Similar trends in serum VEGF-D levels and kidney angiomyolipoma responses with longer duration sirolimus treatment in adults with tuberous sclerosis

Context

We have previously shown that serum VEGF-D is elevated at baseline, correlates with kidney angiomyolipoma size at baseline and 12 months, and decreases with sirolimus treatment in adults with tuberous sclerosis complex (TSC). To further investigate the utility of serum VEGF-D for longer term monitoring of TSC kidney disease, we present VEGF-D level results with 24 month follow-up.

Objective

To compare 24 month VEGF-D levels in two subgroups of sirolimus treated patients (OFF SIROLIMUS AFTER 12 MONTHS or ON SIROLIMUS AFTER 12 MONTHS).

Design and Intervention(s)

Serum VEGF-D was measured in samples collected from subjects enrolled in a phase 2 multicenter trial evaluating sirolimus for the treatment of kidney angiomyolipomas associated with TSC or TSC/LAM. All participants were treated with sirolimus from 0–12 months. During months 12–24, sirolimus was discontinued in one subgroup. The other subgroup was treated with additional sirolimus.

Setting

Adult TSC participants were recruited from six clinical sites in the United States (comprehensive TSC clinics, 5; urology clinic, 1).

Patients

There were 28 TSC patients who completed all 24 months of the study and serum samples were available at 24 months from 18/28 patients.

Main Outcome Measure(s)

We compared the percent change in VEGF-D levels (baseline to 24 months) in patients from the two treatment subgroups.

Results

At 24 months, VEGF-D levels decreased by 67% compared with baseline (to 787±426 pg/ml) in the ON SIROLIMUS AFTER 12 MONTHS group versus a 13% decrease (to 2971±4014 pg/ml) in the OFF SIROLIMUS AFTER 12 MONTHS group (p = 0.013, Mann-Whitney test). A similar trend was observed in kidney angiomyolipoma size but not in pulmonary function tests.

Conclusions Serum VEGF-D may be useful for monitoring response to treatment with sirolimus and kidney angiomyolipoma size in patients with TSC, but confirmation is needed.

Trial Registration

Clinical trials.gov NCT00126672.

GABA(A) receptor active steroids are altered in epilepsy patients with tuberous sclerosis

BACKGROUND

The neuroactive steroid 3alpha, 5alpha-tetrahydroprogesterone is the most potent endogenous positive modulator of gamma-amino-butyric acid (GABA)(A) receptors. There is evidence for a relation between neuroactive steroids and seizure susceptibility.

OBJECTIVE

To evaluate the putative role of counteregulator neuroactive steroids in the occurrence of seizures in patients with tuberous sclerosis.

METHODS

Plasma concentrations of the enantiomers 3alpha, 5alpha- and 3alpha, 5beta-tetrahydroprogesterone (3alpha(s)-THP), which are positive modulators of GABA(A) receptors, were measured in 18 patients, along with their endogenous functional antagonists 3beta, 5alpha- and 3beta, 5beta-THP (3beta(s)-THP), to assess their possible modification compared with control subjects. Neuroactive steroids were assayed using a highly sensitive and specific gas chromatographic/mass spectrometric method.

RESULTS

In the tuberous sclerosis patients with poorly controlled seizures, there was a significantly lower 3alpha(s)/3beta(s)-THP ratio than in seizure-free patients or control subjects.

CONCLUSIONS

The reduced 3alpha(s)/3beta(s)-THP ratio may decrease GABAergic tone, contributing to the appearance of seizures in tuberous sclerosis patients with epilepsy.

Tuberous sclerosis: the incidence of sporadic cases versus familial cases

In 48 families in which tuberous sclerosis occurred, extensive examination presented almost the same incidence of sporadic cases as reported in previous studies. Although inspection of the skin and cranial computed tomography seem to be the most sensitive diagnostic tests available, negative results with these methods do not exclude the diagnosis. Estimation of alpha 2-macroglobulin serum level does not mean an extension of the diagnostic arsenal.

Molecular analysis of the human vitamin D binding protein (group specific component, Gc) in tuberous sclerosis complex (TSC)

Group specific component (Gc) is an abundant plasma protein whose functional role is not clearly established. Gc protein is synthesised in the liver and is known to bind vitamin D, vitamin D metabolites, and G actin; Gc protein is also implicated in macrophage activation. Several polymorphic electrophoretic variants of Gc protein are found in all human populations; the most common alleles are Gc-1f, Gc-1s, and Gc-2. In previous studies, Gc allele frequencies, determined using isoelectric focusing or immunofixation or both, were significantly different in patients with tuberous sclerosis complex (TSC) from matched controls, with an excess of Gc-2 in patients. Linkage association between Gc and TSC is unlikely since the Gc locus maps to chromosome 4q12, whereas the two common forms of TSC map to 9q34 and 16p13.1, respectively. However, a direct cause and effect relationship between Gc protein and TSC symptoms is possible. To investigate further the relationship between the Gc locus and TSC, two Gc restriction site polymorphisms, HaeIII and StyI, were typed in 43 unrelated white subjects with TSC. The frequencies of the restriction site polymorphisms in the TSC patients did not differ from those in control populations. Therefore a direct association between Gc type and TSC is unlikely. The previously reported association was either spurious or the result of typing errors in plasma from subjects with underlying abnormalities in plasma proteins.

Serum factors responsible for unusual induction of plasminogen activator activity in tuberous sclerosis

Peripheral blood lymphocytes derived from tuberous sclerosis (TS) patients showed unusually high levels of plasminogen activator (PA) activity after treatment with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Serum obtained from peripheral blood of TS patients also enhanced the PA activity level when normal control lymphocytes were incubated with the serum prior to MNNG treatment. Factors exhibiting the enhancing activity were eluted with a solution of about 0.70 M KCl on dye-ligand chromatography, which were inhibited on incubation with an anti-human interferon (HuIFN)-beta antibody, but not with anti-HuIFN-alpha or anti-HuIFN-gamma antibodies. Unlike in the case of HuIFN-beta, the eluted samples did not possess antiviral or anticellular activity. Thus, it seems likely that serum from TS patients contains factors which are responsible for the unusual PA induction and which have a similar epitope to HuIFN-beta.

Tuberous sclerosis and parathyroid adenoma

Very little is known about the pathogenesis of tuberous sclerosis. Over the past 10 years, however, increasing numbers of reports on adenomatous diseases in association with tuberous sclerosis have been published. A case of hypercalcaemia and parathyroid adenoma in association with tuberous sclerosis is presented, of which there has been one such report published previously. This association might be another manifestation of this complex disease: it is therefore recommended that plasma calcium concentrations should be measured in such patients.

Tuberous sclerosis: proline and hydroxyproline contents in serum

The serum levels of proline and hydroxyproline were determined by high-performance liquid chromatography using the post-labeled method with o-phthalaldehyde and sodium hypochlorite in 30 patients of tuberous sclerosis (TS) and compared with those in 32 pathological control subjects of similar age. No significant difference in the levels of serum free hydroxyproline was observed between TS and controls in any age group. In the age group of 9 to 18 years, TS showed significantly higher mean free proline levels in serum than controls with a difference of about 50 mumol/L. In both groups of TS and controls, total and free levels of hydroxyproline from ethanol-extractable serum showed similar age-dependent curves with peak values at age 12 years, and there was also no difference in the 2 levels between the 2 groups. It is suggested that this higher free proline level in TS with the autosomal dominant trait may be explained as the abnormal regulation of proline metabolism.

Lymphoblastoid lines and skin fibroblasts from patients with tuberous sclerosis are abnormally sensitive to ionizing radiation and to a radiomimetic chemical

Lymphoblastoid lines, derived by transforming peripheral blood lymphocytes with Epstein-Barr virus, and skin fibroblast lines were established from two patients with tuberous sclerosis. The number of viable lymphoblastoid cells was determined by their ability to exclude the vital dye trypan blue after their irradiation with x-rays or 254 nm ultraviolet light. The growth of fibroblasts was determined by their ability to form colonies after treatment with the radiomimetic, DNA-damaging chemical N-methyl-N'-nitro-N-nitrosoguanidine. The tuberous sclerosis lymphoblastoid lines were hypersensitive to x-rays but had normal sensitivity to the ultraviolet radiation. The tuberous sclerosis fibroblast lines were hypersensitive to the N-methyl-N'-nitro-N-nitrosoguanidine. The hypersensitivity of tuberous sclerosis cells to x-rays and to N-methyl-N'-nitro-N-nitrosoguanidine is believed to reflect defective repair of DNA damaged by these agents and may provide the basis for in vitro, including prenatal, diagnostic tests for tuberous sclerosis.

Possible phenylethylmalondiamide (PEMA) intoxication

We have encountered a case of apparent intoxication with primidone (Mysoline) in a patient with severe renal impairment. Of interest were high serum levels of phenylethyl-malondiamide (PEMA), a metabolite of primidone.