3,5-Diiodo-L-thyronine rapidly enhances mitochondrial fatty acid oxidation rate and thermogenesis in rat skeletal muscle: AMP-activated protein kinase involvement.

Triiodothyronine regulates energy metabolism and thermogenesis. Among triiodothyronine derivatives, 3,5-diiodo-l-thyronine (T(2)) has been shown to exert marked effects on energy metabolism by acting mainly at the mitochondrial level. Here we investigated the capacity of T(2) to affect both skeletal muscle mitochondrial substrate oxidation and thermogenesis within 1 h after its injection into hypothyroid rats. Administration of T(2) induced an increase in mitochondrial oxidation when palmitoyl-CoA (+104%), palmitoylcarnitine (+80%), or succinate (+30%) was used as substrate, but it had no effect when pyruvate was used. T(2) was able to 1) activate the AMPK-ACC-malonyl-CoA metabolic signaling pathway known to direct lipid partitioning toward oxidation and 2) increase the importing of fatty acids into the mitochondrion. These results suggest that T(2) stimulates mitochondrial fatty acid oxidation by activating several metabolic pathways, such as the fatty acid import/beta-oxidation cycle/FADH(2)-linked respiratory pathways, where fatty acids are imported. T(2) also enhanced skeletal muscle mitochondrial thermogenesis by activating pathways involved in the dissipation of the proton-motive force not associated with ATP synthesis ("proton leak"), the effect being dependent on the presence of free fatty acids inside mitochondria. We conclude that skeletal muscle is a target for T(2), and we propose that, by activating processes able to enhance mitochondrial fatty acid oxidation and thermogenesis, T(2) could play a role in protecting skeletal muscle against excessive intramyocellular lipid storage, possibly allowing it to avoid functional disorders.

A91V perforin variation in healthy subjects and FHLH patients.

Familial haemophagocytic lymphohistiocytosis (FHLH) is a heterogeneous autosomal recessive disorder characterized by hyperactivation of monocytes/macrophages. Perforin (PRF1) gene alterations have been documented in 40% of patients with FHLH. Although several mutations have been identified, a clear correlation between the individual molecular alteration and the phenotypic expression of the disease is still unclear. In particular, the role that the A91V substitution plays in the pathogenesis of the disease is still controversial. In the effort to make a conclusive remark to this issue, we here report on the frequency of the A91V mutation in a group of unrelated healthy families obtained from the "Centre d'Etude du Polymorphisme Humain" (CEPH), which are considered representative of the worldwide population. This frequency was compared to that observed in FHLH patients recruited through the Italian National Registry. The frequency in CEPH healthy subjects is 3.7%, thus indicating that the alteration represents a polymorphism. However, the frequency of this alteration in FHLH patients associated with PRF1 mutation is much higher than that observed in controls (26.2%, P = 0.0002), suggesting that the alteration is an important genetic susceptibility factor.

Ancestral founder mutation of the nude (FOXN1) gene in congenital severe combined immunodeficiency associated with alopecia in southern Italy population.

Genetic alterations of the FOXN1 transcription factor, selectively expressed in thymic epithelia and skin, are responsible in both mice and humans for the Nude/SCID phenotype. The first described human FOXN1 mutation was a C792T transition in exon 5 resulting in the nonsense mutation R255X, and was detected in two probands originated from a small community in southern Italy. In this community, four additional children affected with congenital alopecia died in early childhood because of severe infections. In this study, we report on the screening for this mutation in 30% of the village population. This analysis led us to identify 55 heterozygous carriers (6.52%) of the R255X mutation out of 843 inhabitants screened. A genealogical study revealed that these subjects, belonging to 39 families, were linked in an extended 7-generational pedigree comprising 483 individuals. Through the archival database a single ancestral couple, born at the beginning of the 19th century, was identified. To confirm the ancestral origin of the mutation we genotyped two microsatellite markers, D17S2187 and D17S1880, flanking the FOXN1 gene on chromosome 17. The three haplotypes identified, 3/R255X/3, 3/R255X/2 and 3/R255X/1, are consistent with a single ancestral origin for the mutation R255X.

Allogeneic bone marrow transplantation restores IGF-I production and linear growth in a gamma-SCID patient with abnormal growth hormone receptor signaling.

Severe combined immunodeficiency (SCID) is a heterogeneous group of disorders characterized by a severe defect of both T- and B-cell immunity, which generally require allogeneic bone marrow transplantation (BMT) within the first years of life. We previously reported a patient affected with an X-linked SCID due to L183S hemizygous missense gamma chain mutation, whose severe short stature was due to a peripheral growth hormone (GH) hyporesponsiveness associated to abnormal GH receptor (GH-R) signal transduction. In this study, we report the effect of BMT on the GH-R/insulin-like growth factor I (IGF-I) axis. After BMT, the patient showed a significant improvement in linear growth and normalization of basal- and GH-stimulated IGF-I values, which paralleled a fully competent immunological reconstitution. This suggests that cells derived from the hematopoietic stem cell may exert an unexpectedly significant role in producing IGF-I. This may also suggest that stem cell-based therapies may be useful for the correction of non-hematopoietic inherited disorders, such as those of GH-R/IGF-I axis.