Insulin resistance and adipogenesis: role of transcription and secreted factors.

Insulin stimulates carbohydrate uptake by cells and induces their conversion into lipids as a more efficient form of energy storage. Insulin resistance is associated with a decrease in glucose uptake by muscle and adipose cells and also with a decrease in glycogen synthesis on retention of glucose synthesis by liver cells. Disorders in the insulin signaling cascade on development of insulin resistance can be caused by both changes in functioning of transcriptional factors and in the secretion profile of hormone-like substances. Diacylglycerols and ceramides responsible for activation of some kinases and phosphatases can directly trigger these changes in muscle and liver cells. In adipose tissue, insulin mainly stimulates adipogenesis (adipocyte differentiation) and lipogenesis (lipid accumulation in the cells). Thus, studies on the action mechanisms of factors influencing adipogenesis can be of help for understanding the molecular mechanisms of insulin resistance.

Femtosecond formation dynamics of primary photoproducts of visual pigment rhodopsin.

The coherent 11-cis-retinal photoisomerization dynamics in bovine rhodopsin was studied by femtosecond time-resolved laser absorption spectroscopy at 30-fs resolution. Femtosecond pulses of 500, 535, and 560 nm wavelength were used for rhodopsin excitation to produce different initial Franck-Condon states and relevant distinct values of the vibrational energy of the molecule in its electron excited state. Time evolution of the photoinduced rhodopsin absorption spectra was monitored after femtosecond excitation in the spectral range of 400-720 nm. Oscillations of the time-resolved absorption signals of rhodopsin photoproducts represented by photorhodopsin(570) with vibrationally-excited all-trans-retinal and rhodopsin(498) in its initial state with vibrationally-excited 11-cis-retinal were studied. These oscillations reflect the dynamics of coherent vibrational wave-packets in the ground state of photoproducts. Fourier analysis of these oscillatory components has revealed frequencies, amplitudes, and initial phases of different vibrational modes, along which the motion of wave-packets of both photoproducts occurs. The main vibrational modes established are 62, 160 cm(-1) and 44, 142 cm(-1) for photorhodopsin(570) and for rhodopsin(498), respectively. These vibrational modes are directly involved in the coherent reaction under the study, and their amplitudes in the power spectrum obtained through the Fourier transform of the kinetic curves depend on the excitation wavelength of rhodopsin.