D. McCutcheon

A Saturated-Fat Diet during Development Alters Dendritic Growth in Mouse Brain.

The objective of this study was to determine whether an essential fatty acid (EFA)-deficient diet (saturated fat) fed during development would alter the pattern of dendritic growth in pyramidal neurons of mouse occipital cortex. Pregnant and lactating mice were fed either a saturated fat or control diet throughout pregnancy and lactation. At weaning, one female was selected randomly from each litter, and these animals were maintained on their respective diets and reared in an enriched environment for eight weeks. Following this, their brains were processed histologically using a modified Golgi-Cox method, and patterns of dendritic growth were analysed in occipital pyramidal cells. A Sholl concentric circle analysis indicated that, for basilar dendrites, starting at a distance of 62.5 μm, animals fed saturated fat had fewer crossings than controls, which is indicative of either shorter dendrites or of less dendritic branching. Although the analysis of branching order was not significant, the trend seen in these data supports less branching in the saturated fat group, particularly of third- and fourth-order dendrites. Similar effects were seen in the apical dendrites, although to a lesser extent. Covariance analysis indicated that these effects could not be accounted for by the smaller brains in the EFA-deficient group. They can therefore be considered preliminary support for an effect of EFA on the pattern of dendritic development.

Postnatal dietary supplementation with either gangliosides or choline: effects on spatial short-term memory in artificially-reared rats.

Abstract This study addressed the hypothesis that dietary supplementation with either gangliosides or choline during the brain growth spurt would enhance short-term spatial memory. Male Long-Evans rats were reared artificially from postnatal days (PD) 5–18 and were fed diets containing either (i) choline chloride 1250 mg/l (CHL), (ii) choline chloride 250 mg/l and GD3 24 mg/l (GNG) or (iii) choline chloride 250 mg/l (STD). A fourth group (SCK) was reared normally. Rats were weaned onto AIN 93G diet and on PD 35 were trained on a cued delayed- matching-to-place version of the Morris water maze. All groups learned to swim to the beacon that indicated the platform position on the first trial; similarly, on the second un-cued trial, the distance swam to reach the platform decreased to the same extent in all groups over the five days of training. The groups also responded in the same way to an increase in delay between the first and second trial from 1 min to 1 h, showing an increase in the distance swam, accompanied by a decrease in the number of direct swims to the platform. Thus, all rats were equally proficient at using spatial short-term memory, regardless of the choline or ganglioside content of the preweaning diet.

Effects of dietary γ-linolenic acid and prenatal ethanol on mouse brain and behavior

Abstract Pregnant B6D2F1 mice were treated with ethanol (25% Kcal) from days 5–17 of gestation. The diet was supplemented with either 18 : 2n-6 [linoleic acid (LA)] or 18 : 3n-6 [γ-linolenic acid (GLA)] throughout the study. Ethanol reduced 20 and 22 carbon n-6 and n-3 fatty acids in the brains of adult offspring. Feeding of GLA, compared with LA, increased levels of 20: 3n-6 and 22 : 4n-6, but reduced 22: 6n-3, particularly in the offspring of dams administered ethanol during gestation; adult brain weight was also lower in this group. Ethanol reduced the number of viable litters and adult body weight, and GLA reduced birth weight. Neither prenatal ethanol nor GLA affected open-field activity in adult males, nor did either treatment have an effect on the duration of immobility in the forced swimming test. However, GLA did affect circadian activity by increasing running wheel activity during the dark cycle, and decreasing it slightly during the light cycle. These results do not support a beneficial effect of GLA in preventing the developmental effects of ethanol; we suggest caution in the administration of high doses of GLA with ethanol during pregnancy.

Effects of treadmill exercise on weight cycling in female mice

Weight cycling increases food efficiency and rate of weight regain. This study induced weight loss in adult female B6D2F1 mice via dietary energy restriction and exercise to determine whether the weight loss regimen influenced rate of weight regain. Four groups of animals were studied: RES, restricted (food restricted); EX, exercised (treadmill exercised); SC, sham control (treadmill exposure, not exercised); LC, lab chow control (appropriately aged control). Both EX and SC voluntarily reduced food intake to the level of the RES animals. The RES group showed increased food efficiency and rate of weight regain relative to the LC group; this effect was attenuated in both the EX and SC groups. These findings demonstrate that a) the cycling phenomenon occurs in mice, and b) stressors such as forced exercise or exposure to a novel environment can modify the pattern of food efficiency and rate of weight regain engendered by dietary restriction.

Effects of early rearing experience on feeding behavior in B6D2F2 mice.

This work investigated putative factors contributing to the hyperphagia previously observed in mice which had been overfed during the preweaning period by rearing in small litters. In the first study, B6D2F2 mice, reared in small (Sm = 4), medium (Md = 8) and large (Lg = 12) litters, were subjected to a series of diets adulterated with varying concentrations of sucrose octa-acetate (1, 2, 4, and 8%). All animals reduced their food intake in response to the dietary adulteration, with evidence of a dose-response effect, but this response did not differ as a function of litter size. The second study addressed the involvement of the opioid system in the feeding response through the administration of a series of doses of naloxone (0.1, 0.25, 0.5, 1.0, 2.5, and 5.0 mg/kg, or 5, 7.5 and 10.0 mg/kg). Although naloxone treatment did reduce food intake, there was not a clear dose-response relationship. Again, there was no interaction with litter size. These results do not support effects of early rearing on the feeding response to dietary adulteration or to the effects of naloxone administration.

The effects of a marginal essential fatty acid diet in the early neonatal period on whole-body glucose tolerance in artificially reared rats

In infant nutrition, attention has focused on the role of essential fatty acids (EFA), linoleic and linolenic acids, in neural development and visual function. Little is known about how glucose homeostasis may be affected by a marginal EFA (mEFA) diet in early life. This study investigated the effects of a mEFA diet (2.5% linoleic acid, 0.06% linolenic acid) in the early neonatal period on whole-body glucose tolerance in early and adult life in rats that were artificially reared (AR). Male Long-Evans rat pups, reared artificially from postnatal days 5 to 18, were fed a mEFA or a control (CON) diet; a suckle control (SC) group was raised by foster dams. From weaning (day 18) until approximately 70 days of age, rats in the mEFA, CON and half of those in the SC groups were fed a high-fat diet. The remaining rats in the SC group were fed a standard AIN diet after weaning. Oral glucose tolerance tests (OGTT) were performed at days 18 and 46 of age. An intravenous glucose tolerance test (IVGTT) was performed at 70 days of age. The percentage of pancreatic cells staining positive for insulin was determined at 70 days of age. AR lead to impaired glucose tolerance in rats fed the mEFA and CON diets at day 18 compared with the SC group (p = 0.0014), but had no lasting effects on glucose homeostasis up to 70 days of age. A mEFA diet during early post-natal life did not significantly affect glucose tolerance in adulthood, although there was some evidence of altered insulin secretory patterns in this group at 70 days of age. The percentage of cells staining positive for insulin did not differ among groups. Glucose homeostasis seems to be robust to marginal fatty acid intake during the early post-natal period. Possible alterations in insulin secretion resulting from a mEFA diet deserve further study.