Dietary long-chain polyunsaturated fatty acids minimize dexamethasone-induced reductions in arachidonic acid status but not bone mineral content in piglets

An investigation of association between human milk mineral patterns and infant growth

Introduction

Human milk is widely acknowledged as the optimal food for infant aged 0 ~ 6 months. While there has been extensive documentation on the mineral and trace element composition of human milk, results on the relationship between mineral content and infant growth remain mixed. This cross-sectional study aims to explore human milk mineral patterns and to investigate associations between human milk mineral patterns, human milk metabolomic profile and infant growth.

Methods

A total of 200 breast milk samples from seven cities in China was included. Human milk mineral and trace elements was detected by inductively coupled plasma mass spectrometer (ICP-MS). K-means cluster analysis was utilized to derived human milk mineral patterns. Untargeted human milk metabolomic profiles was determined using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Differences of infant growth rate and metabolomic profiles were then compared across patterns identified.

Results

Three human milk mineral patterns were identified. Cluster I was characterized as the highest levels of potassium, magnesium and calcium, while the lowest levels of copper, zinc, manganese and selenium. Cluster II showed the most abundant sodium, iron, zinc, manganese and selenium. Cluster III had the lowest levels of sodium, potassium, magnesium, iron and calcium. Infants of cluster I showed significantly higher length-for-age z score (0.60 ± 2.03, p = 0.03). Compared with other clusters, samples of cluster I showed lower expression of metabolites of arachidonic acid (ARA) and nicotinate and nicotinamide metabolism pathway.

Discussion

A human milk mineral pattern was identified which is related to increased infant growth rate and altered metabolic signature. Future work is needed to understand these human milk patterns in terms of biologic mechanisms and generalization to other populations.

Therapeutic potentials and modulatory mechanisms of fatty acids in bone

Bone metabolism is a lifelong process that includes bone formation and resorption. Osteoblasts and osteoclasts are the predominant cell types associated with bone metabolism, which is facilitated by other cells such as bone marrow mesenchymal stem cells (BMMSCs), osteocytes and chondrocytes. As an important component in our daily diet, fatty acids are mainly categorized as long-chain fatty acids including polyunsaturated fatty acids (LCPUFAs), monounsaturated fatty acids (LCMUFAs), saturated fatty acids (LCSFAs), medium-/short-chain fatty acids (MCFAs/SCFAs) as well as their metabolites. Fatty acids are closely associated with bone metabolism and associated bone disorders. In this review, we summarized the important roles and potential therapeutic implications of fatty acids in multiple bone disorders, reviewed the diverse range of critical effects displayed by fatty acids on bone metabolism, and elucidated their modulatory roles and mechanisms on specific bone cell types. The evidence supporting close implications of fatty acids in bone metabolism and disorders suggests fatty acids as potential therapeutic and nutritional agents for the treatment and prevention of metabolic bone diseases.

The Essentiality of Arachidonic Acid in Infant Development

Arachidonic acid (ARA, 20:4n-6) is an n-6 polyunsaturated 20-carbon fatty acid formed by the biosynthesis from linoleic acid (LA, 18:2n-6). This review considers the essential role that ARA plays in infant development. ARA is always present in human milk at a relatively fixed level and is accumulated in tissues throughout the body where it serves several important functions. Without the provision of preformed ARA in human milk or infant formula the growing infant cannot maintain ARA levels from synthetic pathways alone that are sufficient to meet metabolic demand. During late infancy and early childhood the amount of dietary ARA provided by solid foods is low. ARA serves as a precursor to leukotrienes, prostaglandins, and thromboxanes, collectively known as eicosanoids which are important for immunity and immune response. There is strong evidence based on animal and human studies that ARA is critical for infant growth, brain development, and health. These studies also demonstrate the importance of balancing the amounts of ARA and DHA as too much DHA may suppress the benefits provided by ARA. Both ARA and DHA have been added to infant formulas and follow-on formulas for more than two decades. The amounts and ratios of ARA and DHA needed in infant formula are discussed based on an in depth review of the available scientific evidence.

The effect of fatty acid positioning in dietary triacylglycerols and intake of long-chain n-3 polyunsaturated fatty acids on bone mineral accretion in growing piglets

Long-chain n-3 PUFA (LCPUFA) and palmitate (16:0) positioning in the triacylglycerol (TAG) of infant formula may affect calcium-uptake which could affect bone health. We investigated if a human milk fat substitute (HMFS) with a modified TAG structure holding 16:0 predominantly in the sn-2-position compared with a control (CONT) and if increasing n-3LCPUFA intake giving fish oil (FO) compared with sunflower oil (SO) would affect bone parameters in piglets in two sets of controlled 14d-interventions (n=12/group). We assessed this by dual-energy x-ray absorptiometry, and ex vivo peripheral quantitative computed tomography and mechanical strength. Bone mineral content (BMC) was higher in the FO compared to the SO-group (p=0.03). Despite similar weight gain in HMFS- and CONT-groups, body fat accumulation was higher with HMFS (p<0.001), and BMC, bone area (BA) and cortical BA in femur were lower (p=0.002, p=0.005, and p=0.02, respectively), indicating importance of both n-3LCPUFA and 16:0 TAG-positioning in infant formulas.

The effects of n-3 long-chain polyunsaturated fatty acids on bone formation and growth factors in adolescent boys

INTRODUCTION

Animal studies indicate that n-3 long-chain polyunsaturated fatty acids (LCPUFAs) increase bone formation. To our knowledge, no studies have examined this in growing humans. This study investigated whether bone mass and markers of bone formation and growth were (i) associated with docosahexaenoic acid (DHA) status and (ii) affected by fish oil supplementation, in adolescent boys.

METHODS

Seventy-eight healthy, slightly overweight 13- to 15-y-old boys were randomly assigned to breads with DHA-rich fish oil (1.1 g/d n-3 LCPUFA) or control for 16 wk. Whole-body bone mineral content (BMC), bone area (BA), bone mineral density (BMD), plasma osteocalcin, and growth factors were measured at wk 0 and wk 16, as well as diet, physical activity, and n-3 LCPUFA status in erythrocytes.

RESULTS

Fish oil strongly increased DHA status (P = 0.0001). No associations were found between DHA status and BMC, BA, BMD, or the markers of bone formation and growth at baseline. Furthermore, the fish oil intervention did not affect any of the outcomes as compared with control. However, dose-response analyses revealed a positive association between changes in DHA status and plasma insulin-like growth factor-1 (IGF-1) during intervention (β = 0.24, P = 0.03, n = 78).

DISCUSSION

DHA status and fish oil supplementation were not associated with bone mass or markers of bone formation in adolescent boys, but IGF-1 increased with increasing DHA status.

Maternal supplementation with dietary arachidonic and docosahexaenoic acids during lactation elevates bone mass in weanling rat and guinea pig offspring even if born small sized

Whether post-natal long chain polyunsaturated fatty acids (LCPUFA) elevates bone mineral content (BMC) of small and normal neonates was studied using pregnant rats and guinea pigs fed a control (C) diet or low protein (LP) diet to induce small neonates followed by C or LCPUFA diets during lactation. Measurements (days 3 and 21 post-partum) included BMC and density (BMD) plus bone metabolism. In rats LP reduced birth weight but at day 21 elevated weight and whole body BMC; LCPUFA enhanced spine BMC, tibia BMC and BMD and whole body BMD. In guinea pig pups, at days 3 and 21, LP reduced weight, whole body and regional BMC and BMD whereas LCPUFA reduced day 3 osteocalcin and elevated day 21 spine BMD. LCPUFA minimized loss of whole body BMC in dams and elevated osteocalcin in sows. LCPUFA during lactation enhances bone in normal and small neonates without compromising maternal bone.

The effect of polyunsaturated fatty acids on bone health

The essential polyunsaturated fatty acids (PUFAs) are divided into two classes, n-3 (ω-3) and n-6 (ω-6) and their dietary precursors are α-linolenic (ALA) and linoleic acid (LA), respectively. PUFAs are precursors of a wide range of metabolites, for example eicosanoids like prostaglandins and leukotrienes, which play critical roles in the regulation of a variety of biological processes, including bone metabolism.

A large body of evidence supports an effect of PUFA on bone metabolism which may be mediated by regulation of osteoblastogenesis and osteoclast activity, change of membrane function, decrease in inflammatory cytokines, such as interleukin-1 (IL-1), interleukin-6 (IL-6), and tumour necrosis factor alpha (TNF-α), modulation of peroxisome proliferators-activated receptor γ (PPARγ) and influence in NO secretion and NO synthase.

Animal studies have shown that a higher dietary omega-3/omega-6 fatty acids ratio is associated with beneficial effects on bone health. Human studies conducted in elderly subjects suggest that omega-3 instead of omega-6 has a positive effect on bone metabolism. In spite of increasing evidence, studies conducted in humans do not allow us to draw a definitive conclusion on the usefulness of PUFAs in clinical practice.

Effects of arachidonic acid and docosahexaenoic acid on differentiation and mineralization of MC3T3-E1 osteoblast-like cells

Osteoblasts in culture can differentiate into mature mineralizing osteoblasts when stimulated with osteogenic agents. Clinical trials and in vivo animal studies suggest that specific polyunsaturated fatty acids (PUFAs) may benefit bone health. The aim of this study was to investigate whether arachidonic acid (AA) and docosahexaenoic acid (DHA) affect osteogenesis in osteoblasts and the transdifferentiation into adipocytes. Results from this study show that long-term exposure to AA inhibited alkaline phosphatase (ALP) activity in these cells, which might be prostaglandin E(2) (PGE(2))-mediated. DHA exposure also inhibited ALP activity which was evident after both short- and long-term exposures. The mechanism whereby DHA inhibits ALP activity is not clear and needs to be investigated. Although long-term exposure to PUFAs inhibited ALP activity, the mineralizing properties of these cells were not compromised. Furthermore, PUFA exposure did not induce adipocyte-like features in these cells as evidenced by the lack of cytoplasmic triacylglycerol accummulation. More research is required to elucidate the cellular mechanisms of action of PUFAs on bone.

Bone resorption varies as a function of time of day and quantity of dietary long chain polyunsaturated fatty acids

It is unclear whether dietary arachidonic acid (AA) and docosahexaenoic acid (DHA) alter the circadian rhythms of bone turnover markers, plasma osteocalcin (OC) and urinary N-telopeptide (NTx). We hypothesize that dietary AA and DHA will influence the circadian rhythm of NTx and OC. Piglets were randomized to receive one of four formulas for 15 days: control or control with AA:DHA (0.5:0.1, 1.0:0.2 or 2.0:0.4 g/100 g of fat). Measurements included polyunsaturated fatty acids (PUFA) and plasma OC (sampled at 0900, 1500 and 2100 h on day 15) and urinary NTx:creatinine (collected from 2100 h on day 14-0900 h, 0900-1500 h and 1500-2100 h on day 15). Main effects (litter, diet, time) were identified by mixed model repeated measures ANOVA. In those fed AA and DHA, regression identified relationships among plasma PUFA and NTx. There was a diet (P=.0467) and time (P<.0001) effect on urinary NTx:creatinine, whereby those receiving 1.0:0.2 g/100 g of fat as AA:DHA had the lowest values and values were lowest at 2100 h. Likewise, diet (P=.0001) and time (P< .0001) affected plasma AA and DHA; higher dietary AA and DHA elevated values and time reduced values. There was a diet by time interaction on eicosapentaenoic acid and DHA proportions, suggesting dietary AA and DHA altered their circadian rhythm. In regression, plasma AA and DHA were not associated with urinary NTx:creatinine. Dietary AA and DHA at amounts similar to that found in breast milk reduce bone resorption, but do not alter its circadian rhythm.

Effects of dietary supplementation with flax during prepuberty on fatty acid profile, mammogenesis, and bone resorption in gilts1,2

The possible role of dietary flax on pre-pubertal development of mammary glands and bone resorption was investigated in gilts. Fifty-seven gilts were fed 1 of 4 diets from 88 d of age until slaughter (d 212 +/- 1). Diets were control without flax (n = 14); 10% flaxseed supplementation (n = 13); 6.5% flaxseed meal supplementation (n = 15); and 3.5% flaxseed oil supplementation (n = 15). All diets were isonitrogenous and isocaloric. Jugular blood samples were obtained on d 78 and 210 to establish the fatty acid profile and to determine the concentrations of prolactin, estradiol, and cross-linked N-telopeptides of type I collagen. At slaughter, the mammary glands were excised, parenchymal and extraparenchymal tissues were dissected, and the composition of the parenchymal tissue (protein, fat, DM, and DNA) was determined. Histochemical analyses of the mammary parenchyma were performed, and fatty acid profiles in the extraparenchymal tissue were evaluated. Dietary flax increased (P < or = 0.001) the concentrations of PUFA and decreased those of SFA (P < 0.01) and MUFA (P < or = 0.001) in plasma and extraparenchymal tissues, which was largely due to the inclusion of 10% flaxseed or 3.5% flaxseed oil (P < or = 0.01) but not 6.5% flaxseed meal. Circulating concentrations of prolactin and estradiol were unaltered by treatments (P > 0.1), but concentrations of cross-linked N-telopeptides of type I collagen tended to be greater (P < 0.1) in flax-supplemented gilts. The DM content of parenchymal tissue was the only mammary compositional value affected, showing an increase with flax addition (P < 0.05). No change (P > or = 0.1) in the bromodeoxyuridine labeling index or estrogen receptor localization was observed with treatments. Dietary supplementation with flax as seed, meal, or oil, therefore, brought about the expected changes in the fatty acid profile but had no beneficial effects on mammary development or bone resorption.

Dietary arachidonic acid and docosahexaenoic acid elevate femur calcium and reduce zinc content in piglets

Specific dietary polyunsaturated fatty acids (PUFAs) and long chain PUFAs (LCPUFAs) elevate femur calcium content and enhance calcium balance. Mother's milk is associated with enhanced calcium balance and contains LCPUFAs; arachidonic acid (AA), and docosahexanoic acid (DHA). However, the effect of AA and DHA on calcium metabolism and other bone minerals during infancy is unknown. Thus, piglets received one of four formulas (15 d): control or with AA:DHA (0.5:0.1 g, 1.0:0.2 g, or 2.0:0.4 g/100 g of fat). Calcium absorption, femur mineral composition, and urinary mineral excretion. Main effects identified using two-way analysis of variance (ANOVA) and post hoc analysis conducted using Duncan's multiple range test. Significant effects of diet were observed in femur calcium and zinc content, but not calcium absorption, urinary mineral excretion, femur ash weight, femur phosphorus, or femur magnesium content. The piglets receiving AA:DHA as 1.0:0.2 g/100 g of fat had 1.9% higher mg calcium/g of ash, but 8.6% lower mug zinc/g of ash compared with control. Thus, AA:DHA in a ratio of 5:1 does not affect mineral accretion, but AA plus DHA, in amounts similar to the upper limit of human milk, might be detrimental to bone mineralization over time due to lower zinc.

Body composition in preterm infants who are fed long-chain polyunsaturated fatty acids: a prospective, randomized, controlled trial

The objective of this study was to evaluate growth and body composition of premature infants who were fed formulas with arachidonic acid (ARA; 20:4n6) and docosahexaenoic acid (DHA; 22:6n3) to 1 y of gestation-corrected age (CA). Preterm infants (750-1800 g birth weight and <33 wk gestational age) were assigned within 72 h of first enteral feeding to one of three formulas: control (n = 22), DHA+ARA from fish/fungal oil [DHA+ARA(FF); n = 20], or DHA+ARA from egg/fish oil [DHA+ARA(EF); n = 18]. Human milk feeding was allowed on the basis of the mother's choice. Infants were fed breast milk and/or preterm formulas with or without 0.26% DHA and 0.42% ARA to term CA followed by breast milk or postdischarge preterm formulas with or without 0.16% DHA and 0.42% ARA to 12 mo CA. Body composition was measured by dual-energy x-ray absorptiometry. There were no significant differences among the three study groups at any time point in weight, length, or head circumference. Bone mineral content and bone mineral density did not differ among groups. At 12 mo CA, infants who were fed DHA+ARA-supplemented formulas had significantly greater lean body mass (p < 0.05) and significantly less fat mass (p < 0.05) than infants who were fed the unsupplemented control formula. The DHA+ARA-supplemented formulas supported normal growth and bone mineralization in premature infants who were born at <33 wk gestation. Preterm formulas that had DHA+ARA at the levels and ratios in this study and were fed to 1 y CA led to increased lean body mass and reduced fat mass by 1 y of age.

(n-3) fatty acids reduce the release of prostaglandin E2 from bone but do not affect bone mass in obese (fa/fa) and lean Zucker rats

Childhood obesity is prevalent and linked to the development of Type 2 diabetes mellitus (DM) and poor bone health. Some PUFA enhance bone mass and thus may improve bone health in obese children. The study objective was to determine the effects of dietary (n-6) compared with (n-3) essential PUFA and long-chain PUFA (LCPUFA) on bone in an obese and insulin-resistant state. Male fa/fa (n = 48) and lean Zucker rats (n = 48) were fed diets containing safflower oil [SO, high (n-6) PUFA], flaxseed oil [FXO, high (n-3) PUFA], or menhaden oil [MO, high (n-3) LCPUFA] for 9 wk. Measurements included the following: femur bone area (BA), mineral content (BMC), density (BMD), morphometry and ex vivo release of prostaglandin E(2) (PGE(2)); plasma osteocalcin and C-terminal telopeptides of type I collagen. Differences among groups were detected using 2-way ANOVA. Genotype effects in the fa/fa rats included lower femoral weight, length, BA, and BMC, as well as femoral head and proximal epiphysis widths compared with the lean rats, but BMD was not affected. Femur BA, BMC, and BMD did not differ among the dietary groups, but diaphysis width was elevated in the MO group and PGE(2) release was reduced by the FXO and MO diets. No genotype x diet interactions were observed. These data indicate that the fa/fa Zucker rat is at risk for low bone mass and that dietary (n-3) FA effectively reduce PGE(2) release. Whether reduced PGE(2) will support optimal peak bone mass during childhood and conserve bone mass with aging warrants investigation.

Low levels of dietary arachidonic and docosahexaenoic acids improve bone mass in neonatal piglets, but higher levels provide no benefit

In piglets, feeding arachidonic acid (AA) and docosahexaenoic acid (DHA) in a 5:1 ratio leads to elevated bone mass, but the optimal total quantity requires clarification. We studied bone mass and modeling of piglets that were randomized to receive 1 of 4 formulas for 15 d: control formula or the same formula with various levels of AA:DHA (0.5:0.1 g, 1.0:0.2 g or 2.0:0.4 g AA:DHA/100 g of fat). Measurements included: bone area (BA), mineral content (BMC), and density (BMD) of whole body, lumbar spine, and excised femurs; biomarkers of bone modeling were plasma osteocalcin and urinary cross-linked N-telopeptides of type 1 collagen (NTx), tibial ex vivo release of prostaglandin E(2) (PGE(2)), plasma insulin-like growth factor-1 (IGF-1), and tissue fatty acids. Main effects were identified using ANOVA and post hoc Bonferroni t tests. In supplemented piglets, relations among liver fatty acid proportions and bone mass were assessed using Pearson correlations. Whole body (P = 0.028) and lumbar spine (P = 0.043) BMD were higher in the group supplemented with 0.5:0.1 g AA:DHA/100 g of fat than in controls. Tissue AA and DHA increased in proportion to diet levels. Liver eicosapentaenoic acid (EPA) correlated positively (r > or = 0.38, P < or = 0.05) with whole body and femur BMC and BMD and lumbar spine BMC. Liver AA:EPA ratio correlated negatively (r > or = -0.039, P < or = 0.05) with whole body, femur, and lumbar spine BMC plus whole body and femur BMD. Dietary 1.0:0.2 g AA:DHA/100 g reduced NTx relative to 2.0:0.4 g AA:DHA/100 g of fat (P = 0.039). The diets did not affect the other biochemical variables measured. Low levels of dietary AA:DHA (0.5:0.1 g/100 g of fat) elevate bone mass, but higher amounts are not beneficial.

Polyunsaturated fatty acids: biochemical, nutritional and epigenetic properties

Dietary polyunsaturated fatty acids (PUFA) have effects on diverse physiological processes impacting normal health and chronic diseases, such as the regulation of plasma lipid levels, cardiovascular and immune function, insulin action and neuronal development and visual function. Ingestion of PUFA will lead to their distribution to virtually every cell in the body with effects on membrane composition and function, eicosanoid synthesis, cellular signaling and regulation of gene expression. Cell specific lipid metabolism, as well as the expression of fatty acid-regulated transcription factors, likely play an important role in determining how cells respond to changes in PUFA composition. This review will focus on recent advances on the essentiality of these molecules and on their interplay in cell physiology, leading to new perspective in different therapeutic fields.

The effect of dietary n-3 long-chain polyunsaturated fatty acids on femur mineral density and biomarkers of bone metabolism in healthy, diabetic and dietary-restricted growing rats

INTRODUCTION

Dietary fish oil promotes bone formation in healthy states, but its effect during insulin deficiency or nutrient restriction is unclear.

METHODS

Eighty weanling male rats were randomized to receive an injection of streptozotocin to induce insulin deficiency (diabetes) or saline (control) and a diet containing soy oil or corn + fish oil for 35 days. Half of the saline-injected rats were randomized to 20% dietary restriction. Measurements were growth, biomarkers of bone metabolism and femur bone mass.

RESULTS

Density of femur was elevated in the corn + fish group and reduced in the diabetes group. Plasma osteocalcin and bone prostaglandin E2 (PGE2) were reduced by the corn + fish diet. N-telopeptide, IGF-1, bone PGE2 and urinary Ca were highest and calcitriol lowest in the diabetes group.

CONCLUSIONS

These data suggest that the benefit of a diet high in n-3 long-chain polyunsaturated fatty acid is most advantageous to long bone density in healthy states.

Proximal intestinal absorption of calcium is elevated in proportion to growth rate but not bone mass is small for gestational age piglets

During the first year of life, body calcium content increases faster in relation to body size than any other time during growth. Studies have shown postnatal growth and bone mineralization differences between appropriate for gestational age and small for gestational age infants. The objective of this study was to compare duodenal calcium transport using intestinal ligated loop technique in 21-day-old small for gestational age (birth weight of <1.2 kg) and appropriate for gestational age piglets (birth weight of > or =1.4 kg). Piglets were fed liquid formula between day 5 and 21 of life and monitored daily for weight gain. At day 21 calcium absorption was measured followed by measurement of bone mass using dual energy x-ray absorptiometry. Small for gestational age piglets had greater calcium absorption and growth rate than appropriate for gestational age piglets. Birth weight was negatively related to weight gain and calcium absorption. Weight gain was positively related to calcium absorption. Appropriate for gestational age piglets had significantly higher whole body bone mineral content than small for gestational age piglets even after correction for body size. Whole body bone mineral content was positively correlated with birth weight and negatively correlated with calcium absorption. These observations suggest that small for gestational age piglets are capable of absorbing elevated amounts of calcium in the proximal intestine in support of compensatory growth. However, at 21 days of age small for gestational age piglets are similar in size but have lower bone mass compared to appropriate for gestational age piglets.

Dose response of bone mass to dietary arachidonic acid in piglets fed cow milk-based formula

BACKGROUND

The addition of arachidonic acid (AA) and docosahexaenoic acid (DHA) to infant formula was recently approved in North America. In piglets, dietary AA is linked to elevations in bone mass.

OBJECTIVE

The objective was to investigate the effects of varied amounts of dietary AA on bone modeling and bone mass with the use of the piglet model for infant nutrition.

DESIGN

Male piglets (n = 32) were randomly assigned to receive 1 of 4 formulas supplemented with AA (0.30%, 0.45%, 0.60%, or 0.75% of fat) plus DHA (0.1% of fat) from days 5 to 20 of life. Measurements included biomarkers of bone modeling, fatty acid status, and whole-body and femur bone mineral content; bone area was measured by dual-energy X-ray absorptiometry. Differences among groups were detected with two-factor analysis of variance. Regression analyses were used to determine factors responsible for bone mineral content after dietary AA was accounted for.

RESULTS

Proportions of AA in plasma, liver, and adipose were modified by the dietary treatments, but bone modeling was not affected. Liver AA was positively related to plasma insulin-like growth factor 1 and calcitriol and urinary N-telopeptide. Whole-body bone mineral content was elevated in the piglets fed 0.60% and 0.75% AA and was best predicted by dietary AA and bone resorption.

CONCLUSIONS

This study confirms that dietary AA alters bone mass and clarifies the best amount of AA to add to the diet of pigs born at term. Because the amount of dietary DHA was held constant, whether other amounts of DHA are related to bone mass requires investigation.

Dietary conjugated linoleic acid reduces PGE2 release and interstitial injury in rat polycystic kidney disease

BACKGROUND

Conjugated linoleic acid (CLA) describes positional isomers of linoleic acid (LA). Experimental health benefits of CLA include amelioration of malignancy and inflammatory disease and reduction of adiposity. The Han:SPRD-cy rat model of polycystic kidney disease (PKD) features prominent renal interstitial inflammation and fibrosis that is amenable to dietary modification. We studied CLA supplementation in the modification of inflammatory outcomes in the Han:SPRD-cy rat.

METHODS

Male offspring of Han:SPRD-cy heterozygotes were fed diets, using corn oil or corn oil with a CLA enriched oil (1% of diet by weight as CLA). After 8 weeks, measurements included renal function and morphometry, ex vivo release of renal prostaglandin E2 (PGE2), and renal and hepatic tissue fatty acid profiles.

RESULTS

Urine creatinine was significantly higher in PKD animals fed CLA (P = 0.004), but differences in serum creatinine and creatinine clearance did not quite reach significance in PKD animals. CLA feeding reduced interstitial inflammation (P < 0.001), fibrosis (P = 0.03), and renal PGE2 release (P = 0.02). Cystic change and oxidized low-density lipoprotein (LDL) staining did not change significantly. CLA feeding produced increased renal and hepatic CLA isomers. Hepatic, but not renal, LA proportion was reduced on the CLA diet. The renal proportion of the PGE2 precursor, arachidonic acid (AA), was not changed by diet, but hepatic AA proportion increased significantly with CLA feeding (P= 0.009).

CONCLUSION

CLA reduces renal production of PGE2, without reduced availability of the precursor fatty acid, AA. Short-term feeding of CLA to Han:SPRD-cy rats also has significant renal anti-inflammatory and antifibrotic effects. As inflammation and fibrosis are important components of the progression of chronic renal injury, CLA may be a useful agent in dietary amelioration of renal disease.

Dietary arachidonic acid suppresses bone turnover in contrast to low dosage exogenous prostaglandin E(2) that elevates bone formation in the piglet

This study was designed to compare the effects of dietary arachidonic acid (AA) versus prostaglandin E(2) (PGE(2)) on bone cell metabolism and bone mass. Twenty-eight piglets from 7 litters were randomized to 1 of 4 treatments for 15 days: fatty acid supplemented formula (FA: 0.8% of total fatty acids as AA and 0.1% of total fatty acids as DHA)+PGE(2) injections (0.1mg/kg/day), FA+saline injections, standard formula (STD: n-6:n-3 of 8:1) + PGE(2) injections or STD+saline injections. PGE(2) resulted in elevated osteoblast activity as indicated by plasma osteocalcin and also reduced urinary calcium excretion. Dietary FA resulted in reduced bone resorption as indicated by urinary N-telopeptide and reduced bone PGE(2). Both PGE(2) and FA treatments independently lead to elevated femur mineral content, but the combined treatment caused a reduction. Thus the mechanisms by which PGE(2) and FA lead to enhanced bone mass are distinct.

Modulation of essential (n-6):(n-3) fatty acid ratios alters fatty acid status but not bone mass in piglets

Dietary (n-6) and (n-3) fatty acids have been implicated as important regulators of bone metabolism. The main objective of this research was to define the response of whole-body growth, fatty acid status and bone mass to a reduced dietary (n-6):(n-3) fatty acid ratio. A secondary objective was to determine whether there is an amount of fat x fatty acid ratio interaction for these outcomes. Piglets (n = 32) were randomized to 1 of 4 diets: group 1: [30 g fat/L + (n-6):(n-3) ratio 4.5:1]; group 2: [30 g fat/L + (n-6):(n-3) ratio 9.0:1]; group 3: [60 g fat/L + (n-6):(n-3) ratio 4.5:1]; and group 4: [60 g fat/L + (n-6):(n-3) ratio 9.0:1]. After 21 d, outcomes assessed included growth, fatty acid status and bone mass and metabolism. Growth and bone mass did not differ among the four groups nor did arachidonic acid (AA as g/100 g fatty acids) in plasma, adipose and brain. Piglets fed diets 1 and 3 with the lower (n-6):(n-3) ratio had lower liver AA (P < 0.001). Those fed diets 1 and 2 containing 30 g fat/L had lower docosahexaenoic acid (DHA as g/100 g fatty acids) in liver (P < 0.001), plasma (P = 0.019) and adipose tissue (P = 0.045). However, piglets fed diets 1 and 3 had higher (P < 0.001) brain DHA than those fed diets with a higher (n-6):(n-3) ratio. Higher plasma DHA was associated with less bone resorption (r = -0.44, P = 0.01). Therefore, elevation of dietary (n-3) fatty acids supports growth and fatty acid status while not compromising bone mass. The results may be of relevance to the nutritional management of preterm infants whose DHA status is often too low and bone resorption too high.