Dean Tolan - Academia.edu (original) (raw)

Papers by Dean Tolan

Metabolism is highly interconnected and also has profound effects on other cellular processes. Ho... more Metabolism is highly interconnected and also has profound effects on other cellular processes. However, the interactions between metabolites and proteins that mediate this connectivity are frequently low affinity and difficult to discover, hampering our understanding of this important area of cellular biochemistry. Therefore, we developed the MIDAS platform, which can identify protein-metabolite interactions with great sensitivity. We analyzed 33 enzymes from central carbon metabolism and identified 830 protein-metabolite interactions that were mostly novel, but also included known regulators, substrates, products and their analogs. We validated previously unknown interactions, including two atomic-resolution structures of novel protein-metabolite complexes. We also found that both ATP and long-chain fatty acyl-CoAs inhibit lactate dehydrogenase A (LDHA), but not LDHB, at physiological concentrations in vitro. Treating cells with long-chain fatty acids caused a loss of pyruvate/lact...

Subunit interface mutants of rabbit muscle aldolase form active dimers

Aldolase C is the brain-specific aldolase isoenzyme. In the human brain, aldolase C messenger and... more Aldolase C is the brain-specific aldolase isoenzyme. In the human brain, aldolase C messenger and protein are expressed in a stripe-like pattern in the Purkinje cells of the cerebellum, in the inferior olives and in the Goll and Burdach nuclei of the posterior horn in the spinal cord. Notwithstanding numerous studies have been conducted on aldolase C transcriptional regulation, promoter regions governing brain- and cell-specific expression in human are not yet precisely known. We analysed transcriptional regulation of human aldolase C gene through in vitro and in vivo systems. We previously demonstrated that cAMP increased human aldolase C gene expression in PC12 cells through NGFI-B binding to element D in the distal promoter region of the gene. Here we demonstrate that NGF up-regulates human aldolase C gene expression in PC12 cells. We identified the element E in the distal promoter region as responsive to NGF treatment and demonstrated that USF1 binds to this region thus mediatin...

Journal of Biological Chemistry, 1992

Materials-Restriction enzymes were purchased from Bethesda Research Laboratories, New England Bio... more Materials-Restriction enzymes were purchased from Bethesda Research Laboratories, New England BioLabs, or Boehringer Mannheim. DNA polymerase I was from Bethesda Research Laboratories, DNA polymerase I/Klenow fragment was from Boehringer Mannheirn, T4 DNA ligase was from New England BioLabs. Oligonucleotide primers were synthesized on a Milligen 6500 DNA synthesizer using phosphoramidite chemistry. [a-32P]Deo~yribon~~leoside triphosphates were from Amersham Corp. Nitrocellulose BAS5 and Nytran paper and filters were from Schleicher & Schuell, and radioautography was done with Kodak XAF-5 x-ray film. Genomic clones were isolated from a library of D. melanogaster strain Oregon-R DNA in the vector XEMBL-4 which was a gift from M. Goldberg of Cornel1 University. Blotting Procedures-DNA was prepared from adult D. melanogaster (20) digested with restriction enzymes, electrophoresed, and transferred to Nytran membranes according to the method of Southern (21). RNA was isolated as described previously (22) and analyzed by blotting (23). Blots were probed with random primed deoxyribonucleotide probes generated using the kit supplied by Boehringer 3959 This is an Open Access article under the CC BY license. This is an Open Access article under the CC BY license.

Seminars in Nephrology, 2020

Kidney disease, especially when it is associated with a reduction in eGFR, can be associated with... more Kidney disease, especially when it is associated with a reduction in eGFR, can be associated with an increase in serum urate (uric acid), suggesting that hyperuricemia in subjects with kidney disease may be strictly a secondary phenomenon. Mendelian randomization studies that evaluate genetic scores regulating serum urate also have generally not found evidence that serum urate is a causal risk factor in chronic kidney disease. Nevertheless, this is countered by a large number of epidemiological, experimental, and clinical studies that suggest a potentially important role for Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Journal of Biological Chemistry, 1993

Biomedical SEED Grant 860-BI. The costs of publication of this article were defrayed in part by t... more Biomedical SEED Grant 860-BI. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked ' '~~e r~~~~n~' ' in accordance with 18 U.S.C. Section 1734 soleIy to indicate this fact.

Journal of Biological Chemistry, 1987

The hisT-purF Region of the Escherichia coli K-12 Chromosome IDENTIFICATION OF ADDITIONAL GENES O... more The hisT-purF Region of the Escherichia coli K-12 Chromosome IDENTIFICATION OF ADDITIONAL GENES OF THE hisT AND purF OPERONS*

Frontiers in Aging Neuroscience, 2020

Annals of Nutrition and Metabolism, 2019

The worldwide increase in temperature has resulted in a marked increase in heat waves (heat extre... more The worldwide increase in temperature has resulted in a marked increase in heat waves (heat extremes) that carries a markedly increased risk for morbidity and mortality. The kidney has a unique role not only in protecting the host from heat and dehydration but also is an important site of heat-associated disease. Here we review the potential impact of global warming and heat extremes on kidney diseases. High temperatures can result in increased core temperatures, dehydration, and blood hyperosmolality. Heatstroke (both clinical and subclinical whole-body hyperthermia) may have a major role in causing both acute kidney disease, leading to increased risk of acute kidney injury from rhabdomyolysis, or heat-induced inflammatory injury to the kidney. Recurrent heat and dehydration can result in chronic kidney disease (CKD) in animals and theoretically plays a role in epidemics of CKD developing in hot regions of the world where workers are exposed to extreme heat. Heat stress and dehydra...

Journal of Internal Medicine, 2019

Mass extinctions occur frequently in natural history. While studies of animals that became extinc... more Mass extinctions occur frequently in natural history. While studies of animals that became extinct can be informative, it is the survivors that provide clues for mechanisms of adaptation when conditions are adverse. Here, we describe a survival pathway used by many species as a means for providing adequate fuel and water, while also providing protection from a decrease in oxygen availability. Fructose, whether supplied in the diet (primarily fruits and honey), or endogenously (via activation of the polyol pathway), preferentially shifts the organism towards the storing of fuel (fat, glycogen) that can be used to provide energy and water at a later date. Fructose causes sodium retention and raises blood pressure and likely helped survival in the setting of dehydration or salt deprivation. By shifting energy production from the mitochondria to glycolysis, fructose reduced oxygen demands to aid survival in situations where oxygen availability is low. The actions of fructose are driven ...

American Journal of Physiology-Renal Physiology, 2019

An epidemic of chronic kidney disease of unknown etiology (Mesoamerican nephropathy) has emerged ... more An epidemic of chronic kidney disease of unknown etiology (Mesoamerican nephropathy) has emerged in hot regions of Central America. We have demonstrated that dehydration associated with recurrent heat exposure causes chronic kidney disease in animal models. However, the independent influence of core body temperature on kidney injury has not been explored. In the present study, we tested the hypothesis that kidney injury could be accelerated by increasing body temperature independent of external temperature. Wild-type mice were exposed to heat (39.5°C, 30 min, 2 times daily) with or without the mitochondrial uncoupling agent 2,4-dinitrophenol (DNP) for 10 days. Core temperature, renal function, proteinuria, and renal histological and biochemical analyses were performed. Isolated mitochondria markers of oxidative stress were evaluated from kidney tissue. DNP increased body core temperature in response to heat by 1°C (42 vs. 41°C), which was transient. The mild increase in temperature ...

Journal of hepatology, 2018

Non-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of metabolic syndrome; its... more Non-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of metabolic syndrome; its rising prevalence parallels the rise in obesity and diabetes. Historically thought to result from overnutrition and a sedentary lifestyle, recent evidence suggests that diets high in sugar (from sucrose and/or high-fructose corn syrup [HFCS]) not only increase the risk of NAFLD, but also non-alcoholic steatohepatitis (NASH). Herein, we review the experimental and clinical evidence that fructose precipitates fat accumulation in the liver, due to both increased lipogenesis and impaired fat oxidation. Recent evidence suggests that the predisposition to fatty liver is linked to the metabolism of fructose by fructokinase C, which results in ATP consumption, nucleotide turnover and uric acid generation that mediate fat accumulation. Alterations to gut permeability, the microbiome, and associated endotoxemia contribute to the risk of NAFLD and NASH. Early clinical studies suggest that reducing...

The Journal of clinical investigation, Jan 23, 2018

Increasing evidence suggests a role for excessive intake of fructose in the Western diet as a con... more Increasing evidence suggests a role for excessive intake of fructose in the Western diet as a contributor to the current epidemics of metabolic syndrome and obesity. Hereditary fructose intolerance (HFI) is a difficult and potentially lethal orphan disease associated with impaired fructose metabolism. In HFI, the deficiency of aldolase B results in the accumulation of intracellular phosphorylated fructose, leading to phosphate sequestration and depletion, increased adenosine triphosphate (ATP) turnover, and a plethora of conditions that lead to clinical manifestations such as fatty liver, hyperuricemia, Fanconi syndrome, and severe hypoglycemia. Unfortunately, there is currently no treatment for HFI, and avoiding sugar and fructose has become challenging in our society. In this report, through use of genetically modified mice and pharmacological inhibitors, we demonstrate that the absence or inhibition of ketohexokinase (Khk), an enzyme upstream of aldolase B, is sufficient to preve...

Brain Research, 2017

High fructose consumption in the Western diet correlates with disease states such as obesity and ... more High fructose consumption in the Western diet correlates with disease states such as obesity and metabolic syndrome complications, including type II diabetes, chronic kidney disease, and nonalcoholic fatty acid liver disease. Liver and kidneys are responsible for metabolism of 40-60% of ingested fructose, while the physiological fate of the remaining fructose remains poorly understood. The primary metabolic pathway for fructose includes the fructose-transporting solutelike carrier transport proteins 2a (SLC2a or GLUT), including GLUT5 and GLUT9, ketohexokinase (KHK), and aldolase. Bioinformatic analysis of gene expression encoding these proteins (glut5, glut9, khk, and aldoC, respectively) identifies other organs capable of this fructose metabolism. This analysis predicts brain, lymphoreticular tissue, placenta, and reproductive tissues as possible additional organs for fructose metabolism. While expression of these genes is highest in liver, the brain is predicted to have expression levels of these genes similar to kidney. RNA in situ hybridization of coronal slices of adult mouse brains validate the in silico expression of glut5, glut9, khk, and aldoC, and show expression across many regions of the brain, with the most notable expression in the cerebellum, hippocampus, cortex, and olfactory bulb. Dissected samples of these brain regions show KHK and aldolase enzyme activity 5-10 times the concentration of that in liver. Furthermore, rates of fructose oxidation in these brain regions are 15-150 times that of liver slices, confirming the bioinformatics prediction and in situ hybridization data. This suggests that previously unappreciated regions across the brain can use fructose, in addition to glucose, for energy production.

Journal of Neurophysiology, 2016

Fructose stimulates vasopressin in humans and can be generated endogenously by activation of the ... more Fructose stimulates vasopressin in humans and can be generated endogenously by activation of the polyol pathway with hyperosmolarity. We hypothesized that fructose metabolism in the hypothalamus might partly control vasopressin responses after acute dehydration. Wild-type and fructokinase-knockout mice were deprived of water for 24 h. The supraoptic nucleus was evaluated for vasopressin and markers of the aldose reductase-fructokinase pathway. The posterior pituitary vasopressin and serum copeptin levels were examined. Hypothalamic explants were evaluated for vasopressin secretion in response to exogenous fructose. Water restriction increased serum and urine osmolality and serum copeptin in both groups of mice, although the increase in copeptin in wild-type mice was larger than that in fructokinase-knockout mice. Water-restricted, wild-type mice showed an increase in vasopressin and aldose reductase mRNA, sorbitol, fructose and uric acid in the supraoptic nucleus. In contrast, fruct...