Roger A. King

Circulating insulin-like growth factor I levels in newborn premature and full-term infants followed longitudinally.

Longitudinal circulating levels of insulin-like growth factor I (IGF-I) were measured by radioimmunoassay after acid/ethanol extraction of serum or plasma in 44 appropriate-for-gestational age (AGA) premature infants, 7 small-for-gestational age (SGA) premature infants and 9 AGA full-term infants. The subjects were divided into cohorts with gestational age at birth 26-29 weeks, 30-33 weeks, 34-37 weeks and 38-42 weeks (full-term). The premature infants in this study exhibited diminished growth as compared with normal intrauterine growth. In all but the earliest premature infant cohort there was an immediate fall from the mean fetal IGF-I level, as reflected by the cord value, to a basal postnatal circulating level of IGF-I. The basal level of circulating IGF-I in premature infants was related only to gestational age. It increased slowly from 25 weeks gestation until four weeks after full-term equivalent and was independent of time of birth. Full-term infants were distinguished from early premature infants by the occurrence of a prominent postnatal surge in circulating IGF-I levels that was characterised by a significant (P less than 0.02) increase between day 1 and days 10-15. The SGA and AGA infants in the 34-37 week cohort showed similar profiles of circulating IGF-I with no significant difference in cord values between the two groups.

A novel high-amylose barley cultivar ( Hordeum vulgare var. Himalaya 292 ) lowers plasma cholesterol and alters indices of large-bowel fermentation in pigs

Hordeum vulgare var. Himalaya 292 is a new barley cultivar with altered starch synthesis and less total starch but more amylose, resistant starch (RS) and total and soluble NSP including beta-glucan. To determine its nutritional potential, young pigs were fed diets containing stabilised wholegrain flours from either Himalaya 292, Namoi (a commercial barley), wheat bran or oat bran at equivalent dietary NSP concentrations for 21 d. Serum total cholesterol was significantly lowered by the Himalaya 292 diet relative to wheat bran, indicating that Himalaya 292 retained its hypocholesterolaemic potential. In all groups SCFA concentrations were highest in the proximal colon and decreased towards the rectum. Digesta pH was lowest in the proximal colon and highest in the distal colon. Large-bowel and faecal pH were significantly lower in the pigs fed the barley and oat diets, indicating greater bacterial fermentation. Caecal and proximal colonic pH was lowest and SCFA pools highest in the pigs fed Himalaya 292. Total and individual SCFA were lowest in the mid- and distal colon of the pigs fed Himalaya 292 or oat bran. These data suggest the presence of more RS in Himalaya 292 and suggest that its fermentation was rapid relative to transit. Differences in faecal and large-bowel anaerobic, aerobic, coliform and lactic acid bacteria were relatively small, indicating a lack of a specific prebiotic action. These data support the potential of this novel barley cultivar to improve health through plasma cholesterol reduction and increased large-bowel SCFA production.

Genistein inhibits growth of B16 melanoma cells in vivo and in vitro and promotes differentiation in vitro

Consumption of soy products has been linked to a reduced mortality and morbidity from a number of cancers. Genistein, one of the principal soy isoflavones, has been shown to inhibit the growth of a number of tumour cell lines in vitro; however, a role of genistein in retarding tumour growth in vivo is less well documented. In this study, in addition to examining the effects of genistein on the growth of murine B16 melanoma cells in vitro, we have examined the effects of feeding a genistein‐rich diet on s.c. growth of these tumour cells in mice. In vitro, the melanoma cells showed an increase in sensitivity to genistein with increasing time of exposure, culminating in a 50% growth inhibition (IC50) at 12.5 μM after 7 days. Genistein at 25 μM induced micronucleus formation after 24 hr and at concentrations as low as 2.5 μM induced morphological changes indicative of differentiation. Growth of solid tumours implanted into female C57BL/6J mice was inhibited by 50% when mice were fed genistein for 1 week before and for 1 week after inoculation with B16 melanoma cells. Plasma genistein concentrations at the time of tumour removal were 1.1 μM, which is similar to levels reported in humans consuming diets high in soybeans or soybean products, while control animals had no detectable genistein in plasma. Our results provide additional in vivo evidence suggesting that genistein retards the growth of implanted tumours, adding further to studies suggesting that this isoflavonoid is a biologically active component of soy foods. Int. J. Cancer 72:860–864, 1997.

Dietary resistant starch dose-dependently reduces adiposity in obesity-prone and obesity-resistant male rats

BackgroundAnimal studies show that diets containing resistant starch (RS) at levels not achievable in the human diet result in lower body weight and/or adiposity in rodents. We aimed to determine whether RS dose-dependently reduces adiposity in obesity-prone (OP) and obesity-resistant (OR) rats.MethodsMale Sprague–Dawley rats (n=120) were fed a moderate-fat, high-energy diet for 4 wk. Rats that gained the most weight (40%) were classified as obesity-prone (OP) and obesity-resistant (OR) rats were the 40% that gained the least weight. OP and OR rats were randomly allocated to one of six groups (n=8 for each phenotype). One group was killed for baseline measurements, the other five groups were allocated to AIN-93 based diets that contained 0, 4, 8, 12 and 16% RS (as high amylose maize starch) for 4 wk. These diets were matched for total carbohydrate content. At 0, 4 and 7 wk from the start of the study insulin sensitivity was calculated by homeostasis model assessment of insulin resistance (HOMA-IR) and adiposity was determined by dual-energy X-ray absorptiometry (DXA). At 8 wk, rats were euthanized and fat pad weights, intestinal digesta short chain fatty acid (SCFA) pools and plasma gut hormone levels were determined.ResultsObesity prone rats gained less weight with 4, 12 and 16% RS compared to 0% RS, but the effect in OR animals was significant only at 16% RS. Irrespective of phenotype, diets containing ≥8% RS reduced adiposity compared to 0% RS. Energy intake decreased by 9.8 kJ/d for every 4% increase in RS. All diets containing RS increased total SCFA pools in the caecum and lowered plasma GIP concentrations compared to the 0% RS, whereas plasma GLP-1 and PYY were increased when the diet contained at least 8% RS. Insulin sensitivity was not affected by RS.ConclusionRS in amounts that could be potentially consumed by humans were effective in reducing adiposity and weight gain in OP and OR rats, due in part to a reduction in energy intake, and changes in gut hormones and large bowel carbohydrate fermentation.

Induction of micronucleus formation in mouse splenocytes by the soy isoflavone genistein in vitro but not in vivo

The effects of genistein (one of the major soybean isoflavones), genistein (the glucosylated form of genistein) and etoposide (a topoisomerase 11 inhibitor) have been studied in mouse splenocytes in culture. Genistein (25 microM), genistein (25 microM) and etoposide (0.1 microM) all induced the production of large numbers of micronuclei; however, genistein at 12.5 or 2.5 microM had no clastogenic effect. In a second study, mice were gavaged with 20 mg genistein/kg body weight/day for 5 days (approximately equivalent to a 70 kg human consuming 2.8 kg soybeans/day) and the micronucleus frequency was determined. There was no observable increase in the micronucleus frequency even though the plasma genistein levels in the treated animals were found to be 9.2 +/- 2.0 microM compared with 0.1 +/- 0.0004 microM in the control animals. The results show that even though genistein is capable of inducing micronucleus formation, an event associated with genetic damage, plasma levels are unlikely to be sufficiently elevated to produce such an effect.

Fish Oils Modulate Blood Pressure and Vascular Contractility in the Rat and Vascular Contractility in the Primate

The effect of dietary fish oils on development of hypertension and vascular response in vitro were studied in rats and a primate. Dietary fish oils (MaxEPA and an n-3 ethyl ester concentrate of higher EPA and DHA content) were administered to spontaneously hypertensive (SHR), stroke-prone spontaneously hypertensive (SHR-SP) and a backcross of SHR and Wistar Kyoto (SHR/WKY) rats from 4-16 weeks of age. Blood pressure was monitored during the feeding period and vascular responses measured in the aorta and mesenteric vascular bed in vitro. Depending on the strain of rat used and the composition of the fish oil the attenuation in blood pressure was 10-26 mmHg. Fish oils attenuated the response mediated by sympathetic nerve stimulation or intralumenal norepinephrine in the perfused mesenteric vascular bed preparation from the SHR. This attenuation was more pronounced for fish oils enriched with eicosapentaenoic acid and docosahexaenoic acid and was more prominent in the SHR and SHR/WKY backcross than it was in the SHR-SP. Prostanoid synthesis or nitric oxide modulation of alpha-adrenoceptor responses were shown not to be involved in the attenuation of vascular responses produced by fish oil. The maximum contraction of aortic ring preparations in response to norepinephrine (NE) was significantly smaller in SHR than WKY rats fed olive oil and for SHR rats maintained on fish oils the contraction was close to WKY olive oil values. Evidence was obtained also for a modulation of vasoconstrictor responses by dietary fish oils in the perfused mesenteric bed of the marmoset monkey.

Measurement of phenol and p-cresol in urine and feces using vacuum microdistillation and high-performance liquid chromatography

In this article, we describe a simple, sensitive, accurate, and repeatable method for the measurement of phenol and p-cresol (4-methylphenol) in human urine and feces. We examined a number of parameters to identify an optimal extraction protocol. Purification of sample extracts was achieved by low-temperature vacuum microdistillation. Separation was achieved in approximately 15 min by high-performance liquid chromatography (HPLC) with quantification by fluorescence at 284/310 nm. Limits of detection for phenol were 2 ng/ml for urine and 20 ng/g for feces, and those for p-cresol were 10 ng/ml for urine and 100 ng/g for feces. For comparison, approximate mean values for urine are 3 microg/ml for phenol and 30 microg/ml for p-cresol, and those for feces are 1 microg/g for phenol and 50 microg/g for p-cresol. An experienced analyst can process 60 samples each day using this method.

Effects of enalapril and hydralazine treatment and withdrawal upon cardiovascular hypertrophy in stroke-prone spontaneously hypertensive rats.

OBJECTIVE To test the hypothesis that effects of angiotensin converting enzyme (ACE) inhibitors upon resistance vessel structure are responsible for their ability to cause long-term reduction in blood pressure. DESIGN Stroke-prone spontaneously hypertensive (SHRSP) and Wistar-Kyoto (WKY) rats were treated with enalapril or hydralazine from 4 to 15 weeks of age. Effects upon tail-cuff blood pressure, left ventricular hypertrophy and structural indices of the superior mesenteric artery (SMA) and its resistance vessels were assessed at 11 weeks of treatment and up to 11 weeks post-treatment. METHODS Left ventricular hypertrophy was assessed by left ventricular weight:body weight ratios. Evidence of vascular structural change was obtained from tissue weight:body weight ratios, levels of RNA, DNA and expression of alpha-actin and elastin messenger (m)RNA. RESULTS The effects of enalapril and hydralazine upon left ventricular hypertrophy in SHRSP were consistent with their respective effects upon blood pressure. Both drugs prevented the development of medial hypertrophy in SMA and resistance vessels. This was accompanied by substantial reductions in RNA:DNA ratios. Alpha-actin mRNA levels were not affected by either drug but elastin mRNA levels were reduced by both drugs. During the first 12 days post-treatment there was evidence of structural change in SMA accompanying the increases in blood pressure but importantly not in the resistance vessels. CONCLUSION The effects of enalapril upon left ventricular hypertrophy and mesenteric arterial hypertrophy are totally consistent with responses to blood pressure and the persistence of structural changes post-treatment does not underlie the ability of the ACE inhibitors to persistently suppress hypertension.

Long term postnatal development of insulin secretion in early premature infants

The postnatal development of insulin secretion was studied in a group of premature infants (26-30 weeks gestation at birth) for periods up to 110 days after birth and in a small group of full-term infants (38-42 weeks gestation) for up to 47 days after birth. Circulating insulin levels were measured before, and at 30 min after the commencement of a glucose infusion given either parenterally or enterally depending on conceptual age and the mode of nutrition of the infant. The insulin response was assessed as the ratio of the increase in plasma insulin concentration to the increase in blood glucose concentration at 30 min. There was a small insulin response to glucose on day 1 in the premature infants and this increased slowly over the remainder of the study period regardless of the route of administration of glucose or of the mode of nutrition. The full-term infants were more responsive over the seven postnatal weeks in which they were studied. It is concluded that early premature infants can take up to eighteen weeks to develop an ability to respond fully to hyperglycaemia with insulin secretion even though full oral nutrition had been established over the last twelve weeks.

Depressed Cheek Cell Sodium Transport in Human Hypertension

Na+ transport activity was measured in cheek cells from untreated hypertensive subjects and age-matched normotensive controls identified from a blood pressure screening program. Cheek cells were isolated by a simple mouth wash procedure and Na+ transport activity was measured as the proton-dependent uptake of 22Na+ using a rapid filtration assay. The rate of Na+ uptake was about 45% lower in hypertensive subjects and this difference persisted in a follow up study 2 years later involving those subjects who remained untreated for their hypertension. The proton independent Na+ uptake was also reduced by about 46% in the hypertensive group. The increase in the rate of cheek cell Na+ transport with increasing transcellular proton gradient values was also significantly lower in hypertensive subjects. The reduced cheek cell Na+ transport observed in hypertensive subjects may indicate decreased activity of the Na+/H+ antiporter and/or changes in the ion permeability properties of the cheek cell plasma membrane in the hypertensive state. This novel assay provides a biochemically based method for discriminating between normotensive and hypertensive subjects and makes use of tissue which can be obtained in a relatively non-invasive manner.