Proposal of non-invasive experimental model to induce scoliosis in rats

Background: In the literature, there are several experimental models that induce scoliosis in rats; however, they make use of drugs or invasive interventions to generate a scoliotic curve. Objectives: To design and apply a non-invasive immobilization model to induce scoliosis in rats. Methods: Four-week old male Wistar rats (85 +/- 3.3 g) were divided into two groups: control (CG) and scoliosis (SG). The animals in the SG were immobilized by two vests (scapular and pelvic) made from polyvinyl chloride (PVC) and externally attached to each other by a retainer that regulated the scoliosis angle for twelve weeks with left convexity. After immobilization, the abdominal, intercostal, paravertebral, and pectoral muscles were collected for chemical and metabolic analyses. Radiographic reports were performed every 30 days over a 16-week period. Results: The model was effective in the induction of scoliosis, even 30 days after immobilization, with a stable angle of 28 +/- 5 degrees. The chemical and metabolic analyses showed a decrease (p<0.05) in the glycogenic reserves and in the relationship between DNA and total protein reserves of all the muscles analyzed in the scoliosis group, being lower (p<0.05) in the convex side. The values for the Homeostatic Model Assessment of Insulin Resistance indicated a resistance condition to insulin (p<0.05) in the scoliosis group (0.66 +/- 0.03), when compared to the control group (0.81 +/- 0.02). Conclusions: The scoliosis curvature remained stable 30 days after immobilization. The chemical and metabolic analyses suggest changes in muscular homeostasis during the induced scoliosis process.

Análise de força muscular e composição corporal de mulheres com Síndrome dos Ovários Policísticos

OBJETIVOS: Comparar os parâmetros metabólicos, a composição corporal e a força muscular de mulheres com Síndrome dos Ovários Policísticos (SOP) em relação a mulheres com ciclos menstruais ovulatórios. MÉTODOS: Estudo caso-controle com 27 mulheres com SOP e 28 mulheres controles com ciclos ovulatórios, com idade entre 18 e 37 anos, índice de massa corpórea entre 18 e 39,9 kg/m², que não praticassem atividade física regular. Níveis séricos de testosterona, androstenediona, prolactina, globulina carreadora dos hormônios sexuais (SHBG), insulina e glicemia foram avaliados. Índice de andrógeno livre (FAI) e resistência insulina (por HOMA) foram calculados. As voluntárias submetidas avaliação de composição corporal por dobras cutâneas e absorciometria de raio X de dupla energia (DEXA) e testes de força muscular máxima de 1-RM em três exercícios após procedimento de familiarização e de força isométrica de preensão manual. RESULTADOS: Os níveis de testosterona foram mais elevados no grupo SOP em relação ao CO (68,0±20,2 versus 58,2±12,8 ng/dL; p=0,02), assim como o FAI (282,5±223,8 versus 127,0±77,2; p=0,01), a insulina (8,4±7,0 versus 4,0±2,7 uIU/mL; p=0,01), e o HOMA (2,3±2,3 versus1,0±0,8; p=0,01). O SBHG foi inferior no grupo SOP comparado ao controle (52,5±43,3 versus 65,1±27,4 nmol/L; p=0,04). Não foram observadas diferenças significativas na composição corporal com os métodos propostos entre os grupos. O grupo SOP apresentou maior força muscular no teste de 1-RM nos exercícios supino reto (31,2±4,75 versus 27,8±3,6 kg; p=0,04) e cadeira extensora (27,9±6,2 versus 23,4±4,2 kg; p=0,01), assim como nos testes de força isométrica de preensão manual (5079,6±1035,7 versus 4477,3±69,6 kgf/m²; p=0,04). Ser portadora de SOP foi um preditor independente de aumento de força muscular nos exercícios supino reto (estimativa (E)=2,7) (p=0,04) e cadeira extensora (E=3,5) (p=0,04). Assim como o IMC no exercício de força isométrica de preensão manual do membro dominante (E=72,2) (p<0,01), supino reto (E=0,2) (p=0,02) e rosca direta (E=0,3) (p<0,01). Nenhuma associação foi encontrada entre HOMA-IR e força muscular. CONCLUSÕES: Mulheres com SOP apresentam maior força muscular, sem diferença na composição corporal. A RI não esteve associada ao desempenho da força muscular. Possivelmente, a força muscular pode estar relacionada aos níveis elevados de androgênios nessas mulheres.

Association of acanthosis nigricans and skin tags with insulin resistance

Insulin resistance is a metabolic disorder in which target cells fail to respond to normal levels of circulating insulin. Insulin resistance has been associated with presence of acanthosis nigricans and acrochordons. It is known that early diagnosis and early initial treatment are of paramount importance to prevent a series of future complications. These dermatoses may represent an easily identifiable sign of insulin resistance and non-insulin-dependent diabetes.

Changes in food intake, metabolic parameters and insulin resistance are induced by an isoenergetic, medium-chain fatty acid diet and are associated with modifications in insulin signalling in isolated rat pancreatic islets

LLong-chain fatty acids are capable of inducing alterations in the homoeostasis of glucose-stimulated insulin secretion (GSIS), but the effect of medium-chain fatty acids (MCFA) is poorly elucidated. In the present study, we fed a normoenergetic MCFA diet to male rats from the age of 1 month to the age of 4 months in order to analyse the effect of MCFA on body growth, insulin sensitivity and GSIS. The 45% MCFA substitution of whole fatty acids in the normoenergetic diet impaired whole body growth and resulted in increased body adiposity and hyperinsulinaemia, and reduced insulin-mediated glucose uptake in skeletal muscle. In addition, the isolated pancreatic islets from the MCFA-fed rats showed impaired GSIS and reduced protein kinase Ba (AKT1) protein expression and extracellular signal-related kinase isoforms 1 and 2 (ERK(1/2)) phosphorylation, which were accompanied by increased cellular death. Furthermore, there was a mildly increased cholinergic sensitivity to GSIS. We discuss these findings in further detail, and advocate that they might have a role in the mechanistic pathway leading to the compensatory hyperinsulinaemic status found in this animal model.