Treatment with supplementary arginine, vitamin C and zinc in patients with pressure ulcers: A randomised controlled trial

Background & Aims
Nutrients putatively implicated in pressure ulcer healing were evaluated in a clinical setting.

Methods
Sixteen inpatients with a stage 2, 3 or 4 pressure ulcer randomised to receive daily a standard hospital diet; a standard diet plus two high-protein/energy supplements; or a standard diet plus two high-protein/energy supplements containing additional arginine (9 g), vitamin C (500 mg) and zinc (30 mg). Nutritional status measurements (dietary, anthropometric and biochemical) and pressure ulcer size and severity (by PUSH tool; Pressure Ulcer Scale for Healing; 0=completely healed, 17=greatest severity) were measured weekly for 3 weeks.

Results
Patients’ age and BMI ranges were 37–92 years and 16.4–28.1 kg/m2, respectively. Baseline PUSH scores were similar between groups (8.7±0.5). Only patients receiving additional arginine, vitamin C and zinc demonstrated a clinically significant improvement in pressure ulcer healing (9.4±1.2 vs. 2.6±0.6; baseline and week 3, respectively; P<0.01). All patient groups presented with low serum albumin and zinc and elevated C-reactive protein. There were no significant changes in biochemical markers, oral dietary intake or weight in any group.

Conclusions
In this small set of patients, supplementary arginine, vitamin C and zinc significantly improved the rate of pressure ulcer healing. The results need to be confirmed in a larger study.

Differential effects of arginine, glutamate and phosphoarginine on Ca2+-activation properties of muscle fibres from crayfish and rat

The effects of two amino acids, arginine which has a positively charged side-chain and glutamate which has a negatively charged side-chain on the Ca²⁺-activation properties of the contractile apparatus were examined in four structurally and functionally different types of skeletal muscle; long- and short-sarcomere fibres from the claw muscle of the yabby (a freshwater decapod crustacean), and fast- and slow-twitch fibres from limb muscles of the rat. Single skinned fibres were activated in carefully balanced solutions of different pCa (-log₁₀[Ca²⁺]) that either contained the test solute (“test”) or not (“control”). The effect of phosphoarginine, a phosphagen that bears a nett negative charge, was also compared to the effects of arginine. Results show that (i) arginine (33-36 mmol l^-1) significantly shifted the force–pCa curve by 0.08–0.13 pCa units in the direction of increased sensitivity to Ca²⁺-activated contraction in all fibre types; (ii) phosphoarginine (9–10 mmol l^-1) induced a significant shift of the force–pCa curve by 0.18–0.24 pCa units in the direction of increased sensitivity to Ca²⁺ in mammalian fast- and slow-twitch fibres, but had no significant effects on the force–pCa relation in either long- or short-sarcomere crustacean fibres; (iii) glutamate (36–40 mmol l^-1), like arginine affected the force–pCa relation of all fibre types investigated, but in the opposite direction, causing a significant decrease in the sensitivity to Ca²⁺-activated contraction by 0.08–0.19 pCa units; (iv) arginine, phosphoarginine and glutamate had little or no effect on the maximum Ca²⁺-activated force of crustacean and mammalian fibres. The results suggest that the opposing effects of glutamate and arginine are not related to simply their charge structure, but must involve complex interactions between these molecules, Ca²⁺ and the regulatory and other myofibrillar proteins.

Isolation and restraint stress results in differential activation of corticontrophin-releasing hormone and arginine vasopressin neurones in sheep

This study investigated sex differences in the stress-induced activation of neurons containing corticotrophin-releasing hormone (CRH), arginine vasopressin (AVP) and enkephalin in the paraventricular nucleus (PVN) of gonadectomized male and female sheep. Groups (n=3) of both sexes were either subjected to 90 min isolation and restraint stress (stress group) or were not stressed. Blood samples were taken every 10 min for 90 min prior to and after stress to monitor cortisol levels in plasma. Brains were harvested after 90 min of stress. Stress caused elevation of plasma cortisol levels to a similar extent in both sexes. Double-labeling immunohistochemistry for Fos and either CRH, AVP or enkephalin was undertaken to quantify the numbers of neurons staining for CRH, AVP and enkephalin that also immunostained for Fos. Stress increased Fos immunostaining in all cell types. There was a greater proportion of CRH than AVP neurons activated in stressed animals. There were no sex differences in the activation of CRH and AVP neurons although females had a greater proportion of enkephalin cells staining for Fos than males in both control and stressed animals. There were no differences between control and stressed animals in the proportion of cells co-staining for CRH and AVP. We conclude that isolation and restraint stress activates neurons producing CRH, AVP and enkephalin in sheep and that CRH may play a greater role than AVP in regulating adrenocorticotrophic hormone secretion in response to this stressor in sheep. Finally, isolation and restraint stress does not influence co-localization of CRH and AVP in sheep.

L-Arginine infusion increases glucose clearance during prolonged exercise in humans

Nitric oxide synthase (NOS) inhibition has been shown in humans to attenuate exercise-induced increases in muscle glucose uptake. We examined the effect of infusing the NO precursor L-arginine (L-Arg) on glucose kinetics during exercise in humans. Nine endurance-trained males cycled for 120 min at 72 ± 1% VO2 peak followed immediately by a 15-min "all-out" cycling performance bout. A [6,6-2H]glucose tracer was infused throughout exercise, and either saline alone (Control, CON) or saline containing L-Arg HCl (L-Arg, 30 g at 0.5 g/min) was coinfused in a double-blind, randomized order during the last 60 min of exercise. L-Arg augmented the increases in glucose rate of appearance, glucose rate of disappearance, and glucose clearance rate (L-Arg: 16.1 ± 1.8 ml·min–1·kg–1; CON: 11.9 ± 0.7 ml·min–1·kg–1 at 120 min, P < 0.05) during exercise, with a net effect of reducing plasma glucose concentration during exercise. L-Arg infusion had no significant effect on plasma insulin concentration but attenuated the increase in nonesterified fatty acid and glycerol concentrations during exercise. L-Arg infusion had no effect on cycling exercise performance. In conclusion, L-Arg infusion during exercise significantly increases skeletal muscle glucose clearance in humans. Because plasma insulin concentration was unaffected by L-Arg infusion, greater NO production may have been responsible for this effect.

Co-localization and distribution of corticotrophin-releasing hormone, arginine vasopressin and enkephalin in the paraventricular nucleus of sheep : a sex comparison

The paraventricular nucleus (PVN) is integral to regulation of the hypothalamo-pituitary-adrenal (HPA) axis and contains cells producing corticotrophin-releasing hormone (CRH), arginine vasopressin (AVP) and enkephalin. We used immunohistochemistry to map these peptides and to resolve the extent of co-localization within PVN cells in intact and gonadectomized male and female sheep. Immunoreactive (ir) CRH, AVP and enkephalin cells were mapped in two rams and two ewes at 180 μm intervals throughout the rostro-caudal extent of the PVN. Similar distributions of AVP-ir cells occurred in both sexes whereas CRH-ir and enkephalin-ir cells extended more rostrally in rams. In groups (n=4) of intact and gonadectomized sheep of both sexes, co-localization and distribution of neuropeptides was influenced by sex and gonadectomy. Males had more AVP and CRH cells than females. Intact animals had more AVP cells than gonadectomized animals. There were no differences between groups in the number or percentage of cells that stained for both CRH and AVP or in the number of cells that stained for both CRH and enkephalin. Differences were observed in the percentage of enkephalin cells that contained CRH with males having a greater percentage of co-localized cells than did females. Differences were also observed in the number and percentage of cells that stained for both enkephalin and AVP; the number of cells that stained for both neuropeptides was greater in males than in females and greater in intact animals than in gonadectomized animals. Differences were observed in the percentage of AVP cells that contained enkephalin, and in the percentage of enkephalin cells that contained AVP with males having a greater percentage of co-localized cells than did females. We conclude that sex and gonadal status affect peptide distribution in the PVN of the sheep which may provide an anatomical basis for sex differences in HPA axis

Effect of an arginine-containing nutritional supplement on pressure ulcer healing in community spinal patients

Objective: To determine whether or not the use of an arginine-containing nutritional supplement could result in signifi cantly shorter pressure ulcer (PU) healing times in people with spinal cord injuries living in the community, compared with a comparative historical control group. Method: Eighteen spinal-cord-injured patients (all part of a hospital spinal outreach service) received 9g of a commercial powdered arginine supplement per day until full PU healing occurred. Healing rates were compared against 17 historical control patients (as assessed by medical history audit). 
Results: Baseline characteristics (age, gender, injury level and time) were similar between groups. Mean ulcer healing times were 10.5 ± 1.3 weeks versus 21 ± 3.7 weeks (p<0.05) in the intervention and control groups respectively. Comparison of healing rates in the intervention group against expected healing rates derived from the medical literature showed that intervention patients had a signifi cantly shorter mean healing time (category 2 PU: 5.5±1.3 weeks versus 13.4 weeks; category 3 PU: 12.5 ± 1.9 weeks versus 18.2 weeks; category 4 PU: 14.4 ± 4.8 weeks versus 22.1 weeks). A diagnosis of diabetes did not significantly alter healing rates in either group. Conclusion: Results from this observational study show a promising benefit of arginine supplementation on PU healing for individuals with spinal cord injury living in the community.

Use of an arginine-enriched oral nutrition supplement in the healing of pressure ulcers in patients with spinal cord injuries : an observational study

Aim: Pressure ulcers are a serious secondary consequence of spinal cord injuries. The objective of the present study was to determine whether an arginine-containing nutritional supplement can reduce the healing time of pressure ulcers in people with spinal cord injuries compared with those not consuming the supplement until full wound healing.

Methods: Thirty-four spinal cord injured patients with a grade 2, 3 or 4 pressure ulcer were prescribed two 237 mL tetrapaks/day of a supplement containing additional protein, arginine, zinc and vitamin C. Pressure ulcer healing was assessed with the Pressure Ulcer Scale for Healing tool.

Results: Twenty patients consumed the nutritional supplement until full pressure ulcer healing had occurred, while 14 patients ceased consuming the supplement before full healing occurred because of intolerance, compliance or taste issues. A 2.5-fold greater rate of healing was observed in patients consuming the supplement until full healing compared with those who ceased taking the supplement (8.5 ± 1.1 weeks vs 20.9 ± 7.0 weeks respectively; P = 0.04). There were no significant differences in age, nutritional status, gender or reason for admission between groups. Comparison of healing rates in the group consuming the supplement to full wound healing against expected rates derived from the medical literature showed a significantly shorter time-to-healing (grade 3 pressure ulcer: 6.5 ± 0.8 weeks vs 18.2 weeks; grade 4: 11.4 ± 2.0 weeks vs 22.1 weeks; P < 0.001).

Conclusion: The present small-scale study demonstrated the potential for specialised wound healing nutritional supplements to shorten the time to pressure ulcer healing in spinal cord injured patients.

Effect of L-arginine infusion on glucose disposal during exercise in humans

Purpose: We have previously shown that local infusion of a nitric oxide synthase (NOS) inhibitor attenuates increases in leg glucose uptake during exercise in humans. We have also shown that infusion of the NOS substrate, L-arginine (L-Arg), increases glucose clearance, although the mechanisms involved were not determined. A potential mechanism for NO-mediated glucose disposal is via interactions with NOS and the energy sensor AMPactivated protein kinase (AMPK). The aim of this study was to determine the mechanism(s) by which L-Arg infusion increases glucose disposal during exercise in humans by examining total NOS activity and AMPK signaling.

Methods: Seven males cycled for 120 min at 64% T 1% V˙ O2peak, during which the [6,6-2H]glucose tracer was infused. During the final 60 min of exercise, either saline alone (Control, CON), or saline containing L-Arg HCl (L-Arg, 30 g at 0.5 gIminj1) was coinfused in a double-blind, randomized, counterbalanced order.

Results: L-Arg increased the glucose rate of disappearance and glucose clearance rate during exercise; however, this was accompanied by a 150% increase in plasma insulin concentration from 65 to 75 min (P G 0.05) that remained significantly elevated until 90 min of exercise. Skeletal muscle AMPK signaling, nNOSK phosphorylation by AMPK, and total NOS activity increased to a similar extent in the two trials.

Conclusions: The increase in glucose disposal after L-Arg infusion during exercise is likely due to the significantly higher plasma insulin concentration.