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H G Preuss

Publications and source records attributed to H G Preuss.

At least 37 records · Page 2Linked to original sources
PubMed1998

Sugar-induced blood pressure elevations over the lifespan of three substrains of Wistar rats.

OBJECTIVE: Since the majority of studies concerned with sugar-induced blood pressure elevation have principally been short-term, the present investigation followed the effects of heavy sucrose ingestion on systolic blood pressure (SBP) and related parameters over the lifespan of three substrains of Wistar rats. METHODS: Two hundred twenty-five rats (75 spontaneously hypertensive rats (SHR), 75 Wistar Kyoto rats (WKY), 75 Munich Wistar rats (WAM) were given one of five diets. The baseline diet in terms of calories derived 32% from sucrose, 33% from protein, and 35% from fat. The remaining four diets derived their calories as follows: a high sugar-low protein diet--52% of calories from sucrose, 15% from protein, and 33% from fat; a high sugar-low fat diet--53% of calories from sucrose, 37% from protein, and 10% from fat; a low sugar-high protein diet--11% calories from sucrose, 56% from protein, and 33% from fat, and a low sugar-high fat--13% of calories from sucrose, 32% from protein, and 55% from fat. RESULTS: All substrains showed the highest systolic blood pressure when ingesting the two diets highest in sucrose. The highest sugar-induced SBP elevation, which remained over the lifespan of all substrains, was found in SHR. WKY had an intermediate elevation. WAM showed the lowest responses, although the average elevation of 6-8 mm Hg was statistically significant. The following parameters could not be correlated with long-term elevation of SBP; body weight, catecholamine excretion, renal function, and plasma renin activity. Only insulin concentrations correlated: insulin concentrations were consistently higher in the two groups of WKY and WAM consuming the high sucrose diets. CONCLUSIONS: High dietary sucrose can chronically increase SBP in three substrains of Wistar rats. Increased concentrations of circulating insulin were found in WKY and WAM suggesting that the glucose/insulin system was involved, at least in these two substrains, in the maintenance of high SBP levels during chronic, heavy sugar ingestion.

Animals↗
PubMed1998

Chromium update: examining recent literature 1997-1998.

Trivalent chromium is an essential nutrient required for sugar and fat metabolism. The majority of people eating typical Western diets consume less than the upper limit of the estimated safe and adequate daily dietary intake, which is set at 50-200 micrograms per day. Insufficient chromium intake is associated with signs and symptoms similar to those seen in diabetes and cardiovascular diseases. The efficacy of chromium in the general population relates to its prevention of deficiency or a reduction in the risk of chronic diseases. It is possible that doses above the estimated safe and adequate daily dietary intake are necessary for the treatment of certain chronic disease states. In a study performed in China, the use of 1000 micrograms of chromium per day (five times above the upper limit of the estimated safe and adequate daily dietary intake) was highly effective in relieving many of the symptomatic manifestations of type 2 diabetes mellitus, including a return of the HbA1C levels into the normal range. Most recent evidence strongly supports the conclusion that there is little fear of toxic reactions from chromium consumption. In addition to type 2 diabetes mellitus, chromium supplementation may be useful to direct overall weight decrements specifically towards fat loss with the retention of lean body mass and to ameliorate many manifestations of aging.

Aging↗
PubMed1997

Effects of diets containing different proportions of macronutrients on longevity of normotensive Wistar rats.

The present investigation examined effects of diets containing different proportions of macronutrients on longevity in two substrains of normotensive Wistar rats--Wistar Kyoto (WKY), the most widely accepted normotensive control for spontaneously hypertensive rats (SHR) and Munich Wistar rats (WAM as designated here). Each substrain was divided into five dietary groups composed of 15 rats each. Compared to a baseline diet composed of near equal calories of sucrose, fat, and protein, the remaining four diets were high sucrose-low protein, high sucrose-low fat, low sucrose-high protein, and low sucrose-high fat. Significantly higher systolic blood pressures were found in the two groups of WKY and WAM ingesting the high sucrose diets compared to the other three groups. The high sucrose groups were also hyperinsulinemic. Although only the group of WKY consuming the high sucrose-low fat diet showed a significantly shortened lifespan, the lifespan of WKY positively correlated with systolic blood pressure when data from all dietary groups were combined. WKY and WAM with an average systolic blood pressure exceeding 150 mm Hg had a significantly shorter lifespan than the rats with lower average blood pressure. Accordingly, elevated systolic blood pressure, especially when the blood pressure exceeds 150 mm Hg, significantly shortens lifespan.

Animal Nutritional Physiological Phenomena↗
PubMed1997

Diet, genetics and hypertension.

It is generally accepted that genetics play a significant role in the pathogenesis of hypertension. Since hypertension often follows kidney transplantation, candidate genes have been sought and found in the kidneys of rats and humans. One well-recognized, inherited influence on blood pressure (BP) occurs via abnormal renal sodium handling in vivo. Further, abnormal renal sodium handling is seen in isolated kidneys of genetically hypertensive rats. People who have a relative inability to handle a sodium load properly, and retain it inappropriately, often develop high BP and are referred to as "salt-sensitive". More than half of patients diagnosed with essential hypertension are salt-sensitive. In contrast to the deleterious effects associated with high sodium intake, many believe that ingestion of more potassium, calcium, and magnesium may influence BP favorably. The beneficial effects of these ions work, at least in part, through an effect on sodium balance, i.e. a diuretic influence. In support of this concept, they lower BP more effectively in salt-sensitive hypertensives. Refined carbohydrates and saturated fats are also associated with salt retention and hypertension. Thus, dietary factors, working directly on their own and/or indirectly via effects on genetic mechanisms, may alter BP favorably or unfavorably.

Animals↗
PubMed1997

Effects of glucose/insulin perturbations on aging and chronic disorders of aging: the evidence.

Among changes associated with aging is a decline in glucose tolerance. The reported causes are increased insulin resistance from receptor and/or post receptor disturbances and diminished pancreatic islet B-cell sensitivity to glucose. Many recent reports indicate that insulin resistance with hyperinsulinemia and/or hyperglycemia contribute to or even causes many chronic disorders associated with aging, i.e., chronic metabolic perturbations including noninsulin-dependent diabetes mellitus, obesity, hypertension, lipid abnormalities, and atherosclerosis. How could such disturbances in glucose/insulin metabolism lead to many chronic disorders associated with aging? In aging, similar to diabetes, the elevation in circulating glucose and other reducing sugars secondary to age-induced insulin resistance can react nonenzymatically with proteins and nucleic acids to form products that affect function and diminish tissue elasticity. Also, perturbations in glucose/insulin metabolism are associated with enhanced lipid peroxidation secondary to greater free radical formation. Free radicals of oxygen are important known causes of tissue damage and have been associated with many aspects of aging including inflammatory diseases, cataracts, diabetes, and cardiovascular diseases. Augmented free radical formation and lipid peroxidation are not uncommon in diabetes mellitus, commonly associated with "premature aging". Ingestion of sugars, fats, and sodium have been linked to decreased insulin sensitivity, while caloric restriction, exercise, ingestion of chromium, vanadium, soluble fibers, magnesium, and certain antioxidants are associated with greater insulin sensitivity. Thus, manipulation of diet by influencing the glucose/insulin system may favorably affect lifespan and reduce the incidence of chronic disorders associated with aging.

Aging↗
PubMed1997

Elevated blood pressure in spontaneously hypertensive rats consuming a high sucrose diet is associated with elevated angiotensin II and is reversed by vanadium.

OBJECTIVE: To determine the changes in serum angiotensin II (Ang II) and endothelin-1 levels induced by vanadium treatment of sugar-fed rats in order to investigate the relationship between changes in blood pressure and Ang II and endothelin-1 levels. METHODS: Male spontaneously hypertensive rats (SHR) were fed starch (control), sucrose, and sucrose plus vanadium compounds at various concentrations. The systolic blood pressure of the rats was estimated by tail-cuff plethysmography. Serum Ang II and endothelin-1 levels were measured by radioimmunoassay. RESULTS: There were increases in systolic blood pressure (by 8%) and in serum Ang II (by 20%) in sucrose-fed SHR compared with control. In sucrose plus vanadium-fed SHR, the lowering of the systolic blood pressure (by 11-16% of the sucrose-fed value) was accompanied by a significant decrease in Ang II levels (by 25-60% of the sucrose-fed value) and an increase in endothelin-1 level (by 61-76% of the sucrose-fed value). CONCLUSION: That Ang II levels are elevated in sucrose-induced hypertension and decreased after vanadium therapy suggests that the renin-angiotensin system plays a role in the induction of hypertension in this model. On the other hand, the elevation of endothelin-1 levels associated with a decreased systolic blood pressure might be secondary to vanadium stimulation of endothelial cells. The data suggest that endothelin-1 is not involved in sugar-induced elevations of the blood pressure.

Angiotensin II↗
PubMed1997

Effects of different chromium compounds on blood pressure and lipid peroxidation in spontaneously hypertensive rats.

In a previous study, we found that oral chromium nicotinate overcame sucrose-induced hypertension in spontaneously hypertensive rats (SHR). Accordingly, we examined more chromium compounds to determine if others were more or less effective in regulating blood pressure (BP) of SHR. Since chromium is postulated to be an antioxidant, we also assessed the ability of different chromium compounds to alter free radical formation measured by determining thiobarbituric acid reactive substances (TBARS). The control group of SHR ingested a diet low in chromium, and 5 other groups ate the same diet with various chromium compounds added at 5 ppm-chloride, acetate, nicotinic acid-glycine-cysteine-glutamic acid (NA-AA), picolinate, and nicotinate. Following this, the rats were challenged with drinking water containing 5% and 10% w/v sucrose. Except for NA-AA, all chromium compounds inhibited the sucrose-induced elevation of systolic BP; and acetate, picolinate, and nicotinate chromium compounds lowered HbAIC below control. Only chromium acetate and nicotinate significantly lowered both hepatic and renal TBARS. Chromium picolinate lowered hepatic TBARS, and chromium chloride and NA-AA lowered neither. We conclude that chromium, rather than a specific ligand, plays a major role in ameliorating sucrose-induced BP elevations and can act as an antioxidant.

Animals↗
PubMed1996

Association of macronutrients and energy intake with hypertension.

Hypertension, a major public health problem, becomes more prevalent during aging. Epidemiological studies suggest that environmental factors such as nutrition may play a major role in blood pressure (BP) regulation. It is generally accepted that obesity and sodium/alcohol consumption are important factors, and many believe that calcium, magnesium and potassium consumption are regulatory as well. Less emphasis has been placed on whether macronutrients influence blood pressure significantly. This review focused on the ability of excess calories and consumption of carbohydrates, fats, and proteins to regulate blood pressure.

Dietary Carbohydrates↗
PubMed1996

CD9 antigen mRNA is induced by hypertonicity in two renal epithelial cell lines.

In diverse organisms, cells adapt to hyperosmotic stress by accumulating organic osmolytes. Mammalian renal medullary cells are routinely under osmotic stress. Two renal cell lines, Madin-Darby canine kidney (MDCK) and PAP-HT25, have been widely used to study mammalian osmotic regulation. In these epithelial cells, extracellular hypertonicity induces gene transcription of proteins directly involved in the metabolism and transport of organic osmolytes. This induction is relatively specific and not part of a generalized stress response. Little is known about the signal transduction pathway between cellular detection of extracellular osmolality and increased specific gene transcription. Here, using differential mRNA display polymerase chain reaction on MDCK cells in isotonic vs. hypertonic medium, we identify a cDNA product corresponding to CD9 antigen mRNA. CD9 antigen is a cell surface glycoprotein originally found in cells of the immune system. Although CD9 antigen has been structurally characterized, its function is unclear. We further demonstrate that CD9 antigen mRNA is present in MDCK and PAP-HT25 cells and that its mRNA abundance is induced by extracellular hypertonicity, but not by heat stress. Also, we show that accumulation of organic osmolytes markedly attenuates the CD9 mRNA induction, as only recently demonstrated with genes involved in the hyperosmotic stress response. This suggests a role for CD9 antigen in this response.

Animals↗
PubMed1996

Adverse metabolic effects of antihypertensive drugs. Implications for treatment.

Adverse metabolic effects have been associated with drugs used in the therapy of hypertension, especially diuretics and beta-blockers. These effects include electrolyte, glucose/insulin, lipid and uric acid disturbances. This may explain, at least in part, why early trials examining the impact of antihypertensive pharmacotherapy with diuretics and beta-blockers showed beneficial effects on coronary artery disease that fell disappointingly short of the predicted effect. Among therapeutic drugs, diuretics cause disturbances in electrolyte homeostasis, e.g. hypokalaemia, hypomagnesaemia, and hyponatraemia. In contrast, ACE inhibitors cause hyperkalaemia under certain circumstances. Both diuretics and beta-blockers, especially nonselective beta-blockers that lack intrinsic sympathomimetic capabilities, have been associated with disturbances in glucose/insulin metabolism and can cause deleterious alterations in the profile of circulating plasma lipids. Hyperuricaemia, associated with diuretic use, appears to be a problem only in those patients who are predisposed to high circulating levels of uric acid.

Animals↗
PubMed1996

Effects of dietary sucrose and fibers on blood pressure in hypertensive rats.

In spontaneously hypertensive rats (SHR), two separate studies examined effects on systolic blood pressure (SBP) and other cardiovascular parameters of different concentrations of sucrose compared to starches, soluble fibers (guar, psyllium), and insoluble fibers (cellulose, wheat bran). In the initial study, four diets were tested. The first diet was relatively high in sucrose calories (50%) and low in protein calories (17%)--"high sucrose"; the second diet was relatively low in sucrose (11%) and high in protein (56%) calories--"low sucrose". The third and fourth diets resembled the first and second diets respectively, but cornstarch replaced sucrose--"high and low starch". Initial SBP in each group averaged approximately 168 mmHg. After 2 weeks of ingesting the special diets, SBP of the high sucrose group rose rapidly and significantly, eventually rising above 200 mmHg by the termination of examination. The other 3 groups maintained the original SBP until after the 3rd week when the low sucrose group developed a rapid and significant SBP elevation approaching 200 mmHg. SBP of high starch and low starch remained below 181 mmHg for the two months of study. Platelets obtained at the termination of the study from the sucrose groups compared to the starch groups showed increased aggregatory responses to collagen and ADP. Further, significant elevations of triglycerides and cholesterol in the high sucrose group were found. The former parameter was also significantly elevated in the low sucrose group. In the second study, adding guar and psyllium to high sucrose diets delayed sugar-induced hypertension, while cellulose and wheat bran virtually showed no effects. Serum insulin concentrations correlated positively with SBP, serum triglycerides, and glucose--not cholesterol. Accordingly, sucrose compared to starch ingestion in SHR can adversely influence SBP and various other cardiovascular risk factors. These effects can be delayed by the presence of soluble fibers, but not insoluble fibers, in the diets.

Animals↗
PubMed1995

Effects of chromium and guar on sugar-induced hypertension in rats.

Ingestion of sugars (sucrose, fructose, glucose) by various rat strains is associated with perturbations in the glucose/insulin system and higher systolic blood pressure (SBP). The association suggests causality, because alterations in insulin metabolism have been found in essential hypertension and many experimental forms of hypertension. To test the hypothesis that sugar-induced SBP elevation is secondary to perturbed insulin metabolism, we examined in 2 experiments effects of chromium and guar, substances known to affect insulin metabolism, on SBP of Spontaneously Hypertensive Rats (SHR). In both studies, sucrose compared to starch ingestion caused significant elevation of SBP; but addition of 2 chromium nicotinate complexes and guar prevented development of sugar-induced SBP elevations. The basal, genetic hypertension of the SHR was not affected by either nutrient. An additional finding in the first study was that sugar-consuming SHR supplemented with chromium had greater BW and increased organ weight (kidney, spleen, and liver) than nonsupplemented SHR. Accordingly, we have shown that two different mechanisms known to ameliorate insulin perturbations, use of chromium and guar, prevent sugar-induced SBP elevations. Since essential hypertension may be due to insulin perturbations and high dose chromium supplementation seems nontoxic, this may prove to be a useful means to lower blood pressure (BP) in some essential hypertensives, as well as diabetic hypertensives. Soluble fiber in the form of guar is also quite effective in favorably influencing sugar-induced SBP elevations.

Animals↗
PubMed1994

Effects of high sugar diets on renal fluid, electrolyte and mineral handling in rats: relationship to blood pressure.

OBJECTIVE: We examined whether sugar-induced systolic blood pressure (SBP) elevations in rats may develop, in part, through a mechanism common to salt-induced hypertension, i.e., renal retention of water and salt. DESIGN: Spontaneously hypertensive rats (SHR) ate four diets: two high (> 50% of calories) and two low (< 12% of calories) in sugar (sucrose). SBP, various urinary parameters, and the renal angiotensin and prostaglandin systems were assessed. RESULTS: SHR consuming diets high in sugar showed significantly decreased urinary volume and excretion of electrolytes, which coincided with increasing SBP. When low sugar diets replaced high sugar diets, SBP and urinary parameters rapidly returned to baseline. SHR received captopril while consuming high sugar diets, and both SBP and urinary parameters assumed baseline values, comparable to ones seen in SHR consuming low sugar diets. A direct angiotensin II receptor antagonist (DuPont 753) did not influence SBP. However, we found decreased PGE2 excretion in SHR consuming excess sugar. CONCLUSIONS: Salt and water retention occur early during sugar-induced hypertension due to reduced renal excretion, consistent with some part in the pathogenesis. The effects of high sugar diets on SBP were not due to angiotensin II inhibition, however, decreased availability of vasodilatory prostaglandins may play a role in the renal events and sugar-induced hypertension in SHR.

Animals↗
PubMed1994

Early lead challenge and subsequent hypertension in Sprague-Dawley rats.

OBJECTIVE: The consequences of chronic, low grade lead (Pb) burden from earlier exposure on development of hypertension (HT) and cardiovascular disease is, at best, controversial, even though many epidemiological studies suggest the possibility. Accordingly, we examined ability of a short-term Pb challenge to cause later developing HT in rats. METHODS: We gave 12 newly weaned Sprague-Dawley rats (SD) a 1% Pb acetate solution to drink for 6 weeks, while 12 control rats drank water. The rats were further subdivided into groups consuming high and low amounts of sugar. All rats were followed for 4 months after cessation of the Pb challenge. RESULTS: Early Pb challenge caused no significant changes in body weight (BW) from controls; however, systolic blood pressures (SBP) of rats initially receiving Pb continued to rise significantly above their respective dietary controls for months after cessation of challenge. While a high sugar diet alone was associated with elevated SBP, high sugar consumers also challenged with Pb had the highest SBP. Protein excretion did not increase, suggesting, along with other evidence, a lack of significant renal damage. CONCLUSIONS: Previous exposure to Pb can cause subsequent chronic elevations in SBP.

Animals↗
PubMed1994

Interplay between sugar and salt on blood pressure in spontaneously hypertensive rats.

Previous experience showed that sucrose ingestion exceeding 50% of total calories consistently increased systolic blood pressure (SBP) in rats, but ingesting 36 or 13% of calories as sucrose did not. In fact, the mean SBP of rats ingesting 36% of calories as sucrose was not different from rats ingesting 13% of calories as sucrose. This was not the case in the present study where the dietary salt content was increased. Adding dietary salt (NaCl) to raise low concentrations of Na (0.14% wt/wt) to higher concentrations (0.80% wt/wt) in diets with 36 and 13% of calories from sucrose significantly elevated SBP in spontaneously hypertensive rats eating both diets, but significantly more in the former. Accordingly, an interplay exists between sugar and salt in SBP regulation, and it is suggested that amounts of sugar characteristically consumed by an average human are capable of increasing BP. Composition of diets, especially with respect to sugar and salt, should be considered when interpreting results from studies on various aspects of hypertension.

Animals↗
PubMed1993

Comparative pharmacological, toxicological and antitumoral evaluation of free and liposome-encapsulated cisplatin in rodents.

The systemic toxicity and efficacy of cisplatin (CDDP) were examined in vitro and in vivo. Procedures were performed before and after the antineoplastic agent was encapsulated into multilamellar liposomes (L-CDDP). In vitro cytotoxicity evaluation in L1210 murine leukaemia and NIH OVCAR human ovarian cancer cells showed IC50 values of 0.14 and 0.05 micrograms/ml with CDDP or L-CDDP, respectively. In vivo, mice injected intravenously with L-CDDP had plasma levels of platinum 4-fold higher than with CDDP. The t1/2 alpha was 2 h and the t1/2 beta exceeded 48 h with L-CDDP; whereas a t1/2 alpha of 15 min and t1/2 beta of 12 h was observed with CDDP. The values of platinum in liver, spleen, kidneys, lungs and heart were substantially higher in L-CDDP-treated compared to CDDP-treated mice. Cytotoxic evaluation of both agents was tested in vitro (murine L1210 leukaemia and NIH OVCAR cell line) and in vivo (male CD2F1 mice). CDDP and L-CDDP showed similar cytotoxicity in tissue culture. At the highest dose given, 12 mg/kg intraperitoneally (i.p.), L-CDDP showed higher antitumour efficacy demonstrated by an increased life span of the mice. The CDDP treatment at the highest dose was lethal to all the tumour bearing mice. The nephrotoxicity in rats (blood urea nitrogen and creatinine evaluation) of L-CDDP administered i.p. was significantly less than with CDDP. In addition, the ability of kidney slices to transport organic anions [para-aminohippurate (PAH)] and consume O2 was substantially decreased in rats treated with free CDDP compared to L-CDDP. Accordingly, the liposomal encapsulation of CDDP attenuates its nephrotoxicity, but allows maintenance of antitumour efficacy and may be a potentially effective modality in clinical settings.

Animals↗
PubMed1993

Rabbit and human renotropin are not epidermal growth factor.

Sera obtained from rabbits and humans after unilateral nephrectomy (uni sera) compared with sera obtained preoperatively (control sera) significantly stimulate 3H-thymidine incorporation into the DNA of cultured renal tissue from the respective species. In contrast, rabbit liver cells in culture are not stimulated by the uni sera compared with control sera obtained from rabbits. Mouse epidermal growth factor (EGF) added to tissue cultures significantly stimulates both kidney and liver cells of rabbits and kidney cells of humans. Antiserum against EGF overcomes, at least to some extent, the enhancing effect of EGF under all circumstances, but does not influence the stimulatory ability of uni serum obtained from rabbit and human kidney cells from the respective species. In addition, the activity of EGF was not different in the presence of uni and control sera. This study corroborates the presence of renotropic activity in the sera of rabbits and humans after removal of functioning renal mass and shows that this activity is not derived from EGF, nor does it work by potentiating some aspect of the EGF system.

Animals↗