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.

Nature of suppressed TSH secretion during undernutrition: effect of fasting and refeeding on TSH responses to prolonged TRH infusions

TSH responses to 4-hr continuous TRH infusions of approximately 0.8 microgram/min were assessed during feeding (1500 Kcal), fasting, and refeeding (1500 Kcal) intervals in 9 euthyroid obese subjects. The total area under the TSH response curve was 1854 +/- 322 muU/ml . 4-hr during feeding, decreased to 1359 +/- 199 muU/ml . 4-hr (p less than 0.01) on the 10th day of fasting, and remained low, being 1405 +/- 185 muU/ml . 4-hr, despite refeeding a 1500 Kcal diet (40% carbohydrate, 40% fat, 20% protein) for 5 days. Baseline serum T3 concentrations were 167 +/- 11 ng/dl during feeding, 86 +/- 8 ng/dl during fasting, and 119 +/- 12 ng/dl during refeeding. The observed decreases in TSH release appeared to correlate with decreased biologic action on the thyroid gland since the net rise in T3 during the infusion was less in fasting and refeeding than in the control (fed) period. Basal serum rT3 levels were 42 +/- 5 ng/dl during feeding, rose as expected to 56 +/- 5 ng/dl during fasting (p less than 0.005), and were completely restored to normal during refeeding (36 +/- 5 ng/dl). These data suggest that: (1) TSH responsiveness to prolonged TRH infusion is diminished during fasting and does not return to control (fed) values despite 5 days of refeeding a 1500 Kcal diet; (2) net T3 increases observed during the TRH infusion are greater in the fed period than in the fasting or refeeding periods; and (3) 5 days of refeeding a 1500 Kcal diet (40% carbohydrate, 40% fat, 20% protein) did not return the T3 to its original fed value whereas rT3 was completely restored to control values. Lastly, since the TSH response was lower both during the early and late phases of the infusion, the decrease in delta TSH to a bolus of TRH during fasting appears to represent one manifestation of a more general suppression of TSH neogenesis associated with caloric deprivation.