Melatonin inhibits fatty acid-induced triglyceride accumulation in ROS17/2.8 cells: implications for osteoblast differentiation and osteoporosis.

Melatonin is produced not only by the pineal gland but by cells of the bone marrow. Moreover, melatonin is known to promote osteogenic differentiation in several cell line models and in multipotential bone marrow mesenchymal stem cells. Fatty acids have been independently shown to direct such cells to acquire the phenotype and molecular characteristics of adipocytes.

Insulin absorption: a major factor in apparent insulin resistance and the control of type 2 diabetes mellitus.

Our experience over many years from 2 diabetes clinics with large patient populations indicated that, apparently, excessive doses of intermediate-acting insulin preparations (150-300 U of NPH insulin), alone or in combination with rapid-acting insulin, generally did not result in acceptable control of fasting blood glucose. We hypothesized that insulin resistance at the tissue level and the known variability of insulin absorption were not satisfactory explanations. To deal with the ambiguities of available data on insulin absorption, we elected to measure insulin bioavailability via a different approach.

Adipocyte differentiation factor (ADF): a protein secreted by mature fat cells that induces preadipocyte differentiation in culture.

A factor that is released into the culture medium of mature adipocytes and promotes the differentiation (adipogenic conversion) of preadipocytes has been partially characterized. The factor acts in a dose-dependent manner on preadipocytes to produce up to a four-fold increase in triacylglycerol (triglyceride) content and a nine-fold increase in glycerol-3-phosphate dehydrogenase (GPDH) activity, a marker of the late phase of differentiation of preadipocytes. The material appears to be a protein, since it has a molecular weight (Superose-12 gel exclusion chromatography) of about 53 kDa, an isoelectric point (pl) of 4.

Catecholamine-sensitive lipolysis in the rat: different loci for effect of age on the lipolytic cascade in epididymal vs perirenal fat cells.

The biochemical locus of the decrease of lipolytic responsiveness to catecholamines in the aging rat has not heretofore been completely identified. Although increased sensitivity to the inhibitory action of adenosine is the likely explanation for the decrease during maturation, the nature of the age effect during senescence has been unclear. In order to determine whether the proximal or distal portion of the lipolytic pathway is involved, we have studied the lipolytic effect of the distally acting cyclic AMP analogue, 8-(4-chlorophenylthioadenosine)3'5'-monophosphate (cyclic) (Cl-cAMP) on rat fat cells from both the epididymal and perirenal fat pads of mature (6 mo) and senescent (24 mo) Fischer 344 rats.