Greater Lipid Oxidation Research Articles

Estimating In Vitro Protein Digestion and Protein Digestibility Corrected Amino Acid Score of Chicken Breasts Affected by White Striping and Wooden Breast Abnormalities.

An understanding regarding impacts of growth-related myopathies, i.e., white striping (WS) and wooden breast (WB), on the quality of dietary protein from cooked chicken breast is still limited. This study aimed at comparing protein content and in vitro protein digestion and estimating the in vitro protein digestibility corrected amino acid score (PDCAAS) of cooked chicken meat exhibiting different abnormality levels (i.e., normal, WS, and WS + WB). The results show that the WS + WB samples exhibited lower protein content, greater cooking loss, and greater lipid oxidation than those of normal samples (p < 0.05). No differences in protein carbonyls or the myofibril fragmentation index were found (p ≥ 0.05). Cooked samples were hydrolyzed in vitro using digestive enzyme mixtures that subsequently mimicked the enzymatic reactions in oral, gastric, and intestinal routes. The WS + WB samples exhibited greater values of free NH2 and degree of hydrolysis than the others at all digestion phases (p < 0.05), suggesting a greater proteolytic susceptibility. The in vitro PDCAAS of the WS + WB samples was greater than that of the other samples for pre-school children, school children, and adults (p < 0.05). Overall, the findings suggest that the cooked chicken breast with the WS + WB condition might provide greater protein digestibility and availability than WS and normal chicken breasts.

PSVII-17 Differential Freeze/Thaw Rates Affect Water-Holding Capacity and Lipid Oxidation in Beef Rib Primal Cuts

Abstract Fresh meat is vulnerable to microbial contamination and loss of quality. Hence, freezing is used to mitigate these issues during transport and storage. However, freezing may negatively impact the same quality characteristics it was meant to preserve, resulting in products that are dissatisfying to the consumer. During the freezing process of meat, water forms ice crystals of various shapes and sizes. The degree of ice crystal growth, mainly due to the freezing rate, has been shown to affect several meat quality characteristics, including tenderness, juiciness, and color. Previous research has primarily evaluated the effect of freezing/thawing on the quality of beef retail cuts. To the best of our knowledge, however, minimal research has been devoted to examining the impact of freezing/thawing on the quality of beef primal and sub-primal cuts. Therefore, this study aimed to gain deeper insight into the histological, ultrastructural, and physiochemical changes occurring in whole beef ribs in response to different freezing/thawing treatments. To achieve our objective, we purchased 32 choice beef rib primals from a local harvest facility 24 h postmortem. Ribs were vacuum packaged and randomly divided into four groups (8 ribs/group). The first group was frozen in a −20 °C freezer (slow freezing), stored in the same freezer for 12 weeks, and thawed at 4 °C for 24 h (slow thawing). The second group was frozen in an ultralow temperature freezer (−80 °C; fast freezing), stored in the same freezer for 12 weeks, and thawed at 4 °C for 48 h. The third and fourth groups were frozen and stored in the same manner as groups one and two, respectively, but were thawed in a water bath (10 °C) for 8 h (fast thawing). Two 2.5-cm-steaks from the middle and each end were collected to represent the entire rib. One steak from each of the three areas was used for color, cook loss, and tenderness evaluation, while the other three supplied tissue for drip loss and lipid oxidation analysis. Data were analyzed using the mixed model of SAS with P ≤ 0.05 considered significant. No differences were observed in color or tenderness between the treatments (P &amp;gt; 0.05). However, slow thawing increased drip loss, regardless of the freezing rate (P &amp;lt; 0.05). Greater cook loss was observed in the fast frozen-slow thawed samples compared with fast frozen-fast thawed samples (P &amp;lt; 0.05). The slow frozen-fast thawed steaks had greater lipid oxidation than the slow frozen-slow thawed treatment (P &amp;lt; 0.05). In general, our data show that subjecting whole beef rib sections to fast freezing may reduce water loss at the expense of increased lipid oxidation. This demonstrates that additional research is needed to further optimize beef primal cut storage.

Hormonal Cycling And Substrate Oxidation At Rest And During Exercise: A Systematic Review And Meta-analysis

Fluctuations of endogenous and exogenous sex hormones across the menstrual cycle (MC) and oral contraceptive (OC) cycle have been suggested to influence rest and exercise substrate metabolism in females. However, there is no clear consensus on the relationship between substrate oxidation and MC or OC phase in females. PURPOSE: This systematic review and meta-analysis aimed to examine the impact of MC and OC cycle phase on substrate oxidation in females at rest and during moderate-intensity continuous exercise. METHODS: Five databases were searched to identify studies including female participants assessed during ≥2 hormonal cycle phases and substrate oxidation determined at rest and/or during moderate-intensity continuous exercise via indirect calorimetry. Data were excluded if substrate metabolism was experimentally manipulated, collected earlier than 5 min into exercise, or if a physiological “steady-state" could not be achieved during exercise. Pairwise meta-analyses examined the effect of MC phase, follicular versus luteal, and OC phase, inactive versus active, on the standardized mean difference (SMD) of each substrate oxidation measurement. Study quality was assessed using a modified Downs and Black checklist, and certainty of the evidence was determined using GRADE criteria. RESULTS: 51 eligible trials were identified for analysis. Analysis of MC phases from 24 studies for resting trials (n = 487) and 23 studies for exercise trials (n = 441) observed that RER was unaffected in the luteal versus follicular phase at rest (SMD = 0.03, 95% CI = -0.16, 0.21, P = 0.78; very low certainty) or during exercise (SMD = -0.01, 95% CI = -0.20, 0.19, P = 0.95; very low certainty). Analysis of OC phase from 7 studies (n = 122) found that RER was lower in the active versus inactive OC phase during exercise (SMD = -0.40, 95% CI = -0.77, -0.03, P = 0.03; low certainty). CONCLUSIONS: We found no effect of MC phase on substrate oxidation at rest or during moderate-intensity continuous exercise. The active OC phase may be associated with greater lipid oxidation during moderate-intensity continuous exercise than the inactive OC phase, indicating a possible effect of exogenous rather than endogenous hormones on substrate oxidation during exercise.

Effect of Dry-Aging on Quality and Palatability Attributes and Flavor-Related Metabolites of Pork Loins.

This study evaluated the effect of dry-aging on quality, palatability, and flavor-related compounds of pork loins. Ten pork loins were obtained at 7 days postmortem, divided into three equal portions, randomly assigned into three different aging methods (wet-aging (W), conventional dry-aging (DA), and UV-light dry-aging (UDA)), and aged for 21 days at 2 °C, 70% RH, and 0.8 m/s airflow. The results showed similar instrumental tenderness values across all treatments (p > 0.05), while DA and UDA had a greater water-holding capacity than WA (p < 0.05). Both DA and UDA were observed to have comparable color stability to WA up to 5 days of retail display (p > 0.05). Greater lipid oxidation was measured in both DA and UDA at the end of display compared to WA (p < 0.05). The UV light minimized microorganisms concentration on both surface and lean portions of UDA compared to other treatments (p < 0.05). The consumer panel was not able to differentiate any sensory traits and overall likeness between the treatments (p > 0.05). Metabolomics analysis, however, identified more flavor-related compounds in dry-aged meat. These findings suggested that dry-aging can be used for pork loins for value-seeking consumers, as it has a potential to generate unique dry-aged flavor in meat with no adverse impacts on meat quality and microbiological attributes.

Early-Onset Physical Inactivity and Metabolic Dysfunction in Tumor-bearing Mice Is Associated with Accelerated Cachexia.

Male C57BL/6J mice (12 wk of age) were injected with 1 × 106 LLC cells or phosphate-buffered saline (PBS) subcutaneously in the right flank, and tissue was collected 26-28 d after cell injection. Tumor volume was measured every 5 d throughout the study to calculate the tumor growth rate. Fifteen days after tumor inoculation, a subset of PBS (n = 11) and LLC (n = 16) mice were individually housed in metabolic Comprehensive Laboratory Animal Monitoring System cages for 5 d. LLC mice exhibited greater body weight loss (-5.1%), decreased muscle mass (-7%), decreased fat mass (-22%), and increased plasma interleukin-6 (212%) compared with PBS mice. Before the onset of cachexia, total cage activity was decreased in tumor-bearing mice. Cage activity was negatively associated with tumor mass and positively associated with hindlimb muscle mass. In addition, LLC mice had greater lipid oxidation than PBS mice. LLC mice exhibit early-onset physical inactivity and altered systemic lipid oxidation, which are associated with the eventual development of cachexia.

Quality attributes of lamb meat from European breeds: Effects of intrinsic properties and storage

The sustainability of the European sheep farming sector can be ensured through the high and consistent quality of products, although the concept of meat quality, being multifaceted, is challenging to keep up by farmers and producers. The objectives of this study were (i) to evaluate quality attributes (CIE L*, a*, b*, lipid oxidation, cooking loss and Warner-Bratzler texture test) of lamb meat during cold storage originating from eight European breeds raised under their normal production systems (n = 292 lambs); and (ii) to elucidate the influence of storage and intrinsic properties (cold carcass weight [CCW], ultimate pH [pH24], water activity [aw], and proximate composition) on the aforementioned quality attributes measured on the 3rd, 9th and 15th day post slaughter. All meat quality properties displayed a high variability due to the breed × production systems, although, as a whole, L*, a*, b*, TBARs and cooking loss increased during storage (P < 0.001), whereas the tenderisation process was of non-linear decay nature (P = 0.001). While production system – taken across breeds – was not found to affect meat cooking losses, it heavily influenced CCW, producing intensive systems heavier (P < 0.001) carcasses (21.4 kg) than those raised in semi-extensive (14.9 kg) and extensive systems (13.8 kg). On the 15th day of storage, TBARs from intensive systems was significantly (P < 0.001) higher than those of extensively raised lambs (0.839 mg MDA/kg vs. 0.299 mg MDA/kg, respectively). Although the extensive and semi-extensive systems initially produced less tender meat (P < 0.05) than intensive systems, on the 15th day of storage, meat from extensive (23.4 N/cm2) and semi-extensive systems (24.4 N/cm2) presented as good tenderness quality (P < 0.10) as that of the intensive systems (22.1 N/cm2). Within breed × production systems, higher CCW or intramuscular fat was associated to darker meat (P < 0.001 and P = 0.014), higher redness (P < 0.001 for both), greater lipid oxidation (P = 0.016 and P < 0.001), and lower slope (P = 0.014 and P = 0.004) and force (P = 0.027 and P = 0.001). The only intrinsic property that heavily affected most of the quality attributes was ash content, since meat of higher ash content presented higher luminosity (P = 0.008), and lower redness (P < 0.001), yellowness (P < 0.001), TBARS (P < 0.001), cooking loss (P = 0.002) and tenderness (P < 0.001). The elucidation of the impact of intrinsic properties on the lamb meat quality attributes during storage can help breeders and producers modify current flock management, feeding strategies and pre-slaughter and slaughter practices towards quality improvement or meeting particular consumers’ demands.

Effects of High-Grain Diet on the Quality of Meat and Carcass of Lambs and Economic Indices of Various Diets

The Brazilian sheep farming sector suffers from low productivity, related to the extensive animal production system and low availability of native fodder during most of the year. An alternative to the systems would be the use of a diet without roughage, allowing greater weight gain and better quality carcasses. The aim of this study was to investigate the effects of diets containing different proportions of grains on the quality of carcass and meat of lambs as well as the economic indices of various diets. Three diets containing different proportions of concentrate and roughage (100:0, 80:20, and 60:40) were supplied. The concentrate comprised 85% whole-grain corn and 15% commercial pelletized supplement. Twenty-four male lambs (no racial pattern; average body weight, 20.9 &amp;plusmn; 1.0 kg; age, 6 months) were randomly allotted to three collective bays for 52 days. Subsequently, the animals were slaughtered, and further analyses were performed. The diet with 100% concentrate achieved overall higher carcass yield, lower weight loss on cooking, and greater lipid oxidation. However, no diet affected weight gain, slaughter weight, carcass length and thorax depth, pH, temperature, color, water-holding capacity, and meat shear force (P &amp;gt; 0.05). The best economic indices were obtained with the diet containing 100% concentrate. Therefore, based on the results obtained, the use of 100% concentrated diet for lambs is the most suitable practice to improve the sheep production from a productive and economic point of view.

Fresh Beef Quality from Cattle Fed Field Peas During Pasture and Finishing Phases of Production

This study evaluated the use of field peas during two phases of production on fresh beef quality. Cattle (n = 232) were assigned to one of six dietary treatments in a 3x2 factorial design consisting of 3 pasture and 2 finishing supplementations. The pasture phase consisted of 1) no supplement, 2) field peas at 0.5% body weight (BW), or 3) dry-rolled corn supplement at 0.5% BW. The finishing phase consisted of 1) no field peas or 2) field peas at 20% dry-matter basis. Strip loin samples, aged 14 d, were subjected to retail display (RD) for an additional 7 d. Tenderness via Warner-Bratzler shear force (WBSF) and Slice Shear force (SSF), objective (L*, a*, and b*) and subjective color, lipid oxidation (TBARS) and fatty acid composition were evaluated. Dietary treatment had no effect on tenderness. Steak discoloration was low (&amp;lt; 3%). All objective color measurements displayed interactions between pasture and finishing diets (L*, P = 0.0035; a*, P = 0.0189; b*, P &amp;lt; 0.0001) yet no consistent patterns among treatments could be identified. Extended aging periods would be required to visually influence consumer color perception. Beef finished with field peas had slightly greater lipid oxidation than samples from cattle not receiving field peas during finishing (1.56 vs. 1.44 mg malonaldehyde/kg tissue, respectively; P = 0.0541). There was a significant interaction between pasture and finishing treatments for C15:1 (P = 0.0331). Feeding field peas during the pasture phase increased C 18:2 (P = 0.0381) relative to cattle supplemented with corn; cattle without supplement in the pasture phase had intermediate amounts of C18:2. Total saturated, unsaturated, monounsaturated, and polyunsaturated fatty acids (P &amp;gt; 0.05) were unaffected by dietary treatments. Field peas may be used for cattle with minimal negative impact on fresh meat quality.

Dissociation of muscle insulin sensitivity from exercise endurance in mice by HDAC3 depletion.

Type 2 diabetes and insulin resistance are associated with reduced glucose utilization in the muscle and poor exercise performance. Here we find that depletion of the epigenome modifier histone deacetylase 3 (HDAC3) specifically in skeletal muscle causes severe systemic insulin resistance in mice but markedly enhances endurance and resistance to muscle fatigue, despite reducing muscle force. This seemingly paradoxical phenotype is due to lower glucose utilization and greater lipid oxidation in HDAC3-depleted muscles, a fuel switch caused by the activation of anaplerotic reactions driven by AMP deaminase 3 (Ampd3) and catabolism of branched-chain amino acids. These findings highlight the pivotal role of amino acid catabolism in muscle fatigue and type 2 diabetes pathogenesis. Further, as genome occupancy of HDAC3 in skeletal muscle is controlled by the circadian clock, these results delineate an epigenomic regulatory mechanism through which the circadian clock governs skeletal muscle bioenergetics. These findings suggest that physical exercise at certain times of the day or pharmacological targeting of HDAC3 could potentially be harnessed to alter systemic fuel metabolism and exercise performance.

Effects of Addition of Linseed and Marine Algae to the Diet on Adipose Tissue Development, Fatty Acid Profile, Lipogenic Gene Expression, and Meat Quality in Lambs.

This study examined the effect of linseed and algae on growth and carcass parameters, adipocyte cellularity, fatty acid profile and meat quality and gene expression in subcutaneous and intramuscular adipose tissues (AT) in lambs. After weaning, 33 lambs were fed three diets up to 26.7 ± 0.3 kg: Control diet (barley and soybean); L diet (barley, soybean and 10% linseed) and L-A diet (barley, soybean, 5% linseed and 3.89% algae). Lambs fed L-A diet showed lower average daily gain and greater slaughter age compared to Control and L (P < 0.001). Carcass traits were not affected by L and L-A diets, but a trend towards greater adipocyte diameter was observed in L and L-A in the subcutaneous AT (P = 0.057). Adding either linseed or linseed and algae increased α-linolenic acid and eicosapentaenoic acid contents in both AT (P < 0.001); however, docosahexaenoic acid was increased by L-A (P < 0.001). The n-6/n-3 ratio decreased in L and L-A (P < 0.001). Algae had adverse effects on meat quality, with greater lipid oxidation and reduced ratings for odor and flavor. The expression of lipogenic genes was downregulated in the subcutaneous AT (P < 0.05): acetyl-CoA carboxylase 1 (ACACA) in L and L-A and lipoprotein lipase (LPL) and stearoyl-CoA desaturase (SCD) in L-A. Fatty acid desaturase 1 (FADS1), fatty acid desaturase 2 (FADS2) and fatty acid elongase 5 (ELOVL5) were unaffected. In the subcutaneous AT, supplementing either L or L-A increased peroxisome proliferator-activated receptor gamma (PPARG) and CAAT-enhancer binding protein alpha (CEBPA) (P < 0.05), although it had no effect on sterol regulatory element-binding factor 1 (SREBF1). In the intramuscular AT, expression of ACACA, SCD, FADS1 and FADS2 decreased in L and L-A (P < 0.001) and LPL in L (P < 0.01), but PPARG, CEBPA and SREBF1 were unaffected.

Effect of beta glucan and carboxymethyl cellulose on lipid oxidation and fatty acid composition of pre-cooked shrimp nugget during storage

Oil extraction from the pre-cooked shrimp nugget with carboxymethyl cellulose and β-glucan was evaluated for peroxide value (PV), p-anisidine value, thiobarbituric acid (TBA) and fatty acid composition in frozen storage for a period of 4 months. After 4 months of frozen storage, Control and CMC shrimp nugget with the highest TBARS values had the greater lipid oxidation than samples containing β-glucan. However, no significant differences were found in BG and CMC + BG samples at 120 days of storage (p > 0.05). p-anisidine value of shrimp nuggets oil without β-glucan were significantly higher than those of shrimp nugget oil containing β-glucan and during storage (p < 0.05). The BG + CMC treatment showed the highest amount of polyunsaturated fatty acids after 120 days. Also, our data showed that there were positive correlations among the results of antioxidant capacities and total phenolic acids of the samples. In conclusion, this result revealed that β-glucan added to shrimp nugget can significantly retard the process of lipid peroxidation during storage.

Effect of early postmortem enhancement of calcium lactate/phosphate on quality attributes of beef round muscles under different packaging systems

The objective was to determine the influence of calcium lactate/phosphate enhancement on quality of beef round cuts in high-oxygen modified atmosphere (HiOx-MAP; 80% O2/20% CO2). Mm. semimembranosus (SM), semitendinosus (ST), and adductor (AD) were divided and assigned to water-injected control (CON), 3mM phosphate (STP), or 200mM calcium lactate/3mM phosphate (CAL/STP) treatments at 24h postmortem. Steaks (n=10) were vacuum packaged (VAC) and stored for 9days, then displayed for 7days in VAC or HiOx-MAP. Lipid oxidation, pH, surface color, star probe, and sensory characteristics were evaluated. HiOx-MAP resulted in greater lipid oxidation, more discoloration, and decreased sensory quality of steaks (P<0.05) compared to VAC. However, CAL/STP enhancement significantly reduced lipid oxidation of all steaks, decreased ST and SM star probe values, and improved tenderness of HiOx-MAP packaged AD and SM (P<0.05). Results suggest that CAL/STP enhancement has beneficial effects on lipid stability and sensory attributes of beef round cuts under HiOx-MAP.

Influence of Hormonal Status on Substrate Utilization at Rest and during Exercise in the Female Population

During exercise, substrate utilization plays a major role in performance and disease prevention. The contribution of fat and carbohydrates to energy expenditure during exercise is modulated by several factors, including intensity and duration of exercise, age, training and diet, but also gender. Because sex hormone levels change throughout a woman's lifetime (in connection with puberty, the menstrual cycle, use of oral contraceptives and menopause), the female population has to be considered specifically in terms of substrate utilization, and metabolic and hormonal responses to exercise. Before puberty, there is no difference between males and females when it comes to substrate oxidation during exercise. This is not the case during adulthood, since women are known to rely more on fat than men for the same relative intensity of exercise. Among adult women, the menstrual cycle and use of oral contraceptives may influence substrate oxidation. While some authors have noted that the luteal phase of the menstrual cycle is connected with greater lipid oxidation, compared with the follicular stage, other authors have found no difference. Among oral contraceptive users, fat oxidation is sometimes increased during prolonged exercise with a concomitant rise in lipolytic hormones, as well as growth hormone. If this result is not always observed, the type of oral contraceptive (monophasic vs triphasic) and hormone doses may be implicated. Menopause represents a hormonal transition in a woman's life, leading to a decline in ovarian hormone production. A decrease in fat oxidation is consequently observed, and some studies have demonstrated a similar respiratory exchange ratio during prolonged exercise in postmenopausal women and in men. As is the case during puberty, no sex difference should thus appear after menopause in the absence of hormonal replacement therapy (HRT). Results concerning women who take HRT remain conflicting. HRT may act on fat loss by increasing lipid metabolism, but this depends on how the treatment is administered (orally vs transdermally). To better understand the role of ovarian hormones in substrate oxidation, studies have made use of animal protocols to investigate cellular mechanisms. Estradiol and progesterone seem to have opposite effects, with greater lipid oxidation when estradiol is used alone. However, the concentrations used (physiological levels or pharmacological doses) may considerably modify fuel selection. In cases where conflicting data are observed in studies of substrate utilization and prolonged exercise in women, methodological reasons must be called into question. Too many parameters, which oftentimes are not specified, may modulate substrate utilization and metabolic and hormonal responses to prolonged exercise. Although information is generally provided about the type of exercise, its duration and the subjects' training level, detailed information is not always given about the subjects' nutritional state and, more specifically, the hormonal status of female subjects. The primary purpose of this review was to identify the impact of hormonal status on substrate oxidation among female subjects at rest and during exercise. A second aim was to describe gender differences in substrate utilization during exercise.

The Effect of Different Level of Air Steam Saturation During Cooking in the Oven and Vacuum Storage on the Quality of Turkey Meat

The effect of cooking in hot air combined with steam and vacuum storage on the quality of turkey meat was studied. The use of steam during cooking decreased cooking losses of turkey meat, and at the same time caused a greater lipid oxidation. The higher rate of SH groups oxidation was found in meat heated with 20, 50 and 90% steam than in meat heated with 0% and 70% steam. Thermal processing caused a decrease in unsaturated fatty acids and an increase in saturated fatty acids content; the smallest changes were demonstrated in meat heated with 20% steam. After thermal processing meat cooked with higher steam (50, 70, 90%) was characterized by better juiciness and tenderness. During storage samples heated in hot air alone and with 20% steam showed lower content of malondialdehyde and better flavour than others samples.

Metabolic Responses To A Single Low-carbohydrate And Low-fat Meal At Rest And During Exercise In Adult Females

PURPOSE: The present study examined the metabolic response to a single low-carbohydrate (LC) and low-fat (LF) meal at rest and during exercise in females. METHODS: All data are reported as the mean + standard deviation. Subjects included 8 premenopausal females who engaged in aerobic activity for > 3 days/week for at least 6 months (age 33.0 + 6.3 years, BMI 26.8 + 3.5 kg/m2, body fat 30.9 + 6.1%, and peak oxygen consumption (VO2peak) 41.8 + 5.7 ml/kg/min). Subjects completed a LC and LF testing session administered in random order and after a 12 hr fast. Respiratory gas exchange (RER) measurements were taken for 20 min fasted before the test meal was consumed, for 55 min postprandial (PP), and during 30 min of treadmill exercise performed at 60 to 65% of VO2peak. Blood was collected for assessment of glucose (G), insulin (IN), triglycerides (TG), and free fatty acids (FFA) during the final 10 min of the fasting and PP time periods and immediately post-exercise (PE). G, FFA, and TG were analyzed using enzymatic assays. IN was analyzed using the ELISA technique. The LF meal provided 396 kcal (78% carbohydrate, 7% fat, and 15% protein). The LC meal provided 392 kcal (15% carbohydrate, 68% fat, and 18% protein). Repeated Measures Factorial ANOVAs were computed for LC and LF over time. RESULTS: No significant differences (p > 0.05) existed between test meals for fasting values of RER, G, IN, TG, or FFA. PP IN (µU/ml) levels were significantly lower (p < 0.05) following LC compared to LF (10.7 + 6.1 vs. 26.0 + 21.0). PE FFA (mEq/L) levels were significantly greater (p < 0.05) following LC (1.1 + 0.3 vs. 0.5 + 0.3). PE TG (mg/dL) levels were significantly greater (p < 0.05) following LC (152.0 + 53.1 vs. 114.4 + 40.9). RER was significantly lower (p < 0.05) from 0 to 25 min PP and from 25 to 55 min PP after LC (0.72 + 0.04 vs. 0.80 + 0.04 and 0.75 + 0.03 vs. 0.86 + 0.04). RER during exercise was significantly lower (p < 0.05) after LC (0.81 + 0.04 vs. 0.86 + 0.04). CONCLUSIONS: In moderately active adult females, ingestion of a single LC meal resulted in greater lipid oxidation at rest and during exercise as compared to a single LF meal. Although macronutrient distribution appears to have dictated substrate utilization in the present study, more research is needed regarding the long-term effects of macronutrient redistribution with and without exercise on substrate utilization.

Kinetics of oxidation of the lipids and proteins of cod sarcoplasmic reticulum.

Lipid and protein oxidation in an NADH-Fe enzymic and an ascorbate-Fe nonenzymic system were determined simultaneously. The nonenzymic iron-reducing system gave rapid oxidation of lipid that leveled off at values much lower than those achieved in the enzymic system, which showed a continuous increase over the 1 or 2 h incubation times used. Protein sulfhydryl oxidation was more rapid in the nonenzymic system for total and accessible sulfhydryl groups, but the enzymic system oxidized the inaccessible sulfhydryl groups more rapidly. Both lipid and protein oxidations appeared to begin simultaneously. In the enzymic system, more lipid oxidation was achieved on a molar basis than oxidation of protein sulfhydryl groups, while in the nonenzymic system this was reversed. These data probably reflect the site specificity of the production of oxidizing elements in the two systems. The greater lipid oxidation in the enzymic system suggests that this may be the more important ferric iron-reducing system during storage of fish muscle.

Singlet oxygen, but not oxidizing radicals, induces apoptosis in HL-60 cells.

Oxidizing species (OS), produced by photosensitization or derived from cytotoxic agents, activate apoptotic pathways. We investigated whether two different OS, formed at the same subcellular sites, have equivalent ability to initiate apoptosis in HL-60 cells. Our previous work showed that absorption of visible light by rose bengal (RB) produces singlet oxygen exclusively, whereas absorption of ultraviolet A produces RB-derived radicals in addition to singlet oxygen. Singlet oxygen, but not the RB-derived radicals, induced nuclear condensation and DNA fragmentation into nucleosome-size fragments in a dose dependent manner. In contrast, the RB-derived radicals caused greater lipid oxidation than singlet oxygen. These results indicate that different OS, produced at the same subcellular sites, do not have the same ability to induce apoptosis and that the ability of an OS to initiate lipid oxidation does not necessarily correlate with its ability to induce apoptosis.

Substrate utilization in leg muscle of men after heat acclimation.

Eight men were heat acclimated (39.6 degrees C and 29.2% rh) for 8 days to examine changes in substrate utilization. A heat exercise test (HET), (cycling for 60 min; 50% maximal O2 consumption) was performed before (UN-HET) and after (ACC-HET) the acclimation period. Muscle glycogen utilization (67.0 vs. 37.6 mmol/kg wet wt), respiratory exchange ratio (0.85 +/- 0.002 vs. 0.83 +/- 0.001), and calculated rate of carbohydrate oxidation (75.15 +/- 1.38 vs. 64.80 +/- 1.52 g/h) were significantly reduced (P less than 0.05) during the ACC-HET. Significantly lower (P less than 0.05) femoral venous glucose (15, 30, and 45 min) and lactate (15 min) levels were observed during the ACC-HET. No differences were observed in plasma free fatty acid (FFA) and glycerol concentrations or glucose, lactate and glycerol arteriovenous uptake/release between tests. A small but significant increase (P less than 0.05) above resting levels in FFA uptake was observed during the ACC-HET. Leg blood flow was slightly greater (P greater than 0.05) during the ACC-HET (4.64 +/- 0.13 vs. 4.80 +/- 0.13 l/min). These findings indicate a reduced use of muscle glycogen following heat acclimation. However, the decrease is not completely explained by a shift toward greater lipid oxidation or increased blood flow.