulinemia, whereas it did not change in the elderly. Glucose concentrations and muscle uptake were not different between groups at baseline and during hyperinsulinemia. Leg phenylalanine net balance was not different at baseline and significantly increased in both groups with hyperinsulinemia (P<0.05) but to a greater extent in the young (P<0.05). Muscle protein synthesis increased only in the young during hyperinsulinemia. Muscle protein breakdown did not significantly change in either group, although it tended to decrease in the elderly. Changes in muscle protein synthesis were correlated with changes in leg amino acid delivery (R=0.89; P=0.0001) and blood flow (R=0.90; P<0.0001). In conclusion, skeletal muscle protein synthesis is resistant to the anabolic action of insulin in older subjects, which may be an important contributor to the development of sarcopenia.

Steroid-free regimen is increasingly employed in kidney transplant recipients across transplant centers. However, concern remains because of unknown impact of such approach on long-term graft and patient survival. We studied outcomes of steroid-free immunosuppression in a population-based U.S. cohort of kidney transplant recipients.

All adult solitary kidney transplant recipients engrafted between January 1, 2000 and December 31, 2006 was stratified according to whether they were selected for steroid-free or steroid-containing regimen at discharge. Multivariate Cox regression models were used to estimate graft and patient survival. The impact of practice pattern on steroid use at individual transplant centers was analyzed.

Among 95,755 kidney transplant recipients, 17.2 % of them were steroid-free at discharge (n=16,491). Selection for steroid-free regimen was associated with reduced risks for graft failure and death at 1 year (HR 0.78, 95% CI 0.72-0.85, and 0.73, 95% CI 0.65-0.82, respectively, p<0.0001) and 4 years (HR 0.83, 95% CI 0.78-0.87, and 0.76, 95% CI 0.71-0.83, respectively, p<0.0001). This association was mostly observed at individual centers where less than 65% of recipients were discharged on steroid-containing regimen.

De novo steroid-free immunosuppression as currently practiced in the US appears to carry no increased risk of adverse clinical outcomes in the intermediate term.

Purpose

Autofluorescence fundus imaging using an adaptive optics scanning laser ophthalmoscope (AOSLO) allows for imaging of individual retinal pigment epithelial (RPE) cells in vivo. In this study, the potential of retinal damage was investigated by using radiant exposure levels that are 2 to 150 times those used for routine imaging.

Methods

Macaque retinas were imaged in vivo with a fluorescence AOSLO. The retina was exposed to 568- or 830-nm light for 15 minutes at various intensities over a square ½° per side. Pre-and immediate postexposure images of the photoreceptors and RPE cells were taken over a 2° field. Long-term AOSLO imaging was performed intermittently from 5 to 165 days after exposure. Exposures delivered over a uniform field were also investigated.

Results

Exposures to 568-nm light caused an immediate decrease in autofluorescence of RPE cells. Follow-up imaging revealed either full recovery of autofluorescence or long-term damage in the RPE cells at the exposure. The outcomes of AOSLO exposures and uniform field exposures of equal average power were not significantly different. No effects from 830-nm exposures were observed.

Conclusions

The study revealed a novel change in RPE autofluorescence induced by 568-nm light exposure. Retinal damage occurred as a direct result of total average power, independent of the light-delivery method. Because the exposures were near or below permissible levels in laser safety standards, these results suggest that caution should be used with exposure of the retina to visible light and that the safety standards should be re-evaluated for these exposure conditions.

Purpose

Retinal pigment epithelial (RPE) cells are critical for the health of the retina, especially the photoreceptors. A recent study demonstrated that individual RPE cells could be imaged in macaque in vivo by detecting autofluorescence with an adaptive optics scanning laser ophthalmoscope (AOSLO). The current study extended this method to image RPE cells in fixating humans in vivo and to quantify the RPE mosaic characteristics in the central retina of normal humans and macaques.

Methods

The retina was imaged simultaneously with two light channels in a fluorescence AOSLO; one channel was used for reflectance imaging of the cones while the other detected RPE autofluorescence. The excitation light was 568 nm, and emission was detected over a 40-nm range centered at 624 nm. Reflectance frames were registered to determine interframe eye motion, the motion was corrected in the simultaneously recorded autofluorescence frames, and the autofluorescence frames were averaged to give the final RPE mosaic image.

Results

In vivo imaging demonstrated that with increasing eccentricity, RPE cell density, and mosaic regularity decreased, whereas RPE cell size and spacing increased. Repeat measurements of the same retinal location 42 days apart showed the same RPE cells and distribution.

Conclusions

The RPE cell mosaic has been resolved for the first time in alert fixating human subjects in vivo using AOSLO. Mosaic analysis provides a quantitative database for studying normal and diseased RPE in vivo. This technique will allow longitudinal studies to track disease progression and assess treatment efficacy in patients and animal models of retinal disease.

It is recognized that both whey protein and essential amino acids (EAA) are stimuli for muscle protein anabolism. The aim of the present study was to determine if the effects of whey protein ingestion on muscle protein accrual in elderly are due solely to its constituent EAA content. Fifteen elderly humans were randomly assigned to ingest a bolus of either 15 g of whey protein (WY), 6.72 g of essential amino acids (EAA), or 7.57 g of non-essential amino acids (NEAA). We utilized the leg arterio-venous model to measure the leg phenylalanine balance (PB), which is an index of muscle protein accrual. PB (nmol·min−1·kg lean leg mass−1) during the 3.5 hours following the bolus ingestion improved in the WY (−216 ± 14 vs −105 ± 19; P < .05) but not in the EAA (−203 ± 21 vs −172 ± 38; P > .05) or NEAA groups (−203 ± 19 vs −204 ± 21; P > .05). The insulin response (ulU·ml−1 210 min−1) during the same period was lower in both the NEAA (48 ± 40) and EAA (213 ± 127) when compared to the WY (1073 ± 229; P < .05). In conclusion, whey protein ingestion improves skeletal muscle protein accrual through mechanisms that are beyond those attributed to its essential amino acid content. This finding may have practical implications for the formulation of nutritional supplements to enhance muscle anabolism in older individuals.

Background

Although it has been suggested that alterations of nerve fiber layer vasculature may be involved in the etiology of eye diseases, including glaucoma, it has not been possible to examine this vasculature in-vivo. This report describes a novel imaging method, fluorescence adaptive optics (FAO) scanning laser ophthalmoscopy (SLO), that makes possible for the first time in-vivo imaging of this vasculature in the living macaque, comparing in-vivo and ex-vivo imaging of this vascular bed.

Methods

We injected sodium fluorescein intravenously in two macaque monkeys while imaging the retina with an FAO-SLO. An argon laser provided the 488 nm excitation source for fluorescence imaging. Reflectance images, obtained simultaneously with near infrared light, permitted precise surface registration of individual frames of the fluorescence imaging. In-vivo imaging was then compared to ex-vivo confocal microscopy of the same tissue.

Results

Superficial focus (innermost retina) at all depths within the NFL revealed a vasculature with extremely long capillaries, thin walls, little variation in caliber and parallel-linked structure oriented parallel to the NFL axons, typical of the radial peripapillary capillaries (RPCs). However, at a deeper focus beneath the NFL, (toward outer retina) the polygonal pattern typical of the ganglion cell layer (inner) and outer retinal vasculature was seen. These distinguishing patterns were also seen on histological examination of the same retinas. Furthermore, the thickness of the RPC beds and the caliber of individual RPCs determined by imaging closely matched that measured in histological sections.

Conclusion

This robust method demonstrates in-vivo, high-resolution, confocal imaging of the vasculature through the full thickness of the NFL in the living macaque, in precise agreement with histology. FAO provides a new tool to examine possible primary or secondary role of the nerve fiber layer vasculature in retinal vascular disorders and other eye diseases, such as glaucoma.

Background & Aims

With advancing age there is a gradual decline in muscle mass, strength and function. The aim of this study was to determine if regular intake of a nutritional supplement containing essential amino acids (EAA) + arginine could reverse these responses in elderly subjects.

Methods

Twelve glucose intolerant subjects (67.0 ± 5.6 (SD) years, 7 females, 5 males) ingested 11 g of EAA + arginine two times a day, between meals for 16 weeks. Diet and activity were not otherwise modified. Lean body mass (DEXA) was measured every 4th week. Maximal leg strength was tested and functional tests were performed at week 0, 8, 12, and 16.

Results

Lean body mass (LBM) increased during the study (p = 0.038). At week 12, the average increase in LBM was 1.14 ± 0.36 kg (p < 0.05 vs baseline), whereas at week 16, the increase was 0.60 ± 0.38 kg (NS vs baseline). The lower extremity strength measure score (sum of individual knee flexors and extensors 1-repetition maximum, n = 10) was 127.5 ± 21.8 kg at baseline, and average increase during the study was 22.2 ± 6.1% (p < 0.001). Improvements were also observed in usual gait speed (p = 0.002), timed 5-step test (p = 0.007), and timed floor-transfer test (p = 0.022).

Conclusion

Supplementation of the diet with EAA + arginine improves lean body mass, strength and physical function compared to baseline values in glucose intolerant elderly individuals.

Background & Aims

Cancer and oncological therapy are associated with a progressive physical deterioration, malnutrition, and enhanced inflammatory burden. Our considerable data showing the strong anabolic potential of amino acids led us to test whether amino acids can acutely stimulate muscle protein synthesis in cancer patients (CA) undergoing intense chemotherapy.

Methods

Mixed muscle fractional synthesis rate (FSR), rates of phenylalanine appearance and disappearance (Ra and Rd), and net phenylalanine balance (NB) were measured during a primed constant infusion of L-[ring-2H5]phenylalanine. Blood and muscle tissue samples were collected in the basal state and following ingestion of 40 g of amino acids (AA) given in 30 mL boluses every 10 minutes for 3 hours. Serum and tissue cytokines and NF-κB expression in skeletal muscle were measured and compared to normative, healthy older controls (OC).

Results

Skeletal muscle TNF-α, IL-6, and NF-κB were elevated in CA. FSR and model-derived protein synthesis (Rd) increased significantly from basal to AA (FSR: 0.052 ± 0.009 vs. 0.120 ± 0.008 %•h-1, P<0.001; Rd: 23.1 ± 4.1 vs. 36.4 ± 5.0 nmol•min-1•100mL leg-1, P≤0.05). Model-derived protein breakdown (Ra) remained unchanged from basal to AA.. Phenylalanine NB improved from a negative basal value (-16 ± 2) to zero (0.8 ± 6 nmol•min-1•100 ml leg-1, P≤0.05) following AA.

Conclusion

Despite advanced cancer, ongoing therapy, and an enhanced inflammatory burden, amino acids were capable of acutely stimulating muscle protein synthesis in these patients.

Background

Insulin resistance is often associated with increased levels of intracellular triglycerides, diacylglycerol and decreased fat β-oxidation. It was unknown if this relationship was present in patients with acute insulin resistance induced by trauma.

Methods

A double blind placebo controlled trial was conducted in 18 children with severe burn injury. Metabolic studies to assess whole body palmitate oxidation and insulin sensitivity, muscle biopsies for mitochondrial palmitate oxidation, diacylglycerol, fatty acyl Co-A and fatty acyl carnitine concentrations, and magnetic resonance spectroscopy for muscle and liver triglycerides were compared before and after two weeks of placebo or PPAR-α agonist treatment.

Results

Insulin sensitivity and basal whole body palmitate oxidation as measured with an isotope tracer increased significantly (P = 0.003 and P = 0.004, respectively) after PPAR-α agonist treatment compared to placebo. Mitochondrial palmitate oxidation rates in muscle samples increased significantly after PPAR-α treatment (P = 0.002). However, the concentrations of muscle triglyceride, diacylglycerol, fatty acyl CoA, fatty acyl carnitine, and liver triglycerides did not change with either treatment. PKC-θ activation during hyper-insulinemia decreased significantly following PPAR-α treatment.

Conclusion

PPAR-α agonist treatment increases palmitate oxidation and decreases PKC activity along with reduced insulin sensitivity in acute trauma, However, a direct link between these responses cannot be attributed to alterations in intracellular lipid concentrations.

Background

The incidence of vaccine-preventable diseases is directly related to the number of unvaccinated children. Parents who refuse vaccination of their children frequently express concerns about vaccine safety. The Internet can influence perceptions about vaccines because it is the fastest growing source of consumer health information. However, few studies have analyzed vaccine criticism on the Web.

Objective

The purposes of this paper are to examine vaccine criticism on the Internet and to analyze the websites in order to identify common characteristics and ethical allegations.

Methods

A structured Web search was conducted for the terms “vaccine,” “vaccination,” “vaccinate,” and “anti-vaccination” using a metasearch program that incorporated 8 search engines. This yielded 1138 Web pages representing 750 sites. Two researchers reviewed the sites for inclusion/exclusion criteria, resulting in 78 vaccine-critical sites, which were then abstracted for design, content, and allegations.

Results

The most common characteristic of vaccine-critical websites was the inclusion of statements linking vaccinations with specific adverse reactions, especially idiopathic chronic diseases such as multiple sclerosis, autism, and diabetes. Other common attributes (≥ 70% of websites) were links to other vaccine-critical websites; charges that vaccines contain contaminants, mercury, or “hot lots” that cause adverse events; claims that vaccines provide only temporary protection and that the diseases prevented are mild; appeals for responsible parenting through education and resisting the establishment; allegations of conspiracies and cover-ups to hide the truth about vaccine safety; and charges that civil liberties are violated through mandatory vaccination.

Conclusions

Vaccine-critical websites frequently make serious allegations. With the burgeoning of the Internet as a health information source, an undiscerning or incompletely educated public may accept these claims and refuse vaccination of their children. As this occurs, the incidence of vaccine-preventable diseases can be expected to rise.