Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0028754 (obesity)
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Estrogenic compounds are the most important group of drugs that can induce hypertension. Studies have shown an incidence of significant hypertension amounting to less than 1% after 1 year of taking oral contraceptives and about 2% after 5 years. The ratio of the incidence of hypertension among ''takers'' to that of ''nontakers'' has been assessed at 1.8 by 1 study and 2.6 by another. Small but significant increments in systolic and diastolic pressures can be discerned during the first 2 years of treatment. Cessation of treatment has resulted in pressures returing to pretreatment levels within 3 months. In those previously normal the highest readings during oral contraceptive use were only 155/90 mm of Hg. Severe hypertension is more likely to occur in the predisposed, and malignant hypertension has been reported. Previous hypertension, toxemia of pregnancy, obesity, and nephropathy are predisposing conditions. Although progestagens, used alone, do not cause clinical hypertension the incidence of hypertension associated with an estrogen-progestogen combination was directly related to the dose of progestagen used. Weight gain is often observed in oral contraceptive users and is occasionally accompanied by edema and hypertension. There is a marked increase in the circulating level of renin substrate (angiotensinogen) which is caused by the estrogen component of the pill. The increase in renin substrate is associated with increase in plasma levels of renin activity, angiotensin 2, and aldosterone, together with a fall in plasma renin concentration. The suppression of plasma renin concentration can persist for weeks after stopping the pill. The factors responsible for hypertension are probably intrinsic and may be either neural, vascular, or renal. Patients taking oral contraceptives should have blood pressure checks at 6-month intervals, and more frequently in high risk cases. In the management of those with only mild blood pressure elevation, such patients should change to a preparation with the lowest available estrogen dosage, 30 mcg of ethinyl estradiol, or reserve the method for use during crucial periods of family planning. With moderate hypertension the oral contraceptive should be suspended for 3-6 months. If the blood pressure falls, oral contraceptives should not be resumed but another method recommended. Continuing hypertension requires further study and possibly elective sterilization. Severe hypertension requires withdrawal of the pill, urgent investigation, and treatment. Other drugs may cause hypertension. Management of these patients is outlined. Structural formulae of progesterone, norethisterone acetate, medroxyprogesterone acetate, and norgestrel are shown.
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PMID:Drug-induced hypertension: pathogenesis and management. 18 40

The most important side effects of oral contraceptives (OCs) and their incidence, together with advice and monitoring of the patient at risk, are pointed out. There is a mild increase in blood pressure in longterm contraceptive use caused by increased angiotensinogen production by the liver. It is significant only for women with a history of familial hypertension, diabetes mellitus, or pre-eclampsia. Smoking increases this risk. Urinary tract infections are 25-50% more frequent in pill users. Glucose tolerance is slightly decreased. Contraceptives' diabetogenic effect is higher in women with hereditary tendency for diabetes, latent diabetes, and/or obesity. They are contraindicated in latent diabetes. Findings are contradictory in their effects on cholesterol and triglyceride serum level, but the pill is contraindicated in lipid metabolism disorders. There is an increased incidence in cholecystitis and cholelithiasis in pill-users (70-80 additional cases/100,000 user years). Liver diseases, intrahepatic cholestasis, occur rarely and benign liver tumors have not conclusively been proved to be caused by the pill. A variety of laboratory findings have been related to contraceptive use and drug interactions occur with barbiturates, rifampicin, hydantoin, and phenylbutazone. Blood coagulation is increased, partially by increased production of various blood coagulation factors; but more importantly, by a decreased synthesis of antithrombin III, a natural protective mechanism against intravascular coagulation. This increases thrombosis risk. Risk doubles with simultaneous cigarette smoking. Various epidemiological studies indicate a 5-10 fold increase in thromboembolism and thrombophlebitis, deep vein thrombosis, and pulmonary embolism. There is a correlation between contraceptive use and cerebrovascular disorders and myocardial infarction. This risk increases with age and years of pill use. The pill is contraindicated with symptoms of thrombophlebitis and thromboembolism, sickle cell anemia, proposed surgery, and longterm immobilization. Overall risk factors are not too high. Recommendations for rational pill use related to age are given and further contraindications are mentioned.
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PMID:[Adverse effects of oral contraceptives]. 55 52

Recent studies have found that angiotensinogen is expressed in white and brown fat pads, and adipocytes have been implicated as a primary source of angiotensinogen in several other tissues. The functional significance of this unexpected expression is unknown. To address this, we studied angiotensinogen messenger RNA (mRNA) expression and angiotensinogen secretion in adipose tissue and isolated adipocytes comparing fasted and refed rodents and those with genetic obesity with normal controls. Control 2-month-old Sprague-Dawley rats, those fasted for 3 days, or those fasted for 2 days and refed for 6 days were killed, and adipocytes were isolated from epididymal fat pads using collagenase digestion. Angiotensinogen mRNA was reduced to 14.6 +/- 2.3% of control levels under fasted conditions and increased to 228 +/- 53% of control levels after refeeding. Angiotensinogen release from adipocytes was reduced to 33% of control levels by fasting and increased to 183% by refeeding. These effects of fasting and refeeding on angiotensinogen regulation were tissue specific since liver angiotensinogen mRNA and serum angiotensinogen concentrations were unaffected. Systolic blood pressure, however, was modulated by fasting and refeeding in a manner parallel to adipocyte angiotensinogen expression. In related experiments, angiotensinogen secretion per epididymal fat pad of the ob/ob mouse model of obesity was increased an average of 3.4-fold compared with control. We conclude angiotensinogen expression in white adipocytes is regulated nutritionally in a tissue-specific manner. We propose that adipocyte angiotensinogen could play a previously unrecognized role in regulating adipose tissue blood supply and thereby fatty acid efflux from fat.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Tissue-specific nutritional regulation of angiotensinogen in adipose tissue. 155 65

Several large family studies are reviewed to identify results suggesting single gene traits contributing to the occurrence of hypertension in humans. Segregation analysis in families has suggested major gene effects for several highly heritable traits associated with hypertension. These include recessively segregating high sodium-lithium countertransport (major gene H2 = 34%), additively segregating low urinary kallikrein excretion (major gene H2 = 51%), and recessively segregating hyperinsulinemia (major gene H2 = 33%). In some families, hypertension and metabolic abnormalities (dyslipidemia, hyperinsulinemia, and obesity) seem to be related to several candidate genes studied but not conclusively proven (LPL deficiency mutations, dense LDL subfractions, or NIDDM with hyperinsulinemia). More recently, DNA markers have identified genes promoting hypertension. Glucocorticoid-remediable aldosteronism (GRA) promotes a rare but unusual form of hypertension that is unresponsive to ordinary medications but very responsive to glucocorticoid medications. GRA has been found in hypertensive persons with a specific mutation of the 11 beta-hydroxylase gene on chromosome 8q21. Many persons with essential hypertension carry a common "susceptibility gene" at the angiotensinogen locus (chromosome 1q4) identified using linkage studies in siblings, association studies, and in studies of preeclampsia and hypertension in pregnant women. These first two well-established genetic loci promoting human hypertension represent two ends of a broad spectrum. The rare "determinant" gene for GRA by itself seems to produce severe hypertension and early strokes. The angiotensinogen (AGT) "susceptibility" gene is very common (30% of Utah Caucasians) and seems to predispose to hypertension but probably requires other genetic and environmental influences to be fully expressed.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Evidence for single gene contributions to hypertension and lipid disturbances: definition, genetics, and clinical significance. 798 84

Angiotensin II exerts its action via at least two distinct receptor subtypes designated AT1 and AT2. AT1 receptors seem to be responsible for most of the known angiotensin II effects while the role of AT2 receptors is not yet clear. Adipocytes of adult rats express exclusively the AT1 subtype. Angiotensin II stimulates prostacyclin release in adult rat adipocytes and in mouse preadipocytes. In the latter prostacyclin release is completely blocked by an AT2 receptor antagonist. Adipocyte angiotensin II receptors seem to be regulated by age and fat mass. Blockade of these receptors by an AT1 antagonist seems to prevent adipose tissue hypertrophy. Moreover, adipose tissue contains all the main components of the renin-angiotensin system such as angiotensinogen, angiotensin converting enzyme, angiotensin II and angiotensin II receptors. Angiotensinogen expression in adipocytes is stimulated by a high fat diet concurrent with enlargement of fat mass, associated with insulin resistance. Angiotensin converting enzyme inhibitors improve insulin sensitivity. Taken together, there is evidence of interaction between insulin and angiotensin II in regulation of adipose tissue metabolism and cellularity. Clarification of these interactions could lead to significant progress in pharmacological treatment of obesity and its comorbidity.
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PMID:The role of angiotensin II and its receptors in regulation of adipose tissue metabolism and cellularity. 878 38

The renin-angiotensin system (RAS) plays a crucial role in the regulation of fluid volume, thereby influencing blood pressure (BP). Obesity is an important risk factor for hypertension, however the physiologic basis for this relationship has not been clarified. In a population survey we examined the potential relationship between the RAS and obesity. Based on community sampling, 449 individuals were recruited from metropolitan Kingston, Jamaica. Serum angiotensin-converting enzyme (ACE) and circulating angiotensinogen levels were measured and the associated genes were typed for previously described polymorphisms. Obese individuals (body mass index > 31) had significantly higher serum ACE and angiotensinogen levels, this relationship persisted for ACE in multivariate analyses controlling for BP, hypertension status, age, and gender. The insertion/deletion polymorphism of the ACE gene was associated with variation in the levels of ACE, but inconsistently with body mass index. Variants of the angiotensinogen gene leading to amino acid substitutions at positions 174 and 235 did not influence levels either of angiotensinogen or obesity. These data suggest that obesity may alter the levels of ACE and angiotensinogen, and provide a potential pathway through which obesity leads to elevation of BP.
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PMID:ACE, angiotensinogen and obesity: a potential pathway leading to hypertension. 914 Jul 97

A close relationship between obesity and hypertension has been recognized, and plasma angiotensinogen concentrations (p-AGT) have been reported to correlate with blood pressure (BP). However, little is known about AGT in obese patients with hypertension. To define the role of AGT in obese hypertension, we measured p-AGT in obese patients. The subjects were 42 obese patients diagnosed on the basis of a body mass index (BMI) of more than 25 kg/m2, and 21 sex- and age-matched nonobese patients, whose BMI was less than 25 kg/m2. The hypertensive patients had not previously received antihypertensive drugs. P-AGT (P < .05) and mean BP (P < .0001) was increased in the obese patients as compared with the nonobese patients. Positive correlations were observed between BMI and p-AGT, mean BP and p-AGT, and BMI and mean BP (all P < .05). However, after adjustment for blood pressure, p-AGT was not different between groups, and after adjustment a positive correlation remained only between BMI and mean BP. These results suggested the possible involvement of increased p-AGT in hypertension in obese patients, although this may be a secondary change to hypertension or obesity.
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PMID:Plasma angiotensinogen concentrations in obese patients. 919 8

Wistar fatty rats (WFR) show obesity and obesity-related features, including hypertension. In this study, we examined the expression of angiotensinogen mRNA in a variety of tissues at different times in WFR and control Wistar lean rats (WLR). WFR were obese and hypertensive at 16 and 24 wk. Plasma renin activity and plasma angiotensinogen concentration showed age-dependent increases in WFR but decreases in WLR. Northern blot analysis showed no significant differences in the levels of hepatic and renal angiotensinogen mRNA between WFR and WLR, and the levels of fat and adrenal angiotensinogen mRNA were lower in WFR than in WLR. On the other hand, the levels of cardiac angiotensinogen mRNA at 16 and 24 wk and those of aortic angiotensinogen mRNA at 16 wk were significantly higher in WFR than in WLR. These results show that the expression of tissue angiotensinogen mRNA is regulated differently in WFR and WLR and indicate that the development of hypertension in WFR is accompanied at least temporally with increases in plasma angiotensinogen concentration as well as in cardiac and aortic angiotensinogen mRNA. Moreover, these results suggest the existence of obesity hypertension-linked and tissue-specific regulation of angiotensinogen gene expression.
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PMID:Modulation of tissue angiotensinogen gene expression in genetically obese hypertensive rats. 922 81

Hypertension and diabetes mellitus are common chronic conditions which frequently coexist. Diabetic nephropathy is a major cause of elevated blood pressure in patients with insulin-dependent diabetes mellitus (IDDM). Diabetic nephropathy, arterial sclerosis, obesity and association of essential hypertension can be the causes of hypertension in patients with non-insulin-dependent diabetes mellitus (NIDDM). Ambulatory blood pressure monitoring has revealed that the nocturnal fall of blood pressure is blunted in patients with diabetic nephropathy. A blunted diurnal blood pressure variation is seen in microalbuminuric diabetic patients and even in some normoalbuminuric patients. Accumulating data suggest that normalisation of blood pressure in hypertensive IDDM patients is most important to minimise the loss of kidney function. Angiotensin converting enzyme (ACE) inhibitors have been reported to be effective in postponing the development of nephropathy and in slowing its progression. Whether only ACE inhibitors have such beneficial renal effects on diabetic nephropathy is under discussion. While many studies have suggested that insulin resistance and hyperinsulinaemia are related to an elevated blood pressure in hypertensive patients, there does not seem to be enough evidence to prove that insulin per se can raise blood pressure in humans. Neither an insulin infusion within a physiological range nor sustained hyperinsulinaemia and insulin resistance (e.g. patients with insulinoma, cystic ovary syndrome) have been associated with an elevated blood pressure. Insulin resistance in some hypertensive patients may be a consequence of a decreased blood flow due to an increased peripheral resistance. Preliminary evidence suggests that low birth weight or impaired fetal growth is related to hypertension and NIDDM. Familial clustering of diabetic nephropathy suggests the contribution of genetic susceptibility and/or environmental inheritance. The frequent association of nephropathy with hypertension has led to research on the genes related to hypertension (ACE, angiotensinogen). Nevertheless, to date no reliable and clinically useful genetic marker has been found. Attempts to correct the metabolic abnormalities derived from diabetes are a new topic in the treatment of diabetic nephropathy. The effects of HMG CoA reductase inhibitors (antihypercholesterolaemic drugs), aldose reductase inhibitors (inhibitors of the polyol pathway) and glycation inhibitors (inhibitors of formation of advanced glycosylation end-products) on diabetic nephropathy have been evaluated in animal studies and in some clinical trials. Thus far, results with HMG CoA reductase and aldose reductase inhibitors have been somewhat conflicting. The potential therapeutic role of glycation inhibition in the treatment of diabetes deserves further study.
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PMID:Diabetic nephropathy. Its relationship to hypertension and means of pharmacological intervention. 925 79

Two developments in molecular genetics will profoundly influence our understanding and the diagnosis of cardiovascular disorders. First, the identification of genes responsible for monogenic and polygenic traits by analysis of e.g. large pedigrees and affected sib pairs provides invaluable data regarding the role of specific genes in common diseases like arteriosclerosis, hypertension, diabetes, thrombosis/hemostasis and obesity. Besides the insights into the underlying pathophysiology, this knowledge will permit to identify persons at high risk for disease development. These patients can then obtain a targeted intervention. The second development is related to the availability of new analytical tools for molecular biology. New methods such as sequencing by hybridisation (SBH), DNA-array technology or matrix assisted laser desorption/ionisation-time of flight mass spectroscopy (MALDI-TOF) permit sequence analysis of complete genes within hours. Automated PCR-technologies with homogenous amplicon detection formats simplify PCR and permit its use in the routine laboratory setting. Considering cardiovascular diseases there is a number of genes involved in lipid metabolism (apolipoproteins, lipoprotein receptors, lipolytic enzymes), thrombosis/hemostasis (platelet receptors, pro- and anticoagulant proteins, fibrinogen, PAI's), hypertension (angiotensin converting enzyme, angiotensinogen) glucose metabolism (glucose transporters, enzymes) and obesity (hormones, receptors), that are interesting candidates for sophisticated genetic risk assessment. Furthermore, there are also gene candidates involved in processes of early atherogenesis and chronic inflammation such as complement proteins, cell adhesion molecules, and cellular receptors and enzymes. Most of these gene candidates were derived from pathophysiologic knowledge and subsequent epidemiological studies. However, it is foreseeable that in the coming years genes will be identified which were not known so far to be involved in cardiovascular diseases. Genetic studies will be of prime importance in this area, as is exemplified by animal models. In the long term, analysis of these candidate genes before the implementation of therapy will permit a targeted intervention approach towards high risk patients. This will reduce the overall costs of health care without reducing the quality.
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PMID:Recent advances in molecular genetics of cardiovascular disorders. Implications for atherosclerosis and diseases of cellular lipid metabolism. 965 2


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