Life-long protein malnutrition in the rat (Rattus norvegicus) results in altered patterns of craniofacial growth and smaller individuals

Integration and the Developmental Genetics of Allometry

Allometry refers to the ways in which organismal shape is associated with size. It is a special case of integration, or the tendency for traits to covary, in that variation in size is ubiquitous and evolutionarily important. Allometric variation is so commonly observed that it is routinely removed from morphometric analyses or invoked as an explanation for evolutionary change. In this case, familiarity is mistaken for understanding because rarely do we know the mechanisms by which shape correlates with size or understand their significance. As with other forms of integration, allometric variation is generated by variation in developmental processes that affect multiple traits, resulting in patterns of covariation. Given this perspective, we can dissect the genetic and developmental determinants of allometric variation. Our work on the developmental and genetic basis for allometric variation in craniofacial shape in mice and humans has revealed that allometric variation is highly polygenic. Different measures of size are associated with distinct but overlapping patterns of allometric variation. These patterns converge in part on a common genetic basis. Finally, environmental modulation of size often generates variation along allometric trajectories, but the timing of genetic and environmental perturbations can produce deviations from allometric patterns when traits are differentially sensitive over developmental time. These results question the validity of viewing allometry as a singular phenomenon distinct from morphological integration more generally.

Choline Supplementation Prevents a Hallmark Disturbance of Kwashiorkor in Weanling Mice Fed a Maize Vegetable Diet: Hepatic Steatosis of Undernutrition

Hepatic steatosis is a hallmark feature of kwashiorkor malnutrition. However, the pathogenesis of hepatic steatosis in kwashiorkor is uncertain. Our objective was to develop a mouse model of childhood undernutrition in order to test the hypothesis that feeding a maize vegetable diet (MVD), like that consumed by children at risk for kwashiorkor, will cause hepatic steatosis which is prevented by supplementation with choline. A MVD was developed with locally sourced organic ingredients, and fed to weanling mice (n = 9) for 6 or 13 days. An additional group of mice (n = 4) were fed a choline supplemented MVD. Weight, body composition, and liver changes were compared to control mice (n = 10) at the beginning and end of the study. The MVD resulted in reduced weight gain and hepatic steatosis. Choline supplementation prevented hepatic steatosis and was associated with increased hepatic concentrations of the methyl donor betaine. Our findings show that (1) feeding a MVD to weanling mice rapidly induces hepatic steatosis, which is a hallmark disturbance of kwashiorkor; and that (2) hepatic steatosis associated with feeding a MVD is prevented by choline supplementation. These findings support the concept that insufficient choline intake may contribute to the pathogenesis of hepatic steatosis in kwashiorkor.

Measures of Relative Dentary Strength in Rancho La Brea Smilodon fatalis over Time

The late Pleistocene megafaunal extinction of approximately 12,000 years ago, included the demise of Smilodon fatalis, a hypercarnivore from the Rancho La Brea deposits, which has been studied across time by looking at different deposits or pits to determine morphological size and shape changes and trends during this time. To better understand functional aspects of these changes, this study focused on a measure of jaw strength over time, which can give an indication of morphological changes within the jaw that cannot be seen using surface morphometrics. By radiographing dentaries, cortical bone can be seen, which provides an estimate of resistance to bending forces while biting, and can be measured and used as an indicator of jaw strength. Measurements were taken at repeatable locations on the dentary of the depth of the cortical bone, and of a standardized measure of cortical bone, which allows for the comparison between different individuals. Specimens included those of five different pits ranging from about 37 Kybp to 13 Kybp (just before the extinction of S. fatalis). No significant difference was found in the depth of jaws at any of the measurement points from any of the pits. However, significant differences were found in both the actual thickness of cortical bone, and the standardized thickness of cortical bone at the lower P4 between pit 13 (which had the lowest amount of bone) and pit 61/67 (which had the highest). These conclusions support other studies that have shown that individuals in pit 13 were under physiological and perhaps dietary stress, which may be reflected in the deposition of cortical bone, while the opposite trend is seen in the individuals in pit 61/67. Our results further support findings suggesting Smilodon did not appear to be morphologically most vulnerable right before its extinction.

Shape covariation between the craniofacial complex and first molars in humans

The occurrence of mutual genetic loci in morphogenesis of the face and teeth implies shape covariation between these structures. However, teeth finalize their shape at an early age, whereas the face grows and is subjected to environmental influences for a prolonged period; it is therefore conceivable that covariation might modulate with age. Here we investigate the extent of this covariation in humans by measuring the 3D shape of the occlusal surface of the permanent first molars and the shape of the craniofacial complex from lateral radiographs, at two maturations stages. A sample of Greek subjects was divided into two groups (110 adult, 110 prepubertal) with equally distributed gender. The occlusal surfaces of the right first molars were 3D scanned from dental casts; 265 and 274 landmarks (including surface and curve semilandmarks) were digitized on the maxillary and mandibular molars, respectively. The corresponding lateral cephalometric radiographs were digitized with 71 landmarks. Geometric morphometric methods were used to assess shape variation and covariation. The vertical dimension of the craniofacial complex was the main parameter of shape variation, followed by anteroposterior deviations. The male craniofacial complex was larger (4.0-5.7%) and was characterized by a prominent chin and clockwise rotation of the cranial base (adult group only). Allometry was weak and statistically significant only when examined for the sample as a whole (percent variance explained: 2.1%, P = 0.0002). Covariation was statistically significant only between the lower first molar and the craniofacial complex (RV = 14.05%, P = 0.0099, and RV = 12.31%, P = 0.0162, for the prepubertal and adult groups, respectively). Subtle age-related covariation differences were noted, indicating that environmental factors may influence the pattern and strength of covariation. However, the main pattern was similar in both groups: a class III skeletal pattern (relative maxillary retrusion and mandibular protrusion), hyperdivergency, forward rotation of the posterior cranial base and upward rotation of the anterior cranial base were associated with mesiodistal elongation of the lower molars and height reduction of their distal cusps. This pattern mimics phylogeny in humans, where flexion and counterclockwise rotation of the cranial base, considered advantageous to survival, co-occur with tooth reductions that cannot be easily explained in evolutionary terms. The similarity of the phylogenetic and covariation patterns seems to support the pleiotropic gene hypothesis.

Leonardo da Vinci meets celiac disease

BACKGROUND AND AIM

Leonardo da Vinci's face symmetry derives from 3 equal craniofacial segments: trichion-nasion (tn), which represents the superior third of the face, nasion-subnasal (ns) that is the medium third of the face, and subnasal-gnathion (sg) that is the length of the lower third of the face. It has been reported that adult subjects with celiac disease (CD) can be identified on the basis of a greater extension of the forehead in comparison to the medium third of the face, with a high tn/ns ratio. The aim of the present study was to investigate the correlation between facial asymmetry and CD in childhood and adulthood.

METHODS

We studied 126 biopsy-proven patients with CD (76 children and 50 adults) and 102 healthy controls (43 children and 59 adults). Their faces were photographed; the pictures were edited using a software program to calculate the facial segments.

RESULTS

The tn length was significantly different between adult celiac and adult controls (7.43 ± 1.46 cm vs 6.38 ± 1.73 cm, P = 0.001). The cutoff of 6.5 cm tn, derived from receiver operating characteristic curve analysis, identified 43 of 50 patients (sensitivity 86%), but 34 of 59 controls were positive (specificity 54.2%). The positive predictive value was 56%; however, the tn/ns ratio was not significantly different between celiacs and controls. Neither the tn length nor the tn/ns ratio in celiacs correlated to the time of gluten exposure.

CONCLUSIONS

Adults, but not children, with celiac disease show a forehead extension significantly greater than controls, but this test's specificity appears too low to be used in the screening of CD.

Experimental evidence for nutrition regulated stress resistance in Drosophila ananassae

Background

The amount and quality of nutrients consumed by organisms have a strong impact on stress resistance, life-history traits and reproduction. The balance between energy acquisition and expenditure is crucial to the survival and reproductive success of animals. The ability of organisms to adjust their development, physiology or behavior in response to environmental conditions, called phenotypic plasticity, is a defining property of life. One of the most familiar and important examples of phenotypic plasticity is the response of stress tolerance and reproduction to changes in developmental nutrition. Larval nutrition may affect a range of different life-history traits as well as responses to environmental stress in adult.

Principal Findings

Here we investigate the effect of larval nutrition on desiccation, starvation, chill-coma recovery, heat resistance as well as egg to adult viability, egg production and ovariole number in Drosophila ananassae. We raised larvae on either protein rich diet or carbohydrate rich diet. We found that flies consuming protein rich diet have higher desiccation and heat shock resistance whereas flies developed on carbohydrate rich diet have higher starvation and cold resistance. Egg production was higher in females developed on protein rich diet and we also found trade-off between egg production and Egg to adult viability of the flies. Viability was higher in carbohydrate rich diet. However, sex specific viability was found in different nutritional regimes. Higher Egg production might be due to higher ovariole number in females of protein rich diet.

Conclusion

Thus, Drosophila ananassae adapts different stress tolerance and life-history strategies according to the quality of the available diet, which are correlated with phenotypic adjustment at anatomical and physiological levels.

Catch-up and targeted growth following variable duration protein restriction: effects on bone and body mass

Protein malnutrition leads to growth retardation that can be reversed through catch-up growth, once normative nutrition is restored. Because growth is a dynamic process, catch-up capacity is likely influenced by the maturity of the animal and/or the duration of the insult, in addition to the type of insult experienced. We compared length of malnutrition, sexual dimorphism, body mass, and skeletal growth. Eighty Rattus norvegicus were divided into 10 treatment groups (five diets; male and female) and followed for more than 1 year. At weaning, animals were placed on either a control or low-protein isocaloric diet. Three experimental groups were switched to the control diet at 40, 60, or 90 days. Beginning with 21 days of age, animals were weighed daily and radiographed throughout the study. To determine the presence of catch-up growth, growth rates (GRs) were calculated (linear regression) for 20-day time spans before and after diet changes and compared among treatment groups. Targeted growth was measured as final size or as the coefficient of variation with age. These results show that 1) protein-restricted animals experience catch-up growth with dietary rehabilitation; 2) for females, catch-up GRs are proportional to GRs in control animals at the same age as the timing of dietary rehabilitation but not for males; and 3) targeted growth was observed in some, but not all, aspects of anatomy. The length of the tibia and humerus was indistinguishable from controls, regardless of length of malnutrition or gender, whereas the ulna and male body mass exceeded control sizes. Although most measures decreased in variation with ontogeny, the tibia failed to do so. These results support a complex biological regulation of catch-up and targeted growth. The implications for selection are that flexible and responsive developmental trajectories may have an advantage over those programed into a single size.

Protein and carbohydrate composition of larval food affects tolerance to thermal stress and desiccation in adult Drosophila melanogaster

Larval nutrition may affect a range of different life history traits as well as responses to environmental stress in adult insects. Here we test whether raising larvae of fruit flies, Drosophila melanogaster, on two different nutritional regimes affects resistance to cold, heat and desiccation as well as egg production and egg-to-adult viability. We raised larvae on a carbohydrate-enriched and a protein-enriched growth medium. We found that flies developed on the high protein medium had increased heat and desiccation tolerance compared to flies developed on the carbohydrate-enriched medium. In contrast, flies developed on the carbohydrate-enriched growth medium recovered faster from chill coma stress compared to flies developed on a protein-enriched medium. We also found gender differences in stress tolerance, with female flies being more tolerant to chill coma, heat knockdown and desiccation stress compared to males. Egg production was highest in females that had developed on the protein-enriched medium. However, there was a sex-specific effect of nutrition on egg-to-adult viability, with higher viability for males developing on the sucrose-enriched medium, while female survival was highest when developing on the protein-enriched medium. Our study indicates that larval nutrition has a strong impact on the ability to cope with stress, and that the optimal nutrient composition varies with the type of stress.

Longitudinal regional brain volume changes quantified in normal aging and Alzheimer's APP x PS1 mice using MRI

In humans, mutations of amyloid precursor protein (APP) and presenilins (PS) 1 and 2 are associated with amyloid deposition, brain structural change and cognitive decline, like in Alzheimer's disease (AD). Mice expressing these proteins have illuminated neurodegenerative disease processes but, unlike in humans, quantitative imaging has been little used to systematically determine their effects, or those of normal aging, on brain structure in vivo. Accordingly, we investigated wildtype (WT) and TASTPM mice (expressing human APP(695(K595N, M596L)) x PS1(M146V)) longitudinally using MRI. Automated global and local image registration, allied to a standard digital atlas, provided pairwise segmentation of 13 brain regions. We found the mature mouse brain, unlike in humans, enlarges significantly from 6-14 months old (WT 3.8+/-1.7%, mean+/-SD, P<0.0001). Significant changes were also seen in other WT brain regions, providing an anatomical benchmark for comparing other mouse strains and models of brain disorder. In TASTPM, progressive amyloidosis and astrogliosis, detected immunohistochemically, reflected even larger whole brain changes (5.1+/-1.4%, P<0.0001, transgenexage interaction P=0.0311). Normalising regional volumes to whole brain measurements revealed significant, prolonged, WT-TASTPM volume differences, suggesting transgene effects establish at <6 months old of age in most regions. As in humans, gray matter-rich regions decline with age (e.g. thalamus, cerebral cortex and caudoputamen); ventricles and white matter (corpus callosum, corticospinal tract, fornix system) increase; in TASTPMs such trends often varied significantly from WT (especially hippocampus). The pervasive, age-related structural changes between WT and AD transgenic mice (and mouse and human) suggest subtle but fundamental species differences and AD transgene effects.

Effect of maternal food restriction during gestation on early development of F1 and F2 offspring in the rat-like hamster (Cricetulus triton)

Maternal food restriction (FR) may have strong and long-term effects on body weight, brain and behavior development of offspring. However, it is still not well understood whether such an effect is carried over to the next generation. Our objective was to examine the differences of maternal behavior, body growth, cranial growth and early development of F1 and F2 offspring of rat-like hamsters between a FR group and a control group. Results show that FR has a significant influence on maternal gathering behavior. The body weight of F1 offspring was significantly lower in the food-restricted group compared with that of the control animals, while the body weight of food-restricted F2 offspring was not significantly different from that of the control group. The physical development and neurodevelopment of food-restricted F1 and F2 offspring were significantly delayed compared to the controls. These results suggest that FR in female rat-like hamsters affected negatively the body growth of F1 offspring, and the physical and neurodevelopment of both F1 and F2 offspring. The effect of maternal FR on F2 offspring was smaller than that on F1 offspring. These factors may, in turn, play an important role in the population regulation of this species.