MODY 2 causado por mutaciones en la glucoquinasa: una aproximación a nivel molecular / MODY 2 caused by glucokinase mutations: a molecular approach

La diabetes MODY 2 es un tipo de diabetes monogénica producida por una mutación en la enzima glucoquinasa, generando un fenotipo hiperglicémico. Para posibles fines terapéuticos o de diagnóstico, se debe conocer esta proteína, una enzima monomérica de la familia de las hexoquinasas, encargadas de convertir glucosa en glucosa-6-fosfato, el primer paso de la glicolisis. La glucoquinasa se caracteriza por sus propiedades cinéticas únicas: tiene una afinidad mucho menor por el sustrato que las demás hexoquinasas y no es inhibida por su producto. Se encuentra principalmente en páncreas e hígado (ßGK y LGK, respectivamente), donde como sensor regula los distintos estados metabólicos de estos tejidos, y controla la glicemia a nivel sistémico. Las formas ßGK y LGK se diferencian a nivel transcripcional, pues el gen posee dos promotores distintos, específicos para cada tejido. A nivel hormonal, la actividad de esta enzima es regulada selectivamente de manera tejido-específica por glucosa, insulina y otras proteínas reguladoras. La isoforma hepática puede ser secuestrada hacia el núcleo por la proteína reguladora de glucoquinasa (GKRP, por su sigla en inglés). La principal característica de la enzima glucoquinasa es su inusual regulación alostérica, propiedad que le permite adoptar dos conformaciones principales, una cerrada (activa) y otra súper-abierta (inactiva). Se han desarrollado distintas drogas activadoras de glucoquinasa, las cuales se unen al sitio alostérico de la enzima y estabilizan a la proteína en su estado cerrado. En esta revisión se describen las características estructurales y propiedades regulatorias que posee la enzima glucoquinasa, relacionándolas con su rol en el desarrollo de la diabetes MODY 2. También se profundiza en las implicancias moleculares de algunas mutaciones descritas que originan MODY 2, y se abordan los efectos de moléculas activadoras de glucoquinasa.

Diabetes MODY 2 or GCK-MODY is a type of monogenic diabetes produced by a mutation in the glucokinase enzyme, generating a hyperglycemic phenotype. This protein, a monomeric enzyme of the hexokinase family, is responsible for converting glucose into glucose-6-phosphate, the first step of glycolysis. Glucokinase is characterized by its unique kinetic properties: it has a much lower affinity for its substrate than other hexokinases and is not inhibited by its product. It is found mainly in pancreas (ßGK) and liver (LGK), where it acts as a sensor regulating the different metabolic states of these tissues, and ultimately, controlling systemic glycemia. The two forms ßGK and LGK differ at a transcriptional level, because the gene presents two different tissue-specific promoters. The activity of glucokinase in liver and pancreas is regulated by glucose, insulin and other regulatory proteins. The liver isoform can be sequestered to the nucleus by the glucokinase regulatory protein (GKRP). The main characteristic of the enzyme is its unusual allosteric regulation, a property that allows the protein to adopt a closed (active) conformation, and a super-open (inactive) conformation. Different glucokinase activating drugs have been developed, which bind to the allosteric site of the enzyme and stabilize glucokinase in its closed state. This review describes the structural and regulatory properties of the glucokinase enzyme, and its role in the development of MODY 2 diabetes. The molecular implications of some mutations that originate MODY 2 are also described, and the effects of glucokinase activating molecules are addressed.

MODY probability calculator for GCK and HNF1A screening in a multiethnic background population

ABSTRACT Objective We aimed to identify the frequency of monogenic diabetes, which is poorly studied in multiethnic populations, due to GCK or HNF1A mutations in patients with suggestive clinical characteristics from the Brazilian population, as well as investigate if the MODY probability calculator (MPC) could help patients with their selection. Subjects and methods Inclusion criteria were patients with DM diagnosed before 35 years; body mass index < 30 kg/m2; negative autoantibodies; and family history of DM in two or more generations. We sequenced HNF1A in 27 patients and GCK in seven subjects with asymptomatic mild fasting hyperglycemia. In addition, we calculated MODY probability with MPC. Results We identified 11 mutations in 34 patients (32.3%). We found three novel mutations. In the GCK group, six cases had mutations (85.7%), and their MODY probability on MPC was higher than 50%. In the HNF1A group, five of 27 individuals had mutations (18.5%). The MPC was higher than 75% in 11 subjects (including all five cases with HNF1A mutations). Conclusion Approximately one third of the studied patients have GCK or HNF1A mutations. Inclusion criteria included efficiency in detecting patients with GCK mutations but not for HNF1A mutations (< 20%). MPC was helpful in narrowing the number of candidates for HNF1A screening.

Hallazgo de una nueva mutación en una familia chilena con diabetes monogénica: caso clínico / Finding of a new mutation in a Chilean family with monogenic diabetes: report of one case

We report a 21 years old woman, without offspring, with diabetes mellitus diagnosed at 17 years of age, without ketosis or weight loss. Her body mass index was 18 kg/m2. Her C peptide was normal (2.3 ng/ml) and diabetes mellitus type 1 autoantibodies were negative. A monogenic diabetes Maturity Onset Diabetes of the Young (MODY) was proposed. Her family study disclosed a diabetic father and a brother with altered fasting glucose levels. The University of Exeter score for MODY yielded a 75.5% probability of MODY2. In the genetic-molecular study of the glucokinase gene (MODY2), the patient had a mutation at position 1343 of exon 10, corresponding to a heterozygous substitution of guanine by adenine (1343 G >A). The same mutation was found in her father and brother. This mutation is different from those previously described in the literature. The described change determines that a glycine is replaced by aspartic at amino acid 448 of the enzyme (non-synonymous substitution). The diagnosis of MODY2 was therefore confirmed in the patient and her father. The mutation was inherited by paternal line.

Diabetes mellitus por mutación en el gen de glucokinasa: caso clínico / Diabetes mellitus caused by a mutation of glucokinase gene: report of an affected family

Maturity-Onset Diabetes of the Young (MODY) refers to a heterogeneous group of monogenic diabetes. Unlike other types of MODY characterized by genetic defects in transcription factors, MODY 2 is triggered by metabolic alterations caused by mutations of glucokinase (GCK), the first enzyme of the glycolytic pathway. We report a three-generation Chilean family with multiple cases affected with this disease. The index case is a patient who presented severe neonatal hyperglycemia (831 mg/dl, without ketosis) requiring continuous infusion of insulin, which was suspended after 48 hours with normalization of blood glucose. Subsequently, continuous glucose monitoring at 4 months of age revealed 47% of tissue glucose levels above 140 mg/dl, with fasting glucose levels between 120 and 166 mg/dl. The genetic analysis revealed a previously reported mutation in heterozygous state of the GCK gene (c.148C>T; p.His50Tyr). This mutation was also identified in more than one affected relative in the last two generations, with a transmission pattern suggestive of dominant inheritance. GCK gene sequencing led to a correct molecular diagnosis of MODY 2 while bioinformatic analysis indicated the possible molecular causes of the enzyme dysfunction. The knowledge of the molecular diagnosis allowed an adequate medical treatment for this disease.

Presentaciones poco frecuentes de diabetes tipo MODY: el ejemplo de MODY tipo 5 y las formas de novo de MODY tipo 2 / Infrequent presentations of MODY diabetes: the example of MODY type 5 and de novo forms of MODY type 2

La diabetes tipo MODY se produce por alteraciones en genes relacionados con el metabolismo de la célula beta pancreática. El tipo 2 es uno de los más frecuentes y se produce por alteraciones en el gen GCK (glucoquinasa) y el tipo 5 es mucho menos frecuente y se produce por alteraciones en el gen HNF1B (factor nuclear hepático 1B). Se presentan con herencia autosómica dominante, aunque se ha descripto la presencia de mutaciones de novo. El objetivo del trabajo fue buscar mutaciones en el gen GCK en pacientes sin antecedentes familiares pero con características clínicas de MODY2 y mutaciones en el gen HNF1B en pacientes con características clínicas de MODY5 con y sin antecedentes familiares. Para ello a partir de ADN se realizó la secuenciación de cada gen por el método de Sanger o por secuenciación de nueva generación. Como resultado, se hallaron mutaciones en el gen GCK en cuatro pacientes sin antecedentes familiares y mutaciones en el gen del HNF1B en dos pacientes, uno de ellos sin antecedentes familiares. Como conclusión puede afirmarse que las mutaciones de novo en el gen de la GCK son más frecuentes de lo descripto, por lo cual se recomienda el estudio del gen en pacientes con características compatibles aún sin antecedentes familiares. También es importante el estudio del gen HNF1B en pacientes con características típicas ya que deben tratarse no sólo por sus alteraciones renales sino por la diabetes presente; de esta manera se logra un correcto diagnóstico para instaurar el tratamiento más adecuado

Diabetes MODY 2: reporte de dos casos con nueva mutación en el gen de glucokinasa / MODY 2: report of two cases with a new gene mutation in GCK

La diabetes MODY (Maturity Onset Diabetes of the Young) comprende un grupo heterogéneo de enfermedades monogénicasque se caracterizan por la disfunción de las células β. Se estima que ellas son responsables de 2-5% de los casos de diabetes. Seconocen más de 200 mutaciones en el gen de la glucoquinasa (GCK). En este trabajo se expone el caso de dos hermanas enlas cuales se realizó el diagnóstico de MODY 2 a través del estudio genético, hallándose una mutación del gen de la GCK nodescripto previamente en la bibliografía.

MODY (maturity onset diabetes of the young) includes a heterogeneous group of monogenic diseases which are characterized bydysfunction of beta cells. It accounts for 2-5% of all cases of diabetes. Over 200 mutations in the glucokinase (GCK) gene are known.In this paper we discuss the cases of two sisters in which the diagnosis of MODY 2 was performed by genetic studies, and report thefinding of a mutation in the GCK gene not previously described in the literature.

Maturity onset diabetes of young type 2 due to a novel de novo GKC mutation / Diabetes monogênica tipo MODY com início na juventude causado por uma mutação GKC de novo não descrita anteriormente

Maturity Onset Diabetes of Young (MODY) is a heterogeneous group of monogenic disorders that result in β-cell dysfunction, with an estimated prevalence of 1%-2% in industrialized countries. MODY generally occurs in non-obese patients with negative autoantibodies presenting with mild to moderate hyperglycemia. The clinical features of the patients are heterogeneous, depending on the different genetic subtypes. We pretend to report a case of MODY type 2 caused by a novel de novo CGK mutation, highlighting the importance of the differential diagnosis in pediatric diabetes. A 13-year-old, healthy and non-obese girl was admitted for investigation of recurrent hyperglycemia episodes. She presented with persistent high levels of fasting blood glycemia (> 11.1 mmol/L) and had no familial history of diabetes. The blood glucose profile revealed an impaired fasting glucose of 124 mg/dL (6,9 mmol/L) with a normal oral glucose tolerance test. Fasting insulinemia was 15 mg/dL (90.1 pmol/L), HOMA-IR was 3.9 and hemoglobin A1c was 7.1%. Pancreatic autoantibodies were negative. Genetic testing identified a novel missense heterozygous mutation in exon 5 of GCK gene c.509G > T (p.Gly170Val), not present on the parents. This result established the diagnosis of MODY type 2. Clinical identification of patients with MODY remains a diagnostic challenge, especially when familial history is absent. Molecular diagnosis is very important for establishing an individualized treatment and providing a long term prognosis for each type of MODY.

O diabetes da maturidade com início na juventude (MODY) é um grupo heterogêneo de doenças monogênicas que resultam em disfunção das células β, com uma prevalência estimada de 1-2% nos países industrializados. O MODY geralmente ocorre em pacientes não obesos, negativos para autoanticorpos e que apresentam hiperglicemia de leve a moderada. As características clínicas dos pacientes são heterogêneas e dependem do subtipo genético. Pretende-se relatar um caso de MODY tipo 2 causado por uma mutação GKC de novo não descrita anteriormente, demonstrando a importância do diagnóstico diferencial no diabetes pediátrico. Uma menina de 13 anos de idade, saudável e não obesa, foi admitida em um hospital para investigação de episódios recorrentes de hiperglicemia. Ela apresentava níveis altos e persistentes de glicemia de jejum (> 11,1 mmol/L) e não havia histórico familiar de diabetes. O perfil glicêmico sanguíneo revelou glicose de jejum de 124 mg/dL (6,9 mmol/L), com resultados normais no teste oral de tolerância à glicose. O resultado da insulinemia de jejum foi 15 mg/dL (90,1 pmol/L), do HOMA-IR foi 3,9 e da hemoglobina A1c foi de 7,1%. Os autoanticorpos pancreáticos foram negativos. A análise genética identificou uma nova mutação heterozigota missense no éxon 5 do gene GCK c.509G > T (p.Gly170Val), não encontrada nos país. Esse resultado estabeleceu o diagnóstico de MODY tipo 2. A identificação clínica dos pacientes com MODY permanece um desafio diagnóstico, especialmente quando não existe um histórico familiar. O diagnóstico molecular é muito importante para se estabelecer um tratamento individualizado e oferecer um prognóstico de longo prazo para cada tipo de MODY.

Clínica y tratamiento de la diabetes tipo MODY / Clinical treatment for MODY diabetes

El término MODY (Maturity Onset Diabetes of the Young) proviene de la antigua clasificación de la DM que la subdividía en aquellas que comenzaban en la juventud de las que lo hacían en la edad adulta. En la actualidad, se las encuadra dentro de aquellos cuadros caracterizados por “defectos genéticos en la función de la célula beta”. Es una forma monogénica de la enfermedad cuyo denominador común es la hiposecreción de insulina como factor desencadenante primario. Actualmente se han identificado 13 subtipos de MODY. Si bien MODY representa aproximadamente el 1-2% de los pacientes con DM, se estima que un gran porcentaje de los casos se encuentran sin diagnosticar. En cuanto a la frecuencia relativa, MODY 2 y MODY 3 representan alrededor del 60-80% de los casos, y MODY 1 el 10% de los mismos. En general, los pacientes con MODY se caracterizan por tener: 1) DM de comienzo en la edad joven, en general menores de 25 años; 2) fuerte influencia familiar; 3) sin estigmas de insulinorresistencia; 4) insulinodependencia; 5) ausencia de autoanticuerpos relacionados con DM autoinmune. El diagnóstico de MODY trae aparejado implicancias pronósticas, terapéuticas y sobre consejo genético. Aquellos pacientes con mutación en glucoquinasa (MODY2) habitualmente no desarrollan complicaciones crónicas tanto micro como macrovasculares y en general no requieren tratamiento farmacológico, mientras que aquellos con mutaciones en HNF-1α (MODY3) tienen tendencia a complicaciones microvasculares y poseen la característica de presentar hiperrespuestas a dosis bajas de sulfonilureas, incluso en algunas ocasiones presentan hipoglucemias severas.

Clinical follow-up of two Brazilian subjects with glucokinase-MODY (MODY2) with description of a novel mutation / Seguimento clínico de dois pacientes brasileiros com MODY-glicoquinase (MODY2) e descrição de uma nova mutação

Mutations in the glucokinase gene (GCK) account for many cases of monogenic diabetes featuring maturity-onset diabetes of the young type 2 (MODY2). The clinical pattern of this form of hyperglycemia is rather stable, with a slight elevation in blood glucose, which is usually not progressive. Patients rarely require pharmacological interventions and microvascular complications related to diabetes are unusual. We describe the clinical follow-up of two cases of MODY2 with two different mutations in GCK gene, one in exon 7, p.Glu265Lys (c.793 G> A), which has been previously described, and a novel one, in exon 2, p.Ser69Stop (c. 206C> G). The clinical course of both cases shows similarity in metabolic control of this form of diabetes over the years. Arq Bras Endocrinol Metab. 2012;56(8):490-5.

Mutações no gene da glicoquinase (GCK) são determinantes de uma forma de diabetes monogênico denominada de MODY2 (maturity-onset diabetes of the young, tipo 2). O padrão clínico dessa forma de distúrbio glicêmico é bastante estável, com hiperglicemia leve, geralmente não progressiva. Intervenções farmacológicas raramente são necessárias e complicações crônicas secundárias ao diabetes são infrequentes. Descrevemos o acompanhamento clínico de dois casos de MODY2 com duas mutações diferentes, uma no éxon 7, p.Glu265Lys (c.793 G>A) já descrita anteriormente, e outra inédita no éxon 2 p.Ser69Stop (c. 206C>G). A evolução clínica de ambos os casos demonstra uma semelhança no padrão metabólico dessa forma de diabetes ao longo dos anos. Arq Bras Endocrinol Metab. 2012;56(8):490-5.

Incidental mild hyperglycemia in children: two MODY 2 families identified in Brazilian subjects / Hiperglicemia incidental em crianças: duas famílias com MODY 2 identificadas em brasileiros

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. Arq Bras Endocrinol Metab. 2012;56(8):519-24.

O diabetes do tipo MODY (maturity-onset diabetes of the young) caracteriza-se por herança autossômica dominante, início precoce da hiperglicemia e defeitos na secreção de insulina. Os subtipos de MODY apresentam diferenças genéticas, metabólicas e clínicas. O MODY 2 é caracterizado por hiperglicemia leve assintomática e raramente requer tratamento farmacológico. O diagnóstico preciso de MODY é importante para se determinar o tratamento e o prognóstico. Relatamos duas mutações no gene GCK em heterozigose identificadas durante investigação de baixa estatura. Caso 1: paciente do sexo masculino, com 14 anos, pré-púbere, avaliado por atraso constitucional do crescimento e da puberdade. Durante o acompanhamento, apresentou glicemia de jejum alterada (113 mg/dL), aumento de HbA1c (6,6%) e anticorpos anticélulas β negativos. Seu pai e dois irmãos também apresentavam glicemia levemente elevada. A mãe tinha glicemia normal. Foi identificada no gene GCK uma mutação missense em heterozigose, p.Arg191Trp. Dezoito membros da família foram rastreados e 11 apresentavam essa mutação. Caso 2: paciente do sexo masculino, com 4 anos, em avaliação por baixa estatura. Não apresentou alterações laboratoriais, exceto por glicemia elevada (118 mg/dL). Anticorpos anticélulas β foram negativos. Seu pai, uma tia paterna e a avó paterna também apresentavam glicemia discretamente elevada, e a mãe, glicemia normal. A mutação missense em heterozigose, p.Glu221Lys, foi identificada no paciente-índice e em 4 membros da família. Todos os pacientes afetados apresentavam hiperglicemia leve. Essas mutações não foram identificadas nos indivíduos com glicemia normal. O rastreamento de mutações no gene GCK deve ser considerado em pacientes com hiperglicemia crônica leve e de início precoce, história familiar de glicemia elevada e anticorpos anticélulas β negativos. Arq Bras Endocrinol Metab. 2012;56(8):519-24.

Glucokinase gene promoter -30G>A polymorphism: a cross-sectional association study with obesity, diabetes Mellitus, hyperlipidemia, hypertension and metabolic syndrome in an Iranian hospital / Polimorfismo -30G

OBJECTIVE: A -30G>A single nucleotide polymorphism in the promoter region of the glucokinase gene has been previously associated with obesity, insulin resistance and diabetes. The present study aimed to evaluate the association of this polymorphism with obesity and its comorbidities in a population from Northeast Iran. METHODS: Five hundred and forty-two subjects aged 18 to 65 years were included in the study and divided into normal (BMI<25, n=220), overweight (2530, n=187) groups. All subjects were genotyped for the -30G>A polymorphism using the polymerase chain reaction-restriction fragment length polymorphism technique. RESULTS: The genotypes and allele frequencies of the three groups did not differ significantly (p>0.05). When the study population was categorized according to diabetes mellitus, hyperlipidemia, hypertension and metabolic syndrome status, no significant difference in -30G>A genotypes and alleles was found between the subgroups with and without these disorders (p>0.05), apart from a significantly higher frequency of the G allele in the hyperlipidemic vs. non-hyperlipidemic subgroup (p<0.05). CONCLUSION: The findings of the present study do not support an association between the -30G>A polymorphism and high body mass index in the Iranian population.

OBJETIVO: O polimorfismo de nucleotídeo único -30G>A, na região promotora do gene da glucoquinase, já foi associado à obesidade, resistência insulínica e diabete. O objetivo deste estudo foi avaliar a associação deste polimorfismo com a obesidade e suas comorbidades em uma população do nordeste iraniano. MÉTODOS: Quinhentos e quarenta e dois indivíduos com idades entre 18 e 65 anos foram divididos em três grupos: normal (BMI<25, n=220), sobrepeso (2530, n=187). Todos os indivíduos foram genotipados para o polimorfismo -30G>A através da técnica da reação em cadeia da polimerase - polimorfismo do comprimento do fragmento de restrição. RESULTADOS: As frequências dos genótipos e alelos dos 3 grupos não diferiram entre si (p>0,05). Quando a população de estudo foi categorizada de acordo com a presença de diabete, hiperlipidemia, hipertensão arterial e síndrome metabólica, os genótipos e alelos -30G>A dos subgrupos com e sem essas doenças não diferiram entre si (p>0,05), exceto por uma frequência maior do alelo G no grupo de hiperlipidêmicos quando comparados aos não hiperlipidêmicos (p<0,05). CONCLUSÃO: Os achados do presente estudo não confirmam uma associação entre o polimorfismo -30G>A e excesso de peso na população iraniana.

HNF1α mutations are present in half of clinically defined MODY patients in South-Brazilian individuals / Mutações HNF1α estão presentes na metade dos pacientes da região sul do Brasil clinicamente diagnosticados com MODY

Maturity-onset diabetes of the young (MODY) is a monogenic form of diabetes mellitus characterized by autosomal dominant inheritance, early age of onset, and pancreatic beta cell dysfunction. Heterozygous mutations in at least seven genes can cause MODY. In the present study we investigated the relative prevalence of GCK (glucokinase) and HNF1α (hepatocyte nuclear factor 1α) mutations, the more frequent causes of MODY, in 13 South-Brazilian families with multiple cases of diabetes consistent with MODY. Heterozygous variants in GCK and HNF1α genes were observed respectively in one (7.7 percent), and six (46.2 percent) families. The six HNF1α variants are likely to cause diabetes in the families where they were observed. However, we could not ascertain whether the GCK Gly117Ser variant found in one family is a causal mutation. In conclusion, we have confirmed in a South-Brazilian population that HNF1α mutations are a common cause of monogenic diabetes in adults selected with strict clinical diagnostic criteria.

O maturity-onset diabetes of the young (MODY) é uma forma monogênica de diabetes melito caracterizada por herança autossômica dominante, de instalação precoce, como disfunção da célula beta pancreática. Mutações heterozigotas em pelo menos sete genes causam MODY. No presente estudo, investigamos a prevalência relativa das mutações da GCK (glucokinase) e HNF1α (hepatocyte nuclear factor 1α), as causas mais freqüentes de MODY, em 13 famílias sul-brasileiras com múltiplos casos de diabetes consistentes com MODY. Variantes heterozigotas nos genes da GCK e HNF1α foram observadas, respectivamente, em uma (7,7 por cento) e em seis (46,2 por cento) famílias. As seis variantes do HNF1α provavelmente causaram o diabetes nas famílias nas quais foram observadas. No entanto, não se pode afirmar que a variante GCK Gly117Ser encontrada em uma família seja a mutação causal. Em conclusão, confirmamos que, em uma população do sul do Brasil, as mutações HNF1α são uma causa comum de diabetes monogênico em adultos selecionados com critérios clínicos diagnósticos estritos.

Conservation of glycolytic oscillations in Saccharomyces cerevisiae and human pancreatic b-cells: a study of metabolic robustness

The present study compares two computer models of the first part of glucose catabolism in different organisms in search of evolutionarily conserved characteristics of the glycolysis cycle and proposes the main parameters that define the stable steady-state or oscillatory behavior of the glycolytic system. It is suggested that in both human pancreatic b-cells and Saccharomyces cerevisiae there are oscillations that, despite differences in wave form and period of oscillation, share the same robustness strategy: the oscillation is not controlled by only one but by at least two parameters that will have more or less control over the pathway flux depending on the initial state of the system as well as on extra-cellular conditions. This observation leads to two important interpretations: the first is that in both S. cerevisiae and human b-cells, despite differences in enzyme kinetics and mechanism of feedback control, evolution seems to have kept an oscillatory behavior coupled to the glucose concentration outside the cytoplasm, and the second is that the development of drugs to regulate metabolic dysfunctions in more complex systems may require further study, not only determining which enzyme is controlling the flux of the system but also under which conditions and how its control is maintained by the enzyme or transferred to other enzymes in the pathway as the drug starts acting.

Specific insulin and proinsulin secretion in glucokinase-deficient individuals

Glucokinase (GCK) is an enzyme that regulates insulin secretion, keeping glucose levels within a narrow range. Mutations in the glucokinase gene cause a rare form of diabetes called maturity-onset diabetes of the young (MODY). An early onset (less than 25 years), autosomal dominant inheritance and low insulin secretion stimulated by glucose characterize MODY patients. Specific insulin and proinsulin were measured in serum by immunofluorimetric assays (IFMA) during a 75-g oral glucose tolerance test (OGTT). Two kindreds (SA and LZ) were studied and compared to non-diabetic unrelated individuals (control group 1) matched for age and body mass index (BMI). In one kindred, some of these subjects were also obese (BMI>26 kg/m2), and other family members also presented with obesity and/or late-onset NIDDM. The MODY patients were also compared to a group of five of their first-degree relatives with obesity and/or late-onset NIDDM. The proinsulin profile was different in members of the two MODY kindreds. Fasting proinsulin and the proinsulin/insulin ratio were similar in MODY members of kindred LZ and subjects from control group 1, but were significantly lower than in MODY members of kindred SA (P<0.02 and P<0.01, for proinsulin and proinsulin/insulin ratio, respectively). Moreover, MODY members of family SA had higher levels of proinsulin and proinsulin/insulin ratio, although not significantly different, when compared to their first-degree relatives and to subjects from control group 2. In conclusion, we observed variable degrees of proinsulin levels and proinsulin/insulin ratio in MODY members of two different kindreds. The higher values of these parameters found in MODY and non-MODY members of kindred SA is probably related to the obesity and late-onset NIDDM background present in this family.

Estudo do gene da glicoquinase em famílias brasileiras com suspeita de diabete melito da maturidade no jovem e estudo da secreçäo de insulina e pró-insulina nos indivíduos afetados / Study of the gene of glicoquinase in Brazilian families with suspicion of diabetes mellitus of the maturity in the young and study of secretions insulin and pro-insulin in the affected individuos

O diabete melito da maturidade no jovem (DMMJ) é caracterizado pelo seu aparecimento precoce (25 anos) e herança genética autossômica dominante. DMMJ é uma síndrome geneticamente heterogênea, sendo que mutaçöes do gene da enzima glucokinase (GCK) säo a sua causa mais freqüente, na França. Através da técnica do polimorfismo de conformaçäo de fitas simples (SSCP) näo radioativa foi realizado o estudo do gene da GCK em 17 famílias com suspeita clínica de DMMJ. As bandas com migraçäo anômala observadas foram seqüenciadas. Foram encontradas mutaçöes nos exons 7 e 9 do gene da GCK em duas famílias (Q e P), respectivamente, e uma alteraçäo no exon 1 na família J. Neste caso, a filha do propósito apresentou uma variaçäo homozigótica em dois exons (1a e 1b), que sugere um polimorfismo, uma vez que a ausência da funçäo da GCK é aparentemente incompatível com a sobrevivência. A família Q apresentou uma mutaçäo no exon 7, transformando uma glutamina em códon de parada na posiçäo 248, que foi detectada no propósito e em três filhos. Os demais membros da família que näo eram diabéticos, inclusive os pais do propósito, näo apresentaram a mutaçäo. O estudo de impressöes digitais de DNA confirmou a paternidade, sendo este indivíduo a primeira mutaçäo desta família. A família P apresentou uma mutaçäo no exon 9, transformando de valina para um códon de parada na posiçäo 401. A alteraçäo foi dectada no propósito, no seu filho, e em 5 de seus irmäoa que apresentavam hiperglicemia. A mutaçäo näo foi encontrada na mäe, na tia e na irmä do propósito, todas com obesidade e diabete näo insulino-dependente de desenvolvimento tardio. O pai do propósito, já falecido (portador obrigatório) näo foi testado. Teste oral de tolerância à glicose (TTG) foi realizado nas famílias com mutaçäo na GCK para estudo da secreçäo de insulina e pró-insulina, utilizando para isto, ensaios específicos. Verificamos que a secreçäo de insulina encontrava-se diminuida nos indivíduos GCK-mutantes em ambas as famílias. A secreçäo de pró-insulina encontrava-se dentro dos valores da normalidade nos indivíduos da família Q e aumentada nos indíduos da família P. Com três indivíduos desta última família apresentavam diabete sem mutaçäo para o gene da GCK, isto sugeria a presença de outro gene diabetogênico nesta família. A pró-insulina esteve positivamente correlacionada à obesidade (r=o,66; p<0,0001) e foi a variável independente que mais se associou ao índice da massa corporal...(au)