Aidas Kriauciunas

Serum immunoreactive-leptin concentrations in normal-weight and obese humans.

BACKGROUND Leptin, the product of the ob gene, is a hormone secreted by adipocytes. Animals with mutations in the ob gene are obese and lose weight when given leptin, but little is known about the physiologic actions of leptin in humans. METHODS Using a newly developed radioimmunoassay, wer measured serum concentrations of leptin in 136 normal-weight subjects and 139 obese subjects (body-mass index, > or = 27.3 for men and > or = 27.8 for women; the body-mass index was defined as the weight in kilograms divided by the square of the height in meters). The measurements were repeated in seven obese subjects after weight loss and during maintenance of the lower weight. The ob messenger RNA (mRNA) content of adipocytes was determined in 27 normal-weight and 27 obese subjects. RESULTS The mean (+/- SD) serum leptin concentrations were 31.3 +/- 24.1 ng per milliliter in the obese subjects and 7.5 +/- 9.3 ng per milliliter in the normal-weight subjects (P < 0.001). There was a strong positive correlation between serum leptin concentrations and the percentage of body fat (r = 0.85, P < 0.001). The ob mRNA content of adipocytes was about twice as high in the obese subjects as in the normal-weight subjects (P < 0.001) and was correlated with the percentage of body fat (r = 0.68, P < 0.001) in the 54 subjects in whom it was measured. In the seven obese subjects studied after weight loss, both serum leptin concentrations and ob mRNA content of adipocytes declined, but these measures increased again during the maintenance of the lower weight. CONCLUSIONS Serum leptin concentrations are correlated with the percentage of body fat, suggesting that most obese persons are insensitive to endogenous leptin production.

Regulation of Expression of ob mRNA and Protein by Glucocorticoids and cAMP

Regulation of obese gene (ob) expression in ob/ob and db/db mice and in cultured rat adipocytes was examined. It has been demonstrated that exogenous human OB protein (leptin) treatment reduces food intake and weight gain, as well as insulin, glucose, and corticosterone levels in ob/ob mice. In the present report we show that leptin treatment down-regulates endogenous adipose ob mRNA. However, treatment of isolated rat adipocytes with 100 ng/ml human or murine leptin had no direct effect on expression of endogenous ob mRNA, suggesting that leptin may be able to down-regulate its own expression by an indirect, non-autocrine mechanism. Glucocorticoids increased both ob mRNA levels and secreted leptin levels in vitro. Conversely, agents that increase intracellular cAMP, such as β-adrenergic agonists or BtcAMP itself, decreased ob mRNA expression and leptin secretion. Therefore, increased glucocorticoid levels and decreased sympathetic neural activity may contribute to the elevated ob mRNA expression observed in genetically obese, hyperglucocorticoid rodents. Furthermore, leptin might regulate its own expression through a feedback mechanism involving the hypothalamic pituitary axis.

Orally bioavailable GSK-3α/β dual inhibitor increases markers of cellular differentiation in vitro and bone mass in vivo

GSK‐3, a component of the canonical Wnt signaling pathway, is implicated in regulation of bone mass. The effect of a small molecule GSK‐3 inhibitor was evaluated in pre‐osteoblasts and in osteopenic rats. GSK‐3 inhibitor induced osteoblast differentiation in vitro and increased markers of bone formation in vitro and in vivo with concomitant increased bone mass and strength in rats.

Acylation of Human Insulin With Palmitic Acid Extends the Time Action of Human Insulin in Diabetic Dogs

To test whether the binding of insulin to an endogenous serum protein can be used to extend the time action of insulin, human insulin was acylated at the epsilonamino group of Lys(B29) with palmitic acid to promote binding to serum albumin. Size-exclusion chromatography was used to demonstrate specific binding of the resulting analog, [N∈-palmitoyl Lys(B29)] human insulin, to serum albumin in vitro, and the time action and activity of the analog were determined in vivo using overnight-fasted, insulin-withdrawn diabetic dogs. In the diabetic animal model, the duration of action of [N∈-palmitoyl Lys(B29)] human insulin administered intravenously was nearly twice that of unmodified human insulin, and the plasma half-life was nearly sevenfold that of the unmodified protein. Administered subcutaneously, [N∈-palmitoyl Lys(B29)] human insulin had a longer duration of action; a flatter more basal plasma insulin profile; and a lower intersubject variability of response than the intermediate-acting insulin suspension Humulin L (Lilly, Indianapolis, IN). These studies support the concept that modification of insulin to promote binding to an existing serum protein can be used to extend the time action of human insulin. In addition, the time action, pattern, and decreased variability of response to [N∈-palmitoyl Lys(B29)] human insulin support the development and further testing of this soluble insulin analog as a basal insulin to increase the safety of intensive insulin therapy.

Aryl propanolamines : comparison of activity at human β3 receptors, rat β3 receptors and rat atrial receptors mediating tachycardia

The in vitro activity of four aryl propanolamines was compared to two prototypic β3 receptor agonists, CGP 12177 and CL316243 at the human β3 receptor, the rat β3 receptor in the stomach fundus and receptors mediating atrial tachycardia. L‐739,574 was the most potent (EC50=9 nM) and selective agonist at the human β3 receptor with high maximal response (74% of the maximal response to isoproterenol). A phenol‐biaryl ether analogue possessed modest affinity for the human β3 receptor (EC50=246 nM), but was highly efficacious with a maximal response 82% of the maximal response to isoproterenol. The other derivatives were intermediate in potency with low maximal responses. These agonists at the human β3 receptor did not activate the rat β3 receptor in the rat stomach fundus. In fact, the aryl propanolamines (10−6 M) inhibited CL316243‐induced activation of the rat β3 receptor. Thus, agonist activity at the human β3 receptor translated into antagonist activity at the rat β3 receptor. L739,574 and the phenol biaryl ether increased heart rate via β1 receptors. Although CGP12177 produced atrial tachycardia, neither the indole sulphonamide nor biphenyl biaryl ether did, although both had high affinity for the human β3 receptor. Thus, the atrial tachycardic receptor was not identical to the human β3 receptor. These studies (a) characterized four aryl propanolamines with high affinity at the human β3 receptor, (b) found that they were antagonists at the rat β3 receptor, an observation with profound implications for in vivo rat data, and (c) established that the rodent atrial non‐β1, β2 or β3 tachycardic receptor was also unrelated to the human β3 receptor.

Combination of a Beta adrenoceptor modulator and a norepinephrine-serotonin uptake inhibitor for the treatment of obesity.

We report the novel combination of a selective beta adrenoceptor modulator and a norepinephrine-serotonin uptake inhibitor (sibutramine) with potential for the treatment of obesity. The synthesis and characterization of 6-[4-[2-[[(2S)-3-(9H-carbazol-4-yloxy)-2-hydroxypropyl]amino]-2-methylpropyl]phenoxy]pyridine-3-carboxamide (LY377604), a human β3-adrenergic receptor agonist and β1- and β2-adrenergic receptor antagonist with no sympathomimetic activity at the β1- and β2-adrenergic receptors, is reported. Some in vivo data in both rats and humans is presented.

Effects of surface hydrophobicity on the structural properties of insulin

Publisher Summary This chapter discusses the effects of increasing the surface hydrophobicity of a globular protein. It has chosen to address this by comparing the conformational stability of a model protein in the presence and absence of a hydrophobic group attached covalently to a specific surface residue. Human insulin (HI) has been selected as the model protein because of its relatively small polypeptide for which there is a wealth of structural, chemical, and biological information. In addition, the insulin molecule possesses a rich conformational chemistry distinguished by thoroughly characterized structural transitions and ligand binding processes. The derivative bearing a surface hydrophobic group that is the subject of this study is N ɛ -palmitoylLys B29 human insulin (Pal-HI). In this chapter, Lys B29 has been chosen as the acylation site because of the simplicity of its conjugation chemistry. This residue resides in the C-terminus of the B-chain, which is a region of the insulin molecule known to be extremely flexible, and this region probably plays a minor role in the folding and unfolding process of unmodified insulin.