Duchenne muscular dystrophy (DMD) is an X-linked inherited neuromuscular disease characterized by progressive weakness and severe muscle wasting. Alterations in carbohydrate metabolism are often associated with neuromuscular disorders. We performed oral glucose tolerance tests and insulin binding studies on erythrocytes from 17 DMD and 8 normal males. Furthermore, we measured insulin binding to erythrocytes from 12 normal males and from 11 mothers and 10 sisters of affected males. As a group, DMD patients had mild glucose intolerance and both fasting and postabsorptive marked hyperinsulinemia (insulin resistance). Levels of glucose and insulin, expressed as incremental areas under their respective curves, were significantly elevated in the wheelchair-ridden patients. Incremental areas of glucose (0-2 h) and insulin (0-5 h) were 42 +/- 5 mg/dl X h (mean +/- SEM) and 96 +/- 18 microU/ml X h, respectively, in normal subjects and 71 +/- 6 (P less than 0.05) and 206 +/- 30 (P less than 0.05), respectively, in the wheelchair-confined DMD patients. All of the ambulatory DMD males had normal oral glucose tolerance tests. Insulin binding to erythrocytes was 20-30% lower (P less than 0.01) in all DMD patients than in normal males appropriately matched for age and degree of sexual development. This difference in binding was a result of lower affinity of the insulin receptor in DMD erythrocytes. On the other hand, insulin binding to fibroblasts was the same in normal males and DMD patients, suggesting that the abnormality of erythrocyte binding in DMD is probably not genetically induced. Insulin binding to erythrocytes and monocytes was the same in all females studied, regardless of whether they were carriers of the DMD gene. Our results suggest that abnormal insulin binding in DMD erythrocytes is an acquired rather than genetic abnormality, but insulin binding is not helpful in the identification of carrier females. The defect in insulin binding in DMD is present before the development of insulin resistance, which occurs only in severely immobilized patients. Thus, the cause of the insulin resistance in DMD may reside at steps beyond the binding of insulin to its receptor.

Genetic mechanisms of sex determination involve a network of interacting genes. Molecular analyses of rare patients with sex reversal or sexual ambiguities have been critical in the identification of new genes for sexual development. SRY, an HMG-box transcription factor, triggers male sex determination. When the dosage sensitive sex reversal (DSS) locus, containing the nuclear hormone receptor DAX1, is duplicated, the result is XY sex reversal and hypogonadotropic hypogonadism (HH); mutations in DAX1 cause adrenal hypoplasia congenita (AHC). Here we describe two patients with a new clinical association of male pseudohermaphroditism with sex-reversed external genitalia and AHC. In both patients, normal female genitalia were noted at birth and each had an episode of adrenal insufficiency before two months of age. They had absent steroidogenesis, AHC and HH. Abdominal magnetic resonance imaging (MRI) showed adrenal hypoplasia or aplasia, and pelvic MRI revealed neither gonads nor any Mullerian structures. The patients' karyotypes were 46,XY. Molecular genetic studies revealed no mutations in SRY, DAX1, or SF1, another nuclear hormone receptor. We present alternative hypotheses to explain this unusual association: (1) one or more additional sex-determining genes within the DSS locus, possibly acting in synergy with DAXl; or (2) one or more genes not linked to DSS involved in both gonadal and adrenal development.

We report on a male infant with congenital hypoparathyroidism who developed primary hypothyroidism at 3 months and insulin-dependent diabetes mellitus at 25 months. He had evidence of widespread and progressive neurologic dysfunction characterized by severe developmental delay, blindness, deafness, seizures, atrophy of the cerebellar and frontal lobes, and elevated spinal fluid protein. Also noted were renal hypoplasia, hyporeninemic hypoaldosteronism, chronic anemia, persistent elevation of liver transaminase levels, abnormal intraventricular cardiac conduction, reduction in numbers of helper T-cells, and distinctive facial anomalies. The child died of multiorgan failure at 29 months. A mitochondrial basis for the syndrome was considered but a molecular mechanism has, as yet, not been identified.

During the infusion of insulin in vivo, the rate of activation of glucose disposal lags significantly behind the rate of increase in serum insulin levels. To determine whether this delay was related to transcapillary transport of insulin, we determined increments in serum insulin levels, glucose disposal rates (GDR), and insulin receptor (IR) kinase activity measured during continuous infusions of insulin (40 and 120 mU.m-2.min-1) administered to 8 nondiabetic males; similar studies were done at 1,200.m-2.min-1 in 2 of the subjects. Half-maximal insulin levels were achieved at a mean of 4.9 and 7.2 min during the 40 and 120 mU.m-2.min-1 clamps, respectively, with corresponding half-maximal GDR stimulation at a mean of 59 and 47 min. Unlike the rise in insulin levels, IR kinase activation was much slower with half-maximal activity occurring at approximately 40-60 min in the 2 clamps. Thus, the rise in serum insulin levels in each clamp was much faster than the increment in either kinase activity or glucose disposal. Insulin infusion increased both IR kinase and GDR maximally approximately 10-fold, with half-maximal stimulation at approximately 3,600 and approximately 700 pM, indicating spare kinase for glucose disposal. These results demonstrate that the delay in stimulation of glucose disposal by insulin is related to a rate-limiting step between the intravascular space and the cell-surface of skeletal muscle. This may involve delayed transendothelial transport of insulin.

We report on a girl with short stature, mental retardation, mutism, "coarse" facial appearance, and papillary-follicular thyroid carcinoma. She had dup(20p) derived from a paternal balanced translocation [(12p;20p)]. We speculate that the carcinoma in our patient may be related to the deletion of material from 12p resulting in absence of genetic material normally required for the suppression of thyroid tumorigenesis.

OBJECTIVE To report the cases of and to describe two unrelated Guamanian patients with an unusual form of congenital adrenal hyperplasia resulting from 17 alpha-monooxygenase deficiency (P-450C17). DESIGN Patient series. SETTING Referral center. PATIENTS Two phenotypic females of Guamanian descent, unrelated, and referred for evaluation of hypertension and delayed sexual development. INTERVENTIONS Diagnosis by measurement of specific adrenocortical precursors and initiation of therapy with dexamethasone. Documentation of response by decrease in circulating concentrations of metabolites and decrease in blood pressure. CONCLUSIONS The finding of a rare autosomal recessive disorder in two unrelated persons from a small genetic pool in Guam suggests that this may result from the same molecular defect and may be present in this population at an unexpectedly high incidence. Lack of suspicion frequently leads to unnecessary delay in diagnosis of this condition.

OBJECTIVE:To determine the cause of absent sexual development in a 17-year-old girl with end-stage renal disease.DESIGN:Case study.PARTICIPANT:Seventeen-year-old girl with end-stage renal failure.INTERVENTIONS:None.MEASUREMENTS/MAIN RESULTS:The patient had phenotypically normal external female genitalia, müllerian duct hypoplasia, and no ovaries. Her serum gonadotropin levels were in the castrate range at baseline and after gonadotropin-releasing hormone stimulation. Her karyotype, in lymphocytes and cultured fibroblasts, was 46,XX. Analysis of genomic DNA, following polymerase chain reaction-amplication with oligonucleotide primers corresponding to the Y-encoded zinc finger protein ZFY and the testis-determining SRY gene, showed Y chromosome material in a male control but none in the patient.CONCLUSIONS:The results suggest a diagnosis of Frasier syndrome, a disorder characterized by true gonadal dysgenesis and end-stage renal disease occurring in normal phenotypic girls. Although previously reported only in individuals with a 46,XX karyotype, our studies indicate that Frasier syndrome may also occur in 46,XX girls. Delayed puberty is not uncommon in renal failure. This case illustrates the importance of measuring gonadotropin levels in teenage girls with delayed puberty and renal failure, particularly if the origin of the renal disease is obscure.

A 17-year-old boy with insulin-dependent diabetes mellitus developed ketoacidosis and transitory shock. After resolution of his metabolic imbalance, he developed an acute abdomen prompting exploratory surgery. A section of necrotic ileum was found and resected.

Mandibuloacral dysplasia (MAD) is a syndrome with onset in midchildhood. The predominant characteristics of MAD include flexion contractures; mandibular hypoplasia; loss of body fat; atrophic, speckled skin; and progressive osteolysis of the clavicles. We studied three males with MAD. Each had lipodystrophy of the extremities, with sparing of the face and neck. All had moderate hyperlipidemia. In response to oral glucose, each had a diabetic response, with peak insulin levels between 2870 and 22,960 pmol/L. Insulin-stimulated glucose disposal was determined in two patients with MAD. At an insulin infusion rate of 120 mU/m2 per minute, glucose disposal was less than 25% of that measured at similar levels of insulinemia in nondiabetic control subjects, indicating marked insulin resistance in patients with MAD. The insulin resistance occurred without obesity, excessive levels of counterregulatory hormones, or anti-insulin-receptor antibodies. We suggest that MAD is a previously undescribed form of lipodystrophic insulin-resistant diabetes mellitus.

To assess the relationship between insulin receptor (IR) kinase activity and insulin action in vivo in humans, we measured glucose disposal rates (GDR) during a series of euglycemic clamp studies. Simultaneously, we measured IR kinase activity in IRs extracted from skeletal muscle obtained by needle biopsy at the end of each clamp. By preserving the phosphorylation state of the receptors as it existed in vivo at the time of biopsy, we could correlate GDR and IR kinase in skeletal muscle. Eight nondiabetic, nonobese male subjects underwent studies at insulin infusion rates of 0, 40, 120, and 1,200 mU/m2 per min. Kinase activity, determined with receptors immobilized on insulin agarose beads, was measured at 0.5 microM ATP, with 1 mg/ml histone, followed by SDS-PAGE. Insulin increased GDR approximately sevenfold with a half-maximal effect at approximately 100 microU/ml insulin and a maximal effect by approximately 400 microU/ml. Insulin also increased IR kinase activity; the half-maximal effect occurred at approximately 500-600 microU/ml insulin with a maximal 10-fold stimulation over basal. Within the physiologic range of insulin concentrations, GDR increased linearly with kinase activation (P less than 0.0006); at supraphysiologic insulin levels, this relationship became curvilinear. Half-maximal and maximal insulin-stimulated GDR occurred at approximately 20 and approximately 50% maximal kinase activation, respectively. These results are consistent with a role of the kinase in insulin action in vivo. Furthermore, they demonstrate the presence of a large amount of "spare kinase" for glucose disposal.

Mandibuloacral dysplasia (MAD) is a syndrome characterized by partial lipodystrophy and a distinct phenotype, which includes progressive osteolysis of the mandible and clavicles, cutaneous atrophy, joint contractures, and diabetes mellitus. We now describe the results of hyperinsulinemic glucose clamps performed in conjunction with indirect calorimetry in two subjects with MAD. At a glucose level of 5 mmol/L and insulin concentration of over 6.5 x 10(4) pmol/L, glucose disposal rates were less than 20% of maximum insulin-stimulated glucose disposal in five nondiabetic controls. Basal hepatic glucose output was elevated in the two patients and was incompletely suppressed by a 1200 mU/m2.min infusion of insulin. Glucose and lipid oxidation rates were inappropriately elevated, reflecting marked hypermetabolism. Pharmacological concentrations of insulin failed to normally suppress lipid oxidation, diminish FFA levels, or adequately suppress glucagon levels. In summary, MAD is a unique form of lipodystrophic diabetes characterized by typical somatic features, extreme insulin resistance, and marked hypermetabolism.

We report an infant with a craniopharyngioma which was detected in utero. Maternal uterine ultrasonography, done at 27 weeks because of polyhydramnios, revealed a 4 cm midline mass near the base of the fetal skull. At 31 weeks, magnetic resonance imaging of the maternal abdomen confirmed the presence of a mass in the region of the third ventricle and revealed hydrocephalus. Two days post-partum a computed tomography (CT)-guided needle biopsy of the mass was performed and recovered tissue which was histologically consistent with a craniopharyngioma. The infant's postnatal period was complicated by seizures, which were treated with phenobarbital, and by progressive hydrocephalus, necessitating placement of a ventriculo-peritoneal shunt. He also received therapy for central hypothyroidism and diabetes insipidus. The infant's parents refused permission for attempted resection of the tumour and he died at 8 weeks of age. This represents the second reported case of an antenatally detected craniopharyngioma. Four other cases of different intracranial tumours have been detected in utero using ultrasound, with no reported survivors past 3 days of age. There is a uniformly poor prognosis of such infants, but earlier diagnosis and intervention may change this result.

We identified a possible endogenous substrate (pp185) of the insulin-receptor kinase in human adipocytes by treating intact cells with insulin and immunoblotting the cellular extracts with polyclonal antiphosphotyrosine antibody. This 185,000-Mr protein was phosphorylated on tyrosine residues in response to insulin in both rat and human adipocytes. The time course of pp185 phosphorylation at 37°C was rapid and corresponded closely to insulin-receptor autophosphorylation but preceded insulin-stimulated glucose transport. Unlike many growth factor receptors, including the insulin receptor, pp185 was not adsorbed to wheat-germ agglutinin. We found that pp185 phosphorylation occurred at 12°C and that the phosphoprotein was associated with both cytoplasmic and membrane fractions at this temperature. Furthermore, pp185 phosphorylation was induced to the same extent as insulin by vanadate and hydrogen peroxide, compounds previously shown to mimic the biologic effects of insulin. In addition, dose-response analysis of insulin-stimulated glucose transport, receptor autophosphorylation, and pp185 phosphorylation resulted in ED50 values of 0.3, 12, and 12 ng/ml, respectively. These results demonstrate the magnitude of “spare” autophosphorylation and pp185 phosphorylation with respect to glucose transport stimulation in human adipocytes. To determine whether the insulin resistance characteristic of non-insulin-dependent diabetes mellitus (NIDDM) and obesity is associated with a defect in receptor autophosphorylation and/or endogenous substrate phosphorylation, we estimated the extent of β-subunit and pp185 phosphorylation in adipocytes from NIDDM, obese, and healthy subjects. Although the efficiency of coupling between receptor activation and pp185 phosphorylation was normal in obesity and NIDDM, the capacity for insulin-receptor autophosphorylation was ∼50% lower in NIDDM subjects compared with nondiabetic obese or lean subjects. Thus, the absolute level of pp185 phosphorylation in response to insulin stimulation would be lower in adipocytes from NIDDM subjects. We conclude that pp185 is directly phosphorylated by the insulin-receptor kinase in vivo and may serve as a mediating step to the biologic effects of insulin in human adipocytes. Furthermore, the extent of pp185 phosphorylation is compromised in adipocytes from NIDDM subjects and may contribute xto the insulin resistance associated with this disorder.

We used anti-insulin-receptor and anti-phosphotyrosine antibodies to elucidate the mechanism of decreased insulin-receptor tyrosine kinase activity observed in subjects with non-insulin-dependent diabetes mellitus (NIDDM). Lectin-purified insulin receptors were labeled with 125I-labeled NAPA-DP-insulin and autophosphorylated in the presence of 500 microM unlabeled ATP. Immunoprecipitation occurred in 43 +/- 8% of the autophosphorylated, 125I-labeled receptors from nondiabetic subjects with anti-phosphotyrosine antibodies in contrast to 100% immunoprecipitation with anti-insulin-receptor antibodies. Anti-phosphotyrosine antibodies immunoprecipitated only 14 +/- 6% of NIDDM receptors (P less than .05 vs. nondiabetic receptors). A significant correlation existed between maximal insulin-stimulated receptor tyrosine kinase activity and the proportion of receptors immunoprecipitated by anti-phosphotyrosine antibodies (r = .76, P less than .01). These results suggest that human adipocytes contain two distinct receptor populations, both of which bind insulin but only one of which is capable of insulin-stimulated tyrosine phosphorylation. In nondiabetic subjects, 40-50% of the receptors that bind insulin are capable of insulin-stimulated tyrosine autophosphorylation. The proportion of receptors that bind insulin but are incapable of insulin-stimulated tyrosine autophosphorylation is increased in NIDDM; the magnitude of this increase correlated with the magnitude of the decrease in kinase activity.

Insulin-stimulated kinase activity of adipocyte-derived insulin receptors is reduced in subjects with non-insulin-dependent diabetes mellitus (NIDDM) but normal in obese nondiabetics. To assess the reversibility of the kinase defect in NIDDM, insulin receptor kinase activity was measured before and after weight loss in 10 NIDDM and 5 obese nondiabetic subjects. Peripheral insulin action was also assessed in vivo by glucose disposal rates (GDR) measured during a hyperinsulinemic (300 mU/M2 per min) euglycemic clamp. In the NIDDMs, insulin receptor kinase activity was reduced by 50-80% and rose to approximately 65-90% (P less than 0.01) of normal after 13.2 +/- 2.0 kg (P less than 0.01) weight loss; comparable weight loss (18.2 +/- 1.5 kg, P less than 0.01) in the nondiabetics resulted in no significant change in insulin receptor kinase activity. Relative to GDR measured in lean nondiabetics, GDR in the NIDDMs was 35% of normal initially and 67% (P less than 0.01) of normal after diet therapy; weight loss in the nondiabetics resulted in an increase in GDR from 53 to 76% of normal (P less than 0.05). These results indicate that the insulin receptor kinase defect that is present in NIDDM is largely reversible after weight reduction. In contrast, the improvement in GDR, in the absence of any change in insulin receptor kinase activity in the nondiabetics, suggests that the main cause of insulin resistance in obesity lies distal to the kinase.

We studied the kinase activity of partially purified insulin receptor preparations from various rat and human tissues. Time courses for in vitro autophosphorylation were determined, and times to reach half-maximal (t1/2 max) and maximal (tmax) 32P incorporation were compared. Insulin receptors from rat muscle, liver, and fat had a t1/2 max of 7-10 min and a tmax of 60 min; human-derived insulin receptors had a t1/2 max in excess of 30 min and a tmax of 120 min. A spectrum of autophosphorylation time courses was present in human tissues; placenta-derived receptors exhibited a t1/2 max of 13 min while receptors from monocytes and fibroblasts had t1/2 max values of 60 and 80 min, respectively. The ATP Km for autophosphorylation of human-derived receptors was 5-fold greater than that of rat-derived receptors (266 +/- 27 vs. 48 +/- 8 microM, respectively). In contrast, when the receptors were first maximally prephosphorylated, the ATP Km values for substrate phosphorylation of human- and rat-derived receptors were equivalent (12.5 and 11.4 microM). Kact values for Mn were comparable in both human- and rat-derived adipocyte receptors. In addition to the functional differences between species, the apparent mol wt of the beta-subunit of rat-derived receptors (96,000) was consistently greater than that of human-derived receptor beta-subunits (93,000). In contrast to these in vitro findings, the ability of insulin to stimulate receptor kinase activity in isolated adipocytes was rapid, with a maximal effect by seconds. This was comparable for both rat and human tissues, suggesting that the in vitro autophosphorylation differences may not govern kinase activity in vivo.

Recent studies have led to an enhanced understanding of cellular alterations that may play an important role in the pathophysiology of non-insulin-dependent diabetes mellitus (NIDDM). The insulin receptor links insulin binding at the cell surface to intracellular activation of insulin's effects. This transducer function involves the tyrosine kinase property of the beta-subunit of the receptor. It was found that adipocytes from subjects with NIDDM had a 50 to 80 percent reduction in insulin-stimulated receptor kinase activity compared with their non-diabetic counterparts. This defect was relatively specific for the diabetic state since no decrease was observed in insulin-resistant non-diabetic obese subjects. The reduction in kinase activity was accounted for by changes in the ratio of two pools of receptors, both of which bind insulin but only one of which is capable of tyrosine autophosphorylation and subsequent kinase activation; 43 percent of the receptors from non-diabetic subjects were capable of autophosphorylation compared with only 14 percent in the NIDDM group. A major component of cellular insulin resistance in NIDDM involves the glucose transport system. Exposure of cells to insulin normally results in enhanced glucose transport mediated by translocation of glucose transporters from a low-density microsomal intracellular pool to the plasma membrane. It was found that cells from NIDDM subjects had a marked depletion of glucose transporters in both plasma membranes and low-density microsomes, relative to obese non-diabetic control participants. Obese non-diabetic persons had a normal number of plasma membrane transporters but a reduced number of low-density microsome transporters in the basal state compared with lean control volunteers; insulin induced the translocation of relatively fewer transporters from the low-density microsome to the plasma membrane in the obese subgroups. In addition to the diminished number of glucose transporters, cells from both NIDDM and obese subjects had impaired functional activity of glucose carriers since decreased whole-cell glucose transport rates could not be entirely explained by the magnitude of the decrement in the number of plasma membrane transporters. Thus, impaired glucose transport is due to both a numerical and functional defect in glucose transporters. The cellular content of high-density microsomal transporters was the same in lean and obese control volunteers and NIDDM subjects, suggesting that transporter synthesis is normal and that cellular depletion results from increased protein turnover once transporters leave the high-density microsomal subfraction. Thus, the defects in NIDDM can be dissociated from those in non-diabetic obesity. In NIDDM, alterations exist at the level of the receptor kinase and the glucose transporter; in obesity, the defects include alterations in glucose transport but not in the receptor kinase.