Clinical trial NCT01505803: The Effect of a Nutritional Supplement in Individuals With Type 2 Diabetes Mellitus: a Pilot Study
Official title: The Effect of a Nutritional Supplement on Cardiometabolic, Inflammatory, and Oxidative Stress Markers in Individuals With Type 2 Diabetes Mellitus: a Pilot Study
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: PHASE1
Conditions: Diabetes Mellitus, Type 2
Insulin Resistance
Keywords: Type 2 diabetes mellitus
Dietary supplements
Hyperglycemia
Insulin resistance
Dyslipidemia
Inflammation
Oxidative stress
Zinc
Omega 3
Lead sponsor: University of Sydney
Sponsor class: OTHER
First posted: 2012-01-09
Enrollment: 48
Sex: FEMALE
Minimum age (years): 48
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: no
Allocation: RANDOMIZED
Intervention model: PARALLEL
Primary purpose: TREATMENT

Brief summary: Diabetes Mellitus (DM) is a major risk factor for cardiovascular disease, with 50% of diabetes-associated deaths being attributed to cardiovascular complications. The characterising features of DM include: the presence of chronic hyperglycaemia, consequent upon decreased secretion or action of insulin; dyslipidaemia; and enhanced levels of oxidative stress and inflammation. Zinc and omega 3 polyunsaturated fatty acids have been shown to influence each of these outcomes via several mechanisms. This pilot study will examine the effect of nutritional supplements containing zinc and omega 3 on these outcomes in a population with type 2 DM.

Detailed description: The prevalence of type 2 DM and related-complications continues to increase. Diet is a significant factor in the aetiology of type 2 DM. Intakes of zinc and omega 3 fatty acids may modulate glycaemic control, lipid metabolism, and inflammatory processes in the disease. Zinc is involved in many biological processes that include enzyme action, stabilisation of cell membranes, regulation of gene expression, and cell signalling. Zinc supplementation has been demonstrated to improve glycaemic control in both animals and humans. The normalising effect of zinc on glucose homeostasis may relate to its involvement in insulin metabolism. Zinc functions in the synthesis, storage, secretion, and action of insulin. Omega-3 also enhances glycaemic control and dietary supplementation with omega-3 polyunsaturated fatty acids has been shown to improve insulin sensitivity in subjects with DM. Both zinc and omega-3 function to mediate lipid metabolism. Zinc supplementation has been found to be associated with a beneficial increase in HDL cholesterol concentrations in individuals with type 2 DM. The mechanism may again involve insulin, which has been proposed as an independent predictor of plasma HDL. Omega-3 directly activates transcription factors that regulate lipid metabolism and is known to decrease serum triglyceride levels in DM. Zinc appears to beneficially impact oxidative stress-related parameters in DM via a range of mechanisms, including the regulation of copper,zinc superoxide dismutase, metallothionein, NF-κB and nitric oxide signaling. The purpose of this pilot study is to explore the effect of zinc and omega 3 supplementation on hyperglycaemia, dyslipidaemia, chronic inflammation, and oxidative stress in a population with type 2 DM.

This study will recruit 48 postmenopausal women with type 2 DM. Participants will be randomly allocated to one of 4 groups for a period of 12 weeks: placebo, zinc, omega 3, or zinc + omega 3 supplementation. Usual dietary intake will be assessed before and after the trial period using 2-day estimated food records, which will be checked by a research dietitian. Blood samples will be collected from all participants at the start of the intervention (week 0) then at 4 weekly intervals (weeks 4, 8, 12) by qualified phlebotomists. Blood samples will be analysed for plasma zinc, plasma lipids and fatty acids, markers of inflammation and oxidative stress, and indicators of glycaemic control. An aliquot of blood will also be used for the measurement of zinc transporter mRNA levels utilising real-time quantitative PCR techniques.

Eligibility criteria: Inclusion Criteria:

* Female, postmenopausal
* Type 2 diabetes (controlled by diet and lifestyle; or oral hypoglycaemic medication (i.e. metformin) for not more than 7 years)
* Normal Glomerular Filtration Rate (GFR) and normal microalbumin/creatine ratio
* No nutritional supplements in the 6 weeks prior to the trial \& continuing through the trial period
* Non-smoking

Exclusion Criteria:

* Diagnosed with current major illness (renal disease, significant cardiovascular disease, gastrointestinal disorders, cancer, or other significant disorder likely to interfere with zinc metabolism)
* Taking medications that are likely to interfere with zinc metabolism

Primary outcomes:
measure: Plasma lipids (total cholesterol, HDL cholesterol, LDL cholesterol, triglycerides)
timeFrame: 12 weeks
measure: Glycaemic control (glucose, insulin, HbA1c)
timeFrame: 12 weeks
measure: Inflammation & oxidative stress (CRP, TNF-α, IL-1, IL-2, IL-6, IL-10 F2 isoprostanes, NF-κB, MPO, other)
timeFrame: 12 weeks
Secondary outcomes:
measure: Zinc transporter mRNA expression in peripheral blood mononuclear cells
timeFrame: 12 weeks
measure: Plasma zinc
timeFrame: 12 weeks
measure: Plasma fatty acids
timeFrame: 12 weeks
Other outcomes:
Locations:
city: Sydney
country: Australia
facility: University of Sydney
state: New South Wales
Study officials:
affiliation: University of Sydney
name: Samir Samman
role: PRINCIPAL_INVESTIGATOR
affiliation: University of Sydney
name: Meika Foster
role: PRINCIPAL_INVESTIGATOR
References:
citation: Foster M, Petocz P, Samman S. Effects of zinc on plasma lipoprotein cholesterol concentrations in humans: a meta-analysis of randomised controlled trials. Atherosclerosis. 2010 Jun;210(2):344-52. doi: 10.1016/j.atherosclerosis.2009.11.038. Epub 2009 Nov 29.
citation: Foster M, Samman S. Zinc and redox signaling: perturbations associated with cardiovascular disease and diabetes mellitus. Antioxid Redox Signal. 2010 Nov 15;13(10):1549-73. doi: 10.1089/ars.2010.3111.
citation: Foster M, Hancock D, Petocz P, Samman S. Zinc transporter genes are coordinately expressed in men and women independently of dietary or plasma zinc. J Nutr. 2011 Jun;141(6):1195-201. doi: 10.3945/jn.111.140053. Epub 2011 Apr 13.