Growth deceleration and bone metabolism in nutritional dwarfing rats

Oxidative stress response to air particle pollution in a rat nutritional growth retardation model

Air pollution consisting of gases and particulate matter-(PM) represents a health problem in cities worldwide. However, air pollution does not impact equally all individuals, as children appear to be more vulnerable subpopulations. Air pollution and malnutrition are two distinct factors that have been associated with oxidative damage. Therefore, the interaction between environmental exposure and nutritional status in populations at risk needs to be explored. The aim of this study was to examine oxidative metabolism in lung, heart and liver in malnourished young rats exposed to residual oil fly ash (ROFA). A Nutritional Growth Retardation (NGR) model was developed in weanling male rats placed on a 20% restricted balanced diet for 4 weeks. Then, NGR and control rats were intranasally instilled with either ROFA (1mg/kg BW) or phosphate buffered saline (PBS). Twenty-four hr post-exposure lung, heart and liver were excised, and serum collected. ROFA induced lung and liver inflammation in control and NGR animals as evidenced by lung polymorphonuclear neutrophil (PMN) recruitment and alveolar space reduction accompanied by liver lymphocyte and binucleated hepatocyte level increase. In lung and liver, antioxidant defense mechanisms reduced lipoperoxidation. In contrast, only in NGR animals did ROFA exposure alter heart oxidative metabolism leading to lipid peroxidation. Although histological and biochemical tissue alterations were detected, no marked changes in serum liver and heart systemic biomarkers were observed. In conclusion, NGR animals responded differently to PM exposure than controls suggesting that nutritional status plays a key role in responsiveness to ambient air contaminants.

Effect of chronic undernutrition on body mass and mechanical bone quality under normoxic and altitude hypoxic conditions

Both undernutrition and hypoxia exert a negative influence on both growth pattern and bone mechanical properties in developing rats. The present study explored the effects of chronic food restriction on both variables in growing rats exposed to simulated high-altitude hypoxia. Male rats (n 80) aged 28 d were divided into normoxic (Nx) and hypoxic (Hx) groups. Hx rats were exposed to hypobaric air (380 mmHg) in decompression chambers. At T0, Nx and Hx rats were subdivided into four equal subgroups: normoxic control and hypoxic controls, and normoxic growth-restricted and hypoxic growth-restricted received 80 % of the amount of food consumed freely by their respective controls for a 4-week period. Half of these animals were studied at the end of this period (T4). The remaining rats in each group continued under the same environmental conditions, but food was offered ad libitum to explore the type of catch-up growth during 8 weeks. Structural bone properties (strength and stiffness) were evaluated in the right femur midshaft by the mechanical three-point bending test; geometric properties (length, cross-sectional area, cortical mass, bending cross-sectional moment of inertia) and intrinsic properties of the bone tissue (elastic modulus) were measured or derived from appropriate equations. Bone mineralisation was assessed by ash measurement of the left femur. These data indicate that the growth-retarded effects of diminished food intake, induced either by food restriction or hypoxia-related inhibition of appetite, generated the formation of corresponding smaller bones in which subnormal structural and geometric properties were observed. However, they seemed to be appropriate to the body mass of the animals and suggest, therefore, that the bones were not osteopenic. When food restriction was imposed in Hx rats, the combined effects of both variables were additive, inducing a further reduction of bone mass and bone load-carrying capacity. In all cases, the mechanical properties of the mineralised tissue were unaffected. This and the capacity of the treated bones to undergone complete catch-up growth with full restoration of the biomechanical properties suggest that undernutrition, under either Nx or Hx conditions, does not affect bone behaviour because it remains appropriate to its mechanical functions.

High-fat diets affect energy and bone metabolism in growing rats

BACKGROUND

High-fat diets are usually associated with greater weight (W) gain and body fat (BF). However, it is still unclear whether the type and amount of fat consumed influence BF. Additionally, dietary fat intake may also have consequences on skeletal health.

OBJECTIVE

To evaluate in healthy growing rats the effects of high-fat diets and type of dietary fat intake (saturated or vegetable oils) on energy and bone metabolism.

METHODS

At weaning, male Wistar rats (n = 50) were fed either a control diet (C; fat = 7% w/w) or a high-fat diet (20% w/w) containing either: soybean oil, corn oil (CO), linseed oil (LO), or beef tallow (BT) for 8 weeks. Zoometric parameters, BF, food intake and digestibility, and total and bone alkaline phosphatase (b-AP) were assessed. Total skeleton bone mineral density (BMD) and content (BMC), BMC/W, spine BMD, and bone volume (static-histomorphometry) were measured.

RESULTS

Animals fed BT diet achieved lower W versus C. Rats fed high-fat vegetable oil diets showed similar effects on the zoometric parameters but differed in BF. BT showed the lowest lipid digestibility and BMC. In contrast, high vegetable oil diets produced no significant differences in BMC, BMC/W, BMD, spine BMD, and bone volume. Marked differences were observed for LO and BT groups in b-AP and CO and BT groups in bone volume.

CONCLUSION

BT diet rich in saturated fatty acids had decreased digestibility and adversely affected energy and bone metabolisms, in growing healthy male rats. There were no changes in zoometric and bone parameters among rats fed high vegetable oil diets.

Role of the insulin-like growth factor system in epiphyseal cartilage on the development of Langshan and Arbor Acres chickens, Gallus domesticus

We measured the mRNA transcript expression patterns for members of the insulin-like growth factor (IGF) system during embryonic and postnatal development in epiphyseal cartilage from Langshan (LS) and Arbor Acres (AA) chickens. Insulin-like growth factor binding protein (IGFBP)-2 expression was positively correlated with IGF-I from embryonic day (E) 14 to postnatal d (P) 0 and with IGF-II from E14 to P14 but negatively correlated with IGF-I from P0 to P42 and IGF-II from P14 to P42. Expression of IGFBP-5 correlated positively with IGF-I from E14 to P0 but negatively from P0 to P28. The results suggest that these genes are regulated in a coordinated fashion during development. A negative correlation was found between IGFBP-7 and IGF-II during P0 to P42. A positive correlation was found between IGFBP-3 (E14 to E18, P14 to P42) and IGF-IR and between IGFBP-3 (E14 to P0, P14 to P42) and IGF-I. The endocrine factors can be integrated with nutrition to regulate animal growth. In our study, AA chickens were fed a nutrient-rich AA diet, and LS chickens were fed either an AA diet or a less-rich diet. The LS and AA chickens fed the same AA diet showed no differences in IGF-I, IGF-I receptor, IGFBP-2, IGFBP-5, IGFBP-7, and IGFBP-3 but did still show differences in IGF-II. Our data indicate that these select genes may show linked expression during certain periods of development and that differences in gene expression respond differently to nutrient intake in LS and AA chickens.

Fat targets for skeletal health

Emerging evidence points to a critical role for the skeleton in several homeostatic processes, including energy balance. The connection between fuel utilization and skeletal remodeling begins in the bone marrow with lineage allocation of mesenchymal stem cells to adipocytes or osteoblasts. Mature bone cells secrete factors that influence insulin sensitivity, and fat cells synthesize cytokines that regulate osteoblast differentiation; thus, these two pathways are closely linked. The emerging importance of the bone-fat interaction suggests that novel molecules could be used as targets to enhance bone formation and possibly prevent fractures. In this article, we discuss three pathways that could be pharmacologically targeted for the ultimate goal of enhancing bone mass and reducing osteoporotic fracture risk: the leptin, peroxisome proliferator-activated receptor gamma and osteocalcin pathways. Not surprisingly, because of the complex interactions across homeostatic networks, other pathways will probably be activated by this targeting, which could prove to be beneficial or detrimental for the organism. Hence, a more complete picture of energy utilization and skeletal remodeling will be required to bring any potential agents into the future clinical armamentarium.

Effects of long-term calcium intake on body weight, body fat and bone in growing rats

Increased calcium intake may reduce body weight and fat in non-growing individuals. This study explored the long-term effects of high versus low calcium intake on body weight, body fat, BMC, BMD and bone size in growing male and female rats. Ninety male and 90 female Sprague-Dawley rats were randomly assigned either to a high calcium (1%) or low calcium (0.25%) diet from age 3 weeks until 40 weeks. Half of the animals were fed ad libitum, and half of the animals were on an adjusted feeding schedule (the food intake of the low calcium animals was reduced to maintain equal body weight with high calcium animals of the same gender). DXA and radiographic measurements (femur and skull length and width) were collected at the age of 4, 13 and 34 weeks. Growing male rats fed the low calcium diet ad libitum gained more weight and more fat than rats on a high calcium diet. When food intake was controlled, male rats on the low calcium diet still had a greater fat mass (despite their similar body weight) and smaller skeletal measurements than the high calcium animals. Growing female rats initially responded like the males: when fed ad libitum low calcium animals had an increased body weight and fat mass; when food intake was controlled the low calcium animals had a greater fat mass and smaller skeletal measurements. However, these differences were found at 13 weeks and not at 34 weeks, suggesting a transient effect with no long-term differences between high and low calcium intake in the growing female rats.

Metabolic status in growing rats fed isocaloric diets with increased carbohydrate-to-fat ratio

OBJECTIVE

A low-fat diet is hypothesized to be associated with significant weight loss. However, most previous studies have been limited to low-fat, low-calorie restrictive diets. This study evaluated the effect of isocaloric diets given "ad libitum" but different in relative amounts of fat and carbohydrate on body size, energy metabolism, body composition, insulin-like growth factor-1, and leptin serum levels in growing Wistar rats.

METHODS

Weanling male rats were fed with one of three diets that contained a ratio of carbohydrate to fat of 1:1, 2:1, or 3:1. Food intake, body weight, body length, oxygen consumption, and body composition were measured at ages 21 to 50 d. Serum levels of insulin-like growth factor-1 and leptin were also determined.

RESULTS

Energy intake was similar across groups. The ratio of body weight to body length remained adequate throughout the experimental period. However, groups that received 3:1 and 2:1 showed increased weight and progressive decreases in energy expenditure, body fat composition, and serum level of leptin, but the ratio of insulin-like growth factor-1 to body length was not affected.

CONCLUSIONS

Dietary substitution of fat with carbohydrates contributes to weight gain by decreasing energy expenditure and possibly by decreasing leptin secretion.

Mandibular bone remodeling under a choline-deficient diet: a histomorphometric study in rats

BACKGROUND

A deficiency of lipotropic factors in the rat induces renal, hepatic, and/or hematic damage. The aim of the present study was to evaluate the effect of a choline-deficient diet and refeeding on mandibular bone remodeling.

METHODS

Fifty Wistar rats were divided into 5 groups: group 1 (G1): control diet for 15 days; group 2 (G2): choline-deficient diet for 15 days; group 3 (G3): control diet for 30 days; group 4 (G4): choline-deficient diet for 30 days; and group 5 (G5): choline-deficient diet for 15 days and control diet for 15 days. All animals were sacrificed by ether overdose. The mandibles were resected, radiographed, decalcified, processed, and embedded in paraffin. Bucco-lingually oriented sections were obtained at the level of the interradicular bone of the medial roots of the left first molar, and stained with hematoxylin and eosin (H & E). Bone tissue density and bone remodeling were determined histomorphometrically. Body weight, food intake, hematocrit, and hemoglobinemia were also recorded.

RESULTS

Microscopic observation revealed that osteogenesis was lower in rats fed a choline-deficient diet, at both 15 and 30 days, and that this decrease did not revert with a control diet. Histomorphometric evaluation showed 37% and 27% reduction in bone tissue density at 15 and 30 days, respectively, and a 30% decrease in bone formation at 30 days, compared to controls.

CONCLUSION

In this experimental model, a choline-deficient diet led to altered bone remodeling as observed by a marked reduction in osteogenesis.