Ronald Margolis

The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) celebrates in 2010 its 60(th) year as an institute of the National Institutes of Health. NIDDK has been fundamental in providing support for research in endocrinology, fostering research to elucidate basic principles of endocrine signaling leading to understanding of diseases and disorders of hormone action. Over this time span, a move to a more molecular level in understanding of the basis of hormone action has emerged and been supported by NIDDK, with many advances finding their way into a new journal, Molecular Endocrinology. The merging of disciplines that has made this possible constitutes a major force for further progress as NIDDK moves forward over the next 60 yr. Together, NIDDK and Molecular Endocrinology have served as catalysts for advancing knowledge in the field, energizing new paradigms that have led to advances in the clinic.

A detailed investigation was conducted to determine the precise subcellular localization of the rate-limiting enzymes of hepatic glycogen metabolism (glycogen synthase and phosphorylase) and their regulatory enzymes (synthase phosphatase and phosphorylase phosphatase). Rat liver was homogenized and fractionated to produce soluble, rough and smooth microsomal fractions. Enzyme assays of the fractions were performed, and the results showed that glycogen synthase and phosphorylase were located in the soluble fraction of the livers. Synthase phosphatase and phosphorylase phosphatase activities were also present in soluble fractions, but were clearly identified in both rough and smooth microsomal fractions. It is suggested that the location of smooth endoplasmic reticulum (SER) within the cytosome forms a microenvironment within hepatocytes that establishes conditions necessary for glycogen synthesis (and degradation). Thus the location of SER in the cell determines regions of the hepato...

The Nuclear Receptor Signaling Atlas (NURSA) was established as a trans-National Institutes of Health resource to develop, accrue, and communicate information about the nuclear receptor (NR) superfamily of ligand-dependent and -independent transcription factors. NRs have broad involvement in the regulation of development, reproduction, and metabolism. Receptors for thyroid hormones represent important members of the NR superfamily with key roles in development and homeostasis. NURSA has attempted to create a resource for information on NRs, associated coregulators, and ligands. The Web portal (www.NURSA.org) creates a window through which the general research community can gain access to data generated by NURSA investigators and linked from other sources. The molecule pages provide detailed curated information about the NR superfamily and allow the user to search for information useful to their own specific research problems. With the application of bioinformatics solutions, analyse...

ABSTRACT A daily rhythm was demonstrated in levels of specific activity for the Na, K-ATPase and glucose-6-phosphatase enzymes in adrenal and renal subcellular fractions in the rat. A bimodal daily rhythm was observed for 5′-nucleotidase in a renal subcellular fraction. The rats were maintained on a 12:12 light-dark (LD) regimen. Animals were killed at approximately 4-hour intervals.The daily rhythm in Na, K-ATPase and glucose-6-phosphatase activities persisted in animals maintained under continuous illumination (LL) and continuous darkness (DD). The 5′nucleotidase activity persisted under LL, and under DD.The data from the enzyme assays were analyzed by fitting to a cosinor regression model designed to assess the rhythmic nature of the findings. A linear transformation method was applied to assess the closeness of fit to the cosinor regression model.The Na, K-ATPase and glucose-6-phosphatase activities appeared to be endogenous circadian rhythms. Glucose-6-phosphatase activity in renal fractions appeared to be influenced by the feeding cycle. The 5′-nucleotidase enzyme appeared to have an ultradian rhythm. The ultimate derivation and significance of these observed rhythms remains to be determined; however, they appear to be independent of the light-dark cycle.

Effects of inhibition of protein synthesis by actinomycin D (ACT) on the acute stimulation of hepatic gluconeogenesis and glucose-6-phosphatase (G6Pase) by the glucocorticoid, dexamethasone (DEX), in adrenalectomized (ADX) rats, were investigated using both morphological and biochemical means. Examination of ultra-thin sections of liver in the electron microscope revealed that ACT, administered alone or with DEX, resulted in a failure of hepatic glycogen accumulation to occur. Smooth endoplasmic reticulum (SER) appeared similar to that of the ADX-untreated animals, with occasional suggestions of increased amounts of membrane in ACT-treated animals. G6Pase activity in homogenates was increased, as was activation of the enzyme under all experimental conditions, when compared with ADX-untreated controls. The DEX-induced increase in G6Pase activity in SER failed to occur to any appreciable extent in ACT-treated animals. Plasma glucose levels increased slightly when ACT and DEX were present simultaneously. It is suggested that ACT countered the inductive effects of DEX on hepatic glycogen synthesis, but only partially suppressed acute stimulation of gluconeogenesis. A possible superinduction of G6Pase enzyme synthesis through increased efficiency of translation of extant mRNA is discussed. It is proposed that ACT inhibited the formation of appropriate SER membranes and/or other components necessary for glycogen accumulation.

Fetal hyperglycemia and hyperinsulinemia, as induced by administration of streptozotocin to pregnant rats, during late gestation resulted in the onset of the major period of hepatic glycogen synthesis and accumulation at days 19-20 of gestation (22 days = term) rather than at days 20-21, as for normal fetuses. In addition, sustained high levels of liver synthase phosphatase and phosphorylase phosphatase activities prevented the normal term increase in activation of phosphorylase and inactivation of synthase in hyperglycemic/hyperinsulinemic fetuses. The suppression of term fetal changes in phosphorylase activation in particular contributed to the maintenance at term of fetal liver in a condition favoring glycogenesis rather than glycogenolysis.

The purpose of this study was to investigate the possible role of calcium-activated neutral protease in the disorganization and dissolution of the myofibrils of the rat soleus that occurs following tenotomy. Rats were killed 3, 5, 7, 14, 21, and 42 days after tenotomy of the soleus, and the muscles were removed and assayed for calcium-activated protease activity. Maximal protease activity occurred 1 week after tenotomy, at the time when myofibril organization is completely disrupted. Activity was still high 2 and 3 weeks after the operation, but returned to normal levels by 6 weeks, when muscle histology had returned to normal. The time course of the calcium-activated protease activity corresponded closely to the time course of the morphological changes. Thus, calcium-activated neutral protease may play a major role in myofibrillar proteolysis following tenotomy and in making the myofibril susceptible to proteolytic attack by other, less specific proteases.

The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) celebrates in 2010 its 60(th) year as an institute of the National Institutes of Health. NIDDK has been fundamental in providing support for research in endocrinology, fostering research to elucidate basic principles of endocrine signaling leading to understanding of diseases and disorders of hormone action. Over this time span, a move to a more molecular level in understanding of the basis of hormone action has emerged and been supported by NIDDK, with many advances finding their way into a new journal, Molecular Endocrinology. The merging of disciplines that has made this possible constitutes a major force for further progress as NIDDK moves forward over the next 60 yr. Together, NIDDK and Molecular Endocrinology have served as catalysts for advancing knowledge in the field, energizing new paradigms that have led to advances in the clinic.

Insulin-deficient diabetes mellitus results in diminished capacity of the liver to accumulate glycogen. One site of metabolic lesion in the diabetic liver is at the level of the synthase-activating enzyme, synthase phosphatase. This activity is progressively diminished with increasing severity of chemically induced diabetes in both soluble and smooth endoplasmic reticulum (SER) associated subfractions. Insulin administration via an implanted miniosmotic pump or via intrahepatic islet transplantation increased synthase phosphatase activity, particularly in SER. Hepatic glycogen synthesis and accumulation was enhanced as well. The data support a role for insulin in maintenance of the ability of the liver to synthesize and accumulate glycogen mediated either directly or indirectly through SER-synthase phosphatase activity.

The chronically hyperinsulinemic Zucker fatty rat, with peripheral insulin resistance and glucose intolerance, represents a model of noninsulin dependent diabetes mellitus (NIDDM). These animals have elevated hepatic glycogen levels. Hepatic levels of synthase phosphatase and phosphorylase phosphatase, which are diminished in the IDDM rat, were markedly increased in the obese rats. Glyburide, a sulfonylurea used in treatment of NIDDM, resulted in reduced levels of glycemia and increased insulin levels in Zucker rats. Hepatic glycogen levels were increased, as was the activation of glycogen synthase, although there were no effects of drug administration on synthase phosphatase or phosphorylase phosphatase activities. G6P levels were increased by glyburide in lean rats but not in obese animals. These effects of glyburide on liver glycogen metabolism are accounted for via potentiation of the glycogenic effects of insulin.

Adrenalectomized 24-h fasted rats lack the ability to synthesize and accumulate hepatic glycogen. In addition, the ability of liver glycogen synthase to respond to acute glucose administration is muted. The defect has been localized to the level of smooth endoplasmic reticulum-associated synthase phosphatase activity which is greatly reduced in adrenalectomized fasted rat liver. In vivo exposure to dexamethasone increases hepatic glucose output and hepatic glycogen synthesis and accumulation by 2-6 h after administration. Smooth endoplasmic reticulum synthase phosphatase activity is increased, and activation of glycogen synthase is restored. Ambient insulin concentrations are increased by steroid administration and appear to have a role in restoration of the ability to activate glycogen synthase, and consequently to restore the ability to synthesize and accumulate hepatic glycogen.

The roles of insulin, adrenal corticol hormones, and nutritional factors in the regulation of hepatic glycogen metabolism were investigated by means of fasting and refeeding normal and adrenalectomized (ADX) rats. More specifically, the hypothesis in question in this study is that certain hepatic phosphoprotein phosphatases are targets of insulin action in liver. In anesthetized rats, the hepatic glycogen concentration and the activities of hepatic glycogen synthase, glycogen synthase phosphatase, glycogen phosphorylase, and phosphorylase phosphatase were correlated with peripheral plasma glucose and immunoreactive insulin levels. Hepatic phosphatase activities were measured in (soluble) the high speed supernatant and smooth endoplasmic reticulum (SER). Fasting resulted in expected diminutions in circulating glucose and insulin levels and loss of hepatic glycogen. These changes were greater in ADX rats. The percentage of hepatic glycogen synthase in the active or I form increased with fasting in normal rats, but did not change in ADX rats. Hepatic synthase phosphatase activities were decreased in SER by fasting in both normal and ADX rats, but to a much greater extent in the latter; soluble synthase phosphatase was much less affected by fasting. The percentage of phosphorylase in the active or a form was significantly decreased in normal, but not ADX, rats. Phosphorylase phosphatase activities were not significantly changed by fasting in any of the subcellular fractions in normal liver, but were increased in the hepatic SER of ADX rats. Refeeding fasted rats for 2 and 6 h resulted in increased hepatic glycogen, activation of glycogen synthase, and increased circulating levels of both insulin and glucose. Refeeding also caused increases in SER-associated synthase phosphatase activity in ADX animals. SER phosphorylase phosphatase activities were significantly increased by refeeding in normal rats, but were decreased in ADX rats. Regression analysis of the data suggested statistically significant positive correlations between insulin levels and SER synthase phosphatase activity in ADX animals, on the one hand, and SER synthase phosphatase and the percentage of synthase in the I form, on the other. No statistically significant correlation between insulin levels and phosphorylase phosphatase activities could be demonstrated. These results are compatible with the hypothesis that glycogen synthase phosphatase activity in liver, especially that associated with SER, is subject to physiological regulation by circulating levels of insulin. In contrast, phosphorylase phosphatase activity seems to be much less influenced by changes in the circulating insulin level. The results are compatible with the proposition that SER-associated phosphoprotein phosphatases are physiologically relevant in the regulation of hepatic glycogen metabolism.(ABSTRACT TRUNCATED AT 400 WORDS)

Biochemical and morphological studies were performed on livers from normal, adrenalectomized (ADX), and ADX and dexamethasone (DEX)-treated rats to investigate the effects of glucocorticoids on microsomal membrane synthesis. Overnight fasted normal, ADX and ADX rats treated 2 or 4 h with DEX received [3H]leucine and [14C]glycerol. Livers were removed, and tissue specimens were prepared for electron microscopy and tissue fractionation. Liver microsomal subfractions were prepared and subsequently washed to produce rough and smooth microsomal membranes. Radioactivity and membrane composition were determined, and glucose-6-phosphatase activity was measured in washed microsomal membranes. Adrenalectomy caused decreased microsomal membrane synthesis. Two and 4 h of DEX administration restored microsomal membrane synthesis to normal levels. ADX also caused an alteration in composition of the microsomal membranes (reflected in decreased phospholipid-protein ratios), which was restored to normal levels by 4 h after DEX administration. The earliest effects of the hormone on membrane synthesis were observed in smooth microsomes as part of a smooth endoplasmic reticulum (SER) proliferation. These findings were supported by observations made with the electron microscope. The proliferating SER was enriched in at least one component: glucose-6-phosphatase. Although the specific relationship of SER to glucocorticoid action remains unclear, the interpretation is offered that SER proliferation and alteration in glucose-6-phosphatase distribution are component parts of the total response of the hepatocyte to glucocorticoids.

... Our laboratory has re cently demonstrated that the morphological and func tional differences among these plasma membrane do mains reflect differences in protein composition (Bartles et al., 1985a,b; Dunn et al., 1986; Hubbard et al., 1985; Roman and Hubbard, 1983). ...

Nuclear receptors (NRs) represent a class of ligand-dependent and -independent transcription factors with importance to the regulation of development, reproduction, and metabolism. The emergence of new understanding of the structure, function, and role in disease of NRs provides new insights into the interaction between genetics and the environment, with NRs representing new targets for the development of therapeutic agents. NRs play key roles in bone health and contribute to our understanding of diseases and disorders that result in osteopenia and osteoporosis. The Nuclear Receptor Signaling Atlas (http://www.nursa.org) is an online repository of information about NRs and provides a community-wide resource designed to help catalyze new advances in biology and medicine.

... 1994;101: 925-930. 3. Polito E, Leccisotti A. Epithelial malignancies of the lacrimal gland: survival rates after ex-tensive and conservative therapy. Ann Ophthalmol. ... Ron Margolis, BA Stephen S. Couvillion, MD Elias C. Mavrofrides, MD Ditte Hess, CRA Timothy G. Murray, MD ...

... Lydia Aguilar-Bryan (Baylor College of Medicine, TX, USA) reported that mice lacking K ATP are normoglycemic. ... The Developing Pancreas Genome Project discussed by Klaus Kaestner (http://www.cbil.upenn.edu/EPConDB/) is a source of high-quality cDNA from mouse and ...