Role of PTEN in TNFα induced insulin resistance.

AIMS/HYPOTHESIS: PTEN may play a reversible role in TNFα induced insulin resistance, which has been linked to obesity-associated insulin resistance (IR). METHODS: Western blots for PTEN and p-Akt were performed on H-411E liver cells incubated with insulin, TNFα, and in selected experiments VO-OHpic vanadium complex in the presence and absence of PTEN siRNA. Total PTEN was compared to ß-actin loading control and p-Akt was compared to total Akt. RESULTS: Western blot and Real Time RT-PCR experiments showed increased PTEN after TNFα treatment (p = 0.04); slightly decreased PTEN after insulin treatment; and slightly increased PTEN after insulin + TNFα treatment. PTEN siRNA markedly inhibited the TNFα-induced increase in PTEN (p < 0.01) without significantly changing the p-Akt levels. The vanadium complex, exhibiting insulin-like effects, also significantly prevented the TNFα-induced increase in PTEN. Combining insulin and VO-OHpic was additive, providing both proof of concept and insight into mechanism. DISCUSSION: The PTEN increase due to TNFα treatment was reversible by both PTEN siRNA knockdown and VO-OHpic treatment. Thus, PTEN is identified as a potential new therapeutic target for reducing IR in Type 2 DM.

Metformin Associated With Increased Survival in Type 2 Diabetes Patients With Pancreatic Cancer and Lymphoma.

BACKGROUND: The biguanide drug metformin is one of the most commonly used medications for the treatment of type 2 diabetes mellitus. Diabetics are at an increased risk for cancer. Previous studies have demonstrated improved outcomes in patients taking metformin suffering from prostate, colon, lung, thyroid, and esophageal cancers. Metformin's main antineoplastic mechanism of action is thought to be mediated through inhibition of mammalian target of rapamycin, inhibition of hypoxia-inducible factor 1 (HIF-1) alpha, and activation of p53. We investigated the overall survival of type 2 diabetic patients on metformin with pancreatic cancer and lymphoma using the Computerized Patient Record System at the Veterans Affairs Medical Center, Memphis TN. METHODS: Lymphoma and pancreatic cancer patients with type 2 diabetes were sorted into an experimental (metformin) group and a control (nonmetformin) group. Patients were compared on baseline characteristics including race, body mass index, and age. Cancer outcomes including overall survival, metastasis, recurrences, and incidence of new malignancies were recorded. Hemoglobin A1C, creatinine and cancer treatment modalities were recorded and compared. Statistical analyses used included unpaired t tests and Chi-squared tests. RESULTS: There was significantly greater overall long-term survival in the metformin group compared to the nonmetformin group for lymphoma (5.89 vs 1.29 years, P < 0.001) and for pancreatic cancer (0.68 vs 0.22 years, P = 0.016). Cancer treatment modalities in both groups were comparable. CONCLUSIONS: Metformin is associated with a significant, positive effect of increased overall survival in type 2 diabetes patients with pancreatic cancer and lymphoma. These results are encouraging, and prospective studies should be done to further investigate metformin's effects in cancer.

A critical role of Sp1 transcription factor in regulating gene expression in response to insulin and other hormones.

Specificity protein 1 (Sp1) belongs to a family of ubiquitously expressed, C(2)H(2)-type zinc finger-containing DNA binding proteins that activate or repress transcription of many genes in response to physiological and pathological stimuli. There is emerging evidence to indicate that in addition to functioning as 'housekeeping' transcription factors, members of Sp family may be key mediators of gene expression induced by insulin and other hormones. The founding member of the family, Sp1, by virtue of its multi-domain organization, potential for posttranslational modifications and interactions with numerous transcription factors, represents an ideal mediator of nuclear signaling in response to hormones. Insulin regulates the sub-cellular localization, stability and trans-activation potential of Sp1 by dynamically modulating its post-translational modification by O-linked beta-N-acetylglucosamine (O-GlcNAc) or phosphate residues. We briefly review the recent literature demonstrating that an involvement of Sp-family of transcription factors in the regulation of differential gene expression in response to hormones is more common than previously appreciated and may represent a key regulatory mechanism.

Gatifloxacin produces both hypoglycemia and hyperglycemia: a retrospective study.

BACKGROUND: Gatifloxacin, until recently one of the most commonly prescribed antibiotics, has been shown to produce hypoglycemia. METHODS: To further examine the effects of Gatifloxicin (G) on blood glucose (BS), we conducted a retrospective chart review on 264 inpatients, examining for both hypoglycemia and hyperglycemia, comparing G with another quinolone, Ciproflaxin (C), and nonquinolone, Ceftriaxone (R). RESULTS: We found that of 292 patient encounters, 28 hypoglycemia and 48 hyperglycemic events occurred. Patients given G were 5 times as likely to become hypoglycemic as C (P < 0.01) and 9 times as likely as those given R (P < 0.02). Patients given G were 5.6 times more likely to develop hypoglycemia (P < 0.001) than the combined group, R+C. Conversely, patients treated with G were 3.8 times as likely to become hyperglycemic as those give C (P < 0.01) and 9.8 times as those given R (P < 0.01). With C and R combined, those given G were 5.2 times as likely to develop hyperglycemia (P < 0.01). Looking at patient encounters where G was given, we found that having preexisting diabetes mellitus (DM) was positively associated with hypoglycemia (21/144, P < 0.001). Steroid use (P < 0.05) and being in the ICU (P < 0.01) were also positively associated with hyperglycemia (38/144, P < 0.01). CONCLUSIONS: In summary, G was clearly associated with both hypoglycemia and hyperglycemia compared with C and R. The risk of hyperglycemia increased in the presence of DM, steroid use, and "sick enough" to be in the intensive care unit.

Metformin: Possible Use of a Diabetes Drug in Treatment of Cancer.

The biguanide drug metformin used for treating Type 2 diabetes has anticancer properties and affects many pathways involving glucose metabolism, energy balance, and cell survival. A number of retrospective clinical studies have indicated a reduced risk of cancer and improved cancer outcomes in Type 2 diabetic patients taking metformin. Several of its effects are mediated through the induction of cellular stress and subsequent activation of AMP kinase, but many other mechanisms act independently of AMP kinase activation. Metformin has been shown to inhibit the effects of tumor necrosis factor (TNF)-alpha. TNF-alpha interferes with insulin signaling to produce insulin resistance in the insulin signaling pathway and promotes apoptosis through NF-KB in the apoptosis pathway. In addition, metformin reduces cellular proliferation by decreasing the amount of available insulin or by directly affecting the mammalian target of rapamycin complex involved with regulating protein synthesis. It can prevent tumors from acquiring stem cell-like properties, upregulate apoptotic pathways, and bolster the immune system's fight against cancer. Gaining a greater understanding of metformin's various mechanisms of action will continue to elucidate metformin's role as an effective treatment for cancer.

Metformin Has Positive Therapeutic Effects in Colon Cancer and Lung Cancer.

BACKGROUND: Metformin (MF), a diabetic drug, has antineoplastic activity as adjuvant therapy for breast cancer and prostate cancer. MF is thought to work via inhibition of mammalian target of rapamycin and activation of p53 and liver kinase B1 via adenosine 5'-monophosphate-activated protein kinase. We investigated survival, recurrences and metastasis in patients with type 2 diabetes mellitus (DM2) along with colorectal cancer (CC) or lung cancer (LC) taking MF using the electronic medical record in Memphis Veterans Affairs Medical Center (colon, n = 202; lung, n = 180). MATERIALS AND METHODS: Patients with CC or LC and DM2 on MF were compared to controls taking any medication except MF. Recurrences, metastases, secondary cancers, survival and carcinoembryonic antigen levels were compared using t test and chi-squared test. Inclusion criteria were based on MF use, CC or LC diagnosis and DM2. RESULTS: For CC, the MF group noted fewer deaths (48% versus 76%, P < 0.001), recurrences (4% versus 19%, P = 0.002), metastases (23% versus 46%, P = 0.001), better 5-year survival rates (57% versus 37%, P = 0.004), overall survival years (5.7 versus 4.1, P = 0.007) and greater carcinoembryonic antigen decrease (72% versus 47%, P = 0.015). MF was associated with improved 5-year survival rates (29% versus 15%, P = 0.023) and overall survival years (3.4 versus 1.8, P < 0.001) in LC. CONCLUSIONS: Our study shows that MF therapy is associated with significantly better prognosis in patients with CC and improved survival in LC. Patients with CC on MF had fewer recurrences and metastases. Differences in metabolic pathways between CC and LC likely account for the differences in the effect of MF.

Metformin Has a Positive Therapeutic Effect on Prostate Cancer in Patients With Type 2 Diabetes Mellitus.

OBJECTIVE: Prostate cancer and type 2 diabetes mellitus (DM2) are both common diseases found in the elderly male population. The diabetic drug, metformin, has been shown to have antineoplastic properties and demonstrated better treatment outcomes when used as adjuvant therapy in patients with breast cancer. The hormonally-sensitive cancer analogous to breast cancer in men is prostate cancer. We investigated improved survival, lower risks of recurrences, and lower, more stable levels of prostate-specific antigen (PSA) in patients with DM2 along with prostate cancer on metformin. METHODS: Patients with prostate cancer along with DM2 who remained on metformin were compared with controls who were not on metformin matched by age, weight, race and Gleason score cancer staging. The endpoints of our study included final PSA values, number of recurrences, metastases and number living for each group. RESULTS: There were significantly fewer deaths (23% versus 10%), fewer recurrences (15% versus 8%), fewer metastases (5% versus 0%) and fewer secondary cancers (17% versus 6%) in the metformin group (P < 0.004). The final PSA value was lower in the metformin-treated group with a result approaching significance (P = 0.067). The primary treatments for prostate cancer (ie, surgery, radiation and androgen depletion) were found to be comparable in both the groups. CONCLUSIONS: Our retrospective study shows that adjuvant metformin therapy leads to a better prognosis in prostate cancer. Not only are PSA levels controlled for several years but also there are significantly fewer cancer recurrences in metformin-treated patients. Overall, these results are promising and should be followed up with a prospective study to assess long-term survival.

Insulin stimulates and diabetes inhibits O-linked N-acetylglucosamine transferase and O-glycosylation of Sp1.

Insulin stimulates both the biosynthesis of transcription factor Sp1 and its O-linked N-acetylglucosaminylation (O-GlcNAcylation), which promotes nuclear localization of Sp1 and its ability to transactivate calmodulin (CaM) gene transcription. To investigate this further, we incubated H-411E liver cells with insulin (10,000 microU/ml) and quantified the subcellular distribution of O-GlcNAc transferase (OGT) and O-GlcNAc-modified Sp1. We also examined the phosphorylation of Sp1 using both Western blot and incorporation of 32P into Sp1. The results demonstrate that insulin, but not glucagon, stimulates OGT synthesis and enhances cytosolic staining of OGT (histochemical). Insulin increases O-GlcNAc-Sp1, which peaks at 30 min, followed by decline at 4 h. In contrast, insulin initiates phosphorylation of Sp1 early, followed by a continued increase in phosphorylated Sp1 (PO4-Sp1) at 4 h. A reciprocal relationship between O-GlcNAc-Sp1 and PO4-Sp1 was observed. To explore the pathophysiological relevance, we localized OGT in liver sections from streptozotocin (STZ)-induced diabetic rats. We observed that staining of OGT in STZ-induced diabetic rat liver is clearly diminished, but it was substantially restored after 6 days of insulin treatment. We conclude that insulin stimulates CaM gene transcription via a dynamic interplay between O-glycosylation and phosphorylation of Sp1 that modulates stability, mobility, subcellular compartmentalization, and activity.

Genomes, transcriptomes, and proteomes: molecular medicine and its impact on medical practice.

The human genome project and the technological breakthroughs it has produced have moved the field of molecular medicine forward with breathtaking speed. This will impact not only the advance of scientific discoveries and the way science is conducted but also the clinical practice of medicine. In this review we explain the basic principles of these new technologies. Their potential use and impact are demonstrated by using diabetes mellitus as an example of a common and serious medical disorder. Finally, several potentially adverse consequences of "excessive" knowledge are discussed.

Paradoxical regulation of Sp1 transcription factor by glucagon.

Insulin is a potent regulator of Sp1 transcription factor. To examine if glucagon, which usually antagonizes insulin, regulates Sp1, we assessed the levels of Sp1 by Western blotting from H-411E cells exposed to glucagon with or without insulin. Glucagon alone (1.5 x 10(-9) to 1.5 x 10(-5) M) stimulated Sp1 accumulation but inhibited insulin's (10,000 microU/ml) stimulatory effect on Sp1. We also assessed the effect of TNF-alpha, wortmannin, a PI3K inhibitor, and cAMP-dependent protein kinase inhibitor on Sp1 accumulation. While TNF-alpha (5 ng/ml) blocked insulin-stimulated Sp1, it failed to block stimulation of Sp1 by glucagon (1.5 x 10(-5) M). Similarly, wortmannin inhibited insulin- but not glucagon-stimulated Sp1, whereas protein kinase inhibitor had an opposite effect. Thus, insulin acts primarily via PI3K, and glucagon apparently stimulates through a cAMP-dependent pathway. Insulin increased the staining intensity of Sp1 seen exclusively in the nuclei of H-411E cells. Sp1 was demonstrable in both nucleus and cytoplasm after glucagon treatment. Finally, as judged by immunoblotting to specific antibody, insulin but not glucagon, stimulated O-glycosylation of Sp1. Thus, unique signaling mechanisms mediate the response of Sp1 to glucagon in the presence or absence of insulin.

Matrix-dependent bias in total thyroxine measurement on the Beckman Access.

BACKGROUND: Total thyroxine assays continue to be an integral part of thyroid status testing. We experienced a significant number of elevated total thyroxine values in patients with normal thyroid stimulating hormone and thyroxine binding globulin concentrations using the Beckman Access and hypothesized that these were due to a sample matrix effect. METHODS: We compared the total thyroxine assays on the Beckman Synchron, Beckman Access, and Dade Dimension using individual patient specimens and two uniform matrices: a serum pool and an albumin-based matrix that were both supplemented with L-thyroxine to span the linear assay range. RESULTS: Access total thyroxine values in individual patient specimens exhibited sporadic positive bias as high as 77 nmol/l (6 microg/dl) when compared to the Synchron and Dimension. The use of uniform matrices had little effect on the Synchron in comparison to the Dimension but significantly improved the agreement between the Access and the Dimension or Synchron as indicated by a statistically significant improvement in correlation coefficients. CONCLUSIONS: The Access total thyroxine assay is prone to a variable and clinically significant positive bias that is mediated by a component of the sample matrix.

Impact of medical student research in the development of physician-scientists.

CONTEXT: A decline in the number of physician-scientists has been identified in the United States for at least two decades. Although many mechanisms have been proposed to reverse this trend, most of these have concentrated on MD/PhD programs, research in sub-specialty fellowships, and other approaches later in physician training. Few have emphasized early medical student research experiences as a contributing solution. OBJECTIVE: To determine the effect of a medical student research experience on career choices and attitudes about biomedical research. DESIGN, SETTING, AND PARTICIPANTS: We jointly report 25 years of experience with National Institutes of Health (NIH)-sponsored Medical Student Research Fellowship programs (MSRFs) at two colleges of medicine, the University of Tennessee Health Science Center and Vanderbilt University. In both programs, students work during the summer of their first or second year of medical school on a research project that is mentored by an established scientist and participate in a structured program (lectures, visiting professor). MAIN OUTCOME MEASURES: We gathered data using pre- and postresearch fellowship questionnaires to assess (a) quality of research experiences; (b) tabulation of productivity, that is, presentations, abstracts, publications, and awards; (c) long-term tracking of former program participants; (d) comparison of residency placements by medical student researchers; and (e) comments from former program participants on the effects of their students' research experiences on career choices. RESULTS: During this time, approximately 1,000 medical students participated in the two programs. Follow-up data (for short-term evaluations, 96-132 respondents with a response rate > 82%; for long-term evaluations, 88-118 respondents with a response rate > 29-33%) strongly suggest (a) interest in an academic career increased, (b) one-third to half of former student respondents considered themselves to be in academic medicine, (c) the vast majority of students conducted additional research after their medical student research experience, and (d) a large number of students were currently doing research or had published or presented their work at scientific meetings. CONCLUSIONS: Over two decades of experience with NIH-sponsored medical student research programs at two medical schools strongly support the ability of these programs to interest medical students in research and academic careers. MSRFs should be included in strategies to reverse the decline in the number of physician-scientists.

Thyrotoxicosis presenting as hypogonadism: a case of central hyperthyroidism.

Herein, we present a case of central thyrotoxicosis with well-documented serial therapeutic interventions. Thyroid-stimulating hormone (TSH)-secreting pituitary tumors represent a rare cause of hyperthyroidism. It is being diagnosed more frequently with the third-generation TSH assay. Many conditions can produce normal or elevated TSH levels in combination with elevated thyroid hormone levels. The differential diagnosis includes resistance to thyroid hormone (RTH, Refetoff's syndrome), assay interference from anti-T4/T3 and heterophile antibodies, elevated or altered binding proteins, drugs affecting peripheral metabolism, and noncompliance with thyroid replacement therapy. In contrast to RTH, our patient presented had high alpha-subunit-to-TSH molar ratio, failed TSH response to thyrotropin-releasing hormone stimulation, and a large pituitary mass. Normal or high TSH in the presence of elevated T4 or T3 is a fairly common clinical scenario with many etiologic possibilities. This TSH-producing adenoma represents an unusual initial clinical presentation, as hypogonadism appeared before features of thyrotoxicosis were appreciated. This case represents the most modern therapeutic approach to the management of this rare disease. Our patient has done well on octreotide with control of thyrotoxicosis and an additional 30% shrinkage of his tumor mass.

Does subclinical hyperthyroidism predispose to cocaine addiction?

OBJECTIVE: To investigate the relationship between subclinical hyperthyroidism and cocaine abuse. METHODS: Using the computerized patient medical record system at the Veterans Affairs Medical Center in Memphis, Tennessee, we identified the following 3 groups: (1) cocaine abusers without hyperthyroidism; (2) patients with hyperthyroidism without cocaine abuse; and (3) patients with hyperthyroidism and cocaine abuse. In 1,191 patients taken from the same clinic population, we calculated the prevalence of cocaine abuse alone, hyperthyroidism alone, and both diagnoses together to examine whether a relationship existed between hyperthyroidism and cocaine abuse. RESULTS: We found the following prevalences: (1) 37.7 per 1,000 patients with cocaine abuse; (2) 18.8 per 1,000 with hyperthyroidism (primarily subclinical); and (3) 65.4 per 1,000 with both hyperthyroidism and cocaine abuse. We found a highly statistically significant correlation between subclinical hyperthyroidism and cocaine abuse (P<<.01 by χ² test) in this population of Veterans Affairs patients. No other significant correlations were found. CONCLUSION: In our study population, we found a strong correlation between hyperthyroidism (overt or subclinical) and cocaine abuse. Several theoretical mechanisms may explain these findings, but further prospective studies are needed to clarify this complex relationship.

Composite pheochromocytoma-ganglioneuroma: a rare experiment of nature.

OBJECTIVE: To present a rare case of composite pheochromocytoma-ganglioneuroma (Pheo-GN) of the adrenal medulla, review the related literature, and discuss the clinical features, pathologic findings, behavior, and management of such tumors. METHODS: A case report of a patient with composite Pheo-GN of the adrenal gland is presented. Using the online database PUBMED, we searched and analyzed all cases of composite pheochromocytoma reported in the English-language literature during the past 70 years. RESULTS: On computed tomography, a 61-year-old man was incidentally found to have a 3.8-cm nonadenomatous right adrenal lesion. Adrenalectomy revealed a 5-cm mass consistent with composite Pheo-GN. To date, 45 cases of composite pheochromocytomas have been reported during the past 70 years, 71% of which coexisted with ganglioneuromas. These tumors occurred with approximately equal frequency in male and female patients, the majority of whom were from 40 to 60 years old. Only 14 cases have been reported in the United States. Bilateral tumors were found in 3 cases. The mean size was 4 to 6 cm. Preoperatively, functional evidence was found in 76.3% of all composite pheochromocytomas (and in 67% of Pheo-GN). Only one Pheo-GN was found to have liver metastatic lesions at the time of autopsy; the rest were not aggressive. CONCLUSION: To our knowledge, this is the first literature review describing the characteristics and behavior of all reported cases of composite pheochromocytomas, with an emphasis on those with ganglioneuromas. Composite pheochromocytoma is a rare variant of a relatively uncommon disease diagnosed by pathologists only. Fortunately, the treatment of such an entity remains the same as for any pheochromocytoma.

Nonalcoholic Fatty liver disease and metabolic syndrome in hypopituitary patients.

BACKGROUND: Increased incidence of cardiovascular mortality and nonalcoholic fatty liver disease (NAFLD) has been reported in hypopituitarism, but previous studies did not correct for obesity in these patients. Therefore, it remained unclear if endocrine deficiency in hypopituitarism is associated with metabolic consequences independent of obesity. This study was designed to determine the burden of cardiovascular disease and NAFLD in hypopituitarism. METHODS: We performed a retrospective case-control analysis of hypopituitary patients at Veterans Affair Medical center, Memphis, from January 1997 to June 2007. After matching for age, gender, obesity, and race, relevant data were abstracted from the subjects' records to determine the presence of hypopituitarism, cardiovascular risk factors, and fatty liver disease. Cases and controls were characterized by descriptive statistics and compared using chi(2) and Student t tests. RESULTS: Hypopituitary patients exhibited higher prevalence of hypertension- 88% versus 78% (P < 0.03), hypertriglyceridemia-80% versus 70% (P = 0.05), low high-density lipoprotein cholesterol-84% versus 70% (P < 0.001), and metabolic syndrome-90% versus 71% (P < 0.001). Patients also had higher mean plasma glucose levels-228 +/- 152 versus 181 +/- 83 mg/dL (P < 0.01). Despite higher preponderance of cardiovascular risk factors in hypopituitary patients, prevalence of cardiovascular morbidity was similar in both groups (P > 0.3). Hypopituitary patients had higher elevations in serum aminotransferase levels and hyperbilirubinemia-24% versus 11% (P < 0.01), as well as higher international normalized ratio (INR) and hypoalbuminemia 40% versus 23% (P < 0.01). CONCLUSIONS: There is an increased prevalence of metabolic syndrome and liver dysfunction consistent with NAFLD in hypopituitarism. Although hypopituitary patients had higher prevalence of cardiovascular risk factors than controls, they were not disproportionately affected by cardiovascular disease.