Insulin-mediated regulation of decidual protein induced by progesterone (DEPP) in adipose tissue and liver

We analyzed the profile of the genes expressed in human adipose tissue and identified the fat-derived molecules, adiponectin and aquaporin 7, which modulate glucose and lipid metabolism. The same Bodymap analysis revealed abundant expression of the decidual protein induced by progesterone (DEPP) in the white adipose tissue. Northern blot analysis confirmed that human DEPP mRNA was highly expressed in white adipose tissue. Mouse DEPP mRNA was detected in heart, lung, skeletal muscle, and white adipose tissue under feeding state. In contrast, under fasting state, mouse DEPP mRNA was enhanced in lung, skeletal muscle, and white adipose tissue and it appeared also in the liver and kidney, suggesting up regulation of DEPP by fasting. Because fasting-induced DEPP expression was observed in insulin-sensitive organs, we investigated the regulation of DEPP in white adipose tissue and liver. During adipogenesis of mouse 3T3-L1 cells, DEPP mRNA increased in a differentiation-dependent manner similar to adiponectin and aquaporin 7. Treatment of cultured 3T3-L1 mature adipocytes, rat H4IIE, and human HepG2 hepatoma cells with insulin significantly decreased DEPP mRNA levels in dose- and time-dependent manners. IN VIVO experiments showed significant decrease of hepatic and adipose DEPP mRNA levels in refed mice, compared to fasted animals, and also showed significant increase in DEPP mRNA in streptozotocin-induced insulin-deficient diabetic mice. These results indicate that DEPP is a novel insulin-regulatory molecule expressed abundantly in insulin-sensitive tissues including white adipose tissue and liver.

Impact of glycerol gateway molecule in adipocytes

Glycerol is one of the essential nutrients in the mammalian body. Glycerol released from adipocytes is delivered to the liver and used for gluconeogenesis. The molecular mechanism of glycerol transport across the cell membrane remains unclear. AQPadipose, which we identified in human adipose cDNA project and later found to be human AQP7, is expressed in adipose tissue, and upregulated during fasting. AQP7 belongs to the aquaglyceroporin subfamily to permealize glycerol as well as water. Loss of function mutation of AQP7 in human caused disturbance of normal rise of plasma glycerol. Disruption of AQP7 gene in mice resulted in profound hypoglycemia during prolonged fasting because of impaired glycerol supply to the liver. In obesity, AQP7 is overexpressed in visceral fat,accompanied by portal hyperglycerolemia and systemic hyperglycemia. Considered together, these works indicate that AQP7 functions as a glycerol gateway molecule in adipocytes.

Blockade of Angiotensin II type-1 receptor reduces oxidative stress in adipose tissue and ameliorates adipocytokine dysregulation

Dysregulated production of adipocytokines may be involved in the development of atherosclerotic cardiovascular disease in metabolic syndrome and chronic kidney disease (CKD) associated with metabolic syndrome. The aim of this study was to determine the effects of treatment with angiotensin II (Ang II) type-1 receptor blocker (ARB) on the regulation of adipocytokines. Olmesartan, an ARB, significantly blunted the age- and body weight-associated falls in plasma adiponectin both in genetically and diet-induced obese mice, without affecting body weight, but had no effect on plasma adiponectin levels in lean mice. Olmesartan also ameliorated dysregulation of adipocytokines in obesity, such as tumor necrosis factor-alpha, plasminogen activator inhibitor-1, monocyte chemotactic protein-1, and serum amyloid A3. Olmesartan significantly reduced reactive oxygen species originating from accumulated fat and attenuated the expression of nicotinamide adenine dinucleotide phospho hydrogenase oxidase subunits in adipose tissue. In cultured adipocytes, olmesartan acted as an antioxidant and improved adipocytokine dysregulation. Our results indicate that blockade of Ang II receptor ameliorates adipocytokine dysregulation and that such action is mediated, at least in part, by targeting oxidative stress in obese adipose tissue. Ang II signaling and subsequent oxidative stress in adipose tissue may be potential targets for the prevention of atherosclerotic cardiovascular disease in metabolic syndrome and also in metabolic syndrome-based CKD.