Mitigation of Hematopoietic Syndrome of Acute Radiation Syndrome by 1-Palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol (PLAG) is Associated with Regulation of Systemic Inflammation in a Murine Model of Total-Body Irradiation.

The growing risk of accidental radiation exposure due to increased usage of ionizing radiation, such as in nuclear power, industries and medicine, has increased the necessity for the development of radiation countermeasures. Previously, we demonstrated the therapeutic potential of the acetylated diacylglycerol, 1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol (PLAG), as a radiation countermeasure by mitigating radiation-associated mortality and hematopoietic acute radiation syndrome (H-ARS) in BALB/c mice after a lethal dose (LD70/30) of gamma-ray total-body irradiation (TBI). In this study, we show that PLAG mitigates symptoms of H-ARS, as characterized by mature blood cell recovery and restoration of bone marrow cellularity, by regulating systemic inflammation. Log-rank test demonstrated that high levels of WBCs, lymphocytes and neutrophils on day 10 post-TBI resulted in significantly improved survival rate. PLAG significantly enhanced the nadir values of all major blood cell types as well as bone marrow cellularity. A single TBI at LD70/30 induced an immediate increase in the blood levels of CXCL1 (12.5 fold), CXCL2 (1.5 fold), IL-6 (86.9 fold), C-reactive protein (CRP; 1.3 fold) and G-CSF (15.7 fold) at 6 h post-TBI, but the cytokine levels returned to baseline level afterward. When the irradiated mice started to die around 15 days post-TBI, they exhibited a second surge in blood levels of CXCL1 (49.3 fold), CXCL2 (87.1 fold), IL-6 (208 fold), CRP (3.6 fold) and G-CSF (265.7 fold). However, PLAG-treated groups showed a significant decrease in these same blood levels (P < 0.001). Considering the inverse correlation between inflammatory cytokine levels and hematological nadirs, PLAG exerts its therapeutic effects on H-ARS by regulating inflammatory cytokine production. These data suggest that PLAG has high potential as a radiation countermeasure to mitigate H-ARS after accidental exposure to radiation.

1-Palmitoyl-2-Linoleoyl-3-Acetyl-rac-Glycerol (PLAG) Mitigates Monosodium Urate (MSU)-Induced Acute Gouty Inflammation in BALB/c Mice.

Acute gouty arthritis is an auto-inflammatory disease caused by the deposition of monosodium urate (MSU) crystals in joints or tissues. Excessive neutrophil recruitment into gouty lesions is a general clinical sign and induces a pain phenotype. Attenuation of successive periods of neutrophil infiltration might be a beneficial approach to achieve therapeutic efficacy. In this study, the activity of 1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol (PLAG) in attenuation of excess neutrophil infiltration was assessed in gout-induced lesions of BALB/c mice. Neutrophil infiltration in MSU-induced gouty lesions was analyzed using immunohistochemical staining. ELISA and RT-PCR were used to measure attenuation of expression of the major neutrophil chemoattractant, CXC motif chemokine ligand 8 (CXCL8), in a PLAG-treated animal model and in cells in vitro. The animal model revealed massive increased neutrophil infiltration in the MSU-induced gouty lesions, but the PLAG-treated mice had significantly reduced neutrophil numbers in these lesions. The results also indicated that the MSU crystals stimulated a damage-associated molecular pattern that was recognized by the P2Y6 purinergic receptor. This MSU-stimulated P2Y6 receptor was destined to intracellular trafficking. During intracellular endosomal trafficking of the receptor, endosome-dependent signaling provided expression of CXCL8 chemokines for neutrophil recruitment. PLAG accelerated initiation of the intracellular trafficking of the P2Y6 receptor and returning the receptor to the membrane. This process shortened the intracellular retention time of the receptor anchoring endosome and subsequently attenuated endosome-dependent signaling for CXCL8 expression. These study results suggested that PLAG could be used for resolution of acute inflammation induced in gout lesions.

Mitigating Effects of 1-Palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol (PLAG) on Hematopoietic Acute Radiation Syndrome after Total-Body Ionizing Irradiation in Mice.

Acute radiation syndrome (ARS) occurs as a result of partial- or whole-body, high-dose exposure to radiation in a very short period of time. Survival is dependent on the severity of the hematopoietic sub-syndrome of ARS. In this study, we investigated the mitigating effects of a lipid molecule, 1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol (PLAG), on the kinetics of hematopoietic cells, including absolute neutrophil count (ANC), red blood cells (RBCs) and platelet counts, in mice after gamma-ray total-body irradiation (TBI). Male and female BALB/c mice (11 weeks old) received a LD70/30 dose of TBI. PLAG significantly and dose-dependently attenuated radiation-induced mortality (P = 0.0041 for PLAG 50 mg/kg; P < 0.0001 for PLAG 250 mg/kg) and body weight loss (P < 0.0001 for PLAG 50 and 250 mg/kg) in mice. Single-fraction TBI sharply reduced ANC within 3 days postirradiation and maintained the neutropenic state (ANC < 500 cells/µl) by approximately 26.8 ± 0.8 days. However, administration of PLAG attenuated radiation-induced severe neutropenia (ANC < 100 cells/µl) by effectively delaying the mean day of its onset and decreasing its duration. PLAG also significantly mitigated radiation-induced thrombocytopenia (P < 0.0001 for PLAG 250 mg/kg) and anemia (P = 0.0023 for PLAG 250 mg/kg) by increasing mean platelet and RBC counts, as well as hemoglobin levels, in peripheral blood. Moreover, delayed administration of PLAG, even at 48 and 72 h after gamma-ray irradiation, significantly attenuated radiation-induced mortality in a time-dependent manner. When compared to olive oil and palmitic linoleic hydroxyl (PLH), only PLAG effectively attenuated radiation-induced mortality, indicating that it has a distinctive mechanism of action. Based on these preclinical observations, we concluded that PLAG has high potential as a radiation countermeasure for the improvement of survivability and the treatment of hematopoietic injury in gamma-ray-induced ARS.

PLAG (1-Palmitoyl-2-Linoleoyl-3-Acetyl-rac-Glycerol) Modulates Eosinophil Chemotaxis by Regulating CCL26 Expression from Epithelial Cells.

Increased number of eosinophils in the circulation and sputum is associated with the severity of asthma. The respiratory epithelium produces chemokine (C-C motif) ligands (CCL) which recruits and activates eosinophils. A chemically synthesized monoacetyl-diglyceride, PLAG (1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol) is a major constituent in the antlers of Sika deer (Cervus nippon Temminck) which has been used in oriental medicine. This study was aimed to investigate the molecular mechanism of PLAG effect on the alleviation of asthma phenotypes. A549, a human alveolar basal epithelial cell, and HaCaT, a human keratinocyte, were activated by the treatment of interleukin-4 (IL-4), and the expression of chemokines, known to be effective on the induction of eosinophil migration was analyzed by RT-PCR. The expression of IL-4 induced genes was modulated by the co-treatment of PLAG. Especially, CCL26 expression from the stimulated epithelial cells was significantly blocked by PLAG, which was confirmed by ELISA. The transcriptional activity of signal transducer and activator of transcription 6 (STAT6), activated by IL-4 mediated phosphorylation and nuclear translocation, was down-regulated by PLAG in a concentration-dependent manner. In ovalbumin-induced mouse model, the infiltration of immune cells into the respiratory tract was decreased by PLAG administration. Cytological analysis of the isolated bronchoalveolar lavage fluid (BALF) cells proved the infiltration of eosinophils was significantly reduced by PLAG. In addition, PLAG inhibited the migration of murine bone marrow-derived eosinophils, and human eosinophil cell line, EoL-1, which was induced by the addition of A549 culture medium.

The short-term effect of diacylglycerol oil consumption on total and dietary fat utilization in overweight women.

Diacylglycerol (DAG) is a natural component of edible oils with metabolic characteristics distinct from those of triacylglycerol (TAG). Consumption of DAG oil (containing > 80% DAG) induces greater fat oxidation than consumption of TAG oil. We compared the effects of 4 days of DAG oil consumption with those of TAG oil consumption on total and dietary fat oxidation over 24 h in overweight women using a whole-room respiratory chamber. Overweight (BMI (kg/m²) ≥ 25) females participated in this double-blind, crossover-controlled trial. The subjects consumed test diets containing either TAG or DAG oil as 15% of their total caloric intake (mean test oil intake was 33.0 ± 3.1 g/day) during each 4-day treatment. Fat oxidation and energy expenditure were measured in a respiratory chamber on the 4th day of each treatment. Compared with TAG oil, DAG oil consumption significantly increased total fat oxidation and dietary fat oxidation in overweight subjects. Total energy expenditure (TEE) and carbohydrate (CHO) oxidation did not significantly differ between DAG oil and TAG oil consumption in overweight subjects. Compared with TAG oil, DAG oil consumption enhanced total fat oxidation and dietary fat oxidation in overweight subjects. The enhanced fat metabolism in overweight subjects that consumed DAG oil partly explains the greater loss of body weight and body fat related to DAG oil consumption in weight-loss studies.

[Therapeutic application of diacylglycerol oil for the metabolic syndrome].

Excess adiposity has been shown to play a crucial role in the development of the metabolic syndrome. Characteristics for dyslipidemia in the metabolic syndrome are elevated fasting and postprandial triglyceride (TG) and decreased high-density lipoprotein-cholesterol (HDL-C). Diacylglycerol(DAG) has been suggested to suppress postprandial hyperlipidemia and promote negative caloric balance by increasing energy expenditure, due to intestinal physiochemical dynamics that differ from triacylglycerol (TAG). Our study (Study 1) demonstrated that DAG suppressed postprandial increase in TG-rich lipoprotein, very low density lipoprotein (VLDL), and insulin as compared with TAG in young male individuals. Further, our another study using the apolipoprotein C-II deficient subject demonstrated that DAG suppressed postprandial increase in VLDL-cholesterol and remnant-like particle-cholesterol compared with TAG, suggesting that DAG suppress postprandial TG-rich lipoprotein independent of lipoprotein lipase. Study 1 also showed that DAG significantly increased plasma serotonin, which is mostly present in intestine and mediates thermogenesis, proposing a possible mechanism for a postprandial increase in energy expenditure by DAG. Our studies presented DAG-mediated amelioration in postprandial TG-rich lipoprotein, insulin, and energy metabolism, indicating the therapeutic application of DAG for the metabolic syndrome.

Dietary diacylglycerol oil has no effect on hypertriacylglycerolaemia in lipoprotein lipase-deficient cats.

A commercially available vegetable oil containing a high concentration (87 %, w/w) of diacylglycerol (DAG) has been investigated in humans and animals for potential beneficial effects in reducing serum TAG concentrations in fasting and postprandial states. Effects of DAG oil as a sole dietary fat source (25 % metabolisable energy) were evaluated in a feline model of hypertriacylglycerolaemia. Eleven adult (1.5 (sem 0.1) years) male cats deficient of lipoprotein lipase (LPL) catalytic activity from a heritable point mutation of the LPL gene were acclimatised to a semi-purified diet containing TAG oil for 21 d. After assignment into two groups, pair-matched by serum TAG concentrations (range 6.1-31.6 mmol/l), the cats were fed the diet with either TAG or DAG oil for 8 d. The dietary fat source was crossed-over and presented for 8 d more. Non-fasting serum concentrations of TAG, cholesterol and NEFA were measured on days 6-8 and days 14-16. Dietary fat source (DAG v. TAG) did not significantly affect food intake (491 (sem 16) v. 486 (sem 14) kJ/kg0.67), body weight or serum concentrations (mmol/l) of TAG (37.1 (sem 4.5) v. 33.9 (sem 3.4)), cholesterol (4.8 (sem 0.3) v. 4.8 (sem 0.2)) and NEFA (1.4 (sem 0.2) v. 1.4 (sem 0.2)). The results show that for a feeding trial of 8 d, DAG oil was well accepted and tolerated by cats but did not reduce hypertriacylglycerolaemia resulting from a deficiency of LPL catalytic activity.

One-year ad libitum consumption of diacylglycerol oil as part of a regular diet results in modest weight loss in comparison with consumption of a triacylglycerol control oil in overweight Japanese subjects.

OBJECTIVE: The objective of this study was to investigate the effect of 1-year ad libitum consumption of diacylglycerol oil on body weight and serum triglyceride in Japanese men and women. DESIGN/SUBJECTS/INTERVENTION: In a 1-year double-blind, placebo-controlled parallel trial with clinic visits at month 0, 3, 6, 9, and 12, a total of 312 Japanese men (n=174) and women (n=138) (aged 22 to 73 years) with body mass index (calculated as kg/m(2)) > or =25 and/or fasting serum triglyceride level > or =150 mg/dL (1.70 mmol/L) (aged 22 to 73 years) were randomly assigned to the diacylglycerol (n=155) or triacylglycerol (n=157) group. Participants substituted their usual home cooking oil with the assigned test oils. MAIN OUTCOME MEASURES: Changes in anthropometrics and serum triglyceride level were monitored at 3-month intervals across a 12-month period. RESULTS: In the intention-to-treat analysis, body weight decreased significantly in the diacylglycerol group when compared to the triacylglycerol group (P=0.013). Changes in body weight and body mass index during the study period differed between the two groups by 0.87 kg (P=0.002) and 0.32 kg (P=0.002), respectively. Participants with higher initial body mass index or greater percentage of total fat intake as diacylglycerol exhibited greater reduction in body weight. Total energy intake and physical activity were not significantly different between the groups during the study. Serum triglyceride levels decreased significantly from values in individuals with hypertriglyceridemia, but did not differ between groups. CONCLUSIONS: Modest body weight reduction was observed after 1-year ad libitum consumption of diacylglycerol oil as part of a regular diet in comparison to that of triacylglycerol oil; weight loss was greatest in participants who were obese at baseline. The weight reduction observed in diacylglycerol group was attributed to the substitution of usual home cooking oil with diacylglycerol, because total energy intake and physical activity did not differ between groups.

Diacylglycerol oil for the metabolic syndrome.

Excess adiposity has been shown to play a crucial role in the development of the metabolic syndrome. The elevated fasting and postprandial triglyceride-rich lipoprotein levels is the central lipid abnormality observed in the metabolic syndrome. Recent studies have indicated that diacylglycerol (DAG) is effective for fasting and postprandial hyperlipidemia and preventing excess adiposity by increasing postprandial energy expenditure. We will here discuss the mechanisms of DAG-mediated improvements in hyperlipidemia and in postprandial energy expenditure, and effects of DAG oil on lipid/glucose metabolism and on body fat. Further, the therapeutic application of DAG for the metabolic syndrome will be considered.

Effects of phytosterols in diacylglycerol as part of diet therapy on hyperlipidemia in children.

BACKGROUND: The incidence of hyperlipidemia in children is increasing in Japan, but drug therapy for such children is limited. The ingestion of 4% phytosterols-containing diacylglycerol (PS/DAG) decreases serum total cholesterol and low density lipoprotein cholesterol (LDL-C) concentrations in adults. In the present study, we examined the effect of PS/DAG as part of a diet therapy in pediatric patients with hyperlipidemia. METHODS: Pediatric patients with hyperlipidemia with > or =5.18mmol (200 mg/dL) serum total cholesterol and/or >or =1.70mmol (150 mg/dL) triglycerides (N=22) ingested bread containing PS/DAG (total daily intake, 10g) for 6 months. Blood chemistry was examined prior to and 2, 4, 6 months after the initiation of ingestion, and 4 months after the ingestion period. RESULTS: No significant differences in energy intake or cholesterol intake during the study period were found. After 4 months of ingestion of PS/DAG, LDL-C, lipoprotein(a) [ Lp(a)], free fatty acids and total ketone bodies decreased significantly. In seven patients with familial hypercholesterolemia, total cholesterol and remnant-like lipoprotein particles (RLP)-cholesterol also significantly decreased in addition to LDL-C and Lp(a). CONCLUSIONS: PS/DAG improves serum lipid metabolism in pediatric patients with hyperlipidemia for whom drug therapy is limited, suggesting that PS/DAG may reduce the risk of developing various diseases induced by hyperlipidemia.

Effects of diacylglycerol oil on adiposity in obese children: initial communication.

Several studies have shown that diacylglycerol (DAG) oil may suppress accumulation of body fat in adults compared to triacylglycerol (TAG) oil. In this study, we investigated the effect of DAG oil as part of dietetic therapy in obese children. The participants were 11 male and female obese children who were under treatment at the outpatient clinic (four boys, seven girls, age: 7-17 years old). Daily-use cooking oil was changed to DAG oil, and the effects on abdominal fat areas, adipocytokines, and serum lipids were investigated. The total and subcutaneous fat areas significantly decreased in the 5th month after ingestion of DAG oil. Leptin was significantly lower than the initial level after ingestion of DAG oil. The ingestion of DAG oil decreased both the abdominal fat area and leptin in obese children, suggesting that DAG oil prevents obesity in children as well as in adults.

Serum retinol, alpha-tocopherol, and beta-carotene levels are not altered by excess ingestion of diacylglycerol-containing plant sterol esters.

BACKGROUND: Diacylglycerol (DAG) suppresses the postprandial increase in serum triglycerides, and has antiobesity effects. On the other hand, plant sterol esters (PSE) lower serum cholesterol levels in hypercholesterolemia. Thus, DAG-containing PSE (PSE/DAG) would be expected to maintain an appropriate serum cholesterol level and decrease the risk of arteriosclerotic disorders. Several recent studies, however, report negative effects of PSE on serum fat-soluble (pro)vitamin levels. The objective of this study was to investigate the effect of PSE/DAG on serum retinol, beta-carotene, and alpha-tocopherol levels using a threefold excess of the effective dose obtained in our previous study. METHODS: A randomized placebo-controlled double-blind parallel study was performed in healthy and mildly hypercholesterolemic subjects, in which the subjects ingested 1.2 g PSE/30 g DAG for 2 weeks in the form of mayonnaise-type products. Triacylglycerol (TAG) mayonnaise was used as a control. RESULT: There were no subjective adverse effects or changes in serum retinol, alpha-tocopherol, and beta-carotene levels, abdominal symptoms, hematologic values, or blood biochemical values. CONCLUSION: Ingestion of a threefold excess of PSE/DAG for 2 weeks had no adverse effects compared to ingestion of conventional TAG mayonnaise.

Weight loss effect of dietary diacylglycerol in obese dogs.

Obesity in dogs and cats have been increasingly recognized in recent years. Because obesity underlies various diseases, pet owners and veterinarians have an important responsibility to help animals lose weight and maintain their health. Diet therapy, however, is typically based on limited calorie intake and animals may suffer stress from hunger and this is also a concern to animal owners. For this reason, many clients drop out of weight control programmes. In the present study, we focused on dietary diacylglycerol (DAG) as a potentially effective ingredient for canine weight control without caloric restriction. We replaced a portion of the fat in dog food with either DAG or triacylglycerol (TAG), referred to as DAG or TAG diets here, and fed overweight beagle dogs (body condition score of 4 or higher) with either the DAG or TAG diet for a 6-week period. Results indicated that, even though the food composition other than fat type were identical, dogs fed the DAG diet showed a statistically significant reduction in body weight averaging a 2.3% reduction within 6 weeks while the TAG-fed dogs maintained their obese body weights. In addition, the DAG group also showed a reduction in body fat content, serum triglyceride and total cholesterol concentrations. These results suggest the possibility of developing a pet food using DAG to control weight and serum lipid levels without compromising caloric intake.

Dose-dependent cholesterol-lowering effect of a mayonnaise-type product with a main component of diacylglycerol-containing plant sterol esters.

OBJECTIVE: The objective of this study was to investigate the effective dose of plant sterol ester (PSE)-enriched diacylglycerol (DAG) oil for healthy subjects with mild hypercholesterolemia. METHODS: A randomized, placebo-controlled, double-blind, parallel study was performed in patients with mild hypercholesterolemia; 0.0, 0.3, 0.4, and 0.5 g of PSE was dissolved in 15 g of a DAG-containing mayonnaise-type product; and 15 g/d of the product was administered 4 wk. RESULTS: Total serum cholesterol levels were significantly decreased as a result of the ingestion of at least 0.4 g/d of PSE, and serum low-density lipoprotein cholesterol levels were significantly decreased by the ingestion of at least 0.3 g/d of PSE. CONCLUSIONS: Daily ingestion of 15 g of DAG plus mayonnaise containing at least 0.4 g/d of PSE for 4 wk may significantly decrease cholesterol.

Diacylglycerol: efficacy and mechanism of action of an anti-obesity agent.

Obesity is at the forefront of global health issues and directly contributes to many chronic illnesses. Several dietary components show promise in the treatment of obesity, one of which is oil rich in diacylglycerols (DAGs). Present objectives are to examine scientific knowledge concerning DAG to assess evidence supporting the effects on substrate oxidation rates, body weight and fat mass, and blood lipids, and to assess safety, as well as elucidate potential mechanisms of action. DAG can be synthesized by an enzymatic process to produce mainly 1,3-isoform DAG. This 1,3-DAG oil is believed to have the ability to increase beta-oxidation, to enhance body weight loss, to suppress body fat accumulation, and to lower serum triacylglycerol levels postprandially. While certain animal and human studies indicate that consumption of 1,3-DAG has positive physiological effects, others report no effect. The mechanisms of action of DAG are suggested to decrease the resynthesis of chylomicrons as well as shunting them directly to the liver through the portal vein, where they are oxidized. This increased fat oxidation may influence control of food intake by increasing satiety. Further study into the precise mechanism is required to understand its effects. Safety studies show no risks in consuming a diet rich in DAG oil. Overall, consumption of oils with higher amounts of DAG, specifically 1,3-DAG, may be useful in the battle against obesity.

Dietary diacylglycerol reduces postprandial hyperlipidemia and ameliorates glucose intolerance in Otsuka Long-Evans Tokushima Fatty (OLETF) rats.

OBJECTIVE: The aim of the present study was to determine the effects of dietary diacylglycerol (DG) on the metabolism of lipids and glucose in type II diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats. METHODS: In experiment 1, the rats were orally administered 10 mL/kg of a triacylglycerol (TG) or DG emulsion (15% [w/v] oil), and the subsequent changes in the serum lipid levels were compared. In experiment 2, the rats were fed diets containing 15% DG or TG oil. After 22 weeks, the serum levels of lipids, glucose, and cytokines were determined. In addition, an oral glucose tolerance test (OGTT) was performed on the rats. RESULTS: Administration of an oral fat load caused marked hypertriglyceridemia with a peak at 2 h. Oral DG loading reduced the serum TG increase; the difference between the groups was significant at 4 and 6 h (P < 0.05). Diacylglycerol also markedly reduced the serum free fatty acid concentration increase due to the fat load. After 22 weeks of feeding, dietary DG reduced serum TG levels in the non-fasting state. Moreover, an OGTT revealed enhanced glucose disposal in the DG-fed rats compared with the TG-fed rats. Serum levels of adiponectin, an important insulin-sensitizing adipocytokine, were higher in the DG-fed rats than in the TG-fed rats (P < 0.05). In addition, DG-feeding reduced serum levels of C-reactive protein, a cardiovascular risk factor (P < 0.05). CONCLUSION: These results suggested that dietary DG improves lipid metabolism and glucose tolerance, and retards the progress of diabetes mellitus in OLETF rats.

Diacylglycerol-induced protection against injury during ischemia and reperfusion in the rat heart: comparative studies with ischemic preconditioning.

The role of protein kinase C (PKC) activation in ischemic preconditioning remains controversial. Since diacylglycerol is the endogenous activator of PKC and as such might be expected cardioprotective, we have investigated whether: (i) the diacylglycerol analog 1,2-dioctanoyl-sn-glycerol (DOG) can protect against injury during ischemia and reperfusion; (ii) any effect is mediated via PKC activation; and (iii) the outcome is influenced by the time of administration. Isolated rat hearts were perfused with buffer at 37 degrees C and paced at 400 bpm. In Study 1, hearts (n=6/group) were subjected to one of the following: (1) 36 min aerobic perfusion (controls); (2) 20 min aerobic perfusion plus ischemic preconditioning (3 min ischemia/3 min reperfusion+5 min ischemia/5 min reperfusion); (3) aerobic perfusion with buffer containing DOG (10 microM) given as a substitute for ischemic preconditioning; (4) aerobic perfusion with DOG (10 microM) during the last 2 min of aerobic perfusion. All hearts then were subjected to 35 min of global ischemia and 40 min reperfusion. A further group (5) were perfused with DOG (10 microM) for the first 2 min of reperfusion. Ischemic preconditioning improved postischemic recovery of LVDP from 24+/-3% in controls to 71+/-2% (P < 0.05). Recovery of LVDP also was enhanced by DOG when given just before ischemia (54+/-4%), however, DOG had no effect on the recovery of LVDP when used as a substitute for ischemic preconditioning (22+/-5%) or when given during reperfusion (29+/-6%). In Study 2, the first four groups of study were repeated (n=4-5/group) without imposing the periods of ischemia and reperfusion, instead hearts were taken for the measurement of PKC activity (pmol/min/mg protein+/-SEM). PKC activity after 36 min in groups (1), (2), (3) and (4) was: 332+/-102, 299+/-63, 521+/-144, and 340+/-113 and the membrane:cytosolic PKC activity ratio was: 5.6+/-1.5, 5.3+/-1.8, 6.6+/-2.7, and 3.9+/-2.1 (P=NS in each instance). In conclusion, DOG is cardioprotective but under the conditions of the present study is less cardioprotective than ischemic preconditioning, furthermore the protection does not appear to necessitate PKC activation prior to ischemia.

Effect of diacylglycerols on osteoclastic bone resorption.

We studied the effect of various synthetic diacylglycerols (DAGs) on bone resorption by rat and chick osteoclasts. 1-stearoyl-2-arachidonoyl-sn-glycerol (DAG IV), at a concentration of 100 microM, caused a significant reduction in resorption pit number in both species at 6 and 24 hours without any toxic effect. Over a 6-hour incubation period, a significant inhibition was seen at 10 and 100 microM in both species. 1,2-dioctanoyl-sn-glycerol (DAG I) and 1,2-dihexanoyl-sn-glycerol (DAG III) caused a marked inhibition of resorption by rat osteoclasts at 6 hours, but there was recovery of bone-resorptive ability over a 24-hour incubation period. DAGs with the -rac conformation failed to have any effect on bone resorption. In time-lapse video studies, osteoclast motility was not influenced by any of the DAGs at any of the concentrations used. Our results indicate that DAGs with the -sn conformation inhibit bone resorption, and DAGs with the -rac conformation do not. The finding that DAGs, the physiological activators of protein kinase C (PKC), inhibit bone resorption provides further evidence for an important role of the PKC pathway in the regulation of osteoclast activity.