Table 4.
Protective effects of carotenoids against diabetic complications—animal study evidence.
| Carotenoid name | Administration | Experimental design | Treatment | Duration | Results | References | |
|---|---|---|---|---|---|---|---|
| Upregulation | Downregulation | ||||||
| Lutein and zeaxanthin | Oral, diet | Transgenic db/db type-2 diabetic mice | Formulated diet containing 1% (kCal) of wolfberry | 8 weeks | 1. Improved the thickness of the whole retina 2. Restored the inner nuclear layer and photoreceptor layer, the integrity of RPE, and the ganglion cell number | (81) | |
| Lutein | Gastric tube | Alloxan-induced mice | 0.2 mg/kg/day | 14 days | Restored retinal and hippocampal levels of GSH and GPx activity compared to control group | 1. Reduced serum, retinal and hippocampal levels of MDA 2. Prevention of increase in NFκB activity in the diabetic retina and hippocampus | (82) |
| Zeaxanthin | Oral, dietary supplement | STZ-induced diabetic rats | 0.02% or 0.1% (w/w) zeaxanthin | 8 weeks | 1. Increased GSH/GPx activity 2. Elevated mitochondrial SOD | 1. Inhibited diabetes-induced retinal oxidative damage 2. Prevented diabetes-induced elevation in retinal VEGF and ICAM-1 3. Decreased NFkB activity | (83) |
| Lycopene | Oral, solution | STZ-induced diabetic rats | 20 mg/kg/day | 8 weeks | 1. Increased level of HDL-C 2. Increased Akt/PKB phosphorylation and SOD activity in diabetic renal tissues | 1. Decreased levels of blood urea nitrogen, 24 h urea protein and creatinine. 2. Reduction in serum TC, TG, and LDL-C 3. Decreased levels of MDA content and expression of CTGF | (84) |
| Lycopene | Oral, solution | STZ-induced diabetic rats | 5, 10, and 15 mg/kg/day | 10 weeks | Increased otal antioxidative capacity and the activities of antioxidants including CAT, SOD, and GPx | 1. Decreased FBG 2. Decreased oxidative stress biomarkers incl. GHb, ox-LDL, and MDA 3. Decreased TNF-α and CRP | (85) |
| Astaxanthin | Oral, dietary supplement | Diabetic db/db mice | 0.02% (w/w) astaxanthin | 12 weeks | 1. Lowered blood glucose level 2. Inhibition of increases in urinary albumin and 8-OHdG 3. Reduced the mesangial area/total glomerular area ratio | (86) | |
| Astaxanthin | Oral, dietary supplement | Diabetic db/db mice with diabetic retinopathy | 25 or 50 mg/kg/day | 8 weeks | 1. Inhibited apoptosis of RGCs 2. Decreased levels of oxidative stress markers, including superoxide anion, MDA, 8-OHdG and MnSOD activity in the retinal tissue | (87) | |
| Astaxanthin or lutein | Oral, solution | STZ-induced diabetic rats | 0.6 mg/kg or 3 mg astaxanthin, or 0.5 mg/kg lutein daily | 6 weeks | Increased levels of antioxidant enzymes (heme oxygenase-1 and peroxiredoxin) | 1. Reduced levels of oxidative stress mediators (8-hydroxy-2′-deoxyguanosine, nitrotyrosine, and acrolein) in ocular tissues 2. Reduced levels of inflammatory mediators (ICAM-1, MCP-1, and fractalkine) 3. Reduced activity of the NF-κB | (88) |
RPE, retinal pigment epithelia; GSH, glutathione; GPx, glutathione peroxidase; MDA, malondialdehyde; NF-κB, nuclear factor kappa-light-chain-enhancer of activated B cells; STZ, streptozotocin; HDL-C, high-density lipoprotein cholesterol; PKB, protein kinase B; SOD, superoxide dismutase; TC, total cholesterol; TG, triglycerides; LDL-C, low-density lipoprotein cholesterol; MDA, malondialdehyde; CTGF, connective tissue growth factor; CAT, catalase; FBG, fasting blood glucose; GHb, glycosylated hemoglobin; ox-LDL, oxidized-LDL; TNF-α, tumor necrosis factor alpha; CRP, C-reactive protein; 8-OHdG, 8-hydroxydeoxyguanosine; RGCs, retinal ganglion cells; MnSOD, manganese superoxide dismutase; ICAM-1, intercellular adhesion molecule-1; MCP-1, monocyte chemoattractant protein-1.