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N Ruderman

Publications and source records attributed to N Ruderman.

14 recordsLinked to original sources
PubMed2001

Acute regulation of fatty acid oxidation and amp-activated protein kinase in human umbilical vein endothelial cells.

It is generally accepted that endothelial cells generate most of their ATP by anaerobic glycolysis and that very little ATP is derived from the oxidation of fatty acids or glucose. Previously, we have reported that, in cultured human umbilical vein endothelial cells (HUVECs), activation of AMP-activated protein kinase (AMPK) by the cell-permeable activator 5-aminoimidazole-4-carboximide riboside (AICAR) is associated with an increase in the oxidation of (3)H-palmitate. In the present study, experiments carried out with cultured HUVECs revealed the following: (1) AICAR-induced increases in palmitate oxidation during a 2-hour incubation are associated with a decrease in the concentration of malonyl coenzyme A (CoA) (an inhibitor of carnitine palmitoyl transferase 1), which temporally parallels the increase in AMPK activity and a decrease in the activity of acetyl CoA carboxylase (ACC). (2) AICAR does not stimulate either palmitate oxidation when carnitine is omitted from the medium or oxidation of the medium-chain fatty acid octanoate. (3) When intracellular lipid pools are prelabeled with (3)H-palmitate, the measured rate of palmitate oxidation is 3-fold higher, and in the presence of AICAR, it accounts for nearly 40% of calculated ATP generation. (4) Incubation of HUVECs in a glucose-free medium for 2 hours causes the same changes in AMPK, ACC, malonyl CoA, and palmitate oxidation as does AICAR. (5) Under all conditions studied, the contribution of glucose oxidation to ATP production is minimal. The results indicate that the AMPK-ACC-malonyl CoA-carnitine palmitoyl transferase 1 mechanism plays a key role in the physiological regulation of fatty acid oxidation in HUVECs. They also indicate that HUVECs oxidize fatty acids from both intracellular and extracellular sources, and that when this is taken into account, fatty acids can be a major substrate for ATP generation. Finally, they suggest that AMPK is likely to be a major factor in modulating the response of the endothelium to stresses that alter its energy state.

3-O-Methylglucose↗
PubMed2000

Exercise diminishes the activity of acetyl-CoA carboxylase in human muscle.

Studies in rats suggest that increases in fatty acid oxidation in skeletal muscle during exercise are related to the phosphorylation and inhibition of acetyl-CoA carboxylase (ACC), and secondary to this, a decrease in the concentration of malonyl-CoA. Studies in human muscle have not revealed a consistent decrease in the concentration of malonyl-CoA during exercise; however, measurements of ACC activity have not been reported. Thus, whether the same mechanism operates in human muscle in response to physical activity remains uncertain. To investigate this question, ACC was immunoprecipitated from muscle of human volunteers and its activity assayed in the same individual at rest and after one-legged knee-extensor exercise at 60, 85, and 100% of knee extensor VO2max. ACC activity was diminished by 50-75% during exercise with the magnitude of the decrease generally paralleling exercise intensity. Treatment of the immunoprecipitated enzyme with protein phosphatase 2A restored activity to resting values, suggesting the decrease in activity was due to phosphorylation. The measurement of malonyl-CoA in the muscles revealed that its concentration is 1/10 of that in rats, and that it is diminished (12-17%) during the higher-intensity exercises. The respiratory exchange ratio increased with increasing exercise intensity from 0.84 +/- 0.02 at 60% to 0.99 0.04 at 100% VO2max. Calculated rates of whole-body fatty acid oxidation were 121 mg/min at rest and 258 +/- 35, 264 +/- 63, and 174 +/- 76 mg/min at 60, 85, and 100% VO2max, respectively. The results show that ACC activity, and to a lesser extent malonyl-CoA concentration, in human skeletal muscle decrease during exercise. Although these changes may contribute to the increases in fat oxidation from rest to exercise, they do not appear to explain the shift from mixed fuel to predominantly carbohydrate utilization when exercise intensity is increased.

Acetyl-CoA Carboxylase↗
PubMed1999

The effect of AMP-activated protein kinase and its activator AICAR on the metabolism of human umbilical vein endothelial cells.

In several non-vascular tissues in which it has been studied, AMP-activated protein kinase (AMPK) appears to modulate the cellular response to stresses such as ischemia. In liver and muscle, it phosphorylates and inhibits acetyl CoA carboxylase (ACC), leading to an increase in fatty acid oxidation; and in muscle, its activation is associated with an increase in glucose transport. Here we report the presence of both AMPK and ACC in human umbilical vein endothelial cells (HUVEC). Incubation of HUVEC with 2 mM AICAR, an AMPK activator, caused a 5-fold activation of AMPK, which was accompanied by a 70% decrease in ACC activity and a 2-fold increase in fatty acid oxidation. Surprisingly, glucose uptake and glycolysis, the dominant energy-producing pathway in HUVEC, were diminished by 40-60%. Despite this, cellular ATP levels were increased by 35%. Thus activation of AMPK by AICAR is associated with major alterations in endothelial cell energy balance. Whether these alterations protect the endothelium during ischemia or other stresses remains to be determined.

AMP-Activated Protein Kinases↗
PubMed1999

Increased amounts of farnesylated p21Ras in tissues of hyperinsulinaemic animals.

We have recently demonstrated that insulin activates farnesyltransferase (FTase) and thereby increases the amounts of cellular farnesylated p21Ras in 3T3-L1 fibroblasts, adipocytes and vascular smooth muscle cells. We postulated that hyperinsulinaemia might considerably increase the the cellular pool of farnesylated p21Ras available for activation by other growth factors. To examine the role of in vivo hyperinsulinaemia in regulating farnesylated p21Ras, we measured the amounts of farnesylated p21Ras in tissues of hyperinsulinaemic animals. Liver, aorta, and skeletal muscle of ob/ob mice, and mice made obese and hyperinsulinaemic by injection of gold-thioglucose contained greater amounts of farnesylated p21Ras than tissues of their lean normoinsulinaemic counterparts. Similarly, farnesylated p21Ras was increased (67 vs. 35 % in control animals, p<0.01) in the livers of hyperinsulinaemic Zucker rats (fa/fa). Reduction of hyperinsulinaemia by exercise training (2 h/day for 7-8 weeks) resulted in decreases in the amounts of farnesylated p21Ras in these animals. Increased farnesylated p21Ras in hyperinsulinaemic animals reflected increasing increments in the activity of FTase in ob/ob mice (2-fold increase) and fa/fa Zucker rats (3.5-fold increase), while the total amounts of Ras proteins remained unchanged. In contrast to insulin-resistant hyperinsulinaemic animals, denervated insulin-resistant rat soleus muscle (in the presence of normoinsulinaemia) showed normal amounts of farnesylated p21Ras. In summary, these data confirm increased amounts of farnesylated p21Ras in tissues of hyperinsulinaemic animals.

3T3 Cells↗
PubMed1998

The metabolically obese, normal-weight individual revisited.

Nearly 20 years ago, it was suggested that individuals exist who are not obese on the basis of height and weight, but who, like people with overt obesity, are hyperinsulinemic, insulin-resistant, and predisposed to type 2 diabetes, hypertriglyceridemia, and premature coronary heart disease. Since then it has become increasingly clear that such metabolically obese, normal-weight (MONW) individuals are very common in the general population and that they probably represent one end of the spectrum of people with the insulin resistance syndrome. Available evidence also suggests that MONW individuals could account for the higher prevalence of type 2 diabetes, cardiovascular disease, and other disorders in people with a BMI in the 20-27 kg/m2 range who have gained modest amounts of weight (2-10 kg of adipose mass) in adult life. Specific factors that appear to predispose MONW, as well as more obese individuals, to insulin resistance include central fat distribution, inactivity, and a low VO2max. Because these factors are potentially reversible and because insulin resistance may contribute to the pathogenesis of many diseases, it is our premise that a compelling argument can be made for identifying MONW individuals and treating them with diet, exercise, and possibly pharmacological agents before these diseases become overt, or at least early after their onset. One reason for doing so is that disorders such as type 2 diabetes may be accompanied by irreversible consequences, e.g., ischemic heart disease and nephropathy, at the time of diagnosis or shortly thereafter. Another is that MONW individuals in general should be younger and more amenable and responsive to diet and exercise therapy than are obese patients with established disease. That long-term diet and exercise can work is suggested by two large studies in which, over 5-6 years, the incidence of diabetes was diminished in nonobese and minimally obese patients with impaired glucose tolerance. Based on these considerations and the emerging worldwide epidemic of type 2 diabetes, we believe that studies to assess whether therapies aimed at young MONW individuals can prevent the development of type 2 diabetes and other diseases, including perhaps obesity itself, are urgently needed.

Adult↗
PubMed1990

Exercise in therapy and prevention of type II diabetes. Implications for blacks.

The rationale for the use of exercise in the treatment of type II (non-insulin-dependent) diabetes and its special implications for Blacks are reviewed herein. When performed on a regular basis, exercise may improve glycemic control and improve several risk factors for coronary heart disease including hypertriglyceridemia, hypertension, and hyperinsulinemia. In addition, it may be a useful adjunct to diet in producing weight loss. The metabolic benefits of exercise in part appear to be related to its ability to enhance insulin sensitivity. Benefits are short lived after discontinuing exercise. Because of problems with compliance and concurrent medical problems, many patients with type II diabetes are not good candidates for an exercise-diet program. For this reason, the optimum target population may be people at risk for type II diabetes and premature atherosclerosis. Such a population might include the offspring of patients with these disorders and individuals with impaired glucose tolerance, hyperinsulinemia, gestational diabetes, and/or an android pattern of fat distribution. Type II diabetes is more common in Blacks than in the general population. In most instances, it is associated with cardiovascular risk factors benefited by exercise. Despite this, there are no available studies regarding the effects of regular exercise in Blacks with type II diabetes or those at risk for it.

Black or African American↗
PubMed1985

Intranasal aerosolized insulin. Mixed-meal studies and long-term use in type I diabetes.

We assessed the efficacy of intranasal aerosolized insulin containing laureth-9 as a surfactant in patients with Type I diabetes by fasting studies in 8 patients, mixed-meal studies in 15, and long-term home use in 8. The intranasal insulin (1 U per kilogram of body weight in 1 per cent laureth-9) was rapidly absorbed (in 15 minutes); it lowered the plasma glucose level by 50 per cent in 45 minutes in fasting normal controls and by 50 per cent in 120 minutes in fasting diabetics. The glucose-lowering potency depended on the insulin dose and surfactant concentration. Nasal irritation was proportional to surfactant concentration, with great variability among subjects. After intranasal insulin used before meals (1 U per kilogram in 1 per cent laureth-9), the two-hour postprandial glucose level increased above before-meal levels by 38 mg per deciliter, as compared with 191 mg per deciliter after intranasal placebo in patients with Type I diabetes (P less than 0.05). An outpatient feasibility study examining three months of use of intranasal aerosolized insulin before meals as a supplement to Ultralente insulin revealed that the aerosol was well tolerated, with glycemic control (as indicated by the percentage of glycohemoglobin, home glucose measurements, and hypoglycemic reactions) comparable to that during a subsequent three-month period of conventional subcutaneous insulin treatment. The results suggest that intranasal insulin has potential as an adjunct to subcutaneous insulin in the therapy of Type I diabetes.

Absorption↗
PubMed1984

Specific susceptibility to mucormycosis in murine diabetes and bronchoalveolar macrophage defense against Rhizopus.

To assess the influence of diabetes mellitus in predisposing to pulmonary mucormycosis, a murine model of streptozotocin-induced diabetes was used. Intranasal inoculation of Rhizopus oryzae into diabetic mice resulted in mucormycotic infection with histopathology resembling pulmonary mucormycosis observed in humans. There was no mortality nor infection in inoculated normal mice. Diabetic mice had fatal infections caused by R. oryzae but significantly reduced mortality following inoculation with Aspergillus fumigatus. These findings reflect the specific enhanced susceptibility to mucormycosis observed in human diabetics. Normal bronchoalveolar macrophages formed part of an efficient defense against R. oryzae by inhibiting germination, the critical step in the conversion of R. oryzae to its tissue invasive phase. Bronchoalveolar macrophages inhibited spore germination in vitro and appeared to help prevent germination in vivo. In contrast, spore germination occurred in diabetic mice following intranasal inoculation. Diabetic bronchoalveolar macrophages had a decreased ability to attach to hyphae. In diabetic mice, bronchoalveolar macrophages could damage spores or hyphae of R. oryzae, but serum factors appeared to both promote spore germination and impair attachment of macrophages to spores. This murine model of diabetes mellitus provides an opportunity for evaluation of the relative importance of cell and serum-mediated host factors in the pathogenesis of mucormycosis.

Acid Phosphatase↗
PubMed1976

Alanine metabolism and gluconeogenesis in the rat.

The metabolism of alanine and several other gluconegoneic substrates was studied in anesthtized fed and fasted rats, i.e., rats with low and high rates of gluconeogenesis. Glutamine was released by the hindquarter (muscle) in both groups, whereas lactate, pyruvate, and alanine were taken up in fed rats and were released during starvation. Despite this, blood levels of alanine, lactate, and pyruvate were diminished in fasting rats, suggesting increased extraction by liver. Treatment of fasted rats for 24 h with phloridzin caused glycosuria and secondarily led to hypoglycemia and an intensification of the chargesobserved with fasting, i.e., hyperketonemia, hyperglucagonemia, and increased gluconeogenesis (assessed by urea N excretion). Blood alanine was decreased, even though the release of alanine from muscle was increased. Pretreatment with triamcinolone and administration of exogenous alanine both attenuated the hypoglycemia and ketosis, It is concluded that 1) in states of heightened gluconeogenesis, alanine release from muscle may not keep pace with extraction by liver and blood alanine decreases; 2) the release of alanine, lactate, and pyruvate from muscle parallel each other suggesting common control factors; and 3) in the red state muscle is an important site of lactate disposition.

Alanine↗