Geraniol, a natural monoterpene, ameliorates hyperglycemia by attenuating the key enzymes of carbohydrate metabolism in streptozotocin-induced diabetic rats

Figures & data

Table 1. Effect of geraniol on body weight, fluid and food intake of normal control and experimental rats.

	Body weight (g)		Fluid intake (mL/rat/day)		Food intake (g/rat/day)
Groups	Initial	Final	Before	After	Before	After
Normal control	206.34 ± 15.71	214.30 ± 16.32^a	67.52 ± 5.14	67.23 ± 5.12^a	15.68 ± 1.19	18.09 ± 1.38^a
Normal + geraniol (400 mg/kg b.w.)	207.47 ± 15.89	215.84 ± 16.53^a	69.09 ± 5.29	71.54 ± 5.48^a	16.15 ± 1.24	19.28 ± 1.48^a
Diabetic control	211.13 ± 16.08	136.60 ± 10.40^b	76.44 ± 5.82	187.91 ± 14.31^b	56.88 ± 4.33	72.28 ± 5.50^b
Diabetic + geraniol (100 mg/kg b.w.)	210.75 ± 16.14	188.89 ± 14.4^c	73.27 ± 5.61	126.53 ± 9.69^c	53.12 ± 4.07	38.90 ± 2.98^c
Diabetic + geraniol (200 mg/kg b.w.)	208.28 ± 15.95	197.14 ± 15.5^d	74.99 ± 5.74	97.63 ± 7.48^d	55.76 ± 4.27	30.26 ± 2.09^d
Diabetic + geraniol (400 mg/kg b.w.)	207.99 ± 15.93	198.25 ± 15.72^d	70.88 ± 5.43	94.42 ± 7.23^d	54.97 ± 4.21	29.12 ± 2.00^d
Diabetic + glyclazide (5 mg/kg b.w.)	206.33 ± 15.80	200.43 ± 15.89^d	74.0 ± 5.67	90.96 ± 6.97^d	57.14 ± 4.38	25.23 ± 1.93^d

Values are given as mean ± SD from six rats in each group.

Values not sharing a common superscript letter^(a–d) differ significantly at p < 0.05 (DMRT).

Figure 1. Effect of geraniol on the levels of oral glucose tolerance test in normal control and experimental rats.

Figure 2. Effect of geraniol on the levels of plasma insulin and glucose in normal control and experimental rats.

Table 2. Effects of geraniol on the levels of Hb and HbA_1C in normal control and experimental rats.

Parameters/Groups	Hb (g/dL)	HbA1c (%Hb)
Normal control	15.32 ± 1.32^a	6.46 ± 0.45^a
Normal + geraniol (200 mg/kg b.w.)	15.00 ± 1.32^a	6.15 ± 0.44^a
Diabetic control	7.9 ± 0.55^b	15.42 ± 0.88^b
Diabetic + geraniol (200 mg/kg b.w.)	12.01 ± 0.88^c	11.22 ± 0.88^c
Diabetic + glyclazide (5 mg/kg b.w.)	12.95 ± 0.88^c	12.03 ± 0.88^c

Values are given as mean ± SD from six rats in each group.

Values not sharing a common superscript letter^(a–c) differ significantly at p < 0.05 (DMRT).

Table 3. Effect of geraniol on the activities of carbohydrate metabolic enzymes in the tissues of normal control and experimental rats.

Parameters/groups	Normal control	Normal + geraniol (200 mg/kg b.w.)	Diabetic control	Diabetic + geraniol (200 mg/kg b.w.)	Diabetic + Glycazide (5 mg/kg b.w.)
Glycolytic enzyme
Hexokinase
Liver (units/g protein)	155.61 ± 11.92^a	154.23 ± 11.75^a	112.16 ± 8.59^b	138.60 ± 10.56^c	140.31 ± 10.75^c
Glucose 6-phosphate dehydrogenase
Liver (×10^−4 ml U/mg protein)	5.71 ± 0.43^a	5.30 ± 0.41^a	3.15 ± 0.24^b	4.75 ± 0.36^c	4.62 ± 0.35^c
Kidney (μg/mg protein)	4.55 ± 0.35^a	4.60 ± 0.35^a	2.95 ± 0.22^b	3.82 ± 0.29^c	3.90 ± 0.30^c
Gluconeogenic enzyme
Glucose 6-phosphatase
Liver (μg/mg protein)	0.20 ± 0.02^a	0.16 ± 0.01^a	0.45 ± 0.03^b	0.29 ± 0.02^c	0.26 ± 0.02^c
Kidney (μg/mg protein)	0.19 ± 0.01^a	0.17 ± 0.01^a	0.49 ± 0.04^b	0.25 ± 0.02^c	0.27 ± 0.02^c
Fructose 1,6-bisphosphatase
Liver (μg/mg protein)	0.31 ± 0.02^a	0.35 ± 0.03^a	0.67 ± 0.05^b	0.43 ± 0.03^c	0.47 ± 0.04^c
Kidney (μg/mg protein)	0.28 ± 0.02^a	0.31 ± 0.02^a	0.55 ± 0.04^b	0.47 ± 0.04^c	0.43 ± 0.03^c

Values are given as mean ± S.D from six rats in each group.

Values not sharing a common superscript letter^(a–c) differ significantly at p < 0.05 (DMRT).

Figure 3. (A–E) Represents the microphotographs of pancreatic tissues of normal control and experimental rats in each group (haematoxylin and eosin staining, 40×). (A and B) Normal control and normal control + geraniol (200 mg/kg body weight) treated rats showed normal appearing pancreatic exocrine glands and ducts with Islet of Langerhans. (C) Diabetic rats showing fatty infiltration and shrinkage of islet cells. (D and E) Pancreatic tissues from diabetic + geraniol (200 mg/kg b.w.) and diabetic + glyclazide (5 mg/kg b.w.) treated rats shows normal appearing pancreatic acini with absence of dilation and prominent hyperplastic of islets.

Figure 4. This figure shows the immunoexpression pattern of insulin secreting cells in pancreatic islets observed in the normal control and experimental rats in each group (40×). (A and B) Normal control and normal control + geraniol (200 mg/kg b.w.) treated rats showed normal immunohistochemical expression of insulin secreting cells in pancreatic islets. (C) Diabetic control showed decreased staining of insulin secreting cells in pancreatic islets. (D and E) Diabetic + geraniol (200 mg/kg b.w.) and diabetic + glyclazide (5 mg/kg b.w.) treated rats showed increased insulin secreting cells in pancreatic islets.

Table 4. Effects of geraniol on the levels of immunoreactive cells of insulin in pancreatic islets of normal and experimental rats.

Parameters/groups	% of Insulin positive cells
Normal control	66.14 ± 4.29^a
Normal + geraniol (200 mg/kg b.w.)	69.23 ± 4.84^a
Diabetic control	39.97 ± 3.74^b
Diabetic + geraniol (200 mg/kg b.w.)	67.20 ± 5.04^c
Diabetic + glyclazide (5 mg/kg b.w.)	70.06 ± 5.60^c

Values are given as mean ± S.D from six rats in each group.

Values not sharing a common superscript letter^(a–c) differ significantly at p < 0.05 (DMRT).