Urinary C-peptide creatinine ratio detects absolute insulin deficiency in Type 2 diabetes

AIMS

To determine the prevalence and clinical characteristics of absolute insulin deficiency in long-standing Type 2 diabetes, using a strategy based on home urinary C-peptide creatinine ratio measurement.

METHODS

We assessed the urinary C-peptide creatinine ratios, from urine samples taken at home 2 h after the largest meal of the day, in 191 insulin-treated subjects with Type 2 diabetes (diagnosis age ≥45 years, no insulin in the first year). If the initial urinary C-peptide creatinine ratio was ≤0.2 nmol/mmol (representing absolute insulin deficiency), the assessment was repeated. A standardized mixed-meal tolerance test with 90-min stimulated serum C-peptide measurement was performed in nine subjects with a urinary C-peptide creatinine ratio ≤ 0.2 nmol/mmol (and in nine controls with a urinary C-peptide creatinine ratio >0.2 nmol/mmol) to confirm absolute insulin deficiency.

RESULTS

A total of 2.7% of participants had absolute insulin deficiency confirmed by a mixed-meal tolerance test. They were identified initially using urinary C-peptide creatinine ratio: 11/191 subjects (5.8%) had two consistent urinary C-peptide creatinine ratios ≤ 0.2 nmol/mmol; 9 of these 11 subjects completed a mixed-meal tolerance test and had a median stimulated serum C-peptide of 0.18 nmol/l. Five of these 9 had stimulated serum C-peptide <0.2 nmol/l and 9/9 subjects with urinary C-peptide creatinine ratio >0.2 had endogenous insulin secretion confirmed by the mixed-meal tolerance test. Compared with subjects with a urinary C-peptide creatinine ratio >0.2 nmol/mmol, those with confirmed absolute insulin deficiency had a shorter time to insulin treatment (median 2.5 vs. 6 years, P=0.005) and lower BMI (25.1 vs. 29.1 kg/m(2) , P=0.04). Two out of the five patients with absolute insulin deficiency were glutamic acid decarboxylase autoantibody-positive.

CONCLUSIONS

Absolute insulin deficiency may occur in long-standing Type 2 diabetes, and cannot be reliably predicted by clinical features or autoantibodies. Absolute insulin deficiency in Type 2 diabetes may increase the risk of hypoglycaemia and ketoacidosis, as in Type 1 diabetes. Its recognition should help guide treatment, education and management. The urinary C-peptide creatinine ratio is a practical non-invasive method to aid detection of absolute insulin deficiency, with a urinary C-peptide creatinine ratio > 0.2 nmol/mmol being a reliable indicator of retained endogenous insulin secretion.

Islet autoantibodies can discriminate maturity-onset diabetes of the young (MODY) from Type 1 diabetes

AIM

Maturity-onset diabetes of the young is a monogenic form of familial, young-onset diabetes. It is rare (∼1% diabetes) and may be misdiagnosed as Type 1 diabetes and inappropriately treated with insulin. Type 1 diabetes is characterized by the presence of islet autoantibodies, including glutamate decarboxylase (GAD) and islet antigen-2 (IA-2) antibodies. The prevalence of islet autoantibodies is unknown in maturity-onset diabetes of the young and may have the potential to differentiate this form of diabetes from Type 1 diabetes. The aim of this study was to determine the prevalence of GAD and IA-2 antibodies in patients with maturity-onset diabetes of the young and Type 1 diabetes.

METHODS

We measured plasma GAD and IA-2 antibodies in 508 patients with the most common forms of maturity-onset diabetes of the young (GCK: n = 227; HNF1A: n = 229; HNF4A: n = 52) and 98 patients with newly diagnosed Type 1 diabetes (diagnosed < 6 months). Autoantibodies were considered positive if ≥ 99th centile of 500 adult control subjects.

RESULTS

GAD and/or IA-2 antibodies were present in 80/98 (82%) patients with Type 1 diabetes and 5/508 (< 1%) patients with maturity-onset diabetes of the young. In the cohort with Type 1 diabetes, both GAD and IA-2 antibodies were detected in 37.8% of patients, GAD only in 24.5% and IA-2 only in 19.4%. All five patients with maturity-onset diabetes of the young with detectable antibodies had GAD antibodies and none had detectable IA-2 antibodies.

CONCLUSION

The prevalence of GAD and IA-2 antibodies in maturity-onset diabetes of the young is the same as in control subjects (< 1%). The finding of islet autoantibodies, especially IA-2 antibodies, makes the diagnosis of maturity-onset diabetes of the young very unlikely and genetic testing should only be performed if other clinical characteristics strongly suggest this form of diabetes rather than Type 1 diabetes. This supports routine islet autoantibody testing before proceeding to more expensive molecular genetic testing.

A genetic diagnosis of HNF1A diabetes alters treatment and improves glycaemic control in the majority of insulin-treated patients

BACKGROUND AND AIMS

Hepatocyte nuclear factor-1 alpha (HNF1A) gene mutations are the commonest cause of monogenic diabetes, but patients are often misdiagnosed as having Type 1 diabetes and started on insulin treatment. Patients with HNF1A diabetes are particularly sensitive to the glucose-lowering effect of sulphonylureas, which are the pharmacological treatment of choice. We aimed to assess if patients do change from insulin to sulphonylurea treatment when HNF1A diabetes is confirmed and the impact of this treatment change on long-term glycaemic control.

METHODS

We investigated the clinical course of 43 patients who were insulin treated from diagnosis for a median 4 years (range 1-14) before an HNF1A gene mutation was identified.

RESULTS

Thirty-four patients (79%) stopped insulin following genetic testing and transferred to sulphonylureas. Twenty-four of them (71%) remained off insulin at a median 39 months (range 17-90) post-transfer. The 10 patients who recommenced insulin had a trend towards a longer duration of diabetes (18 vs. 7 years, P = 0.066) compared with those remaining on tablets. The median glycated haemoglobin (HbA(1c)) was good (6.9%; interquartile range 6.3-8.0%) in the patients who remained off insulin and 19/24 patients (79%) achieved HbA(1c) < 7.5% or improved their pre-genetic diagnosis HbA(1c) by > 1.0%. Transfer off insulin was not attempted in eight patients: one of these was planning pregnancy and two chose to remain on insulin.

CONCLUSION

In this observational study we found that a molecular genetic diagnosis of HNF1A diabetes does alter treatment in clinical practice, with 79% attempting transfer to sulphonylureas. Transfer to sulphonylureas was successful in the majority of patients without deterioration in glycaemic control.

The transcription factor 7-like 2 (TCF7L2) gene is associated with Type 2 diabetes in UK community-based cases, but the risk allele frequency is reduced compared with UK cases selected for genetic studies

AIMS

Common polymorphisms in the transcription factor 7-like 2 (TCF7L2) gene are strongly associated with Type 2 diabetes. Many studies include a large proportion of cases enriched for family history or young age of diagnosis and may therefore provide an overestimation of the general population risk. We aimed to compare the impact of TCF7L2 in UK community-based Type 2 diabetic subjects with that in subjects ascertained for genetic studies.

METHODS

We genotyped the TCF7L2 polymorphism rs7903146 in 1068 cases from two sources: 487 from 10 GP practices and 601 ascertained for genetic studies, and 2099 control subjects from two sources: 1099 parents from a birth cohort (population control subjects) and 300 subjects with normal fasting glucose aged > or = 45 years (community control subjects).

RESULTS

When compared with Type 2 diabetes cases ascertained for genetic studies, the risk allele frequency in community-based cases was lower (40 vs. 36%, P = 0.04), but there was no difference in risk allele frequency between community-based control and population-based control subjects (31 vs. 30%, P = 0.61). The T allele of rs7903146 increased Type 2 diabetes risk with an odds ratio (OR) of 1.32 (95% CI: 1.13-1.52; P = 0.0002) in community-based cases, but this OR was lower than the OR of cases enriched for genetic studies [1.58 (95% CI: 1.38-1.80), P = 1.4 x 10(-11)] and the combined OR of meta-analysis of 10 studies to date on rs7903146 [1.48 (95% CI: 1.41-1.54), P < 10(-20)].

CONCLUSION

Common variation in the TCF7L2 gene contributes to Type 2 diabetes risk in UK patients recruited in general practice, but the risk allele frequency may be lower than that in subjects enriched for genetic effects.

GAD antibodies in probands and their relatives in a cohort clinically selected for Type 2 diabetes

AIMS

A subset of patients who present as if they have Type 2 diabetes have positive pancreatic autoantibodies, and have been referred to as having latent autoimmune diabetes in adults (LADA). We assessed the prevalence and clinical characteristics of patients with glutamic acid decarboxylase antibodies (GADA) in a cohort clinically selected for Type 2 diabetes and determined the presence of diabetes and GADA in their first-degree relatives.

METHODS

GADA were measured in 2059 subjects, not known to be related, and clinically selected as having Type 2 diabetes for genetic studies. Clinical characteristics were compared in GADA positive and GADA negative subjects. Diabetes and GAD antibody status were compared in 208 first-degree relatives of GADA positive and GADA negative probands.

RESULTS

Of the subjects, 136 (7%) were GADA positive. Compared with the GADA negative subjects, they were slimmer (P < 0.001), diagnosed at a younger age (P = 0.011) and progressed to insulin faster (P < 0.001). Thirty-three per cent of GADA positive subjects had a first-degree relative with diabetes compared with 42% of GADA negative subjects (P = 0.034). The overall prevalence of GADA was similar in the first-degree relatives of GADA positive and GADA negative probands (4 v 5%), and 19 of 22 (86%) diabetic relatives of GADA positive probands were GADA negative.

CONCLUSION

Despite clinically selecting a Type 2 diabetes cohort, 7% were GADA positive with an altered phenotype. These GADA positive patients had a strong family history of non-autoimmune diabetes. This suggests that, in this subgroup of patients, autoimmune pancreatic beta-cell destruction occurs on a background of Type 2 diabetes genetic susceptibility.

The pediatric cardiology pharmacopoeia: 2004 update

Seven years ago, Pediatric Cardiology published the first version of a review article outlining the various medications used in the field of heart diseases in children. This article is an update and expansion to what we have previously presented. Therapeutic intervention, both surgical and through cardiac catheterization, has enabled cure and palliation of an increasingly expanding spectrum of diseases at earlier ages and with more complex lesions. Refinement of these procedures includes more advanced tools as well as the support of an expanding armament of pharmacopoeia used to stabilize and support patients before, during, and after such procedures. In addition to updating previously published data regarding inotropes, antiarrhythmics, vasodilators, diuretics, sedatives, and analgesics as well as a variety of miscellaneous medications, this article describes the use of pulmonary medications frequently needed in patients with congestive heart failure, pulmonary edema, and chronic lung disease. We also describe the difficult management of withdrawal as a result of use of sedatives and analgesics. The most recent recommendation for subacute bacterial endocarditis prophylactic antibiotic regimens is also described.

Multiple heparin binding domains of respiratory syncytial virus G mediate binding to mammalian cells

Respiratory syncytial virus (RSV) G glycoprotein mediates cell attachment through surface glycosaminoglycans (GAGs). Feldman et al. [10] suggested that specific basic amino acids in residues 184-198 of G defined a critical heparin binding domain (HBD). To further define the G HBD we made a series of truncated G proteins expressed in Escherichia coli. G88 (G residues 143-231), bound to HEp-2 cells in a dose dependent manner and binding was inhibited >99% with heparin. Cell binding of G88 was unaltered by alanine substitution mutagenesis of all basic amino acids in Feldman's region 184-198. A G88 variant truncated beyond residue 198, G58, and G58 fully alanine substituted in the region 184-198, G58A6, bound to HEp-2 cells about half as well and 100-fold less well than G88, respectively. G88 and all alanine substitution mutants of G88 inhibited RSV plaque formation by 50% (ID(50)) at concentrations of approximately 50 nM; the ID(50) of G58 was approximately 425 nM while G58A6 had an ID(50) >1600 nM. These data show that the G HBD includes as much as residues 187-231, that there is redundancy beyond the previously described HBD, and that the cell-binding and virus infectivity-blocking functions of these recombinant G proteins were closely linked and required at least one HBD.

Association of matrix protein of respiratory syncytial virus with the host cell membrane of infected cells

The matrix protein of paramyxoviruses plays an important role in virus assembly through its interactions with cell membrane, virus envelope and virus nucleocapsid. In the present study, we investigated the possible association of respiratory syncytial virus (RSV) matrix (M) protein with the plasma membrane of infected cells. Using confocal microscopy we found that M was present at the cytoplasmic side of the plasma membrane. We used flotation gradients to purify membranes from RSV infected cells and treated them with cold Triton X-100 to obtain lipid rafts in the insoluble fraction. Western blot of the lipid raft fraction with specific antibodies showed that it contained M, as well as G (attachment) and N (nucleocapsid) proteins. We also found that RSV purified on sucrose gradients contained lipid raft markers. Together, our data suggest that RSV uses lipid rafts for assembly and budding.

Stability of dobutamine hydrochloride in peritoneal dialysis solutions

The stability of dobutamine hydrochloride in peritoneal dialysis solutions at 4, 26, and 37 degrees C was determined. Dobutamine (as the hydrochloride salt) was added to dialysis solutions containing 1.5% or 4.25% dextrose to concentrations of 2.5, 5.0, and 7.5 mg/mL. Samples were stored at 4, 26, and 37 degrees C to mimic refrigerator, room, and body temperature, respectively. At 0, 4, 8, and 24 hours, the samples were analyzed in triplicate by stability-indicating high-performance liquid chromatography to determine the percentage of drug remaining. More than 90% of the drug was retained under all storage conditions in 1.5% dextrose dialysate containing an initial dobutamine hydrochloride concentration of 5.0 or 7.5 micrograms/mL. The mean concentration in the samples containing an initial dobutamine hydrochloride concentration of 2.5 micrograms/mL and stored at room temperature remained greater than 90% of the initial concentration for the first four hours and then decreased to less than 90%. Dobutamine was stable in 4.25% dextrose dialysate regardless of the initial concentration or the storage condition. Dobutamine hydrochloride 5.0 and 7.5 micrograms/mL in 4.25% dextrose dialysis solution was stable under all the test conditions. Dobutamine hydrochloride 2.5 micrograms/mL was stable in 1.5% dextrose dialysate for only four hours at room temperature.