N. Claassen

Supplemented Gamma-Linolenic Acid and Eicosapentaenoic Acid Influence Bone Status in Young Male Rats: Effects on Free Urinary Collagen Crosslinks, Total Urinary Hydroxyproline, and Bone Calcium Content

The effect of different ratios of the prostaglandin precursors gamma-linolenic (GLA) and eicosapentaenoic (EPA) acids on bone status in growing rats measured as a function of free urinary pyridinium crosslinks and hydroxyproline levels was investigated. Male Sprague-Dawley rats were weaned onto an essential fatty acid deficient diet and from their fifth week, different groups of rats received a balanced, semisynthetic diet, supplemented with different ratios of GLA:EPA supplied as a mixture of evening primrose oil (EPO) and fish oil (FO). Controls were supplemented with linoleic (LA; sunflower oil) and alpha-linolenic (ALA; linseed oil) acids (3:1) or a commercially available rat chow. Animals were terminated at 84 days and femur length, ash weight, calcium content, free urinary pyridinium crosslinks (Pyd and Dpyd), total hydroxyproline (Hyp), and creatinine levels measured. Free urinary Pyd and Dpyd are good indicators of bone status and they correlated well with Hyp. Pyd and Dpyd excretion were significantly decreased in the higher GLA:EPA dietary groups and correlated well (r = 0.7) with Hyp levels. Concomitantly, bone calcium content increased significantly in the same dietary groups. These results suggest that diet supplementation with relatively high GLA:EPA ratios are more effective in inhibiting bone resorption than LA:ALA.

The effect of different n-6 n-3 essential fatty acid ratios on calcium balance and bone in rats

Prostaglandins (PGs) are known to have various effects on bone metabolism. The supplementation of essential fatty acids (EFAs), the precursors of PGs, leads to increased intestinal calcium absorption and calcium balance. It is, however, not known whether increased calcium absorption and calcium balance will enhance the calcium content in bone. Male Sprague-Dawley rats (n = 40) aged 5-12 weeks were supplemented with EFAs. The main dietary EFAs, linoleic acid (LA) and alpha-linolenic acid (ALA) were administered in a ratio of 3:1 as a control group. The conversion of LA to ALA to the PG precursors is slow, with the first step, delta-6-desaturation being rate limiting. Fatty acids beyond this rate-limiting step, gamma-linolenic acid (GLA, n-6) and eicoapentaenioc acid (EPA, n-3), were administered to different groups in the ratios 3:1, 1:1 and 1:3 to explore the impact of different ratios of n-6 and n-3 EFAs. Intestinal calcium absorption (mg/24 h) increased by 41.5% in the 3:1 supplemented group, compared with the control group. The decrease in urinary calcium (mg/24 h) correlated with the increase in n-3 level. The calcium balance (mg/24 h) and bone calcium (mg/g bone ash) increased significantly in the 3:1 (41.5% and 24.7%) group, compared with the control. The increase in bone calcium might be attributed to an EFA-induced increase in circulating PGs. An increased synthesis of PGs acting on target bone cells, as well as changes in membrane fluidity, may underlie these observations.

Omega-3 fatty acids modulate ATPases involved in duodenal Ca absorption

Dietary supplementation with fish oil that contains omega-3 polyunsaturated fatty acids has been shown to enhance bone density as well as duodenal calcium uptake in rats. The latter process is supported by membrane ATPases. The present in vitro study was undertaken to test the effect of omega-3 fatty acids on ATPase activity in isolated basolateral membranes from rat duodenal enterocytes. Ca-ATPase in calmodulin-stripped membranes was activated in a biphasic manner by docosahexanoic acid (DHA) (10-30 microg/ml) but not by eicosapentanoic acid (EPA). This effect was blocked partially by 0.5 microM calphostin (a protein kinase C blocker). DHA inhibited Na,K-ATPase (-49% of basal activity, [DHA]=30 microg/ml, P <0.01). This effect could be reversed partially by 50 microM genistein, a tyrosine kinase blocker. EPA also inhibited Na,K-ATPase: (-47% of basal activity, [EPA]=30 microg/ml, P <0.01), this effect was partially reversed by 100 microM indomethacin, a cyclo-oxygenase blocker. Omega-3 fatty acids are thus involved in multiple signalling effects that effect ATPases in BLM.

Eicosapentaenoic acid and docosahexaenoic acid supplementation increases calcium balance

Sprague Dawley rats were supplemented with either fish oil, evening primrose oil or sunflower oil (control) for 12 weeks. Calcium balance and fatty acid analyses of plasma and intestinal membranes were performed at week 12. Fish oil decreased faecal calcium excretion significantly leading to an increased calcium balance (p < 0.05). Increased unsaturation of the intestinal membranes in the fish oil group may facilitate calcium absorption.

Ectopic calcification of rat aortas and kidneys is reduced with n-3 fatty acid supplementation

Supplementation with essential fatty acids has been shown to prevent the experimentally induced ectopic calcification of the kidneys known as nephrocalcinosis. Male Sprague-Dawley rats were fed a semi-synthetic diet supplemented with different essential fatty acids while being injected for a period of 10 days with calcium glubionate. After 3 weeks their kidneys and aorta were removed and the respective calcium content measured compared to the control, saline injected animals. Lipoic acid-EPA, fish oil (EPA rich) as well as the EPA monoester reduced the calcium concentration of both the kidneys and the aorta towards control values. Lipoic-EPA was the best absorbed of the three compounds and its combination of anti-oxidant together with EPA lowered the calcium content of both the aortas and the kidneys.

Effect of arachidonic acid on duodenal enterocyte ATPases.

Duodenal ion transport processes are supported by ATPase enzymes in basolateral membranes of the enterocyte. In vivo studies have shown that long term n-6 poly-unsaturated fatty acid (PUFA) supplementation in rats causes increases in intestinal Ca absorption, coupled with a higher total calcium balance and bone calcium content. The present in vitro study was undertaken to test the effect of arachidonic acid (AA), a highly unsaturated (and thus physiologically potent) member of the n-6 PUFA family, on ATPases in enterocyte basolateral membranes isolated with a sorbitol density gradient procedure. This paper presents results which show that AA inhibits Na+,K+-ATPase in a dose-dependent manner (-67% of basal activity at a concentration of 30 microg/ml, P < 0.005) but that this effect is not mediated by protein kinase C, as shown by the use of the protein kinase C blocker calphostin (0.5 microM). Indomethacin (IDM) at 0.1 mM, a cyclo-oxygenase blocker, could also not reverse the inhibitory effect of AA on Na+,K+-ATPase. Ca2+-ATPase, on the other hand, is not affected significantly (-10%, P > 0.05) by arachidonic acid at 30 microg/ml.

The evaluation of aspects of the chain of survival at gymnasiums in the Pretoria area

Abstract Background Sudden cardiac death related to exercise is an uncommon problem, but is perhaps the single biggest challenge to sports medicine practitioners. Although the overall risk of death due to cardiac causes is substantially reduced in those who exercise regularly, the risk is temporarily increased during exercise. The causes of sudden cardiac death related to exercise vary according to age and are divided into two groups. Firstly, those under 35 years, where structural abnormalities of the heart pose a risk. The most common congenital abnormality is hypertrophic cardiomyopathy (HOCM), which occurs in up to two per 1 000 births. Secondly, those above 35 years, where coronary artery disease is the leading cause of sudden cardiac deaths. The most frequent initial rhythm documented in witnessed cardiac arrest is ventricular fibrillation (VF). The most effective treatment for VF is defibrillation. The probability of successful defibrillation decreases by approximately seven to 10 percent for every minute that defibrillation is delayed. VF tends to convert to asystole within a few minutes if left untreated. No matter what the setting—home, community or hospital—the majority of successful adult resuscitations depend on early defibrillation.5 Public education and training are crucial aspects of any effort to reduce cardiac death. Because the majority of sudden cardiac deaths occur outside the hospital, it is clear that the community must be recognised as the ‘ultimate coronary care unit’. Communities with a high number of lay persons trained in life-saving techniques such as cardiopulmonary resuscitation (CPR) and the use of automated external defibrillators (AEDs) may achieve resuscitation rates as high as 49% for patients with a documented out-of-hospital VF. CPR is a critical component of BLS (basic life support). Prompt bystander CPR is crucial to all resuscitation efforts. In the absence of prompt bystander CPR, successful resuscitation of out-of-hospital cardiac arrest victims is unlikely, despite the availability of trained paramedics with a rapid response time. CPR performed while waiting for defibrillation appears to prolong VF and contribute to the preservation of heart and brain function. The purpose of the study was to evaluate aspects of the chain of survival in gymnasiums in the Pretoria area. This chain of survival was evaluated against the Basic Life Support (BLS) system known in cardiac resuscitation. Methods Twelve gymnasiums in the Pretoria area were included in the study. A structured questionnaire was given to a staff member of each gymnasium after explanation of the purpose of the study. Results Of the gymnasiums visited, 83% had emergency telephone numbers at hand, while 100% of the staff had CPR training (75% in the last year). Half of the gymnasiums visited had automated external defibrillators (AEDs) available and the staff members at the respective gymnasiums had been trained in the use thereof. Conclusion The partaking gymnasiums in the Pretoria area are well prepared for cardiac emergencies. It is recommended that fitness instructors, medical practitioners and the general public working out in gymnasiums be familiar with the chain of survival, especially how to operate an AED.