Bases Genéticas do Diabetes Mellitus Tipo 2

Incidental mild hyperglycemia in children: two MODY 2 families identified in Brazilian subjects

Maturity-onset diabetes of the young (MODY) is characterized by an autosomal dominant mode of inheritance, early onset of hyperglycemia, and defects of insulin secretion. MODY subtypes described present genetic, metabolic, and clinical differences. MODY 2 is characterized by mild asymptomatic fasting hyperglycemia, and rarely requires pharmacological treatment. Hence, precise diagnosis of MODY is important for determining management and prognosis. We report two heterozygous GCK mutations identified during the investigation of short stature. Case 1: a prepubertal 14-year-old boy was evaluated for constitutional delay of growth and puberty. During follow-up, he showed abnormal fasting glucose (113 mg/dL), increased level of HbA1c (6.6%), and negative β-cell antibodies. His father and two siblings also had slightly elevated blood glucose levels. The mother had normal glycemia. A GCK heterozygous missense mutation, p.Arg191Trp, was identified in the proband. Eighteen family members were screened for this mutation, and 11 had the mutation in heterozygous state. Case 2: a 4-year-old boy investigated for short stature revealed no other laboratorial alterations than elevated glycemia (118 mg/dL); β-cell antibodies were negative. His father, a paternal aunt, and the paternal grandmother also had slightly elevated glycemia, whereas his mother had normal glycemia. A GCK heterozygous missense mutation, p.Glu221Lys, was identified in the index patient and in four family members. All affected patients had mild elevated glycemia. Individuals with normal glycemia did not harbor mutations. GCK mutation screening should be considered in patients with chronic mild early-onset hyperglycemia, family history of impaired glycemia, and negative β-cell antibodies.

Genetic and clinical characteristics of maturity-onset diabetes of the young

Genetic factors play an important role in various forms of diabetes mellitus (DM), but inheritance is complex and interacts with environmental factors. Although in most cases type 2 DM (T2DM) and T1DM are polygenic disorders, several monogenic forms have been identified. Among them, maturity-onset diabetes of the young (MODY) has been the most intensively investigated. MODY is a group of six different forms of monogenic diabetes, characterized by insulin secretion defects in pancreatic beta-cells, supposed to be responsible for 2-5% of all cases of diabetes. The most common are MODY2 and MODY3, caused by mutations in the genes encoding glucokinase and hepatocyte nuclear factor 1-alpha respectively. MODY2 is characterized by glucose sensing defects, leading to an increase in insulin secretion threshold. This causes lifelong sustained and mild hyperglycaemia from birth, most often in non-diabetic levels. Diagnosis is incidental in most cases. These patients are asymptomatic, seldom need treatment and rarely present chronic complications. MODY3 is characterized by a severe insulin secretion defect in response to glucose. Diagnosis is made usually in adolescence and early adulthood, often by osmotic symptoms. Hyperglycaemia is progressive, and patients frequently need treatment with oral drugs or insulin some time in their follow up. This group seems to have a marked sensitivity to sulphonylureas compared to other types of diabetes. The recognition of MODY as a monogenic disorder and a thorough understanding of its pathophysiology are important for correct diagnosis and treatment, with great impact on prognosis. Besides, the study of these forms of diabetes brings important contributions to the understanding of glucose homeostasis as a whole.

Avaliação dos resultados da atenção multiprofissional sobre o controle glicêmico, perfil lipídico e estado nutricional de diabéticos atendidos em nível primário

OBJETIVO: Avaliar o resultado da intervenção multiprofissional sobre o controle glicêmico, o perfil lipídico e o estado nutricional de diabéticos atendidos em nível primário em Belo Horizonte, MG. MÉTODOS: Analisaram-se a glicemia, o índice de massa corporal e o perfil lipídico de 190 diabéticos tipo 2 (31 a 83 anos), atendidos no período de 1993 a 2000. Os dados foram coletados no momento inicial (primeira consulta de nutrição) e após três meses, tendo alguns sido coletados também uma terceira vez (6 meses após a primeira consulta). RESULTADOS: Inicialmente foram observados valores médios e medianos elevados, para índice de massa corporal, glicemia de jejum, colesterol total, LDL-c e triglicerídeos. Nos primeiros três meses após a intervenção, houve redução do índice de massa corporal (de 28,3 para 27,8kg/m²), glicemia de jejum (de 178,5 para 135,0mg/dL), colesterol total (de 251,0 para 230,0mg/dL), LDL-c (de 185,5 para 159mg/dL) e triglicerídeos (de 243,0 para 190,0mg/dL), não ocorrendo alteração dos níveis de HDL-c. Os pacientes com índice de massa corporal <30kg/m² e os com diabetes de manifestação mais recente, obtiveram melhores resultados. CONCLUSÃO: Os resultados deste estudo indicam que o atendimento multiprofissional é importante para o controle do diabetes, devendo ser iniciado precocemente.