A neuropathic deficit, decreased sweating, is prevented and ameliorated by euglycemia in streptozocin diabetes in rats

Oral Nanocurcumin Alone or in Combination with Insulin Alleviates STZ-Induced Diabetic Neuropathy in Rats

Diabetes mellitus (DM), a multifaceted metabolic disorder if not managed properly leads to secondary complications. Diabetic peripheral neuropathy (DPN) is one such complication caused by nerve damage that cannot be reversed but can be delayed. Recently, diabetes patients are using dietary supplements, although there remains a general skepticism about this practice. Curcumin (CUR), one such supplement can help prevent underlying low-grade inflammation in diabetes, but it is plagued by poor oral bioavailability. To better understand the role of bioavailability in clinical outcomes, we have tested double-headed nanosystems containing curcumin (nCUR) on DPN. Because CUR does not influence glucose levels, we have also tested the effects of nCUR combined with long-acting subcutaneous insulin (INS). nCUR with or without INS alleviates DPN at two times lower dose than unformulated CUR, as indicated by qualitative and quantitative analysis of the hind paw, sciatic nerve, spleen, and L4-6 spinal cord. In addition, nCUR and nCUR+INS preserve hind paw nerve axons as evident by the Bielschowsky silver stain and intraepidermal nerve fibers (IENF) density measured by immunofluorescence. The mechanistic studies further corroborated the results, where nCUR or nCUR+INS showed a significant decrease in TUNEL positive cells, mRNA expression of NLRP3, IL-1β, and macrophage infiltration while preserving nestin and NF200 expression in the sciatic nerve. Together, the data confirms that CUR bioavailability is proportional to clinical outcomes and INS alone may not be one of the solutions for DM. This study highlights the potential of nCUR with or without INS in alleviating DPN and warrants further investigation.

Diabetic neuropathy: electrophysiological and morphological study of peripheral nerve degeneration and regeneration in transgenic mice that express IFNbeta in beta cells

Diabetic neuropathy is one of the most frequent complications in diabetes but there are no treatments beyond glucose control, due in part to the lack of an appropriate animal model to assess an effective therapy. This study was undertaken to characterize the degenerative and regenerative responses of peripheral nerves after induced sciatic nerve damage in transgenic rat insulin I promoter / human interferon beta (RIP/IFNbeta) mice made diabetic with a low dose of streptozotocin (STZ) as an animal model of diabetic complications. In vivo, histological and immunohistological studies of cutaneous and sciatic nerves were performed after left sciatic crush. Functional tests, cutaneous innervation, and sciatic nerve evaluation showed pronounced neurological reduction in all groups 2 weeks after crush. All animals showed a gradual recovery but this was markedly slower in diabetic animals in comparison with normoglycemic animals. The delay in regeneration in diabetic RIP/IFNbeta mice resulted in an increase in active Schwann cells and regenerating neurites 8 weeks after surgery. These findings indicate that diabetic-RIP/IFNbeta animals mimic human diabetic neuropathy. Moreover, when these animals are submitted to nerve crush they have substantial deficits in nerve regrowth, similar to that observed in diabetic patients. When wildtype animals were treated with the same dose of STZ, no differences were observed with respect to nontreated animals, indicating that low doses of STZ and the transgene are not implicated in development of the degenerative and regenerative events observed in our study. All these findings indicate that RIP/IFNbeta transgenic mice are a good model for diabetic neuropathy.

Uncontrolled hemorrhage in insulin-dependent diabetic rats

OBJECTIVES

Diabetes mellitus (DM) is a known risk factor for higher morbidity and mortality after trauma. The authors tested the hypothesis that there is a difference in the response to uncontrolled hemorrhage between normal euglycemic rats and insulin-dependent diabetic rats.

METHODS

Thirty-one adult male Sprague-Dawley rats were used in this study. Fifteen streptozocin (STZ)-injected rats became diabetic (DM+) 2 weeks after treatment. Sixteen rats served as nondiabetic controls (DM-). All rats were anesthetized with Althesin and their femoral arteries were catheterized via cutdown, allowing continuous monitoring of vital signs. Sixteen (eight DM-, eight DM+) rats underwent uncontrolled hemorrhage by 75% tail amputation. Fifteen (eight DM-, seven DM+) rats served as non-hemorrhage controls. The mean arterial pressure (MAP), lactate, and cumulative hemorrhage volume per 100 g were measured pre-hemorrhage and then every 15 minutes post-hemorrhage for 2 hours. Data were reported as mean +/- standard deviation. Interval data were analyzed by analysis of variance (two tails, alpha = 0.05).

RESULTS

Pre-hemorrhage glucose was significantly higher (p < 0.001) in the DM+ (357.9 +/- 22.2 mg/dL) versus DM- (125.7 +/- 9.7 mg/dL) rats. At baseline, there was no significant difference in weight, MAP, or lactate between DM+ and DM- rats. Body-weight-adjusted mean cumulative hemorrhage volume was significantly greater (p < 0.04) in diabetic rats (2.52 +/- 0.15 cm(3)/100 g body weight) than the nondiabetic rats (1.86 +/- 0.25 cm(3)/100 g body weight).

CONCLUSIONS

Compared to nondiabetic rats, diabetic rats suffered a greater blood loss after the same uncontrolled vascular injury.

Effects of topiramate on mouse eccrine sweat gland responsiveness to heat exposure

Young mice (2 weeks old) were given topiramate daily for 1 month, and sudomotor function was evaluated utilizing impression mould techniques to determine the number of sweat glands reactive to heat exposure and sweat output per gland on the plantar surface of mice hind-paws. Immunohistochemical quantitation of protein gene product 9.5, choline acetyltransferase and tyrosine hydroxylase in footpads was determined after topiramate treatment. While a 25% decrease in the number of secreting sweat glands and a 42% decline in sweat output per gland were observed following topiramate treatment, no significant differences were noted in sudomotor innervation, expressed as length of choline acetyltransferase, tyrosine hydroxylase and protein gene product 9.5 immunoreactive nerve profiles in single secretory coils or in sweat gland sizes within the secretory coil area. Long-term topiramate stimulation resulted in a reduction in the number of reactive sweat glands, without changes in sweat gland innervation, suggesting that the diminished responsiveness of the glands to heat exposure induced by topiramate might have resulted from a decrease in the intrinsic regulatory activity of sweat glands, as opposed to the loss of periglandular neurotransmitters or the impairment of the structure of the glands.

Redistribution of sudomotor responses is an early sign of sympathetic dysfunction in type 1 diabetes

Patients with diabetic neuropathy typically have decreased sweating in the feet but excessive sweating in the upper body. Previous studies of sudomotor function in diabetes have included patients with longstanding disease. The present study was designed to test for the early presence of sudomotor dysfunction and to characterize its relation to glycemic control and other aspects of peripheral nerve function. A total of 37 patients (10 males, 27 females) enrolled in a longitudinal study, in which autonomic function was evaluated annually for 3 years. Patients enrolled 2-22 months after the diagnosis of type 1 diabetes. Forty-one age- and sex-matched healthy control subjects were also studied. Sweat production in response to acetylcholine stimulation was dramatically increased in the forearm at the time of the first evaluation (1.67 +/- 0.24 micro/cm2 in the diabetic patients vs. 1.04 +/- 0.14 microl/cm2 in the control subjects, P < 0.05). Likewise, the ratio of sweating in the forearm to sweating below the waist was higher in the diabetic patients (0.553 +/- 0.07 microl/cm2) than in the control subjects (0.385 +/- 0.04 microl/cm2, P < 0.05). Forearm sweat was negatively associated with the renin-toprorenin ratio and vanillylmandelic acid (VMA) excretion (P < 0.025), tests of sympathetic nerve function. The ratio of sweating in the forearm to sweating in the foot was likewise increased in diabetic patients with poor glycemic control. We interpret this redistribution of sudomotor responses to be indicative of sympathetic nerve injury and conclude 1) that the sympathetic nervous system is especially vulnerable to the adverse effects of chronic hyperglycemia and 2) that sympathetic dysfunction can be detected very early in type 1 diabetes.

Evaluation of direct and axon reflex sweating in the mouse

The nicotinic axon reflex-mediated sudomotor response was studied in mice and rats by recording the impressions of sweat droplets made in silicone molds after local injection of nicotine, and compared with sweating induced by acetylcholine and pilocarpine. Nicotine failed to activate mouse plantar sweat glands at any of the concentrations used (from 3 x 10(-6) to 3 x 10(-1) M). On the contrary, both acetylcholine and pilocarpine produced a dose-dependent increase in the number of secreting sweat glands. The location of sweat glands reactive to pilocarpine and acetylcholine was similar and restricted to the pads near the site of injection. We conclude that the sudomotor axon reflex response mediated by nicotinic receptors is not present in the mouse and the rat.

Changes in cholinergic responses of sweat glands during denervation and reinnervation

Functional sudomotor responses have been studied in sweat glands reinnervated after sciatic nerve crush and partially denervated by cisplatin intoxication in the mouse. The sudomotor function mediated by the sciatic nerve was evaluated by silicone imprints on the plantar surface of the hindpaws. Five days after nerve crush, completely denervated sweat glands became unresponsive to cholinergic stimulation with pilocarpine. During the following weeks, the number of reinnervated, reactive sweat glands increased progressively to reach a maximum of 89% of preoperative control counts by 40 days after nerve crush. At this time, the mean volume of sweat secreted per gland was normal, but reinnervated glands showed a secretory activity abnormally sustained over time after pilocarpine stimulation and, on the other hand, had an increased resistance to the inhibition of secretion induced by atropine. The effects of cisplatin administration on sudomotor function were investigated in two groups of mice, one treated with high doses of cisplatin (10 mg/kg/week for 4 weeks) and another treated with low doses of cisplatin (5 mg/kg/week for 8 weeks). Cisplatin intoxication produced abnormal sudomotor responses indicative of denervation from cumulative doses of 10 mg/kg. The first abnormality found was a partial resistance of sweat glands to atropine, followed by a decrease in the sweat output per gland and finally a decline in the number of sweat glands activated by pilocarpine. These abnormalities in the sudomotor responses were more pronounced in mice treated with a high dose than in those with a lower dose regime.

Pain threshold in diabetic rats: effects of good versus poor diabetic control

Pain threshold was assessed via tail flick latency in streptozotocin diabetic rats following a 1-month period of either good or poor diabetic control. Additionally, tail flick latencies were determined under test conditions of euglycemia (60-120 mg/dl) and hyperglycemia (greater than 250 mg/dl) for both groups of diabetic rats. Conditions of hyperglycemia resulted in a significant decrease in tail flick latency in diabetic animals maintained in good as well as poor diabetic control. However, tail flick latencies for animals in the good but not in the poor diabetic control group increased when animals were euglycemic at the time of testing. Animals in the poor diabetic control group continued to have reduced tail flick latencies even after acute normalization of blood glucose levels. These results suggest that chronic states of hyperglycemia that attend prolonged periods of poor diabetic management may lead to persistent alterations in pain threshold. In contrast, the reduced pain threshold of rats maintained in good diabetic control was reversed by a normalization of blood glucose levels. These findings provide evidence for two patterns of hyperalgesia in diabetic rats: (1) a readily reversible form in well-maintained diabetic rats that is altered by reducing circulating blood glucose levels to control values and (2) a more persistent form found in poorly controlled diabetic rats that does not respond to acute normalization of blood glucose.

Decreased sweat-gland number and function in patients with alopecia areata

In this study the number and function of sweat glands on the dorsum of the hand and foot were evaluated using a silastic imprint method. Twenty patients, 11 females and nine males with either alopecia areata, alopecia totalis, or alopecia universalis were included in the study. Patients showed a significant decrease in activated sweat-gland number and function compared to matched controls (P less than 0.001). There was no significant relationship between the degree of sweat-gland dysfunction and extent of hair loss, concurrent illnesses, or treatment. These findings suggest that eccrine sweat-gland function is compromised in patients with alopecia areata.