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Biomedical subjects

Marlena C Kruger

Publications and source records attributed to Marlena C Kruger.

10 recordsLinked to original sources
PubMed2006

Effect of calcium fortified milk supplementation with or without vitamin K on biochemical markers of bone turnover in premenopausal women.

OBJECTIVE: We compared the effect of supplementation with a fortified skimmed milk product (high calcium skim milk) with or without added phylloquinone (vitamin K(1)) on markers of bone formation and resorption in premenopausal women. METHODS: Eighty-two women 20 to 35 y of age were randomly allocated to three groups. Two groups received two daily servings of high calcium skim milk (1000 mg/d of extra calcium) with or without added phylloquinone (80 microg/d) for 16 wk, and a third control group received no supplementation. Bone density was assessed at baseline and the bone markers, total osteocalcin, type I N-terminal procollagen peptide, and cross-linked C-telopeptide of type I collagen were measured at baseline and at weeks 2, 12, and 16. Serum phylloquinone and undercarboxylated osteocalcin were measured in the control and vitamin K-supplemented groups at weeks 0 and 16. RESULTS: Baseline values for age, body mass index, and bone density did not differ across groups. In vitamin K-supplemented women, mean serum phylloquinone concentrations increased from 0.27 to 0.76 microg/L (P < 0.05) and undercarboxylated osteocalcin concentrations decreased from 9.68 to 4.46 microg/L (P < 0.05) over 16 wk. Plasma cross-linked C-telopeptide of type I collagen, total osteocalcin, and type I N-terminal procollagen peptide levels decreased significantly in both supplemented groups compared with the control group over 16 wk (cross-linked C-telopeptide of type I collagen >30%, total osteocalcin and type I N-terminal procollagen peptide >15%). CONCLUSION: Fortified milk supplementation in premenopausal women reduced bone turnover significantly. Phylloquinone fortification substantially improved vitamin K status but had no demonstrable additive effect on bone turnover in this short-term study.

Adult↗
PubMed2006

Detrimental effect of eicosapentaenoic acid supplementation on bone following ovariectomy in rats.

Although several studies have reported a positive effect of n-3 essential fatty acids (EFAs) on bone density post-ovariectomy, the role of specific EFAs has yet to be fully elucidated. In this study, ovariectomised (OVX) rats were supplemented with 0.1 g (LOW) or 1.0 g (HIGH) of eicosapentaenoic acid (EPA)/kg body weight for 9 weeks. Bone mineral density (BMD), 25-hydroxyvitamin D(3) and plasma fatty acid profile were compared to those of OVX and sham animals fed a non-supplemented diet. BMD decreased significantly in all OVX (P<0.001) but not sham rats. There was no difference in BMD between the LOW group and OVX controls. BMD was significantly lower in the HIGH group compared to OVX and sham controls. 25-hydroxyvitamin D(3) levels were significantly higher in both the LOW and HIGH groups compared to OVX controls (P=0.0006 and 0.02, respectively). In conclusion, high-dose EPA supplementation exacerbated the effects of ovariectomy on BMD.

Animals↗
PubMed2006

Anthocyanin absorption and antioxidant status in pigs.

The effect of a simultaneous intake of food or flavonoids on anthocyanins absorption and antioxidant status in pigs was investigated. Twelve male pigs at 27.1 +/- 0.7 kg BW fitted with jugular venous cannulae were maintained in individual metabolic crates. The animals were each given one of three dietary treatments in random order: blackcurrant powder (BC) to give a dose of 100 mg total ACNs/kg BW mixed either with water and sugar (Diet A), cereal (Weet-Bix), milk, and sugar (Diet B), or cereal, milk, sugar, and an additional flavonol (rutin, approximately 100 mg/kg BW) (Diet C). The four major anthocyanins of BC, delphinidin-3-glucoside, delphinidin-3-rutinoside, cyanidin-3-glucoside, and cyanidin-3-rutinoside, were identified and quantified by HPLC-PDA in all three diets. In the pig plasma, four peaks with a reversed pattern to those of anthocyanins in the BC extract were detected. The total amount of anthocyanins absorbed was not significantly different between the three diets, but the rate of absorption and subsequent decline was slower following administration of diet B and C than diet A. All three diets increased antioxidant capacity when measured by the FRAP assay but not when measured by the ORAC and non-protein ORAC assay. However, the increase was delayed and did not appear until 4 h after ingestion, at a time when plasma anthocyanin levels had returned to baseline. The present study demonstrates that the simultaneous intake of food or other flavonoids delays the absorption profile for anthocyanins. Our results also suggest that the increase in antioxidant capacity is not due to dietary anthocyanins but may be due to metabolites that result from anthocyanin consumption.

Absorption↗
PubMed2006

Effects of arachidonic acid, docosahexaenoic acid, prostaglandin E(2) and parathyroid hormone on osteoprotegerin and RANKL secretion by MC3T3-E1 osteoblast-like cells.

Bone is continuously remodeled through resorption by osteoclasts and the subsequent synthesis of the bone matrix by osteoblasts. Cell-to-cell contact between osteoblasts and osteoclast precursors is required for osteoclast formation. RANKL (receptor activator of nuclear factor-kappaB ligand) expressed on osteoblastic cell membranes stimulates osteoclastogenesis, while osteoprotegerin (OPG) secreted by osteoblasts inhibits osteoclastogenesis. Although polyunsaturated fatty acids (PUFAs) have been implicated in bone homeostasis, the effects thereof on OPG and RANKL secretion have not been investigated. MC3T3-E1 osteoblasts were exposed to the n-6 PUFA arachidonic acid (AA) and the n-3 PUFA docosahexaenoic acid (DHA); furthermore, the bone-active hormone parathyroid hormone (PTH) and the effects thereof were tested on OPG and RANKL secretion. Prostaglandin E(2) (PGE(2)), a product of AA metabolism that was previously implicated in bone homeostasis, was included in the study. AA (5.0-20 microg/ml) inhibited OPG secretion by 25-30%, which was attenuated by pretreatment with the cyclooxygenase blocker indomethacin, suggesting that the inhibitory effect of AA on OPG could possibly be PGE(2)-mediated. MC3T3-E1 cells secreted very low basal levels of RANKL, but AA stimulated RANKL secretion, thereby decreasing the OPG/RANKL ratio. DHA suppressed OPG secretion to a smaller extent than AA. This could, however, be due to endogenous PGE(2) production. No RANKL could be detected after exposing the MC3T3-E1 cells to DHA. PTH did not affect OPG secretion, but stimulated RANKL secretion. This study demonstrates that AA and PTH reduce the OPG/RANKL ratio and may increase osteoclastogenesis. DHA, however, had no significant effect on OPG or RANKL in this model.

Animals↗
PubMed2005

Is docosahexaenoic acid more effective than eicosapentaenoic acid for increasing calcium bioavailability?

Experimental animal and human studies have indicated that long chain polyunsaturated fatty acids (LCPUFA) may enhance calcium absorption, reduce urinary calcium excretion, and increase bone calcium content. In the present study, the effect of LCPUFA, as provided in evening primrose oil, fish and tuna oils, on calcium bioavailability was investigated. Growing male rats were fed a semi-synthetic diet for 6 weeks, after which calcium absorption, bone mineral density (ex vivo), bone calcium content, and bone biomechanics were measured. Calcium absorption, ex vivo bone mineral density, and bone calcium content were significantly higher in the animals fed tuna oil compared with those of a control group fed corn oil. Significant correlations were found between the docosahexaenoic acid (DHA) (22:6n-3) content of the red cell membranes and bone density and bone calcium content. DHA increased accretion of calcium in bone significantly more so than eicosapentaenoic acid (EPA) (20:5n-3).

Animals↗
PubMed2005

The effect of whey acidic protein fractions on bone loss in the ovariectomised rat.

Bovine milk has been shown to contain bioactive components with bone-protective properties. Earlier studies on bovine milk whey protein showed that it suppressed bone resorption in the female ovariectomised rat. A new osteotropic component was subsequently identified in the whey basic protein fraction, but bone bioactivity may also be associated with other whey fractions. In the present study, we investigated whether acidic protein fractions isolated from bovine milk whey could prevent bone loss in mature ovariectomised female rats. Six-month-old female rats were ovariectomised (OVX) or left intact (sham). The OVX rats were randomised into four groups. One group remained the control (OVX), whereas three groups were fed various whey acidic protein fractions from milk whey as 3 g/kg diet for 4 months. Outcomes were bone mineral density, bone biomechanics and markers of bone turnover. Bone mineral density of the femurs indicated that one of the whey AF over time caused a recovery of bone lost from OVX. Plasma C-telopeptide of type I collagen decreased significantly in all groups except OVX control over time, indicating an anti-resorptive effect of whey acidic protein. Biomechanical data showed that the AF may affect bone architecture as elasticity was increased by one of the whey AF. The femurs of AF-supplemented rats all showed an increase in organic matter. This is the first report of an acidic whey protein fraction isolated from milk whey that may support the recovery of bone loss in vivo.

Animals↗
PubMed2004

Osteoprotegerin-receptor activator of nuclear factor-kappaB ligand ratio: a new approach to osteoporosis treatment?

Osteoporosis, the most commonly occurring bone disease, is characterized by enhanced bone fragility and increased risk of fracture. Bone remodeling is the process in which bone is broken down by osteoclasts and then built back again by osteoblasts. In healthy adult bone, these two processes are balanced and a constant level of bone mass is maintained. Some of the proteins involved in the interaction between osteoblasts and osteoclasts have recently been identified. Receptor activator of nuclear factor-kappaB (RANK) ligand is produced by osteoblasts and exerts its effects through binding to its receptor (RANK) on osteoclast precursor cells. Binding results in activation of osteoclasts. Osteoblasts also produce osteoprotegerin (OPG), a potent inhibitor of osteoclast formation and a decoy receptor for RANK. The relative ratio of OPG and RANK ligand in the bone marrow microenvironment may determine the number of active osteoclasts, bone resorption rate, and bone mass. OPG is currently under investigation for osteoporosis treatment.

Animals↗
PubMed2003

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.

Absorption↗
PubMed2003

The effect of fructooligosaccharides with various degrees of polymerization on calcium bioavailability in the growing rat.

Maximizing peak bone mass during adolescence may be the key to postponing and perhaps preventing bone fractures due to osteoporosis in later life. One mechanism to maximize peak bone mass is to maximize calcium absorption, and it has been suggested that inulin and oligofructose might be one of the ways of doing so. In this study, fructooligosaccharides with various degrees of polymerization have been compared in terms of impact on calcium absorption, bone density, and excretion of collagen cross-links in the young adult male rat. The various oligosaccharides were oligofructose (DP2-8), inulin (DP>23), and a mixture of 92% inulin and 8% short-chain oligofructose (DP2-8). Measuring ex vivo bone mineral density (BMD) and bone mineral content (BMC) showed that BMD was significantly higher in the group fed inulin (DP>23) in both femurs, whereas BMC was significantly higher in the spine. The excretion of fragments of Type 1 collagen decreased in all groups over the 4 weeks of feeding, but the decrease was most significant in the group fed inulin (DP>23). Several hypotheses have been offered to explain the effect of the fructooligosaccharides on calcium absorption and retention. These include the production of organic acids that would acidify the luminal contents and enhance solubility and hence absorption, or possibly a mechanism via calbindinD9k. This study is unique in that it compares the different fructooligosaccharides in the same model, and it clearly shows that the various fructans do not have the same effect. In our model, inulin (DP>23) had the most significant effect on calcium bioavailability.

Animals↗