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Biomedical subjects

R S Kushwaha

Publications and source records attributed to R S Kushwaha.

At least 19 recordsLinked to original sources
PubMed1999

Chronic physiologic hyperinsulinemia impairs suppression of plasma free fatty acids and increases de novo lipogenesis but does not cause dyslipidemia in conscious normal rats.

Type 2 diabetes mellitus and obesity are characterized by fasting hyperinsulinemia, insulin resistance with respect to glucose metabolism, elevated plasma free fatty acid (FFA) levels, hypertriglyceridemia, and decreased high-density lipoprotein (HDL) cholesterol. An association between hyperinsulinemia and dyslipidemia has been suggested, but the causality of the relationship remains uncertain. Therefore, we infused eight 12-week-old male catheterized conscious normal rats with insulin (1 mU/min) for 7 days while maintaining euglycemia using a modification of the glucose clamp technique. Control rats (n = 8) received vehicle infusion. Baseline FFAs were 1.07+/-0.13 mmol/L, decreased to 0.57+/-0.10 (P < .05) upon initiation of the insulin infusion, and gradually increased to 0.95+/-0.12 by day 7 (P = NS vbaseline). On day 7 after a 6-hour fast, plasma insulin, glucose, and FFA levels in control and chronically hyperinsulinemic rats were 32+/-5 versus 116+/-21 mU/L (P < .005), 122+/-4 versus 129+/-8 mg/dL (P = NS), and 1.13+/-0.18 versus 0.95+/-0.12 mmol/L (P = NS); total plasma triglyceride and cholesterol levels were 78+/-7 versus 66+/-9 mg/dL (P = NS) and 50+/-3 versus 47+/-2 mg/dL (P = NS), respectively. Very-low-density lipoprotein (VLDL) + intermediate-density lipoprotein (IDL), low-density lipoprotein (LDL), and HDL2 and HDL3 subfractions of plasma triglyceride and cholesterol were similar in control and hyperinsulinemic rats. Plasma FFA correlated positively with total (r = .61, P < .005) triglycerides. On day 7 after an 8-hour fast, hyperinsulinemic-euglycemic clamps with 3-3H-glucose infusion were performed in all rats. Chronically hyperinsulinemic rats showed peripheral insulin resistance (glucose uptake, 15.8+/-0.8 v 19.3+/-1.4 mg/kg x min, P < .02) but normal suppression of hepatic glucose production (HGP) compared with control rats (4.3+/-1.0 v 5.6+/-1.4 mg/kg x min, P = NS). De novo tissue lipogenesis (3-3H-glucose incorporation into lipids) was increased in chronically hyperinsulinemic versus control rats (0.90+/-0.10 v 0.44+/-0.08 mg/kg x min, P < .005). In conclusion, chronic physiologic hyperinsulinemia (1) causes insulin resistance with regard to the suppression of plasma FFA levels and increases lipogenesis; (2) induces peripheral but not hepatic insulin resistance with respect to glucose metabolism; and (3) does not cause an elevation in VLDL-triglyceride or a reduction in HDL-cholesterol.

Animals↗
PubMed1998

Effect of naturally reduced ovarian function on plasma lipoprotein and 27-hydroxycholesterol levels in baboons (Papio sp.).

Female baboons over 15 years of age develop irregular menstrual cycles, an indication of declining ovarian function similar to that occurring in perimenopausal women. To determine the effect of declining ovarian function on plasma lipoprotein metabolism and plasma oxysterols, we measured plasma lipoprotein and 27-hydroxycholesterol levels in 86 female baboons from 15-28 years of age with regular (n = 51) and irregular (n = 35) menstrual cycles. We sampled blood and liver while they were consuming a basal diet and after consuming a high cholesterol and high fat diet for 7 weeks. On the basal diet, baboons with irregular cycles had higher VLDL + LDL/HDL cholesterol ratios (P = 0.034). After consuming the HCHF diet for 7 weeks, total plasma (P < 0.001) and VLDL + LDL (P < 0.001) cholesterol concentrations and VLDL + LDL/HDL sterol ratios (P < 0.001) increased in both cycle groups; whereas HDL cholesterol concentrations increased only in baboons with regular cycles (P = 0.009). As a result, HDL cholesterol concentrations (P = 0.006) were lower and VLDL + LDL/HDL cholesterol ratios (P = 0.002) were higher in baboons with irregular cycles on the HCHF diet. Plasma 27-hydroxycholesterol concentrations were higher in baboons with regular cycles than in those with irregular cycles on both basal (P = 0.018) and HCHF (P = 0.037) diets and were positively correlated (P < 0.001) with hepatic sterol 27-hydroxylase activities on both diets. Hepatic sterol 27-hydroxylase activities were negatively correlated with the VLDL + LDL/HDL cholesterol ratios on the HCHF diet (r = -0.342, P = 0.033). These results suggest that declining ovarian function changes the plasma lipoprotein pattern to one that is more atherogenic. Ovarian failure is also associated with decreased concentrations of plasma 27-hydroxycholesterol (the major oxysterol of plasma), and the decrease in plasma 27-hydroxycholesterol concentration was due to the decrease in hepatic sterol 27-hydroxylase activity. The effects of ovarian failure on plasma lipoprotein metabolism and plasma 27-hydroxycholesterol may be mediated by the decreased production of estrogen in perimenopausal baboons. Thus, the perimenopausal baboon is an excellent model for menopause and can be used for studies that cannot be conducted in women.

Animals↗
PubMed1998

Effect of dietary lipids on hepatic and extrahepatic sterol 27-hydroxylase activity in high- and low-responding baboons.

Our previous studies found that low low-density lipoprotein (LDL)-responding baboons compared with high LDL-responding baboons have higher hepatic sterol 27-hydroxylase activity when consuming a high-cholesterol and high-fat (HCHF) diet. The present studies were conducted to determine whether the extrahepatic activity of sterol 27-hydroxylase is also higher in low-responding baboons and to assess whether the enzyme is regulated at the protein level. We measured the hepatic sterol 27-hydroxylase activity and protein level and plasma 27-hydroxycholesterol concentration in six low- and six high-responding baboons on both the basal and the HCHF diet. We also compared the sterol 27-hydroxylase activity in the adrenal gland and 27-hydroxycholesterol concentration in blood lymphocytes from high- and low-responding baboons consuming the HCHF diet. With the HCHF diet, the plasma 27-hydroxycholesterol concentration and hepatic sterol 27-hydroxylase activity and protein level increased rapidly in low responders, but not in high responders. Blood lymphocytes of low-responding baboons cultured in the presence of lipoprotein-deficient serum (LPDS) had lower cholesterol concentrations than those from high-responding baboons. Addition of exogenous 27-hydroxycholesterol to the culture medium of blood lymphocytes decreased the cellular cholesterol concentration. Plasma 27-hydroxycholesterol and hepatic sterol 27-hydroxylase activity and protein levels were negatively correlated with the plasma VLDL + LDL cholesterol concentration and VLDL + LDL/HDL cholesterol ratio after 6 weeks on the HCHF diet, but not on the chow diet. The results suggest that sterol 27-hydroxylase activity in both hepatic and extrahepatic tissues attenuates the dietary responsiveness in baboons, and the enzyme activity is not regulated by the specific activity of the protein.

Adrenal Glands↗
PubMed1996

Effect of estrogen and progesterone on the expression of hepatic and extrahepatic sterol 27-hydroxylase in baboons (Papio sp).

Sterol 27-hydroxylase plays an important role in cholesterol metabolism in hepatic and extrahepatic tissues. To determine whether female sex steroid hormones influence its expression, we measured plasma and hepatic 27-hydroxycholesterol, hepatic mRNA levels, activity of sterol 27-hydroxylase, and adrenal mRNA levels of this enzyme in baboons (n = 6 per group) treated with placebo, estrogen, estrogen + progesterone, and progesterone. We also measured hepatic cholesterol concentration and hepatic acyl coenzyme A:cholesterol acyltransferase (ACAT) activity to determine their relationship with hepatic sterol 27-hydroxylase activity. Plasma 27-hydroxycholesterol concentration was increased by estrogen and estrogen + progesterone and was negatively correlated with plasma (P = .090) and LDL (P = .026) cholesterol concentrations. Similarly, hepatic sterol 27-hydroxylase activity was increased by estrogen and estrogen + progesterone and was negatively correlated with plasma (P = .056) and LDL (P = .052) cholesterol concentrations but was positively correlated with hepatic and plasma 27-hydroxycholesterol concentrations (P < .001). Hepatic ACAT activity was increased by progesterone (P < .004) and was positively correlated with plasma (P = .002) and LDL (P = .009) cholesterol concentrations but was negatively correlated with hepatic sterol 27-hydroxylase activity (P = .035). Hepatic and adrenal gland mRNA levels for sterol 27-hydroxylase were increased by estrogen alone or in combination with progesterone (P < .05). Hepatic sterol 27-hydroxylase activity was positively correlated with hepatic mRNA levels (P < .001), an observation suggesting that estrogen increases the activity of sterol 27-hydroxylase by increasing its synthesis. Hepatic cholesterol concentration was not influenced by the hormone treatment. These observations suggest that estrogen alone or in combination with progesterone increases the synthesis of sterol 27-hydroxylase in hepatic and extrahepatic tissues, and the increased activity of hepatic sterol 27-hydroxylase resulting from the increased synthesis is associated with a hypolipidemic effect on plasma LDL levels. Furthermore, progesterone alone increases the hepatic ACAT activity, but given in combination with estrogen progesterone does not have the same effect on hepatic ACAT activity. The effect of estrogen on hepatic ACAT activity may be mediated by sterol 27-hydroxylase and its effect on cholesterol metabolism (decreased cholesterol synthesis and increased output of cholesterol in the bile) in liver.

Adrenal Glands↗
PubMed1995

Relationships of plasma and hepatic variables with rates of plasma low-density lipoprotein apolipoprotein B metabolism in baboons fed low- and high-fat diets.

These studies were conducted to determine relationships of plasma low-density lipoprotein (LDL) cholesterol concentrations and hepatic mRNA levels for apolipoprotein (apo) B, LDL receptor, and hepatic hydroxymethyl glutaryl coenzyme A (HMG CoA) synthase with plasma LDL apo B production and catabolic rates in baboons maintained on a low-cholesterol, low-fat chow diet and on a high-cholesterol, high-fat (HCHF) diet. Twelve baboons with LDL cholesterol levels ranging from low to high on the HCHF diet but with similar high-density lipoprotein (HDL) cholesterol levels were selected from a colony of selectively bred pedigreed baboons. LDL apo B turnover and hepatic mRNA concentrations for apo B, LDL receptor, and HMG CoA synthase were measured on a chow diet and again on a HCHF diet fed for 14 weeks. LDL apo B fractional catabolic rates decreased and production rates increased on the HCHF diet. Hepatic mRNA concentrations for apo B were not affected by the HCHF diet. Hepatic LDL receptor and HMG CoA synthase mRNA concentrations decreased on the HCHF diet as compared with the chow diet. LDL apo B fractional catabolic rate was negatively correlated with plasma cholesterol, LDL cholesterol, LDL apo B, and LDL apo B production and positively correlated with hepatic LDL receptor and HMG CoA synthase mRNA concentrations and with plasma LDL triglyceride to cholesterol ratio on the chow diet but not on the HCHF diet. LDL apo B production was positively correlated with plasma cholesterol, LDL cholesterol, and LDL apo B on the HCHF diet and negatively correlated with LDL triglyceride to cholesterol ratio on both chow and HCHF diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Effect of dietary cholesterol and fat on the expression of hepatic sterol 27-hydroxylase and other hepatic cholesterol-responsive genes in baboons (Papio species).

Our studies of baboons with low and high responses to dietary cholesterol and fat suggest that low-responding baboons increase the activity of hepatic sterol 27-hydroxylase, an important enzyme of bile acid synthesis, considerably more than do high-responding baboons when challenged with a high-cholesterol, high-fat (HCHF) diet. The present studies were conducted to determine whether hepatic sterol 27-hydroxylase mRNA levels and plasma 27-hydroxycholesterol concentrations also differed with dietary responsiveness. Sixteen adult male baboons with a wide range of VLDL cholesterol plus LDL cholesterol (VLDL+LDL cholesterol) response to an HCHF diet were selected. They were examined first while on a chow diet and then after 1, 3, 6, 10, 18, 26, 36, 52, 72, and 104 weeks on the HCHF diet. Plasma and lipoprotein cholesterol concentrations increased rapidly during the first 3 weeks and stabilized thereafter. On the basis of the response in VLDL/LDL cholesterol, we selected five low-responding, four medium-responding, and five high-responding baboons for more intensive study in more detail. In low responders, the major increase in serum cholesterol concentration was in HDL cholesterol, whereas in medium and high responders it was in both VLDL+LDL and HDL cholesterol. In low and medium responders, serum or VLDL+LDL cholesterol did not change after 3 weeks of consumption of the HCHF diet, whereas in high responders VLDL+LDL cholesterol declined between 78 and 104 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Individuality of lipemic responses to diet.

The objective of this review is to assemble reports dealing with variability in the lipemic responses of both humans and experimental animal models to dietary fat and cholesterol; to extract indications of the metabolic processes controlling responsiveness; and, if possible, identify allelic variations in genes that are responsible for these difference in responses to diet. There is strong evidence of genetic control of lipemic responsiveness to dietary fat and cholesterol in several animal species (rabbit, swine, mouse, marsupial, squirrel monkey, rhesus monkey, cynomolgus monkey and baboon). Variations in bile acid secretion and cholesterol absorption are the metabolic variables most commonly associated with responsiveness. The metabolic process most frequently associated with human responsiveness is low density lipoprotein apoB production rate. The mechanism controlling dietary responsiveness varies among species and, in humans, probably among individuals. No genetic polymorphism is unequivocally identified as responsible for individual variability.

Animals↗
PubMed1994

Effect of dietary lipids on plasma activity and hepatic mRNA levels of cholesteryl ester transfer protein in high- and low-responding baboons (Papio species).

We compared the effects of dietary cholesterol, type of fat (coconut oil v corn oil), and phenotype (low low-density lipoprotein [LDL] response v high LDL response) on the plasma activity and hepatic mRNA levels of cholesteryl ester transfer protein (CETP). In a crossover design, eight high- and eight low-LDL-responding baboons were fed a series of diets with increasing amounts of cholesterol (0.05, 0.15, 0.45, and 1.35 mg/kcal) with either coconut oil or corn oil. All diets were fed for 7 weeks each. plasma and lipoprotein cholesterol concentrations, plasma lecithin:cholesterol acyltransferase (LCAT) and CETP activity, and hepatic mRNA levels for CETP and apolipoprotein (apo) A-I were measured after 6 weeks on each diet. Data were analyzed in two steps, ie, the effect of the initial change from chow to 0.05 mg cholesterol with each fat and the effect of the stepwise increase in cholesterol from 0.05 to 1.35 mg/kcal with each fat. High-responding baboons, as expected, showed a more pronounced increment in plasma LDL cholesterol at all dietary cholesterol levels, particularly with coconut oil as the dietary fat. Plasma high-density lipoprotein 2 (HDL2) and HDL3 cholesterol increased as dietary cholesterol increased on both the coconut and corn oil diets, with a greater increase in high-responding baboons than in low-responding baboons. The stepwise increase in dietary cholesterol increased plasma LCAT activity in both high- and low-responding baboons fed the coconut oil diet, but not in those fed the corn oil diet. Dietary cholesterol, regardless of type of fat, increased plasma CETP activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Metabolic mechanisms for responses to dietary cholesterol and fat in high and low LDL responding baboons (Papio sp.).

These studies were conducted to determine how plasma low density lipoprotein (LDL) cholesterol levels respond to dietary cholesterol, fed in increasing amounts with either corn oil or coconut oil diets, in high as compared to low LDL responding baboons; and to determine how apolipoprotein (apo) B transcription levels are modulated in response to dietary lipids. Eight high and eight low LDL responding pedigreed adult baboons, balanced for sire, age, sex, and weight, were challenged for successive 7-week periods with increasing levels of dietary cholesterol combined with either coconut oil or corn oil. At the end of each dietary period, plasma and lipoprotein lipids, apoB, apoA-I, and hepatic mRNA levels for apolipoproteins were measured. As dietary cholesterol increased, plasma cholesterol concentrations (mostly LDL cholesterol) increased in both phenotypes and with both types of fat, but phenotypic differences were greater with coconut oil. There was not a consistent dose-response relationship of plasma or LDL cholesterol levels to increasing intakes of dietary cholesterol. Neither dietary cholesterol, type of dietary fat, nor LDL phenotype affected hepatic apoB or apoE mRNA levels. In a second experiment to resolve the inconsistent dose-response to dietary cholesterol, we fed the animals varying levels of dietary cholesterol combined with coconut oil, and separated the challenge periods with intervening 12-week chow periods. Plasma and LDL cholesterol and apoB concentrations rose consistently with increasing dietary cholesterol, and the slope of the increase diminished at the higher doses. The results suggest that genetic differences in the initial response of LDL cholesterol to dietary cholesterol and saturated fatty acids are not due to the differences in hepatic transcription of apoB, and that the preceding dietary intake of cholesterol and saturated fatty acids is a major determinant of the response of plasma lipids and the associated metabolic processes to a dietary challenge. The response of baboon plasma LDL cholesterol concentrations to dietary cholesterol, when fed with saturated fatty acids, is similar to that of humans.

Animals↗
PubMed1993

Differences in 27-hydroxycholesterol concentrations in plasma and liver of baboons with high and low responses to dietary cholesterol and fat.

Selective breeding has produced baboon progeny that have low or high response in plasma low-density lipoprotein (LDL) cholesterol when fed a high cholesterol and high fat (HCHF) diet. We examined differences in bile acid metabolism between low and high responding baboons by measuring the most abundant oxysterol in plasma and liver. Low responding baboons had higher concentrations of plasma and liver 27-hydroxycholesterol than high responding baboons on the HCHF diet but not on the chow diet. The increased hepatic 27-hydroxycholesterol in low responders was associated with an increase in sterol 27-hydroxylase activity as compared to high responders. These studies suggest that the hepatic sterol 27-hydroxylase is induced by dietary cholesterol and this induction is much higher in low responding baboons.

Animals↗
PubMed1993

The role of cholesterol absorption and hepatic cholesterol content in high and low responses to dietary cholesterol and fat in pedigreed baboons (Papio species).

Selective breeding has produced baboon families with low and high plasma cholesterol responses to dietary cholesterol and fat. We used 12 high- and 12 low-responding (mainly in low-density lipoprotein [LDL] cholesterol) pedigreed baboons to determine whether cholesterol absorption and hepatic cholesterol concentration are associated with these responses. We measured cholesterol absorption first on the chow diet, which was low in cholesterol and fat, and after 3 and 13 weeks on the challenge diets, which contained 0.45 mg cholesterol/kcal and 40% of calories as either coconut oil or corn oil. Plasma, lipoprotein, and hepatic cholesterol concentrations were measured 1 week after cholesterol absorption measurements. High-responding baboons had higher percentage cholesterol absorption than low-responding baboons on both chow and challenge diets, regardless of the type of dietary fat. Both high and low responders had higher percentage cholesterol absorption with corn oil than with coconut oil. High responders also had higher hepatic cholesterol concentrations than low responders on chow and after consuming the challenge diets for 4 weeks. After consuming the challenge diets for 14 weeks, low responders fed coconut oil had hepatic cholesterol levels equal to those of high responders, while low responders fed corn oil continued to have low hepatic cholesterol levels. Thus, percentage cholesterol absorption is consistently higher in high-responding baboons regardless of diet, but hepatic cholesterol concentration varies with duration of challenge and type of fat. The results suggest that both cholesterol absorption and hepatic cholesterol concentration regulate cholesterolemic responses to diet, but by different mechanisms.

Animals↗
PubMed1993

Characterization of cholesteryl ester transfer protein inhibitor from plasma of baboons (Papio sp.).

Selective breeding has produced families of baboons that accumulate large high density lipoproteins (HDL1) when challenged with a high cholesterol and high fat (HCHF) diet. In the plasma isolated from these high HDL1 baboons there is a factor that decreases the transfer of cholesteryl ester from HDL to lower density lipoproteins. The purpose of these studies was to identify and characterize this inhibitor of cholesteryl ester transfer. A protein with molecular mass of approximately 4 kDa was detected in greater amounts in the plasma lipoproteins of high HDL1 baboons fed the HCHF diet than in plasma lipoproteins of low HDL1 baboons. This 4 kDa protein appeared to associate with apolipoprotein (apo) A-I, resulting in modified apoA-I with an apparent molecular mass of 31 kDa. A small amount of modified apoE was also identified with a molecular mass of 41 kDa. N-terminal amino acid sequencing of the 4 kDa peptide identified it as an N-terminal fragment of apoC-I. Like apoC-I, the fragment is also a slightly basic protein (pI 7.1). The apoC-I fragment and modified apoA-I presented at equimolar concentrations exhibited similar inhibition of cholesteryl ester transfer protein (CETP) activity in HDL of low HDL1 baboons. On the basis of baboon apoC-I amino acid sequence and the molecular mass of the inhibitor peptide, a peptide corresponding to the N-terminal 38 amino acids of apoC-I was synthesized chemically. This synthetic peptide also inhibited CETP activity in vitro. Rabbit polyclonal antisera prepared against the 38 amino acid synthetic peptide recognized the 4 kDa molecular mass inhibitor protein, apoC-I (6.6 kDa), and the modified apoA-I protein (31 kDa molecular mass) in the plasma lipoproteins of high HDL1 baboons. On the other hand, the antibody detected only apoC-I in the plasma lipoproteins of low HDL1 baboons. The IgG fraction isolated from antiserum raised against the synthetic inhibitor peptide increased cholesteryl ester transfer from HDL of high HDL1 baboons, whereas the IgG antibody against CETP decreased cholesteryl ester transfer from HDL of both high and low HDL1 baboons. These studies suggest that the CETP inhibitor is an N-terminal fragment of apoC-I, and this fragment also modifies apoA-I and apoE in the plasma.

Amino Acid Sequence↗
PubMed1992

Metabolism of apolipoprotein B in members of a family with accelerated atherosclerosis: influence of apolipoprotein E-3/E-2 pattern.

Familial combined hyperlipidemia (FCHL) appears to be the most common, simply inherited hyperlipidemia strongly associated with coronary heart disease. In the family examined in this study, two of the siblings who met diagnostic criteria for FCHL had extensive clinical atherosclerosis before age 30, unusually premature for this form of hyperlipidemia. Lipoproteins and low-density lipoprotein (LDL) apolipoprotein (apo) B metabolism were characterized in these siblings in an attempt to gain insight into the cause of the rapid atherosclerosis in the two siblings so affected. LDL apo B production rates were very high in all three siblings (25 to 30 mg/kg/d), consistent with FCHL. beta-Very-low-density lipoprotein-beta (beta-VLDL) was present in the plasma of both siblings with accelerated atherosclerosis. The isoapolipoprotein E pattern in both of these siblings was E-3/E-2. In the third sibling, who was free of premature clinical atherosclerosis and lacked plasma beta-VLDL, the pattern was E-3/E-3. Thus, the heterozygote apo E-3/E-2 pattern may be related to the accumulation of beta-VLDL in persons with a very high apo B production rate. The abnormal accumulation of beta-VLDL may be one of the possible explanations for the rapid, premature atherosclerosis in the two siblings with FCHL in this kindred. Both male members in this kindred also had low levels of high-density lipoproteins, and thus may have had an additional risk of developing atherosclerosis due to this lipoprotein abnormality as well.

Adult↗
PubMed1991

Effect of estrogen and progesterone on the hepatic cholesterol 7-alpha-hydroxylase activity in ovariectomized baboons.

Cholesterol 7 alpha-hydroxylase activity was measured in livers from ovariectomized baboons fed a high cholesterol high saturated fat diet and maintained in four groups: untreated controls, estrogen (100 micrograms/g per week), progesterone (3 mg/kg per day) and estrogen + progesterone. Estrogen treatment alone increased hepatic 7 alpha-hydroxylase activity by 2.7-fold, whereas progesterone treatment alone did not influence hepatic 7 alpha-hydroxylase activity. The increase in 7 alpha-hydroxylase activity in estrogen + progesterone group was similar to that in the estrogen group.

Animals↗
PubMed1991

Metabolic regulation of plasma apolipoprotein E by estrogen and progesterone in the baboon (Papio sp).

Apolipoprotein (apo) E plays an important role in the metabolism of lipoproteins. To determine the effects of estrogen and progesterone on plasma levels and metabolism of apo E, we used 12 ovariectomized baboons fed a cholesterol- and fat-enriched diet. These baboons were divided into four groups and treated with estrogen, progesterone, estrogen + progesterone, and a placebo control. After 10 months, although the lipid levels were not different among the treatment groups, low-density lipoprotein (LDL)/high-density lipoprotein (HDL) ratios in the estrogen + progesterone group were significantly lower than those in the control and progesterone groups. Estrogen alone or in combination with progesterone decreased plasma apo E levels significantly compared with those in the control group. Plasma apo E levels in the progesterone group were similar to those in the control group. In all groups, most (greater than 60%) of the apo E was present in HDL. HDL apo E concentrations in the estrogen and estrogen + progesterone groups were significantly lower than those in the control and progesterone groups. To determine the metabolic mechanisms of these changes in apo E levels, turnover studies were conducted by injection of iodinated apo E-labeled very-low-density lipoprotein (VLDL) and HDL. Residence times were calculated using multicompartment modeling. Progesterone alone and in combination with estrogen decreased residence times of apo E injected in both HDL and VLDL compared with estrogen alone and control groups. Progesterone alone also increased the apo E production rate compared with other groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Influence of dietary lipids on hepatic mRNA levels of proteins regulating plasma lipoproteins in baboons with high and low levels of large high density lipoproteins.

Selective breeding of baboons has produced families with increased plasma levels of large high density lipoproteins (HDL1) and very low (VLDL) and low (LDL) density lipoproteins when the animals consume a diet enriched in cholesterol and saturated fat. High HDL1 baboons have a slower cholesteryl ester transfer, which may account for the accumulation of HDL1, but not of VLDL and LDL. To investigate the mechanism of accumulation of VLDL + LDL in plasma of the high HDL1 phenotype, we selected eight half-sib pairs of baboons, one member of each pair with high HDL1, the other member with little or no HDL1 on the same high cholesterol, saturated fat diet. Baboons were fed a chow diet and four experimental diets consisting of high and low cholesterol with corn oil, and high and low cholesterol with lard, each for 6 weeks, in a crossover design. Plasma lipids and lipoproteins and hepatic mRNA levels were measured on each diet. HDL1 phenotype, type of dietary fat, and dietary cholesterol affected plasma cholesterol and apolipoprotein (apo) B concentrations, whereas dietary fat alone affected plasma triglyceride and apoA-I concentrations. HDL1 phenotype and dietary cholesterol alone did not influence hepatic mRNA levels, whereas dietary lard, compared to corn oil, significantly increased hepatic apoE mRNA levels and decreased hepatic LDL receptor and HMG-CoA synthase mRNA levels. Hepatic apoA-I message was associated with cholesterol concentration in HDL fractions as well as with apoA-I concentrations in the plasma or HDL. However, hepatic apoB message level was not associated with plasma or LDL apoB levels. Total plasma cholesterol, including HDL, was negatively associated with hepatic LDL receptor and HMG-CoA synthase mRNA levels. However, compared with low HDL1 baboons, high HDL1 baboons had higher concentrations of LDL and HDL cholesterol at the same hepatic mRNA levels. These studies suggest that neither overproduction of apoB from the liver nor decreased hepatic LDL receptor levels cause the accumulation of VLDL and LDL in the plasma of high HDL1 baboons. These studies also show that, in spite of high levels of VLDL + LDL and HDL1, the high HDL1 baboons had higher levels of mRNA for LDL receptor and HMG-CoA synthase. This paradoxical relationship needs further study to understand the pathophysiology of VLDL and LDL accumulation in the plasma of animals with the high HDL1 phenotype.

Animals↗
PubMed1990

Metabolic regulation of apoproteins of high-density lipoproteins by estrogen and progesterone in the baboon (Papio sp).

To determine the metabolic regulation of the apoproteins of high-density lipoproteins (HDL) by estrogen and progesterone, 12 ovariectomized and hysterectomized baboons were fed a high cholesterol, high fat diet and were divided into four groups. One of these groups was the untreated control and the remaining three groups were treated with estrogen, progesterone, or a combination of both. After 10 months of treatment, there were significant differences in HDL apolipoprotein (apo) A-I and apo A-II levels in these groups. The apo A-I level was highest in baboons treated with the combination therapy, followed by those treated with estrogen. Baboons treated with progesterone and those in the control group had similar levels of apo A-I. Baboons treated with both estrogen and progesterone and estrogen alone had significantly higher levels of apo A-I than those in the control or progesterone group. Baboons treated with hormones had higher apo A-II levels than controls, and those treated with the combination therapy had the highest level. Metabolic studies suggested that both estrogen and progesterone increased apo A-I and apo A-II production. Progesterone also increased the fractional catabolic rate of apo A-I, but not of apo A-II. On the other hand, estrogen did not affect the fractional catabolic rate of either apo A-I or apo A-II. Thus, increased apo A-I content of HDL in baboons treated with both estrogen and progesterone or estrogen alone appears to be due to increased apo A-I synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗