Patients with pseudohypoparathyroidism type Ib (PHP-Ib) have hypocalcemia and hyperphosphatemia due to renal parathyroid hormone (PTH) resistance, but lack physical features of Albright hereditary osteodystrophy. PHP-Ib is thus distinct from PHP-Ia, which is caused by mutations in the GNAS exons encoding the G protein α subunit. However, an imprinted autosomal dominant form of PHP-Ib (AD-PHP-Ib) has been mapped to a region of chromosome 20q13.3 containing GNAS. Furthermore, loss of methylation at a differentially methylated region (DMR) of this locus, exon A/B, has been observed thus far in all investigated sporadic PHP-Ib cases and the affected members of multiple AD-PHP-Ib kindreds. We now report that affected members and obligate gene carriers of 12 unrelated AD-PHP-Ib kindreds and four apparently sporadic PHP-Ib patients, but not healthy controls, have a heterozygous approximately 3-kb microdeletion located approximately 220 kb centromeric of GNAS exon A/B. The deleted region, which is flanked by two direct repeats, includes three exons of STX16, the gene encoding syntaxin-16, for which no evidence of imprinting could be found. Affected individuals carrying the microdeletion show loss of exon A/B methylation but no epigenetic abnormalities at other GNAS DMRs. We therefore postulate that this microdeletion disrupts a putative cis-acting element required for methylation at exon A/B, and that this genetic defect underlies the renal PTH resistance in AD-PHP-Ib.

The human body, when under threat, elicits a set of neuroendocrine responses, including an increased secretion of glucocorticoids (GCs) and catecholamines from the adrenal gland and the activation of the sympathetic nervous system. These hormonal secretions allow a "fight or flight" response by mobilizing endogenous substrate and inducing a state of insulin resistance in the liver and skeletal muscles. Although the stress response was essential in ancient times to survive physical aggression, this threat has disappeared in our industrialized societies. However, in today's environment, the same stress responses can be elicited by emotional stimuli or professional and social stress. Such psychological stress may be protracted and unrelated to an increased metabolic demand. Thus, the energy mobilized is not used but is stored in visceral fat depots by the combined action of hypercortisolism and hyperinsulinemia. In addition, chronic activation of the stress system causes suppression of the gonadal, growth hormone (GH), and thyroid axes. These metabolic disturbances, in concert, lead to the clinical expression of a number of comorbidities including central obesity, hypertension, dyslipidemia, and endothelial dysfunction, all components of the metabolic syndrome and cardiometabolic risk factors. Moreover, chronic stress has deleterious effects on the brain and, in particular, affects hippocampal structure and function leading to cognitive and mood disturbances. Importantly, this stress-induced clinical phenotype is likely to be exaggerated in the presence of physical inactivity, resulting in a "stress-induced/exercise deficient" phenotype. Assuming that the stress response is a neuroendocrine mechanism that occurs in anticipation of physical action, then physical activity should be the natural means to prevent the consequences of stress. Indeed, accumulating evidence documents the beneficial effects of regular exercise in preventing or ameliorating the metabolic and psychological comorbidities induced by chronic stress. These benefits are thought to derive from a central effect of exercise to reduce the sensitivity to stress and also peripheral actions influencing metabolic functions and, in particular, insulin sensitivity and the partitioning of fuels toward oxidation rather than storage. It is concluded that chronic psychosocial stress, in the presence of physical inactivity, is likely to contribute to the epidemic of cardiometabolic and emotional disease of our current society. The way to prevent and combat this burden is by regular exercise.

Normal menopause is associated with vascular endothelial dysfunction, an early stage of atherosclerosis. The effect of premature ovarian failure (or premature menopause) on endothelial function in young women is unknown. Endothelial function was assessed in 18 women with premature ovarian failure before and after 6 months of hormone therapy and was compared with the endothelial function of 20 age- and body mass index-matched premenopausal women. Brachial artery diameter was measured both during hyperemia (an index of endothelium-dependent vasodilation) and in response to glyceryl trinitrate (an index of endothelium-independent vaso-dilation). Flow-mediated dilation was significantly lower in women with premature ovarian failure at baseline (increase in brachial artery diameter during hyperemia by 3.06 +/- 4.33%) than in control women (increase by 8.84 +/- 2.15%; P < 0.0005). Glyceryl trinitrate-induced vasodilation did not differ between the groups. After hormone therapy for 6 months, flow-mediated dilation was improved in women with premature ovarian failure, increasing by more than 2-fold (7.41 +/- 3.86%; P < 0.005 compared with pretreatment) and reaching normal values (P not significant compared with control women). Glyceryl trinitrate-induced vasodilation did not change after treatment in women with premature ovarian failure. Young women with premature ovarian failure have significant vascular endothelial dysfunction. Early onset of endothelial dysfunction associated with sex steroid deficiency may contribute to the increased risk of cardiovascular disease and mortality in young women with premature ovarian failure. Hormone therapy restores endothelial function within 6 months of treatment.

No abstract

No abstract