Gnas is an imprinted gene with multiple gene products resulting from alternative splicing of different first exons onto a common exon 2. These products include stimulatory G protein ␣-subunit (Gs␣), the G protein required for receptor-stimulated cAMP production; extralarge Gs␣ (XL␣s), a paternally expressed Gs␣ isoform; and neuroendocrine-specific protein (NESP55), a maternally expressed chromogranin-like protein. G s␣ undergoes tissue-specific imprinting, being expressed primarily from the maternal allele in certain tissues. Heterozygous mutation of exon 2 on the maternal (E2 m؊/؉ ) or paternal (E2 ؉/p؊ ) allele results in opposite effects on energy metabolism. E2 m؊/؉ mice are obese and hypometabolic, whereas E2 ؉/p؊ mice are lean and hypermetabolic. We now studied the effects of Gs␣ deficiency without disrupting other Gnas gene products by deleting G s␣ exon 1 (E1). E1 ؉/p؊ mice lacked the E2 ؉/p؊ phenotype and developed obesity and insulin resistance. The lean, hypermetabolic, and insulin-sensitive E2 ؉/p؊ phenotype appears to result from XL␣s deficiency, whereas loss of paternalspecific Gs␣ expression in E1 ؉/p؊ mice leads to an opposite metabolic phenotype. Thus, alternative Gnas gene products have opposing effects on glucose and lipid metabolism. Like E2 m؊/؉ mice, E1 m؊/؉ mice had s.c. edema at birth, presumably due to loss of maternal Gs␣ expression. However, E1 m؊/؉ mice differed from E2 m؊/؉ mice in other respects, raising the possibility for the presence of other maternal-specific gene products. E1 m؊/؉ mice had more severe obesity and insulin resistance and lower metabolic rate relative to E1 ؉/p؊ mice. Differences between E1 m؊/؉ and E1 ؉/p؊ mice presumably result from differential effects on Gs␣ expression in tissues where Gs␣ is normally imprinted.G protein ͉ genomic imprinting ͉ pseudohypoparathyroidism

ABSTRACT. Objective. The objective of this study was to evaluate differences in the pharmacodynamic (PD) profile of 2 second-generation extended-release (ER) formulations of methylphenidate (MPH): Metadate CD (MCD; methylphenidate HCl, US Pharmacopeia) extended-release capsules, CII, and Concerta (CON; methylphenidate HCl) extended-release tablets, CII. Little empirical information exists to help the clinician compare the PD effects of the available ER formulations on attention and behavior. Previous studies have shown that the near-equal doses of MCD and CON provide equivalent, total exposure to MPH as measured by area under the plasma concentration time curve, yet their pharmacokinetic (PK) plasma concentration versus time profiles are different. We previously offered a theoretical PK/PD account of the similarities and differences among available ER formulations based on the hypothesis that all formulations produce effects related to MPH delivered by 2 processes: 1) an initial bolus dose of immediate-release (IR) MPH that is expected to achieve peak plasma concentration in the early morning and have rapid onset of efficacy within 2 hours of dosing, which for the MCD capsule is delivered by 30% of the total daily dose as uncoated beads and for the CON tablet is delivered by an overcoat of 22% of the total daily dose; and 2) an extended, controlled delivery of ER MPH that is expected to achieve peak plasma concentrations in the afternoon to maintain efficacy for a programmed period of time after the peak of the initial bolus, which for the MCD capsule is delivered by polymer-coated beads and for the CON tablet by an osmotic-release oral system. According to this PK/PD model, clinical superiority is expected at any point in time for the formulation with the highest MPH plasma concentration.Methods. This was a multisite, double-blind, doubledummy, 3-way crossover study of 2 active treatments (MCD and CON) and placebo (PLA). Children with confirmed diagnoses of attention-deficit/hyperactivity disorder were stratified to receive bioequivalent doses of MCD and CON that were considered to be low (20 mg of MCD and 18 mg of CON), medium (40 mg of MCD and 36 mg of CON), or high (60 mg of MCD and 54 mg of CON), and in a randomized order each of the study treatments was administered once daily in the morning for 1 week. On the seventh day of each treatment week, children attended a laboratory school, where surrogate measures of response were obtained by using teacher ratings of attention and deportment and a record of permanent product of performance on a 10-minute math test at each of the 7 classroom sessions spread across the day at 1.5-hour intervals. Safety was assessed by patient reports of adverse events, parent ratings on a stimulant side-effects scale, and measurement of vital signs.Results. The analyses of variance revealed large, statistically significant main effects for the within-subject factor of treatment for all 3 outcome measures (deportment, attention, and permanent product). The interactions of treatment...

The G protein G s α is essential for hormone-stimulated cAMP generation and is an important metabolic regulator. We investigated the role of liver G s -signaling pathways by developing mice with liver-specific G s α deficiency (LGsKO mice). LGsKO mice had increased liver weight and glycogen content and reduced adiposity, whereas survival, body weight, food intake, and metabolic rates at ambient temperature were unaffected. LGsKO mice had increased glucose tolerance with both increased glucose-stimulated insulin secretion and increased insulin sensitivity in liver and muscle. Fed LGsKO mice were hypoglycemic and hypoinsulinemic, with low expression of hepatic gluconeogenic enzymes and PPARγ coactivator-1. However, LGsKO mice maintained normal fasting glucose and insulin levels, probably due to prolonged breakdown of glycogen stores and possibly increased extrahepatic gluconeogenesis. Lipid metabolism was unaffected in fed LGsKO mice, but fasted LGsKO mice had increased lipogenic and reduced lipid oxidation gene expression in liver and increased serum triglyceride and FFA levels. LGsKO mice had very high serum glucagon and glucagon-like peptide-1 levels and pancreatic α cell hyperplasia, probably secondary to hepatic glucagon resistance and/or chronic hypoglycemia. Our results define novel roles for hepatic G s -signaling pathways in glucose and lipid regulation, which may prove useful in designing new therapeutic targets for diabetes and obesity.

There is a major resurgence of interest in brown adipose tissue (BAT) biology, particularly regarding its determinants and consequences in newborns and infants. Reliable methods for non-invasive BAT measurement in human infants have yet to be demonstrated. The current study first validates methods for quantitative BAT imaging of rodents post mortem followed by BAT excision and re-imaging of excised tissues. Identical methods are then employed in a cohort of in vivo infants to establish the reliability of these measures and provide normative statistics for BAT depot volume and fat fraction. Using multi-echo water-fat MRI, fat- and water-based images of rodents and neonates were acquired and ratios of fat to the combined signal from fat and water (fat signal fraction) were calculated. Neonatal scans (n = 22) were acquired during natural sleep to quantify BAT and WAT deposits for depot volume and fat fraction. Acquisition repeatability was assessed based on multiple scans from the same neonate. Intra- and inter-rater measures of reliability in regional BAT depot volume and fat fraction quantification were determined based on multiple segmentations by two raters. Rodent BAT was characterized as having significantly higher water content than WAT in both in situ as well as ex vivo imaging assessments. Human neonate deposits indicative of bilateral BAT in spinal, supraclavicular and axillary regions were observed. Pairwise, WAT fat fraction was significantly greater than BAT fat fraction throughout the sample (ΔWAT-BAT = 38%, p<10−4). Repeated scans demonstrated a high voxelwise correlation for fat fraction (Rall = 0.99). BAT depot volume and fat fraction measurements showed high intra-rater (ICCBAT,VOL = 0.93, ICCBAT,FF = 0.93) and inter-rater reliability (ICCBAT,VOL = 0.86, ICCBAT,FF = 0.93). This study demonstrates the reliability of using multi-echo water-fat MRI in human neonates for quantification throughout the torso of BAT depot volume and fat fraction measurements.