Abstract:
Tight glycemic control and prevention of secondary complications are the most important goals of
pharmacological treatment of diabetes mellitus. The inadequate responses to oral hypoglycemic
agents may be attributed to inadequate post-receptor events even when insulin levels are quite
sufficient, and associated with oxidative stress induced by long-term hyperglycemia. The
administration of antioxidants such as zinc, magnesium, selenium, vitamin A and vitamin E may
improve tissue responses to insulin and increase the efficacy of drugs which act through this
pathway. Further, there is a possibility of enhancing the drug effect by giving an antioxidant and
the patients might be happy to take the low doses.
This study was designed to evaluate the effects of zinc with or without other anti-oxidants
(magnesium, selenium, vitamin A and vitamin E) on the diabetic control, lipid profile and renal
function in type 2 diabetic patients. Further, it was designed to establish serum zinc levels among
healthy individuals. The study population consisted of previously diagnosed (for at least 2 years)
adult patients with Type II diabetes mellitus who were being folio wed-up at the Teaching
Hospital, Karapitiya outdoor clinics. Controls for the study were selected from healthy volunteers
from the staff of the Teaching Hospital and Faculty of Medicine, Karapitiya as well as from the
Bope-Poddala Health Division.
There were 96 patients with diabetes (33 males and 63 females) recruited for the study. Similar
number of age and sex-matched healthy individuals were included in the control group. The age
ranged from 37.0 to 65.0 years with a mean of 54.7±8.0 years in both groups. The mean fasting
blood sugar (FBS) among diabetic subjects was 6.14±1.2mmol/L whereas it was 5.07±0.8mmol/L
(p<0.001) in healthy controls. The mean post prandial blood sugar (PPBS) among those with
diabetes was 9.76±2.7mmol/L and that of healthy subjects was 6.1±1.3mmol/L (pO.OOl). The
serum zinc level among subjects with diabetes (8.5±5.1pmol/L) was significantly low when
compared with age and sex matched healthy subjects (13.8±6.0 pmol/L, p<0.001).There was no
significant correlation between FBS and fasting serum zinc level among either diabetes subjects
(r=0.16; p=0.13) or healthy subjects (r=-0.012; p=0.91).
In the second phase the diabetic subjects were randomly allocated to 3 groups; 29 subjects were
supplemented, with oral zinc sulfate (22 mg/day) and multivitamin/mineral (zinc+MVM)
preparation; 31 subjects the same MVM preparation without zinc; and 36 were given a matching
placebo, for a period of 4 months in a single blinded study. After 4 months of supplementation, investigations similar to the baseline were performed (i.e., blood glucose (fasting and post
prandial), HbAic%, serum zinc, insulin, creatinine and lipid profile). Compared to the baseline, the
Zinc+MVM group had a mean reduction of FBS by -0.33 (SEM, 0.21) mmol/L (p =0.05). The
FBS change observed in the MVM (+0.19±0.31 mmol/L) and the control groups
(+0.43±0.23mmol/L) were not statistically significant (p=0.89). The PPBS level also reduced
significantly (p=0.04) in the Zinc+MVM group with a mean change of -1.55+0.56mmol/L after
the intervention.
When FBS was >5.56mmol/L (>100mg/DL) the supplementation, with or without zinc had
showed a significant effect on FBS but no such effect seen at FBS <5.56mmol/L. In Zinc+MVM
group, FBS level dropped to 6.21±0.85mmol/L from the baseline 6.76±0.58mmol/L, whereas in
the MVM group baseline FBS level of 6.96±1.20mmol/L dropped to 6.61±1.07mmol/L. At the
PPBS level of >8.89 mmol/L (>160.0 mg/dL) reduction in mean PPBS was shown with the
intervention in all groups. The HbAic% level reduced irrespective of the baseline levels in
Zinc+MVM supplemented individuals. When the baseline HbAic% level was <6.0, the
Zinc+MVM group had a significant net reduction (mean level of 5.63+0.15 at the baseline and
5.53+1.27 after the intervention, p<0.05). Zinc+MVM supplementation caused a significant
decrease triglycerides (p=0.02), total cholesterol (p=0.005), LDL (p=0.05) and an increase in
HDL (p=0.002) when compared with placebo supplementation.
This research programme adds useful information to the existing treatments for type II diabetes
mellitus which may in future help to to reduce non-communicable disease burden in the country
by helping better treatment of type II diabetes.