Does growth hormone have a role in essential hypertension? Its relationship with circadian blood pressure and insulin resistance

AJH–April 2002–VOL. 15, NO. 4, PART 2

hypotensive therapy is indicated for all forms of hypertension, the observed variation in blood pressure trends over time may reflect fundamental differences in pathophysiology and prognosis. Key Words: Diabetes Mellitus, Aging, Diastolic Pressure

P-446 PREVALENCE OF RENAL IMPAIRMENT IN TYPE 2 DIABETES: A PRIMARY CARE-BASED STUDY Rafael Marin, Manuel Gorostidi, Salvador Tranche, Leocadio Rodriguez-Man˜ as, Jose Abellan. Nephrology, Hospital Covadonga, Oviedo, Asturias, Spain; Nephrology, Hospital Jarrio, Coan˜ a, Asturias, Spain; Primary Care, El Cristo, Oviedo, Asturias, Spain; Geriatrics, Hospital Getafe, Getafe, Madrid, Spain; Primary Care, San Andre´ s, Murcia, PIRDDOS Study Group, Spain. The purpose of the study was to determine the prevalence of renal impairment, and to assess its significance, within type 2 diabetics attending primary care settings. We performed a cross-sectional observation of patients with type 2 diabetes being the first 20 unselected cases seen by 178 family physicians from 16 of the 17 departments of Spain. Following variables were determined: serum creatinine, and glucose concentrations, HbA1c, proteinuria (dipstick test in a first-voided morning urine sample), blood pressure level, and associated cardiovascular disease. Data from 3583 type 2 diabetics were evaluated. Mean age was 64⫹/-10 years being 45% male. A serum creatinine ⫽ or ⬎1.2 mg/dl was observed in 523 (15.5%) patients. Proteinuria was present in 794 (23.5%) cases, being ⫽ or ⬎2⫹ in 215 (6.5%) subjects. Patients with a serum creatinine ⫽ or ⬎1.2 mg/dl were older, showed a higher blood pressure level, and suffered from more cardiovascular disease (32.0 vs. 19.5%) than those with a serum creatinine ⬍ 1.2 mg/dl. In a multivariate analysis, this difference continued to be significant (OR 1.47; 95% CI 1.14 to 1.90; p⫽0.002). Patients with proteinuria showed a higher prevalence of cardiovascular disease (OR 1.83; 95% CI 1.47 to 2.27; p⬍0.0001) than those without proteinuria. This association was continuous with an increasing pattern from the no proteinuric to the ⫽ or ⬎2⫹ proteinuric patients (p⬍0.001). There is a high prevalence of renal impairment, approximately of 25%, within type 2 diabetic patients seen at the primary care level. These patients have a higher cardiovascular disease prevalence than type 2 diabetics with no clinic renal disease. Key Words: Type 2 Diabetes, Renal Disease, Epidemiology

P-447 MAGNESIUM METABOLISM IS TO ESSENTIAL HYPERTENSION WITH INSULIN RESISTANCE Hy Tian, A.Q. Ma, Y.T. Xi. Department of Cardiology, First Hospital, Xi’an, Shaanxi, China. Objective: To investigate the correlating factors of insulin resistance (IR) and the effect of magnesium metabolism in essential hypertension (EH). Method: Erythrocyte insulin receptor (EIR), the concentrations of erythrocyte Mg2⫹, Ca2⫹, Na⫹, K⫹ and ATP, and 24-hour urinary excretion of Mg2⫹, Ca2⫹, Na⫹, K⫹ were analyzed. 30 normotensive subjects and 47 patients with essential hypertension were evaluated in the study. IR was assessed by means of insulin sensitivity index (ISI ⫽ 1/fast glucose multiply fast plasma insulin). The correlation analysis and the stepwise multiple linear regression analysis were used to clarify correlate factors of IR. Results: (1) ISI, erythrocyte concentration of Mg2⫹, K⫹, urinary excretion of Mg2⫹, low insulin affinity binding site of EIR (RT2) were significantly lower, however, insulin affinity binding site of KD2, concentrations of erythrocyte Ca2⫹, Na⫹ were significantly higher in the EH patients than those in the contro1s. (2) In group of EH, ISI were

POSTERS: Obesity, Insulin Resistance, Diabetes

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negatively correlated with mean arterial blood pressure, body mass index, waist hip ratio, familial history of EH ( r ⫽ - 0.614, P ⬍ 0.001; r ⫽ 0.374, P ⬍ 0.01; r ⫽ - 0.386, P ⬍ 0.01; r ⫽ - 0.472, P ⬍ 0.01), but ISI were positively correlated to RT2, erythrocyte concentration of Mg2⫹ , K⫹ ( r ⫽ 0.301, P ⬍ 0.01; r ⫽ 0.395, P ⬍ 0.05; r ⫽ 0.315, P ⬍ 0.05). (3) RT2 was positively correlated to erythrocyte concentration of Mg2⫹ and urinary excretion of Mg2⫹, Ca2⫹, (r⫽0.279, P⬍0.05; r⫽0.391, P⬍0.01; r⫽0.281, P⬍0.05). (4) erythrocyte concentration of Mg2⫹ was positively correlated to urinary excretion of Mg2⫹, Ca2⫹ and erythrocyte concentration of K⫹ ( r ⫽ 0. 445, P ⬍ 0.01; r ⫽ 0.357, P ⬍ 0.01; r ⫽ 0.387, P ⬍ 0.01 ) Conclusion: (1) Down-regulation insulin receptor might play an important role in pathogenesis of IR and might correlate to magnesium metabolism. (2) Abnormality magnesium metabolism might be a key linkage between IR and essential hypertension. Calcium and potassium metabolism may be involved in the occurrence of insulin resistance through affecting magnesium metabolism. Key Words: Insulin Resistance, Insulin Receptor, Magnesium

P-448 DOES GROWTH HORMONE HAVE A ROLE IN ESSENTIAL HYPERTENSION? ITS RELATIONSHIP WITH CIRCADIAN BLOOD PRESSURE AND INSULIN RESISTANCE Delia Garrido, Maia Akopian, Aurora Renauld, Antonio O. Olivieri, Adolfo Zavala, Carlos A. Feldstein. Hypertension Program, Hospital de Clinicas San Martin, Buenos Aires, Argentina. We recently reported (J Human Hypertens 2001) in patients with active acromegaly higher levels of serum growth hormone (GH) in normotensives and hypertensives with nondipper profile than in those with dipper profile. The aim of this study was to evaluate the role of GH and IGF-I in BP circadian rhythm regulation in essential hypertension and its relationship with insulin resistance. Seventy-eight glucose-tolerant (2hour plasma glucose ⬍140 mg/dL) mild-to-moderate hypertensive patients (SBPⱖ140 and/or DBPⱖ90 mm Hg (49.1⫾14.5 years) and 27 matched normotensive controls were included. They were assigned to a 2-hour oral glucose (75g)-tolerance test (OGTT). Insulin resistance was estimated by fasting insulin, fasting insulin/glucose ratio, the homeostasis model insulin resistance index (Homa’s index) and the sum of plasma insulin levels 0, 30, 60, and 120 min after the OGTT (⌺IRI). Serum GH and insulin-like growth factor-I were determined. Within 48 h of OGTT, 24-hour ambulatory blood pressure monitoring (ABPM) was performed. The patients who exhibited falls (⬎10%) in SBP and DBP during the 11 PM to 7 AM night-time period were classified as dippers, all those not exhibiting this characteristic being considered non-dippers. During the OGTT the mean insulin level, mean insulin:plasma glucose ratio, ⌺IRI and Homa’s index were significantly higher in hypertensives than those for normotensives whereas insulinogenic index was higher in normotensives than in hypertensives. Correlations of BP and insulin levels were not significant. There were 47 dippers and 31 nondippers. We found no significant differences in insulin resistance indices between these two types of circadian behavior of BP. Serum GH was higher in nondippers than in dippers (2.20 ⫾2.06 vs 0.32 ⫾ 0.48 ng/mL; p⬍0.03). In conclusion, our findings that essential hypertensives with a non-dipping profile have higher levels of serum GH suggest some role of this hormone in the circadian BP profile that does not seem to be related to insulin resistance. Key Words: GH, Insulin Resistance, ABPM