Richard G. Peterson

Sympathetic innervation of murine thymus and spleen: evidence for a functional link between the nervous and immune systems.

Sympathetic innervation was demonstrated in both perivascular and parenchymal regions of murine thymus and spleen. Catecholamine varicosities were associated with mast cells in these areas. The antibody response to sheep red blood cells of 7 week old mice that had been sympathectomized with six-hydroxydopamine (6OHDA) at birth was significantly elevated compared with saline treated controls. Alpha-methyl tyrosine (alpha-MT) and 6OHDA treatment of mice, producing a more complete sympathectomy, showed a significantly enhanced anti-SRBC response with respect to mice treated with alpha-MT or 6OHDA alone. Catecholamine levels in thymus, spleen, and adrenals of both experimental and control mice were measured using liquid chromatography with electrochemical detection (LCEC). The present study suggests that the sympathetic nervous system has a functional role in modulating the humoral immune response in vivo.

Effect of dietary fat on the development of non-insulin dependent diabetes mellitus in obese Zucker diabetic fatty male and female rats

The obese Zucker diabetic fatty male rat (ZDF/Gmi¿trade mark omitted¿-fa) has become a widely used animal model of NIDDM, in contrast to the obese ZDF females that rarely develop NIDDM. However, preliminary observations suggest that obese ZDF females may become diabetic on high-fat diets. Therefore, we studied the effect of dietary fat on development of NIDDM, dyslipidemia, and alterations in organ-specific serum panels in obese ZDF males and females. Results indicated different effects of dietary fat-content on development of diabetes in males and females. Males, even on low fat-content diets, developed diabetes but the process was accelerated as a function of dietary fat-content, whereas only the highest fat-content diet induced development of NIDDM in obese ZDF females. Additionally, triglyceride/apolipoprotein B ratios demonstrated gender-specific differences in the nature of circulating lipoprotein particles independent of diabetic state with values for females approximately twice those of males indicating more highly triglyceride-enriched lipoprotein particles in females. We conclude that the obese ZDF female rat has the potential to become an important animal model of NIDDM especially in women where few models currently exist.

Effects of streptozotocin diabetes on the noradrenergic innervation of the rat heart: A longitudinal histofluorescence and neurochemical study

The effects of the age of induction and total duration of streptozotocin diabetes on the sympathetic noradrenergic innervation of the rat heart was examined with glyoxylic acid induced histofluorescence to demonstrate the distribution of noradrenergic fibers within the heart, and with high performance liquid chromatography with electrochemical detection to measure tissue levels of the neurotransmitter norepinephrine. Diabetes was induced in male Sprague-Dawley rats at 1, 2, and 4 months of age. Within each of these groups, diabetic rats survived for periods of 1, 2, and 4 months. Additional groups of diabetic rats survived to a chronological age of 8 months. Norepinephrine levels in the hearts of diabetic rats were increased over those of control rats in all groups at 1 month duration of diabetes. Ventricles were generally affected to a greater extent than atria. At 2 months duration of diabetes, ventricular levels remained elevated while atrial norepinephrine levels were at or below control levels. At 4 months duration of diabetes, and in all groups at 8 months of age, the norepinephrine levels were at or below control levels, except in the ventricles of rats induced at 4 months of age, which remained elevated. Histofluorescence studies demonstrated the presence of axon bundles and varicose noradrenergic profiles in the diabetic rat hearts, distributed in a pattern similar to that seen in controls. However, at 1 month duration of diabetes in all groups, the density of noradrenergic varicosities in diabetic rat hearts appeared increased with abundant branched profiles. These results are surprising, since studies on genetic models of diabetes have suggested decreased norepinephrine levels in the heart. The present study suggests that during the early phases of streptozotocin induced diabetes, noradrenergic nerves are still intact and may be susceptible to pharmacologic manipulation. The later fall of norepinephrine levels back to or below control levels may indicate actual neuronal damage, suggesting that early intervention may be necessary to protect these nerves from degeneration. This issue is potentially important in view of the reported toxic effects of high NE levels on the heart, and the high incidence of death from myocardial infarct in diabetic humans with autonomic neuropathy.

A quantitative comparison of motor and sensory conduction velocities in short- and long-term streptozotocin- and alloxan-diabetic rats.

Motor and sensory conduction velocities were measured in the sural and tibial nerves of streptozotocin (stz)-diabetic, alloxan-diabetic, and age-matched control rats. Conduction velocity (CV) determinations were made 2 weeks and 2, 4, 8, and 12 months following the induction of diabetes. CVs of control, stz-diabetic, and alloxan-diabetic rats were compared at each time period by one way analysis of variance and when appropriate by the Newman-Keuls multiple range test for multiple comparisons. Reductions of 10-20% in CV of diabetic rats were observed in several classes of sensory and motor nerve fibers. Larger reductions (31 and 38%) were seen in 2 classes of sensory nerve fibers in 12 month stz-diabetic rats. Sensory CV was slowed earlier and more frequently than motor CV. Differential involvement was also seen among the several classes of sensory nerve fibers examined. Slower conducting sensory fibers appeared to be affected earlier and more frequently than faster conducting sensory fibers. Comparing alloxan-diabetic with stz-diabetic rats revealed significant differences in CV 8 months after the induction of diabetes. Motor and sensory CVs of the tibial nerve were slower in stz-diabetic rats than in alloxan-diabetic rats. In general, the neuropathy appeared to be less severe and to develop later in the alloxan-diabetic rats. These data suggest that the neuropathy of stz- and alloxan-diabetes is primarily sensory in nature, and that the neuropathy in these 2 widely used models of diabetes may not be entirely equivalent.

Soy Protein and Isoflavones Influence Adiposity and Development of Metabolic Syndrome in the Obese Male ZDF Rat

Background/Aims: Previously, we demonstrated that soy protein ameliorates the diabetic phenotype in several rodent models of obesity and metabolic syndrome (MS). This study was designed to further elucidate factors related to adiposity, glycemic control, and renal function in male Zucker Diabetic Fatty (ZDF/Leprfa) rats. Methods: Animals were randomly assigned to one of four diets: control, casein (C); low isoflavone (LIS) soy protein; high isoflavone (HIS) soy protein, or casein + rosiglitazone (CR) for 11 weeks. At sacrifice, physiological, biochemical, and molecular parameters were determined. Results: Body weight and total adiposity were higher in LIS and CR diet groups despite lower food intake. Additionally, these animals exhibited differential regulation of adipose-specific proteins (PPAR-γ and GLUT4) and enzyme activity (FAS and GPDH). HIS-fed animals had reduced total and liver adiposity. Glycemic control was prolonged in both soy-based and rosiglitazone (RGZ) groups. Renal dysfunction was significantly reduced in soy-fed and RGZ-treated rodents as demonstrated by lower levels of proteinuria and dilated tubules with proteinaceous casts. Conclusion: Collectively, these data provide evidence that soy protein with low or high isoflavone content may have therapeutic significance in reducing severity of diabetes, MS, and renal disease as demonstrated in this preclinical model.

Lipoprotein alterations in 10- and 20-week-old Zucker diabetic fatty rats: Hyperinsulinemic versus insulinopenic hyperglycemia☆

Lipoprotein and apolipoprotein parameters were studied in the male Zucker diabetic fatty (ZDF) rat at 10 and 20 weeks of age, corresponding to hyperinsulinemic and insulinopenic type 2 diabetes mellitus, respectively. At both ages, ZDF rats had elevated serum triglycerides, free fatty acids, and corticosterone, whereas 20-week ZDF rats had reduced thyroid hormones. At 10 weeks, the hyperlipidemia was confined to elevations in pre-beta triglyceride-rich (d < 1.006 g/mL) lipoproteins. By 20 weeks, all lipoprotein density fractions were increased compared with lean rats, with substantial increases in both low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol. In ZDF rats, there was a progressive increase in apolipoprotein B (apo B) from 1.9 times control at 10 weeks to three times control at 20 weeks. The increase in apo B was accompanied by a shift of apo B, particularly B100, from very-low-density lipoprotein (VLDL) into denser lipoproteins corresponding to intermediate-density lipoproteins plus LDLs (1.006 < d < 1.063 g/mL). In Zucker and 10-week ZDF rats, in the presence of hyperinsulinemia, the increase in serum apo B was predominantly apo B48 present in VLDL. By 20 weeks, when ZDF rats are insulinopenic, the mass ratio of B48:B100 shifted from 2.7 to 0.7. The shift was associated with a decrease in hepatic-edited apo B mRNA. Apo E increased in lean rats between 10 and 20 weeks of age. Although apo E also increased in ZDF rats, the increase by 20 weeks was less than that of lean rats. The molar ratio of apo E to B in VLDL was decreased in ZDF rats. In lean rats, greater than 50% of apo E was present in HDL, in contrast to ZDF rats, where less than 20% of apo E was present in HDL. VLDL apo E shifted to denser fractions by 20 weeks of age, similar to apo B. The apo C level was more than double compared with the level in lean rats and was redistributed from the HDL fraction to lipoprotein fractions containing apo B. Both apo A-I and apo A-IV levels more than doubled between 10 and 20 weeks in ZDF rats. The ZDF rat model may be useful in comparative studies of lipoproteins during diabetic progression from hyperinsulinemia to insulinopenia.

Reduced sensory and motor conduction velocity in 25-week-old diabetic [] mice

Abstract Motor and sensory conduction velocities were measured in sural and tibial nerves of 25-week-old genetically diabetic ( db db ) mice and their nondiabetic littermates. For motor conduction velocity determination, the sciatic nerve was stimulated at the hip and the tibial nerve subsequently stimulated at the ankle while recording interosseous muscle potentials from needle electrodes placed in the foot. Sensory conduction velocities were determined by recording compound action potentials directly from sural and tibial nerves at the ankle after sciatic nerve stimulation. Control and diabetic conduction velocities were compared by Students t test. The motor conduction velocity was reduced by approximately 20% from the control, and the distal motor latency was increased in db db mice by 22% more than the control latency. Conduction velocity was also reduced in some sensory fibers, an observation not previously reported in the db db mouse. Sensory fibers most severely affected were the faster-conducting fibers of the sural nerve, whose conduction velocity was decreased by 18% from the control. Slower-conducting sensory fibers in sural and tibial nerves were only midly affected, whereas fast-conducting sensory fibers of the tibial nerve appeared to remain normal. These data suggest that not all nerve fibers react alike to the diabetic state in the genetically diabetic ( db db ) mouse.

Degenerative neuropathy in insulin-treated diabetic rats

Peripheral neuropathic alterations associated with diabetes and its treatment with insulin were studied in alloxan-induced diabetic rats. Treatment regimens included daily injections of Protamine Zinc Insulin (PZ), daily injections of Ultralente Insulin and subcutaneously implanted osmotic minipump delivered insulin. Non-diabetic and untreated diabetic groups served as controls. Two separate but similar studies were run, one lasting 4 weeks and the other 8 weeks. Conduction velocities performed on both sensory and motor nerves revealed no statistically significant differences among groups. Anatomical analysis of teased fibers from tibial nerves showed a significant number of fibers with ovoids, consistent with Wallerian-type axonal degeneration, only in the treated diabetic groups. Degeneration was especially severe in the PZI-treated group. Metabolic studies were performed using incorporation of radioactive isotopes ([3H]fucose, [14C]leucine) into myelin proteins of sciatic nerves. The ratio of [3H]fucose/[14C]leucine for the PZI-treated group was significantly decreased when compared to the control groups in both the 4 and 8 week study whereas the minipump-treated group showed no statistically significant difference from the control group in either study. Similar decreases in this ratio have been seen in conditions of peripheral nerve degeneration. It is concluded that daily injections of PZI insulin result in significant nerve degeneration in the alloxan diabetic rat, while continuous levels of insulin delivered by osmotic minipumps result in less degeneration.

Glycogen accumulation in tibial nerves of experimentally diabetic and aging control rats

Tibial nerves of streptozotocin-diabetic, alloxan-diabetic, and age-matched control rats were examined at 2 weeks and 2, 4, 8, and 12 months following the induction of diabetes. Glycogen-like granules accumulated within perineurial and Schwann cells of only the diabetic animals. This accumulation may reflect a metabolic abnormality in these cells which could account for the reduced conduction velocities seen in the peripheral nerves of these same diabetic rats (Moore et al. 1980a). Glycogen-like granules were also present and increased with age in myelinated axons of both diabetic and control rats. Quantitative data suggest that axonal accumulation of glycogen-like granules is related to aging or injury related phenomena to which diabetic axons may be more susceptible.

The fatty acid composition of glycerolipids in nerve, brain, and other tissues of the streptozotocin diabetic rat

The fatty acid composition of individual glycerolipids in brain and sciatic nerve of rats made diabetic with streptozotocin and sacrificed 8 weeks later was determined and compared to the alterations that occurred in liver and kidney glycerlipids. A substantial decrease in the proportion of arachidonic acid and increases in the relative content of linoleic and docosahexenoic (22∶6n3) acids occurred in the phosphoglycerides of visceral tissues from diabetic animals as reported by others. In contrast, except for a small rise in the percentage of linoleic acid, no consistent changes in fatty acid composition of phosphatidylcholine, phosphatidylethanolamine, ethanolamine plasmalogen, phosphatidylinositol or phosphatidylerrine from brain or nerve were detected. The fatty acids of triacylglycerol associated with nerve exhibited alterations similar to those characteristic of liver. The differences which developed as a result of diabetes were completely prevented if animals were maintained continuously on insulin commencing shortly after administration of streptozotocin. It is concluded that the fatty acid composition of brain and nerve phosphoglycerides are unusually resistant to alteration in the diabetic animal and that consequently, changes in bulk membrane fluidity are unlikely to contribute to functional abnormalities displayed by diabetic peripheral nerve.