Tendências do diabetes mellitus no Brasil: o papel da transição nutricional Trends in diabetes mellitus in Brazil: the role of the nutritional transition

A prevalência do diabetes mellitus tipo 2 tem se elevado vertiginosamente e espera-se ainda um maior incremento. Na América Latina há uma tendência do aumento da freqüência entre as faixas etárias mais jovens, cujo impacto negativo sobre a qualidade de vida e a carga da doença ao sistema de saúde é relevante. O aumento das taxas de sobrepeso e obesidade associado às alterações do estilo de vida e ao envelhecimento populacional, são os principais fatores que explicam o crescimento da prevalência do diabetes tipo 2. As modificações no consumo alimentar da população brasileira - baixa freqüência de alimentos ricos em fibras, aumento da proporção de gorduras saturadas e açúcares da dieta - associadas a um estilo de vida sedentário compõem um dos principais fatores etiológicos da obesidade, diabetes tipo 2 e outras doenças crônicas. Programas de prevenção primária do diabetes vêm sendo desenvolvidos em diversos países, cujos resultados demonstram um impacto positivo sobre a qualidade de vida da população.<br>Prevalence of type 2 diabetes mellitus has increased rapidly and is expected to increase even further. In Latin America countries there is an upward trend among the younger age groups, with a major negative impact on the quality of life and burden of the disease for the health care system. Increasing rates of overweight and obesity associated with lifestyle changes and aging of the population are the main contributing factors to the increasing prevalence of type 2 diabetes. Dietary shifts in the Brazilian population (low frequency of fiber-rich foods and heavy consumption of saturated fatty acids and sugars) and sedentary lifestyle are the main risk factors for obesity, type 2 diabetes, and other chronic diseases. Diabetes prevention programs are being promoted in several countries with results showing improvement in quality of life

Effects of dietary fatty acids on insulin sensitivity and secretion

Globalization and global market have contributed to increased consumption of high-fat, energy-dense diets, particularly rich in saturated fatty acids( SFAs). Polyunsaturated fatty acids (PUFAs) regulate fuel partitioning within the cells by inducing their own oxidation through the reduction of lipogenic gene expression and the enhancement of the expression of those genes controlling lipid oxidation and thermogenesis. Moreover, PUFAs prevent insulin resistance by increasing membrane fluidity and GLUT4 transport. In contrast, SFAs are stored in non-adipocyte cells as triglycerides (TG) leading to cellular damage as a sequence of their lipotoxicity. Triglyceride accumulation in skeletal muscle cells (IMTG) derives from increased FA uptake coupled with deficient FA oxidation. High levels of circulating FAs enhance the expression of FA translocase the FA transport proteins within the myocites. The biochemical mechanisms responsible for lower fatty acid oxidation involve reduced carnitine palmitoyl transferase (CPT) activity, as a likely consequence of increased intracellular concentrations of malonyl-CoA; reduced glycogen synthase activity; and impairment of insulin signalling and glucose transport. The depletion of IMTG depots is strictly associated with an improvement of insulin sensitivity, via a reduced acetyl-CoA carboxylase (ACC) mRNA expression and an increased GLUT4 expression and pyruvate dehydrogenase (PDH) activity. In pancreatic islets, TG accumulation causes impairment of insulin secretion. In rat models, beta-cell dysfunction is related to increased triacylglycerol content in islets, increased production of nitric oxide, ceramide synthesis and beta-cell apoptosis. The decreased insulin gene promoter activity and binding of the pancreas-duodenum homeobox-1 (PDX-1) transcription factor to the insulin gene seem to mediate TG effect in islets. In humans, acute and prolonged effects of FAs on glucose-stimulated insulin secretion have been widely investigated as well as the effect of high-fat diets on insulin sensitivity and secretion and on the development of type 2 diabetes