Previous studies have found that female rats are less sensitive than males to hypothalamic-pituitary-adrenal axis feedback inhibition by exogenous glucocorticoid administration. To determine whether estrogen contributesSex differences in HPA axis regulation in rodents have been demonstrated by a number of investigators, and these differences are generally attributed to activational effects of gonadal steroids on elements of the hypothalamic-pituitary-adrenal axis in females, although there is also evidence that testosterone inhibits HPA axis activity in males (Handa et al. 1994). Female rats have higher levels of total plasma corticosterone (Kitay 1963). Female rats also have higher plasma corticosterone binding globulin levels, which likely contributes to findings of similar free corticosterone levels in male and female rats. Compared with male rats, female rats also have a greater ACTH response to stress, faster onset of corticosterone secretion after stress, and a faster rate of rise of corticosterone (Le Mevel et al. 1979;Jones et al. 1972; Young 1996). Several studies suggest that estradiol plays a role in enhanced stress responses in female

Congenital generalized lipodystrophy (CGL) is a rare autosomal recessive disorder characterized by near total absence of body fat since birth with predisposition to insulin resistance, diabetes, hypertriglyceridemia and hepatic steatosis. Three CGL loci, AGPAT2, BSCL2 and CAV1 have been identified previously. Recently, mutations in polymerase I and transcript release factor (PTRF) were reported in five Japanese patients presenting with myopathy and CGL (CGL4). We report on novel PTRF mutations and detailed phenotype of two male and three female patients with CGL4 belonging to two pedigrees of Mexican origin (CGL7100 and CGL178) and one pedigree of Turkish origin (CGL180). All patients had near total loss of body fat and congenital myopathy manifesting as weakness, percussion-induced muscle mounding and high serum creatine kinase levels. Four of them had hypertriglyceridemia. Three of them had atlantoaxial instability. Two patients belonging to CGL178 pedigree required surgery for pyloric stenosis in the first month of life. None of them had prolonged QT interval on electrocardiography but both siblings belonging to CGL7100 had exercise-induced arrhythmias. Three of them had mild acanthosis nigricans but had normal glucose tolerance. Two of them had hepatic steatosis. All patients had novel null mutations in PTRF gene. In conclusion, mutations in PTRF result in a novel phenotype that includes generalized lipodystrophy with mild metabolic derangements, myopathy, cardiac arrhythmias, atlantoaxial instability and pyloric stenosis. It is unclear how mutations in PTRF, which plays an essential role in formation of caveolae, affect a wide variety of tissues resulting in a variable phenotype.

Lipoprotein lipase (LPL) is a hydrolase that cleaves circulating triglycerides to release fatty acids to the surrounding tissues. The enzyme is synthesized in parenchymal cells and is transported to its site of action on the capillary endothelium by glycophosphatidylinositol (GPI)-anchored high-density lipoprotein-binding protein 1 (GPIHBP1). Inactivating mutations in LPL; in its cofactor, apolipoprotein (Apo) C2; or in GPIHBP1 cause severe hypertriglyceridemia. Here we describe an individual with complete deficiency of GPIHBP1. The proband was an Asian Indian boy who had severe chylomicronemia at 2 months of age. Array-based copy-number analysis of his genomic DNA revealed homozygosity for a 17.5-kb deletion that included GPIHBP1. A 44-year-old aunt with a history of hypertriglyceridemia and pancreatitis was also homozygous for the deletion. A bolus of intravenously administered heparin caused a rapid increase in circulating LPL and decreased plasma triglyceride levels in control individuals but not in two GPIHBP1-deficient patients. Thus, short-term treatment with heparin failed to attenuate the hypertriglyceridemia in patients with GPIHBP1 deficiency. The increasing resolution of copy number microarrays and their widespread adoption for routine cytogenetic analysis is likely to reveal a greater role for submicroscopic deletions in Mendelian conditions. We describe the first neonate with complete GPIHBP1 deficiency due to homozygosity for a deletion of GPIHBP1.Electronic supplementary materialThe online version of this article (doi:10.1007/s10545-011-9406-5) contains supplementary material, which is available to authorized users.

Patients with MDP syndrome have a few overlapping but some distinct clinical features as compared with MAD, suggesting that it is a novel syndrome. The molecular basis of MDP syndrome remains to be elucidated.

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