Long-term effect of dietary α-linolenic acid or decosahexaenoic acid on incorporation of decosahexaenoic acid in membranes and its influence on rat heart in vivo

Abstract

The present study was designed to evaluate whether long-term intake of dietary alpha-linolenic acid (ALA), supplied as whole grain-extruded linseed, can increase endogenous production of n-3 long-chain polyunsaturated fatty acids (FAs) in healthy adult rats and influence the heart rate (HR) and adrenergic response in the same way as docosahexaenoic acid (DHA)-rich diets. DHA enrichment was evaluated using FA analysis of tissue phospholipids after 8, 16, 24, and 32 wk of feeding in male Wistar rats randomly assigned to three dietary groups (n = 8 in each group): a reference fat diet (RFD), an ALA-rich (ALA) diet, and a DHA-rich (DHA) diet. At 1 wk before the animals were killed, under anesthesia, HR was measured from ECG recordings during an adrenergic stimulation challenge (n = 8). There was a significant increase of DHA in the cardiac membrane in the ALA group compared with the RFD group. DHA content in the cardiac membrane was approximately 10% in the ALA group vs. 20% in the DHA group and 4% in the RFD group. The cardiac FA profile was established after 2 mo and remained essentially unchanged thereafter. Regardless of the diet, DHA in the heart decreased with age. Nevertheless, DHA content in the heart remained at >15% in the DHA group and remained greater in older rats fed the ALA diet than in younger RFD-fed rats. Basal HR decreased in the ALA group (395 +/- 24.9 beats/min) to a level between that of the DHA and RFD groups (375 +/- 26.4 and 407 +/- 36.7 beats/min, respectively). Both n-3 dietary intakes contribute to enhancement of the chronotropic response to adrenergic agonist stimulation. Regulation of HR by neurohumoral mediators may be controlled by lower content of DHA, e.g., by a dietary supply of extruded linseed (ALA).

Rat heart cannot synthesize docosahexaenoic acid from circulating α-linolenic acid because it lacks elongase-2

“…Dietary a-LNA has been investigated with regard to prevention of cardiovascular disease (58)(59)(60). Dietary a-LNA can reduce cardiac arrhythmias and heart rate in rats, although less effectively than dietary EPA or DHA (58,61).…”

“…Dietary a-LNA can reduce cardiac arrhythmias and heart rate in rats, although less effectively than dietary EPA or DHA (58,61). We do not know the rate of DHA consumption by the heart, but now know that liver conversion of dietary a-LNA to DHA can maintain the heart DHA concentration in the absence of dietary DHA (31,32).…”

Dietary fatty acids alter left ventricular myocardial gene expression in Wistar rats

“…Previous work revealed that male Wistar rats fed PUFA-enriched diets had stable myocardial fatty acid compositions after 2 months of treatment. [12] A dietary treatment duration of 12 weeks was used in an effort to produce LVH while limiting the development of comorbidities. Food intake and body weights were measured twice weekly.…”

Mechanisms underlying the cardioprotective effects of omega-3 polyunsaturated fatty acids

“…Premenopausal women exhibit a better efficiency for the conversion of ALA to EPA than those found in postmenopausal women and in men. In rats, maximum incorporation of less than 1% ALA was shown to accumulate in cardiac PL within 8 weeks of a 32-week feeding study with 15.8 g of ALA/kg diet [67].…”