ABSTRACT
Carbohydrate-based low molecular weight gelators (LMWGs) are compounds with the capability to self-assemble into complex molecular networks within a solvent, leading to solvent immobilization. This process of gel formation depends on noncovalent interactions, including Van der Waals, hydrogen bonding, and π-π stacking. Due to their potential applications in environmental remediation, drug delivery, and tissue engineering, these molecules have emerged as an important area of research. In particular, various 4,6-O-benzylidene acetal-protected D-glucosamine derivatives have shown promising gelation abilities. In this study, a series of C-2-carbamate derivatives containing a para-methoxy benzylidene acetal functional group were synthesized and characterized. These compounds exhibited good gelation properties in several organic solvents and aqueous mixtures. Upon removal of the acetal functional group under acidic conditions, a number of deprotected free sugar derivatives were also synthesized. Analysis of these free sugar derivatives revealed two compounds were hydrogelators while their precursors did not form hydrogels. For those protected carbamates that are hydrogelators, removal of the 4,6-protection will result in a more water-soluble compound that produces a transition from gel to solution. Given the ability of these compounds to form gels from solution or solution from gels in situ in response to acidic environments, these compounds may have practical applications as stimuli-responsive gelators in an aqueous medium. In turn, one hydrogelator was studied for the encapsulation and release of naproxen and chloroquine. The hydrogel exhibited sustained drug release over a period of several days, with the release of chloroquine being faster at lower pH due to the acid lability of the gelator molecule. The synthesis, characterization, gelation properties, and studies on drug diffusion are discussed.
ABSTRACT
PURPOSE: To examine potential detrimental long-term effects of acute diet-induced weight loss on visceral adiposity, insulin resistance, cortisol, and adipokines in obese individuals at risk for type-2 diabetes. DATA SOURCES: Anthropometric measures (height, weight, waist circumference), self-report instruments, abdominal computed tomography (CT) scan, and blood samples (glucose, insulin, interleukin-6, leptin, adiponectin) were obtained from a convenience sample of 20 participants at baseline, after a 28-day low-calorie diet (800 kcal/day) intervention, and again 6 months later. CONCLUSIONS: Fifteen of 20 participants completed the 28-day diet intervention and had a mean weight loss of 15 pounds. Comparison between baseline, postdiet, and 6-month data, demonstrated that although participants had significant improvements after the diet, they regained fat mass, particularly in the visceral area. IMPLICATIONS FOR PRACTICE: Clinicians may need to revise recommendations for using low-calorie diets to achieve weight loss. Diet-induced weight cycling may contribute to dysregulation of metabolism and have long-term detrimental consequences for accumulation of visceral adipose tissue. The likelihood of success is low, with high dropout rates, and those patients who achieve weight loss are very likely to regain it. Thus, the perceived short-term benefits of calorie-restricted diets in this population likely do not outweigh the potential long-term detrimental effects.
