Biomedical subjects

A Petridou

Publications and source records attributed to A Petridou.

8 recordsLinked to original sources

PubMed2006

Does the intensity of an exercise programme modulate body composition changes?

Exercise training is a useful component of weight maintenance programmes. Although energy expenditure, not intensity or duration, seems to determine the amount of weight loss attributable to exercise, it is not clear whether changes in the components of body mass are also insensitive to these parameters. Thus, the aim of the present study was to compare the effect of two isoenergetic exercise training programmes, one of low and one of high intensity, on body composition. Fourteen healthy premenopausal untrained women were divided into two equivalent groups, which exercised on treadmill at 45 or 72 % of V(O2max) four times a week for three months, spending 1548 kJ (370 kcal) per exercise session. No dietary intervention was applied. Body mass decreased significantly in both groups but more in the low-intensity than the high-intensity group (by mean +/- SD, 3.3 +/- 1.3 vs. 1.9 +/- 0.9 kg, p = 0.032). The decrease in fat mass was significant in both groups (3.1 +/- 1.2 vs. 2.4 +/- 1.5 kg, respectively) but not significantly different between them. Fat-free mass did not change significantly in either group, although the difference between groups tended to be significant (decrease by 0.2 +/- 0.7 kg in the low-intensity group vs. increase by 0.5 +/- 0.6 kg in the high-intensity group, p = 0.058). In conclusion, exercise training at 45 % of V(O2max) without dietary restriction produced a higher weight loss than at 72 % of V(O2max), whereas the higher intensity tended to maintain fat-free mass, possibly, in part, through the smaller weight loss. Thus, both programmes may prove useful in eliciting favourable changes depending on which target (weight loss or maintenance of fat-free mass) is of higher priority.

Adult↗

PubMed2006

Mitochondrial phospholipids of rat skeletal muscle are less polyunsaturated than whole tissue phospholipids: implications for protection against oxidative stress.

The fatty acid composition of phospholipids is an important determinant of membrane function. Although the mitochondria play a pivotal role in skeletal muscle function, the fatty acid composition of their individual phospholipids has not been examined. The purpose of this study was to determine the fatty acid profile of each phospholipid in rat skeletal muscle mitochondria and compare it with that of the whole muscle. Lipids were extracted from the gastrocnemius muscles of 10 Wistar rats, and phospholipids were separated by thin-layer chromatography. The fatty acid composition of each phospholipid was then determined by gas chromatography. The same procedure was applied to a mitochondrial preparation from these muscles. We found that the fatty acid composition of the individual mitochondrial phospholipids (phosphatidyl choline, phosphatidyl ethanolamine, cardiolipin, phosphatidyl inositol, phosphatidyl serine, sphingomyelin, and lysophosphatidyl choline) and of the total mitochondrial phospholipids differed markedly (P < 0.05) from the fatty acid composition of the corresponding whole muscle phospholipids. Notably, the mitochondrial phospholipids had higher percentages of MUFA [13.9 (2.1) vs. 10.3 (0.9)] and lower percentages of PUFA [34.8 (4.3) vs. 39.5 (5.2)] and n6 fatty acids [25.0 (2.5) vs. 27.6 (2.5)]. Overall, the mitochondrial phospholipids had a lower unsaturation index than whole muscle phospholipids [135 (20) vs. 161 (26)]. Because PUFA are susceptible to peroxidation, unlike saturated fatty acids and MUFA, we propose that the low polyunsaturation of mitochondrial phospholipids is the result of selective pressure toward membranes that are more resistant to oxidative damage by reactive oxygen species produced in their vicinity. The negative effect of the low polyunsaturation on membrane fluidity may be counterbalanced by the higher percentage of MUFA and the known low cholesterol content of mitochondrial membranes.

Animal Feed↗

PubMed2006

Assessment of brown adipose tissue activity in rats by 99mTc-sestamibi uptake.

Brown adipose tissue (BAT) physiology and imaging have recently attracted considerable attention. BAT is characterized both by enhanced perfusion and increased mitochondrial activity. (99m)Tc-sestamibi is a lipophilic cationic tracer that concentrates in mitochondria. Data on the accumulation of (99m)Tc-sestamibi in BAT are currently lacking. This study investigates the in vivo (99m)Tc-sestamibi uptake in rat BAT. (99m)Tc-sestamibi was administered in male Wistar rats of various age and body size. (99m)Tc-sestamibi uptake was measured in vitro in BAT and white fat (WF) together with cytochrome c oxidase activity. Both (99m)Tc-sestamibi uptake and cytochrome c oxidase activity were higher in BAT than in WF (P<0.05). (99m)Tc-Sestamibi uptake in both BAT and WF was negatively related to body weight (r = -0.96 and -0.89, respectively) as was the BAT/WF uptake ratio (r = -0.85). These data show a higher (99m)Tc-sestamibi uptake in BAT compared to WF, in agreement with the high mitochondrial content and respiratory activity of the former. The strong negative correlation between (99m)Tc-sestamibi uptake in BAT and body weight (negative allometry), is in accordance to increased needs of thermogenesis in smaller animals. Implications of increased (99m)Tc-sestamibi uptake in BAT in radionuclide imaging are also discussed.

Adipose Tissue, Brown↗

PubMed2005

Comparison of the phospholipid and triacylglycerol fatty acid profile of rat serum, skeletal muscle and heart.

Although several studies have analyzed the fatty acid profile of phospholipids (PL) and, to a lesser degree, triacylglycerols (TG) in one or more tissues concurrently, a systematic comparison of the fatty acid composition of different tissues and/or lipid classes is lacking. The purpose of the present study was to compare the fatty acid composition of major lipid classes (PL and TG) in the rat serum, soleus muscle, extensor digitorum longus muscle and the heart. Lipids were extracted from these tissues and analyzed by a combination of thin-layer chromatography and gas chromatography. We found many significant differences in various tissues and lipid classes. Serum had the most distinct fatty acid profile in PL but this "uniqueness" was less apparent in TG, where differences among tissues were in general less frequent than in PL. These two skeletal muscles exhibited similar fatty acid composition in both lipid classes despite their different muscle fiber type composition, denoting that fiber type is not a major determinant of the fatty acid composition of rat skeletal muscle. The fatty acid profile of heart PL was the most different from that of the other tissues examined. PL were rich in polyunsaturated fatty acids, whereas TG were rich in monounsaturated fatty acids. Although the reasons for the differences in fatty acid profile among the tissues examined are largely unknown, it is likely that these differences have an impact upon numerous biological functions.

Acetyltransferases↗

PubMed2004

Effect of prior exercise on lipemia after a meal of moderate fat content.

OBJECTIVE: Prior exercise has been repeatedly shown to reduce lipemia after meals of exaggerated fat content (over 60% of total energy). The aim of the present study was to investigate whether the same applies to meals closer to the composition of the typical Western diet and explore whether exercise affects the release of dietary fat into the bloodstream. DESIGN: Randomized counterbalanced. SETTING: Laboratory. SUBJECTS: Nine healthy young male volunteers. INTERVENTION: Subjects consumed a meal of moderate fat content (35% of total energy, 0.66 g/kg body mass) 14 h after having either cycled for 1 h at 70-75% of maximal heart rate or rested. Macadamia nuts were used as the main source of dietary fat to trace its entry into the circulation because of their unusual fatty acid composition. Blood samples were drawn before the meal and for 8 h postprandially. RESULTS: Plasma triacylglycerol concentrations and total area under the triacylglycerol concentration vs time curve (AUC) were significantly lower after exercise (P = 0.001 and 0.003, respectively; effect size for the latter, 0.84). However, incremental (above baseline) AUC was not affected by exercise significantly. When controlling for differences in baseline plasma concentrations, only the fatty acids that were more abundant in the meal than in plasma triacylglycerols were decreased in the early postprandial period following exercise, implying either a suppressive effect of exercise on the rate of triacylglycerol release from the intestine or a more rapid chylomicron clearance after meal consumption. CONCLUSIONS: Exercise performed between 15 and 14 h before a meal of moderate fat content reduced postprandial lipemia, mainly by lowering fasting triacylglycerols. The effect of exercise on postprandial triacylglycerol metabolism may be mediated, at least in part, by attenuated release of dietary fat from the intestine.

Adult↗

PubMed2004

Effect of chronic wheel running on the fatty acid composition of phospholipids and triacylglycerols in rat serum, skeletal muscle and heart.

AIM: The purpose of this study was to examine the effects of long-term wheel running on the fatty acid composition of phospholipids (PL) and triacylglycerols (TG) in rat serum, skeletal muscle (soleus and extensor digitorum longus) and heart. METHODS: To this end, the relevant tissues of 11 trained male Wistar rats were compared with those of 14 untrained ones. RESULTS: There were several significant differences between the two groups regarding the concentrations and percentages of individual fatty acids in serum PL and TG, with most differences appearing in the fatty acid distribution of PL. Monounsaturated fatty acids of muscle PL were significantly lower in the trained rats. Estimated elongase activity was significantly higher, whereas Delta(9)-desaturase activity was significantly lower in the trained muscles. Monounsaturated fatty acids of PL were also significantly lower in the trained hearts. The fatty acid composition of PL in the skeletal muscles and the heart adapted to training in a comparable manner, whereas most of the changes in the fatty acid profile of TG were tissue-dependent. Judging from the magnitude of the effect sizes and the percentage differences between trained and untrained animals, there were many large effects of chronic exercise on the fatty acid composition of the tissues examined. CONCLUSION: Long-term wheel running modified the fatty acid profile of PL and TG in rat serum, skeletal muscle and heart, and could thus be considered as a modulator of tissue fatty acid composition.

Animals↗

PubMed2003

Hematologic and biochemical profile of juvenile and adult athletes of both sexes: implications for clinical evaluation.

The aim of the present study was to compare the values of seventeen hematologic and biochemical parameters between juvenile and adult athletes and non-athletes of both sexes. 579 athletes and 241 non-athletes participated in the study. We measured packed-cell volume, hemoglobin, red blood cell count, white blood cell count, platelet count, iron, glucose, urea, triacylglycerols, total cholesterol, high-density lipoprotein cholesterol, total/high-density lipoprotein cholesterol ratio, calcium, magnesium, creatine kinase, as well as alanine and aspartate aminotransferases. We found significant differences according to age, sex, and physical activity in the majority of the parameters. The effect size of physical activity on most parameters was small (< 0.5); however, that on packed-cell volume, glucose, urea, calcium, magnesium, and creatine kinase was moderate to high (0.5 to 0.8). It is remarkable that three of the highest effect sizes of physical activity appeared on parameters thought to be under tight homeostatic control (i. e., glucose, calcium, and magnesium). We conclude that physical training influences most of the biochemical parameters routinely measured in athletes, although, in some cases, its effect appears to be of limited biological importance. Therefore, clinical assessment on the basis of blood tests has to take into account not only the age and sex, but also the training status of individuals.

Adaptation, Physiological↗

PubMed2001

Effect of supplementation with conjugated linoleic acid on human serum lipids and body fat.

Conjugated linoleic acid (CLA) is a natural component of meat and dairy products with anticarcinogenic, fat lowering, antiatherogenic and anticatabolic activity in animals. The purpose of this study was to examine the effect of CLA supplementation to humans on body fat, certain biochemical parameters of serum, and the CLA content of serum lipids. Twenty-two volunteers were divided into a study group and a control group in a doubly blind design. The study group received 0.7 g of CLA for four weeks and 1.4 g of CLA for the next four weeks, while the control group received placebo. Diet was controlled and no significant differences in energy or macronutrient intake were found between the two groups. Measurements were taken at baseline, four weeks, and eight weeks. The sum of the thickness of ten skinfolds, percentage body fat calculated from it and fat mass was significantly reduced in the CLA group during the second period (P < 0.004) but not overall during the study. Serum HDL-cholesterol decreased significantly (P < 0.001) and triacylglycerols as well as total cholesterol tended to decrease in the CLA group during the first period. The CLA content of serum non-esterified fatty acids, triacylglycerols, phospholipids, and cholesteryl esters increased gradually with supplementation; the CLA content of total serum lipids doubled at the end of the study compared to baseline. Phospholipids had the highest CLA content regardless of supplementation. These data indicate that supplementation with 0.7-1.4 g CLA daily for 4-8 weeks may modulate body fat and serum lipids, as well as increase the CLA content of serum lipids in humans.

Journal Article↗