Low plasma renin activity in diabetes. Relation to urine prostaglandin excretion

Acute and chronic effects of thromboxane A2 inhibition on the renal hemodynamics in streptozotocin-induced diabetic rats

We examined acute and chronic effects of thromboxane (TX) A2 inhibition on the renal hemodynamics at early and late stage of untreated streptozotocin (STZ)-induced diabetic rats. Two weeks and 28 weeks after the induction of diabetes, renal blood flow (RBF) under anesthesia was measured with an electromagnetic flowmeter before and after TXA2 inhibition. In two-week-old diabetic rats, a specific TXA2 synthetase inhibitor, OKY-046, or a specific TXA2 receptor antagonist, Sulotroban, increased renal vascular resistance (RVR) and ameliorated the hyperperfusion. The renal vasoconstrictive effect of OKY-046 was blunted by an angiotensin converting enzyme (ACE) inhibitor, MK422, or an angiotensin II receptor antagonist, Saralasin. On the contrary, OKY-046 ameliorated the renal hypoperfusion by decreasing RVR in 28-week-old diabetic rats. Chronic oral administration of OKY-046 ameliorated not only the renal hyperperfusion but increased urinary albumin excretion (UAE) at two weeks, but also the renal hypoperfusion, filtration fraction and UAE at 24 weeks. It is suggested that TXA2 might, at least in part, play important roles in the hyperperfusion by modulating activity of the renin-angiotensin system at an early stage of untreated diabetic rats and in the hypoperfusion at the late stage of untreated diabetic rats, and that TXA2 is also involved in the increase of UAE. These results support roles for TXA2 in the progression of renal injury in STZ-induced diabetic rats.

Impaired response to angiotensin II in type 1 (insulin-dependent) diabetes mellitus. Role of prostaglandins and sodium-lithium countertransport activity

The pathogenesis of diabetic nephropathy remains elusive. A role for renal prostaglandins in antagonizing the hormonal effects of renin-angiotensin II has been postulated as a putative factor leading to hyperfiltration in patients with Type 1 (insulin-dependent) diabetes mellitus. Our aim was to elucidate the effects of angiotensin II on kidney haemodynamics and on blood pressure in eight normal subjects, in nine normotensive, in nine hypertensive with normal sodium-lithium countertransport activity in erythrocytes, in seven hypertensive without and in eight hypertensive Type 1 diabetic patients with microalbuminuria and with high sodium-lithium countertransport activity in erythrocytes. Angiotensin II infusion (4 ng.kg-1.min-1 for 60 min) decreased the glomerular filtration rate to a greater extent in normal subjects (-20%), than in normotensive patients (-5% p less than 0.01), in hypertensive patients with normal sodium-lithium countertransport activity in erythrocytes (-8% p less than 0.01) in hypertensive patients with high sodium-lithium countertransport (-6% p less than 0.01) and in hypertensive microalbuminuric patients (-5% p less than 0.01) with Type 1 diabetes. The urinary excretion rate of vasodilatory prostaglandins was two-three fold higher in all patients than in normal subjects. Acute indomethacin treatment restored a normal response to angiotensin II infusion in normotensive patients, but did not change the renal haemodynamic response in normal subjects. With regard to hypertensive patients with and without microalbuminuria indomethacin treatment restored a normal response to angiotensin II in some but not all patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma renin activity and urinary kallikrein excretion in response to intravenous furosemide in diabetic patients

The responsiveness of renin-angiotensin and kallikrein-kinin systems to furosemide challenge has been investigated in forty-six diabetic patients (34 NIDDM/12 IDDM), subdivided into Group I (uncomplicated DM), Group II (DM with hypertension), Group III (DM with nephropathy), Group IV (DM with hypertension and nephropathy) and a control group of 10 healthy volunteers. Plasma renin activity (PRA) was estimated by radioimmunoassay in blood samples drawn before and 10 min after furosemide administration (0.5 mg/kg i.v.). Urinary kallikrein levels were measured by bioassay using estrogenized rat uterus preparation in 4h urine samples collected before and after the diuretic. Urinary Na+ and K+ were also measured. The basal PRA in diabetics was not significantly different from controls, whereas, urinary kallikrein levels were markedly low in all patients. Both PRA and kallikrein levels increased after furosemide in controls while in diabetics this response was severely blunted. In a subset of Group I, a paradoxical fall in PRA and kallikrein levels was noted after furosemide, an effect similar to that observed in patients with nephropathy (Group III). This response in absence of clinical and biochemical parameters of nephropathy indicates early derangement of renal hemodynamic mechanisms heralding the onset of nephropathy.

Glomerular hyperfiltration and urinary prostaglandins in type 1 diabetes mellitus

In order to determine whether glomerular hyperfiltration in diabetes is related to renal prostaglandin production we have studied the urinary excretion of PGE2, 6-keto-PGF1 alpha, and TXB2 in two sex, age and duration of diabetes matched groups of 9 and 10 Type 1 diabetic patients with either normal (mean 121, range 105-129 ml min-1 1.73 m-2) or supranormal glomerular filtration rate (154, 135-206 ml min-1 1.73 m-2). A group of 15 matched healthy volunteers served as control subjects. Urine was collected overnight for an uninterrupted period of at least 6 h. All studies in the patients were performed during insulin-induced sustained euglycaemia to prevent the confounding effect of variable degrees of blood glucose control on urinary prostaglandin excretion. Blood pressure was normal in all subjects. Urinary excretion of 6-keto-PGF1 alpha was significantly higher in the patients with glomerular hyperfiltration (median 17.1, range 4.5-33.6 ng h-1) than in those without (8.8, 1.5-13.8 ng h-1; p less than 0.05) or in normal control subjects (9.6, 5.2-15.5 ng h-1; p less than 0.05). No significant differences were found in the excretion rates of PGE2 and TXB2 between the three groups. Under conditions of controlled plasma glucose and insulin concentrations the urinary excretion of 6-keto-PGF1 alpha, the stable breakdown product of PGI2, a compound of endothelial, possibly glomerular, origin was elevated only in the diabetic patients with glomerular hyperfiltration.

Sex differences in weight loss among adults with type II diabetes mellitus

The treatment of choice for Type II or non-insulin-dependent diabetes mellitus is a behavioral program for the management of weight. However, compliance with this lifelong dietary regimen is often poor. In the current investigation male and female adults with diagnosed Type II diabetes were randomly assigned to either a behavior modification, a cognitive modification, a cognitive-behavior modification, or a control group. Patients were evaluated in terms of weight, percentage of body fat, and glycosylated hemoglobin measures. Men lost significantly more weight than women and subjects in the behavior modification group lost more weight and demonstrated greater decreases in diabetes control than subjects in the cognitive-behavior modification, cognitive, and control groups. A significant interaction indicated that diabetic men may benefit more from behavioral weight reduction programs than diabetic women. Several explanations for these findings are considered.

Renal kallikrein in diabetic patients with hypertension accompanied by nephropathy

We measured the 24-h excretion of urinary kallikrein in 27 patients with Type 2 (non-insulin-dependent) diabetes and in 10 normal control subjects. Mean (+/- SD) kallikrein excretion in diabetic patients with nephropathy (6.2 +/- 2.4 naphthyl units (NU)/day, n = 13) was significantly lower than in control subjects (12.8 +/- 3.4 NU/day, p less than 0.01) and in diabetic patients without nephropathy (9.4 +/- 3.4 NU/day, n = 14, p less than 0.05). Kallikrein excretion in hypertensive diabetic patients with nephropathy (5.1 +/- 1.6 NU/day, n = 8) was significantly lower (p less than 0.05) than in normotensive patients with nephropathy (8.3 +/- 2.1 NU/day, n = 5). There were no significant differences in kallikrein excretion rate (24-h excretion of urinary kallikrein/24-h creatinine clearance) among control subjects (9.9 +/- 4.3 NU/ml), diabetic patients with (9.0 +/- 3.2 NU/ml) and without (9.3 +/- 3.5 NU/ml) nephropathy. However, kallikrein excretion rate in hypertensive diabetic patients with nephropathy (7.7 +/- 3.3 NU/ml) was significantly lower (p less than 0.05) than in normotensive diabetic patients with nephropathy (11.8 +/- 2.0 NU/ml, n = 10). Respective basal and post-stimulated (with intravenous furosemide 40 mg plus 60 min ambulation) plasma aldosterone concentrations measured in control subjects and in hypertensive diabetic patients with nephropathy were similar and increased to the same extent in the 2 groups (5.5 +/- 3.2 versus 5.3 +/- 3.2 and 9.3 +/- 2.6 versus 10.5 +/- 3.4 ng/ml), although the respective plasma renin activity tended to be lower in diabetic patients than in control subjects (0.7 +/- 0.6 versus 1.3 +/- 0.9 and 1.8 +/- 1.8 versus 3.0 +/- 2.6 ng-1 . ml-1 . h-1).(ABSTRACT TRUNCATED AT 250 WORDS)