Dietary canola and soybean oil fed to SHRSP rat dams differently affect the growth and survival of their male pups

Fully hydrogenated canola oil extends lifespan in stroke-prone spontaneously hypertensive rats

Background

Canola oil (Can) and several vegetable oils shorten the lifespan of stroke-prone spontaneously hypertensive rats (SHRSP). Although similar lifespan shortening has been reported for partially hydrogenated Can, the efficacy of fully hydrogenated oils on the lifespan remains unknown. The present study aimed to investigate the lifespan of SHRSP fed diets containing 10 % (w/w) of fully hydrogenated Can (FHCO) or other oils.

Methods

Survival test: Upon weaning, male SHRSP were fed a basal diet for rodents mixed with one of the test oils —i.e., FHCO, Can, lard (Lrd), and palm oil (Plm) throughout the experiment. The animals could freely access the diet and drinking water (water containing 1 % NaCl), and their body weight, food intake, and lifespan were recorded.

Biochemical analysis test: Male SHRSP were fed a test diet with either FHCO, Can, or soybean oil (Soy) under the same condition, except to emphasize effects of fat, that no NaCl loading was applied. Soy was used as a fat source in the basal diet and was set the control group. Blood pressures was checked every 2 weeks, and serum fat levels and histological analyses of the brain and kidney were examined after 7 or 12 weeks of feeding.

Results

During the survival study period, the food consumption of FHCO-fed rats significantly increased (15–20 % w/w) compared with that of rats fed any other oil. However, the body weight gain in the FHCO group was significantly less (10–12 %) than that in the control group at 9–11 weeks old. The FHCO (> 180 days) intervention had the greatest effect on lifespan, followed by the Lrd (115 ± 6 days), Plm (101 ± 2 days), and Can (94 ± 3 days) diets. FHCO remarkably decreased the serum cholesterol level compared with Can and the systolic blood pressure from 12 to 16 weeks of age. In addition, while some rats in the Can group exhibited brain hemorrhaging and renal dysfunction at 16 weeks old, no symptoms were observed in the FHCO group.

Conclusion

This current study suggests that complete hydrogenation decreases the toxicity of Can and even prolongs the lifespan in SHRSP.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12944-021-01540-7.

Choice of diet impacts the incidence of stroke-related symptoms in the spontaneously hypertensive stroke-prone rat model

The spontaneously hypertensive stroke-prone (SHRSP) rat is a commonly used model of cerebrovascular disease and hypertension. SHRSP rats have been shown to develop stroke-related symptoms (SRS) by age 14 weeks when fed a purified diet, such as AIN-93G, supplemented with 1% NaCl. We conducted a pathology pilot study to compare the incidence of SRS in SHRSP rats fed either AIN-93G (with 1% NaCl in drinking water) or commercially available rat chow (with 4% NaCl in the diet), starting at 8 weeks of age. These results prompted us to analyze data from 5 earlier feeding trials using SHRSP rats. Overall, we found that SHRSP rats fed AIN-93G purified diet for 8 or 17 weeks did not demonstrate SRS (n = 18), whereas all SHRSP rats fed lab chow exhibited SRS at age 15.1 ± 0.6 weeks (n = 23). In addition, SHRSP rats fed lab chow had decreased mass gain starting at age 13 weeks, as well as decreased feed efficiencies after the first 5 weeks of feeding (p < 0.05). In conclusion, our data suggest that diet composition is a major contributor to the onset of stroke in SHRSP rats and that diet choice should be critically evaluated based on endpoint measures in the SHRSP model.

Testosterone-lowering activity of canola and hydrogenated soybean oil in the stroke-prone spontaneously hypertensive rat

Canola and some other types of oil unusually shorten the survival of stroke-prone spontaneously hypertensive rats (SHRSP), compared with soybean oil, perilla oil and animal fats. Since differential effects of canola and soybean oil on steroid hormone metabolism were suggested by a preliminary DNA microarray analysis as a reason for this, the steroid hormone levels in the serum and tissues of SHRSP fed different oils were investigated. The testosterone levels in the serum and the testes were found to be significantly lower in the canola oil group than in the soybean oil group, while no significant differences were detected in the corticosterone and estradiol levels in tissues. In a second experiment, it was found that hydrogenated soybean oil, with a survival-shortening activity comparable to that of canola oil, also decreased the testosterone level in testes to a similar degree. The testosterone-lowering activity of canola and hydrogenated soybean oil observed in SHRSP was considered in relation to other factors possibly affecting the physiology of SHRSP.

Hypertension induced by omega-3 polyunsaturated fatty acid deficiency is alleviated by alpha-linolenic acid regardless of dietary source

Omega-3 polyunsaturated fatty acid deficiency, particularly during the prenatal period, can cause hypertension in later life. This study examined the effect of different sources of alpha-linolenic acid (canola oil or flaxseed oil) in the prevention of hypertension and other metabolic symptoms induced by an omega-3 fatty acid-deficient diet. Dams were provided one of three experimental diets from 1 week before mating. Diets were either deficient (10% safflower oil-DEF) or sufficient (7% safflower oil+3% flaxseed oil-SUF-F; or 10% canola oil-SUF-C) in omega-3 fatty acids. The male offspring were continued on the maternal diet from weaning for the duration of the study. Body weight, ingestive behaviors, blood pressure, body composition, metabolic rate, plasma leptin and brain fatty acids were all assessed. The DEF animals were hypertensive at 24 weeks of age compared with SUF-F or SUF-C animals; this was not evident at 12 weeks. These results suggest that different sources of ALA are effective in preventing hypertension related to omega-3 fatty acid deficiency. However, there were other marked differences between the DEF and, in particular, the SUF-C phenotype including lowered body weight, adiposity, leptin and food intake in SUF-C animals. SUF-F animals also had lower, but less marked reductions in adiposity and leptin compared with DEF animals. The differences observed between DEF, SUF-F and SUF-C phenotypes indicate that body fat and leptin may be involved in omega-3 fatty acid deficiency hypertension.

Dietary canola oil suppressed growth of implanted MDA-MB 231 human breast tumors in nude mice

Long chain omega 3 (n-3) fatty acids, eicosapentaenoic (EPA) and/or docosahexaenoic acid (DHA), have been shown to suppress growth of most cancer cells. In vivo, alpha linolenic acid (ALA, 18:3n-3) can be converted to EPA or DHA. We hypothesized that substituting canola oil (10% ALA) for the corn oil (1% ALA) in the diet of cancer bearing mice would slow tumor growth by increasing n-3 fatty acids in the diet. Sixty nude mice received MDA-MB 231 human breast cancer cells and were fed a diet containing 8% w/w corn oil until the mean tumor volume was 60 mm3. The dietary fat of half of the tumor bearing mice was then changed to 8% w/w canola oil. Compared to mice that consumed the corn oil containing diet, the mice that consumed the canola oil containing diet had significantly more EPA and DHA in both tumors and livers, and the mean tumor growth rate and cell proliferation in the tumor were significantly slower (P<0.05). About 25 days after diet change, mice that consumed the corn oil diet stopped gaining weight, whereas the mice that consumed the canola oil diet continued normal weight gain. Use of canola oil instead of corn oil in the diet may be a reasonable means to increase consumption of n-3 fatty acids with potential significance for slowing growth of residual cancer cells in cancer survivors.

Dietary lipids impacts on healthy ageing

Healthy ageing is gaining attention in the lipid nutrition field. As in vivo biomarkers of healthy ageing, we have evaluated the survival, learning/memory performance, and physical potencies in rodents fed a diet supplemented with high-linoleic acid (LNA, omega6) safflower oil or high-alpha-linolenic acid (ALA, omega3) perilla oil for long periods. The results suggested that perilla oil with a low omega6/omega3 ratio is beneficial for healthy ageing. In order to address this issue further, we determined the survival of stroke-prone SHR (SHRSP) rats fed a conventional rodent diet supplemented with 10% fat or oil. Survival was longer with omega3-rich oils compared with omega6-rich oils. However, some kinds of vegetable oils and hydrogenated oils shortened the survival of SHRSP rats to an unusual degree (ca. 40% compared with that of omega6-rich oil) that could not be accounted for by the fatty acid and phytosterol composition of the oils. The observed decrease in platelet counts was associated with pathological changes in the kidney and other organs. Dihydro-vitamin K1 is proposed as a likely candidate as a stroke-stimulating factor in hydrogenated oils. Thus, factors other than fatty acids (omega6/omega3 balance) and phytosterols must be taken into account when fats and oils are evaluated in relation to healthy ageing.

Methods for nutrigenomics and longevity studies in Drosophila: effects of diets high in sucrose, palmitic acid, soy, or beef

Nutrigenomics is the study of gene-nutrient interactions and how they affect the health and metabolism of an organism. Combining nutrigenomics with longevity studies is a natural extension and promises to help identify mechanisms whereby nutrients affect the aging process, life span, and, with the incorporation of age-dependent functional measures, health span. The topics we discuss in this chapter are genetic techniques, dietary manipulations, metabolic studies, and microarray analysis methods to investigate how nutrition affects gene expression, life span, triglyceride levels, total protein levels, and live weight in Drosophila. To better illustrate nutrigenomic techniques, we analyzed Drosophila larvae or adults fed control diets (high sucrose) and compared these with larvae or adults fed diets high in the saturated fat palmitic acid, soy, or 95% lean ground beef. The main results of these studies are, surprisingly, that triglyceride and total protein levels are significantly decreased by the beef diet in all adults, and total protein levels are significantly increased in male flies fed the soy diet. Furthermore, and less surprisingly, we found that all three experimental diets significantly decreased longevity and increased the length of time to develop from egg to adult. We also describe preliminary microarray results with adult flies fed the different diets, which suggest that only about 2-3% of the approx 18,000 genes have significantly altered mRNA expression levels compared with flies fed a control sucrose diet. The significance of these results and other types of nutrigenomics and longevity analyses is discussed.

Effects of cooking plant oils on recurrent aphthous stomatitis: a randomized, placebo-controlled, double-blind trial

OBJECTIVE

One-third of the total population seems to develop minor recurrent aphthous stomatitis (RAS) during their lifetime. However, well-controlled dietary intervention studies to prevent minor RAS are very rare. The objective of the present study was to investigate whether the prevalence of RAS decreased with perilla oil (rich in alpha-linolenic acid).

METHODS

Thirty subjects (8 men and 22 women) who had minor RAS at least once a month were randomly allocated to a soybean oil group or a perilla oil group in a double-blind manner (experimental phase) after a run-in phase of 4 mo during which subjects used a reference oil, the most popular cooking oil in Japan, or a 50/50 mixture of soybean oil and rapeseed oil. During the experimental phase, subjects were asked to use soybean oil or perilla oil as the sole cooking oil for 8 mo. Blood samples were collected at the start and end of the experimental phase for fatty acid analysis of total plasma phospholipid fraction. Occurrence and needed days for healing of minor RAS were recorded during the two phases and compared.

RESULTS

alpha-Linolenic acid concentrations in the plasma phospholipid fraction increased significantly in both groups during the experimental phase to a similar extent. The prevalence of minor RAS in the experimental phase decreased significantly in both groups compared with the run-in phase to a similar extent, without intergroup differences.

CONCLUSION

Perilla oil, which is rich in alpha-linolenic acid, was not superior to soybean oil in preventing minor RAS. There was a possibility that avoiding rapeseed oil might be beneficial for prevention of minor RAS.

Exploration for unknown substances in rapeseed oil that shorten survival time of stroke-prone spontaneously hypertensive rats. Effects of super critical gas extraction fractions

To identify the causative substances for the shortening of survival time by rapeseed (Canola) oil in stroke-prone spontaneously hypertensive rats (SHRSP), SHRSP were fed on a standard chow supplemented with 10 w/w% soybean oil (control), rapeseed oil, one of the fractions of rapeseed oil obtained by super critical gas extraction (SCE) under a pressure of 180-bar or 350-bar, at 40 degrees C, or the residue from the extraction (with 0.5% NaCl in drinking water). In another series of experiment, SHRSP were fed for 8 weeks on the above-mentioned diets without salt loading and autopsied. Fatty acid compositions in these diets were similar, except in the soybean oil diet, and phytosterol contents were: (diet containing) 180-bar fraction>residue>rapeseed oil>350-bar fraction>soybean oil. Survival times in the rapeseed oil, 350-bar fraction and residue groups were shorter than, whereas that in the 180-bar fraction was similar to in the soybean oil group. In the 8-week feeding experiment, chronic nephropathy was found frequently in the groups other than the soybean oil group. The heart weights were higher in the rapeseed oil and residue groups. Cerebral necrosis was found in the residue group. Taken together, the followings are concluded, (1) Neither the fatty acid composition, nor the amount of phytosterols in the diets appeared to be decisive in the shortening of life. (2) SCE appeared to produce a safe (180-bar) fraction, though it failed to separate clearly the causative substances into specific fractions. (3) The factors that facilitate the genetic disease of SHRSP appear to exist in rapeseed oil. However, they might not be identical to those responsible for the life-shortening, since there were no findings common across the rapeseed oil, 350-bar and residue groups, which showed similar life-shortening.

Needs to Change the Direction of Cholesterol-related Medication—A Problem of Great Urgency

The cholesterol hypothesis implies that reducing the intake of saturated fatty acids and cholesterol and increasing that of polyunsaturated fatty acid are effective in lowering serum total cholesterol (TC), and thereby reducing the incidence of coronary heart disease (CHD). However, these dietary recommendations are essentially ineffective in reducing TC in the long run, but rather increase mortality rates from CHD and all causes. The reported "apparent relative risk of high TC in CHD mortality" (the ratio of mortality at the highest/lowest TC levels) varied several-fold among populations studied. The incidence of familial hypercholesterolemia (FH) in a population was proposed to be a critical factor in the observed variability, which could be accounted for by assuming that 1) the high CHD mortality rate in high-TC groups is mainly a reflection of the incidence and severity of FH, and 2) high TC is not a causative factor of CHD in non-FH cases. This interpretation is supported by recent observations that high TC is not positively associated with high CHD mortality rates among general populations more than 40-50 years of age. More importantly, higher TC values are associated with lower cancer and all-cause mortality rates among these populations, in which relative proportions of FH are likely to be low (circa 0.2%). Although the effectiveness of statins in preventing CHD has been accepted in Western countries, little benefit seems to result from efforts to limit dietary cholesterol intake or to TC values to less than approximately 260 mg/dl among the general population and the elderly. Instead, an unbalanced intake of omega6 over omega3 polyunsaturated fats favors the production of eicosanoids, the actions of which lead to the production of inflammatory and thrombotic lipid mediators and altered cellular signaling and gene expression, which are major risk factors for CHD, cancers, and shorter longevity. Based on the data reviewed here, it is urgent to change the direction of current cholesterol-related medication for the prevention of CHD, cancer, and all-cause mortality.