effect of pufa on male & female reproduction

Effect of PUFA on Male & Female ReproductionSupervisor: Dr. Alijoo Presenter: M. Behroozlak

Jul. 2014

Introduction • Fats and oils include both saturated fatty acids (SFA) and

mono- and polyunsaturated fatty acids (MUFA and PUFA, Tables 1 for summary abbreviations used).

• PUFAs have more than one double bond present within the molecule and are further classified into three groups on the basis of their chemical structure:

omega-3 (n-3), omega-6 (n-6) and omega-9 (n-9), where the first double bond is located 3, 6, or 9 carbons from the methyl end of the molecule.

2

Nutritionally important n-6, n-3 PUFA

3

Introduction• Animals cannot synthesize n-6 or n-3 fatty acids de novo

as they lack the appropriate fatty acid desaturase enzymes.

• The n-6 PUFA linoleic acid (LA) and the n-3 PUFA a-linolenic acid (ALA) therefore need to be provided in the diet as they are absolutely necessary for numerous processes, including growth, reproduction, vision, and brain development

4

n-6, n-3 PUFA metabolic pathway

• The main dietary n-6 PUFA is LA, which is abundant in vegetable oils such as corn, safflower, sunflower and rapeseed oils. Most n-3 PUFAs are derived from ALA, found mainly in the chloroplasts of green vegetables and grass.

• These two essential fatty acids can be converted in the liver to longer chain PUFAs by desaturation and elongation enzyme systems common to both pathways

5

6Liver

Mechanisms by which PUFAs can affect Reproduction

PUFAs and Prostaglandins:• Twenty carbon PUFAs are the direct precursors of a larg

group of physiologically active compounds called eicosanoid which include prostaglandins (PGs), thromboxanes, leukotrienes and lipoxins.

• The 1- and 2-series PGs are derived from the n-6 PUFAs DGLA and AA respectively, whereas the 3-series PGs are derived from EPA.

• The synthesis of PGs in tissues throughout the body is a very tightly regulated process.

7

Functions of PGs related to reproduction

• Prostaglandins are key hormones both in terms of cervical ripening and myometrial contractility, which are essential for mammalian parturition. Therefore, the connection can be made between changes in dietary intake of PUFAs and the ensuing changes in gestational length.

• Changes in PUFA intake through altering the pattern of prostaglandin production may influence either the timing or efficiency of the onset of labour.

9


• In general, animals or humans fed diets high in n-3 PUFAs exhibited an increase in gestational length.

• This has been attributed to the changed pattern of PG synthesis, which gives rise to an increase in the generation of 3-series prostaglandins.

• Since 3-series prostaglandins are less potent than the 2-series prostaglandins (e.g. in terms of inducing contraction) normally associated with parturition, the suggestion is that the biological activity of these 3-series prostaglandins is insufficient to induce the vigorous myometrial contractions associated with normal labour. 10


• Evidence exists to support the idea that normal onset of labour is associated with an increase in n-6 PUFA derived dienoic prostaglandins:

(1) plasma levels of linoleic and arachidonic acid (both n-6) are higher than those of linolenic acid, EPA and DHA (all n-3) in women in labour.

(2) levels of arachidonic acid increased throughout pregnancy, with highest levels being observed during labour, followed by a rapid decline postpartum;

(3) levels of linoleic acid (the precursor of arachidonic acid) increased in uterine arteries during pregnancy. 11

Synthesis of prostaglandins (PG)

12

Diet

PUFA

(PTGS1,2)

PUFAs and Steroidogenesis

• AA and its metabolites have long been implicated in steroidogenesis through direct effects on the steroidogenic machinery (e.g., steroid acute regulator [STAR] protein, cytochrome P450, family 11, sub family A, polypeptide 1 enzyme [CYP11A1]), or indirect effects via PGs.

13

STAR plays a critical role in regulating steroid synthesis


• In Leydig cells, inhibition of endogenous release of AA inhibited dibutyryl cAMP-induced steroid synthesis as well as STAR promoter activity, Star mRNA and STAR protein, whereas addition of exogenous AA reversed all these effects.

14

AA can stimulate the production of testosterone via effects on STAR.


• In contrast, the age-dependent inhibition of testosterone production involves the suppression of STAR as a consequence of oxidative stress. The cause of the latter is not known for certain, but is correlated with excessive AA flux through the PTGS2 pathway.

• PUFAs can also regulate adrenal steroidogenesis. Basal corticosterone synthesis was stimulated by LA.

15

PUFAs and Preterm Labor

• Preterm birth occurs in about 10% of all human pregnancies and is associated with 70% of neonatal deaths.

• Both fetal and maternal tissues, including amnion, chorion, and decidual endometrium, synthesize PGs in. The levels of PGs along with their synthetic enzymes (mainly PTGS2) increase either before or at the time of labor.

16


• PUFAs may thus be able to influence the timing of parturition through alterations to PG or adrenal steroid synthesis. A diet high in n-6 PUFAs is generally thought to be associated with an increased risk of preterm delivery.

• In women, low n-3 PUFA consumption during pregnancy is also associated with a higher risk of preterm labor and low birth weight. Conversely, a diet high in n-3 PUFA is associated with an increase in gestational length and birth weight in rats and human populations with high fish consumption.

17


• Women with a previous preterm delivery had a significantly lower recurrence following EPA and DHA supplementation in comparison with a placebo group, reducing the risk from 33% to 21%.

• A further trial that provided women with DHA-enriched eggs found fewer low-birth-weight and preterm babies and a larger placental size.

18

PUFAs and Male Fertility

• Long chain PUFAs have been detected in the spermatozoa of man and a variety of livestock species including both mammals (ram, bull, boar) and birds (chickens, ducks, turkeys).

• In birds, the most abundant were the n-6 PUFAs AA (5%–9%) and docosatetranoic acid (22:4 n-6,15%–21%). These were synthesized from LA, which was the most abundant PUFA in the diet (15%), but was present at a lower concentration in spermatozoa (2%–3%).

• Altering the PUFA sources in the diet resulted in concomitant changes in the n-6 and n-3 composition of sperm (e.g., boar, cockerel) 19

PUFAs and Male Fertility• Spermatozoa require a high PUFA content to provide the

plasma membrane with the fluidity essential at fertilization.

• However, this makes spermatozoa particularly vulnerable to attack by reactive oxygen species (ROS), initiating a lipid peroxidation cascade that can seriously compromise the functional integrity of these cells, and lifestyle factors promoting oxidative stress have clear associations with reduced fertility.

20

PUFAs and Male Fertility• The fluids bathing the spermatozoa during their passage

through the male reproductive tract are endowed with highly specialized secreted forms of antioxidant enzymes.

• The latter include members of the glutathione peroxidase and periredoxin families as well as superoxide dismutase and a host of small molecular mass free radical scavengers, including carnitine, tyrosine, uric acid, and vitamin C.

21

Seminal plasma is recognized as one of the most powerful antioxidant fluids known to man.


• Experiments on chickens have shown that feeding more PUFAs in the diet reduced the antioxidant status and quality of the semen (sperm concentration, semen volume).

• The importance of lipid peroxidation in this context was suggested by the ability of vitamin E, a chain breaking antioxidant, to reverse the negative impact of PUFA supplementation.

22


• A causative relationship between the retention of high levels of unsaturated fatty acid and ROS generation was indicated by a recent study indicating that exposure of human spermatozoa to the PUFAs LA, AA, and DHA triggered free radical generation, lipid peroxidation, and DNA damage in human spermatozoa.

23

A proposed mechanism by whichunsaturated fatty acids might generate oxidative

stress in human spermatozoa.

24

Fats and egg yolk• Fats present in the egg yolk are the main source of energy

for the developing chick embryo. It was shown that alteration in the fatty acid profile of yolk fat decreased chick embryonic survival.

• Effects of fats on decrease hatchability: Dietary cyclopropene fatty acids (i.e. sterculic and

malvalic acids) are examples of the fatty acids that significantly decrease the hatchability of eggs supposedly by increasing the ratio of stearic (C18:0) to oleic acid (C18:1, n−9) in the egg yolk.

25

Effects of fats on decrease hatchability

Similar to cyclopropene fatty acids, adverse effects on hatchability of fertile eggs were observed when conjugated linoleic acid (CLA) was fed in a low-fat diet.

Dietary CLA caused a decrease in the levels of C16:1(n−7) and C18:1(n−9) and an increase in the levels of C16:0 and C18:0 in the egg yolk, probably by down regulating stearoyl-CoA denaturize, an enzyme catalyzing the conversion of C16:0 and C18:0 into C16:1(n−7) and C18:1(n−9), respectively.

26

C18:1(n−9)

• C18:1(n−9) in the egg yolk was shown to play an important role in the esterification of cholesterol and the subsequent uptake of yolk lipid by the chick embryo. If the ratio of C18:0 to C18:1(n−9) in the egg yolk exceeded 0.3, embryo mortality occurred.

27

C18:1(n−9) plays an important role in chick embryo development and survival.

Effects of various dietary fats on hatchability in fertile eggs

28

• Adding O appeared to reduce the residual yolk possibly by increased transport of yolk components from yolk sac into the chick liver compared to those from the groups of CLA.

• These data showed that transport of yolk components from yolk sac into chick was reduced in the CLA + LA and CLA group compared to those from the CLA +O or LA group.

30

Effect of UFA on hatch

• If the maternal diet contained additional oils high in unsaturated fatty acids, even though the percentage of C18:1(n−9) in the egg yolk dropped to 24%, percent hatch of eggs was not influenced compared to the control (Aydin, 2006).

• In the present study, this suggests that lowering C18:1(n−9) of egg yolk by maternal dietary CLA may not be the cause of the embryo mortality in fertile eggs.

31

The total UFA may be a more important predictor of hatchability.

Effect of n-3/n-6 fatty acid ratio on Reproduction in male

• Sperm cells contain very high proportions of polyunsaturated fatty acids (PUFA), and normal spermatozoa possess a higher percentage of the most representative PUFA (C22:6 n-3) than those detected in blood serum phospholipids and in other cell membranes.

• The lipid composition, the degree of PUFA unsaturation, and the proportion of sperm PUFA have been shown to affect sperm quantity.

• The n-6 PUFA and the n-3 PUFA need to be provided in the diet.

32

Effect of n-3/n-6 fatty acid ratio on Reproduction

• Researchers have shown the beneficial role of an appropriate dietary n-3/n-6 ratio for embryo development and health.

• It is thought that both man and livestock species evolved on a diet with an n-6 to n-3 PUFA ratio of 1-2:1 but modern dietary trends have increased this ratio. It now ranges from 10:1 to 25:1 in westernized human populations.

33

Therefore, in both human and animal diets thereare grounds for maintaining the proper ratio of n-6 and n-3 PUFAs dietary intakes to promote reproduction.

Effects of different ratio of N-3/N-6 on semen characteristics

• The male rats were fed diets containing 7% oil from soybean and flaxseed for 60 days. The basic formulation of the experimental diets contained supplemental ratios of soybean oil (SO): flaxseed oil (FO), namely 100:0, 75:25, 50:50, 25:75, and 0:100. The ratios of dietary n-3/n-6 PUFAs were 0.13, 0.40, 0.85, 1.52, and 2.85.

34

Effects of different ratios of N-3/N-6 PUFAs on testis histological changes

• Compared with the control group, better spermatogonial development and more uniform distribution of chromatin around the nuclear membrane was observed in the group with a n-3/n-6 PUFA ratio of 1.52 (diet 4).

35

Effects of different ratios of N-3/N-6 PUFAs on the serum hormone levels

36

Lipid content of sperm and dietary fat

• Research has shown that diets containing distinct lipid sources differentially modified the lipid contents of the sperm head and body membranes, resulting in significant improvement in semen quality.

• Al-Daraji et al. found the proportion of n-3 fatty acids in spermatozoa from Japanese male quail fed fish oil compared with corn oil was higher (9.6% vs. 4.3%) and that of n-6 fatty acids was lower (22.4% vs. 33.3%).

• The sperm of flaxseed-fed rabbits had an n-3/n-6 ratio two times higher compared with the control because of the increasing dietary n-3/n-6 ratio. 37

Results about n-3/n-6 ratio • Results of this study clearly indicate that the ratios of

n-3/n-6 PUFAs in the diet have a great influence on sperm quality traits and reproductive performance, and that a n-3/n-6 PUFAs ratio of 1.52 improved the reproductive capacity of male rats.

38

A balanced n-3/n-6 PUFA ratio will be beneficial to male reproduction. Therefore there is a necessity to determine an appropriate n-3/n-6 PUFA ratio in

man and different male animals in the future.

Effect of Dietary Fat on the Fatty Acid Composition and Fertilizing Ability of Fowl Semen

• The reproductive efficiency of male fowl, especially the heavy breeds, needs to be improved. In mammals, the lipid composition of sperm membranes plays a major role in the physicochemical modifications leading to fertilization.

• In birds, the lipid composition of spermatozoa may have an influence on fertility.

39

PUFA & Phospholipids

• In all species, phospholipids are the major lipid components of spermatozoa, and they contain large amounts of polyunsaturated fatty acids (PUFAs).

• In the chicken, the PUFA composition in the brain and retina (phospholipid-rich tissues) also depends on the PUFA composition in the diet, either directly or via the egg yolk from which lipids are transferred to the embryo. As with the brain and the retina, PUFA deficiency could alter the fatty acid composition of spermatozoa and their biological functions.

40

Effect of dietary fat on semen traits

41

Effect of dietary fat on Fatty acid composition of spermatozoa & seminal plasma

42

Effect of dietary fats on fertility

• Since the two diets were isolipidic, the difference in fertility may result from the differences in the n-6/n-3 ratios that were found in both seminal plasma and spermatozoa.

• The difference in phospholipid fatty acids of spermatozoa (97% of the fatty acids are in phospholipids) induced by the diet may have modified the membrane structures, fluidity, and/or susceptibility to peroxidative damage.

• These modifications may have affected the viability of the spermatozoa in the female reproductive tract and/or their fusion capacity, inducing modifications of fertility rates.

44

Distribution of fatty acids of fowl spermatozoa

• The present data confirm the unique distribution of fatty acids of fowl spermatozoa compared to that of mammals and fishes.

• Mainly four major components: 16:0, 18:0, 18:1n-9, 22:4n-6. Whatever the diet, chicken spermatozoa contain very large amounts of 22:4n-6, the major PUFA, whereas this fatty acid was not detected in mammalian species or in trout.

• Moreover, 22:5n-3 and 22:6n-3, which were found in large amounts in mammalian spermatozoa

45

Distribution of fatty acids of fowl spermatozoa

• It is clear from the present data that the fowl sperm can incorporate dietary PUFAs, either directly (22:5n-3 and 22:6n-3) or after elongation and desaturation of shorter precursors (20:4n-6 and 22:4n-6 from 18:2n-6).

• Our data lead us to conclude that: 1) fowl sperm seem to exhibit a unique fatty acid

composition, 2) the transfer of essential fatty acids from the diet to the

semen is effective, and 3) this transfer may have biological effects on the

fertilizing ability of semen. 46

effect of pufa on male & female reproduction

Health & Medicine