Staffan Björck

Cholesterol: A Renal Risk Factor in Diabetic Nephropathy?

In a prospective follow-up of 30 patients with type 1 diabetes and nephropathy, serum cholesterol, triglycerides, apolipoprotein Al and B, and lipoprotein(a) were determined to study their relationship to the rate of decline in glomerular filtration rate. The patients had proteinuria and advanced nephropathy with a mean +/- SD glomerular filtration rate of 39 mL/min/1.73 m2. The decline in glomerular filtration rate was determined during 2.5 +/- 0.5 years. High serum cholesterol, triglycerides, and apolipoprotein B were correlated to a more rapid deterioration in kidney function. The rate of decline in glomerular filtration rate was 1.0 +/- 2.5 mL/min/yr in the 10 patients with the lowest cholesterol level, compared with 4.5 +/- 3.2 mL/min/yr in the patients with the highest serum cholesterol (P = 0.015). The combined effect of the measured lipids, blood pressure, type of antihypertensive treatment, protein intake, proteinuria, and hemoglobin A1C on the rate of decline in glomerular filtration rate was assessed by multiple regression analysis. The measured factors together had a high explanatory power for the rate of decline in glomerular filtration rate. In this model, 73% of the variation in decline in glomerular filtration rate was explained by the measured variables (multiple r2 = 0.73). Low cholesterol and treatment with an angiotensin-converting enzyme inhibitor were the strongest predictors of a favorable renal prognosis. This suggests that hypercholesterolemia is an important risk factor for diabetic nephropathy.

Extracorporeal (“ex vivo”) connection of pig kidneys to humans. I. Clinical data and studies of platelet destruction

Abstract: The pioneering experiment by Welsh et al. (Immunological Lett 1991:29:167–170) connecting a pig kidney to the human circulation has been repeated in a modified manner. Two volunteer dialysis patients were pretreated by daily plasmapheresis on days ‐2,‐1, and 0 to remove the naturally occurring anti‐pig xenoantibodies. The anti‐pig lymphocytotoxic liters were reduced from 1:8 to 1:2 in patient 1 and from 1:8 to 1:1 in patient 2. No steroids or immunosuppressive drugs were administrated before or during the experiments. A sterile pig kidney was extracorporeally (“ex vivo”) connected to the patients a/v fistula using an arterial and a venous pump similar to a dialysis. The two experiments gave different results. In the first experiment the perfusion pressure was kept at 100 mmHg for the initial 25 min by reducing the pump speed until the minimum blood flow of 30 ml/min was reached. Thereafter, the pressure rose continuously and the experiment was terminated at 65 min at a perfusion pressure of 200 mmHg. The patient did not feel any discomfort during the perfusion. In the second experiment, a stable blood flow of 200 ml/min was reached at a pressure of 100 mmHg after a few minutes. The perfusion was terminated at 15 min when the patient developed chest and abdominal pain, hypotension, and electrocardiographic signs of myocardial ischemia. The patient recovered quickly. In the first experiment, small volumes of clear urine was produced until the pressure rose above 100 mmHg, which resulted in hematuria. In the second experiment clear urine (4 ml/min) was produced. 51Chromium clearance values were after 15 min <1 ml/min for kidney 1 and 12 ml/min (8 ml/min/100 g) for kidney 2. A drastic reduction in platelet count (128 to 48 and 64 to 8 × 109/1, respectively) during the passage through the kidney was found in blood samples collected simultaneously before and after the organ. No change in hemoglobin values and leucocyte counts were found. Light‐ and electron‐microscopical analysis of the kidney tissues revealed for kidney 1 focal areas with obliteration of the glomerular and peritubular capillaries by platelets and PMN cells and severe damage of the endothelial cells comparable to a picture of a hyperacute rejection. In kidney 2, all vessels were patent but in the capillaries large amount of membrane fragments were detected by electron microscopy and a discrete damage of the endothelial cells were seen in some segments. No intact platelets were present in the vascular tree. These human experiments support the hypothesis that hyperacute rejection of pig to human xenografts is delayed in time by removal of the preformed anti‐pig xenoantibodies. A new finding was a very rapid destruction of platelets occurring in the kidney of patient 2 who had very low liters of xenoantibodies. The humoral immune response is described in detail in an accompanying paper (Rydberg et al., this issue).

Acute Renal Failure after Analgesic Drugs Including Paracetamol (Acetaminophen)

Seven patients with acute renal failure after ingestion of analgesic drug combinations including paracetamol were seen. They presented with oliguric renal failure and restitution of renal function was complete. Only 2 patients had severe liver damage and 2 patients had no signs of liver abnormality. Renal biopsies, studied by light and electron microscopy, in 3 patients showed focal tubular epithelial cell necrosis. Focal vascular damage, predominantly of endothelial cells, was also present in all specimens. This vascular injury was found in various locations in the kidney, including the glomerular and peritubular capillaries and small arterioles. This suggests that microvascular damage is an important mechanism for the renal injury after analgesic drugs.

Extracorporeal ("ex vivo") connection of pig kidneys to humans. II. The anti-pig antibody response.

Abstract: Pig kidneys were extracorporeally “ex vivo” connected to the circulation of two volunteer male dialysis patients (Breimer et al., this issue). The patients were pretreated by daily plasmapheresis for 3 consecutive days, which reduced the anti‐pig lymphocytotoxic titer from 8 to 2 in the first patient and from 8 to 1 in the second patient. The anti‐pig hemagglutinating titers were reduced from 32 to 4 in the first patient and from 2 to 1 in the second patient. No drugs, except heparin, were given. The perfusion lasted for 65 min in patient 1 and the experiment was terminated due to increased vascular resistance in the pig kidney. Ultrastructural investigation showed a picture similar to a hyperacute vascular rejection. Immunohistochemical studies showed a weak staining of IgM antibodies, but no IgG in the small arteries and glomeruli.

Cure of zygomycosis caused by a lipase-producing rhizopus rhizopodiformis strain in a renal transplant patient

A 40-year-old man with renal failure due to membranous glomerulonephritis received a cadaveric renal transplant and immunosuppressive therapy with cyclosporine, azathioprine and steroids. Initially the transplantation was successful. 12 days after the transplantation, however, serous secretion appeared in the wound. Later, black necrosis was seen. Fungal culture showed growth of a zygomycete species. Rhizopus rhizopodiformis, with high in-vitro resistance to amphotericin B, flucytosine, fluconazole, ketoconazole and itraconazole. The MIC value for the allylamine derivative SF86-327 (Exoderil) was 1.6 micrograms/ml. Microscopic examination of sections from a surgical revision showed necrosis of the fat tissue and massive hyphal invasion of the perirenal fat, which contained semi-crystalline material anisotropic as seen in polarized light and characteristically staining with rubeanic acid. These histological data indicate a lipase-induced in-vivo splitting of lipids into fatty acids. In-vitro R. rhizopodiformis showed very high extracellular lipase production. 11 days after initiation of amphotericin B therapy cultures and sections remained positive for rhizopus. Amphotericin B was therefore supplemented with Exoderil orally, cyclosporine and steroids were maintained, and azathioprine was discontinued. The wound granulated, shrank, and healed completely in 10 weeks.

Physiological and histological characterisation of a pig kidney in vitro perfusion model for xenotransplantation studies.

A pig kidney perfusion model aimed for use in immunological and physiological xenotransplantation research has been developed. Organ viability was characterised by clearance studies, functional response to hormones/diureticum and by light microscopical examination. The pig kidney was perfused in a specially designed plexiglass chamber, using a roller pump and a small membrane oxygenator (O2/CO2, 95/5). The recirculating perfusate used was autologous pig blood diluted by Tyrodes solution to a hematocrit of 30%, at a total starting volume of 600-650 ml. The temperature was 37 degrees C. It was crucial for good organ function that the nephrectomy operating time, as well as the warm (1-2 min) and cold ischemia (average 43 min) times were minimized. The average total perfusion time was 151 minutes. Physiological parameters were measured during 10-15 minute periods at average times of 40, 63, 88 and 142 minutes. The clearance values of inulin in these periods were 54 +/- 13, 59 +/- 15, 48 +/- 23, 27 +/- 5 and for PAH; 103 +/- 14, 121 +/- 14, 106 +/- 30, 114 +/- 34 ml/min/100 g tissue weight. The plasma flows were 123 +/- 12, 155 +/- 17, 136 +/- 36 and 206 +/- 57 ml/min/100 g. The injection of 0.5 micrograms of alpha ANP to the perfusate resulted in a significant decrease in vascular resistance, and increase in urine production (+107%), as well as sodium (+112%) and potassium (+46%) excretion. Ten mg furosemide doubled the urine production and sodium excretion, while potassium excretion increased marginally. The number of leucocytes decreased by 39% during the perfusion, while the platelet count was unaffected. Light microscopy of the renal tissue after termination of the experiments revealed endothelial damage to variable extent. Loss of endothelial cells was most obvious at the level of arcuate and interlobular arteries, while the endothelium was intact in larger arteries and veins. Accumulation of polymorphonuclear granulocytes was found predominantly in the peritubular vessels, and to a lesser degree in the cortical venules. In the tubular cells, only minimal epithelial swelling and irregular cytoplasmic vacuolisation was found. Thus, a good functional viability can be maintained during 2 hours in vitro perfusion, although a decline in function as well as structural damage can be seen at the end of the experiment.

Diabetes mellitus, the Renin-Angiotensin System, and Angiotensin-Converting Enzyme Inhibition

Many traditional antihypertensive drugs are linked to various effects that may cause concern in the hypertensive diabetic patient. The favorable tolerability of angiotensin-converting enzyme (ACE) inhibitors in essential hypertension makes it likely that they will be well tolerated when used in diabetic patients. Data from ongoing studies support the theory that ACE inhibitors lower blood pressure to the same extent in hypertensive diabetics as in patients with essential hypertension. ACE inhibitors do not seem to affect glucose homeostasis adversely; they may even improve glucose tolerance to a small degree. The renal effects of ACE inhibitors in animal experiments suggest a renal-protective effect that can make them especially valuable.

Renin Secretion in Advanced Diabetic Nephropathy.

Low basal and stimulated plasma renin activity (PRA) levels have been reported in patients with diabetic nephropathy (DN). We have measured PRA before and after stimulation with captopril in 28 patients with DN and in 25 control patients. Renal function impairment was similar in both groups. Most patients were treated with furosemide. In 19 patients with DN the PRA-response to dihydralazine was also studied. PRA before and after captopril were higher in the DN than in the control group (p less than 0.001). PRA increased from 4.6 +/- 3.6 to 6.3 +/- 5.3 in the DN, and from 1.8 +/- 2.7 to 2.7 +/- 3.4 in the control patients. The increases in PRA, caused by decreased angiotensin II feed-back inhibition, were comparable. PRA did not increase after dihydralazine despite a pronounced blood-pressure reduction. The difference in response to these stimuli indicate selective lesions involving both the sympathetic innervation and the renal baroreceptor function in DN. Overhydration is a plausible explanation to the low PRA earlier reported in DN. The results thus indicate that a preserved renin secretion capacity is present in DN. Differences in PRA between the both groups can only partly be explained by other factors than DN. Our findings indicate a role for the reninangiotensin-system in hypertension in DN.