Regulation of growth-related genes by nutrition in paralarvae of the common octopus (Octopus vulgaris).

The common octopus (Octopus vulgaris) is a species of great interest to the aquaculture industry. However, the high mortalities registered during different phases of the octopus lifecycle, particularly the paralarvae stage, present a challenge for commercial aquaculture. Improvement of diet formulation is seen as one way to reduce mortality and improve growth. Molecular growth-markers could help to improve rearing protocols and increase survival and growth performance; therefore, over a hundred orthologous genes related to protein balance and muscle growth in vertebrates were identified for the common octopus and their suitability as molecular markers for growth in octopus paralarvae explored. We successfully amplified 14 of those genes and studied their transcription in paralarvae either fed with artemia, artemia + zoea diets or submitted to a short fasting-refeeding procedure. Paralarvae fed with artemia + zoea had higher growth rates compared to those fed only with artemia, as well as a significant increase in octopus mtor (mtor-L) and hsp90 (hsp90-L) transcription, with both genes also up-regulated during refeeding. Our results suggest that at least mtor-L and hsp90-L are likely linked to somatic growth in octopus paralarvae. Conversely, ckip1-L, crk-L, src-L and srf-L had expression patterns that did not match to periods of growth as would be expected based on similar studies in vertebrates, indicating that further research is needed to understand their function during growth and in a muscle specific context.

Isotope geochemistry reveals ontogeny of dispersal and exchange between main-river and tributary habitats in smallmouth bass Micropterus dolomieu.

Radiogenic strontium isotope ratios (87 Sr:86 Sr) in otoliths were compared with isotope ratios predicted from models and observed in water sampling to reconstruct the movement histories of smallmouth bass Micropterus dolomieu between main-river and adjacent tributary habitats. A mechanistic model incorporating isotope geochemistry, weathering processes and basin accumulation reasonably predicted observed river 87 Sr:86 Sr across the study area and provided the foundations for experimental design and inferring fish provenance. Exchange between rivers occurred frequently, with nearly half (48%) of the 209 individuals displaying changes in otolith 87 Sr:86 Sr reflecting movement between isotopically distinct rivers. The majority of between-river movements occurred in the first year and often within the first few months of life. Although more individuals were observed moving from the main river into tributaries, this pattern did not necessarily reflect asymmetry in exchange. Several individuals made multiple movements between rivers over their lifetimes; no patterns were found, however, that suggest seasonal or migratory movement. The main-river sport fishery is strongly supported by recruitment from tributary spawning, as 26% of stock size individuals in the main river were spawned in tributaries. The prevailing pattern of early juvenile dispersal documented in this study has not been observed previously for this species and suggests that the process of establishing seasonal home-range areas occurs up to 2 years earlier than originally hypothesized. Extensive exchange between rivers would have substantial implications for management of M. dolomieu populations in river-tributary networks.

A method for detecting recent changes in contemporary effective population size from linkage disequilibrium at linked and unlinked loci.

Estimation of contemporary effective population size (Ne) from linkage disequilibrium (LD) between unlinked pairs of genetic markers has become an important tool in the field of population and conservation genetics. If data pertaining to physical linkage or genomic position are available for genetic markers, estimates of recombination rate between loci can be combined with LD data to estimate contemporary Ne at various times in the past. We extend the well-known, LD-based method of estimating contemporary Ne to include linkage information and show via simulation that even relatively small, recent changes in Ne can be detected reliably with a modest number of single-nucleotide polymorphism (SNP) loci. We explore several issues important to interpretation of the results and quantify the bias in estimates of contemporary Ne associated with the assumption that all loci in a large SNP data set are unlinked. The approach is applied to an empirical data set of SNP genotypes from a population of a marine fish where a recent, temporary decline in Ne is known to have occurred.

Selection and sex-biased dispersal in a coastal shark: the influence of philopatry on adaptive variation.

Sex-biased dispersal is expected to homogenize nuclear genetic variation relative to variation in genetic material inherited through the philopatric sex. When site fidelity occurs across a heterogeneous environment, local selective regimes may alter this pattern. We assessed spatial patterns of variation in nuclear-encoded, single nucleotide polymorphisms (SNPs) and sequences of the mitochondrial control region in bonnethead sharks (Sphyrna tiburo), a species thought to exhibit female philopatry, collected from summer habitats used for gestation. Geographic patterns of mtDNA haplotypes and putatively neutral SNPs confirmed female philopatry and male-mediated gene flow along the northeastern coast of the Gulf of Mexico. A total of 30 outlier SNP loci were identified; alleles at over half of these loci exhibited signatures of latitude-associated selection. Our results indicate that in species with sex-biased dispersal, philopatry can facilitate sorting of locally adaptive variation, with the dispersing sex facilitating movement of potentially adaptive variation among locations and environments.

Contemporary population structure and post-glacial genetic demography in a migratory marine species, the blacknose shark, Carcharhinus acronotus.

Patterns of population structure and historical genetic demography of blacknose sharks in the western North Atlantic Ocean were assessed using variation in nuclear-encoded microsatellites and sequences of mitochondrial (mt)DNA. Significant heterogeneity and/or inferred barriers to gene flow, based on microsatellites and/or mtDNA, revealed the occurrence of five genetic populations localized to five geographic regions: the southeastern U.S Atlantic coast, the eastern Gulf of Mexico, the western Gulf of Mexico, Bay of Campeche in the southern Gulf of Mexico and the Bahamas. Pairwise estimates of genetic divergence between sharks in the Bahamas and those in all other localities were more than an order of magnitude higher than between pairwise comparisons involving the other localities. Demographic modelling indicated that sharks in all five regions diverged after the last glacial maximum and, except for the Bahamas, experienced post-glacial, population expansion. The patterns of genetic variation also suggest that the southern Gulf of Mexico may have served as a glacial refuge and source for the expansion. Results of the study demonstrate that barriers to gene flow and historical genetic demography contributed to contemporary patterns of population structure in a coastal migratory species living in an otherwise continuous marine habitat. The results also indicate that for many marine species, failure to properly characterize barriers in terms of levels of contemporary gene flow could in part be due to inferences based solely on equilibrium assumptions. This could lead to erroneous conclusions regarding levels of connectivity in species of conservation concern.

Parthenogenesis in a whitetip reef shark Triaenodon obesus involves a reduction in ploidy.

Genetic analysis of a female whitetip reef shark Triaenodon obesus and her stillborn pup, assumed to be of parthenogenetic origin, revealed that the pup was homozygous at all 24 nuclear-encoded microsatellites assayed, consistent with the idea that diploidy in the pup had been restored via terminal fusion. Flow cytometric analysis, however, indicated that the genome size of the pup was no more than half that of the mother, and microscopy revealed that nuclear volume was c. 1.73 times larger in the mother than in the pup. Together these data suggest that the pup was genetically haploid, developing directly from an unfertilized egg; as far as is known, this is the first observation of a spontaneously produced haploid vertebrate.

Does mating behaviour affect connectivity in marine fishes? Comparative population genetics of two protogynous groupers (Family Serranidae).

Pelagic larval duration (PLD) has been hypothesized to be the primary predictor of connectivity in marine fishes; however, few studies have examined the effects that adult reproductive behaviour may have on realized dispersal. We assessed gene flow (connectivity) by documenting variation in microsatellites and mitochondrial DNA sequences in two protogynous species of groupers, the aggregate spawning red hind, Epinephelus guttatus, and the single-male, harem-spawning coney, Cephalopholis fulva, to ask whether reproductive strategy affects connectivity. Samples of both species were obtained from waters off three islands (Puerto Rico, St. Thomas and St. Croix) in the Caribbean Sea. Despite the notion that aggregate spawning of red hind may facilitate larval retention, stronger signals of population structure were detected in the harem-spawning coney. Heterogeneity and/or inferred barriers, based on microsatellites, involved St. Croix (red hind and coney) and the west coast of Puerto Rico (coney). Heterogeneity and/or inferred barriers, based on mitochondrial DNA, involved St. Croix (coney only). Genetic divergence in both species was stronger for microsatellites than for mitochondrial DNA, suggesting sex-biased dispersal in both species. Long-term migration rates, based on microsatellites, indicated asymmetric gene flow for both species in the same direction as mean surface currents in the region. Red hind had higher levels of variation in microsatellites and lower levels of variation in mitochondrial DNA. Long-term effective size and effective number of breeders were greater for red hind; estimates of θ(f) , a proxy for long-term effective female size, were the same in both species. Patterns of gene flow in both species appear to stem in part from shared aspects of larval and adult biology, local bathymetry and surface current patterns. Differences in connectivity and levels of genetic variation between the species, however, likely stem from differences in behaviour related to reproductive strategy.

A genetic linkage map of red drum, Sciaenops ocellatus.

Second-generation, sex-specific genetic linkage maps were generated for the economically important estuarine-dependent marine fish Sciaenops ocellatus (red drum). The maps were based on F(1) progeny from each of two single-pair mating families. A total of 237 nuclear-encoded microsatellite markers were mapped to 25 linkage groups. The female map contained 226 markers, with a total length of 1270.9 centiMorgans (cM) and an average inter-marker interval of 6.53 cM; the male map contained 201 markers, with a total length of 1122.9 cM and an average inter-marker interval of 6.03 cM. The overall recombination rate was approximately equal in the two sexes (♀:♂=1.03:1). Recombination rates in a number of linkage intervals, however, differed significantly between the same sex in both families and between sexes within families. The former occurred in 2.4% of mapped intervals, while the latter occurred in 51.2% of mapped intervals. Sex-specific recombination rates varied within chromosomes, with regions of both female-biased and male-biased recombination. Original clones from which the microsatellite markers were generated were compared with genome sequence data for the spotted green puffer, Tetraodon nigroviridis; a total of 43 matches were located in 17 of 21 chromosomes of T. nigroviridis, while seven matches were in unknown portions of the T. nigroviridis genome. The map for red drum provides a new, useful tool for aquaculture, population genetics, and comparative genomics of this economically important marine species.

Effects of cholesterol diets on vascular function and atherogenesis in rabbits.

Vascular endothelial dysfunction is an important early event in atherogenesis. To evaluate the effects of different levels of cholesterol-containing diets on vascular function and atherogenesis, 17 New Zealand White male rabbits were randomized into four groups: Control with noncholesterol, 10-week 0.5% (0.5C-10) or 1% cholesterol (1C-10), and 14-week 0.5% cholesterol (0.5C-14) feedings. After 10 or 14 weeks, the aortas were harvested for studies of vascular endothelial function and percentage surface lipid lesions. The 0.5% and 1% cholesterol feedings resulted in the same degree of hypercholesterolemia independent of the level and period of cholesterol feeding. There was a decreased trend in vascular endothelial-dependent relaxation to acetylcholine in cholesterol-fed rabbits. Fourteen-week cholesterol feeding induced the least vascular dilation at a concentration of 10-7 M acetylcholine (-38 +/- 3%, -23 +/- 4%, -23 +/- 2%, and -15 +/- 5% in control, 0.5C-10, 1C-10, and 0.5C-14 groups, respectively, P = 0.003). More cumulative exposure of arterial walls to cholesterol induced more surface lipid lesions in the aorta (r = 0.877, P < 0.001). There was a negative relationship between aortic lesions and vasodilation (r = -0.557, P = 0.020 for calcium ionophore; r = -0.463, P = 0.062 for acetylcholine). We conclude that the 0.5% and 1% cholesterol feedings induce similar degrees of hypercholesterolemia. However, aortic lipid lesions and vascular reactivity are dependent on cumulative exposure to cholesterol rather than serum cholesterol level only. Furthermore, decreased vascular endothelial relaxation in cholesterol-fed rabbits was related to lipid plaques in the aorta.

Relationship between insulin-mediated glucose disposal by muscle and adipose tissue lipolysis in healthy volunteers.

The present study was performed in 17 nondiabetic subjects and was initiated to determine whether enhanced adipose tissue lipolysis, either basal or catecholamine induced (isoproterenol), and/or resistance to insulin inhibition of isoproterenol-stimulated lipolysis were correlated with resistance to insulin-mediated glucose disposal by muscle. Insulin-mediated glucose disposal was assessed by determining the steady state plasma glucose (SSPG) concentration during the insulin suppression test [180 min infusion of somatostatin (350 micrograms/h), insulin (25 mU/m2min), and glucose (240 mg/m2.min)]. On another occasion, plasma FFA and glycerol concentrations were determined at the end of 3 sequential infusion periods (IP): IP1, somatostatin (350 micrograms/h) plus basal insulin replacement (5 mU/m2.min); IP2, somatostatin (350 micrograms/h), insulin (5 mU/m2.min), and isoproterenol (270 ng/m2.min); and IP3, somatostatin (350 micrograms/h), isoproterenol (270 ng/m2.min), and insulin (10 mU/m2.min). SSPG concentrations correlated with FFA concentrations during all 3 infusion periods after adjustment for age, gender, body mass index, insulin concentration, and ratio of waist to hip girth (IP1:r = 0.61; P < 0.03; IP2: r = 0.70; P < 0.01; IP3: r = 0.65; P < 0.02). Correlations between SSPG and glycerol concentrations were also highly statistically significant (IP1: r = 0.62; P < 0.03; IP2: r = 0.65; P < 0.02; IP3: r = 0.70; P < 0.01). These results demonstrate for the first time that plasma FFA and glycerol concentrations are increased commensurate with the degree of resistance to insulin-mediated glucose disposal at a basal insulin level, in response to isoproterenol stimulation, and after insulin inhibition of isoproterenol-stimulated lipolysis.

Comparison of the hemodynamic and metabolic effects of low-dose hydrochlorothiazide and lisinopril treatment in obese patients with high blood pressure.

Patients with high blood pressure tend to be insulin resistant, glucose intolerant, hyperinsulinemic, and dyslipidemic. Since these metabolic defects are accentuated by obesity, we thought it important to compare the effects of 3 months' treatment with either lisinopril (20 mg/day) or low dose hydrochlorothiazide (12.5 mg/day) on blood pressure and glucose, insulin, and lipoprotein metabolism in obese patients with hypertension. There were 14 patients in each group, and they were similar (mean +/- SE) in age (54 +/- 3 v 50 +/- 4 years), gender (nine men/five women), and body mass index (33.4 +/- 0.8 v 33.9 +/- 0.9 kg/m2). Patients treated with lisinopril had a somewhat greater fall in both systolic (18 +/- 3 v 10 +/- 3 mm Hg) and diastolic (12 +/- 2 v 8 +/- 1 mm Hg) blood pressure, but only the change in systolic pressure was statistically significant (P < .05). Plasma glucose, insulin, and triglyceride concentrations were measured at hourly intervals from 8 AM to 4 PM (breakfast at 8 AM and lunch at 12 PM), and there was a modest increase in all three variables following hydrochlorothiazide treatment (P < .05 to P < .09). However, daylong plasma glucose, insulin, and triglyceride concentration did not change with lisinopril treatment. Finally, neither the ability of insulin to mediate glucose disposal nor fasting lipid and lipoprotein concentrations, changed with either treatment. In conclusion blood pressure decreased significantly following treatment with either lisinopril (20 mg/day) or hydrochlorothiazide (12.5 mg/day).(ABSTRACT TRUNCATED AT 250 WORDS)

Relation between insulin resistance, hyperinsulinemia, postheparin plasma lipoprotein lipase activity, and postprandial lipemia.

We examined the relation between insulin resistance, plasma glucose and insulin responses to meals, lipoprotein lipase (LPL) activity, and postprandial lipemia in a population of 37 healthy nondiabetic individuals. Plasma glucose and insulin concentrations were determined at frequent intervals from 8 AM through midnight (breakfast at 8 AM and lunch at noon); resistance to insulin-mediated glucose disposal was determined by measuring the steady-state plasma glucose (SSPG) concentration at the end of a 180-minute infusion of glucose, insulin, and somatostatin; LPL activity was quantified in postheparin plasma; and postprandial concentrations of triglyceride (TG)-rich lipoproteins were assessed by measuring the TG and retinyl palmitate content in plasma and the Svedberg flotation index (Sf) > 400 and Sf 20 to 400 lipoprotein fractions. Significant simple correlation coefficients were found between various estimates of postprandial lipemia and SSPG (r = .38 to .68), daylong insulin response (r = .37 to .58), daylong glucose response (r = .10 to .39), and LPL activity (r = -.08 to -.58). However, when multiple regression analysis was performed, only SSPG remained independently associated with both postprandial TG and retinyl palmitate concentrations. These data provide evidence that insulin resistance plays an important role in regulating the postprandial concentration of TG-rich lipoproteins, including those of intestinal origin.

Why do low-fat high-carbohydrate diets accentuate postprandial lipemia in patients with NIDDM?

OBJECTIVE: To understand why low-fat high-carbohydrate (CHO) diets lead to higher fasting and postprandial concentrations of triglyceride (TG)-rich lipoproteins in patients with non-insulin-dependent diabetes mellitus (NIDDM). RESEARCH DESIGN AND METHODS: Patients with NIDDM were placed randomly on diets containing either 55% CHO, 30% fat, and 15% protein or 40% CHO, 45% fat, and 15% protein for 6 weeks, followed by crossover to the other diet. Test meals at the end of each diet period were consumed at 8:00 A.M. and 12:00 P.M. (noon) and contained 20 and 40% of daily calories, respectively. Vitamin A was also given at noon, and TG-rich lipoproteins of intestinal origin were identified by the presence of vitamin A esters. Frequent measurements were made throughout the 24-h study period of plasma glucose, insulin, and TG concentrations. Plasma samples obtained from 12:00 P.M. (noon) until 12 A.M. (midnight) were subjected to ultracentrifugation, and measurements were made of TG and vitamin A ester concentrations in plasma and in both the Svedberg flotation constant (Sf) > 400 (chylomicron) and Sf 20-400 (chylomicron remnant) lipoprotein fractions. In addition, very-low-density lipoprotein (VLDL)-TG turnover rate was estimated by following the decay of [3H]VLDL-TG. Finally, postheparin lipoprotein lipase and hepatic lipase activities were measured at the end of each dietary period. RESULTS: Mean +/- SE hourly concentrations of glucose (8.0 +/- 0.8 vs. 7.5 +/- 0.7 mmol/l), insulin (184 +/- 26 vs. 158 +/- 19 pmol/l), and TG (2.8 +/- 0.2 vs. 2.1 +/- 0.2 mmol/l) were higher (P < 0.05-0.001) after the 55% CHO diet. The 55% CHO diet also led to an increase (P < 0.05-0.01) in the mean +/- SE hourly concentrations of vitamin A esters in plasma (2.3 +/- 0.3 vs. 1.6 +/- 0.1 mumol/l) and in both the chylomicron (2.0 +/- 0.3 vs. 1.4 +/- 0.1 mumol/l) and chylomicron remnant fractions (0.36 +/- 0.04 vs. 0.14 +/- 0.03 mumol/l). In addition, the VLDL-TG production rate was higher (17.2 +/- 1.4 vs. 12.8 +/- 1.0 mg.kg-1.h-1, P < 0.003) and the VLDL-TG fractional catabolic rate lower (0.22 +/- 0.02 to 0.28 +/- 0.02 l/h, P < 0.005) after the 55% CHO diet. Finally, there was an increase in lipoprotein lipase activity (7.0 +/- 0.8 to 8.1 +/- 0.7 mumol free fatty acids released .ml-1.h-1, P < 0.02) in response to the CHO-enriched diet. CONCLUSIONS: A low-fat high-CHO diet in patients with NIDDM led to 1) higher day-long plasma glucose, insulin, and TG concentrations; 2) postprandial accumulation of TG-rich lipoproteins of intestinal origin; 3) increased production of VLDL-TG; and 4) increased postheparin lipoprotein lipase activity. These data provide a mechanism for the hypertriglyceridemic effect of CHO-enriched diets in patients with NIDDM and demonstrate that multiple risk factors for coronary heart disease are accentuated when these individuals consume diets recommended to reduce this risk.

Additive effects of obesity, hypertension, and type 2 diabetes on insulin resistance.

Resistance to insulin-mediated glucose disposal has been previously shown to be increased in association with obesity, high blood pressure, and non-insulin-dependent diabetes mellitus. We initiated the present study to quantify the separate effects of hypertension and non-insulin-dependent diabetes mellitus on insulin resistance in both nonobese and obese subjects. To accomplish this, 88 subjects were divided into the following five experimental groups: normal blood pressure, nonobese (n = 17); normal blood pressure, obese (n = 18); high blood pressure, nonobese (n = 18); high blood pressure, obese (n = 19); and high blood pressure, obese, non-insulin-dependent diabetes mellitus (n = 16). Plasma glucose and insulin concentrations were measured before and after a 75-g oral glucose load. Resistance to insulin-mediated glucose disposal was estimated by determining the steady-state plasma insulin and glucose concentrations during the last 30 minutes of a continuous infusion of somatostatin (5 micrograms/min), exogenous insulin (25 mU/m2 per minute), and glucose (240 mg/m2 per minute). Since the steady-state plasma insulin concentrations are similar in all subjects, the higher the steady-state plasma glucose, the more insulin resistant the individual. Nonobese subjects with normal blood pressure had the lowest plasma glucose and insulin responses and steady-state plasma glucose concentrations, and their values were significantly different from the other four groups. Obese or nonobese subjects with high blood pressure had significantly higher plasma glucose responses and steady-state plasma glucose concentrations than did their respective weight-matched control subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Dietary fructose effects on lipoprotein metabolism and risk for coronary artery disease.

In this chapter I have attempted to review the current literature drawing on those studies that I believe provide the best scientific evidence in regard to this issue. When those studies that provide the best scientific evidence are reviewed, there is evidence that increasing dietary fructose consumption can significantly increase fasting plasma triglyceride and cholesterol concentrations. Specifically, these changes are associated with an increase in both VLDL and LDL particles, without any apparent change in HDL particle concentrations. It appears that the magnitude of the deleterious effects vary depending on such factors as age; sex, baseline glucose, insulin, and triglyceride concentrations; the presence of insulin resistance; and the amount of dietary fructose consumed. Finally, not all studies are consistent in these findings, however, the positive data cannot easily be dismissed and may be of substantial clinical importance. This is particularly true given the fact that: 1) these deleterious changes occur in the absence of any beneficial effect on lipoprotein metabolism, and 2) these abnormalities in lipoprotein metabolism appear to be greater in those individuals already at an increased risk for coronary artery disease.

Plasma insulin, C-peptide, and proinsulin concentrations in obese and nonobese individuals with varying degrees of glucose tolerance.

Conventional immunoassays to quantify insulin concentration do not differentiate between insulin and proinsulin. Thus, previous conclusions as to the relationship between the development of hyperglycemia in patients with noninsulin-dependent diabetes mellitus (NIDDM) and pancreatic insulin secretory function may have been confounded by not being able to determine the contribution made by plasma proinsulin to the putative measurements of plasma insulin concentration in these patients. The current study was initiated to address this issue by making specific measurements of plasma insulin, proinsulin, and C-peptide concentrations in 42 individuals: 14 with normal glucose tolerance, 12 with impaired glucose tolerance (IGT), and 16 with NIDDM. The study population was further subdivided into a nonobese (body mass index, < 30 kg/m2) and an obese (body mass index, > 30 kg/m2) group. Mixed meals were given at 0800, 1200, and 1800 h, and blood was removed at 0800 h (before the meal) and at hourly intervals from then until 1600 h. Plasma glucose concentrations throughout the sampling period were slightly, but significantly (P < 0.01), greater in patients with IGT than in normal individuals. Patients with NIDDM had markedly elevated glycemic excursions, greater than either of the other two groups (P < 0.002). Both plasma immunoreactive insulin and C-peptide concentrations from 0800-1600 h were higher (P < 0.002-0.001) in patients with either IGT or NIDDM than in the group with normal glucose tolerance. Although day-long plasma immunoreactive insulin and C-peptide concentrations were higher, on the average, in patients with IGT compared to those with NIDDM, the difference was not statistically significant. Plasma proinsulin concentrations were highest in patients with NIDDM (P < 0.002), lower in those with normal glucose tolerance (P < 0.002), and intermediate in patients with IGT. When the calculated "true" insulin concentration was determined by taking the proinsulin content into consideration, patients with IGT had the highest day-long levels, with the lowest values found in the control population (P < 0.002). Although absolute values varied as a function of obesity, the generalizations outlined above were found in both weight groups. These results show that ambient plasma proinsulin concentrations increase as glucose tolerance declines. However, true plasma insulin concentrations in response to mixed meals remain highest in patients with IGT, lowest in normal individuals, and intermediate in patients with NIDDM. Thus, previous conclusions that absolute day-long plasma insulin concentrations are not lower than normal in patients with NIDDM do not appear to result from an inability to differentiate true insulin from proinsulin.

Lactate production and pyruvate dehydrogenase activity in fat and skeletal muscle from diabetic rats.

This study was initiated to explore the possibility that an increase in the supply of gluconeogenic precursors contributes to the overproduction of glucose by the liver in NIDDM patients. To address this issue, a form of experimental NIDDM was produced in rats by injecting a low dose (38 mg/kg) of STZ and comparing lactate and alanine production and PDH activity in skeletal muscle and isolated adipocytes from normal and diabetic rats. Skeletal muscle lactate production was measured by using a hindlimb perfusion technique and was significantly greater (P < 0.01) in the diabetic rats compared with two groups of control rats: one perfused at normal glucose levels and the other perfused at glucose concentrations comparable with those observed in diabetic rats. Alanine production by hindlimb from diabetic rats was 46% greater than hindlimbs from control rats perfused at normal glucose levels (P < 0.01) but was not significantly greater than control rats perfused at diabetic glucose levels. The percentage of glucose converted to lactate by muscle from both control groups was 4-5%, significantly lower than the 18% conversion rate observed in diabetic animals (P < 0.001). An increase in the ratio of lactate produced/glucose transport by isolated adipocytes from diabetic rats also was observed when measured in both the basal state (0.65 +/- 0.12 vs. 0.15 +/- 0.03, P < 0.01) and in the presence of maximal amounts of insulin (0.15 +/- 0.02 vs. 0.04 +/- 0.01, P < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Demonstration of a relationship between white blood cell count, insulin resistance, and several risk factors for coronary heart disease in women.

In order to evaluate the relationship between peripheral white blood cell (WBC) count, insulin-mediated glucose uptake, and several risk factors for coronary heart disease (CHD), WBC, plasma glucose and insulin responses to a 75-g oral glucose challenge, fasting plasma cholesterol, high-density-lipoprotein (HDL)-cholesterol, and triglyceride concentration, and systolic and diastolic blood pressure were determined in 63 consecutive female volunteers with normal glucose tolerance. The results demonstrated the presence of statistically significant correlation coefficients between WBC count and both insulin-mediated glucose disposal (r = 0.50, P less than 0.001) and insulin response to oral glucose (r = 0.50, P less than 0.001). Furthermore, WBC count correlated with plasma glucose response to oral glucose (r = 0.48, P less than 0.001), fasting plasma triglyceride (r = 0.37, P less than 0.005) and HDL-cholesterol concentrations (r = -0.38, P less than 0.005), and systolic (r = 0.22, P less than 0.1) and diastolic (r = 0.27, P less than 0.05) blood pressure. However, the only two variables significantly correlated with WBC count in multivariate regression analysis were insulin resistance (r = 0.49, P less than 0.01) and insulin response (r = 0.35, P less than 0.05). These data indicate that WBC count is significantly correlated with changes in carbohydrate and lipoprotein metabolism and blood pressure that increase the risk of CHD. However, it appears that these relationships are secondary to resistance to insulin-mediated glucose uptake and hyperinsulinaemia.

Delayed removal of 125I-labeled very low density lipoprotein from plasma of rats with insulin-deficient diabetes mellitus.

The present studies demonstrate that the removal rate of exogenously labelled 125I-VLDL-protein is prolonged when total serum from insulin-deficient rats combined with isolated 125I-VLDL is injected into normal recipient rats (6.8 +/- 0.7 vs 4.2 +/- 0.4 min; p < 0.01), but not when 125I-VLDL-protein is isolated and injected alone (4.2 +/- 0.8 vs 4.3 +/- 0.8 min). Furthermore, the present studies demonstrate that when isolated 125I-VLDL-protein is recombined with either VLDL-free (d > 1.006 g/ml), or lipoprotein-free serum (d > 1.215 g/ml) from insulin-deficient rats, the defect in removal rate of VLDL-protein observed in total serum is reestablished (125I-VLDL + VLDL-free serum from insulin-deficient rat vs that from normal rat: 7.6 +/- 1.2 vs 4.6 +/- 0.7 min, p < 0.05; and 125I-VLDL + lipoprotein-free serum from insulin-deficient rat vs that from normal rat: 6.4 +/- 0.7 vs 4.1 +/- 0.4 min, p < 0.01). These data suggest that a factor or factors exist in lipoprotein-free serum of insulin-deficient rats which interfere with the normal removal of 125I-VLDL. Since we have previously demonstrated a prolongation in the removal rate of endogenously labeled VLDL-3H-TG, the defect in removal of VLDL from the plasma of insulin-deficient rats appears to include both the lipid and protein moieties of the VLDL particles.

Effect of nicotinic acid on plasma glucose concentration in normal individuals.

In order to assess the ability of nicotinic acid to decrease plasma glucose concentration, normal individuals were given continuous four hour infusions of either nicotinic acid (NA), somatostatin (SRIF), NA + SRIF, or 0.9% NaCl (Saline). Plasma non-esterified fatty acid (NEFA) concentration decreased to about one-fourth of the basal value in response to either NA or NA + SRIF, associated with statistically significant decreases in plasma glucose concentration. The ability of NA and NA + SRIF to decrease plasma glucose concentration was seen despite the fact that plasma insulin concentrations also fell significantly during both infusions. Although plasma glucose concentration fell significantly in response to both NA and NA + SRIF, the effect of NA + SRIF was approximately twice as great as that seen with NA alone. The augmented hypoglycaemic effect of NA + SRIF as compared to NA alone was associated with a concomitant fall in plasma glucagon concentration. In contrast, plasma glucose concentration did not change following Saline, and was actually higher than baseline after the infusion of SRIF alone. These results provide evidence that NA can lower plasma glucose concentration in normal volunteers, and suggests that this is mediated by the NA-associated decrease in plasma NEFA concentration.