Peter Kühnen

Proopiomelanocortin Deficiency Treated with a Melanocortin-4 Receptor Agonist

Patients with rare defects in the gene encoding proopiomelanocortin (POMC) have extreme early-onset obesity, hyperphagia, hypopigmentation, and hypocortisolism, resulting from the lack of the proopiomelanocortin-derived peptides melanocyte-stimulating hormone and corticotropin. In such patients, adrenal insufficiency must be treated with hydrocortisone early in life. No effective pharmacologic treatments have been available for the hyperphagia and obesity that characterize the condition. In this investigator-initiated, open-label study, two patients with proopiomelanocortin deficiency were treated with setmelanotide, a new melanocortin-4 receptor agonist. The patients had a sustainable reduction in hunger and substantial weight loss (51.0 kg after 42 weeks in Patient 1 and 20.5 kg after 12 weeks in Patient 2).

The Neuroendocrine Circuitry Controlled by POMC, MSH, and AGRP

Obesity is one of the most challenging health problems worldwide. Over the past few decades, our knowledge concerning mechanisms of weight regulation has increased tremendously leading to the identification of the leptin-melanocortin pathway. The filling level of energy stores is signaled to the brain, and the information is integrated by hypothalamic nuclei, resulting in a well-orchestrated response to food intake and energy expenditure to ensure constant body weight. One of the key players in this system is proopiomelanocortin (POMC), a precursor of a variety of neuropeptides. POMC-derived alpha- and beta-MSH play an important role in energy homeostasis by activating melanocortin receptors expressed in the arcuate nucleus (MC3R) and in the nucleus paraventricularis (MC4R). Activation of these two G protein-coupled receptors is antagonized by agouti-related peptide (AgRP). Naturally occurring mutations in this system were identified in patients suffering from common obesity as well as in patients demonstrating a phenotype of severe early-onset obesity, adrenal insufficiency, red hair, and pale skin. Detailed understanding of the complex system of POMC-AgRP-MC3R-MC4R and their interaction with other hypothalamic as well as peripheral signals is a prerequisite to combat the obesity epidemic.

Identification of PENDRIN (SLC26A4) Mutations in Patients With Congenital Hypothyroidism and “Apparent” Thyroid Dysgenesis

CONTEXT Congenital hypothyroidism, the most frequent endocrine congenital disease, can occur either based on a thyroid hormone biosynthesis defect or can predominantly be due to thyroid dysgenesis. However, a genetic cause could so far only be identified in less than 10% of patients with a thyroid dysgenesis. OBJECTIVES Exome sequencing was used for the first time to find additional genetic defects in thyroid dysgenesis. PATIENTS AND METHODS In a consanguineous family with thyroid dysgenesis, exome sequencing was applied, and findings were further validated by Sanger sequencing in a cohort of 94 patients with thyroid dysgenesis. RESULTS By exome sequencing we identified a homozygous missense mutation (p.Leu597Ser) in the SLC26A4 gene of a patient with hypoplastic thyroid tissue, who was otherwise healthy. In the cohort of patients with thyroid dysgenesis, we observed a second case with a homozygous missense mutation (p.Gln413Arg) in the SLC26A4 gene, who was additionally affected by severe hearing problems. Both mutations were previously described as loss-of-function mutations in patients with Pendred syndrome and nonsyndromic enlarged vestibular aqueduct. CONCLUSION We unexpectedly identified SLC26A4 mutations that were hitherto diagnosed in thyroid dyshormonogenesis patients, now for the first time in patients with structural thyroid defects. This result resembles the historic description of thyroid atrophy in patients with the so-called myxedematous form of cretinism after severe iodine deficiency. Most likely the thyroid defect of the two homozygous SLC26A4 gene mutation carriers represents a kind of secondary thyroid atrophy, rather than a primary defect of thyroid development in the sense of thyroid agenesis. Our study extends the variable clinical spectrum of patients with SLC26A4 mutations and points out the necessity to analyze the SLC26A4 gene in patients with apparent thyroid dysgenesis in addition to the known candidate genes TSHR, PAX8, NKX2.1, NKX2.5, and FOXE1.

Glucose-Dependent Insulinotropic Polypeptide Reduces Fat-Specific Expression and Activity of 11β-Hydroxysteroid Dehydrogenase Type 1 and Inhibits Release of Free Fatty Acids

Glucose-dependent insulinotropic polypeptide (GIP) has been suggested to have direct effects on nonislet tissues. GIP also reportedly increased glucose uptake and inhibition of lipolysis in adipocytes after inhibition of the intracellular cortisone-cortisol shuttle 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). We here analyzed whether GIP modifies lipid metabolism and further elucidated the relation between GIP, 11β-HSD1, and fatty acid metabolism. GIP reduced activity of 11β-HSD1 promoter constructs and the expression and activity of 11β-HSD1 in differentiated 3T3-L1 adipocytes in a time- and dose-dependent fashion. This was paralleled by a reduction of free fatty acid (FFA) release and a reduced expression of key enzymes regulating lipolysis in adipose tissue. Preinhibition of 11β-HSD1 completely abolished GIP-induced effects on FFA release. To investigate the acute effects of GIP in humans, a randomized clinical trial was performed. GIP lowered circulating FFAs compared with saline control and reduced expression and ex vivo activity of 11β-HSD1 and adipose triglyceride lipase expression in subcutaneous fat biopsies. Our data suggest that GIP reduces FFA release from adipose tissue by inhibition of lipolysis or by increased reesterification. This process appears to depend on a modification of 11β-HSD1 activity. In general, the presented data support that GIP has direct and insulin-independent effects on adipose tissue.

Long-Term Lanreotide Treatment in Six Patients with Congenital Hyperinsulinism

Background: Medical treatment is a substantial therapeutic measure to achieve glycemic control and prevent hypoglycemic brain damage without surgery in patients with congenital hyperinsulinism (CHI). However, only few drugs are available and even fewer are approved as a medical therapy to maintain normal blood glucose levels. The established therapies are demanding for caregivers and complicated by different side effects such as gastrointestinal symptoms, hypertrichosis, and obesity. Therefore, it is important to develop new strategies to improve blood glucose control. Methods: We report the use of the very-long-acting somatostatin analogue lanreotide autogel in 6 patients with CHI over a mean duration of 40.8 months. Blood glucose levels before and after the start and dosage titration of lanreotide in these patients are compared. Results: In 3 of 6 patients, switching to lanreotide raised mean blood glucose levels and reduced individually as well as overall the risk for hypoglycemic episodes (odds ratio 0.38) significantly. Conclusion: Lanreotide autogel can be used as an alternative pharmacological treatment and may be beneficial in conservatively treated patients with CHI.

Somatic mutations and progressive monosomy modify SAMD9 -related phenotypes in humans

It is well established that somatic genomic changes can influence phenotypes in cancer, but the role of adaptive changes in developmental disorders is less well understood. Here we have used next-generation sequencing approaches to identify de novo heterozygous mutations in sterile &agr; motif domain–containing protein 9 (SAMD9, located on chromosome 7q21.2) in 8 children with a multisystem disorder termed MIRAGE syndrome that is characterized by intrauterine growth restriction (IUGR) with gonadal, adrenal, and bone marrow failure, predisposition to infections, and high mortality. These mutations result in gain of function of the growth repressor product SAMD9. Progressive loss of mutated SAMD9 through the development of monosomy 7 (–7), deletions of 7q (7q–), and secondary somatic loss-of-function (nonsense and frameshift) mutations in SAMD9 rescued the growth-restricting effects of mutant SAMD9 proteins in bone marrow and was associated with increased length of survival. However, 2 patients with –7 and 7q– developed myelodysplastic syndrome, most likely due to haploinsufficiency of related 7q21.2 genes. Taken together, these findings provide strong evidence that progressive somatic changes can occur in specific tissues and can subsequently modify disease phenotype and influence survival. Such tissue-specific adaptability may be a more common mechanism modifying the expression of human genetic conditions than is currently recognized.

Recessive mutations in PCBD1 cause a new type of early-onset diabetes

Mutations in several genes cause nonautoimmune diabetes, but numerous patients still have unclear genetic defects, hampering our understanding of the development of the disease and preventing pathogenesis-oriented treatment. We used whole-genome sequencing with linkage analysis to study a consanguineous family with early-onset antibody-negative diabetes and identified a novel deletion in PCBD1 (pterin-4 α-carbinolamine dehydratase/dimerization cofactor of hepatocyte nuclear factor 1 α), a gene that was recently proposed as a likely cause of diabetes. A subsequent reevaluation of patients with mild neonatal hyperphenylalaninemia due to mutations in PCBD1 from the BIODEF database identified three additional patients who had developed HNF1A-like diabetes in puberty, indicating early β-cell failure. We found that Pcbd1 is expressed in the developing pancreas of both mouse and Xenopus embryos from early specification onward showing colocalization with insulin. Importantly, a morpholino-mediated knockdown in Xenopus revealed that pcbd1 activity is required for the proper establishment of early pancreatic fate within the endoderm. We provide the first genetic evidence that PCBD1 mutations can cause early-onset nonautoimmune diabetes with features similar to dominantly inherited HNF1A-diabetes. This condition responds to and can be treated with oral drugs instead of insulin, which is important clinical information for these patients. Finally, patients at risk can be detected through a newborn screening for phenylketonuria.

Diabetes caused by insulin gene (INS) deletion: clinical characteristics of homozygous and heterozygous individuals

BACKGROUND Mutations of the preproinsulin gene (INS) account for both permanent neonatal diabetes (PND) and adult-onset diabetes. The molecular mechanism of complete INS deletion has recently been published and we now add clinical data of homozygous and heterozygous subjects as well as the detailed mapping of the 646 bp deletion of the INS gene. METHODS Location and size of the INS deletion was mapped in one case with PND and INS genotype of the whole family was further characterized by breakpoint-spanning PCR. The phenotype of monoallelic loss of INS was studied in 33 adult family members of a large consanguineous kindred with INS deletion. RESULTS The 646 bp deletion was found in two individuals with PND that included exons 1 and 2 of the INS gene (chr11: g.2138434_2139080del646) and results in loss of approximately half of the preproinsulin protein. The two boys with homozygous INS deletion (D/D) presented with reduced birth weight, PND within the first 24 h of life and complete absence of C-peptide. Adult family members with the N/D had diabetes onset with earliest 25 years, while the oldest subject without diabetes was 45 years. INS-deletion-diabetes was initially treated with oral antidiabetic drugs but then transferred to insulin within 5-16 years. Overall, N/D-subjects (n=11) had a higher risk to develop insulin-dependent diabetes up to the fifth decade, if compared with normal subjects (n=22). CONCLUSION Complete loss of the human INS gene results in neonatal diabetes, while heterozygous INS deletion is a strong risk factor for developing insulin-dependent diabetes at adult age.

Two Novel GATA6 Mutations Cause Childhood-Onset Diabetes Mellitus, Pancreas Malformation and Congenital Heart Disease

Background:GATA6 mutations are the most frequent cause of pancreatic agenesis and diabetes in human sporadic cases. In families, dominantly inherited mutations show a variable phenotype also in terms of endocrine and exocrine pancreatic disease. We report two novel GATA6 mutations in an independent cohort of 8 children with pancreas aplasia or hypoplasia and diabetes. Methods: We sequenced GATA6 in 8 children with diabetes and inborn pancreas abnormalities, i.e. hypoplasia or aplasia in which other known candidate genes causing monogenic diabetes and pancreatic defects had been excluded. Results: We found two novel heterozygous GATA6 mutations (c.951_954dup and c.754_904del) in 2 patients with sporadic pancreas hypoplasia, diabetes and severe cardiac defects (common truncus arteriosus and tetralogy of Fallot), but not in the remaining 6 patients. GATA6 mutations in carriers exhibited hypoplastic pancreas with absent head in 1 patient and with increased echogenicity and decreasing exocrine function in the other patient. Additionally, hepatobiliary malformations and brain atrophy were found in 1 patient. Conclusion: Our 2 cases with novel GATA6 mutations add more phenotype characteristics of GATA6 haploinsufficiency. In agreement with an increasing number of published cases, the wide phenotypic spectrum of GATA6 diabetes syndrome should draw the attention of both pediatric endocrinologists and geneticists.

Generation of integration free induced pluripotent stem cells from fibrodysplasia ossificans progressiva (FOP) patients from urine samples

Fibrodysplasia ossificans progressiva (FOP) is an extremely rare, autosomal dominant transmitted genetic disease. Patients experience progressive bone formation replacing tendons, ligaments, muscle and soft tissue. Cause of FOP are gain-of-function mutations in the Bone Morphogenetic Protein (BMP) receptor Activin A receptor type 1 (ACVR1) (Kaplan et al., 2008). The most common mutation is R206H, which leads to the substitution of codon 206 from arginine to histidine (Shore et al., 2006). Here, we describe the derivation and characterization of two hiPSC lines from two FOP patients, both carrying the mutation R206H. Cells were isolated from urine and reprogrammed using integration free Sendai virus vectors under defined conditions.