José Timsit

Clinical Spectrum Associated with Hepatocyte Nuclear Factor-1β Mutations

Context Maturity-onset diabetes of the young type 5 (MODY5) is an uncommon variant of a dominantly inherited disease associated with mutations in the hepatocyte nuclear factor-1 (HNF-1) gene. We know little about its spectrum except that it may include urogenital abnormalities. Contribution This multicenter study describes 8 probands with MODY5 and known nondiabetic kidney disease and 5 offspring. Each proband had a different mutation in the HNF-1 gene. Probands and offspring had various renal abnormalities, including dysplastic kidneys and renal cysts. Some also had genital tract abnormalities, pancreatic atrophy, and abnormal liver enzyme levels. Implications Maturity-onset diabetes of the young type 5 is genetically and phenotypically heterogeneous. The Editors The prevalence of diabetes mellitus is estimated to be 6% to 7% in western industrialized countries; type 2 diabetes mellitus accounts for 90% of the cases (1). Maturity-onset diabetes of the young (MODY) is defined by the occurrence, typically before age 25 years, of nonketotic diabetes mellitus due to a primary defect of insulin secretion, along with autosomal dominant inheritance. With the exception of MODY2, which is due to mutations in the glucokinase gene, the identified MODY subtypes are related to mutations of transcription factor genes: hepatocyte nuclear factor-4 (HNF-4) for MODY1, HNF-1 for MODY3, insulin promoter factor-1 for MODY4, HNF-1 for MODY5, and neurogenic differentiation factor-1 for MODY6. The subtypes of MODY may account for 2% to 5% cases of type 2 diabetes, with types 3 and 2 representing 65% and 15% of these cases, respectively. The other subtypes of MODY are thought to be rare (2). Maturity-onset diabetes of the young type 5 was initially described in a Japanese family as the association of early-onset diabetes and nephropathy (3). Heterogeneous phenotypes, including diabetes, renal abnormalities, and genital malformations, were subsequently described through isolated case reports in white and Japanese populations (3-16). Currently, all but 2 families (6, 16) with MODY5 demonstrated autosomal dominant inheritance of private mutations. In our report, using a standardized evaluation, we describe clinical and genetic findings in 13 patients from 8 unrelated families with novel HNF-1 mutations. Detailed phenotypic analysis underlines the systemic spectrum of the disease and its wide variability, leading to different modes of presentation. We also confirm that MODY5 may occur because of de novo mutation in HNF-1. These findings may help to define criteria for HNF-1 gene testing. Methods Patients Participants were recruited from the patients of 2 departments of diabetes, 1 internal medicine department, and 1 nephrology department, on the basis of the following clinical characteristics: 1) diabetes (fasting plasma glucose level 7.0 mmol/L [126 mg/dL]), suggesting a MODY phenotype if diabetes occurred before 40 years of age, if the patient was not obese (body mass index < 30 kg/m2), and the patient did not have islet-cell antibodies and glutamic acid decarboxylase autoantibodies; 2) impaired renal function (creatinine clearance < 1.34 mL/s [<80 mL/min]) without diabetic retinopathy and albumin excretion greater than 0.5 g/d (17); and 3) kidney structural abnormalities (reduced kidney size, presence of cysts, or both). A family history of diabetes was not a criterion. A total of 20 unrelated white patients were identified from clinic lists and screened for HNF-1 mutation: 13 men and 7 women with a mean (sd) age of 26 8 years, a mean body mass index of 23.4 2.7 kg/m2 at onset of diabetes, and functional and structural renal abnormalities at presentation. The Ethics Committee of Necker Hospital, Paris, France, approved the study, and all participants gave written informed consent. Clinical Evaluation Clinical history of diabetes mellitus and renal involvement were recorded by using a standardized examination of the patients and their relatives. Creatinine clearance was calculated according to the Cockcroft-Gault formula (18). Imaging studies of the kidneys, consisting of ultrasonography and intravenous urography or computed tomography, and renal biopsy specimens were reviewed by a nephrologist and a renal pathologist. Genital tract abnormalities were assessed by ultrasonography. Endogenous insulin secretion was assessed by measuring C-peptide plasma concentration (Bio-Rad Specific C-Peptide, Bio-Rad, Marne la Coquette, France) before and 6, 10, and 15 minutes after intravenous injection of 1 mg of glucagon (19). Pancreas structure was assessed by computed tomography. Pancreas exocrine function was evaluated by measuring fecal fat excretion and elastase concentration (Schebo-Biotech, Guiessen, Germany). Liver biopsy was performed in 3 patients whose liver test results were persistently abnormal. Mutation Analysis of the HNF-1 Gene Genomic DNA was extracted from peripheral blood samples by standard procedures. The minimal promoter, the coding region of the 9 exons, and exon-intron boundaries of the HNF-1 gene were screened for mutations by direct sequencing as previously described (3). Direct diagnosis of the mutations identified in probands was offered to first-degree relatives (parents, siblings, and offspring) regardless of their clinical status. Results Molecular Analysis A mutation of HNF-1 was found in 8 of the 20 unrelated patients. Among 19 of 35 first-degree relatives from 6 unrelated families tested, 5 of 8 offspring had inherited a mutation. None of the 8 mutations have been reported to date. All are located in the DNA-binding domain (20). Five are point mutations resulting in amino acid substitutions (also called missense mutations) that affect residues conserved in HNF-1 human, pig, mouse, rat, xenopus, and salmon sequences. Two other mutations are nonsense mutations resulting in a truncated protein lacking the 3-part of the DNA-binding domain and the C-terminal transactivation domain. The last mutation is localized in the splice donor site of intron 2 at the highly conserved +1 position. Another base change (GA) at the same position was described in a Japanese family with MODY5 (8). No nucleotide variant was detected in 212 control chromosomes of unrelated nondiabetic white participants and in 170 chromosomes of patients with classic type 2 diabetes. In 4 families (families 1, 5, 6, and 8), cosegregation of a HNF-1 mutation and MODY5 phenotype was consistent with dominant inheritance because 5 affected offspring inherited the mutation detected in the proband. A de novo mutation was demonstrated in 2 probands (patient II-1, family 6, and patient II-1, family 7). In each case, the probands parents were not carriers of the mutation. Parental relationships were confirmed by using microsatellite markers (data not shown). Two relatives in family 3 (patients I-2 and II-1) and 2 relatives in family 6 (patients I-1 and I-2) had diabetes mellitus but did not exhibit the corresponding mutation of HNF-1. Clinical Phenotype Diabetes was present in all probands and in 2 offspring (patient III-1, family 1, and patient II-1, family 8) with a mutation. Five patients presented with clinical symptoms, including severe metabolic decompensation in 2 patients, at age 1 year (patient II-1, family 8) and 13 (patient II-1, family 6) years, respectively. In the 5 other patients, diabetes was found by routine plasma glucose measurement. Clinical characteristics were consistent with a defect of insulin secretion: All patients were lean at diagnosis, ketosis was observed in 2 patients, and progression of the disease was observed in 3 patients who ultimately required insulin therapy. Endogenous insulin response to intravenous glucagon, assessed in 7 of the 8 probands, disclosed heterogeneous degrees of impairment, but residual insulin secretion was detectable in all probands. In patient II-1, family 6, endogeneous insulin secretion was measurable 22 years after diabetes was revealed by severe ketoacidosis. No patient had diabetic retinopathy or neuropathy. Pancreas atrophy was found in 5 of the 6 patients assessed by abdominal computed tomography (Table 1 and Figure). No pancreas calcification or cyst was noticed. No patient exhibited symptoms of overt pancreatic exocrine deficiency. However, of the 7 probands tested, 6 had a subclinical defect of pancreas exocrine function (Table 1 and Figure). Table 1. Characteristics of Mutations, Diabetes, Pancreas Exocrine Function, and Liver Tests in 8 Probands with Hepatocyte Nuclear Factor-1 Mutations Figure. Pancreas and kidney abnormalities in patients with hepatocyte nuclear factor-1 ( HNF-1 ) mutation. A B C. A arrow arrowheads B C. arrowheads arrows D. E F. HNF-1 E. F. arrow * Renal involvement was found in all probands (Table 2) and 4 offspring. In the probands, age at recognition of kidney disease ranged from 18 to 41 years. All exhibited structural kidney abnormalities, including decreased kidney size, ranging from 85 to 105 mm in height with global cortical loss, and a cystic pattern (Figure). Pelvicaliceal abnormalities were observed in 6 of the 7 patients who were tested and consisted of clubbing or tiny diverticulae of the calices or mild pelvic dilatation without obstructive uropathy (Figure). All probands also had mild to moderate renal failure with creatinine clearance ranging from 0.48 to 1.28 mL/s (29 to 77 mL/min). On follow-up, the mean annual decrease of creatinine clearance ranged from 0 to 0.03 mL/s (0 to 2 mL/min). It averaged 0.02 mL/s per year (1.1 mL/min per year) in the 4 patients who were followed for 14 to 16 years (Table 2). Since the clinical, biological, and radiologic characteristics of renal disease made the diagnosis of diabetic glomerulopathy very unlikely, a kidney biopsy was performed in 6 probands. No proband exhibited diabetic glomerulosclerosis. Interstitial fibrosis was observed in all biopsy specimens. Enlarged glomeruli were observed in 4 cases, associated with glom

Age-dependent HLA genetic heterogeneity of type 1 insulin-dependent diabetes mellitus.

The association of insulin-dependent diabetes mellitus (IDDM) with certain HLA alleles is well documented in pediatric patients. Whether a similar association is found in adult-on-set IDDM is not clear, although the disease occurs after the age of 20 in 50% of cases. HLA class II DRB1, DQA1, and DQB1 alleles were studied in 402 type I diabetics and 405 healthy controls (all Caucasian) using oligonucleotide typing after gene amplification. Alleles DRB1*03, DRB1*04, DQB1*0201, DQB1*0302, DQA1*0301, and DQA1*0501 were indeed enriched in diabetics and the highest relative risk was observed in patients carrying both the DRB1*03-DQB1*0201 and the DRB1*0402 or DRB1*0405-DQB1*0302 haplotypes. However none of these alleles, or specific residues, could alone account for the susceptibility to IDDM. Furthermore, there were major differences in HLA class II gene profiles according to the age of onset. Patients with onset after 15 yr (n = 290) showed a significantly higher percentage of non-DR3/non-DR4 genotypes than those with childhood onset (n = 112) and a lower percentage of DR3/4 genotypes. These non-DR3/non-DR4 patients, although presenting clinically as IDDM type 1 patients, showed a lower frequency of islet cell antibodies at diagnosis and a significantly milder initial insulin deficiency. These subjects probably represent a particular subset of IDDM patients in whom frequency increases with age. The data confirm the genetic heterogeneity of IDDM and call for caution in extrapolating to adult patients the genetic concepts derived from childhood IDDM.

Maternally Inherited Diabetes and Deafness: A Multicenter Study

Mitochondrial (mt) gene abnormalities cause disease due to defects in oxidative production of energy (1). In 1990, Goto and colleagues (2) described the co-segregation of a syndrome called mitochondrial encephalopathy, lactic acidosis, and strokelike episodes (which is sometimes associated with diabetes) and an A to G transition at position 3243 of mtDNA, encoding transfer RNA leucine (tRNALeu [UUR]). In 1992, a subtype of diabetes called maternally inherited diabetes and deafness (MIDD) was reported to co-segregate with the same point mutation (3, 4). Maternally inherited diabetes and deafness was initially characterized by matrilineal transmission, associated hearing loss, or both, without major neurologic defects. In MIDD, diabetes seems to be due primarily to a defect in insulin secretion (4-9), while insulin sensitivity is unaltered (8, 10). An estimated 0.5% to 2.8% of diabetic patients have MIDD (9, 11-16). Because most reported series have been small, the clinical description of MIDD and its course, particularly the occurrence of diabetic complications, remains incomplete. The aims of our study were to delineate the clinical presentation of MIDD, including involvement of other organs, in a large series of patients and to assess the prevalence of diabetic microvascular and macrovascular complications. Methods Patients We conducted this prospective multicenter descriptive study between September 1995 and December 1999. A questionnaire was sent to all members of the French Association for the Study of Diabetes (ALFEDIAM) in order to assess the clinical presentation of MIDD in a large series of patients. A total of 52 patients were included as a result of the questionnaire, and 19 patients were recruited directly from Lariboisire Hospital. The 3243 mtDNA mutation was identified in 40 probands who were selected primarily because they had both diabetes and deafness. Family screening identified 31 additional carriers of the mutation. All patients were white and European, except one who was of Caribbean origin. Three patients had mitochondrial encephalopathy, lactic acidosis, and strokelike episodes associated with diabetes. Among the 68 remaining patients, 54 had overt diabetes, 2 had impaired glucose tolerance, and 12 were healthy carriers. The study conformed to the principles of the Declaration of Helsinki, and all patients gave informed consent. Measurements We used a structured interview and a standardized examination of the patients and of their relatives to ascertain a family history of diabetes and hearing loss and to determine glucose tolerance disorders, treatment, diabetic complications, and associated manifestations. Abnormalities in glucose tolerance were diagnosed on the basis of the 1997 criteria outlined by the American Diabetes Association (17). Accordingly, diabetes was defined as a fasting plasma glucose level of 7 mmol/L (126 mg/dL) or greater on two occasions, a plasma glucose level of 11 mmol/L (200 mg/dL) or greater 2 hours after a 75-g oral glucose load, or both. In our study, we report only on the 54 patients with overt diabetes. Obesity was defined as a body mass index (BMI) of 30 kg/m2 or greater, body weight excess was defined as a BMI of 25 kg/m2 or greater, and low body weight was defined as a BMI less than 18.5 kg/m2 (18). Hemoglobin A1c level was assayed by using high-performance liquid chromatography. Islet-cell antibodies, antibodies to glutamic acid decarboxylase 65, or IA2 antibodies were determined in 32 cases. Hypertension was defined as a blood pressure exceeding 140/85 mm Hg on two occasions after 10 minutes in the resting position or as the use of antihypertensive treatment (19). Diagnosis of macrovascular complications (coronary heart disease, lower-limb arteriopathy, cerebrovascular disease) and diagnosis of cardiomyopathy were based on medical records, clinical examination, and appropriate tests (echocardiography, ultrasonography). We determined 24-hour urinary albumin excretion, proteinuria, and plasma creatinine concentration. A standardized ophthalmologic examination was performed in 49 patients, including ophthalmoscopy after pupillary dilation, color photographs, and fluorescein angiography, all of which were read by the same investigator. The retinal epithelium alterations were graded according to published criteria (20, 21). Molecular Studies The A to G 3243 mtDNA mutation was identified in peripheral blood leukocytes in 70 patients and from a buccal smear in 1 patient. Total DNA was extracted from the peripheral blood by using the conventional salting-out procedures. The 3243 mutation was detected by using 2% agarose electrophoresis after polymerase chain reaction amplification of a 294base pair fragment and enzymatic digestion with Apa I, as described elsewhere (2, 22). Statistical Analysis Data were stored and analyzed by using SPSS for Windows (SPSS Inc., Chicago, Illinois). Data are expressed as the mean (SD), with ranges indicated in parentheses. Differences in BMI and hemoglobin A1c levels among patient groups were assessed by using KruskalWallis analysis of variance. Correlations were analyzed by using the Spearman nonparametric rank correlation coefficient. Results Diabetes All 54 patients with overt diabetes (21 men, 33 women) had a fasting plasma glucose level greater than 7 mmol/L (126 mg/dL) when diabetes was diagnosed. Diabetes was diagnosed by systematic screening in 32 patients (59%). In the 22 remaining patients (41%), diabetes was revealed by the occurrence of polyuria, which was associated with ketoacidosis in 4 patients (7%). Age at diagnosis of diabetes was 38.8 9.6 years (range, 12 to 67 years); in 25 patients, diabetes was diagnosed before age 35. At the time of the study, the mean patient age was 50.0 10.3 years (range, 31 to 71 years), and diabetes duration was 11.8 8.7 years (range, 0 to 37 years). Diabetes was noninsulin-dependent in 22 patients (41%); 9 of 22 were treated with diet alone, and 13 were treated with sulfonylureas, metformin, or both. Twenty-five patients (46%) required insulin after experiencing secondary failure with a combination of maximally dosed sulfonylureas and metformin 9.9 5.8 years (range, 1 to 28 years) after diabetes was diagnosed. In 7 patients (13%), diabetes was insulin-dependent from its onset. Islet-cell antibodies were present in only 1 patient. A first-degree family history of diabetes was present in 33 of 40 probands (83%), and a maternal family history of diabetes was present in 29 probands (73%). No patient with MIDD was obese (Table), and 19 of 50 patients (38%) had low body weight. No correlation was found between BMI and hemoglobin A1c level, age, or diabetes duration. However, BMI and hemoglobin A1c values differed among patient groups according to treatment (Table). Table. Hemoglobin A1c Level and Body Mass Index in 54 Patients with Maternally Inherited Diabetes and Deafness Deafness Bilateral neurosensory hearing loss was present in 53 of 54 patients (98%). Hearing loss was clinically significant in all patients and was documented by audiography in 28 patients. Fourteen patients (26%) required a prosthetic hearing aid. Age at diagnosis of deafness was 34.6 13.9 years (range, 2 to 61 years). Twenty-five of 40 probands (63%) had a maternal history of deafness. Diabetes was the first clinical manifestation of the disease in 24 patients, and hearing loss was the first manifestation in 23 patients. In 7 patients, both conditions were diagnosed simultaneously. Macular Pattern Dystrophy We previously reported the presence of a characteristic macular pattern dystrophy in patients with MIDD (20). In our current study, macular pattern dystrophy was present in 42 of 49 examined patients (86%). Age at discovery was 46.5 10.8 years (range, 27 to 71 years). In 6 patients, the pigmented lesions were very small and were localized to the macula (grade 1) (Figure 1, top). In 27 patients, the deposits were more extensive and were localized around the macula and the optic disc (grade 2). In the 9 patients with advanced macular pattern dystrophy, the macula had patches of retinal atrophy (grade 3) (Figure 1, bottom). No correlation was found between grade of macular pattern dystrophy and age or diabetes duration. Figure 1. Macular pattern dystrophy. Top. Bottom. Visual acuity was normal in 43 of 49 patients (88%). Among patients with retinal atrophy, 4 had a visual acuity of 20/50 to 20/32 and 2 had a visual acuity below 20/63. Of the latter 2 patients, 1 had severe astigmatism and 1 had diabetic macular edema. Refraction was between +3 and 3 diopters in all patients with MIDD, except in 1 patient with severe astigmatism. No ocular nerve atrophy was observed. Neuromuscular Disorders Muscular disorders were observed in 22 of 51 documented cases of MIDD (43.1%). Patients reported painful muscle weakness that affected lower limbs during prolonged walking or running. In the 6 patients in whom it was performed, muscle biopsy showed ragged-red fibers typical of mitochondrial myopathy (Figure 2). Eight patients had cardiomyopathy; echocardiography showed typical left ventricular hypertrophy in all. Symptoms of congestive heart failure were present in 2 patients. A preexcitation syndrome (WolffParkinsonWhite) was present in 2 patients, and atrial fibrillation was seen in 1 patient. Mitochondrial myopathy was present in 4 of 8 patients with cardiomyopathy. Coronary heart disease was present in 4 of 54 patients (7%), and clinically significant peripheral artery lesions were observed in 2 of 54 patients. Hypertension was present in 15 of 53 patients (28%). Ocular motor palsy was present in 2 patients from the same family, and cerebellar ataxia with cerebellar atrophy on nuclear magnetic resonance imaging was seen in another patient. Atrophic changes in the brain were observed in the 4 other patients who underwent nuclear magnetic resonance imaging. Neuropsychiatric disturbances were present in 9 of 51 patients (18%). The

Identification of 14 new glucokinase mutations and description of the clinical profile of 42 MODY-2 families

Summary Mutations in glucokinase are associated with defects in insulin secretion and hepatic glycogen synthesis resulting in mild chronic hyperglycaemia, impaired glucose tolerance or diabetes mellitus. We screened members of 35 families with features of maturity-onset diabetes of the young for mutations in the glucokinase gene and found 16 different mutations. They included 14 new mutations in the glucokinase gene: 9 missense mutations (A53S, G80A, H137R, T168P, M210T, C213R, V226M, S336L and V367M); 2 nonsense mutations (E248X and S360X); a deletion of one nucleotide resulting in a frameshift (V401del1); a substitution of a conserved nucleotide at a splice acceptor site (L122-1G → T); and a 10 base pair deletion that removed the GT of the splice donor site and the following eight nucleotides (K161 + 2del10). In addition, we found two previously identified mutations: R186X and G261R. Study of 260 subjects with glucokinase-deficient hyperglycaemia from 42 families with 36 different GCK mutations made it possible to define the clinical profile of this subtype of non-insulin-dependent diabetes mellitus (NIDDM). Hyperglycaemia due to glucokinase deficiency is often mild (fewer than 50 % of subjects have overt diabetes) and is evident during the early years of life. Despite the long duration of hyperglycaemia, glucokinase-deficient subjects have a low prevalence of micro- and macro-vascular complications of diabetes. Obesity, arterial hypertension and dyslipidaemia are also uncommon in this form of NIDDM. [Diabetologia (1997) 40: 217–224]

Effects of chronic growth hormone hypersecretion on intrinsic contractility, energetics, isomyosin pattern, and myosin adenosine triphosphatase activity of rat left ventricle.

We studied papillary muscle mechanics and energetics, myosin phenotype, and ATPase activities in left ventricles from rats bearing a growth hormone (GH)--secreting tumor. 18 wk after tumor induction, animals exhibited a dramatic increase in body weight (+101% vs. controls) but no change in the ventricular weight/body weight ratio. The maximum isometric force of papillary muscles normalized per cross-sectional area rose markedly (+42%, P less than 0.05 vs. controls), whereas the maximum unloaded shortening velocity did not change. This was observed despite a marked isomyosin shift towards V3 (32 +/- 5% vs. 8 +/- 2% in controls, P less than 0.001). Increased curvature of the force-velocity relationship (+64%, P less than 0.05 vs. controls) indicated that the muscles contracted more economically, suggesting the involvement of V3 myosin. Total calcium- and actin-activated myosin ATPase activities assayed on quickly frozen left ventricular sections were similar in tumor-bearing rats and in controls. After alkaline preincubation, these activities only decreased in tumor-bearing rats, demonstrating that V3 enzymatic sites were involved in total ATPase activity. These data demonstrate that chronic GH hypersecretion in the rat leads to a unique pattern of myocardial adaptation which allows the muscle to improve its contractile performance and economy simultaneously, thanks to myosin phenoconversion and an increase in the number of active enzymatic sites.

Cardiovascular Effects of the Somatostatin Analog Octreotide in Acromegaly

OBJECTIVE To determine the cardiovascular effects of the somatostatin analog octreotide in patients with acromegaly. DESIGN Prospective nonrandomized study. SETTING Referral-based endocrinology clinic. PATIENTS Seven patients with active acromegaly, three of whom had refractory congestive heart failure. The other four patients were free of symptoms associated with heart failure. INTERVENTIONS All patients were treated with octreotide, 100 to 500 micrograms subcutaneously three times daily. The three patients with heart failure continued to receive cardiovascular therapy (angiotensin converting enzyme inhibitors, digitalis, diuretics). MEASUREMENTS AND MAIN RESULTS During octreotide therapy, patients showed a rapid decrease in growth hormone and insulin-like growth factor 1 (IGF-1): Mean levels (+/- SD) fell from 28.1 +/- 32.7 micrograms/L to 5.2 +/- 8.3 micrograms/L and 740 +/- 126 micrograms/L to 372 +/- 64 micrograms/L, respectively (P less than 0.025). Plasma volume returned to normal and heart rate decreased significantly. In the four patients without heart failure, right-heart catheterization done before and after 3 months of octreotide therapy showed an 18.3% +/- 11% reduction in stroke volume and a return to normal of the cardiac index. The three patients with congestive heart failure, evaluated before and after 40 days and up to 2 years of therapy, showed a dramatic clinical improvement that was associated with an increase in stroke volume (by 24% to 51%). In these patients, the cardiac index remained in the normal range, filling pressures were markedly decreased, and pulmonary wedge pressure returned to normal. This improvement was sustained for up to 3 years in the two patients with heart failure who were receiving long-term treatment. CONCLUSION The rapid and sustained cardiac improvement seen in our patients shows that octreotide therapy for patients with acromegaly may be highly beneficial, even in those patients with advanced cardiac failure.

The Type and the Position of HNF1A Mutation Modulate Age at Diagnosis of Diabetes in Patients with Maturity-Onset Diabetes of the Young (MODY)-3

OBJECTIVE—The clinical expression of maturity-onset diabetes of the young (MODY)-3 is highly variable. This may be due to environmental and/or genetic factors, including molecular characteristics of the hepatocyte nuclear factor 1-α (HNF1A) gene mutation. RESEARCH DESIGN AND METHODS—We analyzed the mutations identified in 356 unrelated MODY3 patients, including 118 novel mutations, and searched for correlations between the genotype and age at diagnosis of diabetes. RESULTS—Missense mutations prevailed in the dimerization and DNA-binding domains (74%), while truncating mutations were predominant in the transactivation domain (62%). The majority (83%) of the mutations were located in exons 1- 6, thus affecting the three HNF1A isoforms. Age at diagnosis of diabetes was lower in patients with truncating mutations than in those with missense mutations (18 vs. 22 years, P = 0.005). Missense mutations affecting the dimerization/DNA-binding domains were associated with a lower age at diagnosis than those affecting the transactivation domain (20 vs. 30 years, P = 10−4). Patients with missense mutations affecting the three isoforms were younger at diagnosis than those with missense mutations involving one or two isoforms (P = 0.03). CONCLUSIONS—These data show that part of the variability of the clinical expression in MODY3 patients may be explained by the type and the location of HNF1A mutations. These findings should be considered in studies for the search of additional modifier genetic factors.

Mutation screening in 18 Caucasian families suggest the existence of other MODY genes

Summary Maturity-onset diabetes of the young (MODY) is a heterogeneous subtype of non-insulin-dependent diabetes mellitus characterised by early onset, autosomal dominant inheritance and a primary defect in insulin secretion. To date five MODY genes have been identified: hepatocyte nuclear factor-4 alpha (HNF-4α/MODY1/TCF14) on chromosome 20 q, glucokinase (GCK/MODY2) on chromosome 7 p, hepatocyte nuclear factor-1 alpha (HNF-1α/MODY3/TCF1) on chromosome 12 q, insulin promoter factor-1 (IPF1/MODY4) on chromosome 13 q and hepatocyte nuclear factor-1 beta (HNF-1β/MODY5/TCF2) on chromosome 17cen-q. We have screened the HNF-4α, HNF-1α and HNF-1β genes in members of 18 MODY kindreds who tested negative for glucokinase mutations. Five missense (G31D, R159W, A161T, R200W, R271W), one substitution at the splice donor site of intron 5 (IVS5nt + 2T→A) and one deletion mutation (P379fsdelT) were found in the HNF-1α gene, but no MODY-associated mutations were found in the HNF-4α and HNF-1β genes. Of 67 French MODY families that we have now studied, 42 (63 %) have mutations in the glucokinase gene, 14 (21 %) have mutations in the HNF-1α gene, and 11 (16 %) have no mutations in the HNF-4α, IPF1 and HNF-1β genes. Eleven families do not have mutations in the five known MODY genes suggesting that there is at least one additionnal locus that can cause MODY. [Diabetologia (1998) 41: 1017–1023]

Clinical pharmacokinetics of octreotide. Therapeutic applications in patients with pituitary tumours.

SummaryAmong somatostatin analogues, octreotide is the most extensively studied. Its pharmacodynamic properties are similar to those of somatostatin, with a wide spectrum of inhibitory effects on anterior pituitary function, pancreas and gut endocrine secretions, and gastrointestinal functions. Compared with the somatostatin, octreotide is highly resistant to enzymatic degradation and has a prolonged plasma half-life of about 100 minutes in humans, allowing its use in the long term treatment of various pathological conditions. Differential effects of octreotide on endocrine secretions such as growth hormone (GH) and insulin in healthy volunteers, as well as variable efficacy in the treatment of endocrine tumours, may relate to the distribution of somatostatin receptor subtypes.The volume of distribution of octreotide ranges from 18 to 30L. Calculated serum distribution half-life ranges from 72 to 98 minutes. In blood, octreotide is mainly distributed in the plasma, 65% being bound to lipoproteins. After subcutaneous injection, absorption appears rapid and complete and bioavailability is about 100%. Mean peak plasma concentrations are between 2 and 4 µg/L in patients receiving 50 to 100µg. Peak concentrations are reached within 20 to 30 minutes and are 20 to 40% of corresponding values after intravenous injection. Peak concentrations and values for areas under the plasma concentration-time curve linearly correlate with the dosage. The elimination half-life is about 90 to 110 minutes. Total clearance in healthy individuals is about 160 ml/min (9.6 L/h). Hepatic metabolism of octreotide is extensive (30 to 40%) and about 11 to 20% of the dose is excreted unchanged in the urine.Among pituitary tumours, GH- and thyrotrophin-secreting adenomas are the most sensitive to octreotide. Octreotide has been widely used in the treatment of acromegaly. 50 to 80% of the patients respond to daily multiple subcutaneous injections with insulin-like growth factor-1 (IGF1) levels being normalised in about 40 to 50% of them. Neither desensitisation with long term therapy nor rebound phenomena after octreotide withdrawal have been noticed in these studies.Even in patients with partial response, clinical symptoms improved. Octreotide daily dosages needed to achieve optimum responses may vary greatly from one patient to another. In a minority of patients complete resistance to octreotide was observed and was not always related to the absence of somatostatin receptors in the tumour. The wide spectrum of effects of octreotide in humans accounts for adverse effects seen during long term treatment, primarily cholelithiasis.Other modes of administration are efficient. In particular, continuous subcutaneous infusion allows the use of a smaller dosage, but is more effective than multiple injections in some patients. Intranasal administration is now also being investigated and seems promising.

No Major Role for the CTLA-4 Gene in the Association of Autoimmune Thyroid Disease With IDDM

IDDM is a T-cell-mediated autoimmune disease depending on both genetic and environmental susceptibility factors. The HLA class II region (IDDM1) and the insulin promoter region (IDDM2) account for -50 and 10%, respectively, of IDDM genetic risk. At least 15 other IDDM susceptibility markers have been identified by genomewide scanning studies (1). One must consider that IDDM is a heterogeneous disorder that can vary in terms of age at clinical onset, duration of hyperglycemia before strict insulin dependency, existence of familial aggregation, occurrence of complications, and presence of extrapancreatic autoimmune diseases, so that different genes might influence the course or the presentation of the disease. The CTLA-4 gene, which has been mapped to the IDDM12 locus (2q33), is a good candidate gene in IDDM (2). Apart from recognition of major histocompatibility complex (MHC)/peptide complex by the T-cell receptor (TCR), T-cell activation requires a co-stimulatory signal mediated by CD28/B7 interaction. The CTLA-4 gene encodes a T-cell surface molecule whose binding to the B7 molecule on antigen-presenting cell delivers a negative signal to the T-cell and can mediate its apoptosis (3). Thus, CTLA-4 expression on T-cells might well influence the course of an ongoing immune process. CTLA4-deficient mice develop a severe lymphoproliferative disease with multiorgan lymphocytic infiltration and tissue destruction, including the pancreas (4,5). In the same respect, the blockade of the CD28/B7 co-stimulatory signal prevents the occurrence of diabetes but not of insulitis in the NOD mouse model, suggesting that it either promotes a shift of the immune response or makes an additional signal unavailable for the final destructive stage (6). Recently, linkage to IDDM of a point mutation in exon 1 of CTLA-4 (position 49 A/G) leading to a Thr/Ala substitution in the leader peptide has been