Deleterious effect of chronic high-dose ethanol intake on biomechanical bone properties and periodontal status.

To evaluate the effect of high-graduation chronic ethanol (EtOH) intake on bone and periodontal tissues of rats. Male Wistar rats (250 g) were divided into two groups of n = 12 each one. EtOH (5 ml of 3 g/kg) was administered to the experimental group by gastric gavage twice a day for 20 days and the control group received water under the same conditions. The rats were euthanized and used to perform biochemical determination in plasma and gingival tissue, and histological and biomechanical studies in the femur and mandibular tissues. Alcohol increased both TNFα (p < 0.01) and PGE2 (p < 0.05) in plasma and gingiva (p < 0.05) as compared to controls. In addition, EtOH increased the alveolar bone loss as evidenced by the increased distance between the cement enamel junction and the alveolar crest (p < 0.01), the lower % of interradicular bone expressed as bone area/total area (B.Ar/T.Ar, p < 0.05) and the larger periodontal space (p < 0.05), as compared to controls. Likewise, the mandibular microtomographic analysis in alcoholized rats revealed a lower % of interradicular bone volume/total volume (BV/TV, p < 0.05), greater trabecular separation (p < 0.05) and greater % trabecular porosity (p < 0.05) than controls. No biomechanical alteration was observed in lower jaws, while the femur of alcoholized rats presented a decrease in the structural bone properties (p < 0.001), as a systemic consequence of deterioration of the diaphyseal architecture (p < 0.01) without changes in material properties. The consumption of high doses of alcohol produces deleterious effects on periodontal tissues that could be due not only to local but also systemic effects.

Mandibular biomechanical behavior of rats submitted to chronic intermittent or continuous hypoxia and periodontitis.

BACKGROUND: The aim of this study was to investigate the effects of exposure to continuous (CH) and intermittent (IH) hypoxia on biomechanical properties of the mandible and periodontal tissue of animals submitted to experimental periodontitis (EP) when applying loads in a hypoxic environment. METHODS: Adult female Wistar rats were exposed during 90 days to IH or CH (simulated high altitude of 4200 m above sea level). Fourteen days prior to the euthanasia, EP was induced to half of the animals of each group. RESULTS: Only in the rats with EP, IH decreased the maximum capacity of the mandible to withstand load and the limit of elastic load. Indicators of intrinsic properties of the bone material were significantly reduced by both types of hypoxia in rats with EP. Hypoxia enhanced the alveolar bone loss induced by EP in the buccal side of the mandible, without showing additional effects in lingual or interradicular bone. Hypoxia increased prostaglandin E2 content in gingival tissue of healthy animals and further elevated the E2 levels increased by EP. CONCLUSIONS: When periodontitis is present, hypoxic stress induces a decrease in mineral properties that ultimately affects the ability of the mandible to resist load, mainly during intermittent exposure to hypoxia. These effects on bone may be related to the higher levels of prostaglandin E2 reached in the surrounding gingival tissue. The findings of this study may stimulate strategies to prevent unwanted effects of hypoxia on periodontal tissues.

Changes in PGE2 signaling after submandibulectomy alter post-tooth extraction socket healing.

Saliva is very important to oral health, and a salivary deficit has been shown to bring serious problems to oral health. There is scant information about the mechanisms through which salivary glands participate in post-tooth extraction socket healing. Therefore, the aim of the present study was to investigate the effect of submandibulectomy (SMx), consisting of the ablation of submandibular and sublingual glands (SMG and SLG, respectively), on PGE2 signaling and other bone regulatory molecules, such as OPG and RANKL, involved in tooth extraction socket healing. Male Wistar rats, 70 g body weight, were assigned to an experimental (subjected to SMx) or a control group (sham operated). One week later, the animals in both groups underwent bilateral extraction of the first mandibular molars. The effect of SMx on different stages of socket healing after tooth extraction (7, 14, and 30 days) was studied by evaluating some parameters of inflammation, including PGE2 and its receptors, and of bone metabolism, as well as by performing bone biomechanical studies. SMx increased TNFα and PGE2 content as well as cyclooxygenase-II (COX-II) expression in tooth socket tissue at almost all the studied time points. SMx also had an effect on mRNA expression of PGE2 receptors at the different time points, but did not significantly alter osteoprotegerin (OPG) and RANKL mRNA expression at any of the studied time points. In addition, an increase in bone mass density was observed in SMx rats compared with matched controls, and the structural and mechanical bone properties of the mandibular socket bone were also affected by SMx. Our results suggest that the SMG/SLG complex regulates cellular activation and differentiation by modulating the production of molecules intervening in tooth extraction socket repair, including the PGE2 signaling system, which would therefore account for the higher density and resistance of the newly formed bone in SMx rat.

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.

Efficacy of phytosterols and fish-oil supplemented high-oleic-sunflower oil rich diets in hypercholesterolemic growing rats.

Phytosterols (P) and fish-oil (F) efficacy on high-oleic-sunflower oil (HOSO) diets were assessed in hypercholesterolemic growing rats. Controls (C) received a standard diet for 8 weeks; experimental rats were fed an atherogenic diet (AT) for 3 weeks, thereafter were divided into four groups fed for 5 weeks a monounsaturated fatty acid diet (MUFA) containing either: extra virgin olive oil (OO), HOSO or HOSO supplemented with P or F. The diets did not alter body weight or growth. HOSO-P and HOSO-F rats showed reduced total cholesterol (T-chol), non-high-density lipoprotein-cholesterol (non-HDL-chol) and triglycerides and increased HDL-chol levels, comparably to the OO rats. Total body fat (%) was similar among all rats; but HOSO-F showed the lowest intestinal, epididymal and perirenal fat. However, bone mineral content and density, and bone yield stress and modulus of elasticity were unchanged. Growing hypercholesterolemic rats fed HOSO with P or F improved serum lipids and fat distribution, but did not influence material bone quality.

Effect of physical consistency of food on the biomechanical behaviour of the mandible in the growing rat.

This study investigated the effect of a soft diet, given to growing rats, on the biomechanical behaviour of the mandible. Female rats, 30 d of age, received an ordinary diet in the form of pellets (i.e. hard-diet group), and another group of female rats received the same diet, but ground and mixed with water, forming a paste (i.e. soft-diet group). The experiment lasted 8 wk. Body-weight and body-length gains were not affected by the consistency of the diet. No significant differences were found between groups concerning the length, height, and area of the right hemimandible. Mechanical properties of the right hemimandibles were determined using a three-point bending test, in which bones were stressed on a perpendicular line immediately posterior to the posterior face of the third molar. Structural properties (load at yielding, load at fracture, structural stiffness, and elastic energy absorption) and geometric properties of the fracture section (cross-sectional area, cortical area, and moment of inertia) were significantly lower in hemimandibles of rats of the soft-diet group than in those of rats of the hard-diet group. Material properties of the mandibular bone tissue (elastic modulus and maximal elastic stress), which were estimated through appropriate equations, did not differ between groups. It was concluded that the reduced physical consistency of the diet, possibly associated with a reduced masticatory load, diminished the skeletal load-bearing capacity of the mandible in growing rats. This observed reduction in the bone structural behaviour was attributed to changes occurring at the level of bone mass and its geometrical properties because intrinsic properties of the bone material tissue were unaffected.

Periodontal status and mandibular biomechanics in rats subjected to hyposalivation and periodontitis.

Xerostomia emerges as a consequence of salivary gland hypofunction, and seriously compromises the integrity of hard and soft oral tissues, whileperiodontitis is an infectious disease characterized by biofilm accumulation, inflammation and alveolar bone resorption. AIM: The aim this study was to compare the deleterious effects caused by experimental hyposalivation, periodontitis, and the combination of both on periodontal tissues and mandibular biomechanics in rats. MATERIALS AND METHOD: Hyposalivation (group H) was induced through bilateral submandibulectomy. Periodontitis (group EP) was induced by injecting LPS (1 mg/ml) into the gingiva of the first lower molars. A third group was subjected to both conditions (group H+EP). Alveolar bone loss was evaluated by micro-computed tomography and histomorphometric analysis, and gingival inflammatory mediators were assessed by specific techniques. Biomechanical properties were evaluated in mandible. RESULTS: Alveolar bone loss increased similarly in groups H, EP and H+EP compared to control. Metalloproteinase (MMP2 and MMP9) activity was similar in H and control, but higher in groups EP and H+EP (MMP2: C 9644+2214, EP 34441+3336, H 5818+1532, H+EP 42673+3184; MMP9: C 5792+961, EP 14807+861, H 9295+520, H+EP 4838+1531). The rest of the inflammatory mediators evaluated increased in groups H, EP and H+EP to a greater or lesser extent with respect to the control, although in most cases, they were higher in groups EP and H+EP than in group H. The biomechanical properties of the mandible increased in group H compared to the other three groups. CONCLUSIONS: Both hyposalivation and periodontitis cause periodontal damage, but hyposalivation also produces biomechanical alterations, causing more extensive deleterious effects than periodontitis.

La xerostomía surge como consecuencia de la hipofunción de las glándulas salivales y compromete seriamente la integridad de los tejidos orales duros y blandos, mientras que la periodontitis es una enfermedad infecciosa caracterizada por la acumulación de biofilm, inflamación y reabsorción ósea alveolar. OBJETIVO: El objetivo del presente estudio fue comparar los efectos deletéreos causados por la hiposalivación y la periodontitis experimental, y la combinación de ambas sobre los tejidos periodontales y la biomecánica mandibular en ratas. MATERIALES Y MÉTODOS: La hiposalivación (H) se indujo mediante una submandibulectomía bilateral. Por otra parte, la periodontitis (PE) se indujo mediante la inyección de LPS (1 mg/ml) en la encía de los primeros molares inferiores. Otro grupo se sometió a ambas condiciones (H+PE). La pérdida ósea alveolar se evaluó mediante tomografia microcomputarizada y análisis histomorfométrico, mientras que los mediadores inflamatorios gingivales fueron determinados mediante técnicas específicas. Se evaluaron las propiedades biomecánicas en la mandíbula. RESULTADOS: La hiposalivación aumentó la pérdida ósea alveolar en comparación con el control de forma similar a la PE y H+PE. La actividad de las metaloproteinasas (MMP2 y MMP9) fue similar en los grupos H y control, pero resultó mayor en los grupos PE y H+PE (MMP2: C 9644+2214, PE 34441+3336, H 5818+1532, H+PE 42673+3184; MMP9: C 5792+961, PE 14807+861, H 9295+520, H+PE 24838+1531). El resto de los mediadores inflamatorios evaluados aumentaron en mayor o menor medida en los grupos H, PE y H+PE respecto al control, aunque en la mayoría de los casos fueron superiores en los grupos PE y H+PE respecto al grupo H. Sin embargo, las propiedades biomecánicas de la mandíbula aumentaron en el grupo H con respecto a los otros grupos. CONCLUSIONES: Tanto la hiposalivación como la periodontitis causan daño periodontal, pero la hiposalivación también produce alteraciones biomecánicas, provocando efectos deletéreos más extensos que la periodontitis.

[Operational mechanism modification of bone mechanostat in an animal model of nutritional stress: effect of propranolol]. / Modificación del mecanismo operacional del mecanostato óseo en un modelo de estrés nutricional por efecto del propranolol.

INTRODUCTION: Propranolol (P) treatment exerts a preventive effect against the detrimental consequences to bone status in mildly chronically food-restricted growing rats (NGR) by an increment in cortical bone and by improving its spatial distribution. OBJECTIVE: To study the effect of beta-blocker on operational mechanism of bone mechanostat in an animal model of nutritional stress. MATERIAL AND METHODS: Weanling male Wistar rats were randomly assigned to four groups: control (C), C + P (CP), NGR and NGR + P (NGRP). C and CP rats were fed freely with the standard diet. NGR and NGRP rats received, for 4 weeks, 80% of the amount of food consumed by C and CP respectively, the previous day, corrected by body weight. Propranolol (7 mg/kg/day) was injected ip 5 days per week, for four weeks in CP and NGRP rats. C and NGR received saline injections at an identical dosage regimen. Body weight and length were determined during the experimental period. Dietary intake was registered daily. Animals were sacrificed after 4 weeks of food restriction. Immediately, cuadriceps, femur and tibiae from each animal were dissected and weighed, and histomorphometric and mechanical studies were performed. Serum a-CTX, osteocalcin, intact PTH, calcium and phosphorous were determined. Body protein (% prot) was measured in all groups. RESULTS: Food restriction induced detrimental effects on body and femoral growth, load-bearing capacity (Wf), % prot and cuadriceps weight in NGR us. C (p < 0.01). beta-blocker did not modify anthropometric and bone morphometric parameters in NGRP and CP us. NGR and C, respectively (p > 0.05). However, Wf NGRP vs. NGR was significantly higher (p < 0.01). alpha-CTX was significantly higher in NGR vs. C (p < 0.01). No significant differences were observed in alpha-CTX levels between CP, NGRP and C (p > 0.05). Serum osteocalcin, intact PTH, calcium and phospho- rous showed no significant difference between groups (p > 0.05). CONCLUSION: These results suggest that modeling increase in bone mass and strength in NGRP rats could be due to an anticatabolic interaction of the beta-blocker propranolol on operational mechanism of bone mechanostat in an animal model of nutritional stress.

Growth inhibition in rats fed inadequate and incomplete proteins: repercussion on mandibular biomechanics.

This study describes the effects of feeding growing rats with a diet containing inadequate and incomplete proteins on both the morphological and the biomechanical properties of the mandible. Female rats aged 30 d were fed freely with one of two diets, control (CD, 301 Cal/100g) and experimental (ED, 359 Cal/100g). CD was a standard laboratory diet, while ED was a synthetic diet containing cornflower supplemented with vitamins and minerals. Both diets had the same physical characteristics. Control (C) and experimental (E) animals were divided into 4 groups of 10 animals each. C40 and E40 rats were fed CD and ED, respectively, for 40 d; C105 were fed the CD for 105 d; and E105 were fed the ED for 40 d and then the CD for the remainder of the experimental period (65 d). Mandibular growth was estimated directly on excised and cleaned bones by taking measurements between anatomical points. Mechanical properties of the right hemimandible were estimated by using a 3-point bending test to estimate the structural properties of the bone. Geometric properties of both the entire bone and the cross-section were determined. Bone material properties were calculated from structural and geometric properties. The left hemimandibles were ashed and the ash weight obtained. Rats fed the ED failed to achieve normal body weight gain. Complete catch-up was observed at the end of nutritional rehabilitation. Mandibular weight and length were negatively affected by the ED, as were the cross-sectional area, the mineralized cortical area, and the cross-sectional moment of inertia. All of these parameters showed incomplete catch-up. The structural bone mechanical properties indicative of strength and stiffness were negatively affected. Intrinsic material properties, as assessed by the modulus of elasticity and maximal elastic stress, were within normal values. In summary, the experimental bone was weaker than the control and structurally incompetent. The bone considered was smaller than the control bone, showing a significant reduction in the cross-sectional area and the moment of inertia. However, material properties as well as the ash fraction and degree of mineralization were similar in E and C bones. Therefore, the E bone was weaker than the C bone because of its smaller bone mass, which appears to have been negatively influenced by the ED in relation to its effects on overall body mass.

Effect of fried sunflower oil intake on mandibular biomechanical competence of growing rats.

Previous studies by us demonstrated that the consumption of thermally oxidized oil diet adversely affects body growth, lipid metabolism, bone mass and femur biomechanical competence. AIM: The aim of this study was to evaluate the effects of a diet containing fried sunflower oil on the mandible of growing rats. MATERIALS AND METHOD: Male Wistar rats (21±1 day old) (n=21) were assigned at weaning to one of three diets for 8 weeks: a control diet (C), a diet containing sunflower oil (SFO) or a diet containing sunflower oil that had been repeatedly heated (SFOx); both SFO and SFOx were mixed with commercial rat chow at 13% (w/w). The consistency and viscosity of the 3 diets were similar. Zoometrics and food intake were recorded weekly. At wk=8, mandibular growth was assessed by measurements of anatomical points of cleaned bones, and mandible biomechanical competence was assessed to estimate the structural properties of the bone. Statistical analysis was performed by SPSS v. 20.0. RESULTS: Rats fed SFOx diet attained the lowest final body weight (P=0.0074), mandibular weight (P=0.0001) and mandibular \length (P=0.0002). Load bearing capacity (Wf;N), load of yielding (Wy;N) and stiffness (Wy/dy;N/mm) of the mandible were negatively affected by both sunflower oil diets (fresh and fried) (P=0.001; P=0.002; P=0.003, respectively) though SFOx induced the most significant reduction in Wy/dy (C:44.4(5.4) > SFO:36.1(2.1) > SFOx: 26.3(3.7) N/ mm; P=0.003). The deleterious effect of SFOx on mandibular growth was more accentuated on the posterior part of the bone (C:11.4(0.3)=SFO:11.2(0.2)>SFOx: 10.7(0.2) mm; p=0.0005); the anterior/ posterior ratio (C:1.25(0.02)=SFO:1.27(0.02)

En estudios previos hemos demostrado los efectos adversos del consumo de una dieta rica en aceite termooxidado sobre el crecimiento corporal, el metabolismo de los lípidos, la masa ósea y la competencia biomecánica del fémur. OBJETIVO: El objetivo de este trabajo fue investigar el efecto de una dieta rica en aceite de girasol termooxidado (AGX) sobre los parámetros morfométricos y biomecánicos de la mandíbula de rata en crecimiento. Materiales y Método: Ratas macho Wistar de 22±1 días de edad (n=21) recibieron durante 8 semanas una de 3 dietas: control (C); dieta comercial, una dieta suplementada con aceite de girasol (AG) y una dieta suplementada con AGX. La consistencia y la viscosidad de las dietas fueron similares. Los parámetros zoométricos y el consumo de dieta se registraron semanalmente. A T=8, los animales se eutanasiaron y se obtuvieron las hemimandíbulas. El crecimiento mandibular se estimó por medidas morfométricas entre puntos anatómicos y las propiedades estructurales por biomecánica. El análisis estadístico se realizó por SPSS v. 20.0. RESULTADOS: Las ratas alimentadas con AGX presentaron menor peso corporal final (p=0.0074), peso mandibular (p=0.0001) y longitud mandibular (p=0.0002). Las propiedades estructurales de la mandíbula, Wf (p=0.001), Wy (p=0.002) y Wy/dy (p=0.003), se vieron afectadas negativamente en ratas alimentadas con AG o AGX, respecto a C; pero la rigidez ósea (Wy/dy) en AGX fue significativamente menor (C:44.4(5.4) > SFO:36.1(2.1) > SFOx: 26.3(3.7) N/mm; p=0.003). El efecto deletéreo del AGX sobre el crecimiento mandibular fue más acentuado en la región posterior (C:11.4(0.3)=SFO:11.2(0.2)>SFOx: 10.7(0.2) mm; p=0.0005). La relación anterior/posterior (C=1.25 (0.02); AG= 1.27(0.02) y AGX=1.32(0.03), p=0.001) indica que AGX indujo deformación mandibular. CONCLUSIONES: El efecto adverso del consumo de una dieta rica en AGX durante el crecimiento podría afectar los parámetros morfométricos y la biomecánica ósea en términos de rigidez ósea.

Effects of lead exposure on growth and bone biology in growing rats exposed to simulated high altitude.

The existence of children living at high altitude suffering from lead (Pb) poisoning prompted us to investigate the long term effects of this pollutant on growth and bone biology in growing rats maintained at simulated high altitude (SHA). Pb and hypoxia (HX) significantly reduced body weight (-9.4 % and -24 %; p < 0.01) and length (-3 % and -8 %; p < 0.01); decreased femoral ultimate load (-16 % and -40 %; p < 0.01) and femoral energy absorption capacity (-18 % and -74 %; p < 0.01). Oral pathologic alterations were observed in experimental groups. Our findings revealed growth retardation and damages on femoral and mandibular bones that predispose to fractures.

Lead bone toxicity in growing rats exposed to chronic intermittent hypoxia.

Lead chronic intoxication under hypoxic conditions revealed growth retardation in growing rats and damages on femoral and mandibular bones that predispose to fractures. These findings aimed us to investigate if bone material and geometric properties, bone mass in terms of histomorphometry or antioxidant capacity are also impaired in such experimental model. Combined treatments significantly reduced hemimandible cross sectional geometry and intrinsic stiffness (-16% and -34%); tibia and hemimandible bone volume (-45% and -40%) and growth plate cartilage thickness (-19%). These results show a previously unreported toxic effect of lead on mandible however, longer studies should be necessary to evaluate if an adaptation of bone architecture to maintain structural properties may occur and if the oxidative stress can be identified as the primary contributory agent in the pathogenesis of lead poisoning.

Aluminum bone toxicity in immature rats exposed to simulated high altitude.

Aluminum (Al) is an element to which humans are widely exposed. Chronic administration induces a negative effect on bone tissue, affecting collagen synthesis and matrix mineralization. Its toxic effects are cumulative. Hypobaric hypoxia induces stress erythropoiesis, leading to hypertrophy of the erythropoietic marrow affecting the bone. This study was designed to evaluate the risk of Al bone toxicity among immature rats maintained at simulated high altitude (SHA) by mechanical assessment of stiffness and strength, calculation of some indicators of bone material and geometrical properties, as well as blood determinations. Forty growing rats were divided into control and experimental groups whether injected with vehicle or Al, as Al(OH)(3), three times a week for 3 months. Half of each group was exposed to hypobaric conditions (HX) by placing the animals in a SHA chamber. Both treatments negatively affected structural properties of bones, decreasing the maximum capacity to withstand load, the limit elastic load and the capacity of absorbing energy in elastic conditions. Al administration significantly depressed mandible structural stiffness, although diaphyseal stiffness was not modified. Indicators of bone material intrinsic properties, elastic modulus and stress, were significantly reduced by Al or HX. Treatments increased the diaphyseal sectional bending moment of inertia, suggesting that femur, but not mandible, compensates for the decline in the material properties with an adaptation of its architecture to maintain structural properties. The different biomechanical behaviors between the two kinds of bone are probably due to their different embryological origin and specific functions, as mandible is a bone that adjusts its strength to biting forces, whereas femur is designed to support load.

Bone mineral density and bone strength from the mandible of chronically protein restricted rats.

UNLABELLED: The present investigation was performed to assess the biomechanical repercussion of protein malnutrition imposed on rats between the 26th and 135th days of postnatal life on the mandible, which is not a weight-bearing bone but supports the loads related to the masticatory activity. Female Wistar rats aged 26 d (n = 14) were placed on either a 4%-protein diet (ICN 960254, P4 group) or a 20%-protein diet (ICN 960260, P20 group) and killed 111 d later. Both body weight and length were recorded regularly. The mandibles were dissected and cleaned of adhering soft tissue. Mandibular growth was estimated directly by taking measurements between anatomical points. Areal Bone Mineral Density (BMD) was estimated using a bone densitometer (LUNAR DPX-L). Mechanical properties of the right hemimandible were determined using a three-point bending mechanical test to obtain the load/deformation curve and estimate the structural properties of the bone. Results were summarized as means +/- SD. Comparisons between parameters were performed by Student's t test. A 75% reduction in body weight and a 32% reduction in body length were observed in P4 rats. Like body size, mandibular weight, length, height and area (index of mandibular size) were negatively affected by P4 diet, as was the posterior part of the bone (posterior to molar III). The anterior part (alveolar and incisor alveolar process) was not affected by age or diet. The "load capacity" extrinsic properties of the mandible (load fracture, stiffness, yielding point) were between 43% and 64% of control value in protein restricted rats. BMD was similar in both groups of animals. CONCLUSION: 1) Chronic protein malnutrition imposed on rats from infancy to early adulthood reduces the growth of the posterior part of the mandible without inducing changes in the anterior part, which produces some deformation of the bone in relation to age-matched rats; and 2) the significant reduction of strength and stiffness of the mandible seem to be the result of an induced loss of gain in bone structural properties as a consequence of a correlative loss of gain in both growth and mass, yet not in bone material properties.

Improved bone status by the beta-blocker propranolol in an animal model of nutritional growth retardation.

The aim of the present research was to study if the beta-blocker propranolol, which is known to increase bone mass, could reverse the adverse skeletal effects of mild chronic food restriction in weanling rats. Male Wistar rats were divided into four groups: control, control+propranolol (CP), nutritional growth retardation (NGR) and nutritional growth retardation+propranolol (NGRP). Control and CP rats were fed freely with the standard diet. NGR and NGRP rats received, for 4 weeks, 80 % of the amount of food consumed by the control and CP rats, respectively. Results were expressed as mean values and sem. Food restriction induced detrimental effects on body and femur weight and length (P < 0.05) and bone structural and geometrical properties (P < 0.001), confirming results previously shown in our laboratory. However, the beta-blocker overcame the deleterious effect of nutritional stress on load-bearing capacity, yielding load, bone stiffness, cross-sectional cortical bone area and second moment of inertia of the cross-section in relation to the horizontal axis without affecting anthropometric, histomorphometric and bone morphometric parameters. The results suggest that propranolol administration to mildly chronically undernourished rats markedly attenuates the impaired bone status in this animal model of growth retardation.

A new target to ameliorate the damage of periodontal disease: The role of transient receptor potential vanilloid type-1 in contrast to that of specific cannabinoid receptors in rats.

BACKGROUND: Transient receptor potential vanilloid type-1 (TRPV1) is expressed in oral tissues cells and its activity can be regulated by inflammation products and anandamide. The aim of the present study was to evaluate the effects of blocking TRPV1 or specific cannabinoid receptors 1 (CB1r) and 2 (CB2r) on periodontal status of rats subjected to experimental periodontitis (EP). METHODS: Male rats were distributed in groups 1) control, 2) lipopolysaccharide-induced EP (LPS), and 3) LPS plus capsazepine (Capz, TRPV1 antagonist) application (LPS+Capz). EP was induced by injections of LPS (1 mg/mL) around first molars and treatment was performed with Capz (2 µg/mL) applied locally during 6 weeks. Additional experiment was performed by applying CB1r and CB2r antagonists (AM251 and AM630) to rats with EP. RESULTS: Capz prevented alveolar bone loss (ABL) on the external crests and in the interradicular bone of the first molars (periodontal space height: LPS, 270.7 ± 33.5µm versus LPS+Capz, 216.4 ± 19.9 µm; P <0.01). Inflammatory mediators, like tumor necrosis factor-alpha and prostaglandin E2 , increased by LPS-induced EP, were diminished in gingival tissue of rats treated with Capz. In contrast, application of AM251 and AM630 exacerbated ABL and gingival inflammatory mediators, increased by LPS, altering also biomechanical properties. CONCLUSIONS: TRPV1 blockade attenuates periodontal impairment in EP rats, since it reduces local inflammation, unlike CB1r and CB2r blockade. This work lays the foundation for developing therapeutics in humans based on the pharmacological manipulation of these receptors to treat periodontal disease.

Effect of fried sunflower oil intake on mandibular biomechanical competence of growing rats / Efecto del consumo de aceite de girasol termooxidado sobre la competencia biomecánica de la mandíbula, en animales en crecimiento

ABSTRACT Previous studies by us demonstrated that the consumption of thermally oxidized oil diet adversely affects body growth, lipid metabolism, bone mass and femur biomechanical competence. Aim: The aim of this study was to evaluate the effects of a diet containing fried sunflower oil on the mandible of growing rats. Materials and Method: Male Wistar rats (21±1 day old) (n=21) were assigned at weaning to one of three diets for 8 weeks: a control diet (C), a diet containing sunflower oil (SFO) or a diet containing sunflower oil that had been repeatedly heated (SFOx); both SFO and SFOx were mixed with commercial rat chow at 13% (w/w). The consistency and viscosity of the 3 diets were similar. Zoometrics and food intake were recorded weekly. At wk=8, mandibular growth was assessed by measurements of anatomical points of cleaned bones, and mandible biomechanical competence was assessed to estimate the structural properties of the bone. Statistical analysis was performed by SPSS v. 20.0. Results: Rats fed SFOx diet attained the lowest final body weight (P=0.0074), mandibular weight (P=0.0001) and mandibular /length (P=0.0002). Load bearing capacity (Wf;N), load of yielding (Wy;N) and stiffness (Wy/dy;N/mm) of the mandible were negatively affected by both sunflower oil diets (fresh and fried) (P=0.001; P=0.002; P=0.003, respectively) though SFOx induced the most significant reduction in Wy/dy (C:44.4(5.4) > SFO:36.1(2.1) > SFOx: 26.3(3.7) N/ mm; P=0.003). The deleterious effect of SFOx on mandibular growth was more accentuated on the posterior part of the bone (C:11.4(0.3)=SFO:11.2(0.2)>SFOx: 10.7(0.2) mm; p=0.0005); the anterior/ posterior ratio (C:1.25(0.02)=SFO:1.27(0.02)<SFOx:1.32(0.03); p=0.0001) indicated that SFOx induced mandibular deformation. Conclusion: Consumption of SFOx diet during growth could affect mandibular morphometric properties and biomechanical competence, in terms of bone stiffness.

RESUMEN En estudios previos hemos demostrado los efectos adversos del consumo de una dieta rica en aceite termooxidado sobre el crecimiento corporal, el metabolismo de los lípidos, la masa ósea y la competencia biomecánica del fémur. Objetivo: El objetivo de este trabajo fue investigar el efecto de una dieta rica en aceite de girasol termooxidado (AGX) sobre los parámetros morfométricos y biomecánicos de la mandíbula de rata en crecimiento. Materiales y Método: Ratas macho Wistar de 22±1 días de edad (n=21) recibieron durante 8 semanas una de 3 dietas: control (C); dieta comercial, una dieta suplementada con aceite de girasol (AG) y una dieta suplementada con AGX. La consistencia y la viscosidad de las dietas fueron similares. Los parámetros zoométricos y el consumo de dieta se registraron semanalmente. A T=8, los animales se eutanasiaron y se obtuvieron las hemimandíbulas. El crecimiento mandibular se estimó por medidas morfométricas entre puntos anatómicos y las propiedades estructurales por biomecánica. El análisis estadístico se realizó por SPSS v. 20.0. Resultados: Las ratas alimentadas con AGX presentaron menor peso corporal final (p=0.0074), peso mandibular (p=0.0001) y longitud mandibular (p=0.0002). Las propiedades estructurales de la mandíbula, Wf (p=0.001), Wy (p=0.002) y Wy/dy (p=0.003), se vieron afectadas negativamente en ratas alimentadas con AG o AGX, respecto a C; pero la rigidez ósea (Wy/dy) en AGX fue significativamente menor (C:44.4(5.4) > SFO:36.1(2.1) > SFOx: 26.3(3.7) N/mm; p=0.003). El efecto deletéreo del AGX sobre el crecimiento mandibular fue más acentuado en la región posterior (C:11.4(0.3)=SFO:11.2(0.2)>SFOx: 10.7(0.2) mm; p=0.0005). La relación anterior/posterior (C=1.25 (0.02); AG= 1.27(0.02) y AGX=1.32(0.03), p=0.001) indica que AGX indujo deformación mandibular. Conclusiones: El efecto adverso del consumo de una dieta rica en AGX durante el crecimiento podría afectar los parámetros morfométricos y la biomecánica ósea en términos de rigidez ósea.

Increased intrinsic stiffness and mineralization in femurs of adult rats after high intensity treadmill running training.

BACKGROUND: Physical activity plays a tremendous role in determining bone mechanical behavior, which is superimposed to gravidity. OBJECTIVE: Compare the geometric and material responses of the rat femur to a high intensity treadmill running training of a relatively short duration, as assessed by 3-point mechanical test. METHODS: Mature male rats (180.0 ± 30 g) were assigned (7 rats/group) to no exercise (NE) or treadmill exercise (EX). After a preconditioning period, the running speed was set at 45 cm.seg-1 during 2 wks, frequency 5 d/wk, 2-hour sessions/day. Body weight and weight of the crural quadriceps were registered at euthanasia. The right femur was mechanically tested through 3-point bending. The left femur was ashed to estimate bone mineral content. Geometric and material bone properties were estimated directly or calculated by appropriate equations. RESULTS: 1) Final body weight was 14% reduced in EX rats, while the crural quadriceps was 47% increased. Yield and fracture loads, and structural stiffness were significantly higher in the EX rats, as were the apparent elastic modulus, the bone mineral content and the degree of mineralization. Geometric properties were not affected. CONCLUSIONS: High intensity treadmill running training increases bone strength and stiffness by increasing material stiffness and mineralization, without affecting geometric bone parameters.

Mechanical mandible competence in rats with nutritional growth retardation.

OBJECTIVE: In order to provide a better understanding of the sympathetic nervous system as a negative regulator of bone status, the aim of the study was to establish the biomechanical mandible response to different doses of a ß-adrenergic antagonist such as propranolol (P) in a stress-induced food restriction model of growth retardation. METHODS: Rats were assigned to eight groups: Control (C), C+P3.5 (CP3.5), C+P7 (CP7), C+P14 (CP14), NGR, NGR+P3.5 (NGRP3.5), NGR+P7 (NGRP7) and NGR+P14 (NGRP14). C, CP3.5, CP7 and CP14 rats were freely fed with the standard diet. NGR, NGRP3.5, NGRP7 and NGRP14 rats received, for 4 weeks (W4), 80% of the amount of controls food consumed. Propranolol 3.5, 7 and 14mg/kg/day was injected ip 5days per week in CP3.5 and NGRP3.5, CP7 and NGRP7, CP14 and NGRP14, respectively. At W4, zoometry, mandible morphometry, static histomorphometric and biomechanical competence were performed. RESULTS: A dose of Propranolol 7mg/kg/day induced interradicular bone volume accretion reaching a mandible stiffness according to chronological age. CONCLUSION: These findings evidenced that sympathetic nervous system activity is a negative regulator of mandible mechanical competence in the nutritional growth retardation model. Propranolol 7mg/kg/day, under the regimen usage, seems to be appropriate to blockade SNS activity on mandible mechanical performance in NGR rats, probably associated to an effect on bone mechanostat system ability to detect disuse mode as an error.

Absorción mineral y retención ósea en ratas normales en crecimiento por el consumo de un yogur experimental reducido en lactosa que contiene galactooligosacáridos (GOS) / Mineral absorption and bone retention in normal growing rats by consumption of an experimental lactose-reduced yogurt containing galactooligosaccharides (GOS)

Introducción: Los GOS son prebióticos naturales presentes en la leche materna que pue-den obtenerse enzimáticamente a partir de la lactosa de leche de vaca durante la fabricación de yogur. El producto lácteo resultante será reducido en lactosa y contendrá prebióticos y bacterias potencialmente probióticas. Sin embargo, mantendrá la baja relación Ca/Pi que aporta la leche de vaca, lo que podría alterar el remodelamiento óseo y la mineralización. Objetivo: comparar si un yogur reducido en lactosa que contiene GOS (YE) ofrece ventajas adicionales respecto de un yogur regular sin GOS (YR) sobre las absorciones (Abs) de Ca y Pi, retención y calidad ósea durante el crecimiento normal. Al destete, ratas machos fueron divididas en 3 grupos alimentados con AIN ́93-G (C), YE o YR durante 28 días. Resultados: YE mostró el mayor aumento de lactobacilos fecales; producción de ácidos grasos de cadena corta especialmente p, profundidad de las criptas colónicas y menor pH cecal. El %AbsCa y %AbsPi aumentó en el siguiente órden: YE> YR> C (p < 0,05). El contenido de Ca y Pi en fémur, la densidad y contenido mineral óseos y los parámetros biomecánicos fueron similares en YE y C, mientras que YR mostró valores significativa-mente menores (p < 0,05). Conclusiones: YE aumentó las Abs y biodisponibilidad de minerales, alcanzando la retención y calidad ósea de C. El aumento en las Abs observado en YR no logró obtener la retención y calidad ósea de C. Conclusión: YE habría contrarrestado el efecto negativo del mayor aporte de Pi de la leche de vaca y sería una buena estrategia para lograr el pico de masa ósea y calidad del hueso adecuados, especialmente en individuos intolerantes a la lactosa. (AU)

Breast milk contains an optimal calcium/phosphate (Ca/Pi) ratio and GOS. These natural prebiotics can be enzymatically produced via cow's milk lactose inyogurt manufacture. This milk product is low in lactose and contains prebiotics and potentially probiotic bacteria but maintains a low Ca/Pi ratio that could alter bone remodeling and mineralization. We evaluated if a lactose-reduced yogurt containing GOS (YE) offers additional advantages over regular yogurt without GOS (YR) on Ca and Pi absorption (Abs), bone retention and quality during normal growth. Weaning male rats were divided into 3 groups fed AIN'93-G (C), YE or YR for 28 days. Results: YE showed the highest increase in fecal lactobacilli; short-chain fatty acids production, especially propionate and butyrate; intestine crypt depth, and the lowest cecal pH. AbsCa% and AbsPi% increased in this order: YE> YR> C (p <0.05). Ca and Pi content in femur, bone density and mineral content, and biomechanical parameters were similar in YE and C, while YR showed the significantly lowest value (p < 0.05). Conclusions: YE increased mineral Abs reaching the retention and bone quality of C. Although YR increased Abs, bone retention and quality did not achieve C values. Seemingly, YE compensated for the negative effect of the higher Pi supply and would be a good strategy to achieve adequate peak bone mass and bone quality, especially in lactose intolerant individuals. (AU)